WO1981001448A1

WO1981001448A1 - Interlocking telescoping assembly

Info

Publication number: WO1981001448A1
Application number: PCT/US1980/001498
Authority: WO
Inventors: J Porhammer
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-11-13
Filing date: 1980-11-07
Publication date: 1981-05-28
Anticipated expiration: 1982-05-13

Abstract

An interlocking telescoping assembly includes an inner member (10) that slides lengthwise and rotates inside a bore extending through an outer member (12). An outer locking surface (26) of generally constant diameter extends along the length of the inner member. The tubular outer member has a short, fixed locking ring section (14) and an adjacent long tubular section (16) of greater inside diameter than the locking ring. The locking ring is integrally formed with the wall of the outer member and has an inside locking surface (18) of generally constant diameter. The inner and outer locking surfaces, in cross-section, each have opposite semi-circular curved sections each of slightly different radius of curvature to provide an improved locking function. Such an assembly avoids moving parts which reduce reliability and do not favor fiber glass fabrication. The assembly may find use as an adjustable filler for sailboats.

Description

INTERLOCKING TELESCOPING ASSEMBLY

Background

Field of the Invention

This invention relates to interlocking telescoping assemblies, and more particularly to an improved means for locking two or more sections of telescoping tubes. Description of the Prior Art

In the past, there have been a number of uses for interlocking telescoping assemblies. Typical of such uses are camera tripods, extensible booms, adjustable rudder control tillers for sailboats and many industrial uses. The latter are preferably useful because the tiller can be conveniently stored in a retracted position when not in use, and then slid outwardly to an extended position and locked for use and then unlocked and returned to the retracted position.

Some prior art telescoping assemblies are complicated and require separate moving parts which can increase pro¬ duction costs and reduce the reliability of the telescoping assembly; and they do not necessarily lend themselves to fiber glass fabrication, for example.

It can be desirable to manufacture a telescoping assembly from plastic parts. A plastic telescoping device has several adjvantages over a metal one, namely, more flexibility, resistance to disabling dents, and a non-

OMPI conductor of electricity. A telescoping assembly made from plastic parts should be designed so that tooling costs as well as production costs are reasonable. Prior art tele¬ scoping assemblies, usually of aluminum, have included inne and outer tubes that are rotated relative to one another fo frictionally locking them against further telescoping.- If the tubular components are made of plastic, they can be susceptible to cracking or splitting when one component is twisted tightly into contact with the other for locking.

Some multiple section telescoping assemblies require considerable time to deploy or retract, where each adjacent pair of sections must be separately locked or unlocked for deployment to the extended position or retracted to the collapsed position. This invention provides an improved interlocking telescoping assembly which is simple in construction and facilitates manufacture from separate integral molded plastic parts that provide a light-weight, inexpensive telescoping assembly, without requiring separate moving parts, locking devices, or the like. The telescoping- assembly also facilitates manufacture from plastic com¬ ponents with reasonable tooling and production costs, and with good reliability during prolonged use. The invention also facilitates construction of multiple section telescoping assemblies that can be easily and quickly deployed or retracted.

Summary of the Invention

Briefly, one embodiment of the telescoping assembly includes an elongated inner member having.an outer locking surface of generally constant diameter along the length of the inner member, and an elongated tubular outer member having a bore extending through it for slidably receiving the inner member. The wall of the outer member has a first relatively shorter section forming a fixed locking

ring, also referred to as a lock, and a second relatively longer tubular section, also referred to as a barrel, adjacent to and extending from the locking ring. The portion of the bore extending through the lokcing ring has a generally constant diameter for forming an inner locking surface. The locking surfaces of the inner member and outer member are configured so that relative rotation of the members in a first direction permits relative sliding movement of the inner member in the bore. Relative rotation of the inner and outer members in the opposite direction produces frictional engagement between the two locking surfac^es to lock the two members against .relative sliding movement or further rotation. The por¬ tion of the bore extending through the second tubular section is of greater inside diameter than the inner locking surface for permitting the inner member to be locked at any point along its length by frictional engagement with the locking ring.

