US3597885A

US3597885A - Work holder for machine tools

Info

Publication number: US3597885A
Application number: US757060A
Authority: US
Inventors: Ismael Gonzales
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-09-03
Filing date: 1968-09-03
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10

Abstract

The invention is an improved work holder embodying a dead center for use in the headstock of power tools such as grinding equipment. A dead center is provided in the form of a rod having a pointed end which is nonrotatable but retractable against a spring in a chuck. The chuck is provided with a rotating body having a faceplate mounted on a bearing in such a way that the end of the workpiece comes flush against the faceplate on the rotating member. In this manner, precision of concentricity with respect to the workpiece and precision with respect to linear dimensions is maintained in working on similar workpieces.

Description

United States Patent m13,597,ss5

Ismael Gonzales 6457 Tokay Road, Tujunga, Calif. 91042 [21 Appl. No. 757,060

[22] Filed Sept. 3, 1968 [45] Patented Aug. 10, 1971 [72] Inventor [54] WORK HOLDER FOR MACHINE TOOLS Primary Examiner-Wayne A. Morse, Jr. Attorney-Herzig & Walsh ABSTRACT: The invention is an improved work holder embodying a dead center for use in the headstock of power tools such as grinding equipment. A dead center is provided in the form of a rod having a pointed end which is nonrotatable but retractable against a spring in a chuck. The chuck is provided with a rotating body having a faceplate mounted on a bearing in such a way that the end of the workpiece comes flush against the faceplate on the rotating member. In this manner, precision of concentricity with respect to the workpiece and precision with respect to linear dimensions is maintained in working on similar workpieces.

Patented Aug. 10, 1971 3,597,885

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WORK HOLDER FOR MACHINE TOOLS SUMMARY OF THE INVENTION The invention relates to an improved work holder for use in machine or power tools. An exemplary form of the invention is described in detail herein adapted in a precision grinding machine.

The work holder of the invention basically is an improved chuck embodying a dead center adapted'for use in the headstock of the machine. The improved device embodies a retractable dead center, that is, a stem having a conical pointed end which can retract a limited amount into the chuck against a spring. Additionally, the improved device embodies a rotatable faceplate mounted on a bearing on the device, the piece being worked on when in position being held by the retractable dead center and flush against the rotatable faceplate.

The invention provides a solution to a problem in the art, and an appreciation of the nature of the improvement can be had from an understanding of the problem that it solves. A typical example of the problem is found in the grinding of cylindrical parts in a precision grinding machine. For example, the part may be a generally cylindrical part which might be a spool to be used in a sleevetype of valve. The spool is to have spaced annular grooves ground or milled in it at specified linear distances from the end of the spool. During grinding,

the concentricity must be held within rather precise tolerances and even more particularly the linear distances of the annular grooves from the end of the spool must be held within precise tolerances. When a number of like parts are to be ground in this manner using previously known equipment, maintenance of the required degree of precision in the tolerances was difficult and required repeated tedious attention to the dead cen ters in the headstock and tailstock of the machine, particularly that in the headstock, this being the end of the work to which the rotative effort is applied. The dead center in previously known types of equipment is, of course, subject to wear and impairment in respect to precision in setting up the adjustments of the machine from one workpiece to another. A dead center is, of course, a center that does not rotate with the work. In the device of the herein invention as stated, the dead center member which is in the form of a carbide rod retracts into the chuck in which it is mounted against a spring. Mounted on a bearing around the chuck is a member which carries the faceplate. Thus, when the workpiece is put in the machine its end engages the retractable dead center which retracts into the chuck with the end of the workpiece coming flush against the rotating faceplate of the unit. Thus, concentricity from one piece to the next is maintained by the dead center and the precision of the linear dimensions, that is, the dimensions of the annular grooves from the end of the workpiece are maintained by the flush engagement of the end of the workpiece with the faceplate of the device. Since it is mounted on bearings and rotates with the workpiece there is no friction or impairment of the linear precision from piece to piece. Thus, during the course of grinding a large number of pieces a substantial amount of work and attention is eliminated because of obviating the need for constant rechecking and readjustment to maintain the precision of the linear dimensions as described.

A primary object is to provide an improved dead center unit capable of simultaneously maintaining precision with respect to concentricity of workpieces and also with respect to precision of the grinding or the like at predetermined distances from the end of the workpiece.

A further object of the invention is to provide an improved dead center member or unit for use in machines of the type described which is mounted to be retractable within a rotatable faceplate so that the workpiece retracts the dead center and comes into flush engagement with the faceplate.

