CA1143306A - Clutch assembly for electrically operated retractable jack - Google Patents

Abstract

Abstract of the Disclosure An electrically operated retractable jack for leveling a vehicle.
The jack is automatically retractable from a vertical position into a hori-zontal stowage position under the vehicle. The jack may be operated indivi-dually or a plurality of jacks may be used in leveling the corners of a vehicle. The jacks may be raised and lowered by control switches mounted inside the vehicle without the need of the operator getting outside the vehicle. The jack makes use of a torque limiting clutch which prevents overloading of the motor and prevents the jack from locking up during raising or lowering of the jack. The clutch comprises a drive gear having several spaced valleys in one of its flat surfaces and a drive plate with apertures aligned with the valleys. Balls disposed in the apertures extend into the valleys and are spring biased into the valleys. The biasing force deter-mines the torque which can be transmitted because when this predetermined torque is reached the balls roll freely into and out of the valleys.

Description

~433~6 This invention relates generally to clutch assemblies and, in particular, to such an assembly which may be used with an electrically operated retractable jack for mounting on a vehicle.
Heretofore, there have been a variety of electrical, hydraulic, and mechanical operated jacks used for leveling vehicles, trailers, or the like. Generally, the most common jacks are jacks mounted on the corners of a vehicle, or on the tongue of a trailer which raise and lower the vehicle and trailer in a vertical direction. These jacks have no provision for re-tracting the jack from a vertical position to a stowed horizontal position underneath the vehicle.
Also a common problem of a vehicle jack is the jack may have a sufficient initial torque to raise the vehicle to a level position, but after an extended period of time, the jack assembly locks up and the operator is unable to lower the vehicle. This problem is particularly true when added weight is loaded on to the vehicle or a shift in position takes place sub-sequent to the leveling of the vehicle. An excess torque is therefore nec-essary to lower the vehicle.
There are prior art jacks which are retractable from a vertical position into a horizontal position, but these jacks are complex in design and construction and have been found to have limited commercial acceptance.
The retractable jacks use offset pivot arms or a pivot cam for automatically pivoting the jacks into a horizontal position.
e subject invention is particularly useful in combinat~n with a jack wh~ch automatically retracts from a vertical position into a horizontal stowage position underneath the vehicle so that the vehicle is ready to travel.

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:' ~33~)6 The jack is automatically lowered from a horizontal position into a vertical position and in a position for extending the jack, leveling, and stabili~ing the vehicle. -The jack may be mounted in various arrangement combinations under-neath a vehicle, such as on the four corners of the vehicle, the rear corners, and at the center of the front of the vehicle, or any other desired position.
The jack also may be used for a tire change without having to use a hand-operated jack.
The jacks may be electrically wired to a control panel inside the vehicle so that the operator may level the vehicle without having to go out-side. Each jack has its own individual electric motor drive unit, therefore should one jack fail the remaining jacks will operate independently for leveling the vehicle. The electric driven jacks provide the advantages over hydraulic and pneumatic jacks by eliminating fluid supply lines, valving, fluid leakage, and cold weather start up problems.
The invention provides a torque limiting clutch suitable for use with an electrical motor and gear drive that prevents the overloading of the motor and prevents the jack from locking up during both the raising and lowering of the jack. A greater amount of torque is provided to the jack by the limiting clutch when lowering the vehicle than for raising the vehicle.
According to a broad aspect of the present invention, there is provided a clutch assembly including: a drive clutch gear having a flat surface extending perpendicularly to the rotational axis of the gear, the surface having at least a pair of radially extending valleys disposed at ~ annularly spaced positions, the sides of the valleys being bevelled with the ; bevel of one side of the valleys disposed at a first angle and the bevel of ~ ;;~ the opposite side of the valleys disposed at a second angle different from ~ . . ~ .

