US2407222A - Grinding machine - Google Patents

Description

Sept. 10, 1946.

M. B; BOYCE 2,407,222

GRINDING MACHINE Filed Oct. 12, 1945 3 SheetsSheet l P f 9 M. BOYCE 7 2,407,222

GRINDING MACHINE Filed Oct. 12, 1945 3 Sheets-Sheet 3 Invert ?02-.

Patented Sept. 10, 1946 UNITED STATES PATENT OFFICE GRINDING MACHINE Y Malcolm B. Boyce, Havel-hill, Mass. I Application October 12, 1945, Serial No. 622,017

9 Claims.

This invention relates to improvements in grinding machines and more particularly to machines which can safely and accurately grind small-diameter parts and elements, such as pins whose diameters may be of the order of eight to twenty thousandths of an inch, for example. However, the invention has general application forgrinding axially straight elements and parts whose diameters may vary from a few thousandths of an inch upward.

Itis among the objects of the invention to provide a grinding machine in which the grinding action occurs simultaneously at opposite sides of the work, with the pressure on the work approximately balanced, whereb there is little or no tendency to bend or otherwise distort the work during the grinding operation; as frequently happens when attempt is made to grind small-diameter elements and parts according to conventional grinding procedures. I employ two grinding wheels in disk or ring form, each mounted for rotation about a common axis and each resiliently urged toward the other for resiliently engaging work between them. Two or a larger even number of driven work-holding chucks are mounted adjacent to the peripheries of the grinding wheels, each chuck being diametrically opposite another and the axes of the individuals of each diametrically opposite pair of chucks being parallel to each other and tangent to some imaginary concentric circle within the circumference of the wheels, so that similar work pieces held and rotated in oppositely disposed chucks can project between the wheels and, by their rotation, cause rotation of the grinding wheels in opposite directions, thereby to effect grinding of the work pieces.

Another object is to provide a grinding machine wherein a pair of grinding wheels are resiliently urged into grinding relation. to rotated work pieces which induce rotation of the grinding wheels, with means for Varying the resilient pressure exerted by the grinding wheels on the work pieces.

A further object is to provide a grinding machine in which the grinding effect is produced by two opposed grinding surfaces resilientl urged toward each other and against work pieces engaged between them, with the opposed grinding surfaces rotated in opposite directions by rotation of the work.

Yet another object is to provide a grinding machine having a pair of grinding members resiliently urged against work held between them, and having means for setting a limit for relative movement of the members toward the work thereby to predetermine the diameter to which any particular piece of work may be ground.

It is, moreover, my purpose and object generally to improve the construction and operation of grinding machines.

In the accompanying drawings:

Figure 1 is a front elevation of a grinding machine embodying features of my invention;

Figure 2 is a top plan View of the machine of Figure l, on a smaller scale;

Figure 3 is a cross-sectional view on line 3-3 of Figure 2, on a larger scale, and omitting the work-holding chucks and their supports; and

Figure 4 is a front elevation, somewhat diagrammatic, of a modificationhaving a multiplicity of work-holding chucks.

Referring to the drawings, the embodiment of the invention shown in Figs. 1-3 is designed for grinding simultaneously four similar work pieces Ill whose end portions i2 which are to be ground are engaged between the opposed faces of two grinding wheels which are indicated generally at M and iii. The grinding wheels are slidably and rotatably mounted on a horizontal shaft [8 which in turn is rigidly sup-ported. at its ends in stationary uprights 20 on a base 22. A coil spring 24 is loosely coiled about shaft iii and has one end bearing against the grinding wheel l4 and its other end engaged against a slide member 26 which is loose on shaft iii and which depends into sliding engagement with the top surface of base 22, it having a foot 2'! resting on the base, and the foot having a threaded opening 28 therethrough in which one threaded portion- 30 of a screw 32 is threadedly engaged. Screw 32 is rotatably mounted in the uprights 2i) and is anchored against axial travel, so that any rotation of screw 32 effects movement of slide member 26 along shaft 18, thereby to increase or decrease the pressure exerted by spring 24 on grinding wheel l4, Similarly, a coil spring 34 is engaged around shaft 18 between the grinding wheel l6 and a slide member 36 whose foot 3'1 has a threaded opening 38 in which a threaded portion of screw 32 is threadedly engaged. The threaded portions 36 and 40 of the screw have right and left hand threads respectively so that any rotation of the screw 32, as by the handle 42, eiiects equal movements' of slide members 26 and 36 but in opposite directions, thereby to increase or decrease equal- 1y thepressure applied to each grinding wheel It, IS by their respective springs 24 and 34.

