Abstract:
A prosthetic suspension unit for cushioning shocks in amputees is provided. The prosthetic suspension unit has a first member adapted to be secured to a first prosthetic member and a stop located in the first member. An attachment member is adapted to be secured to a second prosthetic member. A bearing member is operative between the attachment member and the first member such that the attachment member may slide freely in an axial direction relative to the first member. An elastomeric energy storage element is positioned within the first member and includes a first portion abutting the stop. A second portion abuts a face axially moveable with the attachment member to compress the storage member upon application of load by the user.

Description:
RELATED APPLICATIONS 
     This is a Continuation Application of U.S. patent application Ser. No. 08/775,544 filed Dec. 31, 1996 now U.S. Pat. No. 5,961,556. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention is directed to a linear energy management unit or cush. More particularly, the present invention is directed to an energy management unit having a long stroke. This cush is an improvement over that which is described and claimed in U.S. Pat. No. 5,511,759 entitled “Hydraulic Chair Height Adjustment Mechanism” in which the assignee of the present invention has an interest, which is hereby incorporated by reference. 
     In the above cited patent, a closed-cell microcellular urethane foam member which is coated with a fluid-impervious urethane material is placed in the fluid compartment of a seat height adjustment device. An elastomeric bladder is used to store energy and to raise the seat to a fully extended position from which adjustment can be made. The hydraulic fluid used in the adjustment mechanism is incompressible and would provide anyone sitting in the chair a jolt or shock. The purpose of the cush is to provide a softer feel, to effectively cushion the system such that when a person is first seated in the chair, the incompressible fluid can compress something other than his or her backside. 
     There are several problems with this type of cush. Firstly, it is limited in its ability to effectively cushion a load, i.e., it has a short stroke. Secondly, there is no possibility to preload the cush. This is important as adjustable height chairs are brought into regulatory compliance. Current test standards require that the chair be able to have adjustability over a given stroke length when loaded with a weight of 130 lbs. Without the benefit of a preload, the seat will sag under load and additional stroke length will need to be afforded resulting in added component length and added expense. Thirdly, repeated cycling in the fluid environment results in some of the cells of the cush collapsing further reducing the cushioning effectiveness of the device. 
     In order to make the energy management unit more effective, as well as more versatile, i.e., capable of use in other applications, a significant re-thinking of the cush was necessary. The preferred embodiments of the present design provide an energy management unit that is a self-contained capsule which can simply be inserted into the system with which it is used. The elastomeric portions of the cush are isolated from the hydraulic fluid of the host system so that costly coatings can be avoided. Further, the present cush design is a linear device with an extended stroke to provide significantly greater cushioning than was previously possible. 
     A relatively unstable, collapsible elastomeric member is provided with guide means throughout its length (either circumferential or longitudinal). This elastomeric member is confined within a cylindrical sleeve to stabilize its movement. One end of the sleeve is plugged and the other end is provided with a slidable piston. The elastomeric member may be precompressed a desired amount (for the seat height adjuster application, by an amount sufficient to offset the 130 lb. weight). A protruding piston head can be provided with an O-ring to provide a sealing engagement with an inner cylinder which houses the capsulized cush to isolate the elastomeric member from the working fluid. The guide means engages the internal surface of the guide tube and provides damping of movement between the piston and the guide tube. A second embodiment for non-fluid applications is also provided. Adjustment capability for the precompression of the elastomeric means can be provided for appropriate applications. 
     Other features, advantages and characteristics of the present invention will become apparent after a reading of the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following figures depict the preferred embodiments of the present invention, like items bearing like reference numerals and, in which 
     FIG. 1A is a partial cross-sectional side view of a first embodiment of the energy management unit of the present invention in a seat height adjuster; 
     FIG. 1B is a partial cross-sectional side view of a prior art seat height adjuster with the cush the present invention is designed to replace; 
     FIG. 1C is an adjustable seat height chair in which the present invention can be used; 
     FIG. 2A is a partial cross-sectional side view of a second embodiment of the energy management unit of the present invention; 
     FIG. 2B is an end view of one embodiment of the energy storage device of the present invention; 
     FIG. 2C is a cross-sectional end view of the piston rod taken along line  2 C— 2 C in FIG. 2A; 
     FIG. 3A is a cross-sectional side view of a third embodiment of the energy management unit of the present invention for a different application; and 
     FIG. 3B is an end view of the piston used in this third embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the energy management unit of the present invention is shown in FIGS. 1A, with a slight variation shown in FIG. 2A, generally at  120 . FIG. 2A shows the cush  120  itself while FIG. 1A depicts it in use in a seat height adjuster  16 . As seen in FIG. 1C, chair  10  includes a pedestal  12  which is supported on casters  14 . Seat height adjustment mechanism  16  is housed in support tube  30 , while chair  10  is provided with a cushioned seat  18  and seat back  20 . Cush  120  will be described in conjunction with FIG.  2 A. 
