GB2169846A - Twin chamber press - Google Patents

Abstract

A press e.g. for baling rubber, is provided which has two pressing chambers 2,3 which are fixed in position and a movable hydraulic ram 5 which can be selectively positioned above a particular chamber and which can extend into and retract from that chamber. The ram is adapted to compress material in a chamber into which it is extended and to extract the compressed material from the chamber when it is retracted. The platten 7 is provided with projections which penetrate the compressed material and remain anchored within it until the material is released therefrom by a mechanical release system at a selected location 4 from where it is conveyed to a nearby packing station. One chamber can be loaded with material whilst material in another chamber is under compression. The hydraulic circuit of the press allows a set pressure to be developed in the ram and then maintains this set pressure at a constant value for a predetermined length of time during compression. <IMAGE>

Description

SPECIFICATION twin chamber press This invention relates to a twin chamber press and, in particular, to a twin chamber press for baling natural rubber.

Conventionally, natural rubber baling presses have consisted of one fixed chamber of steel construction with either one or two fixed hydraulic rams to effect the baling and the extraction of the baled rubber from the chamber.

One such press is the GEC 60-Ton Automatic Baling Press which comprises a single fixed chamber closed by a top platten which moves on two screws and a bottom platten which is actuated by a hydraulic cylinder. In operation, the top platten is raised to allow the chamber to be loaded with raw material and then lowered to seal the chamber. The bottom platten then moves upwards to compress the natural rubber into a bale and, once the compression has been completed, the top platten is then raised so that the bottom platten may push the finished bale up and out of the chamber.

However, such single chamber presses only have a low production capacity due to the fact that the finished bale must be extracted from the chamber before the material to form the next bale can be loaded.

In an attempt to increase production capacity, twin chamber presses were developed which enabled the loading of raw material into one chamber and the baling of rubber in the other chamber to be effected simultaneously.

These twin chamber type presses use either one or two fixed hydraulic rams for baling and ejecting the finished bale and in all cases have chambers which are movable either by sliding or rotating. For instance, the Cuthrie 60 Ton Hydraulic Rotary Press has twin chambers which can be freely rotated through 1800 about the vertical in either direction to enable them to interchange positions. The press also includes two fixed hydraulic rams, one of which is positioned above one chamber station and travels down to compress the contents of the chamber and the other of which is positioned below the other chamber station and pushes up to eject a finished bale. Thus, in operation, whilst rubber is under compression in one chamber, a previously finished bale is automatically ejected from the other chamber and the chamber then reloaded with fresh rubber.Both chambers are then rotated through 1800 to a position where the chamber containing fresh rubber is underneath the compression ram and the cycle is again repeated.

However, the chambers must be rotated manually, which requires considerable effort on the part of the operator, since a loaded chamber can weigh about a ton, and consequently there is a high risk of injury to the operator.

Moreover, the press must occupy more space in a plant than its actual physical size warrants so as to allow room for rotation of the chambers.

It is therefore an object of the present invention to obviate these problems by providing a press which still enables both baling and loading fuctions to be undertaken simultaneously whilst at the same time being compact and requiring no great physical effort on the part of the user to operate it.

According to the present invention there is provided a press comprising at least two pressing chambers and a ram for compressing material in either of said chambers, said ram being movable from one chamber to the other.

Preferably, the ram is a hydraulic ram which can be selectively positioned above a particular chamber and can extend into and retract from that chamber.

Preferably, the ram is adapted to compress material in the chamber into which it is extended and to extract the compressed material from the chamber when it is retracted.

It is also preferred that the ram be provided with means for engaging the compressed material and means for releasing the compressed material at a selected location. This selected location may be a discharge station which comprises a series of gravity or driven roller conveyors to convey the compressed material to a nearby packing station and may be situated between a pair of chambers.

The engaging means preferably comprises at least one projection which is shaped to penetrate the compressed material and to remain anchored within it after penetration and, more preferably, comprises a plurality of conical studs attached to posts of smaller diameter than the base of the studs which extend downwardly from the base of the ram in such a way that the apices of the studs point downwards.

