US2224423A - Process and apparatus for finishing preground articles - Google Patents

Description

Dec. 10, 1940. G W -B|NN5 v 2,224,423

PROCESS AND APPARATUS FOR FINISHING PREGROUND ARTICLES ATTORNEY.

G. W. BINNS De. 1o, 1940.

PROCESS AND APPARATUS FOR FINISHING PREGROUND ARTICLES 2 Sheets-Sheet 2 Filed June 8, 1939 III III|||Il||||l|IIIIIIIIIIIIIHIIIIIIIIII|||||||| 220:7 &\\\\\\\\\\\ \\\\\\\\\\\\\\\\\\\N &\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ 1NVENTOR. 6220?@ J5/ms' ATTORNEY.

Patented Dec. 10,` 1940 UNITED STATES PROCESS AND APPARATUS FOR FINISHING PREGROUND ARTICLES George W. Binns, Cincinnati, Ohio, assignor to Cincinnati Grinders Incorporated, Cincinnati, Ohio, a corporation of Ohio Application June s, 1939. serial Nc. 278,063 Y 4 Claims.

When a work piece leaves a conventional grinding machine of either the center or centerless type. microscopic examination of the surface reveals that it has a deilnite texture or a nap which 5 may be defined as fine lines extending circumferentially about the. work and lying in cross sectional planes which arev substantially perpendicular to the axis of work rotation. These lines, which are really grooves, are cut by the granulations on the surface of thewheel, and since the axis of the work was parallel to the axis of the grinding wheel during the grinding operation, these grooves lie in planes which are perpendicular to the axis of the work. It will thus be obvious that the surface is relatively rough and consists of alternate projections and hollows.`

If such a surface is subjected to wear the high points of the projections will naturally wear away first and also very quickly, whereby the mum by the time that the'work has been reduced to its desired size. 3 Another object of this invention is to provide an improved process for nnishing preground Asurfaces. A further object of this .invention is to provide one form of apparatus for performing the process ,s described herein.

Other objects'- and advantages of the present invention should'be readily apparent by reference to the following speciiication, considered in conjunction with the accompanyingdrawings forming a part thereof and it is to be understood that any modiiications may be made in the exact structural details there shown and described, within the scope of the appended claims without departing from or exceeding the spirit of the ina vention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is a front elevation of an apparatus for performing the process of this invention.

50 Figure 2 is a diagrammatic view illustrating one manner of performing the ilrst step in the processo! this invention.

Figure 3 is a diagrammatic view illustrating the second step in the process.

Figure 4 is a diagrammatic view of the electri- Figure 8 is a diagrammatic view illustrating I the composite result of the process.

It is recognizedin the grinding 'art that the finish produced by a conventional grinding operation is not sumciently fiat for parts which are to be used in the manufacture .of precision machinery, requiring close tits, measurable in micro-inches. The grains of the abrasive members utilized in conventional grinding operations must be suiilciently large to remove the excess vstock left for -grinding purposes in a reasonably short time with the result that the nal surface has what is termed grinding lines running circumferentially about the work.

'I'he analysis 'of the surface shows that these lines are line grooves with the result that the surface is composed of a series of alternate projections and depressions. It is the peaks of these projections which apparently wear away very quickly when the part is put to use producing the. undesirable wear after-very short usage,

Aiter the projections have been somewhat fiattened, the rate of-wear is then very slow.

This invention deals with a process and apparatus for producing a surface which does not have such marked projections 'and depressions,

. thus eliminating the possibility of quick initial wear when the part is put to use.

, Referring to Figure of the drawings there is illustrated on a cylindrical work piece Ill the direction-of the grindng lines Il with respect to the axis of rotation l2 ofthe work which are produced by a conventional grinding operation.

