US2254784A - Grinding wheel feeding mechanism - Google Patents

Description

H. A. SILVEN GRINDING WHEEL FEEDING MECHANISM Filed June 5, 1940 .I 8 m an. a w N 2. 1 M E 31| 0l m 6 8 V z m l n \2 ,m Y s 2 i@ w am. 5 m.\ VX H. I Nvo 4. T l e \5 5 e 71;@ w 5 H 1 4. 6m 2 I H 4 4 6 m6 Q, H f O\ 1.1" .nlv E 5 G QLJMZS H 5 5\\\ l W. W 6 m w 4 m a T w w E Q sept. 2, 1941.

Examiner UNITED STATES PATENT OFFICE GRINDING WHEEL FEEDING MECHANISM Herbert A. Silven, Worcester, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application June 5, 1940, Serial No. 338,967

2 Claims.

The invention relates to grinding machines, and more particularly to a hydraulically operated grinding wheel feeding mechanism.

One object of the invention is to provide a simple and thoroughly practical, hydraulically operated grinding wheel feeding mechanism. Another object of the invention is to provide a suitable wheel feeding mechanism so that the infeeding movement of the grinding wheel may be precisely controlled to grind successive work pieces to a predetermined size. Another object of the invention is to provide a backlash eliminating mechanism whereby the operating parts of the feeding mechanism are always maintained with a pressure in one direction.

A further object of the invention is to provide a fluid pressure operated mechanism for maintaining a predetermined pressure op the wheel slide in one direction so that the thrust of the feeding mechanism parts is always in positive control of the wheel feeding movement. A further object of the invention is to provide a hydraulic piston and cylinder mechanism which applies a predetermined pressure on the wheel slide in one direction so as to pick up the lost motion of the feeding mechanism parts to facilitate precise duplication of parts in production grinding. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which is shown one of various possible embodiments of the mechanical features of this invention,

Fig. l is an end elevation of a grinding machine, having parts broken away and shown in section to illustrate the improved wheel feeding mechanism together with a hydraulic piping and wiring diagram, and

Fig. 2 is a fragmentary cross-sectional view, on an enlarged scale, of the hydraulic Wheel slide actuating mechanism.

A grinding machine has been illustrated in the drawing comprising a base I which supports a transversely movable wheel slide II which is mounted on transversely extending ways (not shown) on the base I0. 'I'he wheel slide II supports a rotatable grinding wheel I2 which is mounted on one end of a rotatable wheel spindle well known mechanism, such as by means of a pulley I4 mounted on the other end of the wheel spindle I3 which is connected by means of a driving belt I5 with a suitable source of power, such as an overhead drive shaft or the like.

The base I0 also supports a longitudinally traversable work supporting table I 8 which is arranged to be traversed longitudinally relative to the base I0 on a flat way I9 and a V-way 20. The table I8 is provided with a rotatable work support including a headstock 2| and a footstock (not shown), each of which is provided with work supporting centers rotatably to support a Work piece 22 in operative relation with the grinding wheel I2. The longitudinally movable table I 8 may be traversed longitudinally by a manually operable traverse mechanism including a manually operable traverse wheel 25 which is mounted on the outer end of a rotatable shaft 26. The shaft 26 is journalled in a bearing 21 formed in the front face of the base I0. A gear 28 is mounted on the inner end of the shaft 26 which meshes with a rack bar 29 depending from the under side of the table I8. While a direct driving connection is provided between the hand Wheel 25 and the rack bar 29, it will be readily apparent that a reduction gear mechanism, such as is old and well known in the art, may be employed, if desired. For a more complete disclosure of such a mechanism for traversing the work supporting table I8 either manually or by power, reference may be had to the expired U. S. patent to C. H. Norton, No. 762,838, dated June 14, 1904.

