GB2077957A - Press apparatus - Google Patents

Abstract

A press for pressing powders and clays, has an electro-hydraulic control system to control a pressing ram and tool 14, a loading device 18 and an ejector ram and die, or ejector holding device 16, to fill, press and eject material from a body 10. The system responds to cams moved by the rams to actuate limit switches, and provide selectively presettable programmes for pressing cycles which start and finish with the rams in parking positions, provides an inching mode for setting up the limit switches, and provides for single cycle or automatic continuous cycling operation. The programmes include multiple filling of the body 10, double pressing and tamping the material, reciprocation of the loading device 16, pressing to thickness and pressing to density. <IMAGE>

Description

SPECIFICATION Press apparatus This invention concerns press apparatus for pressing material such as powder or clay.

Mechanical powder compacting presses, controlled by cams, are well known, and have well known disadvantages and limitations such as the need to design a set of cams for each particular shape of pressed powder article to be produced. To avoid this need and obviate some of the other disadvantages and limitations, hydraulically actuated presses have been used in which the stroke of the rams, used to move the die or pressing tool parts, can be set by means of adjustable mechanical stops.Although such hydraulic presses remove the need for the very great skills required to produce the cams, the setting of the stops still requires considerable skill and time, and the presses have other disadvantages and limitations, so that it is quite common for a manufacturer to have to employ both types of presses to produce a range of different articles from powders, and to employ different machines for pressing articles from wet clay.

What is needed is press apparatus which, with appropriate fittings, can be used to press a variety of powders, and which affords a reduction of the time and costs of setting up the apparatus to produce an article; and which can preferably be adapted and provided with other fittings for pressing articles from wet clay.

According to the present invention there is provided press apparatus comprising a body around a die or tool space, an upper die or tool holder device connected to a first ram so as to be movable between a lower pressing position proximal to said space and an upper position remote from said space, a lower die or tool holder device connected to a second ram so as to be movable relative to said space between an upper ejecting position and a lower position, a loading device movable transversely over said space from a position adjacent one side of said space to an actuated position by means of a third ram, ram control means adapted to control the rate of movement of said rams, and electric control means adapted to actuate the ram control means, wherein said electric control means comprises limit switches responsive to the operation of the rams, and a control system which is presettable to determine automatically the sequence and timing of the strokes of the rams in a pressing cycle, and which is responsive to the limit switches to limit the strokes of the rams and to ensure that the devices are parked in predetermined ones of said positions at the start of each pressing cycle; and wherein the control system is adapted to be switched to a setting up condition in which it can be manually controlled to move the rams.

Some, at least, of said limit switches are preferably adjustable to permit adjustment of the positions relative to said space.

The control system preferably includes interlocks which function as integral parts of the control system when the latter is set to control a pressing cycle, and which function in the setting up condition to enable the press, when actuated manually, to be controlled so that damage to the press and press tools is prevented and so that the said devices can be automatically halted when they reach their parking positions.

The control system may include override means to enable said interlocks to be partially negated in the setting up condition, to facilitate, for example, cleaning or changing of an upper die or tool.

The ram and electric control means may include safety means for removing power from the rams in the setting up condition, except whilst said control system is being actively manually controlled, so as to inhibit any movement of the rams due to a failure or minor malfunction of the control means.

The rams are preferably hydraulically operated, and the safety means preferably comprises a dump valve in the hydraulic power supply line, which is normally open and is capable of being closed by electrical energisation of an actuating solenoid.

The limit switches in a preferred embodiment include respective switches for each of the aforesaid positions of said devices together with further switches therebetween responsive to the devices reaching intermediate position, and the control system is presettable so as to be selectively responsive to actuation of said further switches to actuate the ram control means to limit, vary the rate of or alter the sequence of said strokes, whereby to provide variations of a basic pressing cycle.

For example, the loading device can be used to move a pressed article from the top of said space to a discharge point to the other side of the space, as the loading device is moved to charge the space with powder for pressing. Some powders may, for various reasons, not flow to fill the space properly in a single reciprocation of the loading device so that one or more further reciprocations may be required thereby considerably increasing the time required to fill the space. However, one of said further switches may be brought into effect to greatly reduce the strokes of the further reciprocations to minimise the time involved. The stroke reduction may be effected suddenly to impart a shock to the powder to break up any coherent masses of powder especially in the loading device.

Another of said further switches can be utilised to vary the rate of descent of the upper holder device in mid-stroke to give a fast initial approach to the space followed by a slower further action, and the control system may be presettable so that said further action is a progressive action or a tamping action.

The basic pressing cycle may be varied by means of some of said further switches to give a double cycle wherein the lower holder device is held in an intermediate position during a first filling period, and wherein the lower holder device is lowered to and held in its lower position during: (a) a firsttamping, light pressing, or pressing operation; (b) a second filling period; and (c) the descent of the upper holder device for final pressing, whereby to enable difficulties and faults due to incomplete filling of said space or voids in the pressed article to be avoided.

The control system preferably includes one or more adjustable or presettable timers to enable said strokes to be modified. For example, a timer may be included to modify the actuation of the ram control means so that the initial fraction of the upward movement of the upper holder device, after a pressing stroke, is restricted to a slow rate for a predetermined time before a rapid upward return to the parking position.

Most of the limit switches are preferably mechanically actuated by means of abutments which are entrained to move with said devices but not be subjected to any working loads applied to said devices, but one or more of said switches may be responsible to hydraulic pressures applied to one or more of the rams.

The invention also provides hydraulic or pneumatic press apparatus having a ram actuable by control means to cause a die or tool supported by a holder device to press a material in a confined space, wherein the control means is adapted to cause a tamping action ofthedieortool by causing intermittent reversal or variation of the pressure applied to the ram during that stroke of the ram which causes the die or tool to press said material.

The invention further provides hydraulic or pneumatic press apparatus adapted to provide a pressing cycle, for pressing powders, wherein a first amount of powder is fed into and pressed in a space to first predetermined limits, and a second amount of powder is added to said first amount and the total thereof pressed in said space to second predetermined limits, An embodiment of the invention is described hereinafter, by way of example, with reference to the accompanying diagrammatic drawings, wherein:: Figure 1 shows press apparatus of the invention in front elevation; Figure 2 is a diagram showing the schematic arrangement of rams and ram control means of the apparatus, together with limit switches; Figures 3 and 4 show portions of a schematic circuit diagram of electric control means which incorporates said switches; Figure 5 is a circuit diagram of a part of said electric control means which is employed to actuate a tamping action of the apparatus; Figures 6 and 7 show a modified form of the circuit diagram shown in Figures 3 and 4; and Figure 8 is a diagram of the functions of a rotary programme control switch shown in Figures 6 and 7.

Referring to Figure 1, the apparatus as shown includes a body 10 in which a space is defined so as to have an upper opening, flush with a table 11 of the body 10, and a lower opening. The body is rigidly supported on a main frame 12 of the apparatus.

