US3064485A - Cycle starting mechanism - Google Patents

Description

1962 M. A. HALL 3,06

CYCLE STARTING MECHANISM Filed Aug. '22, 1960 s Sheets-Sheet 1 INVENTOR.

MITCHELL A. HALL BY 1 ATTORNEY M. A. HALL CYCLE STARTING MECHANISM Filed Aug. 22, 1960 5 Sheets-Sheet 2 "W 2 34 88 7 X l L 36'; I

.z I. I 22 j 1 9 HUI. e4 36" INVENTOR. MITCHELL A. HALL BY M4, 4, ATTORN EY Nov. 20, 1962 M. A. HALL 3,064,485

CYCLE STARTING MECHANISM Filed Aug. 22, 1960 5 Sheets-Sheet 3 ,3 9,4 6 55k 70 a a I 5 1a H i 90' 5%. ,w j V77%//// 52 I I 4e INVENTOR.

MITCHELL 4. HALL Nov. 20, 1962 M. A. HALL CYCLE STARTING MECHANISM 5 Sheets-Sheet 4 Filed Aug. 22, 1960 INVENTOR.

MITCHELL A. HALL ATTORNE Nov. 20, 1962 M. A. HALL 3,064,485

CYCLE STARTING MECHANISM Filed Aug. 22, 1960 5 Sheets-Sheet 5 INVENTOR. MITCHELL A. HALL Y ATTORNEY United States Patent Ofifice 3,064,485 CYCLE STARTING MECHANISM Mitchell A. Hall, 445 Rossini-d Ave, Fort Thomas, Ky. Filed Aug. 22, 1960, Ser. No. 51,168 15 Claims. (Ci. 74-102) The present invention relates to a cycle starting mechanism for automatic electric switches or contactors designed to open and close a multiplicity of electric circuits in predetermined succession, during a specified period of time. Such automatic electric switches or contactors generally consist of a series of discs or drums each fixed upon a common shaft which is rotated by means of a synchronous electric motor, the discs or drums being notched peripherally to co-operate with movable contacts serving to open or close electric circuits, depending upon the nature and extent of the notches of the discs or drums.

In switches of the character mentioned, the driven shaft carrying the contact actuating discs is rotated very slowly through a cycle of operation which in extent is less than a full rotation of the shaft. Rotation of the shaft is started, upon completion of each cycle, by manually closing the circuit of the synchronous motor which drives the shaft, this closing of the motor circuit being effected such as, by way of example, by actuating a coin slide after placing proper coins or tokens in the slide. The shaft continues to rotate, through less than a full rotation, until a full succession of switching operations is completed; then with a final switch opening, the circuit of the synchronous motor is broken automatically to complete the cycle of operation and to immobilize the shaft in readiness for another manual closing of the motor circuit through the agency of the coin slide.

Switches and coin slides as above mentioned may be employed in connection with service machines such as clothing washers and dryers, for example, or in other machines designed to perform a function or service upon the deposit of coins or tokens by a patron. In the case of washing machines which are automatic, the control switch will ordinarily include a multiplicity of electric contacts and circuits, which open and close in predetermined order, to start and stop a series of washing, draing, tumbling, rinsing, and other necessary operations con stituting a cycle of operation performed within a predetermined time period governed by a set of stop contacts controlling the synchronous electric motor of the switch mechanism.

An object of the present invention is to provide reliable and effective means for initiating a cycle of machine operation, through the agency of a coin slide, and which is not subject to damage or destruction due to the employment of abusive treatment or deliberate attempts to disable the machine.

Another object is to facilitate and expedite adjusting the cycling mechanism for accurate and efiicient performance, without resort to painstaking and time-consuming labor.

A further object is to minimize maintenance expense and frequent servicing of coin-constrolled machines which operate upon a cyclic plan to perform a desired function or service.

Another object of the invention is to provide means for initiating a cycle of timed operation for automatic machines, characterized by simplicity of construction and operation.

Another object is to ensure the cycle timer against faulty operation by reason of calculated misuse or tampering on the part of persons seeking to obtain free service, or service in addition to that which the machine is intended to perform, within a given period of time.

The foregoing and other objects are attained by the means described herein and illustrated upon the accompanying drawings, in which:

3,064,485 Patented Nov. 20, 1952 FIG. 1 is a side elevational view, partly broken away, showing a coin slide and timer switch combination em bodying the present invention, and which may be used to control the operation of a service machine, such as an automatic washer, for example.