The grinding wheels [4, [6 may be of any suitable form and construction providing opposed surfaces between which the work to be ground may be engaged. As herein represented, each wheel includes a ring 44 of abrasive material removably secured respectively on the wheel bodies 46 and 48, as by a spaced series of retaining screws 59 threaded through the annular flanges 52, 54 respectively on the wheel bodies 46 and 48, the outer ends of the screws engaging an inclined inner surface of a ring 44, the inclination of which surface is such that a screw 50 forces the ring against the wheel body outward of the flange 52 or 54. Preferably the wheel body 48 has an axially extending sleeve 56 projecting toward the wheel body 46 and closely surrounding shaft I8, and wheel body 46 has a larger diameter sleeve 58 for engaging over sleeve 56 thereby to minimize the possibility of abrasive or abraded particles be-fouling the wheel bearings, which advantageously may include anti-friction bearing units as indicated at 66. Preferably the antifriction bearings will be needle bearings as shown which can more readily eliminate play to the end that precision grinding results may be attained. The sleeve 58 conveniently may be exteriorly threaded for receiving the internally threaded micrometer stop ring 62 whose setting along the sleeve 58 can predetermine the ultimate diameter of the work which is being ground. A look nut 84 may be provided on sleeve 53 for locking the stop ring in any particular setting.

Any suitable lubricating means may be provided for the working surfaces of the grinding wheels, such as the gravity flow device 66 shown in Fig. 3, having a restricted nozzle 68 adapted for intermittent drop-by-drop supply of lubricant to the abrading surfaces of the wheels, or the lubricant may be supplied in a steady stream in particular cases.

Referring now more particularly to Fig. l, the work pieces Ii! are mounted in individual chucks I0, 12, I4 and 16. Each chuck is hollow, for receiving work, or an arbor which carries the work, of diameters up to the internal diameter of the chuck. Chucks It, I2 are rotatably mounted one above the other in the parallel uprights I8, 80 at one side of the grinding wheels, and chucks I4 and I6 are similarly mounted at the other side of the grinding wheels, in the parallel uprights 82, at. The uprights 78, 80 preferably are integral with or attached to a horizontal slide member 86 which has a dove-tail Sliding connection to base 22 as at 88, with a usual adjusting screw iii) for adjusting the slide member on the base 22 thereby to properly position the axes of the chucks I'd, I2 relative to the cleavage or space between the opposed faces of the grinding wheels.

The chucks l4 and 16 are similarly mounted one above the other at the other side of the wheels in the parallel uprights 82, 84 which are carried by slide member 92 on base 22. A screw 94 permits adjustment of this slide member, the same as the slide member 86.

The chucks Ill and I2 are rotated in the same direction, as by the belt 96 passing over the pulleys 98, I82, respectively on chuck I3 and on chuck 12. As seen in Fig. 2, the belt 96 passes also over a drive pulley II2 ondrive shaft I64 which may be driven from any suitable source of power such as the variable speed electric motor Chucks I4 and I6 both are rotated in direction opposite to the direction of rotation of chucks I6, I2, this being accomplished by a crossed belt I08 passing over pulleys III] and II 2 on the chucks and over drive pulley II 4 on the drive shaft I04.