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~1~33~6 the first angle to control the torques at which the clutch staTts to slip when rotated in opposite directions; a drive plate having one side of the plate disposed adjacent the flat surface of the gear and at least a pair of apertures annularly spaced in accordance with the spacing of the valleys in the flat surface; a pair of balls disposed in the apertures of the drive plate and extending into the valleys in the flat surface of the gear; a disc spring disposed against the balls on the opposite side of the drive plate from the drive clutch gear and biasing the balls into the valleys in the flat surface of the gear; and a driven gear operatively coupled to the drive plate for rotation therewith, whereby below a predetermined drive torque in a given direction the drive plate and driven gear are rotated by engagement of the balls with the drive plate and above the predetermined torque the balls exit from the valleys to cause slippage of the drive clutch gear relative to the drive plate.
The present invention and that of Application Serial No. 290,917 will now be described in more detail with reference to the accompanying drawing, in which Figure 1 is a perspective view of a recreational vehicle having an electrical retractable jack mounted on the four corners of the vehicle and on the center of the front bumper;
Figure 2 is a perspective view of the jack in a retracted position and shown in dotted lines in an extended position;
Figure 3 is a side view of the jack in a horizontal retracted position;
Figure 4 is a side view of the jack at an angle from the retracted position;
Figure 5 is a side view of the jack in a lowered vertical position;

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11~;33~6 Fi.gure 6 is a side view of the jack in a vertical extended position;
Figure 7 is a front view of the individual elements of the .am assembly;
Figure 8 is a front view of the individual elements of the clutch assembly according to the present invention; and Figure 9 is a front view of the individual elements of the drive assembly.

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In Figure 1, the electrical retractable jack is designated by general reference numeral 10. In this view, the jack 10 is seen mounted on the corners and the front bumper of a recreational vehicle 12. me jacks 10 may be mounted in various arrangement combinations on the vehicle 12 such as the four corners of the vehicle, the two rear corners and the center of the front of the vehicle, or any other desirable combination. The jacks 10 are electrically operated and may be wired to a control panel inside the vehicle 12. me jacks 10 may be powered by the vehicle's battery or any other alter-nate electrical power source. me operator of the jack 10 need not leave the inside of the vehicle when leveling the vehicle 12. The vehicle 12 is leveled and stabilized by rotating the jacks 10 into a vertical position, and extending the jack 10 onto the ground surface.
The system described herein has the advantage of providing remote, individual control of each jack assembly 10 with minute leveling and stabili-zation adjustments possible from a single location within the vehicle. Appro-priate leveling devices, such as bubble levels, may be positioned near the control panel so that the operator may observe them during the leveling operation. Also, the operator need not leave the vehicle 12 when retracting the jacks 10 from the ground surface and raising them into a retracted hori-zontal position under the vehicle 12 prior to travel.
Figure 2 is a perspective view of the jack 10 and illustrates the jack 10 in a horizontal retracted position and in dotted lines in a vertical extended position.
Hydraulic and pneumatic systems are capable of providing as much lifting power and linear travel as conventional jack mechanical incline screw ~.143;306 arrangements, depending upon piston and cylinder sizes and their operatingpressures. Associated with hydraulic and pneumatic systems, however, are the d:isadvantages of lengthy and cumbersome supply lines to each individual unit, complex control and check valves, flexible coupling problems, cold weather operational difficulties, pipe flow losses and joint and seal leakage.
For the invention described herein, all of these problems have been eliminated by the utilization of an electrically powered drive assembly 15 which not only provides a high torque level for the jack screw in the ram assembly l6, but also provides the power for retracting the jack 10 into the horizontal stowed position shown in Figure 2.
The jack 10 includes a "U" shaped channeled mounting bracket 14, a drive assembly 15 pivotally attached to the bracket 14, a ram assembly 16 attached to the lower end of the drive assembly 15, and a retraction assembly 18 disposed around the ram assembly 16 and pivGtally attached to the bracket 14.
The bracket 14 is shown having a cut away portion in one end thereof exposing a main pivot pin 20 which is attached to the sides of the bracket 14 and is received through pivot supports 22 inte~grally formed in the sides of a motor housing 24. The motor housing 24 is part of the drive assembly 20 15. A torsion spring 25 is disposed between the pivot supports 22 and around the pin 20. The torsion spring 25 includes one end which is biased against the top of the bracket 14. The other end of the spring 25 is biased against the side of the motor housing 24. The jack 10 when lowered from the horizon-tal retracted position is biased downwardly and towards the vertical position by the weight of the jack 10 and the spring 25.
: -5-11~33~:?6 The drive assembly 15 includes the motor housing 24, an electric motor, gearing, and a clutch assembly, which are discussed in detail under Figures 8 and 9. The lower end of the drive assembly 15 is secured to the top of the ram assembly 16.
The ram assembly 16 includes a hollow outer jack tube 26 with a hollow inner jack tube 28 slidably received therein. me lower end of the inner jack tube 28 includes a jack pad mounting plate 30, threaded to receive a bolt for attachment of an annular extension pad 33 as is required for the incremental adjustment of overall length to accommodate various vehicle heights above the ground surface. The underneath surface of the jack pad mounting plate 30, or extension pad 33 when used, provides a bearing surface against the ground when the vehicle is raised on the ground surface by the jack 10.
The retraction assembly 18 includes a hollow annular shaped retrac-tion sleeve 32 with pivot inserts 34 integrally formed in the sides thereof and extending outwardly therefrom. The sleeve 32 is received around the outer and inner jack tubes 26 and 28. The retraction assembly 18 further includes a pair of elongated retraction links 36. me lower end of the retraction links 36 are pivotally attached to the pivot inserts 34. The upper end of 20 the links 36 are pivotally attached to the mounting bracket 14 by a pin 40.
The pin 40 is disposed below and to the left of the main pivot pin 20. By offsetting the position of the pin 40 with the pin 20 on the bracket 14, the retraction assembly 18 provides means for automatically pivoting the ram assem-bly 16 and drive assembly 15 upwardly to a horizontal stowage position in the bracket 14.

