Title:
FLUIDIC CONTROL FOR MATERIAL CUTTER
United States Patent 3648552


Abstract:
A material cutting device having hydraulic actuating means for moving a clamp into engagement with the material and for moving a knife through the material after it is clamped is controlled by a fluidic circuit including a four input NOR gate connected to a pair of manually operated switches. A time delay circuit is included between the switches and the NOR gate to allow time delay in the operation of the switches by the operator.



Inventors:
BRADLEY EDGAR R
Application Number:
05/055657
Publication Date:
03/14/1972
Filing Date:
07/17/1970
Assignee:
HARRIS-INTERTYPE CORP.
Primary Class:
Other Classes:
72/2, 83/380, 83/390, 83/544, 83/639.7
International Classes:
B26D1/08; B26D7/02; (IPC1-7): B26D7/24
Field of Search:
83/68,380,390,544,639,926G 72
View Patent Images:
US Patent References:
3173327Knife bar stop1965-03-16Rupp
3118338N/A1964-01-21Barley
3054317Hydraulically powered shear1962-09-18Castle, Jr.
2545549Safety control for machines1951-03-20Guill et al.



Primary Examiner:
Yost, Frank T.
Claims:
What is claimed is

1. In a material cutting apparatus including

2. The apparatus of claim 1 further including means for returning said clamp and said knife to their initial positions in the event either one or both of said fluidic sensors is released by the machine operator prior to the completion of the cutting operation.

3. The apparatus of claim 1 further including time delay means for delaying the actuation of said knife to permit said clamp to engage the material prior to cutting.

4. The apparatus of claim 1 wherein said fluidic sensors includes a pair of normally open fluidic sensors arranged to be closed upon manual actuation, said sensors being connected to said gate means for energization of said fluidic control circuit and to provide for deenergization of said control circuit upon the opening of either one or both of said sensors to stop the movement of said knife into said material.

5. The apparatus of claim 1 wherein said pair of fluidic sensors are normally open fluidic switches arranged to be closed upon manual actuation thereof, said apparatus further including means for preventing said control circuit from actuating said clamp and said knife unless said switches are released following a previous actuation of said control circuit.

6. The apparatus of claim 1 further including means for preventing continued operation of said control circuit in the event of interruption of said power supply.

7. The apparatus of claim 1 further including a means for holding said clamp and said knife in a down position.

8. The apparatus of claim 1 further including a means for returning said knife to initial position in the event said knife is stalled during cutting cycle.

9. The apparatus of claim 1 further including a second pair of fluidic switches connected to said knife actuating means to prevent movement of said knife during the removal and change of said knife.

10. The apparatus of claim 1 further including means for continuing the operation of said control circuit after said fluidic sensors have been actuated simultaneously or within said time limits upon the continued actuation of one of said fluidic sensors.

Description:
BACKGROUND OF THE INVENTION

In material cutting devices, such as paper cutters, the sequence of the cutter operation is often controlled by solenoids positioned in hydraulic lines through which hydraulic pressure is supplied to cylinders for moving a clamp into engagement with the material and for moving a knife through the material once it is clamped. Hydraulic devices are used since substantial forces are necessary to effect the cutting of the material. Since great forces are employed, safety devices are used to prevent injury to the machine operator including control switches which must be actuated by the operator using both hands, and in this way assurance is provided that the operator's hands will not be under either the clamp or the knife as these components are lowered into position.

The control devices used in prior art machines, such as shown in U.S. Pat. No. 3,118,338, use solenoid controlled valves and electrical switches to control the sequence of operation. The sequence must be such that after the operator has used both hands to close the cycle start switches, the clamp first engages the material to hold it securely, and thereafter the knife cuts through the material. Once the material is cut, both the knife and the clamp are returned to their previous position in preparation for a new cutting cycle.

SUMMARY OF THE INVENTION

This invention relates to a novel control circuit for use with paper cutters employing fluidic logic devices for insuring that the operator's hands are away from the clamp and knife prior to initiating the cutting cycle, and for controlling the sequence of the machine operation. The fluidic control circuit also provides safety and control features which permit the knife to be replaced while insuring that the knife actuating mechanism is not inadvertently triggered.

