Patent GB-1513862-A (GB)
Title: Fluid pressure apparatus for operating a thrust-applying ram
IPC: B21J7/28
Filed: 1974-05-28
Abstract: 1513862 Hydraulic presses P J HARE LTD 23 May 1975 [28 May 1974] 23519/74 Heading B5F A press comprises a ram 13, Fig. 1A-1B, operated by liquid pressure applied to a piston 18 which is biased in the working direction, a valve 82 for selectively connecting the cylinder space 21 ahead of the piston to a source of compressed gas or venting the space, and means for operating the valve 82 to vent the space 21 so that the piston 18 is moved by the biasing means, the liquid pressure being applied before completion of the ramstroke, after which the valve 82 is operated to return the pistons against the biasing means by compressed gas. The press also includes an air-liquid intensifier 28 supplied by a logic valve 60 which is connected to an air logic valve 53. The valve 53 is operated by a post 55 on the ram 14 and its position is adjustable. Also connected to the tandem logic valve 82 is a time delay device 86 and a jack 85 having a lost-motion connection with a part 88 connected to a guard 48 which is raised by a spring 63. The biasing means is a coil spring 27 surrounding a stop-post screwthreaded into the ram and projecting through the piston to bear against an abutment 65 in one direction of movement and, by means of a collar 64, against the cylinder head 15 in the other direction. A low-pressure cup-ring 25A is provided in one groove of the piston 18 and a two-part high-pressure ring 24, 25 in another groove 22, the inner part 24 being of synthetic rubber and the other part 25 of p.t.f.e. To operate the press the guard 48 is lowered until an associated part 80 actuates the valve 82 to vent the cylinder space 21 and allow the spring 27 to move the ram. Compressed air is also fed to the delay device 86 and to the jack 85 to lock the guard. When the post 55 releases a roller 59, logic valve 53 transmits a fluid pressure signal to the valve 60 so as to set the valve for supplying air to the intensifier 28. A piston 40 in the intensifier is driven down against a return spring 43 so that its plunger 41 closes passages 42 and forces hydraulic liquid behind the piston 18. At completion of the ram-stroke, a signal from the device 86 re-sets the valve 82 to supply compressed air to the space 21 for returning the ram. The supply to valve 53 and jack 85 is also shut-off, thus re-setting valve 60 to vent the space above piston 40 through a silencer 61 and allow return of the piston by spring 43, and also return of the ram-piston 18. One or two interconnected baffles 44 are provided in the intensifier. The jack 85 and reversing timer 86 may be omitted if re-setting of the valve 82 is to be by release of the guard. In another construction, Fig. 2 (not shown), the intensifier (28) is co-axial with the rampiston (18) and its plunger (41) shuts off a port (68) leading to a remote liquid reservoir. In another form, Fig. 3 (not shown), the press is operated by a pedal-valve (69) and includes a pulse generator (91), a safety logic valve (70) and a tandem logic valve (82A) which is operated by a pulse from the generator (91) and not by a guard. A ring guard (73) is provided and if obstructed in its downward movement with the ram (13), operates the safety valve (70) by means of a rod (93), thus resetting the tandem valve (82A) to re-connect the space between the ram-piston to a supply of compressed air. A modification of the press of Figs. 1A, 1B includes replacing the tandem valve 82 with two spaced push-button operated logic valves, the valves being in series with the valve 53 and in parallel between the source of compressed air and the cylinder space 21. Thus either of the push-button valves would vent the space 21 but both must be operated to supply the input of valve 53. In another modification, the valve 82 is operated by a fluid pressure signal from a pilot valve actuated by a hand-lever on the ram-arm 54.