TECHNICAL FIELD

[0001] This invention relates to walking aids with resiliently-mounted feet, intended to alleviate problems experienced by users of conventional walking aids arising from shock loading transferred to the muscles of the hands, wrists, arms and shoulders; and to other apparatus incorporating resiliently-mounted feet or castors.

BACKGROUND OF THE INVENTION

[0002] Physiotherapists have evidence that suggests that the muscles of the shoulder in particular and the muscles of the hands, wrists and arms are stressed when using normal walking aids. Persons who have sustained several tears of the muscles of the shoulder tend to experience difficulty when using a rigid, uncushioned walking stick, crutch or Zimmer frame. Similarly, persons who have osteo-arthritis or rheumatoid arthritis often experience problems when using rigid support aids. Those who have hip and knee arthritis and have rotator cuff regeneration or tears in the shoulder also tend to be uncomfortable with rigid walking aids.

[0003] In order to alleviate such problems, walking aids with shock-absorbing feet have been proposed. One such device is described in GB-A-23 18510, in which the foot member slides telescopically over an upper sleeve, a spring providing for resilience in the sliding movement. However, in order to provide selective resilience according to the weight of the user, it is necessary to change the spring for another one of different spring rate. Additionally, although prior art shock-absorbing feet can be retrofitted to existing walking aids, there is a tendency for the feet to work loose and even to become detached from the shaft of the walking aid in use.

[0004] What has been needed but heretofore unavailable is a walking aid with a resiliently mounted foot that does not suffer from the above disadvantages of the prior art.

[0005] It is desirable that the ground-contacting ferrule of a walking aid can rotate axially with respect to the shaft, in order to promote user comfort and convenience. However, it has been found in practice that freedom of rotation in known apparatus, while not necessarily theoretically excluded, is in practice not smooth but on the contrary is subject, under twisting movement exerted by the user on the handle, to intermittent periods of rotational freedom separated by intervals of sticking, in which static friction and kinetic friction alternate with consequential rotational jarring experienced by the user.

[0006] In an attempt to overcome this problem, it has been proposed to introduce ball or roller bearings to enhance the freedom of rotation but it has surprisingly been found that the resulting walking aid is potentially disadvantageous or even dangerous in that, if placed on the ground at an angle to the vertical, the ferrule tends to rotate under pressure, resulting in the lower end of the shaft moving sideways and the walking aid failing to support the user's weight. There has thus long existed a need for an improved walking aid that includes, for example, a rotatable ground-contacting ferrule that provides for controlled or limited but nevertheless smoothly operating rotation.

SUMMARY OF THE INVENTION

[0007] According to one aspect of the present invention, a walking aid comprises a shaft and a foot assembly, in which the foot assembly comprises in combination a sleeve member and a foot member adapted for relative axial sliding movement and including spring means resiliently to restrain said sliding movement, the sleeve member being adapted for attachment to the shaft and including grip means for inhibiting or preventing removal from the shaft once attached thereto.

[0008] The shaft may be the leg or a leg of a crutch or walking frame or may be attached to the lower end of such a leg, which includes solid and tubular legs.

[0009] In another aspect, the invention provides a foot assembly suitable for attachment to the shaft of a tubular walking aid or a tubular leg of a walking aid, the foot assembly comprising in combination a sleeve member and a foot member adapted for relative axial sliding movement and including spring means resiliently to restrain said sliding movement, the sleeve member including grip means for inhibiting or preventing removal from the tubular leg once attached thereto.

[0010] Preferably, the foot member comprises a base element to which a conventional rubber or plastics ferrule or shoe is attached, the base element being connected to a neck member which is journalled in the sleeve member with a compression spring therebetween, the neck member being provided at its upper or distal end with a screw thread to receive a retaining and resilience-adjustment nut. One or more bushes, also known as bushings, may be provided between the neck and sleeve members to facilitate axial sliding movement and, desirably, a relative axial rotational ability.

