WO1998042292A9

WO1998042292A9 - Shock absorbing ambulatory assist device

Info

Publication number: WO1998042292A9
Application number: PCT/US1998/005993
Authority: WO
Filing date: 1998-03-23
Publication date: 1999-03-11

Abstract

A shock absorbing unit that can be used with existing crutch designs includes an assembly for adjusting the shock absorption of the unit to enable the unit to be used comfortably with a wide range of patients. The adjustable shock absorbing crutch has an upper frame with an arm engaging portion and an extension tube. The crutch also includes a tip member with a lower extension tube engaged with the upper frame extension tube. A shock absorber (50) is positioned intermediate of the upper frame and the tip member. The shock absorber comprises a first bearing plate (78) including a first bearing surface and a second bearing plate (84) having a second bearing surface. The shock absorber also includes a resilient member (82a) positioned between and resting against the first and second bearing plates. The first and second bearing plates are spaced apart such that the resilient member is compressed. The shock absorber also includes compression adjustment unit (68, 69) for adjusting the space between the first and second bearing surfaces, thereby adjusting the compression of the resilient member.

Description

SHOCK ABSORBING AMBULATORY ASSIST DEVICE

Related Applications This application claims the benefit of United States Provisional Patent Application Serial No. 60/041,100, filed March 24, 1997, and the benefit of U.S. Patent Application Serial No. 08/848,320, converted to a provisional patent application by petition filed 8 January 1998.

Field of the Invention The present invention relates to mobility assist devices, and more particularly relates to walking aids.

Background of the Invention Walking aids such as crutches, canes, walkers, gurneys, and the like are typically used to improve the mobility of an injured or disabled person. Many of the users of the devices are elderly or injured and. sensitive to the configuration and stiffness of the walking aids.

For example, conventional crutches are configured to be positioned to rest against a tender part of the anatomy, i.e., under the arm. Unfortunately, this sensitive area must bear the force of the upper end of the crutch as the individual repeatedly introduces his or her body weight thereon. The force can be rather jarring, particularly as the crutch tip strikes the ground. Moreover, the magnitude of the force can vary at different points in the crutch support range. For example, the force experienced by the user as the crutch strikes the ground and the tip is slightly forward of the user's underarm differs from that experienced as the tip is directly above or rearward of the underarm. In addition, the magnitude of the force can vary with the height and weight of the user. This repeated jarring motion can make the load-bearing region under the arm very painful, even to such a degree that the individual stops using the crutches entirely. Further, many elderly persons use stiff canes. Unfortunately, the unforgiving stiffness of the cane introduce jarring forces against the wrist. This can be very painful and can even potentially injure users with sensitive orthopedic conditions such as osteoporosis.

As such, it has been the goal of many walking aids to reduce the discomfort associated with the devices. For example, many of the walking aids use rubber components on the floor engaging the tip of the device to help absorb some of the impact forces introduced thereto. Other devices such as canes or crutches have proposed employing a spring between the crutch tip and the upper frame of the crutch in an attempt to absorb forces that are transmitted between the user and the floor.

For example, U.S. Patent No. 2,528,706 to Osbom proposes positioning a spring on the exterior of the tube adjacent the tip end of a crutch.

Unfortunately, the spring is exposed and therefore unprotected against environmental corrosion and externally inflicted impact forces, each of which can potentially affect the life and shock absorbency of the device. In addition, the configuration of the spring on the crutch provides relatively small spring bearing surfaces between the opposing tip end and crutch leg end of the device; these can potentially introduce concentrated loads and premature wear thereon.

Other devices have proposed employing springs of differing shapes, sizes, and degrees of complexity, and positioned at various positions on and within a crutch. For example, U.S. Patent No. 2,426,594 to Buell et al. proposes a spring which extends between a fixedly secured plug on the top end and the upper end of the tubular lower segment of the crutch. As such, the spring acts against forces introduced by the moveable lower segment. Buell et al. also proposes a hydraulic piston which cooperates with a spring to enhance the shock absorbency of the device. Other examples of spring-loaded devices include U.S. Patent No. 1,334,208 to Ames, and U.S. Patent 665,439 to Hough.

The devices described hereinabove typically are complicated in design and are limited in their usefulness to certain users. Moreover, notwithstanding the use of springs and other shock absorbers, these devices typically transmit the magnitude of the impact force of the crutch contacting the ground in a single directional vector. Thus, the user often experiences discomfort in attempting to accommodate such an impact force.

In addition, typically a crutch user fails to use a crutch so that it stands completely upright as the user shifts his weight to the crutch. Instead, the crutch is often tilted slightly, with the upper end of the crutch being positioned nearer the user's body than the tip. As a result, a torque is generated along the axis of the crutch that is absorbed by the user's wrist and shoulder. Often, this torque is of sufficient magnitude to cause significant chronic discomfort to the user's hand, wrist and shoulder.

