GB2051651A

GB2051651A - Die-cutting machine

Info

Publication number: GB2051651A
Application number: GB8018816A
Authority: GB
Original assignee: Atom SpA
Current assignee: Atom SpA
Priority date: 1971-09-01
Filing date: 1980-06-09
Publication date: 1981-01-21
Also published as: GB2051651B; FR2151524A5

Description

1 GB 2 051651 A 1

SPECIFICATION

Die-cutting machine This invention concerns a die-cutting machine 70 having a head lowerable at a fast rate hydrau lically and raisable hydraulically.

The machine can comprise a hydraulic cir cuit connected to a supply of pressure fluid and to first and second chambers at a base of a lowerable and raisable column carrying the head, said hydraulic circuit comprising a con trol valve actuable by electric operating means, said control valve having a slide which is slidable in a body of the control valve to establish a fluid communication between the supply an a first conduit which opens into the first chamber for raising the column and to establish fluid communication between the supply and a second conduit which opens into the second chamber for lowering the column.

Such a machine can be of the flag type in which the head or flag can be pivoted about the vertical axis of the column.

A flag type die-cutting machine has a base with a work level carrying a hollow punch, and a side upright in which slides the column carrying at its upper end the head having an undersurface constiuting a striking surface to co-operate with the punch. A control device which raises and lowers the head normally comprises the hydraulic circuit filled through a feed pump with working fluid which after entering the control valve, is communicated by that valve to one or other of the first and second conduits which lead into the first and second cylindrical chambers at the lower end or base of the column. The control valve is actuated by an electric circuit which changes the energy state of an electromagnet to cause movement of the slide in the control valve to determine which of the conduits receives pressurised fluid.

One of the major drawbacks in a flag type die-cutting machine, which has a detrimental effect on productivity, is the dead time of the head downstroke and raising phases. In reality, since the cutting phase (i.e. the phase when the head is pressing the material to be cut against the punch) is the working phase of the die-cutting machine, other dead times exist, e.g. the pivoting or angular displacements of the head about the column axis to move the head nearer or further away from the hollow punch and the time required for an 120 operator to replace the cut material, for example a piece of leather, by new material. Strictly speaking, the dead time of head raising may be considered inevitable, if one con- siders that during the head raising phase, the operator is free to rotate the head in the direction in which the hollow punch is moved away.

Therefore, if it is desired to reduce dead time in a die-cutting machine, one way is to reduce the time taken to lower the head towards the hollow punch.

Another drawback in control devices in known die-cutting machines is the need to provide a respective end of lowering stroke motion for each type of hollow punch used, i.e. a suitable end of stroke motion compatible with the height of the hollow punch used. When punches of low height are used after higher punches or vice versa, the end of lowering stroke motion must be adjusted each time by means of a potentiometer provided in the electric control circuit. If this is not done and a low punch used after a high one cutting will not be complete, while, vice versa, if a high punch is used after a low one, the punch will be driven by the head into a block normally provided on the work level.

According to the invention there is provided a die-cutting machine having a head lowerable at a fast rate hydraulically and raisable hydraulically, comprising a hydraulic circuit connected to a supply of pressure fluid and to first and second chambers at a base of a lowerable and raisable column carrying the head, said hydraulic circuit comprising a control valve actuable by electric operating means, said control valve having a slide which is slidable in a body of the control valve to establish a fluid communication between the supply and a first conduit, which opens into the first chamber for raising the column and to establish fluid communication between the supply and a second conduit which opens into the second chamber for lowering the column, a sequence valve being included in said first conduit, a third fluid conduit branching from said second conduit near to the second chamber, said third conduit opening at its other end into a third chamber in which a piston slides, and said piston carrying a mobile contact of a pressure switch connected to the electric operating means.

It is possible to construct such a machine to cut material so that the head is lowered relatively fast until it touches the material on the punch whereupon the approach speed of the head is slowed automatically irrespective of the height of the punch, thus eliminating the need to make an adjustment to vary the end of stroke motion each time a punch is substituted for one of a different height.

