CUTTING MACHINE WITH POSITIVELY CONTROLLED PRESSING AND CUTTING PROCESS

Abstract

A cutting machine includes a cutting support for material to be cut, a vertically movable blade bar which bears a blade for cutting the cut material located thereon, a cutting drive for vertically moving the blade bar, a vertically movable clamping bar for pushing down the material to be cut and a pressing drive for vertically moving the clamping bar. The cutting drive and the pressing drive are formed by a single drive which rotates a cam disc to and fro, wherein the blade bar is motion-coupled to the cam disc via a first coupling mechanism which acts on the cam disc eccentrically to the axis of rotation thereof. The clamping bar is motion-coupled to the cam disc via a second coupling mechanism, the one end thereof acting on the outer contour of the cam disc.

Claims

1. A cutting machine comprising: a cutting support for material to be cut; a vertically movable blade bar which bears a blade for cutting the cut material located thereon; a cutting drive for vertically moving the blade bar; a vertically movable clamping bar for pushing down the material to be cut and a pressing drive for vertically moving the clamping bar; wherein the cutting drive and the pressing drive are formed by a single drive which rotates a cam disc to and fro, and wherein the blade bar is motion-coupled to the cam disc via a first coupling mechanism which acts on the cam disc eccentrically to the axis of rotation thereof, and the clamping bar is motion-coupled to the cam disc via a second coupling mechanism, the one first end thereof acting on an outer contour of the cam disc; and a foot pedal for the manual vertical movement of the clamping bar, said foot pedal being motion-coupled both to the clamping bar and to the other second end of the second coupling mechanism, in order to lift away the first end of the second coupling mechanism from the outer contour of the cam disc by actuating the foot pedal.

2. The cutting machine according to claim 1, wherein the outer contour of the cam disc is configured such that in the forward mode of the drive the clamping bar always moves downwardly in advance of the blade.

3. The cutting machine according to claim 1, wherein the outer contour of the cam disc, viewed in a forward direction of rotation, has a front contour portion, and a rear contour portion, wherein the front contour portion rises more steeply radially outwardly than the rear contour portion.

4. The cutting machine according to claim 1, wherein the outer contour of the cam disc is configured such that the creation of the desired pressing force during the pressing process is virtually completed by the start of the cutting process and is maintained during the cutting process.

5. The cutting machine according to claim 1, wherein the first coupling mechanism has a connecting rod which acts, in particular is articulated, on the cam disc eccentrically to the axis of rotation thereof.

6. The cutting machine according to claim 1, wherein the second coupling mechanism has a piston/cylinder hydraulic device or a compression spring, the one first end thereof bearing on the outer contour of the cam disc, in particular by means of a guide roller.

7. The cutting machine according to claim 6, wherein the first end of the piston/cylinder hydraulic device or the compression spring is pretensioned by means of the force of a spring so as to bear against the outer contour of the cam disc.

8. The cutting machine according to claim 6, wherein the piston/cylinder hydraulic device has a pressure control valve in order to adjust the control pressure which is required in order to push a piston into a pressing cylinder of the piston/cylinder hydraulic device.

9. The cutting machine according to claim 6, wherein the piston of the piston/cylinder hydraulic unit is subjected during the entire pressing/cutting cycle to a pushing-out force which pushes the piston out of the cylinder hydraulic unit.

10. The cutting machine according to claim 9, wherein the pushing-out force is provided by a compression spring or a gas pressure spring unit.

11. The cutting machine according to claim 9, wherein the pushing out force is provided by a permanent overpressure in the piston/cylinder hydraulic unit.

12. The cutting machine according to claim 1, wherein a foot pedal deflection linkage engages directly in a deflection mechanics which acts between the second coupling mechanism and the clamping bar.

13. The cutting machine according to claim 12, wherein a foot pedal deflection linkage has a gas pressure spring.

14. The cutting machine according to claim 2, wherein the outer contour of the cam disc, viewed in a forward direction of rotation, has a front contour portion, and a rear contour portion, wherein the front contour portion rises more steeply radially outwardly than the rear contour portion.

15. The cutting machine according to claim 7, wherein the piston/cylinder hydraulic device has a pressure control valve in order to adjust the control pressure which is required in order to push a piston into a pressing cylinder of the piston/cylinder hydraulic device.

16. The cutting machine according to claim 7, wherein the piston of the piston/cylinder hydraulic unit is subjected during the entire pressing/cutting cycle to a pushing-out force which pushes the piston out of the cylinder hydraulic unit.

17. The cutting machine according to claim 8, wherein the piston of the piston/cylinder hydraulic unit is subjected during the entire pressing/cutting cycle to a pushing-out force which pushes the piston out of the cylinder hydraulic unit.