Thus, the fluidic control circuit for controlling the operation of the clamp and knife of a material cutting apparatus includes a pair of fluidic switches accessible to the operator which, when actuated, cause the clamp to engage the material and the knife to cut the material. The fluidic switches preferably are connected to fluidic devices which have first and second outputs controlled by the actuation of the switches. Time delay circuits are connected between the first output of each fluidic device and a NOR gate, while the second outputs are connected directly to the NOR gate. The NOR gate is therefore responsive to the actuation of the fluidic sensors and will provide an output only if the switches are operated simultaneously or within the time limits established by the time delay means. The output of the NOR gate is applied to other fluidic devices which cause the clamp to engage the material and the knife to cut the material.

Accordingly, it is an object of this invention to provide an improved cutting machine of the type described wherein fluidic devices are used to control the sequence of machine operation and wherein one of said devices is a four input NOR gate which provides an output to initiate a cutting cycle only if the operator uses both hands to actuate safety switches; and to provide a unique fluidic control circuit wherein time delay means are included between the operator actuated switches and the NOR gate to permit some variation in the actuation time of the switches without inhibiting the operation of the cutting apparatus.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a material cutter on which the fluidic control circuit of this invention may be used; and

FIG. 2 is a detailed schematic diagram of the fluidic control circuit of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, a material cutting apparatus 10 includes a table 12 for supporting a stack of material 13 which is moved on the table by a backgauge 15. The material 13 is held securely against the table 12 by clamp 17 for cutting by knife 18.

Since considerable force is used to hold the material 13 and to move the knife through the material, safety means are provided to prevent the operator's hands from being in the vicinity of either the clamp 17 or the knife 18 during use. The safety means includes two hand operated switches 20 and 21, both of which must be actuated and held by the operator before the machine cycle can be initiated.

Hydraulic means are used to operate both the clamp and the knife. In the embodiment of the invention shown herein, the clamp is moved by a hydraulic motor 25 which is connected through a link 26 and arm 27 to a shaft 30 extending beneath the table 12. Draw bars 31, attached to the clamp 17, are connected to the shaft 30 through links 33 and arms 34. The shaft 30 is rotated in a clockwise direction, as shown in FIG. 1, to urge the clamp 17 toward its uppermost position by hydraulic pressure through valve 35. When hydraulic pressure is applied to the motor 25 through valve 36, the shaft 30 will rotate in a counterclockwise direction and move the clamp 17 downwardly into engagement with the material 13. The magnitude of the force exerted on the material may be adjusted by pressure regulator 38.

The knife 18 is drawn into and through the material 13 by the operation of the hydraulic motor 40 which is connected to the knife through an arm 41 and connecting rod 42. The position of the knife 18 is sensed by an up sensor 45 and a down sensor 46. The function of these sensors will be explained in detail later.

Power to the hydraulic motor 40 is supplied by a pump 50 through one of two valves 51 and 52. As will be explained, valves 51 and 52 are opened to move the knife after the clamp securely holds the material in place and after the operator has actuated the switches 20 and 21.

Certain sequences of operation are followed in a safe and efficient material cutting device. In this invention the clamp 17 must precede the knife 18 in its downward movement, and both operator actuated switches 20 and 21 must be held closed until the knife 18 reaches the bottom of its stroke. Both switches 20 and 21 must be then released to allow the knife and clamp to return to their uppermost positions. If control switches 20 and 21 are released during the down cycle of the knife 18 and the clamp 17, the clamp will continue down to engage the material, and then stop. The knife will stop automatically any time either one of the control switches 20 and/or 21 is released.

The invention also includes means for holding both the knife and the clamp in a down position by an appropriate switch 55. If the knife becomes stalled during cutting, the knife may be returned to the top of its stroke by actuating an appropriate control switch 56. Control switches 57 and 58 are provided to prevent the knife from moving downwardly during the changing of the knife blade. The clamp circuit is controllable independently of the knife circuit so that the clamp pressure can be adjusted by the operator according to the type and width of material to be cut.

The fluidic elements shown in FIG. 2 are of conventional design, and the symbols used to represent these elements are also well known to those skilled in the art.

Referring now to FIG. 2 which is a schematic diagram of a fluidic circuit controlling the operation of the material cutting apparatus shown in FIG. 1, the hand held switches 20 and 21 are spring biased to the normally open position. Thus, when these switches are closed by the operator, this will be detected by back pressure switches 63 and 64, respectively. Back pressure switches 63 and 64 are devices which normally receive an air supply from a source Ps and direct the air through the O2 output. Closing the input port S will cause the output to switch from O2 to O1, and this occurs upon the actuation of the switches 20 and 21.

