Shaft drive for a power loom

Abstract

The heddle shaft (1) according to the invention combines a traditional heddle machine (2) with an eccentric toothed gearing to purposely allow the heddle shaft (1) to dwell for longer periods of time in the upper and lower reversing region and to reduce any accelerations that occur. This permits an increase in the weaving speed and/or the weaving widths. For a particularly advantageous embodiment, a coupling device is additionally provided, which gives the heddle shaft (1) a pendulum movement with a stroke ranging from a few millimeters to centimeters during the idle phases, meaning when no sheds are formed. As a result of the pendulum movement of the heddle shaft (1) in the upper or lower reversing region, the acceleration loads on the heddle shaft (1) can be further reduced.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of German Patent Application No. 10 2005 059 911.7, filed on Dec. 15, 2005, the subject matter of which, in its entirety, is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a shaft drive for a power loom, provided with one or several heddle shafts.

Power looms are generally provided with several heddle shafts in the form of rectangular, vertically positioned frames. These heddle shafts accommodate heddles for guiding the on the whole horizontally extending warp threads, so as to move them vertically up and down for the shed forming. In the process, the heddle shafts normally execute an up and down swinging movement, generated by a so-called shaft drive and/or a heddle machine. The shaft drive is a gear for converting the rotational driving movement to a back and forth movement, wherein the shaft essentially follows a sinusoidal function.

Starting with this basic principle, various modifications are known from prior art.

For example, document DE 69702039 T2 discloses a shaft drive provided with a coupling device for triggering an up and down movement of the shaft as needed, wherein means are provided for reducing the otherwise occurring jolt during the engagement and disengagement of the coupling device.

Document DE 103 43 377 B3 discloses a shaft drive which can be optionally activated or deactivated, wherein the heddle shaft executes a swinging movement while the drive is deactivated, in one of its dead center positions. With this measure, the acceleration forces acting upon the heddle shaft are minimized.

Document DE 195 38 018 A1 furthermore discloses a shaft drive with modulation gear, which functions to delay the dwell time for the heddle shafts in the extreme stroke positions (dead center positions). In particular for wide textile width, this is designed to increase the shed standstill angle for the weft yarn intake, relative to the drive shaft rotation, thereby keeping the shed open for a longer period of time.

A modulation gear of this type is expensive. In addition, it has turned out that the cams and the modulation gears on the whole require a relatively large structural volume. It is therefore the object of the present invention to create an improved shaft drive.

SUMMARY OF THE INVENTION

The above object generally is achieved according to the invention with the shaft drive according to claim 1:

The shaft drive according to the invention is provided with a drive assembly, consisting of drive shaft, a power take-off, and a gear mechanism that is arranged in-between. The gear mechanism comprises an eccentric toothed gearing with a non-constant transmission ratio. The transmission ratio depends on the angular position of the drive shaft. The eccentric toothed gearing preferably contains at least two toothed gears with non-constant radius, wherein these toothed gears are in a state of constant engagement. Each uniform rotation of the input shaft thus causes a non-uniform rotation of the following shaft that is driven by the eccentric toothed gearing. The eccentric toothed gearing thereby generates a modulation of the rotational speed, wherein the modulation interval is set for one input shaft rotation. The generated rotational speed modulation is furthermore predetermined as a result of the shape of the gears of the eccentric toothed gearing. In any case, it cannot be further influenced at this location of the drive assembly.

The eccentric toothed gearing represents a simple and cost-effective solution for achieving a heddle shaft movement that deviates considerably from the sinusoidal shape, in particular if the heddle shaft dwells for a longer period in the upper or lower extreme position (dead center position) than is the case for the approximately sinusoidal movement and must travel faster through the transitional region between the upper and lower dead center position than would be the case for a sinusoidal movement. The eccentric toothed gearing is thus capable of transmitting considerable torque, while the structural size and the material use are low. Thanks to modem production methods (CNC production), an eccentric toothed gearing can be produced in series and cost-effectively. Despite the longer dwell time in the dead center positions (extreme stroke positions) and despite the faster travel over the distance between both extreme stroke positions, the torque increases before and after the extreme stroke positions can be minimized. In the process, a polynomial to the seventh power is selected as the law of motion for the shaft, at least for one preferred embodiment, wherein the torque increase during the introduction and completion of the movement is soft.

In principle, this shaft drive is suitable for continuously operating heddle shafts (eccentric machines) as well as for heddle shafts that must be started and stopped (heddle machines), for example, for generating complicated weaving patterns. In that case, the gearing is provided with a coupling device, which in one operating position transmits the driving movement without problem and, in a second operating position, interrupts the transmission of the movement. By extending the dwell time for the shaft in the extreme stroke positions, a longer time interval and a larger angle region is provided there for engaging and disengaging the coupling device, wherein the engaging and disengaging occurs essentially without load and with a minimum torque as well as minimum rotational speed for the coupling elements. Load jolts and the coupling load are reduced and/or minimized.

