WO1992001171A2

WO1992001171A2 - Spring device

Info

Publication number: WO1992001171A2
Application number: PCT/GB1991/001162
Authority: WO
Inventors: Linval Rodney
Original assignee: Linval Rodney
Priority date: 1990-07-12
Filing date: 1991-07-12
Publication date: 1992-01-23
Also published as: GB9015337D0; WO1992001171A3; GB9300376D0

Abstract

A spring device (10) comprises a first piston (12) operable within a first cylinder (14), and a second piston (16) operable within a second cylinder (18). The interiors of the two cylinders (14, 18) are in communication such that a chamber (22) comprising pressurised gas is formed between the first piston (12) and the second piston (16). A second chamber (28) comprising pressurised gas is formed between the second piston (16) and the second cylinder (18). In use when a force is applied to move the first piston (12) into the first cylinder (14), the movement of the first piston (12) is resisted by the fluid in the chamber (22). This, in turn, causes the second piston to move against the resistance of the gas in the second chamber (28). The result is a resilient resistance to the depression of the first piston (12) and a storage of energy in the device. When the force is alleviated, the resilience of the device (10) urges the pistons (12, 16) to their rest positions.

Description

Spring Device

The present invention is concerned with spring devices and especially but not exclusively to spring devices for presses used in the formation of profiled metal panels.

Conventionally, profiled metal panels such as car body panels are pressed from a flat sheet of metal. The metal is placed on a profiled press plate. An upper press plate, with a complementary profile, is hydraulically or pneumatically lowered to form the profiled panel. Removing the newly formed panel from the press often proves difficult, especially when the shape of the profile is such that the panel tends to clasp the press-plate.

Various devices to facilitate the removal of the panel from the plate have been produced, these being often unreliable, expensive to maintain and incapable of functioning consistently and repetetively.

Further, the profiling of panels often requires shapes to be produced that cannot be conventionally provided within the press, for example apertures or small re-entrant formations.

It is an object of the present invention to provide an improved spring device suitable for use in presses.

According to the present invention there is provided a spring device comprising first and second pistons, a chamber between the pistons and containing compressible fluid, and resilient means operable to resist the second piston moving to increase the volume of the chamber, any movement of the first piston to reduce the said volume being resisted by a combination of the compression of the fluid and the resilience of the resilient means.

Preferably the resilient means is resiliently compressible. Preferably the resilient means is a fluid, preferably a gas which may be pressurised. Alternatively, the resilient means may be a mechanical spring.

The first piston may be operable within a first cylinder and, the second piston operable within a second cylinder. Preferably the first cylinder is of smaller diameter than the second cylinder and the first cylinder is located wholly or partly within the second cylinder. The second piston is preferably annular. The annular piston preferably encircles and is movable along the first cylinder. Preferably seal means is provided between the annular piston and the second cylinder whose sealing efficiency tends to increase with the pressures in the respective cylinders. The seal means may comprise upper and lower plates and a resilient seal sandwiched therebetween such that as the pressure in the cylinders increase, the plates are urged together and squeeze the resilient seal so that its outer surface is urged against the second cylinder.

Preferably the resilient means encircles the first cylinder. Preferably the resilient means is located in the second cylinder.

Preferably the first cylinder communicates with the second cylinder through at least one aperture formed in the wall of the said first cylinder, the said apertures allowing compressible fluid to pass therethrough during operation to provide communication between the pistons. Preferably the or each aperture is so located as to maintain communication between the cylinders during the whole range of movement of the pistons. Alternatively, the first and second cylinders may be remote from each other and interconnected by means of passages through which compressible fluid may pass.

Preferably valve means is provided to control communication of the first cylinder with a pressurised compressible fluid reservoir, so that the pressure of the fluid within the first cylinder may be controlled. The valve means is preferably located in a wall or an end of the first cylinder. Preferably the valve means comprises a pressure sensor which is operable to sense the pressure of the fluid within the first cylinder and to automatically control the communication between the cylinder ^"and the pressurised fluid in the reservoir by means of the valve, to maintain constant pressure within the first cylinder. Preferably the aforementioned automatic control can be overridden to permit manual control of the pressure within the cylinder.

Valve means and fluid reservoir as hereinbefore described, may be provided to control the pressure of fluid within the second cylinder.

