Abstract:
An adjustable length shaft assembly including a handle portion and an extensible shaft. An upper end of the shaft includes a set of locking teeth. The handle has an internal locking mechanism with a tooth rack to accommodate the locking teeth. A control handle is rotated in a first direction, rotating the teeth away from the tooth rack, where the teeth are in a disengaged, unlocked position. With the teeth unlocked, the shaft can be longitudinally adjusted to achieve the desired length. Then, the control handle is rotated in a second direction, rotating the teeth into the tooth rack, where the teeth are in an engaged, locked position. In this manner, the teeth and the tooth rack provide a plurality of positive locking positions, each position providing a different shaft length.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to length-adjustable shafts or poles, for use in a variety of applications, including golf clubs, light stands, music stands, camera tripods, walking sticks, canes, shower curtain rods, ski poles, cleaning implements, and extendible tools. More specifically, the invention pertains to an adjustable length shaft having an internal locking mechanism with teeth and accommodating teeth recesses, the teeth and recesses providing a plurality of positive locking positions, each position providing a different shaft length. 
     2. Description of the Prior Art 
     Prior art shafts having adjustable lengths, have been used for many years for a wide variety of applications. Each of these applications has its own functional and aesthetic requirements for the shaft construction which is employed. As a consequence, a number of different mechanisms have been developed to satisfy the particular application requirements. 
     For example, a telescopic shaft arrangement using a rotatable nut and a compression ring locking mechanism, has been very popular for light duty camera tripods, walking sticks, canes, and extendable poles. An even simpler construction, using a telescopic shaft in combination with a transverse set screw or bolt for compressively locking the shaft, has been used successfully for certain non-demanding applications such as support shafts for music stands and lighting stands. Stronger adjustable length shafts, using a telescopic square tube construction with a flip lever compression lock, have also been developed. These stronger shafts are used for heavier duty tripods, and other applications where the ability to withstand greater axial forces is important. Lastly, a rod construction including a screw-extensible threaded shaft, having a disc foot on its exposed end, has been used for many years as an adjustable support rod for shower curtains. 
     The above-described prior art constructions have not been used successfully for a number of other demanding applications which could benefit from appropriately featured adjustable length shafts. One of these applications is for adjustable length golf clubs. The reasons are several. Golf clubs must be clean in construction and appearance, to satisfy the consumers&#39; aesthetic requirements. Consequently, flip levers, set screws, and even compression ring mechanisms are not well received for this application. In short, the adjustable length golf club shaft must look substantially identical to a standard fixed length golf club shaft, to be acceptable. 
     Also, an adjustable length shaft for a golf club must have the same feel as a fixed length shaft, even to be considered by the golfing community. Golfers are notoriously critical and demanding, particularly when it comes to their equipment, so an adjustable shaft that exhibited looseness, lateral play or axial slippage of any sort, would simply be unacceptable. 
     And, an adjustable length shaft in this application must be both fast and easy to adjust, and positive in its locking capabilities, to be acceptable for golfers. Similar requirements exist for adjustable ski poles, both as to aesthetic and functional aspects. 
     Thus, the need exists for an improved adjustable shaft construction, which can be used in a variety of fields, and will also satisfy the demanding criteria for golf club and ski pole applications. 
     SUMMARY OF THE INVENTION 
     The adjustable-length shaft assembly of the present invention includes a handle and an elongated shaft. The shaft has an upper portion which extends axially within the handle, and is axially adjustable for locking therein. The shaft includes a tooth plate at its upper end. Preferably, two sets of teeth extend from the plate, one on each side of the plate, for more balanced distribution of locking forces and for additional strength. If the shaft assembly is to be used as part of a golf club, a club head is mounted on the lower end of the elongated shaft. For other applications, different articles or other structures may be attached to the shaft or to the handle portion of the assembly. 
