US2469255A - Pattern controlled grinding wheel dressing mechanism - Google Patents

Description

May 3, 1949- F. A. BARNES 2,459,255

PATTERN CONTROLLED GRINDING WHEEL DRESSING MECHANISM Filed Nov. 18, 1944 INVENTOR.

FREDERICK A. BARNES B Y [foray 6/ jATTORNEY Patented May 3, 1949 PATTERN CONTROLLED GRINDING WHEEL DRESSING MECHANISM Frederick A. Barnes, Cleveland Heights, Ohio, as-

signor to Bailey Meter Company, a corporation of Delaware Application November 18, 1944, Serial No. 564,056

Claims.

This invention relates to grinding machines having a rotatable abrasive former whose general profile or contour dictates the final shape of a work piece which is to be finished by contact with the abrasive material; in other words, a form grinder.

When numerous work pieces are to be ground to the same final shape it is usual to provide a grinding wheel or stone having a corresponding shape. However, such a stone soon wears and departs from the accurate shape to which the work must conform.v Periodically then the stone must be dressed, formed or shaped to the original desired contour. Many times, therefore, during the life of the stone its original form must be duplicated. This has in the past been a time consuming job by a highly skilled mechanic. In many instances it is necessary to remove the grinding wheel from the grinder in order to form dress it. It is the object of my present invention to provide means in connection with a grinding machine whereby such a grinding wheel may be dressed in place and without changing its operational relation to the grinding machine and work centers.

It is to be understood that in the present specificaion and claims I am considering a well known type of grinding machine and well known process of forming a work piece by means of an abrasive material. The various terms used herein are representative only and are not used in any limiting sense. For example, the abrasive action is one of attrition or wearing away of material from the work piece, and may be accomplished through contact of the work with an abrasive material. Either the work piece or the abrasive material, or both, may be moved relative th one to the other. The abrasive material may be termed a stone, wheel, former, or other language common to the trade. The reshaping of the stone to its original desired shape, contour or profile may be spoken of as dressing the stone, facing it or forming it and similar language without being restrictive. The desired procedure regardless of terminology) is one of returning the shape of the stone to correspondence with its original shape.

I herein use the terms contour, profile, shape, form and the like interchangeably and in a broad sense and not with any limiting distinction be- I tween the profile of a two dimensional silhouette or the surface configuration of a three dimensional body for example. By strict definition one might be led to believe that profile is only the edge shape of a two dimensional silhouette. Usually it is spoken of as the edge shape of a thin plate template for example, although such a template is a three dimensional object. Usually contour is the surface configuration, or at least a portion of the surface of a three dimensional object. I intend-to make it clear that in speaking of profile or contour or shape I mean the general configuration of either the forming stone or of the work piece. By duplicating the contour of the stone I mean that its general shape is th same as it was originally, although perhaps at a different diameter relation due to wear and reshaping.

In the drawings:

Fig. 1 is a diagrammatic plan view of a portion of a standard grinder to which my invention has been applied.

Fig. 2 is a diagrammatic illustration of the pneumatic and hydraulic control circuits employed in the embodiment of my invention shown in Fig. 1.

Fig. 3 is a transfer valve arrangement of Fig. 2.

Referring now to Fig. 1, I show my invention applied to any well known type of grinder wherein a work piece may be held between centers I, 2 and rotated thereby in predetermined direction and speed. In proper relation to the work piece I show a shaped grinding stone 3 mounted for rotation upon a spindle 4. Well known means may be provided for indexing the stone 3 toward or away from th axis of the centers I, 2. Inasmuch as the grinding operation forms no part of my invention, it appears unnecessary to go into further detail in this regard. A particular improvement of the present invention is in connection with the reshaping of the abrasive stone 3 after it has become worn or has departed from its original contour or shape. This is ordinarily done by a diamond point dressing tool, such as 5, adjustably mounted in a'tool holder 6. The tool holder is mounted on and carried by a crossslide 1 movable toward or away from the stone 3 along ways 8 through the agency of a piston 8 acting through a piston rod III.