An upper die or tool holder device 14 is disposed above said space and is shown supporting a top die, which upper device 14 is carried by a top ram (shown as 15 in Figure 2) within an upper part of the main frame 12.

A lower die or tool holder device 16 is disposed partially below said space and is carried by a bottom ram 17. The lower device 16 may carry an ejector tool which cooperates with or serves as part of bottom die in said space, but may carry the bottom die.

A loading device 18 is supported for movement along the table 11 by an arm actuated by a transverse die fill ram 19 supported on an exterior of the main frame 12.

The said devices 14, 16 and 18 have outriggers 13 which carry cams for actuating limit switches as hereinafter described.

The main frame 12 also carries a control panel 20 of the electrical control means, and a lower part of the main frame houses a motor 21 (Figure 4), a pump 22 and a reservoir 23 (Figure 2).

The apparatus is shown provided with fittings for pressing powder, which fittings include a powder hopper 24, a rotary valve 25 actuable by the outrigger 13 on the upper device 14, and a discharge chute 26 for the table. The loading device 18 comprises a powder feed assembly which is arranged to receive powder from the valve 25 and to convey the powder to the space, and said assembly has a leading end 27 which is adapted to move pressed articles from above said space and along the table to the chute 26.

The apparatus can alternatively be provided with fittings for pressing articles from wet clay, e.g. an extended table, and an assembly for indexing a slab or block of clay along the table, shearing pieces from the clay and moving each piece to the space, which assembly serves as an alternative loading device 18 in which the movement of the pieces is controlled by the die fill ram 19 via the arm. Modified dies allowing surplus clay to be spewed therebetween or to be ejected via a spume would be needed togetherwith provision for manual or automatic removal of the articles.

The apparatus is provided with hydraulic ram control means, shown in Figure 2, which includes solenoid actuated normally closed valves HV1 to HV8 and normally open valves HV9 which control the following ram movements: HV1 - Top ram fast down, (with HV2).

HV2 - Top ram slow down.

HV3 - Top ram fast up, (with HV4) HV4- Top ram slow up.

HV5- Bottom ram up.

HV7 - Bottom ram down.

HV6 - Transverse ram right (which moves the device 16 to the left as shown in Figure 1).

HV8 - Transverse ram left (which moves the device 16 to the right as shown in Figure 1) HV9 - Shunts the pressure supply from the pump 22, to HV1 to HV8, to the reservoir 23.

Variable restrictors 30 to 35, which are shunted by respective non-return valves to allow full supply flow, restrict the return lines from the rams via the normally closed valves, except for valves HV1 and HV3 which have unrestricted returns in parallel with HV2 and HV4.

The restrictors can be adjusted or preset to control the rate of movement of the rams.

A pressure gauge, safety valve, stop valve, and pressure limiting valve VP are provided for the supply line from the pump, in known manner.

The apparatus is also provided with electrical control means, which includes limit switches shown in Figure 2 and a control system. A first form of the control system is shown in Figures 3 to 5, and offers three main programmes of operation which are pre-selected by a three position rotary programme selector switch S5.

In a start-cycle condition, the rams are in parking positions in which: (a) The top ram is fully "up" to a preset limit; (b) The bottom ram is fully "up" to a preset limit; (c) The transverse ram is fully "left" (Figure 2) to a preset limit.

The first programme is a basic cycle for pressing to thickness in which (a) The transverse ram 19 moves "right" (Figure 2) and stops above the space or die cavity defined in said space.

(b) The bottom ram 17 moves down and exposes the die cavity.

(c) Ram 19 moves "left" filling the cavity with powder and then stopping at its extreme "left" limit.

(d) Top ram 15 moves "down" fast until the tool just enters the die cavity, then slowly approaches the powder in the cavity until it reaches its predeter mined lower limit.

(e) Top ram 15 moves "upwards" slowly for a few thousandths of an inch and then moves quickly upwards until it reaches its upper limit.

(f) Bottom ram moves "upwards" until it reaches its predetermined stop, ejecting the pressed article in the process.

The cycle is complete.

The machine may be programmed for single-cycle operation or to cycle continuously by setting switch S1 to the desired position, and may be used for pressing articles from clay.

In the second programme, for pressing to a density, the cycle of operation is as above, except that in step (d) the top ram moves slowly into the die until the predetermined hydraulic pressure is obtained. A signal derived from this pressure causes the top ram to function as in step (e) and the remainder of the cycle is as above.

The third programme is for pressing deeper articles having peculiar depressions within the die cavity which cannot normally be pressed by the other programmes.

The third cycle is: (a) Ram 19 moves "right" and stops above the die cavity.

(b) Bottom ram moves down part way and stops.

(c) Ram 19 moves "left" filling the cavity with powder in the process and then stopping at its "left" limit stop.

(d) Bottom ram moves down to its lower limit stop.

(e) Top ram moves down fast until the die just enters the cavity die, then slowly approaches and lightly compacts the powder to a pre-set pressure.

(f) On attaining this pressure the top ram slowly moves upwards for a few thousandths of an inch and continues fast upwards until it reaches its upper limit stop.

(g) Ram 19 moves "right" and recharges the die cavity.

(h) Ram 19 moves "left" and stops.

(j) The top ram moves down quickly, then slowly approaches and presses to a predetermined thickness controlled by a limit switch.

(k) The top ram moves upward slowly then continues quickly until the limit is reached.

(m) The bottom ram moves upwards and ejects the compact.

In the first programme the switch S1 is set to the closed position, key-switch S2 is set to operating position (i.e. anti-clockwise) and switch S3 is set to Auto (anti-clockwise) position so as to apply power to line Afrom line D which is supplied via stop button BP9 via guard controlled switches GS1,2 when motor start button PB8 is pressed to energise RMT which latches in via RMT1 and closes RMT2, 3 and 4 to supply three-phase power to the motor 21.

The cycle is started by pressing button PB1Awhich energises relay RLAwhich latches in via its contact RLA1.

The bottom ram is fully up so that limit switch B1 S is actuated, B1S1 is closed and relay B1 R is energised. The ram 19 is parked fully left closing switch E1S1 so that relay El R is energised via E1S1. The top ram is parked fully up closing T1S so that T1 R is energised via T1S2.

Power is then applied on line C to the control circuits via B1 R3, S1 and RLA5 contacts.

The only circuit permitted to operate is that controlling HV6, the hydraulic valve which effects the die-fill "right" movement.

The ram 19 moves right until limit switch E2S is hit, which changes-over closing E2S1, energising E2R which latches in via E2R1 contacts, and removes the supply from HV6. The ram stops. In moving right the ram 19 leaves switch E1S to open contacts E1S1 and de-energise relay El R to close El R4 contacts.

The energisation of E2R relay closes E2R3 and E2R5 contacts which supply power to solenoid valve HV8 via normally closed RLJ2 and El R4 contacts.

