GB2114261A

GB2114261A - Transmission for converting uniform rotary input into an irregular rotary output

Info

Publication number: GB2114261A
Application number: GB08301871A
Authority: GB
Inventors: Reinhard Deutsch
Original assignee: Hauni Werke Koerber and Co KG
Current assignee: Koerber AG
Priority date: 1982-01-25
Filing date: 1983-01-24
Publication date: 1983-08-17
Also published as: DE3202242A1; GB8301871D0; IT8319251A0; IT1193616B; JPS58128557A

Abstract

A transmission wherein the uniform rotary movement of an input shaft 2 is converted into an irregular rotary movement of an output shaft 4 has a first gear 7 which carries an eccentrically mounted pivotable link 17 and is rotatably mounted on the output shaft 4, a second gear 9 which has an endless cam groove 11 and is rotatably mounted on the output shaft 4, a follower 23 provided on the link and extending into the cam groove, a first gear segment provided on the link and meshing with a second gear segment 21 on the output shaft, a third gear 24 which is driven by the input shaft and meshes with the first gear 7, and a fourth gear 26 which is driven by the input shaft 2 and rotates the second gear 9, either directly or through a reversing gear 27. The first and second gears rotate relative to one another, either in the same direction or in opposite directions, whereby the first gear segment rotates the second gear segment and the output shaft with a degree of irregularity which is dependent upon the configuration of the cam groove. <IMAGE>

Description

SPECIFICATION Transmission for converting uniform rotary movements of an input element into irregular rotary movements of an output element.

The present invention relates to transmissions in general, and more particularly to improvements in transmissions of the type wherein uniform rotary movements of an input element are converted into irregular rotary movements of an output element.

Regular rotary movements of an input shaft can be converted into irregular rotary movements of an output shaft in a number of ways, e.g., by resort to a so called star-wheel transmission/wherein the star wheel is or can be tipped with rollers. Exmples of such transmissions are those known as stepping transmissions which are manufactured and sold by Miksch GmbH, D-7320 Goppingen, federal Republic Germany under the designation "Schrittgetriebe CF3". Such transmissions are used, for example, in various types of packing machines, automatic assembly lines, industrial robots and for many other purposes. The output shaft can be driven in stepwise fashion at a desired rate of acceleration from zero speed and/or a desired rate of deceleration back to zero speed.

A drawback of the aforediscussed commercially available transmissions is that they are quite expensive because their component parts must be machined with utmost precision. Moreover, such transmissions are quite sensitive and they cannot be used in machines or production lines wherein the output shaft must perform minute angular movements.

The invention is embodied in a transmission which servies to convert a uniform rotary movement into an irregular rotary movement (e.g., into a rotary movement which includes alternating accelerated and decelerated movements, alternating rotary movements and intervals of idleness, alternating rotary movements in a clockwise or counterclockwise direction and/or a combination of these).The transmission comprises a rotary first shaft or an alalogous imput element, a prime mover or other suitable means for imparting to the input element the aforementioned uniform rotary movement, a second shaft or an analogous rotary output element which is to receive the aforesaid irregular rotary movement carrier means which is rotatable about the axis of the output element and can but need not be rotatably mounted directly on the output element, means for rotating the carrier means in response to rotation of the input element, cam means which is roatable about the axis of the output element and defines an endless cam face (the cam means may but need not be rotatably mounted directly on the output element), means for kinematically connecting the carrier means with the cam means (preferably through the medium of the input element), an eccentric link or analogous coupling means including follower means for tracking the cam face, means for pivotably mounting the coupling means on the carrier means so that the coupling means can pivot back and forth in response to relative angular movement between the cam means and the carrier means and as a result of tracking of the cam face by the follower means (whereby the configuration of the cam face determines the extent and the frequency of pivotal movement of coupling means relative to the carrier means during each revolution of the cam means relative to the carrier means and/or vice versa), and means for transmitting torque from the coupling means to the output element.

The torque transmitting means can comprise a member which is rotatable about the axis of and can be made integral with the output element.

The connecting means can comprise means for transmitting rotary motion from the input element to the cam means so that the rotational speed of the cam means deviates from the rotational speed of the carrier means, so that the cam means and the carrier means rotate in opposite directions and/or so that the cam means and the carrier means rotate in the same direction. The means for imparting to the input element the aforementioned uniform rotary movement can comprise a constant-speed or a variable-speed electric motor or another suitable prime mover, and the connecting means preferably derives motion from the prime mover to rotate the cam means, i.e. the cam means and the carrier means can receive rotary motion from one and the same prime mover.