Advantageously the sequence valve comprises a second slide which slides in a body of the sequence valve to establish communication between first and second portions of the first conduit through a fourth chamber in the sequence valve and respectively interrupt communication between the fourth chamber and a discharge fifth conduit from the sequence valve, a bore with a blind end extends axially of the second slide from one end of the slide, the first portion of the first conduit leads from the control, a fifth conduit leads from the first portion and opens into the sequence 2 GB2051651A 2 valve to communicate with the blind ended bore, at the other end of the second slide the slide and body of the sequence valve define a fifth chamber in which opens a sixth conduit which opens at its other end into the control valve at substantially the same position along the control valve as the second inlet conduit opens into said control valve.

Preferably a working thrust surface on said other end of the second slide is larger than that provided by the blind end of the bore.

Because it is possible to construct the aforesaid machine so the head has a fast downstroke this increase in speed can result in increased productivity. Also the provision of the pressure switch enables the machine to be constructed so that the downwardly moving head can come smoothly to rest on the punch. 20 The machine may also be constructed so that hydraulic pressure in the various conduits, is less than the pressure in the hydraulic circuits in known die-cutting machines. This makes it possible to work with less stress and use smaller pumps and propulsors with consequent economic advantages. The invention will now be further described, by way of example, with reference to the accompanying drawings in which:30 Figure 1 is a side view partly in section of a 95 die-cutting machine formed according to the invention; Figure 2 is a schematic diagram on an enlarged scale of the hydraulic and electric control in the machine in Fig. 1 during the raised head supporting phase; Figure 3 is a view of the arrangement in Fig. 2 during the fast approach phase of the head towards the punch; Figure 4 is a view of the arrangement in Fig. 2 during cutting of material on the punch; Figure 5 is a view of the arrangement in Fig. 2 during the head raising phase; Figure 6 is a diagrammatic sectional view on an enlarged scale of the control and sequence valves in Figs. 2 to 5, and Figure 7 is an enlarged sectional view of the base of the column in Fig. 1. With reference to the drawings a flag type die-cutting machine 1 has a base 2, carrying a work support 3 on top of which is located a work level upon which the sheet material is arranged, e.g. shoe leather, and a hollow punch used to cut the material A tubular upright 5 rises from the base 2. A tubular column 6 slides in the upright 5 and supports a flag or head 7 having a striking surface 8.

The head 7 can rotate around the axis of the column 6, and move vertically with the column to approach or move away from the punch 4 as the column is raised or lowered by means of an operating device shown in vari ous phases of its operation in Figs. 2 to 5.

The operating device comprises a hydraulic 130 circuit indicated generally at 9. One end of the hydraulic circuit 9 is connected to a feed pump 10 and the opposite end to a lower end or base 6a of the column 6.

A control valve 11 is provided in the hydraulic circuit 9. The control valve 11 is operated by an electric control 12 and is provided with a slide 13 disposed in body 14 of the valve 11 to plape a feed conduit 15 from the pump 10 into fluid connection with a first conduit 16 and a second conduit 17 which open into the base 6a of the column 6.

As shown in Fig. 7 the column 6 has a hollow base 6a with an internal annular pro- trusion 6b which slides along a stationary piston 18 which makes fluid tight sealing contact with the protrusion. The piston 18 is tightly connected by an annulus 19 to the lower end of the upright 5.

At the foot of the base 6a is a disc-shaped closing element 20 with a central hole to permit the column to slide along the piston 18 in a fluid tight manner. In a position between the annular protrusion 6b and the closing element 20, the piston 18 has an external annular protrusion 21 with a groove 22 holding an annular seal 23 over which the inner surface of base can slide in fluid tight manner. The combination of the piston 18 with its protrusion 21 and the protrusion 6b and the closing element 20 defines an upper cylindrical chamber 24 and a lower cylindrical chamber 25.

The conduit 17 opens into the lower cylin- drical chamber 25 through an end section 1 7a axially machined in the body of the piston 18 parallelly to an end section 1 6a of the conduit 16 which opens into the upper chamber 24.