[0011] The grip means may comprise a resiliently-compressible element associated with the sleeve member for force-fitting within the shaft, whereby the sleeve member is retained within the shaft by friction forces acting between the resiliently-compressible member and the internal wall of the shaft. Preferably, however, the grip means comprises an element adapted to permit the sleeve member to be slidingly inserted within the shaft but which expands radically to assume a jamming position on attempted withdrawal thereof. Such an arrangement may be provided by for example an expandable ring such as a rubber or plastics O ring or a snap-ring, which may also be made from metal, carried in an annular groove formed in the external surface of the sleeve member, the groove having a sloping or chamfered wall which urges the ring to expand to jam against the shaft wall on relative movement between the sleeve member and shaft in a direction of movement whereby the sloping or chamfered wall is the trailing or rear wall.

[0012] When using walking aids according to the invention, the user experiences more surefooted ground contact than with rigid devices, even on slippery surfaces, the light spring force ensuring a more stable initial contact and the full load being gradually applied as the spring compresses. There is thus less of a tendency for the foot to slip or skid away when placed on the ground at an angle to the vertical. Furthermore, the sleeve member is desirably free to rotate axially about the foot member; such freedom of rotation not only promotes even wear and hence a considerably extended life to the ground-contacting ferrule but also manifestly improves user comfort and convenience, in that any twisting motion as between the user and the walking aid is more readily accommodated by the walking aid.

[0013] In yet another aspect, the present invention provides walking aid apparatus comprising a handle portion and a shaft portion including a ground-contacting ferrule, the apparatus comprising telescopically-mounted relatively rotatable elements and spring means acting between said elements resiliently to restrain relative compression movement, in which the bearing surfaces of the spring means and at least one element comprise sliding friction-reducing materials whereby rotation between the handle portion and the ferrule accommodates twisting movement as between the user and the ground in a controlled manner.

[0014] By “sliding friction-reducing materials” in this specification is meant a materials couple which reduces the friction between at least one end of the spring means and the associated element, relative axial rotation being accommodated by sliding movement therebetween. It has been found that the use of sliding friction-reducing materials results in controlled rotation as between the spring means and at least one of the telescopic elements with considerable benefits to the user in avoiding tortional loading to the wrist, elbow and/or shoulder joints which can be especially painful to those who suffer from arthritis, without the disadvantages arising from uncontrolled rotation such as results from the use of ball or roller bearings.

[0015] The bearing surface of the at least one element which is capable of axial rotation relative to the spring means may be an integral part of the element itself or alternatively may comprise a separate friction-reducing element having a spring-contacting surface and an oppositely-facing surface which bears against a seat of said element, rotational sliding movement taking place between the spring means and the separate element and/or between the separate element and the seat. The sliding friction-reducing element preferably comprises an annular washer, which may be configured as a cup washer, the cup comprising the spring-facing surface and a peripheral wall to encompass the extremity of the spring means. The material from which the sliding friction-reducing element is formed should preferably be sufficiently hard to be accurately machined with a substantially flat seat-facing area while providing for the required degree of friction with the other material of the couple to give controlled rotation under load conditions. Suitable materials include engineering plastics materials such as acetal-type copolymers which may optionally be glass- or fiber- reinforced. However, the choice of material is to some extent governed by the diameter of the ferrule or at least the ground-contacting lower surface thereof, since a larger-diameter ferrule will have a greater resistance to twisting movement on the ground and, hence, a material with less inherent lubricity is preferred for the friction-reducing means, in order to provide the desired controlled rotation. Where the seat of the telescopic element bears directly on the spring means, similar criteria as to the choice of materials apply.

[0016] The telescopically-mounted relatively rotatable elements typically comprise an outer sleeve element and an inner spindle element, the elements being capable both of relative axial sliding movement to accommodate compression and expansion as a load is applied to or released from the handle portion of the apparatus and of relative axial rotation to accommodate twisting movement as between the user and the ground in use.

[0017] The spring means may be any resilient element and may comprise for example a helical spring, a pneumatically- or hydraulically-controlled strut or a resilient elastomeric material; conventionally, a helical stainless steel spring is used but other resilient materials or assemblies may equally be used in the inventive apparatus. The inner or spindle telescopically-mounted element may have an inner co-axial neck portion of reduced diameter, an annular gap being defined between the neck portion and the sleeve element and which accommodates the spring means which, conveniently, comprise a helical spring. However, in another arrangement, the inner telescopically mounted element has an inner end face which bears, directly or via a friction-reducing element, on one end of the spring means. In such an arrangement, the spring means may comprise a block, typically a cylindrical block, of resilient elastomeric material. In yet another arrangement, the spring means bears directly on the ferrule or is integrally formed with the ferrule from a suitable elastomeric material. The spring means is preferably pre-loaded so that, even when in the fully-extended position of the telescopically-mounted elements, the spring means nevertheless remains partially compressed, thereby causing the apparatus to exhibit the controlled rotation property under a no-load or very light loading exerted on the apparatus through the handle portion.

