US2949297A

US2949297A - Presses for treating material in the form of sheets

Info

Publication number: US2949297A
Application number: US650361A
Authority: US
Inventors: Bobst Henri
Original assignee: Bobst SA
Current assignee: Bobst Mex SA
Priority date: 1956-04-16
Filing date: 1957-04-03
Publication date: 1960-08-16
Anticipated expiration: 1977-08-16
Also published as: FR1170343A; DE1039822C2; CH329746A; DE1039822B

Description

H. BOBST v 2,949,297 PRESSES FOR TREATING MATERIAL IN THE FORM OF SHEETS Aug. V16 1960 Filed April 3. 1957 PRESSEQ FOR TREATHIG MATERIAL IN THE FORM SHEETS Henri Bobst, Lausanne, Switzerland, assignor to J. Bobst and Son S.A., Lausanne, Switzerland, a corporation of Switzerland Filed Apr. '3, 1957, Ser. No. 650,361

Claims priority, application Switzerland Apr. 16, 1956 8 Claims. (Cl. 271-45) The present invention'relates to presses for treating material in the form of sheets such as, for example, sheets of cardboard or paper, with the object of cutting or shaping the same.

According to the present invention there is provided a press for the treatment of material in the form of sheets conveyed by a pair of endless chains which are moved and stopped alternately, the said chains passing over a pair of wheels whose shaft is keyed in movable blocks which are subjected to an action intended to tension the springs. Further, means are provided for varying the tension applied to the conveyor chains synchronously with the operations of the press, in such a way that the said tension is less during the phases when the chains are stopped than between said phases.

For a better understanding of the invention, a preferrcd embodiment thereof will now be described with reference to the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates a press in which might be embodied features of the invention; and

Fig. 2 illustrates a detail of the invention.

Fig. 1 of the accompanying drawing shows a press wherein sheets are conveyed by means of a pair of endless chains which carry intermediate bars provided with grippers.

1 is the frame of the said press, 2 an upper plate and 3 the lower plate. It will be assumed that the lower plate 3 is lifted and lowered alternately in order to cut out or form the sheets which the endless chains 4 convey by means of spaced gripper bars 5 which are carried between the chains. To this end, the said chains are stopped each time that a sheet is introduced into a gripper bar, while another sheet is simultaneously treated between the two plates.

The chains 4 are guided principally by the pairs of chain wheels 6 and 7, and if necessary by other wheels, rollers or appropriate members (not shown).

-It will be understood that there are a plurality of chains and chain wheels, and that they are arranged in pairs whose two components are superposed and thus shown as only one element in the drawings.

Since the gripper bars 5 must take up a well defined position both at the instant when the sheet is taken up and at the instant when a sheet is being treated, pairs of stops are provided at 8 and 9 against which a mechanism, driven synchronously with the operations of the press, momentarily pushes the gripper bars, either displacing them in their normal direction of conveyance (in the illustrated example, in the direction of the arrow) or in the opposite direction, depending on the type of mechanism envisaged.

This possibility of imparting to two gripper bars an independent movement in order to bring them into contact with stops makes it necessary to allow the chains a certain flexibility so as to allow sections of the chain between the two stops or otherwise to be de-tensioned momentarily.

Up to the present time, this has been provided for, for

Patented Aug. 16, 1960 example, by keying the shaft of the pair of wheels 7 in blocks 10 which are movable in slideways, and which are returned by springs 11 in the direction causing the chains to be tensioned.

However, the force which these springs exert must not impede the eflicient operation of the truing means for determining the position of the two gripper bars each time the chains are halted. Therefore the value of the said force is limited.

Now, in large presses, the whole assembly of chains and bars is of substantial size, and the inertia effects resulting therein make themselves felt on all the members guiding the chains, both at the instant when they are immobilized and at the instant when they resume travelling.

If the springs 11 are too weak, this would inevitably lead to irregularities in chain tension and in the carrying of the gripper bars, and this would lead to the power of the tensioning elements being increased beyond the limit defined thereinbefore.

The present invention solves the problem which is posed by providing means for modifying the tensile stress applied to the conveying chains synchronously with the operations of the press, in such a manner that this tension is less during the periods when chains are immobilized than between such periods.

In Fig. 2, 7 again designates the wheels conveying the chains 4, and the blocks 10 on the wheels shaft 12 are capable of moving back and forth in slideways 13. Elastic members, which are not illustrated in the drawings, act in the manner of the springs 11 of Fig. l, tensioning the chains 4 by applying a tr-active force to the wheels 7 in the direction of the arrow 14.

This tractive force is suificient to insure regular ten sioning of the chains in the condition of rest, while the operations necessary for the displacement of the gripper bars in order to bear against the stops oblige certain portions of the chains to be detensioned.

Auxiliary springs or resilient devices 16 are adapted to exert an additional pressure, in the same direction as the tractive force 14, on the blocks 10 of the shaft 12, through the intermediary of straps or split rings 15 which do not rotate since the chain wheels are freely rotatable on their shaft. This arrangement is identical at both ends of the shaft 12.

Each spring 16 is wound about a rod 17 of an eccentric 18 and is held under a certain appropriate tension between s-houlders or washers 2d and 2%, the position of the latter washer being adjustable by action of the nuts 21. The said rod has a head 22 capable of sliding in a radial recess in the strap 15.

Rotation of the pin 19 of the eccentric brings the spring 16 into action and out of action alternately. Fig. 2 shows the spring in the inactive position.

