GB2233728A

GB2233728A - Cam-plate oscillating drive

Info

Publication number: GB2233728A
Application number: GB9014671A
Authority: GB
Inventors: Norbert Thuenker
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1989-07-06
Filing date: 1990-07-02
Publication date: 1991-01-16
Anticipated expiration: 2010-07-02
Also published as: FR2649461A1; DE3922186C2; GB2233728B; JPH0348053A; FR2649461B1; GB9014671D0; DE3922186A1

Abstract

In a cam-plate oscillating drive an energy-storage device 12 engages a driven oscillating part 8 in such a manner that the energy-storage device is storing a maximum of stored energy at the points of reversal of the respective oscillating motion to thereby compensate for the cyclically occuring irregularity of the drive torque. The present cam-plate oscillating drive can be utilised with particular advantage for the compensation of the cyclically occurring irregularity of drive torques arising in the case of an oscillating pre-gripper of a sheet-fed rotary printing press. <IMAGE>

Description

A

DESCRIPTION Cam-Plate OsCillatin Drive

The invention relates to a cam-plate oscillating drive according to the defining clause of claim 1.

Such a cam-plate oscillating drive is known from DE-OS 36 26 185, with there being compensation for torques created as the result of the generation of cyclical motions out of rotary motions. Provided for this purpose is an apparatus that engages a rotating part and that executes cyclical motion, with said apparatus, by means of an energy-storage device in the form of a spring, exerting a force on the rotating part, said force compensating for the torque fluctuations. In this connection, the corresponding components engage revolving machine parts of the drive and do not reduce the forces and moments between the driving members and the oscillating output.

The object of the invention is to design an oscillating drive of the above-indicated kind in a simple-tomanufacture manner such that there are, on the whole, favourable conditions with respect to the occurring forces, such that there is a reduction in the forces and moments between a driving member and a driving part in the form of an oscillating part.

The object of the invention is achieved by the features according to the characterizing clause of claim 1.

The subclaims represent advantageous further developments of the design according to the invention.

Such a design results in an oscillating drive of the above-mentioned kind, with said oscillating drive being characterized by a high utility value. In contrast to j 2 the prior art, the energystorage device engages the oscillating part, which is driven by means of a cam plate, in such a manner that the energy- storage device has its maximum charge at the points of reversal of the oscillating motion. In this manner, the forces and moments between the cam plate and the oscillating part are reduced with a concomitant increase in the service life of these components. The cam-plate oscillating drive according to the invention is designed such that the kinetic energy of the moving oscillating part is applied to the energy- storage device during the deceleration phase and is removed during the acceleration phase. Mechanical springs or also pneumatic cylinders may serve as energy-storage devices. The fact that the energy-storage device has its maximum charge at the points of reversal guarantees that, as a rule, there is an approximate exchange of energy between oscillating part -kinetic energy- and energy-storage device -potential energy-. The camplate oscillating drive ensures in simple manner that the oscillating part is always positively controlled up to its point of reversal. In order to transmit the motion from the revolving cam plate to the oscillating part, use is made of a sensing roller and of a roller lever permanently connected to the oscillating part. For the purpose of positive tracking, the cam roller may be guided in a grooved cam. It is also possible for there to be a positive friction-type pickoff of the cam plate by the oscillating part. Furthermore, it is also possible to employ two roller levers, offset with respect to one another in angle and in their planes, which interact with two oppositely shaped cam plates on the drive shaft. The coordination is such in this connection that the lifting- off of the one roller lever is in each case prevented by the contacting of the corresponding cam plate by the other roller lever, with said cam plates

3 being provided likewise on planes that are offset with respect to one another. The forces that are applied from the cam onto the cam roller during the acceleration and deceleration phases of the oscillating part are compensated for and/or reduced by the energy-storage device. One version is characterized in that a lever is attached in rigid connection to the oscillating part, said lever interacting with the energy-storage device through the intermediary of a connecting rod. Consequently, depending on the position of the oscillating part, the energystorage device is also influenced by the lever. In order, at the points of reversal of the oscillating part, to minimize the torque of the energystorage device acting on the oscillating part, in another variant, the lever interacts with the energy-storage device through the intermediary of a campiece. Preferably, the cam of the cam-piece is sensed or felt by a sensing member, said sensing member interacting with the energy-storage device. It is possible for said sensing member likewise to be in the form of a roller. In the end regions, it is possible for the rise of the cam to be reduced to such an extent that, in spite of high spring forces in the corresponding positions of the gear-drive unit, only a small torque acts on the oscillating part, i.e. when the cam roller is supported on these end regions.