The O2 outputs of both back pressure switches 63 and 64 are connected directly to a fluidic NOR-gate 65. The NOR gate is designed to provide an output at O2 when no control signal is applied to its inputs. If a control signal is applied to any one of its inputs, a signal will be present at its O1 output. Thus, prior to the closure of the switches 20 and 21, the NOR-gate 65 will be provided with an output from the O2 outputs of both back pressure switches 63 and 64. Only if both switches are closed will an input be removed from the NOR-gate 65.

Both the O1 outputs of back pressure switches 63 and 64 are applied as inputs to the NOR-gate 65 through time delay circuits which include resistors R1 and R2 and capacitors C1 and C2. Therefore, for the time interval determined by these time delay circuits, NOR-gate 65 will provide an output signal from its O2 output to a fluidic flip-flop 66. This flip-flop is a bistable device which will respond to a control signal to provide an output which will continue until a different control signal is received. In this case, an input at control port C1 will cause a signal from output port O1 which will continue until an input is sensed at control port C2. The O1 output of flip-flop 66 is tied to the control input of fluidic OR-gate 67, and the output from this OR gate is connected to a clamp down transducer 70, which converts the fluidic control signals into the proper form so that hydraulic pressure will be applied to motor 25 through valve 36 and move the clamp 17 into engagement with the material 13.

To summarize, therefore, simultaneous closure of switches 20 and 21, or closure within the time limits established by the time delay circuits R1, C1 and R2, C2, will cause a momentary output from the NOR-gate 65 to the trigger flip-flop 66 causing the clamp down transducer to energize thus moving the clamp from its uppermost position into engagement with the material 13.

An output signal from O2 output of NOR-gate 65 is also applied to control port C1 of fluidic flip-flop 72, causing its O1 output to apply a control signal to fluidic OR-gate 73 which will actuate the knife down transducer 75 thus starting the knife to move through the material 13. The knife down transducer controls the valve 51 to supply fluid to the motor 40 and thus move the knife 18 through the material. In the preferred embodiment of the invention, it has been found that the clamp will engage the material securely prior to the knife starting through the material. In other embodiments, it may be desirable to provide a time delay circuit R4, C4 between the O1 output of flip-flop 72 and OR-gate 73 to insure that the clamp engages the material before the knife.

When the knife reaches the bottom of its stroke, this is detected by a down sensor 46 which causes an output from back pressure switch 78 to be applied to the C2 control port of flip-flop 80. At this time, an output from O2 of flip-flop 80 will be applied to control port C2 of flip-flop 72 switching this flip-flop off and deenergizing the knife down transducer 75, and at the same time the signal will be applied to the control port C1 of OR-gate 82, and its O1 output will trigger inhibited OR-gate 83 which will energize the knife up transducer 85 which, in the embodiment shown, controls valve 52 (FIG. 1). The inhibited OR-gate 83 is a device wherein a signal on either control port C1 or C3 may be overridden by a signal on control input C2.

When the knife reaches the top of its stroke, it is detected by an up sensor 45 which is connected directly to back pressure switch 90. The O1 output of the back pressure switch is connected to the inhibit control input C2 of the inhibited OR-gate 83, thus deenergizing the knife up transducer 85. At the same time, the O1 output of back pressure switch 90 provides an input to a fixed one shot 92 which is a device providing an output pulse from its output O1 for a fixed duration, typically 10 milliseconds, regardless of the duration of the control signal beyond the fixed duration. An output from the fixed one shot 92 is applied to flip-flop 66, thus deenergizing the clamp down transducer 70 and allowing the clamp to return to its original position through the action of the hydraulic motor 25 and control valve 35. Thus the clamp does not release the material until after the knife has reached the top of its stroke. The output from fixed one shot 92 is also applied to the C1 input of flip-flop 80 thus removing the knife up signal which will require the operator to recycle the cycle control switches 20 and 21 before another clamping and cutting cycle can be executed.

A circuit is also provided through latching loop OR-gate 95 which holds control signals on flip-flops 72 and 80 to prevent them from switching in case of failure of the power supply or in the event that the power supply line becomes pinched, closed or severed. This device also sets the flip-flops 72 and 80 in a predicted startup position. A latching loop OR gate, when initially supplied with power, will provide a signal at its O2 output and when an input signal is thereafter applied to control port C1, its output will switch to O1, and a restriction R3, equivalent to a two nozzle load, will force part of the signal to the control port C3, thus providing a latching input signal. This latching signal will cause the output of the gate to remain at O3 when the signal at control port C1 is removed. An input signal at control port C2 will cause the output signal to switch back to output C2 and deactivate the latching loop.