A plurality of resilient means may be provided within the device. The resilient means may comprise a plurality of springs, which may be arranged in parallel

In a further alternative, the or each resilient means may be located outside the second cylinder and connected to the interior of each cylinder by means of one or more plungers, sealingly operable within the second cylinder.

A plurality of first cylinders as aforesaid may communicate with a common second cylinder. ^—

Two devices as defined above may be connected together to provide fluid communication between the chambers of the devices.

The relative orientations of the first and second devices may differ such that the direction of movement of the pistons of the first device differs front that of the pistons of the second device.

The second piston may carry a punch or other shape forming means, whereby increased fluid pressure within the first device is conveyed to the second piston to move the punch or other shape forming means. Preferably the compressible fluid is hydraulic fluid.

An embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Fig. 1 is a partial cross-section of a spring device according to the present invention;

Fig. 2 is a partial cross-section of an alternative spring device according to the present invention;

Fig. 3 is a partial cross-section of a further alternative spring device according to the present invention;

Fig. 4 is a partial cross-section of part of a still further alternative spring device according to the present invention;

Fig. 5 is a diagrammatic partial cross-section of another alternative spring device and a pressure regulating system according to the present invention; Fig. 6 is a schematic representation of an application of the devices of the present invention; and

Fig. 7 is a schematic representation of a further application of the devices.

Fig. 1 shows a spring device 10 comprising a first piston 12 operable within a first cylinder 14, a second, annular piston 16 operable within a second annular cylinder 18, around and concentric with the first cylinder 14. The interiors of the two cylinders 14, 18 are in communication through apertures 20 in the first cylinder. A chamber 22 is thus formed between the first piston 12 and the second piston 16, and having two portions, one within the first cylinder and one within the second cylinder.

The chamber 22 contains compressible fluid, preferably hydraulic fluid.

A second chamber 28 is formed between the second piston 16 and the second cylinder 18 and is located around the first cylinder 14, and separated from the first chamber 22 by the second piston 16. Pressurised gas is provided in the second chamber 28. A valve V, is provided connecting the second chamber 28 to a gas supply and exhaust means (not shown) A further valve V_? is provided to connect the first chamber 22 to a hydraulic fluid supply and exhaust means (see later) .

The valves V.. and V„ enable the amount and pressure of gas and hydraulic fluid in the respective chambers 28, 22 to be controlled. Such control may be effected manually when the device is not in use, enabling the pressures of the two chambers 28, 22 when the device is "at rest" to be finely controlled to provide a device with the desired spring characteristics. Conveniently the gas pressure is maintained at around 150 bar (see later).

Further automatic control may be effected as hereinafter described with reference to Fig. 5.

In use, when a force is applied to depress the first piston 12, in the direction F, ±he first piston 12 moves to reduce the volume of the first chamber 22, and is resisted by an increase in fluid pressure in the chamber 22. This, in turn, causes the second piston 16 to move against the resistance of the pressurised gas in the chamber 28 to try to relieve the pressure increase in the first cylinder 22. The result is a resilient resistance to the depression of the first piston 12, the resistance having characteristics determined by the pressure and nature of the gas in the chamber 28 the nature and quantity of fluid in the first chamber 22, and the relative dimensions within the device.

The device described can therefore be installed in a press with the piston 12 under a sheet to be profiled, so that the piston 12 is depressed as the press closes, and pushes the profiled sheet off the press as the press opens. The energy required to force the piston 12 into the cylinder 14 is at least partially stored within the device 10. Upon release of the force, the pressure of the gas and the fluid in the respective chambers 28, 22 relax to force the piston 12 out of the cylinder 14.

Fig 2 shows a second device 110, similar to that hereinbefore described, in which the second annular piston 116 comprises an upper annular plate 117 and a lower annular plate 119. Two annular rubber seals 121,123 of different diameter are sandwiched between the plates 117,119 and held in position therebetween by the second cylinder 118 and a locating protrusion 125 extending from the upper plate 117, toward the lower plate 119. In use, the strength of the seal between the respective seals 121, 123 and the cylinder 118 increases as the pressures within the chambers 122,128 increase, as a result of the increased pressures urging the plates 117,119 together thereby squeezing and flattening the seals 112,123 and urging them against the cylinder 118.

Fig. 3 shows a third device 210 of generally similar structure as hereinbefore described, but in which the resilient means comprises a mechanical comp-ression spring 226 located in the second chamber 228. The spring 226 functions in a similar way to the pressurised gas, and the characteristics of the spring can be altered to achieve the desired overall characteristics of the device.