     Cush  120  includes relatively unstable, collapsible elastomeric means  122  which is contained within cylindrical sleeve  124 . Cylindrical sleeve  124  provides elastomeric means  122  with controlled, stable deflection. One end of sleeve  124  is closed by plug  126  which is secured in place by crimping sleeve  124  as at  128 . The opposite end of sleeve  124  is closed by a cylindrical collar  130  which is similarly held in place by crimping sleeve  124  as, at  132 . A first end of piston rod  134  extends through collar  130  and engages an upper end  136  of elastomeric means  122 . A second end of piston rod  134  has a piston head  138  formed thereon with an O-ring  140  extending thereabout for sealingly engaging an inner cylinder  62 . 
     As best seen in FIG. 2B, elastomeric means  122  is provided with guide means in the form of longitudinal ribs  142  running the length of the elastomeric means  122 . The radially outermost surface of guide means  142  will be provided with a lubricant to reduce wear. The collapse of elastomeric means  122  into contact with the inner surface of sleeve  124  will produce damping to relative motion between piston rod  134  and cylindrical sleeve  122 . The elastomeric means  122  is preferably made of natural rubber, although other materials such as urethane and Hytrel plastics may be used, as well. The durometer of the material in the elastomeric means  122  preferably falls in the range of between 50 and 80. 
     The piston rod  134  is preferably made of a rigid plastic material and of cruciform cross section as shown in FIG. 2C, the radially extending ribs  144  providing maximum strength for minimum material usage and weight. Plug  126  will be similarly shaped. At a plurality of locations along its length, radially extending flanges  146  are provided to stabilize the piston rod  134  against canting within the sleeve  122 . Depending on the desired length of the piston rod  134 , either two (FIG. 2A) or three (FIG. 1A) flanges  146  will generally prove sufficient. 
     As can be seen in each of FIGS. 1A and 2A, the distance between lowermost surface of piston rod  134  and uppermost surface of plug  126  is fixed by crimpings at  132  and  128 , respectively. The amount of preload provided the system can be adjusted by controlling the length of elastomeric means  122 . It will typically be desired, for the seating application, to provide a preload equal to between 10% and 50% of the ultimate load of the elastomeric means  122  by compressing the elastomer between 5% and 40% of its uncollapsed length. As has been mentioned, the preload is necessary to prevent the seat height adjuster  16  from sagging under the specified test load, currently 130 lbs. 
     Comparing FIGS. 1A and 1B, it can be seen that much remains the same in the seat height adjuster  16 . An outer support tube  30  receives column tube subassembly  32  in its open end  34 . Subassembly  32  can move freely within tube  30  as inner support tube  46  slides within self-lubricating bearing  42 . A lower portion  38  of support tube  30  tapers inwardly toward bottom  36 . Cylinder  62  houses piston rod assembly  64  and has an open upper end  72 . Valve mechanism  66  is attached to the upper end of support tube  46  and seat washer  137  closes open upper end  72  of cylinder  62 . Valve mechanism controls the flow of hydraulic fluid to and from inside cylinder  62  from and to space  106  and, subsequently, into expandable bladder  68  through openings  90  in upper end  88 . By storing the hydraulic fluid in the expandable bladder  68 , energy is saved to lift the chair to its fully extended position for subsequent re-adjustment. End cap  76  includes a hub portion  78 , which has a throughbore  80 , and a cylindrical skirt  82  which captures lower end  92  of bladder  68 . 