The carrier means can comprise or constitute a first gear, and the cam means can comprise or constitute a second gear. The means for rotating the carrier means then preferably comprises a third gear (e.g. a gear which is rigidly secured to and coaxial with the input eiement) which transmits torque to the first gear) (e.g. by being in direct mesh with the first gear), and the connecting means then comprises a fourth gear which is arranged to transmit torque to the second gear (the fourth gear can be rigid with and can be driven by the input element, and can be in direct mesh with the second gear or it can drive the second gear through one or more intermediate gears).

The input element can be coaxial with the output element. The aforementioned second gear, which can constitute or form part of the cam means, can be provided with an endless cam groove and the aforementioned cam face is then provided in such cam groove to be tracked by a follower means which preferably comprises or constitutes a roller or an analogous rotary element.

The coupling means can comprise a first toothed portion (e.g., a first gear segment), and the torque transmitting means can comprise a second toothed portion (e.g., a second gear segment) which meshes with the first toothed portion.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved transmission itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

Figure 1, is a schematic elevational view of a transmission which embodies the present invention, with the casing omitted and with a portion of the carrier means broken away; and Figure 2 is a sectional view substantially as seen in the direction of arrows from the line Il-Il of Fig. 1.

The transmission which is shown in Figs. 1 and 2 comprises a housing or case 1 for an input shaft 2 and an output shaft 4. The shafts 2, 4 are parallel to one another and are rotatable in antifriction ball bearings 6. The input shaft 2 is or can be driven at a uniform rotational speed by a prime mover 3, e.g., a constant-speed or a variable-speed electric motor.

The output shaft 4 supports a carrier 8 which is rotatable relative to the output shaft on two antifriction ball bearings 1 3. The carrier 8 includes a gear 7 in mesh with a gear 24 which is rigidly secured to the input shaft 2. Thus, the RPM of the carrier 8 is always proportional to the RPM of the input shaft 2.

The output shaft 4 further carries a cam 9 which constitutes a gear driven by a gear 26 on the input shaft 2 through the medium of an intermediate gear 27 which ensures that the carrier 8 and the cam 9 rotate in opposite directions. The cam 9 rotates on a ball bearing 14 and a needle bearing 16.

A coupling member or link 17, which includes a gear segment, is eccentrically mounted on the carrier 8 by a pivot pin 18 which is parallel to the output shaft 4 and is installed in antifriction needle bearings 19.

The gear segment of the coupling member 1 7 meshes with a torque transmitting member 21 which is rigid or integral with the output shaft 4. The member 21 can constitute a second gear segment.

The coupling member 1 7 further carries a pin 22 for a follower including two coaxial rollers 23 extending into an endless cam groove 11 which is machined into the lefthand end face 1 2 of the cam 9 (as viewed in Fig. 2). The cam groove 11 surrounds an endless cam face 11 a which is tracked by the rollers 23 of the follower on the pin 22 of the coupling member 17. The cam face 1 lain- cludes a portion MA which is disposed at a maximum distance from the axis of the output shaft 4, and a portion Ml which is located at a minimum distance from the axis of the output shaft.This means that, when the carrier 8 completes one full revolution relative to the cam 9 and/or vice versa, the coupling member 1 7 is pivoted once back and forth about the axis of the pivot member 18, i.e., the coupling member is pivoted once back and forth relative to the carrier 8. This, in turn, entails a corresponding oscillatory movement of the output shaft 4 relative to the gear 7 of the carrier 8 because the gear segment of the coupling member 1 7 is in mesh with the torque transmitting gear segment 21.

As mentioned above, the gear 24 on the input shaft 2 meshes directly with the gear 7 of the carrier 8. Therefore, the input shaft 2 and the carrier 8 rotate in opposite directions (note the arrows 28 and 29 in Fig. 1). The gear 26 meshes with the cam 9 through the medium of the intermediate (reversing) gear 27, i.e., the shaft 2 and the cam 9 rotate in the same direction (compare the arrows 28 and 32 in Fig. 1). The direction in which the output shaft 4 of the illustrated transmission rotates when the prime mover 3 drives the input shaft 2 is indicated by the arrow 33.

