US3020682A

US3020682A - Poishing machine for balance wheels

Info

Publication number: US3020682A
Application number: US64117A
Authority: US
Inventors: August L Spetzler; John A Richards
Original assignee: General Time Corp
Current assignee: General Time Corp
Priority date: 1960-10-21
Filing date: 1960-10-21
Publication date: 1962-02-13
Anticipated expiration: 1979-02-13

Description

Feb. 13, 1962 A. L. sPETzLER ETAL 3,020,532

POISING MACHINE FOR BALANCE WHEELS '7 Sheets-Sheet 1 Filed 001'.. 2l, 1960 WIIIIIH H UIIIIIIIIIIIIIIIIIHHH HIIH H I|I||||I||| lllllllllll l I lllll I CAD Feb. 13, 1962 A. L. sPETzLER ETAL 3,020,682

PoIsING MACHINE FOR BALANCE wEEELs '7 Sheets-Sheet 2 Filed Oct. 21, 1960 Feb. 13, 1962 A. L. sPETzLER ETAL 3,020,682

POISING MACHINE FOR BALANCE WHEELS Filed Oct. 2l. 1960 7 Sheets-Sheet 3 ullllnlll LS) l 53 c' ,5 E 'i TH lll Feb. 13, 1962 A. sPETzLER ETAL 3,020,582

PoIsING MACHINE FOR BALANCE WHEELS 7 Sheets-Sheet 4 Filed Oct. 21, 1960 sth-.5 pet r* ard. -J lQjh-rommaf a Ac mm vw. N o uw m1 QT 9 vo m w A E Feb. 13, 1962 A. sPETzLER ETAL POISING MACHINE FOR BALANCE WHEELS '7 Sheets-Sheet 5 Filed OO'C. 2l, 1960 L53 Mvg; NTO RJ CR Pei-3 u dany-L Ofi ' -r-rorawBY-f* Feb. 13, 1962 A. L. sPETzLER ETAL 3,020,682

PoIsING MACHINE FoR BALANCE WHEELS Filed oct. 21, 19Go '7 sheets-sheet e CAT-ro rams yf Feb. 13, 1962 A. L. SPETZLER ETAL 3,020,682

PoIsING MACHINE EoR BALANCE WHEELS '7 Sheets-Sheet '7 Filed OCT.. 2l, 1960 3,020 682 PGHSING MACHWE FR BALANCE WHEEAS August L. Spetzler, Peru, and .lohn A. Richards, Ugresby, lll., assignors to General Time Corporation, New York, N.Y., a corporation of Delaware Filed Get. 21, 1960, Ser. No. 64,ll7 l Claims. (ill. 51-145) The present invention relates to the problem of accurately balancing or poising the balance Wheels of watches and clocks.

In the past it has been conventional practice to po1se the balance Wheels for watches and clocks by individually mounting them between horizontal centers, allowing them to settle under the force of gravity, and then advancing a drill or spotter into engagement with the heavy side to remove material, tending to restore the center of gravlty to the axis of the wheel. After the initial cut, the wheel is turned out of position and allowed to settle and additional material is removed. This is repeated several times until the wheel comes to rest in a random position. This procedure requires patient, highly skilled operators, but even the most highly skilled must use trial and error in order to achieve a condition of near balance. As the condition of balance is approached, there is less and less torque available for pendulous setting, and when the unbalanced torque' is less than the friction imposed by the bearings the process can go no further. Moreover, the trial and error procedure is relatively time consuming so that the output per operator per shift is limited. Finally, there is a relatively wide variation in the iinal product depending upon the skill of the operator and the chance for human error so that some wheels may get through the balancing operation without being balanced to the required degree.

Accordingly, it is an object of the present invention to provide a poising machine which is capable of producing accurately poised balance wheels for watches and clocks and which overcomes the disadvantages of conventional procedures. More particularly, it is an object to provide a poising machine capable of being operated by a single operator and having an output on the order of live to ten times that of a skilled operator using conventional balancing equipment. It is an object to provide a poising machine which is automatic in operation and in which each wheel is processed in exactly the same way, achieving precise balance within closely held limits. Consequently, it is an object to provide a balancing machine which is consistent and which is free of human judgment or human error, producing balance wheels capable of meeting the most stringent civilian and military requirements.

lt is a further object of the invention to provide a poising machine and procedure in which all of the wheels are put through the same cycle and finally balanced to the same degree, even though the wheels are fed into the machine having a wide range of initial unbalance. More specifically, it is an object to provide a poising machine which is capable of handling the small percentage of wheels which are supplied into the machine in an initially balanced condition without imparting a net unbalance.

lt is another object to provide a poising machine which does not rely upon gravity for orienting a balance Wheel but which employs centrifugal force and which is capable of applying a pendulous torque many times that of gravity to achieve equilibrium more promptly and with a higher degree of accuracy, particularly when near the condition of balance. In this connection it is an object to provide a poising machine in which the static bearing friction no longer serves as a severe limitation on the degree of precision which may be attained. Y

lt is an object of the invention in one of its aspects to States arent provide a poising machine in which the excess material is removed by abrasion or grinding distributed over a substantial part of the periphery as contrasted with the localized drilling or spotting conventionally used. It is a more specific object to provide novel means for cycling the grinding operation so that grinding occurs in steps of successively shorter duration so that progressively less material is removed and in which almost any desired degree of accuracy may be achieved simply by extending the cycle to use an increased number of progressively shorter grinding steps.

It is still another object of the invention to provide a poising machine which is capable of use with a Wide range of sizes, from the balance wheels used in large clocks and timing devices to balance wheels used in small movements of Wristwatches and which is particularly well suited for the handling of miniature Wheels used in small ladies Wristwatches which are difdcult to balance by conventional' procedures. lt is a related object to provide a poising machine which does not place any undue stress on the pivot bearings during the grinding of material from the periphery of the wheel. In one of its aspects itis an object to provide a poising machine in which novel means are provided for supporting the wheel during the actual grinding so that the grinding reaction need not be borne by the pivots.

