Shock absorbing post assembly for crutch and bicycle seat applications

A shock absorbing post assembly includes an outer tube, inner shaft, guide elements, and spring member. The outer tube has an exterior surface with circumferential portions along an outer cylinder encompassing the outer tube and outer races formed longitudinally between opposite ends of and spaced apart circumferentially about the outer tube. The outer races are within the outer cylinder between and inwardly of the circumferential portions of exterior surface. The inner shaft is received in and partially extends above the outer tube and has an exterior surface with circumferential portions along an inner cylinder encompassing the inner shaft and inner races formed longitudinally between opposite ends of and spaced apart circumferentially about the inner shaft in alignment with outer races of the outer tube so as to provide pairs of aligned outer and inner races. The inner races are within the inner cylinder between and inwardly of the circumferential portions of the exterior surface of the inner shaft. Guide elements are between and extend within pairs of aligned outer and inner races so as to permit reciprocatory sliding movement of the inner shaft relative to the outer tube and thereby allow the inner shaft to extend from and retract into the outer tube between extended and depressed positions. The spring member is disposed in the outer tube below the inner shaft so as to yieldably support the inner shaft at the extended position relative to the other tube while permitting the inner shaft to retract into the outer tube toward the depressed position in response to the post assembly receiving a shock impact thereon.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention generally relates to bicycle shock absorbing devices
 and, more particularly, is concerned with a shock absorbing post assembly
 for both crutch and bicycle seat applications.
 2. Description of the Prior Art
 Various designs of shock absorbing devices have been proposed over the
 years for the purpose of reducing transmission of shock impacts and
 vibrations to a cyclist and thereby increasing riding comfort and
 performance in all modes of cycling. Existing bicycle seat posts offer a
 convenient and accessible location on a bicycle for installation of such
 devices. The rising popularity of mountain biking, involving riding over
 rough terrain which causes jolts to the spine of the cyclist, has
 heightened interest in continued development and refinement of shock
 absorbing bicycle seat post devices.
 One design approach of prior art shock absorbing bicycle seat post devices
 has been to provide an outer tube, an inner tube telescopingly received in
 the outer tube and extending from an upper end thereof, a race or races
 formed in one or both of the outer and inner tubes along portions of the
 lengths thereof, ball bearings disposed in the races or races, and a
 compressible body disposed within the outer tube between lower ends of the
 outer and inner tubes. Representative examples of such prior art devices
 are disclosed in U.S. Pat. No. 575,152 to Fogg, U.S. Pat. Nos. 600,365 and
 636,726 to Hindmarsh, U.S. Pat. No. 601,978 to Nevill, U.S. Pat. No.
 664,184 to Stoll, U.S. Pat. No. 686,156 to Snyder, U.S. Pat. No. 5,044,648
 to Knapp, Italian Pat. No. 421,323 to Ponzecchi, and French Pat. No.
 885,282 to Vaglio. While most of these prior art seat post devices may
 function satisfactorily under the specific conditions for which they were
 designed, many of these prior art devices introduce drawbacks in that they
 are complicated and costly to manufacture and difficult to assemble and
 unduly increase the overall weight of the bicycle seat post.
 Consequently, a need still exists for a shock absorbing post assembly which
 will overcome these drawbacks without introducing any new drawbacks in
 their place.
 SUMMARY OF THE INVENTION
 The present invention provides a shock absorbing post assembly designed to
 satisfy the aforementioned need. The shock absorbing post assembly of the
 present invention is adapted for a crutch application as well as a bicycle
 seat application. The shock absorbing post assembly is of simple
 construction, low cost to manufacture, easy to assemble and only minimally
 increases the overall weight of the crutch or bicycle seat.
 Accordingly, the present invention is directed to a shock absorbing post
 assembly for use in conjunction with a crutch, a bicycle seat and other
 comparable applications. The shock absorbing post assembly basically
 comprises an elongated outer tube, an elongated inner shaft, a plurality
 of guide elements, and a spring means.
 The outer tube includes an exterior surface with circumferential portions
 lying along an outer cylinder encompassing the outer tube and a plurality
 of outer races formed longitudinally along and spaced apart
 circumferentially from one another about the outer tube. The outer races
 are disposed within the outer cylinder between and inwardly of the
 circumferential portions of the exterior surface of the outer tube. The
 inner shaft is at least partially received in the outer tube such that the
 inner shaft extends beyond the outer tube. The inner shaft includes an
 exterior surface with circumferential portions lying along an inner
 cylinder encompassing the inner shaft and a plurality of inner races
 formed longitudinally along and spaced apart circumferentially from one
 another about the inner tube and respectively in alignment with the outer
 races of the outer tube so as to provide a plurality of pairs of aligned
 outer and inner races. The inner races are disposed within the inner
 cylinder between and inwardly of the circumferential portions of the
 exterior surface of the inner shaft.