In one embodiment, the inner locking surface has a first circularly curved section of a first relatively shorter radius of curvature and ari opposite second cir¬ cularly curved section of a second relatively longer radius of curvature. Similarly, the outer locking sur¬ face has a third circularly curved section of a third relatively shorter radius of curvature and an opposite fourth circularly curved section of a fourth relatively longer radius of curvature. The radius of the first surface is greater than the radius of the third surface but less than that of the fourth surface. Relative rotation of the inner and outer members causes the longer fourth radius to be wedged into the smaller first radius.

OMPI ° The barrel section of the outer tube can have its inside surface tapering wider starting from the locking ring and progressing away from the locking ring, which can facilitate ease of manufacture.

These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings.

Drawings

FIG. 1 is a fragmentary side elevation view showing an interlocking telescoping assembly in the form of an adjustable tiller for sailboats; FIG. 2 is an end elevation view of tubular outer telescoping member taken on line 2-2 of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view of a slidable inner telescoping member of the telescoping assembly taken on line 4-4 of FIG. 1;

FIG. 5 ^"is a cross-sectional view taken on line 5-5 of FIG. 1 and showing the inner and outer telescoping members in an unlocked position; FIG. 6 is a cross-sectional view similar to FIG. 5 showing the same two members in a locked position;

FIG. 7 is a semi-schematic side elevation view illustrating the telescoping assembly with multiple telescoping sections; and FIG. 8 is an end elevation view taken on line 8-8 of FIG. 7.

Detailed Description

FIGS. 1 through 6 show an extendible tiller for sail¬ boats which is an example of one use of the interlocking telescoping assembly of this invention. The extendible tiller comprises an elongated rod 10 that telescopes in¬ side an outer tube 12. The slidable rod is also referred to herein as an inner member, and the outer tube is also referred to herein as an outer member.

The outer tube has a relatively shorter first section forming a locking ring 14 adjacent a first end 15 of the tube, and a substantially longer second tubular section 16 extending from the locking ring for the remaining length of the outer tube and terminating at a second end 17 of the tube. The locking ring 14 can also be referred to as a lock, and the tubular section 16 can be referred to as a barrel.

The outer tube is open at both ends, and a bore extending lengthwise through the tube includes a rela¬ tively shorter first bore section forming an inner lock- ing surface 18 of the locking ring 14. The bore is stepped up at the end of the inner locking surface to form an annular shoulder 19 and a relatively longer second bore section 20 extending from the shoulder through the remainder of the tube. The inner locking surface 18 has a substantially uniform diameter for the length of the locking ring section 14. The longer second section 20 of the bore is of greater inside diameter than the inner surface, and the second section of the bore tapers wider in diameter starting at the end ofthe locking ring and progressing away from the locking ring toward the second end 17 of the tube. The second section of the bore is preferably circular in transverse cross-section, i.e., in a plane perpendicular to the axis of the tube.

The outer tube, in the region of the locking ring, has a greater wall thickness than that of the remainder of the tube. Preferably, the exterior surface of the outer tube is tapered from end to end with the same general taper as the inside surface 20, and so the longer second section 16 of the tube has a substantially uniform wall thickness along its length.

The tiller can include a hinge (not shown) affixed to the end of either the outer tube or the rod, and a hand.le or grip (not shown) attached to the end opposite the hinge end. The hinge is used to secure the tiller to a mechanism for controlling the position of a rudder (not shown) in re¬ sponse to steering motion of the tiller. One member is thus fixed so that the other can be rotated about its axis relative to the fixed member.

The rod 10 has an outer locking surface 26 of substan¬ tially uniform diameter for essentially the entire length of the rod. The outer locking surface cooperates with the inner locking surface 18 of the locking ring section 14 for locking or unlocking the rod relative to the outer tube. The rod can be twisted in one direction for unlocking the cooperating locking surfaces and twisted in an opposite direction for locking the cooperating locking surfaces. This and other locking and unlocking functions will be described in greater detail below.

