GB2072092A - Press with a stroke terminating means - Google Patents

Abstract

A press with a stroke terminating means which is operative to terminate a stroke upon completion of an electrical circuit between two contact members 14 and (16). One contact member (16) moves with a movable platen and one of the contact members 14 is movable on a slide towards or away from the other contact member and is lockable in position on the slide by locking means 20 to thereby set the position at which an approach stroke will terminate. The member 14 comprises a rod supported in a holder 22 on a spring 32 and is provided with an electrical connection 28. The holder 22 is urged upwards by a spring 34 and passes through a hole 40 in a lever 36 which is pivotal between a position in which it locks the holder against vertical movement and a position in which the holder can pass freely through the hole 40. <IMAGE>

Description

SPECIFICATION Press with stroke terminating means This invention is concerned with a press with stroke terminating means operative to terminate an approach stroke of the press.

Many different kinds of stroke terminating means are known for presses. Among these are those which rely upon movement of the platens causing comple tion of an electrical circuit either through the wo rk piece between the platens or through a cutting tool which is pressed through the workpiece, for example to cut a shape outtherefrom. This kind of stroke ter minating means suffers from the disadvantages that, if the workpiece is non-conductive a circuit cannot be made therethrough, while if the workpiece is con ductive, a circuit through the cutting tool is com pleted prematurely before the tool has cut through the workpiece.

It is an object of the present invention to provide a press with stroke terminating means which is opera tive to terminate an approach stroke of the press upon completion of an electrical circuit which is operative independently of whether the workpiece to be operated on by the press is conductive or non conductive.

The invention provides a press comprising a sup porting framework, two platens between which workpieces to be operated upon are positioned, the platens comprising a first platen supported bythe framework and a second platen mounted for move ment towards or away from the first platen, and moving means operable to move the second platen towards the first platen in an approach stroke of the press, the press also comprising stroke terminating means operative to terminal an approach stroke of the press upon movement of the second platen caus ing completion of an electrical circuit, the stroke terminating means comprising two contact mem bers, a first of which is mounted for movement with the second platen so that, during an approach stroke, the first contact member approaches the sec ond of the contact members, the stroke terminating means being operative to terminate an approach stroke upon the contact members coming into con tact and thereby completing an electrical circuit through the contact members, one of the contact members being mounted on a slide for movement towards or away from the other contact member, and the stroke terminating means also comprising locking means operable to lock said one of the contact members in position on its slide to thereby set the position at which an approach stroke will termi nate.

In order to facilitate setting of the stroke of the press, the second contact member is mounted on the slide which is on the framework of the press and is arranged to be engaged by the first contact member, during a stroke-setting approach stroke of the press in which the stroke terminating means is rendered inoperative, and to be moved by the first contact member until the second platen reaches the position at which it is desired to terminate a subsequent operative approach stroke, whereupon the locking means is operated to lock the second contact member in position on its slide.

To further facilitate setting of the stroke, the second contact member is spring-urged towards the first contact member so that, when released by the locking means, the second contact member moves towards the first contact member.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a press which is illustrative of the invention. It is to be understood that the illustrative press has been selected for description by way of example.

In the drawings: Figure 1 is a perspective view of the illustrative press; Figure 2 is an elevational view, on a larger scale that Figure 1, of part of the stroke terminating means of the illustrative press; and Figure 3 is a diagrammatic view of electrical circuitry of the stroke terminating means of the illustrative press.

The illustrative press comprises a supporting framework 4 (Figure 1) and two platens, a lower platen 6 and an upper platen 8, between which workpieces to be operated upon by the press are placed.

The lower platen 6 is supported by the framework 4 and the upper platen 8 is mounted on a head portion 9 which is mounted on a vertically movable column 10 for movement towards or away from the lower platen 6. The press also comprises moving means (not shown) operable to move the upper platen 8 towards the lower platen 6 in an approach stroke of the press or away from the lower platen 6 in a return stroke of the press. The moving means is hydraulic and operates to move the column 10 and therefore the head portion 9 and the upper platen 8. The moving means is operative to cause an approach stroke under high cutting pressure, when a solenoid valve SV1 (Figure 3) is energised alone, but to cause an approach stroke under low setting pressure, when the valve SV1 and a solenoid valve SV2 are energised together. A return stroke is caused by energisation of a solenoid valve SV3.