The releasing means preferably comprises means for pushing the compressed material free of the engaging means and may take the form of a member mounted on the ram for movement towards and away from the ram and means for actuating movement of the member at the selected location. It is preferred that the member is a bar which is resili ently supported on the ram by a plurality of resilient members and that the actuating means comprises a cam mounted on the ram which operates on engaging a projection attached to the frame of the press at the selected location as the ram moves laterally from one chamber to another.

It is preferred that the press also includes means for attaining a predetermined pressure in the ram and means for maintaining that pressure at a constant value for a predetermined length of time during compression. Preferably, the means for attaining a predetermined pressure and the means for maintaining that pressure comprises a double pump con sisting of a fixed displacement, high volumelow pressure pump and a variable displacement, low volume-high pressure pump.

It is also preferred that the press includes a hydraulic circuit which is operated by a hydraulically actuated spool valve which is itself controlled by pilot pressure directed by a solenoid operated pilot valve.

Preferably, the press also includes means for preventing normal operation of the press when the platten is not correctly aligned with the chamber into which it is to extend.

It is particularly preferred that the press be used for compressing rubber.

The present invention also provides a method of compressing material, e.g. rubber,which involves the steps of loading material into a first chamber whilst material in another chamber is under compression from a ram, then moving the ram out of the other chamber and extracting the compressed material at the same time, moving the ram to the first chamber loaded with uncompressed material, causing the ram to compress the material in the first chamber, and during this operation, loading the other chamber with further material for compression, and subsequently repeating the above steps in alternate chambers.

A preferred embodiment of the invention is now described with reference to the accompanying drawings in which: Figure 1 is a rear elevation of a press according to the invention.

Figure 2 is a plan view of the press of Figure 1; Figure 3 is a front elevation of part of the press of Figure 1 showing in detail the griprelease system mounted on the press platten.

Figure 4 is a side elevation of the grip-release system of Figure 3.

Figure 5 is a front elevation of the drive mechanism of the press of Figure 1 mounted on the main frame; Figure 6 is a schematic drawing of the hydraulic circuit employed in the press of Figure 1; Figure 7 is a side elevation of the hydraulic tank of the press of Figure 1; and Figure 8 is a schematic diagram showing a working cycle of the press of Figure 1.

A general description of the preferred embodiment will be given first and this will be followed by a more detailed description of the apparatus in question and its- mode of operation.

The press 1 illustrated in Figure 1 basically comprises two immovable chambers 2,3, a discharge station 4 located between chambers 2 and 3, and an hydraulic ram 5 which is mounted on a fixed horizontal track 6 and can travel horizontally from right to left and viceversa and can be selectively positioned over one or other of chambers 2 and 3. A horizontal platten 7 is attached to the lower end of ram 5 for compressing material in chamber 2 or 3 when the ram is lowered into the chamber. Platten 7 is also equipped with a griprelease system for engaging and releasing material which has been compressed into a cohesive mass or bale.

Safety gates 52,53 are also provided which are fixed to the top of chambers 2 and 3 respectively at the front of the chambers as shown in Figure 1, thus allowing access to chambers 2,3 from one side of the press only. Another safety gate 54 is attached to the ram assembly 5 at the rear of the press as shown in Figures 1 and 2. This safety gate 54 moves with ram assembly 5 thus preventing access to areas where the ram is operating at all times. Consequently, it is only possible to gain access to a chamber for loading uncompressed material when the ram is compressing material in the other chamber.

To begin a working cycle of the press 1, ram 5 is positioned over one of the chambers, e.g. 2, which has been preloaded with a standard weight of raw material e.g. crumb or string rubber. Ram 5 then travels down into chamber 2 to compress the material, the griprelease system engaging the bale as it is formed under compression. Whilst the material in chamber 2 is under compression, chamber 3 is loaded with fresh material. Once the required degree of compression has been attained, ram 5 is raised, lifting the bale with it until it is clear of chamber 2. Ram 5 then moves horizontally towards chamber 3, the grip-release system being actuated during the course of this movement so as to release the bale over discharge station 4. Ram 5 continues to move until it is positioned above chamber 3 ready to repeat the compression phase in chamber 3.During this compression, chamber 2 is again loaded with fresh material. A complete working cycle of the system is shown schematically in Figure 8.

The construction and operation of press 1 will now be described in more detail.

