Abstract:
Walking aids are described which are of simple construction but which allow for both resilience, i.e. the part of the walking aid which is gripped by the user and the ground-engaging end ( 3 ) can be resiliency pressed together, as well as a degree of angular flexibility so that the end ( 3 ) stays aligned with the ground even if the stick, crutch or the like ( 1 ) is angled relative thereto. This is achieved in particular by the use of a bellows structure ( 2 ) between the shaft ( 1 ) of a walking aid and a ground-engaging foot ( 3 ).

Description:
FIELD OF INVENTION 
     This invention relates to walking aids and, in particular, to the piece of a walking aid which engages with the ground. 
     BACKGROUND OF INVENTION 
     Walking aids include walking sticks, canes, crutches and the like which are used by individuals to assist in supporting them by taking some of the weight which would otherwise be borne by the feet alone. The walking aid is usually held in the hand in the case of a walking stick or cane, on the arm in the case of certain forms of crutch and underneath the arm in the case of other types. In all of these cases, an important desideratum is that the engagement between the base of the walking aid and the ground surface is adequate to prevent slipping. This may be achieved, for example, by a very small ground-engaging surface such as a spike or narrow ferrule, but this is not ideal, particularly if the walking aid is to be used indoors where such a small surface, because of the high pressure it generates, may cause damage to floors, carpets or the like. 
     An alternative approach is to have a high friction surface, larger area pad; rubbery end caps which fit over walking sticks and the like are well known. There are several commercially available designs, none of which is ideally suited to all conditions and many of which are inflexible insofar as the degree of grip they give depends very strongly on the angle between the support surface and the longitudinal axis of the cane or stick itself. EP-A-0605935 discloses a crutch tip incorporating two different materials with a view to improving the grip, but this will only operate properly when the crutch shaft is vertical. 
     A number of suggestions have been made in the patent literature to avoid this difficulty by enabling the end to swivel. Examples of such disclosures are EP-A-0112141, FR-A-2715559 and U.S. Pat. No. 5,865,204. 
     The greater the resistance of the foot slipping, so the greater the resistance of the cane to twisting, i.e. rotation about its elongate axis. This can make for discomfort in use, and accordingly it is known to provide, between the ground-engaging member and the stick or cane itself, a degree of rotational freedom. 
     A separate issue, of particular importance in the case of crutches but nevertheless also in the case of walking sticks, is the relative axial incompressibility of the stick itself. There have been a number of suggestions in the patent literature to provide walking aids with resilient feet, i.e. ones which are resiliently mounted on the shaft of the walking aid itself. These normally take the form of some type of telescoping arrangement with an internal spring. Examples of these are disclosed in GB-A-124691, WO 00-10502, U.S. Pat. No. 2,888,022, U.S. Pat. No. 2,856,943, U.S. Pat. No. 2,397,499, GB-A-613046, DE-U-8751507 and U.S. Pat. No. 2004/0035453. 
     DE-C-4136210 discloses an alternative approach to providing resilience in a crutch. It has a telescoping section with a cellular polyurethane elastomer cylindrical member as a shock absorber. U.S. Pat. No. 4,881,564 discloses a crutch tip with a deformable skirt and including a damping pad. 
     Many of the constructions disclosed in the various patent publications identified above are complex and susceptible in particular to failure in use on account of wear and tear, or the penetration of dust and grit into moving parts. 
     SUMMARY OF INVENTION 
     According to a first aspect of the present invention there is provided a walking aid such as a crutch, walking stick or the like having at its ground-engaging end a generally transverse end wall, formed on an end piece, wherein the end piece is fitted to a lower end of a shaft, and wherein the end piece, intermediate the portion fitted on to the shaft and the transverse ground-engaging end wall, is both axially compressible and laterally bendable whereby to enable the grounding-engaging end wall to lie flat against a surface with the shaft at an angle not normal thereto and simultaneously to absorb resiliently an axial load applied to the shaft. 
     While it is possible to conceive of end pieces of different construction, for example air-filled sealed ball or sac, the preferred construction of the end piece is one incorporating a bellows section. A bellows section may be compressed axially with the “folds” approaching one another evenly, or it may allow the folds to be compressed more on one side and less on the other (or even expanded on the other), so enabling the end piece effectively to bend. 
