TECHNICAL FIELD

The invention relates to a pushbar for a wheelchair according to the appended claims.

BACKGROUND AND PRIOR ART

A wheelchair user often makes use of hand rims on the wheels of the wheelchair, which the user can grasp to force the wheels to turn and thus propel the wheelchair. In special cases, an accompanying person may push the wheelchair by grasping handles, which are connected to the wheelchair frame. The wheelchair handles may be designed in different ways depending on the type of wheelchair. Wheelchairs may also be foldable and demountable arranged, which make them suitable for transpor tation in for example a vehicle.

One type of know handles for wheelchairs are fixed to the wheelchair frame and ex tend rearward from the wheelchair frame. When folding and demounting the wheel chair, the handles are disconnected and removed from the wheelchair frame by means of threaded fasteners.

SUMMARY OF THE INVENTION

Despite known prior art, there is a need to develop a pushbar for a wheelchair, which overcome or at least alleviates problems of prior art. A further need is to develop a pushbar for a wheelchair, which is easy to connect to and disconnect from a wheel chair in a short period of time. A further need is to develop a pushbar for a wheel chair, which is ergonomic to use for a person who accompanies a user of the wheel chair. A further need is to develop a pushbar for a wheelchair, which is reliably at tached to the wheelchair, when connected to the wheelchair.

Hence, an object of the invention is to develop a pushbar for a wheelchair, which overcome or at least alleviates problems of prior art. A further object of the invention is to develop a pushbar for a wheelchair, which is easy to connect to and disconnect from a wheelchair in a short period of time.

A further object of the invention is to develop a pushbar for a wheelchair, which is er gonomic to use for a person who accompanies a user of the wheelchair.

A further object of the invention is to develop a pushbar for a wheelchair, which is re liably attached to the wheelchair, when connected to the wheelchair.

The herein mentioned objects may be achieved by the above-mentioned pushbar for a wheelchair and the method according to the appending claims.

According to an aspect of the present disclosure, a pushbar for a wheelchair is pro vided. The pushbar for a wheelchair comprising an elongated bar provided with a first end portion and a second end portion; a handlebar attached to the elongated bar at the first end portion of the elongated bar, which handlebar is configured to be graspa- ble by a person; a first clamp arranged on the elongated bar at a position between the first and second end portions; a second clamp attached to the elongated bar at the second end portion of the elongated bar, wherein the first clamp is configured to be releasably connected to a first attachment member of the wheelchair, and the sec ond clamp is configured to be releasably connected to a second attachment member of the wheelchair.

The wheelchair may have a configuration, which is adapted for any size of a user of the wheelchair. Thus, the wheelchair may have a size, which is adapted for an adult. Alternatively, the wheelchair may have a size, which is adapted for a child. The wheelchair has a number of wheels. The wheelchair has a seat for the user of the wheelchair. The wheels and the seat are connected to a frame of the wheelchair. The frame may be made of tubular elements in order to save weight of the wheelchair.

The tubular elements for the frame may be made of steel, aluminum, titanium, carbon fiber, fiberglass, plastics or any other suitable material. The elongated bar of the pushbar may be straight or curved. The handle bar is con figured to be graspable by a person. The person may be an attendant for the user of the wheelchair. The handle bar has an ergonomic configuration, so that the person grabbing the handle bar gets a firm grip of the handle bar. The handle bar may be made of a tubular element covered by a grip-friendly material.

The elongated bar may be made of a tubular profile having any cross sectional shape. The handlebar may be attached to the elongated bar at the first end portion of the elongated bar by means of a coupling element. Alternatively, the handlebar may be an integrated portion of the elongated bar.

The wheelchair has at least two attachment members to which the pushbar may be coupled. The attachment members may be arranged at a distance from each other, which increases the stabilization and firm connection of the pushbar, when the pushbar is connected to the wheelchair. The attachment members may be arranged on a rear portion of the wheelchair, so that the pushbar can be connected to a rear portion of the wheelchair. As a result, the accompanying person may grab the handle bar behind the wheelchair and pushing the wheelchair in its forward direction. By grasping the handle bar, the accompanying person may take control of the wheel chair for propelling and steering the wheelchair in any direction.

