CA1263266A - Remote control apparatus - Google Patents

Abstract

ABSTRACT

Apparatus enabling a vehicle operator to remotely control the positioning of an object, such as a rear view mirror, pivotally mounted on the exterior of the vehicle.
The apparatus includes a support member for the object to be positioned, a base member attached to the vehicle exterior and a ball and socket joint connecting the support member so the base member. There are a pair of linkages, each includ-ing a helical spring extending between the base member and the support member. Each linkage is actuable to pivot the support member about a respective one of two mutually trans-verse pivotal axes. Each linkage is driven by a reversible motor operated by a four position switch inside the vehicle.

Description

2~i REMO'rE CONTROL APPA:RATUS

BACKGROUND OF THE INVENTION
The present invention relates generally to remote control apparatuses and more particularly to an apparatus which enables the operator of a vehicle to remotely control the positioning of an object~ such as a rear view mirror or a spotlight, mounted on the exterior of the vehicle.
In a typical remote control apparatu~ of the gen-eral type to which the present invention relates, the object to be remotely controlled, such as a rear view mirror, is mounted on a support member which in turn is pivotally mount-ed~ as by a ball and socket arrangement, on a base member or housing which in turn is mounted on either the left side or right side of the vehicle (typically an automobile or truck).
The mirror support member is mounted for pivotal movement, relative to the base member, about a pair of mutually trans-verse pivotal axes, e.g., a vertical axis and a horizontal axis.
Extending between the base member and the support member are a pair of linkages each comprising structure actu-able to pivot the support member about a respective one of its two pivotal axes. Eack linkage is connected to the sup-port member at a position radially spaced from the main pivot point of the support member, and each connection between a linkage an~ the ~upport member is angularly spaced 90 from the other connection.
Mounted on the base member are a pair of reversible driving motors each for actuating one of the linkages. The driving motors are controlled by a single four-position switch accessible to the vehicle operator. This switch may ~2~3~

be moved back and forth in a first pair of opposed directions to pivot the support member about one of its pivotal axes, and the switch may be moved back and forth in a second pair of opposed directions, transverse to the first pair, to pivot the support member about the other of it~ pivotal axes.
The connection between each linkage and the support member must accommodate pivotal movement of the support mem-ber about both of its mutually transverse pivotal axes. In the prior art this has been accomplished by providing a ball and socket joint at each connection between a linkage and the support member. Typically, the linkage included an ex-ternally threaded member connected to a ball and socket joint at the support member and driven by an internally threaded member in turn driven by a gear train connected to a motor.
All of the linkage described in the preceding sentence was mounted on the base member, and the resulting package was relatively large. Moreoverl it was relatively expensive to use a ball and socket joint for connecting each of the link-ages to the support member. In addition, the it of the ball within the socket necessarily was not too tight, and there was play between the ball and the socket. As a result, during movement of the vehicle along a highway, for example, the support member and attached mirror vibrated relative to the base member.
A remote control apparatus of the type described above is disclosed in Kurz, UOS. Patent No. 3,609,014 issued September 28, 1971 and entitled "~lectric Remote Control Rear View Mirrorn.

~2~i3~6 SUI~ RY OF THE INVENTION
The drawbacks and deficiencie~ of prior art apparatuses of the type described above are eliminate-3 by a remote control apparatus in accordance with the present in-vention.
The linkage oE the present invention employs a helical ~pring extending between the base member and the support member. This helical spring has a longitudinal axis and a terminal end engaging the support member. The helical spring is mounted for axial movement relative to the base member to pivot the support member about one of its pivotal axes~ Because the helical spring is resilient, it bends elastically in response to pivotal movement of the support member about either of its pivotal axes, thereby accommodat-ing the pivotal movement of the support member.
The mechanical structure which moves the helical spring in an axial direction comprises a bushing element having an axis of rotation corresponding to the axis of the helical spring and an internal axial opening within which the helical sprina extends. The bushing element is seated on the base member and mounted thereon for rotation about its axis. There is an externally threaded member (e~g., a set screw) having an axis parallel to ~he axis of the helical spring and mounted on the bushing element so that the exter-nally threaded member revolves abou~ the axis of the bushing element in response to axial rotation of the bushing element.
The helical spring has a plurality of laps defining external threading around the periphery of the helical spring.
The externally threaded member extends into the internal axial openinq of the bushing element to engage the external threading on the helical spring to move the helical spring ~263Z66 axially in r~sponse to revolving movement by the externally ~hreaded member.
The present invention eliminates the relatively expensive ball and socket joint utilized with each of the two linkages by the prior art and~ instead, employs helical springs and set screws which are shelf items and are rela-tively inexpensive.
Another advantage o the present invention i5 that the helical spring acts as a vibration dampener to reduce vibration by the support member relative to the base member.
Other features and advantages are inherent in the structure claimed and disclosed or will become apparent to those skilled in the art from the following detailed descrip-tion in conjunction with the accompanying diagrammatic draw-ings.