The tool 5, tool holder 6, cross-slide I .and

, i 3 piston 9 are mounted on 'a carriage ll movable axially of th stone 3 along ways l2 through the agency of a, hydraulic piston l3'acting through.

a piston rod Ii. Thus movement of the dressing tool 5, toward'or away from the periphery of the stone 3, is produced by movement of the piston 9, while travel oi the dressing tool 5 axially along the stone'3 is accomplished through the agency of the piston 13. For controlling the positioning of the pistons 9 and I3 I provide a pneumatic control system.;having a tracer assembly l5 cooperating-with a pattern or template 16. The housing of the tracer assembly i5 is rigidly fastened to the cross-slid 1 and carried therewithalong the ways 8 relative to the shaped edge of the template l6. The template 16 being 6' rigidly mounted .to .the machine base l1 as at '18 and l9. 1

The tracer assembly l5 forms no part ofmy present invention and may b of the type disclosed inmy copending application Serial No.

524,705," to :which reference may be had for a more detailed consideration. I believe it will suflice here to say that th assembly includes a tracer or'feeler arm 20 adapted to contact the shapededge ofthe template l6 as the carriage i 5 moves along the ways l2. In other words, the tracer arm 23 continually scans the profile of the template l6 and controls the bleed to atmosphere 1 'of a substantially constant pressure supply of pneumatic and hydraulic circuits for controlling the servomotors 9 and I3 by the tracer l 5 in such manner that the piston 9 will position the crossslide and consequently the dressing tool 5 transversely relative to the stone 3 as it is traveled longitudinally along the stone 3. The action is such that if the contacted edge of the template l6 is-a straight line, parallel to the axis of the stone 3, then the stone 3 will be dressed to cylindrical form. Ifthe contacted edge of the template IB is a straight line, but inclined to the axis of the stone 3, then the stone will be shaped to a taper. The particular showing of Fig. 1 is in general of opposed tapers spaced by a cylindrical section merely by way of example.

Air under pressure from any convenient source is passed through a pressure regulator 2| and orifice 22 to a header 23 from which the tracer assembly l5 bleedsto the atmosphere. As the discharge from the tracer [5 to the atmosphere vvaries, the pressure in the header 23 between the orifice 22 and the tracer assembly i5 will vary, and such controlled air pressure (representative Drainage from the pilot. 25 is returned to the sump through a; pipe 33.

In connection, with the hydraulic piston i3 and adjustable fluid resistance 21 I'provide switching valves and 36 arranged to be moved together to either a normal or a;rapid traverse". position of operation of the piston 13. The valves 35 and 36 are shown in Fig.2 in the "normal of changesin contourof the template I6) is ef- I fective upon 'a bellows 24 of a pilot valve assembly 25, and simultaneously upon a bellows 26 of l a fluid resistance assembly '21. The pilot valve 25 and fluid'resistance 21 are fullydescribed in my copending application Serial No; 524,705, and

' the copending application of'Clarence Johnson Serial No. 524,707.,

I show an oil pump 28 driven by a motor 29 and drawing its supply of oil from a sump 30.

011 under pressure is supplied the. pilot valve 25 by the pump 28vthrough a pipe 3|. From the pilot valve 2,5 oil is supplied to one side or the operating position. Oil under pressure fromv the pump 28 is forced through a pipe 31, the valve 36, and a pi e 38 to one side of the piston I3. Oil from the other side of the piston through a pipe 39, the valve. 36,-the valve 35, a

pipe 49, the adjustable fluid resistance 21, and a pipe M to the sump 30. The regulation of the variable resistance 21 determines the rate of flow of oil through the pipe 39, and consequently the rate oftravel of the piston rod 14 toward the left in Fig. 2. Thus the rate of longitudinal travel of the droessing tool 5 along the stone 3 is controlled by the variable resistance 21to passage of oil therethrough from the left-hand side of piston l3 (Fig. 2).