The grip-release system associated with platten 7 is best illustrated in Figures 3 and 4.

The "grip" part of the system consists of four equally spaced conical studs 8 which are attached to the underside of the platten 7 by short posts 9 so that their apices point downwards. Thus, as the platten 7 is compressing raw material in one of the chambers 2,3, the studs 8 become embedded in the compressed material at a short depth beneath the surface equal to the length of the posts 9. Consequently, as the platten 7 is raised, the bale of compressed material is lifted with it due to the shape of the studs which stay anchored in the compressed material.

The "release" part of the system consists essentially of two kicker bars 10 and a cam mechanism for actuating them. Four holes 11 with stepped walls are provided in platten 7, each of which has a vertical post 12 passing through it. The two kicker bars 10 are se cured to the bottom of posts 12 so that each kicker bar links a pair of posts and the two kicker bars lie parallel to each other. The kicker bars 10 are held flush to the underside of platten 7 by four compression springs 13 which are located one in each of the four holes 11. A post 12 passes through the core of each spring 13 and each spring is seated at its lower end on a step in the wall of the hole 11 in which it is located. Two cross bars 14 are provided which have a hole at each end of suitable diameter to allow a post 12 to be threaded through the hole.These cross bars 14 are fitted over a post 12 at each of their ends so that each cross bar links a pair of posts 12 and the two cross bars lie parallel to each other and to kicker bars 10. Each crossbar 14 lies on top of a pair of compression springs 13 and is firmly secured in position by lock nuts 15.

Two generally circular moving cams 16 sit on cross bars 14 and are each secured by a cam pin 17 between a pair of brackets 18 which are welded onto platten 7. The cam pin 17, which acts as a pivot, passes through the moving cam 16 at a point some distance away from the true centre of the cam. The compression springs 13 thus bias the cross bars 14 up into engagement with the cams 16, and normally bias the kicker bars 10 up into engagement with the underside of platten 7. Two trapezoidal fixed cams 19 are bolted to two fixed cam mounting bars 20 which are located on each side of the main frame of the press and run parallel to the cross bars 14 and kicker bars 10. These fixed cams 18 are positioned directly above discharge station 4 and in line with moving cams 16. Four cam positioning devices 21 are welded to the fixed cam mounting bars 20, two devices 21 being welded on each bar.A pivoted kicker 22 is attached to each cam positioning device and each kicker 22 is held in a vertical position by a tension spring 23 so that the kicker 22 can only swing away from the springs 23 i.e. outwards towards the edges of the machine.

The "release" mechanism is actuated as the moving ram 5 travels horizontally from left to right and viceversa. As the moving ram 5 travels over discharge station 4, moving cams 16 come into contact with fixed cams 19 which exert pressure on moving cams 16 thereby forcing them to rotate about their cam pins 17. As each cam 16 rotates, it presses, due to its eccentric movement, against a cross bar 14 and forces it downwards. The cross bars 14, which are firmly secured to kicker bars 10 via posts 12, in turn force the kicker bars 10 to move downwards away from the platten 7, thus forcing the bale of compressed material free of studs 8 so that the bale lands on discharge station 4.Ram 5 continues moving in the same direction throughout this operation and thus, as the ram moves past the fixed cams 19, the pressure on moving cams 16 is released and compression springs 13, which have been compressed between cross bars 14 and the platten 7 during the bale release phase, are able to expand thus pushing cross bars 14 back to their preset positions, the cross bars 14 in turn retracting kicker bars 10 to their original positions.

Cam positioning devices 21 act to ensure that moving cams 16 are correctly oriented as they approach fixed cams 19. As moving ram 5 travels towards fixed cams 19, if a moving cam 16 is incorrectly positioned, its cam pin will contact a cam positioning device 21 stationed in front of fixed cam 19 and force moving cam 16 into its correct position. After moving cam 16 has traversed fixed cam 19, the kicker 22 positioned at the rear of fixed cam 19 will swing outwards against the bias of tension springs 23 so that it does not interfere with moving cam 16 after it has tracked past fixed cam 19. Thus cam positioning devices 21 can only influence a moving cam 16 as the moving cam 16 is approaching a fixed cam 19.

