WO1990013506A1

WO1990013506A1 - Tire lift/carrier winch with self-locking gear train

Info

Publication number: WO1990013506A1
Application number: PCT/US1990/002423
Authority: WO
Inventors: Howard E. Chana
Original assignee: Sparton Corporation
Priority date: 1989-05-01
Filing date: 1990-05-01
Publication date: 1990-11-15

Abstract

An apparatus such as a tensioning device, winch, especially a tire/lift carrier winch, and the like includes a rotatable spool (20) on which a chain or cable (C) is wound to raise a load such as a tire carrier (TT) to a desired position, and a gear train (16, 18) that is self-locking to hold the load in the desired position at all angular positions of an input drive shaft (2) of the winch.

Description

TIRE LIFT/CAERIER WINCH

WITH SELF-LOCKING GEAR TRAIN Field Of The Invention

The present invention relates to apparatus such as tensioning devices, winches, especially tire lift/carrier winches, and the like and, more

particularly, to an improved self-locking gear train to be used with such apparatus to hold a load in a desired position; e.g., to hold a tire carrier in a desired stowed position on a vehicle. Background Of The Invention

In the development of spare tire storage winches or hoists for trucks, vans and possibly

automobiles, attempts have been made to insure that the spare tire carrier is held or locked in its stowed position on the vehicle during prolonged operation of the vehicle.

The Watanabe U.S. Patent 3,874,536 and the Denman U.S. Patent 4,544,136 employ a gear train of the known eccentric type for rotating a spool on which a chain or cable connected to the tire carrier (the load) is wound to raise the tire carrier to a stowed position usually beneath the vehicle and to lower the tire carrier if necessary to use the spare tire. These patents indicate that this type of eccentric gear train is self-locking in that, once the tire carrier is lifted to the stowed position, it will be held at that position and reverse movement of the load (i.e., release of the tire carrier as well as unwinding of the chain or cable) will be prohibited by reason of some unexplained locking action produced between the pinion gear (external gear) and ring gear (internal gear) of the gear train.

However, in actual practice, spare tire lift/carrier winches having such an eccentric gear train are known to unwind the chain or cable as well as release the load from the stowed position during use, especially during prolonged use under conditions of vibrations typically associated with vehicle use. In attempts to overcome the problem, prior art workers have resorted to the use of friction springs or other supplemental friction sources in the gear train to resist rotation of the gear train components in the unwinding direction during use on the vehicle. These attempts, although somewhat successful, increase the cost of the tire lift/carrier winch and reduce reliability of the winch as supplemental friction

(e.g., friction spring tension) can decrease with time and wear. The Iida U.S. Patent 4,059,197 describes a tire lift/carrier winch having a gear train of the eccentric type wherein the gear train is designed to produce a "pilgrim-step" motion that locks the tire carrier in position. However, this locking technique suffers from a severe limitation in that the load

(i.e., the tire carrier) must be held and located in its stowed position when the crank is located in a specific selected angular position where, at that crank position, the speed ratio of the gear train is zero or even very slightly negative. The speed ratio is defined as the output speed (of the ring gear) divided by the input speed (of the crank drive shaft).

Location of the crank at the desired aforementioned special angular position for tire stowage could be impossible or at least very difficult to insure for the many production installations of a vehicle spare tire stowage system because of the many tolerances, variable tire sizes, wheel shapes, etc. that have to be taken into consideration. Moreover, even if the crank is located at the desired angular position for obtaining the designed "pilgrim-step" motion, a small amount of unwinding could still occur and allow the tire carrier and chain or cable to fall or unwind to some extent as a result of vibrations and the like during travel of the vehicle. As a result, some slack may be present in the chain or cable and the tire carrier may not be located at the desired full height, stowed position. Slack in the chain or cable is to be avoided as it can lead to fatigue damage of the chain or cable as well as other winch components and shorten the useful life thereof.

It is an object of the invention to provide an improved apparatus such as a winch, especially a tire lift/carrier winch, having a gear train of the eccentric type wherein the gear train is self-locking to prevent unwinding of the chain or cable (hereafter collectively referred to as the cable) and release of the load (e.g., the tire carrier) from a desired position (e.g., the full height, stowed position on a vehicle).

