US3299578A

US3299578A - Apparatus for trimming grinding wheels

Info

Publication number: US3299578A
Application number: US389879A
Authority: US
Inventors: Benjamin F Bregi; Donald P Bush; Edward Z Krygier
Original assignee: National Broach and Machine Co
Current assignee: Nachi Machining Technology Co
Priority date: 1964-08-17
Filing date: 1964-08-17
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

Jan. 24, 1967 B. F. BREGI ET AL 3,299,578

APPARATUS FOR TRIMMING GRINDING WHEELS Filed Aug. 17, 1964 FIG. I

-, 1 .mvENTORs l p 32 BENJAMlN F. BREGI- DONALD E BUSH BY EDWARD KRYGIEB/ 4% 7 9/ 14am ATTORNEYS United States Patent 3,299,578 APPARATUS FOR TRIMMING GRINDING WHEELS Benjamin F. Bregi, Grosse Pointe Shores, and Donald P.

Bush and Edward Z. Krygier, Royal ()ak, Mich, assignors to National Breach & Machine Company, Detroit, Mich., a corporation of Michigan Filed Aug. 17, 1964, Ser. No. 389,879 27 Claims. (Cl. 51-5) The present invention relates to apparatus for trimming grinding wheels.

It is an object of the present invention to provide a trimmer for a grinding wheel in which the path of the trimming element is caused to correspond substantially exactly to a plurality of paths on a helicoidal surface to be ground by the wheel.

It is a further object of the present invention to provide a trimmer for a grinding wheel which comprises a template having a three-dimensionally curved guide surface, means for mounting said template with said guide surface confronting a grinding surface located at the side adjacent the edge of the wheel, a trimmer device movable in a multiplicity of different paths generally transversely between the grinding surface of the wheel and the guide surface of the template.

It is a further object of the present invention to provide trimming mechanism as described in the preceding paragraph in which the trimmer device comprises a body, an elongated member movable longitudinally through said body, said member having a template follower at one end and a wheel trimming element at the other end.

It is a further object of the present invention to provide a grinder as described in the foregoing in which the template and trimmer device are adjustable so as to position the body and the elongated member with the axis of the elongated member substantially perpendicular to the axis of the helicoidal member to be ground by the wheel, or substantially parallel to the axis of the wheel.

It is a further object of the present invention to provide a grinder comprising a frame, a slide movable recti linearly on said frame, a support on said slide for supporting a work piece having a helicoidal surface thereon for rotation about the axis of the helicoid, a grinding wheel, means mounting the grinding wheel in position adjacent the path of movement of the work piece, means for driving the grinding wheel in rotation, means for adjusting the grinding wheel about an axis perpendicular to the axis of the grinding wheel and to the axis of the work piece, a template adjustably mounted on said frame for adjustment into an operating position, and means for fixing the template in such adjusted position, said template having a three-dimensionally curved guide surface confronting a grinding surface at the side of the grinding wheel adjacent an edge thereof, and a trimmer device movable in a multiplicity of different paths transversely between the grinding surface of the wheel and the guide surface of the template.

Other objects and features of the invention will become apparent as the description proceeds, especially When taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a simplified perspective view of a grinder incorporating the trimming mechanism disclosed herein.

FIGURE 2 is a diagrammatic view illustrating the relationship between the grinding surface of a grinding wheel, the helicoidal surface of a work piece, and a template.

FIGURE 3 is a fragmentary enlarged perspective view showing a preferred form of trimming mechanism.

FIGURE 4 is a perspective view of the template.

While the present invention finds its greatest field of utility in grinding gears or splines, in its broader aspect it is not so limited and may find utility in forming helicoidal surfaces on any work piece. However, the present disclosure for the most part will be limited to a description of the invention as applied to a gear grinding machine, and more particularly, a machine for grinding helical gears.

Reference is made herein to a helicoidal surface and by this expression there is intended to delineate a surface such as the flank surface of a tooth of a helical gear. While many tooth forms are known, a standard and widely used tooth form is involute. Accordingly, the helicoidal surface to which reference is made herein may be an involute helicoid; that is, a surface generated by movement of an involute line along a helical path, the involute line following a base cylinder whose axis is the axis of the helicoid.

