US2434615A - Dressing device for grinding wheels - Google Patents

Description

Jan. 13, 1948. w. w. HOPKINS DRESSING DEVICE FOR GRINDING WHEELS Filed Ma y 1'7, 1945 BY a 9 6 ATTORNE JS Patented Lian. 13, 1948 UNI-TED STATES GP'FICE V 23134516 I nRiassiNG DEVICE. FOR GRINDING WHEELS William Walter fiopkins, Springfield Mass. ApplicationMay 17, 1945385211 se il'sslz 'oiaiiils. (o1. 125 113 This invention relates 'to'an improved'dressing device for grinding wheels.

In the prior practice, an industrial diamond is mounted in a support,'the grinding wheel is rotated, the diamond is;moved jback and forth on a'curve, corresponding to the cross sectional shape of a desired dressing, the wheel'and dia- 'mond are moved against each other by'small steps, and the diamond; grooves the wheel step by-wstep until the desired "formds made. The

:form is an annular groove having'a precision cross sectional-shape. .This is allvery well known.

In some kinds of Work,"a special problem is. presentedto the killed-man'wanting to dress a wheel to-a shapei thatis notadapted to be made by the most usual. method, For example, the dressing of a small groovexto be. made in'the grinding wheel, with a semi-circular cross section having aa s inch radius presentsa special problem. The radius is too small to use'the most usual dressing method. When" precision is needed in such an"instance,one Way to get it is to shape a diamond for the desired cross sec tional curve and press the shaped tool (diamond) radially against the grinding .wheel. to dress the latter. It is an expensive Wayand'not. only that, it is far from a convenient wayibecaus'e such a small andexpensive. tool quickly gets defective.

The diamond even when welded to'itsiholder snaps off after little use and the precision shape is worn away after little use.

With these circumstances as a background, I have invented a new and inexpensive device to do the work t dressin g;= Itsis particularly adapt ed to convenience and precision in making dressings of small cross sectional shapes as in the specific example already given, and it is also adapted-for making dressings of comparatively large cross sectional shapes.

The new device, its mode of operation and the.

results will be disclosed and referred to in connection with the accompanying drawings,

Fig. l isaside view of the device andindicates the relationof the work to the cutting diamond" and a way of feeding the work in the operation;,

Fig. '8 is a section "taken" along thefsam' line as Fig'."5 but with the parts in ene extreme position;.an'd' w 3 L Fig'fiis an'en'd viewgthe me as FigQZQwith parts broken'awa'y The iull lin position shows the war su port against a 'st'opand the diamond point scribing an afiz in 'a grinding' wheel, partially shown, and the dpttedlines'ShOW the am;

and its tOOYsuppOrt aga st a stop to prevent it from hitting nie rmdin x r ln the exarnpl'e'bftheinvention' shown by these drawings': v

. The diamond icutting' elem t"'l 'is'-vve lded' on the end ofiholding rod 2; This is snaab y incune ed for? adjustment in? anoth'e'fholding "rod 3, the

IO... extends rearwardly through bore H andbe-g At .itsrea'r end a collar l2- w. isjastened by set .scr'ew'sl3fi The collar l2 and The collar' I2- is part of a. ,frictionclutch. T This clutch is made up of ,collar, 1.2 which -on. its inner face}. has 'an yond ,the'cylinder l.

the shaft [0 must move'togeth'er.

annular. series. of recesses .and' in. each recess a coiledi spring" is-jbotto'medlThe' springs press .on its. outer face engaged with opposite holes on the inner iface. ofcollar [2... Thus the disc'iun'der springpressiire may move .jaxia'lly of. shaftilfl between ciolla'r l,2.'and the adjacent face ofsfrarnel part 8, and both clutch piartsmusti turn withshaft ID lutch is assembled ,and. mounted; asindicated, so. that. therer-is; considerable friction tojthe turnin of shaft 1.0. in cylinder 1 because of the clutch parts. which turnwith the rod. 'The" it'an'd slide relatively,being feathered. on theshaft .forjthis purposa- DiscJI4..has.two pins. l4

friction is. between disc 1.4 and frame 8.

outer position but permitting .it to be'pushdin wardly.j.,A.r'ada1 V;shaped.-grdove. L6,. on the innerl. .face oLdisc l4, cooperates with pin [5, as will be described.

