US2579540A - Gripper release mechanism for sheet handling machines - Google Patents

Description

Dec. 25, 1951 H. BOBST 2,579,540

GRIPPER RELEASE MECHANISM FOR SHEET HANDLING MACHINES Filed April 11, 1946 Inventor HEM?! Baasr fldtorneys Patented Dec. 25, 1951 GRIPPER RELEASE MECHANISM FOR SHEET HANDLING MACHINES Henri Bobst, Lausanne, Switzerland Application April 11, 1946, Serial No. 661,302 r In Switzerland April 12, 1945 r 1 The present invention relates to release mechanism for the grippers of machines for working sheets of paper, cardboard or the like.

In such machines, the said sheets are transported by gripper bars placed between two endlesschains disposed in parallel relationship, and the bars stop successively at a registering station, where the associated grippers seize the sheets one by one, at a working station and at a deliverystation where the grippers are opened thereby stacking the sheets.

A special mechanism is provided at the delivery station for opening the grippers when desired and functioning normally as long as the sheets arrive and leave the bars in. good order, one by one.

Since normal operation can easily involve an accident causing a stoppage likely to damage certain parts of the mechanism or even twistthe bars, it is the object-of the present invention to provide a mechanism insuring the proper delivery and obviating any accident of this kind by stopping the machine in good time.

To this end, the parts which open the grippers oscillate upon an axle rotating in bearing supported by pivoting elements, and held by spring detent in a normal position from which they depart only when the opening mechanism is actuated by an exceptional outside directive force, the pivoting of the elements under consideration having the result of stopping the machine and with it the forward movement of the bars.

In the accompanying drawing which shows an embodiment of the mechanisms according to the present invention, given by way of example:

Figure 1 is avertical section view taken along the longitudinal axis of the machine, that is according to a median plane situated between the two chains;

Figures 2 and 8 are sections of two couplings producing spring detent; and

Figure 4 shows the mechanism in a perspective view.

On a fixed axle I two chain-wheels are mounted for free rotation one of which is shown in dot and dash line and marked 2. The position of the chain carried by this wheel is shown in the same way and marked 3. The chains convey gripper bars 4, of which one is shown in transverse section, with a blade spring 5 forming a gripper and a plunger 6 which rising, may cause the opening of this gripper.

Each bar has as many springs and plungers as it has grippers and, in the reception position 9 Claims. (Cl. 271-79) in which it is shown, there are provided as many abutment screws 1 disposed opposite the plungers to cooperate therewith.

Each screw is supported by an arm 8 of a common rotative axle 9 oscillated by a lever [0, in turn actuated :by the links I l and I2, through bell-crank lever I3 pivoted at I4.

A momentary displacement of the links H and I2 in the direction of the arrow l5 causes the axle 9 to oscillate anti-clockwise in relation to the drawing, and the screws 1 open the grippers 5 by means of the plungers 6, allowing the sheet transported by the bar 4 to fall in the direction of the arrow It on the stack H. The displacement of link I2 is most conveniently caused and timed in the manner described in copending application Serial Number 663,396, filed April 19, 1946.

The perspective view of Figure 4 shows clearly the main part of the above mentioned elements.

At each end, the axle 9 is jeurnalled in bearings each forming a part of an oscillatory ele ment of which the drawing shows one in the shape of a triangularly shaped plate 18, fixed to the frame IQ of the machine by fixed pivot 28. This plate is is however held against rotation by a pin 2 I, of which the head co-operates, under the action of a spring 22 (see Fig. 2) with a conical hole 23 of the wall of the frame l9. It may be said that this coupling maintains the plate It by spring detent in its normal position, as shown.

This detent is in particular sufficient to prevent the reaction, arising from the opening op eration of the grippers, from displacing the plate 18. This reaction is anyway practically negligible, because upon opening of the grippers, the pressure exerted by the link I I and the resistance ofiered by the opening efiort are practically parallel to each other, having a resultant passing very near the centre of the pivot 20, therefore not able to impart a torque to the plate [8 sumcient to disengage it.