18. The cutting machine according to claim 13, wherein a foot pedal deflection linkage has a gas pressure spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention is shown in the drawings and is described in more detail with reference to an exemplary embodiment. In the drawings:

[0045] FIGS. 1a, 1b show a cutting machine according to the invention in a front view (FIG. 1a) and in a rear view (FIG. 1b), wherein in FIG. 1b a foot pedal for a manual actuation of a clamping bar of the cutting machine is not shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The cutting machine 1 shown in FIGS. 1a, 1b comprises a cutting support 2 for material to be cut, for example a paper stack, a blade bar 3 which is vertically movable (in this case obliquely downwardly) and which bears a blade 4 for cutting the material to be cut which is located thereon, a vertically movable clamping bar 5 for pushing down the material to be cut and a drive in the form of a drive motor 6 as a cutting drive for vertically moving the blade bar 3 and as a pressing drive for vertically moving the clamping bar 5.

[0047] The drive motor 6 rotates a cam disc 7 in each case by ca. 180° to and fro. The blade bar 3 is motion-coupled to the cam disc 7 via a first coupling mechanism A in the form of a connecting rod 8, which is articulated eccentrically on the cam disc 7 relative to the axis of rotation thereof. The clamping bar 5 is motion-coupled to the cam disc 7 via a second coupling mechanism B in the form of a piston/cylinder hydraulic device 9, the one first end 9a thereof bearing against the outer contour 10 of the cam disc 7. In the exemplary embodiment shown, the first end 9a is formed by the free end of a piston or a piston rod 11 of the hydraulic device 9, said free end bearing a guide roller 12. The guide roller 12 is pushed by means of a spring 13 so as to bear against the outer contour 10 of the cam disc 7. The end of a pressing cylinder 14 of the hydraulic device 9 remote from the piston rod 11 forms the other second end 9b of the hydraulic device 9, said second end being connected to a deflection mechanism 15 which actuates the clamping bar 5.

[0048] If the cutting is activated by actuating an electrical switch, for example, the drive motor 6 which rotates the cam disc 7 starts up, the connecting rod 8 for the blade actuation also being fastened thereto in a rotationally movable manner. The fastening of the connecting rod 8 to the cam disc 7 takes place at a distance from the axis of rotation of the cam disc 7 so that the cam disc 7 functions as a crankshaft. If the cam disc 7 rotates, the connecting rod 8 is pulled downwardly. The other end of the connecting rod 8 is rotatably fastened to the blade bar 3 and pulls this blade bar downwardly together with the blade 4 within an oblique guide slot 16 for the cutting process.

[0049] The outer contour 10 of the cam disc 7, i.e. the radial distance from the axis of rotation, is designed such that in forward mode the clamping bar 5 always moves downwardly in advance of the blade 4. The clamping bar 5 thus always protrudes downwardly over the blade 4 until it bears against the cut material and starts the actual cutting process. As a result, the operator safety is increased in the event that the pressing/cutting process is stopped (for example by switching off the main switch) before the blade 4 comes into engagement with the cut material.

[0050] The outer contour 10 of the cam disc 7 has, viewed in the forward rotational direction, a front contour portion 10a and a rear contour portion 10b. In this case, the front contour portion 10a rises radially outwardly more steeply than the rear contour portion 10b. The gradient of the outer contour 10 is thus very steep at the start, so that the pressing process is virtually completed by the start of the cutting process. Thus the available motor power of the drive motor 6 during the pressing/cutting process is divided into time periods such that in each case virtually the entire motor power is available for the two sub-processes. The hybrid functionality consisting of the electromechanical blade direct drive which is optimal for the cutting process and the pressing force which is optimal for the cut material pressing process which is able to be hydraulically adjusted over a wide range, is implemented by simply one drive motor 6 and one pressing cylinder 14 and thus at low cost.

[0051] The pressing cylinder 14 is directly connected to the deflection mechanism 15 of the cut material pressing and the piston rod 11 is coupled via the guide roller 12 to the outer contour 10 of the cam disc 3. The pressing cylinder 14 thus itself forms a part of the deflection mechanism 15 and moves as a whole until the cut material is reached during the pressing process. Then only the piston rod 11 moves substantially relative to the pressing cylinder 14 in order to create the adjusted pressing force.

[0052] The mode of operation of the cutting machine 1 is as follows:

[0053] 1. Motor forward mode: pressing and cutting are activated:

[0054] 1.1 Functional sequence part 1—the clamping bar 5 meets no resistance: The cam disc 7 rotates and thereby displaces the guide roller 12 together with the piston rod 11. Thus the piston rod 11 moves according to the shape of the cam disc 7. Since the clamping bar 5 is freely movable, the deflection mechanism 15 fastened thereto and the pressing cylinder 14 are also freely movable. Thus the pressing cylinder 14 may move to the same extent as the piston rod 11. In other words, the piston rod 11 is not pushed into the pressing cylinder 14. Thus no oil is displaced in the pressing cylinder 14 and thus no oil pressure is created in the system.