It is an object of the invention in another of its aspects to provide a poising machine which employs a grinding member of ne abrasive material with novel means for renewing the grinding surface so that the grinding characteristics remain consistent over long periods of time and which thus requires only infrequent renewal.

it is another obiect of the present invention to provide a poising machine and a carrier for loading a plurality of balance wheels in which wheels may simply be dropped into place without exercise of care or attention and with automatic centering incident to closure of the bearings upon the ends of the spindle. It is an object to provide a machine for automatically poising balance wheels in which the operator is required only for the feeding of parts into the machine and which is so arranged that the operators time is fully utilized. It is a related object to provide a poising machine which may be operated by a relatively unskilled operator contrasted with the highly trained and skilled operators previously required in manual poising operations. It is another object of the invention t0 provide a poising machine capable of acting upon a large number of Wheels simultaneously and having novel means for automatically unloading the machine so that the finally balanced wheels are quickly discharged for immediate reloading with untreated wheels. It is, therefore, an object to provide a poising machine in which the amount of down time for loading and unloading is minimized and forms but a small fraction of the total operating cycle. Thus wheels are produced eciently in a minimum cycling time.

It is another object of the present invention to provide a poising machine which operates at a high rate of speed but which nevertheless is safe, having a novel interlock arrangement preventing touching by the hands of the operator when the machine is in motion.

Finally, it is an object to provide a poising machine which may be constructed at relatively low cost and which is simple and straightforward in operation, capable of being operated for long periods of time without care or maintenance.

Other objects and advantages of the invention will become apparent upon reviewing the attached detailed description and upon reference to the drawing in which:

FIGURE 1 is a front view of a machine constructed in accordance with the present invention.

FIG. 2 is a right hand side view of the machineV of FIG. 1 with the cover broken away in order to view the balance wheel carrier.

FIG. 3 is a perspective of a typical balance wheel balanced in the machine of FIG. 1.

FIG. 4 is a plan view of the driving table including the means for laterally oscillating the grinding frame.

FIG. 5 is a section taken along the line 5 5 in FIG. 4.

FIG. 6 is a section taken along the line 6 6 in FIG. 2 on the Wheel drive shaft.

FIG. 7 is an enlarged view showing a portion of the carrier wheel with balance wheels mounted thereon.

FIG. 8 is a section taken 0n the line 8-8 in FIG. 7 showing an enlarged view of a single balance wheel holding assembly with jaws separated to receive the balance wheel.

FIG. 9 is a section taken on the line 9-9 in FIG. 7 showing a balance wheel in registered position and the limits of lateral oscillating movement of the belt.

FIG. 10 is a fragmentary section taken on the line IO-i) in FIG. 6 of a one way clutch used to advance the grinding belt.

FIG. l1 is an alternative grinding medium in the form of an abrasive-coated metal leaf.

FIG. 12 is another alternative employing a high speed grinding wheel.

FIG. 13a is a profile of a typical balance Wheel after the taking of the first cut.

FIG. 13b shows the balance wheel following the taking of the second cut.

FIG. 13e shows the nal shape of the balance wheel produced by the present machine.

FIG. 14 is a wiring diagram showing the means for energizing the clutches, brakes and interlocks forming a part of the present machine.

FIG. l5 is a fragmentary view showing the means for effecting release of the balance wheels.

FIG. 16 shows a modied means for producing lateral oscillation of the belt and employed in an alternate form of the invention.

FIG. 17 is a fragmentary side View of a modified program cam employed in conjunction with the mechanism of FIG. 16.

FIG. 18 is a diagram showing a complete grinding cycle characteristic of the arrangement shown in FIGS. 16 and 17.

FIG. 19 is a fragmentary' side view of the carrier wheel and an alternate form of belt advancing mechanism used with the mechanism of FiGS. 16 and 17.

FIG. 20 is a fragmentary view looking along the line 20-20 in FIG. 19.

While the invention has been described in connection with certain preferred embodiments, it will be understood that the invention is not necessarily limited to such embodiments and that we intend to cover the various equivalent and alternative constructions included within the spirit and scope of the appended claims.

Referring now to FIGS. l and 2 of the drawing a poising machine, generally indicated at 20, includes a right hand poising unit 21 and a left hand poising unit 22. Centered between them is a main spindle housing 23 which is supported on a worktable 24. For mounting the table 24 a frame 25 is provided which preferably includes four supporting legs 26 defining a space for the driving and cycling means. Directly below the table 24 is a table 27 (FIG. 2) which carries the cycling mechanism and having an adjacent cross shaft assembly generally indicated at 28.

In accordance with the present invention a carrier wheel is provided for rotating a plurality of balance wheels with their axes in tangential position on the carrier wheel S0 that when the carrier wheel is rotated at a high rate of speed each of the balance wheels is oriented with its heavy side facing radially outward with abrasive means being provided at the periphery of the carrier wheel for successively engaging the presented edges of the balance wheels for removing material therefrom until a condition of balance is achieved. Thus within the

balancing assemblies

21, 22

respective carrier wheels

31, 32 are mounted for rotation on

individual shafts

33, 34.

