Method and system for forming a recess in a tubular workpiece

Abstract

A roller support block 10 supports rolling rollers (6˜9) in four stages and moves in a guide hole (13) of a pipe holder (5) to sequentially bring the rolling roller into pressure contact with a pipe (2) held immovable by the pipe holder (5) through an aperture (35) made in the pipe holder (5). In this process, the first-stage rolling roller (6) first comes into rolling pressure contact with the pipe for preliminary shaping of a recess. Subsequently, the second-stage and third-stage rolling rollers (7, 8) advance the preliminary shaping to enlarge and deepen the recess. Finally, the fourth-stage rolling roller 9 finally shapes the recess to a first locking groove (3 or 4).

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Patent Application No. PCT/JP2004/015542, filed Oct. 14, 2004 (incorporated herein by reference), which in turn claims priority from Japanese Patent Application No. JP2003˜353242, filed Oct. 14, 2003.

FIELD OF THE INVENTION

The present invention relates to a method and a system for forming a recess in a tubular workpiece like a pipe.

BACKGROUND OF THE INVENTION

Modern compartment seats of vehicles are equipped with headrests to protect passengers' heads upon collision. Headrests are typically attached to seat backs via stays, and users can adjust them in height by pulling them up or pushing them down. A typical mechanism for adjustment of the headrest's height includes hooks anchored in a seat back, and a series of locking grooves formed along each headrest stay.

In the history of headrests, their stays were first made of solid rods that are round in cross section, and solid rods were substituted by pipes (hollow cylinders). Further, along with recent movements toward lightweight vehicles, the use of thin-wall pipes is desirable.

In case of solid rods and thick-wall pipes, locking grooves can be formed by locally cutting their walls with a cutter on a milling machine. However, grooves in thin-wall pipes, having walls thinner than the required depth of locking grooves, cannot be formed by cutting. Therefore, a different method is required to form grooves that indent from outer circumferential surfaces of thin-wall pipes to define sharp engagement surfaces having angled edges at their outer ends to maintain reliable engagement with hooks.

Japanese Patent Laid-open Publication No. JP-H08-90126 proposes a method of forming locking grooves of a headrest stay of a support rod of a handbrake by inserting a core member inside a pipe and depressing the outer circumferential surface of the pipe with a punch.

Japanese Patent Laid-open Publication No. JP-2000-197922 proposes a method of forming a recess in a hollow shift fork shaft of a manual transmission for receiving a check ball by suing a press machine under the presence of a core member inserted into the hollow shaft. This publication also proposes a method of removing the core member from the shaft after forming the recess by rotating the core member having a unique configuration.

Japanese Patent Laid-open Publication No. JP-2002-137673 is directed to a method of forming locking grooves at opposed positions of two longer parallel segments of a headrest stay made of a channel-shaped pipe having the two longer segments connected by one shorter segment. This publication proposes to form locking grooves by thrusting the pipe between a pair of roll punches located face to face under the presence of support rolls set aside the roll punches to support them.

Japanese Patent Laid-open Publication No. JP-2002-210519 proposes a method of forming locking grooves of a headrest stay through two manufacturing steps, i.e. a preliminary shaping step and a final shaping step. In the preliminary step, this method forms a recess indenting from the circumferential surface of a pipe by driving a rotating punch down onto the exposed circumferential surface of the pipe while supporting the pipe in an arcuate groove of a holder. In the next final shaping step, this method forms the locking groove by moving a press punch along a guide groove while covering the full circumference of the pipe with a holder cover having the guide groove extending along the recess.

Japanese Patent Laid-open Publication No. JP-2003-9991 proposes a method of forming locking grooves of a headrest stay by thrusting a punch having an end surface of a unique configuration onto a pipe.

Japanese Patent Laid-open Publication No. JP-2003-71522 proposes a method of forming locking grooves of a headrest stay by thrusting a press tool having a unique configuration onto the circumferential surface of a pipe while driving the tool transversally of the lengthwise direction of the pipe under the presence of a core member inserted in the pipe.

To form a recess required to define such a sharp engagement surface at a portion of the outer circumferential surface of a pipe, just like a locking groove of a headrest stay, it is important to prevent bluntness of the edge of an engagement surface in the recess as the above-introduced publications point out as well.

In addition, complicated tasks or steps for forming such recesses in a pipe invite an increase of the cost. Therefore, to reduce or minimize the cost, it is advantageous that recesses of a desired configuration can be formed in a pipe in a single manufacturing step.

SUMMARY OF THE INVENTION

Under the circumstances, there is a need for a method and a system capable of forming a recess of desired configuration in a tubular workpiece like a pipe in a single continuous step.

It is also desirable that such a recess can be formed in a tubular workpiece without inserting a core member inside the workpiece.