In Fig. 3 I show the passage relation of the switching valve 35, 36 for a rapid return of the piston rod I 3 from left to right of Fig. 2. It is, of course, apparent that the'piping may be so arranged that the controllable rate of travel is from left to right and the rapid return from right to left should that be desired. In any event Fig. 3 shows the connection'for a rapid return of the tool to the beginning of its working travel. Oil from the pump 23 passes directly through the pipe 31, the valve 36 and the pipe 39; while oil from the right-hand side of the piston 13 passes directly through the pipe 38, the valve 33, the valve 35, and the pipe M tov the sump 30. On the rapid return of the piston rod I3 there is no throttling of its speed of travel by the variable resistance 21, and thus the dressing tool is traversed to the right at a maximum speed.

.In general, the operationv of the system illustrated in Figs. 1, 2 and 3 is as follows. If the contacted edge of the template !6 is a straight line parallel to the axis of the stone 3, the air pressure established within the pipe 23 is such that the bellows 2t and 26 (and the movable parts of the assemblies 25, 21* positioned thereby) provide a normal condition of operation. The pilot valve 25 locks oil in the pipes 32, 33 so that the piston rod 3 is not moving and the tool travels a cutting path parallel to the axis of the stone 3. At the same time the variable fluid resistance 21 is in a position to provide a normal speed of travel of the piston rod 13 moving the dressing tool 5 at a uniform rate along the stone 3.

If the profile of the template it recedes from the axis of the stone 3, or advances toward the axis of the stone 3, the air pressure within the pipe 23 is correspondingly varied in proper direction to increase or decrease the air pressure within the bellows 24 and 26 and to cause a corresponding positioning of the movable element of the pilotv valvev25 and'of the fluid resistance 21. Such movement causes the piston 9 to position the dressingtool 5-toward or awayfrom-the axis of the stone 3 and thus reproduce upon the stone 3' the contour of the master template l6.

At the same time any departure .(in either direc-' longitudinal travel of the dressing tool 3 from l3 passes right to left on the drawing will be at a speed slower than the normal speed depending upon the rate of travel of the dressing tool toward or away from the axis of the stone 3. If, for example, the profile of the template l6 includes a shoulder at right angle with the axis of the stone 3, then there will be a complete stoppage of longitudinal travel of the dressing tool 5 while the tool is advancing directly toward the axis of the stone or is receding directly therefrom. Movement of the tracer arm 20 either toward or away from the contacted edge of the template I6 from a normal or neutral position results in a decrease in speed of travel of the dressing tool 5 in its longitudinal direction from its normal speed of travel and irrespective as to whether the tool is advancing towards the axis of the stone 3 or is receding therefrom.

After a complete travel of the dressing tool has been accomplished from right to left (for example) then a rapid return of the tool to the right may be accomplished by moving the.

switching valves 35, 36 to the position shown in Fig. 3 wherein the connections to the opposite sides of piston 13 are reversed and the variable resistance 21 is made non-effective.

In general, I have not felt it necessary to show any of the ordinary indexing or hand adjusting means by which 'the actual position of the dressing tool 5 in the tool post 6 and relative to the cross-slide I may be arranged for most eflicient dressing of the stone 3. Nor have I felt it necessary to show any of the indexing means whereby the reproduction of the contacted profile of the template It; may be accomplished upon the stone 3 at a proportionately smaller diameter ratio than the previous dressing These adjustment and indexing possibilities are common practice and form no part of the present invention. Furthermore, I have not felt it necessary to show any means for moving the dressing tool 5away from the stone 3 and out of operative position after the dressing is completed and the stone 3 is being used in normal manner for abrasive action upon a work piece held between the centers I. 2.