A handle H, in the form of a radius rod fastened to cylinder 1, and extending through the slot shown in the frame 8, see Fig. 1, provides means for rocking the cylinder 1 in its frame bearing and such rocking is back and forth about the cylinder aXis.

As stated before, shaft II] is carried in the eccentric bore ll of cylinder I. So, when the cylinder 1 is rocked back and forth by handle I1, the rocking axis being the cylinder axis, then shaft ill will have its axis moved back and forth over an are whose radius is the amount of the eccentricity or offset of the shaft I axis with the cylinder axis, This is indicated by the center lines in Fig. 1 and the centers in the other figures.

With the construction so far described, one grinding wheel dressing operation will be described. The diamond l is adjusted so its cutting point coincides with or is on the axis of shaft I0 and fixed there. A flat portion on the upper side of block 6 adjacent its end may be made a precision base for setting the diamond point to this adjustment. It is desired to provide for great precision in the setting stated. The handle I! may have a line to coincide with a line on frame 8 when the handle is exactly vertical, at which time the rod 2 holding the diamond is also vertical, detent groove I6 is vertical, and detent IE is in its groove l6. At this time the axis of shaft I0 is set above axis of cylinder 1 and on a vertical line passing through both axes. This is the starting position of the device. When the device is set in this position, the grinding wheel to be dressed is moved down by adjustment of the work holder H indicated in Fig. 1, until the diamond is just touching the periphery of the grinding wheel. It is from this position that the grinding wheel will be fed, by indexing feeding means, indicated at I, to move the work toward the tool (diamond) in precision steps, for example steps of five thousandths of an inch each. The result of the preparation setting of the work and the tool for operation is indicated generally in Fig. 1. It will be understood that means not shown will rotate the grinding wheel.

From the preparation just described the operation will be to move the tool in an arc away from the work by turning the handle l1. Then the work holder moves the grinding wheel down with a precision step. The grinding wheel is rotated. Then the handle I! is rocked to swing the tool against the work and back and forth, in an arc. This are has a radius equal to the offset of shaft ID from axi of cylinder 1. The diamond will dress an annular groove in the wheel with depth equal to the precision measurement of one step in feeding the work against the diamond. This of course assumes that the grinding wheel has a fiat periphery to start the sinking of a groove in it. Between each two feeding working steps of the work holder, handle I1 is rocked enough to dress an annular groove to the depth of one feeding step. Of course the depth of the groove will gradually increase with the addition of each feeding step and the following dressing step. If we assume that the radius of the arc in which the diamond is swung in each such dressing step is a large enough radius, the whole dressing of the groove may proceed as stated until it has a depth equal to such radius. Or if we assume that the groove to be finished is a shallow one, in the example it is /32 inch, of less depth than the said radius, there will be no special difficulty, as by the tool holder not having room to clear the sides of the groove when it gets to the bottom of the shallow depth. The special difliculty with small deep grooves will be further explained. The operation of the device thus generally described is to show that the device is adapted to dress the groove in the grinding wheel with great precision. It is useful for that purpose.

The device, however, is particularly adapted in a special way for dressing a grinding wheel with one or more small grooves, those grooves with a small radius and relatively deep or deep enough to cause trouble when the operation is only on the order of that above described. The trouble referred to is the difliculty in getting the tool holder. to clear the sides of the groove being dressed.

The device is adapted to do such particular work by the provisions now to be explained.

