Patent GB-650125-A (GB)
Title: Improvements in work-clamps of electric resistance flash-butt welding and heating machines
IPC: B23K11/04
Filed: 1948-05-21
Abstract: 650,125. Electric welding. RESISTANCE WELDERS, Ltd., GORDON, S. H., and THOMSON, C. May 21, 1948, No. 13830. [Class 83 (iv)] [Also in Group XXIX] In an electric resistance welding machine for flash-butt, projection or spot welding, or a heating machine, the cylinder of an intensifier for increasing the clamping pressure on a workpiece is mounted substantially vertically and is closed at its lower end and a ram and plunger extend downwardly into the cylinder and pass above the intensifier cylinder through a liquid reservoir or through spaces freely connected thereto so that liquid leaking past the ram or plunger during operation of the machine is returned to the reservoir. Fig. 1 shows a fixed electrode block 11 and a movable electrode block 12 together with the operating mechanism for the movable electrode block. Air under pressure supplied at 51 is controlled by a rotary valve 48 and in one position of the valve the air passes to spaces at the lower ends of cylinders 21, 27. Plungers 18, 31 are raised and the electrode block 12 retracted. When the valve is turned through 180 degrees from the position shown, air is directed to the upper end of the cylinder 21, and the upper and lower ends of the cylinder 27 and the lower end of the cylinder 21 are connected to an exhaust pipe 54. The plunger 18 is moved down and the electrode block 12 is moved into contact with the work through the medium of bell-crank levers 15, 16 and the links 14, 17. When it is desired to apply clamping pressure to the work the valve 48 is turned through 90 degrees into a position in which air pressure is applied to the upper and lower ends of the cylinder 27 and both ends of the cylinder 21 are connected to exhaust. The plunger 31 is driven down and its lower end, acting in an intensifier cylinder 34, produces a rise in pressure which acts on the under side of a ram 24 which is connected to the cylinder 27  and to the bell-crank lever 16 and clamping pressure is applied to the work. In the upper position of the plunger 31 grooves on flats 46 at the lower end of the plunger connect the. intensifier cylinder through a clearance space 33 with a reservoir 42, radial ports 45 in the ram connect the clearance space 33 with a clearance space 37 or with this space and the reservoir, depending on the position of the ram in its cylinder. The reservoir is closed by a bellows 44 connected at one end to the cylinder and at the other end to the ram 24. No leakage of oil from the intensifier can take place since the possible leakage paths from the intensifier cylinder lead back to the reservoir. Leather and like packings are dispensed with, the relatively moving parts having ground fits.  Fig. 4 shows a modification in which a movable electrode block 62 which co-operates with a fixed electrode block 63 is connected to an intensifier cylinder 65. The block is moved into engagement with the work by air cylinders 66 and then clamping pressure is applied by supplying air under pressure to the upper end of a cylinder 67 in which works a piston 73 carrying a plunger 74. In the modification shown in Fig. 5 the electrode blocks (not shown) are mounted respectively on a fixed head 84 and a lever 85. The operation is as follows: when air under pressure is supplied to the lower end of a cylinder 94 a piston 99 is raised and takes with it by virtue of a head 101 on the lower end of its plunger 98 an intensifier piston 95. The piston 95 abuts against a hollow member 96 which is also raised and the member 96 carries a cross-head 88 which, through the medium of a link 87, operates the lever 85 and brings the movable electrode into contact with the work. Air pressure is then applied to the upper end of the cylinder and the lower end connected to exhaust so that the plunger 98 is forced down and a high pressure exerted on the lower end of the intensifier piston and thus on the work. When it is desired to release the clamping pressure air is exhausted from the upper end of the cylinder 94 and supplied to the upper end of cylinder 113 to move down a piston 115 which through its rod 116 unseats a valve 119 and releases liquid from the intensifier cylinder 103. The,. liquid level in a reservoir 93 is maintained above the highest point reached by the meeting, faces of the piston 95 and member 96 which contain grooves 124, so that no air can be sucked into the intensifier cylinder. A step 123 limits the downward movement of the piston 95. The piston 95 and the plunger 98 are a ground fit respectively in liners 107 and 127. Specification 631,603 is referred to in the Provisional Specification.