Objects and Summary of the Invention In view of the foregoing, it is a first object of the present invention to provide a walking assist device which is able to absorb shocks while being economical, easy to manufacture, and light weight. It is a second object of the invention to provide a walking aid that effectively absorbs shock over the entirety of the crutch support range.

It is a further object of the invention to provide a shock absorbing mechanism which is contained within the tube of the crutch and thereby protected from external hazards and associated damage. It is another object of the present invention to provide a shock absorbing mechanism that can reduce the torque absorbed by the user when the crutch is tilted during use.

These and other objects are satisfied by the present invention, which relates to a shock absorbing unit that can be used with existing walking assist device designs and includes means for adjusting the shock absorption of the unit to enable the unit to be used comfortably with a wide range of patients.

The walking assist device comprises a frame having an upper patient engaging portion and a lower extension tube which includes a plurality of longitudinally spaced apart openings for adjusting the length of the walking assist device. The device also includes a tip member having an extension tube telescopically engaged with the frame. The tip member is configured to contact the ground.

Engaging means are also present for engaging at least one of the frame extender tube openings to retain the tip member in a desired position to the frame. A shock absorber is positioned intermediate of the frame and the tip member. The shock absorber comprises an adjustable plate defining a first bearing surface thereon and at least one opening therethrough, along with a stationary plate which defines a second bearing surface thereon. The stationary plate is spaced apart from the adjustable plate. The shock absorber also includes a resilient member positioned between and resting against the first and second bearing plates.

In a preferred embodiment, the frame, the tip member, and the adjustable plate are configured such that the tip member is free to rotate about an axis of travel longitudinal to the device. Additionally, the resilient member is configured to bias the tip member against rotation about the axis of travel.

In another preferred embodiment, the resilient member comprises polymeric material which has a spring constant between about 115 pounds/inch and about 165 pounds/inch.

These and other aspects, features, and advantages of the present invention are explained in detail in the specification set forth below.

Brief Description of the Drawings Figure 1 is a front view of a crutch having a shock absorbing unit disposed therein. Figure 2 is a side view of the crutch of Figure 1.

Figure 3 is a top section view of the shock absorbing unit of the crutch taken along lines 3-3 of Figure 1.

Figure 4 is a front section view of the shock absorbing unit taken along lines 4-4 of Figure 3. Figure 5 is a side section view of the shock absorbing unit taken along lines 5-5 of Figure 3.

Figure 6 is a perspective view of an alternative embodiment of a shock absorbing unit of the present invention.

Figure 7 is a front section view of the shock absorbing unit of Figure 6.

Figure 8 is a side section view of the shock absorbing unit of Figure 6. Figure 9 is an alternative embodiment of a crutch of the present invention having a shock absorbing unit integrated with the tip portion of the crutch. Figure 10 is an enlarged front section view of the shock absorbing unit and tip of Figure 9.

Figure 11 is a front view of an embodiment of a walking assist device having a shock absorbing unit of the invention disposed therein. Figure 12 is an enlarged front section view of the shock absorbing unit of Figure 11 with the resilient member in an uncompressed condition.

Figure 13 is an enlarged front section view of the shock absorbing unit described in Figure 12 with the resilient member in a compressed condition.

Figure 14 is an environmental view of an individual employing a walking assist device of Figure 11.

Figure 15 is a perspective view of the shock absorbing unit of Figure 12 showing the rotational capability of the unit.

Figure 16 is an exploded view of a shock absorbing unit of the present invention. Figure 17 is a side view of the shock absorbing unit of Figure 16 in an assembled, undeflected condition.

Figure 18 is a side view of the shock absorbing unit of Figure 17 in a deflected condition.

Figure 19 is a graph plotting the force-deflection curve for a polymeric plug of the present invention.

Detailed Description of the Invention

The present invention will now be described more particularly hereinafter with reference to the accompanying drawings, in which present embodiments of the invention are shown. The invention may, however, be embodied in many different forms and is not limited to the embodiment set further herein; rather, these embodiments are provided so that the disclosure will fully convey the scope of the invention to those skilled in this art.

Referring now to the drawings, Figures 1 and 2 illustrate a shock absorbing crutch 20 of the present invention. The crutch 20 comprises an upper frame 22, a tip member 40, and a shock absorbing unit 50. Each of these components is described in greater detail hereinbelow.

The upper frame 22 has a user-engaging cushion 24 at its upper end which is configured to fit under the arm and shoulder of a user. The upper frame 22 also includes a generally horizontally disposed handle 26 that the user can hand-grasp during use. At its lower end, the upper frame 22 includes a vertically disposed extension tube 28. The extension tube 28 is hollow and includes number of apertures 30 arranged in vertical columns on opposite sides thereof. The apertures 30 are positioned along the extension tube 28 so that each aperture 30 aligns with a corresponding aperture 30 on the opposite side of the extension tube 28.