     As can be seen by comparing FIGS. 1A and 1B, the cush  120  of the present invention replaces and performs the functions of both cush  220  and piston  64 . Plug  126  has an extension  127  that includes an annular recess that receives a retaining ring  129  that engages the lower surface of bottom  36  so that cush  120  is secured to support tube  30  and moves therewith, just as piston  64  did in the previous device of U.S. Pat. No. 5,511,759. Valve  66  still controls the flow of fluid to and from inside cylinder  62  from and to inside bladder  68  through space  106 . O-ring  140  seals the hydraulic fluid in space  106  out of cush  120  and, hence, protects elastomer  122  from contact with such fluid. In the cush  120  of the present invention, a reduced amount of hydraulic fluid is required and the fluid flow is shielded from possible interference from the internal cush. 
     A third embodiment of the cush of the present invention is shown in FIGS. 3A generally at  120 ′. Sleeve  124 ′ is stopped at one end by plug  125 ′, sleeve  124 ′ being crimped at  128 ′ to secure the plug  125 ′ in the desired position. Sleeve  124 ′ is provided with a reinforcement ring  129 ′ in those applications where sleeve  124 ′ is a structural member. In this embodiment, the elastomeric means  122 ′ is made up of a plurality of generally cylindrical units  123 ′. Each cylindrical unit has a radially extending flange  121 ′, the plurality of flanges  121 ′ fitting snugly in sleeve  124 ′ and serving as the guide means in this embodiment. This elastomeric means  122 ′, like its predecessor, is inherently unstable. The close fitting sleeve  124 ′ provides means to stabilize the collapse of the elastomer by its piston  134 ′. The opposite (upper) end of sleeve  124 ′ is closed by cylindrical collar  130 ′ which slidingly receives piston rod  134 ′, piston head  146 ′ engaging the upper end of elastomeric means  122 ′. The majority of the length of piston rod  134 ′ has a square configuration (FIG. 3B) which is received in a like shaped opening  135 ′ in cylindrical collar  130 ′. 
     A cylindrical external attachment means  150 ′ is received over the upper end of sleeve  124 ′. A slide bearing  152 ′ is received by the internal periphery of attachment means  150 ′ to facilitates relative axial movement of attachment means  150 ′ to sleeve  124 ′. An axial bore  141 ′ through piston rod  134 ′ is threaded and receives a fastener  154 ′. This fastener  154 ′ secures attachment means  150 ′ to piston rod  134 ′, with a cylindrical portion  137 ′ of piston rod  134 ′ being received in a similarly shaped recess  155 ′. Piston rod  134 ′ will move concurrently with external attachment means  150 ′ to collapse elastomeric means  122 ′, with square shaft in square opening  135 ′ preventing relative rotation between sleeve  124 ′ and attachment means  150 ′. For appropriate applications, plug  125 ′ can have a bore  157 ′ that is threaded to receive an adjustment bolt  158 ′. Bolt  158 ′ bears against washer  160 ′ and by adjusting its position relative to plug  125 ′, the amount of precompression of elastomeric means  122 ′ can be varied. (This feature would preferably not be added to the leg prosthesis application, disclosed herein, in order to avoid user tampering which could result in personal injury.) 
     One potential application for this third embodiment is as a prosthetic leg. Prosthetic limbs lack some of the resiliency their natural counterparts have and make walking more difficult. By employing the cush  120 ′ of the present invention, the resiliency provided by various components of the leg is effectively restored. In use, the cush  120 ′ as shown in FIG. 3A will be received in adapters  162 ′ in prosthetic foot  16 ′ and  163 ′ in stump cap  165 ′. Lower and upper ends of cush  120 ′ are received in, for example, 31 mm adapters manufactured by Hosmer US identified by part no. 39504. It will be understood that the specified adapter is regarded as merely exemplary and that the cush  120 ′ of the present invention could be configured to operate with other adapters, as well. In addition, the cush of the present invention is not limited to application with seat height adjusters and leg prostheses, but can be used in a variety of other applications where energy management is desired. 
     Various changes, alternatives and modifications will become apparent to one of ordinary skill in the art following a reading of the foregoing specification. It is intended that all such changes, alternatives and modifications as fall within the scope of the appended claims be considered part of the present invention.