Method and system for controlling draw tension on thread in a sewing system

Abstract

A method of controlling draw tension on thread wrapped around a bobbin that is mounted operatively on a case for movement relative to the case around an axis. The method includes the steps of: predetermining a desired thread draw tension to be achieved with the bobbin operatively mounted on a case using a predetermined mounting process; and, before operatively mounting the bobbin on the case, selectively controlling the at least one parameter of at least one of the thread and bobbin in a correlative manner to the desired thread draw tension with the bobbin operatively mounted on a case using the predetermined mounting process.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to sewing systems and, more particularly, to a method and system through which the draw tension on thread withdrawn from a supply on a bobbin can be controlled.

[0003] 2. Background Art

[0004] Stitching operations in sewing systems are commonly carried out by continuously withdrawing thread from a wrapped supply thereof on a bobbin. Typically, a bobbin case has a generally cylindrical construction and defines a receptacle within which the bobbin nests. The bobbin case has a post which is directed through a core on the bobbin to guide rotational movement of the bobbin relative to the case. In a typical system design, thread departing from the bobbin is directed through an opening/slot in the peripheral wall of the case and engaged, as by a rotary loop taker, to be tensioned thereby and drawn off of the bobbin.

[0005] In operation, the bobbin is rotated at a relatively high speed. As the draw tension is removed, the momentum of the moving bobbin, with the wrapped thread thereon, tends to cause the bobbin to continue rotating. In the absence of a resistive force on the bobbin, thread backlash may result. To remedy this situation, it may be necessary to manually untangle the line on the bobbin or, in an extreme case, cut the thread from the bobbin, and either replace the bobbin with a bobbin that is pre-wound or rewind thread on the active bobbin. In any event, the backlash problem potentially represents a loss in productivity attributable to system down time.

[0006] Various mechanisms have been devised to avoid the backlash problem. The inventor herein has developed systems which generate a resistive force between the bobbin the case which avoids backlash, but does not significantly impair the rotation of the bobbin, as necessary to withdraw thread during operations.

[0007] In one such system, a magnetic attractive/repulsive force is generated between parts of the bobbin and associated case to resist rotation therebetween. In another system, axially extending members cooperate between the bobbin and case to frictionally produce a force between the bobbin and case that resists rotation.

[0008] In addition to controlling backlash, draw tension is commonly adjusted as a particular application may dictate. Thus, virtually all sewing systems incorporate a thread draw tension adjusting capability. One of the most commonly used systems employs a spring element which captures the thread, at the point it departs radially through the case opening/slot, against the radially outwardly facing surface of the case. The captive force on the thread is variable through an adjusting screw associated with the spring element.

[0009] Another tension controlling/adjusting mechanism is shown in U.S. Pat. No. 6,152,057, commonly assigned with this invention. In this mechanism, thread departing from the case opening/slot is wrapped around an elongate rod. The draw resistance is dictated by the degree of contact between the thread and rod, which depends upon the diameter of the rod and the number of turns of thread therearound.

[0010] The process of setting the desired draw tension in conventional systems can be onerous. The draw tension is affected by many different aspects of the sewing system. For example, the anti-backlashing structure, as described above, produces a resistive force to rotation that affects draw tension. Draw tension is further affected by, among other things, the tack of the thread, the shape of the thread, the material defining the thread, the fiber make-up of the thread, the wrapping pattern of the thread on the bobbin, the wrapping tension of the thread around the bobbin, etc.

[0011] Heretofore, sewing systems have been designed so that thread draw tension is selectively adjusted by an operator through a mechanism separate from the bobbin, once the bobbin is installed. In a typical sewing system, numerous bobbin/case assemblies are simultaneously utilized. For each such bobbin/case assembly, individual draw tension adjustments are carried out, as by adjusting a set screw and thereby the captive spring force against thread at the outside of the casing, controlling the wraps on the projecting rod, etc. This is normally done on a trial and error basis, requiring potentially numerous preliminary adjustments to be made on each of multiple bobbin/case assemblies before actual sewing operations can be carried out.

[0012] To the knowledge of the inventor herein, no effort has been made by anyone in the industry to control all the different parameters that affect thread draw tension in such a manner that using a simple, consistent, installation process for the bobbin, a resulting draw tension will predictably result. Instead, the industry has dealt with the problem of time intensive system adjustment resulting from an uncontrolled selection of different combinations of parameters, i.e., thread texture, thread tack, thread shape, etc., without coordinatingly choosing these parameters for a predictable draw tension outcome. As a result, those in the industry continue to make multiple adjustments on each of multiple bobbin/case assemblies in their systems to control thread draw tension. Each time a system change is made, such as the replacement of one bobbin with another, the exercise of carrying out adjustments must be undertaken anew.