Further object and additional advantages of the invention will become apparent from the following detailed description and annexed drawings, wherein:

LII

FIG. 1 is a partial pictorial view of a typical precision grinding machine in which the invention may be adapted;

FIG. 2 is a sectional view of a preferred form of chuck embodying the invention and adapted for use in the headstock of I a machine like that of FIG. 1;

FIG. 3 is an enlarged sectional view showing the device of the invention embodied in a machine like that of FIG. 1;

FIG. 4 is a view ofa modified form of driver plate that may be embodied in the device.

Referring now to the various figures of the drawings, FIG. I is a partial view of a typical form of precision grinding machine. The machine has a stand or base It) as conventional in this type of machine with a table, platform or bed I2 at the top. Mounted on the machine is a headstock assembly designated generally at 14 which embodies the usual drive motor and power transmission means for delivering rotary power to the chuck which is part of the headstock. Power transmission means are enclosed within the housings l6 and 18, the improved work holding chuck of the invention being designated generally at 20. The machine has a rotary face plate 22 carrying dog 24 that engages the work for rotating it as will be described.

The machine is provided with the usual manual adjustments for adjusting the headstock assembly and tailstock assembly of the machine. The tailstock assembly is designated generally at 30. In the tailstock assembly is a dead center member 32 and adjustment means are included as indicated at 34.

The machine shows a workpiece in position to be worked on as designated at 36. As an example the workpiece may be of a type as previously referred to such as by way of example a cylindrical member in the form of a spool to be used in a sleeve valve. Parallel annular grooves are to be grounded into the workpiece. Numeral 40 designates a typical grinding wheel in a housing 42 and to which fluid is supplied through a pipe 44 from a tank 46. Power for the grinding wheel is supplied by a motor 50 through transmission means as designated at 52.

FIGS. 2 and 3 are cross-sectional views of the chuck in which the invention is embodied.

FIGS. 2 and 3 show a preferred exemplary form of the invention wherein the unit embodies a chuck in the form of a tapered cylindrical body 56, the left end having an external taper for insertion into a socket into which it is held. The body 56 has a bore 60, the end of which is threaded as shown at 62. Received in this bore is the carbide rod 64 which is the dead center having a conical tapered pointed end as designated at '66. The dead-centering rod 64 is urged outwardly by a coil spring 70 in the bore 60 which is held in position by screw plug 72 in the threaded end of the body 56.

The dead-centering rod 64 has a transverse groove 76 in it that has a flat bottom as shown and engaging in this groove extending through a sidewall of the body 56 is a set screw 78 which by engaging in the groove prevents the dead-centering rod from rotating but allows it to retract a limited amount into the bore 60 as will be described.

The body 56 has a part 82 of intermediate external diameter an end part 84 of smaller external diameter. Mounted on the diameter 82 is a roller bearing 86 which seats against the square shoulder between the larger diameter and the intermediate diameter 82 of the body 56. It is held in position by a snap ring 90 that seats in an annular groove the part of the body 56 of intermediate diameter 82. Journaled on the hearing 86 is a rotatable cylindrical body 92 having a bore 94 and a smaller bore 96 at the opposite end. The bore 94 is threaded at the end as designated at 100 and received in this bore is a threaded closure member 102 and positioned between this closure member and the bearing 86 is a flexible scaling member 104 which may be of a conventional type. It should be understood that other types of seals may be used at this point in the unit such as O-ring type seals similar to those to be described presently. Such O-ring seal might be disposed in the bore of the closure member 102.

Attached to the right end of the cylindrical body 92 is the faceplate member 110. It has a bore 112 ofa size to be spaced radially from the part of the body 56 of smaller diameter 84 and interposed between these parts are a group of sealing O- ring 114. The member 110 has a eounterbore or another bore 116 of smaller diameter than the bore 112 and positioned between the bottom of this bore and end of the body 56 is a sealing O-ring 120.

The member 110 has a flange part 122 that fits into the bore 96 in the body 92 and the unit or member 110 has an extending flange 124 that fits against the end surfaces of the cylindrical body 92 and is secured thereto by screws 126. The member 110 has a tapered end surface as designated at 128 and a flat end face as designated at 130.

Faceplate 110 is readily removable for substitution of other faceplates to accommodate workpieces of different diameters and having end bores ofdifferent sizes.