Referring still to Figures 1 and 2, the tip member 40 extends downwardly from the extension tube 48 of the upper frame. The tip member 40 includes an extension tube 42 which has a tip plug 44 at its lower end. The extension tube 42 is sized to fit within the cavity of the upper frame extension tube 28 and slide relative thereto. The tip plug 44, which is configured to contact the ground during use, is typically formed of rubber or some other non- slip material to improve traction for the crutch user. Those skilled in this art will recognize the illustrated upper frame 22 and tip member 40 as typical of that known in this art. Absent the shock absorbing unit 50, the tip member extension tube 42 would typically include apertures that can align with the apertures 30 in the extension tube 28. The extension tube 42 would be slidably inserted into the extension tube 28, and a pin or bolt would be inserted through the apertures 30 and the aperture in the extension tube 42 to set a desired crutch length. Of course any number of upper frame and tip member combinations can be used with the present invention. It is preferred that the combinations be height-adjustable and that the tip member be able to slide relative to the upper frame as described above. Referring now to Figures 3 through 5, the shock absorbing unit 50 includes both an upper block 52 and a lower assembly 70. The upper block 52, which serves to interconnect the shock absorbing unit 50 to the upper frame 22, comprises an upper plate 54, a lower plate 56, and a cylindrical side wall 58 that define therein a cavity 59. Within the cavity 59, a pair of spring members 62a, 62b are generally horizontally disposed; each is fixed at one end to a portion of the interior surface of the side wall 58. Each spring member 62a, 62b, which is typically formed of spring steel, includes at its free end a detent pin 64a, 64b. The detent pins 64a, 64b are positioned on the spring member 62a, 62b such that when the spring members 62a, 62b are in an extended position (see spring member 62a in Figure 5) the detent pins 64a, 64b extend through apertures 60a, 60b located in the upper block side wall 58.

Connection of the upper block 52 with the upper frame 22 is best illustrated in Figure 5, which shows that the detent pins 64a, 64b can, in the extended position, also extend through a corresponding pair of apertures 30 in the upper frame extension tube 28. This configuration fixes the upper block 52 relative to the upper frame 22. Also, by deflecting the detent pints 64a, 64b so that they take a retracted position within the cavity 59 (shown by spring member 62b in Figure 5), the upper frame extension tube 28 is free to slid relative to the tip member extension tube 42 so that the detent pints 64a, 64b can extend through a different pair of apertures 30 and therefore adjust the total length of the crutch 20.

Referring still to Figures 3 through 5, a tensioning bolt 68 extends through an aperture 54a in the upper plate 54, proceeds through the cavity 59, and continues through an aperture 56a in the lower plate 56. The tensioning bolt 68 includes a knob 69 over its head that rests against the upper surface of the upper plate 54. The tensioning bolt 68 also includes a nut 66 fixed thereto which rests below and against the lower surface of the lower plate 56.

Referring now to Figures 4 and 5, the lower assembly 70 includes an upper plate 72, upper and lower bearing plates 78, 84, a pair of bolts 76a, 76b, and a pair of springs 82a, 82b. The upper plate 72 resides on and covers the upper end of the tip member extension tube 42. It includes therein two apertures 74a, 74b through which the bolts 76a, 76b are inserted. The upper plate 72 also includes a centrally located aperture 75 through which the tensioning bolt 68 extends after extending through the aperture 56a in the lower plate 56. A nut 73 is fixed to the tensioning bolt 68 and resides below and rests against the lower surface of the upper plate 72.

Each of the bolts 76a, 76b extends downwardly from its fixed and countersunk position within the upper plate 72 and extends through both the upper bearing plate 78, which is positioned below the upper plate 72, and the lower bearing plate 74, which is positioned below the upper bearing plate 74. Nuts 86a, 86b are threaded on the ends of, respectively, the bolts 76a, 76b below the lower bearing plate 84. The upper bearing plate 78 includes a nut 80 fixed to the underside thereof. The nut 80 receives the lower end of the tensioning bolt 68 and is threaded to enable the tensioning bolt 68 to rotate therein. The upper bearing plate 78 is configured to be moveable relative to the bolts 76a, 76b along their longitudinal axes.

Each of the springs 82a, 82b is coiled about a respective bolt 76a, 76b between the upper bearing plate 78 and the lower bearing plate 84. The springs

82a, 82b are sized and configured such that they are in compression between the upper and lower bearing plates 78, 84 irrespective of their relative positions. The springs 82a, 82b can be nonlinear or linear. The springs are typically configured to provide spring constants (k) between about 10 pounds per inch ("lbs./in.") to about 50 lbs./in. and preferably configured to provide spring constants between about 25 lbs./in. to about 35 lbs./in. More preferably, the springs are configured to provide a spring constant of about 30 lbs./in.