SUMMARY OF THE INVENTION

[0013] In one form, the invention is directed to a method of controlling draw tension on thread wrapped around a bobbin that is mounted operatively on a case for movement relative to the case around an axis. The method includes the steps of: predetermining a desired thread draw tension to be achieved with the bobbin operatively mounted on a case using a predetermined mounting process; and, before operatively mounting the bobbin on the case, selectively controlling the at least one parameter of at least one of the thread and bobbin in a correlative manner to the desired thread draw tension with the bobbin operatively mounted on a case using the predetermined mounting process.

[0014] In one form, the step of controlling the at least one parameter involves controlling thread tack.

[0015] The step of controlling the at least one parameter may involve controlling thread gauge.

[0016] The step of controlling the at least one parameter may involve controlling material defining the thread.

[0017] The step of controlling the at least one parameter may involve controlling thread shape.

[0018] In one form, the thread has a plurality of fibers. The step of controlling the at least one parameter may involve controlling structural interaction of the fibers defining the thread.

[0019] The step of controlling the at least one parameter may involve defining the bobbin so as to control a magnetic interaction of the bobbin and case that resists rotation of the bobbin relative to the case with the bobbin operatively mounted on the case.

[0020] The step of defining the bobbin may involve controlling parameters of a metallic component on the bobbin to magnetically interact with an element on the case.

[0021] The step of defining the bobbin may involve controlling parameters of a magnetic element on the bobbin to magnetically interact with at least one of (a) a metallic element and (b) a magnetic element on the case.

[0022] The step of controlling the at least one parameter may involve defining the bobbin so as to control frictional interaction of the bobbin and case that resists rotation of the bobbin relative to the case with the bobbin operatively mounted on the case.

[0023] The step of defining the bobbin may involve selecting a material defining at least a part of the bobbin.

[0024] The step of defining the bobbin may involve providing a flexible component on the bobbin that is biasably urged against the case with the bobbin operatively mounted on the case.

[0025] The step of defining the bobbin may involve providing a surface that produces a frictional resistance to rotation when borne against by a flexible component on the case with the bobbin operatively mounted to the case.

[0026] The step of controlling the at least one parameter may involve controlling the configuration of the bobbin.

[0027] In one form, thread is wrapped around the bobbin with a wrapping pattern and the step of controlling the at least one parameter involves controlling the wrapping pattern.

[0028] In one form, thread is wrapped around the bobbin with a wrapping tension and the step of controlling the at least one parameter involves controlling the wrapping tension.

[0029] The invention is further directed to a method of controlling draw tension on thread wrapped around a bobbin and mounted operatively on a case for movement relative to the case around an axis. The method includes the steps of: providing a first bobbin with a supply of thread wrapped around the first bobbin so that with the first bobbin operatively mounted on a first case using a predetermined mounting process, a first thread draw tension results; providing a second bobbin with a supply of thread wrapped around the second bobbin so that with the second bobbin operatively mounted on the first case using the predetermined mounting process, a second thread draw tension different than the first thread draw tension results; choosing a desired thread draw tension by selecting to operatively mount to the first case one of the first and second bobbins; and operatively mounting the one of the first and second bobbins to the first case.

[0030] The method may further include the step of predetermining approximately first and second magnitudes of thread draw tension resulting with each of the first and second bobbins operatively mounted on the first case using the predetermined mounting process, and identifying the first and second magnitudes to facilitate selection by a user of one of the first and second bobbins for use.

[0031] The invention is further directed to combination of a first and second bobbin. The first bobbin has a supply of a first thread wrapped around the first bobbin so that with the first bobbin operatively mounted upon a case having a first construction using a predetermined mounting process, a thread draw tension with a first magnitude results. The second bobbin has a supply of thread wrapped around the second bobbin so that with the second bobbin operatively mounted upon a case having the first construction using the predetermined mounting process, a thread draw tension, with a magnitude of predetermined tension predetermined to be greater or less than the first magnitude, results. The first and second bobbins, with their respective thread supplies, can be selectively operatively mounted upon a case having the first construction to select greater or lesser thread draw tension.

[0032] The combination may further include a first case having the first construction upon which the first and second bobbins can be interchangeably operably mounted.

[0033] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in tack on the first and second threads.

[0034] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in gauge of the first and second threads.

[0035] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in material defining the first and second threads.

[0036] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in shape of the first and second threads.

[0037] The first and second threads may each be defined by a plurality of fibers. The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in structural interaction of fibers defining the first and second threads.

[0038] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in magnetic interaction between a case having the first construction and the first and second bobbins.

[0039] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in a frictional interaction between the case having the first construction and the first and second bobbins.

[0040] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in configuration of the first and second bobbins.

[0041] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in wrapping pattern of the first and second threads around the first and second bobbins.

[0042] The difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction may be attributable to at least a difference in a wrapping tension for the first and second threads around the first and second bobbins.

