Patent GB-554870-A (GB)
Title: Improvements in fluid power transmission systems
IPC: B23Q5/26
Filed: 1942-01-21
Abstract: 554,870. Drilling. VICKERS, Inc. Jan. 21, 1942, No. 889. Convention date, Jan. 10, 1941. tclass 83 (iii)] A hydraulic feed control for use in step by step deep hole drilling, the drill being returned periodically to clear the hole, has a valve mechanism giving rapid advance, slow feed, and quick return. The dog that causes the change from rapid approach to slow feed is frictionally connected to a rod moving with the drill and is arrested after contact with a switch which operates a time-lag relay to shift the valve to rapid return. During this delay the dog slips on the rod so that after rapid reversal the next rapid approach extends over a greater distance. The valve mechanism 24 is a standard unit such as is described in Specification 516,397, [Group XXIX]. The drill-head 40 is fed by a piston 38 in a double acting cylinder 36 and during feed the exhaust through the pipe 42 is controlled by a valve 43 so that the drill will not descend by gravity alone but a back pressure must build up sufficient to open the valve. When pressure is supplied to 42 for the quick return a check valve 41 opens. The Figure shows the parts in the stop position at the end of a cycle, pump delivery at 18 being byepassed to the sump at 22. Closing of the starting press-button 70, connects one pole of a circuit L1 via 76 to energize a solenoid 28 and shift the valve 26 to rapid advance position RA in which the pipes 18, 34 are directly connected. The solenoid is connected to the other pole of the circuit L2. The button also establishes a holding circuit at 72 at the same time closing contacts in the lead 78 of the switch 54. Just before the drill reaches the work, dog 64, frictionally mounted on the rod 44 attached to the head 40, shifts the valve 26 to feed position. The valve mechanism illustrated provides for both a coarse feed (position CF) and a fine feed (position FF). In the coarse feed a throttle valve 31 is included between the pipes 18 and 22 and for the fine feed an additional throttle valve 33 is included. As ased for step by step drilling only one rate of feed is employed. Immediately after shifting the valve 26 a screw 68 on the dog 64 closes the switch 66 and arrests the dog from further movement. The switch 66 energizes a time lag relay 92 which, after drilling has proceeded for the desired time, actuates the solenoid 32 and shifts the valve 26 to the rapid return position RR. Just before completion of the return stroke dog 52 closes switch 54 to energize solenoid 28 and move the switch to position RA. The dog 64 is now in position 64a and rapid advance now takes place through a greater distance before the valve is shifted to feed position. This cycle continues until the drilling is completed when a dog 46 actuates a switch 48 causing (a) opening of the switch 72 and consequent disabling of the switch 54, (b) solenoid 62 is energized projecting stop 60 into the path of dog 64, and (c) solenoid 32 is energized moving valve 26 to RR position. Actuation of the switch 54 is this time ineffective and return continues until dog 56 moves the valve to stop position S completing the cycle. During this return the stop 60 resets the dog 64 in its original position, a cam 58 then acting on a cross pin on the stop to return it and allow the dog to pass. The valve 35 maintains a constant pressure drop across the throttle valves irrespective of variations in resistance to feed. An excess pressure valve 20 byepasses excess fluid from the constant delivery pump 10 to the sump. Specificatian 423,999 is referred to.