WO2001017798A1

WO2001017798A1 - A ferrule for a stick or a crutch

Info

Publication number: WO2001017798A1
Application number: PCT/SE2000/001587
Authority: WO
Inventors: Staffan Skeppstedt; Karl Peter Olsson
Original assignee: Person- Och Organisationspoetik I Sverige Ab
Priority date: 1999-09-09
Filing date: 2000-08-17
Publication date: 2001-03-15
Also published as: AU7325600A; SE9903197D0; WO2001017798A8; SE514507C2; SE9903197L

Abstract

A ferrule for the shaft of a walking stick, walking cane, crutch, umbrella, roller-ski staff or like device. The ferrule is intended to support against an underlying surface (6) and has a convex supporting surface (7) which faces towards the underlying surface and which is orientated to roll against said underlying surface (6) in a longitudinal direction as the shaft is swung essentially in the direction of movement. The effective width of the supporting surface (7) transversely to the longitudinal direction of said supporting surface generally increases from the region of the intersection between the shaft axis and the supporting surface (7), in both directions of the longitudinal extension of the supporting surface.

Description

A FERRULE FOR A STICK OR A CRUTCH

The present invention relates to a ferrule for the shaft of a walking stick or crutch where the end of the ferrule that lies proximal to the walking surface has a supporting surface that curves outwardly from the end of the shaft and which is orientated to generate a rolling action against the underlying walk surface in a longitudinal direction as the shaft is swung about the ferrule resting on said surface.

Shafts fitted with such ferrules are known to the art from U.S. 4,899,771, U.S. 5,103,850, U.S. 5,353,825 and U.S. 5,409,029.

Walking sticks or crutches that are fitted with such a convex rolling ferrule have a generally uniform effective width in their longitudinal direction, and the effective supporting surface is flat when viewed in sections transversely to the longitudinal direction.

This has been found to present certain drawbacks in using the walking stick or crutch. One drawback is that the actual ferrule should have relatively high rigidity, for good reasons. When the walking stick and ferrule are designed to provide stable abutment with a horizontal underlying surface as the stick swings in a vertical plane during rolling action of the ferrule, everything will be satisfactory provided that the stick swings solely in the vertical plane.

This is not the case in the practical use of a walking stick or crutch. For instance, the shaft will often be inclined obliquely upwards and inwards from its supporting point in relation to the user. In such a case, the load that is transferred through the shaft and the ferrule to the underlying surface will engage at a distance from the shaft axis. This results in a turning moment (torque) in the inclined plane of the stick, said turning moment being particularly noticeable when the stick approaches the vertical plane. An abrupt change in this turning moment occurs under all circumstances, when/if the stick is swung into the vertical plane. This is a disconcerting effect. It will also be understood that certain rotational effects occur about the axis of the shaft, when an inclined walking stick fitted with such a ferrule rolls against the underlying surface essentially in the direction of movement of the user. The object of the present invention is to eliminate one or more of the aforesaid drawbacks either completely or partially.

This object is achieved with a ferrule constructed in accordance with the accompanying independent Claim.

Further embodiments of the invention will be apparent from the dependent Claims.

Taking its starting point from a ferrule that has a convex surface facing towards the underlying surface so as to roll thereagainst as the shaft is swung around the point of abutment of the ferrule with said surface, the invention is characterised in that the rolling surface of the ferrule has an effective width that increases generally from the area of intersection between the shaft axis and the rolling surface in a direction towards both ends of said surface.

In preferred embodiments, the rolling surface includes an opening between the central region of said surface and its respective ends, such that the effective support surface will be defined generally by support strips that lie closely adjacent to each other or connect with one another at the centre of the ferrule.

When the walking stick/ferrule slopes laterally upwards and inwards towards the user, the support surface will contact the underlying surface along one side edge whose distance from the longitudinal centre line of the support surface (said line being generally parallel with the rolling direction) increases towards the ends of the support surface.

If the support surface has at each end triangular openings whose widths decrease in a direction towards the centre of the ferrule, the edges of the triangular openings will enhance the friction of the ferrule against the underlying surface in the roll-off direction.

