Field of the Invention This invention relates to a cutter mechanism and, more particularly, to guillotine types of cutters particularly adapted to cut paper stock and the like.

Description of the Related Art It is often desirable in printing and other paper-processing concerns to cut stacks of paper stock, card stock, label stock, and the like into multiple stacks of smaller size stock. This cutting process is accomplished, ordinarily, in a guillotine type of cutter which includes a clamp mechanism adapted to abut the stack of paper and hold it during the reciprocating stroke of the knife. The knife is transverse to a cutting bed and the clamp is positioned directly behind and parallel to the knife.

In conventional cutters of the type described, the clamping mechanism is typically powered by a hydraulic cylinder. The paper cutting knife is powered, conventionally, by either a hydraulic cylinder ram or an electric motor operating in conjunction with a drive train including a clutch, flywheel, worm drive and the like.

In the former case. the hydraulic cylinder is utilized to pull the knife toward the bed upon which the paper is positioned and, after the cut has been completed, raise it to its starting position. In the latter case, the knife is usually connected to a rotating eccentric member by means of a connecting rod and the eccentric member rotated periodically to bring the knife into and out of engagement with the paper as desired.

The hydraulic cylinder type of knife is preferred because a hydraulic system allows a single motor to power both knife and clamp without any loss of power or accuracy. This arrangement is widely accepted in the industry despite the fact that this method of powering the clamp suffers from a major disadvantage.

When a guillotine paper cutter is used to cut smaller stock from a parent sheet, the cutter is initially set for high clamping force. For example, when cutting labels from parent stock, the parent stock has a large surface area and requires

a maximum force to retain the stock in place as it is being cut. As the cutter makes its initial cuts. strips of long narrow or reduced width stock are trimmed from the parent sheet. The final label stock is cut from these strips. But, when cutting these labels, the clamp pressure on the strip stock must be reduced because the reduced width results in a reduced surface area of the strip stock. If the clamp force is not reduced, the strip stock would receive compression damage and the final labels would be disfigured.

It is an object of the broader aspects of this invention to provide a cutter mechanism of the type described embodying a hydraulic circuit and electrical control therefor operative to control the clamping force in a predetermined sequence.

SUMMARY OF THE INVENTION According to the invention, a cutting apparatus for simultaneously cutting sheets of stacked stock material comprises a support table having an upper surface that is sized to support the stock stack. A cutting blade having a longitudinal edge is positioned above the support table. The cutting blade is movable between a retracted position, where the edge is away from the support table upper surface, to a cutting position, where the edge is adjacent the support table upper surface. The movement of the cutting edge between the retracted position and the cutting position defines a cutting plane. Positioned above the support table upper surface is a clamp that is movable between a retracted position, where the clamp is above the stock stack, and a clamping position, where the clamp abuts and applies a force to a top of a stock stack, to compress the stock stack and hold its position relative to the support table upper surface. A controller is operatively connected to the clamp to thereby set the clamp force based on the particular cut in a cutting sequence.

Preferably, the clamp force is decreased as the paper or stock width is decreased to prevent the deformation of the stock stack during cutting. The cutting apparatus can comprise a backgauge for abutting a rear surface of the stock stack. The controller can further comprise a sensor for determining the backgauge distance and generating a distance signal representative of the backgauge distance. The distance signal is used by the controller to set the location of the backgauge.

The controller can further include a microprocessor coupled to the clamp to set the clamp force based thereon. The microprocessor can include a

memory in which is stored a table of corresponding clamp force values and for each cut in the cutting sequence and sets the clamping force for each cut. The controller can further comprise an input device through which the table of corresponding clamp force values and backgauge distance values are stored in the microprocessor memory for each cut in the cutting sequence, preferably by the direct input of a user via the input device.

In another embodiment, the invention comprises the method of cutting stacked sheets of paper stock (defining a stock stack with a front face, rear face, top face, bottom face, and side faces) with a cutting apparatus comprising a support table having an upper surface sized to support the bottom face of the stacked stock. A cutting blade having a longitudinal edge is positioned above the support table and movable between a retracted positioned, where the edge is away from the support table upper surface. to a cutting position, where the edge is adjacent the support table upper surface. The movement of the edge between the retracted position and the cutting position defines a cutting plane. A backgauge is movably mounted to the support table upper surface and faces the cutting plane. The backgauge is adapted to support the rear face of the stock stack. A clamp is positioned above the support table upper surface and movable between a retracted position, where the clamp is above the support table upper surface, and a clamping position, where the clamp abuts and applies a clamping force to the top face of the stock stack, to compress the stock stack and hold its position relative to the support table upper surface. The method of cutting the stock stack includes selecting a clamping force according to the determined stock stack width, applying the selected clamping force to the top face of the stock stack by moving the clamp from the retracted position to the clamping position, and then cutting the stock stack by moving the blade from the retracted position to the cutting position.

