US3739528A

US3739528A - Grinding machine

Info

Publication number: US3739528A
Application number: US00143930A
Authority: US
Inventors: E Robillard; H Uhtenwoldt
Original assignee: Cincinnati Milacron Heald Corp
Current assignee: Cincinnati Milacron Heald Corp
Priority date: 1971-05-17
Filing date: 1971-05-17
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19

Abstract

A grinding machine in which the abrasive wheel grinds not only a cylindrical surface, but also spaced radial surfaces of a workpiece, and in which a dressing apparatus is provided for dressing the end surfaces of the wheel.

Description

United States Patent Robillard et al.

[ June 19, 1973 GRINDING MACHINE 1,936,731 11/1933 Perkins 125 11 ST 3,098,328 7 1963 Fournier.... 51/165 R [751 Inventors- Edward Valley 3,403,480 10 1968 Robillard 5l/165.87

Herbert R. Uhtenwoldt, Worcester, both of Mass. FOREIGN PATENTSOR APPLICATIONS [73] Assignee: Cincinnati Milacron-Heald Corp., 231,330 5/1969 U.S.S.R 51/16587 Worcester, Mass.

[22] Filed: May 17, 1971 Primary Examiner-Harold D. Whitehead Att --N S. 131 d tt 21 Appl. No.: 143,930 omey Oman ge 52 us. (:1 51/5, 51/165.87, 51/327 ABSTRACT [51] Int. Cl B241) 5/06 [58] Field 61 Search 51 /165.87, 165.88, A gmdmg 9? whch the abraswe wheel f not only a cylmdrlcal surface, but also spaced radIal 51/165.91,165.93,165.78, 165, 5,327

surfaces of a workplece, and In WllllCl'l a dressmg appa- [56] References Cited $222118 pr0v1ded for dressmg the end surfaces of the UNITED STATES PATENTS 2,077,363 4/1937 Hulbert 125/11 ST 5 Claims, 3 Drawing Figures TABLE \N ADI.

\ urr-ur- DREabEe J? J0 14 X-Suu: l j

LU LU 415 26 15 BALL SCREW uau; s-rzvvmc MOTOR -MovAe1.! TABLE s'roF-s GEAR TRAAN PATENIED 9375 3 739.528

' sum 1v or 3 TABLE \N ADI.

\ FT-UP cassava I? r41 WK E 26 i 34 1O 44-46 I X$\-\DE 5 45 E WHEELHEAD f I k LU LIJ 45/ .26 5 15 BALL 5CREW C f LTABLE 5119mm. MOTOR LMOVABL! TABLE STOPS 11 AR TRAN FiG INVENTORS. EDWARD Q. fiomLLARb HERBERT RUHTEuwoLnT Minx PATENIED- WORK? \ECE TABLEOUT SETT \NG WHEELWE'AR compausmou l' .005 DECCLERA'HON g- AcCELtRA'flON DECELER ATE ON F\NAL. TABLE STROKE sums 0f 3 GR\ND\NG WHEEL ACCELERATE ON HRST TABLE s-moxz TABLE. IN SETT\NG DWELL.

ADJUSTABLE 'HNE DELAY "TO PRODUCE FLAT SURFACE Pisa.

WHEELWEAR coMPcuamwN oos'oecz\.emr\ou {r ACCELERA'HON GRINDING MACHINE BACKGROUND OF THE INVENTION In the art of finishing workpiece surfaces by the abrasive method, it is often desirable to grind not only a longitudinal or cylindrical surface of revolution on a workpiece, but also certain generally radial surfaces. A workpiece in which this situation exists would be repre sented by a roller bearing outer race with a groove having a rectangular cross-section with a cylindrical surface at the ends of which exists a purely radial surface. In the past, these operations have been performed by so-called plunge grinding wherein the wheel has the exact shape of the groove and is moved radially directly into the roughly-formed groove for the finishing operation. The difficulty with this method of approach to the problem is that it is very difficult to dress the end surfaces of the wheel which have been dulled by the plunge-grinding without, at the same time, reducing the size of the groove, i.e., the distance between the two parallel radial surfaces. Usually, the wheel has been dressed by using a diamond form dresser having the exact shape of the desired groove, but the problem still exists that it is difficult, if not impossible, to dress the end surfaces of the wheel without changing the dimensions of the groove. Attempts to overcome this difficulty have resulted in very expensive and delicate equipment which have not been wholly satisfactory from the point of view of repeatability of dimension and other qualities of the finished workpiece. For instance, if one desires to dress the end surfaces of a grinding wheel in the same way that is conventionally performed on the peripheral surface of the grinding wheel, compensation must be made for the amount of abrasive wheel that has been removed. If the wheel is not so dressed, not only does the quality of the finished surface suffer, but the grinding operation takes longer, which is unacceptable in the case of an expensive automatic grinding machine. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine including means for dressing the end surfaces of a cylindrical abrasive wheel.