There is a further need for a method and a system capable of forming such a recess in a tubular workpiece having a thin wall like a thin-wall pipe.

It is also desirable that such a recess can be formed in a tubular workpiece having a thin wall and a high tensile force such as a thin-wall, highly tensile pipe.

It is also desirable that a recess having a sharp engagement surface having an angled edge, such as a locking groove, can be formed on a tubular workpiece having a thin wall such as a thin-wall pipe in a single step.

It is also desirable that such a recess can be formed in a straight tubular workpiece like a straight pipe before it is bent to a channel-shaped member, for example, such as a headrest stay.

According to an embodiment of the invention, there is provided a method of forming a recess in a tubular workpiece comprising:

• • preparing a set of rolling rollers in multiple stages capable of sequentially interfering the workpiece in an intersecting direction;
  • having the rolling rollers sequentially get into pressure contact with the workpiece by relative movement between the rolling rollers and the workpiece to bring about preliminary shaping and final shaping and thereby form the recess in the workpiece; and
  • preparing a workpiece holder capable of holding the workpiece immovable by enveloping the workpiece and having an aperture through which the rolling rollers can sequentially interfere with the workpiece, wherein the rolling rollers get into pressure contact with the workpiece through the aperture.

In this method, a workpiece holder having an aperture is preferably used to support the workpiece and expose a portion of the workpiece to be processed for forming the recess. To ensure that the recess defines a sharp engagement surface having an angled edge, at least a portion of the contour of the aperture adjacent to the engagement surface of the recess in the workpiece preferably makes substantially no gap from the contour of the final-stage rolling roller.

According to another embodiment of the invention, there is provided a system for forming a recess in a tubular workpiece comprising:

• • a roller support block that holds a set of rolling rollers in multiple stages aligned in a row and permits the individual rolling rollers to rotate; and
  • a workpiece holder having a workpiece-receiving hole substantially equal in cross-sectional configuration to the workpiece and capable of holding the workpiece immovably in the workpiece-receiving hole, said workpiece holder having an aperture exposing a part of the workpiece held in the workpiece-receiving hole,
  • wherein the rolling rollers sequentially come into pressure contact with the workpiece through the aperture along with relative movement between the roller-receiving block and the workpiece holder, and thereby performing preliminary shaping and final shaping sequentially to form a recess in the workpiece.

The workpiece holder may be divided in the moving direction of the roller support block. In case the roll support block moves vertically, the workpiece holder is divided to upper and lower portions, and one of the divisional portions may be moved to grip or release the workpiece inserted between them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining the basic concept of the present invention;

FIG. 2 is a cross-sectional view of a locking groove formed to indent from the outer surface of a pipe typically used as a headrest stay;

FIG. 3 is a cross-sectional view of another locking groove formed to indent from the outer surface of a pipe typically used as a headrest stay;

FIG. 4 is a cross-sectional view taken along the IV-IV line of FIG. 3:

FIG. 5 is a diagram for explaining the outer circumferential configuration of rolling rollers used to form the locking groove shown in FIG. 3;

FIG. 6 is a diagram for explaining a modification in positions of the rolling rollers;

FIG. 7 is a perspective view of a pipe holder that is a component of a test system;

FIG. 8 is a perspective view of a roller support block that is a component of the test system;

FIG. 9 is a diagram showing how the rolling rollers locally depress a pipe;

FIG. 10 is a diagram showing the contour of an aperture through which the rolling rollers can locally depress the pipe;

FIG. 11 is a schematic plan view of a common roller support block preferably employed in a mass production type system;

FIG. 12 is a schematic front elevation of the common roller support block preferably employed in the mass production type system;

FIG. 13 is a schematic diagram of a modified system having rolling rollers held stationary to form recesses in moving pipes;

FIG. 14 is a diagram for explaining the outline of a mass production type system remodeled from a press; and

FIG. 15 is an upper diagonal view of a guide member having a guide hole and a pipe holder, which are located side by side.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments and specific examples of the present invention will now be explained in detail with reference to the drawings.

FIG. 1 shows the basic concept of the invention for forming a recess in a tubular workpiece typically of a metal. The recess-forming system shown in FIG. 1 is used to form locking grooves of a headrest stay.

The headrest stay, as a final product, is a channel-shaped or M-shaped member made by bending a straight pipe to two longer pipe segments and one shorter pipe portion connecting the longer pipe segment, as already known in the art. The longer pipe segments have a plurality of locking grooves formed in intervals in their axial directions. The illustrated headrest stay has a first locking groove 3 (approximately 1.5 mm deep) having a channel-shaped cross section as shown in FIG. 2, and a second locking groove 4 (approximately 1.5 mm deep) defined by a vertical plane and an opposed tapered plane as shown in FIGS. 3 and 4. The recess-forming system 1 can be used to form these first and second locking grooves 3, 4.