The discharge station 4, as illustrated in Figures 1 and 2, comprises a series of gravity or driven roller conveyors which convey bales which have been released from platten 7 to a nearby packing station. At the packing station the bales are lifted from the conveyor to a packing table where they are wrapped e.g. by a shrink wrapping process, and packed on wooden pallets ready for transportation.

The ram 5 is moved horizontally by means of a chain and sprocket drive mechanism as shown in Figure 5. A motor 24 is mounted on a bracket which is fixed to the main frame.

The out-put shaft of the motor 24 drives a drive sprocket 25 which is coupled to a torque limiter 26. A drive chain 27 is looped around the drive sprocket 25 and a series of idler sprockets 28, the loop being completed by coupling the two ends of the drive chain 27 to the moving ram 5. The ram 5 is rested on rollers 29 which run along fixed tracks 6 (see Fig.1). At each end of the two tracks 6 there is a preset stopper 30 which stops and positions the ram 5 and a limit switch 31 which cuts off the power supply to motor 24.

The tension of the drive chain 27 is adjusted by tensioner 32 which is mounted on the same bracket as the motor 24.

The motor 24 can be controlled to rotate in either sense i.e. forward or reverse. Thus, to move the ram in one direction, say towards chamber 2, an appropriate control button is pressed which causes the motor to rotate in the required direction, thus causing the chain 27 to pull the ram 5 in the desired direction.

As the ram 5 approaches the end of tracks 6, it contacts the preset stopper 30 which stops the moving ram 5 and, at the same time, positions the ram 5 over chamber 2. Just before the ram 5 contacts the stopper 30, the limit switch 31 is activated and cuts off the power supply. Any overrun of the motor is then taken up by the torque limiter 26. Movement towards chamber 3 is accomplished by pressing the appropriate control button which causes motor 24 to rotate in the opposite direction, the operational sequence is identical to that described above.

The vertical movement of ram 5, which occurs during the compression and lifting phases of the working cycle, is controlled by a special hydraulic system which is schematically illustrated in Figure 6. This special hydraulic system is in turn controlled electrically by the use of solenoid operated valves.

In conventional hydraulic presses, when the ram travels down into a chamber to compress raw material, the pressure in the system is allowed to build up to a predetermined level and then shut off, exhausting hydraulic fluid to a reservoir in the process. However, once the pressure has been shut off, the compressed material pushes up as a result of its own elasticity thus producing a bale which is not at the required degree of compression.

It is therefore an importantfeature of the hydraulic system of the present invention that it enables a constant pressure to be applied to the raw material whilst it is under compression i.e. pressure is maintained at a predetermined level for a specified period of time to ensure that the bale attains the required degree of compression. In the preferred embodiment described, this is accomplished by the use of a constant pressure double pump.

The elements of the hydraulic circuit will now each be described in turn and this will be followed by a description of the operation of the hydraulic circuit as a whole.

Referring to Figure 6, a constant pressure double pump 32 is utilised which is powered by an electric motor 33 and consists of a fixed displacement high volume-low pressure Vane Pump 32a and a variable displacement low volume-high pressure Piston Pump 32b.

The Vane Pump pressure is controlled by a pressure unloading valve 34, connected between Vane Pump 32a and the cylinder line, and the Piston Pump pressure, which is variable, is controlled by a builtin sensor-compensator.

The double pump 32 is used to extract maximum efficiency from the press during the three stages of its operational sequence i.e.

(1) Approach (2) Press/Dwell (3) Retract. During "Approach", that is, when the ram travels from the fuliy retracted position to when it comes into contact with the raw material in the chamber, the delivery to the hydraulic cylinder is the combined flow of both pumps, 32a and 32b. However, when the platten comes in contact with the raw material, the raw material offers resistance to the platten and this in turn creates a pressure build-up in the system. When this reaches a pre-set pressure, pressure unloading valve 34 is actuated and unloads the flow from Vane Pump 32a back to the tank. Thus, during "Press" the flow to the cylinder is from Piston Pump 32b only, the compensator adjusting the pump output to whatever is required to develop and maintain the pre-set pressure.After the "Dwell" period has elapsed, the platten is retracted and flow is once again from both pumps, 32a and 32b. Because unrequired fluid is returned to the tank during "pressing", only a small volume of fluid is under constant pressure and this therefore results in a reduction of heat build-up and prolongs the life of the hydraulic components.

