GB190908274A - Improvements in and relating to Die Heads of Screwing Machines. - Google Patents

Abstract

8274. Chatwin. A., Chatwin, J., and Chatwin, T., [trading as Chatwin, T.], and Chatwin, T. P., and Virtue, J. April 6. S c r e w i n g; dieheads.-The dies of a screwing-machine are released from the work, without stopping the machine, by the use of a brake to retard a cam which is normally held in a position for closing the dies by a spring, but is overrun by the die-head when the brake is applied. The dies D, Fig. 1, are adjusted by a cam C with eccentric ribs c', which is provided with an annular groove c<2> to receive a. spring E. The spring is connected at one end to a pin b<3>, which fixes a block B in a conical or stepped concentric slot a<1> in the die-head, and at the other end to a pin on the cam, which passes through a concentric slot in the block B, so as to allow relative motion between the cam and die-head. The spring tends to press the dies inwards, and the diameter of cut is varied by the adjustment of the block in the slot a<1>. A brake, shown as a band brake F, is operated to retard the cam and open the dies, the tension of the spring being used to close the dies when the brake is released. The brake may be operated by a screw, or automatically, as shown in Fig. 6, in which the movable end of the brake is engaged by a screw stop on a spindle g<1>, which is advanced by being rotated in a fixed nut through the agency of a pinion g<6> and a rackbar H. The spindle g' may also have an operating- handle. When the required length of thread is cut, a tappet j<2> raises a gravity or spring catch h<5> from a recess h<4> in the bar H, which is moved forwards by a spring h<2> to release the dies. The work saddle, which carries the tappet-bar F, is withdrawn by hand, and the tappet j<1>, the position of which is adjusted to the length of thread, moves back the bar H to release the brake and close the dies. Left hand threads may be cut by the use of suitable cams and dies, and a catch consisting of a spring plunger mounted in a bracket may engage the cam pin to prevent the cams from running back during heavy screwing. According to the Provisional Specification, a quadrant brake and a hinged catch may be used.