The recess-forming system 1 can be used to form locking grooves in a pipe bent to the shape of a headrest stay from a straight pipe as existing techniques do. Moreover, the recess-forming system 1 can form locking grooves in a straight pipe before being bent to the form of a headrest stay. That is, locking grooves 3, 4 can be formed in a straight pipe of a predetermined length by the recess-forming system 1, and the straight pipe may be bent later to manufacture a channel-shaped or M-shaped headrest stay.

To manufacture various types of headrest stays, it is advantageous to form a desired number of locking grooves 3, 4 in metal pipes bent to the forms of final products, including channel-shaped and M-shaped ones. Actually, there are many types of headrest stays. For example, some have locking grooves only in opposed surfaces of longer pipe segments opposed to each other. Some have them in the opposed planes and the planes behind the opposed planes. Some have them on one or both of front and rear planes. Therefore, if the locking grooves 3, 4 are formed after the pipes are bent to the shapes of the final products, it is necessary to prepare different forming dies for respective types of headrest stays. However, if the locking grooves 3, 4 can be formed before the pipes are bent to the shapes of the final products, the straight pipes, already having locking grooves, can be bent later so as to bring the grooves 3, 4 at locations required for the individual types of headrest stays. Thus, various types of headrest stays can be manufactured.

The recess-forming system 1 includes a pipe holder 5 for holding a pipe stationary, and a roller support block 10 that supports a plurality of rolling rollers (rolling dies for form rolling) 6˜9. The pipe holder 5 includes a fixing block 11 and a main holder block 12 that can tightly hold a pipe between them to prevent the pipe 2 from displacement in its lengthwise direction and rotation about the axial line. The pipe holder 5 has a guide hole 13 formed to extend in the vertical direction at a position adjacent the pipe 2.

The rolling rollers 6˜9 are supported by the roller support block 10 to align in intervals along the axial line of the guide hole 13, and supported for free rotation on the roller support block 10 by individual shafts 15˜18. The roller support block 10 is inserted into the guide hole 13 from above to work out a desired recess, i.e. the locking groove 3 or 4, in the pipe 2 during a single reciprocal movement, preferably first down and next up, in the guide hole 13.

For easier explanation, the rolling rollers are individually named the first-stage rolling roller 6, second-stage rolling roller 7, third-stage rolling roller 8, and fourth-stage rolling roller 9 from the one first entering into the guide hole 13 to the one finally entering same as shown in FIG. 1. Further, the first-stage rolling rollers to the fourth-stage (final-stage) rolling rollers 6˜9 are often called the first rolling rollers to the fourth-stage (final-stage) rolling rollers 6˜9 hereafter. The support shafts 15˜18 of the first to fourth rolling rollers 6˜9 lie on a common vertical line L parallel to the direction of relative movement between the rolling rollers 6˜9 and the pipe 2, and diameters D of the first to fourth rolling rollers 6˜9 gradually increase from the first rolling roller 6.

In greater detail, diameter D1 of the first rolling roller 6 nearest to the guide hole 13, that is, nearest to the pipe 2 in position, is smaller than the diameter D2 of the second rolling roller 7 upwardly next to the first rolling roller 6. The diameter D2 of the second rolling roller 7 is smaller than the diameter D3 of the third rolling roller 8. The diameter D3 of the third rolling roller 8 is smaller than the diameter D4 of the fourth rolling roller 9. Here is the relation of D1<D2<D3<D4.

Outer circumferential surfaces of the first to fourth rolling rollers 6˜9 have outer circumferential surfaces (hereinafter often called shaping surfaces as well) corresponding to the shape of the first locking groove 3 (FIG. 2) or the second locking groove 4 (FIGS. 3 and 4). FIG. 5 shows the shaping surface of the fourth rolling roller 9 (solid line) together with shaping surfaces of the first to third rolling rollers 6˜8 (broken lines). It will be readily understood from FIG. 5 that a groove (second groove 4 of FIG. 3 in the illustrated example) first depressed shallow by the first rolling roller 6 is gradually increased in width and depth by the second and third rolling rollers 7, 8 until reaching to the width and depth finally made by the fourth rolling roller 9. That is, the fourth rolling roller 9, which is the final-stage rolling roller, finishes the final configuration of the first locking groove (FIG. 2) or the second locking groove 4 (FIGS. 3 and 4) of the pipe 2.

More specifically, when the roller support block 10 moves under the guide by the guide hole 13 of the pipe holder 5, the first rolling roller 6 first rolls on the pipe 2 while keeping tight contact therewith and locally depresses the outer circumferential surface of the pipe 2 in form of a recess. Subsequently, the second and third rolling rollers 7, 8 gradually getting larger in diameter sequentially roll on the pipe 2 to enlarge and deepen the recess. That is, the amount of depression for the recess made by sequential compression from the rolling rollers increases gradually. After that, the fourth rolling roller 9 as the final-stage rolling roller rolls on the pipe 2, and further enlarge and deepen the recess, and here is completed the final configuration of the first locking groove 3 or the second locking groove 4.