Another object of this invention is the provision of a grinding machine having means for reciprocating the grinding wheel in a groove having substantial radial surfaces to grind these surfaces alternately at the ends of the reciprocation.

.A further object of the present invention is the provision of a grinding machine making use of the end surface of the abrasive wheel, provision being made for dressing the ends and for compensating at the time of dress for the removal of portion of the abrasive wheel.

It is another object of the instant invention to provide a grinding machine for grinding grooves by reciproca tion instead of plunge, which machine is simple and inexpensive to manufacture and which is capable of a long life of useful service with a minimum of maintenance.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the invention consists of a grinding machine for generating a surface of revolution on a workpiece having a base, a workhead table mounted on the base and having a holder to support the workpiece, and a wheelhead table mounted on the base and having a rotatable spindle for carrying an abrasive wheel. Feed means is provided for bringing about relative movement transversely of the axis of the surface of revolution between the tables to bring a cylindrical surface of revolution between the tables to bring a cylindrical surface of the wheel into grinding contact with the work piece. A dressing apparatus is provided including two spaced facing diamonds for dressing the end surfaces of the wheel. Traverse means is provided for bringing about relative movement longitudinally of the axis in cluding a means to place the wheel in a first position generally co-extensive with the said surface of the workpiece and means to place the wheel in a second position co-extensive with the said dressing apparatus.

A means is provided which is operative to reciprocate the wheel on a first stroke to bring one end surface into grinding contact with a radial portion of the workpiece surface and then to bring the other end surface into grinding contact with another radial portion of the workpiece surface.

Another means is provided which is operative to move the wheel on a second stroke to bring the said one end surface of the wheel into dressing contact with one of the diamonds and then to move the said other end surface of the wheel into dressing contact with the other of the diamonds.

More specifically, a control is connected to the first and second means to lengthen the second stroke at the time of every dressing operation and to lengthen the first stroke by a commensurate amount.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a plan view of a grinding machine embodying the principles of the present invention,

FIG. 2 is an electrical schematic diagram showing the controls for a stepping motor forming part of the invention, and

FIG. 3 is a diagrammatic view showing the manner in which the abrasive wheel is reciprocated within a groove in a workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, wherein are best shown the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is shown as having a base 11 on which is mounted a workhead table 12 and a wheelhead table 13. The workhead table 12 is mounted on ways 14 for sliding motion longitudinally under the impetus of an hydraulic cylinder 15. Similarly, the wheelhead table 13 is mounted on ways 16 for transverse motion under the influence of a hydraulic cylinder 17. Mounted on the wheelhead table is a wheelhead 18 in which is rotatably mounted a spindie 19 on the outer end of which is mounted an abrasive wheel 21. This wheel is of the usualcylindrical type having a cylindrical peripheral surface 22 and two

radial end surfaces

23 and 24.

Mounted on the workhead table 12 is an upper table 25 which is mounted on ways 26 for longitudinal motion over the top of the table 12 under the impetus of a hydraulic cylinder 27. Mounted on the upper surface of the table 25 is a workhead 28 suitably constructed to support and rotate a workpiece 29 which has a groove 31 which is to be finished by the abrasive process.

Also mounted on the upper table 25 is a dresser 32 for dressing the cylindrical surface of the abrasive wheel 21 and a dresser 33 for dressing the

end surfaces

23 and 24. The dresser 33 is provided with a swingable element 34 which is hinged on a longitudinal pivot shaft 35. The element has two parallel spaced arms 36 and 37 having parallel facing surfaces from which extend facing diamonds. The dresser 33 is provided with a pneumatic cylinder 49 which serves to swing the element 34 about its axis.

The underside of the table 12 is provided with a recess 38 in which lies a compensating slide 39 which is slidably carried on the upper surface of the table 12. The slide 39 is moved longitudinally by means of a ball screw 41 operated through a gear train 42 by a stepping motor 43. The slide 39 is provided with a finger 44 having opposite longitudinally-directed faces provided with hardened metal buttons 45 and 46. The button 46 is arranged to contact a button 47 mounted on a vertical surface of the table 25, while the button 45 is arranged to contact an adjustable stop 48 which faces the surface with the button 47.

