GB481423A - Improvements in expanding wheels and other rotary members - Google Patents

Abstract

481,423. Grinding machines. DUDLEY, W., and MORRIS, B. O. Sept. 9, 1936, No. 1565/38. Divided out of 481.362. [Class 60] In a grinding-machine wherein the spindle of the grinding wheel 11 is driven through variable-speed gearing, a stop member is interconnected by electrical means with the gearing so that said member must be adjusted before the spindle can be rotated at increased speed, such adjustment being prevented by contact of the member with the periphery of the wheel 11 unless the state of wear of the latter is sufficient to justify the increase of speed. 'The -speed gear shown in Fig. 1 includes an expanding pulley 12 driving the spindle through a belt 13, the rim of the pulley being constituted by spaced tread bars adapted to be moved towards or away from the axis. A contact member 40 actuated by movement of the work rest or holder 18 co-operates with a series of studs 39, each of which is electrically connected to a corresponding stud 37 of another series co-operating with a contact arm 36 linked to a slidable member 26. The members 36. 40 are connected in the circuit of the motor driving the pulley 12 so that, if one of them is moved without the other, the motor stops. The member 26 carries a part 24 formed with a lug 29 disposed outside the orbit of the projecting ends 17 of the pulley tread bars. Thus, as the member 26 is moved to the left by operation of the arm 36 following a movement of the rest 18 towards the wheel 11, consequent on wear of the latter, the lug 29 allows the diameter of the pulley to be increased only by a corresponding amount. A second lug 28 is formed on the member 24 inside the orbit of the bar ends 17 to prevent movement of the member 26 without corresponding adjustment of the pulley. An electric circuit including a signal device may be completed when the bar ends 17 contact with either of the lugs 28 and 29. Alternatively, the member 24 may, as shown, be pivoted on the member 26, a toggle spring 31 normally holding the member 24 in the position shown relative to the member 26, so as to hold electric contacts 32 and 33, connected in the circuit of the motor, in engagement. If either of the lugs 28 or 29 is struck by the bar ends 17, the member 24 is knocked up, separating the contacts and thus stopping the motor. In a form wherein the pulley can be adjusted while running by means of a fork, the latter is coupled to one contact arm while the rest is linked to a second contact arm. Where a group of machines are employed, the contact devices 56, 57 of the various machines may be arranged in series, as shown in Fig. 4, but each is shunted by a signal lamp 61. Thus, if an attempt is made to operate any machuie ineorrectly, the corresponding lamp lights up. The circuit also includes a lamp 62 which is normally lit but which dims when one of the lamps 61 is lit. Specification 481,362 is referred to. The Provisional Specification includes an arrangement in which a member corresponding to the part 24 is mechanically connected to the work rest.