To use the crutch 20, the patient begins with the upper frame 22 separated from the tip member 40 and the shock absorbing unit 50. The patient rotates the knob 69 relative to the upper plate 54 to move the upper bearing plate 78 relative to the lower bearing plate 84 (see Figure 3). This movement of the upper bearing plate 78, which is driven by the interaction between the threads of the bolt 68 and the nut 80 that is fixed to the underside of the upper bearing plate 78, "presets" the compression level of the springs 82a, 82b. Preferably, the user presets the compression in the springs 82a, 82b to a desired level based on the tension markings 55 located on the upper surface of the upper plate 54. The tension markings can correspond to the patient's weight, the hardness and composition of the underlying surface, and other factors as desired. It is preferred that the markings include reference to the patient's weight, as it has been determined that this factor can be extremely important in presetting the compression of the springs 82a, 82b for comfortable use. In general, the spring should be preset at a higher compression for a heavier patient.

Next, the patient selects a desired crutch length by compressing the spring members 62a, 62b and inserting the tip member extension tube 42 into the upper frame extension tube 28. Because the spring members 62a, 62b are retracted, the upper frame extension tube 28 is slidable relative to the tip member extension tube 42. When the upper and lower extension tubes are moved to a position in which a desired pair of apertures 30 of the upper frame extension tube 28 align with the apertures 60a, 60b of the upper block side wall, the spring members 62a, 62b can be released; the detent pins 64a, 64b extend through both the apertures 60a, 60b and the apertures 30 to set and retain a desired length of the crutch 20 (see spring member 62a in Figure 5). When a patient uses the crutch 20 and therefore applies weight to the user engaging cushion 24, that force is transmitted to the tip plug 44 and the extension tube 42. Because the extension tube 42 is free to slide within the upper frame extension tube 28, it does so. Thus, the upper plate 72 is drawn toward the upper block lower plate 56. Movement of the upper plate 72 causes the lower bearing plate 84, which is fixed relative to the upper plate 72, to be drawn toward the lower plate 56. However, the upper bearing plate 78 is fixed relative to the upper frame extension tube 28 and, therefore, does not move nearer the lower plate 56. Because the upper and lower bearing plates 78a, 84 move nearer one another, the springs 82a, 82b are further compressed and absorb energy that would ordinarily be transferred to the patient. As a result, the jarring force experienced by the patient under the arms is reduced considerably.

The ability to increase or decrease the "stiffness" of the crutch 20 can provide a more customized shock absorption for patients based on the patient's weight. Further, this feature can also allow an individual patient to adjust the device according to a patient's break-in period, as typically a patient has less tolerance when first using the device and which changes as the patient builds up a tolerance for the device. Moreover, the patient can easily adjust and counteract the effect of the walking surface by increasing or decreasing the shock absorption of the device. For example, a patient may desire a relatively stiff device in the home on flooring such as carpeting, but may prefer a less stiff crutch for use on hard surfaces such as concrete, hardwood flooring, or pavement.

Notably, the illustrated shock absorbing unit 50 is configured for integration with an existing crutch design. The upper frame 22 can retain its original configuration, and the tip member 40 needs only the attachment of the shock absorbing unit 50. Moreover, the shock absorbing unit 50 is contained within, and is therefore protected by, the extension tube 42 of the tip member 40, and is less exposed to possible damage from external sources than pπor art crutches.

An alternative embodiment of a shock absorbing unit of the present invention is illustrated in Figures 6 through 8 and is designated broadly at 100. The shock absorbing unit 100 is illustrated attached to a tip portion 90 having an extension tube 92 with a cylindrical side wall 98 much like that illustrated in

Figures 1 through 5.

Referring again to Figures 6 through 8, the shock absorbing unit 100 includes a solid housing 102 having an internal cavity 104, an upper portion 106 having an internal cavity 104, an upper portion 106 having a diametric groove 108 formed therein, and a lower cap 110 that completes the cavity 104.

The housing 102 fits within the upper portion of the side wall 98 of the tip portion 90, with the upper portion 106 of the housing 102 extending outwardly therefrom. Still referring to Figures 6 through 8, a connection block 111 having a transverse aperture 112 extending therethrough is connected with the housing

102 through a plunger 114 that is attached to an upper bearing plate 116. The plunger 114 extends into the housing cavity 104 through an aperture 107 in upper portion 106 of the housing 102. Within the cavity 104, the upper bearing plate 116 rests against a spring 118, which contacts a lower bearing plate 120 at its opposite end

(Figures 7 and 8). The lower bearing plate 120 is fixed to a bolt 122 that extends through an aperture 110a in the lower cap 110. The bolt 122 is threaded through a nut 124 which is fixed to the internal surface of the lower cap 110. A knob 126 is attached to the end of a bolt 122 that resides outside the housing cavity 124. The knob is accessible to the user to knob access apertures 128 located in the tip portion side walls 90.

