EP3868352B1 - Forearm crutch - Google Patents

Description

The invention relates to a forearm crutch, comprising a support tube with a contact surface on the underside, a handle that protrudes from the support tube in the direction of walking, and a forearm clamp or cuff arranged above the handle for guiding the forearm, the handle and the forearm clamp or cuff being closed integrated into a shaped upper part terminating the support tube at the top, and wherein the side of the shaped upper part facing away from the handle can serve as a contact surface when the forearm crutch is leaned against a wall or a piece of furniture.

A generic forearm crutch is in the utility model specification DE 20 2006 010 732 U1 disclosed. There the problem is addressed that such a crutch very often tends to fall over when parked. This document therefore proposes providing the upper part of the crutch with a covering made of a material with good surface adhesion, with neoprene or cellular rubber being particularly recommended as the covering material.

The previous inventor thus prevents a generic forearm crutch from slipping sideways. However, there is another reason why parked crutches fall over. This second reason results from the small contact area at the lower end of the support tube. On the one hand, this area is relatively small, approximately on the order of 2 to 5 cm ² , and with a slightly inclined forearm crutch, only the edge of it has contact with the ground. As a result, a parked crutch only finds an unstable balance, and without slipping in the upper contact point, it can still roll sideways around the lower, very small contact area and finally tip over. this effect cannot be avoided even with a non-slip covering on the upper end of the support tube.

A distinction must be made between two different set-down situations: A crutch can be leaned against a wall or other vertical surface, in which case only the upper edge of the crutch comes into contact with the wall or surface, especially in the area of a forearm clamp or - cuff. In order to avoid slipping and/or falling over in this case, it has already been proposed to provide two lateral rubber knobs at the level of the forearm clamp, cf DE 103 08 044 A1 .

On the other hand, it is often the case that a wall or vertical contact surface is not available, e.g. when someone sits down at a table in the middle of the room in a restaurant. There, the crutch can often only be leaned against the edge of a table or, at best, against the backrest of a chair. The upper edge of the crutch does not come into contact with the edge of the table or chair back, but rather an area below the forearm clamp or cuff, and thus also below the two DE 193 08 044 A1 provided rubber knobs, so that they cannot prevent falling over in such a case. At the level of a plastic upper part or the support tube, however, the crutch usually has a cylindrical geometry and therefore tends to roll or slip sideways and thus ultimately to fall over.

The document DE20209938U discloses a crutch having all the technical features set forth in the preamble of claim 1.

The disadvantages of the prior art described result in the problem that initiated the invention of further developing a generic forearm crutch in such a way that it does not tend to slip sideways, especially when it is placed on an approximately horizontal edge, e.g. of a piece of furniture Rolling or tipping around the bottom contact area.

mit ε ≥ 1 mm, bspw. ε ≥ 2 mm, bevorzugt ε ≥ 5 mm, oder ε ≥ 10 mm wobei der horizontale Abstand zwischen zwei die Anlagefläche seitlich begrenzenden Randkanten sich von der Höhe des Handgriffs zu der Höhe der Unterarmschelle oder -manschette allmählich vergrößert.The solution to this problem is achieved with a generic crutch in that a rolling axis running through the center of gravity of the crutch and through the contact surface runs at a distance d(h) in the walking direction in front of the contact surface at a longitudinal coordinate h measured along the rolling axis in the area of the shaped upper part , wherein the formed upper part has a cross-section perpendicularly penetrated by the rolling axis in the area of the contact surface, a circumference with a maximum radius r(h) being able to be rewritten in such a way that it has at least two mutually distant points of contact with the cross-section of the contact surface, and where applies , throughout the section at each longitudinal coordinate h between the longitudinal coordinate h ₁ at the level of the handgrip and the longitudinal coordinate h ₂ at the level of the forearm clamp or cuff: $$\mathrm{right}\left(\mathrm{H}\right)-\mathrm{i.e}\left(\mathrm{H}\right)>\mathrm{e}>0,$$

with ε ≥ 1 mm, e.g. ε ≥ 2 mm, preferably ε ≥ 5 mm, or ε ≥ 10 mm, the horizontal distance between two edges laterally delimiting the contact surface gradually increasing from the height of the handle to the height of the forearm clamp or cuff enlarged.