BRIEF DESCRIPTION OF THE D~AWINGS
Fig. 1 is a plan view of a remote control apparatus in accordance with an embodiment of the present invention, with the support member removed;
Fig. 2 is a slde elevational view taken along line 2--2 in Fig. 1 and with the support member in place;
Fig. 3 is a sectional view taken along line 3--3 in Fig. 1 and with the support member in place;
Fig. 4 is a sectional view taken along line 4--4 in Fig. 1 and with the support member in place;
Fig. 5 is a bottom view of the apparatus;
Fig. 6 is a fragmentary, sectional view of the apparatus showing the suppor~ member pivoted along one axis in a first sense;

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Fig. 7 is a fragmentary, sectional view, similar to Fig. 6, showing the support member pivoted along the one axis in a second sense, opposite the first sense;
Fig. 8 is a fragmentary, sectional view of the linkage employed in the apparatus; and Fig. 9 is an exploded perspective of the linkage.

DETAILED DESCRIPTION
Referring initially to Figs. 1-5, there is illus-trated an embodiment of a remote control apparatus in accor-dance with the present invention and comprising a base member or housing having Eirst and second housing portions 21, 22 respectively. The two housing portions are detachably con-nected with conventional fasteners such as screws ~not shown) Integral with first housing portion 21 is a socket 23 within which is rotatably mounted a ball 24 secured by a screw 25 to a second or support member 26 in turn supporting a mirror 27. The housing is mounted in a conventional manner on the side of an automobile or similar vehicle, employing conventional mounting structure (not shown). When so mount-ed on the side of a vehicle, support member 26 and mirror 27 would be in a vertical disposition rather than in the hori-zontal disposition shown in the drawings as a matter of con-venience of illustration~
Extending in opposite directions from ball 24 are a pair of pins 28, 28 each rotatably and tiltably received in a respective slot 29, 29 on socket 23. Ball and socket joint 23, 24 and the pins 28, 28 and slots 29, 29 mount sup-port member 26 for pi~otal movement, relative to housing 21, 22, about a pair of mutually transverse pivotal axes 50, 51 (Figs. 3 and 4). Pivotal axis 50 corresponds to ~2~;3~

the axis of pins 28, 28, and ~ivotal axis 51 is perpendicular to axis 50.
Support member 26 is caused to pivot about the two pivotal axes 50, 51 by a pair of linkages 30, 30 each spaced radially ~rom ball and socket joint 23, 24 and angularly s~aced from each other by an angle of 90~ Referring to Figs. 3-4 and 8-9, each linkage 30 comprises a helical spring 31 extending between housing 21, 22 and support member 260 The two helical springs extend through respective opening5 47, 48 in the housing. Each helical spring 31 has a longitudinal axis and an outer terminal end 32 fixedly secured to support member 26 (Fig. 3), as by pressing.
Axial movement of helical spring 31 causes support member 26 to be pivoted about one of its pivotal axes, and structure which mounts helical spring 31 for axial movement will now be described.
Indicated at 34 is a bushing element having an exterior 35 and an internal axial opening 36 within which helical spring 31 extends. Housing portion 22 includes a stepped part 37 on which is seated a correspondingly stepped part 38 on bushing element 34. Bushing element 34 has an axis of rotation corresponding to the axis of helical spring 31, and the seating of the bushing element's stepped part 38 on stepped part 37 of housing portion 22 mounts bush-ing element 34 for rotation about this axis.
Bushing element 34 has a radially extending slot 39 having an inner open end at the bushing element's internal axial opening 36 and an outer end at the bushing element's exterior 35. Receivea within radial slot 39 is an externally threaded member or set screw 40 having an axis parallel to the axis of helical sPring 31. Disposed around the outside ~326~