Since the energy-storage device is intended to compensate for inertia forces and to store kinetic energy, it is necessary for there to be either a onceonly adjustment to a constant machine speed or a continuous adjustment or control to a variable machine speed. Firstly, the appropriate adjustment is possible in that the power arm of the lever is variable in length in order to adapt to the rotational speed. Secondly, an appropriate adjustment is permitted in that the spring preload or the spring rate is adjustable. As already mentioned above, the energy-storage device may be in the form of a mechanical spring. One possible form is that of a leaf spring, with the free end of a connecting member being swivel-connected to said leaf spring and being adjustably mounted on the lever. It would likewise be possible to employ a torsion bar. The connecting member is adjustable in relation to the power arm of the lever, thereby permitting a suitable adjustment to a variable machine speed. If the lever constitutes the cam-piece, it is possible to fix the cam roller on a rocker, said rocker being engaged by a spring acting as the energy-storage device. Adaptation to the speed of the machine can be effected by adjusting the preload of the spring. All possible types of mechanical springs as well as pneumatic spring elements can be used as energy-storage devices.

If the motion sequence of the oscillating part differs very greatly on the forward and return strokes, it is necessary, in designing the energystorage device and the components lying between it and the oscillating part, to select a compromise, such that either both motion ranges are equally optimized or one motion range - principally the more important one - is given the best possible power equalization.

The cam-plate oscillating drive described herein can be utilised with particular advantage for the compensation of the cyclically occurring irregularity of drive torques arising in the case of an oscillating pregripper of a sheet-fed rotary printing press.

In the description which now follows, two representative embodiments of the invention are explained with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view of a first embodiment of a cam-plate oscillating drive according to the invention, this being shown at a stage in which the driven oscillating part is being moved to the right of the Figure; Fig. 2 likewise shows a schematic representation of a cam-plate oscillating drive, relating to the second embodiment; and Fig. 3 shows a corresponding graph to represent the compensation of torque.

According to the first embodiment, shown in Fig. 1, the reference figure 1 identifies a drive shaft, which is set in rotation in arrow direction x by a drive unit (not illustrated). Non-rotatably seated on the drive shaft 1 is a disc 2, which comprises at one of its end faces a grooved cam 3. In the example selected for explanation here, the grooved cam 3 is composed of two cam sections a and b, extending concentrically with respect to the drive shaft 1, which are connected to one another by means of cam sections c, d. The cam section a is at a greater distance from the shaft mid-point than the cam section b. Furthermore, the cam section c is shorter than the cam section d.

Projecting into the grooved cam.3 is a sensing roller 4, the diameter of which is adapted approximately to the width of the grooved cam 3. The sensing roller 4 is held at the free end of a roller lever 5, which is permanently connected to the bearing-side end of an oscillating part 6. The latter may be a pregripper on sheet-fed rotary printing presses. The oscillating part 6 is rotatably disposed in the machine frame in the bearing point 7.

The bearing-side end of the oscillating part 6 is further connected to a lever 8, on which is displaceably, but lockably, seated a slide 9, to which one end of a connecting rod 10 is swivel-connected. The other end of the connecting rod 10 engages an energy- storage device 11, which is in the form of a leaf spring 12. One end of the leaf spring 12 is clamped in fixed manner at 13, while the other end is suitably connected to the free end of the connecting rod 10.

If the drive shaft 1 of the cam-plate oscillating drive is revolving in arrow direction x, the oscillating part 6 is set in a cyclical reciprocating motion by the plate 2 and its grooved cam 3 as well as by sensing roller 4 and roller lever 5. When the sensing roller 4 passes through cam section c, the oscillating part 6 is moved in a clockwise direction out of the left-hand end position into the right-hand end position. Cam section d results in the opposite motion phase from right to left. Situated between both motion phases are the end positions of the oscillating part 6, which are produced by the concentric cam sections a and b. In both motion phases, the oscillating part is initially accelerated and then decelerated. In the acceleration phase, the energystorage device 11 is brought out of a tensioned state with a high energy level into a relaxed state without energy or with little energy. In the deceleration phase, the energy-storage device again attains a high energy level. The conversion of the potential energy of the energy-storage device into kinetic energy of the oscillating part and vice versa results in a considerable reduction in the drive torque at the cam plate and in the forces between grooved cam 3 and sensing roller 4.

The superposition of the torque fluctuations is illustrated with reference to Fig. 3. Plotted on the ordinate of the graph is a torque, while the abscissa illustrates an angle of rotation over a full revolution. The curve 14 of the drive torque for kinetic energy is illustrated by solid lines, while the - 8 dotted curve 15 corresponds to the drive torque for potential energy. The sum of these torques results in the dash-dotted curve 16. It is apparent from the latter that the torque peaks lie relatively close to the abscissa in both the positive and negative directions.