FIG. 2 is a top plan view of the device of FIG. 1, partly broken away in the interest of clarity of disclosure.

FIG. 3 is an exploded View of the improved cycle starting mechanism of the invention associated with the timer switch.

FIG. 4 is an enlarged cross-sectional view taken on line 44 of FIG. 2, and showing the cycle starting mechanism in the normal home position.

FIG. 5 is a cross-section taken on line 55 of FIG. 4.

FIG. 6 is a cross-section taken on line 6-6 of FIG. 4.

FIG. 7 is a top plan view of the cycle starting mechanism in the normal or home position, and showing its relationship to a coin slide plate in readiness to actuate the starting mechanism.

FIG. 8 is a view similar to FIG. 7, showing the starting mechanism actuated by the coin slide plate.

FIG. 9 is a view similar to FIG. 7, showing the starting mechanism and its relationship to the cycle timer shaft, immediately following actuation by and retraction of the coin slide plate.

FIG. 10 is a plan view of a cam such as might be substituted for a cam shown in F IG. 9.

FIG. 11 is a fragmentary top plan view of an actuator arm adjustment lock, constituting a modification of the adjustment lock shown in FIG. 5.

FIG. 12 is a fragmentary cross-sectional View taken on line 12-12 of FIG. 11.

Referring to FIGS. 1 and 2, the character 14 indicates a conventional timer switch which may be of the type disclosed in US. Patents 3,011,041, 2,245,763, or 2,118,427. The switch has a multiplicity of electric terminal pairs 16, 18, and 20, others of which are not shown, said pairs of terminals being adapted for connection with various electrical devices of a service machine, to control the machine and its operating sequence. If the service machine is an automatic washer, for example, the switch terminals may be connected to various electrical devices in the machine for controlling the sequence and duration of washing, draining, tumbling, rinsing, and perhaps other necessary functions characterizing the machine.

Within the housing of the timer switch 14 is an upright shaft 22, adapted to be slowly rotated by means of a synchronous electric motor 24. Motor 24 is to be energized throughout a complete cycle of operation of the machine controlled by the timer switch, which may be a matter of twenty minutes, for example; and during that time period the shaft 22 will be rotated less than a full turn. At the end of the time period, the timer switch will open the circuit of motor 24 to immobilize the motor and the switch shaft 22, the complete cycle of operation of the service machine having been completed.

To begin another cycle of operation of the service machine, a patron is required to deposit a proper coin or token in the slide plate 26 of a coin slide 28, and advance the slide plate to a fully extended position at which the slide plate actuates a re-starting mechanism for the timer switch and its synchronous electric motor 24. Then, as before stated, the service machine will perform the desired or expected cycle of operation for which the patron has paid.

Within the timer switch housing may be located a series of discs or drums, not shown, which are rotatable with shaft 22 and which in rotating will close and open the electrical circuits of the various terminals 16, 18, 20, in predetermined sequence and for predetermined periods of time, as may be required in order to properly actuate the several constituents of the service machine, until'its cycle of operation is completed. Thereupon, the synchronous electric motor 24 will be de-energize until the same or another patron actuates the coin slide 28.

The coin slide may be mounted upon a shelf 36 within a box 32, which houses also the cycle timer 14 and its associatedparts. The cycle timer may be fixedly supported upon a side of the box by means of an angle bracket 34 and screws 36; As shown by FIGS. 1 and 2, the coin slide and the cycle timer are positioned within box 32, so that a freely rotatable roller 38 fixed upon the inner end of coin slide plate 26 will, upon advancement of the coin slide, strike and move an actuator arm 40 of the cycle starting mechanism for the timer switch. FIG. 8 shows the actuator arm 40 moved from the FIG. 7 position, by advancement of roller 38 carried by the coin slide plate. The normal inactive position of the actuator arm and coin slide plate, is as indicated upon FIGS. 2 and 9. As is usual, the coin slide plate is urged always to the retracted position by the action of a spring incorporated therein, as at 29, FIG. 1.

The function of the actuator arm 40 is to place the switch shaft 22 in a position to close the synchronous motor contacts each time that the coin slide is advanced to initiate a cycle of machine operation. It is necessary to understand, in this connection, that a complete cycle of machine operation involves rotation of shaft 22 through a number of circle degrees less than 360 degrees, so that at the end of a cycle, the shaft stops short of its cycle-starting position. Consequently, it is necessary to advance the shaft manually, through the agency of the coin slide, through the number of remaining circle degrees required to bring the shaft into position for closing a pair of connects in the synchronous motor circuit, to repeat the operating cycle.