of bushing element 34 at slot 39 is a springable, split-ring retainer 41 which retains set screw 40 in slot 39. Retainer ring 41 is composed of springable or resilient material.
The structure described in the preceding portion of this paragraph mounts set screw 40 for revolving movement about the axis of bushing element 34 in response to rotation of the bushing element about its axisL
Helical spring 31 has a plurality of laps 33, 33 defining external threading around the periphery of the heli-cal spring. Retainer 41 normally urges set screw 40 radially inwardly in slot 39 so that the threads on set screw 40 nor-mally engage the external threading 33 on helical spring 31.
~he pitch on the threads of set screw 40 is opposite to the pitch on the external threading 33 o helical spring 31.
Revolving movement of set screw 40 about ~he axis of bushing element 34, while the threads on set screw 40 are engaged with external threadinq 33 on helical spring 31, causes axial movement by the helical spring~
Integral with exterior 35 of bushing element 34 is a worm gear 43 driven by a worm 44 mounted on the shaft 45 of a reversible electric motor 46. Bushing element 34 is thus rotated by actuating electric motor 46. As noted above, the rotation of bushing element 34 causes set screw 40 to revolve about the axis of the bushing element, in turn moving helical spring 31 axially out of or into internal axial opening 36 of bushing element 34. Axial movement of helical spring 31 in turn causes pivotal movement of support member 26 abou~ one of its pivotal axes.
Helical spring 31 moves axially out of or into the bushing element's internal axial opening 36 depending upon the sense in which set screw 40 xevolves about the axis of ~2~ 6 bushing element 34. The bushing element is mounted for rota-tion on the stepped part 37 of housing portion 22 in both clockwise and counterclockwise senses. Similarly, set screw 40 is mounted for revolving movement about the axis of bushing element 34, in either a clockwise or a counterclock-wise sense, depending upon the sense in which bushing ele-ment 34 is rotated. More specifically, rotation o~ bushing element 34 in a clockwise sense about its axis causes set screw 40 to revolve about the axis of bushing element 34 in a clockwise sense, and rotation o~ bushing element 34 in a counterclockwise sense causes set screw 40 to revolve in a counterclockwise sense.
As noted above, support member 26 is mounted by ball and socket 23, 24 for pivotal movement about a pair of mutually transverse pivotal axes 50, 51. Axial movement of the helical spring 31 illustrated in Fig. 3 causes support member 26 to pivot about axis 50 (Fig. 4), while axial move-ment of the helical spring 31 shown in Fig. 4 causes support member 26 to pivot about the axis 51 (Fig. 3).
Each helical spring 31 is composed of resilient material, such as spring steel, which permits elastic bending of the helical spring in response to pivotal movement of support member 26 about either of its pivotal axes 50, 51.
When support member 26 pivots about pivotal axis 50, in response to axial movement by the helical spring 31 shown in Fig. 3, that helical spring bends in a plane perpendicular to pivotal axis 50. On the other hand, when support member 26 is pivoted about its other axis 51, in response to axial movement of the helical spring 31 illustrated in Fig. 4, the helical spring 31 illustrated in Fig. 3 bends in ~3~