     An elongated, tubular, inner sleeve is located within the handle, surrounding the upper portion of the shaft. The sidewall of the inner sleeve includes upper and lower pairs of cam surfaces, on opposing sides of the inner sleeve. The sidewall cam surfaces resemble a dog-leg, or a dual angled slot, in configuration. These cam surfaces progress from a lower left-hand end upwardly to an upper right-hand end. The inner sleeve also includes an angled cam surface at its lower end. The lower end cam surface extends on a straight angle, from an upper left-hand position downwardly toward a lower right-hand position. A pin detent is provided adjacent the lower right-hand position. 
     Lastly, the inner sleeve includes a pair of opposing longitudinal tooth plate slots, each approximately 90 degrees rotated from the sidewall cams, and extending generally the same distance between them. The longitudinal plate slots accommodate both sides of the tooth plate, so as to allow sliding of the plate and axial adjustment of the shaft within the inner sleeve. However, the sides of the longitudinal slots restrict any rotational movement of the shaft, relative to the sleeve. 
     The handle portion of the shaft assembly also includes a tubular housing, positioned about the inner sleeve. The housing is comprised of a left hand shell and a right hand shell. Each shell includes upper and lower cam followers which engage a respective sidewall cam surface of the inner sleeve. Each shell further includes an elongated tooth slot in its sidewall portion. Each tooth slot has a tooth rack extending along one side. The tooth slots have a transverse dimension which is sufficient to accommodate sliding of the tooth plate when it is rotated into an unlocked position. 
     A tubular outer sleeve is also provided around the housing. The outer sleeve includes sidewall recesses which are engaged by locking fingers, extending slightly outwardly from the sidewalls of each of the shells of the housing. In this way, the outer sleeve acts to hold the two shells together, and to prevent them from rotating. 
     A blocking pin is transversely positioned across the upper ends of the outer sleeve and the housing. Holes are provided in the sidewalls of the outer sleeve and the housing for securing the pin in place. A cam-bias spring is located within the upper end of the housing. The spring is captive between the upper end of the inner sleeve and the blocking pin, providing a downward bias force against the inner sleeve. 
     A tubular control handle is located about the lower portion of the outer sleeve. The control handle includes a cam pin extending inwardly toward the inner sleeve, passing first through a transverse cutout in the lower end of said outer sleeve and then through a housing cam in the lower end of the housing. The cam pin thereby engages the angled cam surface at the lower end of the inner sleeve. The cam pin detent at the lower end of the angled cam surface secures the cam pin and the control handle in an unlocked position, so the shaft can be axially adjusted to set the proper length for the shaft assembly. 
     Upper and lower plastic brake rings surround a lower portion of the shaft, within the confines of the control handle. The brake rings include partial gaps in their sidewalls, so that axial forces applied to the end of either brake causes the ring to compress radially upon the shaft and lock it in place. The upper end of the upper brake ring impinges upon the lower edge of the housing. The lower end of the lower brake ring nests against an annular, angled wall of the control handle. A brake spring between the two rings maintains them in spaced relation, and transmits axial forces between the upper ring and the lower ring. 
     To change the effective length of the shaft assembly, the control handle is rotated in a clockwise direction, in relation to the outer sleeve and the housing. This moves the cam pin along the angled cam surface of the inner sleeve and along the housing cam surace. This urges the inner sleeve upwardly, causing the upper cam surface of the inner sleeve to rotate the inner sleeve and the teeth on the end of the shaft, away from the housing and the teeth rack. The spring at the upper end of the housing becomes increasingly compressed. Continued clockwise rotation causes the teeth and the tooth rack entirely to disengage, as the cam pin engages the cam pin detent in the inner sleeve. Concurrently, the cam pin moving against the downwardly directed housing cam surface urges the control handle downwardly with respect to the lower end of the handle. This releases compressive forces on the brake spring and axial forces on the brake rings, thereby freeing the shaft. The shaft may now be moved axially, upwardly or downwardly, until the shaft assembly assumes the desired overall length. 