114335~6 Each of the retraction links 36 includes a concave portion 41 along the length thereof for providing an area of weakness of both links 36 so that they would collapse or bend prior to overloading the internal components of the ram assembly 16 should the jack 10 be prevented from retracting into the bracket 14 by an obstruction.
A novel secondary feature of the retraction links 36 is the utili-zatiOn of the concave portion 41 to provide an adjustment in overall linkage length. The length of both retraction links 36 between the pivot 40 and in-sert pivot 34 should be the same for proper performance of the retraction cycle. The design of the links 36 and the selections of material yield pro-perties is such that the links bend with ease when overloaded, but maintain their lengths under normal operation. Any difference in length of the two links 36 is eventually reduced to a proper working length by the action of the retraction sleeve 32 applying a compressive end loading on the longest link 36 first. Thus, the linkage is self-adjusting under these circumstances.
In addition to the foregoing features, the length of the links 36 determines the amount of angular displacement the jack 10 undergoes during retraction into a stowed position. Lengthening the links 36 increases the rotational arc and shortening reduces the amount of angular arc. This is useful in the initial installation of the jack 10 on vehicles having obstruc-tions or components in the area of attach~ent which might interfere with proper operation of the system. Lengthening of the links 36 is accomplished by partially flattening the concave portion 41.
In Figure 3, the jack 10 is seen in a horizontal retracted position.
In this position, the inner jack tube 28 has been retracted in the ram assembly .

11433~6 16 until the annular edge of the jack pad mounting plate 30 has come in con-tact with the bottom edge of the retraction sleeve 32. The compressive force of the inwardly moving inner jack tube 28 is distributed equally around the circumference of the retractable sleeve 32 by the jack pad mounting plate 30.
This force in turn is distributed onto the retraction links 36 through the pivots 34 and because of the offset in the pivots 40 in bracket 14, the jack 10 is rotated upwardly in a counterclockwise direction. The jack 10 is held in place in the horizontal stowage position in the bracket 14 as long as the electric motor 104 is de-energized with the jack pad mounting plate 30 biased against the end of the retraction sleeve 32. Since sufficient friction is present in the gearing of the drive assembly 15 and the screw of the ram assembly 16, coupled with the magnetic braking action of the electric motor 104, the jack 10 is self-locking in whatever position it has attained when electrical power is discontinued. This has the particular advantage of elim-inating complex mechanical locking devices to hold the jack 10 in the stowed position for travel or to prevent vehicle 12, which has been leveled and stabilized, from self-lowering.
The annular retraction sleeve 32, in combination with the retrac-tion links 36 is advantageous in that it provides a more uniform application of force onto pivots 40 for retraction. The length of links 36 can be kept short such that thin, lightweight materials can be utilized for the links 36 without subjecting these parts to excessive column bending while under com-pressive loading. Since the load of the ram assembly 16 is distributed uniformly about the circumference of the annular sleeve 32, the use of thin-walled, lightweight tubing for the sleeve is also warranted.

