DEVICE FOR CONTROLLING A PAPER CUTTING MACHINE

Abstract

A device for controlling a paper cutting machine which has a press-down bar and a cutting bar, wherein the press-down bar is operable by a spring-biased single-side action hydraulic press cylinder and the cutting bar is operable by a rotary motor which is adapted to be coupled to a cutting bar via a gearcase and a friction clutch, and wherein the friction clutch is operable by a hydraulic coupling cylinder biased by a spring, comprising a hydraulic pressure source which is connected to the press cylinder via a first pressure line and a controllable on-off valve, two parallel controllable circulation valves which are connected to the pressure line and join the pressure line to the tank when at rest, a controllable cutting simulator valve assembly which restricts the pressure from the press cylinder and the volume of hydraulic medium flowing thereto, a second pressure line leading to the coupling cylinder and joined to the first hydraulic pressure source or a separate second hydraulic pressure source, two controllable second circulation valves which are connected to the pressure line which and join the second pressure line to the tank when at rest, and a control device for driving the individual controllable valves, characterized in that at least one of the first circulation valves is defined by an electrically controllable proportional valve and an electric control device is provided, at least for driving the proportional valve.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Two embodiments of the invention will be described below with reference to the drawings.

FIG. 1 shows a hydraulic circuit layout for a control device according to the invention.

FIG. 2 shows a hydraulic circuit layout modified with respect to FIG. 1 for a control device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated

A press cylinder 10 and a coupling cylinder 12 can be recognized in FIG. 1. Both of them are of the one-sided action type where the pistons are restored by a spring 12 and 14, respectively. The press cylinder 10 actuates the press-down bar of a paper cutting machine which is not shown, where if a hydraulic pressure is applied the press-down bar is displaced from the upper dead-centre position to the lower one. The spring 12 provides for a return stroke in the inverse direction. The coupling cylinder 12 actuates the coupling elements of a friction clutch with the clutch being opened or disengaged by means of the spring 14. As is known the clutch serves for building up the drive train between a driving motor, e.g. an electric motor, and the cutting bar, not shown either, of the paper cutting machine, where a worm gear which actuates the cutting bar via a crank mechanism is seated on the output side of the clutch. Such a construction is known per se.

In FIG. 1, a pump 16 delivers a hydraulic medium into a pressure line 20 through a filter 18. The line communicates with the piston space of the press cylinder 10 via a control valve 22. Connected to the pressure line 20 are a first proportional valve 24 and a second proportional valve 26, as is a two-way valve 28. All valves 22 to 28 can be driven by means of an electric control 30 which is outlined only schematically here.

The electric control also includes a processor by which the various functions yet to be described may be executed according to predetermined programs.

The proportional valves 24, 26 may be set to a desired pressure, i e. if they are switched to be fully open the hydraulic medium passes into a tank line 32 which is led to the tank 34. The pressure is varied in the pressure line 20 depending on the way of driving, so that an arbitrary pressure can be generated on the press cylinder 10 if the valve 22 is controlled so as to open, which is done by means of the electric control 30 as well. The valve 28 is a pure on-off valve which either is opened or closed. Its circuit includes a throttle valve 36 which limits the volume of the flow medium passing to the tank 34.

The pressure line 20 also has connected thereto a pressure sensor 38 the signals of which are provided to the electric control device 30.

Finally, FIG. 1 allows to identify a rotary potentiometer 40 the output of which goes to the electric control device 30.

Another pump 42 is coupled, via a filter 44, to another pressure line 46 which communicates with the piston space of the coupling cylinder 12. However, the pump 42 may be omitted if a common pump having an additional flow divider is employed for the two cylinders 10, 12. Connected to the pressure line 46 are a proportional valve 48 and an on-off valve 50 both of which receive control signals from the electric control device 30. The pressure line 46 also has connected thereto a further pressure sensor 52.

The circuit layout shown is sufficient to realize all functions for a paper cutting machine. Those are briefly explained below.