[0043] In one form, the first bobbin has a first flange with a peripheral edge and the second bobbin has a second flange with a second peripheral edge, each of which face a radially inwardly facing surface on a case having a first construction to which the first and second bobbins are selectively operatively mounted. A difference between thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in interaction of the first and second peripheral edges with the radially inwardly facing surface on the case having the first construction, to which the first and second bobbins are operatively mounted.

[0044] The invention is further directed to the combination of a case and a bobbin. The case has a radially inwardly facing surface extending around a space. The bobbin has an axis and a first axially facing flange with a peripheral edge facing the radially inwardly facing case surface. The case and bobbin are configured so that the peripheral edge of the flange does not contact the radially inwardly facing surface of the case around the entire peripheral edge.

[0045] In one form, the case and bobbin are configured so that the peripheral edge of the flange does not contact the radially inwardly facing surface of the case.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 is a schematic representation of a sewing system, including a case to which bobbins with thread supplies thereon can be selectively mounted to select an operating thread draw tension, according to the present invention;

[0047] FIG. 2 is a partially schematic representation of the sewing system in FIG. 1 and showing in cross section the case with one of the bobbins, with its associated thread supply, operatively mounted thereon;

[0048] FIG. 3 is an exploded perspective view of side-walled bobbins that can be interchangeably mounted to the case in FIG. 2, according to the present invention;

[0049] FIG. 4 is an enlarged, fragmentary, elevation view of one form of frictional element for controlling thread draw tension on the sewing system in FIGS. 1 and 2;

[0050] FIG. 5 is a view as in FIG. 4 of another form of friction element for controlling thread draw tension;

[0051] FIG. 6 is a view as in FIG. 3 wherein the interchangeable bobbins have a sideless construction;

[0052] FIG. 7 is an enlarged, cross-sectional view of one thread to be used on the bobbins of FIGS. 2, 3 and 6 and having a tack composition thereon;

[0053] FIG. 8 is a view as in FIG. 7 wherein the tack composition has a different thickness;

[0054] FIG. 9 is a cross-sectional view of one thread to be used on the bobbin, and having a first gauge;

[0055] FIG. 10 is a view as in FIG. 9 with the thread having a different gauge;

[0056] FIG. 11 is a cross section of one thread to be used on the bobbins of FIGS. 2, 3, and 6 and having a squared cross-sectional shape;

[0057] FIG. 12 is a view as in FIG. 11 wherein the shape is oval;

[0058] FIG. 13 is a view as in FIGS. 11 and 12 wherein the shape is round;

[0059] FIG. 14 is a view as in FIGS. 11-13 wherein the shape is flat;

[0060] FIG. 15 is a fragmentary, elevation view showing magnetic elements cooperating between the case and flanges on the bobbins in FIGS. 2 and 3;

[0061] FIG. 16 is a view as in FIG. 15 with a different arrangement of magnetic elements;

[0062] FIG. 17 is a fragmentary, cross-sectional view cooperating portions on the bobbins and case in FIG. 6, wherein magnetic particles are dispersed to produce a magnetic attractive force between the bobbins and case;

[0063] FIG. 18 is a view as in FIG. 17 wherein the concentration of the magnetic particles is different than that in FIG. 17;

[0064] FIG. 19 is a view as in FIG. 15 wherein flexible elements projecting from one of the case and bobbins is biased frictionally against the other of the case and bobbins to retard relative rotation between the case and bobbins;

[0065] FIG. 20 is a view as in FIG. 19 wherein the flexible elements have a different configuration so as to have different bending and frictional characteristics;

[0066] FIG. 21 is a schematic representation of one winding pattern for thread around the bobbins in FIGS. 3 and 6; and

[0067] FIG. 22 is a view as in FIG. 21 showing another form of wrapping pattern for the thread around the bobbins;

[0068] FIG. 23 is a fragmentary, cross-sectional view of one of the bobbins in FIG. 3 operatively mounted on the case;

[0069] FIG. 24 is a plan view of an alternative form of bobbin, according to the invention, operatively mounted on a case that is shown in schematic form; and

[0070] FIG. 25 is a fragmentary, plan view of a further modified form of bobbin and having a projection therefrom to control contact between the bobbin and a case to which the bobbin is operatively mounted.

DETAILED DESCRIPTION OF THE DRAWINGS

[0071] In FIG. 1, a sewing system is shown at 10 incorporating a kit/combination of components 12, according to the present invention. More specifically, the system 10 consists of a case 14 upon which first and second bobbins 16,18, respectively, are selectively, operatively mounted. The bobbin 16 has a first thread supply 20 with the bobbin 18 having a second thread supply 22 wrapped therearound. Thread 20, 22 from the operative bobbin 16,18 is drawn off of the bobbin through a thread drawing mechanism 24, that may be a rotary loop taker, or the like.