The ram 19 moves left until E1S limit switch is hit to energise E1R via E1S1, and E1 R4 contacts are opened removing power from HV8 which stops the ram movement. The energising of E2R relay also supplies power to solenoid valve HV7 via E2R5, the now closed B1R4 contacts, the S5C switch which bypasses B3S1 contacts, and the normally closed B2S2 limit switch. The bottom ram moves down.

Thus the operation of limit switch E2S by the die fill ram 19 moving right also causes the bottom ram to move down and expose the die cavity.

The ram 19 in moving fully left strikes E1S limit switch, energising E1R (via E1S1) and closing E1R2 contacts, so that power is applied to RLB via RLA2, the normally closed RLD4, limit switch T1 R1 contacts) which are closed by the top ram in its fully up position) B2S1 contacts (which are now closed by the bottom ram being fully down to the limit set by B2S limit switch) and the now closed El R2 contacts.

Relay RLB operates closing RLB2 contacts and supplying power to HV2 and HV1 hydraulic valves simultaneously via L1S2andT2S1 limit switches and the now closed RLD5 contacts.

The top ram moves down quickly until limit switch T2S is hit to open T2S1 to de-energise HV1 hydraulic valve. The top ram continues to be moved down to HV2 until L1S is hit. This opens L1S2 and deenergised HV2 stopping the movement of the top ram. L1S1 contacts also close to energise RLD via the normally closed limit-switch contact T1 51. HV4 also energises. RLD latches in via RLD1.

The energising of HV4 causes the top ram to move upwards slowly. Time-delay contacts RLD3 close after a pre-set delay and solenoid valve HV3 becomes energised. The ram moves up quickly until it hits TiS limit switch. ContactT1S1 breaks and RLD de-energises. Timed-delay contacts RLD4 close after a pre-settime. Contact RLD2 delay closes and when T1 R2 closes, RLE is energised via B1 R2, El R3 (closed by the position of die-fill ram) and S5B contacts. RLE energises and latches in via RLE1.

The upward stroke of the top ram thus causes the bottom ram to move upwards after a short delay and eject the article by energising hydraulic valve HV5.

The ram moves up until it hits limit switch B1 S which energises B1 R via B1 S1 and opens contacts B1 R2.

Normally-closed contacts RLD4 have a delayedmake after de-energising of RLD. This delay is to ensure that the bottom ram has moved off B2S and thus opened B2S1, before RLD4 closes, whereby to inhibit the top ram from moving downwards again until the appropriate part of the cycle.

The bottom ram is once again "up", B1 R3 contacts are closed and power is still applied to the control system on line C. The apparatus will cycle automaticaily.

In the single cycle mode switch S1 is set fully clockwise no power is supplied to the control circuits until PB1 B is pressed, because the bottom ram in the up position actuates B1 S limit switch to open B1 S2 contacts and close B1 S1 to actuate B1 R to close B1R3; and the die fill ram in the "left" position actuates E1S to open E1S2 and close E1S1 contacts.

When PB1 B is pressed, power is supplied, the die fill ram moves right, allowing E1S2 contacts to close and bypass PB1B and B1R3.

Before E1S is operated again the bottom ram will have moved down allowing B1 S2 to close. Thus power is supplied throughout the cycle via E1S2 or B1 S2, until the end of cycle when both these switches are open. The machine stops.

In the above cycles, the loading device 18 can be made to judder, i.e. to oscillate above the die cavity for a pre-determined time via timed-contacts B2R1 and thus promote better die filling facilities with certain "difficult" powders. The mode is: As the die fill ram moves right it strikes E3S1 which energises RLJ via B2R1 and B3S4 or B2R2.

Relay RW becomes energised and latches in via RW1 only to be unlatched by E2S2 at the limit of the ram stroke. Contacts RLJ3 also close but, since the ram is already moving right, have no function on this part of the cycle.

On the return stroke of the die fill ram, however, B1 R1 becomes open due to the bottom ram descending to its limit. In descending it hits switch B2S, which energises B2R via B2S3 and operates the delayed-time for the normal closed slow to open B2R1 contacts. On the return stroke of the die fill ram, limit switch E3S1 is hit, energising RLJ which latches in. Normally closed contact RLJ2 opens, de-energising HV8 and preventing any further movement to the left. RLJ3 contacts also close and energise hydraulic valve HV6 via E2S1 causing the ram to move to the right. Limit switch E2S is hit, unlatching RW which allows RLJ2 to close and move the ram to the left. The oscillations continue until the timed-contacts B2R1 become open when, since RLJ cannot become energised, the die fill ram continues to move to the left and stops in the fully left position.

The press continues with the rest of the normal cycle. If judder is not required then the time on contact B2R1 is set to zero delay.

All the foregoing are the basic functions of the machine with the programme switch S5 set fully anti-clockwise.

In the second programme, with the following exceptions, the control system functions as previously described. A pressure limit switch LPS is first set to the desired pressure to enable a compact density to be achieved. With the programme switch S5 set to the central position pressure switch PLS and relay RLK are brought into circuit. As the top ram moves down it operates the slow approach switch T2S1 to cause this switch to changeover.

The die or tool upon touching the powder within the die cavity, causes the pressure to build up in the top ram, and on attaining the desired pressure LPS will close, energising RLK. Contacts RLK1 are timed to delay-make and thus enable a pressure-dwell time to be incorporated. (The pressure switch is set to operate at a pressure slightly less than that to which the pressure regulator VP is set). At the end of this time RLK1 contacts close and energise RLD via T1S1.

The top ram moves upwards and the press operates as before the remainder of the cycle.

In the third programme, limit switch L2S is set out of reach of the ram, and the start of cycle conditions are as previously described, but the programme switch is now set fully clockwise and RLK1 timed contacts are set to zero time i.e. instantaneous. At the start of the cycle the die fill ram moves right until E2S is hit. E2R is energised via E2S1. E2S2 opens.

Contact E2R5 closes and energises RLF via B1 R4 (closed by bottom ram being fully up) and normally closed switch contacts B3S1 and B2S2. RLF latches in via RLF1 and hydraulic valve HV7 becomes energised causing the ram to move downwards until B3S is hit. B3S1 is opened and RLF drops out. HV7 de-energises and stops the ram. As E2R becomes energised R2R3 also closes and the die fill ram moves to the left until it hits limit switch E1S1 which energises El R and opens El R4, stopping further movement of the ram. Meanwhile E2R4 is latched open and prevents the die fill ram moving to the right via a now closed E2S1. As El R energises, contacts El RI close, to by-pass now open B3S1, and energise RLF via a now closed B3S2 and B2S2 contacts. The bottom ram moves down until switch B2S is hit when B2S2 opens and prevents further downward movement. The operation of limit switch B2S closes B2S1 contacts and RLB energises, via the closed contacts of RLA2, RLD4, T1 R1, El R2 and B2Sl, latching in via RLB1.

Top ram moves down quickly as HV1 is energised via RLB2, L1S2 and T2S1 contacts. As T2S limit switch is hit, this changes-over T2S1. The downward movement opens Tri 52 de-energising Ti R and unlatching E2R as T1 R4 is opened.