The extent to which the shaft 22 requires manual rotation by means of the actuator arm and the coin slide, in order to reach the cycle-starting position, will be a constant factor in any given machine. However, in different machines having different functions or operating periods, the distance through which the shaft requires manual rotation in order to reach cycle-starting position, may vary according to the nature and extent of the operating cycle. Solely for the purpose of illustration or example in connection with the present disclosure, it may be assumed that a full operating cycle requires a 240 degree rotation of shaft 22 for closing and opening the various contacts of the timer switch, until the synchronous motor is stopped by reason of the breaking of its electrical circuit by the timer switch. Accordingly, there remains 120 degrees of rotation of; the shaft through which the shaft must be advanced manually by the coin slide, in order to restore the shaft to starting position for subsequent cycling by closing the synchronous motor circuit.

Referring to FIGS. 4 and 5', it will be noted that shaft 22' at its upper end carries one or more flats 42, against which may impinge the set-screws 44 of a centrally bored hub 46, to secure the hub for rotation with the shaft. Fixed to the hub, concentrically with shaft 22, is a ratchet wheel 46 which is shown in detail upon FIG. 6. The ratchet wheel may have a single tooth 48, in the specific apparatus illustrated by way of example, adapted upon each full' rotation of the ratchet wheel to engage a pawl 50. The pawl is pivotally mounted as at 52 upon one face of an adjustment plate or disc 54, which latter is centrally apertured at 56 to loosely surround the upstanding neck 58- of hub 46.

Upon the upper planar face 60 of disc 54 rests the actuator arm 40, said arm being apertured at 62 intermediate its ends, to loosely surround an upstanding concentric neck 64 of disc 54 whereby the actuator arm under certain conditions may be rotated to adjusted positions relative to the disc. A washer 66 applied tightly about the neck 58 of hubv 46, and peened thereon at 68, holds 4 the actuator arm in position upon the planar face 60 of disc 54.

An adjustment means is provided for selectively fixing the actuator arm 46 upon the face of disc 54, in different diametral positions upon the disc. Such adjustment means may comprise a screw 70 passing through aligned holes 72 and 74 and-provided in the arm 40 and in an underturned end portion thereof, to clamp. the underturned portion 76 against a face of disc 54. By this means the actuator arm may be locked upon the disc in various adjusted positions of rotation.

FIGS. 11 and 12 illustrate an alternative locking adjustment wherein the actuator arm 740 overlying the disc 754 is provided with an internally threaded opening 742', receptive of a screw 744, which clamps a pressure plate 7 46 against the disc 754 for fixing the actuator arm upon the disc. With either form of locking adjustment, the actuator arm may be selectively positioned across the disc, and locked thereto.

The character 78 indicates a tension spring having opposite ends 80 and 82 anchored to pawl 50 and to a lug 34 on disc 54, whereby the pawl is constantly urged against the periphery of ratchet wheel 46. Accordingly, rotation of the disc 54 and the actuator arm 40' in one direction manually, will serve to rotate the timer switch shaft 22 whenever pawl 50 moves into engagement with the ratchet wheel tooth 48'.

The actuator arm 40 may be limited in its swinging movement, by means of stationary spaced stops or posts 86 and 88 (FIGS. 2 and 8), suitably mounted upon the top of the timer switch casing. The actuator arm nor- 'mally is yieldingly urged against stop 86 by means of any acceptable form of spring, such as the wire loop spring 90. The normal or home position of the arm is shown in FIG. 2, whereas FIG. 8 shows it in the displaced position resulting from a full advancement of the coin slide plate 26.

At the termination of any operating cycle, the switch shaft 22 will be found disposed in the relationship illustrated by FIG. 7, wherein the tooth 48 of ratchet wheel 46 will repose at the proper location to accommodate pawl 50. In this situation, the synchronous motor is de-energized and shaft 22 is at rest.