The present invention is particularly applicable to trimming a grinding wheel used in form grinding. In this grinding operation the edge portion of the wheel may be trimmed so as to provide opposed grinding surfaces at opposite sides of the wheel adjacent its periphery, in which case the grinding wheel may be used in an oncenter relationship and grind two opposed involute tooth surfaces in an operation in which the gear is advanced axially and is given a rotation as required by its lead or helix angle. Preferably however, the form grinding operation is carried out by trimming only one side portion of the Wheel adjacent an edge thereof so that the wheel may be used in an off-center relationship, as is well understood in the art.

As is well understood, if a spur gear is ground, the edge portion or portions of the grinding wheel may be trimmed to the exact cross-sectional contour of the tooth surface. Thus, where the tooth is of involute form, the side or sides of the grinding wheel adjacent the edge may be trimmed to the exact cross-sectional involute contour of the tooth surface. However, where the grinding operation is carried out on a helical gear, heel and toe interference results in the formation of a tooth surface on the gear which differs materially from the radial cross-section configuration of the active portion of the grinding wheel. Thus, if the radial cross-section of the grinding wheel is the desired involute, the heel and toe interference will result in a tooth formation on the gear which differs from the desired involute shape.

Moreover, it has been found that this variation between the shape of the tooth surface on the gear and the crosssectional shape of the active surface of the grinding Wheel is a function of wheel diameter so that as the wheel wears, there must be a continuous change in the shape of the trimmed area to maintain uniform accurate results on the gear.

In accordance with the present invention a trimmer is provided which causes the trimming element or diamond thereof to move relative to the grinding wheel so as to trace out a surface which is identical with the helicoidal surface of the workpiece. Thus, where heel and toe interference would result, the grinding wheel is trimmed to eliminate the material which would cause such interference. As a result, the grinding wheel is automatically trimmed by a simple operation to a contour required to produce the required helicoidal surface on the Work piece.

Referring to FIGURE 1 there is shown a gear grinder comprising a frame 10 on which a slide or table 12 is mounted for reciprocation longitudinally of the frame in rectilinear ways indicated at 14. Intermediate the ends of the frame and at one side thereof is a column 16 which is mounted for angular adjustment about a vertical axis by conventional means (not shown), the vertical axis extending substantially centrally through the grinding wheel W. The wheel W is mounted on a slide 18 capable of verticle adjustment by suitable means such for example as the hand wheel 24 and is adapted to be driven in rotation at grinding speeds by a motor mounted within the column 16. Mounted on the table 12 is a headstock 22 which includes conventional indexing mechanism (not shown) and which is adapted to receive an arbor or the shaft 24- of a helical Work gear G, the other end of the arbor or shaft being mounted in a tail-stock 26'.

In order to provide for helical advance of the gear G as the table is moved to cause the gear to move back and forth below the grinding wheel W, suitable mechanism is provide-d which may take the form of a lead bar 28 coupled to the shaft or arbor 24 and movable through a fixed nut 30 so that rotation is imparted to the gear G in timed relation to its axial advance. It will be appreciated that the column 16 is angularly adjusted to cause the grinding wheel to occupy the appropriate inclined plane in accordance with the helix angle of the gear G.

The trimming mechanism is indicated generally in FIGURE 1 and comprises a template support bracket 32 fixed to the frame 10, and a trimmer device carried by the table or slide 12, as will subsequently be described in detail.

Before referring to the detailed trimming mechanism, reference is made to FIGURE 2. In this figure there is shown a portion of a grinding wheel W, the grinding surface of which is indicated at 36 and which in this instance is of substantially involute radial cross-section. The grinding wheel is capable of grinding the surface 38 of the tooth 40 of a gear as the gear is moved parallel to its axis and is rotated in accordance with its helix angle. During this operation of course, the grinding wheel remains in a fixed position and is driven in rotation at grinding speeds.