The shaping surfaces of the first to third rolling roller 6˜8 used for preliminary shaping preferably has the relation of similar figures with the outer circumferential geometry of the final-stage rolling roller 9 used for final shaping as shown in FIG. 5. In a test actually carried out by using a first rolling roller 6 having a relatively acuminate shaping surface, the mark of the first rolling roller 6 was retained in the groove of the pipe 2 even after the final shaping by the final-stage rolling roller 9. Therefore, it is desirable that shaping surfaces of the first to final rolling rollers have the relation of similar figures.

The foregoing explanation has been made as using four rolling rollers 6˜9 to form the first locking groove 3 or the second locking groove 4 in the pipe 2 by sequentially bringing them into tight rolling contact with the pipe 2 transversally of the pipe 2. However, the number of stages of the rolling rollers is not limitative, and more stages (but not less than two) may be used for preliminary shaping and final shaping altogether.

The foregoing explanation has been made as using a plurality of rolling rollers 6˜9 getting greater in diameter from the one first entering into the guide hole 13 to the one finally entering into the guide hole 13, and aligning their rotation centers on a common vertical line L. In this case, the rolling rollers may be equal in thickness as well, or may be different in thickness.

Alternatively, the rolling rollers may be equal in diameter. In this case, as shown in FIG. 6, the individual rolling rollers should be supported to lay their rotation centers gradually offset from that of the rolling roller 6 first compressing the workpiece 2 to the rolling roller finally compressing the pipe 2 by ΔL each in a direction normal to the direction of relative movement between the rolling rollers 6˜9 and the pipe 2. Thereby, the biting depth B (FIG. 5) of the rolling rollers into the pipe 2, corresponding to the amount of depression of the pipe 2, can be increased gradually from that of the first compressing rolling roller 6 to that of the finally compressing rolling roller 9. In this modification using rolling rollers equal in diameter, shaping surfaces of the rolling rollers may be either identical or similar (different in thickness) as explained with reference to FIG. 5.

FIG. 6 shows a roller support block 10 supporting three rolling roller 6˜8. In this example, the first and second rolling rollers are used for preliminary shaping, and the uppermost third rolling roller 8 is used for final shaping.

FIGS. 7 and 8 show a test system 30 actually prepared as a recess-forming system according to an embodiment of the invention to confirm expected effects of the present invention. Hereunder, explanation is omitted about some of the components of the test system 30, which are identical to components already explained in conjunction with FIG. 1, by simply identifying them with common reference numerals.

FIG. 7 shows a pipe holder 5 of the test system 30. The pipe holder 5 has a pipe-receiving horizontal hole 31 horizontally penetrating the holder main body 12 and having a round cross section. Diameter of the pipe-receiving horizontal hole (hereafter simply called pipe hole) 31 is approximately equal to the diameter of the pipe 2 as a workpiece such that, when the pipe 2 is inserted into the pipe hole 31, there is substantially no clearance between the pipe 2 and the pipe hole 31. The pipe holder 5 further includes a sub block attached to one side surface of the holder main body 12 and having a horizontal groove continuous from the pipe hole 31; and a fixing block 11 having a horizontal groove 33 and removably attached to the sub block. When the fixing block is attached to the sub block, their horizontal grooves can make a pipe hole continuous from the pipe hole 31 in the holder main block 12. Therefore, after the pipe 2 is inserted in and through the pipe hole 31 of the holder main body 12 to partly lie on the horizontal groove of the sub block, once the fixing block 11 is tightly attached to the sub block by bolts 34, the pipe 2 is enveloped over its entire circumference by the pipe holder 5 and prohibited in lengthwise displacement and rotation about its axis.

It is sufficient for the pipe holder 5 to envelope the entire circumference of the pipe 2 only in its segment nearest to the portion where the recess should be formed. The other segments of the pipe 2 need not be enveloped by the pipe holder over its entire circumference. Therefore, the terms, “envelope the pipe 2” used herein should be construed to envelope a part of the pipe 2, in which a recess should be formed. The pipe holder 5 enveloping the pipe 2 has a rectangular guide hole 13 vertically penetrating the pipe holder 5 at a location adjacent to the pipe hole 31.

FIG. 8 shows a roller support block 10 that is another component of the test system 30. The roller support block 10 includes a main body 40 having a rectangular cross-section and supporting two rolling roller 6, 7 to permit free rotation in a vertically spaced relationship.