The top ram enters the partially filled die cavity until it meets the powder and builds up pressure.

Pre-set pressure switch LPS will operate and energise RLK via normally closed RL4 contacts. RLK1 contacts close and energise RLD which returns the top ram to its upward position as previously described.

With the bottom ram in its down position, B1S3 is closed. As RLK energises it closes RLK2 contacts which latch in RLR relay via RLR2 contacts. Contacts RLR3 also close and when the top ram reaches limit switch Ti S contact T1 R4 closes causing the die fill ram to move right via RLE2, RLR3, E2S1 and E2R4.

E2S operates bringing in relay E2R and latching in via E2R1. (Contacts E2R4 open. This prevents the die fill ram from moving right again as it exposes limit switch E2S).

The contacts E2R3 close and die fill ram moves left until E1S is hit which energises El Rand opens E1R4 preventing further movement. Ti R relay unlatches E2R relay.

E2R relay also closes E2R2 which energises RLT via the now closed RLR2 contacts, and latches via RLT1. Contacts RLT2 also close. As relay El R energises it closes El R2 causing the top ram to move down again.

The slow approach switch T2S1 operates but RLK is now inhibited by RLR4 contacts which are open.

Contacts RLR1 are now closed and when the top ram hits L1S1, RLD is energised and the top ram moves upwards until it hits the top limit switch T1 S. The delay on RLD4 prevents it from returning downwards at this stage. The relay Ti R operates and closes T1 R2 contacts. RLE becomes energised via RLD2, Ti R2, B1 R2, El R3, and RLT2 and latches in.

RLE2 contacts open and prevent the die fill ram moving to the right. Hydraulic valve HV5 energises and the bottom ram moves up ejecting the compact.

The cycle is complete.

An additional facility which may be incorporated within any of the aforementioned control systems provides for the progressive downward movement of the top ram to be interrupted by partial return movements giving rise to a vibratory ortamping action of the top ram. This feature is particularly advantageous in the processing of plastic clays, certain semi-dry powders and pressing peculiarly shaped compacts.

Referring to Figure 5, the control system comprises a variable low frequency multivibrator which alternately switches powerto HV1 and HV3, the fast down and fast up hydraulic control valves.

The Mark-space ratio of the oscillator is so arranged that the duration of power in the downward direction exceeds that in the upward direction.

Thus the ram will always migrate downwards until the appropriate limit switch is hit.

A small bias applied to the emitter of M2V ensures that MiV will always be the first to energise and thus a fast down movement will always precede the fast up movement.

With pre-set hydraulic flow rates the magnitude of tamping, or top ram vibration, will be a function of the half-cycle oscillation. Thus a reduced frequency will produce a large displacement and an increased frequency a smaller displacement. The frequency is adjusted to give the desired degree of tamping.

The multivibrator is brought into the control circuit at F and G by closing S6 in line D. As the top ram descends and strikes limit switch T2S2 the oscillator isenergised via TX1 and M1V1 will first close, then open, and M2V1 will open and close alternately with M1V1. Thus power is alternatively applied to HV1, via M1V1 and HV3 via M2V1.

The ram will vibrate downwards until limit switch L1S1 is hit. This causes RLD to energise which opens contact RLD6 and stops the multivibrator which opens contact RLD6 and stops the multivibrator which opens M1V1 and M2V2 contacts. Simultaneously power is removed from HV2 and HV1 hydraulic valves, preventing further downward movement. RLD1 supplies power to HV4. RLD3, delayed contacts, supply power to HV3.

The ram will move first slowly and then quickly up as previously described in this document. It is worth noting that as the ram moves up it will once again close T2S1 but RLD is now operative and contact RLD6 will be open thus inhibiting the multivibrator during the return stroke of the ram.

inching buttons are incorporated in the control system primarily for setting up to aliow manually actuated bi-directional movements of each of the three hydraulic rams. As a safety precaution and to obviate long term creep due to hydraulic oil leaking through control valves and cylinders, the hydraulic dump valve is included in the hydraulic system.

This valve is taken out of circuit only when one of the above cycles is in progress or whilst any one of the inching buttons is depressed, i.e. pressure is only applied to the various hydraulic rams when movement or force is required.

During automatic cycling the hydraulic dump valve is switched out of circuit by normally open relay contact RLA4.

The inching buttons are as follows: PB2 which has a contact PB2A which controls RLB2 direct as the automatic control line C is taken out of circuit by setting switch S3 to the inching mode i.e. clockwise to energise line B to the inching buttons. RLB2 controls the downward movement (slow) of the top ram, but pressing PB2 will be ineffective if BS21 is not closed by the die fill ram being parked.

PB3 actuates HV4 to cause the top ram to move upwards to the parking position wherein it opens T1S1.

PB4A controls HV5 to move the bottom ram up to the parking position, but is rendered ineffective if the top ram and die fill ram are not parked.

PB5 controls HV7 to move the bottom ram downwards to the limit set by B2S2.

PB6 controls HV8 to cause the die fill ram to move left.

PB7 controls HV6 to cause the die fill ram to move right, but is rendered ineffective if the top ram is not parked (RLA3 normal open contact is provided to block any reverse energisation via line C when PB7A is closed).

BP2, 4, 5, 6 and 7 have contacts B which energise HV9, which can also be energised by PB3C.

BP3B is provided in line D to T1 R to enable the limit set by T1 S to be overriden to enable the top ram to be moved upwards beyond its normal uppermost position to the extreme mechanical limit of the top ram, whereby to facilitate cleaning and changing of the dies.

It will be readily appreciated that a completely inexperienced person can cause the rams to be moved to their parking positions simply by pressing the appropriate inching buttons without any risk of damage arising to the apparatus, due to the buttons acting via components of the automatic control system which effectively provide safety interlocks in the inching mode.

The inching mode is also available to suitably qualified persons who wish to operate the machine with the safety guards removed or rendered ineffective, and this facility can be obtained by means of the key operated switch S2 which can be turned, by means of a key, to the clockwise position whereby to take power directly from PB9 to line B via its contacts S2A, and at the same time its contacts S2B provide a reverse powerfeedto PB8to allowthe motorto be operated independently of the guard switches.

In all conditions of the apparatus the emergency stop button PB9 is effective and cannot be taken out of circuit.

A fuse 40 is provided which safeguards the control system.

Switch S4 is actuated to remove power from line A if the powder level in the hopper 24 falls below a predetermined level, and lights lamp L4 on the control panel 20.

It will be readily appreciated that the limits of the strokes, partial strokes and individually controlled movements of the rams can be adjusted by altering the positions of the cams and/orthe limit switches relative to the rams, and by altering the shapes of the cams and, in the pressure limited cycle, varying the setting of LPS. Also the rate of ram movement can be varied by varying the overall hydraulic supply pressure, the restrictors 30 to 35 and selecting which valve is used to actuate the top ram. The timing of said movements is controlled in response to actuation of the limit switches in conjunction with the aforementioned timed contacts, and optionally the multivibrator.