In the inoperative position of the paper cutting machine, it must be sure that the cylinders 10, 12 are not operated. The valves 24, 26 of the press circuit and the valves 48 and 50 of the cutting circuit are opened in such case. This allows the hydraulic medium to freely flow back to the tank 34, a certain circulation pressure of 2-3 bar being acceptable. However, the pressure would be insufficient to cause an actuation of the cylinders 10, 12 even if the control valve 22 was opened. The valve 22 is controlled by the control device so as to open at the outset of the cutting process. The desired press-down force is adjusted via the proportional valve 24, for example, with the proportional valve 26 being driven by a pressure which is higher by about 10 bar. However, the functions of the valves 24, 26 may also be interchanged. Since the press cylinder 10 is to be kept from being loaded at once with the full press-down force the proportional valve 24 is driven by a ramp function of from 10 to 20 bar, for example, over a period of about 100 to 200 milliseconds. The valve 28 may also be closed during the process described, but needs to be closed after the closure of the valves 24, 26 at the latest. Once the press-down bar has reached the point of contact and the cutting bar has completed the cutting process the control valve 22 will be closed. The proportional valves 24, 26 may be opened completely, which minimizes the energy demand in the press circuit.

To keep damage from delicate cutting materials, it is possible to drive the press-down bar in such a way that it sets down gently on the paper stack. This is also done by driving the proportional valve 24, i.e. in response to a sensor which is not shown and finds out when the press-down bar approaches the paper stack. Afterwards, the desired press-down force may be built up again and be regulated to the setpoint predetermined in the electric control device 30 by means of the pressure sensor 38.

If there is a certain press-down force on the press cylinder 10, the press cylinder, under a spring load, travels towards the upper dead-centre position, namely at a relatively slow speed. As soon as the pressure is increased the press-down bar is displaced again towards the lower dead-centre position, which is done at a predetermined pressure. The period of time during which this process is performed may be preset by the control device 30, which causes the proportional valve 24, for example, to temporarily build up a pressure of about <10 bar in the press cylinder (cutting optimization). Another cutting process is released in the described manner subsequently.

The so-called cutting simulator function is achieved by the control device opening the on-off valve 28, by which action the throttle valve 38 restricts the maximum hydraulic fluid volume which is allowed to flow to the press cylinder 10. At this stage, one of the proportional valves 24, 26 prefixes a pressure which is adjusted by the potentiometer 40. The potentiometer is actuated either by the hand or foot of an operator, thus allowing for the adjustment of a predetermined pressure in the press cylinder via one of the proportional valves 24, 26 with the second one, in turn, being set to a pressure which is higher by 10%, This way enables the working pressure to be adjusted between 10 and 20 bar, for example.

The circulation for the cutting circuit is brought about by the proportional valve 48 and the on-off valve 50. A circulation pressure <3 bar is obtained also here. The two valves 48, 50 are closed for cutting and the coupling pressure is adjusted on the proportional valve 48. It ranges between 50 and 100 bar. For a prevention of too intense an acceleration of the cutting bar, it is possible to build up the coupling pressure gently at the beginning so that the clutch will drag more or less. This significantly reduces the sideward forces acting on the cutting machine.

After the lower dead-centre is reached, the valve 48 is set to a lower pressure which is sufficient to move the cutting bar to the upper dead-centre position. As is known the coupling force may be the lower the smaller is the force to be applied to the cutting bar. During the return stroke, it is possible already to re-charge the rotary accumulator which usually is provided, which enables to save energy with the paper cutting machine in operation.

A diagnostic check may be made by means of the pressure sensor 38 and the further pressure sensor 52. When in the circulating position in the press circuit, the two valves 24, 26 require to be opened. The pressure must not exceed a certain level here.

The same holds true for the valves 50, 48 which, when in the circulating position, are only allowed to generate a minimal pressure. The two control circuits for the cylinders 10, 12 may be monitored even when in operation. If the forces to be applied are under a regulation it will be possible to maintain a desired press-down force throughout the range of working temperatures.

The hydraulic circuit layout of FIG. 2 only differs slightly from the one of FIG. 1. Therefore, like parts are designated by like reference numbers.

In the layout of FIG. 2, the valves 28, 24 of FIG. 1 are substituted for by a three-way valve 56 which also is driven by the electric control device 30. The valve has three switching positions which include a blocking position, a circulating position and a throttling position. The circulating position corresponds to the circulating position of the proportional valve 24 of FIG. 1 The valve 56 is switched into the blocking position in the pressing mode. The throttling position is needed, for instance, during the cutting simulator function to achieve a pressure regulation to a desired safety pressure when the flow rate is prefixed. For example, a pressure of from 10 to 20 bar is set here. The functions of “cutting optimization” and “gentle pressing” may be realized either by the valve 26 or valve 56,

The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.