Now, if an operating cycle is to. be started, shaft 22 must be rotated in clockwise direction to an extent necessary for placing the synchronous motor contacts of the timer switch in closed circuit condition, and this is accomplished by advancing the coin slide plate 26 in the manner of FIG. 8. Here it will be noted that roller 38 of the coin slide has struck and moved the actuator arm 40 to an advanced position at which the arm has stopped against the stationary post 88. The actuator arm in so moving to advanced position has carried with it the disc 54 and the pawl 50 thereto attached, and. since the pawl was in engagement with tooth 48 of the ratchet wheel, the latter was likewise moved in clockwise direction to rotate the shaft 22' and all the contact discs within the switch acting to. close-circuit certain of the switch terminals 16, 18, 20, including a set of contacts feeding'current to the timer switch motor 24. Motor 24 having been so started, it will slowly drive the shaft 22 and its switch contactor discs, to bring about a sequential succession of switch operations necessary to produce the desired performance of the machine controlled by the timer apparatus.

As previously stated, the shaft 22 and ratchet wheel 46 will, upon completion of the operating cycle, reach the situation. illustrated by FIG. 7, at which all action is stopped and the apparatus is poised for a subsequent operation by advancement of the coin slide.

It may here be noted that advancement of the coin slide plate, after deposit of a proper coin or token, is a momentary operation only, because the coin slide plate is spring-returnedin accordance with common practice. The actuator arm 40 likewise is returned to the. normal or home position against stop 86, FIG. 9, by the action of spring 90. Arm 40 remains in the home position throughout the operating cycle of the timer switch, as the shaft 22 and ratchet wheel 46- progress under the moving influence of motor 24 to the position of FIG. 7, at which the operating cycle is ended.

It is important to note that once the actuator arm 40 has been advanced from the FIG. 7 position to the FIG. 8 position for starting the operating cycle, no amount of subsequent coin slide manipulation resorted to for jamming the mechanism, or obtaining free or extended play, will have any effect upon the regular and intended performance of the cycle timer. This is due to the fact that the tooth 48 of the ratchet wheel has moved out of the area of influence of the actuator arm, and remains mechanically independent thereof throughout the entir operating cycle of the machine. It is accordingly impossible to jam the mechanism, obtain free play, or injure the working parts by any form of coin slide manipulation, because manipulation of the coin slide can only idly swing the actuator arm between the limits of posts or stops 86 and 88, independently of the timer operation. Post 88 marks the point at which the operating cycle is initiated, and the actuator arm cannot be swung past the post. Moreover, the length of travel of the coin slide plate preferably is limited within the coin slide itself, to prevent forcing the actuator arm against the post or stop 88, thereby further protecting the operating parts against the forces or abusive-coin-slidemanipulation.

In any case where the operating cycle may be performed within the scope of very limited rotation of the timer switch shaft 22, it may be desirable to equip the ratchet wheel 46 with two or more teeth such as 48, thereby to avoid the need for a very long advancement of the coin slide plate in order to initiate an operating cycle. FIG. shows a ratchet Wheel 246 so modified, having three ratchet teeth 248 for the purpose. Whenever a multiple-toothed ratchet wheel is employed, care should be exercised to avoid bringing any tooth into pawl-engaging position during the course of a cycle of machine operation, for if care is not observed in this regard, a patron might by early coin slide advancement cut short an operating cycle in progress and prematurely start a new operating cycle. This would result in a waste of time and money for the patron, but would not disable the machine.

The rectangular opening 94 of the actuator arm 40 is merely a socket in which the loop 96 of spring 90 may be anchored. Spring 9%] may have intermediate convolutions 98 loosely surrounding the hub 46, simply for the purpose of extending the spring length to soften its force and prolong the life thereof by reducing the possibility of localized crystallization.

The character 100, FIGS. 1 and 2, indicates a guide on bracket 34, having an upturned lip 102 the purpose of which is to stabilize the coin slide plate when extended and exerting force upon the actuator arm 40. The guide may not be necessary if the slide plate is made sufficiently rigid to resist bending or upward deflection upon advancement against the actuator arm.

In conclusion, it may be noted that application of the herein disclosed cycle starting mechanism to any cycle timer is rendered quick and easy by reason of the fact that all necessary adjustments may be performed at the easily accessible adjustment screw 70 (or 744), rather than at the partially hidden set-screw 44 (FIG. 4). In devices which require adjustment at set-screws such as 44, in order to index the actuator arm relative to a shaft such as 22, the work of indexing is very tedious and time-consuming; and with the possibility that the setscrews after several adjustments will invariably mutilate the shaft, accuracy of adjustment becomes exceedingly difiicult if not impossible. With the present arrangement, the mechanic will simply lock the hub 46 to shaft 22 in any position by means of the set-screws 44, and then proceed to obtain a fine and accurate indexing of the parts at the readily accessible adjusting screw 70 (or 744 in FIG. 11). Indexing consists in simply loosening the screw '70, advancing the actuator arm fully by means of the coin slide plate, rotating the disc 54 clockwise until the switch closes the circuit of the synchronous motor 24, and then tightening the adjusting screw 70.