A Wheel feeding mechanism is provided for manually feeding the grinding wheel I2 toward and from the Work piece 22, which comprises a half nut 30 depending from the under side of the wheel slide I I. The half nut 30 meshes with or engages a rotatable cross feed screw 3l. A forwardly extending portion 32 of the feed screw 3| is slidably keyed within a rotatable sleeve 33. 'I'he rotatable sleeve 33 is formed as an integral part of a rotatable shaft 34 which is supported in bearings 35 and 36 formed in the base I0 of the machine. A manually operable feed wheel 31 is mounted on the outer end of a stud 38. The stud 38 carries a pinion 39 which meshes with a gear 40 mounted on the outer end of the rotatable shaft 34 so that a manual rotation of the feed wheel 31 serves to rotate the feed screw 3| in either direction to cause a forward or rearward feeding movement of the grinding wheel I2 and I3. The wheel spindle I3 may be driven by any 55 its supporting wheel slide II. The feed wheel 31 may be provided with a micrometer adjusting mechanism 4| which is substantially identical with that shown in the above-mentioned prior U. S. pategt to Norton. This micrometer adjusting mechanism serves precisely to adjust a stop abutment relative to the manually operable infeed wheel 31 to compensate for wear of the grinding wheel and to facilitate setting up the machine for grinding work pieces to a predetermined size.

In the preferred construction the wheel slide II is arranged so that it may be moved toward and from the work piece 22 to grind the same to a predetermined size by means of a fluid pressure actuated grinding Wheel feeding mechanism. As illustrated in the drawing, the rear end of the feed screw 3| is rotatably supported in a slidably keyed bearing 45 which is in turn supported in a casing 46 on the base I0 of the machine. A fluid pressure cylinder 41 is either attached to or formed integral with the casing 46 and contains a slidably mounted piston 48 which is connected by a piston rod 48 with the bearing member 45 and is arranged so that when fluid under pressure is admitted to a cylinder chamber 50, the piston 48 will be moved toward the right (Figs. 1 and 2), transmitting a corresponding movement through the feed screw 3| and the half nut 30 to move the wheel slide II and grinding wheel I2 rearwardly to an inoperative position. Similarly, when fluid under pressure is admitted to a cylinder chamber 5I, a rapid approaching movement of the grinding wheel I2 and the wheel slide II will be obtained.

A fluid pressure system is provided to supply fluid under pressure for moving the piston 48 so as to cause a forward or rearward feeding movement of the grinding wheel I2. This system may comprise a reservoir 55 which is formed as a box-like section within the base I and serves to convey fluid under pressure through a pipe 58 to a motor driven fluid pressure pump 51. The pump 51 forces fluid under pressure through a pipe 58 to a control valve 58. The control valve 58 is preferably a piston type valve comprising a valve stem B0 having formed integrally therewith valve pistons 8|, 62, 63 and 64. Fluid under pressure passing through the pipe 58 enters a valve chamber 85 (Fig. 2) located between the valve pistons 82 and 63 and passes through a passage 66 into the cylinder chamber 50 to move the piston 48 to its rearward position with the grinding wheel I2 separated from the work piece 22, as indicated in the drawing. During the rearward movement of the piston 48 toward the right (Figs. 1 and 2), fluid is exhausted from the cylinder chamber through a passage 61, into a valve chamber 88 located between the valve pistons 6I and 62, and out through a pipe S8 which exhausts Into the reservoir 50.

Similarly, when the valve stem 80 is shifted toward the left into its reverse position, fluid under pressure from the pump passing through the pipe 58 and entering the valve chamber 55 will pass through the passage 81 into the cylinder chamber 5| to cause a forward feeding movement of ,the wheel slide and grinding wheel I2, that is, toward the left (Figs. 1 and 2). During the movement of the piston 48 toward the left, fluid within the cylinder chamber 50 passes out through the passage 68 into a valve chamber 10 located between the valve pistons 83 and 64 and passes out through a pipe 1| which connects with the pipe 68 and thereby exhausts fluid into the reservoir 55.