     To lock the shaft assembly, the control handle is rotated counter-clockwise in relation to the outer sleeve and the housing. As the cam pin disengages from the detent, the angled surface of the inner sleeve, under downward forces from the cam-bias spring at the upper end of the housing, begins to move downwardly in relation to the housing. Under this downward motion, the upper and lower cam surfaces of the inner sleeve in conjunction with the cam followers on the housing, cause the teeth protruding from the inner sleeve to rotate toward the tooth rack on the housing. As rotation of the control handle continues, the teeth mesh with the tooth rack, locking the shaft against axial movement. Concurrently, the cam pin moving against the upwardly directed housing cam surface, moves the control handle upwardly. This compresses the brake spring, imposing greater axial forces on the brake rings. The brake rings compress on the shaft, further preventing axial or lateral movement of the shaft. A locking detent in the extreme counter-clockwise end of the housing cam surface locks the cam pin securely in place. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a right front perspective of a golf club, incorporating the length-adjustable shaft of the present invention; 
     FIG. 2 is a perspective view of a camera tripod, incorporating the length-adjustable shaft of the present invention; 
     FIG. 3 is a perspective view of a ski pole, incorporating the length-adjustable shaft of the present invention; 
     FIG. 4 is an exploded left front perspective of the golf club of FIG. 1; 
     FIG. 5 is a fragmentary cross-sectional view of the grip and the control handle, showing the control handle in a locked position; 
     FIG. 6 is a laid-out side elevational view of the left hand and right hand shells of the housing, showing the control handle pin in a locked position, and the outline of the laid-out inner sleeve being shown in broken line; 
     FIG. 7 is a transverse, cross-sectional view, taken on the line  7 — 7  in FIG. 5; 
     FIG. 8 is a transverse, cross-sectional view, taken on the line  8 — 8  in FIG. 13; 
     FIG. 9 is a fragmentary, longitudinal, cross-sectional view, taken on the line  9 — 9  in FIG. 5; 
     FIG. 10 is a view as in FIG. 5, but showing the control handle mid-way between a locked and an unlocked position; 
     FIG. 11 is a view as in FIG. 6, but showing the control handle pin mid-way between a locked and an unlocked position; 
     FIG. 12 is a fragmentary, longitudinal, cross-sectional view, taken on the line  12 — 12  in FIG. 10; 
     FIG. 13 is a view as in FIG. 5, but showing the control handle in an unlocked position; 
     FIG. 14 is a view as in FIG. 6, but showing the control handle pin in an unlocked position; and, 
     FIG. 15 is a view as in FIG. 11, but showing the control handle pin in a locked position with the shaft fully extended. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, the adjustable-length shaft assembly  11  of the present invention includes a handle  12  and an elongated shaft  13 . The shaft  13  has an upper portion  14  which extends axially within the handle, for adjustment to the desired position before it is locked securely therein. The shaft  13  includes a plug  16  at its upper end  17 . Plug  16  has a reduced diameter section  18  at its lower end, for insertion within upper end  17 . The upper end of plug  16  includes a rectangular slot  19 , passing through the axis of plug  16  and extending from one side of the plug to the other. The slot  19  is sized to accommodate a tooth plate  21 . The tooth plate  21  is secured within the slot by means of a pair of press-fitted pins  20 , passing transversely through the split portions of the plug and the plate therebetween. Preferably, tooth plate  21  includes two sets of locking teeth, one set extending from each side of the plate. (See, FIGS. 4 and 8) The sets of locking teeth extend perpendicularly from the plate, in opposing directions. As will be more apparent herein, using two sets of locking teeth provides a more balanced distribution of locking forces and additional strength. 
     If the adjustable length shaft assembly is to be used as part of a golf club  22 , an iron or wood club head  23  is secured to the lower end of the elongated shaft  13 . Handle  12  may include a resilient gripping material on its outer surface, consistent with conventional golf club construction. For this application, an adjustable length shaft allows younger golfers initially to use full size clubs with a reduced length shaft, and then later, the shaft length may be extended to whatever length is appropriate. The adjustable length shaft may also be used for training or practice, and to determine experimentally the golf club shaft length which works best for a given golfer for a particular golfing situation. 