To use the crutch, the aperture 112 in the connection block 111 is aligned with a desired pair of apertures in the upper frame of the crutch. A pin or bolt (not illustrated) is inserted through a desired pair of apertures in the upper frame (such as those illustrated at 30 in Figures 1 and 2) and through the aperture 112 to fix the connection block 111 relative to the crutch upper frame.

This connection selects a desired crutch length. A particularly suitable connection pin is a quick-release pin, such as a recessed-button style pin manufactured by McMaster-Carr, Atlanta, Georgia.

In operation, when the patient's weight is applied to the crutch, the tip portion 90 is free to slide within the upper frame of the crutch. However, the movement is resisted by the compression of the spring 118 between the lower bearing plate 120, which moves with the tip portion 90, and the upper bearing plate 116, which is fixed relative to the upper frame. The compression of the spring 108 absorbs energy applied to the crutch. As a result, the force transmitted to the patient during use is decreased considerably. As with the crutch illustrated in Figures 1 through 5, the shock absorbing unit 100 is also tension adjustable. Rotation of the knob 126 causes the bolt 122 to rotate within the nut 124. This action causes the lower bearing plate 120 to translate relative to the upper bearing plate 116, thereby adjusting the magnitude of the present compression in the spring 118. As with the embodiment illustrated in Figures 1 through 5, the shock absorbing unit 100 can easily be employed with existing crutch configurations; the shock absorbing unit can be inserted into the open top end of a tip member, then connected quickly with an existing upper frame. The shock absorbing unit 100 is also protected from external damage by the side wall 98 of the extension tube 92. In addition, this embodiment enables the patient to adjust the preset compression in the spring 118 while the upper frame and the tip member are connected.

An additional crutch embodiment is illustrated in Figures 9 and 10. The crutch 130 illustrated therein includes an upper frame 132 having a user engaging cushion 134, a handle 136, and an upper extension tube 138 much as that illustrated in Figures 1 through 8. A lower extension tube 140 having a tip plug 142 is attached to the upper frame 132 via a shock absorbing unit 150.

The shock absorbing unit 150 includes a hollow housing 152 having a top surface 154, a cylindrical side wall 156, and a bottom surface 158. The upper extension tube 138 extends through an aperture 154a in the top surface

154 and is fixed relative to the housing 152 via a set screw 160, which extends through a set serew aperture 167 in the side wall 156. An upper bearing plate 162 is attached to the side walls 156 via a pair of tension adjustment screws 164, which extend through vertical slots 156a, 156b in the side wall 156. A lower bearing plate 170 is fixed to the lower extension tube 140, which extends through an aperture 158a in the bottom surface 158. A spring 168 extends between the upper and lower bearing plates 162, 170.

In operation, force transmitted to the tip plug 142 by the patient is transmitted to the lower extension tube 140. Because the lower bearing plate

170 is fixed to the lower extension tube 140, it moves relative to the upper extension tube 138. However, the upper bearing plate 162 is fixed relative to the hollow housing 152 and therefore the upper extension tube 138, so movement of the lower bearing plate 170 is resisted by the spring 168. Accordingly, the force transmitted to the user engaging cushion 134 is dampened. The present compression of the spring 168 can be adjusted depending on the weight of the user by loosening the tension adjustment screws 164 and sliding the upper bearing plate 162 relative to the lower bearing plate 170. A further embodiment of the present invention is illustrated in Figures

11-15. Figure 11 depicts an adjustable shock absorbing walking assist device denoted as 200. The walking assist device 200 generally includes a frame 210 which has an upper patient engaging portion 220 and a lower extension tube 230. A plurality of longitudinally spaced apart openings 240 are also present and serve to adjust the length of the walking assist device. Engaged with the lower extension tube 230 is a tip member 250. The tip member 250 is configured to contact the ground and includes an extended tube 255 along with a tip plug 265 attached to the end of the extended tube 255. The extended tube 255 is preferably and illustratively telescopically engaged with the frame 210. A shock absorber 260 interconnects the frame 210 and the tip member 250.

Engaging means 270 such as a pin or bolt is provided to engage at least one of the openings 240 in the lower extension tube 230, and retain the tip member 250 in a desired position relative to the frame 210.

Figure 12 depicts the shock absorber 260 in greater detail. More specifically, the shock absorber 260 includes a first bearing member (e.g., an adjustable plate) 280 which defines a first bearing surface 290 thereon. An opening 300 through plate 280 is also present. Spaced apart from the adjustable plate 280 is a second bearing member (e.g., a stationary plate) 310 which defines a second bearing surface 320 thereon. Positioned between and resting against members 280 and 310 is resilient member 330. Advantageously, the resilient member 330 possesses spring constant values which are able to effectively absorb shocks over a wide range of impact forces. The resilient member 330 has an initial spring constant (k) between about 115 pounds per inch and about 165 pounds per inch. More preferably, the initial spring constant of the resilient member 330 is about 130 pounds per inch. The force-deflection curve illustrated in Figure 19 exhibits the nonlinear behavior preferred for the resilient member 330; i_e_, the force required to induce a deflection increases logarithmically with increasing deflection. The resilient member 330 is formed from various materials which are able to satisfy the above spring constant values. Preferably, the resilient member 330 comprises polymeric material, although other resilient materials, such as spring steel, are also suitable. A preferred polymeric material is a multi-cell polyurethane, such as one made by Urethane Rubber Inc., Port Sanilac, Michigan. A polymeric material having a Shore A Durometer value of about 45 is preferred, as such a material provides a desirable balance between absorption of shock imparted to the device 200 and elastic recovery to provide a lift or assist to the user as the force is released.

