506,971. Drilling and drill-testing machines. KENYON, A. S. G. July 7, 1938, Nos. 20077 and 35645. [Class 83 (iii)] In a drilling or drill-testing machine the drill is rotatably mounted in a fixed head and the work table is fed resiliently towards the drill, clamping means being provided for preventing undue movement of the table when the drill breaks through the work. The machine oomprises a fixed head I supported by four columns 2 and carrying a spindle 15 for the drill 17 which is rotated by gearing 16 and belt 14, from an external source of power. The work table 6 has brackets at the comers carrying ball-bearing rollers 10 which engage guide surfaces 11 on the columns and is fed upwards by two or more sets of pulley blocks and cables 3, 5 and adjustable weights 4. A damping force is applied to the table by one or more dashpots 18 attached to the columns 2 having piston rods 19 connected to brackets on the table, the damping force being arranged so that it does not impede the feed but comes into action when the drill breaks through. The rate of feed before cutting commences may be adjusted by connecting opposite ends of the dashpot by pipes 20 and connecting the several systems in parallel by pipes 20a, an adjustable valve 21 being placed in one of the pipes 20 to vary the speed at which the liquid may pass from one end to the other of the dashpots. The system is kept full of liquid by a reservoir 20b. The work table is returned by means of a screwed sleeve 25 connected thereto by a thrust bearing and splined to a shaft 25a driven by bevel and belt gearing 26, 28 from the external source of power, a nut segment 22 for engaging the sleeve being mounted on a fixed support 23 and being movable into and out of contact with the sleeve by a hand-operated screw 31. The movement of the table is also controlled during drilling by rods 33 pinned at 36, Fig. 2, to the under side of the table and carrying at their lower screwed ends adjustable sleeves 40 on which are freely slidable sleeves 39 screwed into cylinders 32a slidable on the rods. Springs 37 are compressed between flanges 38 on the cylinders and the ends of the sleeves 39. The cylinders are supported by the springs 37 resting on the upper ends of the sleeves 40 and the latter are adjusted on the rods 33 so that the upper ends of the cylinders will come into contact with the lower side of the fixed support 23 when the drill commences to break through the work whereby the springs 37 are further compressed by the sleeves 40 to keep the load on the table constant. When the drill has broken through, adjustable rings or lock-nuts 41 on the sleeves 40 engage flanges 39a on the sleeves 39 to prevent further movement of tho table. The compression of the springs 37 is adjusted initially by the sleeves 39 so as to be equal to the feeding pressure applied to the table by the weights.
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