Referring to the means for selectively driving the

shafts

33, 34, torque is supplied by the cross shaft assembly 28. The latter is driven by a motor 40 which is connected by V belts 41 to a sheave 42 mounted at the center of cross shaft 43 at the front of the machine. This cross shaft is suspended below a cross shaft table 44 having a total of six depending brackets 45. Mounted at the right hand side of the cross shaft 43 is an output sheave 50 engaging V belts 51 which extend upwardly into the housing 23 and which are trained about a pulley 52 mounted on the shaft 33. interposed between the cross shaft 43 and the sheave 5G is a clutch 54 of the electrically energized type. To prevent coasting of the carrier wheel 31 when the clutch S is disengaged, a brake 55 is provided which is also of the electrically energized type. As will be later covered in connection with the control circuit, the arrangement is such that the clutch and brake are energized alternatively. For driving the second carrier Wheel 32, a sheave 60 is provided on the left hand side of the cross shaft connected by a V belt 61 to a sheave 62 on the shaft 34. For controlling the sheave 60 a clutch 64 is used having an associated brake 65. Only one of the

carrier wheels

31, 32 is driven at a time so that one wheel may be unloaded and reloaded by an operator while the other is in use.

Arranged in back of the carrier wheel 31 is an abrasive assembly 71 for the purpose of engaging and removing material from the balance wheels mounted on the carrier. A similar abrasive assembly 72 is associated with the carrier Wheel 32. Prior to discussing the abrasive assemblies and the means for driving and controlling the same, more detailed reference will be given to the carrier wheel 31 and to the bearing assemblies at the periphery thereof which are used to carry the individual balance wheels. A typical balance wheel 75 (FIG. 3) has a rim 76 and a spindle 77.

In carrying out the present invention, individual bearing assemblies are mounted at the periphery of the wheel 31 for mounting individual balance wheels 75 with their aXes tangentially positioned. Referring to FIGS. l and 7 several successive bearing assemblies are indicated at 8l, 82 and 83. t will be understood that in a practical case thirty or more of such assemblies may be mounted on a carrier wheel. To facilitate mounting the bearing assemblies, the carrier wheel 31 preferably is made up of

discs

85, 86 defining a peripheral groove between them and having alined outwardly extending projections or guides S7. Takinf7 the bearing assembly 81 by way of example it includes a fixed jaw 91 and a second jaw 92 which is movable to permit insertion and removal of balance wheels. The fixed jaw is anchored in place by pins 93 ani the movable jaw is pivoted on a pin 94 for limited movement supported on each side by the guides 87. For the purpose of biasing the movable jaw toward the fixed jaw, a biasing spring 95 is provided, with the normal or closed position being established by the bottoming of the jaws on one another along their inner surface 96. To separate the jaws and to limit the degree of separation, the movable jaw 92 has a laterally extending operating pin 97 which extends through an opening 98 in the side of the wheel for convenient manipulation.

For mounting the spindle 77 of a balance wheel, the fixed jaw has an adjustable conical bearing 10i with a lock nut 1&2 while the movable jaw has an adjustable conical bearing 103 and a lock nut 104. The bearings are so adjusted that when the movable jaw comes into a seated position, the spindle of the balance wheel is captured between the bearings but with suthcient play so as to allow the balance wheel to rotate freely under action of centrifugal force.

In accordance with one of the aspects of the invention, means are provided for facilitating entry of a balance Wheel between the jaws and for centering the balance wheel so that it is automatically engaged by the bearings when the jaws come together. For this purpose the fixed jaw 91 is radially notched as indicated at 116 (FIGS. 7 and 9), and a pair of spaced supports are provided as indicated at 111, 112 so that when the balance wheel 75 is dropped into position in register with the notch 114i it is temporarily supported on the supports 111, 112 with the spindle of the balance wheel within the conical locus of the bearings 101, 1413. Thus when the movable jaw is released, the spindle 77 of the balance wheel is engaged by the bearings and cammed outwardly into centered position between them, lifting the balance wheel from the supports 111, 112 (dotted position shown at 113) into their operating position. As a result, the balance wheels may be fed in quick succession into the bearing assemblies, one after the other, without any care or attention on the part of the operator and with assurance that each of the balance wheels will be automatically located in a free, bearing supported position.

In accordance with one of the aspects of the invention, related to the above, means are provided for supporting the periphery 76 of the balance Wheel when it is acted upon by the abrasive. To this end, the fixed jaw is provided with an arcuate shoulder 115 which follows the outer periphery of the wheel, and the bearings 1431, 1li@ are so adjusted that the balance wheel clears the shoulder 115 by a small amount on the order of a few thousandths or" an inch when the balance wheel is in its freely supported position. When side thrust is applied to the edge of the balance wheel by the abrasive means to be described, the play between the spindle of the balance wheel and the bearing 1111 is taken up and the balance wheel resiliently deforms so that the outer periphery of it is temporarily supported on the shoulder 115. Consequently the

bearings

161, 103 are largely relieved of the unbalanced forces resulting from abrasive contact.

It will be understood that when the device is put into operation each of the bearing assemblies is loaded with a balance wheel, so that when the carrier is rotated, all of the balance wheels come successively into engagement with the abrasive in the abrasive assembly 71 to which detailed reference will next be made.

In accordance with the present invention an abrasive means is provided adjacent the periphery of the carrier wheel with means for moving the same back and forth so that it is in operative engagement with the balance wheels intermittently and for successively shorter periods of time, removing metal in steps, until balance is achieved. In the preferred embodiment the abrasive means includes a narrow endless belt 12@ of emery cloth or the like mounted on a frame having a base member 121 and a rockin-g member 122, with the rocking member being pivoted to the base member at 123. The abrasive belt 12@ is trained about spaced drums or pulleys 125, 125, 127, supported by the base member. To accommodate belts of different lengths, the pulley 127, as shown, may be mounted on an arm 123 adjustably secured to the base member.

For the purpose of moving the near side of the belt 120 toward and away from the carrier 131, the rocking member 122. is provided with a felt-covered backup roller 131 in back of the belt, which determines the belts position, and with an associated idler pulley 132. An adjustable mount 133 is interposed between the backup pulley and the rocking member 122 to adjust its position with respect to the latter. If desired the idler pulley may be mounted on a bracket 134 pivoted to the rocking member and having an adjustment 135.