The invention first defines a roll axis that runs on the one hand through the contact surface on the underside, for example through its center or through its rear edge area, and on the other hand through the center of gravity of the crutch. This center of gravity can be determined experimentally, for example, by balancing the horizontally aligned support tube with the handle pointing downwards on an edge or cutting edge running transversely to it in order to find the height of the center of gravity along the longitudinal axis of the support tube, and on the other hand the horizontally aligned handle on the edge or cutting edge running transversely to the handle is balanced in such a way that the support tube assumes an upright position in order to determine the position of the center of gravity in the walking direction. The actual center of gravity is then along the support tube at the previously determined height and in the direction of the walking direction approximately parallel handle by the previously determined amount in front of the support tube. This forward displacement results from the fact that both the handle and the forearm clamp or cuff project forward at the upper end of the support tube, i.e. pull the center of gravity forward.

The invention has also recognized that precisely this position of the center of gravity in front of the support tube is responsible for the unstable position of a parked forearm crutch. This is due to the fact that when a crutch is parked, the roll axis defined in this way is inclined backwards, similar to the support tube, so that if the parked crutch tilts slightly to the side around its upper contact point in the area of the contact surface, the center of gravity also rolls to the side and as a result the inclination of the support tube reduces its height above the ground. This releases further energy, which in turn feeds the lateral rolling movement of the parked forearm crutch and thus leads to an unbraked, even accelerated continuation of the rolling movement. In the case of a generic forearm crutch, this movement is therefore not stopped until it has finally fallen over.

However, the invention now provides a special cross-sectional design of the plastic upper part in the area of the rear contact surface of a forearm crutch, namely in such a way that the radius r(h) is a maximum circle circumscribed around the cross-section, but which still has at least two points of contact with the cross-section of the contact surface has, is greater than the distance d(h) between the roll axis and the bearing surface at the height h. Such a dimensioning means that if the crutch rolls or tilts sideways at height h, the distance between the roll axis on the one hand and the rear contact point or contact point increases. As a result, the center of gravity shifts upwards when the support tube is at a slight angle, which requires energy. This energy is withdrawn from the kinetic energy of the rolling or tilting movement and this movement is thereby slowed down and finally shut down. As a result, the unstable equilibrium has now become a stable equilibrium—the forearm crutch according to the invention no longer falls over.

Since the contact surface designed according to the invention extends over the entire height h between the forearm clamp or cuff on the one hand and a handle on the other hand, the crutch can be attached to a horizontal edge, e.g a chair or on the top edge of a dresser, etc., without the risk of it falling over.

Furthermore, it can even be provided that the contact surface configured according to the invention extends along the entire height extension h of the back of an upper part that integrates the forearm clamp or cuff on the one hand and the handle on the other. This provides maximum security against accidental falling over.

It has proven to be advantageous that the two lateral edges of the contact surfaces run laterally next to the support tube in some areas. This measure makes it possible to give the contact surface between the two edges almost any desired horizontal transverse curvature in order to meet the condition according to the invention.

The invention can be further developed such that the two lateral edges of the contact surface are mirror-symmetrical to a plane spanned by the longitudinal axis of the support tube on the one hand and the longitudinal axis of the handle on the other. In such a case, the contact surface can be designed mirror-symmetrically to a pointing in the direction of walking, vertical center plane, which contributes to the fact that the Focus of the crutch is in this center plane and a tendency to tilt sideways is minimal.

The horizontal distance between the two edges in the area of the handle can correspond approximately to the diameter of the pipe support there. As a result, the forearm crutch does not widen in this area and remains handy.

According to the invention, the horizontal distance between the two marginal edges gradually increases from the level of the handle to the level of the forearm band or cuff.

The further up a contact point is, the further the center of gravity of the forearm crutch is shifted away from this contact point in the horizontal direction, and the more unstable the respective position is. In order to compensate for this increasing instability, the contact surface can be widened towards the top so that the stable area becomes larger.

Due to these considerations, the horizontal distance between the two marginal edges in the area of the forearm band or cuff should correspond to at least about half the width of the forearm band or cuff.

It is within the scope of the invention that the curvature radii of the edges are 20 mm or smaller, for example 10 mm or smaller, preferably 5 mm or smaller, in particular 2 mm or smaller. These marginal edges may well be distinctive, as long as they do not pose a risk of injury. The smaller the radius of curvature in question, the wider the actual contact surface can be designed with the overall width of the arrangement otherwise being the same.