a plane parallel to pivotal axis 50 (but perpendicular to pivotal axis 51).
A similar bending movement occurs on the part of the helical spring 31 illustrated in Fig. 4. More particu-larly, when support member 26 is pivoted about its other pivotal axis 51, in response to axial movement of the helisal spring 31 illustrated in Fig. 4, that helical spring bends in a plane perpendicular to pivotal axis 51. On the other hand, when support member 26 is pivoted about pivotal axis 50, in response to axial movement of the helical spring 31 illustrated in Fig. 3, the helical spring 31 illustrated in Fig. 4 bends in a plane perpendicular to axis 50 but parallel to axis 51.
(In the above description, where the helical spring is described as bending in a plane, it is cnly the axis or center line o~ the helical spring which bends in a true geo-metric plane. The helical spring is, of course, three dimen-sional and is thus not capable of literally bending in a true geometric plane but, rather, bends in a multiplicity of planes parallel to the plane in which the helical spring's axis or center line bends.) Radial slot 39 has a width, measured in a direction transverse to the axis of externally threaded member 40, which tapers from the outer open end of the slot to the inner open end of the slot. Slot 39 is wider than the diameter of set screw 40l at the outer open end of the slot~ to permit insertion o set screw 40 into slot 39. The slot is narrower than the diameter of set screw 40, at the inner open end of the slot, to prevent set screw 40 from falling into internal axial opening 36 of bushing element 34. Split retainer ring 41 engages that portion of set screw 40 which is 32~6 radially outer~ost in slot 39, and normally urges set screw 40 radially inwardly in slot 39 toward internal axial opening 36 in bushing element 34.
Slot 39 mounts set screw 40 for movement within the slot in a radial direction relative to the bus'ning element, and retainer ring 41 normally urges the set screw radially inwardly in slot 39 for engagement with the external threading 33 on helical spring 31.
The arrangement described in the precediny para-graph accommodates manual adjustment of support member 26,which may be performed when driving motors 46, 46 and their associated linkages are not operating.
More particularly, support member 26 may be manually grasped and manipulated to pivot about one or both of its pivotal axes. When this occurs, the helical spring 31 which normally moves axially to pivot the support member, during remote controlled operation, i9 itself urged, by the manually pivoted support member, to move axially within internal axial opening 36 of bushing element 34. As noted above, the exter-nal threads on set screw 40 are normally urged by retainerring 41 into engagement with the external threading 33 on helical spriny 31, and this would normally impede axial move-ment of helical spring 31 in the absence of revolving move-ment by the set screw. Nevertheless, axial movement of helical spring 31 urges the non-revolving set screw out-wardly in radial slot 39 against the urging of split retainer ring 41, and because ring 41 is a resilient member, it yields and permits set screw 40 to move radially outwardly. This removes any impediment to axial movement by helical spring 41 in the absence of revolving movement hy the set screw 40, thereby accommodating manual adjustment of support member 26.

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The yieldable nature of retainer ring 41 also accom-modates a situation in which (a) helical spring 31 is restrained against axial movement (e.g., when the apparatus includes stop ~eans for restraining such movement beyond a predetermined limit) and (b) set screw 40 is revolving about the helical spring. In such a situation, opposite forces are acting against the llelical spring. However, the yield-able nature of retainer ring 41 permits set screw 40 to move radially outwardly in slot 39, thereby at least partially removin~ one of the opposing forces acting against the helical spring.
When a helical spring 31 is restrained against further axial movement, but its corresponding set screw 40 is still undergoing revolving movement about the axis of helical spring 31, there is an increase in torque experienced by the motor 46 driving that set screw. Preferably, motor 46 is provided with a torque-responsive device which stops the motor when this occurs.
As shown in Figs. 3, 6 and 7, located at the rear surface S6 of support member 26 are a pair of stops 52, 53 for limiting pivotal movement of the support member about axis 50 of ball and socket joint 23, 24 (Fig. 4). Similarly, as shown in Fig. 4, also located on rear surface 56 of support member 26 are another pair o stops 54, 55 for restricting pivotal movement of the support member about axis 51 of the ball and socket joint (Fig. 3). Typically, pivotal movement is limited to about 12 about each axis 50, 51 so as to define a pivotal cone of about 12 for the ~all and socket joint and support member 26~ Each of the stops 52, 53 or 54, 55 abuts against an adjacent surface 2~i of first housing portion 21 to limit pivotal movement of support member 26.
Referring to Figs. 6 and 7, when stop 53 abuts against first housing portion 21, this prevents further move-ment of the helical spring 31 shown in those figures in an axially outward direction relative to the corresponding bush-ing element 3~. Similarly, when stop 52 abuts against first housing portion 21, this limits further move~ent of the heli-cal spring 31 shown in those figures in an axially inward direc~ion relative to its bushing element 34.
Similar restraints against axial movement occur with respect to the helical spring 31 shown in Fig. 4 when the stops 54, 55 abut against first housing portion 21. More particularly, when stop 55 abuts against first housing portion 21, this restrains further inward axial movement of the helical spring 31 shown in Fig. 4, and when stop 54 abuts against first housing portion 21, this restrains further outward axial movesnent of the helical spring 31 shown in Fig. 4. The helical spring 31 shown in Fig. 4 is angularly spaced 90 from the helical spring 31 shown in Fig. 3.
Helical springs 31, 31, set screws 40, 40 and re-tainer rings 41, 41 are shelf items which are readily avail-able commercially and substantially reduce the cost of the linkages 30, 30 of an apparatus in accordance with the present invention, compared to an apparatus employing ball and socket joints at the same locations.
As previously noted~ housing 21, 22 is rigidly mounted by conventional structure on the side of a vehicle such as an automobile which is driven across a highway and the like. If ther~ is vibration by support member 26 and mirror 27, relative to the housing and vehicle, while the ~3~

vehicle is being driven, the vibration will interfere with the proper functioning of the mirror. Helical springs 31, 31 function as vibration dampeners which substantially reduce vibration on the part of support member 26 relative to hous-ing 21, 22.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