In order to move the rocking member 122 backwardly and forwardly in accordance with a predetermined cycle, an oscillating means 140 is provided (FIG. 2) which includes a cam 141 and a cam follower 142, the latter being mounted on a plunger 143 telescopingly received in a bracket 144. In order to convey movement from the cam follower to the lower end of the rocking member 122, the latter extends down into the path of movement of the plunger and terminates in an abutment 145, with the abutment being held against the end of the plunger by means of tension springs 146. It will thus be apparent that when the cam 141 is rotated, the rocking member 122 is oscillated back and forth through a limited angle in accordance with the program of the cam.

For the purpose of rotating the cam 141 at a slow rate of speed, a motor 150 is used driving V-belts 151 which engage a pulley 152 (FIG. 4) mounted on a right angle speed reducer 153, the latter having

output shafts

154, 155 which extend in opposite directions. The right hand extension 154 carries a clutch 155 and a brake 157 mounted upon a bracket 158. Suitable control means (to be described) are provided for operating the clutch and brake alternatively so that the cam 141 is driven at a slow rate of speed which, in a practical case, may be on the order of two revolutions per minute. This defines a total balancing time of about thirty seconds duration. Prior to describing the specific abrasive cycle in connection with the profile of the cam 141, attention may be turned to the means for transporting the belt 120. In carrying out the invention the belt is not only advanced endwise at a slow rate of speed but is also oscillated back and forth in its plane in order to constantly present a fresh grinding surface to the presented edges of the balance wheels.

Giving attention first to the means for advancing the belt endwise shown in FIGS. 2 and 10, a one way clutch 16@ is employed having an input element 161 and an output element-162 with rollers 163 in between. Connected to the input element 161 is a link 165 which is secured at its right hand end to the rocking member 122 sothat the link reciprocates endwise a small distance each time the member 122 moves back and forth. The resulting oscillation of the input element 161 serves to drive the belt in small increments inthe upward direction as shown in FIG. 2 at an average speed on the order of a few inches per minute.

For the purpose of moving the belt laterally to make use of the entire belt width, the base member 121 of the frame is mounted for limited rocking movement about a shaft 171 which extends fore and aft in the machine, i.e., parallel to the plane of the carrier wheel, and which is mounted in suitable pillow blocks 152 (FIG. 6). The lateral motion of the frame relative to the plunger 143 is accommodated by lateral sliding movement at the interface between the abutmentand the plunger. The means for engaging and oscillating the lower end is set forth in PEG. 4. Here it will be noted that the speed -reducer shaft 154 carries a cam 173 having a cam follower 174 in the form of a plunger telescoped in a bracket 175. The forward end of the plunger 174 is pivoted to a link 176 which engages a bell crank 177, the output end of which is coupled to a transverse reciprocating shaft 178` by a collar 179. The lower end of the base member 121 is attached to the end of the-shaft 178. In operation, the cam 173, acting through the linkage described, produces lateral rocking of the rocking member 122 and the base member 121 which is mounted upon it. The amplitude of the rocking movement depends upon the width of the belt and in a practical case a movement, at the point of engagement of the balance wheels may Abe on the order of 3A".

To summarize the means for driving the abrasive belt 12u, there are three separate movements involved. First there is the rocking into and out of engagement with the balance wheels on the carrier in accordance with a program set up on the cam 141. Secondly, the belt is advanced along its length in increments. Finally the belt is rocked laterally from side to side.

In carrying out the invention, the abrasive belt is brought into engagement with the balance wheels on the rapidly rotating carrier wheel in accordance with a cycle which consists of successively shorter intervals of contact, with the belt being backed away between the intervals to enable each wheel to assume a new equilibrium position. To accomplish this, the cam 141 includes lobes defining a series of valleys of successively shorter length. With the cam driven in the counter-clockwise direction as viewed in FIG. 2, the iirst valley 191 is of substantial length occupying an angle of about 78. The second valley 192 is of shorter extent occupying an angle of about 63. The third valley 193, the fourth valley 194 and the lifth 195 are of successively shorter duration having an angular extent of about 47, 23 and 7 respectively. The cycle is completed on a shut off lobe 197. In a typical operating cycle energization of

clutches

54, 156 causes the carrier wheel 31 to rotate at a high speed, on the order of 1700 r.p.m. and the cam 14.1 to rotate at a slow speed on the order of 2 rpm. As the first point of drop-oir' is reached, the cam follower descends into the valley 191 on the cam bringing the abrasive belt 120 against the presented edges of the balance wheels. The degree of advancement of the belt is limited by an adjustable stop indicated at 200 which determines the inward limit position of the plunger 143 at the base of the rocking member. Having the stop limit the plunger position makes it unnecessary to machine the cam valley radii with a high degree of precision.

'I'he effect of the rst gringing operation upon a typical one of the balance wheels is shown in FIG. 13a. Here it will be noted that material is removed from the periphery of the balance wheel as indicated at 205. This removal does not occur all at once but is the result of numerous separate engagements between the belt and the balance wheel during successive revolutions of the carrier. For example, in a practical machine during the first interval 191 a given balance wheel may be brought into contact with the belt approximately 184 times. Between the successive contacts slight adjusting movement of the wheel occurs so that its heavy side is urged constantly outward as the center of gravity shifts slightly in one direction or the other. In other words, due to removal of material, the balance wheel tends to move or oscillate through a small angle, so that material is ground away, not along a flat, but along an arc 20S. The lirst removal cycle is suticiently long as to take care of the maximum expected initial imbalance.