[0072] According to the invention, with the first bobbin 16 and its thread supply 20 operatively mounted upon the case 14 using a predetermined mounting process, a first magnitude of thread draw tension results as thread 20 is withdrawn from the bobbin 16 through the thread drawing mechanism 24. With the second bobbin 18 and its thread supply 22 operatively mounted upon the case 14 using the predetermined mounting process, the magnitude of the thread draw tension is either greater than, or less than, the first magnitude. Accordingly, the first and second bobbins 16,18, with their respective thread supplies 20,22, can be selectively operatively mounted upon the case 14 to preselect a greater or lesser thread draw tension. Preferably, the magnitude of the thread draw tension, resulting with each of the bobbins 16,18 with its respective thread supply 20,22 operatively mounted upon the case 14, is either approximately or accurately predetermined. Accordingly, the user can, within a range, predetermine and thus select, a desired thread draw tension that results using the bobbins 16,18 with their respective thread supplies 20,22.

[0073] The difference in the thread draw tensions resulting from the selection of the bobbins 16,18 is attributable to a variation in at least one parameter of at least one of the thread 20, 22 and bobbins 16, 18. Before these different parameters are discussed, a more detailed explanation of the sewing system 10 will be made, initially with respect to FIGS. 2 and 3.

[0074] The sewing system 10 in FIGS. 2 and 3 utilizes side-walled bobbins 16,18. The case 14 has a base wall 28 with a peripheral wall 30 extending upwardly therefrom to bound, in conjunction with the base wall 28, a cylindrical thread storage space 32. The case 14 is mounted upon a frame 34 in a conventional manner. A hollow post 36 projects upwardly from the base wall 28 and has a central axis 38. The post 36 has a cylindrical outer surface 40 which is journalled for rotation in bores 42,44 through the bobbins 16,18, respectively. With the bobbins 16,18 operatively mounted on the case 14, as shown in FIG. 2, the bobbins 16,18 are rotatable about the central axis 38 of the hollow post 36.

[0075] The bobbin 16 has axially spaced flanges 46,48 which are attached at the ends of a cylindrical core 50. The flanges 46,48 have axially facing surfaces 52,54 which determine the thread volume capacity for the bobbin 16. The thread supply 20 is wrapped around the core 50 in the space between the flange surfaces 52,54.

[0076] The bobbin 18 has flanges 56,58 at the axial ends of a core 60. The flanges 56,58 have axially facing surfaces 62,64 which bound a space for the thread 22 wrapped around the core 60.

[0077] With the active bobbin 16,18 operatively mounted on the case 14, the thread 20,22 is directed through a radial opening/slot 66 through the case wall 30 in a radial direction to be engaged by the thread drawing mechanism/rotary loop taker 24.

[0078] It is known to control draw tension on the thread 20,22 through a friction element, shown generically at 68 in FIG. 2, and acting against the thread 20,22 as it paid off of the bobbins 16,18. One suitable friction element 68 is construction as shown in FIG. 4 in the form of a leaf spring 72 which is mounted to the peripheral wall 30 of the case 14 and maintained in place by one or more screws 76. The thread 20,22 that departs from the wall opening/slot 66 is captively situated between the leaf spring 72 and the peripheral wall 30. By adjusting the screw(s) 76, the captive force upon the exiting thread 20,22 can be changed to either increase or decrease draw tension on the thread 20,22.

[0079] In an alternative form of friction element 68′, as shown in FIG. 5, an elongate, cantilevered element 78 projects from the peripheral wall 30, as shown in U.S. Pat. No. 6,152,057, the disclosure of which is incorporated herein by reference. The draw tension for the thread 20,22 is variable by changing the degree of wrapping of the thread 20,22 around the cantilevered element 78, as described more fully in U.S. Pat. No. 6,152,057.

[0080] A modified form of bobbin construction is shown in FIG. 6 and is known in the industry as a sideless bobbin. The invention also contemplates practice thereof using sideless bobbins 16′,18′, corresponding to the bobbins 16,18, previously described, in combination with a case 14, as previously described, to include the base wall 28, peripheral wall 30 and hollow post 36 with the central axis 38. The peripheral wall 30 bounds the thread storage space 32.

[0081] The bobbins 16′,18′ have through bores 42′,44′ to receive the cylindrical outer surface 40 of the hollow post 36 with the bobbins 16′, 18′ operatively mounted on the case 14. The thread 20,22 is wrapped around the outer surfaces 80,82, which function as the aforementioned cores 50,60 on the bobbins 16,18.

[0082] The above description is intended to provide potentially different environments in which the present invention can be practiced. The invention can be practiced in virtually any type of sewing system in which thread-carrying bobbins can be interchangeably mounted upon a case. In fact, the invention can actually be practiced by changing at least one parameter of at least one of the thread and bobbin which remains operatively mounted upon a case. Certain, but not all, of the parameters of the thread 20, 22 and the bobbins 16,18,16′,18′ that can be varied, according to the present invention to control thread draw tension in a predetermined manner, are described below.