[0055] 1.2 Functional sequence part 2—the clamping bar 5 meets the resistance of the introduced cut material: The clamping bar 5 is then no longer freely movable downwardly, since it bears against the cut material. Thus the deflection mechanism 15 and therewith the pressing cylinder 14 may also no longer freely move. If the piston rod 11 is now displaced further via the cam disc 7, the pressing cylinder 14 may not move to the same extent as the piston rod 11 and the piston rod 11 is pushed into the pressing cylinder 14. The oil in the pressing cylinder 14 is displaced and via a pressure control valve 17 discharged into a hydraulic oil tank 18. The adjusted control pressure on the pressure control valve 17 determines the force which is required in order to push the piston rod 11 into the pressing cylinder 14. The greater the adjusted pressure, the greater the required force. Thus the force rises with the control pressure, and in turn this means as a counter reaction that the pressure, at which the clamping bar 5 is pressed onto the cut material, also changes via the deflection mechanism 15. The adjustment of the desired pressing force is achieved by the adjustment of the maximum pressure on the pressure control valve 17. This adjustment may take place either manually via an adjusting element fastened to the pressure control valve 17 or electrically via an electromotively driven adjusting element. All of the oil to be displaced is conveyed into the tank at the maximum adjusted pressure. Thus a complex and thereby expensive control unit, which when reaching the desired limit pressure maintains this pressure during the pressing cycle in the system and permits the remaining oil to flow in an unpressurized manner into the tank, is not required.

[0056] The chronological sequences of the functional sequences of parts 1 and 2 are dependent on the height of the introduced cut material:

[0057] In the case of a low introduction height or cutting height, i.e. with a small amount of cut material, the clamping bar 5 and therewith the deflection mechanism 15 and the pressing cylinder 14 may move freely over a large part of the clamping bar movement path, until the clamping bar bears against the cut material. This has the result that the piston rod 11 is pushed only at the end of the pressing process and merely to a small degree into the pressing cylinder 14. Thus only a little oil is displaced in the pressing cylinder 14 and conveyed into the tank. The adjusted overflow pressure during the cutting/pressing cycle is thus only briefly in the system. In the case of a full introduction height or cutting height, i.e. with a large amount of cut material, the clamping bar 5 and therewith the deflection mechanism 15 and the pressing cylinder 14 may freely move only over a small portion of the clamping bar movement path until the clamping bar bears against the cut material. This has the result that already at the start of the pressing process the piston rod 11 is pushed virtually completely into the pressing cylinder 14. Thus virtually all of the oil in the pressing cylinder 14 is displaced and conveyed into the hydraulic oil tank 18. The adjusted overflow pressure during the cutting/pressing cycle is thus present in the system over a long period of time.

[0058] 2. Motor reverse mode: the pressing/cutting process is terminated, the system has reached the adjusted reversal point and moves back into the initial position by the drive motor 16 changing the rotational direction:

[0059] The guide roller 12 acted upon by a spring follows the rotating outer contour 10 of the cam disc 7 which is deflected increasingly less by the cam path thereof in contrast to forward mode. The piston rod 11 fastened to the guide roller 12 thus also moves. The piston rod 11 is pulled out of the pressing cylinder 14. This has the result that oil is suctioned out of the hydraulic oil tank 18. The pressure control valve 17 is to this end bypassed in the opposing direction of flow by a non-return valve (not shown) so that the oil may be suctioned in a virtually unpressurized manner from the hydraulic oil tank 18. If during reverse mode the piston rod 11 has arrived at its extended end position, the pressing cylinder 14 and the clamping bar 5 connected via the deflection mechanism 15 have to follow the piston rod in a positively coupled manner to the upper initial position of the clamping bar 5.

[0060] With the reverse mode of the system, at the start the clamping bar 5 only acts counter to the gravitational force thereof. In some cases, this is not sufficient, however, in order to compensate for the frictional forces of the remaining system (such as for example due to the piston seals). This may lead to the clamping bar 5 either immediately lifting away or at least no longer bearing securely against the cut material, until the blade 4 has arrived in the upper initial position. This is a problem, for example, when cutting cut material which is provided with a self-adhesive film. This cut material tends to adhere slightly to the blade 4 and, if not secured during the return travel of the blade, may slip due to the adhesion. In order to prevent this, the clamping bar 5 may fix the cut material until the blade 4 has arrived again approximately in its upper initial position. Thus it is advantageous to press the clamping bar 5 with a certain fixed force onto the cut material until the cam disc 7 and therewith the piston of the piston/cylinder hydraulic unit 9 have moved back sufficiently far that said piston has arrived in the extended position thereof and in a positively coupled manner entrains the clamping bar 5 upwardly into the initial position thereof. This may be implemented by the technology that the piston of the piston/cylinder hydraulic unit 9 is subjected continuously, i.e. during the entire pressing/cutting cycle, to a force which pushes the piston out of the cylinder hydraulic unit 9. This pushing-out force leads to the cut material being fixed with the predetermined pressing force via the clamping bar 5 coupled to the piston/cylinder hydraulic unit 9 until the cam disc 7 and therewith the positively coupled blade bar 3 together with the blade 4 have arrived approximately in the upper initial position thereof. In the further movement sequence, the piston/cylinder hydraulic unit 9 and therewith the clamping bar 6 are pulled upwardly into the initial position thereof.