     However, the shaft assembly  11  may also be used advantageously for many other applications, where the need for an adjustable length shaft exists. In these circumstances, different articles or other structures may be attached either to the shaft  13  or to the handle portion  12  of the assembly. For example, in FIG. 2, showing a camera tripod  24 , the upper end of the handle  12  is attached to a tripod head  26 . And, leg tips  27  may be fitted on the lower ends of the shafts  13 . In this application, the shaft assembly  11  is used in the same fashion as prior art adjustable shafts, namely, to provide adjustable tripod legs which can be collapsed for storage and transport and extended to a selected height for use. 
     Similarly, in FIG. 3, showing a ski pole  28 , a basket  29  is preferably attached to the lower end of the shaft  13 . A hand strap  31  may also be affixed to the upper end of handle  12 . As with the adjustable shaft golf club, the adjustable shaft ski pole may be used by younger skiers. Also, during different snow or hill conditions, an experienced skier may want to adjust the length of his or her ski poles accordingly. It is apparent that other applications exist for the adjustable length shaft assembly  11 , as discussed in more detail above. 
     Returning now to FIG. 4, an elongated, tubular, inner sleeve  32  is located within the handle, surrounding the upper portion  14  of the shaft  13 . The sidewall of the inner sleeve  32  includes an upper cam surface  33  and a lower cam surface  34 , on opposing sides of the sleeve  32 . Sidewall cam surfaces  33  and  34  resemble a dog-leg, or a dual angled slot, in configuration. These cam surfaces progress upwardly from a lower left-hand end, and then transition, more vertically, to reach an upper right-hand end. This stepped, cam surface configuration effects different rates of movement between certain locking components of the shaft assembly  11 . 
     The inner sleeve  32  also includes an angled cam surface  36 , at its lower end. Cam surface  36  extends on a helical path, from an upper left-hand position downwardly toward a lower right-hand position, as viewed, for example, in FIG. 6. A pin detent  37  is provided adjacent the lower right-hand position. As will be explained below, detent  37  secures certain structures of the assembly  11  in an unlocked position, while the user adjusts the shaft  13  into the desired axial position. 
     The inner sleeve  32  further includes a pair of opposing, longitudinal tooth plate slots  38 , each approximately  90  degrees rotated from the sidewall cams, and extending generally to the same longitudinal extent. Each of the tooth plate slots  38  accommodates a respective side of the tooth plate  21 , so as to allow free longitudinal sliding of the plate  21  and corresponding axial adjustment of the shaft  13  within the inner sleeve  32 . However, it should be noted that the lateral sides of the longitudinal slots  38 , restrict any rotational movement of the plate  21  or the shaft  13  to which it is attached, with respect to the inner sleeve  32 . 
     The handle portion  12  of the shaft assembly  11  also includes a tubular housing  38 , surrounding inner sleeve  32 . Housing  38  has an inner diameter which is just slightly larger than the outer diameter of inner sleeve  32 . The housing  38  is preferably comprised of a left hand shell  39  and a right hand shell  41 . The shells are secured to each other by means of tabs  42  and respective notches  43 . Two shells are used to form the housing  38  because it is easier to assemble the various internal parts of the assembly  11  with the shells temporarily split apart. However, it would also be possible to use a single tube for the housing  38  by employing a different method of assembly. Thus, the invention herein contemplates that both the shell and the single tube constructions are structurally and functionally equivalent, and that one of ordinary skill in the art may have design justifications to substitute one for the other. 
     Each shell includes an upper cam follower  44  and a lower cam follower  46 . Each cam follower  44  and  46  is bent slightly inwardly, toward inner sleeve  32 . In this manner, the upper cam followers  44  engage respective upper cam surfaces  33  of the inner sleeve  32 . Similarly, the lower cam followers  46  engage respective lower cam surfaces  34 . 