The undersurface of the protrusion 6b exposed to the interior of chamber 24 is a working thrust surface on the column 6 of less area than the working thrust surface provided by the upper surface of the element 20 exposed to the chamber 25.

Near to the chamber 25 a conduit 26 branches from the conduit 17. At its other end the conduit 26 opens into a cylindrical chamber 27 in a body of a pressure switch 28. A small piston 29 slides in a fluid tight manner in the cylindrical chamber 27, and is coaxially extended at one end by a rod 30 carrying, at its free end, a mobile contact 31 of the pressure switch 28.

A sequence valve 32 in the conduit 16 has a valve body 33 containing a slide 34. In the drawings the valve body 33 is formed in one piece with the body 14 of the control valve 11, but the bodies 14 and 33 may be separ- ated if desired.

In Fig. 6 the slide 13 of the control valve 11 mainly consists of a small cylindrical shaft with a large number of annular protrusions or lands 35, 36, 37, 38 and 39 located in a substantially cylindrical bore 40 in the body p 3 GB2051 651A 3 14 of the control valve 11. Internal annular protrusions of the body of valve 14, indicated at 41, 42, 43, 44 and 45, protrude from the wall of bore 40. On top of the valve body 14 is a hollow closing element 46, inside which is an annular portion 46a in which slides a shank 47 extending from the slide 13.

A return spring 48 extending around the shank 47 is kept in position by a nut 49 screwed on the free end of the shank.

In the valve body 14 are a discharge con duit 50 and a conduit 51 which opens into the bore 40 at the same level as the conduit 17.

The slide 34 (Fig. 6) of the sequence valve so 32 mainly consists of a small cylindrical shaft with a number of annular protrusions or lands indicated at 52, 53, 54 and 55, and is housed in a substantially cylindrical bore 56 in the valve body 33. This bore is equipped with a number of annular protrusions indicated at 57, 58, 59 and 60 to determine, during axial displacement of the slide 34, combinations which make it possible to open 26 and close paths of the working fluid. In the top of the slide 34 is a blind ended bore 61 in which a return spring 62 is housed. A branch 6 3 from the conduit 16 opens into the blind bore 61. The lower parts of the slide 34 and valve body 33 form a cylindrical chamber 64 connected to the control valve 11 through the conduit 51.

It should be noted that the underside of the slide 34 in cylindrical chamber 64 presents a lower larger working thrust surface than an upper working thrust surface constituted by the blind end of the bore 61.

The electrical means 12 to operate the control valve 11 includes a pushbutton 65 which closes an electric circuit 66 in which an electromagnet 67 is included. When energised, the electromagnet 67 causes axial displacement of the slide 34 in the control valve 11. The electric circuit 66 also includes a relay 87 to interrupt the circuit when it experiences an electric signal initiated by closure of the end of stroke pressure switch 28. The occurrence of this electric signal of adequate strength to operate the relay 87 may be delayed, for a selectively variable predetermined time after closure of the pressure switch 28, by means of an adjustable potentiometer 68.

The electric circuit 66 is connected at termi- nal 69 to a fixed contact 70 of the end of stroke pressure switch 28, while the mobile contact 31 is connected to the electric circuit 66 at terminal 71.

Finally, it should be noted that the electro magnet 67 is de-energised for the duration of 125 the upstroke of the head 7. The upstroke of the head is stopped by the operation of the slide 13 attached to a cable 72 (Fig. 1). One end 72a of the cable is attached to the base of the slide 13. The opposite end 72b of the 130 cable is attached to the inside of a winding race of a braking pully 73 rotatably mounted on the head 7. The pulley 73 is manually rotated by an operating handle 74. The cable 72 passes about pulleys 75 and 76 rotatably mounted in the base 2 and about a pulley 77 rotatably mounted in the column 6. When the operating handle 74 is hand-turned in either direction, the end of the raising stroke of the head 7 is lowered or raised accordingly.

The operation of the die-cutting machine illustrated above will now be described, first referring to Fig. 2 which corresponds to the inoperative state, where the raised head 7 is in the head support phase. It may be seen from Fig. 2 that the pressure of the working fluid in the chamber 24 provides a cushion supporting the column 6 and head 7 in a predetermined raised position.