[0061] The pushing-out force may act, for example, on the piston by means of a compression spring 19 or gas pressure spring unit, wherein the compression spring 19 or gas pressure spring unit may be mounted inside or, as shown in FIG. 1a, outside the piston/cylinder hydraulic unit 9. A further exemplary embodiment may be achieved by a permanent overpressure in the piston/cylinder hydraulic unit 9 which acts as a corresponding spring and pushes the piston permanently with a defined force out of the piston/cylinder hydraulic unit 9.

[0062] FIG. 1a shows a foot pedal 20 for a manual actuation of the clamping bar 5. If the foot pedal 20 is moved downwardly via the foot pedal deflection linkage 21, the clamping bar 5 is pulled downwardly, i.e. in the direction of the introduced cut material. The foot pedal 20 is motion-coupled both to the clamping bar 5 and to the second end 9b of the hydraulic device 9 in order to lift away the first end 9a of the hydraulic device 9 from the outer contour 10 of the cam disc 7 by actuating the foot pedal 20.

[0063] The clamping bar 5 may thus be actuated independently of the electrical pressing/cutting cycle and thus independently of the safety control. This means that when actuating the pressing by means of the foot pedal 20 the operator may handle the paper stack with the pressing device lowered, although the operator is moving in the monitored safety region of the machine. This is permitted since the pressing force is applied by the operator himself by means of the leg pressure thereof. If required, the operator may force out the air between the individual layers of the cut material before the automatic pressing/cutting cycle in a targeted manner by means of the foot pressing device, or may see accurately over the front edge of the lowered clamping bar 5 where the cutting has taken place by the blade arranged directly in front of the clamping bar 5. If required, the operator may realign the cut material when the clamping bar 5 is lowered.

[0064] The decoupling of the foot pressing device from the automatic pressing device is possible mechanically, since when actuating the foot pressing device the deflection mechanism 15 of the pressing mechanism is moved such that the clamping bar 5 is lowered in the direction of the cut material. By means of the deflection mechanism 15 the pressing cylinder 14 fastened thereto also moves with the piston rod 11 together with the guide roller 12. This guide roller lifts away counter to the force of the spring 13 from the outer contour 10 of the cam disc 7. Thus the hydraulic device 9 is moved independently of the position of the cam disc 7.

[0065] If the automatic pressing/cutting process is activated when the foot pressing is actuated, this pressing/cutting process runs as described above. However, at the start of the pressing/cutting process the guide roller 12 and therewith the entire remaining hydraulic device 9 do not bear against the outer contour 10 of the cam disc 7. In other words, without starting the automatic pressing process, the blade 4 is moved downwardly until the cam disc 7 has rotated sufficiently far that the guide roller 12, lifted away by the foot pressing, again comes to bear against the outer contour 10 of the cam disc 7. Only then the adjusted pressing force is created in the system and the blade 4 comes into engagement with the cut material.

[0066] Optionally, the foot pedal deflection linkage 21 may have a gas pressure spring 22. When actuating the foot pedal 20 the gas pressure spring 22 does not retract, i.e. it acts in the manner of a rigid linkage, until a fixed maximum actuating force (fixed spring force of the gas pressure spring 22) is reached. If this maximum actuating force is exceeded, the gas pressure spring 22 is compressed without the remaining system being additionally stressed, until the foot pedal 20 bears against the floor.

[0067] Instead of the piston/cylinder hydraulic device 9 shown, alternatively a compression spring which is compressed in the pressing sequence may also be used (instead of pushing in the piston 11 against the adjusted overflow pressure). The pressing force may then be adjusted within certain limits via the pretensioning of the compression spring. The compression spring has to be limited in its maximum extension—as is the piston/cylinder hydraulic unit 9—since otherwise it would permanently actuate the pressing. To this end, the compression spring either may be completely relaxed in the resting position (the pressing device is in the upper end position) or previously pretensioned by means of a spring path limiter. As a spring path limiting element, for example, a cross member may be installed, running in the centre of the compression spring, washers which limit the compression spring in the maximum extension thereof being located at the ends thereof. The compression spring variant thus follows the cam disc only when it is pretensioned by means of the force of the spring 13 against the outer contour 10 of the cam disc 7.