It is another object of the invention to provide an improved apparatus having a gear train which is self-locking without the need for supplemental friction springs and the like. It is a further object of the invention to provide an improved apparatus having a gear train which is self-locking regardless of the angular position of the input drive shaft; i.e., the gear train is self- locking at all angular positions of the input drive shaft.

It is still a further object of the invention to provide a method of holding the load (e.g., a tire carrier) in a desired position (e.g., a full height, stowed position on a vehicle) using such a self-locking winch gear train.

Summary Of The Invention

The invention contemplates an apparatus such as a tensioning device, winch and the like having a spool rotatable about a rotational axis for winding a cable connected to a load to move (e.g., raise) the load to a desired position (e.g., a stowed position) and a gear train for rotating the spool. The gear train includes (a) an input drive shaft rotatable about the rotational axis of the spool, (b) a crank journal disposed on the drive shaft and having a selected journal radius and a center offset relative to the rotational axis of the spool so as to define a crank arm having a length equal to the distance between the rotational axis and the center of the crank journal, and (c) an external gear (e.g., a pinion gear) disposed in bearing relation on the crank journal and so

restrained against free rotation as to orbit about the rotational axis in mesh with an internal gear (e.g., a ring gear) that is operatively connected to the spool for rotation therewith. The winch is characterized by an improved gear or drive train having a ratio of the journal radius to the length of the crank arm so selected as to establish a torque between the crank journal and the internal gear (pinion gear) in a direction and of a magnitude effective to prevent unwinding of the cable and release of the load from the desired position, whereby the gear train is rendered self-locking at all angular positions of the input drive shaft.

To render the gear train self-locking for a particular apparatus, the ratio of the journal radius to the length of the crank arm is typically selected in accordance with the relationship / where E is

the journal radius, μ is the coefficient of friction between the crank journal and the external gear (pinion gear), D is the length of the crank arm and N is a locking factor for the given gear train. In one embodiment of the invention, N is equal to one (1). To insure gear train self-locking, N must be equal to or greater than one (1). Selection of the ratio of the journal radius to the length of the crank arm in accordance with this relationship will, in effect, provide a torque between the crank journal and the external gear (pinion gear) that at least counters, preferably is greater than, the torque that would be generated on the crank arm by the torque applied on the internal gear (ring gear) as a result of cable tension (i.e., by the load on the cable) such that the cable will not unwind and the load will not release from its desired position (e.g., the stowed position). Moreover, selection of the ratio of the journal radius to the length of the crank arm in this manner will insure that the gear train is self- locking at all angular positions of the input drive shaft of the winch.

A method aspect of the invention involves holding a load (e.g., a spare tire carrier) in a desired position (e.g., a stowed position) by providing the aforementioned ratio of the journal radius to the length of the crank arm to establish the required counter torque between the crank journal and the pinion gear of the winch to render the gear train self- locking. These and other objects and advantages of the invention will become more fully apparent from the following detailed description of the invention taken with the drawings described herebelow. Brief Description Of The Drawings

Figure 1 is an exploded perspective view of a tire lift/carrier winch to which the invention is applicable.

Figure 2 is a side elevation of the gear or drive train of the winch showing the crank journal, pinion gear, torque arm and ring gear. Figure 3 is a schematic representation of the gear train illustrating dimensions thereof involved in the invention.

Figure 4 is a schematic representation of the gear train illustrating forces thereon. Figure 5 is a graph illustrating how the locking factor changes with degrees of rotation of the input drive shaft of the gear train. Figures 6-10 are schematic illustrations of components of the gear train, such as the ring gear, pinion gear and attached torque arm, crank arm, and crank journal showing forces and torques acting

thereon. Fig. 7 is a simplified model of the torque arm and Fig. 10 is a more complex model thereof.