[0018] Preferably, the apparatus includes cylindrical bushes journalled between the cooperating axially slidable surfaces of the telescopically mounted elements, the bushes enhancing the relative axial sliding movement and optionally assisting to a lesser extent in the controlled rotation. The bushes are preferably formed from a suitable plastics material which may comprise nylon or an engineering plastics as in the case of the sliding friction-reducing element.

[0019] The use of a pneumatically- or hydraulically-controlled strut, for example a nitrogen-damped cylinder and piston, for the spring means is advantageous in that the damping force may be adjusted according to the weight of the user by pre-loading to a particular desired gas pressure, for example by the physiotherapist. The ability to increase or decrease the pressure enables stocks of a single unit to be maintained, to be selectively adapted to the requirements of the individual user at the time of supply.

[0020] In an alternative way of pre-loading the spring means, the distal end of the inner telescopically-mounted element may comprise a screw-threaded portion carrying a lock nut which bears on the outer element to adjust its position relative to the inner element, thereby compressing the spring means. The distal end of the outer element may have a counter-bore to accommodate the lock nut; the open end or mouth of the counter-bore may accommodate resilient damping means to act as a cushion for the distal end of the inner element and lock nut on full-load compression of the spring means. Additionally, the proximal end of the outer element, which in use accommodates the spring means, may be formed with an annular groove formed in the wall thereof and which carries a resilient O-ring, preferably supported on an inner-extending shoulder constituted by one wall of the groove. Where the inner element comprises a smaller-diameter neck portion extending co-axially of the cylindrical portion for carrying the spring means and the pre-loading lock nut, an annular shoulder is defined between the cylindrical portion and the neck portion and which makes contact with the O-ring at the position of maximum compression movement while still retaining the ability for controlled rotation. Desirably, where cylindrical bushes are contained in such an arrangement, they are journalled at the proximal end between the cylindrical portion and the inner-facing wall of the sleeve element and at the distal end between the plain part of the neck portion and a smaller-diameter portion of the sleeve element.

[0021] The sub-assembly comprising the telescopically-mounted elements and spring means may be carried, in walking aid apparatus according to the invention, either towards the ferrule end or towards the handle portion end, or indeed at any intermediate location. It has been found in practice, particularly for use by people who are relatively infirm, that provision of the sub-assembly close to the handle portion gives a greater sense of control and hence a greater sense of security.

[0022] The shaft portion of walking aid apparatus according to the invention may comprise an aluminum tube, as in many walking sticks or Zimmer-frames used by people under medical supervision, but may equally be a conventional solid, for example wooden, shaft, if appropriate including a tubular portion for receiving a foot assembly as hereinbefore described, since the invention provides benefits to walking aids such as conventional walking sticks where there is no particular medical condition which requires the use thereof. When used with a metal tubular walking aid, the inner element may be mounted in the tube, whether at the top or bottom thereof, by means of an arrangement as described and comprising grip means for inhibiting or preventing removal from the shaft once attached thereto. Particularly when attached to the upper end of the shaft, both the inner and outer elements may be carried respectively in a cylindrical tube attached to the handle and to the cylindrical shaft using such a grip means. Plastics materials may also be used for the shaft and/or for one or all of the components of the telescopically mounted sub-assembly, provided that the required degree of controlled rotational ability is exhibited as a function of the frictional forces between the rotational bearing surfaces.

[0023] In order to avoid any possibility of a pinching movement as between the outer telescopically-mounted element and the shaft or handle portions in a position at or approaching maximum compression thereof, at least one of the facing edges of the outer element and the shaft or handle portions, preferably both, may be provided with a chamfer so that, even when fully compressed, there remains an annular V-shaped gap between the outer walls thereof.