In FIGURE 2 there is illustrated a template support plate 42 which is angularly adjustable about a vertical axis, the angular setting of the plate being shown by the indicia 44 in association with a gauge mark 46 on the template carrier 48. A template block 49 has at the left side thereof as seen in this figure, a guide surface 50 which is three-dimensionally curved to conform to the threedimensional curvature of the helicoidal surface of the gear tooth 40. Due to the "fact that the helicoidal tooth of a gear is of different height due to wrap-around on the gear, the guide surface of the template will be shaped correspondingly. If with the elements illustrated in FIG- URE 2 in the relationship shown, a trimmer were moved back and forth in a multiplicity of paths conforming to the tooth profile or flank surface of the tooth 40, it will be apparent that the grinding wheel will be trimmed so as to eliminate the heel and toe interference which has previously been referred to.

Mechanism for accomplishing the foregoing is illustrated in detail in FIGURE 3, where the template block 49 is shown :as carried by the plate 42, which in turn is adjusted to the required position on the template carrier 48. The carrier 48 is positioned at a required height above the bracket 32 by a riser 52. It will be observed that the bracket 32 is provided with an elongated T-slot 54 so that the posit-ion of the riser 52 and carrier 48, and hence the template 49, may be adjusted as desired with reference to the location of the grinding wheel W. However, it is important to note that in use during a trimming operation the template 49 remains in a fixed position relative to the grinding wheel.

As pointed out previously, the guide surface 50 of the template conforms to the profile or flank surface of the tooth 40. Thus, in the usual case where the tooth is an involute tooth of a helical gear, the guide surface of the template is an involute helicoid.

Intermediate the wheel W and the template 49 there is provided the trimmer device indicated generally at 34, which comprises a support 56 adjustable longitudinally of the T-slot 58 provided in the table or slide 12. A

height riser 60 is illustrated as positioned atop the support 56, and above the riser 64) is a trimmer block 62 having a pair of laterally extending ears 64 between which is mounted for angular adjustment a trimmer base 66. The angular adjustment of the trimmer base 66 is shown by indicia 66a. The block 62 is also adjustable relative to the slide 56 and riser 60 about a vertical axis provided by a pivot support, the upper end of which is indicated at 67. The trimmer device includes a body 68 which is connected to the trimmer base 66 by a pair of parallel links 70, the links being pivoted to the base 66 as indicated at 72a and to the body 68 as indicated at 74. If desired, a manual operating knob may be connected to the extension of one pivot shaft 7212, or if desired, a motor may be connected to the shaft 72b to impart back and forth oscillation of the body 68.

Located slidably within the body 68 is an elongated member 76 provided intermediate its ends with a spring seat 78 and having a compression spring 80 connected thereto which biases the member toward the template 4?. At the end thereof adjacent the grinding wheel W the elongated member 76 is provided with a trimmer element 82 which conventionally takes the form of 21 diamond. At its opposite end the elongated member 76 is provided with a follower element 84 which is movable over the three-dimensionally curved guide surface 50 of the template.

In use, in order to trim the grinding wheel, the table or slide 12 is traversed to a position in which the gear G is moved away from the grinding wheel W and the trimmer device 34 is moved into position between the grinding wheel W and the template 49. At this time in order to trim the wheel to the required configuration, the body 68 is caused to move back and forth repeatedly as con- 7 strained by the parallel links 70. This causes the body 68 to move in a curved path which may approximate the transverse curvature of the grinding surface of the wheel W. However, the follower element 84 at this time is maintained in contact with the guide surface of the template and accordingly, the trimming element 82 moves in corresponding paths. If at this time the trimmer is movable only in a plane radial of the grinding wheel, it is apparent that the grinding wheel will be trimmed to an involute cross-section but this will not eliminate the problem presented by heel and toe interference. Accordingly, in addition to the movement in a vertical plane occasioned by oscillation of the body 68 as constrained by the links 70, an additional movement is imparted to the body by appropriate movement of the table 12. Thus, in practice the trimming operation may be carried out by causing the table 12 to traverse the trimming mechanism slowly past the grinding wheel while the body 68 is moved repeatedly in the vertical plane. The rate of movement of the table is of course limited because it is essential for the trimming element to make a multiplicity of passes so as to trim the grinding wheel in such a wey as to eliminate heel and toe interference. The result of the foregoing is that the trimming element is caused to move in a multiplicity of closely spaced substantially but not exactly parallel paths. In fact, alternate paths during movement of the trimming element in an upper direction are substantially parallel as are the alternate paths traced during downward movement of the trimming element.