The swinging arm or support 6 has two stops l8, one on each side. They cooperate with adjustable stops l9 one on each side of frame part 8. The latter has a shelf 20 for each stop 19. A convenient construction for this is to thread stop l9 through shelf 20 and supply a lock nut 2| to hold the vertical adjustment of stop l9. By loosening nut 2|, stop l9, screwed in shelf 20, may be given an accurate adjustment by a screw driver applied from the top and nut 2| then tightened. Thus the length of the arc in which arm or support 6 may swing is limited by these stops [8 and I9. This limited length has reference to the operation already described. That operation if tried out to make a full semi-circular groove of /32 inch radius would run into the difficulty beforementioned. When the groove being dressed gets'near its full depth there is not room for the tool and its holder to clear the sides of the groove. This will be seen from Fig. 9, using center C of cylinder 1 for swinging the tool. So the length of the arc is determined by the stops to prevent the continued mode of operation above described and just before the tool would otherwise fail to clear the sides of the groove being dressed.

When the first way of operation is thus stopped, the device will automatically change its way of operation to continue the dressing. The second stage or modified operation is for the purpose of continuing the dressing of the small groove without any interference by the sides of the groove in clearing the tool. This will now be explained.

Up to the time that the tool will continue to dress the small groove to a gradually increasing depth without needing an are greater than that determined by the stops, th cylinder 1 and shaft ii] are rocked as a unit by handle I! (Figs. 6 and 7). When the stops are engaged, handle II can by some extra force continue to rock cylinder 1 alone and further over on each side (Fig. 8). The stops act to prevent shaft I0 rocking as before with cylinder 1 and as if these two pieces were one. The friction clutch and its detent construction, holds them together, as if they were oneuntil the stops cause the clutch to slip. Then cylinder 1 can move without carrying shaft l0 and its tool support 6 in the way it did in the first way. The detent I5 is moved out of its groove l6 (Fig. 8) when handle I! moves cylinder 1 after stops I8, I9 are engaged to stop shaft l0. Cylinder 1, however, carries shaft in and its arm 6 in a new way for the second stage. This new way is to carry shaft l0, support 6, and the tool rods 2 and 3 bodily as a unit, but not on C as the center. When its first stage movement with cylinder 1 is stopped, the cylinder movement is continued. Asshaft l0 cannotcontinuein thee oldaway-thecylinder must cause the shaft ID to: move .in'a new way. The .friction clutchconnesting. these-two parts; cylinder! and shaft l0; permits a relative movement between them;- This imoyement isone of relative rotation of shaft:

in the oifset bore I I of cylinder-1'." The latter of. course continues its movement=on its own axis.

The relative rotation of shaftlfl in its offset bore,-

or-bearing, of course, is on theaxis of such bearing. Such relative rotation causes'the axisof shaft in to move downwardly onan arc. parts connected with shaft. ID; that is swingingzarm or support 6, the tool holder rods'2 and 3,

and .thendiamond point tool. all move downwardly; This is indicated between full and dotted lineipositionsin Fig. 9. In this movement-the diamond point is still being swung on the center 1 Cof' cylinder 1, over -its:cutting are as before. Its tool holder is being translated bodily in a path aswell as the diamond point all take the downward path. This is the pathirequired for the diamond point to finish cutting the semi-circular" or other deep groove by small increments and for thetool holder toclear the sides of the groove. This result follows: because the tool holder is drawn'down out of the wayas the diamond point is .held to the line of work, see Fig. 9. This line is: the continuation of the: same are started by merely swinging the tool on the one center C. Inthe .deep type of small groovesuch mere swingirigis stopped automatically just before the point of the arc, where the tool holderwill interfere. Then as stateduthe diamond point and its tool diamond point follows to finish the-arc shaped cut.

Reference toFig. 9 will indicate-the operationfroma more technical viewpoint.

The are of the dressing within the angle'D, is the same as-the are made in the first way of oper- The down zthework againstthe tool. The-cylinder- H and shaft 10 will be: moved to' make exactly the right are in the dressing.

