GB2076921A

GB2076921A - Guard for hydraulic press

Info

Publication number: GB2076921A
Application number: GB8114609A
Authority: GB
Original assignee: HYDRAULIC ENGINEERING CO Ltd
Current assignee: HYDRAULIC ENGINEERING CO Ltd
Priority date: 1980-05-14
Filing date: 1981-05-13
Publication date: 1981-12-09

Abstract

A hydraulic press incorporates an operator guarding arrangement at the front and rear of the press working area. The rear component of the guarding arrangement is preferably a fixed wire mesh machined rear panel, while the front component of the guarding arrangement may either be a photo- electric light curtain or a mechanical sliding guard which comprises a frame (18) hingeable (19) below the top of the press bed (16). The guard comprises two gates (20) (21) offset from one another and carried by endless timing belts (22). <IMAGE>

Description

SPECIFICATION Improvements relating to hydraulic presses This invention relates to hydraulic presses, especially but not exclusively hydraulic presses for use in coining, calibrating, planishing and cold setting of drop forgings.

With such hydraulic presses operator safety is of prime importance and the object of this invention is to provide a hydraulic press incorporating such a facility.

According to the present invention there is provided a hydraulic press incorporating an operator guarding arrangement at the front and rear of the press working area.

The rear component of the guarding arrangement is preferably a fixed wire mesh machined rear panel.

The front component of the guarding arrangement may be a photo-electric light curtain coupled into the control system of the press so that the press is stopped and returns to its starting position whenever the curtain of light is broken. The press functioning cycle can be initiated each time the operator breaks and then clears the curtain, or the press functioning cycle is initiated after the operator has broken and cleared the curtain twice. In the two latter instances, the guarding aspect is, of course, maintained.

The press functioning cycle may alternatively be initiated by two hand cycle start buttons or a foot switch.

Alternatively the front component of the guarding arrangement is a mechanical sliding guard, normally closing the front of the press during functioning thereof and, opening automatically after completion of the dangerous movement of the press upon release of a lock which is coupled into the press control system to ensure non-functioning of the press when the guard is open.

The mechanical sliding guard preferably comprises two vertically-slidable gates movable in opposed directions under the control of a double-acting pneumatic ram which actuates an endless timing belt to which the gates are tied.

An example of the present invention will now be described with reference to a press of known construction perse but incorporating a mechanical sliding guard arrangement according to the invention.

Reference is now made to the accompanying exemplifying drawings, in which: Figure 1 is a front view of a hydraulic press incorporating the invention; Figures 2 and 3 are respectively front and side elevations of the mechanical sliding guard arrangement; and Figures 4, 4A and 4B illustrate the hydraulic circuit of the press.

The hydraulic press 10 is self-contained and free-standing. It has hydraulic pumping equipment and control valve gear (not shown) at its rear with electrical push-button control 11 at its front.

The press has a frame constituted by two heavy gauge steel plates with the upper part providing a tank 12 for the pump oil. The valve gear is housed between the plates and protected by lockable steel doors.

The main ram and its cylinder are fitted within the frame, the upper moving table 13 being connected to the ram and also push-back cylinders. The moving table has tee slots 14 for mounting tools. The lower fixed table or bed 16 is also provided with toolmounting tee slots and is mounted within the frame and may house the press ejector cylinder attached to the underside of the fixed table.

The mechanical sliding guard arrangement 17 occupies the front daylight area of the press and comprises (see especially Figures 2 and 3) a rectangular box section frame 18 hinged as indicated at 19 to permit hingeing open of the guard which extends below the top of the press bed 16 for tool setting purposes.

The guard comprises two gates 20, 21 offset from one another as can be seen from Figure 3. The gates 20,21 are carried between a pair of endless timing belts 22 which pass around timing belt pulleys 23 carried by shafts 24 extending across the front of the press. A double-acting pneumatic cylinder 25 is coupled to one of the timing belts 22 and its operation either moves gates 20 and 21 apart to allow insertion or removal of a workpiece or together as shown during press functioning.