The first clamp is arranged on the elongated bar at a position between the first and second end portions of the pushbar. The second clamp is attached to the elongated bar at the second end portion of the elongated bar. Thus, the first and second clamps are arranged at distance from each other along the elongated bar, which increases the stabilization and firm connection of the pushbar, when the pushbar is connected to the wheelchair. The distance between the first and second clamps may corre spond to the distance between the attachment members on the wheelchair, so that the first clamp may be connected to the first attachment member of the wheelchair, and the second clamp may be connected to the second attachment member of the wheelchair. Both the first and the second clamp are configured to be releasably con nected to attachment members of the wheelchair. When the pushbar is connected to the backside of the wheelchair, it may be difficult for the user of the wheelchair to maneuver the wheelchair in small spaces, such as small rooms indoors, since it is difficult to the user recognize how far the pushbar ex tends backwards of the wheelchair. Detaching the pushbar from the wheelchair will reduce the extension of the wheelchair and increase the maneuverability of the wheelchair in small spaces.

Such pushbar for a wheelchair will overcome or at least alleviates problems of prior art. The pushbar is easy to connect to and disconnect from a wheelchair in a short period of time. Such pushbar is ergonomic to use for a person who accompanies a user of the wheelchair. Such pushbar is also reliably attached to the wheelchair, when connected to the wheelchair. When there is no need of the pushbar, it should be disconnected from the wheelchair. However, when there is a need of the pushbar it should be connected to the wheelchair. A wheelchair of low weight, such as a small wheelchair for children or a large wheelchair made of materials, such as high strength steel, aluminum, titan and/or carbon fiber, will increase its weight when the pushbar is mounted on the wheelchair. In order to reduce the weight of the wheel chair, the pushbar should be removed from the wheelchair when there is no need of the pushbar.

According to an aspect, the first clamp comprises an adjustment element, which is configured for adjusting the position of the first clamp between the first and second end portions.

Adjustment of the position of the first clamp between the first and second end por tions makes it possible to adjust the position of the first clamp along the elongated bar. Thus, the distance between the first and second clamps are adjustable. The dis tance between the first and the second attachment members of the wheelchair may different between different wheelchairs. In order to enable the connection of the pushbar to a plurality of wheelchairs, the position of the first clamp between the first and second end portions is adjustable. Once the position of the first clamp has been adjusted, the pushbar is easy to connect to and disconnect from the wheelchair in a short period of time. According to an aspect, the second clamp is controllable by a control member ar ranged at the elongated bar.

The control member may be arranged at any position along the elongated bar. By ac tivating the control member, the second clamp is controllable to an opened position.

In the opened position of the second clamp, the second clamp may be connected to and disconnected from the second attachment member of the wheelchair. Since the second clamp is arranged at the second end of the elongated bar, the second clamp may be difficult to reach when connecting and disconnecting the second clamp to and from the second attachment member. The control member may be arranged on a position along the elongated bar, which position is easy to reach when the second clamp should be controlled. When activating the control member, a transmission ele ment, such as a wire, transmits a movement from the control member to the second clamp. Thus, the second clamp is controllable by a control member arranged at the elongated bar or by controlling a locking element directly on the second clamp. According to an aspect, the first and second clamps are configured as quick cou plings.

By configuring the first and second clamps as quick couplings, the pushbar will be easy to connect to and disconnect from a wheelchair in a short period of time. The first and second clamps may be provided with clamp and locking elements which are easy and understandable to maneuver. The clamp and locking elements may be spring biased. When connecting the pushbar to the wheelchair the spring force is overcome by pushing the first and second clamps against the attachment member. When the first and second clamps have taken the correct position at the attachment members, the spring biased clamp and locking elements will return to its original po sition and clamp about the attachment members of the wheelchair. Alternatively or in combination with the spring biased configuration of the clamp and locking elements, the clamp and locking elements may be shaped such that the clamp and locking ele ments take a clamping action through interaction with other clamp and locking ele ments. The first and second clamps may have different configurations and shapes.

According to an aspect, the first clamp comprises a safety lock for preventing the pushbar from unintentionally being disconnected from the wheelchair. The safety lock prevents the first clamp to unintentionally move to an open position and thus loose the gripping or clamping of the first attachment member of the wheel chair. The safety lock will ensure that the pushbar is reliably attached to the wheel chair, when connected to the wheelchair. The safety lock may be released by one hand, and thus allow the first clamp to be disconnected from the first attachment member of the wheelchair.