     Each shell further includes an elongated tooth slot  47  in its sidewall portion. Each tooth slot has a tooth rack  48  extending along one side. The tooth slots  47  have a transverse dimension which is sufficient to accommodate sliding of the locking teeth of tooth plate  21 , when the tooth plate is rotated into a disengaged, unlocked position. 
     A tubular outer sleeve  49  is provided around the housing  38 . Sleeve  49  has an inner diameter which is just slightly larger than the outer diameter of housing  38 . On opposing sidewalls of its lower end, the outer sleeve  49  has longitudinally extending sidewall recesses  51 . Shells  39  and  41  include locking fingers  52 , extending slightly outwardly from the sidewalls of each of the shells. As shown more specifically in FIG. 9, fingers  52  protrude within respective recesses  51 . In this manner, fingers  52  cooperate with outer sleeve  49 , to hold the two shells together and to prevent them from rotating with respect to each other. 
     A blocking pin  53  is also provided, transversely spanning the upper ends of outer sleeve  49  and housing  38 . Pin  53  is installed in place by press fitting it both through holes  54  in the opposing sidewall portions of sleeve  49 , and through holes  56  in shells  39  and  41 . A cam-bias spring  57  is provided within the upper end of housing  38 . Spring  57  is held captive between the upper end of the inner sleeve  32  and the pin  53 , providing a downward bias force against the inner sleeve  32 . 
     A slightly tapered, tubular control handle  58  is located about the lower portion of the outer sleeve  49 . The control handle is the portion of the assembly  11  which the user grips and rotates from a locked position to an unlocked position, and then back again, in the course of making shaft length adjustments. The control handle  58  includes a cam pin  59 , extending inwardly toward the inner sleeve  32 . The cam pin passes first through a transverse cutout  61  in the lower end of said outer sleeve  49 , and then through a housing cam  62 , in the lower end of the housing  38 . A locking detent  63  is provided in the extreme left-handed end of cam  62 . Pin  59  is sufficiently long so that its innermost end engages the angled cam surface  36  at the lower end of the inner sleeve  32 . 
     In order to maintain shaft  13  securely within handle  12 , an upper brake ring  64  and a lower brake ring  66  are provided. Brake rings  64  and  66  surround a lower portion  67  of the shaft  13 , within the confines of the control handle  58 . The brake rings may be made from resilient plastic, or other suitable material. The rings include sidewall gaps  68 , so that converging and opposing axial forces applied to the chamfered ends  69  of brakes cause the rings radially to compress upon the shaft and lock it in place. It will be noted that the upper end of the upper brake ring  64  impinges upon a lower chamfered edge  71  of the housing  38 . And, the lower end of the lower brake ring  66  nests against an annular, angled wall  72  of the control handle  58 . A brake spring  73  between the two rings maintains them in spaced relation, and transmits axial forces between the upper and lower rings. 
     When the control handle  58  is rotated to an extreme lefthand position, as shown for example in FIG. 6, the shaft  13  is locked securely within handle  12 . The cam pin  59  is secured within locking detent  63 , and the inner sleeve  32  has translated downwardly, into a lowered position. This occurs because the angled cam surface  36  rides downwardly over pin  59 , urged by the cam bias spring  57 . Upper cam followers  44  are located within the upper ends of upper cam surfaces  33 , and lower cam followers  46  are located within the upper ends of upper cam surfaces  34 . The locking teeth on tooth plate  21  are rotated into engagement with respective portions of the tooth racks  48 , securely locking the shaft against any axial movement, with respect to the handle  12 . 