Following the iirst removal of material the belt is backed away by striking a lobe between the

valleys

191, 192 on the cam. This gives a balance wheel a sustained length of time to become stably oriented in a new position in which the existing heavy side is outwardly presented. When the cam follower drops into the valley 192 on the cam, the belt is again brought into contact with the balance wheels and removes material as indicated at 206 in FIG. 13b, the removal being distributed over an arc at the periphery of the wheel. Next the belt is withdrawn to allow the balance wheel again to assume an equilibrium position. Following this the belt is brought into grinding engagement with the balance wheels for three successive intervals corresponding to the

portions

193, 194 and 195 on the cam and of successively shorter duration, with the result that the iinished product assumes the perfectly circular outline shown in FIG. 13e. It may be shown that even when the amount of imbalance is extremely small, as in the later stages of the abrading cycle, the centrifugal force, being substantially greater than gravity, brings about prompt reorientation. The latter is facilitated by the normal vibration in the machine which tends to overcome any static friction or stickiness at the bearings.

While the operation has been described in connection with the grinding assembly 71 at the right hand side of the machine, it will be understood that the grinding assembly 72 is a mirror image thereof, and corresponding reference numerals, with-subscript tu have been used to designate corresponding parts.

In the preferred embodiment described above, it is found that the abrasive belt removes material from the edge of the wheel at an adequate rate. The felt covered roller 131, in addition to supporting the belt at a predetermined position during the abrading operation, also eilectively damps out any tendency toward belt tiutter which might interfere with efficient removal. However it will be understood that in lieu of the belt 120, a permanent abrasive member may be employed of the type consisting of particles of tungsten carbide, diamond, or the like embedded in a leaf of metal. rJhus as shown in FIG. ll, an abrasive lear 220 is used mounted upon a bracket 134a secured to the upper end of the rocking member 122 and made adjustable with respect to the latter by an adjusting screw 13511, the mounting being similar to that utilized for the idler pulley in the previous embodiment. The abrasive leaf member 220 is iiexible enough to give slightly upon being engaged by a balance wheel as the carrier rotates, yet stili enough so that there is no possibility of setting up harmonic vibration or flutter. If desired, the leaf 220 may be damped by construction it of a series of laminations or other damping means may be used. It will be understood that even when the leaf member 220 is employed in lieu of the belt 120, the base member 121 is preferably rocked from side to side. The primary advantage of the alternative arrangement is that the upper part of the base member 121, the belt pulleys, and the belt advancing means may be eliminated thereby simplifying the construction.

In accordance with one of the aspects of the present invention, it is contemplated that the abrasive means need not be slow moving or relatively stationary as in the preceding embodiments but may be driven at a high rate of speed. In the embodiment shown in FIG. l2, the belt is replaced by a high speed grinding wheel 230 driven, in the direction indicated, by a motor 231. The motor frame is secured to the rocking member 122 so that the grinding wheel 230 is rocked inwardly and outwardly with respect to the balance wheels on the carrier in accordance with the same cam-controlled program as discussed above. If desired the mounting may be made adjustable as shown at 134b, 13511. In order to minimize the reaction force imposed upon the balance wheels, the speed of the grinding wheel may be extremely high, for example, between 10,000 and 20,000 r.p.m. However, it will be understood that by using a larger diameter wheel than that shown, the spindle speed may be decreased below this value while maintaining a high peripheral speed.

While the invention has been described in connection with abrasion means involving physical contact with the presented edges of the balance wheels, it will be understood by one skilled in the art that in the broader aspects o f the invention material removing means may be provided which operatively engages the balance wheels but which nevertheless does not require actual physical contact. More specifically, spark machining techniques may be employed using an electrode supported on the rocking member 122 and corresponding in approximate size and position to the grinding wheel 230 shown in FIG. l2. It will be understood that under such conditions the disclosed adjusting means may be so adjusted that there is slight clearance between the electrode and the balance wheels even when the rocking member is in its position of maximum advancement. The electrical circuit for supplying the spark machining electrode is a matter within the skill of the art and cross reference may be made to various prior art patents. Because of the possibilities of employing spark machining for material removal, it will be understood that in the claims appended to the specification the term abrasion is used in a broad generic sense to incorporate all of the above means for material removal.

To understand the specific circuit employed for operating the clutches and brakes, reference is made to FIG. 14 where the input lines are indicated at L1, L2 respectively. Arranged across the lines in series with a start pushbutton PB-1 is a contactor or relay R1 having a series of normally open and normally closed contacts designated R11 to R15 inclusive. Normally open contacts R11 comprise a sealing-in circuit having a normally closed pushbutton PB-Z in series therewith. Thus the machine may be started by pressing the start pushbutton PB-1 and stopped at any time by breaking the sealing circuit upon pressing a stop pushbutton F13-2. However, means are provided for causing the control or program cam 141 to complete its cycle of movement once it is started to rotate by pressing the start pushbntton. For this purpose a limit switch LS1 is included in the sealing-in circuit. This limit switch cooperates with the cam 141 (FIG. 5) and closes shortly after the cam begins to move. When a single cycle of rotation of the cam has been completed, the limit switch opens, thereby dropping out relay R1 and terminating further rotation.

In accordance with one of the detailed aspects of the invention a cover or enclosure 240 is provided which is hinged at 241 and which completely encircles the carrier wheel 31 so that the latter cannot be inadvertently touched by the operator when the wheel is in motion. An interlock switch associated with the enclosure opens the circuit to the wheel clutch 54 and closes the circuit to the wheel brake 55 automatically when the cover is open. In the present circuit the interlock arrangement includes a first interlock switch LSZ which is connected in series with the wheel clutch 54 and which is closed only when the enclosure is in place as well as a second interlock switch L53 which is effectively in parallel with the contacts R15 controlling the wheel brake 55. This switch is open when the enclosure is closed to permit denergization of the brake under normal running conditions. However, upon opening the enclosure the interlock closes to apply the brake notwithstanding the fact that the main relay R1 may be energized. The clutch and brake are so rapidly responsive that upon swinging the enclosure outwardly (to the right as shown in FIG. 1) the carrier wheel 31 cornes to an immediate stop before the wall of the enclosure clears the wheel, thus there is no possibility of injury to the operator.