According to an aspect, the first and second clamps comprise clamping surfaces configured to clamp around parallel tubular elements of the first and second attach ment members of the wheelchair.

The first and second attachment members of the wheelchair may be configured as tubular elements. The tubular elements may be a part of the structure frame of the wheelchair. The tubular elements may have a circular cross section. The clamping surfaces of the first and second clamps may have a configuration that correspond to and is adapted to the shape of the tubular elements.

According to an aspect, the handlebar has an annular shape.

The handle bar is configured to be graspable by a person. The annular shape of the handle bar results in an ergonomic configuration, since the person grabbing the han dle bar may grab the handle bar in a number of different positions. The annular shape of the handle bar also results in that the person grabbing the handle bar gets a firm grip of the handle bar. The handle bar may be made of a tubular element cov ered by a grip-friendly material.

According to an aspect, the handlebar is adjustable in relation to the elongated bar.

The handlebar may be adjustable to a position which is ergonomic for the person grabbing the handle bar. A long person may adjust the handle bar to a position, which is different to a position, which is suitable for a short person. The handlebar may be attached to the elongated bar at the first end portion of the elongated bar by means of an adjustable coupling element. The handle bar may be folded in relation to the elongated bar. In addition to increased ergonomics, the handle bar may be folded to a position in relation to the elongated bar, which enables the pushbar to be easy to handle when disconnected from the wheelchair.

According to an aspect, the elongated bar is configured as a telescopic bar compris ing a first bar portion and a second bar portion, which first bar portion is axially dis placeable within the second bar portion.

Configuring the elongated bar as a telescopic bar may increase the adjustment abili ties of the pushbar. Thus, the length of the pushbar may be adapted to persons of different length. The length of the pushbar may be adjusted by positioning the first bar portion and a second bar portion in different positions in relation to each other.

According to an aspect, a telescopic clamp is arranged on the telescopic bar, which telescopic clamp is configured to lock the first and second bar portions in relation to each other.

The telescopic clamp may lock the first and second bar portions in relation to each other. In the locked position the first and second bar portions may not move in rela tion to each other. Thus, the elongated bar has a certain length when the telescopic clamp locks the first and second bar portions in relation to each other. Adjusting the length of the elongated bar is possible when unlocking the telescopic clamp and thereafter displacing the first and second bar portions in relation to each other. When the first and second bar portions has been displaced in relation to each other, so the elongated bar has a suitable length, the telescopic clamp is locked.

According to an aspect of the present disclosure, a wheelchair is provided. The wheelchair comprises a first and a second attachment member, which are configured to receive a pushbar as disclosed herein.

Such wheelchair will receive a pushbar, which is connectable to and disconnectable from the wheelchair by means of one hand. Further, the pushbar will be easy to con nect to and disconnect from a wheelchair in a short period of time. The pushbar will be ergonomic to use for a person who accompanies a user of the wheelchair. Such pushbar will also be reliably attached to the first and the second attachment member of the wheelchair, when connected to the wheelchair.

According to an aspect of the present disclosure, a method for connecting a pushbar to a wheelchair is provided. The pushbar comprises: an elongated bar provided with a first end portion and a second end portion; a handlebar attached to the elongated bar at the first end portion of the elongated bar, which handlebar is configured to be graspable by a person; a first clamp arranged on the elongated bar at a position be tween the first and second end portions; a second clamp attached to the elongated bar at the second end portion of the elongated bar, wherein the first clamp is config ured to be releasably connected to a first attachment member of the wheelchair, and the second clamp is configured to be releasably connected to a second attachment member of the wheelchair. The method comprises connecting the second clamp to the second attachment member of the wheelchair; and connecting the first clamp to the first attachment member of the wheelchair.

The method for connecting the pushbar to a wheelchair starts with the connection of the second clamp to the second attachment member of the wheelchair. The second clamp may be controlled to an opened position by activating a control member, which is arranged at the elongated bar. In the opened position of the second clamp, the second clamp may be connected to the second attachment member of the wheel chair. However, the second clamp may be pushed against the second attachment member, so that spring biased clamp elements or interacting clamp elements will clamp about the second attachment member of the wheelchair.