If either or both of the control switches 20 or 21 are released during a cutting cycle, a control signal from the O2 outputs of their respective back pressure switches 63 or 64 would be applied to the control input of NOR-gate 97 and will also immediately terminate the output from NOR-gate 65. An output from NOR-gate 97 is connected to the inhibit input of gate 73 to deenergize the knife down transducer 75, stopping the knife motion instantaneously. The knife may be continued through a stroke by reclosing both control switches 20 and 21, or it may be returned to the top of its stroke by closing the knife clamp and return switch 56 which is connected to back pressure switch 101, the output of which supplies a control input to flip-flop 83 controlling the knife up transducer 85.

In the event the knife is stalled or becomes wedged in the material during the cutting cycle, it may be returned to the top of its stroke by closing the knife and clamp return switch 56. This causes a signal from the O2 output of the back pressure switch 101 to be applied to the control input C3 of inhibited OR-gate 83, and at the same time applies a control input to the latching loop OR-gate 95 which, as explained above, causes the clamp down transducer 70 and the knife down transducer 75 to become deenergized and allow the clamp and knife to return to their uppermost positions.

Preclamping of the material may also be accomplished by momentarily closing switches 20 and 21 for a time sufficient to lower the clamp. Since, in the preferred embodiment of the invention, there is an inherent time delay between the lowering of the clamp and the lowering of the knife, it is possible to allow the clamp to engage the material and then to release the switches 20 and 21 prior to the knife starting its downward movement. In other embodiments where a time delay circuit 76 is included between the flip-flop 72 and the knife down transducer 75, it is apparent that releasing the switches 20 and 21 prior to the expiration of the time delay will accomplish the same purpose.

The circuit shown in FIG. 2 also includes provisions for changing the knife blade. In the preferred embodiment of the invention, this is accomplished by first lowering the knife and removing those bolts holding the knife blade 105 to the support 106 which are not accessible when the knife is in the up position. Thereafter, the knife is raised and the remainder of the bolts removed with the blade being lowered by means of the knife change knobs 115 and 116 (of the switches 57 and 58) added to the clamp.

In operation, switch 55 is moved from the "normal" position (normally open) to the "stop down" position thereby causing an output from the back pressure switch 111 to be applied to the inhibit input of inhibited OR-gate 82. This prevents the energization of the knife up transducer 85. Closure of switches 20 and 21 will thereafter cause the knife transducer 75 to be energized and move the knife to its down position where some of the blade retaining bolts can be removed.

The switch 55 is then returned to the "normal" position causing the knife up transducer 85 to energize and return the knife to the top of its stroke. Moving switch 55 to the normal position removes the inhibit signal from inhibited OR-gate 82. Since the down sensor 46 is closed, an output signal is applied from the O1 output of back pressure switch 78 to the C2 input of flip-flop 80 and an output signal from the O2 output of the flip-flop applied to the C1 input of inhibited OR-gate 82 will be effective to switch the inhibited OR-gate 83 to energize the knife up transducer 85. Switches 20 and 21 are then momentarily closed to lower the clamp, but not the knife, and the knife change knobs 115 and 116 are removed and manually installed on the clamp. These knobs serve two functions, the first is to prevent outputs from back pressure switches 117 and 118 from being applied to NOR-gate 97 which, as previously explained, controls the knife down transducer 75, and the second purpose is for mechanically supporting the knife blade on the clamp to facilitate its installation and removal.

The knife change knobs 115 and 116, after physically installed on the clamp, and then brought into engagement with the knife by adjusting the hydraulic pressure on the clamp so that the clamp up pressure is slightly greater than the weight of the clamp allowing the clamp to rise slowly to its uppermost position. The remainder of the retaining bolts are then removed and the old knife lowered to the table and a new knife installed. The bolts which are inaccessible when the knife is in the up position are also installed at this time. Removing the knife change knobs 115 and 116 from the clamp allows the knife to then be moved to its down position where the remainder of the retaining bolts are installed.

For some types of operations, both control switches may be actuated to initiate the cutting cycle, and after the knife has begun its downward movement, either one of control switches may be held and the other released while allowing the knife to continue its complete cycle of operation. This may be accomplished by removing the connection 120 for two hand start, left hand hold or removing the connection 121 for two hand start, right hand hold.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.