Claims (27)

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

1. In a remote control apparatus comprising a base member, a second member, means mounting said second member for pivotal movement, relative to said base member, about a pair of mutually transverse pivotal axes, and a pair of linkages between said base member and said second member, each of said linkages comprising means actuable to pivot said second member about a respective one of said pivotal axes, the improvement wherein at least one of said linkages comprises:
a helical spring, extending between said base member and said second member, transverse to said pivotal axes;
said helical spring having a longitudinal axis and a terminal end for engagement with said second member;
said helical spring having a substantially uniform diameter along its entire length between said base member and said second member;
and means mounting said helical spring for axial movement relative to said base member to pivot said second member about one of its pivotal axes;
said terminal end of the helical spring being directly connected to its second member without an intervening mechanical linkage to accommodate the pivotal movement of the second member;
said helical spring comprising resilient means for permitting elastic bending of said helical spring in response to pivotal movement of said second member about either of its pivotal axes;

the elastic bending properties of the helical spring constituting substantially the sole provision for accommodating said pivotal movement of the second member.

2. In a remote control apparatus as recited in claim 1 wherein:
said resilient means of the helical spring comprises means for permitting the helical spring to bend in a first plane, perpendicular to said one pivotal axis of the second member, in response to pivotal movement of the second member about said one pivotal axis.

3. In a remote control apparatus as recited in claim 2 wherein:
said resilient means of the helical spring comprises means for permitting the helical spring to bend in a second plane, parallel to said one pivotal axis, in response to pivotal movement of the second member about the other of its pivotal axes.

4. In a remote control apparatus as recited in claim 1 wherein:
said resilient means of the helical spring comprises means for permitting the helical spring to bend in a plane, parallel to said one pivotal axis, in response to pivotal movement of the second member about the other of its pivotal axes.

5. In a remote control apparatus as recited in claim 1 wherein the other of said linkages comprises:

a second helical spring extending between said base member and said support member;
said second helical spring having a longitudinal axis and a terminal end for engagement with said second member;
and means mounting said second helical spring for axial movement relative to said base member to pivot said second member about the other of its pivotal axes;
said second helical spring comprises resilient means for permitting elastic bending of said helical spring in response to pivotal movement of said second member about either of its pivotal axes.

6. In a remote control apparatus as recited in claim 5 wherein said resilient means for the two helical springs comprises:
means permitting one of said helical springs to bend in one plane and the other of said helical springs to bend in another plane, transverse to said one plane, in response to pivotal movement of the second member about at least one of its pivotal axes.

7. In a remote control apparatus as recited in claim 1 wherein said means mounting said helical spring for axial movement comprises:
a bushing element having an exterior, an axis of rotation corresponding to the axis of said helical spring and an internal axial opening within which said helical spring extends;
means on said base member for seating said bushing element and mounting said bushing element for rotation about its axis;

an eternally threaded member having an axis parallel to the axis of said helical spring;
means mounting said externally threaded member for revolving movement about the axis of said bushing element in response to axial rotation of said bushing element;
said helical spring having a plurality of lap means defining external threading around the periphery of the helical spring;
and means on said externally threaded member for threadedly engaging said external threading on said helical spring to move the helical spring axially in response to said revolving movement of the externally threaded member.

8. In a remote control apparatus as recited in claim 7 wherein:
said mounting means for said bushing element comprises means mounting the bushing element for rotation in both clockwise and counterclockwise senses;
and said mounting means for the externally threaded member comprises means mounting the externally threaded member for said revolving movement about the axis of the bushing element, in either a clockwise or a counterclockwise sense, in response to a corresponding rotation by the bushing element.

9. In a remote control apparatus as recited in claim 8 and comprising:
worm gear means on the exterior of said bushing element;
reversible motor means;

and worm means, coupled to said reversible motor means, for engaging said worm gear means.

10. In a remote control apparatus as recited in claim 7 wherein:
said externally threaded member is separate and discrete from said bushing element and non-integral therewith;
and said mounting means on the externally threaded member comprises a radially extending slot in said bushing element;
said slot defining an opening in the exterior of said bushing element;
said slot comprising means for receiving said externally threaded member therein.