     Such a bellows section may be formed integrally with the remainder of the end piece, most conveniently by moulding. The moulding may be an integral moulding purely of a suitable rubbery or plastics material, or, for example, it may be of a composite material. Alternatively, the bellows section may be located intermediate a socket designed to fit on to the shaft and a ground-engaging foot member designed to contact the surface of the ground, and which may if desired be provided with a tread pattern to reduce the risk of slippage. The foot member may be held captive on the lower end of a bellows member by a retaining ring. 
     A bellows form also provides a high degree of lateral stability due to the stiffness of the pleats which can resist lateral or sideward loads but the hinge points between each pleat allow a large amount of vertical movement; this is of particular value where the walking aid is a crutch. Furthermore, the use of a sealed bellows, in which the air is compressed under load, acts as a damper and the higher the load the greater the damping. It also helps the bellows to recover to its original length once the load is released and the air expands back to its original pressure thereby forcing the bellows towards its original length. A bellows which is made from a stiff material as opposed to a rubbery material, will tend to shorten after time due to creep and permanent deflection at the hinge points. Therefore by using a sealed bellows containing air/gas or a compressible gel or other liquid/gas combination this can be overcome. A bellows made exclusively from a rubbery material may be too flexible for some applications and will not be able adequately to resist the lateral loads. 
     While simple bellows constructions may be appropriate for many cases, it is possible to conceive of using more complex arrangements, for example one in which, in a sealed bellows, there is an internal valve or constriction between two internal chambers, with fluid flow occurring from one to another via the valve or constriction when the bellows is loaded or unloaded. One way of achieving this in simple fashion is to mount two bellows together to form a bellows assembly which has two chambers separated by an air/liquid control device to control the movement of the internal fluid/gas from one chamber to the other and thereby control the rate of compression. By fixing two bellows together at their necks by welding or using a suitable joining device, a control device can be incorporated at the interface. 
     The degree of axial resilience and lateral bendability may be varied widely by appropriate constructional means. These may include the geometry and materials of which the bellows section or the entire end piece is made (for example using a bellows of non-circular cross-section), as well as, for example, the introduction of some form of central compression spring, for example in the form of a standard helical compression spring. However, as noted above, a bellows may be configured as a so-called “gas spring”, i.e. a chamber filled or partly filled with a compressible fluid. The spring characteristics differ from that of a standard helical spring, but this can be of advantage in walking aids, giving a reasonable degree of axial movement under light axial loading with increasingly less movement as loading increases. If a gas spring type of bellows device is used, the particular characteristics may be varied by providing means to increase or decrease the internal pressure at rest. 
     The ground-engaging end of the end piece may be formed integrally with the end piece itself or, for example, may be in the form of an end plate or cap, e.g. of highly wear-resistant material, which is clipped or moulded on to the remainder of the end piece, or adhered or welded thereto. It may have a tread in order to increase grip. In order to avoid risk of penetration by sharp objects which could puncture the bellows, the end cap may include a transverse metal plate. 
     It is preferred to mount the end piece on the shaft of the cane, stick, crutch or the like in a way enabling its rotation about the longitudinal axis of the shaft, or to provide that the end piece itself is constructed so that the ground-engaging portion can be rotated with respect to the shaft-engaging portion around an axis parallel to that of the shaft. A particularly preferred way of achieving this in the case of an end piece incorporating a bellows is to form the end piece of a first portion having an end adapted to engage over the end of the shaft and an opposite socket and a second portion constituting or including a bellows having an axially protruding stub member which may be inserted for free rotation into the socket in the first portion. 
     A particularly elegant way of achieving this is to provide that the socket at its outer end is threaded and that the protuberant portion of the second member is threaded at its outer end, the length of the protuberant portion and depth of the socket being such that the two threads may be engaged one with another and, by continued rotation, then moved out of engagement with one another, with the outer end of the socket portion then engaging around the shaft of the protuberant portion and the distal end of the protuberant portion being located in the base of the socket. 
     Numerous other approaches may be adopted, but, as indicated above, preferred are simple mechanisms which may be easily constructed and fitted together and which are resistant to failure on being subjected to dust, grit, mud, water penetration, etc. 
     The end piece may be constructed so that it will fit on the shaft of any appropriate walking aid, for example by having a socket in it which is usually round for a walking stick or cane and may also be generally rectangular in the case of a crutch made of extruded rectangular section alloy tube. The end piece may have internally tapering ribs in a socket into which the shaft fits in order to provide a firm press-fit connection between the shaft and the end piece. 