If desired, the gear 26 and/or the cam 9 can be replaced with a larger diameter gear or a larger-diameter cam so that the gear which is driven by the input shaft 2 is then in direct mesh with the cam which is rotatable on the output shaft 4. The diameter of the pitch circle of the gear 7 should deviate from the diameter of the pitch circle of the cam 9. In other words, the means for kinematically connected the carrier 8 with the cam 9 can be designed to rotate the cam 9 counter to the direction of rotation of the carrier 8 (at a speed which may but need not be the same as the speed of the carrier) or to rotate the carrier 8 and the cam 9 in the same direction but at different speeds so that the rollers 23 of the follower move along the cam face 11 a and/or vice versa. The connecting means of the illustrated transmission includes the parts 24, 2, 26 and 27.

The operation of the improved transmission is as follows: The prime mover 3 drives the input shaft 2 at a uniform rotational speed in the direction of arrow 28 whereby the shaft 2 drives the gears 24 and 26. The gear 24 drives the carrier 8 via gear 7 in the direction of arrow 29. The gear 26 drives the cam 9 in the direction of arrow 32 through the medium of the intermediate gear 27 which rotates in the direction of arrow 31. Thus, and as stated above, the carrier 8 and the cam 9 rotate in opposite directions.This causes the coupling member 1 7 to pivot relative to the carrier 8 about the axis of the pin 18 as a result of tracking of the cam face 11 a in the groove 11 of the cam 9 by the rollers 23 of the follower on the coupling member 1 7. The extent of pivotal movement of the coupling member 1 7 relative to the carrier 8 depends on the difference between the distances MA and Ml, i.e., on the configuration of the cam face 11 a in the endless groove 11 of the cam 9. The coupling member 1 7 rotates the output shaft 4 through the medium of the torque transmitting gear segment 21 so that the output shaft 4 rotates in the direction of arrow 33.As can be readily seen in the drawing, the angular velocity of the output shaft 4 matches that of the carrier 8 when the coupling member 1 7 does not pivot with reference to the carrier.

When the coupling member 1 7 pivots relative to the carrier 8, such pivotal movement is superimposed upon the angular movement of the carrier 8 due to the fact that the gear segment of the coupling member 1 7 meshes with the gear segment 21. In other words, the output shaft 4 is accelerated or decelerated with reference to the carrier 8 to an extent which is a function of configuration of the cam face 11 a and the cam groove 11, of the direction rotation of the cam 9, and on the extent of angular movement of the cam 9 relative to the carrier 8. The just outlined parameters can be readily selected in such a way that the output shaft 4 is accelerated or decelerated with reference to the input shaft 2 once or more than once during each revolution of the shaft 2.Alternatively, the aforementioned parameters can be selected in such a way that the output shaft 4 is accelerated and decelerated once during each n-th revolution of the input shaft 2. Still further, the configuration of the cam groove 11 and the cam face 1 1a therein can be selected in such a way tht the output shaft 4 comes to a temporary halt between a deceleration and the next-following acceleration. In fact, the improved transmission even renders it possible to carry out so-called pilgrim steps, i.e., the direction of rotation (arrow 33) of the output shaft 4 can be reversed at desired intervals and through preselected angles. Such pilgrim steps cannot be carried out by resort to heretofore known stepping transmissions.

In the improved transmission, the number of decelerations accelerations, intervals of dwell and pilgrim steps, which are carried out by the output shaft 4 in response to each revolution of the input shaft 2, depends not only on the shape of the cam face 11 a but also on the ratio of RPM of the cam 9 relative to the carrier 8. Thus, if the carrier 8 and the cam 9 are driven in the same direction but the cam is driven at a speed which is less than that of the carrier, the output shaft 4 is accelerated and decelerated once only during each n-th revolution of the input shaft 2 (n is a whole number exceeding one). If the cam 9 and the carrier 8 rotate in opposite directions, the output shaft 4 can be accelerated and decelerated n times during each revolution of the input shaft 2 (again, n is a whole number exceeding one).It will be understood that n cannot be increased ad infinitum.

The provision of a common prime mover (3) for the carrier 8 and cam 9 is desirable and advantageous because this ensures that the selected relationship of movements of the carrier and cam can be maintained for any desired period of time without resort to monitoring and/or regulating equipment.