After the second clamp has been connected to the second attachment member, the first clamp is connected to the first attachment member of the wheelchair. The first clamp is connected to the first attachment member by pushing the first clamp against the first attachment member, so that interacting clamp elements will clamp about the first attachment member of the wheelchair. When the interacting clamp elements of the first clamp about the first attachment member, a safety lock of the first clamp is activated for preventing the pushbar from unintentionally being disconnected from the wheelchair. According to an aspect, the method comprises the further step of, before connecting the first clamp to the first attachment member of the wheelchair: adjusting the posi tion of the first clamp by means of an adjustment element.

The first clamp may be connected to the elongated bar bay means of an adjustment connection. By releasing the adjustment connection, the first clamp may be movable along the elongated bar. This results in that the distance between the first and sec ond clamps are adjustable. The distance between the first and the second attach ment members of the wheelchair may different between different wheelchairs. In or der to enable the connection of the pushbar to a plurality of wheelchairs, the position of the first clamp between the first and second end portions is adjustable. Once the position of the first clamp has been adjusted, the pushbar is easy to connect to and disconnect from the wheelchair in a short period of time.

According to a further aspect, the method comprises the further step of: adjusting the length of the elongated bar by axially displacing a first bar portion within a second bar portion of the elongated bar.

The elongated bar may be configured as a telescopic bar comprising a first bar por tion and a second bar portion, which first bar portion is axially displaceable within the second bar portion. Configuring the elongated bar as a telescopic bar may increase the adjustment abilities of the pushbar. Thus, the length of the pushbar may be adapted to persons of different length. The length of the pushbar may be adjusted by positioning the first bar portion and a second bar portion in different positions in rela tion to each other. Alternatively, the length of the pushbar is fixed, without the possi bility to adjust the length of the pushbar.

Configuring the elongated bar as a telescopic bar may increase the adjustment abili ties of the pushbar. Thus, the length of the pushbar may be adapted to persons of different length. The length of the pushbar may be adjusted by positioning the first bar portion and a second bar portion in different positions in relation to each other. Additional objectives, advantages and novel features of the invention will be apparent to one skilled in the art from the following details, and through exercising the inven tion. While the invention is described below, it should be apparent that the invention may be not limited to the specifically described details. One skilled in the art, having access to the teachings herein, will recognize additional applications, modifications and incorporations in other areas, which are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the present disclosure and further objects and advantages of it, the detailed description set out below should be read together with the accompa nying drawings, in which the same reference notations denote similar items in the var ious drawings, and in which: Fig. 1 schematically illustrates a pushbar in a view of perspective according to an ex ample;

Fig. 2 schematically illustrate a side view of a pushbar connected to a wheelchair ac cording to an example;

Fig. 3a schematically illustrates a first clamp in a view of perspective according to an example;

Fig. 3b schematically illustrates the first clamp in fig. 3a in an exploded view;

Fig. 4a schematically illustrates a side view of a second clamp according to an exam ple;

Fig. 4b schematically illustrates the second clamp in fig. 4a in an exploded view; and

Fig. 5 illustrates a block diagram of a method according to an example. DETAILED DESCRIPTION OF THE DRAWINGS

Hereinafter, examples will be described with reference to the accompanying draw ings, wherein for the sake of clarity and understanding of the embodiments some de tails of no importance may be deleted from the drawings. The disclosure is not in tended to limit the scope of the enclosed claims in any way.

Fig. 1 schematically illustrates a pushbar 1 in a view of perspective according to an example. The pushbar 1 comprises an elongated bar 2 provided with a first end por tion 4 and a second end portion 6. The elongated bar 2 is configured as a telescopic bar 8 comprising a first bar portion 10 and a second bar portion 12, which first bar portion 10 is axially displaceable within the second bar portion 12. A telescopic clamp 14 is arranged on the telescopic bar 8, which telescopic clamp 14 is configured to lock the first and second bar portions 10, 12 in relation to each other. A handlebar 16 is attached to the elongated bar 2 at the first end portion 10. The handlebar 16 has an annular shape, which results in an ergonomic configuration for the person grab bing the handlebar 16. The handlebar 16 is adjustable in relation to the elongated bar 2. The handlebar 16 is adjustable by means of an adjustable coupling element 18. A first clamp 20 is arranged on the elongated bar 2 at a position between the first and second end portions 4, 6. A second clamp 22 is attached to the elongated bar 2 at the second end portion 6 of the elongated bar 2. The first clamp 20 is configured to be releasably connected to a first attachment member 24. The second clamp 22 is configured to be releasably connected to a second attachment member 26. The first clamp 20 comprises an adjustment element 28, which is configured for adjusting the position of the first clamp 20 between the first and second end portions 4, 6. The sec ond clamp 22 is controllable by a control member 30 arranged at the elongated bar 2. By activating the control member 30, the second clamp 22 is controllable to an opened position.