[0083] It is known that the degree of tack on thread affects the draw tension using the conventional bobbin/case combination. As shown in FIG. 7, the thread 20 is shown with a tack composition 84 coated on its exposed, outer surface 86. In FIG. 8, a tack composition 84′ is coated on the outer surface 86 of the thread 22. In FIG. 8, the radial thickness T of the tack composition 84 is greater than the corresponding thickness T1 of the tack composition 84 in FIG. 7.

[0084] The magnitude of the draw tension resulting from the use of the threads 20, 22 with the different tack composition thickness can be predetermined approximately, or relatively precisely, for a given construction of the case 14 and using a predetermined mounting process for the bobbins 16,18,16′,18′ upon the case 14. For example, it can be predetermined approximately, or exactly, what magnitude of draw tension will result using the different tack composition thicknesses T, T1 using the case 14 with a single wrap around the friction element 68′ in FIG. 5. The operator can be provided with a simple setup routine which allows a desired thread tack tension to be nominally, or relatively accurately, selected, by picking a bobbin 16,18,16′,18′ from a supply of the bobbins 16,18,16′,18′ having the different tack composition thicknesses, with a predetermined correlation to different thread draw tensions, and operatively mounting the same on the case 14 using the predetermined mounting process. It is also contemplated that one or more additional bobbins 16,18,16′,18′ could be provided with further different tack composition thicknesses correlated to additional thread draw tensions.

[0085] In addition to altering the thickness of the tack composition to cause different thread draw tensions to result, the supply of bobbins 16,18,16′,18′, from which user selection can be made, may have different tack compositions at the same or different thicknesses. As a further option, one of the bobbins 16,18,16′,18′ could have thread 20,22 wound therearound with no tack component, with another bobbin 16,18,16′,18′ having thread 20,22 wound thereon with tack component which accounts for a greater thread draw tension compared to the thread 20,22 with no tack component thereon.

[0086] An additional thread parameter that might be variably controlled is thread gauge. As shown in FIGS. 9 and 10, the thread 20 on the first bobbin 16,16′ may have a first gauge, with the thread 22 on the second bobbin 18,18′ having a second, larger gauge. This difference in gauge accounts for a different thread draw tension with the threads 20,22 wrapped around the bobbins 16,16′ and 18,18′ and the bobbins 16,18,16′,18′ operatively mounted on the case 14 using the same predetermined mounting process.

[0087] Another thread parameter that is variable to change thread draw tension is thread shape, which is explained relative to FIGS. 11-14. In FIG. 13, the thread 20,22 is shown with a round shape. The thread 20,22 could be formed with an elliptical shape, as shown in FIG. 12, a squared shape as shown in FIG. 11, or a flattened state, as shown in FIG. 14. With the thread 20,22 wrapped around the bobbins 16,18,16′,18′, and these bobbins 16,18,16′,18′ operatively mounted on the base 14 using a predetermined mounting process, different predeterminable thread draw tensions result.

[0088] As seen in FIG. 13, the threads 20,22 are made from a plurality of fibers 90. The nature of the fibers 90 defining the threads 20,22 is another parameter that can be varied to change thread draw tension. Further, the structural interaction of the fibers 90, be it the manner in which they are bundled or wrapped, can likewise be controlled to vary resulting thread draw tension. The thickness of the fibers 90 for a given gauge thread 20,22 can likewise be varied.

[0089] It is also known to produce a magnetic attractive/repulsive force between the bobbins 16,18, and case 14 to produce a variable rotational resistance force. As shown in FIG. 15, magnetic elements 94 can be provided on the case 14 and/or bobbins 16,18, on either an axially facing flange surface 96 or axially facing case surface 98. The surface 96,98 confronting the magnetic elements 94 may be metallic to produce an attractive force which resists rotation between the case 14 and bobbins 16, 18 to thereby cause an increase in the thread draw tension. Alternatively, magnetic elements 100 can be provided to cooperate with the magnetic elements 94 and produce a repulsive force which resists rotation between the case 14 and bobbins 16,18, so as to cause an increase in thread draw tension.

[0090] In FIG. 15, multiple magnetic elements 94 and potentially multiple cooperating magnetic elements 94,100 are shown. In FIG. 16, the same arrangement of magnetic elements 94/94,100 is used but with a resulting lesser magnetic force, either repulsive or attractive, produced between the case 14 and bobbins 16,18. Thus, one of the bobbins 16 can be designed to be magnetically attracted/repelled to/from the case 14 with a different force than the other of the bobbins 18.

[0091] A variable magnetic attractive force between the case 14 and bobbins 16′,18′ can be generated using an arrangement as shown in FIGS. 17 and 18. Magnetic particles 104 are dispersed in either the post 36 on the case 14 or on the bobbins 16′,18′ so as to produce an attractive force between the post 36 and bobbins 16′,18′ which resists rotation between the bobbins 16′,18′ and the case 14. The concentration of the particles 104 is less in the bobbin 18′ than in the bobbin 16′ so as to produce different rotational resistance forces.