Fig. 4 shows a second piston 316 and second cylinder 318 of a fourth device 310, which are remote, in use, from a first cylinder (not shown) housing a first piston (not shown). The piston 316 of the device is not annular. Passages 320 allow the first and second cylinders to be connected, so that a chamber is formed between the pistons partially within the passages 320. The chamber is filled with compressible fluid. Two mechanical compression springs 326 are located in parallel within the second cylinder 318, the springs 326 being maintained in position within the chamber 328 by pegs 330 over which the springs are located.

The device of Fig. 4 functions in a similar manner to that of Figs. 1, 2 and 3. That is, movement of the first piston to reduce the volume of the chamber between the pistons is resisted by compression of the fluid in the chamber, which in turn causes the piston 316 to move to increase the chamber volume against the resistance of the springs 326. Thus, the overall spring characteristics can again be changed in various ways. An advantage over the arrangement of Figs. 1,2 and 3 is that the direction of movement of the two pistons no longer need be parallel, and the two cylinders do not need to be close together. Thus, the first piston can be located at the press, but the second piston can be located at a more convenient location remote from the first.

Fig. 5 shows a further arrangement in which the first piston 412 and cylinder 414 are remote from the second piston 416 and cylinder 418, and are interconnected by fluid lines 420 to be operable as hereinbefore described, particularly with reference to Fig. 4. The second chamber 428 in the second cylinder 418 is filled with pressurised gas, similar to the devices of Figs. 1 and 2. A relatively highly pressurised fluid reservoir R is connected to a control box C which in turn is connected by means of an output conduit C to the second cylinder 418, and by means of an input conduit C. to the output from the first cylinder 414. The control box C comprises sensor (not shown) which detect the pressure of fluid from the first cylinder 414, through the input conduit C_τ. The control box C also comprises a valve to control communication between the reservoir R and the second cylinder 418. If during operation of the spring device, a drop in pressure is detected by the sensor, the control box C opens the valve (not shown) to permit passage of pressurised fluid from the reservoir R to the second cylinder 418, through the output conduit C . This automatic control ensures that the pressures within the device and hence the spring characteristics of the device remain constant even in the event of fluid leakage. The reservoir R may be connected to a plurality of devices to simultaneously maintain the pressures in each. It is to be appreciated that a similar reservoir (not shown) may be provided to maintain the gas pressure in the second chamber 428. The control arrangement may be overridden so that the pressures within the system can be manually set.

A single second piston and cylinder arrangement as shown in Fig. 4 could be connected to a plurality of first cylinders located at various positions on the press.

Further, any combination of mec'.anical spring(s), pressurised gas and compressible fluid according to any of the embodiments may be provided within the chambers.

Fig. 6 shows in more detail how devices 10 can be installed for use in a press plate P. The first piston 12, protrudes out of the plate P in a direction parallel to the direction of the pressing action (indicated by the arrows A¹) parallel to the direction of the pressing action. As the metal sheet M is pressed by closing the press, the first piston 12 is forced into the first cylinder 14. The devices 10 store energy by compression of the fluid and the gas (and/or spring(s)).

When the press is opened, the force exerted by the press is released. The energy stored within the devices 10 is released as the gas (and/or spring(s)) and fluid decompress, and the first pistons 12 are forced up to push the profiled panel off the plate P.

It is to be appreciated that as many devices 10 as necessary may be incorporated in the plate P.

A further application of the devices of the present invention is shown in Fig. 7 of the drawings. The fluid chamber of a first de-vice A, of a similar design to that described above in relation to Figs. 4 and 5, is connected to a piston operated punch T in a cylinder B by means of a hydraulic fluid passage H. The device A and the cylinder B are incorporated into a press as described above. Compression of the first device A as the press closes causes a build up of pressure within the device A as described above. This pressure is transmitted to the cylinder B through the hydraulic fluid passages H. The punch T is then forced into the sheet of metal M, thereby punching the sheet at the same time as it is profiled.

Upon release of the press force, the tool T is withdrawn from the sheet M, and the first piston in device A acts to force the sheet M off the press as described above. The pressures within the system is maintained using the control arrangement of Fig. 5.