The invention permits a development in that the lateral edges are raised relative to the inner area of the contact surface are trained. As a result, the contact surface can have a concave cross-section or even have a trough-shaped or even window-shaped depression. When setting down such a forearm crutch, the actual contact points are then in the area of the edge edges.

1. a) eben ist, oder
2. b) konkav gewölbt, oder
3. c) konvex gewölbt mit einem Wölbungsradius, der wenigstens der halben Länge des Handgriffs entspricht, vorzugsweise wenigstens der gesamten Länge des Handgriffs entspricht, insbesondere wenigstens der doppelten Länge des Handgriffs entspricht. In all diesen Fällen ist die erfindungsgemäße Relation zwischen dem Krümmungsradius der Anlagefläche und dem Abstand zu der Rollachse erfüllt.

In principle, the invention allows configurations such that a horizontal cross-section through the contact surface between the two edge edges at least in certain areas

1. a) is flat, or
2. b) concave, or
3. c) convexly curved with a radius of curvature which corresponds to at least half the length of the handle, preferably corresponds to at least the entire length of the handle, in particular corresponds to at least twice the length of the handle. In all of these cases, the relation according to the invention between the radius of curvature of the contact surface and the distance from the roll axis is fulfilled.

In the context of a first, preferred embodiment of the invention, the contact surface can extend between the two edges without interruption. This is a comparatively simple construction, the center of gravity of the forearm crutch being shifted backwards by the extension according to the invention, which acts as a counterweight to the handle, whereby the stability criterion according to the invention is improved.

On the other hand, it is also possible for the contact surface to have at least one recess between the two edge edges. Weight can be saved by a recess, so that the forearm crutch becomes lighter overall. On the other hand, the areas near the lateral edges of the contact surface are most valuable for the stability criterion according to the invention, because they are effective when the crutch is slightly rotated about an axis roughly parallel to the roll axis and finally form the actual axis of rotation and then decide on the stability of the position. The area between these marginal edges, on the other hand, is of secondary importance and can therefore be left out. At most, care should be taken to ensure that the recess is symmetrical to a center plane spanned by the handle and the support tube, in order to minimize the risk of a rolling moment when the forearm crutch is parked.

At least one such recess can be formed as a groove running in the vertical direction, which is flanked on both sides by two halves of the contact surface. In the ideal case, a maximum weight saving can be achieved with a recess in the form of a groove that completely divides the contact surface into two halves in the vertical direction.

Another possible further development of the invention is that the at least one recess is designed as a slot that is open at the top and is delimited by the contact surface at the bottom and on both sides. In particular, when the lateral marginal edges of the enlargement supporting the abutment surface diverge upwards, two remaining marginal regions converge downwards similar to an open-topped "V".

Finally, it is also possible for the at least one recess to be in the form of a trough-shaped depression which is surrounded on all sides by the contact surface like a frame. This also makes it possible, in particular, to connect the lateral edge regions to one another both at the bottom and at the top end, despite the weight saving, in order to achieve maximum stability.

A crutch according to the invention experiences a further improvement in stability in that the contact surface consists of a material with a rough surface structure. Then such a crutch can also be leaned against smooth surfaces, even if they are made of stainless steel, or exposed concrete, glass, tiles, natural stone, woodchip, wood or plastic or artistically designed, uneven ceramic tiles.

As a further measure, the contact surface can consist of a friction-increasing material such as an elastomer or be covered with such a material. Even a fabric covering or soft upholstery of the contact surface is conceivable, so that it can cling to the relevant wall or furniture edge.

The contact surface, or in particular a widening of the plastic upper part that supports it, can be designed as a counterweight to the forward-pointing handle and/or can be provided with a counterweight thereto. With such a construction, the center of gravity of the overall arrangement is shifted backwards against the walking direction and thus moves closer to a furniture edge or wall when the crutches are parked, which is beneficial to stability against the crutches falling over.

The invention further provides that the contact surface is formed integrally with the forearm crutch. For example, it can be designed together with the handle and a forearm clamp or cuff as a common plastic upper part. In such a case, it can be produced as part of a single injection molded part.

On the other hand, it is also possible that the contact surface is manufactured separately and connected or connectable to the crutches, for example by means of adhesive, a Velcro fastener, screws, etc. Such a connection technique also allows conventional crutches to be retrofitted according to the present invention.

According to the invention, it is further provided that the contact surface is provided with a reflector, which is preferably directed backwards. However, it can be better than integrating the reflector into the contact surface itself, to arrange it next to, below or above the actual contact surface, so that its stability against lateral slipping is not impaired.