It should be noted, however, that when the spring 16 is in this inoperative position. there is a slight clearance 23 between the washer 2.0 and the strap 15, the eflect of which is to delay the instant when it is applied against the latter.

Thus, during one complete rotation of the eccentric 19,- there is a dead period or inactive period during which the spring 16 is displaced without having any effect, due to the clearance 23, and an operative period during which it bears against the strap 15 by means of the washer 20. Being already under tension between the washers 20' and 20-, spring 15 develops over a very 5 short distance of travel a pressure which is instantastrap 15 preferably just before the chains are set in motion, during the movement of the latter and at the instant they are immobilized, while the auxiliary tension of the spring 16 is relaxed immediately after stoppage of the chains and during the said stoppage, to be produced again just before they are again set in motion.

In order to achieve this result, it is sufficient to connect the pin 19 of the eccentric to the main shaft controlling operations of the press, which will insure the desired synchronous working.

In the example described and illustrated, the rod 17 is disposed with a certain inclination relatively to the direction in which the-block slides. It will be apparent that any other angle, preferably a smaller angle, is possible, and that it would also be possible to cause the springs 16 to act in the direction of the arrow 14.

It will also be apparent that instead of causing the springs 16 to be tensioned by eccentrics, other mechanisms could be used for this purpose, for example levers and cams, and it would also be possible to use draw springs instead of compression springs.

Referring to Fig. 1, it is also apparent that the tension of the already existing springs 11 could also be modified periodically.

Finally, it would also be possible to tension the chains by partly or wholly hydraulic means, the pressure of the fluid being varied appropriately.

What I claim is:

l. A press for treating sheet material and having a feeding zone and an operational zone comprising an endless conveyor passing through said zones, wheels supporting said conveyor, gripper means on said conveyor for engaging a sheet at the feeding zone and transporting the sheet to the operational zone, stops positioned adjacent the conveyor to engage the gripper means and properly position the same relative to said zones, resilient means coupled to one of the wheels for displacing the same for placing the conveyor under tension to enable a proper positioning of the gripper means, and control means coupled to the resilient means for selectively controlling the tensioning provided thereby to enable a truing of the positioning of the gripper means, said press further comprising a slideway supporting said one wheel for displacement to tension the conveyor, said resilient means engaging the latter said wheel to displace the same in the slideway; said control means engaging the resilient means and providing a force supplementing the forces provided by the resilient means.

2. A press for treating sheet material and having a feeding zone and an operational zone comprising an endless conveyor passing through said zones, Wheels supporting said conveyor, gripper means on said conveyor for engaging a sheet at the feeding zone and transporting the sheet to the operational zone, stops positioned adjacent the conveyor to engage the gripper means and properly position the same relative to said zones, resilient means coupled to one of the wheels for displacing the same for placing the conveyor under tensio'nto enable a proper positioning of the gripper means, and control means coupled to the resilient means for selectively controlling the tensioning provided thereby to enable a truing of the positioning of the gripper means, said resilient and control means providing forces in sub V 4 stantially the same direction, the force of said control means being controllably variable.

3. A press for treating sheet material and having a feeding zone and an operational zone comprising an endless conveyor passing through said zones, wheels supporting said conveyor, gripper means on said conveyor for engaging a sheet at the feeding zone and transporting the sheet to the operational zone, stops positioned adjacent the conveyor to engage the gripper means and properly position the same relative to said zones, resilient means coupled to one of the wheels for displacing the same for placing the conveyor under tension to enable a proper positioning of the gripper means, and control means coupled to the resilient means for selectively controlling the tensioning provided thereby to enable a truing of the positioning of the gripper means, the resilient and control means being coupled for controlling the operation of the resilient means.

4. In a press having a conveyor driven by a wheel resiliently supported for tensioning the conveyor, a control comprising a resilient device for engaging the wheel to provide at least a portion of the tension on the conveyor, and means coupled to the resilient device for controlling the engagement thereof with the Wheel.

5. In a press having power means for operating the press, gripper means on the conveyor for gripping said materials, stops positioned adjacent said conveyor to engage said gripper means and properly position the same in different operation zones, a conveyor for conveying materials to the press, a Wheel for driving the conveyor, a resilient device for urging the wheel in a predetermined direction intended to continuously maintain the conveyor under tension; a control comprising a coupling device connected with the wheel and defining a bore, a rod extending into the bore in a direction having a major component along said predetermined direction, a first shoulder fixed on the rod and spaced from the coupling device, a second shoulder loose on the rod adjacent the coupling device, a spring on the rod between the shoulders for urging the second shoulder against the coupling device, and an eccentric coupled to the rod for controllably urging the same into the bore for the controlled de-tensioning of the conveyor due to the urging of the second shoulder against the coupling device.

6. A control as claimed in claim 5 comprising a shaft for the wheel; said coupling means being a split ring mounted on the shaft.

7. A control as claimed in claim 5 comprising adjustment means on the rod for adjusting the position of the first shoulder to control the tension of said spring.

8. A control as claimed in claim 5 wherein the spring has a length whereby the second shoulder is adapted for being spaced from the coupling means in at least one position of the eccentric.

References Cited in the file of this patent UNITED STATES PATENTS 492,872 Maybach Mar. 7, 1893 733,385 Goldsmith et al. July 14, 1903 2,254,592 Berkeley Sept. 2, 1941 2,512,084 Bobst June 20, 1950 2,664,757 Shaw Jan. 5, 1954