It will be apparent that I have provided apparatus whereby a form grinding stone may be dressed in place without removing it from a grinding machine and with a minimum of interruption in normal production on the grinding machine. Furthermore, with a minimum of effort the operator may check the contour or profile of the grinding stone to ascertain whether I or not wear or deformity have taken place.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A grinding machine having a pair of axially aligned centers for mounting and rotating a workpiece and having a grinding wheel mounted for rotation upon a spindle about an axis parallel to the axis of said aligned centers and movable laterally into contact with the workpiece, apparatus for forming a profile on the grinding wheel, said profile being the complement of a profile required to be ground thereby on the workpiece, said apparatus comprising a carriage member adapted to move longitudinally relative to said spindle, a cross slide mounted on said carriage adapted to move laterally relative to said spindle, a dressing tool carried by said cross slide, pattern controlled pneumatic pressure means including a pattern and tracer means adapted to scan said pattern, said tracer means variably discharging air to atmosphere from a, substantially constant pressure source in accordance with the form of said pattern to thereby produce variations in air pressure corresponding to said pattern between said constant pressure source and said tracer means, a first fluid motor adapted to move the cross slide and tool laterally with respect to said spindle of the grinding wheel, a second fluid motor adapted to move the carriage and cross slide longitudisponsive to said variations in pressure for operin accordance ating said pilot valve means with the form of said pattern, a variable fluid resistance valve regulating the rate of hydraulic fluid passage to or from said second fluid motor and thereby control the speed of travel of said carriage longitudinally relative to said spindle, said fluid resistance valve having a stop position to hold said second fluid motor and carriage longitudinally stationary with respect to said spindle at any given position, andv second pressure responsive means responsive to said variations in pressure for operating said fluid resistance valve in accordance with the form of said pattern, said first and second pressure responsive means jointly controlling said resistance and pilot valves in response to said variations in pressure, whereby a profile parallel to said spindle is formed upon said grinding wheel by the pilot valve stopping the flow of fluid to said first fluid motor and the fluid resistance valve allowing a flow of fluid to said second fluid motor, a profile at right angles to said spindle being formed by the fluid resistance valve stopping the flow of fluid to the second fluid motor and the pilot valve allowing a flow of fluid to said first fluid motor to move the cross slide laterally with respect to the spindle, and profiles other than parallel or right angle profiles being formed on the grinding wheel by the simultaneous movement of both said first and second fluid motors.

2. A grinding machine having a pair of axially aligned centers for mounting and rotating a workpiece and having a grinding wheel mounted for rotation upon a spindle about an axis parallel to the axis of said aligned centers and movable laterally into contact with the workpiece, apparatus for forming a profile on the grinding wheel, said profile being the complement of a profile required to be ground thereby on the workpiece, said apparatus comprising a base' member laterally positioned to one side of said grinding wheel axis, a carriage mounted on said base member for longitudinal travel along one side of said grinding wheel axis, a cross slide mounted on said carriage and adapted to move laterally with respect to said grinding wheel axis,

a tool holder mounted upon said cross slide for holding a dressing tool, said dressing tool adapted to extend from said holder laterally toward said' grinding wheel, pattern controlled pneumatic pressure means including a pattern having a pattern edge and tracer means adapted to scan said pattern edge, said pattern being mounted upon said base on said one side of said axis of the grinding wheel, said pattern edge being on the side of the pattern means opposite said axis of the grinding wheel, a first hydraulic motor aseaa'tt" v,