The valve stem 80 is arranged so that it may be moved endwise to shift the valve 58 into a reverse position so as to cause a forward or rearward feeding movement of the grinding wheel I2. In the preferred form a manually operable control lever 88 is pivotally mounted on a. stud 8| which is in turn supported by a bracket 82 fixedly mounted on the front of the machine base. A lever 82 is also pivotally mounted on the stud 8| andthe lever 82 is flxedly mounted to move with the lever 80. The upper end of the lever 82 is provided with a stud 83 which engages a groove 84 formed in a spool-shaped member which is fixedly mounted on the forward end of the valve stem 60. It will be readily apparent from the foregoing disclosure that movement of the lever 80 in a. counterclockwise direction will shift the valve 58 into the reverse position to initiate a forward feeding movement of the grinding wheel. Similarly, movement of the lever 80 into the position illustrated in Fig. 1 shifts the valve into its reverse position to cause a rearward separating movement of the grinding wheel I2 relative to the work piece 22.

As illustrated in the drawings, an electrically operated control mechanism is provided for shifting the valve 58 into its rearward position to cause a separating movement between the wheel and the work piece. `A solenoid 85 is xedly mounted within the machine base. The solenoid 85 is connected by means of a link 86 with the lever 82. When the solenoid 85 is energized, the valve 58 is automatically shifted into the position illustrated in Figs. 1 and 2. The energize.- tion of the solenoid 85 is controlled in a manner to be hereinafter described.

A uid pressure controlled feed regulating mechanism is provided for modifying the rapid approaching movement caused by the piston 48 so as to produce the desired slow uniform infeeding movement of the grinding wheel I2. In the preferred construction, a self-contained dash pot feed regulator is provided comprising a pair of dash Dot cylinders 80 and 8| which contain dash pot pistons 82 and 83, respectively. The

dash pot pistons 82 and 83 and their respective cylinders and 8| are arranged with their axes parallel to each other and spaced on diametrically opposite sides of the= piston rod 48. The dash pot pistons 82 and 83 are normally held in a rearward (right-hand) position by means of springs 84 and 85, respectively. Adjustable stop screws 88 and 81 are provided to limit the rearward movement of the dash pot pistons 82 and 83, respectively. A slidable sleeve 88 is supported on the rearward end of the piston rod 48. The sleeve 88 is adjustably positioned on the rod 48, it being provided with an internally threaded portion which is screw threaded onto a reduced threaded portion |00 on the piston rod 48. A lock nut IOI is provided whereby the sleeve 88 may be readily locked in adjusted position.

I'he rapid forward feeding movement of the grinding wheel I2 and wheel slide II continues until the sleeve 88 on the threaded portion |08 of the piston rod 48 engages the right-hand end face of the dash pot pistons 82 and 83, respectively. Contnued movement of the piston rod 48 moves the sleeve 88 and continued movement serves to move the dash pot pistons 82 and 83 in a direction toward the left, so as to reduce the rapid approaching movement of the grinding wheel I2 toward the work piece 22 to a slower but predetermined grinding feed due to the fact that fluid confined within the dash pot cylinders 90 and 9|, respectively, must exhaust through a restricted aperture to be hereinafter described. The dash pot cylinders 90 and 9| are interconnected by a passage |02. Fluid conflned within the dsh pot cylinders 90 and 9| must exhaust; through a passage |03, a needle valve |04, and through a passage |05, into a uid reservoir |06. By adjusting the aperture of the needle valve |04, a desired and predetermined infeeding movement of the grinding wheel |2 may be obtained.

When uid under pressure is admitted to the cylinder chamber 50 to cause a rearward movement of the piston 48, the sleeve 98 is also moved rearwardly so as to release the compression of the springs 94 and 95, respectively, which returns the dash pot pistons 92 and 93, respectively, to their rearward position (Figs. 1 and 2). The rearward movement of the dash pot pistons 92 and 93 is limited by the adjustment of the stop screws 96 and 91, respectively. During the rearward movement of the dash pot pistons 92 and 93, a suction is created within the dash pot cylinders 90 and 9|, respectively, which serves to aid in drawing fluid from the reservoir |06, through a pipe |01 and a ball check valve |08, rapidly to fill the dash pot cylinder chambers 90 and 9| for the next infeeding movement of the grinding wheel I2. During the infeeding movement of the dash pot pistons 92 and 93, fluid within the dash pot cylinders 90 and 9|, respectively, serves to hold the ball check valve |08 closed so that fluid within the dash pot cylinders 90 and 9| is forced out through the passage |03 and the needle valve |04, into the reservoir |06, to control the rate of infeeding movement as desired.