The rod can slide back and forth in the bore of the outer tube in the unlocked condition. The length of the rod is essentially the same as that of the outer tube. Thus, the rod can be fully retracted into the outer tube, or the effective overall length of the tiller can be doubled by twisting the rod about its axis to unlock it, sliding the rod nearly out of the outer tube, and then twisting the rod in an opposite direction to relock it in the outer tube. The overall length of the tiller can be

MPI adjusted to any desired length between these two extremes by sliding the rod out of the tube to the desired length and rotating it to lock it at the desired length.

The opposite end of the rod that remains inside the outer tube is enlarged relative to the locking surface 26 of the tube for providing a stop 30 to prevent the rod from sliding entirely out of the tube. The stop 30 has an out¬ side diameter that abuts the shoulder 19 and prevents the rod from sliding through the smaller inside diameter of the locking ring.

The locking function of the telescoping assembly is provided by similar and complimentary configurations of the inner locking surface 18 of the locking ring 14 and the outer locking surface 26 of the slidable rod 10. The inner locking surface of the tube has a first circularly curved surface portion 32 with a relatively smaller or minor radius of curvature r. and an opposite, secpnd circularly curved surface portion-34 with a relatively larger or major radius of curvature R.. In the illustrated embodiment, the first and second curved surfaces are sub¬ stantially semi-circular, their respective axes of rotation are offset along a common diameter 35 and they are tangent at a common point on said common diameter, i.e., at a point 37 illustrated in FIG. 2. On the opposite side of the curved surface, the first surface portion 32 is flattened along its length at 36 immediately adjacent an elongated stop ridge 38 formed at the juncture of the two surface portions. The purpose of the flat area is twofold. It increases the step at 38 for greater contact area with the step at 46. It also allows a larger radius at 32 than would be possible with a larger step at 38. The ridge 38 is straight and extends lengthwise the entire length of the inner locking surface in a direction parallel to the axis of the outer tube. In one embodiment, the radius r, of the first surface portion 32 is approximately 0.465 inch and the radius R of the second surface portion 34 is approximately 0.48 inch.

The outer locking surface of the slidable rod includes a third circularly curved surface portion 40 with a rela- tively smaller or minor radius of curvature r and an oppo¬ site fourth circularly curved surface portion 42 with a relatively larger or major radius of curvature R . In the illustrated embodiment, the surface portions 40 and 42 are each semi-circular, and their centers of curvature are off- set slightly along a common diameter 42 illustrated in FIG. 4. Although the major and minor surface portions could meet precisely at a common tangent, as with the inner locking surface 18, a tangent slope 44 is formed at- a junc¬ ture along one side of the sliding rod. On the opposite side of the rod, a pronounced straight stop ridge 46 is formed at the juncture between the two curved surface por¬ tions. The stop ridge 46 is parallel to the axis of the slidable rod and extends for essentially the entire length of the rod. In the illustrated embodiment, the stop ridge 46 has a height of approximately 0.05 inch, as represented by the dimension a in FIG. 4. The centers of ^'curvature of the two curved surface portions are offset by a distance b of approximately 0.0175 inch. The height of the tangent offset 44, represented by the dimension c in FIG. 4, is approximately 0.015 inch. Thus, the minor radius of curvature r is approximately 0.4425 inch, and the major radius of curvature Rs is approximately 0.475 inch. The minor radius of curvature rs of the sliding^J rod is smaller than the minor radius of curvature r. inside the outer tube. t The major radius of curvature R of the sliding rod is larger than the minor radius of curvature r, of the outer tube but less than the major radius of curvature R, of the major outer tube. These similar and complimentary locking surfaces allow the rod to be rotated about its axis to an unlocked position inside the locking ring for sliding the rod in the bore through the outer tube. The rod can be rotated about its axis in an opposite direction to cause it to frictionally bind against the inner locking surface of the locking ring. This locking and unlocking function is understood best by referring to FIGS. 5 and 6. FIG. 5 illustrates the slidable rod rotated to an unlocked position relative to the outer tube. In this position, the minor and major radius portions of the rod are adjacent complementary minor and major radius portion of the inner locking surface, respectively. This provides a slight separation space between the locking ring and the sliding rod entirely around their adjacent surfaces which frees the rod for sliding axial movement in the outer tube. In using the telescoping mechanism as an extendable tiller, the rod is initially unlocked by rotating it in a .counterclockwise direction (with reference to FIG. 5) while the outer tube remains fixed. The stop ridges 38 and 46 abut one another to provide a stop against further counter¬ clockwise rotation of the rod when the rod is in the un¬ locked position. The rod then can be slid lengthwise out of the tube to a desired length for tiller control, after which the rod is rotated in a clockwise direction to lock the rod inside the locking ring, as illustrated in FIG. 6. By rotating the rod in the clockwise direction, while the outer tube remains fixed, the outer locking surface of the rod frictionally binds or wedges against the inside lock¬ ing surface of the locking ring, which locks the two members against relative sliding movement as well as fur¬ ther rotation of the rod in the clockwise direction. Following use of the tiller, the rod can be unlocked by rotating it in the counterclockwise direction to free the rod for sliding movement back into the tube, after which the rod can be rotated in a clockwise direction for locking it in the retracted position.