In accordance with one of the detailed aspects of the invention, means are provided for stripping the balance wheels from the carrier wheel following completion of the balancing cycle. For this purpose a stripper liever 25d is provided centrally pivoted at 251 and having a handle 252. At the rear end of the stripper lever 1s a stripper nger 253 which is elevated into the path of movement of the release pins 97 (see FIGS. 7 and 15) which extend at right angles to the carrier wheel. Thus when the carrier wheel is manually rotated, each of the release pins 97 is brought into wiping engagement with the stripper finger. This separates the jaws associated with each release pin so that the balance wheels are free to fall by action of gravity down a chute 255 into a suitable receptacle. In order to release the wheel brake 55 so that it may be manually rotated, an auxiliary limit switch L84 is provided in series with the brake and which is arranged in the path of movement of the enclosure 240 as shown in FIG. 1 so that it is operated (opened) when the enclosure is swung downwardly into its fully opened position as shown in the dotted lines in this ligure. The stripper lever is, as shown in FIG. 2, mechanically interlocked with the enclosure so that it cannot be operated when the enclosure is in its Vertical closed position. This is brought about by positioning the lever so that the enclosure, when vertical, is in the path of movement of the lever producing interference at 256.

While the control arrangement applicable to the right hand portion has been illustrated at FIG. 14, it will be understood that an identical enclosure and control circuit are employed at the left hand portion of the machine.

Alternate form of belt feeding and oscillating mechanism In the embodiment described above the control cam`` 141, acting through appropriate linkage, serves to feed the abrasive belt inwardly and outwardly a plurality of times during a complete grinding cycle and with the belt being simultaneously oscillated from side to side through a small angle. In accordance with an alternate form of the invention means are provided for feeding the abrasive belt inwardly and outwardly only once during a grinding cycle with means for oscillating the belt cyclically from side to side to a position where the belt is clear of the balance wheels thereby freeing the balance wheels for reorientation a large number of times during the grinding cycle.

Thus, referring to FIGS. 16 and 17, the control cam indicated at 3119, instead of being of the star shape illustrated in FIG. 2 with a plurality of rises and dwells, is formed of a simple, though slightly non-symmetrical eccentric. Riding upon carn 30) is cam follower 301, and the linkage associated with the cam follower may be the same as previously described. The shape of the cam 300 is such that the belt is moved toward the balance wheels rather rapidly and withdrawn gradually. Plotting belt feed as a function of cam rotation, the feed should follow the characteristic generally set forth at 302 in FIG. 18, with a total feeding stroke, in a practical case, on the order of 0.010 inch. The feeding characteristic at the end of the grinding cycle is preferably asymptotic as indicated at 303.

For the purpose of oscillating the abrasive belt 120 from side to side through a plurality of cycles during the feeding operation, and with the belt being moved clear of the balance wheels in each cycle, the mechanism shown in FIG. 16 is preferably employed. As in the previous embodiment the base members 121 and 121a are rocked from side to side by a reciprocable shaft 178. However, instead of employing a bell crank for actuating shaft 178, a rotary cam 31@ is used, mounted upon a shaft 311 and having a cam follower 312, the latter being pinned or otherwise secured to the shaft 178. For the purpose of rotating the shaft 311 at a speed which is substantially greater than the speed of the control cam 300, a gear box or the like 315 is employed which is coupled to the shaft 311 via bevel gears 316, 317. The

Vgear box 315 may be coupled to any suitable source of power, for example, to the same shaft which is driven via belts 151 (FIG. 2) from the motor 150, the latter being well within the skill of the art. In a preferred embodiment the speed is such as to produce lateral cy,- cling of the abrasive belt approximately once everythree seconds while the control cam 300 undergoes a single revolution per minute. Since the abrasive belt moves through a sufficient angle as to clear the balance wheels,

this insures that the balance wheels are freed to assume a new equilibrium position at least twenty times during the grinding cycle. By adjusting the swing of the b'ase members 121, 121e so that the belts clear the balance wheels `on both sides, i.e., at each end of the lateral stroke, the number of times that the balance wheels are freed during the grinding operation may be doubled.

, A typical grinding sequence may be clearly pictured upon reference to FIG. 18. As the control cam rotates,

the abrasive belt is fed radially inward toward the balance wheels. During'the first lateral pass of the belt, a shallow grinding cut is made as indicated at 321. During the second pass, which occurs three seconds later, a heavier cut is made as indicated at 322, the belt having been fed inwardly toward the balance wheels in the interim. The control cam is so shaped that maximum depth of feed 'is achieved after a limited number of lateral passes of the belt, with the cut at the maximum feed position being indicated at 323 in FIG. 18. Once the maximum depth of cut has been achieved, the belt is slowly retracted so that the belt acts in progressively lesser degree upon the balance wheels during the successive lat- 11 eral passes until, finally, at the end of the cycle, an extremely shallow finishing cut is made as indicated at 324.