The forward feeding movement of the grinding wheel |2 as controlled by the dash pot pistons 92 and 93, respectively, continues until an adjustable stop collar |09 carried by the sleeve 98 engages a xed stop surface ||0 on the rear face of the dash pot cylinder head. A pair of locking collars serve to maintain the stop collar |09 in adjusted position.

In order to obtain a nish grinding operation with the grinding wheel l2 held immovable in its forward position, it is desirable to provide a suitable control mechanism whereby the grinding wheel may be maintained in its foremost position for a predetermined time interval. In the preferred construction, an adjustable electrical time delay relay ||5 is so connected as to regulate and control the shifting movement of the feed control valve 59 so as to control the extent of the finish grinding operation. A normally open limit switch ||6 is supported on a bracket H1 on the rear of the feeding mechanism. A detent |8 carried by one of the collars is positioned in the path of an actuating roller H9 on the limit switch H6. The limit switch I|6 is adjustably positioned on the bracket IIT so that it may be adjusted in such a position that the detent H8 will engage the roller ||9 and close the switch I|6 when the sleeve |09 moves into engagement with the stop surface ||0. When the limit switch I6 closes, it sets the time relay ||5 in motion and the grinding operation continues for a predetermined time interval according to the setting of the time relay, after which the time relay operates to close a circuit and energize the solenoid 85. Closing of the solenoid 85 shifts the control valve 59 into its reverse position to admit fluid under pressure from the pipe 58 into the valve chamber 65 and through the passage 66 into the cylinder chamber 50 to cause a rearward movement of the piston 48, thus separating the grinding wheel I2 from operative engagement with the work piece 22. By adjustment of the time relay ||5, the dwell period of flnish grinding on the work piece 22 may be varied as desired.

In order to eliminate the effect of any backlash in the feeding mechanism parts, a mechanism is provided for applying a definite and predetermined pressure on the wheel slide Il. In the feeding mechanism shown in the drawing, a mechanism has been provided for applying a constant and predetermined pressure or Dull on the wheel slide in a rearward direction so that the thrust of the feed screw 3| together with the piston 48 is always in a given direction and any lost motion or backlash between the nut 30 and the screw 3l together with the slidable bearing member 45 is thus taken up always in the same direction. In the preferred form a fluid pressure operated mechanism is provided comprising a fluid pressure cylinder |20 which contains a slidably mounted piston |2|. The cylinder |20 is adjustably supported by a bracket |22 which is fixed on the rear of the wheel feeding mechanism. The upper end of the bracket |22 is provided with a cylindrical aperture |23 within which the cylinder |20 fits. The upper part of the bracket |20 is slotted and the two spaced parts thereof provided with clamping or binder screws |24 and |25 by means of which the cylinder |20 maybe readily clamped in adjusted position in fixed relationship with the bracket 22. This adjustment between the cylinder |20 and the bracket |22 is provided to facilitate setting up the machine for grinding work pieces of different diameters.

A piston rod |26 is connected at one end to the piston |2I. The other end of the piston rod |26 is connected by means of a bracket |21 with the rear face of the wheel slide A pipe |28 is connected to the pipe 58 so as to receive direct pressure from the pump 51 and admit fluid under pressure to a cylinder chamber |29 so that at all times during the operation of the feeding mechanism, fluid pressure is applied to the piston |2I tending to move it in a direction toward the right, thus pulling back in a rearward direction on the wheel slide |I so that the thrust of the feeding mechanism parts is always in a rearward direction during the forward or rearward movement of the wheel slide. An adjustable valve |34 is provided in the pipe line |28 by means of which the passage of fluid under pressure through the pipe |28 may be varied as desired.