Two check valves 35,36, which allow flow in one direction only, are used in the circuit for different purposes. Check valve 35 is connected between the high pressure and low pressure pumps and serves to prevent high pressure fluid from flowing into the low pressure line, that is, it prevents flow from Piston Pump 32b to Vane Pump 32a. On the other hand, check valve 36 is positioned in the high pressure line downstream of Piston Pump 32b and serves to create a back pressure in the system which is needed to supply the pilot pressure required to operate the main control valve. Thus, check valve 36 basically functions as a restriction valve.

A pilot operated control valve 37 is used to control the movements of ram 5. This valve is actuated hydraulically because the size of solenoid required to actuate it would be too large to be practical. However, a smaller solenoid operated directional valve 38 is used to control the pilot flow to the spool of the main valve 37. The main valve spool is spring centred and a certain pressure, equal to the back pressure created by check valve 36, must be applied to one end of the spool to overcome the spring and shift the spool. If the required pressure is applied to spool chamber R, the spool will shift towards chamber L and vice-versa. If no pressure is applied, the spool will centre in a neutral position due to the action of the spring.

In operation, pilot pressure is tapped from the high pressure line and connected to solenoid operated valve 38 at inlet port P. The outlet port A of valve 38 is connected to spool chamber R of main valve 37 and outlet port B is connected to spool chamber L of main valve 37. Thus, when a solenoid C is energised, the spool of solenoid valve 38 shifts upwards as shown in Figure 6 and the connections are such that the pilot pressure is directed along line 60 to spool chamber L of main valve 37 thus shifting the spool towards chamber R i.e. to the right in Figure 6. This causes the main hydraulic pressure to be directed to the bottom of the cylinder of ram 5 along line 61 thus raising the ram.When solenoid C is de-energised, the spool of solenoid valve 37 shifts back to the centre under the action of the spring cutting off the pilot pressure to main valve 37 and the spool of the main valve 37 thus moves back to the central neutral position. When solenoid D is energised, the spool of solenoid valve 38 shifts downwards as shown in Figure 6 and the connections are such that the pilot pressure is directed along line 62 to spool chamber R of main valve 37 thus shifting the main spool towards chamber L i.e. to the left in Figure 6.

This allows the main hydraulic pressure to be directed along line 63 to the top of the cylinder of ram 5 thus causing ram 5 to travel downwards into the chamber and press the material therein.

A choke block or pilot choke 39 is connected between solenoid valve 37 and main valve 38 to slow spool travel for smoother reversals thus preventing "Hammering" due to a sudden release of pressure. the choke block 39 functions as a meter-out restriction valve, allowing free pilot flow to the end of main spool 37 but restricting flow outof the opposite end, thus reversing flow gradually and cushioning the spools contact when it shifts.

A filter 41 is placed in the return line to filter out any contamination before the hydraulic fluid returns to the tank and two strainers 42,43 are placed at the suction inlet of each pump to ensure maximum protection of pumps 32a,32b.

A pressure gauge 44 is connected to read the main cylinder pressure and a gauge isolator or shut-off valve 45 is provided to prolong the life of gauge 44 by isolating it from the system except when it is desired to make a reading.

The components of the hydraulic circuit are housed within a hydraulic tank 46 mounted on a plinth 47 as shown in Figure 7. The hydraulic tank 46 and its internal piping are designed to minimise heat build up. For instance, the suction strainers 42,43 and return line filter 41 are at opposite ends of the tank and three baffle plates 48, which extend between opposing walls of the tank, are placed between filter 41 and strainers 42,43 to interrupt the linear flow of hydraulic fluid. Thus the hydraulic fluid has to make a series of up and down movements to flow around the baffle plates 48 before it can reach the strainers from the filter. This up and down movement increases the distance the oil has to travel inside the tank and therefore creates a cooling effect.

An electro-hydraulic safety device is incorporated into the circuit to unload pressure and thus protect the press from damage in case the platten hits the sides of the chamber during approach due to misalignment. The essential element of this safety device is a modular pressure switch 40 which is used to make or break electrical circuits operating solenoid operated valves or other devices used in the system at selected pressures.