It will be noted that these lines lie in planes which are substantially perpendicular to the axis of rotation and this is because thework is held substantially parallel to the axis ,of rotation of the grinding element. 'I'he ilrst step of the process .of this invention is to' subject the work piece I0 in the condition shown in Figure 5 to an abrasive element which has a grain smallery than the original grinding element, as,-.for example.

two or three times smaller, and maintaining the axis of the work at a small acute angle relative to the axis of the abrasive element while travers- A ing the work past the grinding element whereby a cross wiping effect is obtained which will proure 8.

duce grinding lines, such as those indicated by the reference numeral I3 in Figure 6. Because of the nner grain of the wheel used in this nrst step, the grinding lines produced will not be as axis of the grinding wheel which is the opposite or negative of the first-named acute angle and which will produce grinding lines lying at the angle indicated by the lines Il in Figure '1. -This will tend to further reduce or flatten off the original projections without producing new grooves which would aggravate the situation. The composite results of these steps are shown in Fig- The process further includes in the first step the utilization of the nnest grained wheel for rotating the work while grinding with the coarser grained wheel, and then in the second step of rotating the work with the coarser grained wheel while the nnest grained wheel is doing the grinding. The work is moved relatve t this pair `oi? wheels in the same direction regardless of which wheel is doing the grinding.

The first step of the process is illustrated in Figure 2 in which the reference numeral I5 represents the coarser grained wheel and the reference. numeral I6 represents the nner grained wheel. The work piece III is supported 'between these wheels on a work rest blade I1 and the wheel I6 is rotated in the direction of the arrow I8 at a relatively slow rate to effect rotation of the work in the direction of the arrow I9. The wheel I is rotated at a relatively fast rate to effect the grinding. T he top of the work rest blade makes a slight acute angle to the plane determined by the axes 20 and 2I of the respective grinding wheels whereby the axis of travel 22 of the work is also inclined to this plane, thus producing the cross wiping effect connoted by the lines I3 in Figure 6. The inclination of the grinding wheels is such that the work is caused to travel automatically in the direction of the arrow 23.

The second step of the process is illustrated in Figure 3 and inthis ngure the coarser grained wheel I5 is rotated in 4the direction of -the arrow 24 which is opposite to its direction of rotation shown in Figure 2, and its rate of rotation is relatively slow -to-efi'ect rotation ofthe work in the direction of arrow 25, while the nner grained wheel I3 is rotated at a relatively fast rate and in the direction of arrow 23 to en'ect the grinding. Since the inclination of the wheels with respect to the surface of the work rest blade has not changed, theJ work wi1i. automatlcally feed in the same direction as indicated by the arrow 23.

It will thus be evident that an improved process has been provided for nnishing preground parts which .consists in subjecting the part lto an brasive element of a grain finer than theV orig al elements whichv did the pregrinding, traversing the part relative to the abrasive element along a path angularly related with respect lto the axis of the element and which is different from the angular relationship between the path of thework and the axis of the wheel in the pregrinding operation, whereby a cross wiping effect is produced; subjecting the part to a second abrasive element of a still nner grain, traversing the work relative to the last-named element along a path which is angularly related to the axis of rotation thereof and different from the angle in the first two cases whereby a second cross wiping effect is produced.

Considered more specincally, the process consists of presenting a work piece to a pair of grinding elements of different grains, rotating the work with the nner grained wheel and simultaneouly grinding the work with the coarser grained wheel; and then rotating the work with the coarser grained wheel and simultaneously grinding the work with the nner grained wheel.

As an example of an apparatus for performing the h'erein described process of nnishing, a machine is shown in Figure 1 of the drawings comprising a bed 26 upon which is mounted a pair of adjustable supports 21 and 28. 'I'hese supports are guided for movement relative to the bed 26 and may be adjusted by the screws 29 and 30 respectively. The support 21 carries a grinding Wheel head 3l in which the grinding wheel I5 is rotatably journal'ed. The head 3I is attached to the support 21 for angularadjustment about the horizontal a'xis indicated by line 32, which passes through the longitudinal center of the grinding wheel axis 23.

The grinding wheel I6 is .iournaled at opposite ends in the head 33 which is attached to the support 28 for angular adjustment about the axis 32. IA work rest blade I1 is supported on the bed 26 intermediate the wheels I5 and I8 and for illustrative purposes -the top surface of this blade may be considered as lying in a horizontal plane.

Conventional means not illustrated may be utilized for raising or lowering this blade for changes in work size. The axes 20 and 2I and the work rest blade lie in parallel vertical planes but the axes 20 and 2| are angularly adjusted in their respective vertical planes about the horizontal axis 32 with the result that lthe plane determined thereby makes an acute angle with respect to a horizontal plane, and therefore, with A respect to the top surface of the work rest blade.