The cylinder 25 also moves a cam bar 26 to operate limit switches 27, 28 (one being normally open and the other normally closed) to allow press functioning (gates 20,21 closed) or inhibit press functioning (gates 20, 21 open).

The rear guard (not shown) to the working area of the press is constituted by a simple fixed wire mesh machined rear panel. This is sufficient since all workpieces are inserted into the working area from the front of the press.

Press operation will now be described with reference to Figures 4, 4A, 4B.

Upon initiation of press functioning by the operator solenoid 29 is energised, operating valve 30 to open admission valve 31 permitting oil flow to ram 32, at the same time solenoid 33 is energised operating valve 34 to close pump unloading valve 35 diverting pump flow from the tank 36 into the circuit.

Solenoid 37 is also energised, operating valve 38, closing decompression valve 39, preventing any loss of fluid from the ram 32 to tank 36. Energisation of solenoids 40 and 41 also take place operating valves 42 and 43, opening valves 44 and 45, permitting oil to flow from the side return rams 46 and 47 into main ram 32. This allows the moving table 13 of the press to fall, the speed of which is controlled by the resistance to the oil flow of the fixed orifices in the choke check valves 48 and 49.

When the moving table 13 with tooling fitted contacts the workpiece, pressure starts to rise operating pressure switch 50 and de-energised solenoids 40 and 41 close valves 44 and 45. These are held closed by main line pressure selected by valves 51 and 52, thus isolating side rams 46 and 47.

The working pressure of the main ram 32 rises until the value set by the variable pressure relief valve 53 is attained, which lifts and allows oil to flow through the choke check valve 53Athe pressure drop across which operates pressure switch 54. This stops further pressurisation of the main ram 32 by deenergising all solenoids. Admission valve 31 is closed preventing escape of pressure from main ram 32 and pump unloading valve 35 is opened.

Also at this stage decompression valve 39 is opened allowing pressure in the main ram 32 to fali at a controlled rate. When the initial setting of pressure switch 50 is reached it resets and signals solenoid 33 to energise closing pump unloading valve 35, allowing oil to flow through valves 44 and 45, which now act as return valves, and into the side return rams 46 and 47 returning the moving table 13 to the top of its stroke.

If during press function downwards solenoids 40, 41,29 and 37 are de-energised leaving solenoid 33 energised there is a complete arrest of press move mentfollowed by return movement of the moving table to the top of its stroke.

Should all solenoids be de-energised during its down function complete arrest of press movement will take place.

If a hydraulic pipe in the circuit bursts at any time other than signalled down, the press freezes, valves 44 and 45 locking the side return rams 46 and 47 in position.

It is to be noted that the press has a duplicated safety system, i.e. either side return ram has the capability of a hold or return function should its opposite number malfunction.

Claims

1. A hydraulic press incorporating an operator guarding arrangement at the front and rear of the press working area.

2. A hydraulic press according to claim 1, in which the front component of the guarding arrangement is a photo-electric light curtain coupled into the press control system so that the press is stopped and returns two its starting position whenever the curtain of light is broken.

3. A hydraulic press according to claim 1, in which the front component of the guarding arrangement is a mechanical sliding guard, normally closing the front of the press during functioning thereof and, opening automatically after completion of the dangerous movement of the press upon release of a lock which is coupled into the press control system to ensure non-functioning of the press when the guard is open.

4. A hydraulic press according to claim 3, in which the mechanical sliding guard comprises two vertically-slidable gates movable in opposed directions under the control of a double-acting pneumatic ram which actuates an endless timing belt to which the gates are tied.

5. A hydraulic press according to any one of claims 1 to 4, in which the rear component of the guarding arrangement is a fixed wire mesh machined rear panel.

6. A hydraulic press, substantially as hereinbefore described with reference to the accompanying drawings.