The two rolling roller 6, 7 are rotatably attached to the support block main body 40 via support shafts 15, 16 intersecting with a vertical axial line L in alignment with the axial line of the support block main body 40. Diameter D1 of the first rolling roller 6 located lower is slightly smaller than the diameter D2 of the second rolling roller 7 located upper as the final stage.

The roller support block 10 is inserted into the guide hole 13 of the pipe holder 5 from above to position the first rolling roller 6 lower. The guide hole 13 defines a pair of opposed vertical grooves 37 (see FIG. 7) having a cross-sectional geometry corresponding to the shaping surfaces of the first and second rolling rollers 6, 7 that project outwardly from side surfaces of the main body 40 of the roller support block 10 (see FIG. 8). It will be readily understood from the configuration of the vertical grooves 37 in the guide hole 13 that the rolling rollers 6, 7 have shaping surfaces (outer circumferential surfaces) suitable for forming the locking groove 4 shown in FIG. 3.

One (37a) of the opposed vertical grooves 37 in the guide hole 13, which is adjacent to the pipe-receiving horizontal hole 31, partly interferes with the pipe-receiving horizontal hole 31 and communicates with it through an aperture 35 (see FIG. 9). The shaping surfaces of the first and second rolling rollers 6, 7 can compress the pipe 2 through the aperture 35.

FIG. 10 shows a part of the pipe 2 already having the locking groove 4, and shows where the aperture 35 is positioned relative to the groove 4 when the groove is formed. The hatching in FIG. 10 shows the position of the aperture 35. The aperture 35 has a contour in form of the peripheral edge of the locking groove 4. However, a gap C may be provided between a perpendicular wall surface 36 (see FIG. 7) of the vertical groove 37 in the guide hole 13 and the perpendicular side surfaces 6a, 7a (see FIG. 9) of the first-stage and second-stage rolling rollers 6, 7 for forming the engagement surface 4a of the looking groove 4a. The perpendicular wall surface 36, perpendicular side surfaces 6a, 7a and engagement surface 4a are planes perpendicular to the lengthwise direction of the pipe 2 held in the pipe-receiving hole 31. In this test system 30, the gap C equals 0.1˜0.2 mm approximately. However, in case of forming a locking groove configured as shown in FIG. 2 or 3, it is desirable to reduce the gap C to approximately zero in order to form the sharp engagement surface 4a with a clearly angled edge. Therefore, to form the sharp engagement surface 4a with a sharply angled edge, it is desirable that the aperture 35 has substantially no gap (C is substantially zero) relative to the final-stage rolling roller 7. The wording, “sharp engagement surface with (or having) a clearly angled edge”, means that the engagement surface of the recess extends straight inward of a workpiece in the direction crossing the lengthwise axis of the workpiece at a right angle, and makes a clearly angled edge at its terminal end nearer to the outer circumferential surface of the workpiece. The wording, “sharply angled edge”, means that the border between the engagement surface 4a and the outer circumferential surface of the pipe 2 or an intervening surface makes a clear angle not blunt or rounded. In case the engagement surface of the recess is formed to extend straight inward of the workpiece directly from the outer circumferential surface of the workpiece like those of the recesses 3 and 4 shown in FIGS. 2 and 3, the “sharply angled edge” is the border between the engagement surface and the outer circumferential surface of the workpiece. In this case, the angle of the sharply angled edge is approximately a right angle. In another form of recess (not shown) having an inner wall surface first sloping down inward of from the outer circumferential surface of the workpiece and then turns to the direction perpendicularly to the lengthwise axis of the pipe, the edge of the engagement surface pertains to the border between the engagement surface and the sloping surface, and the angle of the edge will become larger than 90°.

In use of the test system 30, the pipe 2 is set in the pipe holder 5 and fixed from lengthwise displacement and rotation about the axis. Then, the roller support block 10 in the guide hole 13 is moved first down and next up to make one reciprocal motion. Thus, the locking groove 4 is formed in the pipe 4. In the process of forming the locking groove 4, since the pipe holder 5 envelopes the entire circumference of the pipe 2, the test system 30 can prevent undesirable deformation of the pipe 2 caused by compression onto the pipe by form rolling.

The pipe 2 used in the test was a high tension material, having a tensile strength not lower than 650 N/mm², sized 12.7 mm in diameter and having the wall 1.4 mm thick. As a result, the locking groove 4 obtained has been confirmed to be in a practically satisfactory level without bluntness at the corner of the engagement surface 4a.

The problem of bluntness or dullness of the edge of the engagement surface was examined. As a result, although the above-mentioned gap C around 0.1˜0.2 mm is acceptable, it has been confirmed more effective to minimize the gap C relative to the final-stage rolling roller 7 in order to make an angled edge at the outer end of the engagement surface 4a. In the test system 30 intended to form grooves shown in FIG. 2 or 3, the contour of the aperture 35 is substantially the same as the contour of the final-stage rolling roller 7.