It is important, according to the invention, that the axes of all of the chucks, and the work held therein, shall be tan ent to some imaginary circle inside the periphery of the grinding wheels and concentricwith the aXis of the wheels. The imaginary circle may be large or small as desired but it is essential for eflicient grinding results that the axis of each chuck be tangent to the same imaginary circle. Also it is important to have each chuck, and more especially the work held by each chuck, diametrically opposite another chuck with work therein, so that there will be a generally balanced effect on the wheels. This diametrically opposed relation of work pieces between the wheels tends to cause floating of the wheels on shaft i3, thereby minimizing friction and facilitating attainment of precision grinding results.

In Fig. 1, the axes of all four chucks are extended by dot and dash "lines to show their tangency to the imaginary circle 5 it) which is represented by dot and dash lines.

It will be obvious from the foregoing description of the embodiment shown in Figs. 1-3 that the driven work pieces i0, rotating between the grinding wheels I4, IE, will cause rotation of the wheels in opposite directions and, because of the positions of the rotating work pieces relative to the circuitous path of each abrasive particle engaging the work, the wheels effectively grind the work without any tendency to bend the smalldiameter pins which are shown. By preliminarily setting the micrometer stop ring 62 so that it stops relative movement of the wheels toward each other when the space between their grinding faces has width equal to the desired ultimate diameter of the Work, uniform precision grinding results may be attained on work pieces having such small diameters that prior grinding machines could not grind them.

While I have shown four work chucks in Fig. l, the upper chuck at one side together with the lower chuck at the opposite side may be omitted without affectin the efficient operation of the machine.

Also a larger even number of chucks may be spaced at intervals around the periphery of the wheel as indicated more or less diagrammatically in Fig. 4, where sixteen work chucks IE8 are represented, each rotatably mounted in bearings I2l, I22 projecting outward from a vertical plate I24. A common flexible drive shaft I26 has one and connected to the shaft I28 of motor i343 and is arranged in a circular loop with bearings I32 at intervals all around the loop. Each chuck I I8 has a pulley I I9 thereon which is belt-driven from the flexible drive shaft by means of individual belts I34 each of which is trained over a chuck pulley H9 and over one of the pulleys I36 on the drive shaft, with a pair of idler pulleys I38 (only one of each pair being visible) for properly directing each belt.

The grinding wheels, only one of which appears, as indicated generally at I40, are slidably and rotatably mounted on shaft M2 within the circle of the chucks, the shaft being supported in end uprights I44, only one of which appears in Fig. 4. The axes of all of the chucks I58 are tangent to the imaginary circle indicated by dot and dash lines at I 46.

In a construction like that of Fig. 4, rotation of the flexible drive shaft I26 rotates all of the chucks H8, and the work therein, causing the grinding wheels to rotate in opposite directions,

with grinding action on the work as described in connection with the embodiment of Figs. 1-3.

The speed with which any particular grinding operation will be accomplished in any grinder embodying my present invention, will depend upon the speed of rotation of the chucks and the Work and the amount of pressure exerted on the grinding wheels, tending to force them toward each other. By employing a variable speed motor, or some other means for varying the effective rotative speed of the chucks, the speed of rotation of the work may be selected as desired. Also the pressure on the wheels may be adjusted uniformly and simultaneously by turning the screw 32 (Fig. 3).

Obviously the speed of grinding also will be affected by the character of the abrasive surfaces of the grinding wheels. A coarse, hard abrasive surface will grind faster than a less hard smoother surface.

The operation of this grinder is based on the fact that as the work and the grinding rings revolve the grinding surfaces slip, to a certain extent, axially of the work. This slipping, which helps the grinding to take place, occurs because the direction of travel of any given point on the surface of the work in contact with the abrasive ring does not coincide with the direction of travel of any given work-contact point on the surface of the abrasive ring. The grindingeffect which this difierence of direction of travel induces is the direct result of. the tangential position of the work.

