US2526796A - Precision grinding machine - Google Patents

Description

Oct. 24, 1950 G. ASBRIDGE PRECISION GRINDING MACHINE Filed May 5, 1948 Wm M.

Patented Oct. 24, 1950 PRECISION GRINDING .MACHINE George Herbert Asbridge, Altrincham, England,

assignor to The Churchill Machine Tool Company Limited, Altrincham, England, a British company ApplicationMay 5, 1948, Serial No. 25,198 In Great Britain May 19, 1947 1 Claim.

This invention relates to precision grindin machines and has for its object to provide improved means for grinding workpieces to size automatically in either internal or external grinding machines.

In accordance with my invention, the machine is provided with upper and lower tables, the upper one being hingedly or pivotally mounted upon the lower table and having thereon means for carrying the workpiece to be ground, the lower table having mounted thereon a former upon which a part upon the upper table rests so that if the former is traversed or moved so that the said part is moved from a low position on the former to a high position, theupper table will be rocked about its pivots and the workpiece thereon will be ground to size and each subsequent piece will be ground to the same size for a similar movement or" the former.

The invention further comprises a combined electrical and hydraulic control means for the machine which gives a fully automatic cycle to the machine.

Referring to the accompanying explanatory drawings Figure 1 is a general view of a grinding machine with control means giving a fully automatic cycle of operations after the cycle has been commenced with a hand controlled movement.

Figure 2 is an end view of the machine.

Figure 3 is an electrical diagram of the control connections,

The grinding machine comprises an upper table a carrying a headstock b and tailstock c and supports d into which each workpiece e is placed so that it can be engaged by the tailstock spindle or centre ,f and supported between the headstock and tailstock centres clear of the supports d.

The grinding wheel head g is carried rigidly on the part h. The grinding wheel is shown at z.

The table a is pivotally carried by the lower table 7' which can slide along the machine bed in the usual manner to move the workpiece across the grinding wheel 2'. If desired the pivotal connection between the tables a and 7' may be constituted by knife edges. Upon the lower table 7' is longitudinally traversible a slide is having a former m mounted. thereon upon which rests a part n, known as a knudger, secured to the underside of the upper table adjacent to the edge of the table or opposite to that at which the grinding wheel i is situated. The pivotal supports of the upper table are at the side thereof at which the grinding wheel is situated.

The slide k is coupled to a piston p in a double 2 acting hydraulic cylinder q. The fiow of hydraulic fluid to and its exhaustion from the cylinder (1 is by way of the pipes 'r., s leading to a cylinder t containing a valve u moved in one direction by a solenoid 22 and in the other direction by a spring in. Pressure fluid is supplied to the cylinder t by the pipe :0 fed by the gear type pump z are the exhaust pipes leading from the ends of the cylinder t.

The tailstock c has its centre moved in a, direction to engage the workpiece by the spring 4 and in the other direction by a hydraulic piston 5 in a cylinder 6 having a fluid connection I leading to a fluid control valve 8 which is moved to the right in Figure 1 by the hand lever 9 and to the left in such figure by the solenoid in acting through the hand lever. As shown, the valve 8 is in a position in which pressure fluid from the pump y is passing by way of the pipe H and the cylinder 2 to the pipe I and so to the cylinder 6 in the tailstock, to hold the tailstock centre 1 in its inoperative withdrawn position. When the said centre 1 is in this position a contact plate 13 on the spindle of the piston 5 is clear of the contacts l4 so that an electric circuit through the latter is broken.

A contact plate it upon the stem of the piston p is adapted in one position of the plunger to bridge the electric contacts it and in the other position of the piston to bridge the contacts H.

The stem of the piston p also carries a cam l8 which 'when the plunger is in its right hand position engages and operates a contact plate I9 causing it to close contacts 25.

The operation of the machine is controlled as follows: When the handle 9 is moved to the right in Figure 1, the pipe I is put in communication with the exhaust pipe 2! and so the cylinder 6 is exhausted, thus allowing the spring 4 to advance the tailstock centre f and engage the workpiece carried on the supports d and carry it so that it is supported between the head stock and tailstock centres. The contact plate G3 now closes the contacts i i which as shown in Figure 3 connects the solenoid o between the mains 22, 23 so that it is energised. The feed valve 11. is moved against the spring to and causes pressure fluid to pass from pipe at to pipe 1' (s being exhausted). This results in the piston p being moved to the right and traversing the former m, up which the part it rides and tilts the table a. The workpiece e is therefore fed against the grinding wheel and ground to size. At the end of the stroke of piston p, contacts 29 are closed by the plate [9 operated by the cam l8. Contacts [6 have been opened and contacts I! closed. Closing of contacts I! energises the relay 24 which closes the normally open contacts 25 and 26. 25 is in series with the solenoid l0 and 26 is connected across the contacts ll. 21 is a dwell relay which is energised when the contacts 20 are closed and after a predetermined interval of time opens the contacts 28 and deenergises the solenoid u so that the feed valve u is reversed and the piston p returned to its initial position with the former m clear of the part 12. When this occurs the contacts I! are opened and [6 closed. Relay 24 is maintained in circuit via contacts 26. When contacts iii are closed, the solenoid i0 is energised and pressure fluid passed via the valve 8 to the tailstock cylinder 6 to cause the tailstock centre to be withdrawn from the workpiece e which drops on to the supports d. At the same time the contacts M are opened which de-energises the entire electrical circuit. This is now in correct condition to repeat the cycle after the handle 9 has been moved.

What I claim is:

A precision grinding machine comprising, in

combination, a grinding wheel, an upper table, a

tailstock and a headstock carried by said table, a lower table, a pivotal connection between the upper and lower tables at the grinding wheel side of the tables, a former, a slide carrying said former traversible longitudinally upon said lower table at the side of the latter opposite to that at which the grinding wheel is situated, a part upon the underside of the upper table resting on said former so as to tilt the upper table as the slide is traversed, a spring moving the tailstock centre to its operative position, a hydraulic plunger withdrawing said centre from its operative position with means closing an electric circuit when the centre is in its service position, a valve controlling the hydraulic fluid operating said plunger, a hand lever for moving said valve in a direction to release pressure fluid from said plunger, a solenoid to operate said valve to cause pressure fluid to be applied to said plunger, a hydraulic plunger traversing the former-carrying slide, closing two sets of contacts when the former is traversed to its position to give maximum tilt to the upper table and closing one set of contacts when the former is in its out of service position, a valve controlling the passage of hydraulic fluid to one or other side of said last mentioned plunger, such valve being moved by a solenoid against spring pressure, one of the two sets of contacts controlled by the plunger of the slide carrying the former closing a circuit through a dwell relay controlling contacts in the circuit of the solenoid operating the slide plunger, whilst the other of the two sets of contacts close a circuit through a relay which closes normally-open contacts in the circuit of the solenoid operating the valve of the tailstock plunger and normally-open contacts between said other of the two sets of contacts, so that the slide plunger has its motion reversed after the slide has moved the former to a maximum extent and finally the tailstock plunger control valve solenoid is energised, causing the tailstock centre to be withdrawn and the complete electrical circuit de-energised.

GEORGE HERBERT ASBRIDGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,082,734 Grifling et a1 June 1, 1937 2,178,848 Booth Nov. 7, 1939 2,185,490 Flygare Dec. 12, 1939 2,448,551 Schroeder Sept. '7 ,1943

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