Detailed Description Of The Invention

Referring to Fig. 1, a tire lift/carrier winch W is shown including an input crank or drive shaft 2 rotatable about axis Y and an optional overload clutch 4 having a clutch drive plate 6 and a clutch driven plate 8 disposed adjacent the drive plate and having a plurality of clutch springs 10 thereon. The gear or drive train of the winch W includes the drive shaft 2, an eccentric crank cam 13, a torque arm 14 with a pinion drive gear 16 having external teeth 16b attached thereon, and an annular driven ring gear 18 having internal teeth 18b. The gear train drives a sheave or spool 20 in rotation about axis Y in one direction to wind cable C thereon and in a opposite direction to unwind cable C therefrom. The above- described winch components are disposed in operative side-by-side relation on the drive shaft 2 between the opposing housing plates 22,24 that are connected together by suitable means, such as rivets 26 to enclose the winch components. Each housing plate 22,24 includes rivet-receiving holes 22a, 24a to this end.

Each housing plate 22,24 includes respective coaxial apertures (only aperture 24b shown) to

rotatably receive the opposite ends of the drive shaft 2 in a manner known in the art. One end 2a of the drive shaft 2 extends outside the housing plate 22 when the winch components are assembled and includes a crank cross bore 2b by which the input drive shaft 2 can be rotated to lift or lower a vehicle tire carrier TT (shown schematically) connected to the free end 58a of the cable C, Fig. 1. The driven plate 8 of the overload clutch 4 includes a hub 8a extending axially toward the torque arm 14. The hub 8a receives and is keyed to the eccentric cam 13 (having diametral keys received in the hub keyways) for rotation therewith. The hub 8a and the cam 13 have coaxial centers or axes Z offset from the axis Y. The center or axis of the opening 13a in the cam 13 is coaxial with axis Y to receive the drive shaft 2. In this embodiment of the invention, the cam 13 and the hub 8a in which the cam is received form a crank journal 9 having a radius equal to the outer radius of hub 8a relative to center Z. As those skilled in the art will appreciate, the eccentric cam 13 can be disposed on the drive shaft 2 without

enclosure in the hub 8a; e.g., as shown in U.S. Patent 4,544,136. In this embodiment, the cam 13 itself would constitute a crank journal having a radius equal to the radius of the cam 13 relative to its center Z.

The torque arm 14 includes the pinion 16 fastened thereon by suitable means (e.g., bent tabs 14a) concentric to the centers or axes Z of the hub 8a and the cam 13. The torque arm also includes an opening 14b receiving the eccentric hub 8a and an extension 14c having an elongate slot 14d. The hub 8a is received in typical bearing fit or relation in the opening 14b in the torque arm 14 and in the

central opening 16a in the pinion gear 16 such that the hub 8a and torque arm/pinion gear are relatively movable at their interface. The elongate slot 14d receives the intermediate shaft portion 26a of one of the rivets 26 holding the housing plates 22, 24

together. The slotted extension 14c and intermediate shaft portion 26a (functioning as a pivot pin) cooperate to impart oscillatory motion to the torque arm 14 and to cause the pinion gear 16 to orbit

(reciprocably rotate) about the axis Y when the crank drive shaft 2 is rotated. When the drive shaft 2 is rotated, the drive plate 6 and the driven plate 8 rotate about axis Y with the hub 8a and the cam 13 rotating eccentrically about axis Y by virtue of their centers or axes Z being offset relative to axis Y.

The ring gear 18 includes a central opening 18a receiving the pinion gear 16 attached on the torque arm 14 and includes multiple inner teeth 18b that mesh with the outer teeth 16b of the pinion gear 16. In this illustration, the teeth 16b,18b are defined by inside and outside radii (which are different from one another) such that the teeth have a variable pressure angle as will be explained hereinbelow. The ring gear 18 includes side face 18c facing the side plate 50 of the spool 20. The side face 18c of the ring gear includes a plurality of integrally formed studs 18d extending parallel to one another and to the axis of rotation Y of the drive shaft 2. Each stud 18d is received in press fit in a respective coaxially aligned hole 50a formed in the side plate 50 in order to drive the sheave or spool 20 in rotation about axis Y.