While the sequence has been described above in terms of belt feed toward the work, it will be understood that the belt is resilient so that there is a corresponding variation in the pressure of the belt against the work, with the pressure increasing rather abruptly and then diminishing gradually as shown. To enhance resiliency the back up roller 151 (PEG. 2) may be surfaced with a soft resilient layer or offset upwardly so that reliance is placed upon the resilience of the belt itself (FIG. 19). Moreover, the roller 131 and pulley 125 may be crowned so that the face of the belt is convex. Thus as the belt is progressively moved with respect to the work there will be a variation not only in the pressure applied by the belt but also in the duration of Contact of the belt, with maximum contact occurring during the times of maximum feed and greatest pressure. This has been indicated by the variation in the width of the vertical bars in FIG. 18. The result is to provide .a further refinement in the tapering oil of the cut as the belt is gradually retracted. The crowning of the Supporting pulleys and the resulting convexity of the belt in the present embodiment also has the advantage that engagement of the work with lthe belt will occur gradually rather than abruptly and there is no possibility that imperfections or irregularities at the edge of the belt will have any effect upon the grinding operation. Consequently there is no need to inspect the belts carefully in order to insure that the edges thereof are in perfeet condition at the time that they are installed.

it will be apparent to one skilled in the art that where the abrasive belt is cycled from side to side clear of the balance wheels numerous times during each grinding operation, and with the gradual withdrawal of the belt from the work, each of the balance Wheels is given numerous opportunities to reorient itself with the heavy side out so that an even finer degree of balance may be achieved than is possible employing the previously described embodiment of the invention.

For the purpose of insuring that reorientation of the balance wheels takes place promptly even though the balance wheels are approaching their balanced condition, auxiliary means are provided for imparting vibration to the carrier wheel thereby to overcome any tendency toward sticking due to static friction.

Referring to FIGS. 19 and`20 this is accomplished in the present instance by providing on the carrier Wheel a series of weighted buttons, for example five in number, as indicated at 331-335. These buttons are preferably formed in the shape of rivets having their shanks respectively received in openings provided in the carrier wheel. For pressing the buttons into seated position leaf springs 341-345 are used. To cyclically unseat the buttons as the carrier wheel rotates, a stationary ramp or cam 336 is mounted on the frame of the machine and in the path of movement of the tips of the Shanks of the respective buttons. Thus, upon striking the cam 336 the buttons are unseated iiexing the associated springs, and when the buttons ride clear of the cam they are released for snapping into seated position by the springs. The result is to vibrate the carrier Wheel laterally at a high repetitive rate; for example, where the carrier Wheel rotates at approximately 1700 r.p.m., vibration occurs at the rate of 850 vibrations per minute. Selecting the proper weight of button, the proper stiffness of the associated springs and the right amount of displacement is well Within the skill of the art, and it is found that none of these factors is particularly critical.

In carrying out the alternate form of the invention means are provided for indexing the abrasive belt forwardly once during each complete grinding cycle. This is accomplished by coupling the input element 162 of the clutch 150 to a solenoid 35i) which is in series with a switch 351 associated with the control cam 300 and so arranged that the solenoid is energized once during each revolution of the control cam. For connecting the clutch element to the solenoid, the clutch is provided with a laterally protecting arm 352 which is arranged in the path of movement of a lever 353 which is centrally pivoted at 35d. A pivot 355' is provided at the end of the lever for pinning the same to the armature 356 of the solenoid. A return spring 357 acts downwardly upon the arm 352. Thus each time the solenoid is actuated rocking of the lever 353 and arm 352 takes place thereby to index the belt and present a fresh abrasive surface.

It is apparent from what has already been said that the device described above amply fulfills the objects earlier set forth. The device is rapid and automatic in operation and docs not require any exercise 0f skill or judgment required by conventional balancing procedures yet fully utilizes the services of the operator simply in loading and unloading. Five to ten times the production of a conventional skilled operator may be realized. The device achieves a high degree of balancing accuracy, and while it is well suited to a wide range of wheel size, it is found to be particularly useful for the small wheels difficult to balance by conventional means.

What is claimed is;

l. ln a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in tangential position, means for rotating the carrier wheel at a high speed so that each balance Wheel assumes a position of equilibrium with its heavy side out, and means at the periphery of the carrier wheel for engaging the balance Wheels thereon in succession and for removing material from the presented heavy sides thereof until a condition of balance is achieved.

2. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in tangential position, means for rotating the carrier wheel at a high speed so that each balance wheel assumes a position of equilibrium with its heavy side out, and means at the periphery of the carrier wheel for engaging the balance Wheels thereon in succession and in progressively lesser degree for removing material from the presented heavy sides thereof until a condition of balance is achieved.

3. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier Wheel at high speed so that each balance wheel assumes a position of equilibrium, with its heavy side out, abrasive means at the periphery of the carrier wheel for presenting an abrasive surface for engaging the balance wheels in succession to remove material therefrom, and means for relatively moving the abrasive means cyclically into and out of engagement with the presented edges of the balance wheels.

4. in a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at high speed so that each balance wheel assumes a position of equilibrium with its heavy side out, abrasive means at the periphery of the carrier wheel for presenting an abrasive surface, said abrasive means having a limit stop for positioning the abrasive surface in light grazing contact with the balance wheels so that they are engaged in succession for removal of material therefrom, and means for relatively moving the abrasive means cyclically into and out of engagement with the limit stop for progressively shorter periods of engagement.

5. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at high speed so that each balance wheel assumes a position of equilibrium with its heavy side out, abrasive means at the periphery of the carrier wheel for presenting an abrasive surface for engaging the balance wheels in succession to remove material therefrom, and means for relatively moving the abrasive surface cyclically from side to side.

6. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier at a high speed so that each balance wheel is positioned with its heavy side out, a belt of abrasive material having means for supporting the same facing the carrier wheel together with means for bringing the belt cyclically into contact with the presented edges of the balance wheels as the carrier wheel rotates, and means for relatively shifting the belt from side to side upon rotation of the carrier wheel.

7. In a poising machine for balance Wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier at a high speed so that each balance wheel is positioned with its heavy side out, a belt of abrasive material having means for supporting the same facing the carrier wheel together with means for bringing the belt cyclically into contact with the presented edges of the balance wheels as the carrier wheel rotates, means for advancing the belt progressively about its supporting means, and means for relatively shifting the belt from side to side.

8. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having a plurality of bearing assemblies about its periphery for mounting balance wheels with the axis of each of them oriented in substantial tangential position, each of said bearing assemblies including a pair of jaws having conical bearings, at least one of said jaws being movable and having means for biasing the same axially inward to a normal spindle engaging position, a jaw operator associated with each bearing assembly for separating the jaws to permit insertion of a balance wheel therebetween, means for rotating the carrier wheel at high speed, grinding means for acting upon the presented edges of the wheels in succession as the wheel rotates, and means acting upon said operators for successively releasing the balance wheels as the carrier wheel is slowly turned upon completion of the grinding operation.

9. In a poising machine for balance Wheels and the like the combination comprising a rotary carrier Wheel having separable bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, so that each balance wheel is positioned with its heavy side out when the wheel is rotated, relatively movable abrasive means adjacent the periphery of the carrier wheel for successively engaging the presented edges of the balance wheels as the carrier wheel is rotated, a cover protectively surrounding the carrier Wheel, programmed means for driving the carrier wheel and the movable abrasive means throught a predetermined operating cycle so that each balance Wheel is brought into a condition of balance, means for operating upon the separable bearings for stripping the balance wheels from the carrier wheel for gravity discharge of the same. and interlock means coupled to the cover for disabling the Vstripping means when the cover is in place and for disabling the driving means when the cover is removed.

10. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position so that each balance wheel is positioned with its heavy side out when the wheel is rotated, relatively movable abrasive means adjacent the periphery of the carrier wheel for successively. engaging the presented edges of the balance Wheels as theV carrier wheel is rotated, a removable cover protectively surrounding the carrier wheel, programmed means for driving the carrier wheel and the abrasive means through a predetermined operating cycle so that each balance wheel is brought into a condition of balance, and interlock means operated incident to removal of the cover for terminating rotation of the carrier wheel.

11. In a poising machine for balance wheels and the like the combinationpcomprising a rotary carrier Wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the ycarrier. wheel at a high speed so that each balance wheel is positioned with its heavy side out, an abrasive member arranged adjacent the periphery of the carrier wheel for engaging the presented edges of the balance wheels for removal of material therefrom, a movable frame for mounting the abrasive member, means including a cam and cam follower for moving said frame toward and away from the carrier wheel so that the abrasive member is brought into engagement with the balance wheels for progressively shorter time intervals until bal ance is achieved, means for shifting the frame from side to side to constantly present a fresh area of abrasive to said balance wheels.

l2. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel Ahaving bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at a high speed s0 that each balance wheel is positioned with its heavy side out, material removing means arranged adjacent the periphery of the carrier wheel, a movable frame for mounting the material removing means and for moving the latter radially into and out of engagement with the edges of the balance wheels, said frame having programmed means for coutrolling the movement so that the material removing means is brought into engagement with the balance wheels for progressively shorter time intervals until balance is achieved.

13. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in tangential position, means for rotating the carrier wheel at a high speed so that each balance wheel yassumes a position of equilibrium with its heavy side out, and material removing means at the periphery of the carrier Wheel for cyclically engaging the balance wheels thereon in succession and for progressively shorter periods for removing material from the presented heavy side thereof until a condition of balance is achieved, the initial period of engagement being suiliciently long so that the amount of material removed in such period exceeds the maximum expected initial unbalance expected in the batch of balance wheels being treated.

14. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in tangential position, means for rotating the carrier wheel at a high speed so that each balance wheel tends constantly to assume a position of equilibrium with its heavy side out, means at the periphery of the carrier wheel for engaging the balance wheels thereon in succession and for removing material from the presented heavy sides thereof until a condition of `balance is achieved, and means for imparting vibration to said carrier wheel thereby to overcome static friction at the bearings and facilitating reorientation of the balance wheels as the same approach a condition of balance.

15. ln a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at high speed so that each balance wheel tends constantly to assume a position of equilibrium with its heavy side out, means including an abrasive belt stationed opposite the edge of the carrier wheel, means for feeding said abrasive belt radially inward and slowly outward, means for moving the abrasive belt from side to side through a plurality of cycles during said feeding movement with the abrasive member being moved clear of the balance wheels during each cycle so that the balance wheels are free to assume a new position of equilibrium during each such cycle, and means coupled to the feeding means for indexing the belt forwardly along its length.

16. ln a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at high speed so that each balance wheel tends constantly to assume a position of equilibrium with its heavy side out, means including an abrasive belt stationed opposite the edge of the carrier wheel, means for feeding said abrasive belt radially inward and outward, and means for moving the abrasive belt from said to side through a plurality of cycles during said feeding movement with the abrasive member being moved clear of the balance wheels during each cycle so that the balance Wheels are free to assume a new position of equilibrium during each such cycle.

17. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in substantially tangential position, means for rotating the carrier wheel at high speed so that each balance wheel tends constantly to assume a position of equilibrium with its heavy side out, means including an abrasive member stationed opposite the edge of the carrier wheel, means for feeding said abrasive member radially inward and slowly outward, and means for moving the abrasive member from side to side through a plurality of cycles during said feeding movement with the abrasive member being moved clear of the balance wheels during each cycle so that the balance wheels are free t0 assume a new position of equilibrium during each such cycle.

18. In a poising machine for balance wheels and the like the combination comprising a rotary carrier wheel having bearings about its periphery for mounting a plurality of balance wheels with the axis of each of them oriented in tangential position, means for rotating the carrier wheel at a high speed so that each balance wheel tends constantly to assume a position of equilibrium with its heavy side out, means at the periphery of the carrier wheel for engaging the balance wheels thereon in succession and for removing material from the presented heavy sides thereof until a condition of balance is achieved, and means on said carrier wheel for vibrating the same thereby to overcome static friction at the bearings and facilitating reorientation of the balance wheels as the same approach a condition of balance, and a stationary actuator for acting upon the vibrating means incident to rotation of the carrier wheel.

Eddison July 7, 1942 Noack et al. May l0, 1960