In the embodiment illustrated in Fig. 2, identical components have been given identical reference numbers. In contrast to the first embodiment, the lever 8' forms a cam-piece 17. Viewed from the bearing pin 7, said cam-piece 17 is of divergent proportions. On the end side, it is equipped with a cam 18, the end regions 19, 20 of which extend more or less concentrically with respect to the bearing pin 7. Interacting with the cam 18 is a cam roller 21, which is rotatably held at the free end of a single-arm rocker 22. The upper region of the rocker 22, the latter being swivelable about a fulcrum 23, is engaged by an energy-storage device 24, which, as in the above-explained specimen embodiment, is in the form of a spiral tension spring 25. The end of the tension spring 25 opposite the rocker 22 is attached to an adjusting member 26. By displacement of the latter in the indicated double-arrow direction, it is possible to adjust the spring preload in order to make an adaptation to the rotational speed.

According to Fig. 1, this adaptation to the rotational speed is achieved in that the slide 9 is likewise moved in the indicated double-arrow direction and is then adjusted.

Since the energy-storage devices 11, 24 are intended to compensate for inertia forces and to store kinetic energy, it is necessary for there to be either a onceonly adaptation to a constant machine speed or a continuous adaptation or control to a variable machine - 9 speed. According to the first embodiment in Fig. 1, this adaptation is obtained by changing the spring travel. In the second embodiment, a similar adaptation is achieved by changing the spring preload.

When, in the embodiment shown in Fig. 2, the sensing roller 4 passes through the cam section b, the oscillating part 6 remains in its position. In this case, the cam roller 21 is supported at the end region 20. As soon as the roller 4 engages the cam section c, the cam roller enters the falling cam section 18', with the result that the previously stored potential energy of the force-storage device 24 is reduced while supporting the swiveling of the oscillating part 6 in a clockwise direction. The occurring torque is opposed to the drive torque, with the result that the contact pressure between sensing roller 4 and cam plate or grooved cam 3 remains relatively small. When the roller 4 passes through the centre of the cam section c, the cam valley 18'' is reached, and the energy-storage device 24 is at a low level. By the time the cam section a is reached, the cam roller 21 has reached the other high point of the cam 18 in the vicinity of the region 19, and the energy-storage device is again charged.

Also in this second version, the torques produced by the energy-storage device are opposed to the drive torques.

A further possible version would be to dispose two cam plates one behind the other on the drive shaft 1. The cams of said cam plates would, in this case, be oppositely shaped and are sensed or felt by two roller levers, said roller levers being at different angles to one another and lying in different planes.

- It will be understood that the invention has been described above purely by way of example, and that various modifications of detail can be made within the ambit of the invention.

11 -

Claims

1. A cam-plate oscillating drive which provides for the cyclically occurring irregularity of its drive torques to be compensated for by means of an energystorage device, said energy-storage device providing torques opposed to the drive torques, wherein the energy-storage device engages a driven oscillating part in such a manner that the energy- storage device is storing a maximum of stored energy at the points of reversal of the respective oscillating motion.

2. A drive according to claim 1, wherein the said driven oscillating part is driven by means of a grooved cam.

3. A drive according to claim 1 or 2, wherein a positive friction-type pickoff from the cam plate is obtained by the said driven oscillating part.

4. A drive according to any of the preceding claims, wherein a roller lever which senses the cam plate or grooved cam is assigned to the said driven oscillating part.

5. A drive according to any of the preceding claims, wherein the said driven oscillating part has two roller levers, said two roller levers being angularly offset with respect to one another, being disposed in different planes, and interacting with respective complementarily shaped cam plates mounted on the drive shaft, the arrangement being such that the lifting-off of each roller lever is prevented by the contacting of the respective cam plate by the other roller lever.

6. A drive according to any of the preceding claims, wherein a lever is rigidly connected to the said driven oscillating part, said lever interacting with the energystorage device.

7. A drive according to claim 6, wherein the lever interacts with the energy-storage device through the intermediary of a cam-piece.

8. A drive according to claim 6, wherein the lever has an operative arm which is variable in respect of its effective length, whereby adjustments are enabled to be made in order to adapt the compensating mechanism to different rotational speeds.

9. A drive according to any of the preceding claims, wherein the energystorage device has an adjustable spring preload.

10. A drive according to claim 6 or 8, or claim 9 when read with claim 6 or 8, wherein the energy-storage device comprises a leaf spring, a connecting rod being swivel-connected at one of its ends to said leaf spring and being additionally connected to the lever, and the position at which it is connected to the lever being adjustable.

11. A drive according to claim 7, or claim 9 when read with claim 7, wherein the cam-piece interacts with a rocker, said rocker being engaged by the energystorage device.

12. A drive according to claim 1, substantially as described with reference to any Figure or Figures of the accompanying drawings.

1 1 13 -

13. A sheet-fed rotary printing press oscillating pregripper having a cam- plate oscillating drive according to any of the preceding claims.

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