The spool 20 includes the side plate 50, another side plate 51 spaced therefrom by a spool center plate 52 as well as a cable C disposed between the side plates 50, 51. The cable C includes the free end 58a adapted for connection to a load, such as the tire carrier TT, and a second end 58b having a cable end fitting 70 coupled thereon; e.g., crimped, die cast, molded or otherwise secured on or made integral with the end 58b. The end fitting 70 includes opposite transversely extending ears 74 (only one shown) that are rotatably received in an aperture 76 in each side plate 50, 51 to rotatably support the end fitting 70 adjacent and outboard of a flat exterior shoulder 68 on the center sheave plate 52 between the side plates 50, 51.

The spool or sheave side plates 50,51 and center plate 52 are joined together to form the spool 20 by three rivets 53 extending through aligned holes 50a,51a,52a in the respective sheave plates 50,51,52. Spool plates 50,51,52 include a respective central opening 50b, 51b,52b through which the drive shaft 2 extends. The spool plates 50,51,52 are in bearing relation on the drive shaft 2. A cable guide member 65 is disposed in the housing plates 22,24 when the winch components are assembled. In particular, the cable guide 65

includes a slot 65a aligned with a slot 24c in the bottom wall of the housing plate 24. The cable C extends through these slots outside the housing to the vehicle spare tire carrier TT, which, together with the spare tire thereon, constitutes the load to be raised or lowered by the winch. An anti-reverse pawl 67 is also provided in the winch construction and includes a forked arm 67a with a slot 67b. The forked arm overlies flat surface 65b on the guide member 65 such that the slot 67b straddles the slot 65a. The cable C passes through the slot 67b as it exits or enters the winch W through the aforementioned slots 24c, 65a. The pawl 67 also includes a pawl arm 67c which is adapted to engage the axially extending tabs 8c, 8d on the driven plate 8 to prevent excessive rotation of the spool 20 in the unwind direction (counterclockwise rotation) and to prevent rewinding of the spool 20 in the wrong direction as fully explained in U.S. Patent

4,535,973, the teachings of which are incorporated herein by reference. The winch W is typically attached to the bottom of a vehicle by attachment flanges 22c on the housing 22 and by suitable fasteners (not shown) extending through holes provided in the flanges 22c. The overload clutch 4 functions to permit rotation of the spool 20 upon rotation of the drive shaft 2 when the load on the spool 20 is within a maximum prescribed limit but to prevent rotation of the spool 20 in the event the load thereon exceeds the prescribed limit; e.g. in the event the cable C is subjected to an overload situation such as when upward movement of the tire lift/carrier is

obstructed for some reason or when the tire

lift/carrier is already at its final full height position. The clutch 4 is described in copending application entitled "Clutch For Tire Lift/Carrier Winch" (attorney docket number P-369 Sparton) of common assignee, the teachings of which are

incorporated herein by reference. As shown in Fig. 1 and Fig. 2, the spool 20 is connected to the ring gear 18 (i.e., the internal gear) such that both the ring gear 18 and the spool 20 rotate about axis Y. The input drive shaft 2 also rotates about the Y axis . As mentioned above, the crank journal 9 (formed of eccentric cam 13 and hub 8a) is disposed on the drive shaft 2 with its center or axis Z offset (displaced) relative to axis Y. The crank journal 9 and the pinion gear 16 (the external gear) are concentric relative to the center or axis Z. Internal and external in reference to the gears 16,18 refers to the surface (inside or outside) where the gear teeth are located. The crank journal 9 locates and forces the pinion gear 16 to orbit about axis Y in mesh with the ring gear 18 at a rotating location in line with the crank throw. However, the pinion gear 16 is

restrained from free rotary motion about the center or axis Z by the torque arm 14 which is itself restrained by the intermediate shaft portion 26a, Fig. 1, at point X. Other means to restrain the free rotation of the pinion gear 16 can be used, such as, the cross-slide linkage described in the Watanabe Patent 3,874,536 or the means shown in the Iida Patent 4,059,197. An arrangement like that shown in Figs. 1-2 will provide, for one complete revolution of the drive shaft 2, an angular rotation of the ring gear 18 of:

As mentioned hereinabove, the gear teeth 16b, 18b are of the type formed by different inside and outside radii; e.g., such as the gear shown in Fig. 2, although the invention is not so limited (e.g., involute gear teeth with a constant tooth pressure angle as well as other tooth configurations can be used). The gear teeth shown in Figs. 1-2 provide a tooth form that has a pressure angle therebetween varying between a maximum pressure angle and minimum pressure angle. The minimum pressure angle for the pinion gear 16 occurs where the inside and outside radii of a given tooth join each other and is shown as angle θ in Fig. 2. The minimum gear tooth pressure angle is used in the following analysis to insure that the gear train is self-locking in the context of this invention.

Fig. 3 is a schematic of the gear train shown in Fig. 2 with the important dimensions of the gear train labeled as follows: A = The pitch radius of the ring gear 18 B = The pitch radius of the pinion gear 16 C = Distance between drive shaft center (Y) and the center (X) of pinion gear pivot pin 26a

D = Crank arm (distance between shaft center

(Y) and center Z of pinion gear 16 and crank journal 9)

E = Outer radius of the crank journal 9

Φ = Angle of torque arm pivot guide slot 12d relative to main axis of pinion gear 16 and torque arm 14

Also shown in Fig. 3 is TR which is the torque directly applied to the ring gear 18 or the torque developed on the ring gear 18 by the cable hoist tension. The torque Tc on the crank arm D is also shown and is the torque that would have to be supplied to the crank arm D at axis Y to just balance the ring gear torque T_R if the gear train were 100% efficient. Designations X, Y and Z are the same as those labeled in Figs. 2-4.

In accordance with the invention, back-up or release of the tire carrier TT (load) from the desired full height, stowed position on the vehicle is

prevented when the friction torque Tf developed between the pinion gear 16 and the crank journal 9 is equal to or greater than the torque Tc described earlier on the crank arm D; i.e., Tf≥Tc. If torque Tf is equal or greater than torque Tc, the actual Tc torque on the crank arm D will be zero and the gear train will be self-locking. The ratio of the friction torque Tf developed at the crank journal 9 to the torque Tc (i.e.,

will be called the locking safety factor (S.F.). For a self-locking gear train, the locking factor (S.F) must be at least equal to 1 but preferably greater than 1 for all angular positions of the input drive shaft 2. If this locking factor (S.F.) calculates less that 1, the gear train will be gear reducing, non-locking drive train and require supplemental friction, such as a friction spring or the like, to retain the load in the stowed position. In order to compute the friction torque Tf, a value of the coefficient of friction (μ) between the crank journal 13 and the pinion gear 16 has been assumed. In the following analysis to generate Fig. 5, a value of .19 was assumed and is published as the coefficient of friction that exists for mild steel lubricated with Rape oil. For any particular gear train, the coefficient ( μ ) should be determined for the materials and lubricants being used. Moreover, in the following analysis, the gear train or tooth

efficiency is assumed to be 100%.

Fig. 4 illustrates the actual forces acting on the pinion gear 16 and torque arm 14 as follows: a = The tangential force on the pinion gear tooth a = T R/A

b = The radial force on the pinion gear tooth

L

d = The tangential force of the crank journal applied to the pinion gear 16

L

*

f = The radial force of the crank journal

applied to the pinion gear 16

e = The perpendicular force (to the slot 14d) that reaction pin 26a (or other retaining device) applies to the torque arm 14 α = The angular position of the crank journal

9 from the original starting position, α = 0 when the pivot pin center (X), the crank center (Y) and the crank journal center (Z) are in their straight line extended position (vertical centerline or axis V) γ = The resulting angle of the pinion gear and torque arm centerline to the vertical starting centerline V of the gear train for a given angle α

Tc = Torque on the crank journal 9

Bc c \

Tf = Friction torque between the crank journal 9 and pinion gear 16

*See Appendix A for derivation of these equations, which derivation involves the assumption that force e is always

horizontal to centerline V.