The relays, solenoid valves and switches involved in producing the reciprocatory motion of the loading device may be arranged to reverse the direction of motion in an abrupt manner so as to jolt the powder in the loading device, but may be adjustable to give a gentle reversal if necessary.

In the first embodiment, upon pressing to density the timed contacts RLK1 may be used to give time for the pressure on the top ram to reach the limit set by VP. Also in the first embodiment limit switch L2S serves as a safety device to prevent damage to the die tools in the event of the downward movement of the top ram not being arrested by actuation of L1 S or by a powder blockage or misfeed causing a late actuation of LPS.

In the modified embodiment shown in Figures 6,7 and 8, which employs the hydraulic system shown in Figure 2, the electrical system is similar to the first embodiment and employs many of the same components which are indicated by the same reference characters as those employed in respect of the first embodiment, but there are several variations in the interconnections between components to give four main programmes of operation.

Referring to Figure 8, the programme selector switch has seven positions, which is clockwise order are: (1) Afirstinching position; (2) Asecond inching position; (3) The first programme for pressing to thickness; (4) The second programme for pressing to density; (5) Athird programme for a singie filling with double pressing action to press to either thickness or density, which is not offered by the first embodiment; (6) Afourth programme for a double filling and double pressing operation which has superseded the third programme in the first embodiment; and (7) A reverse position, which can be utilized to enable further interconnections and components (not shown) to be employed to give an additional programme or a predetermined variation of one of the above programmes.

The circuit includes further relays B3R (controlled by limit switch B3S contact B3S3), RLY and RLX (for tamping), and RLP (controlled by LPS on position 4 of S5 for the second programme) as relay RLK is controlled by L2S in this embodiment, which limit switch L2S is used instead of L1 S in some of the programmes.

In the first programme switch S5 is set to position 3; the switches S1, S2 and S3 are set as hereinbefore described; and PB1A is pressed to energise RLA.

The bottom ram is fully up so that limit switch B1 S is actuated, B1 S1 is closed and relay B1 R is energised. The ram 19 is parked fully left closing switch E1S1 so that relay El R is energised via E1S1. The top ram is parked fully up closing T1S so thatT1R is energised via T1S2.

Power is then applied on line C to the control circuits via B1R3, S1 and RLA5 contacts.

The only circuit permitted to operate is that controlling HV6, the hydraulic valve which effects the die-fill "right" movement.

The ram 19 moves right until limit switch E2S is hit, (which changes-over closing E2S1) energising E2R which latches in via E2R1 contacts, and removes the supply from HV6. In moving to the right ram 5.9 opens limit switch E1S1 which de-energises relay E1R. The ram stops.

The energisation of E2R relay closes E2R3 and the de-energising of relay E1R closes contacts E1 R4 which supply power to solenoid valve HV8 via normally closed RLJ2 and RLF2 contacts. The ram 19 moves left until El S limit switch is hit to energise E1R via Eel 51, and E1 R4 contacts are opened remov ing power from HV8 which stops the ram movement.

The energising of E2R relay also supplies power to solenoid valve HV7 via E2R5, the now closed B1 R1 contacts, the S5C switch which bypasses B3S1 contacts, and the normally closed B2S2 limit switch.

The bottom ram moves down. Thus the operation of limit switch E2S by the die fill ram 19 moving right also causes the bottom ram to move down and expose the die cavity.

The ram 19 in moving fully left strikes El Si limit switch, energising El Rand closing E1R2 contacts, so that power is applied to RLB via RLA2, the normally closed RLD4, limit switch T1 R1 contacts (which are closed by the top ram in its fully up position) B2S1 contacts (which are closed by the bottom ram being fully down to the limit set by B2S limit switch) and now closed El R2 contacts. Relay RLB operates closing RLB2 contacts and supplying power to HV2 and HV1 hydraulic valves simultaneously via the now closed RLD7 contacts and L1S2 and T2S1 limit switches.

The top ram moves down quickly until limit switch T2S is hit to open T2S1 to de-energise HV1 hydraulic valve. The top ram continues to be moved down by HV2 until L1 S is hit. This opens L1 S2 and deenergises HV2 stopping the movement of the top ram. L1S1 contacts also close to energise RLD via the now closed switch contacts S5F and the normally closed limit-switch contact T1S1. HV4 also energises. RLD latches in via RLDi.

The energising of HV4 causes the top ram to move upwards slowly. Time-delay contacts RLD3 close after a pre-set delay and solenoid valve HV3 becomes energised. The ram moves up quickly until it hits TiS limit switch. Contact T1S1 breaks and RLD de-energises. Timed-delay contacts RLD4 close after a pre-settime. Contact RLD2 delay closes and when TiR2 closes, RLE is energised via B1R2, E1 R3 (closed by the position of die-fill ram) and S5B contacts. RLE energises and latches in via RLE1.

The upward stroke of the top ram thus causes the bottom ram to move upwards after a short delay and eject the article by energising hydraulic valve HV5.

The ram moves up until it hits limit switch B1S which energises B1 R via B1S1 and opens contacts B1 R2.

Normally-closed contacts RLD4 have a delayedmake after de-energising of RLD. This delay is to ensure that the bottom ram has moved off B2S and thus opened B2S1, before RLD4 closes, whereby to inhibit the top ram from moving downwards again until the appropriate part of the cycle.

The bottom ram is once again "up", B1 R3 contacts are closed and power is still applied to the control system on line C. The apparatus will cycle automatically.

In the single cycle mode, switch S1 is set fully clockwise no power is supplied to the control circuits until PB B is pressed, because the bottom ram in the up position actuates B1S limit switch to open B1S2 contacts and close B1S1 to actuate B1 R to close B1R3; and the die fill ram in the "left" position actuates EiS to open E1S2 and close E1S1 contacts.

When BP B is pressed, power is supplied, the die fill ram moves right, allowing EiS2 contacts to close and bypass PB B and B1 R3.

Before E1S is operated again the bottom ram will have moved down allowing B1 S2 to close. Thus power is supplied throughout the cycle via El S2 or B1 S2, until the end of cycle when both these switches are open. The machine stops.

In the above cycles, the loading device 18 can be made to judder, i.e. to oscillate above the die cavity for a pre-determined time, and thus promote better die filling facilities with certain "difficult" powders, by closing switch S7. With switch S7 closed the mode is: As the die fill ram moves right it strikes E3S1 which energises RLJ via switch S5G, switch S7 and contacts B2R1. Relay RLJ becomes energised and latches in via RLJ1 only to be unlatched by E2S2 at the limit of the ram stroke when E2R relay latches in via E2S1 and E2R1 contacts, E2R2 contacts becoming open. Contacts RLJ3 also close, but since the ram is already moving right, have no function on this part of the cycle.