'20 and every point of shaft iifl' varm 6, rods 2 and 3,

'35 holder is given a translatingmovement in which all parts are drawn downwardly, while the ation swinging the diamond point back and forth from center 0. When, the wheel is dressed with? such an arc and to the depth of'its center from its chord, the way of'operation' is changed. It'is assumed that the .ends of said are represent the Now it will be seen from ;Fig.'c9 that the im portant thing is forthediamondpoint I to continue-to swing over the same are as before and extend the arc to make the dressing deeper. It will also be seen that if the whole operation were attempted by swinging the tool holder on center C the tool sides would engage the work and interfere with maln'ng the deep small groove. It will finally be seen that this is prevented by a bodily movement of the tool sides downwardly and away from the groove while the diamond point is moved along the extended portions of the are beyond the sides of angle D in Fig. 9.

In this respect the device automatically changes its way of operation between the first and second dressing parts of the whole operation to make a small deep groove. All the operator need do, after the original setting of the device as in Fig. 1, is to swing handle I! back and forth and feed Within a considerable-scope; the radius of the i groove to be-dres'sed may-be changed andthe same device used; That is the same parts may beused to make difierent size grooves except the part represented by cylinder 1. This" cylinder 1 of the example is specially made for a roove of inch radius- The cylinder alone controls the-groove size as-all the other parts are adapted for use in making different sizes; when a differ-- ent size groove is wanted, another cylinder-is suppliedr It is in all respects like cylinder l except for the amount of offset between its axisand theaxis of thebore l Ithrough the cylinder; see Fig; 5. This offset is made different and to' correspond with the different radius wanted for" the groove to be dressed. It would bemadeg .inch or /8 inch to make a groove smaller than the example of '3 inch. Thedevice described with a set of similar cylinders corresponding to" groove sizes wanted is the way in which the"- device would be put into the shop. The frictionclutch parts i2 and M are readily removable from'shaft it. Supporting arm 6,shaft l0, and

cylinder 7 are readily removable from thefram'e' as" a unit by movement tothe right in Fig. 1. Then one cylinder such as I with one positionof offset bore 5! may be substituted for the cylinder with a differently positioned offset'bore H', and the parts reassembled to make a different size groove'tha'n before. 7 While a good deal of description of theideviceand its use seems de-' sirable for its disclosure, there are not many parts, there are. no real complications, and the whole device is economical for manufacture and adapted for use in precision dressing ofgrind ing wheels. The only'skill required is that of'pre- 'cision in setting the parts for work and that is plain measurement skill. The operation after it is once set up does not require skilL-but the mere swinging of handle H and the intermittent feedof the work holder between cutting steps.

In the operation above described I considerthe function of detent idand groove it very l helpful. When handle Ii has swung overfor stop it on support 6 to engage stop is; the engagement occurs as thearc of angle D, Fig. 9, 1

is finished. As handle 1'! swings further'o-ver' the arc is extended down to the end as seenin Fig. 9. In this movement of the tool from full to dotted line positions the tool holder 2-3 is not swinging on point C.

whole are to the other corner, it is important to start swinging the tool holder 23' on center C about when it reaches full line position of Fig; 9'. 1

Otherwise the tool sides would begin to inter-- fere with the work. The 'tool holder begins to swing on center C in the dressing operation from left to right as the holder reaches the full line position shown. This action is insured by detent I5 engaging in groove I5 at just about this time. Then the parts, shaft l0 and cylinder 1. will not slip relatively as they might otherwise do and miss the time for beginning the swing on center C to do the work right.

Having disclosed the invention I claim:

1. A device for dressing grinding wheels, comprising a cylindrical body provided with an end to end cylindrical bore with the axis of the bore offset by an amount equal to the desired radius of a groove to be dressed in a grinding wheel and said axis also parallel to the cylindrical body axis, a tool support to hold a cutting tool point on the axis of said bore to swing in aplane at right angles to the line of such axis, a shaft mounted in said bore and carrying said tool support for its swinging movement, a frame with bearing means to mount said cylindrical body, means to rock the cylindrical body about its axis to move the axis of said shaft in an are having a radius equal to the amount of the shaft axis offset from the cylindrical body axis.