This general solution of Tf and Tc for all angles of α using the basic assumption that force e operates horizontally (i.e., perpendicular to vertical centerline or axis V of Figs. 2-4) was developed and is shown in Appendix A. The general equations for Tf and Tc are as follows:

& _f * fa *

/

The general equation for locking of the gear train under these conditions is as follows:

Gear train is self-locking if Tf≥Tc, thus

O

Resulting in the equation (I) for self-locking as follows:

Using this equation and a value of .19 for the

coefficient of friction between the crank journal and the pinion gear, a gear train that would be locking at all angular positions of the input drive shaft 2 was established and is plotted in Fig. 5.

Taking into account the angles γ and Φ greatly complicates the solution of the equations. Appendix B provides this more complex solution including angle γ as well as ∅ . The solution for self-locking of the gear train is shown in Appendix B and is as follows:

W

Care must also be taken in selecting angles for ∅, which can be between 0 and 180 degrees, since a band of angles in the middle of this range (0-180 degrees) may provide an inoperable functional situation which this equation may not easily identify.

It should be noted that the aforementioned solutions (e.g., equations I, II) for a self-locking gear train have some important similarities; that is: / U Y y (III)

Given that the number from under the square root sign will always be at least 1, if the quantity

is equal to or greater than 1, the gear train should always be self-locking when

(IV)

where E, μ and D are as defined above.

Thus, in accordance with the invention, the winch W is provided with a gear train that is self- locking regardless of the angular position of the input drive shaft 2 by selecting the ratio of the crank journal radius (E) to the length of the crank arm (D) in accordance with equation IV. In operation of the tire lift/carrier winch W including a gear train rendered self-locking in

accordance with the invention, the crank drive shaft 2 is rotated in a direction to wrap the cable C on the spool 20. Such rotation of the drive shaft 2 causes the pinion gear 16 to orbit about the axis Y in mesh with the ring gear 18 and thus to rotate the ring gear 18 and the spool 20 connected drivingly thereto about axis Y. When the tire carrier TT is raised to the desired full height, stowed position on the vehicle, the operator simply stops rotation of the crank drive shaft 2, usually indicated by the tire carrier TT abutting a stop (not shown) on the vehicle. As a result of the self-locking character of the gear train, the raised tire carrier TT will be held or retained in the full height, stowed position on the vehicle without unwinding of the cable C or release of the tire carrier TT from the stowed position during use. There thus is no need for a supplemental friction device in the gear train. Moreover, there is no slackening of the cable C as a result of any pilgrim-step motion of the gear train as could occur in U.S. Patent 4,059,197. The tire carrier TT may be readily lowered simply by rotating the crank drive shaft 2 in the opposite direction to unwind the cable C from the spool 20.

The invention thus provides a self-locking gear train for the winch W without complicating the operation of the winch W, i.e., operation of the winch W remains quite simple.

While certain preferred embodiments of the invention have been described above, those familiar with the art will recognize that various modifications and changes can be made therein for practicing the invention as defined by the following claims which are set forth after Appendix A and B.

APPENDIX A

Referring to Figs 2, 3 and 6:

θ = Pressure angle of gear teeth between ring

gear & pinion gear

T_R = Torque on ring gear

Tc = Torque on crank

α = Angular position of crank from starting

position where pivot journal 4 crank center are in straight line extended position

C = Shaft csnter to pivot pin distance

D = Crank radius (throw)

E = Crank journal radius

A = Pitch Radius of ring gear

B = Pitch Radius of pinion gear

a = Tangential force on tooth

b = Radial force on tooth

Forces on ring gear 18:

A·a=

tan θ =

h = a tan θ

b = tan θ

APPENDIX A (cont)(2)

Forces on pinion gear 15 and crank:

Referring to Fig 7

d = Tangential force on crank

cos α =

= C cos α

®+0-C cosα+0

sin α

= C sinα

+B)a=0 (moments about X)

0 = f.C sinα-b·C sinα-d(Ccosα+D)+a(Ccosα+D+B) 0 = f·C sinα-b·C sinα-d·C cosα-d-D+a·C cosα+a·D+a·B