Because the effective ferrule supporting surface or supporting surfaces, which may be defined by two or more, for instance three, mutually intersecting strips, provides/provide a continuous rolling action both longitudinally and transversely in the absence of jumps in the lateral turning moment about the ferrule, walking sticks and crutches fitted with such ferrules will be far more pleasant to use. Furthermore, because the side edges of the effective supporting surface converge towards the centre, and because said supporting surface has at each end a central wedge-shaped opening whose apex faces towards the centre of the ferrule surface, the ferrule will have good contact with the underlying surface, with respect to friction and grip. Additional advantages are achieved when the support strips are curved, as seen in the supporting surface. The width of the support strips may increase towards the periphery of the supporting surface. A peg-accommodating hole may be provided in the centre of the ferrule.

The invention will now be described by way of example with reference to the accompanying drawings.

Fig. 1 is a schematic illustration of a crutch fitted with an inventive ferrule.

Fig. 2 is a side view of an inventive ferrule.

Fig. 3 is a front view of the ferrule.

Fig. 4 shows the ferrule in perspective.

Fig. 5 is a side view of another embodiment of an inventive ferrule.

Fig. 6 is a side view of the subject of Fig. 5.

Fig. 1 illustrates a crutch that includes a handle part 2 which has connected thereto a shaft

3 that carries at one end a ferrule 5 which supports against an underlying surface 6. The ferrule 5 has a convex supporting surface 7 that faces towards the surface 6. When the crutch is used, the ferrule 5 is intended to roll against the surface 6 as the user moves forwards, so that the shaft 3 will swing in a generally vertical plane that includes the direction of movement about the point of contact of the ferrule 5 with the underlying surface 6. The convex surface of the ferrule 5 will preferably have a centre of curvature on or in the proximity of the axis of the shaft 3.

Fig. 2 is a view of the ferrule corresponding to the illustration in Fig. 1. Fig. 3 shows the ferrule as seen from the left or the right in Fig. 2.

It will again be seen from Fig. 2 that the ferrule 5 has an upwardly extending shaft-part which may typically include a blind hole that fits the end of the shaft 3. It will also be seen that the ferrule 5 of Fig. 2 carries at its bottom part a load distributing plate 71 that is generally rectangular in shape (Fig. 4) and has a longest edge length in the intended direction of movement.

It will be seen from Figs. 2 to 4 that arranged on the underside of the plate 71 are two mutually intersecting support strips that extend in crossing axial planes to the axis of the shaft 3. The lower ends of the support strips terminate in a single-curved surface that is defined by the convex contour line 73, which illustrates the rolling surface in Fig. 2.

As the ferrule 5 rolls against the underlying surface 6 during movement of the user, the point of contact between the underlying surface 6 and the ferrule is displaced continuously along the contour line 73.

As a study of Fig. 3 will show, corresponding conditions occur with respect to swinging of the walking stick/ferrule in a lateral plane about the points at which the strips 72 support against the surface 6. It will thus be seen from Fig. 3 that the transverse contours of the strips 72 at said lower end lie generally around the arc of a circle whose centre of curvature lies at or close to the axis of the shaft 3.

Because the surface of the ferrule in contact with the underlying surface 6 is defined by the contoured bottom edges of the strips 72, the strips 72 will afford a particularly good grip against said underlying surface. Moreover, the ferrule is able to roll along rolling arcs that intersect said strips along planes that are parallel with the longitudinal edge of the plate 1 and also parallel with the axis of the shaft 3.

The ferrule which is fitted to the shaft 3 in the indicated relationship with the shaft handle device 2, provides a continuous rolling action generally in the movement direction and, at the same time, enables desired inclination of the crutch, or walking stick, and the ferrule to be achieved transversely to the movement direction, wherewith this transverse inclination may also be varied during a movement cycle in the absence of any abrupt changes in the turning moment that is developed at the ferrule as a result of the centricity between the load transfer position and the axis of the shaft 3.

The surface of the ferrule coacting with the underlying surface 6 can be considered to depart from a spherical surface or an ellipsoidal surface in which openings have been made, such that the effective supporting surface will have the form of a number of striplike parts that extend generally radially from the shaft axis, for instance so that said effective surface will have a generally X-shape when said surface is formed by two mutually crossing support strips, with the intersection point of the X lying on the shaft axis..

Although Fig. 1 shows a shaft 3 that is provided with a handle 2 and a forearm support so as to form a crutch, it will be obvious that the invention can also be applied to a conventional walking stick or to an umbrella that is also designed as a walking stick or to cane, that have solely one single handgrip, for instance a handle that extends perpendicular to the shaft 3 or parallel therewith, or that has the form of a knob.