The coupling arrangement of one preferred embodiment permits a pendulum movement of the power take-off, or generates such a movement, in case of an interruption of the drive movement. The pendulum movement on the one hand can be used to minimize the accelerations of the heddle shaft and, on the other hand, to create synchronous phases in which the coupling can softly engage or disengage.

The coupling device for the preferred embodiment is installed between the eccentric toothed gearing and the power take-off. The eccentric toothed gearing can either be a component of a standard shaft drive or can be embodied as supplementary gear. In the latter case, it is advantageous that existing shaft drives can still be used and that a single eccentric toothed gearing is sufficient to generate a modulated rotational movement for all power take-offs of the heddle machine. In individual cases, it may make sense to provide two or more eccentric toothed gearings, which generate different output movements at their output shafts. With weaving looms having eccentric cam plates, these different output movements can be used for directly operating the eccentric cam plates. With heddle machines, these different output movements can be used to drive the coupling devices.

The eccentric toothed gearing is preferably provided with spur wheels having a whole number ratio of the teeth, relative to each other. For a preferred embodiment, the number of teeth on the toothed gears is the same. As a result, a transmission ratio of 1:1 is obtained on the whole, meaning on the average, wherein this transmission ratio is above or below one at each rotational angle, in dependence on the respective rotational position of the toothed gears relative to each other. The toothed gears of one simple exemplary embodiment are elliptical in shape, wherein toothed gears of this type can be slightly counterbalanced and increase and/or reduce the transmission ratio twice during one rotation of the input shaft. A connected eccentric cam plate for the power take-off of the shaft drive can thus be delayed in both extreme positions. With this measure, the angle at which the shed is at a standstill can be increased, meaning more time is available for inserting the weft yarn into the shed.

Details of advantageous embodiments of the invention follow from the drawings, the specification, or the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate an exemplary embodiment of the invention, wherein:

FIG. 1 is a schematic total view of a heddle shaft and a shaft drive;

FIG. 2 shows the details of the heddle machine and heddle shafts, in a view from above;

FIG. 3 illustrates the shaft drive according to FIGS. 1 and 2 in a schematic block diagram;

FIG. 4 is a schematic representation of an eccentric toothed gearing for the shaft drive according to FIG. 3;

FIG. 5 is a basic representation of a coupling device for the shaft drive according to FIG. 3; and,

FIG. 6 is a diagram illustrating the shaft stroke in dependence on the angle of rotation for the drive shaft.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a heddle shaft 1 with thereto assigned heddle machine ore dobby 2, which drives the shaft via a rod assembly, embodied as lever gear 3. FIG. 2 shows that additional heddle shafts 1a, 1b, etc. are provided parallel to the heddle shaft 1, wherein these shafts are also driven by the heddle machine 2. Insofar, this arrangement is a traditional arrangement. The heddle shafts, which function to drive heddles 4 up and down as indicated by arrow 5, are moved up and down by the lever gear 3. For this, the swinging movement (arrow 7), executed by a rocker 6 functioning as power take-off for the heddle machine 2 is converted by the lever gear 3 into the vertically directed shaft movement with the aid of a steering gear 8, an angle lever 9, 10, and a connecting rod 11.

As shown in FIG. 2, the heddle machine 2 is provided with rockers 6a, 6b as power take-off for driving the additional heddle shafts 1a, 1b. These rockers are driven by means of a shaft 13, via coupling devices 12, 12a, and 12b. The shaft 13 is stimulated to execute a non-uniform rotation, meaning a rotation with modulated angle speed, by an eccentric toothed gearing 14. The eccentric toothed gearing 14 is preferably driven with uniform rotations via a drive shaft 15 by a drive source 16 in the form of an electric motor, which can be a component of a weaving loom. The eccentric toothed gearing 14 together with the coupling devices 12, 12a, 12b forms a gear mechanism 17, for which the rockers 6, 6a, 6b form the power take-off.

The drive assembly formed in this way is again shown schematically in FIG. 3 for a single power take-off. The coupling device 12 in this case is optional and is used for driving an eccentric shaft 18 with eccentric cam plate 19, which drives the rocker 6, not shown in further detail herein, by means of a connecting rod 20. The coupling device 12 is provided with at least one input in the form of an input shaft 22. The input shaft 22 executes a rotation with modulated speed, wherein the directional sense remains unchanged. The coupling device 12 in one switching position can transmit this rotational movement to the eccentric shaft 18.