2. A device for dressing grinding wheels, comprising a cylindrical body provided with an end to end cylindrical bore with the axis of the bore offset by an amount equal to the desired radius of a groove to be dressed in a grinding wheel and said axis also parallel to the cylindrical body axis, a tool support to hold a cutting tool point on the axis of said bore to swing in a plane at right angles to the line of such axis, a shaft mounted in said bore and carrying said tool support for its swinging movement, a frame with bearing means to mount said cylindrical body, means to rock the cylindrical body about its axis to move the axis of said shaft in an are having a radius equal to the amount of the shaft axis offset from the cylindrical body axis, said cylindrical body, shaft, and frame being readily separable so as to substitute a similar cylindrical body with a bore having another amount of offset from the body axis to change the radius of the are for movement of the shaft axis.

3. A device for dressing grinding wheels, comprising a cylindrical body provided with an end to end cylindrical bore with the axis of the bore offset and parallel to the cylindrical body axis, a tool support to hold a cutting tool point on the axis of said bore to swing in a plane at right angles to the line of such axis, a shaft mounted in said bore and carrying said tool support for its swinging movement, a frame with bearing means to mount said cylindrical body, means to rock the cylindrical body about its axis to move the axis of said shaft in an arc having a radius equal to the amount of the shaft axis offset from the cylindrical body axis, friction clutch means normally preventing relative turning movement between the cylindrical body and the shaft, stop means adapted to limit the length of arc in which the cylindrical body and shaft may rock as a unit and means including said stop means, adapted to permit a further rocking movement of the cylindrical body beyond the ends of such are to cause relative turning movement of the shaft in its offset bore While maintaining the axis of such shaft on the line of the limited are as extended beyond its aforesaid limited length.

4. A device for making annular grooves on the circular face of a disc, said device comprising a frame with a vertical portion having a horizontal bearing, a precision made cylinder mounted to rock in said bearing, a radial handle on the cylinder to rock it, a shaft mounted with its axis precisely offset from the axis of the cylinder and extending through the cylinder for rotation, a friction clutch mounted between the shaft and cylinder and adapted to normally prevent such rotation, and to permit movement of said handle to rock the cylinder and shaft as a unit, a tool support-connected to said shaft having means to hold the point of a cutting tool exactly on the axis line of said shaft, cooperating stops on said frame and tool support, such stops being adjustable to determine the limits of a rocking movement of cylinder and shaft without relative rotation, whereby upon extended movement of said handle said clutch slips for the cylinder to rock further and for the shaft to be turned relatively to the cylinder whereby the shaft axis and said cutting tool point can continue to describe an arc of the same radius and the tool support can be moved bodily to direct the sides of the tool into positions which will not interfere with the cutting operation substantially as described.

5. A device for the purpose described comprising a frame having a horizontal bearing, a cylindrical body to swing over a long are about its own axis in said bearing, a shaft mounted in a corresponding bore through said cylindrical body to act as a bearing for the shaft to turn in said body with the axis of said shaft and its bearing being parallel to and offset above the axis of said cylindrical body by an amount equal to the desired radius of a groove to be dressed in a grinding wheel, a tool support mounted on said shaft adapted to hold the point of a tool on the axis line of said shaft, a handle to swing said body, a friction clutch mechanism connecting said cylindrical body and said shaft tending to resist relative movement of said shaft and body for them to sometimes swing as a unit and sometimes slip relatively to one another, said mechanism including a notch and cooperating detent to help resist against such movement, cooperating stops to cause slipping in said friction clutch mechanism when the handle is operated to complete the portion of the said long are in the swinging arc of said body adjacent each end of said movement.

WILLIAM WALTER HOPKINS.

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

UNITED STATES PATENTS Number Name Date 2,312,347 Madsen Mar. 2, 1943 2,372,732 Norris et a1. Apr. 3, 19 5

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