The invention can also be applied to roller-ski sticks whose shaft is provided with an otherwise conventional stick handle.

The effective supporting surface of the ferrule shown in Figs. 2-4 will be seen to have an X-shape in plan view, wherewith the effective surface has different radii of curvature in two mutually perpendicular axial planes to the ferrule attachment box (or the end of said shaft).

It will be understood, however, that the effective supporting surface may have generally uniform radii of curvature in their axial planes, wherewith said radii of curvature may also have a common centre of curvature, suitably on the shaft axis. The effective supporting surface is formed by the exposed edges 73 of mutually crossing strips 72, so as to form a pattern in which the edges of said strips mutually form a substantial angle relative to one another and also to the primary rolling direction of the ferrule along the movement path, such as a direction perpendicular thereto. Naturally, the effective supporting surface may include exposed edge parts of several such strips that preferably extend generally radially to the shaft and fulfil the aforesaid conditions with respect to a substantially continuous rolling action of the ferrule in longitudinal and transversal directions.

In a further development of the invention (Figs. 5 and 6), the surface 73 of the supporting strips 72 that is in contact with the underlying surface has a non-straight longitudinal extension. Moreover, the width of the supporting surface 73 of said strips may increase from the central region of the ferrule in a direction towards the periphery of the supporting surface. This provides a further improvement with respect to the grip of the ferrule against the underlying surface and its co-action with said surface.

Fig. 6 shows that the strips 72 that mutually intersect at the centre of the ferrule extend in a generally S-shape configuration, so that the parts of the strips extending from the centre of the ferrule towards the periphery of the supporting surface will have the form of arcuate parts that are conveniently uniformly orientated and equidistant in the peripheral direction of the supporting surface.

An axially penetrating passageway for receiving an anti-slip stud on the end of the shaft of the stick is provided at the centre of the ferrule in the regions where the strips 72 intersect. By allowing the ferrule to be connected to the shaft via a ramp guide or screw guide (not shown) and also by enabling the ferrule to be rotated relative to said shaft, the ferrule can be displaced axially by, for instance, rotating the ferrule manually relative to the walking stick or crutch, so as to move the stud through the passageway into an exposed position, and also to withdraw the stud from said position. The ramp or screw guide will conveniently have end positions that define stable end positions for the stud.

The ferrule may conveniently be injection moulded from a material that has a high wear strength, appropriate elasticity and favourable friction. Examples of such material are thermoplastic elastomers (TPE), such as thermoplastic polyurethane (TPU).

Claims

1. A ferrule for the shaft of a walking stick, walking cane, crutch, roller-ski staff or like device, wherein said ferrule is intended to support against an underlying surface (6), and wherein the ferrule has a supporting surface (7) that is convex towards said supporting surface and which is orientated to roll against the underlying surface (6) in a longitudinal direction as the shaft is swung in the direction of movement essentially about the ferrule resting on the underlying surface, characterised in that the effective width of the supporting surface (7) against the underlying surface transversely to the longitudinal direction of the supporting surface generally increases from the region of intersection between the shaft axis and the supporting surface (7) in both directions in the longitudinal extension of the supporting surface.

2. A ferrule according to Claim 1, characterised in that the supporting surface is comprised of support strips (72) that intersect one another in the central region of the ferrule.

3. A ferrule according to Claim 2, characterised in that the support strips (72) have a non-straight extension as seen in the axial direction of the ferrule.

4. A ferrule according to Claim 3, characterised in that the support strips (72) have a generally S-shape as seen in the axial direction of the ferrule.

5. A ferrule according to Claim 4, characterised in that as seen in the axial direction of the ferrule said support strips (72) include parts that have the shape of portions of the segment of a circle that extend from the central region of the ferrule to the periphery of the supporting surface and that are mutually uniformly orientated and spaced equidistantly in the peripheral direction of the supporting surface.

6. A ferrule according to any one of Claims 1-5, characterised in that the ferrule includes in its central region a through-penetrating passageway (75) for permitting passage of an anti-slip stud.

7. A ferrule according to any one of Claims 2-6, characterised in that the width of the support strips (72) in the supporting surface increases in a direction towards the periphery of said supporting surface.

8. A ferrule according to Claim 2, characterised in that the support strips (72) are non- straight as seen in a plane normal to the ferrule axis.

9. A ferrule according to any one of Claims 1-8, characterised in that the support strips (72) extend generally radially to the ferrule axis.