In grinders of the general type to which the invention relates there is a more or less definite relationship or ratio between the diameter of the work to be ground and the outside diameter of the abrasive rings or wheels. This grinder may be constructed in a wide variety of sizes. A twochuck or four-chuck grinder designed for grinding small work to extremely small diameters will have abrasive rings or wheels only a few inches in diameter. A two-chuck or four-chuck grinder designed for grinding work several inches in diameter will have abrasive rings or wheels several feet in diameter. Between these two extremes there may be a considerable number of different sizes of grinders, each size being designed for grinding work of certain sizes.

The number of chucks built into a grinder is a factor which will aifect the above mentioned ratio. A twenty-chuck grinder designed for grinding small work may, for example, have abrasive rings or wheels of approximately the same diameter as the abrasive rings or wheels in a twochuck or in a four-chuck grinder designed for grinding relatively large work.

When grinding certain types of work it will be necessary to mountthe work on an arbor and insert the arbor in the chuck. An example of this type of work is the outside ring element of a ball bearing. This element could be mounted on an arbor for precision grinding in this grinder.

I claim as my invention:

1. A grinding machine comprising a pair of members having annular surface portions in opposed relation, at least one of which surface portions has abrading elements thereon, means supporting said members for relative rotation of the members about the axis of said annular surface portions and for relative axial movement of the members toward and from each other, means resiliently urging said members relatively axially toward each other, a pair of rotary work holders adjacent the peripheries of said members and at planes of said opposed annular surface portionsof said members, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the vwork holder into position to be engaged between said opposed annular surface portions of said members, and means for rotating the work holders in opposite directions thereby to cause grinding relative rotation of said members by theretating portions of the Work engaged therebetween.

2, A grinding machine comprising a pair of members having annular surface portions in opposed relation, at least one of which surface portions ha abrading elements thereon, means supporting said members for relative rotation of the members about the axis of said annular surface portions and for relative axial movement of the members toward and from each other, means resiliently urging said members relatively axially toward each other, a pair of rotary work holder adjacent th peripheries of said members and at diametrically opposite locations with respect to the axis of said members, said work holders having mutually parallel axes spaced equally at opposite sides of the axis of said members and in a common plane between and parallel with the planes of said opposed annular surface portions of said members, said work holders being located and adapted to hold work with a portion of the work in each. holder projecting axially of the Work holder into position to be engaged between said opposed annular surface portions of said members, means for rotating the work holders in opposite directions thereby to cause grinding relative rotation of said members by the rotating portions of the work engaged therebetween, and adjustable means for predetermining the limit of relative axial movement of the members toward each other, thereby to predetermine the ultimate diameter of the Work which is being ground.

3. A grinding machine comprising a pair of members having annular surface portions in opposed relation, at least one of which surface portions has abrading elements thereon, mean supporting said members for relative rotation of the members about the axis of said annular surface portions and for relative axial movement of the members toward and from each other, means resiliently urging said members relatively axially toward each other, a pair of rotary work holders adjacent the peripheries of said members and at diametrically opposite locations with respect to the axis of said members, said work holders having mutually parallel axes spaced equally at onposite sides of the axis of said members and in a common plane between and parallel with the planes of said opposed annular surface portions of said members, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the work holder into position to be engaged between said opposed annular surface portions of said members, means for rotating the Work holders in onposite directions thereby to cause grinding relative rotation of said members by the rotating portions of the work engaged therebetween, and means for varying the pressure exerted by said resilient means on at least one of said pair of members.

4. A grinding machine comprising a pair of wheels each having an annular abrading surface portion, means supporting said wheels rotatably and slidably with their said abrading surface portions in opposed relation, means resiliently urging said wheels axially toward each other, a pair of rotary work holders adjacent the peripheries of said wheels and at diametrically opposite locations with respect to the axis of the wheels, said work holders having mutually parallel axes spaced equally at opposite sides of the axis of said wheels and in a common plane between. and parallel with the planes of said abrading surface portions of the wheels, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the holder into position to be engaged between said opposed abrading surface portions of the wheels, and means for rotating the work holders in opposite directions thereby to cause grinding rotation of the wheels in opposite directions b the rotating portions of the work engaged between them.