The illustrative press also comprises stroke terminating means 12 operative to terminate an approach stroke of the press upon movement of the upper platen 8 causing completion of an electrical circuit. The stroke terminating means comprises two contact members, one of which is in the form of a rod 14 and the other of which is formed by a shoulder 16 of the head portion 9 of the press which forms the upper platen 8. One of the contact members, namely the shoulder 16, is mounted for movement with the upper platen 8 so that, during an approach stroke, it approaches the rod 14.One of the contact members, namely the rod 14, is mounted on a slide for movement towards or away from the other contact member and the stroke terminating means 12 also comprises locking means 20 operable to lock the rod 14 in position on its slide to thereby set the position at which an approach stroke will terminate.

Upon the contact members 14 and 16 coming into contact thereby completing an electrical circuit through the contact members 14 and 16, the stroke terminating means 12 is operative to terminate an approach stroke of the press.

The slide on which the rod 14 is mounted is provided by a box 18 (Figures 1 and 2) attached to the framework 4 beneath the shoulder 16. The rod 14 is contained in a vertically-extending cylindrical holder 22. The cylindrical holder 22 has an electrically insulating plug 24 in each end thereof and the rod 14 extends through these plugs 24 so that it is insulated from the holder 22 and projects from each end of the holder 22. The lower portion of the rod 14 is screw threaded and, below the lower plug 24, carries three nuts 26 which secure an electrical connection 28 and a plate 30 of insulating material to the rod 14. The rod 14 is supported in the holder 22 on a spring 32 and is slidable downwards in the holder 22 against the action of the spring 32 which acts between the lower plug 24 and a shoulder on the rod 14.The spring 32 allows the upper portion of the rod 14to yield into the holder 22. It should be noted that the spring 32 is spaced from the holder 22 and does not make electrical contact therewith.

The holder 22 is slidable vertically on the box 18 and is urged upwardly by a spring 34 which acts between the insulating plate 30 and a lever 36 of the locking means 20 mounted on the box 18 for pivoting movement about a pivot pin 38. The lever 36 has a hole 40 therethrough through which the holder 22 passes. The lever 36 is pivotal between a locking condition (shown in Figure 2) in which the lever 36 engages the holder 22 in the hole40 and holds it locked against vertical movement and a release condition (reached by pivotal movement anti-clockwise as shown in Figure 2) in which the holder 22 can pass freely through the hole 40. The stroke terminating means 12 also comprises a solenoid S1 mounted in the box 18 and operable when energised to move the lever 36 into its release condition by pushing it up against a stop 42 mounted on the box 18.

The illustrative press also comprises two control buttons 44 (Figure 1 and 3) mounted on the head portion 9 by which approach strokes of the press are controlled. To initiate an approach stroke of the press, an operator thereof must touch both buttons 44 simultaneously so that a very small current flows through his body between the buttons 44. The con nections to the buttons 44 are shown in Figure 3.

As shown in Figure 3, one of the buttons 44 is connected to an earth Line L1 while the other is con nected to a line L2 which carries a positive D.C. voltage. When the buttons 44 are connected, they cause operation of an inverting amplifier Al and an amp lifier A2 causing both of them to produce a signal on their output. When operated, the inverting amplifier Al passes a pulse via a capacitor C1 to a NAND gate N1 and a signal to a three-input AND gate G1 The amplifier A2, when operated, also passes a pulse via a capacitor C2 to the NAND gate N1 and a signal to the AND gate G1.

When the NAND gate N1 receives two simultaneous pulses, indicating that both buttons 44 have been touched simultaneously, it removes the signal from its output which is connected to a flip-fiop formed by two NAND gates N2 and N3. The loss of this signal causes the flip-flop to alter its output to send a signal to the AND gate Gi to which it is connected. The AND gate G1 is now receiving signals on all its inputs and sends a signal to an amplifier A3 and a pulse via a capacitor C3 to a timer T1. The timerT1 does not react to this pulse which is a positive-going pulse but the amplifier supplies powerto the aforementioned solenoid valve SV1 so that the head portion 9 is moved downwards.

If the approach stroke is to be under high cutting pressure, only the valve SVl is energised, the valve SV2 which is also supplied with power by the amp lifierA3 being switched out of the circuit by a first set of contacts SS1 of a setting switch of the press.

However, if the approach stroke is to be under low setting pressure during which, as will be seen, the stroke terminating means 12 is rendered inoperative, the operator operates the setting switch to close the contacts SS1 before touching the buttons 44 and the valves SV1 and SV2 both receive power.