[0092] The rotational resistance forces can be controlled/varied by using different metal compositions for the bobbins 16′, 18′ which would be attracted differently to the magnetic particles 104 on the case post 36. Also, magnetic particles 104 can be provided in both the post 36 and bobbins 16′,18′ to produce a repulsive force that resists rotation between the case 14 and bobbins 16′,18′. The concentration of the magnetic particles 104 in both the post 36 and bobbins 16′,18′ can be changed to produce the range of desired, predeterminable thread draw tensions with the bobbins 16′,18′ operatively mounted on the case 14. This same concept can be produced with the bobbins 16, 18, described above.

[0093] The inventor herein has also designed a rotation retarding mechanism using flexible, friction generating components on one of the case 14 and bobbins 16,18, which bear against the other of the case 14 and bobbins 16,18. As shown in FIG. 19, flexible elements 106 project from one of the surfaces 96,98, identified in FIGS. 15 and 16, to be pressed biasably against the other surface 98,96. As show in FIG. 20, flexible elements 108, functioning in like manner, are provided and have a more rigid construction to have different bending and frictional characteristics than the flexible elements 106. Accordingly, different thread draw tensions result from the use of the flexible elements 106,108 on bobbins 16,18 that are mounted upon the case 14.

[0094] It is also contemplated that part, or all, of the cooperating surfaces on the case 14 and bobbins 16,18,16′,18′, could be made from different materials to account for different thread draw tension. For example, the first bobbins 16,16′ could be made with surfaces, that contact the case 14, made from one material having first frictional characteristics, with the same surfaces on the second bobbin 18, 18′ made from a different material than that of the first bobbins 16,16′ and having different frictional characteristics so as to account for different thread draw tensions with the bobbins 16,16′;18,18′ mounted operatively upon the case 14. The texture of the cooperating surfaces on the case 14 and bobbins 16,16′,18,18′ can also be changed to achieve this same end.

[0095] The frictional interaction of the bobbins 16, 16′, 18, 18′ may be controlled by treating a surface on the bobbin 16, 16′, 18, 18′, or interposing an element or a composition between the bobbins 16, 16′, 18, 18′ and case 14. As one example, cardboard may be used to define one or more of the flanges 46, 48, 56, 58 on one or more of the available bobbins 16, 16′, 18, 18′. The cardboard can be treated, as by impregnation with a lubricant, such as silicone, or the like. A coating might be applied to cardboard, or other material on the bobbin 16, 16′, 18, 18′, such as a wax material.

[0096] As a further alternative, a lubricant might be applied selectively to one or both surfaces on the case 14 and or bobbin 16, 16′, 18, 18′ which move guidingly against one another during operation of sewing system 10. A silicone lubricant is an exemplary lubricant suitable to control thread draw tension resulting with the bobbin 16, 16′, 18, 18′ operatively mounted on the case 14.

[0097] Another parameter that may be varied is the thread wrapping pattern. As shown in FIGS. 21 and 22, the threads 20,22 can be wrapped around the bobbins 16,16′,18,18′ in a pattern extending substantially orthogonal to the central axis 110 of the bobbins 16,16′,18,18′, as shown in FIG. 21, or in a bias pattern, as shown in FIG. 22. These patterns are only exemplary of the many different patterns that might be used.

[0098] Further, the wrapping tension for the thread 20,22 can be varied from one bobbin 16,16′,18,18′ to the next to account for a variable thread draw tension.

[0099] Still further, by using different configurations of the bobbins 16,16′,18,18′ in the selectable group, different, desired thread draw tensions can be arrived at. As one example, the different configurations of the bobbins can have a different relationship between the outer edges 114, 116, respectively, on the flanges 45, 48 on the exemplary bobbin 16 and the radially inwardly facing surface 118 of the case 14, as seen in FIG. 23. In actuality, there is a slight radial gap D that exists between the radially inwardly facing surface 120 bounding the bore 42 through the bobbin 16 and the outer post surface 40. There is likewise a radial gap D1 between the flange edge 114 and the case surface 118 and a radial gap D2 between the flange surface 116 and the case surfaces 118. By controlling the dimensions D1, D2, D3, the interaction between the bobbin 16 and case 14 can be selectively controlled so that a) the bobbin 16 cannot shift within the space 32 bounded by the case 14 sufficiently to allow either flange edge 114, 116 to contact the case surface 118, b) the bobbin 16 can shift radially so that one of the two flange edges 114, 116 can contact the case surface 118, and c) the bobbin 16 can shift radially so that both of the flange edges 114, 116 can contact the case surface 118. Thus, different configurations of bobbin 16, 18 can be developed with which there is potentially a) no contact permitted between the flange edges 114, 116 and the case surface 118, b) contact by one or both of the flange edges 114, 116 and the case surface 118, and c) variable degrees of contact force between one or both of the flange edges 114, 116 and the case surface 118, all of which conditions account for different thread draw tensions with the bobbins 16, 18 operatively mounted on the case 14.