This provides the necessary cross wiping effect that is obtained on the work and it also deteranism for 4truing wheels in this manner is `old and well known and forms no part of the pres- Vent invention, it will not be describedindetail here.

The mechanism for controlling the rate and direction of the rotation of the wheels will now be described.l

The grinding wheel I5 is driven by a prime mover such as the electric motor 3l which has a drive pulley 35 connected by a belt 33 to a large pulley r31 iixed on shaft 33. The shaft 33 also carriesa small pulley 33 which is connects ed by a belt Il to pulley II integral with the shaft 42 that supports the grinding wheel. An idler pulley 43 may be provided for removing the slack in belt 40 whenever the grinding wheel support is adjusted. It will be noted that the drive 5 connections are such that if the electric motor drive pulley is rotated in a clockwise direction, it will effect clockwise rotation of the grinding wheel I5 which would correspond vto the directionv of rotation of this wheel illustrated in Figi0 ure 2.

The grinding wheel I8 is rotated by similar mechanismcomprising the electric motor 43 having a drive pulley 4.4 which is connected bya belt 45 to a large pulley 46. The latter isv attached to a shaft 41 which also carries a small pulley 48 connected by belt 43 to the grinding wheel pulley 50.' An idler 5| isV also provided for adjusting the tightness of the belt 49. It

should also be noted that clockwise rotation of the motor pulley 44 will cause clockwise rotation of the grinding wheel I6 which corresponds to the direction of rotation of this wheel in Figure 2 of the drawings. j

It will now be apparent that if bothA of the electric motors are rotated in a clockwise direction that the grinding wheels will be rotated in a direction to satisfy the conditions shownin Figure 2 As previously described, however, the wheel i6 must rotate at a slow rate relative to the rate .30 of rotation of wheel I5. In the step shown in Figure'3, the direction of rotation 'of both wheels is changed, and in addition their rates of rotation are inversely changed with wheel I5 rotating at a slow rate and wheel I6 rotating at a fast rate.

An electricalfcontrol circuit for the electric motorshas been provided as shown in Figure 4, which is so contrived that by the use of a single control elemenaeither condition of operation may l be selected. In this figure the motors are as- 40 sumed to be direct current motors which are supplied from the power mains 52 and 53. The field coil of the motor 34 is indicated by the reference numeral 54 and the armature by the reference numeral 55. The field coil -of the motor 43 is indicated by. the reference numeral 56 and the armature by the reference numeral 51. One end of each of the field coils are connected in parallel to the blade 58 of the cut-outswitch 59. 'I'he other ends of these coils are connected to the.

-55 versal of the motors is, therefore, effected by changing the direction of flow of the current in the armatures and the rate is varied by selec` tively cutting in or short circuiting the resistances 6I and 62. Y 60 All of this is selectively obtained by a single control. member comprising a five-pole double throw switch 63. The poles 64 andL 65 of this switch are connected to the brushes 66and 61 respectively of the motor amature 55. 55 68 and 69 are connected to brushes. 10 and 1I of the motor amature 51. The pole 12 is connected by line 1 3. directly to the blade 86 of switch 53. When the switch is thrown down, as viewed in Figure 4, the positive main 62 is connected to 70 switch contacts 14, 1s and through switcnbiades 16 and 11 to armature brushes 66 and 1I ofthe respective motors whereby the current will flow through both 'motors in the same manner, thus causing the same direction or rotation which, for 75 purposes of description, may be arbitrarily as The poles sumed to be'in a clockwise direction. 'Ihis will cause rotation of the grinding wheels in the re-` spective directions indicated in Figure 2. TheI vbrush |51A of motor 34 is connected through switch'blade 18 and contact 18 to branch line 80 5 minates at the lower end of eld coil 58. Since 15 no other outlet is provided, the current must ilow ythrough the resistance 62 to the negative main 53,

thus causing the motor 43 to rotate at a slow rate.

It will now be apparent that when the switch is thrown down that both motors will be rotated in 20 .the same direction but one motor will be rotated Y at'a fast rate and the other at a slow rate.

