Patent GB-654926-A (GB)
Title: Improvements in or relating to control mechanism for controlling and limiting the movements of machine parts
IPC: G05G21/00
Filed: 1946-06-01
Abstract: 654,926. Controlling grinding machines. RIGID, Ltd. June 1, 1946, No. 16710. Convention date, June 2, 1945. [Class 60] [Also in Groups XXII and XXIX] In mechanism for automatically controlling and limiting the movements of a machine part, a number of control elements exerting different control operations are arranged to be consecutively actuated by a single servomotor piston, the movement of which to a selected position is controlled by a slide valve, which at selected points in the movement of the machine part is moved independently of the piston by cams adjustably mounted on the machine part. As shown, a milling machine table 3, carrying adjustable cam-plates 37-40 mounting control cams 41-48, is movable horizontally with respect to a control box 2, which to raise and lower the table is mounted on, and is vertically displaceable with regard to, a guide member 1 having secured thereto a machine part 58 adjustably mounting similar cam-plates. Each pair of cams on the table 3 co-operates in turn as the table moves horizontally with followers 35, 36 disposed respectively on a control bush 28 and a rod 29 held apart by a spring 30 and collars 31, 32. A rack 27 secured to the bush 28 engages a pinion 6 mounted on a spindle 5 to which is keyed a hand lever 4. The pinion 6 also engages a rack integral with a piston slide valve 7 and may engage a rack 53 secured to a similar bush 54 co-operating with a rod 55 for moving the table vertically. The valve 7 is slidable in the hollow rod 8 of a piston 19 and is formed with control edges 9, 10 co-acting with ports 23, 24 in the rod 8 and a port 11 which communicates through an axial passage 12 with exhaust. The piston cylinder 20 is provided with ports 21, 22 supplying pressure fluid to opposite sides of the piston 19, which pressure fluid, when the piston and valve are in their neutral positions, passes through the ports 23, 24, 11 and the passage 12 to exhaust. A rack on the rod 8 engages a pinion 13 secured to a cam-disc 14 having cam slots 15, 17 arranged to co-act with the ends of bellcrank levers 16, 18 controlling reversing and speed changing mechanisms respectively. Movement of the hand-lever 4 from position O to positions A and B moves the table 3 to the left at low and high speeds respectively and to positions A<SP>1</SP> and B<SP>1</SP> to the right at low and high speeds. To operate the machine automatically the hand lever 4 is moved to its selected position, e.g. B<SP>1</SP> whence the table 3 moves to the right at high speed and the rack 27, bush 28 and rod 29 move as a single unit to raise the followers 35, 36 to their highest positions whilst the valve 7 moves to the right to increase the opening of the right hand end of the cylinder 20 to exhaust. This piston 19 then moves to the right to follow-up the movement of the valve and rotate the cam disc 14 clockwise to move the levers 16, 18 to positions A<SP>1</SP> B<SP>1</SP> respectively. On the engagement of the followers 35, 36 with the cams on the plates 39, 40, 37 and 38 in that order, the table moves to the right at high speed up to the plate 39, then at low or " feeding speed " between the plates 39 and 40, reverses at the plate 40, then moves to the left at high speed between the plates 40 and 37 (the plates 39 and 38 being byepassed), and again reverses at the plate 37, to move to the right at low speed between plates 37 and 38 and finally at high speed between plates 38 and 39 to complete the cycle of operations. In a similar manner the control box 2 and the table 3 may be raised and lowered by the engagement of followers 57, 56 mounted on the rod 55 and the bush 54 respectively with similar cams mounted on the machine part 58. In the event of failure of the pressure fluid the sequence of operations may be carried out by manual movement of the lever 4 to its various operating positions. The invention may also be applied to the movement of the tables of grinding &c. machines.