Fig. 2 schematically illustrate a side view of a pushbar 1 connected to a wheelchair 32 according to an example. The wheelchair 32 may have a number of wheels 34, wherein only one wheel 34 is shown in fig. 2. The wheelchair 32 is provided with a seat 36. The wheels 34 and the seat 36 are connected to a frame 38 of the wheel- chair 32. The frame 38 may be made of tubular elements 40. The frame 38 may com prise the first and second attachment members 24, 26. The first clamp 20 is releasa- bly connected to the first attachment member 24 of the wheelchair 32, and the sec ond clamp 22 is releasably connected to the second attachment member 26 of the wheelchair 32.

Fig. 3a schematically illustrates the first clamp 20 in a view of perspective according to an example. The first clamp 20 may be configured as a quick coupling, so that the pushbar 1 (fig. 1 ) will be easy to connect to and disconnect from the wheelchair 32 (fig. 2) in a short period of time. In fig. 3a, the first clamp 20 is shown in a locked or closed position about the first attachment member 24. The first clamp 20 comprises three clamp elements 42, 44, 46, which are configured to interact with each other. In the locked position, the three clamp elements 42, 44, 46 grip the first attachment member 24. The three clamp elements 42, 44, 46 are configured to form a first open- ing 48, which accommodate and grip the first attachment member 24. A first clamp element 42 of the three clamp elements, are pivotable about a first pivot shaft 50, which extends in parallel with the first opening 48. A second clamp element 44 is configured to be connected to and to grab the first clamp element 42 in order to lock the first clamp element 42 in the locked position of the first clamp 20. A third clamp element 46 is a safety lock 52 for preventing the first clamp element 42 and thus the pushbar 1 from unintentionally being disconnected from the first attachment member 24. The three clamp elements 42, 44, 46 are pivotally arranged in a first clamp hous ing 54. The first clamp 20 comprises clamping surfaces 55, which are configured to clamp around at least a part of the first attachment member 24, which may have the shape of a tubular element 40.

Fig. 3b schematically illustrates the first clamp 20 in fig. 3a in an exploded view. The first clamp element 42 is connected to the first clamp housing 54 by means of the first pivot shaft 50. The first clamp element 42 is provided with protrusions 57. A bore 59 for the first pivot shaft 50 is arranged in the first clamp element 42. The protrusions 57 of the first clamp element 42, are arranged on the opposite side of the bore 59 than that part of the first clamp element 42, which is provided with the clamp surface 55. The protrusions 57 will interact with the first attachment member 24 when con- necting the first clamp 20 to the wheelchair 32. The second clamp element 44 is con nected to the first clamp housing 54 by means of a second pivot shaft 56. The third clamp element 46 is connected to the first clamp housing 54 by means of the second pivot shaft 56. The second pivot shaft 56 is configured as a crankshaft, which results in a pivotal movement of the second clamp element 44 about two shafts. This move ment of the second clamp element 44 results in that the second clamp element 44 is able to grip a hook shaped portion 60 of the first clamp element 42. In order to re lease or disconnect the first clamp element 42 from the first attachment member 24 (fig. 3a), the third clamp element 46 is brought in a direction away from the second clamp element 44. Thereafter, the second clamp element 44 is raised upwards and is brought forward in order to disconnect the second clamp element 44 from the hook shaped portion 60 of the first clamp element 42. Finally the first clamp element 42 may be pivoted forward in order to release the first attachment member 24. The ad justment element 28 is arranged on the first clamp housing 54. The adjusting element comprises 28 a screw 62 and a nut 64. By loosening the screw 62 and the nut 64, the position of the first clamp 20 may be adjusted along the elongated bar 2 (fig. 1 ).