The locking function provided by the rod and locking ring is best understood as follows . The maximum inner diameter R_ + IL, is greater than the maximum rod diameter Rr, + R_ς. However, the minimum inner diameter R + R is less than the rod diameter R_<- + R_ς. Using the dimensions given for radii and offsets, R_ + R_™ = R_ + R_s .at about 30° rotation. In practice, -the less difference between the inner and outer dimensions, the greater the contact area and the better the lock hold. This, in turn, would reduce stop ridges 46 and 38 below practical limits and could allow the inner" rod to counter-rotate under the stop ridge 38. The larger the stop ridges the less the hold action of the lock. Counter-rotation is terminated before any wedging action occurs. It can be seen from the numeric dimensions given above that a compromise between large steps and near similar radii has been achieved. Diameter r, + r, is reduced by milling in the flat 36. This requires the reduction of r . The dimension and offset of r was computed to cause locking with flat 36 at about 30°.

The cooperating locking surfaces of the sliding rod and locking ring are designed to provide frictional contact over a substantial area in the locked position.. The cir¬ cular curvatures of both locking surfaces cooperate to pro¬ duce locking by an "ovalization" technique, owing to the nearly identical radii of curvature of the cooperating locking surfaces in the locked position. .This can distri¬ bute frictional contact around a major portion of the locked surfaces. This locking function is different from that of complementary locking surfaces that, in transverse cross-section, are spiral in configuration, i.e., of pro- gressively increasing radius, rather than constant radius or circular in configuration. Complementary locking surfaces of spiral configuration can have a tendency to grab, when rotated to a locking position, producing a wedging action that also concentrates frictional engage¬ ment in a localized region. This can cause craking or splitting of a telescoping assembly made of plastic com¬ ponents. In contrast, the present invention spreads the frictional contact over a reasonably large surface area, which produces smoother locking and unlocking movements as well as avoiding localized concentration of frictional forces when locked. The circular cross-sectional con¬ figurations of the sliding rod and the outer tube greatly reduce the complexity and cost of tooling when compared with spiral surface configurations.

Light-weight and low-cost interlocking telescoping assemblies can be manufactured from synthetic resinous materials according to principles of this invention. In one embodiment, the outer tube is constructed from phenolic_, or epoxy resin reinforced with fiber glass filaments. Although the outer member can be extruded of either a filament reinforced resin, or metal, with the lock section added on later, this invention is best utilized when the lock and barrel are integral, either stamped or laminated on a mandrel. When made on a mandrel it is possible to vary the filament material between lock and barrel to suit the applica¬ tion requirements. Identical resins ensure perfect integration between the two. Good wear resistance, stiffness and strength can be achieved by having the lock made of cross-wound nylon and the barrel of lengthwise glass fibers. Since the lock does not travel the length of this tube, little cross-Winding is necessary to prevent splintering due to lock side pressure, resulting in material savings and a better strength-to-weight ratio. The sliding rod can be manufactured from a variety of hard plastic materials preferably capable of manufacture by pull-trusion techniques. This produces a slidable rod that can resist compression forces of locking without causing splintering at the locking surface, while permitting fabrication as a tubular member with reasonably thin wall thickness that can support such compressive loads.