In an approach stroke under high cutting pressure, the downwards movement of the head portion 9 continues until either the operator releases the buttons 44 or the shoulder 16 contacts the rod 14. If the operator releases either of the buttons 44, the gate G1 loses one of its input signals and the amplifier A3 removes the power supply to the valve SV1; this arrangement is for safety. If the operator does not release the buttons 44, the shoulder 16 contacts the rod 14 thereby earthing it. The connection 28 of the rod 14 is connected via a second set of contacts SS2 of the setting switch to an input of the NAND gate N3 of the flip-flop and, when the rod 14 is earthed, the flip-flop changes its output removing the signal from the AND gate Gl.The AND gate G1 now signals the amplifier A3, which removes the power from the valve SV1 terminating the approach stroke, and sends a negative-going pulse to the timerT1 which starts. The timer T1 is also started if the buttons 44 are released during an approach stroke.

The timer T1 once started supplies powerto the aforementioned solenoid valve SV3 which causes the head portion 9 to move away from the lower platen 6. When the timer to times out, it removes the power supply from the valve SV3 and the head portion 9 comes to rest.

If the approach stroke is to be under low setting pressure, the contacts SS2 disconnect the rod 14 from the gate N3 so that contact between the shoul der 16 and the rod 14 will not terminate the stroke which must therefore be terminated by release of the buttons 44. Instead the contacts SS2 connect the gate N3 to the output of the timer Tl via a capacitor C3 so that, when the timerT1 times out the flip-flop will be re-set. The contacts SS1, as mentioned above, allow a power supply to reach the valve SV2 but they also allow a powersupplyto reachtile aforementioned solenoid S1 which is connected in parallel with the valve SV2.

Energisation of the solenoid S1, as mentioned above, releases the lock on the holder 22 which thereupon moves upwards under the action of the spring 34 until either the rod 14 contacts the shoulder 16 orthe spring 34 reaches equilibrium. As the head portion 9 descends, the shoulder 16 contacts the rod 14 (as mentioned above this does nottermi- nate the stroke) and subsequent movement of the head portion 9 causes the holder 22 to be moved downwards by the shoulder 16. When the operator considers that the upper platen 8 has reached the position at which it is desired to terminate a subsequent operative approach stroke, he releases the buttons 44 whereupon the solenoid valves SV1 and SV2 are de-energised as is the solenoid S1 causing the approach stroke to terminate and the locking means 20 to operate to lock the holder 22 and hence the rod 14 in position on its slide.

The stroke terminating means of the illustrative press can be seen to be operative independently of whethertheworkpieceto be operated upon by the press is conductive or non-conductive.

Claims (7)

1. A press comprising a supporting framework, two platens between which workpieces to be operated upon are positioned, the platens comprising a first platen supported by the framework and a second platen mounted for movement towards or away from the first platen, and moving means operable to move the second platen towards the first platen in an approach stroke ofthe press, the press also comprising stroke terminating means operative to terminate an approach stroke of the press upon movement of the second platen causing completion of an electrical circuit, the stroke terminating means comprising two contact members, a first of which is mounted for movementwith the second platen so that, during an approach stroke, the first contact member approaches the second of the contact members, the stroke terminating means being operative to terminate an approach stroke upon the contact members coming into contact and thereby completing an electrical circuit through the contact members, one of the contact members being mounted on a slide for movement towards or away from the other contact member, and the stroke terminating means also comprising locking means operable to lock said one of the contact members in position on its slide to therebysetthe position at which an approach stroke will terminate.

2. A press according to claim 1 wherein the second contact member is mounted on the slide which is on the framework of the press.

3. A press according to claim 2 wherein the first contact member is provided by an abutment of a portion of the press which forms the second platen.

4. A press according to either one of claims 2 and 3 wherein the second contact member is arranged to be engaged by the first contact member during a stroke-setting approach stroke of the press in which the stroke terminating means is rendered inoperative, and to be moved by the first contact member until the second platen reaches the position at which it is desired to terminate a subsequent operative approach stroke, whereupon the locking means is operated to lock the second contact member in position on its slide.

5. A press according to claim 4 wherein the second contact member is spring-urged towards the first contact member so that, when released by the locking means, the second contact member moves towards the first contact member.

6. A press according to any one of claims 1, 2, 3, 4 and 5 wherein said one of the contact members is contained in a holder from which it is electrically insulated and on which the locking means acts, the contact member being supported in the holder on a spring.

7. A press substantially as hereinbefore described with reference to and as shown in the accompanying drawings.