It is also possible to provide the coupling device with several input shafts 22, 21. All input shafts can respectively be coupled to the eccentric toothed gearing 14 and can respectively be driven with the modulated speed (see FIG. 3). It is furthermore possible to control the input shaft 21 directly with the aid of the drive source 16 and via the drive shaft 15.

The input shaft 22 preferably executes a non-uniform rotation, without change in direction. This rotational movement is converted to a back and forth rotating movement with the aid of additional means, not shown herein, such as an eccentric cam plate or cams/cam followers. In the switching and/or coupling position shown in FIG. 3, the coupling device 12 transmits this rotational pendulum movement to the eccentric shaft 18.

The input shaft 22 and the input shaft 21 are driven by means of the eccentric toothed gearing 14, which comprises two spur wheels 23, 24 that are attached in the center of the respective shafts and have a non-constant radius. The spur wheels 23, 24 are illustrated in FIG. 4. For the present exemplary embodiment, they are approximately elliptical in shape and are embodied such that they constantly mesh. They have identical numbers of teeth and thus define an average transmission ratio of 1:1. As a result of the changing diameters, however, the uniform rotation of the spur wheel 23 forces a continuously accelerated and delayed rotation of the spur wheel 24. For each rotation, the spur wheel 24 is accelerated twice and delayed twice, wherein the acceleration and delay in both acceleration/delay phases is identical if the toothed gear is embodied symmetrical. This leads to symmetrical movement laws for the shaft (apart from distortions, which can be caused by the lever gear 3 and the connecting rod 20). The spur wheels 23, 24, however, can also be embodied more or less asymmetrical in order to generate two different, spaced apart movement modulations during a complete rotation, at the 180° distance.

In order to equalize the rotation of the drive shaft 15, it is preferably provided with a balancing weight 25, so that the load fluctuations are mostly kept away from the drive source 16 and the drive source 16 has a uniform load.

FIG. 5 illustrates a possible embodiment for the coupling device 12. For a more complete description of same, as well as for alternative embodiments, we point to document DE 103 43 377 B3. The coupling device 12 is provided with a cam 26 that is driven by the input shaft 21 and forms a pendulum drive 28 together with the cam follower 27. The cam follower 27 is connected to a coupling disk 29, which performs a back and forth rotating movement. In contrast, an additional coupling disk 30, which is arranged concentric to the coupling disk 29, executes a rotational movement that is preset by the input shaft 22. The coupling disk 30 is fixedly connected to the input shaft 22. The eccentric shaft 18 is connected to a disk 31 that forms the power take-off for the coupling device 12. The disk 31 is provided with a pawl 32, which alternatively engages in the coupling disk 29 or the coupling disk 30 with the aid of the switching levers 33, 34, positioned swinging, and are moved via a selection finger 35 on an activation lever 36. This lever oscillates back and forth with the aid of electromagnets 37, 38, thereby activating either the switching lever 33 or the switching lever 34. Springs 39, 40 pre-stress the switching levers 33, 34 in the desired direction.

The heddle machine 2 described so far operates as follows:

During the operation, it is assumed that the drive shaft 15 rotates uniformly and the input shafts 21, 22 execute a rotational movement as a result of the eccentric toothed gearing, installed in-between, which movement is accelerated and delayed with each rotation and then accelerated and delayed again. Starting with the assumption that the coupling device 12 continuously connects the input shaft 22 with the eccentric shaft 18, this results in a movement at the rocker 6 and/or the heddle shaft 1, which is characterized by the curve I drawn into FIG. 6. The curve I illustrates the stroke of the heddle shaft 1, in dependence on the rotation of the drive shaft 15. By neglecting the distortion of the movement law, possibly caused by the lever gear 3 and if applicable the connecting rod 20, a shaft movement according to curve II would result for a uniform rotation of the input shaft 22. This would be the case if the spur wheels 23, 24 would be embodied as standard spur wheels with constant radius. The curve II corresponds to a sinusoidal function. As can be seen, however, the eccentric toothed gearing 14 delays the movement of the input shaft 22 relative to the movement of the drive shaft 15 whenever the heddle shaft 1 is located in its upper and lower reversing region. In the area of transition between both reversing regions, the eccentric toothed gearing 14 accelerates the input shaft 22 relative to the drive shaft 15 and delays the input shaft 22 in the end regions. In other words, while the heddle shaft 1 is in the upper and lower reversing regions, the input shaft 22 clearly rotates slower than the drive shaft 15, whereas it rotates noticeably faster at other times. The heddle shaft 1 consequently remains in the upper and lower reversing regions over a longer rotational angle of the drive shaft 15, thereby increasing the time for the weft yarn insertion. This is particularly important for wide weaving looms and high machine speeds.