In accordance with the invention, the tip member 250, the adjustable plate 280, the stationary plate 310, and the frame 210 are preferably configured such that the frame 210 is free to slide relative to the tip member 250. Figures 12, 13 and 15 illustrate the axis of travel as longitudinal axis 1. As shown in Figure 12, the resilient material 330 is positioned in the shock absorber 260 so as to bias the adjustable plate 280 against sliding movement relative to the axis of travel I. In other words, although the resilient member 330 allows for movement of the adjustable plate along axis 1, (as shown in Figure 13) member 330 applies an opposite force against the plate 280 to provide support to the user.

It is preferred that the resilient member 330 be sized such that the travel of the adjustable plate 280 to relative to the stationary plate 310 is between about and ³A of an inch for the typical crutch user (less than 250 pounds). This is shown in the curve of Figure 19. This magnitude of travel has proven to significantly reduce the jarring aspects of crutch use while reducing instability due to shock absorption. Figure 14 illustrates a user 400 employing a walking assist device 200 of the invention. As shown, a user-engaging cushion 410 is present at the upper end of frame 210 and fits under the arm and shoulder of the user. A handle 420 disposed in the general horizontal direction is present and is grasped by the user 400. As shown, the extension tube 230 is vertically arranged to conform to the height of the user such that the tip member 255 touches the ground while the user-engaging cushion 410 rests under the user's arm. By virtue of the spring constant values of resilient member 330 contained in walking assist device 200, and since adjustable plate 280 is movable relative to the stationary plate 310 along the axis of travel 1, resilient member 330 is able to compress sufficiently such that device 200 absorbs an impact shock and simultaneously provides support to the user.

As demonstrated in Figure 15, the configuration of the tip member 250, the adjustable plate 280, and the stationary plate 310 is advantageous in that the resilient member 330 is free to rotate around the axis of travel 1. At the same time, the resilient member 330 is configured to bias the tip member 250 against rotation on the ground. Because of this, the tip member 250 rotates relative to the frame 210 a certain amount. As a result, the torque often transmitted to and absorbed by the user during use of the walking assist device 200 is reduced. Another embodiment of a shock absorber unit of the ambulatory assist device of the present invention is illustrated in Figures 16 through 18. As best seen in Figures 16 and 17, the shock absorber unit 500 comprises a steel pin 510, a tube insert 520 having a longitudinal aperture 522 extending vertically therethrough, a urethane plug 530 having a longitudinal aperture 532 extending vertically therethrough, and a detent receiver 540 with a recess 542. The pin

510 extends through apertures 522, 532 to fixedly press-fit into the recess 542. The tube insert 520 includes a lip 524 that rests upon the upper edge of the tip tube 550; the body 526 of the tube insert 520 is sized and configured to form an interference fit with the inside surface of the tip tube 550. The detent receiver 540 also includes a horizontally-extending aperture 544 that can receive a clip

546 or other interconnecting means to interconnect the shock absorber unit 500 to the upper portion of a crutch-, walker, cane, prosthesis, or other ambulatory support device. The pin 510 is sized such that the plug 530 is slightly compressed when the head 512 of the pin rests against the lower surface of the tube insert 520. The plug 530 and the tube insert 520 are free to rotate and translate relative to the shaft 514 of the pin 510. The plug 530 is resilient and preferably formed from a polymeric material, such as a multicell urethane resin. The discussion above regarding the characteristics of the resilient member 330 of Figures 11 through 15 is equally applicable to the plug 530.

In operation, a force applied to the upper portion of the ambulatory support device causes the upper portion to move downwardly relative to the tip tube 550 (see Figure 18). This movement causes the detent receiver 540 and the pin 510 to move downwardly. This movement is resisted by the plug 530, which is fixed relative to the tip tube 550 due to the interference fit of the tube insert 520 within the tip tube 550. As a result, shock associated with the downward force is absorbed by the plug 530.