Instead of or in addition to a reflector, the contact surface can be provided with a light source directed backwards, so that the crutch is clearly visible in the dark. Again, it may be advantageous not to integrate this light source directly into the contact surface, but to arrange it next to, above or below it.

Finally, it corresponds to the teaching of the invention that a battery or a rechargeable battery for feeding the light source is arranged in the handle or in the support tube. A battery or accumulator compartment can also be arranged in a rearward widening that carries the actual contact surface.

Fig. 1

eine herkömmliche Unterarmgehstütze in einer Seitenansicht;

Fig. 2

eine erste Ausführungsform einer erfindungsgemäßen Unterarmgehstütze in einer Seitenansicht;

Fig. 3

die Ausführungsform der Erfindung gemäß Fig. 2 in einer perspektivischen Ansicht schräg von hinten, wobei das Stützrohr abgebrochen dargestellt ist;

Fig. 4

einen Schnitt durch die Fig. 2 entlang der Linie IV - IV;

Fig. 5

eine zweite Ausführungsform der Erfindung in einer der Fig. 3 entsprechenden Ansicht; sowie

Fig. 6

eine dritte Ausführungsform der Erfindung in einer der Fig. 3 entsprechenden Ansicht.

Further features, details, advantages and effects based on the invention result from the following description of a preferred embodiment of the invention and from the drawing. This shows:

1

a conventional crutch in a side view;

2

a first embodiment of a crutch according to the invention in a side view;

3

according to the embodiment of the invention 2 in a perspective view obliquely from behind, wherein the support tube is shown broken;

4

a cut through the 2 along line IV - IV;

figure 5

a second embodiment of the invention in one of 3 corresponding view; such as

6

a third embodiment of the invention in one of 3 corresponding view.

A crutch 1 consists of a support tube 2 with a contact surface 3 on the underside for support on a floor 4 or some other underground.

The contact area 3 is preferably part of a foot piece 5 which is designed, for example, as a cap made of rubber or a comparable material and is attached to the lower end of the support tube 2 .

The support tube 2 itself can either be designed in one piece or be telescopically extendable.

In the latter case, it consists of a lower tube 6 and an upper tube 7, the longitudinal axes 8, 9 of which are concentric with one another. One of the two tubes 6, 7 - usually the upper one - is slightly larger in diameter and accommodates the other tube in a longitudinally displaceable manner.

In the case of a telescopically extendable support tube 2, a height adjustment is provided, i.e. a possibility for locking the two tubes 6, 7 in different intermediate positions.

A rasterized locking possibility can be realized, for example, in that one of the two tubes 6, 7 - preferably the outer tube 7 - be designed with a plurality of bores at different heights, wherein one on the other - preferably inner - tube 6 radially led and pushed outwards by a spring pin can engage. By pushing this pin into the hole in question, the tubes 6, 7, which are initially locked into one another, can be displaced relative to one another and can then be locked together again in a new position by locking the pin into another hole.

A stepless adjustment and/or locking option could be realized with a screw and/or clamping technique, in which case the interlocking ends of the two parts of the telescoping support tube 2 could be designed to be mutually adjustable and lockable with interlocking threaded sections and/or with a clamping device .

At the upper end of the support tube 2 is a plastic upper part 10, which is preferably designed as a molded part, in particular as an injection molded part, and has a shaft 11 that extends the support tube 2 upwards, with a handle 12 that protrudes laterally in the lower shaft area and a Upper shaft area arranged forearm clamp 13 or cuff for leading recording of the forearm.

The handle 12 usually faces forward in the direction of walking and can have an ergonomic design with indentations for each finger and/or can be designed with a reflector at the front end. The handle 12 is preferably slightly inclined towards the front, for example at an angle of 10° to 30° with respect to the horizontal.

The forearm clamp 13 can have two lateral legs 14 which grip the forearm of the person concerned on both sides; a forearm cuff could be closed in the form of a ring and therefore completely enclose the forearm of the person concerned.

For ergonomic reasons, the shaft 11 of the plastic upper part 10 is preferably inclined slightly backwards relative to the support tube 2, for example at an angle of 10° to 30°. The longitudinal axis of the shaft 11 of the plastic upper part 10 passes through the plane spanned by the two legs 14 of the forearm cuff 13 or by the ring of a forearm cuff, so that in particular the two legs 14 of the forearm cuff 13 are inclined upwards in the walking direction .