11. In a remote control apparatus as recited in claim 10 wherein:
said slot comprises means for removably receiving said externally threaded member;
and said linkage comprises means, located at the exterior of said bushing element, normally urging said externally threaded member radially inwardly in said slot for engagement with said external threading on said helical spring.

12. In a remote control apparatus as recited in claim 11 wherein:
said urging means comprises springable, split-ring retainer means disposed around the outside of said bushing element at said slot.

13. In a remote control apparatus as recited in claim 10 wherein:
said slot extends radially between said internal axial opening and said exterior of the bushing element;
said slot having an inner open end at said internal axial opening and an outer open end at the exterior of the bushing element;
said slot having a width, measured in a direction transverse to the axis of said threaded member, which tapers from said outer end to said inner end of the slot;
said slot being wider than the diameter of the externally threaded member, at the outer open end of the slot, to permit insertion of the threaded member into said slot;
said slot being narrower than the diameter of the externally threaded member, at the inner end of the slot, to prevent the externally threaded member from falling into the internal axial opening of the bushing element.

14. In a remote control apparatus as recited in claim 10 wherein:
said slot comprises means mounting said externally threaded member for movement within said slot in a radial direction relative to said bushing element;
and said linkage comprises means, located at the exterior of said bushing element, normally urging said externally threaded member radially inwardly in said slot for engagement with said external threading on said helical spring.

15. In a remote control apparatus as recited in claim 14 wherein:
said urging means comprises means for permitting said externally threaded member to move radially outwardly in said slot in response to axial movement by said helical spring in the absence of revolving movement by the externally threaded member.

16. In a remote control apparatus as recited in claim 14 wherein:
said apparatus comprises means for restraining said helical spring against movement in an axial direction beyond a predetermined limit;
said urging means comprises means for permitting said externally threaded member to move radially outwardly in said slot when said helical spring is restrained against further axial movement and said externally threaded member is revolving about the mutual axis of the bushing element and the helical spring.

17. In a remote control apparatus as recited in claim 16 wherein:
said urging means, comprises means for permitting said externally threaded member to move radially outwardly in said slot in response to axial movement by said helical spring in the absence of revolving movement by the externally threaded member.

18. In a remote control apparatus as recited in claim 17 wherein:

said urging means is a yieldable member engaging that portion of said externally threaded member which is radially outermost in said slot.

19. In a remote control apparatus as recited in claim 10 wherein:
said externally threaded element is a cylindrical element.

20. In a remote control apparatus as recited in claim 1 wherein:
said helical spring comprises means for dampening vibration by said base member relative to said second member.

21. A bushing assembly comprising:
a bushing element having an axis of rotation and comprising an exterior and an internal axial opening;
a radial slot extending between said internal axial opening and said exterior and defining an opening in said exterior;
an externally threaded member having an axis parallel to the axis of said bushing and received within said radial slot;
said externally threaded member being separate and discrete from said bushing element and non-integral therewith;
means, comprising said radial slot, mounting said externally threaded member for revolving movement about the axis of said bushing element in response to axial rotation of said bushing element;
and means, located at the exterior of said bushing element, normally urging said externally threaded member radially inwardly in said slot toward said internal axial opening in the bushing element.

22. The bushing assembly of claim 21 and further comprising:
a helical spring having a longitudinal axis and received within said internal axial opening in said bushing element.

23. The bushing assembly of claim 22 wherein:
said helical spring has a plurality of lap means defining external threading around the periphery of the helical spring;
and said externally threaded member comprises means normally threadedly engaging said external threading on said helical spring.

24. The bushing assembly of claim 21 and comprising:
worm gear means around said exterior of the bushing means.

25. The bushing assembly as recited in claim 21 wherein:
said urging means comprises springable, split-ring retainer means disposed around the outside of said bushing element at said slot.

26. The bushing assembly as recited in claim 21 wherein:
said slot has an inner open end at said internal axial opening and an outer open end at the exterior of the bushing element;
said slot having a width, measured in a direction transverse to the axis of said threaded member, which tapers from said outer end to said inner end of the slot;
said slot being wider than the diameter of the externally threaded member, at the outer open end of the slot, to permit insertion of the threaded member into said slot;
said slot being narrower than the diameter of the externally threaded member, at the inner open end of the slot, to prevent the externally threaded member from falling into the internal axial opening of the bushing element.

27. The bushing assembly as recited in claim 21 wherein:
said externally threaded element is a cylindrical element.