In this configuration, as with the embodiment of Figures 11 through 15, the upper portion of the ambulatory support device is free to rotate about a longitudinal axis 1' relative to the tip tube 550. This is because the pin 510 is free to rotate within the tube insert 520 and the plug 530, but cannot rotate relative to the detent receiver 540, which is fixed to the upper portion of the ambulatory support device. The friction resulting from the compression of the plug 530 between the tube insert 520 and the detent receiver 540 causes the upper and lower surfaces of the plug 530 to "move with" the surfaces of the tube insert 520 and the detent receiver 540 that they contact. As a result, the plug 530 resists the relative rotation, and thus absorbs the energy imparted by such rotation rather than it being absorbed by a user of the ambulatory support device. This resistance to rotation increases with increased application of force, so the device is at its most resistive state to rotation when the application of force is at its greatest (such as when the user of a crutch has the crutch positioned in an essentially vertical position). Fortunately, this corresponds to the position in which the resistance to rotation should be at its highest.

The walking assist device of the present invention may be employed in the form of various specific structures. For example, the walking assist device may be, but is not limited to, a cane, crutch, walker, prosthesis, or other type of equipment. The selection of the above may be made by the user based upon the performance requirements of a given situation.

The embodiments illustrated and described above disclose typical embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

THAT WHICH IS CLAIMED

1. A shock absorbing patient walking assist device, comprising: a frame having an upper patient engaging portion and a lower extension tube which includes a plurality of longitudinally spaced apart openings for adjusting the length of said walking assist device; a tip member having an extended tube telescopically engaged with said frame, said tip member configured to contact the ground; engaging means for engaging at least one of said frame extender tube openings to retain said tip in a desired position relative to said frame; an adjustable plate defining a first bearing surface thereon and including at least opening formed therethrough; a stationary plate defining a second bearing surface thereon spaced apart from said adjustable plate; and a resilient member positioned between and resting against said adjustable plate and said stationary plate, wherein said resilient member comprises polymeric material and has a spring constant between about 115 pounds/inch to about 165 pounds/inch, said adjustable plate being movable relative to said stationary plate along an axis of travel, and said resilient member biasing said adjustable plate against such movement.

2. A walking assist device according to Claim 1, wherein said resilient material has a spring constant of about 130 pounds/inch.

3. A walking assist device according to Claim 1, wherein said polymeric material comprises a multicell polyurethane.

4. A walking assist device according to Claim 1, wherein said frame, said tip member, and said adjustable stationary plate are configured such that said tip member is free to rotate about said axis of travel and wherein said resilient member is configured to bias said tip member against such rotation.

5. An adjustable shock absorbing ambulatory support, comprising: an upper frame having an engaging portion and an extension tube; a tip member including a lower extension tube engaged with said upper frame extension tube; and a shock absorber interconnecting said upper frame and said tip member, said shock absorber comprising: a first bearing member including a first bearing surface; a second bearing member having a second bearing surface spaced apart from said first bearing member; and a resilient member positioned between and resting against said first and second bearing members and having a spring constant between about 115 pounds/inch to about 165 pounds/inch.

6. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said resilient member has a force constant of about 130 pounds/inch.

7. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said resilient member comprises a polymeric material.

8. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said polymeric material comprises a multicell polyurethane.

9. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said shock absorber resides within said upper and lower extension tubes.

10. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said upper frame extension tube includes a plurality of apertures positioned along the length thereof, and wherein said crutch further comprises means for engaging a selected one of said apertures to enable the length of said crutch to be adjusted.

11. An adjustable shock absorbing ambulatory support according to Claim 5, wherein said shock absorbing ambulatory support is selected from the group consisting of a crutch, a cane, and a prosthesis.

12. An adjustable shock absorbing crutch, comprising: an upper frame having an arm engaging portion and an extension tube; a tip member including a lower extension tube engaged with said upper frame extension tube; a shock absorber positioned intermediate of said upper frame and said tip member, and shock absorber comprising: a first bearing plate including a first bearing surface; a second bearing plate having a second bearing surface spaced apart from said first bearing plate; a resilient member positioned between and resting against said first and second bearing plate, said first and second bearing plates being spaced such that said resilient member is compressed; and compression adjustment means for adjusting the space between said first and second bearing surfaces, thereby adjusting the compression of said resilient member.

13. An adjustable shock absorbing crutch according to Claim 12, wherein said compression adjustment means includes a longitudinally extending threaded member which extends through one of said first and second bearing plates.

14. An adjustable shock absorbing crutch according to Claim 12, wherein said shock absorber is connected with and contained within said upper and lower extension tubes.

15. An adjustable shock absorbing crutch according to Claim 12, wherein said crutch further comprises visible indicia of compression corresponding to predetermined deployment positions of said compression adjustment means.

16. An adjustable shock absorbing crutch according to Claim 12, wherein said upper frame extension tube includes a plurality of apertures positioned along the length thereof, and wherein said crutch further comprises means for engaging a selected one of said apertures to enable the length of said crutch to be adjusted.

17. An adjustable shock absorbing crutch according to Claim 12, wherein said compression adjustment means is externally accessible without disassembly of said upper frame and said tip member.

