Abstract:
A dampening mechanism includes a pair of coaxially aligned inner and outer components with ends disposed in telescoping relation with an interposed resilient elastomeric member comprising a monolithic polymeric structure comprising a hollow body within the end of the outer component, and receiving the end of the inner component with the body including an attachment portion secured to the outer component, and a support portion supporting the inner component. The body portion includes a plurality of equally spaced webs extending between the attachment portion and support portion. In one form, the body is generally cylindrical and disposed between the inner surface of the outer component and the outer surface of the inner component in telescoping relation and frictionally engaging the telescoping components.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Phase of International Application Number PCT/US2013/033805, filed Mar. 26, 2013 and claims priority pursuant to Title 35 USC §119(e) to U.S. Provisional Application No. 61/616,725, filed Mar. 28, 2012, the entire specification and drawings of which are hereby incorporated by reference herein as if fully set forth herein. 
    
    
     BACKGROUND 
     This disclosure relates to a dampening mechanism for coaxially aligned relatively translatable components. More particularly, it relates to such a mechanism comprising a resilient monolithic member interposed between the relatively translatable components that provides dampening through elastic tensile deformation. 
     Telescoping components are employed in a variety of applications. One important example is found in personal support devices such as crutches, canes, ski poles, trekking poles, and the like. Many forms of such personal support devices include a resilient connection between coaxially aligned, connected tubular support shafts to cushion impact loading. Known forms of these devices employ a compression coil spring between the coaxial, relatively movable shaft segments that compresses on application of load to absorb shock and cushion the impact associated with use. Such springs are susceptible to buckling or other undesired characteristics associated with deformation, which, over time, deteriorate the spring function and overall utility of the device. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure is directed to an arrangement for a reciprocal connection between coaxial components of a support structure comprising an elastomeric element that absorbs load and develops a restoring force through tensile elongation. 
     The resilient element of the present disclosure is a molded member interposed between the relatively slidable ends of coaxially aligned telescoping support components. It provides resilient restoring force to the components through extension of the element in tension. It also provides a sleeve-like journal between the telescoping components to reduce frictional resistance and maintain coaxial alignment. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the resilient elastomeric member of the present disclosure. 
         FIG. 2  is a plan view of the resilient elastomeric member of the dampening mechanism prior to insertion into one of a pair of telescoping components. 
         FIG. 3  is a plan view, in section, of the dampening mechanism installed between telescoping components, in an unstressed condition. 
         FIG. 4  is a plan view, in section, of the assembled telescoping components with the resilient elastomeric member in tension. 
     
    
    