Preferably, the method comprises the advancing of a portion of the stock stack through the cutting plane after the cutting of the stock stack and repeating the steps of selecting an appropriate clamping force, applying the selected clamping force, and cutting the stack stock. The method can also include the setting of the backgauge by monitoring the distance of the backgauge from the cutting plane. The monitoring of the backgauge distance can comprise rotating a leadscrew fixed relative

to the support table and threadably connected to the backgauge while determining the backgauge distance by monitoring the rotational movement of the leadscrew relative to a reference position and converting the rotational movement to the backgauge distance. The clamping force can be selected from a table of corresponding clamping force values for each cut in the cutting sequence. The table of clamping force values is created by a user of the cutting machine and can include corresponding backgauge distances.

BRIEF DESCRIPTION OF THE DRAWINGS These as well as other objects of this invention will be readily understood by those skilled in the art with reference to the following specification and accompanying figures in which: FIG. 1 is a front-elevational view of the novel cutter; FIG. 2 is a side-elevational view of the cutter of FIG. 1 : FIG. 3 is a fragmentary, perspective view of the rear table portion of the cutter illustrating specifically the clamping mechanism; FIG. 4 is a schematic illustration of the hydraulic circuitry; FIG. 5 is a schematic illustration of the clamp and drive apparatus therefor ; FIG. 6 is a perspective view of parent stock before cutting; FIG. 7 is a perspective view of a strip cut from parent stock ; FIG. 8 is a perspective view of end size paper cut from a strip: and FIG. 9 is a schematic illustration of control computer relation to the positioning, knife, and clamp assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is a paper cutter having a programmable clamp force and includes a conventional paper cutter controlled by a control computer. The control computer controls several subsystems including positioning the stock or paper for cutting, selecting the cut sequence, and setting the clamp pressure.

More particularly, the control computer controls a motor and a control valve, whereby the paper position relative to a knife assembly and the clamping force applied by the clamp assembly to the paper are controlled, respectively. as predetermined by the operator and input to the control computer. Multiple clamp

pressure settings can be inputted for a single job. with each clamp pressure setting corresponding to a particular stock position on the table correlating to stock size as it is trimmed. In other words, the operator inputs the clamp pressure and stock length for a particular cut for each cut in the cutting sequence. The controller then sets the paper length and cutting pressure for each cut in the sequence.

FIGS. 1 and 2 illustrate the apparatus of the invention as including a frame assembly 10 having floor-abutting pads 11 and a series of uprights 12. Upon the uprights 12 is supported in generally horizontal fashion a stock supporting table 13. An overhead arm 14 is supported above the table 13 by upwardly extending supports 16. The paper stick 17 (see FIG. 2) is positioned directly beneath a knife assembly 20.

The knife assembly 20 comprises a knife carriage 21 supported from overhead arm 14 by means of a pair of pivotable hinge members 22. Extending from the left-hand side (as shown in FIG. 1) of the knife carriage 21 is an ear 24.

Connected between ear 24 and a suitable bracket 27 on the frame of the machine is a telescopic shaft 25. Shaft 25 has a compression spring 26 positioned thereover and which functions to bias the knife assembly 20 in its raised position during utilization of the apparatus. A knife 28 is locked to the carriage 21 by suitable mounting screws 29. Conventional adjustment screws (not shown) are provided for making elevational adjustments of the knife with respect to the carriage to compensate for minor tolerance discrepancies in the drive assembly. The knife 28 spans the cutting table.

The hinges 22 are pivoted to the overhead arm 14 and the knife carriage 21 as indicated at 23 in such a manner that the knife assembly can drop into abutment with the stick 17 in a downward and sideways direction. The relative lengths and positions of the hinges 22 will depend. of course, upon the particular type of cutting action desired. They can be designed in such a manner that the knife blade stays parallel to the overhead arm 14 or, as shown, such that one extremity of the knife blade lies slightly below the other extremity thereof during the cutting operation, the two extremities reaching the same level upon contact with the stick.

The knife drive assembly 30, shown best in FIGS. 1 and 2, comprises a hydraulic rotary actuator 31 having a shaft 32 extending from the forward and rearward extremities thereof. The actuator 31 is carried by a suitable bearing structure

33 and has affixed to the forward shaft extremity thereof an eccentric arm 34. Bearing structure 33 may include, if desirable, a gear reduction mechanism. Pivotably affixed to eccentric member 34 at 37 is a connecting rod 35. The opposite extremity of connecting rod 35 is pivotably affixed to the knife carriage 21 as indicated at 36.