[0100] The configuration of the bobbins 16, 18 may be changed, from one to the next, by altering the peripheral shape of one or both of the flange edges 114′, 116′, as shown in FIG. 24. As seen in FIG. 24, the flange edges 114′, 116′ have a polygonal shape which results in there being a number of circumferentially spaced, discrete locations at A, B, C, D, E at which there is point contact between the representative bobbin 16″ and the case surface 118. The polygonal shape shown to achieve this result is only exemplary. To vary the thread draw tension resulting from the operative mounting of different bobbins 16″, the number, or shape of the contact locations, could be controlled/varied.

[0101] A similar effect can be produced by forming discrete radial projections 124 on the representative flange 46 of the bobbin 16, as by embedding a separate element 125 therein. Alternatively, the projections 124 could be formed as one piece with the flange 46.

[0102] It has been found that by eliminating the contact, or the contact area, between the bobbin flange outer edges 114, 116 and case surfaces 118, for a given bobbin setup with a particular set of parameters, thread draw tension fluctuation is unexpectedly constant as a supply of thread 20 is exhausted therefrom. In conventional bobbin designs, contact between the outer edges 114, 116 and case surface 118 is anticipated substantially continuously since the bobbin is urged radially outwardly due to centrifugal forces thereon and the carried supply of thread. To achieve the improved effect, the radial dimension on a conventional bobbin flange may be reduced by design, or altered after manufacture, to diminish contact between the flange edges 114, 116 and case surface 18 altogether, or reduce the contact area or contact pressure between the flange edges 114, 116 and case surface 118. Aside from controlling fluctuation in the thread draw tension for a particular bobbin over the operating period during which a supply of thread thereon is exhausted, this concept can be used to provide a plurality of bobbins selectively usable to cause different predetermined thread draw tensions to result with the bobbins operatively mounted on a case.

[0103] Other variations in configuration of the bobbins are contemplated by the present invention. As just one other example, the configuration may be changed to control in different manners the way in which thread is paid off of the bobbin. Virtually any change in shape that produces a change in which thread is paid off, or the bobbin interacts with a case to which it is operatively mounted, are contemplated by the present invention.

[0104] It is contemplated that at least two bobbins 16,16′,18,18′, and potentially a multitude of bobbins 16,16′,18,18′, could be made available with different parameters for the bobbins 16,16′,18,18′ and/or the thread 20,22 wrapped therearound. That is, a single parameter, or two or all of the above-described parameters, may be varied to produce desired alternative thread draw tensions with the bobbins 16, 16′, 18, 18′ operatively mounted in the case using a predetermined mounting process. As noted above, the thread draw tension resulting from incorporation of any of the plural bobbins 16,16′,18,18′ with the varied bobbin/thread parameters can be identified to the user with approximate, or precise thread draw tensions predetermined to result from operative mounting of that particular bobbin 16,16′,18,18′ on a case using a predetermined mounting process. As a result, once the user ascertains which thread draw tension is desired, a bobbin 16,16′,18,18′ capable of causing the desired thread draw tension can be selected and operatively mounted upon the case 14 following routine mounting steps. Accordingly, gross, and potentially even fine, adjustments at each bobbin/case combination can be avoided. The particular bobbins 16,16′,18,18′ can be marked and grouped either by gross ranges of thread draw tension which they will cause or by more precise thread draw tensions which they will account for if operatively mounted to the case 14 using a predetermined mounting process.

[0105] Further, in a basic system that does not incorporate a thread draw tension adjustment capability, into the case, predeterminable adjustment can be achieved by strategically using bobbins with parameters controlled/varied, as described above.

[0106] While the invention has been described with particular reference to the drawings, it should be understood that various modifications could be made without departing from the spirit and scope of the present invention.

Claims

1. A method of controlling draw tension on thread wrapped around a bobbin that is mounted operatively on a case for movement relative to the case around an axis, the method comprising the steps of:

predetermining a desired thread draw tension to be achieved with the bobbin operatively mounted on a case using a predetermined mounting process; and

before operatively mounting the bobbin on the case, selectively controlling at least one parameter of at least one of the thread and bobbin in a correlative manner to the desired thread draw tension.

2. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises controlling thread tack.

3. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises controlling thread gauge.

4. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises controlling material defining the thread.

5. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises controlling thread shape.

6. The method of controlling draw tension on thread according to claim 1 wherein the thread comprises a plurality of fibers and the step of controlling the at least one parameter comprises controlling structural interaction of the fibers defining the thread.

7. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises defining the bobbin so as to control a magnetic interaction of the bobbin and case that resists rotation of the bobbin relative to the case with the bobbin operatively mounted on the case.

8. The method of controlling draw tension on thread according to claim 7 wherein the step of defining the bobbin comprises controlling parameters of a metallic component on the bobbin to magnetically interact with an element on the case.