     In accordance with a second aspect of the present invention, there is provided a walking aid such as a crutch, walking stick or the like incorporating an elongate shaft and including, between the shaft and a ground-engaging end piece or between two sections of the shaft a resilient bellows structure adapted to impart an overall resilient compressibility to the walking aid in the direction of the elongate shaft. 
     Where the bellows structure is incorporated into the shaft itself, the sections of the shaft either side may be configured to ensure that the resilience is maintained but without the shaft being able to bend materially about the bellows. This may be achieved, for example, by locating the bellows in a hollow section of a part of the elongate shaft with the other part carrying a sleeve which is a telescopic fit over the first part of the shaft. 
     The bellows structure incorporated into the shaft is preferably a sealed bellows structure acting as an air spring between the two parts of the shaft. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention is illustrated by way of example with reference to the accompanying drawings in which: 
         FIG. 1  is an axial sectional view of the lower end of a walking aid including an end piece in accordance with the present invention; 
         FIG. 2  is a similar axial section showing an alternative embodiment; 
         FIG. 3  is a further axial section showing a further embodiment; 
         FIG. 4  is an axial section of part of a stick or crutch according to a further embodiment; and 
         FIGS. 5 to 10  are diagrammatic axial sections of further end pieces for use in constructing walking aids according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to  FIG. 1 , the shaft of a walking aid such as a stick or crutch is denoted  1  and has fitted to its base an end piece consisting of a sealed integral moulded bellows unit  2  around the lower end of which is clipped a relatively hard moulded rubber cap  3 . 
     The upper end of the bellows unit  2  has a pair of lateral protuberant beads  5  which are a press fit inside shaft  1 . Located between the bellows portion of bellows unit  2  and the lower end of shaft  1  is a steel washer  6  which distributes the axial load on the top of the bellows unit  2 . 
     As can be readily appreciated, the angle of the shaft  1  may be varied as indicated by the double-headed arrow  10 , with the ground-engaging cap  3  staying fixed in position. At the same time, if the shaft  1  is axially loaded, then the axial extent of bellows  2  decreases. 
       FIG. 2  shows an arrangement similar to  FIG. 1  and the same reference numerals are used for corresponding components. However, as shown in  FIG. 2 , the upper end of the bellows  2  is set in an intermediate short sleeve member  12  which is fitted between shaft  1  and bellows  2 . 
     Upwardly, member  12  has an annular groove defined between an inner cylindrical wall  14  and an outer cylindrical wall  15 , with the lower end of shaft  1  penetrating into the groove. Resilient ribs  16  are moulded on to the wall  14  and serve to engage the interior wall of shaft  1  to hold member  12  firmly on shaft  1 . 
     Member  12  also has a depending annular skirt  18  which assists in controlling the location of the bellows  2 . On the interior cylindrical wall of member  12  are annular ribs  21  which are of such a size, shape and resilience that ribs  5  on the top of the bellows  2  can be pushed past them so that the bellows  2  is lodged in member  12  and held captive in it as shown in  FIG. 2 . The dimensions are such that the bellows  2  is a loose fit and accordingly can rotate about the longitudinal axis of shaft  1  relative to that shaft. 
       FIG. 3  shows yet a further version where there is a bellows between a shaft  1  and an intermediate piece  22  on the one hand and a ground-engaging end cap  3  on the other. In the case illustrated in  FIG. 3 , however, the intermediate piece  22  consists of a double-ended sleeve having a transverse dividing wall  25  across it. Wall  25  acts as a stop to limit the degree of insertion of shaft  1  into member  22 . Ribs  26  ensure a tight frt. 
     The lower portion of the member  22  is in the form of a socket  28  into which a bellows  24  is screwed. The top end of bellows  24  has a couple of turns of helical thread  29  on it and the lower portion of sleeve  28  likewise a couple of turns of helical thread  31  on it. As shown, threads  29  and  31  can be made to cross over one another leaving the bellows  24  and end cap  3  rotatably set in the socket portion  28  of the intermediate member  22 . 
     As shown in  FIG. 3 , the upper end of the bellows  24  is closed by a sealing bung  33 . If it is desired to stiffen the resistance of the bellows  24  to axial compression, air may be injected through bung  33  which is then sealed within bellows  24  under whatever pressure is appropriate. The axial spring characteristics of bellows  24  may also be changed by introducing a certain quantity of liquid into the interior of bellows  24 . 