Various modifications may be made without departing from the spirit and scope of the present invention. For example, a hydraulic spring may replace the mechanical or pneumatic spring. Various different configurations, including those described, can be adopted for the pistons and cylinders. Any suitable arrangement may be employed to maintain the pressure in the system. The resilient means may be located outside the second chamber, but connected thereto by means of a plunger sealingly operable within the said chamber. Thus would allow easy access to and maintenance of mechanical springs.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

C l a ims :

1. A spring device comprising first and second pistons, a chamber between the pistons and containing compressible fluid, and resilient means operable to resist the second piston moving to increase the volume of the chamber, any movement of the first piston to reduce the said volume being resisted by a combination of the compression of the fluid and the resilience of the resilient means.

2. A spring device according to claim 1, in which the resilient means is resiliently compressible.

3. A spring device according to claim 1 or claim 2, in which the resilient means is a fluid.

4. A spring device according to any preceding claims, in which the resilient means is a gas.

5. A spring device according to claim 4, in which the gas is pressurised.

6. A spring device according to claim 1 or claim 2, in which the resilient means is a mechanical spring.

7. A spring device according to any preceding claim, in which the first piston is operable within a first cylinder and the second piston operable within a second cylinder.

8. A spring device according to claim 7, in which the first cylinder is of smaller diameter than the second cylinder .

9. A spring device according to claim 8, in which the first cylinder is located wholly or partly within the second cylinder.

10. A spring device according to any preceding claim, in which the second piston is annular.

11. A spring device according to claim 10, in which the annular piston encircles and is movable along the first cylinder .

12. A spring device according to claim 10 or 11, in which seal means is provided between the annular piston and the second clyinder whose sealing efficiency tends to increase with the pressure in the respective cylinders.

13. A spring device according to claim 12, in which the seal means comprises upper and lower plates and a resilient seal sandwiched therebetween such that as the pressure in the cylinders increase, the plates are urged together, and squeeze the resilient seal so that its outer surface is urged against the second cylinder.

14. A spring device according to any of claims 7 to 13, in which the resilient means encircles the first cylinder .

15. A spring device according to any of claims 7 to 14, in which the resilient means is located in the second cylinder.

16. A spring device according to any of claims 7 to 15, in which the first cylinder communicates with the second cylinder through at least one aperture formed in the wall of the said first cylinder, the said apertures allowing compressible fluid to pass therethrough during operation to provide communication between the pistons.

17. A spring device according to claim 16, in which the or each aperture is so located as to maintain communication between the cylinders during the whole range of movement of the pistons.

18. A spring device according to any of claims 12,13,16 or 17 when dependent on claims 7 or 8, in which the first and second cylinders are remote from each other and interconnected by means of passages through which compressible fluid may pass.

19. A spring device according to any of claims 7 to 18, in which valve means is provided to control communication of the first cylinder with a pressurised compressible fluid reservoir, so that the pressure of the fluid within the first cylinder may be controlled.

20. A spring device according to claim 19, in which the valve means comprises a pressure sensor which is operable to sense the pressure of the fluid within the first cylinder and to automatically control the communication between the cylinder and the pressurised fluid in the reservoir by means of the valve, to maintain constant pressure within the first cylinder.

21. A spring device according to claim 20, in which the aforementioned automatic control can be overridden to permit manual control of the pressure within the cylinder.

22. A spring device according to any of claims 7 to 21, in which valve means and fluid reservoirs are provided to control the pressure of fluid within the second cylinder.

23. A spring device according to any preceding claim, in which a plurality of resilient means is provided within the device.

24. A spring device according to any of claims 7 to 23, in which the or each resilient means is located outside the second cylinder and connected to the interior of each cylinder by means of one or more plungers, sealingly operable within the second cylinder.

25.- A spring device according to any of claims 7 to 24, in which a plurality of first cylinders communicate with a common second cylinder.

26. A spring device according to any preceding claims, in which two devices are connected together to provide fluid communication between the chambers of the devices.

27. A spring device according to claim 26, in which the relative orientations of the first and second devices differ such that the direction of movement of the piston of the first device differs from that of the pistons of the second device.

28. A spring device according to claim 26 or 27, in which the second piston carries a punch or other shape forming means, whereby increased fluid pressure within the first device is conveyed to the second piston to move the punch or other shape forming means.

29. A spring device substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings .

30. A spring device substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings .

31. A spring device substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings .

32. A spring device substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.

33. A spring device substantially as hereinbefore described with reference to Fig. 5 of the accompanying drawings.