Contacts E2R5 close and energise RLF via B1 RI, S5C and B2S2. RLF1 latches in bottom ram descends until B2S2 is struck and the ram stops. The bottom ram in descending hits switch B2S, which energises B2R via B2S3 and operates the delayed-time for the normal closed slow to open B2R1 contacts. On the return stroke of the die fill ram, limit switch E3S1 is hit, energising RLJ which latches in. Normally closed contacts RLJ2 opens, de-energising HV8 and preventing any further movement to the left. RLJ3 contacts also close and energise hydraulic valve HV6 via RLJ4 and E2S1 causing the ram to move to the right. Limit switch E2S is hit, unlatching RLJ which allows RLJ2 to close and move the ram to the left.

The oscillations continue until the timed-contacts B2R1 become open when, since RLJ cannot become energised, the die fill ram continues to move to the left and stops in the fully left position. The press continues with the rest of the normal cycle. If judder is not required when the timer on contact B2R1 is set to zero or S7 can be left open.

All the foregoing are the basic functions of the machine with the programme switch S5 set to position 3.

In the second programme, with the following exceptions, the control system functions as previously described but L1S is adjusted downwards so as to be non-effective in the cycle, but is left in circuit as a safety device to prevent tool damage if powder is not fed to the cavity. A pressure limit switch LPS is first set to the desired pressure to enable a compact density to be achieved. With the programme switch S5 set to position 4, pressure switch LPS and relay RLP are brought into circuit. As the top ram moves down and operates the slow approach switch T2S1 this switches changes-over.

The die or tool upon touching the powder within the die cavity, causes the pressure to build up in the top ram, and on attaining the desired pressure LPS will close, energising RLP. Contacts RLP1 are timed to delay-make and thus enable a pressure-dwell time to be incorporated. (The pressure switch is set to operate at a pressure slightly less than that to which the pressure regulator VP is set). At the end of this time RLP1 contacts close and energise RLD via T1 S1 and S5F. The top ram moves upwards and the press operates as before for the remainder of the cycle.

In the third programme, the start of cycle conditions are as previously described but the programme switch is now set to position 5. The abutment on the top ram which normally operates limit switch T2S to maintain contact with this switch for the entire slow-approach stroke, is asymetrical and is rotated through 90" so as to be ineffective apart from the first few millimetres of the slow approach stroke. Thus T2S now has a make and break function on the down stroke as the ram moves past it. In this mode the top ram will perform a double-pressing action.

For this programme limit switch L1 S is set out-ofreach of the ram. At the start of the cycle the die fill ram moves right until E2S is hit. E2R is energised via E2S1 and latches in via E2R1 contacts. Contacts E2R5 close and RLF becomes energised via the now closed B1 R1, B2S2 and S5C contacts. The bottom ram descends until B2S2 limit switch is hitwhen RLF becomes de-energised. The energising of E2R relay causes the die fill arm to move left as previously described and on reaching the fully left position causes the top ram to descend. In this mode switch L2S is never reached and so RLK plays no part, similarly RLR and RLT.

The top ram in its descent, momentarily operates T2S1 which energises relay RLP which latches in via S5H, S5J and RLP2 contacts. Contacts RLP1 have a pre-settable time-delay before closing and by varying this time in conjunction with the slowvelocity of the top ram an effective press-to-density is achieved by virtue of sustained pressure on the compact. After the delay contacts RLP1 close and relay RLD becomes energised via RLP1, switch S5A, T2S2 and T1S1 contacts.

The top ram ascends as previously described and in so doing unlatches relay RLP via RLD7 contacts.

As RLD operates contacts LRD5 close and RLD6 open, causing relay RLX to energise and latch in via RLX3 contacts. Although RLX2 contacts close, RLY relay does not energise because RLD6 contacts are now open.

The top ram continues to move up until limit switch T2S is struck when RLD becomes deenergised. Contacts RLD6 close and relay RLY energises and latches in via RLY1 contacts.

The top ram starts to move down again after a short delay whilst RLD4 contacts close and energise relay RLB via the now closed RLA2, RLD4, RLX1, E1R2 and B2S1 contacts. Simultaneously RLP relay is momentarily energised via T2S1 and latches in via RLP2 and switches S5H and S5J and relay contacts RLB2 and RLD7. After a delay, timed contacts RLP1 close and energise RLD relay.

Hydraulic valves HV2 and HV1 are de-energised.

Hydraulic valves HV4 is energised and the top ram moves upwards. Limit switch T2S2 is now by-passed by the closed RLY2 contacts.

The ram moves up until limit switch T1S1 is hit.

The cycle now continues as previously described with the bottom tool moving upwards to eject the compact via the energising of hydraulic valve HV5 via RLD2, T1 R2, B1 R2, El R3 and S5B contacts energising relay RLE. Contacts RLE3 open and de-energise relays RLX and RLY unlatching them at the same time. The cycle is complete.

In the fourth programme, the start of cycle condi tions are as previously described, but the program me switch is now set to position 6, and RLP1 timed = contacts are set to zero time, i.e. instantaneous. At the start of the cycle the die fill ram moves right until E2S is hit. E2R is energised via E2S1. E2S2 opens.

Contact E2R5 closes and energises RLF via B1 R1 (closed by bottom ram being fully up) and normally closed switch contacts B3S1 and B2S2. RLF latches in via RLF1 and hydraulic valve HV7 becomes energised causing the ram to move downwards until B3S is hit. B3S1 is opened and RLF drops out. HV7 de-energises and stops the ram. As E2R becomes energised E2R3 also closes and die fill ram moves to the left until it hits limit switch El S1 which energises El R and opens El R4, stopping further movement of the ram. Meanwhile E2R2 and E2R4 become open and prevent the die fill ram moving to the right via a now closed E2S1. As El R energises, contacts El R1 close, to by-pass now open B3S1, and energise RLF via a now closed E2R5 and B2S2 contacts.The bottom ram moves down until limit switch B2S is hit when B2S2 opens and prevents further downward movement. The operation of limit switch B2S closes B2S1 contacts and RLB energises, via the closed contacts of RLA2, RLD4, T1R1, E1R2 and B2S1, latching in via RLB1.

The top ram moves down quickly as HV1 is energised via RLB2, RLT3, S5E and T2S1 contacts. In moving down the top ram exposes switch T1 S which drops out relay Tl R and opens contacts T1 R4, re-setting relay E2R contacts to normal.

As T2S limit switch is hit this changes-over T2S1.

During the first descent of the top ram RLR (control led by RLK) is not energised so that L1 S1 is not effective and thus the top ram enters the partially filled die cavity until it meets limit switch L2S.

Contacts L2S1 close and energise RLD via switch S5F and limit switch T1 S1. Limit switch contacts L2S2 simultaneously change-over to energise relay RLK.

The energising of RLD returns the top ram to its upward position as previously described and T1 R becomes energised.

With the bottom ram in its down position, B1S3 is closed. As RLK energises it closes RLK1 contacts which latch in RLR relay via RLR2 contacts. Contacts RLR3 also close and when the top ram reaches limit switch T1 S, contact T1 R4 closes causing the die fill ram to move right via RLE2, RLR3, E2S1 and E2R4.