FIG. 3 shows the device mounted and positioned in the grinding machine with the workpiece 36 in place. Mounted on the end of the workpiece is a dog 140 secured to the workpiece by a set screw 142. The workpiece has the usual end bore 144 and tapered eounterbore 146 that receives the conical end 66 of the dead center rod which typically is made of carbide. Numeral 150 designates a drive rod extending between the driving member and the dog 140 for rotating the work, this rod engaging a cylindrical lug 152 which is attached to the body 92 by way of a screw 154 so that the entire body 92 and its faceplate rotates about the bearing as the workpiece is rotated.

ln setting up the machine for grinding, the headstock and tailstock are set to receive the workpiece 36 in the manner as shown. In setting up it will be observed that initially the deadcentering rod 64 protrudes from the device as shown in FIG. 2 and when the workpiece is brought against it and fitted to it, the dead-centering rod 64 retracts into its bore with the workpiece coming flush against the faceplate 130 of the body 92. Thus, it will be observed that the end of the dead-centering rod 64 preserves the concentricity as work proceeds from piece to piece. The setting of the chuck embodying the dead center in the machine determines the position of the end face 130, that is, the faceplate and thereby determines the linear positioning of the workpiece in the machine and controls linear dimensions from piece to piece. Since the faceplate rotates with the workpiece there is no friction therebctween and no impairment of precision of the dimensions that are ground in the workpiece as the work proceeds from piece to piece. It is not necessary to make new adjustments set up at intervals while grinding a lot of parts or pieces.

FIG. 4 shows a slightly modified form of the invention embodying an improved way of holding the workpiece. In this form of the invention the parts are like those of the previous embodiment and similarly numbered, except that the end faceplate is provided with the circular screwdriver plate 135 having

screwdriver projections

160 and 162. The end of the workpiece is then provided with radial milled slots or grooves to receive the screwdriver projections and 162, so that the rotation is imparted directly from the faceplate without the use of a dog. The advantage of this is that concentricity and linear tolerances can be maintained without the use of a dog attached to the workpiece for rotating it, and the workpiece can be ground throughout its full length without having to turn it around to finish the grinding with a dog attached to a part of the workpiece.

From the foregoing, those skilled in the art will understand and appreciate the nature and characteristics of the invention and the manner in which it realizes and achieves the objectives as set forth in the foregoing and the many advantages that are apparent from the detailed description.

The foregoing disclosure is representative of a preferred form of the invention and is to be interpreted in an illustrative rather than a limiting sense, the invention to be accorded the full scope of the claims appended hereto.

What 1 claim is:

1. A work holder for holding a rotated workpiece comprising a chuck, a dead-centering member having a pointed end and means mountlng said member 11'] said chuck so that It is axially retractable in a limited amount and nonrotatable with respect to said chuck, rotatable means having a faceplate concentrically mounted around said pointed end, and mounted relative to said chuck and said centering member, and mounted in such a position that the workpiece engages against the rotating faceplate when the dead-centering member is axially retracted away from said rotating faceplate.

2. A work holder as in claim 1 wherein said chuck has a bore, said dead-centering member being mounted in said bore, and a spring positioned to tend to urge the dead-centering member outwardly in the bore.

3. A work holder as in claim 1 wherein said rotatable means comprises a cylindrical member and bearing means interposed between said chuck and said cylindrical member.

4. A work holder as in claim 1 wherein said faceplate is configurated to provide means to directly rotatably engage the end of the workpiece whereby the work holder directly rotates the workpiece without a separate dog.

5. A work holder as in claim 4 wherein said faceplate has radial projection means positioned to be received in slot means formed in the end of a workpiece for directly rotating the workpiece.

6. A work holder as in claim 1 wherein said dead-centering rod has a side flat which has radial end shoulders and means extending through a sidewall of said chuck engaging said fiat to prevent rotation of the dead-centering rod and to limit I relative axial movement.

7. A work holder as in claim 1 including means sealing the interior of the rotatable cylindrical member.

Claims

1. A work holder for holding a rotated workpiece comprising a chuck, a dead-centering member having a pointed end and means mounting said member in said chuck so that it is axially retractable in a limited amount and nonrotatable with respect to said chuck, rotatable means having a faceplate concentrically mounted around said pointed end, and mounted relative to said chuck and said centering member, and mounted in such a position that the workpiece engages against the rotating faceplate when the dead-centering member is axially retracted away from said rotating faceplate.

6. A work holder as in claim 1 wherein said dead-centering rod has a side flat which has radial end shoulders and means extending through a sidewall of said chuck engaging said flat to prevent rotation of the dead-centering rod and to limit its relative axial movement.