The mechanism may be employed with the template 49 and the trimmer device 34 positioned so that the elongated member 76 occupies a plane parallel to the axis of the grinding wheel. Alternatively, by appropriate adjustment of the parts, the longitudinal axis of the member 76 may be substantially perpendicular to the axis of the work gear.

Similarly, while in FIGURE 3 the axis of the elongated member 76 is illustrated as substantially horizontal, it will be readily apparent that by an increase for example in the height of the riser 60 and by a reduction in height of the riser 52, the axis of the elongated member 76 may be caused to incline inwardly and to the right so as to cause the elongated member 76 to extend more nearly perpendicular to the grinding surface of the wheel W.

While the foregoing preferred embodiment of the present invention is very simple and calls for the use of a template of exactly the same shape and size as a portion of the helicoidal surface of a gear tooth, it is within the scope of the present invention to provide a template which may be several times larger and in which the trimmer device intermediate the template and the edge of the grinding wheel is in the form of pantograph mechanism, as is well understood in the art. Accordingly, the template herein is defined as substantially geometrically similar to the helicoidal surface to be ground on the work piece, and by this expression geometrically similar is meant a surface which is substantially identical in shape but which may be quite different in size.

A very important advantage of the present invention is that the trimming mechanism automatically imparts the required configuration to the grinding wheel irrespective of the diameter of the wheel. Thus, as the wheel is worn down in use, and is repeatedly trimmed, the contour of the wheel changes but it is unnecessary to take the change in contour of the wheel in to account. The contour is always exactly that required to eliminate the heel and toe interference and to produce the required contour on the helicoidal surface of the work piece. This of course is always accomplished using the same template 49 which has the required helicoidal surface or a geometrically similar surface thereto.

The drawings and the foregoing specification constitute a description of the improved apparatus for trimming grinding wheels in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What we claim as our invention is:

1. A trimmer for a grinding wheel for use in grinding helicoidal forms, comprising a template having a threedimensionally curved guide surface geometrically similar to a helicoidal surface on a work piece, means for positioning the template in fixed position adjacent the wheel and in parallelism with the position occupied by the work piece surface during grinding, a trimmer device comprising a trimming element in position to traverse a side portion adjacent the edge of the grinding wheel, and follower mechanism connected to the trimming element and including a follower element engageable with the guide surface of the template and effective to move the trimming element in accordance with movement imparted to the follower element by movement over the guide surface of said template, means for moving said trimmer device between said template and wheel to cause said follower element effectively to cover an area of the guide surface and to thereby cause said trimming element to trace out a substantial area intersecting the grinding portion of the wheel which is geometrically similar to the guide surface of said template.

2. A trimmer as described in claim 1 in which the guide surface of said template is substantially identical to the helicoidal surface to be ground on the work piece.

3. A trimmer as described in claim 2 in which said trimmer device comprises a carrier body, an elongated member movable longitudinally in said body, said trimming and follower elements being located at opposite ends of said body.

4. A trimmer as described in claim 3, said body being movable in two different directions both substantially normal to the axis of said member.

5. A trimmer as described in claim 4 in which said template and trimmer device are located such that the axis of said member is substantially parallel to the axis of said wheel.

6. A trimmer as described in claim 4 in which said template and trimmer device are located such that the axis of said member is substantially perpendicular to the axis of the helicoidal surface of the work piece.