In addition, in the upper and lower reversing region it is possible to switch to pendulum operation by using the coupling device 12. This action is described in detail in document DE 103 43 377 B3, to which we refer herewith. The combination of coupling device 12 and eccentric toothed gearing 14 makes it possible to achieve a soft switching in the upper or lower reversing region of heddle shaft 1. The heddle shaft 1 can remain optionally long in the pendulum operation and can be activated, meaning turned on, again without reduction in speed for the drive shaft 15. The switching of the pawl 32 thus occurs at an instant where the coupling disks 29, 30 briefly have a mostly synchronous operation.

The heddle shaft 1 according to the invention combines a traditional heddle machine 2 with an eccentric toothed gearing 14 for purposely extending the dwell times for the heddle shaft 1 in the upper and lower reversing region and for reducing any accelerations that occur. This permits an increase in the weaving speed and/or the weaving widths. For one particularly advantageous embodiment, a coupling device 12 is additionally provided, which is intended to provide the heddle shaft 1 during the idle periods, meaning the period when no sheds are formed, with a pendulum movement having a stroke of a few millimeters to several centimeters. As a result of the pendulum movement of the heddle shaft 1 in the upper or lower reversimg regions, the acceleration loads on the heddle shaft 1 can be further reduced.

It will be appreciated that the above description of the present invention is susceptible to various modification, changes and adaptations, and the same are intend to be comprehended within the meaning and range of equivalents of the appended claims.

Reference Number List:

• 1, 1a, 1b heddle shaft
• 2 heddle machine
• 3 rod assembly, lever gear
• 4 heddles
• 5 arrow
• 6, 6a, 6b power take-off; rocker
• 7 arrow
• 8 guide rod
• 9, 10 angle lever
• 11 connecting rod
• 12, 12a, 12b coupling device
• 13 shaft
• 14 eccentric toothed gearing
• 15 drive shaft
• 16 drive source
• 17 gear
• 18 eccentric shaft
• 19 eccentric cam plate
• 20 connecting rod
• 21, 22 input shafts
• 23, 24 spur wheels
• 25 balancing weight
• 26 cams
• 27 curve follower
• 28 pendulum drive
• 29, 30 coupling disk
• 31 disk
• 32 pawl
• 33, 34 switching lever
• 35 switching finger
• 36 activation lever
• 37, 38 electromagnets
• 39, 40 springs
• I, II curves

Claims

1. A shaft drive (2) for a weaving loom,

with a drive shaft (15) that is connected to a drive source (16) and is driven by this source,

with a power take-off (6) for driving a heddle shaft (1) and

with a gear (17), which is installed between the drive shaft (15) and the power take-off (6) and comprises an eccentric toothed gearing (14).

2. The shaft drive according to claim 1, characterized in that the drive shaft (15) is connected to a balancing weight (25) for evening out its rotation and for balancing the load fluctuations.

3. The shaft drive according to claim 1, characterized in that the power take-off (6) is a lever driven so as to swing.

4. The shaft drive according to claim 3, characterized in that the lever is driven by an eccentric cam plate (19).

5. The shaft drive according to claim 4, characterized in that the eccentric cam plate (19) is driven exclusively in one predetermined rotational direction.

6. The shaft drive according to claim 4, characterized in that the eccentric cam plate (19) is driven primarily in one predetermined rotational direction.

7. The shaft drive according to claim 1, characterized in that the gear (17) is embodied in such a way that two operational modes can be selected, such that the eccentric cam plate (19) in a first operating mode executes a rotation in a predetermined rotational direction and in a second operating mode executes a rotational movement with alternating rotational direction.

8. The shaft drive according to claim 1, characterized in that the gear (17) comprises a coupling device (12).

9. The shaft drive according to claim 8, characterized in that the coupling device (12) has a first operating position, which is characterized by the unimpeded transmission of a driving movement.

10. The shaft drive according to claim 8, characterized in that the coupling device (12) has a second operating position, which is characterized by an interruption of the transmission of the drive movement.

11. The shaft drive according to claim 10, characterized in that the coupling device (12) is embodied in such a way that during the interruption in the drive movement, it transmits a pendulum movement in alternating direction.

12. The shaft drive according to claim 1, characterized in that the eccentric toothed gearing (14) has at least two toothed gears (23, 24), which constantly mesh with each other.

13. The shaft drive according to claim 12, characterized in that the toothed gears (23, 24) are spur wheels.

14. The shaft drive according to claim 1, characterized in that the number of teeth on the toothed gears (23, 24) are at a whole number ratio to each other.

15. The shaft drive according to claim 12, characterized in that the toothed gears (23, 24) have an identical number of teeth.

16. The shaft drive according to claim 1, characterized in that the toothed gears (23, 24) respectively have a substantially elliptical shape.

17. The shaft drive according to claim 1, characterized in that the eccentric toothed gear (14) converts the uniform movement of the drive shaft (15) to a non-uniform movement of an input shaft (21, 22).