A rear-facing reflector may also be located at the upper end of the forearm band 13 or cuff.

When the crutch 1 is parked, the upper area of the rear side of the plastic upper part 10 facing away from the handle 12 pointing in the direction of walking serves as a bearing surface 15 against a wall or a piece of furniture 16, in particular on an edge 17 thereof.

In the embodiment 1 'according to the invention 2 the contact surface 15' is designed in a special way in order to prevent the crutch 1' from falling over when leaning against a piece of furniture 16, in particular against a horizontal upper edge 17 of the same.

In particular, a roll axis 18 is defined for this purpose, which connects the contact area 3 on the ground with the center of gravity 19 of the forearm crutch 1'. Since the center of gravity 19 is typically close to the longitudinal axis 8, 9 of the support tube 2, the roll axis 18 can coincide with that longitudinal axis 8, 9 or run at a small distance from it, in which case the roll axis 18 and the longitudinal axis 8, 9 of the support tube 2 in the area of the contact area 3 meet or cut.

A height h is defined along the roll axis 18 , the zero point of which is at the contact point of the contact area 3 with the ground 4 .

The contact surface 15' preferably extends in the direction of the longitudinal coordinate h between a first height h ₁ , where the (central) longitudinal axis of the handle 12 intersects the rear side of the upper part 10, and a second height h ₂ , where one of the (central) ). Longitudinal axes of the two lateral legs 14 of the forearm clip 13 spanned plane intersects the back of the upper part 10. On the other hand, it is also possible for the contact surface 15 ′ to extend over the entire height h of the back of the upper part 10 .

Furthermore, in the area of the contact surface 15', at every height h along the roll axis 18, a sectional plane Q(h) is defined by the contact surface 15', which is perpendicularly penetrated by the roll axis 18 and contains the point of contact of the contact surface 15' with the edge 17.

how 3 can be seen, the actual contact surface 15 'is limited by two lateral edges 20, the radius of curvature of these edges 20 itself can be relatively small, so for example in the order of 1 mm to 20 mm.

The cross section through the contact surface 15' within the section plane Q(h) follows a curve, in particular between the edge edges 20, which can be circumscribed by at least one circle which touches the curve in question at at least two contact points that are distant from one another, for example in the region of the two edge edges 20 .

The largest circle K, which can be described in this curve, can be degenerated into a straight line, which corresponds to a circle with an infinitely large radius, provided that such a straight line still has two distant contact points to the contact surface 15'.

Now is a prerequisite for a stable position of the crutch 1 'on the edge 17 of the piece of furniture 16 that within the section plane Q (h) of Distance v between the rolling axis 18 and the edge 17 of the piece of furniture 16 or to the point of contact between the contact surface 15' and the edge 17 of the piece of furniture 16 - if the forearm support 1' is aligned in such a way that the handle 12 is as far away from the edge 17 as possible points - is smaller than the radius R of the largest circle that can be rewritten around the contact surface 15' at the relevant height h.

In this case, if the forearm support 1' were to roll sideways along the furniture edge 17, the roll axis 18 would be forced to rise more steeply, as a result of which the center of gravity 19 would have to move upwards. As a result of this raising of the center of gravity 19, the potential energy would increase and the relevant amount of energy would be taken from any kinetic energy caused by the movement, thus slowing down the rolling movement and finally ending it - the forearm crutch 1' thus finds a stable equilibrium and not an unstable equilibrium as with a standard forearm crutch 1.

How to 3 can be seen, the edges 20 can follow the course or the width of the plastic upper part 10 at the respective height h. In this case, the contact surface 15' would be narrower in the lower area of the plastic upper part 10 and wider in the upper area. Such a broadening can be continuous or more pronounced in certain sections than in others. In particular, in the embodiment according to 3 the broadening takes place above all in the upper area, i.e. approximately at the level of forearm clamp 13.

In the embodiment 1 'according to 3 the contact surface 15' is closed, ie free of interruptions.

A cross section through this closed contact surface 15' is shown in 4 to see. It can be seen that this surface has a convex curvature in cross section. This cross-sectionally convex curvature can follow a circular line K or be approximated by a segment of a circle K, the circle K being defined by the position of its center M and by its radius r.