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In the stowed position, the sleeve 32 has the advantage of providing an external sheath for the ram assembly 16, further protecting the internal parts from mud, water, ice or other elements encountered during travel over roads or various kinds of terrain. During either extension or retraction, the sliding sleeve 32 also provides a wiping action which can remove caked mud and ice.
When the inner jack tube 28 is extended outwardly from the ram assembly 16, the force against the annular surface of the retraction sleeve 32 is relieved. The pivoted weight of the jack 10 and the spring 25 then urges the jack 10 downwardly into a vertical position shown in Figure 5.
Figure 4 illustrates the jack 10 at an angle from the vertical.
This position is typical when the inner jack tube 28 is retracted inwardly into the outer jack tube 26, the jack pad mounting plate 30 contracting the retraction sleeve 32 and pivoting the jack 10 upwardly into a horizontal position, or in the reverse mode, the jack is pivoted downwardly into a vertical position.
In Figure 5, the jack 10 is shown in a vertical position. The jack pad mounting plate 30 is no longer in contact with the end of the retraction sleeve 32. In this position, the top of the drive as~embly 15 is adjacent the top of the mounting bracket 14 and~the ram assembly 16 is in position for extending the inner jack tube 28 downward for leveling the vehicle 12.
In Figure 6, the jack 10 is shown in a completely extended position with the inner jack tube 28 extended downwardly from the outer jack tube 26.
In Figure 7, the individual parts of the ram assembly 16 and the _g_ ~1433~6 retraction assembly 18 are illustrated. me ram assembly 16 includes the outer jack tube 26 having a mounting plate 42 with apertures therein for securing the tube 26 to the bottom of the drive assembly 15. me inner jack tube 28 which is slidably received inside the outer jack tube 26 is attached to a jack screw nut 44, which is threadably mounted on a jack screw 46. The nut 44 in-cludes a keyway 48 which is inserted in an indent 50 in the top of the inner jack tube 28 for securing the nut 44 in a rotational direction. me nut 14 is secured longitudinally in the inner jack tube 28 by means of an annular locking ring 51 received by an annular grooving 53 in nut 44 and an annular groove inside the top of the inner jack tube 28. The jack screw 46 includes a stop pin 52 at the lower end thereof to prevent the nut 44 from coming loose from the screw 46.
me upper end of the jack screw 46 includes a drive collar 54 having a pair of washers 56 with a thrust bearing 58 having needle bearings mounted therebetween. The needle thrust bearing 58 and washers 56 are retained on the drive collar 54 and secured to the jack screw 46 by a retainer pin 60 inserted through an aperture in the drive collar 54 and an aperture in the upper end of the jack screw 46. The drive collar 64 is inserted through the tube 26, the aperture in mounting plate 42 and washer S9 upon final assembly of the ram assembly 16 and secured by retaining pin 61.
Although having slightly higher friction, the needle thrust bearing 58 has the advantage of having a considerably thinner profile and a higher thrust load capability than a conventional ball bearing thrust assembly occupying the same diameter. me combination of the mechanical screw jack 46, nut 44 and thrust bearing 58 with the other internal components provides ~ ~ ~3306 a compact ram assembly 16 capable of lifting much greater loads than the prior art mechanical screw fixed jacks which have been available in the past.
The limitations of space beneath a vehicle necessitates that most of the ele-ments of a retractable system such as the jack 10 be as nearly compact as practical. Ground clearance must be maintained both during road travel and erection of the jack 10 to a vertical position prior to leveling and stabil-izing the vehicle 12. Sufficient linear extension of the ram assembly must also be available to perform the leveling and stabilizing task. me physical arrangement and geometric characteristics of the jack 10 described herein 10 fully meets all of these dimensional requirements.
The upper end of the drive collar 54 includes a slot 62 therein.
me slot 62 is received around a jack pin 64 when securing the ram assembly 16 to drive assembly 15. The jack pin 64 is inserted through apertures in jack drive sleeve 66. The ends of the pin 64 are inserted into slots in a jack drive gear 68. me sleeve 66 is received inside the inner circwnference of the gear 68 shown in Figure 9. The gear 68, sleeve 66, and pin 64 assem-bly engage and rotate the drive collar 54 and jack screw 46 assembly shown in Figure 7. The gear 68 is driven by a clutch assembly 70 described in the following paragraphs which relate to Figure 8. Also seen in Figure 7 is 20 the annular retraction sleeve 32 and the retraction links 36.
Several distinct advantages are provided by the selection of the l~in-line~ arrangement of the motor housing 24, drive assembly 15 and the ram assembly 16 and the location of these components with respect to the main pivot 20 on bracket 14. One important advantage can be seen in Figure 3 depicting the retracted or stowed position of the jack 10. The clearance .
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provided beneath the jack 10 components and the ground or other obstacles is at a maximum, thus protecting the motor and other components from impact damage while the vehicle 12 is in motion.
Another advantage gained by the in-line arrangement with the electric motor located near the main pivot 20 is that much shorter electrical wiring leads can be used. These wires may be rotated out of the motor housing 24, through any convenient hole in the bracket 14 near pivot 20 which permits unimpeded, free motion of the wires without damage during retraction or ex-tension of the jack 10. While the vehicle 12 is in a traveling condition, the wiring is also protected from damage, being physically shielded by the motor housing 24 while jack 10 is retracted.
The proximity of the heavier motor housing 24 and drive assembly 15 to the main pivot 20 reduces the amount of power required to raise the pivoted portion of the jack to a horizontal retracted position. In addition, the dynamic loads produced as a result of vertical accelerations experienced by the horizontally stowed jack assembly 10 during road travel are reduced when the heavier components are grouped about the supporting main pivot 20.
Since each suspende~ component produces a movement or torsional loading about the pivot 20 during vertical accelerations produced while the vehicle 12 is traveling and these forces must be reacted, it is advantageous to keep each component movement arm at a minimum as in the jack arrangement presented.
Thus, fatigue life of the retraction links 36, pivot pins 34 and 40 and the retraction sleeve 32, which are already under a static compressive preload during the stowed condition, is greatly improved with the configuration used in the jack 10.