for relatively positioning'the tool and grinding wheel along a first path, a. second hydraulic motor for relatively positioning the tool and grinding wheel-along a second path, said first and second paths being angul-arly related with respect to one another, a fluid pilot valve adapted to control the speed and direction of, travel (g said first fluid motor, the speed or movement'of the tool relative to the grinding wheel along said paratus for forming a profile on the grinding wheel, said profile being the complement of a profile required to be ground thereby on the workpiece, said apparatus comprising a base member laterally positioned to one side of said grinding wheel axis, a carriage mounted on said base member for longitudinal travel along one side of said grinding wheel axis, a cross slide mounted on said carriage and adapted to move laterally with respect to said grinding wheel axis, a tool holder mounted upon said cross slide for holding a dressing tool, said dressing tool adapted to extend from said holder laterally towards said grinding wheel, pattern controlled pneumatic pressure means including a pattern having a pattern edge and tracer means adapted to scan said pattern edge, said pattern being mounted upon said base on the side of the tool holder opposite said grinding wheel, a first hydraulic motor mounted on said carriage on the side thereof opposite said grinding wheel for relato extendfronr said holder laterally toward said grinding wheel, pattern, controlled pneumatic pressure means including a pattern having a pattern edge and tracer means adapted to scan said pattern edge, said pattern being mounted I upon said base on said one side of said axisof the grinding'wheeL'said pattern edge beingon the side or the patternmea'ns opposite said axis of the grinding. wheel, a first -hydraulic. motor for relatively positioning the tool and grinding wheel along said firstpath, a second hydraulic motor for relatively positioning the tool and grinding wheel along said second path, said first and second paths beingi angularly related with respect to one another, a fluid pilot'valve adapted to control the speed and direction of travel or said first fluid motor, the speed of movement of the tool relative to the grinding wheel along said second path'being dependent upon the rate or hydraulic fluid passage to or from the second hydraulic motor, and a variable fluid resistance valve regulating the rate oi! hydraulic fluid pastively positioning the cross slide and tool laterally with respect to said grinding wheel, a second hydraulic motor for moving the carriage longitudinally with respect to said grinding wheel, a fluid pilot valve adapted to control the speed and lateral direction of travel of said first fluid motor, the speed of movement of the carriage longitudinally relative to said grinding wheel being dependent upon the rate of hydraulic fluid passage to or from the second hydraulic motor, and

a variable fluid resistance valve regulating the rate of hydraulic fluid passage to and from said second motor, the pilot valve and resistance valve -jointly controlled by said pneumatic pressure means.

44A grinding machine having a pair of axially grinding wheel axis, a carriage mounted on said base member for movement along a first path,

a cross slide mounted on said carriage and adapted to move along a second path, a tool holder mounted upon said cross clide for holding a dressing tool, said dressing tool adapted sage to and irorn said second motor, the pilotv valve and resistance valve jointly controlled-by said pneumatic pressure means.

5. A grinding machine having a pair of axially aligned centers for mounting and rotating a workpiece and having a grinding wheel mounted for rotation upon a spindle about an axis parallel to the axis of said aligned centers and movablev laterally into contact with the workpiece, apparatus for forming a profile on' the grinding wheel, said profile being the complement of a profile required to be ground thereby on the workpiece, said apparatus comprising a carriage member adapted for movement along a first path, a cross slide mounted on said carriage adapted to move along a secondpath at an angle to said first path, a dressing tool carried by said cross slide, pattern controlled pneumatic pressure means including a pattern and tracer means adapted to scan said pattern, said tracer means variably discharging air to atmosphere from a substantially constant pressure source in accordance with the form of said pattern to thereby produce variations in air pressure corresponding to said pattern between said constant pressure source and said tracer means, a first fluid motor adapted to move the cross slide and tool along said first path, a second fluid motor adapted to move the carriage and cross slide along said second path, pilotvalve means adapted to control the speed anddirection of travel of said first fluid motor, said piio't valve means having a stop position to hold said first fluid motor and cross slide stationary with'respect to said spindle at any carriage along said second path, said fluid resistance valve having a stop position to hold said second fluid motor and carriage stationary with respect to said spindle at any given position, and second pressure responsive means responsive to said variations in pressure for operating said fluid resistance valve in accordance with the form of said pattern, said first and second pressure responsive means jointly controlling said resistance and pilot valves in response to said variations in pressure, whereby a profile parallel to said spindle is formed upon said grind 9 ing wheel by the pilot valve stopping the flow of fluid to one of said fluid motors and the fluid resistance valve allowing a flow of fluid to the other of said fluid motors, a profile at right angles to said spindle being formed by the fluid resistance valve stopping the flow of fluid to said other fluid motor and the pilot valve allowing a flow of fluid to said one fluid motor, and profiles other than parallel or right-angle profiles being formed on the grinding wheel by the simultaneous movement of both said first and second fluid motors.

FREDERICK A. BARNES.

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

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