Pressure switch 40 is in operation while the platten is outside the chamber and is set to cut off the electrical supply to the solenoid valve when a predetermined pressure is reached. If the platten hits the side of the chamber at any time during its approach due to misalignment, pressure switch 40 will shut off the electrical supply to solenoid pilot valve 38 and solenoid D will de-energise. The spool of solenoid valve 38 will then shift back to the centre, under the action of the spring, cutting off the pilot pressure to the main valve 37. This will in turn cause the spool of main valve 37 to shift back to centre rendering the platten motionless and the hydraulic fluid from double pump 32 will be unloaded to the tank.

The predetermined pressure must thus be sufficiently low that no damage can be done to the frame, chamber, platten or other parts of the press before the electrical supply is cut off. Before normal operation can commence, ram 5 must be fully retracted and the misalignment corrected.

If the platten enters the chamber safely, it will trigger a limit switch 49 which will isolate pressure switch 40, thus allowing solenoid valve 38 to continue to direct hydraulic fluid to main valve 37 which in turn will continue to direct hydraulic fluid to the cylinder in ram 5 so that maximum pressure can be obtained.

The press is designed to operate in one of two modes -manual or automatic. The operation in both modes is controlled electrically and the hydraulic operation is the same in both cases. The only difference is that, in the manual mode, the horizontal travel of the ram and the extension/retraction of the ram must be actuated independently whilst, in the automatic mode, the whole sequence can be effected by depressing a single button and the dwell time is controlled by using an electrical timer.

A description of the automatic mode will now be given, by way of example, to show how the various components of the press interact during operation. It should be noted that, at the beginning of each sequence, ram 5 is always located above a chamber, say chamber 3, and the other chamber, i.e. chamber 2, is loaded with raw material e.g. crumb rubber or string rubber.

To begin the sequence, drive motor 24 drives chain 27 to move ram assembly 5 towards chamber 2. As it approaches chamber 2, ram assembly 5 triggers limit switch 31 which cuts off the power supply to motor 24 and ram assembly 5 comes to rest over chamber 2 with the aid of preset stoppers 30.

Limit switch 31 then energises solenoid D on solenoid valve 38 which shifts so that pilot pressure is directed to spool chamber R of main valve 37 causing the spool to shift so that the flow of hydraulic fluid from the double pump is directed to the top of ram cylinder 5.

This causes ram 5 to extend into chamber 2.

As it extends into chamber 2, ram 5 triggers limit switch 49 which isoiates pressure switch 40. The isolation of pressure switch 40 starts the automatic timer which commences an automatic countdown. When the preset constant pressure has been reached, unloading valve 34 unloads the flow from Vane Pump 32a back to the tank. Piston pump 32b continues delivery until the pressure reaches a higher preset pressure at which it is maintained by the operation of the compensator.

Once the timer has finished its countdown, it de-energises solenoid D and energises solenoid C of solenoid valve 38 thus shifting the spool of solenoid valve 38 so that pilot pressure is directed to chamber L of main valve 37. The main valve spool shifts slowly towards chamber R, being slowed by the action of choke block 39, so that the flow of hydraulic fluid from the double pump is directed to the bottom of ram cylinder 5. This causes ram cylinder 5 to retract from chamber 2 lifting the compressed bale with it which is attached to the underside of platten 7 by virtue of studs 8. As it rises, ram 5 triggers a further limit switch 50 (see Figure 6) which cuts off the electrical supply to solenoid C. Solenoid C thus de-energises and the spool of solenoid valve 38 shifts back to a central position under the influence of the spring thus stopping pilot pressure from reaching main valve 37.The spool of main valve 37 therefore also shifts back to its central neutral position and directs the flow of hydraulic fluid from the double pump 32 to the tank, causing ram 5 to stop. This ends one cycle.

It should be noted that ram 5 has stopped above chamber 2 with the bale still attached to platten 7. To release the bale, the drive mechanism must be activated to move ram 5 towards chamber 3, which will already have been loaded with fresh material for pressing, so that the "release" mechanism can eject the bale onto discharge station 4 as described earlier. Consequently, the release operation is usually carried out at the beginning of each automatic cycle.