Through the feed conduit 15 fluid from the feed pump 10 enters the control valve 11 and from here is sent to the discharge conduit 50, through a self-adjusted restriction, to allow the fluid in the chamber 24 to maintain a pres- sure suitable to support the head.

As regards the sequence valve 32, the thrusts on the upper thrust surfaces of the slide 34 are augmented by the spring 62 (Fig. 6) and hold the slide down against the thrust exerted in the chamber 64. As may be seen from Fig. 6, in this phase the land 59 on the slide 34 and the annular protrusion 59 cooperate to form a closure which prevents the working fluid flowing through the discharge conduit 78.

In Fig. 3, the fast approach of the head 7 to the punch 4 (Fig. 1) is initiated by pressing the pushbutton 65 which closes the circuit 66 permitting energising of the electromagnet 67. The slide 13 in the control valve 11 is thus pushed down by the electromagnet and moves the land 38 to a co-operating position alongside the annular protrusion 44 to form a closure which prevents supply of working fluid to the discharge conduit 50. Accordingly the entire hydraulic circuit 9 becomes pressurised.

In this way, a pressure is established in the chambers 24 and 25 which, due to the difference in areas of the thrust surfaces on protru- sion 6b and element 20 (Fig. 6) leads to lowering of the column 6 supporting the head 7. During this phase, the fluid in the chamber 24 is thrust backwards along the conduit 16 and augments the supply by the pump 10 to the conduit 17 feeding the chamber 25. The constant pressure should also be noted in the chamber 27 in the end of stroke pressure switch 28, this chamber being connected in parallel with the conduit 17.

With reference to Fig. 4, when the descending striking surface 8 of the head 7 meets a resistance due, for example, to the presence of the hollow punch 4 on which is the relevant material to be cut, the pressure inside the hydraulic control circuit increases causing 4 GB2051651A 4 upward movement of the slide 34 in the sequence valve 32. Since the working thrust surface at the lower end of the slide 34 is of greater area than the upper thrust surfaces on that slide, the slide 34 is moved upwards to allow the conduit 16 to communicate with the discharge conduit 78 which causes the work ing fluid in the conduit 16 and chamber 24 to flow to the discharge conduit 78 and no longer augment the supply to the conduit 17.

At the same time, as shown in Fig. 4, due to the increased pressure in the hydraulic control circuit and therefore in the conduit 26 to the end of stroke pressure switch 28, the small piston 29 and the rod 30 carrying the mobile contact 31 are displaced upwards. As soon as the mobile contact 31 touches the fixed contact 70 the end of stroke pressure switch 28 initiates the occurence of the elec tric signal which, delayed by the pre-adjusta ble potentiometer 68 for a predetermined time which is a function of the thickness of the material being cut, energises the relay 87 to interrupt the electric circuit 66. At this inter ruption, and for reasons which will be under stood from consideration of the subsequent description with reference to Figs. 5 and 6, the head 7 continues to be lowered but ad vantageously at a much lower speed than that at which the head 7 initially approaches the hollow punch 4. This lower speed is because the fluid supply to the chamber 25 is no longer augmented by the discharge from the chamber 24. This lower approach speed makes more efficient and accurate cutting 100 possible.

In Figs. 5 and 6, when the electric signal delayed by the potentiometer 68 reaches the relay 87, through the interruption of the elec tric circuit 66, the electromagnet 67 is de energized. This allows the return spring 48 to move the slide 13 in the control valve 11 upwards again. The land 38 of the slide 13 co-operates with the annular protrusion 43 to form a closure which prevents the feed of working fluid to the conduit 17 from the pump 10. At the same time, the discharge conduit 50 remaining open, the fluid in the conduit 17 flows to discharge, provoking a fall in pressure in the chamber 64 which causes lowering of the slide 34 in the se quence valve 32. When lowered, this slide 34 opens the conduit 16 and isolates the dis charge conduit 78 therefrom. Thus working fluid is sent from the pump 10 through the control valve 11 and sequence valve 32 and open conduit 16 to pressurise chamber 24.

