Patent GB-699965-A (GB)
Title: Improvements in work-tables for machine tools
IPC: B24B41/00
Filed: 1950-12-14
Abstract: 699,965. Grinding. FOUQUET, E. Dec. 14, 1950, No. 30577/50. Class 60. A machine tool comprises a work-table 9, Fig. 1, mounted on a support 1 displaceable relatively to the frame 4 of the machine, and a mechanical abutment 29 co-operating with the table to displace it relatively to the support and thereby stop the cutting operation independently of stopping the displacement of the support. The work-table 9 is pivoted at 13 to a bracket 1 that may be fed continuously towards a reciprocating grinding wheel 30 or like tool, along guides 2 on the machine base 4, by a piston rod 6. One or more rods 15, influenced by springs 23 which are compressed between the table 9 and flanges 24 on the rods by nuts 18, engage hollows 17 in the lower side of the table to support it in a horizontal plane. A rod 28 is pivoted at 26 to the table' 9 and limits the travel thereof through engagement between the abutment 29 and adjustable nuts 32, 33 on the rod which passes through the abutment. If the piston rod 6 travels a distance h before stopping after the nut 32 has engaged the abutment 29, the table 9 will pivot about the axle 26 moving the workpiece away from the grinding wheel into the position 11'. The grinding machine illustrated in Fig. 4 is the same as that described in Specification 699,966 and is provided with an abutment control unit, Fig. 5, carried by the slide 68 in the path of movement of the work-table 46 so that it may be operated by the work-table to slow down and finally stop the feed movement of the table before instituting a return movement. Feeding motion of the worktable is slowed down as the springs transmitting this motion between the jack-operated support bracket 41 and the table are compressed due to the throttling action of a fluid being forced through a passage 128 in the control unit into a vessel 131 by a plunger 117 engaging the table. This plunger, which is secured with its housing on the slide 68 by a screwed cap 83, moves against the influence of a spring 87 and has a stem 116 provided with parts 117, 118 of reduced diameter which may engage the passage 128. When the end 67 of the plunger 117 has been raised to the position II, the part 118 of the plunger enters the passage 128 and consequently increases the throttling effect. The passage 128 is finally completely sealed by the part 117 of the stem 116 when the end 67 reaches the position III. Continued feeding of the table then forces some of the fluid remaining in the cylinder 79 along an adjacent cylinder 89 to displace a piston 93 against the influence of springs 92, 103. This motion of the piston 93 rocks a lever 98 into engagement with a spring-urged contact 106 to make a circuit through an earth return 120 and a conductor 143 connected to a relay system which stops the motor controlling the flow of fluid to the jack 62, the motor being re-started, in the reverse direction, after a time delay sufficient to allow the springs between the bracket 41 and the work-table 46 to feed the table through a distance E so that the top surface 86 of the plunger 117 comes to rest against the top part 85 of the cylinder 79. To facilitate adjustment of the control unit and the slide 68 without affecting the relay system to the pump motor, a valve 145 is provided which allows fluid to escape from the cylinder 79 into the vessel 131 during adjustment. The positions II and III can be varied by replacing a locating piece 126, disposed between the plunger housing and a flange 125 on a member 124 through which the passage 128 passes, with another of different length. A ball 138, supported on a stem 139 carried by a perforated plate, seats against a conical surface 137 in the vessel 131 when the latter is removed from the plunger housing to prevent loss of fluid.