Referring now to FIG. 2, it can be seen that the motor 43 receives pulses from a driver 51 which, in turn, receives its signal from a pulse-to-step converter 52. The logic circuit 53 is connected by a line 54 to a pulser 55 having acceleration and deceleration functions. A line 56 joins the output of the pulser 55 with the pulse-tostep converter 52. The logic circuit is also connected by a line 57 to a sequencing circuit 58. The circuit 58 is connected to the converter 52 by lines 59 and 61, and by

lines

62 and 63 to a counter 64..

The logic circuit 53 is also connected to the counter 64 by a line 65, while the line 56 is also connected to the counter by a line 66. Also associated with the apparatus is a counter 67 which is provided with a mechanical memory and a circuit 68 containing compensation, dock, and counting circuits. The three

lines

69, 70, and 71 join the counter 67 to the circuit 68. The three

lines

72, 73, and 74 join the counter 67 to a wheel wear counter 75, and line 76 joins the counter 75 to the line 66 and to the line 56, as well as to a line 77 connected to a reversal counter 78. A line 79 joins the logic circuit 53 t the counter 78, while the line 81 joins the circuit 53 to the counter 75.

The operation of the invention will now be readily understood in view of the above description. The grinding machine is used in a conventional grinding cycle involving longitudinal movement between the wheelhead and the workpiece 29, as well as transverse movement for feeding. The longitudinal movement takes place under the impetus of the cylinder which serves to move the table 12 and, therefore, the workpiece 29 to the position in which the wheel 21 lies within the workpiece 29. The hydraulic cylinder 27 serves to move the upper table 25 relative to the lower table 12 and, therefore, relative to the wheelhead 18 in order to bring the

dressers

32 and 33 sequentially into operative relationship to the wheel 21. Normally, the dresser 33 would operate on the wheel 21 as it moves longitudinally from the first position within the workpiece 29 to a second position coextensive with the dresser 33. Once the wheel 21 lies either within the workpiece 29 or the coextensive with the dresser 33, it is moved longitudinally small amounts by the stepping motor 43 cooperating with the stop 47 and with the stop 48. The stroke that is used within the workpiece 29 is the same as the stroke used between the diamonds and the dresser 33. During these strokes, the stop 43 on the table 25 is maintained in a position pressed against the button 46 on the finger 44 of the compensation slide 39. The stroke takes place by introducing pulses of the proper mode into the stepping motor 43 so that the compensation slide 39 moves back and forth and the table 25, therefore, moves with it; the workpiece 29, of course, then moves back and forth over the wheel 21 to produce the grinding operation. In the same way, the dresser 33 moves relative to the wheel 21 to bring it into position to allow the proper dressing operation on the ends of the wheel.

ln FIG. 3, it can be seen that the groove 31 in the workpiece 29 is generally rectangular in cross-section and, therefore, is provided with a cylindrical surface 82 and two opposed, facing,

radial surfaces

83 and 84. The workpiece 29 is moved longitudinally to bring the end surface 23 of the wheel 21 into contact with the radial surface 84 of the groove and, then, at the other end of the stroke, the end surface 24 of the wheel comes in contact with the radial surface 83 of the workpiece. At the same time, the wheelhead is moved by the cylinder 17 into contact with the cylindrical surface 82 and produces a finish grind on that surface also. The cross-feed takes place in the conventional manner and there is no necessity for describing it in detail. The reciprocating movement, however, of the workpiece relative to the wheel is shown in detail in FIG. 3. Because of the fact that the motion takes place under the control of the stepping motor 43 and the stepping motor rotates and feeds the workpiece relative to the abrasive wheel in accordance with the number of pulses, introduced into the motor, their rate of introduction, and so on, it can be seen that it is a very easy matter to give this motion exactly the desired one, including the desired deceleration and acceleration at the ends of the stroke. It can be seen that each movement of the wheel on each side of the centerline consists of an initial setting that was used with the new wheel during setup plus an additional amount equal to wheel wear compensation that is introduced at the time of each dressing operation on the dresser 33.