The column 6 carrying the head 7 is thereby lifted to return the head to the raised position in which the head is supported by the fluid cushion in chamber 24.

It should also be noted that in raising phase the fall in pressure in the conduit 17 is accompanied by an identical fall in the con- duit 26. This allows a return spring 79 to 130 urge the rod 30 downwards with consequent separation of the mobile contact 31 from the fixed contact 70.

Finally, with reference to Figs. 1 and 2, the upward return stroke of the head is stopped when the pull on cable 72 moves the slide 13 downwards until it takes the position shown in Fig. 2.

From the above, it will be understood that the lowered head 7 can approach the hollow punch 4 very quickly, carry out cutting smoothly and then be raised at a lower speed than the approach speed.

The fact that the lifting speed of the head is lower than the approach speed to the hollow punch does not create a serious drawback because the operator must angularly displace the head about the axis of the column 6 and both the lifting and angular displacement can be carried out simultaneously without prolonging the working time involved.

Claims

1. A die-cutting machine having a head lowerable at a fast rate hydraulically and raisable hydraulically, comprising a hydraulic circuit connected to a supply of pressure fluid and to first and second chambers at a base of a lowerable and raisable column carrying the head, said hydraulic circuit comprising a control valve actuable by electric operating means, said control valve having a slide which is slidable in a body of the control valve to establish a fluid communication between the supply and a first conduit which opens into the first chamber for raising the column and to establish fluid communication between the supply and a second conduit which opens into the second chamber for lowering the column, a sequence valve being included in said first conduit, a third fluid conduit branching from said second conduit near to the second chamber, said third conduit opening at its other end into a third chamber in which a piston slides, and said piston carrying a mobile contact of a pressure switch connected to the electric operating means.

2. A die-cutting machine as claimed in claim 1, in which the sequence valve corn- prises a second slide which slides in a body of the sequence valve to establish communication between first and second portions of the first conduit through a fourth chamber in the sequence valve and respectively interrupt communication between the fourth chamber and a discharge fifth conduit from the sequence valve, a bore with a blind end extends axially of the second slide from one end of the slide, the first portion of the first conduit leads from the control, a fifth conduit leads from the first portion and opens into the sequence valve to communicate with the blind ended bore, at the other end of the second slide the slide and body of the sequence valve define a fifth chamber in which opens a sixth conduit i 1 GB2051651A 5 which opens at its other end into the control valve at substantially the same position along the control valve as the second inlet conduit opens into said control valve.

3. A die-cutting machine as claimed in claim 2, in which a working thrust surface on said other end of the second slide is larger than that provided by the blind end of the bore.

4. A die-cutting machine as claimed in claim 1, in which the base of the column is tubular and has an internal annular protrusion, a lower end of the base is closed by a closing element with a central hole through which a second piston extends into the base, the element is a slidable but substantially fluid tight fit on the piston, said piston has an external annular protrusion in sealing but sliding contact with an inner surface of the base of the column and the internal protrusion is in sealing but sliding contact with the second piston, the internal and external protrusions define opposite end of the first cylinder and the external protrusion and the closing ele- ment define opposite ends of the second chamber.

5. A die-cutting machine as claimed in claim 4, in which a working thrust surface exposed to the second chamber and acting on the column is larger than a working thrust surface exposed to the first chamber and acting on the column.

6. A die-cutting machine as claimed in claim 1, in which the electric operating means comprises an electric circuit including an electromagnet to actuate movement of the slide in the control valve, an electrical relay is connected to the end of stroke pressure switch to interrupt said circuit upon experiencing of an electric signal initiated by closure of the pressure switch contacts and variable potentiometer means interposed in an electrical conducting path between the relay and the pressure switch, the arrangement being such that the appearance of said signal at the relay can be delayed for a selectively variable time period after closure of the pressure switch contacts.

7. A die-cutting machine having a head lowerable at a fast rate hydraulically and raisable hydraulically, substantially as hereinbefore described with reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess Et Son (Abingdon) Ltd-1 9 8 1. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.