7. A trimmer for a grinding wheel comprising a template having a three-dimensionally curved guide surface adapted to be positioned to confront a side portion adjacent the edge of a grinding wheel, and a trimmer device having a trimming element and a follower element, means interconnecting said elements to cause said trimming element to move and trace a three-dimensionally curved surface Which is geometrically similar to the guide surface of the template, and means for moving said device to move said trimming and follower elements in a multiplicity of adjacent paths which in total cause the trimming element to trace out the required surface.

8. A trimmer as described in claim 7 in which said trimmer device comprises a carrier body, an elongated member movable longitudinally in said body, said trimming and follower elements being located at opposite ends of said body.

9. A trimmer as described in claim 8, said body being movable in two difierent directions both substantially normal to the axis of said member.

10. A trimmer as described in claim 9 in which said template and trimmer device are located such that the axis of said member is substantially parallel to the axis of said wheel.

11. A grinder comprising a frame, a slide movable rectilinearly on said frame, a work support on said slide including means for supporting a work piece having a helicoidal surface for rotation about the axis of said helicoidal surface with its axis of rotation parallel to the direction of reciprocation, means responsive to movement of said slide to rotate the Work piece, a rotary grinding wheel, means mounting said wheel on said frame for angular adjustment about an axis perpendicular to and intersecting the axis of said wheel and the axis of rotation of a work piece on said work support, means for driving the wheel in rotation, a template on said frame having a helicoidal guide surface geometrically similar to the portion of a helicoidal surface of a work piece at and adjacent the zone of contact with said wheel, said template being fixed to said frame with its guide surface confronting the work contacting zone of the wheel, a trimmer device mounted on said slide for movement therewith into and out of a trimming position interposed between the guide surface of said template and the work contacting zone of the wheel, said trimmer device comprising a follower element movable over the guide surface of said template, a trimming element movable in trimming relation relative to the work contacting zone of said wheel, and means connecting said follower and trimming elements to cause said trimming element to trace out an area geometrically similar to the guide surface of said template.

12. A grinder as defined in claim 11 in which said guide surface is oriented in parallelism with the portion of the helicoidal surface of a work piece at the zone of contact with said wheel.

13. A grinder as defined in claim 11 in which said trimming element is movable repeatedly in generally parallel paths approximately radial of said wheel and is movable transversely of such paths between successive movements in said paths.

14. A grinder as defined in claim 12 in which the guide surface of said template is substantially identical to the helicoidal surface to be ground on the work piece.

15. A grinder as defined in claim 14 in which said trimmer device comprises a carrier body, an elongated member movable longitudinally in said body, said trimming and follower elements being located at opposite ends of said body.

16. A trimmer as defined in claim 15, said body being movable in two different directions both substantially normal to the axis of said member.

17. A trimmer as defined in claim in which said template and trimmer device are located such that the axis of said member is substantially parallel to the axis of said wheel.

18. A trimmer as defined in claim 15 in which said template and trimmer device are located such that the axis of said member is substantially perpendicular to the axis of the helicoidal surface of the work piece.

19. A trimmer as defined in claim 11 which comprises means for adjusting said template about an axis parallel to the axis of adjustment of said wheel.

20. A trimmer as defined in claim 11 which comprises means for relatively adjusting said template and wheel in a plane perpendicular to the axis of rotation of a work piece on said work support.

21. A grinder comprising a frame, a slide movable horizontally and rectilinearly on said frame, a work support on said slide including means for supporting a work piece having a helicoidal surface for rotation about the axis of said helicoidal surface with its axis of rotation parallel to the direction of reciprocation, means responsive to movement of said slide to rotate the work piece, a rotary grinding wheel, means mounting said wheel on said frame in position over a work piece on said work support for angular adjustment about a vertical axis perpendicular to and intersecting the axis of said wheel and the axis of rotation of a work piece on said work support, means for driving the wheel in rotation, a template on said frame having a helicoidal guide surface geometrically similar to the portion of a helicoidal surface of a work piece at and adjacent the zone of contact with said wheel, said template being fixed to said frame with its guide surface confronting the work contacting zone of the wheel, a trimmer device mounted on said slide for movement therewith into and out of a trimming position interposed betwen the guide surface of said template and the work contacting zone of the wheel, said trimmer device comprising a follower element movable over a substantial area of the guide surface of said template, a trimming element movable in trimming relation relative to the work contacting zone of said wheel, and means connecting said follower and trimming elements to cause said trimming element to trace out an area geometrically similar to the guide surface of said template.