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Figure 8 illustrates the individual parts of the torque limiting clutch assembly 70. The assembly 70 provides means for differentially con-trolling the amount of torque applied to the jack screw 46 from the drive motor and gear train. Should the loads on the jack lO become excessive while the ram assembly 16 is operating in either the retraction or leveling mode, the clutch assembly 70 will release at a preset torque level and the drive motor, gearing and ram assembly is prevented from being overloaded to the extent of damage.
The clutch assembly 70 includes a clutch gear shaft 72 for re-ceiving the clutch gear 74 thereon. A lower face 75 of gear 74 includes three channeled valleys 76 therein. The valleys 76 are radially spaced in equal segments about the axis of rotation of the clutch gear 74. Each valley consists of a floor paralleling the face of the clutch gear 74 and at a desig-nated depth with opposing sides beveled at two different inclinations relative to the face 75 of the gear 74.
A clutch drive plate 80 having apertures therein receive ball bearings 78 in the apertures. The ball bearings 78 are physically entrapped ~ both radially and circumferentially within the perforated clutch drive plate ; 80 but possess translational freedom of motion in a direction perpendicular to the facing of the plate 80. The ball bearings 78 are biased directly by conically shaped disc springs 82 against the floor of the valleys 76, the valley slopes or on the gear facing 75 during operation. The springs 82 are retained against the ball bearings 78 by a spacer 84 and retaining ring 86.
The ring 86 is inserted into an annular groove 87 around the shaft 72. A
jack drive pinion gear 88 is attached to the clutch gear shaft 72 by a pin 90.