The sliding rod and outer tube also can be made of metal. In one embodiment, a telescoping device can be made with aluminum components, with a non-tapered outer tube, and with a locking device otherwise according to principles of this invention.

FIGS. 7 and 8 illustrate an alternative form of the invention comprising a multiple section interlocking tele- scoping assembly which includes first, second, third and fourth telescoping sections, 50, 52, 54, 56, of increasing larger inside diameter, repsectively. The smallest dia¬ meter first* telescoping section 50 has a configuration similar to the sliding rod 10 of the two-component tele- scoping mechanism described above. That is, the first section 50 has opposite semi-circular outer surface sec¬ tions of different diameter forming a first straight locking ridge 58 extending along its length.

The first section telescopes inside the second telescoping- section 52 which is a tubular member having an outer surface configuration also similar to the slid¬ ing rod 10 described above, i.e., two -semi-circular wall sections of different diameter that form a straight outer locking ridge 60, extending the length of the tube. The second telescoping section also has a short locking ring section 52 with an inner surface configuration similar to the inside surface of the locking ring of the two- component locking mechanims described above. That is, the inside surface of the locking ring section 52 has opposite

OMPI semi-circular surface sections forming an inside stop ridge 62 that can abut against the stop ridge 58 of the first telescoping section 50, as illustrated in FIG. 8. The inner and outer surface configurations of the third telescoping section 54 are similar to those of second section 5*2, forming a straight inner stop ridge 64 inside a locking ring section 54 of the third sec¬ tion 52. The stop ridge 64 abust against the locking ridge 60 of the second section. A straight outer stop ridge 66 is formed along the outer surface of the third section.

The fourth telescoping section 56 has a configur¬ ation similar to the outer tube 12 of the two-component telescoping mechanism described above. That is, the outer telescoping section 56 has a locking ring section

56 with opposite semi-circular inside surface portions that form a straight inside stop ridge 68 adapted to abut against the outer stop ridge 66 of the third telescoping section 54. In use, relative rotation of each telescoping sec¬ tion inside its cooperating outer ^•section frictionally locks or unlocks the two sections in a manner similar to that described above for the two-component system. The inside ends of the first, second and third sections each have an enlarged region for acting as a stop to prevent each section from sliding out of confirement in its cooperating tubular section. All four telescoping sec¬ tions can be easily and quickly locked or unlocked by simply twisting the first section 50 while holding the fourth section stationary, or vice versa. Finite rota¬ tion of each section in the locking or unlocking direc¬ tion causes each section to rotate the next section for progressively locking or unlocking the entire unit. For example, in unlocking the multiple sections, the abutting stop ridges 58 and 62 provide a means for

M applying a twisting force to the other telescoping sections to release all locking sections from their locked .positions without requiring separate unlocking manuvers for each pair of locked sections. The locking and unlocking functions of the multiple sections can be useful in such applications as tripods, where quick deployment is often necessary.

Thus, the invention provides a simple, inexpensive, light-weight interlocking telescoping assembly, the lock¬ ing ring provides a short fixed locking element that can be locked to any location the length of the greatly longer telescoping member. The structure of the interlocking telescoping elements facilitates light-weight, low cost manufacture from plastic parts, while also avoiding many of the problems associated with interlocking plastic parts.