From the foregoing it will be noted that I have provided simple yet highly effective clutch means actuatable by the slide of a coin-controlled device for initiating an operating cycle of a time mechanism, which clutch means is so constructed and arranged as to preclude its actuation for initiating a subsequent cycle of the timer mechanism until the prior timing cycle has been fully completed. In all prior art devices of which I am aware, subsequent cycles may be initiated while the timer mechanisms are still in a prior cycling operation.

It is to be understood that various modifications and changes in the structural details of the apparatus may be resorted to, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed is:

1. Cycle starting mechanism for a motor-driven electric contactor including a main shaft, an electric motor, a switch connected to said motor so as to control its operation, said motor connected to said main shaft so as to rotate it in one direction, said switch energizing said motor while it drives said main shaft and contactor from a starting position to a terminal position, through a circle are less than a full circle, said starting mechanism comprising a toothed ratchet wheel fixed relative to the main shaft of the contactor, a rockable actuator arm loosely mounted for rotation about the shaft, a spring biased pawl to engage the tooth of the ratchet wheel, and means mounting the pawl for bodily movement with the actuator arm, the swing of the actuator arm being substantially complementary in extent to the arc traversed by the shaft in power rotating from the starting position to the terminal position aforesaid.

2. The device as set forth in claim 1, wherein the combination includes selectively adjustable means for fixing the actuator arm in different rotated positions relative to the tooth upon the ratchet wheel.

3. Cycle starting mechanism for a motor-driven electric contactor including a main shaft, an electric motor, a switch connected to said motor so as to control its operation, said motor connected to said main shaft so as to rotate it in one direction, said switch energizing said motor while it drives said main shaft and contactor from a starting position to a terminal position through a circle are less than a full circle, said starting mechanism comprising a rockable actuator arm loosely mounted for rotation about the shaft through a circle arc swing substantially complementary in extent to the arc traversed by the shaft in power rotating from the starting position to the terminal position aforesaid, an overrunning clutch for engagement in transmitting movements of the actuator arm to the contactor main shaft, and selectively adjustable means for indexing the actuator arm with respect to the main shaft, to predetermine the position of the shaft at which the clutch enters engagement to move the shaft with said arm.

4. In combination, a motor-driven electric contactor including a main shaft rotatable through a complete circle, said shaft being power-rotatable in one direction from a starting position to a terminal position through a circle are less than a full circle in extent, a hub detachably fixed upon the shaft for rotation therewith, a toothed ratchet wheel fixed relative to the hub, an adjustment plate apertured to loosely surround the hub for relative rotation, and an actuator arm apertured to surround the hub for swinging movement about the main shaft and in close proximity to the adjustment plate, a pawl pivoted upon a face of the adjustment plate, and means yieldingly urging the pawl toward the ratchet wheel for engaging the tooth of the latter upon rotation of the adjustment plate relative to said ratchet wheel, and means for selectively clamping the actuator arm in various rotated positions upon the adjustment plate, to index said arm and said pawl relative to the tooth of the ratchet wheel.

5. The device asset forth in claim 4, wherein the combination includes means for limiting the swing of the actuator arm to an extent substantially complementary to the arc traversed by the main shaft in power rotating from the starting position to the terminal position aforesaid.

6. In combination, a motor-driven electric contactor including a main shaft rotatable through a complete circle, said shaft being power-rotatable in one direction from a starting position to a terminal position through a circle are less than a full circle in extent, a hub detachably fixed upon the shaft for rotation therewith, a toothed ratchet wheel fixed relative to the hub, an adjustment plate apertured to loosely surround the hub for relative rotation, and an actuator arm apertured to surround the hub for swinging movement about the main shaft axis and in close proximity to the adjustment'plate, a pawl pivoted upon a face of the adjustment plate, and means yieldingly urg- 7 ing the pawl toward the ratchet wheel for engaging the tooth of the latter upon rotation of the adjustment plate relative to said ratchet wheel,'means for selectively clamping the arm in various rotated positions upon the adjustment plate, and reciprocable means to swing the actuator arm to an extent substantially complementary to the arc traversed by the main shaft in power rotating from the starting position to the terminal position aforesaid.