When the wheel is moved out to be operated on by the dresser 33, the table is pressed by the cylinder, so that the button 47 contacts the button 46 on the compensation slide and the motion to bring. the ends of the wheel into contact with the diamonds takes place on either side of this position as a centerline. In a similar manner, when the wheel 21 lies in the workpiece 29, the stop 48 is used as such a centerline and is adjusted during setup for that particular position. Returning to the condition where the wheel lies between the arms 36 and 37 of the dresser 33, the dresser is in raised posi tion until the wheel has been positioned at one end or the other of the stroke. Then, the cylinder 49 is actuated to swing one of the arms with its diamond downwardly, the diamond contacting the wheel and dressing its end surface. The position is reversed to dress the other end of the wheel. The wheel is then returned to the workpiece which, in some grinding cycles, may be a new workpiece. In any case, the cycle is continued from one workpiece to another. It can be seen, then, that the production of accurately ground workpieces of this type can take place by means of relatively simple apparatus and that the machine automatically compensates for the amount of the abrasive wheel that is re moved during the dressing operation.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent 1. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base,

b. a workhead table mounted on the base and having a holder to support the workpiece, c. a wheelhead table mounted on the base and having a rotatable spindle for carrying an abrasive wheel,

(1. feed means for bringing about relative movement transversely of the axis of the surface of revolution between the tables to bring a cylindrical surface of the wheel into grinding contact with the workpiece, a dressing apparatus including two spaced facing diamonds for dressing the end surfaces of the wheel,

f. traverse means for bringing about relative movement longitudinally of the axis, including a first means to place the wheel in a first position generally co-extensive with the said surface of the workpiece and a second means to place the wheel in a second position generally co-extensive with the said dressing apparatus, the first means being operative to reciprocate the wheel on a first stroke to bring one end surface into grinding contact with a radial portion of the workpiece surface and then to bring the other end surface into grinding contact with another radial portion of the workpiece surface, the second means being operative to move the wheel on a second stroke to bring the said one end surface of the wheel into dressing contact with one of the diamonds and then to move the said other end surface of the wheel into dressing contact with the other of the diamonds.

2. A grinding machine as recited in claim 1, where a control is connected to the first and second means to lengthen the second stroke at the time of every dressing operation and to lengthen the first stroke by a commensurate amount.

3. A grinding machine as recited in claim 1, wherein the dressing apparatus includes a pair of longitudinally spaced arms swingably mounted on a common longitudinal axis, the arms being facing surfaces on which the two diamonds are mounted.

4. A grinding machine as recited in claim 1, wherein the traverse means includes a cylinder for producing the longitudinal movement to the first position and the second position and stepping motor for producing the first and second strokes.

5. A grinding machine as recited in claim 4, wherein the workhead table is provided with a first stop to 10- cate the abrasive wheel in the workpiece at the center of the first stroke and with a second stop to locate the one side and the other of the centers of the strokes.

Claims

1. A grinding machine for generating a surface of revolution on a workpiece, comprising a. a base, b. a workhead table mounted on the base and having a holder to support the workpiece, c. a wheelhead table mounted on the base and having a rotatable spindle for carrying an abrasive wheel, d. feed means for bringing about relative movement transversely of the axis of the surface of revolution between the tables to bring a cylindrical surface of the wheel into grinding contact with the workpiece, e. a dressing apparatus including two spaced facing diamonds for dressing the end surfaces of the wheel, f. traverse means for bringing about relatiVe movement longitudinally of the axis, including a first means to place the wheel in a first position generally co-extensive with the said surface of the workpiece and a second means to place the wheel in a second position generally co-extensive with the said dressing apparatus, the first means being operative to reciprocate the wheel on a first stroke to bring one end surface into grinding contact with a radial portion of the workpiece surface and then to bring the other end surface into grinding contact with another radial portion of the workpiece surface, the second means being operative to move the wheel on a second stroke to bring the said one end surface of the wheel into dressing contact with one of the diamonds and then to move the said other end surface of the wheel into dressing contact with the other of the diamonds.

3. A grinding machine as recited in claim 1, wherein the dressing apparatus includes a pair of longitudinally-spaced arms swingably mounted on a common longitudinal axis, the arms being facing surfaces on which the two diamonds are mounted.

5. A grinding machine as recited in claim 4, wherein the workhead table is provided with a first stop to locate the abrasive wheel in the workpiece at the center of the first stroke and with a second stop to locate the abrasive wheel adjacent the dressing apparatus at the center of the second stroke, and wherein a compensation slide is located between the two stops and is drivingly connected to the stepping motor, so that the introduction of pulses to the stepping motor serves to move the workhead table and workpiece alternately to one side and the other of the centers of the strokes.