If, on the contrary, such members as the abutment screws 1, the arms 8 or the axle 9 undergo an exceptionally directed strain, for example owing to pressure arising from stoppage produced by the transport of several sheets, of a crumpled sheet, etc. in the direction of displacement of the bar 4, it is obvious that these members will tend to be displaced, which will allow the rotation of the plate l8 about the pivot 29, to position It. In this case the pin 21 leaves the conical hole 23.

However, by means of its surface 24 the plate l8 then causes the cam piece to oscillate round its fixed point 26, so that its abutment 21 actuates the switch 28 which, in turn, stops the machine. The drawing shows the switch closed by abutment 21, but the particular wiring might just as well call for opening of the switch in a like manner W a 1 The mechanism shown therefore fulfills the condition proposed, that is to obviate all accidents arising from an accidental stoppage: not only does it stop the machine, but by the displacement of members i, 8 and 9 responsive to the strain of stoppage, it creates adiscontinuity in the delivery sufficient for the passage of at least a part of the disturbing elements. w I

Below the mechanism so far described, the example shown includes a registering member; the purpose of which is to correct the position of the sheets as they fall on the stack II. This membercomprises an axle 29, carrying several arms' s uch as so. A link 31 imparts thereto an oscillatory movement by means of a lever 32. This movement brings the fingers 39 alternatively to the position where they lean against the upper. rear edge of the stack I1, thus constraining the last sheet deposited to alignitselfcorrectly. The extreme position 3| and 32' occupied by the link, and the lever 32 correspond to 7 position 30 of armsBG at each oscillation.

Thedetail of Figure 3 shows finally how the lever 3 2 is coupledto the axle 29 by means of Screw 33, of a pressure spring 3 1 and of a ball 35. penetrating into a' depres'sion of the said axle.

coupling is therefore automatically disengageable and acts as a safety release mechmm to allow arms 39 to free themselves if a stoppage of any kind were to causea resistance or an abnormal strain in the direction of rotation as by the occurrence of jammed or 'buckled sheets at the sheet releasing station. a

The axle 23, once liberated from the lever 32, is thenireeto continue to rotate under the force of the buckled or jammed sheets and carries with it the cam 36 on which leans an abutment screw ofthe cam piece 25. This latter is rotated in thesame direction as by cam 24 to cause displ'acementof the plate l8, i. e. so that its abutment 2'! acts on the switch 28 and stops the machine.

This arrangement constitutes an additional guarantee against all accidents due to a stoppage at, any, point of the station where the sheets are deposited.

What'I claim is:

1. In a machine for working sheets of paper; the combination of sheet conveying bars movable through said machine, gripping means on each of said bars for holding a sheet to the latter, and means at a sheet releasing station operative to release said gripping meansand comprising an oscillatable axle carrying releasing bumpers for releasing engagement with said gripping means, means for oscillating said axle to effect engagement and disengagement between said releasing bumpers and said gripping means, swingable supports for the opposite ends of said axle pivoted for swinging motion about an axis displaced radially from the axis of turning of said axle so that thelatter may move bodily between an op- 'erative position in which said releasing bumpers at said station operative to release said gripping means and comprising an oscillatable axle carrying radially extending bumpers for releasing engagement with said gripping means, at least one radial arm extending from said axle actuat ing rneansconnected to said armand applying an intermittent force to the latter for oscillating said axle to eiTect engagement and disengagement :between said bumpers and said gripping means on successive bars atsaid station, swingable supports forpth'e opposite ends of said axle pivotally mounted for swinging motion about an 7 axis displaced radially from the axis of turning of said axle so that the latter may move bodily between a-n operative position in which said re leasing bumpers are engageable with said grip- The cam piece 25 is finally connected with a V rod 31; the end of which projects from the casing 38 of the machine to form a push knob; making it possible to stop the machine at will. Pressure on this rod causes the cam piece 25 to oscillate in the direction where it acts on the switch 28.