In 4 the point of intersection P between the circular line K and the radius r was still connected to the intersection point of the roll axis 18 through the relevant section plane; this connecting line is denoted by h. Based on the distance d between the center M of the circular line K and the rolling axis 18, the length of the connecting line v can be calculated as a function of the tilting angle α of the vertical plane of symmetry S of the crutch 1' relative to the edge 17 of the piece of furniture 16 as: $$\mathrm{v}={\left[{\left(\mathrm{right}-\mathrm{i.e}\right)}^2+4*\mathrm{right}*\mathrm{i.e}*{\sin }^2\left(\mathrm{a}/2\right)\right]}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}.$$

Since the sine function increases monotonically in the vicinity of the zero point of the argument, this also applies to the square of the sine function, starting from the zero point equally in both directions.

In other words, if α deviates from 0° in any direction, the length v increases, since r and d are constants. However, v indicates for each α the distance of the rolling axis 18 from the edge 17 of the piece of furniture, and thus also the height of the center of gravity of the crutch 1'.

Accordingly, if the crutch 1' rolls laterally through an angle α, the height of its center of gravity always increases, which requires energy. The crutch 1' is therefore able to absorb a certain amount of energy before it falls over. The forearm crutch 1' is thus stable against lateral twisting.

The decisive criterion for this is that the center point M of the circular line K is always in front of the point at which the roll axis 18 penetrates through the relevant section plane is located, in particular by a dimension d > 0, or even by a dimension d >> 0.

This increased stability against the crutch 1' tipping over or slipping sideways can also be achieved with other geometries of the contact surface 15'. For this purpose, the contact surface 15' can also have openings such as windows or gaps. The only criterion is that there are two points P on the circle K that are spaced apart from each other and that can be connected by a circle K with a radius r such that the radius r is greater than the distance d between the center M of the circle K and the intersection point of the roll axis 18 through the section plane.

This then leads to the roll axis 18 being straightened with every tilting—that is, with every increase in the angle α—with the center of gravity lying on the roll axis 18 being raised. Conversely, the center of gravity assumes the lowest position at the angle α=0° and thus stabilizes this alignment of the forearm crutch 1'.

How to 2 can be seen, the contact surface 15' shifts in the upper area of the plastic upper part 10 of the forearm crutch 1' relative to the rolling axis 18 to the rear, ie against the running direction. This means that with the same radius r of the circular line K of the cross-sectionally convex curvature, the center M of the circular line K also moves backwards, until the stability criterion mentioned above, according to which the center M of the circular line K moves before the point at which the roll axis 18 penetrates the relevant cutting plane should be located in the upper area of the contact surface 15' could no longer be fulfilled. An effective countermeasure against such instability when the forearm crutch 1' rests in the upper area of the contact surface 15' is either to increase the radius of curvature r for the entire contact surface 15' according to the position of the roll axis 18 in the uppermost area of the contact surface 15' calculate so that the entire contact surface 15' could then follow a cylinder surface with a sufficiently large radius r, or in not choosing the radius of curvature r to be constant for the entire contact surface 15', but adapting it to the position of the roll axis 18 at the height in question ; the latter would then result, for example, in a conical contact surface 15', which widens from bottom to top, corresponding to a cone standing on its tip.

In the embodiment 1 "according to figure 5 the contact surface 15" on the other hand has a trough-shaped or window-like recess 21 which is completely surrounded by the remaining part of the contact surface 15" similar to the self-contained frame of a window.

In the embodiment 1 ⁽³⁾ according to 6 the contact surface 15 ⁽³⁾ , on the other hand, is interrupted by a slot-shaped notch 22 which is open at the top and which the remaining part of the contact surface 15" embraces laterally and below, similar to a U-shaped frame.

In the context of a further embodiment not shown, this slot-shaped notch 22 could even penetrate the contact surface 15 ⁽³⁾ completely, so that the contact surface 15 ⁽³⁾ would thereby split into two separate halves.