 The guide elements are disposed between and extend within the pairs of
 aligned outer and inner races so as to permit the inner shaft to undergo
 reciprocatory sliding movement relative to the outer tube and thereby
 extend from and retract into the outer tube between corresponding extended
 and depressed positions relative to the outer tube. In a first exemplary
 form, the guide elements includes a plurality of ball bearings. In a
 second exemplary form, the guide elements includes a plurality of
 elongated rods preferably made of low-friction plastic material with the
 ball bearings.
 The spring means is disposed in the outer tube for yieldably supporting the
 inner shaft at the extended position relative to the outer tube while
 permitting the inner shaft to retract into the outer tube toward the
 depressed position in response to the post assembly shaft receiving a
 shock impact thereon. In an exemplary form, the spring means includes a
 body of elastomer material.
 These and other features and advantages of the present invention will
 become apparent to those skilled in the art upon a reading of the
 following detailed description when taken in conjunction with the drawings
 wherein there is shown and described an illustrative embodiment of the
 invention.

DETAILED DESCRIPTION OF THE INVENTION
 Referring to FIGS. 1 and 3 of the drawings, there is respectively
 illustrated first and second embodiments of a shock absorbing post
 assembly, generally designated 10 and 10A, of the present invention for
 use in conjunction with a crutch, a bicycle seat and other comparable
 applications. Each embodiment of the shock absorbing post assembly 10, 10A
 basically includes an outer tube 12, an inner shaft 14, a plurality of
 guide elements 16, and a spring member 18.
 The outer tube 12 of each embodiment of the post assembly 10, 10A is
 preferably elongated, hollow and rigid in its structural makeup, made of a
 suitable material such as aluminum, and has a tubular sidewall 20 which is
 cylindrical in shape. The tubular sidewall 20 of the outer tube 12 defines
 a longitudinal axis A and ha s opposite first and second ends 20A, 20B,
 and an exterior surface 22 extending between the opposite first and second
 ends 20A, 20B. Circumferential portions 22A of the exterior surface 22 lie
 along an outer cylinder 24 encompassing and defined by the outer tube 12
 so as to extend concentrically about the longitudinal axis A of the outer
 tub e 12. The first end 20A of the tubular sidewall 20 of the outer tube
 12 can have fitted thereon a rubber tip T of a crutch or a clamp head H of
 a bicycle seat, both as seen in dashed line form in FIGS. 1 and 3.
 The tubular sidewall 20 of the outer tube 12 has a plurality of outer
 tracks or races 26 of arcuate cross-sectional shape formed longitudinally
 between its opposite first and second ends 20A, 20B and circumferentially
 spaced apart from one another about the outer tube 12. In the first
 exemplary embodiment of FIGS. 1 and 2, the outer races 26 are formed on
 the tubular sidewall 20 of the outer tube 12 by conventional die forming
 techniques. In the second exemplary embodiment of FIGS. 3 and 4, the outer
 races 26 are formed on the tubular sidewall 20 of the outer tube 12 when
 the tube itself is being formed by conventional tube extruding and drawing
 techniques. In both embodiments the outer races 26 extend parallel to one
 another completely between the first and second ends 20A, 20B of the outer
 tube 12 and are disposed within the true outer cylinder 24 of the outer
 tube 12 between and inwardly of the circumferential portions 22A of the
 exterior surface 22 of the tubular sidewall 20 of the outer tube 12.
 The inner shaft 14 of each embodiment of the post assembly 10, 10A is
 telescopically received in the hollow outer tube 12 and has a longitudinal
 axis B substantially coincident with the longitudinal axis A of the outer
 tube 12. The inner shaft 14 is preferably elongated, hollow and rigid in
 its structural makeup, made of a suitable material such as aluminum, and
 has a tubular sidewall 28 which is cylindrical in shape. The tubular
 sidewall. 28 of the inner shaft 14 has opposite first and second ends 28A,
 28B and an exterior surface 30 extending between the opposite first and
 second ends 28A, 28B. Circumferential portions 30A of the exterior surface
 30 lie along an inner cylinder 32 encompassing and defined by the inner
 shaft 14 so as to extend concentrically about the longitudinal axis B of
 the inner shaft 14. The first end 28A of the tubular sidewall 28 of the
 inner shaft 14 extends beyond the first end 20A of the tubular sidewall 20
 of the outer tube 12 and the second end 28B of the tubular sidewall 28 of
 the inner shaft 14 is disposed between the opposite first and second ends
 20A, 20B of the tubular sidewall of the outer tube 12.