9. The method of controlling draw tension on thread according to claim 7 wherein the step of defining the bobbin comprises controlling parameters of a magnetic element on the bobbin to magnetically interact with at least one of (a) a metallic element and (b) a magnetic element on the case.

10. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises defining the bobbin so as to control frictional interaction of the bobbin and case that resists rotation of the bobbin relative to the case with the bobbin operatively mounted on the case.

11. The method of controlling draw tension on thread according to claim 10 wherein the step of defining the bobbin comprises selecting a material defining at least a part of the bobbin.

12. The method of controlling draw tension on thread according to claim 10 wherein the step of defining the bobbin comprises providing a flexible component on the bobbin that is biasably urged against the case with the bobbin operatively mounted on the case.

13. The method of controlling draw tension on thread according to claim 12 wherein the step of defining the bobbin comprises providing a surface that produces a frictional resistance to rotation when borne against by a flexible component on the case with the bobbin operatively mounted on the case.

14. The method of controlling draw tension on thread according to claim 1 wherein the step of controlling the at least one parameter comprises controlling the configuration of the bobbin.

15. The method of controlling draw tension on thread according to claim 1 wherein thread is wrapped around the bobbin with a wrapping pattern and the step of controlling the at least one parameter comprises controlling the wrapping pattern.

16. The method of controlling draw tension on thread according to claim 1 wherein thread is wrapped around the bobbin with a wrapping tension and the step of controlling the at least one parameter comprises controlling the wrapping tension.

17. A method of controlling draw tension on thread wrapped around a bobbin and mounted operatively on a case for movement relative to the case around an axis, the method comprising the steps of:

providing a first bobbin with a supply of thread wrapped around the first bobbin so that with the first bobbin operatively mounted on a first case using a predetermined mounting process, a first thread draw tension results;

providing a second bobbin with a supply of thread wrapped around the second bobbin so that with the second bobbin operatively mounted on the first case using the predetermined mounting process, a second thread draw tension different than the first thread draw tension results;

choosing a desired thread draw tension by selecting to operatively mount to the first case one of the first and second bobbins; and

operatively mounting the one of the first and second bobbins to the first case.

18. The method of controlling draw tension on thread according to claim 17 further comprising the step of predetermining approximately first and second magnitudes of thread draw tension resulting with each of the first and second bobbins operatively mounted on the first case using the predetermined mounting process, and identifying the first and second magnitudes to facilitate selection by a user of one of the first and second bobbins for use.

19. In combination:

a first bobbin having a supply of a first thread wrapped around the first bobbin so that with the first bobbin operatively mounted upon a case having a first construction using a predetermined mounting process, a thread draw tension with a first magnitude results; and

a second bobbin having a supply of a second thread wrapped around the second bobbin so that with the second bobbin operatively mounted upon a case having the first construction using a predetermined mounting process, a thread draw tension, with a magnitude of predetermined tension predetermined to be greater or less than the first magnitude, results,

whereby the first and second bobbins with their respective thread supplies can be selectively operatively mounted upon a case having the first construction to select greater or lesser thread draw tension.

20. The combination according to claim 19 further in combination with a first case having the first construction upon which the first and second bobbins can be interchangeably operably mounted.

21. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in tack on the first and second threads.

22. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in gauge of the first and second threads.

23. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in material defining the first and second threads.

24. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in shape of the first and second threads.

25. The combination according to claim 19 wherein the first and second threads are each defined by a plurality of fibers and a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in structural interaction of fibers defining the first and second threads.

26. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in magnetic interaction between a case having the first construction and the first and second bobbins.

27. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in a frictional interaction between a case having the first construction and the first and second bobbins.

28. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in configuration of the first and second bobbins.

29. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in wrapping pattern of the first and second threads around the first and second bobbins.

30. The combination according to claim 19 wherein a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in a wrapping tension for the first and second threads around the first and second bobbins.

31. The combination according to claim 19 wherein the first bobbin has a first flange with a first peripheral edge and the second bobbin has a second flange with a second peripheral edge each of which edges faces a radially inwardly facing surface on a case having the first construction to which the first and second bobbins are operatively mounted, and a difference between a thread draw tension resulting from the mounting of the first and second bobbins with their respective thread supplies to a case having the first construction is attributable to at least a difference in interaction of the first and second peripheral edges with a radially inwardly facing surface on a case having the first construction to which the first and second bobbins are operatively mounted.

32. In combination:

a case having a radially inwardly facing surface extending around a space; and

a bobbin having an axis and a first axially facing flange with a peripheral edge facing the radially inwardly facing case surface,

wherein the case and bobbin are configured so that the peripheral edge does not contact the radially inwardly facing surface of the case around the entire peripheral edge.

33. The combination according to claim 32 wherein the case and bobbin are configured so that the peripheral edge of the flange does not contact the radially inwardly facing surface of the case.