     Referring now to  FIG. 4 , this is an axial section of a shaft of a walking stick into which a resilient sealed bellows has been incorporated. As can be seen in  FIG. 4 , the upper portion of the shaft  30  slides in a cylindrical sleeve  31  which is fast with the lower portion of the shaft  32 . Mounted in cylindrical sleeve  31  and abutting the top end of shaft portion  32  is a sealed bellows unit  35  which is axially compressible. It may carry suitable end pieces  36  to minimise the wear and prolong its service life. The upper portion of the shaft  30  may be rendered captive in sleeve  31  by any convenient means, for example a pin passing through the base of shaft portion  30  and sliding in a pair of axial slots in sleeve  31 , though that particular method prevents portions  30  and  32  of the shaft twisting about the shaft axis relative to one another. Such twisting movement can be advantageous, as explained above, but if it is not needed, then the shaft may be of other than circular cross-section, for example oval or square. 
     As illustrated in the drawings, use is made of a resilient bellows to provide resilience and, in the case of the embodiments shown in  FIGS. 1 to 3 , bendability of the lowermost part of the walking aid. In any such case, the particular mechanical characteristics of the bellows will depend on its geometry and material of construction. This may be varied widely, but it is not always straightforward to make long relatively narrow bellows. In such a case, two shorter lower aspect ratio bellows may be aligned with one another to provide a composite bellows system in a simple and cost-effective fashion. 
       FIGS. 5 to 10  show diagrammatically a variety of further end piece constructions, each of which is fitted on to the end of a shaft  1 , for example of a walking stick. 
     In  FIG. 5 , a moulded bellows  50  has a socket on one end into which the shaft  1  fits and in its other end has a hole which is plugged by a foot member  51  which essentially seals the bellows. The base of foot member  51  has a ground-engaging tread  52 . 
     Referring to  FIG. 6 , a blow-moulded bellows unit  60  has a groove at one end enabling it to be received into a circular aperture in an end cap  62  which is a press fit on the shaft  1 . A ground-engaging rubber moulding  63  with a tread pattern  64  is held on to the lower end of the bellows  60  by means of a retaining ring  65 . A metal plate  68  is located between the lower end of the bellows  60  and the inside of foot  63  so that if a sharp object should penetrate through the material of foot  63 , it will nevertheless not penetrate into the bellows itself, thus puncturing it. 
       FIG. 7  shows a single piece moulded bellows  70  having a tread formation  71  at its lower end and an integrally moulded socket  72  at its upper end for receiving shaft  1 . 
       FIG. 8  shows an integrally moulded rubber bellows  80  having a tread  81  and which is sealed by a plug  82 . Plug  82  is formed integrally with an end cap  83  into which the shaft  1  fits. 
       FIG. 9  shows a construction including a moulded bellows  90  having a rubber foot  91  held on its lower end by a clip  92 . Foot  91  has a tread  93  and a penetration resistant plate  94  is located between the lower end of bellows  90  and the inner surface of foot  91 . At the top, the upper end of bellows  90  has a single turn screw thread  95  on it which is designed to cooperate with a threaded portion  96  of a collar  97 . Screw thread  95  can pass beyond thread  96  sufficiently to enable the bellows to rotate about the axis of shaft  1  without unscrewing itself from the end. Collar  97  is located on a cup member  98  which has a central aperture. A stud  99  at the top of the bellows  90  may fit loosely. Shaft  1  is a press fit on the inside of cup member  98 . 
       FIG. 10  shows diagrammatically a construction analogous to  FIG. 9 , but where the bellows member itself, denoted  100 , increases in diameter between the threaded portion  101  at its top and a wide foot portion  102  which fits inside a wide moulded foot  103 . Foot  103  is secured by a circular retaining clip  104  and has a tread pattern  105  on its base. The advantage of the structure shown in  FIG. 10  is that the substantially greater surface area of the foot allows the stick, crutch or the like to be stood vertically on the ground without tipping over provided that the ground itself is sufficiently close to horizontal. This is of considerable value when the walking aid is a walking stick because it means that the user can temporarily simply release his or her grip on the stick in order, for example, to carry out some other manual activity, without having to “park” the stick previously in a position from which it can subsequently be retrieved. The user can simply move their hand away from the stick and then grasp it again afterwards.