Claims

I CLAIM:

1. A locking system for telescoping members comprising: an elongated inner member having an outer locking surface of generally uniform diameter along its length; an elongated tubular outer member having a bore extending through it for receiving the inner member, the wall of the outer member having a first relatively shorter section forming a fixed locking ring and a second relatively longer tubular section adjacent to "and extending away from the locking ring, the portion of the bore extending through the locking ring forming an inner locking surface of generally uniform diameter for the length of the locking ring section, the portion of the bore extending through said second tubular section being of greater^' inside diameter than the inside diameter of the inner locking surface; the locking surfaces of ^"the inner and." outer members being configured so that relative rotation of the inner and outer members, in a first direction permits relative sliding movement of the inner member in a bore, and so that relative rotation of the inner and outer members in an opposite second direction produces frictional engagement between the two locking surfaces to lock the inner and outer members against such sliding movement as well as further relative rotation.

2. Apparatus according to claim 1 in which the portion of the bore extending through said second section tapers wider in diameter in a lengthwise direction starting at the locking ring and progressing away from the locking ring.

3. Apparatus according to claim 2 in which the outer member is made of a fiber-reinforced synthetic resinous material.*

4. Apparatus according to claim 3 in which the wall of the outer member forming the locking ring has a greater concentration of cross-wound fibers than the wall portion forming the longer second section of the outer member.

5. Apparatus according to claim 1 including a first stop ridge extending lengthwise along the outer locking surface of the inner member, and a cooperating second stop ridge on the inner locking surface, the two stop ridges being positioned to engage one another upon relative rotation of the inner and outer members toward the unlocked position to prevent further relative rotation of the two members.

6. Apparatus according to claim 1 including stop means on the inner member having a diameter sufficient to slide in the second bore portion, but oversized relative to the inside diameter of the inner locking surface for preventing the inner member from sliding out of said bore past the locking ring.

7. Apparatus according to claim 1 in which the inner locking surface, in transverse cross-section, has a first circularly curved surface with a first relatively smaller radius of curvature and an opposite second circularly curved surface with a second relatively larger radius of curvature; and the outer locking surface, in transverse cross-section, has. a third circularly curved surface with a third radius of curvature smaller than the radius of curvature of an opposite fourth circularly curved surface, the third radius of curvature being smaller than the first radius of curvature, the fourth radius of curvature being greater than the first radius but smaller than the second radius of curvature.

8. Apparatus according to claim 7 in which the first and second surfaces are substantially tangent to one another at one point, and .the third and fourth surfaces are substantially tangent to one another at one point.

O

9. Apparatus according to claim 8 in which the first and second surfaces are generally semi-circular, and the third and fourth surfaces are generally semi-circular.

10. Apparatus according to claim 7 in which the portion of the bore extending through said second section tapers wider in diameter in a lengthwise direction starting at the locking ring and progressing away from the locking ring. •

11. Apparatus according to claim 10 in which the outer member is made of a fiber-reinforced synthetic resinous material.

12. Apparatus according to claim 11 in which the wall of the outer member forming the locking ring has a greater concentration of fibers than the wall portion forming the longer second section"of the outer member.

13. A locking system for telescoping members comprising: an elongated inner member having an outer locking surface of generally uniform diameter extending along the length of the inner member; said outer locking surface, in transverse cross-section, having a first circularly curved portion with a first relatively shorter radius of curvature and an opposite second circularly curved portion with a second relatively longer radius of curvature; and. an elongated tubular outer member having its length defined by a first relatively shorter locking ring section and a second substantially longer section of inside diameter greater than the inside diameter of the locking ring section, the locking ring section being integrally formed with the wall of the outer member and having an inner locking surface of generally uniform inside diameter extending along the length of the locking ring section, said inner locking surface having a third circularly curved portion with a third radius of curvature and an opposite fourth circularly "curved portion with a fourth radius of curvature longer than the third radius of curvature, the radius of said first surface portion being shorter than the radius of the third surface portion, the radius of the second surface portion being greater than the radius of the third surface portion but less than the radius of the fourth surface portion, so that relative rotation of the inner and outer members in a first direction permits relative sliding movement of the inner and outer members, and so that relative rotation of the inner and outer members in the opposite direction produces frictional engagement between the inner and outer locking surfaces to lock the inner and outer members against such sliding movement as well as against further relative rotation; Claim 13 continued the outer locking surface having an outer stop ridge extending along its length, the inner locking surface having an inner stop ridge extending along its length, the two stop ridges being positioned to engage each other upon relative rotation of the inner and outer members toward the unlocked position to prevent further relative rotation of the two members.