When the invention is used to form locking grooves of a headrest stay, two stages through five stages will be sufficient as the multiple stages of rolling rollers for systems of a mass-production model. Additionally, it has been confirmed that minimization of diameters D of the rolling rollers is effective to prevent bluntness because the contact surface of the rolling rollers with the pipe 2 can be reduced. For example, pipes 2 for headrest stays generally have a diameter around 10˜13 mm. For such pipes 2, it is desirable to limit the diameter of the final-stage rolling roller to the diameter of the pipe 2 or to the level of 1˜4 times the diameter of the pipe 2, or preferably in the range of 1˜3 times the diameter of the pipe 2. The pipes 2 used in the test were 12 mm and 12.7 mm in diameter, and the diameter of the final-stage rolling roller was 45 mm.

Heretofore, the test system 30 has been explained. When a recess-forming system of a mass-production model is designed under the same concept, it is recommended to prepare and simultaneously activate some roller support blocks 10 equal to the number of locking grooves 3, 4 to be formed in each pipe 2 to form the desired number of locking grooves 3, 4 at the same time. If each pipe 2 needs some locking grooves 3, 4 in close positions, it is more desirable to modify the roller support block 10 to rotatable support corresponding sets of first to final rolling rollers side by side. That is, as shown in FIGS. 11 and 12, the common roller support block 10 have four support axes 15˜18. The first support axis 15 rotatably supports six first rolling rollers 6(1)˜6(6) side by side as FIG. 11 shows. The second support axis 16 rotatably supports six second rolling rollers 7(1)˜7(6) side by side. Similarly, the third support axis 17 and fourth support axis 18 rotatably support six third rolling rollers 8(1)˜8(6) and six fourth rolling rollers 9(1)˜9(6) side by side, respectively. In this common roller support block 10, the first rolling roller 6(1), second rolling roller 7(1), third rolling roller 8(1) and fourth (final) rolling roller 9(1) constitute one set of rolling rollers for forming one locking groove 3 or 4. Similarly, the first to fourth rolling rollers 6(2), 7(2), 8(2) and 9(2) constitute another set of rolling rollers for forming another locking groove 3 or 4. Thus, the common roller support block 10 shown here supports six sets of rolling rollers, and can be used to form six locking grooves 3, 4 at close positions on one pipe 2 simultaneously. Note that FIG. 12 merely shows the support axes 15˜18 and omits illustration of rolling rollers on these axes.

In a recess-forming system of a mass-production model, the fixing block 11 may be designed to use hydraulic pressure to fix the pipe 2.

FIG. 13 shows a recess-forming system 100 embodying the invention. Hereunder, explanation is omitted about some of the components of the recess-forming system 100, which are identical to components already explained in conjunction with FIG. 1, by simply identifying them with common reference numerals. The recess-forming system 100 is a remodeled machine from a mass-production model press. The roller support block 10 of the recess-forming system 100 is fixed at the lower end of a shaft 101 of a hydraulic cylinder (not shown), and movable up and down.

Below the roller support block 10, a guide member 102 having a guide hole 13 is placed stationary, and a pipe holder 105 is located adjacent to the guide member 102. The pipe holder 105 is composed of a lower holder 106 and an upper holder 107. The upper holder 107 can be moved up and down by the hydraulic cylinder 108.

FIG. 15 is a view of the guide member 102 and the pipe holder 105 taken from a diagonally upper point. As shown in FIG. 15, the guide hole 13 that receives the roller support block 10 is defined by the guide member 102 and the pipe holder 105. On one side surface 105a of the pipe holder 105 defining the guide hole 13, five vertical grooves 109a˜109e are formed to permit rolling rollers to travel. Each of the vertical grooves 109a˜109e has a width substantially equal to the thickness of the outer circumferential portion of the final-stage rolling roller 9. In other words, the roller support block 10 supports five sets of rolling rollers side by side, each set being composed of four rolling rollers 6˜9 arranged in four vertical stages. Thus, the roller support bock 10 can form five locking grooves simultaneously in its single reciprocal movement in the vertical direction.

As shown in FIG. 14, the stationary lower holder 106 and the movable upper holder 107 have horizontal grooves 106a, 107a having a semicircular cross section, respectively. The semicircular grooves 106a, 107a are opposed to each other and, in combination, make a horizontal cylindrical hole receiving the pipe 2. The horizontal cylindrical hole made by the semicircular grooves 106a and 107a is sized substantially equal to the outer contour of the pipe 2 at least over a partial length thereof for receiving the groove-forming portion of the pipe 2. The other part of the horizontal cylindrical hole made by the semicircular grooves 106a and 107a may be sized larger than the diameter of the pipe 2.