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" ~1433C~6 When assembled, the disc springs 82 are pre-set to apply a desig-nated load against the ball bearings 78. me disc springs 82 are in direct contact only with the ball bearings 78 during all phases of clutch operation.
The clutch drive plate 80 serves as a floating member between the disc springs 82 and the clutch gear 74, transmitting only rotational loads from the clutch gear 74 to the clutch gear shaft 72 to which plate 80 is rotatably keyed.
In operation, the clutch gear 74 is driven by the reversible elec-tric motor and gear assembly described in paragraphs which follow. During rotation of the clutch gear 74, the advancing incline of each of the valleys 76 bears against the lower portion of each ball 78 protruding through the drive plate 80, moving the balls upwardly and directly reacting the force pro-duced by the disc springs 82. The loading of the disc springs 82 against each ball 78 increases with upward deflection. The pre-set biasing of the disc springs 82 thus determines the amount of force at which the balls 78 may move upwardly and over the edge of each incline and onto the facing 75 of the clutch gear 74. When the maximum torque threshold is reached, the ball bearings 78 exit and enter each successive valley 76, rolling freely on the facing 75 of the rotating clutch gear 74 and precluding further mechanical engagement between the gear 74 and the drive plate 80. Under this condition, the torque proyided to the ram assembly 16 and hence the maximum load on the jack 10 is prevented from increasing above the designated limit. Torque is provided to the assembly 16 only when the balls are captured and retained in the valleys 76, mechanically engaging the clutch gear 74 and the drive plate ` 80.
The action described in the foregoing also applies while operating :' ' ' ,- ~ , : ' , 119~33q:~6 in a reverse rotational direction, however a differential torque limit is provided by the angular difference in the opposing inclines which bound the valleys 76.
In Figure 9, the drive assembly 18 is illustrated. As discussed under Figure 7, the jack drive gear 68, sleeve 66 and pin 64 engage the top of the drive collar 54. The above are housed inside a;gear housing plate 92 which is threadably attached to a clutch gear housing 94. The gear teeth of the jack drive gear 68 mesh with the gear teeth of the jack drive pinion gear 88. The pinion gear 88 is received through the aperture in the top of the housing 92.
The clutch gear 72 is housed in the clutch gear housing 92 and drive gear housing 100 and is driven by a pinion gear 96 which is part of a motor drive gear 98. The upper portion of the drive gear 98 is received in a drive gear housing 100, which is threadably attached to the clutch gear housing 94 and the motor housing 24.
The drive gear 98 is driven by a motor drive shaft 102 of an elec-tric motor 104. The motor 104 is housed and threadably attached to the motor housing 24 with the shaft 102 extending downwardly therefrom into the drive gear housing 100. Also seen in Figure 9 is the coil spring 25 and pivot pin 20 which are received through apertures in the pivot supports 22 which are an integral part of the motor housing 24.
Changes may be made in the construction and arrangement of the parts or elements of the embodiments as disclosed herein without departing from the spirit or scope of the invention as defined in the following claims.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A clutch assembly including: a drive clutch gear having a flat surface extending perpendicularly to the rotational axis of the gear, the surface having at least a pair of radially extending valleys disposed at annularly spaced positions, the sides of the valleys being bevelled with the bevel of one side of the valleys disposed at a first angle and the bevel of the opposite side of the valleys disposed at a second angle differ-ent from the first angle to control the torques at which the clutch starts to slip when rotated in opposite directions; a drive plate having one side of the plate disposed adjacent the flat surface of the gear and at least a pair of apertures annularly spaced in accordance with the spacing of the valleys in the flat surface; a pair of balls disposed in the apertures of the drive plate and extending into the valleys in the flat surface of the gear; a disc spring disposed against the balls on the opposite side of the drive plate from the drive cluth gear and biasing the balls into the valleys in the flat surface of the gear; and a driven gear operatively coupled to the drive plate for rotation therewith, whereby below a predetermined drive torque in a given direction the drive plate and driven gear are rotated by engagement of the balls with the drive plate and above the predetermined torque the balls exit from the valleys to cause slippage of the drive clutch gear relative to the drive plate.