     With the control handle in a locked position, the control handle  58  is also in a fully raised position. This occurs because the upwardly directed left hand end of the housing cam  62  lifts, or moves the control handle upwardly, with respect to the housing. This effects greater compression of brake spring  73 , causing brake rings  64  and  66  to clamp down on the lower portion  67  of the shaft. The brake rings provide a considerable measure of lateral support, to eliminate slop or play between shaft  13  and handle  12 . The brake rings also provide additional resistance to any axial movement of the shaft. 
     To change the effective length of the shaft assembly  11 , the control handle  58  is first rotated toward the right, into an intermediate position, as shown in FIG.  11 . With the cam pin  59  now sliding against the angled cam surface  36  of the inner sleeve  32 , the inner sleeve is urged upwardly. This causes upper cam followers  44  to slide downwardly with respect to upper cam surfaces  33 . Although lower cam followers  46  are also caused to slide downwardly, there is no surface within the lower right-hand cutout of lower cam surfaces  34  for the followers  46  to engage. Thus, only the upper cam followers  44  and upper cam surfaces  33  are effective to provide relative rotational movement between the housing  38  and the inner sleeve  32  in this unlocking process. 
     The locking teeth on tooth plate  21  are rotated partially out of engagement with respective portions of the tooth rack  48 . The cam pin  59  is now removed from the locking detent  63 , and the control handle, following the downward contour of the housing cam, also moves downwardly with respect to the handle. This causes brake spring  73  to decompress, substantially relieving axial forces imposed upon ring brakes  64  and  66  and effecting release of the shaft. 
     Continued rotation of the control handle  58 , to an extreme right handed position, completes the shaft unlocking process. As shown in FIG. 14, the cam pin  59  has raised the inner sleeve  32  to its highest position, and pin  59  now rests in pin detent  37 . With inner sleeve  32  fully raised, upper cam followers  44  now reside in the lower ends of upper cam surfaces  33 , and lower cam followers  46  reside in the lower ends of lower cam surfaces  34 . The locking teeth on tooth plate  21  are now rotated fully out of engagement with the tooth rack  48 . Because the compressive forces on the brake spring and the axial forces on the brake rings remain relieved, the shaft may now be moved axially, upwardly or downwardly, until the shaft assembly  11  assumes the desired overall length. (See, e.g., the movement shown in FIG.  14 ). 
     The above-recited procedure is simply reversed to lock the shaft in its new, selected position. The control handle  58  is rotated toward the left, moving the cam pin  59  into the intermediate position shown in FIG.  11 . With the cam pin dislodged from pin detent  37 , inner sleeve  32  moves downwardly, with respect to housing  38 . This causes upper cam follower  44  and lower cam follower  46  to slide upwardly within respective cam surfaces  33  and  34 . It should be noted that in this locking process, both the upper and lower cam surfaces are operative, whereas in the unlocking process, only the upper cam surfaces are operative. 
     Because cam surfaces  33  and  34  are stepped, having different angles of inclination, the relative rotational movement between the housing  38  and the inner sleeve  32  takes place at different rates. During the first phase of the rotation, the rate is relatively quick, effected by the lower portions of stepped cam surfaces  33  and  34 . This is effective to rotate tooth plate  21  substantially into engagement with tooth rack  48 . During the second phase of rotation, the rate of rotation is slower, as the upper portion of cam surfaces  33  and  34  is more steeply vertically inclined, effecting less rotational displacement for a given extent of travel. This more gradual rotational rate is effective to mesh the teeth of tooth plate  21  securely within the complementary recesses of tooth rack  48 . 
     Moreover, this phase of the locking process is characterized by the upward travel of the pin  59  within housing cam  62 . This raises control handle  58  with respect to housing  38 , re-compressing upper and lower brake rings  64  and  66 , in the same manner and with the same result, as that previously described. Continued rotation of the control handle  58  finally registers cam pin  59  within locking detent  63 . Now the shaft  13  is securely locked in its new position. Had the user previously adjusted the assembly  11  to its maximum length, the tooth plate  21  would now be positioned within the lowermost part of tooth slot  47 , as shown in FIG.  15 .