Still referring to FIG. 14, the upper holder 107 is urged downward by the hydraulic cylinder 108, and can firmly grip the pipe 2 to prevent undesirable rotation and displacement in the lengthwise direction. While the pipe 2 is gripped firmly in this manner, when the roller support block 10 moves vertically in the guide hole 13 by one reciprocation, sets of the first to final rolling rollers 6˜9 form a corresponding number of locking grooves 3,4 simultaneously. When the piston 108a of the hydraulic cylinder 108 withdraws, the upper holder 107 lifts up and loosens the grip to the pipe 2 to permit it to be removed from the pipe holder 105.

In a certain environment, it may be convenient to divide the pipe holder 105 to right and left holder halves and fix one of these holder halves adjacent to the guide member 102 stationary while permitting the other to move. In this design, when four-stage rolling rollers 6˜9 apply pressure to the pipe 2 during vertical reciprocation of the roller support block 10, the pressure from the rolling rollers 6˜9 may undesirably displace the movable holder half to the right or left though slightly. In this case, the pipe 2 may undesirably deform due to the stress produced by the forming of recesses.

However, in the state where the upper holder 107 overlies the lower holders 106, the semicircular horizontal grooves 106a, 107a make the horizontal cylindrical hole substantially equal in diameter to the pipe 2, and prevents deformation of the pipe 2 when recesses are formed by the rolling rollers 6˜9.

Heretofore, application of the invention to locking grooves of a headrest stay has been explained. However, the invention is of course applicable to formation of recesses for check balls of hollow shift fork shafts. Furthermore, the invention is widely usable for forming recesses in pipes in general.

Although some embodiments have been explained, it should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors and that the present invention contemplates these modifications, combinations, sub-combinations and alterations insofar as they are within the scope of the appended claims or the equivalents thereof. For example, the invention contemplates the following modifications among others.

(1) The embodiments have been explained as moving the rolling rollers 6˜9 relative to the pipe 2 to form the locking grooves 3, 4. However, the system may be designed to move the pipe 2 relative to the rolling rollers 6˜9. That is, it is sufficient that the rolling rollers 6˜9 sequentially interfere with the pipe 2. Therefore, as shown in FIG. 13, a plurality of pipes 2 may be set movable to move transversally of rolling rollers 6˜9 that are rotatable at fixed positions. In this case, the process of forming recesses 3, 4 may be completed either in one-way movement of the pipes 2 transversally of the rolling rollers 6˜9, for example, from left to right, or in one reciprocal movement of the pipes 2.

(2) As a method of supporting the pipe 2, the above-explained embodiment uses the pipe hole 31 (best shown in FIGS. 7 and 9) having a circular cross section. To reliably prevent withdrawal of the pipe 2 while the recesses 3, 4 are formed, it is effective to provide a wall withholding the surface of the pipe 2 opposite from the recess-forming portion (shown by triangles in FIG. 10).

(3) In the foregoing embodiments, the rolling rollers 6˜9 are free-rotation rollers. However, they may be power-driven rollers that can rotate with power from a drive means.

(4) In the foregoing embodiments, a single set of rolling rollers in multiple stages includes a single final-stage rolling roller. However, each set of multi-stage rolling rollers may include two or more final-stage rolling rollers. In this case, two or more final-stage rolling rollers are adjacent to each other, and they are identical in shape and size. In the embodiments aligning the center axes of the rolling rollers on a common straight line L (see FIGS. 1 and 14), two or more final-stage rolling rollers are of course aligned to lay their center axes on the common straight line L. In the embodiment using rolling rollers equal in diameter, although the rolling roller in different stages are sequentially offset by Δ (see FIG. 6), two or more final-stage rolling rollers should be supported to lay their center axes on a common straight line.

Claims

1. A method of forming a recess in a tubular workpiece comprising:

preparing a set of rolling rollers in multiple stages capable of sequentially interfering the workpiece in an intersecting direction;

having the rolling rollers sequentially get into pressure contact with the workpiece by relative movement between the rolling rollers and the workpiece to bring about preliminary shaping and final shaping and thereby form the recess in the workpiece; and

preparing a workpiece holder capable of holding the workpiece immovable by enveloping the workpiece and having an aperture through which the rolling rollers can sequentially interfere with the workpiece,

wherein the rolling rollers get into pressure contact with the workpiece through the aperture.

2. The method according to claim 1 wherein the final-stage rolling roller among the set of rolling rollers, which finally comes into pressure contact with the workpiece, makes substantially no gap between side edges thereof and opposed edges of the aperture, and thereby forms the recess with a sharp engagement surface.

3. The method according to claim 2 wherein the contour of the recess is substantially equal to the contour of the aperture.

