Patent GB-375980-A (GB)
Title: Improvements in grinding or abrading machines
IPC: B24B49/04
Filed: 1931-06-10
Abstract: 375,980. Grinding. BRYANT CHUCKING GRINDER CO., 257, Clinton Street, Springfield, Vermont, U.S.A.-(Assignees of Bryant, W. J. ; Connecticut River Road, Springfield, Vermont, U.S.A.) June 10, 1931, No. 16935. Convention date, June 16, 1930. [Class 60.] Gauges; trueing; rotating tools.-In grinding-machines, a device is provided whereby when the work has been ground to size, an indication is given, which, in the forms described consists in the withdrawal of the grinding- wheel from the work ; a preliminary withdrawal before the work is to size may be provided for trueing the wheel, a second withdrawal then taking place when the work is exactly to size. As applied to an internal grinding machine, the work 2 is held in a rotating support 1 and is ground by a wheel 3, which is provided with a ring 4 of conducting-material softer than the wheel, for example, carbon. As the wheel is fed, this ring closes an electric circuit with another contact 5 so placed that the contact is made when the work is to size, the circuit including a battery 6, and a relay 8, which closes the circuit of a source of potential 9 and a solenoid 10. The core 11 of the solenoid moves a rod 12 carrying a screw 31, which lifts a pawl 29 from a ratchet wheel 18 and moves an arm 13 carrying a pawl 35 so that this moves off a shield 36 and rotates the wheel 18 to withdraw the wheel 3 from the work ; the wheel 18 is rotated in the opposite direction, to feed the wheel 3 into the work by the pawl 29, which is actuated by an arm 27 moved by a cam 25. By the use of a switch 7 a voltage of 8 volts may first be applied to the contacts, whereby the wheel 3 is withdrawn from the work before it is quite to size, the wheel and the ring 4 then being trued and re-inserted in the work, the switch then being set to apply 6 volts. With the same setting of the contact 5, the device will operate to withdraw the wheel 6 when the work is exactly to size. The device also may be applied to a multiple spindle grinding machine having a number of work holders and one fewer grinding-wheel, the sizing being produced by the last wheel of the series, and in this case the fixed contact may be in the form of a ring with which the contact portion of the wheel engages. In a further modification, for long work, a fixed contact is arranged at each end of the work and a contact at each end of the grinding- wheel, so that either may stop the grinding, and in the arrangement shown in Fig. 6, the grinding-wheel 90 has contact portions 91, 92, that 92 being for roughing size and arranged through contact with an element 93 carried by a trueing device 94 to cause trueing by a diamond 95. The device then is thrown out of position, and final sizing is carried out by the contact 91 and an element 96. As applied to a surface grinder, the grinding-wheel 100, Fig. 8, has a peripheral contact ring 101 having its face in the plane of the face 102 of the wheel, and a fixed contact element 104 is provided, whilst for external grinding of cylindrical work, a grinding-wheel similar to that shown in Fig. 6 is used, fixed contact elements being situated at the ends of the work. The Specification as open to inspection under Sect. 91 (3) (a) comprises also an arrangement wherein the contact member 5 is moved by the grinding-wheel to complete a circuit independent of the ring 4, and a modification of that arrangement wherein the movable contact member consists of mercury contained in a tube and adapted successively to contact with two terminals, one controlling rough grinding and the other the final sizing. In a further construction, a pivoted element bears on the grinding-wheel and is rocked thereby to close the circuit when the work is to size, no contact ring being employed on the grinding-wheel. This subject-matter does not appear in the Specification as accepted.