While it is possible to rotate the carrier 8 and/or the cam 9 by mens other than mating gear teeth, the provision of a carrier which is or comprises a gear (7), and of a cam which constitutes or comprises a gear, is desirable and advantageous because this contributes to simplicity and reliability of the transmission. It goes without saying that the gear 7 need not form an integral part of the carrier 8 (i.e., the gear 7 can be manufactured independently of and thereupon affixed to the carrier), and the same applies for the cam 9 and that portion of this cam which meshes with the gear 27.

The provision on the input shaft 2 of gears 24 and 26 which respectively transmit torque to the carrier 8 and cam 9 also contributes to simplicity, compactness and reliability of the transmission. The same holds true for such mounting of the shafts 2 and 4 in the casing 1 that the axis of these shafts are parallel to one another.

That portion of the cam 9 which is formed with the endless groove 11 can be produced independently of the toothed portion of the cam. It has been found, however, that the machining of groove 11 into the end face 1 2 does not present serious problems; such cam exhibits the advantage that the cam proper (namely, the groove 11 and the surface 11 a in the groove) as well as the toothed portion of the cam can be installed in and removed from the casing 1 as a unit.

The improved transmission is susceptible of many additional modifications without departing from the spirit of the invention. For example, the illustrated coupling member 1 7 can be replaced with a two-armed lever one arm of which carries the rollers 23 and the other arm of which is articulately connected with a link; such link is eccentrically connected with the output shaft 4, e.g., to a lever which is affixed to the output shaft.

The compactness of the improved transmission is enhanced by mounting the cam 9 and the carrier 8 directly on the output shaft 4.

Claims

1. A transmission for converting a uniform rotary movement into an irregular rotary movement, comprising a rotary input element; means for imparting to said input element said uniform movement; a rotary output element; carrier means rotatable relative to and being coaxial with said output element; means for rotating said carrier means in response to rotation of said input element; cam means rotatable about the axis of said output element and defining an endless cam face; means for kinematically connecting said carrier means with said cam means; pivotable coupling means including follower means for tracking said cam face; means for eccentrically mounting said coupling means on said carrier means so that said coupling means can pivot back and forth in response to relative angular movement between said carrier means and said cam means and as a result of tracking of said face by said follower means; and means for transmitting torque from said coupling means to said output element.

2. The transmission of claim 1, wherein said torque transmitting means includes a member which is rotatable about the axis of said output element.

3. The transmission of claim 1, wherein said connecting means comprises means for transmitting rotary motion from said input element to said cam means so that the rotational speed of said cam means deviates from the rotational speed of said carrier means.

4. The transmission of claim 1, wherein said connection means comprises means for transmitting rotary motion from said input element to said cam means so that said cam means and said carrier means rotate in opposite directions.

5. The transmission of claim 1, wherein said connecting means includes means for transmitting rotary motion from said input element to said cam means so that said cam means and said carrier means rotate in the same direction.

6. The transmission of claim 1, wherein said means for imparting to said input element said uniform movement includes a prime mover and said connecting means derives motion from said prime mover and is arranged to rotate said cam means.

7. The transmission of claim 1, wherein said carrier means comprises a first gear and said cam means comprises a second gear, said means for rotating said carrier means including a third gear in mesh with said first gear and said connecting means including a fourth gear in mesh with said second gear.

8. The transmission of claim 1, wherein said input element is parallel to said output element.

9. The transmission of claim 8, wherein said carrier means comprises a first gear and said cam means comprises a second gear, said means for rotating said carrier means comprising a third gear rigid with said input element and arranged to transmit torque to said first gear, said connecting means comprising a fourth gear rigid with said input element and arranged to transmit torque to said second gear.

10. The transmission of claim 1, wherein said cam means comprises a gear having an endless cam groove, said cam face being provided in said cam groove.

11. The transmission of claim 10, wherein said follower means comprises a rotary element extending into said groove.

1 2. The transmission of claim 1, wherein said coupling means comprises a first toothed portion and said torque transmitting means comprises a second toothed portion mating with said first toothed portion.

1 3. The transmission of claim 12, wherein said toothed portions are gear segments.

14. The transmission of claim 1, wherein said cam means and said carrier means are rotatably mounted on said output element.

1 5. The transmission of claim 1, wherein said torque transmitting means is integral with said output element.

1 6. A transmission for converting a uniform rotary movement with an irregular rotary movement, substantially as herein described with reference to and as illustrated in the accompanying drawings.