A pressure relief valve |30 is connected by a. pipe |3| with the pressure pipe 58 and serves to maintain a predetermined fluid pressure within the uid pressure system. If for any reason the pressure within the system increases over the set pressure, the relief valve |30 automatically opens and by-passes excess fluid under pressure through a pipe |32 into the reservoir 55. It will be readily apparent from the foregoing disclosure that by applying a definite and predetermined rearward pressure to the wheel slide I during both its forward and rearward feeding movements, the wheel slide I is accurately controlled so that it may be precisely fed into a predetermined stopped position accurately to control the size of successive work pieces 22.

The operation of this improved wheel feed controlling mechanism will be readily apparent from the foregoing disclosure. A work piece 22 is set in position on the headstock and footstock members.

Assuming all of the feed adjustments have been made, the operator shifts the lever 80 in a counterclockwise direction to reverse the feed control2 valve 59 so that uid under pressure fronitle pipe 58 is admitted through the passage 61 into the cylinder chamber 5| to initiate a forward infeeding movement of the grinding wheel I2. At the same time, fluid under pressure passes through the valve |34 which has previously been adjusted. into the cylinder cham- 'oer |29 to maintain the desired and predetermined back pressure on the wheel slide I I during the infeeding movement, thus providing a precisely controlled infeeding movement whereby duplicate work pieces within fine limits may be successively produced.

The infeeding movement of the grinding wheel |2 continues as a rapid approaching movement as governed by the movement of the piston 48 until the collar 98 engages and picks up the dash pots 92 and 93, after which the rapid approaching movement is reduced to a slow, uniform, controlled grinding feed which continues until the stop sleeve |09 engages the stop surface I0 to limit the forward advancing movement of the grinding wheel I2. As the sleeve |09 engages the stop surface I I0, the detent I I8 engages the roller |I9 and closes the limit switch I I6, which sets in motion the time relay IIS, which governs the extent of the finish grinding operation. After the predetermined set interval, the time relay I operates to close the circuit, thereby energizing the solenoid 85, which rapidly shifts the valve stem 60 toward the left to reverse the position of the valve 59, thereby admitting iiuid under pressure into the cylinder chamber 50 to cause a rearward movement of the wheel slide |I and grinding wheel I2.

It will thus be seen that there has been provided by this invention apparatus vin which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine having a rotatable grinding wheel, therefor, a hydraulically operated mechanism including a piston and cylinder operatively connected to move said slide transversely in either direction to produce either a forward or rearward feeding movement of the grinding wheel, a fluid pressure system including a fluid pump to supply fluid under pressure to said cylinder, a feed control valve therefor, a second piston and cylinder, means operatively connecting said piston with said slide, a bracket xedly mounted relative to the base, an adjustable clamping device on said bracket adjustably to support said cylinder, and fluid connections between said pump and said second cylinder continuously to exert a thrust on said slide in one direction during the forward and rearward feeding movement of the slide to eliminate backlash in said feeding mechanism.

2. In a grinding machine having a rotatable grinding wheel, a transversely movable slide therefor. a feeding mechanism including a nut and screw operatively connected to move said slide transversely, a hydraulically operated mechanism including a piston and cylinder operatively connected to move said screw axially in either direction to produce either a forward or rearward feeding movement of the grinding wheel, a uid pressure system including a fluid pump to supply fluid under pressure to said cylinder, a feed control valve therefor, a second piston and cylinder, means operatively connecting said piston with said slide, a bracket xedly mounted on the rear of the base, a cylindrical bore in said bracket to iit the periphery of said second cylinder, means to clamp said cylinder in adjusted position relative to said bracket, and uid connections between said pump and said second cylinder continuously to exert a thrust on said slide in one direction during the forward and rearward feeding movement of the slide to eliminate backlash in said feeding mechanism.

HERBERT A. SILVEN.

a transversely movable slide

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