Claims

1. A device for controlling a paper cutting machine which has a press-down bar and a cutting bar, wherein the press-down bar is operable by a spring-biased single-side action hydraulic press cylinder and the cutting bar is operable by a rotary motor which is adapted to be coupled to a cutting bar via a gearcase and a friction clutch, and wherein the friction clutch is operable by a hydraulic coupling cylinder biased by a spring, comprising a hydraulic pressure source which is connected to the press cylinder via a first pressure line and a controllable on-off valve, two parallel controllable circulation valves which are connected to the pressure line and join the pressure line to the tank when at rest, a controllable cutting simulator valve assembly which restricts the pressure from the press cylinder and the volume of hydraulic medium flowing thereto, a second pressure line leading to the coupling cylinder and joined to the first hydraulic pressure source or a separate second hydraulic pressure source, two controllable second circulation valves which are connected to the pressure line which and join the second pressure line to the tank when at rest, and a control device for driving the individual controllable valves, characterized in that at least one of the first circulation valves (24, 26) is defined by an electrically controllable proportional valve and an electric control device is provided, at least for driving the proportional valve.

2. The device according to claim 1, characterized in that the first two circulation valves are proportional valves (24, 26) and the cutting simulator valve assembly has a controllable on-off valve (28) and a throttle valve (36) for volume restriction,

3. The device according to claim 1, characterized in that the second one of the first circulation valves is a controllable directional valve (56) having three positions which include a blocking position, a throttling position and a circulating position.

4. The device according to claim 1, characterized in that the first pressure line (20) has connected thereto a pressure sensor (38) the outlet of which is coupled to the electric control device (30).

5. The device according to claim 1, characterized in that the electric control device (30) has a sequence program for driving the individual valves which is based on the operation steps of the press-down bar and/or cutting bar.

6. The device according to claim 4, characterized in that the required pressure values for the press cylinder are filed in the electric control device (30) and are compared to the actual pressure values arriving from the pressure sensor (38), for the purpose of regulating the pressure on the press cylinder (10) in the respective operational states.

7. The device according to claim 1, characterized in that the proportional valve (24, 26) is driven from the electric control device (30) via a ramp function for the purpose of slowly building up a pressure on the press cylinder (10) during the start-up phase.

8. The device according to claim 1, characterized in that the electric control device (30) switches the circulation valves into circulation and blocks the on-off valve (22) when the cutting bar has reached its lower dead-centre position.

9. The device according to claim 1, characterized in that the electric control device (30) drives the proportional valve (24, 26) after the press-down bar has reached its lower dead-centre in order to lower the pressure in the pressure line (20) to a reduced value, causing the press-down bar to be raised from a paper stack by a small amount, after which a further pressing cycle of the press-down bar is initiated by the electric control device (30).

10. The device according to claim 1, characterized in that a distance sensor measures the distance of the press-down bar from the paper stack and the electric control device (30) drives the proportional valve (24, 26) so as to temporarily lower the pressure in the pressure line (20) to a reduced pressure level if a signal of the distance sensor detects the approach of the press-down bar to the paper stack,

11. The device according to claim 2, characterized in that a manually operable electric signal generator (40) is connected to the electric control device (30), which opens the on-off valve (28) with the throttle valve (36) electrically and drives the directional valve (56) if the electric signal generator (40) generates a signal and the proportional valve (24, 26) is driven in response to the level of the electric signal.

12. The device according to claim 1, characterized in that a width sensor is provided which measures the width of the paper stack, and the proportional valve (24, 26) is driven by the electric control device (30) so as to cause the press-down bar to produce a predetermined specific surface pressure.

13. The device according to claim 1, characterized in that one of the second circulation valves also is a proportional valve (48) which is adapted to be driven by the electric control device (30).

14. The device according to claim 13, characterized in that the electric control device (30), when the cutting bar is at the upper dead-centre position, drives the proportional valve (48) so as to generate a temporarily lower pressure in the pressure line (46) during a start-up phase of the cutting bar.

15. The device according to claim 13, characterized in that the electric control device (30), after the lower dead-centre position is reached, drives the proportional valve (48) into a reduced pressure in the pressure line (46).

16. The device according to claims 13, characterized in that the second pressure line (46) has connected thereto a second pressure sensor (52) which is coupled to the electric control function (30).