In Figure l of the drawing is also shown,- how orie'sr more arms 39 may be disposed on axle I, each ending in a ro1ler 40 serving as a rest for the -iipfier bars momentarily stopped at the position shown. Assuming that such bars are relatively long, that they must be light and in consequence as small as possible in section, so that the opening pressure of the grippers subjects them to a transversalstrain which is increased if stoppage actuates theabove mechanism', it is important to supportthem at one or more points. This support is. provided by roller 40 resting on the axle I, the section of which is not limited by taking weight 'or obstruction into account.

ping means and an inoperative position in which said releasing bumpers are remote from said gripping means in all oscillated. dispositions of said axle, the swinging axis of said supports being arranged so that said intermittent force and the normalreaction force of said gripping means againstsaid bumpers provide substan tially equal and oppositely directed turning moments about said swinging axis; and yieldable means acting on said supports for maintaining said axle in said operative position so that the occurrence of an excessive reactionforce'betwe'e'n said gripping means and said bumpers imposes a turning moment on said supports to overcome the holding force of said yieldable means and to swing said supports for disposing said axle in said inoperative position of the latter.

3. In a machine for working sheets of paper; the combination as set forth in claim 2, wherein said supports are mounted on adjacent frame members, and wherein said yieldable means in} cludes a retaining member axially slid'abl'e in at least one of said supports, spring means axially U urging said retaining member against the face of the adjacent frame member. and a depres? sion in said face ofthe adjacent frame member located to receive aid retaining member when said axle is in said operative position thereof.

.. 4 in sma k n f r warms hei fi lie the oiirbination i. asset forth in claim 2, rurtnei' including a cam-shaped surface on at least one of said swingable supports., electrically driven operating means for said machine including circuit controlling switch means, and switch actuating means engaged by said cam-shaped surface and operative to dispose said switch means in a circuit open condition when said supports swing with said axle to said inoperative position of the latter.

5. In a machine for working sheets of paper; the combination as set forth in claim 2, further including a pair of parallel chains carrying the opposite ends of said sheet conveying bars, sprocket wheels supporting said pair of chains in the area of said sheet releasing station, a common shaft for said sprocket wheels, at least one radial. arm extending from said shaft and having a roller on its free end to support the successive.

and meansfor oscillating said shaft including a reciprocated link, an actuating radial arm turnable on said shaft and connected to said reciprocated link, and yieldable means normally coupling said actuating arm to said oscillatable 6 M switch means, and switch actuating means engaged by said cam member and operative to dispose said switch means in a circuit open condition when said oscillatable shaft is displaced by the jammed or buckled sheets through an angle greater than the extent of the normal oscillation of said shaft as such normal oscillation is induced by said reciprocated link.

t. In a machine for working sheets of paper} the combination as set forth in claim 7, wherein said switch actuating means includes a pivotally mounted switch actuating plate and a first follower on said plate engaging the cam surface of said cam member, and wherein said cam surface of the cam member is formed with a portion formed with all parts thereof equidistant from the axis of said shaft and normally engaging said first follower and with a radially raised portion engaging said first follower when said shaft is displaced through said greater angle.

9. In a machine for working sheets of paper; the combination as set forth in claim 8, further including a cam-shaped surface on at least one shaft to provide a normal oscillation of said shaft. 1

7. In a machine for working sheets of paper;

the combination as set forth in claim 6, further including means for stopping operation of the comprising a cam member fixed on said oscillatable shaft, electrically driven operating means? for said machine including circuit controlling of said swingable supports, and a second follower REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,079,218 Curtis Nov. 18, 1913 1,826,463 Gibson Oct. 6, 1931 2,138,407

Huck Nov. 219, 1938

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