When the switch is thrown up the-positive main 52 is connected through contacts 85 and 86 and switch blades 18 and 84 to motor brushes 61 and 25- 10, thus causing the armatures to rotate in an opposite direction which will cause rotation oi the grinding wheels in the direction indicated in Figure 3. This time, however, the motor brush 66 is con- 30 nected through blade 16 to line 60, and since the contact 82 is open the return connection to the. negative main 53 must be through the resistance 6| whereby the motor 34 will rotate at a slow rate.

The brush 1I of motor 43 is connected by the 35 switch blade 13 to contact 81 and line lwhich also has a connection to the lower end of ileld coil 56, but the line 86 has a branch vconnection to switch contact 88 which this time is connected through switch blade 83 and line 13 directly to the 40 negative power main 53 whereby the motor 43 will rotate at a fast rate. Thus, the use of a single selector element, the direction of' rotation and the respective rates of rotation may be changed to select the condition shown in Figure 2, or the 45 one shown in Figure 3.

There has thus been provided an improved process and apparatus for finishing cylindrical work pieces and in carrying out the process it will u be obvious that a group of work pieces may be 4passed through the machine with the set-up shown in Figure 2 and then passed through the machine with the' set-up shown in .Figure 3, rather than performing the complete process on one work piece before starting the next one through.

Attention is also invited to the fact that the relative acute angularlty of the wheel axes' with respect to thesurface of the blade need not be exactly the same. For instance, they can be made 00 different to vvary the rate of work feed in the different steps and this will also vary the angle of the cross wiping for the different steps.

What is claimed is: u

l. In a grinding machine, the combination of a 55 pair of opposed grinding wheels of different grains supported for rotation on parallel axes, la work rest blade supported intermediate Vsaid wheels, separate prime movers .for driving said 'wheels, an electrical control circuit for said prime movers, including a reverse switch `for simultaneously changing the direction of rotation of said wheels, separate electrical resistance means in said circuit for reducing the rate of rotation of each prime mover, and means controlled bythe alteruf fil nate positions of said switch for alternately short-circuiting said resistance means whereby for one direction of rotation, the coarser grained wheel will run faster, and for the other direction of rotation the ner grained wheel will run faster.

i. A machine of the character described, in-

cluding a work rest member adapted rotatably to support a work piece, a pair of abrading wheels disposed on opposite sides of the work rest for engagement laterally with a supported work piece, means rotatably mounting said wheels with their axes inclined as respects the potential work path as determined by the work rest, a iirst means operable to rotate one of said wheels in opposite directions and at a different speed in one direction of rotation from the speed in the other direction of rotation, a second means for effecting rotation of the other of said wheels in either direction and at inverse speeds as respects the corresponding directional speeds of the rst wheel. whereby each of said wheels will function as an abrading member in one direction of rotation and a regulating member in the opposite direction of rotation.

3. A machine of the character described, including a work rest member'adapted rotatably to support a work piece, a pair of abrading wheels disposed on opposite sides of the work rest for engagement laterally with a supported Work piece, means rotatably mounting said wheels with their axes inclined in a. common direction as respects the potential work path as determined by the work rest, a first means operable to rotate one of said wheels in opposite directions and at a diierent speed in one direction of rotation i'ro'm the speed in the other direction of rotation,

a second means for eiIecting rotation of the other of said wheels in either direction and at inverse speeds as respects the corresponding directional speeds of the first wheel,'whereby each of said wheels will function as an abrading member in one direction of rotation and a regulating member in the opposite direction of rotation', and a unidirectional feeding movement of the work will be effected by the alternately employable regulating wheels.

4. A machine of the character described, in-A cluding a work rest member adapted rotatably toA support a work piece, a pair of abrading wheels disposed on opposite sides of the work rest for engagement laterally with a supported work piece, means rotatablynmounting said wheels with their axes inclined as respects the potential work pathi as determined by the work rest, a first means operable to rotate one of said wheels in opposite directions and at a diierent speed in one direction of rotation from the speed in the other direction oi' rotation, a second `means for eiecting rotation of the other of said wheels in either direction and at 'inverse speeds as respects the corresponding directional speeds of the rst wheel, whereby each of said wheels will function as an abrading member in one direction of' rotation and a regulating member in the opposite direction of rotation, and a single control device for the respective actuators for jointly determining the direction and rate of actuation of the respective wheels.

GEORGE W. BINNS.

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