With regard to that associated with 4 The stability criterion explained above, according to which the center point M of a circular line K describing or approximating the contact surface 15', 15", 15 ⁽³⁾ should lie in front of the rolling axis 18 as seen in the running direction, is in the embodiments according to figure 5 and 6 to look for a suitable circular line which approximates the remaining contact surface 15", 15 ⁽³⁾ interspersed with interruptions or recesses. For this purpose, either the curvature of the remaining webs of the contact surface 15", 15 ⁽³⁾ can be used, or if necessary this can also be used a straight line should be used, connecting the two rearmost edges of the connects both halves of the 15", 15 ⁽³⁾ . In such a straight line limit case, the midpoint M lies at infinity, and although this is not mandatory, it can be assumed with regard to the stability criterion according to the invention that this midpoint M extends to infinity is located in front of the roll axis 18, so such a connecting straight line satisfies the stability criterion. You should always look for a transverse curvature with the largest possible positive radius of curvature, the center point of which is in front of the roll axis 18; with such an approximation, there is only agreement in at least two points that are spaced apart from one another A division of the contact surface 15", 15 ⁽³⁾ as in the figures 5 and 6 always fulfills this criterion, because a connecting straight line can always be found here that meets these requirements.

In the present invention, the roll axis 18 can be coincident with the longitudinal axis 8, 9 of the support tube 2 or preferably behind that longitudinal axis 8, 9, thereby further reducing the distance between the roll axis 18 and the edge 17, if necessary. This can be achieved in that the contact surface 15, 15', 15", 15 ⁽³⁾ is arranged on the back of a widening 23 of the plastic upper part 10, 10', 10", 10 ⁽³⁾ . The weight of this widening 23 shifts the center of gravity 19 to the rear, ie in the direction of the contact surface 15, 15', 15", 15 ⁽³⁾ .

Such a widening 23 can optionally be integrated with the plastic upper part 10, 10', 10", 10 ⁽³⁾ or be produced as a separate part that can be subsequently attached to an existing forearm crutch 1, 1', 1", 1 ⁽³⁾ . ,. The connection of such a separate widening part 23 to the plastic upper part 10, 10', 10", 10 ⁽³⁾ of the forearm crutch 1, 1', 1", 1 ⁽³⁾ can be effected in a variety of ways, e.g. with glue, Velcro, screws, etc.

The actual contact surface 15, 15', 15", 15 ⁽³⁾ of the forearm crutch 1, 1', 1", 1 ⁽³⁾ can be made of a non-slip material or with a be provided with a non-slip covering, for example made of rubber or the like, and/or it can be provided with a non-slip structure, e.g. with a ribbing or corrugation, or with knobs, etc.

A reflector can also be provided on the back of the forearm crutch 1, 1', 1", 1 ⁽³⁾ in the case of a rearwardly displaced contact surface 15, 15', 15", 15 ⁽³⁾ , for example in a section above the contact surface 15, 15', 15", 15 ⁽³⁾ .

Reference List

1

crutches

2

support tube

3

footprint

4

floor

5

base

6

Pipe

7

Pipe

8th

longitudinal axis

9

longitudinal axis

10

plastic top

11

shaft

12

handle

13

forearm clamp

14

leg

15

contact surface

16

furniture

17

edge

18

roll axis

19

main emphasis

20

border edge

21

recess

22

notch

23

widening

Claims (15)

1. Forearm walking support (1) comprising a support tube (2) with a contact surface (3) on the underside, a handle (12) projecting from the support tube (2) in the walking direction, and a forearm clamp (13) or sleeve arranged above the handle (12) for guiding the reception of the forearm, wherein the handle (12) and the forearm clamp (13) or sleeve are integrated to form a shaped upper part (10) terminating the support tube (2) at the top, and wherein the side of the shaped upper part (10) facing away from the handle (12) is formed as a contact surface (15) when the forearm support (1) is leaned against a wall of a piece of furniture (16), wherein

   a) a rolling axis (18) passing through the center of gravity (19) of the forearm walking support (1) and through the contact surface (3) extends at a distance (d(h)) in the walking direction in front of the contact surface (15) in the region of the shaped upper part (10) with a longitudinal coordinate (h) measured along the rolling axis (18),

   b) wherein the shaped upper part (10) has, in the region of the contact surface (15), a cross-section through which the rolling axis (18) passes perpendicularly, which cross section having a circumference with a maximum radius (r(h)), which can be circumscribed in such a way that it has at least two points of contact with the cross-section of the contact surface (15) which are distant from one another,
   characterized in that

   c) in the entire section at each longitudinal coordinate (h) between the longitudinal coordinate (h₁) at the level of the handle (12) and the longitudinal coordinate (h₂) at the level of the forearm clamp (13) or sleeve applies: $$\mathrm{r}\left(\mathrm{h}\right)-\mathrm{d}\left(\mathrm{h}\right)>\mathrm{\epsilon }>0,$$