From an examination of FIG. 1, it will be apparent that as the eccentric member 34 is rotated by the hydraulic actuator 31, the knife will be pulled downwardly into abutment with the stick 17. When the direction of rotation of the hydraulic actuator 31 is reversed, similarly, the knife will be raised back upwardly to its initial starting position. By making the eccentric member 34 and connecting rod 35 of suitable length and by compensating for minor tolerance discrepancies with the knife adjust screws noted previously, cutting of the stick 17 by the knife 28 can be completely eliminated since the knife will start upwardly as soon as the eccentric member has passed center position. The components should be sized and adjusted, thus. such that the knife 28 comes into slight contact with the stick when the eccentric member 34 is displaced 180° from the position shown in FIG. 1.

The particular actuator utilized in a specific embodiment of this invention will depend. of course, on torque requirements and available pressure in the particular cutting environment.

The clamp assembly, identified generally by the reference numeral 50. is shown best in FIGS. 3 and 5. The clamp assembly comprises a carriage 51 having a clamping surface 52 at the lower extremity thereof that parallels the knife 28. The carriage 51 has a rack 53 depending from each side thereof and the racks 53 are slidably journaled in suitable fashion within the framework of the apparatus behind the knife carriage 21. A shaft 54 is rotatably borne within framework 10 at each of its extremities as indicated at 55. Keyed to the shaft 54 are pinion gears 56 which mesh with the racks 53. Connected to one of the racks 53 is the connecting rod 57 from a suitable hydraulic cylinder 58. When hydraulic cylinder 58 is activated, as will be readily apparent to those skilled in the art, the rack is pulled downwardly or pushed upwardly and the pinion gear and shaft arrangement insure that the force will be applied equally to each side of the clamping assembly. The clamp assembly 50 is utilized to hold the stock in a predetermined position during a particular cutting sequence. The cutting sequence, the clamp pressure and the paper position are

preprogrammed by the operator in a control computer 200 for each cut in the cutting sequence. In order to accomplish this function, the cylinder 58 is actuated in such fashion as to bring the clamping surface 52 into abutment with the stock which, effectively, squeezes the stock between the table 13 and the surface 52. Since the clamping surface 52 is not very deep relative to the support table. the width of the paper stock tends to be the limiting factor regarding the appropriate amount of the clamping pressure. The narrower the width of the stock (the side facing the blade 28) the less must be the clamping force to avoid damaging the stock.

Referring now to FIGS. 2,3 and 9, the table 13 is provided with conventional side plates 18 and a backgauge 219. The backgauge 219 is adjustable relative to the table 13 to provide a reference for the making of a particular cut and is moved by a motor 230, which is controlled by a control computer 200. The backgauge 219 is fixedly attached to a threaded block 234 which traverses a leadscrew 236 below the table 13. The motor 230 rotates the leadscrew 236, which causes the threaded block 234 to move subjacent a slot 238 in the table 13. The particular position of the backgauge 219 is provided to the control computer 200 by an encoder 260, and displayed on a display 232, preferably a conventional CRT, to the operator.

The particular position of the stock is correlated to the size of the stock input into the control computer for the cut in the cut sequence, which determines which preset clamp pressure setting is to be used for the cut.

In accordance with the teachings of the preferred embodiment of this invention, when the clamping pressure has reached a predetermined point, the hydraulic pressure is diverted automatically by the pressure control valve 220 to the hydraulic actuator to bring the knife into slicing or cutting relationship with the stock.

This point is preprogrammed by the operator into the control computer 200.

More particularly, as shown in FIG. 4, the hydraulic system 60 comprises a filter 61 positioned within a suitable reservoir indicated schematically by the reference numeral 59. The filter 61 is connected to a pump 62 driven by motor 63.

The system is provided with a relief valve 64 and a series of suitable shutoff valves 65 and pressure gauges 66. A double solenoid four-way valve 67 interconnects pump 62 and the clamping cylinder 58. The valve is operated by solenoids 68 and 69. The energization of solenoid 68 routes hydraulic pressure to clamping cylinder 58 in such

a direction as to raise the clamping assembly 50 from the stock. The pressure delivered is controlled by the control valve 220, which receives instructions from the control computer 200. Thus, the energization of solenoid 69 routes hydraulic pressure to the clamping cylinder 58 in such a direction as to lower the clamp onto the stock with pressure controlled by the control valve 220 and predetermined by the operator as input in control computer 200.

The pump 62 and the hydraulic actuator 31 are interconnected by a similar double solenoid four-way valve 70. The valve 70 is actuated by solenoids 71 and 72. The energization of solenoids 71 routes hydraulic pressure to actuator 31 in such a direction as to cause the knife to raise while the energization of solenoid 72 routes hydraulic pressure to the actuator 31 in such a direction as to cause the knife to lower.