14. Apparatus according to claim 13 in which the portion of the bore extending through said second section tapers wider in diameter in a lengthwise direction starting at the locking ring and progressing away from the locking ring.

15. Apparatus according to claim 14 in which the outer member is made of a fiber-reinforced synthetic resinous material.

16. Apparatus according to claim 15 in which the wall of the outer member forming the locking ring has a greater concentration of fibers than the wall forming the longer second section of the outer member.

17. Apparatus according to claim 13 in which the first and second surfaces are generally semir-circular, and the third and fourth surfaces are generally semi-circular.

18. A multi-section interlocking telescoping assembly comprising: an inner telescoping section having an outer wall with a first outer locking surface; a tubular outer telescoping section having a bore extending through it with a first inner locking surface; a tubular intermediate telescoping section having an outer wall with a second outer locking surface and a bore extending through it with a second inner locking surface; the first outer locking surface of the inner telescoping section being of substantially uniform diameter and being slidable in a bore of the intermediate telescoping section; the intermediate telescoping section having a relatively short locking ring section adjacent a substantially longer section of greater inside diameter, the second inner locking surface being formed inside the locking ring section; the first outer and second inner locking surfaces being configured so that^'relative rotation of the inner and intermediate telescoping sections in a first direction permits relative sliding movement of the inner section in the bore of the intermediate section, and so that relative rotation of the inner and intermediate sections in an opposite second direction produces frictional engagement between the first outer and second inner locking surfaces to lock the inner and intermediate sections against such sliding movement as well as further relative rotation; the second outer locking surface being of substantially uniform diameter along the outer wall surface of the intermediate section; Clai 18 continued the outer telescoping section having a relatively short locking ring section adjacent a ^• ibstantially longer section of greater inside diameter, the first inner locking surface being for ec inside the locking ring section of the outer telescoping section; the first inner and second outer locking surfaces being configured so that relative rotation of the intermediate and outer telescoping sections in a first direction permits relative sliding movement of the intermediate section in the bore of the outer section, and so that relative rotation of the intermediate and outer sections in an opposite second direction produced frictional engagement between the first inner and second outer locking surfaces to lock the intermediate and outer sections against such sliding movement as well as further relative rotation; the first outer locking surface having an elongated first outer stop ridge adapted for engagement with a cooperating elongated second inner stop ridge inside the second inner locking surface of the intermediate section for preventing further relative rotation between the inner and intermediate sections in the unlocking direction of rotation when the two sections are in an unlocked position; and the first inner locking surface having an elongated first inner stop ridge adapted for engagement with a cooperating elongated second outer ridge on the second outer locking surface of the intermediate section for preventing further relative rotation between the intermediate and outer sections in the unlocking direction of rotation when the two sections are in an unlocked position.

19. Apparatus according to claim 18 in which each inner locking surface, in transverse cross-section, has a first circularly curved surface on one side with a first relatively smaller radius of curvature and a second circularly curved surface on an opposite side with a second relatively larger radius of curvature; and each cooperating outer locking surface, in transverse cross-section has a circularly curved third surface on one side with a third relatively smaller radius of -curvature and circularly curved fourth surface on an opposite side with a fourth relatively larger radius of curvature, the third radius of curvature being smaller than thd first radius of curvature, the fourth radius of 'curvature being greater than the first radius but sιr|aller than the second radius of curvature

20. Apparatus according to claim 19 in which the first and second circularly curved surfaces are generally semi-circular, and the third and fourth circularly curved surfaces are generally semi-circular.

21. Apparatus according to claim 18 in which a relatively longer section of the intermediate and outer members each taper wider in diameter in a lengthwise direction starting at their adjacent locking ring sections and progressing away from such locking ring.

22. Apparatus according to claim 21 in which the locking ring sections of the intermediate and outer members are integrally formed with the outer walls of the intermediate and outer sections.

O-.'