Patent GB-248442-A (GB)
Title: Improvements in means for controlling feeding mechanisms in machines for reducing a body by the removal of material therefrom
IPC: B24B47/20
Filed: 1924-12-01
Abstract: 248,442. Imray, O. Y., (Blanchard Machine Co.). Dec. 1, 1924. Gauging-devices; driving machines.-In a machine for reducing work pieces by removal of material therefrom the feeding means which causes the relative approach of the tool and work is normally inactive and is brought into operation by a work piece which is larger than a predetermined dimension, the feed mechanism being controlled by the friction of a shoe resting against the work. As described with. reference to grinding the work is secured, preferably magnetically, on a table 15 driven from a main driving pulley 35 through change-speed gearing 29, shaft 27 bevel gearing 21 and spur gearing 19. An abrasive wheel 37 is mounted on a spindle 41 carried in bearings on a head 47, vertical feed of the head being effected by a feed screw 51 driven through bevel gearing 55, shaft 57, and bevel gearing 59 from a ratchet wheel 65. The latter is operated by a pawl lever which is reciprocated by a link 71 actuated from the shaft 27, through a vertical rod 85 and crank pin 75. In order to varv the amount of feed the stroke of the feed pawl is determined by a stop plate 93 which may be interposed in the path of a lug 95 on the pawl carrier. The stop plate is carried on a slide 97 formed on a bracket 99 which is formed with arcuate guides moving over corresponding fixed guides 103 and is angularly adjustable about the axis of the ratchet wheel. The guide 103 is graduated to facilitate setting and a further fixed pointer 113 serves for setting the feed wheel. In operation, when the stop plate is retracted, the downward movement of the feed pawl is limited only by the plate 97 but when the plate is brought forward, the downward movement of the pawl is further limited to give either a fine feed or to stop the feed altogether. An auxiliary stop 93<1> adjustably located over a pin 125 passing through the main stop may be used to give a further variation in the feed. The movement of the stop into the path of the feed pawl is effected by a lever 133 controlled from the work itself. A follower 151 rests normally in frictional contact with the work and is carried on a spring pressed lever 163 pivoted to a bracket secured to a collar 173 vertically adjustable on a screwed rod 177, a graduated nut being provided to facilitate this adjustment. The lever 163 carries an electrical contact 199 coacting with a second contact 201 mounted on the collar. The contacts form part of a circuit which includes an electromagnet 143 coacting with an armature on the lever 133 carrying the stop plate. In normal operation the friction between the work and the follower overcomes the spring 193 and the electric circuit is completed, thus withdrawing the stop plate to effect the coarse feed. When the work has been so far reduced that it is no longer in contact with the shoe the. lever 163 moves to break the circuit of the magnet 143 and the stop plate is then moved forward by a spring to reduce or to arrest the feed of the grinding wheel towards the work.