   

   with ε ≥ 1 mm, for with example ε ≥ 2 mm, preferably ε ≥ 5 mm, or ε ≥ 10 mm.

   d) wherein the horizontal distance between two marginal edges (20) laterally bounding the contact surface (15) gradually increases from the height of the handle (12) to the height of the forearm clamp (13) or sleeve.
2. Forearm walking support (1) according to claim 1, characterized in that the contact surface (15) extends over the entire longitudinal extension (h) of the upper part (10), wherein along the entire longitudinal extension (h) of the upper part (10) applies continuously at each longitudinal coordinate (h): $$\mathrm{r}\left(\mathrm{h}\right)-\mathrm{d}\left(\mathrm{h}\right)>\mathrm{\epsilon }>0,$$

   

   with ε ≥ 1 mm, for with example ε ≥ 2 mm, preferably ε ≥ 5 mm, or ε ≥ 10 mm.
3. Forearm walking support (1) according to claim 1 or 2, characterized in that the two lateral marginal edges (20) of the contact surface (15) run at least in regions laterally next to the support tube, preferably the two lateral marginal edges (20) of the contact surface (15) running mirror-symmetrically to a plane spanned by the longitudinal axis (8, 9) of the support tube (2) on the one hand and the longitudinal axis of the handle (12) on the other hand.
4. Forearm walking support (1) according to one of claims 1 to 3, characterized in that the horizontal distance between the two edges (20) in the region of the handle (12) corresponds approximately to the diameter of the support tube (2).
5. Forearm walking support (1) according to one of claims 1 to 4, characterized in that the horizontal distance between the two edges (20) in the region of the forearm clamp (13) or sleeve corresponds at least approximately to half of the width of the forearm clamp (13) or sleeve.
6. Forearm walking support (1) according to one of claims 1 to 5, characterized in that the radii of curvature of the marginal edges (20) are equal to 20 mm or less, for example equal to 10 mm or less, preferably equal to 5 mm or less, in particular equal to 2 mm or less.
7. Forearm walking support (1) according to one of the claims 1 to 6, characterized in that the lateral marginal edges (20) are designed to be raised in relation to the bearing surface (15) .
8. Forearm walking support (1) according to any one of claims 1 to 7, characterized in that a horizontal cross-section through the contact surface (15) between the two marginal edges (20) is at least in regions

   a) planar, or

   b) concavely curved, or

   c) convexly curved with a radius of curvature which corresponds to at least half the length of the handle (12), preferably at least the entire length of the handle (12), in particular at least twice the length of the handle (12).
9. Forearm walking support (1) according to one of claims 1 to 8, characterized in that the contact surface (15) extends between the two marginal edges (20) without interruption.
10. Forearm walking support (1) according to one of claims 1 to 9, characterized in that the contact surface (15) has at least one recess between the two marginal edges (20).
11. Forearm walking support (1) according to claim 10, characterized in that said at least one recess

    a) is designed as a groove extending in the vertical direction flanked by two halves of the contact surface (15) on both sides, or

    b) is designed as an upwardly open slot (22) which is bounded by the contact surface (15) at the bottom and on both sides, or

    c) is designed as a trough-shaped deepening (21) which is surrounded by the contact surface (15) as by a frame.
12. Forearm walking support (1) according to one of the preceding claims, characterized in that the contact surface (15)

    a) is made of a material with a rough surface, so that it can also be used along smooth surfaces such as those made of exposed concrete, woodchip, tiles, glass, natural stone, wood, plastic, stainless steel or artistically designed uneven ceramic tiles, cannot slip off, and/or

    b) is made of or coated with a friction-enhancing material such as an elastomer or is coated with such a material.
13. Forearm walking support (1) according to one of the preceding claims, characterized in that the contact surface (15) is designed as a counterweight to the forward-facing handle (12) and/or is provided with a counterweight thereto.
14. Forearm walking support (1) according to one of the preceding claims, characterized in that the contact surface (15)

    a) is integral with the forearm clamp (13), or

    b) manufactured separately and is connected or connectable to the forearm clamp (13).
15. Forearm walking support (1) according to one of the preceding claims, characterized in that the contact surface (15)

    a) is provided with a reflector, and/or

    b) is provided with a rearwardly directed light source, for the power supply of which a battery or accumulator is preferably arranged in the hand grip (12) or in the support tube (2).

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