Patent GB-853227-A (GB)
Title: Improvements in or relating to a method of and apparatus for vertically actuating the tools of machines for grinding and/or polishing glass
IPC: B24B7/24
Filed: 1957-06-13
Abstract: 853,227. Grinding and polishing glass. GLACERIES DE LA SAMBRE S.A. June 13, 1957, No. 18755/57. Class 60. The upper tool or tools in a machine for grinding and/or polishing glass sheets are supported by a piston 2 operating in a cylinder 1 and adapted to be raised automatically when an increase in pressure in the cylinder results from the passage of a sheet from beneath the tool or tools. Hydraulic fluid from a sump 5 is supplied by a pump 6 to the cylinder 1 secured to a supporting member of the machine through a pipe 4 in which are an adjustable valve 8 opening into a pipe 9 and a non-return valve 7 arranged to close in the event of failure of the pump and to prevent the full weight of the tools damaging the glass. Discharge pipes 10, 11 lead from the pipe 4 to the sump 5 and each is provided with a manually-operable cock 13, 20 and an electro-magnetic valve 14, 21 ; the valve 14 is arranged to close under the action of a pressure-sensitive device 17 connected to a supply 16 when the pressure in the pipe 4 reaches a predetermined maximum value, and the valve 21 arranged to close under the action of a pressure-sensitive device 23 when the pressure in the pipe 4 drops to a predetermined minimum value. A manually-operable valve 12 is included in the pipe 10 to determine the crosssectional area of flow through the pipe 10 and the working pressure and comprises, for example, a needle and adjustable pressure diaphragm. In operation, the valve 8 is adjusted so that with both cocks 13, 20 closed, the upward pressure P<SP>11</SP>, which is indicated on a gauge 24, and supplied by the pump 5, is higher than the downward pressure P<SP>1</SP> caused by the weight of the tool or tools and their associated movable members. The cock 13 is opened and the valve 12 adjusted to lower the upward pressure P<SP>11</SP> until the difference in the pressuress P<SP>1</SP>, P<SP>11</SP> is equal to the desired working pressure between the tool or tools and glass. If, during grinding or polishing, the glass is removed from beneath the tool or tools, their unsupported weight increases the pressure P<SP>11</SP> and operates the device 17 which closes the valve 14 ; the full pressure, as set by the valve 8, then raises the tool or tools to an upper abutment and prevents possible interference between them and any lower tool or tools. To lower the tools, the cock 20 is opened and fluid allowed to discharge through the pipe 11. The tools then descend rapidly until, either the cock 20 is closed, or, when the pressure P<SP>11</SP> drops to the predetermined minimum value, the device 23 actuates the valve 21 and the pressure P<SP>11</SP>, as set by the valve 12, is re-established to lower the tools gently on to the glass at the operating pressure ; an automatic locking device 25 retains the valve 21 closed and is later disconnected after the cock 20 has been closed. When it is desired to stop grinding, the cock 13 is closed which increases the pressure P<SP>11</SP> in the pipe 4 as before to raise the tool or tools. In another arrangement, the valves 8, 14, 21 are replaced by mechanical valves operating against counterweights, and the valve 12, which is also supplied with a counterweight, arranged to close when the pressure in the pipe 10 falls to a predetermined value for which its counterweight is set. In other arrangements, the valves may be inechanical and operate against springs, of pneumatic, electronic, or of mixed form. Specification 763,176 is referred to.