E2S operates bringing in relay E2R and latching in via E2R1. (Contacts E2R4 open. This prevents the die fill ram moving right again as it exposes limit switch E2S.).

The contacts E2R3 close and die fill ram moves left until El S is hit which energises El R and opens E1R4 preventing further movement.

E2R relay also closes E2R7 which energises RLT via the now closed R1 R2 contacts and latches via RLT1. Contacts RLT2 close and contacts RLT3 open.

As relay El R energises it closes El R2 causing the top ram to move down again, simultaneously re-setting relay E2R by unlatching it.

RLT3 contacts are now open and limit switch L1S2 is thus active.

The slow approach switch T2S1 operates but the limited stroke of the top ram fails to operate L2S limit switch due to more powder being now in the die cavity and thus RLK is inhibited.

Because RLR is latched in, contacts RLR1 are closed and when the top ram hits L1 S1 (or actuates LPS if this is preset to be effective), RLP is energised and the relay RLD is energised via RLP1 timed contact so that top ram moves upwards until it hits the top limit switch T1 S. The delay on RLD4 prevents it from returning downwards at this stage. The relay TIR operates and closes TIR2 contacts. RLE becomes energised via RLD2, Tit2, B1R2, E1R3 and RLT2 and latches in. Hydraulic valve HV5 energises and the bottom ram moves up ejecting the compact.

With the switch S1 set fully clockwise, when the bottom ram reaches its upper limit switch B1 S, B1 S2 is opened and EiS2 is already opened by die fill ram being fully to the left. No power flows down rail C and the press cycle stops.

With S1 in the closed position, B1 R3 contacts are closed by BIS energising B1R relay. Power flows down rail C and the cycle will continue.

The programmes 1,2 and 3 where there is only a single die fill action, relay contacts B3R1, E2R6 and RLR4 are by-passed by switch S5G and judder operates as previously described.

In programme 4, judder may be applied to both die fill actions. In this mode B3R1, RLR4 and E2R6 are all in circuit.

The overall function is: Die fill ram moves right and operates limit switch E2S1. E2R relay latches in via E2R1. Contacts E2R2 and E2R4 become open.

In arriving at E2S switch, limit switch E3S1 is operated which energises relay RLJ via B3R contacts B3Rl,and limit switches E2S2 and E3S1. Relay RLJ latches in via RLJ1 contacts. When limit switch E2S is struck, contacts E2S2 open and unlatch relay RLJ.

The die fill ram moves left via the now closed E2R3, RLF2, RLJ2 and El R4 contacts which energise hydraulic valve HV8.

In moving left, the die fill ram operates E3S limit switch which energises relay RLJ via the now closed E2S2, E3S1 and timed contacts B3R1. RLJ latches in via RLJ1.

Relay E2R is still latched in via E2R1 contacts.

Contacts RLJ2 open and de-energise hydraulic valve HV8.

The die fill ram stops moving left. Contacts RLJ4 and RLJ3 are now closed by RLJ being energised.

HV6 becomes energised via these contacts and E2S1 contacts. The die fill ram moves right until it hits limit switch E2S opening E2S1. Relay RLJ becomes de-energised allowing contacts RLJ2 to close and once again energise valve HV8. The ram moves left.

The oscillations will continue until timed contacts B3R1 become open. (On the first movement to the right the bottom ram moves down to limit switch B2S), whilst still maintaining B3S in the closed position.

Following the light pressing action of the top ram, the die fill ram once again moves to the right. The action is similar to that previously described except that B3R1 contact is now held open by the substained energisation of relay B3R, and contacts RLR4 and closed by the first pressing action as previously described. Thus timed contacts E2R6 now perform the same function as did B3R1 during the first part of the pressing cycle.

The provision for inching is similar to that in the first embodiment, but switch S5 provides two inching modes in the second embodiment; the first affords inching for setting up L1 S and B3S, the second affords inching for setting up L2S and B2S.

Also inching buttons PB5A, PB6A and PB7A are of double pole form to prevent back feeding on to normally closed lines from line B and to isolate sections of the circuit during inching; and the supply to the dump solenoid HV9 is taken from line B.

The second embodiment includes switch S6 and the oscillator shown in Figure 5 to provide top tool tamping as described, but utilises contact RLD8 instead of contact RLD6 in the oscillator circuit.

The invention is not confined to the precise details of the foregoing examples, and many variations are possible within the scope of the invention. For example, the rams and ram control system may be pneumatically operated. The limit switches may be actuated by any suitable means representing the positions of the rams or the thrust applied to the top ram. The rams and the control means may be arranged to park the rams in any suitable positions.

Furthermore, an automatic device for removing e.g. lifting, pressed articles from said table may be actuated by and interlocked with the control system, to inhibit a further cycle being started until the pressed article has been removed.

The term powders is used herein as encompassing any pulverulent or particulate material or materials, capable of being fed into and pressed in a die arrangement to form a pressed coherent article.

On pressing to density any suitable adjustable pressure limiting device or pressure sensitive limit switch may be used which results in the ram being halted only after a predetermined ram thrust has been reached.

Claims (27)

1. Press apparatus comprising a body around a die or tool space, an upper die or tool holder device connected to a first ram so as to be movable between a lower pressing position proximal to said space and an upper position remote from said space, a lower die or tool holder device connected to a second ram so as to be movable relative to said space between an upper ejecting position and a lower position, a loading device movable transversely over said space from a position adjacent one side of said space to an actuated position by means of a third ram, ram control means adapted to control the rate of movement of said rams, and electric control means adapted to actuate the ram control means, wherein said electric control means comprises limit switches responsive to the operation of the rams, and a control switch which is presettable to determine automatically the sequence and timing of the strokes of the rams in a pressing cycle, and which is responsive to the limit switches to limit the strokes of the rams and to ensure that the devices are parked in predetermined ones of said positions at the start of each pressing cycle; and wherein the control system is adapted to be switched to a setting up condition in which it can be manually controlled to move the rams.

2. Press apparatus as claimed in Claim 1,wherein at least some of said limit switches are adjustably mounted so as to permit adjustment of the positions relative to said space.

3. Press apparatus as claimed in claim 1 or 2, wherein the control system includes interlocks which function as integral parts of the control system when the latter is set to control a pressing cycle, and which function in the setting up condition to enable the press, when actuated manually, to be controlled so that damage to the press and press tools is prevented and so that said devices can be automatically halted when they reach their parking positions.

4. Press apparatus as claimed in claim 3, wherein the control system includes override means to enable said interlocks to be partially negated in the setting up condition.

5. Press apparatus as claimed in any preceding claim, wherein the ram and electric control means include safety means for removing power from the rams in the setting up condition, except whilst said control system is being actively manually controlled.

6. Press apparatus as claimed in claim 5, wherein the rams are hydraulically operated, and the safety means comprises a dump valve in the hydraulic power supply line, which is normally open and is capable of being closed by electrical energisation of an actuating solenoid.