Assume force e always operates in a horizontal plane

∑Fy =

0=f· coα+d·sinα-a·sinα-b·cosα (forces about Y)

= f·Ccosα+d·C sinα-a·C sinα-b·C cosα

® o ^{i 2} 2

M ^c

4 t

APPENDIX A (c ont)(3)

Pinion gear (continued)

Sub d

0 = f cosα+

sinα-a sinα-b cosα f cosα = b

W N

/ K

Torque on crank:

Referring to Fig.6-8,

Tc = dD

Referring to Figs.8 and 9,

d & f equivalent vector =√ d² +f²

d & f are at 90º to each other

Vector add d & f √d²+f²

μ = Friction at journal bearing

Tf - Resistance torque developed at crank journal

* f j T

α ^{v u}

Gear train is self locking if Tc≤Tf ( 4)

APPENDIX B

Referring to Figs 2, 3 and 6

Forces on ring gear 18:

b = tan θ

₃

d = Tangential force on crank

cosα =

= C cosα

=

C cosα +D =

1 +D

sinα

= C sin α

Fx of e =e·cos(γ+Φ)

Fy of e =e·sin(γ+Φ)

= D sinα

5 = D cosα

Fx of e=e(cosγ cosΦ-sinγ sinΦ)

Fy of e=e(sinγ cosΦ+cosγsinΦ)

Fx of O

;

Fy of e e

Let G

k

Let M

C

Fx of e=e(G-H)

Fy of e=e(M+P)

∑Mx = 0=f·C sinα-d(Ccosα+D)-b-C sind+a(Ccosα+D+B)

U : c

± | 7

re

Claims

I CLAIM:

1. In an apparatus having a spool rotatable about an axis for winding a cable connected to a load to move the load to a desired position and having a gear train for rotating the spool wherein the gear train includes (a) a drive shaft rotatable about said axis, (b) a crank journal disposed on the drive shaft and having a selected journal radius and a center offset relative to said axis so as to define a crank arm having a length between said axis and said center and (c) an external gear disposed on the crank journal and so restrained against free rotation as to orbit about said axis in mesh with an internal gear that is operatively connected to said spool for rotation therewith, the improvement comprising said gear train having a ratio of said journal radius to said length of said crank arm so selected as to establish a torque between the crank journal and the external gear in a direction and of a magnitude effective to prevent unwinding of the cable and release of the load from the desired position, whereby the gear train is rendered self-locking.

2. The winch of claim 1 wherein the ratio of the journal radius to the length of the crank arm is selected in accordance with the relationship:

where E is the journal radius, μ is a coefficient of friction between the crank journal and the external gear, D is the length of the crank arm and N is a locking factor for a given gear train to prevent unwinding of said cable and release of said load from the desired position.

3. The winch of claim 2 wherein said

relationship is .

4. The winch of claim 2 or 3 wherein the external gear and internal gear include teeth having a variable pressure angle therebetween that varies between a maximum pressure angle and a minimum pressure angle and wherein said relationship is based on said minimum pressure angle.

5. In a winch for a vehicle for winding a cable connected to a spare tire carrier on a spool that is rotatable about an axis, wherein a torque is exerted by the spare tire carrier in a direction attempting to unwind the cable from the spool and release the spare tire carrier from a desired stowed position, improved means for driving the spool in rotation to wind the cable thereon comprising: (a) a drive shaft rotatable about said axis,

(b) a crank journal disposed on the drive shaft for rotation therewith, said crank journal having a center offset relative to said axis so as to define a crank arm having a length equal to the distance between said center and said axis and having a selected journal radius relative to said center,

(c) a pinion gear so disposed on the crank journal that said crank journal and pinion gear are relatively movable,

(d) a ring gear in mesh with the pinion gear and rotatable about said axis, said ring gear being cooperatively connected to said spool for rotation therewith, (e) means for so restraining movement of the pinion gear as said drive shaft is rotated about said axis that said pinion gear orbits about said axis in mesh with the ring gear to drive said ring gear and said spool in rotation,

(f) said means for driving the spool in rotation having a ratio of the radius of said crank journal to the length of said crank arm so selected as to establish a counter torque between the pinion gear and the crank journal in a direction opposite to said torque and of a magnitude effective to substantially prevent unwinding of said cable and release of the spare tire carrier from said desired stowed position, regardless of the angular position of said drive shaft.