The hydraulic circuit is completed by means of a pressure reducing valve 73 between pump 62 and valve 67; a sequence valve 74 between valve 70 and actuator 31 on the knife-down side of the line ; a pressure surge relief valve 75 across the actuator 31; and a pilot operated check valve 76 and computer 200 controlled control valve 220 across clamping cylinder 58.

Sequence valve 74 is adjusted such that it opens when the pressure within the system has built up above that required for proper actuation of clamping cylinder 58. Thus, for example, if solenoids 69 and 72 are both actuated, clamping cylinder 58 will be actuated initially to lower the clamp into contact with the stock.

When the clamp is pressing on the stock with the"predetermined"pressure of sequence valve 74 as limited by control valve 220, the sequence valve will open and route the hydraulic fluid to the actuator 31 to bring the knife down on its cutting stroke. The pressure reducing valve 73, of course, limits the maximum pressure exerted upon clamping cylinder 58 in order to avoid any problem of seal failure due to the pressures at the actuator 31.

In use. the computer 200 controls the operation of the clamping assembly 50, as well as the knife assembly 20. Operation of both depends on feedback given to the computer 200 relating the position of the stock 1 on the table 13. More particularly, the operator inputs settings for paper position and clamp pressure to the control computer 200 via the keyboard 282 for each cut in the cutting

sequence. Upon activating the cutter, the control computer 200 actuates motor 230.

The motor rotates the leadscrew 236 such that the threaded block 234 moves the backgauge 219 to the proper, preset position on the table 13. Thus, any loaded stock is arranged properly on the table 13. The particular position of the backgauge 19 is displayed on a display 232 and position feedback is provided to the control computer 200 by the encoder 260.

Upon energization actuation by the operator, the clamping assembly 50 descends into the stock 1. As clamping assembly 50 comes into abutment with the stock, the pressure within the hydraulic system builds up sufficiently to open sequence valve 74 and the hydraulic pressure is routed to actuator 31 in such a direction as to cause the knife assembly 20 to begin its downward movement.

When the eccentric member 34 reaches the bottom of a cycle (approximately 180°), the flow of oil through actuator 31 is reversed and. thus, the knife proceeds upwardly. When the knife reaches its upward, at rest position, the clamping assembly 50 is raised until it reaches its limit, thus completing the cycle.

Should it become desirable to lower the clamp at low pressure for subsequent cuts, the operator simply inputs the pressure settings for each cutting based on the width of stock. That is, the more narrow the stock 1 to be cut as seen in the series of FIGS. 6-8, the less clamp pressure necessary. For example, the strip 2 in FIG. 7 requires less clamp pressure than the parent stock in FIG. 6. Further, the end size sheet 3 in FIG. 8 requires less pressure than the strip 2 in FIG. 7 as the width of sheet 3 is narrower than the width of strip 2. Excess clamp pressure causes disfiguration to the end size sheet 3. The control computer 200 then limits the flow through control valve 220.

The control computer 200 algorithms are relatively simple to one skilled in the art and will not be elaborated upon here. The parameters for the hydraulic and electrical circuits and the torque characteristics of the particular hydraulic actuator utilized will depend, of course, on the particular environment in which the cutter is to operate. By suitable matching of the parameters of the control valve 220 and the sequencing valve 74, the system will complete the preset clamping pressure prior to diversion of the pressure to the actuator 31 and, thus, initiation of the cutting stroke. Each of these operations are performed under the motivation of

hydraulic pressure from an identical source and, thus, the pump 62 and its associated hydraulic system are utilized constantly throughout the cutting cycle.

The hydraulic actuator, in the preferred embodiment of this invention, has been illustrated as running in a first direction to bring the knife toward the table and in a second direction to withdraw the knife from the table. It will be readily apparent to those skilled in the art, however, that other operational schemes can be utilized by proper design of the hydraulic and electrical circuits. It might be desirable, for example, to rotate the actuator in a first direction through an angle sufficient to bring the knife into and withdraw it from cutting relationship with the paper on the table. During the subsequent cycle, in this mode of operation, the actuator would rotate in the opposite direction to again bring the knife into and withdraw it from cutting relation with the paper on the table. The propriety of such an actuation scheme will depend, of course, on the particular operation environment.

While a preferred embodiment of this invention has been illustrated in detail, it will be readily apparent to those skilled in the art that other embodiments may be conceived and fabricated without departing from the spirit of this specification and the accompanying drawings. Such other embodiments are to be deemed as included within the scope of the following claims unless these claims, by their language, expressly state otherwise.