 The tubular sidewall 28 of the inner shaft 14 has a plurality of inner
 tracks or races 34 of arcuate cross-sectional shape formed longitudinally
 between its opposite first and second ends 28A, 28B and circumferentially
 spaced apart from one another about the inner shaft 14. In the first
 exemplary embodiment of FIGS. 1 and 2, the inner races 34 are formed on
 the tubular sidewall 28 of the inner tube 14 by conventional die forming
 techniques so as to extend only for a portion of the length of the inner
 shaft 14. In the second exemplary embodiment of FIGS. 3 and 4, the inner
 races 34 are formed on the tubular sidewall 28 of the inner tube 14 when
 the tube itself is being formed by conventional tube extruding and drawing
 techniques so as to extend the entire length of the inner shaft 14. In
 both embodiments the inner races 34 extend parallel to one another and are
 disposed within the true inner cylinder 32 of the inner shaft 14 between
 and inwardly of the circumferential portions 30A of the exterior surface
 30 of the inner shaft 14. The inner races 34 are respectively aligned with
 the outer races 26 of the outer tube 12 so as to provide pairs of aligned
 outer and inner races 26, 34.
 The guide elements 16 of each embodiment of the post assembly 10, 10A are
 disposed between and extend within respective pairs of aligned outer and
 inner races 26, 34 of the outer tube 12 and inner shaft 14 so as to permit
 the inner shaft 14 to undergo telescoping reciprocatory sliding movement
 relative to the outer tube 14 along their coincident longitudinal axes A,
 B and thereby extend from and retract into the first end 20A of the
 tubular sidewall 20 of the outer tube 12 between corresponding extended
 and depressed positions relative to the outer tube 12, as seen in solid
 and dashed line positions in FIGS. 1 and 3. More particularly, in the
 first exemplary form shown in FIG. 1, the guide elements 16 preferably
 include ball bearings 36. In a second exemplary form shown in FIG. 3, the
 guide elements 16 preferably include the plurality of ball bearings 32 and
 a plurality of elongated rods 38, preferably made of low-friction plastic
 material, in conjunction with the ball bearings 36. Alternatively, the
 elongated rods 38 may be employed without the ball bearings 36.
 Also, in the first exemplary embodiment of FIG. 1, the inner races 34 can
 differ in length so as to prevent accumulation of stress concentrations at
 the ends thereof. There are different numbers of ball bearings 36 disposed
 in the aligned pairs of outer and inner races 26, 34 in the first
 embodiment. In addition, there are plugs 40 inserted at one ends of the
 aligned pairs of outer and inner races 26, 34 to prevent jamming of the
 ball bearings 36 at the one ends. The aligned pairs of outer and inner
 races 26, 34 are closed off at the other ends by the first end 20A of the
 sidewall 20 of the outer tube 12 being crimped inwardly which prevents the
 entire post assembly 10 from coming apart. The aligned pairs of parallel
 outer and inner races 26, 34 and the guide elements 16 therein also
 prevent rotation of the outer tube 12 and inner shaft 14 relative to one
 another.
 The spring member 18 of each embodiment of the post assembly 10, 10A is
 disposed in the outer tube 12 between the second end 28B of the inner
 shaft 14 and the second end 20B of the outer tube 12. The spring member 18
 is compressible so as to yieldably support the inner shaft 14 at the
 extended (solid line) position of FIGS. 1 and 3 relative to the outer tube
 12 while permitting the inner shaft 14 to retract into the outer tube 14
 toward the depressed (dashed line) position of FIGS. 1 and 3 in response
 to the post assembly 10, 10A receiving a shock impact thereon. In the one
 exemplary form illustrated in FIGS. 1 and 3, the yieldable spring member
 18 preferably includes a body 42 of elastomer material, such as rubber or
 the like. The elastomer body 42 can be provided as a single element or a
 plurality of elements. The spring member 18 can take any other suitable
 forms, such as a coil spring or conical spring washers.
 Furthermore, in addition each embodiment of the post assembly 10, 10A can
 further include an annular slider bushing 44 on the second end 28B of the
 inner shaft 14 to assist in guiding movement of the inner shaft 14
 relative to the outer tube 12. Also, each embodiment of the post assembly
 10, 10A may have a circular plug 46 threaded into the second end 20B of
 the outer tube 12 adjacent to the elastomer body 42 to support and upon
 threaded adjustment to change the preloading generated by the yieldable
 elastomer body 44 in the outer tube 12. The second embodiment has snap
 rings 48 fitted into annular grooves in the interior of the outer tube 12
 to hold the post assembly 10A together. Each embodiment of the post
 assembly 10, 10A still further includes an annular boot 50 surrounding the
 portion of the inner shaft 14 which extends beyond the outer tube 12. The
 boot 50 is employed to keep out dirt and grim and prevent dispersal of any
 internal lubricant. In the second embodiment, the boot 50 has a
 bellows-type configuration with a pair of opposing flat areas 50A thereon
 to provide for logos and the like.
 It is thought that the present invention and its advantages will be
 understood from the foregoing description and it will be apparent that
 various changes may be made thereto without departing from the spirit and
 scope of the invention or sacrificing all of its material advantages, the
 form hereinbefore described being merely preferred or exemplary embodiment
 thereof.