5. A grinding machine comprising a pair of wheels each havin an annular abrading surface portion, means supporting said wheels rotatably and slidably with their said abrading surface portions in opposed relation, means resiliently urging said wheels axially toward each other, a pair of rotary work holders adjacent the peripheries of said wheels and at diametrically opposite locations with respect to the axis of the wheels, said work holders having mutually parallel axes spaced equally at opposite sides of the axis of said wheels and in a common plane between and parallel with the planes of said abrading surface portions of the wheels, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the holder into position to be engaged between said opposed abrading surface portions of the wheels, and mean for rotating the work holder in opposite directions thereby to cause grinding rotation of the wheels in opposite directions by the rotating portions of the work engaged between them, said wheels having inter-fitting hub sleeves radially inward of the regions of grinding preventing particles from the grinding regions from getting into the wheel bearings, and an adjustable stop member on the outer one of said sleeves for determining the limit of movement of the wheels toward each other.

6. A grinding machine comprising a pair of wheels each having an annular abrading surface portion, means supporting said wheels rotatably and slidably with their said abrading surface portions in opposed relation, means resiliently urging said wheels axially toward each other, a pair of rotary work holders adjacent the peripheries of said Wheels and at diametrically opposite locations with respect to the axis of the wheels, said work holders having mutually parallel axes spaced equally at opposite sides of the axis of said Wheels and in a common plane between and parallel with the planes of said abrading surface portions of the wheels, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the holder into position to be engaged between said opposed abrading surface portions of the wheels, and means for rotating the work holders in opposite directions thereby to cause grinding rotation of the wheels in opposite directions by the rotating portions of the work engaged between them, said resilient means comprising a coil spring for each wheel resiliently pressing its wheel toward the other wheel, and means for simultaneous equal variation of the spring pressure on the two wheels.

'7. A grinding machine comprising a pair of wheels each having an annular abrading surface portion, means supporting said wheels rotatably and slidably with their said abrading surface portions in opposed relation, means resiliently urging said wheels axially toward each other, a pair of rotary work holders adjacent the peripheries of said wheels and at diametrically opposite location with respect to the axis of the wheels, said work holders having mutually parallel axes spaced equally at opposite sides of the axis of said wheels and in a common plane between and parallel with the planes of said abrading surface portions of the wheels, said work holders being located and adapted to hold work with a portion of the work in each holder projecting axially of the holder into position to be engaged between said opposed abrading surface portions of the wheels, means for rotating the Work holders in opposite directions thereby to cause grinding rotation of the wheels in opposite directions by the rotating portions of the work engaged between them, and means for adjusting the work holders bodily in directions axially of the wheels.

8. A grinding machine comprising a pair of wheels each having an annular abrading surface portion, means supporting said wheels rotatably and slidably with their said abrading surface portions in opposed relation, means resiliently urging said wheels axially toward each other, a plurality of pairs of rotary work holders adjacent the peripheries of said wheels, the individuals of each pair being at diametrically opposite locations with respect to the axis of the wheels, and the axes of the holders of each pair being mutually parallel and spaced equally at opposite sides of the axis of the wheels, the axes of all of the holders being in a common plane between and parallel with the planes of said abrading surface portions of the wheels, said work holder being located and adapted to hold work with a portion of the work in each holder projecting axially of the holder into position to be engaged between said opposed abrading surface portions of the wheels, and a common drive shaft for rotating all of the work holders thereby to cause grinding rotation of the wheels by the rotating portions of Work engaged between them.

9. In a grinding machine, a pair of rotary grinding members resiliently urged toward each other and having opposed annular grinding surfaces, and a pair of work holders adjacent the peripheries of said members and at diametrically opposite sides of said members, said work holders having mutually parallel axes spaced equally on opposite sides of the axis of said members, and each work holder being adapted to hold a work piece with a portion thereof projecting between and engaged by said grinding members, and means'for rotating the work holders in opposite directions thereby to rotate said grinding members by the rotating work engaged between them.

MALCOLM B. BOYCE.

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