     DETAILED DESCRIPTION 
     The dampening mechanism of the present disclosure is depicted in  FIGS. 1 to 4 . It includes a resilient elastomeric member having a monolithic body of molded polymeric material. It possesses the property of resilient elongation and develops an internal restoring force to return to its original configuration. 
     The dampening mechanism comprises a pair of coaxially aligned, telescoping components and an interposed resilient elastomeric member  50 . The telescoping components comprise an outer component  102  and an inner component  104  illustrated here as telescoping cylindrical shafts. 
     It should be appreciated that though the illustrated embodiment discloses cylindrical shafts, the dampening mechanism is suitable for use in any configuration where relatively reciprocating telescoping components are employed. These components may have any desired cross-section, such as oval, square, rectangular or other geometric shape. Moreover, though the outer component  102  must be hollow to receive the inner component  104  in telescoping relation, the components need not have the same cross section. For example, the inner component may be square, or “T” shaped or other suitable cross section. 
     Resilient elastomeric member  50  is intended to be interposed between two coaxially aligned relatively translatable components, intended for use in a generally vertical orientation. As illustrated in  FIGS. 3 and 4 , such components may be tubular shafts arranged coaxially such that one is slidably retained within the other. Such shafts could, for example, form the leg of a crutch, or comprise a ski pole or trekking pole, or any other elongate structure where relative translative motion is desired to absorb shock due to impact loading of one shaft relative to the other. 
     Referring to  FIGS. 3 and 4 , the shaft assembly includes hollow tubular outer shaft or component  102  and an inner shaft or component  104 . As stated, though illustrated as tubular, components  102  and  104  may be any suitable shape, or cross-section. 
     Referring to  FIG. 2 , illustrated outer shaft element  102  has an end  103  arranged to receive end  105  of coaxial inner shaft element  104  in a reciprocal slidable relation with the cylindrical body portion  52  of resilient elastomeric member  50  disposed internally of outer shaft element  102  and externally of inner shaft element  104 . 
     As used herein the term axial means along the longitudinal axis of the shafts. Forward means in the direction of insertion of inner shaft element  104  into telescoping relation with outer shaft element  102 . Rearward means in the opposite direction. The term radial means in a direction perpendicular to the longitudinal axis along which the telescoping elements are axially translatable. The terms radially inner or inward mean toward the longitudinal axis and radially outer or outward means in the opposite direction. As here illustrated, outer shaft element  102  is below and coaxial with inner shaft element  104 . However, this configuration could be reversed with the inner shaft element  104  positioned below the outer shaft element  102 . 
     As seen in  FIGS. 2 to 4 , outer shaft element  102  includes a pair of slots  106  disposed one hundred eighty degrees (180°) apart spaced below open end  103 . Slots  106  have an upper terminus  107  and a lower terminus  109  which define the limit of relative translation between shafts  102  and  104  as will be explained. 
     Shaft  104  includes a pair of engagement pins  110  spaced from the end  105 . As seen in  FIG. 3 , these pins are spring loaded radially outward by leaf springs  112  to be retractable radially into the shaft  104 . 
     The shaft elements  102  and  104  are assembled together to form the shaft assembly by insertion of end  105  of inner shaft  104  into end  103  of outer shaft  102 . The spring loaded pins  110  are pushed radially into shaft element  104  to pass into end  103  of shaft element  102 . Pins  110  engage within slots  106  and spring radially outward into the slots to connect the shafts  102  and  104  in a coaxial relation with axial translation permitted between the limits defined by the upper and lower terminus  107  and  109  of slots  106 . 
     The resilient elastomeric member  50  of the assembly is shown in  FIG. 1 . It comprises a cylindrical molded monolithic body portion  52  having an attachment portion  54  and a support portion  56  connected by spaced elongate webs  58  forming voids  59 . Attachment portion  54  is shown as a radially outward ring. It has a diameter somewhat larger than the diameter of cylindrical body portion  52  and is larger than the internal diameter of the outer shaft element  102 . 
     Elastic energy absorbing resilient member  50  is molded from a polymeric material that provides the qualities of energy absorption on elongation and resiliency sufficient to restore it to its original shape after initial elongation. The element is designed via a proprietary ITW (Dahti) process that orients the crystalline structure of the device which increases tensile strength and adds the elasticity required to absorb energy. It is made available by ITW-Nexus, Des Plaines, Ill. 
     The resilient member  50  may be molded from a variety of materials depending on the requirements of a specific application. It may, for example, be molded from a TPE (Thermoplastic Elastomer) material such as a COPE (Copolyester) material or a TPU (Thermoplastic Urethane) material. Suitable materials are available from Du Pont under the Hytrel® trademark or other commercially competitive materials. 
     After molding, the resilient member  50  is processed by elongation of portions of the structure beyond the yield point to align the crystalline lamellae in one direction. Such processing may proceed as disclosed in U.S. Patent Publication 2012/0153536, published Jun. 21, 2012, and entitled “Pre-deformed Thermoplastic Spring and Method of Manufacture,” the entire specification and drawings of which are hereby incorporated by reference herein as if fully set forth. 
     Referring to  FIG. 2 , resilient member  50  is sized such that the outer surface of cylindrical body portion  52  fits snugly within the end of outer tubular shaft  102 . The radial outward ring portion or attachment portion  54  rests upon end  103  of tubular shaft  102  to fix the position of resilient member  50  within the shaft  102 . In this regard, surface  55  of radial ring  54  serves as a retention or stop surface to limit axial movement of resilient elastomeric member  50  axially inward relative to shaft  102 . 
     Best seen in  FIG. 4 , the inner diameter of resilient elastomeric member  50  is such that it snugly receives the outer diameter of inner shaft  104 . When so inserted, inner shaft  104  is piloted within outer shaft  102  with end  105  resting upon support portion  56  with webs  58  captured between the inner surface of outer shaft  102  and outer surface of inner shaft  104 . 
     Referring to  FIG. 3 , support portion  56  includes a radially inward directed internal wall surface  57 . Wall surface  57  defines a retention or stop surface to limit the axial movement of shaft  104  into resilient elastomeric member  50 . 
     External surface  60  of support portion  56  is somewhat conical or curvilinear and defines a tapered centering node. It provides a forward guide surface to facilitate insertion of resilient elastomeric member  50  into the end of hollow tubular shaft component  102 . 
     Cylindrical body portion  56  and webs  58  of resilient elastomeric member  50  are disposed between the inner surface of the end  103  of outer shaft element  102  and the outer surface of end  105  of inner shaft element  104 . Pins  110  extend through aligned voids  59  into slots  106 . Note that the spaced elongate webs  58  define voids  59  which can be aligned with slots  106  in outer shaft  102  to permit disposition of pins  110  within slots  106 . 
     In  FIG. 3 , the assembly is shown in exploded view. Once assembled, the inner shaft  104  resides coaxially within outer shaft  102 . The axial length of cylindrical body portion  52  and webs  58  are such that the resilient elastomeric element  50  maintains pins  110  at the upper terminus  107  of slots  109 . In this position, the resilient elastomeric member  50  may be stressed or elongated slightly to create a restoring force urging the inner component  104  in the outward direction. 
     On loading of shaft elements  102  and  104 , inner shaft element  104  is urged further into outer shaft element  102 , causing elongation of resilient elastomeric member  50 . Such elongation continues until pins  110  reach the limit of travel within slots  106  and engage lower terminus  109  of slots  106 . Such movement and resultant elongation of resilient elastomeric member  50  cushion the impact of the applied load and, through tensioning elongation, develop a restoring force within resilient elastomeric member  50 . On removal of the applied load, the restoring force urges the inner shaft  104  to return to its original position with pins  110  at upper terminus  107  of slots  106 . 
     Notably, the cylindrical body  52  and webs  58  of resilient elastomeric member  50  are disposed between the relatively translatable shafts  102  and  104  and provide a journaling effect to reduce friction between the relatively translatable shafts and maintain coaxial alignment. 
     The number of webs  58  may be varied to alter the resilient and damping properties of the mechanism to correlate with the expected impact loading experienced during use of the coaxially aligned, translatable shafts. The properties of the dampening mechanism can, therefore, be tuned to the particular application involved. Because the damping mechanism is elastomeric, it is not susceptible to deterioration due to exposure to moisture or other environmental conditions. 
     Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.