7. Press apparatus as claimed in any preceding claim, wherein the limit switches include respective switches for each of the aforesaid positions of said devices together with further switches therebetween responsive to the devices reaching intermediate positions; and wherein the control system is presettable so as to be selectively responsive to actuation of said further switches to actuate the ram control means to limit, vary the rate of or alter the sequence of said strokes.

8. Press apparatus as claimed in claim 7, wherein the control system is presettable to cause the loading device to make a plurality of reciprocations across the top of said space, and to employ one of said further limit switches to cause a reduction of the strokes of the loading device.

9. Press apparatus as claimed in claim 7 or 8, wherein one of said further switches is utilised to vary the rate of descent of the upper holder device in mid-stroke to give a fast initial approach to the space followed by a slower further action.

10. Press apparatus as claimed in claim 9, wherein the control system is presettable so that said further action is a progressive action or a tamping action.

11. Press apparatus as claimed in claim 7, 8,9 or 10, wherein the control system is presettable to utilise some of said further switches to give a double cycle wherein the lower holder device is held in an intermediate position during a first filling period, and wherein the lower holder device is lowered to and held in its lower position during: (a) a firsttamping, light pressing, or pressing operation; (b) a second filling period; and (c) the descent of the upper holder device for final pressing.

12. Press apparatus as claimed in any preceding claim, wherein the control system includes adjustable or presettable timers to enable said strokes to be modified.

13. Press apparatus as claimed in claim 12, wherein one of said timers is utilised to modify the actuation of the ram control means so that the initial fraction of the upward movement of the upper holder device, after a pressing stroke, is restricted to a slow rate for a predetermined time before a rapid upward return to the parking position.

14. Press apparatus substantially as hereinbefore described with reference to Figures 1 to 4, or Figures 1 to 5, or Figures 6 and 7 of the accompanying drawings.

15. Press apparatus having a hydraulic or pneumatic ram actuable by control means to cause a die or tool supported by a holder device to press a material in a confined space, wherein the control means is adpated to cause a tamping action of the die or tool by causing intermittent reversal or variation of the pressure applied to the ram during that stroke of the ram which causes the die or tool to press said material.

16. Press apparatus as claimed in claim 15, wherein said ram is a first ram and the holder device is an upper holder device; wherein the apparatus includes a lower die or tool holder device connected to a second ram so as to be movable relative to said space between an upper ejecting position and a lower position, a loading device movable transversely over said space from a position adjacent one side of said space to an actuated position by means of a third ram; wherein said control means comprises ram control means adapted to control the rate of movement of said rams, and electric control means adapted to actuate the ram control means, wherein said electric control means comprises limit switches responsive to the operation of the rams, and a control system which is presettable to determine automatically the sequence and timing of the strokes of the rams in a pressing cycle, and which is responsive to the limit switches to limit the strokes of the rams and to ensure that the devices are parked in predetermined ones of said positions at the start of each pressing cycle.

17. Press apparatus as claimed in claim 16, wherein the control system is adapted to be switched to a setting up condition in which it can be manually controlled to move the rams.

18. Press apparatus as claimed in claim 17, wherein the control system includes interlocks which function as integral parts of the control system when the latter is set to control a pressing cycle, and which function in the setting up condition to enable the press, when actuated manually, to be controlled so that damage to the press and press tools is prevented and so that said devices can be automatically halted when they reach their parking positions.

19. Press apparatus as claimed in claim 16, 17 or 18, wherein the limit switches include respective switches for each of the aforesaid positions of said devices together with further switches therebetween responsive to the devices reaching intermediate positions; and wherein the control system is presettable so as to be selectively responsive to actuation of said further switches to actuate the ram control means to limit, vary the rate of or alter the sequence of said strokes.

20. Press apparatus as claimed in claim 19, wherein the control system is presettable to cause the loading device to make a plurality of reciprocations across the top of said space, and to employ one of said further limit switches to cause a reduction of the strokes of the loading device.

21. Press apparatus as claimed in claim 19 or 20, wherein the control system is presettable to utilise some of said further switches to give a double cycle wherein the lower holder device is held in an intermediate postion during a first filling period, and wherein the lower holder device is lowered to and held in its lower position during: (a) a firsttamping, light pressing, or pressing operation; (b) a second filling period; and (c) The descent of the upper holder device for final pressing.

22. Press apparatus as claimed in claim 19, 20 or 21, wherein the control includes adjustable or presettable timers to enable said strokes to be modified.

23. Press apparatus as claimed in claim 22, wherein one of said timers is utilised to modify the actuation of the ram control means so that the initial fraction of the upward movement of the upper holder device, after a pressing stroke, is restricted to a lower rate for a predetermined time before a rapid upward return to the parking position.

24. Press apparatus of hydraulic or pneumatic form adapted to provide a pressing cycle, for pressing powders, wherein a first amount of powder is fed into and pressed in a space to first predetermined limits, and a second amount of powder is added to said first amount and the total thereof pressed in said space to second predetermined limits.

25. Press apparatus as claimed in claim 24 comprising a body around a die or tool space, an upper die or tool holder device connected to a first ram so as to be movable between a lower pressing position proximal to said space and an upper position remote from said space, a lower die or tool holder device connected to a second ram so as to be movable relative to said space between an upper ejecting position and a lower position, a loading device movable transversely over said space from a position adjacent one side of said space to an actuated position by means of a third ram, ram control means adapted to control the rate of movement of said rams, and electrical control means adapted to actuate the ram control means, wherein said electric control means comprises limit switches responsive to the operation of the rams, and a control system which is presettable to determine automatically the sequence and timing of the strokes of the rams in a pressing cycle.

26. Press apparatus as claimed in claim 25, wherein the control system includes interlocks which function as integral parts of the control system when the latter is set to control a pressing cycle, and which function in the setting up condition to enable the press, when actuated manually, to be controlled so that damage to the press and press tools is prevented and so that said devices can be automatically halted when they reach predetermined ones of said positions.

27. Press apparatus as claimed in any one of Claims 7 to 11, 19 to 23,27 and 28, wherein at least one of said further limit switches is a presettable pressure switch responsive to pressure applied to one of said rams.

27. Press apparatus as claimed in claim 24,25 or 26, wherein the limit switches include respective switches for each of the aforesaid positions of said devices together with further switches therebetween responsive to the devices reaching intermediate positions; and wherein the control system is presettable so as to be selectively responsive to actuation of said further switches to actuate the ram control means to limit, vary the rate of or alter the sequence of said strokes.

28. Press apparatus as claimed in claim 27, wherein the control system is presettable to cause the loading device to make a plurality of reciprocations across the top of said space, and to employ one of said further limit switches to cause a reduction of the strokes of the loading device.

29. Press apparatus as claimed in any one of claims 24 to 28, wherein the control system includes adjustable or presettable timers to enable said strokes to be modified.

30. Press apparatus as claimed in claim 29, wherein one of said timers is utilised to modify the actuation of the ram control means so that the initial fraction of the upward movement of the upper holder device, after a pressing stroke, is restricted to a slow rate for a predetermined time before a rapid upward return to the upper position.