Fig. 4a schematically illustrates a side view of the second clamp 22 according to an example. The second clamp 22 may be configured as a quick coupling, so that the pushbar 1 (fig. 1 ) will be easy to connect to and disconnect from the wheelchair 32 (fig. 2) in a short period of time. In fig. 4a, the second clamp 22 is shown in a locked or closed position about the second attachment member 26. The second clamp 22 comprises a first locking element 66, which is pivotally arranged about a first pivot pin 68. The second clamp 22 also comprises a second locking element 70, which is piv otally arranged about a second pivot pin 72. The first and second locking elements 66, 70 may be spring biased. When connecting the second clamp 22 to the second attachment member 26, the spring force acting on the first and second locking ele ments 66, 70 is overcome by pushing the second clamp 22 against the second at tachment member 26. When the second clamp 22 has taken the correct position at the second attachment member 26, the spring biased locking elements 66, 70 will re turn to their original position and clamp about the second attachment member 66. Al ternatively or in combination with the spring biased configuration of the first and sec ond locking elements 66, 70 may be shaped such that the first and second locking el- ements 66, 70 take a clamping action through interaction between the first and sec ond locking elements 66, 70. The second clamp 22 comprises clamping surfaces 55, which are configured to clamp around at least a part of the second attachment mem ber 26, which may have the shape of a tubular element 40.

Fig. 4b schematically illustrates the second clamp 22 in fig. 4a in an exploded view. The first locking element 66 is connected to a second clamp housing 74 by means of the first pivot pin 68. The first locking element 66 is spring biased by means of a first spring 76. The second locking element 70 is connected to the second clamp housing 74 by means of the second pivot pin 72. The second clamp 22 is controllable by the control member 30 (fig. 1 ) arranged at the elongated bar 2 (fig. 1 ). By activating the control member 30 (fig. 1 ), the first locking element 66 of the second clamp 22 is con trollable to an opened position. In the opened position of the second clamp 22, the second clamp 22 may be connected to and disconnected from the second attach ment member 26. A transmission element 78, such as a wire connects the control member 30 and the first locking element 66. When activating the control member 30, the transmission element 78 transmits movement from the control member 30 to the first locking element 66 of the second clamp 22, which movement of the transmission element 78 pivots the first locking element 66 about the first pivot pin 68.

Fig. 5 illustrates a method for connecting a pushbar 1 to a wheelchair 32 as disclosed herein. The pushbar 1 comprises: an elongated bar 2 provided with a first end portion 4 and a second end portion 6; a handlebar 16 attached to the elongated bar 2 at the first end portion 4 of the elongated bar 2, which handlebar 16 is configured to be graspable by a person; a first clamp 20 arranged on the elongated bar 2 at a position between the first and second end portions 4, 6; a second clamp 22 attached to the elongated bar 2 at the second end portion 6 of the elongated bar 2, wherein the first clamp 20 is configured to be releasably connected to a first attachment member 24 of the wheelchair 32, and the second clamp 22 is configured to be releasably connected to a second attachment member 26 of the wheelchair 32. The method comprises connecting s101 the second clamp 22 to the second attachment member 26 of the wheelchair 32; and connecting s102 the first clamp 20 to the first attachment member 24 of the wheelchair 32. When connecting s102 the first clamp 20 to the first attachment member 24 of the wheelchair 32, the first attachment member 24 will push against the protrusions 57 of the first clamp element 42. Since the protrusions 57 of the first clamp element 42, are arranged on the opposite side of the bore 59 than that part of the first clamp element 42, which is provided with the clamp surface 55, the first clamp element 42 strives to pivot about the first pivot shaft 50. The pivotal movement of the first clamp element 42 will result in that the clamp surface 55 of the first clamp element 42 pushes the first attachment member 24 into the first opening 48, which will accommodate and grip the first attachment member 24.

The method comprises the further step of, before connecting s102 the first clamp 20 to the first attachment member 24 of the wheelchair 32: adjusting s103 the position of the first clamp 20 by means of an adjustment element 28.

The method comprises the further step of: adjusting s104 the length of the elongated bar 2 by axially displacing a first bar portion 10 within a second bar portion 12 of the elongated bar 2.

The foregoing description of the preferred embodiments has been furnished for illus trative and descriptive purposes. It is not intended to be exhaustive, or to limit the embodiments to the variants described. Many modifications and variations will obvi ously be apparent to one skilled in the art. The embodiments have been chosen and described in order to best explicate principles and practical applications, and to thereby enable one skilled in the art to understand the embodiments in terms of its various embodiments and with the various modifications that are applicable to its in tended use. The components and features specified above may, within the frame work of the embodiments, be combined between different embodiments specified.