4. The method according to claim 1 wherein the multi-step rolling rollers are freely rotatable.

5. The method according to claim 4 wherein diameters of the multistage rolling roller are smaller the four times the diameter of the workpiece.

6. The method according to claim 1 further comprising:

preparing plural sets of the rolling rollers in multiple stages, and using them simultaneously to a plurality of said recesses simultaneously.

7. A method of forming a recess in a tubular workpiece, comprising:

preparing a workpiece holder having an aperture through which the rolling rollers can sequentially interfere with the workpiece and capable of holding the workpiece immovably by enveloping the circumference thereof, and a set of rolling rollers in multiple stages capable of getting in pressure contact with the workpiece through the aperture; and

having the rolling rollers sequentially get into pressure contact with the workpiece through the aperture to bring about preliminary shaping and final shaping and thereby form the recess in the workpiece.

8. The method according to claim 7 wherein all of the rolling rollers in multiple stages are identical in diameter, and center axes of the rolling rollers in different stages are sequentially offset in the direction perpendicular to the lengthwise axis of the workpiece held in the workpiece holder.

9. The method according to claim 7 wherein the rolling rollers in different stages vary in diameter sequentially in one direction, and center axes of all rolling rollers in multiple stages lie on a straight line parallel to the lengthwise axis of the workpiece held in the workpiece holder.

10. A system for forming a recess in a tubular workpiece comprising:

a roller support block that holds a set of rolling rollers in multiple stages aligned in a row and permits the individual rolling rollers to rotate; and

a workpiece holder having a workpiece-receiving hole substantially equal in cross-sectional configuration to the workpiece and capable of holding the workpiece immovably in the workpiece-receiving hole, said workpiece holder having an aperture exposing a part of the workpiece held in the workpiece-receiving hole,

wherein the rolling rollers sequentially come into pressure contact with the workpiece through the aperture along with relative movement between the roller-receiving block and the workpiece holder, and thereby performing preliminary shaping and final shaping sequentially to form the recess in the workpiece.

11. The system according to claim 10 wherein plural sets of rolling rollers in multiple stages are provided.

12. The system according to claim 10 wherein one of the rolling rollers in the final stage in each set makes substantially no gap between a side edge of the outer circumferential portion thereof and the contour of the aperture, and can make a sharp engagement surface having an angled edge in the recess in the workpiece in alignment with the contour of the aperture.

13. A system for forming a recess in a tubular workpiece comprising:

a roller support block that holds a set of rolling rollers in multiple stages vertically aligned in a row and permits the individual rolling rollers to rotate;

a guide member having a guide hole for guiding vertical movements of the roller support block;

a hydraulic cylinder vertically driving the roller support block under the guide by the guide hole; and

a workpiece holder located horizontally adjacent to the guide member and having a workpiece-receiving hole having a contour substantially identical to the cross-sectional configuration of the workpiece at least in a portion thereof for supporting a portion of the workpiece to be processed to form a recess therein, said workpiece holder being capable of holding the workpiece immovably in the workpiece-receiving hole,

wherein said workpiece holder having an aperture through which the rolling rollers can sequentially interfere with the workpiece held immovably in the workpiece-receiving hole to permit the rolling rollers in multiple stages to come into pressure contact with the workpiece and thereby perform preliminary shaping and final shaping sequentially to form the recess in the workpiece.

14. The system according to claim 13 wherein the roller support block supports horizontally aligned plural sets of the rolling rollers in multiple vertical stages.

15. The system according to claim 13 wherein the aperture has a contour substantially equal to the contour of the recess formed in the workpiece.

16. The system according to claim 13 wherein one of the rolling rollers in the final stage makes substantially no gap between a side edge of the outer circumferential portion thereof and a side edge of the aperture, and can make a sharp engagement surface having an angled edge in the recess in the workpiece in alignment with said side edge of the aperture.

17. The system according to claim 13 wherein the workpiece holder is composed of a lower holder half and a upper holder half both having elongated grooves in form of upper and lower halves of said workpiece-receiving hole, said upper holder half being driven vertically by a second hydraulic cylinder.

18. The system according to claim 12 wherein the rolling rollers in multiple stages have the relation of similar figures.

19. A method of forming a recess in a tubular workpiece held immovably, comprising:

preparing a set of rolling rollers identical in diameter and aligned in a row perpendicular to the lengthwise direction of the workpiece; and

having the rolling rollers sequentially roll on and compress the workpiece along with relative movement between the rolling rollers and the workpiece to form a recess at the compressed portion of the workpiece, said recess having a plane perpendicular to the lengthwise direction of the workpiece,

wherein center axes of said rolling roller equal in diameter are gradually offset from an imaginary line parallel to said relative movement so that the amount of depression of the pipe made by sequential compression by the rolling rollers increases gradually.

20. The method according to claim 2 wherein the multi-step rolling rollers are freely rotatable.