From the foregoing description it is apparent that the press of the present invention has a number of advantages over known presses.

For instance, no manual labour is required to shift rotating or sliding chambers as used in other twin chamber presses; only one movable hydraulic ram is used for both high pressure bale compression and low pressure bale lifting functions; the finished bale is released automatically from the ram by means of the special grip-release system and can be automatically conveyed from the press to the next process station; and better bale formation is accomplished by the utilisation of a special hydraulic circuit incorporating a constant pressure pump.

It should be appreciated that, although a press for baling rubber has been described, the press could also be used to compress other materials e.g. paper. Moreover, it will of course be understood that the present invention has been described above purely by way of example and modifications of detail can be made within the scope and spirit of the invention.

Claims (1)

1. A press comprising at least two pressing chambers and a ram for compressing material in either of said chambers, said ram being movable from one chamber to the other.

2. A press according to claim 1 in which said ram is a hydraulic ram.

3. A press according to claim 1 or 2 in which said ram can be selectively positioned above a particular chamber and can extend into and retract from that chamber.

4. A press according to any preceding claim in which said ram is adapted to compress material in the chamber into which it is extended and to extract the compressed material from the chamber when it is retracted.

5. A press according to any preceding claim in which the ram is provided with means for engaging the compressed material and means for releasing the compressed material at a selected location.

6. A press according to claim 5 in which the selected location is a discharge station, the discharge station being situated between said two chambers.

7. A press according to claim 6 in which the discharge station comprises a series of gravity or driven roller conveyors which convey the compressed material to a nearby packing station.

8. A press according to any one of claims 5,6 or 7 in which said engaging means comprises at least one projection which is shaped to penetrate the compressed material and to remain anchored within it after penetration.

9. A press according to any one of claims 5,6 or 7 in which said engaging means comprises a plurality of conical studs attached to posts of smaller diameter than the base of the studs which extend downwardly from the base of the ram in such a way that the apices of the studs point downwards.

10. A press according to any one of claims 5-9 in which said releasing means comprises means for pushing the compressed material free of the engaging means.

11. A press according to claim 10 in which said releasing means comprises a member mounted on said ram for movement towards and away from said ram and means for actuating movement of said member at said selected location.

12. A press according to claim 11 in which said member is a bar which is resiliently supported on the ram by a plurality of resilient members.

13. A press according to claim 11 or 12 which includes a frame along which the ram may travel laterally and in which said actuating means comprises a cam mounted on said ram which operates on engaging a projection attached to said frame at said selected location.

14. A press according to any preceding claim which includes means for attaining a predetermined pressure in said ram and means for maintaining that pressure at a constant value for a predetermined length of time during compression.

15. A press according to claim 14 in which said means for attaining a predetermined pressure and said means for maintaining that pressure at a constant value comprises a double pump consisting of a fixed displacement, high volumelow pressure pump and a variable displacement, low volumehigh pressure pump.

16. A press according to any preceding claim which includes a hydraulic circuit operated by a hydraulically actuated spool valve which is itself controlled by pilot pressure directed by a solenoid operated pilot valve.

17. A press according to any preceding claim which includes means for preventing normal operation of the press when the platten is not correctly aligned with the chamber into which it is to extend.

18. A press according to any preceding claim for use in compressing rubber.

19. A method of compressing material using a press according to any preceding claim which involves the step of loading material into one chamber whilst material in another chamber is under compression.

20. A method of compressing material which involves the steps of loading material into a first chamber whilst material in another chamber is under compression from a ram, then moving the ram out of the other chamber and extracting the compressed material at the same time, moving the ram to the first chamber loaded with uncompressed material, causing the ram to compress the material in the first chamber, and during this operation, loading the other chamber with further material for compression, and subsequently repeating the above steps in alternate chambers.

21. A press substantially as herebefore described with reference to the accompanying drawings.

22. A method of pressing material substan tialiy as hereinbefore described with reference to the accompanying drawings.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1-4 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A press comprising at least two pressing chambers and a ram for compressing material in either of said chambers said ram being movable from one chamber to the other and being adapted to compress material in the chamber into which it is extended and to extract the compressed material from the chamber when it is retracted.

Claims 5-22 above have been renumbered as 4-21 and their appendancies corrected.