7. Thedevice as set forth in claim 6, wherein the combination includes yielding means for constantly urging the actuator arm in a direction of rotation counter to that of the main shaft, and stationary stop means for limiting rotation of the arm by said yielding means.

8. In combination, a motor-driven electric contactor including a main shaft rotatable through a complete circle, said shaftbeing power-rotatable in one direction from a starting position to a terminal position through a circle are less than a full circle in extent, an actuator arm pivotal upon said main shaft and having an end swingable in substantial concentricity to the shaft, a coin slide having a slide. plate movable to contact the end of the actuator arm :and swing said arm to an extent substantially complementary to the arc traversed by the main shaft in power rotating from the starting position to the terminal position aforesaid, and means transmitting movement of the actuator arm to the shaft only at the terminal position of the latter.

9. The device as set forth in claim 8, wherein the combination includes adjustable means associated with the actuator arm, for indexing the arm with relation to the starting position of the shaft.

, 1'0. Incombination, a motor-driven electric contactor including a main shaft rotatable through a complete circle, said shaft being power-rotatable in one direction from a starting position to a terminal position through a circle are less than a full circle in extent, an actuator arm pivotal aboutsaid main shaft and having a free end swingable in substantial concentricity to'the shaft, a reciprocable element supported to contact and move the actuator arm to an extent substantially complementary to the arc traversed by the main shaft in power rotating from the starting position to the terminal position aforesaid, and means operative only when the shaft is in terminal position, to transmit movement of the actuator arm to said I shaft, for advancing the shaft to starting position.

ing from the starting position to the aforesaid terminal position, and means operative only when the shaft is in terminal position to transmit movement of the shaft advancing actuator to said shaft for advancing the shaft to starting position, and adjustable means associated with the shaft-advancing actuator, for indexing said actuator with reiation to the starting position of the main shaft.

13. in combination, a motor driven electric contactor including a main shaft rotatable through a complete circle, said shaft being power rotatable in one direction from a starting position to a terminal position through a circle arc less than a full circle in extent, a shaft advancing actuator movable to an extent substantially compementary to the arc traversed by the main shaft in power rotating from the starting position to the aforesaid terminal position, and means operative only when the shaft is in terminal position to transmit movement of the shaft advancing actuator to said shaft for advancing the shaft 1 to starting position, and a stop against which the actuator is yieldingly but displaceably urged to a position corre sponding to the terminal position of the main shaft.

14. Cycle starting mechanism for a motor-driven electric contactor including a main shaft rotatable through a complete circle, said shaft being power-rotatable in one direction from a starting position to a terminal position through 'a circle arc less than a full circle in extent, said mechanism comprising a hub detachably fixed upon the shaft for rotation therewith, a toothed ratchet wheel fixed relative to the hub, an adjustment plate apertured to loosely surround the hub for relative rotation, and an actuator arm apertured to surround the hub for swinging movement about the main shaft .axis and in close prox- -imity to the adjustment plate, a pawl pivoted upon a face of the adjustment plate, and means yieldingly urging the pawl toward the ratchet wheel for engaging the tooth of the latter upon rotation of the adjustment plate relative to said ratchet Wheel, means for selectively clamping the arm in various rotated positions upon the adjustment plate, and reciprocable means to swing the actuator arm to an extent substantially complementary to the arc traversed by the main shaft in power rotating from the startingposition to the terminal position aforesaid.

15. The device'as set forth inclaim 14, wherein the combination includes yielding means for constantly urging the actuator arm in a direction of rotation counter to that of the main shaft, and stop means for limiting rotation of the arm by said yielding means.

References Cited in the file of this patent UNITED STATES PATENTS 2,586,040 Hoare Feb. 19, 1952 2,732,730 Sernaker Jan. 31, 1956 2,810,798 Taylor Oct. 22, 1957 2,899,622 Greenwald Aug. 11, 1959 2,908,175 Robbins Oct. 13, 1959 2,916,923 Smith et al Dec. 15, 1959 2,923,165 Patzer Feb. 2, 1960 2,940,317 Goodh-ouse June 14, 1960 2,941,052 Taylor June 14, 1960 2,964,599 Greenwald Dec. 13, 1960 2,973,077 Crockett Feb. 28, 1961

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