18. An adjustable shock absorbing crutch according to Claim 12, wherein said shock absorber further comprises an elongated housing and a tension adjustment collar, said housing having opposing first and second ends, said first end adapted to receive said upper frame extension tube, said second end adapted to receive said lower extension tube.

19. An adjustable shock absorbing crutch according to Claim 18, wherein said tension collar defines said first bearing plate and said lower extension tube is attached to said second bearing plate, and wherein movement of said tension collar moves said first bearing plate relative to said second bearing plate to adjust the compression on said resilient member.

20. An adjustable shock absorbing crutch according to Claim 12, wherein said shock absorber further comprises an elongated housing defining a cavity therein, a plunger attached to said first bearing plate, and an externally accessible tension knob in communication with said second bearing plate for adjusting the compression on said resilient member.

21. An adjustable shock absorbing crutch according to Claim 20, wherein said plunger is configured to be attached to said upper frame, and said housing is positioned in said lower extension tube.

22. An adjustable shock absorbing crutch according to Claim 21 , wherein said shock absorber is contained within said upper and lower extension tube.

23. An adjustable shock absorbing crutch according to Claim 12, wherein said shock absorber further comprises a threaded member connecting said tension collar and said second bearing plate, and wherein said second bearing plate extends and retracts according to translation of said tension collar.

24. A shock absorbing patient walking assist device, comprising: a downwardly extending frame having an upper patient engaging portion and a lower extension tube which includes a plurality of longitudinally spaced apart openings for adjusting the length of said paced apart openings for adjusting the length of said walking assist device; engaging means for engaging at least one of said frame extender tube openings to retain said lower extension tube in a desired position; a tip having an extended tube telescopically engaged with said frame extension tube, said tip configured to contact the ground, an adjustable plate defining a first bearing surface thereon and including at least one opening formed therethrough; a stationary plate defining a second bearing surface thereon spaced downwardly apart from said adjustable plate; at least one spring positioned between said adjustable plate and said stationary plate such that said spring rests between and against said first and second bearing surfaces; and means for adjusting the distance between said bearing plates.

25. A walking assist device according to Claim 24, wherein said means for adjusting the distance between said bearing plates is a threaded member which extends through and is attached to said first bearing plate such that said first bearing plate translates in response to rotation of said threaded member.

26. A walking assist device according to Claim 25, wherein said threaded member is a bolt with a head portion configured to define a tension adjustment knob, and wherein said adjustable plate extends and retracts corresponding to rotation of said knob, thereby altering the distance between said adjustable plate and said stationary plate.

27. A walking assist device according to Claim 26, wherein said knob includes adjacently positioned visible indicia of spring compression corresponding to compression of said spring.

28. A walking assist device according to Claim 26, wherein said lower extension tube includes a planar upper plate thereon, and wherein said stationary plate is held in position inside said lower extension tube by a plurality of bolts affixed to said upper plate.

29. A walking assist device according to Claim 24, wherein said at least one spring is two springs.

30. An adjustable shock absorber for a walking aid, comprising: a plunger having a connector block and a downwardly extending portion terminating into a first bearing plate; an elongated housing having opposing top and bottom portions and defining a cavity therein, said top portion configured to slidably receive and downwardly extending portion of said plunger; a lower cap having an aperture formed therein attached to said housing bottom portion; a longitudinally extending threaded member including a knob thereon, said threaded member extending through said lower cap aperture and secured thereto; a second bearing plate disposed in said housing cavity spaced apart from said first bearing plate rotatably engaged with said threaded member; and a resilient member disposed in said housing cavity between said first and second bearing plates, wherein said second bearing plate translates relative to said first bearing plate to adjust the distance therebetween.

31. A shock absorber according to Claim 30, wherein said knob is configured to be externally accessible by an end user.

32. A shock absorber according to Claim 31 , wherein said plunger connector includes a transverse passage therealong.

33. A shock absorber according to Claim 32, wherein said plunger connector is configured to be received a predetermined distance in said housing top portion.

34. A shock absorbing patient walking assist device, comprising: a frame having an upper patient engaging portion and a lower extension tube which includes a plurality of longitudinally spaced apart openings for adjusting the length of said walking assist device; a tip member having an extended tube telescopically engaged with said frame, said tip member configured to contact the ground; engaging means for engaging at least one of said frame extender tube openings to retain said tip in a desired position relative to said frame; an adjustable plate defining a first bearing surface thereon and including at least opening formed therethrough; a stationary plate defining a second bearing surface thereon spaced apart from said adjustable plate; and a resilient member positioned between and resting against said adjustable plate and said stationary plate, said adjustable plate being movable relative to said stationary plate along an axis of travel, and said resilient member biasing said adjustable plate against such movement; wherein said frame, said tip member, and said adjustable stationary plate are configured such that said tip member is free to rotate about said axis of travel and wherein said resilient member is configured to bias said tip member against such rotation.