6. The winch of claim 5 wherein the ratio of the journal radius to the length of the crank arm is selected in accordance with the relationship:

where E is the journal radius, μ is a coefficient of friction between the crank journal and the pinion gear, D is the length of the crank arm and N is a locking factor for a given gear train to prevent unwinding of said cable and release of said spare tire carrier from the desired position.

7. The winch of claim 6 wherein said

relationship is .

8. The winch of claim 6 or 7 wherein the pinion gear and the ring gear include teeth having a variable pressure angle therebetween that varies between a maximum pressure angle and a minimum pressure angle and wherein said relationship is based on said minimum pressure angle.

9. The winch of claim 5 wherein said means for restraining movement of the pinion gear comprises a torque arm having an end portion fastened to said pinion gear for movement therewith and having another end portion restricted in motion.

10. In a method of holding in a desired position a load connected to a cable wound on a spool wherein the spool is driven in cable-winding rotation about an axis using a gear train that includes a drive shaft rotatable about said axis, a crank journal disposed on the drive shaft and having a selected journal radius and a center offset relative to said axis so as to define a crank arm having a length between said axis and said center, and a pinion gear disposed on the crank journal and so restrained against free rotation as to orbit about said axis in mesh with a ring gear that is operatively connected to said spool for rotation therewith, the improvement comprising providing a ratio of the journal radius to the length of the crank arm effective to establish a torque between the crank journal and the pinion gear in a direction and of a magnitude effective to prevent unwinding of the cable and release of the load from said desired position.

11. The method of claim 10 including

providing the ratio of the journal radius to the length of the crank arm in accordance with the relationship:

where E is the journal radius, μ is a coefficient of friction between the crank journal and the pinion gear, D is the length of the crank arm and N is a locking factor for a given gear train to prevent unwinding of said cable and release of said load from the desired position.

12. The method of claim 11 including

13. The method of claim 12 including

providing teeth on the pinion gear and ring gear having a variable pressure angle and basing said relationship on a minimum pressure angle between said teeth.

14. In a method of holding in a desired stowed position on a vehicle a spare tire carrier connected to a cable wound on a spool wherein the spool is driven in cable-winding rotation about an axis using a gear train including a drive shaft rotatable about said axis, a crank journal disposed on the drive shaft and having a selected journal radius and a center offset relative to said axis so as to define a crank arm having a length between said axis and said center, and a pinion gear disposed on the crank journal and so restrained against rotation as to orbit about said axis in mesh with a ring gear that is operatively connected to said spool for rotation therewith, the improvement comprising providing a ratio of the journal radius to the length of the crank arm effective to establish a torque between the crank journal and the pinion gear in a direction and of a magnitude effective to prevent unwinding of the cable and release of the spare tire carrier from said stowed position, regardless of the angular position of said drive shaft.

15. The method of claim 14 including

16. The method of claim 15 including

17. The method of claim 16 including

18. In an apparatus having a spool rotatable about an axis for winding a cable connected to a load to move the load to a desired position and having a gear train for rotating the spool wherein the gear train includes (a) a drive shaft rotatable about said axis, (b) a crank journal disposed on the drive shaft and having a selected journal radius and a center offset relative to said axis so as to define a crank arm having a length between said axis and said center and (c) an external gear disposed on the crank journal and so restrained against free rotation as to orbit about said axis in mesh with an internal gear that is operatively connected to said spool for rotation therewith, the improvement comprising said gear train having a ratio of said journal radius to said length of said crank arm selected in accordance with the

relationship to provide a self-locking gear

tram or m accordance with the relationship / to

provide a gear reducing drive train where E is the journal radius, μ is a coefficient of friction between the crank journal and the pinion gear, D is the length of the crank arm, and N is a locking factor for a given gear train to prevent unwinding of said cable and release of said load from the desired position.