22. A grinder as defined in claim 21 in which the guide surface of said template is identical with and parallel to the portion of a helicoidal work piece surface in the zone of contact with said Wheel.

23. A grinder as defined in claim 22 in which said trimmer device comprises a carrier body, an elongated member movable longitudinally in said body, said trimming and follower elements being located at opposite ends of said body.

24. A grinder as defined in claim 23, said body being movable in a vertical plane relative to said slide and being movable horizontally with said frame to trace out a substantial area of three-dimensionally curved helicoidal surfaces adjacent said wheel.

25. A grinder as defined in claim 23 comprising means mounting said template on said frame for angular adjustment about a vertical axis.

26. A grinder as defined in claim 22 comprising means for adjusting said template horizontally on said frame parallel to the path of movement of said slide.

27. A grinder as defined in claim 22 which comprises a carrier, parallel links connecting said body to said carrier, means for effecting -a relative height adjustment between said wheel and said template, and means for angularly adjusting said carrier about an axis parallel to the path of movement of said slide.

References Cited by the Examiner UNITED STATES PATENTS 1,599,405 9/ 1926 Bugbee. 2,151,802 3/1939 Roman -11 3,067,733 12/1962 Pernack 12511 ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner.

Claims

11. A GRINDER COMPRISING A FRAME, A SLIDE MOVABLE RECTILINEARLY ON SAID FRAME A WORK SUPPORT ON SAID SLIDE INCLUDING MEANS FOR SUPPORTING A WORK PIECE HAVING A HELICOIDAL SURFACE FOR ROTATION ABOUT THE AXIS OF SAID HELICOIDAL SURFACE WITH ITS AXIS OF ROTATION PARALLEL TO THE DIRECTION OF RECIPROCATION, MEANS RESPONSIVE TO MOVEMENT OF SAID SLIDE TO ROTATE THE WORK PIECE, A ROTARY GRINDING WHEEL, MEANS MOUNTING SAID WHEEL ON SAID FRAME FOR ANGULAR ADJUSTMENT ABOUT AN AXIS PERPENDICULAR TO AND INTERSECTING THE AXIS OF SAID WHEEL AND THE AXIS OF ROTATION OF A WORK PIECE ON SAID WORK SUPPORT, MEANS FOR DRIVING THE WHEEL IN ROTATION, A TEMPLATE ON SAID FRAME HAVING A HELICOIDAL GUIDE SURFACE GEOMETRICALLY SIMILAR TO THE PORTION OF A HELICOIDAL SURFACE OF A WORK PIECE AT AND ADJACENT THE ZONE OF CONTACT WITH SAID WHEEL, SAID TEMPLATE BEING FIXED TO SAID FRAME WITH ITS GUIDE SURFACE CONFRONTING THE WORK CONTACTING ZONE OF THE WHEEL, A TRIMMER DEVICE MOUNTED ON SAID SLIDE FOR MOVEMENT THEREWITH INTO AND OUT OF A TRIMMING POSITION INTERPOSED BETWEEN THE GUIDE SURFACE OF SAID TEMPLATE AND THE WORK CONTACTING ZONE OF THE WHEEL, SAID TRIMMER DEVICE COMPRISING A FOLLOWER ELEMENT MOVABLE OVER THE GUIDE SURFACE OF SAID TEMPLATE, A TRIMMING ELEMENT MOVABLE IN TRIMMING RELATION RELATIVE TO THE WORK CONTACTING ZONE OF SAID WHEEL, AND MEANS CONNECTING SAID FOLLOWER AND TRIMMING ELEMENTS TO CAUSE SAID TRIMMING ELEMENT TO TRACE OUT AN AREA GEOMETRICALLY SIMILAR TO THE GUIDE SURFACE OF SAID TEMPLATE.