Patent Abstract:
A adjustable crutch, cane or similar walking aid for assisting everyday movement for temporarily injured and even permanently handicapped persons, the crutch having telescoping crutch tubes encasing a locking gas spring crutches which can instantaneously and controllably be adjusted in length during use, thereby considerably facilitating such common physical activities as sitting down, standing up, negotiating stairs or other obstacles and other similar everyday mobile activities. The locking gas spring functions by internal gas pressure and the telescoping crutch tubes are extended as the internal gas pressure seeks to reach the lowest energy state by maximizing its internal volume. For safety purposes a disengagement mechanism is provided so that extension occurs up to a preset level dictated by the user, and can even be overridden if desired.

Full Description:
FIELD OF TECHNOLOGY  
       [0001]     The present invention relates to crutches, canes or similar walking aids for assisting everyday movement for temporarily injured and even permanently handicapped persons. More particularly, the invention relates to crutches which can instantaneously and controllably be adjusted in length during their use, thereby, among other things, considerably facilitating such common physical activities as sitting down, standing up, negotiating stairs or other obstacles and other similar everyday mobile activities.  
       BACKGROUND OF TECHNOLOGY  
       [0002]     The adjustable crutches presently available in the market basically consist of two telescoping tubes, usually made of a metal or metal alloy, which can be secured relative to one another by means of a variety of mechanical locking mechanisms arranged at regular intervals along the tube parts. A common design of the locking devices is that both of the tube parts are provided with diametrically opposed holes which can be placed in alignment with each other, the locking taking place by inserting a pin, detend or the like through the holes in the two tubes and securing the tubes in a desired position. The purpose of the crutch adjustability in this case makes it possible for two persons of different heights to use the same crutch. A suitable crutch length can be attained for a person depending on that person&#39;s height. Once this length has been determined it is maintained until a different person uses the crutch and the length is readjusted accordingly.  
         [0003]     These types of crutches have several disadvantages which, among other things, are related to the fact that the person is unable to change the length of the crutch during use. For example, because of the fixed crutch length, the person has very little help when sitting down, standing up, using stairs, and other similar everyday mobile activities. During these routine activities the person must rely on arm rests, chair seats, etc. for support. This can be especially difficult for older or more incapacitated persons.  
       OBJECT AND SUMMARY OF THE INVENTION  
       [0004]     There is a need for a crutch which facilitates sitting and standing in a controlled and assisted fashion while ensuring the safety of the user. The present invention is directed at further solutions to address this need.  
         [0005]     In accordance with one aspect of the present invention a crutch is provided having an instantaneously and user controlled adjustable length feature which facilitates activities such as sitting and standing in a controlled and assisted fashion.  
         [0006]     In accordance with another aspect of the present invention the controlled adjustable length feature of the crutch is controlled by the user according to a locking gas spring incorporated between a relatively moveable upper crutch tube and lower crutch tube.  
         [0007]     In accordance with yet another aspect of the present invention the crutch has a handle which the user can grasp to utilize the crutch in the known manner and the handle also comprising an operative means for a controlling a pressure valve in the locking gas spring pressure.  
         [0008]     In accordance with further aspects of the present invention the crutch is provided with a user defined maximum height setting which can be readily changed for different user&#39;s of different heights.  
         [0009]     In accordance with still another aspect of the present invention the user defined maximum height setting includes an automated shut-off mechanism to limit the maximum length of the crutch.  
         [0010]     An adjustable crutch for facilitating mobility comprising a telescoping shaft having an upper and lower crutch tube aligned on a concentric axis, a handle attached to an intermediate portion of the telescoping shaft, a shoulder support attached to the crutch on a first end of the upper crutch tube and a ground engaging butt end positioned at a first end of the lower crutch tube, a locking gas spring comprising a gas cylinder and a moveable piston is positioned inside the telescoping shaft for controlling relative slidable movement between the upper and lower crutch tubes of the telescoping shaft and wherein a control button is positioned on the handle for operating the gas spring, and an automatic disengagement mechanism is provided in the crutch for interrupting operation of the gas spring and limiting extension of the crutch.  
         [0011]     A method of adjusting a crutch for facilitating mobility, the method comprising the steps of aligning a telescoping shaft having an upper and lower crutch tube on a concentric axis, attaching a handle to an intermediate portion of the telescoping shaft, attaching a shoulder support to the crutch on a first end of the upper crutch tube and positioning a ground engaging butt end at a first end of the lower crutch tube, providing a locking gas spring comprising a gas cylinder and a moveable piston inside the telescoping shaft for controlling relative slidable movement between the upper and lower crutch tubes of the telescoping shaft, and actuating a control button positioned on the handle for operating the gas spring, and interrupting operation of the gas spring and limiting extension of the crutch according to a preset extension limit effected by an automatic disengagement mechanism. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a side view of one embodiment of the crutch;  
         [0013]      FIG. 2  is a front view of one embodiment of the crutch;  
         [0014]      FIG. 3  is a cross-sectional front view of one embodiment of the crutch;  
         [0015]      FIG. 4  is a cross-sectional front view of a gas spring of common construction;  
         [0016]      FIG. 5  is a cross-sectional front view of a locking gas spring of common construction;  
         [0017]      FIG. 6  is a cross-sectional side view of an embodiment of the handle portion of the crutch;  
         [0018]      FIGS. 7 and 7 A are an exploded view of the crutch, handle, locking gas piston and valve actuating mechanism;  
         [0019]      FIG. 8  is a further cross sectional view of an embodiment of the handle portion of the crutch;  
         [0020]      FIGS. 9A and 9B  are perspective views of the wedge in combination with a portion of the upper crutch tube and the wedge alone;  
         [0021]      FIG. 10  is a perspective view of the wedge in use on the upper crutch shaft in cooperation with the handle; and  
         [0022]      FIG. 11  is a cross-sectional view of a further embodiment of the handle and piston extension stop mechanism; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     An adjustable crutch  1 , as displayed in a first embodiment shown in  FIGS. 1, 2  and  3  is designed around a locking gas spring, as described in detail below, to facilitate the immediate and safe adjustability, i.e. either the lengthening or shortening of the crutch  1 , by the user at any given time. The crutch  1  includes in general an upper crutch tube  3  and a lower crutch tube  5 , a shoulder support  7 , a butt end  9  and a handle  11 . The lower crutch tube  5  is shown at least partially inserted and telescoping within the upper crutch tube  3  so that upon adjusting the length of the crutch  1 , as described in further detail below, the lower crutch tube  5  is either slidably withdrawn from the upper crutch tube  3  or slidably inserted deeper within the upper tube such that the respective tubes are slidably adjustable with respect to one another.  
         [0024]     The slidable, telescoping relative movement of the upper and lower crutch tubes  3 ,  5  is controlled by the gas spring  21  housed within at least a portion of both the upper and the lower crutch tubes. As is commonly known in the art, the gas spring  21  generally includes a gas cylinder  23 , a piston  25  and a piston rod  27 . As is apparent from  FIG. 3 , the gas cylinder  23  is situated in the lower crutch tube  5  and the piston rod  27  portion of the gas spring  21  is affixed at one end to the upper crutch tube  3  with the opposing end of the piston rod  27  attached within the piston  25  and is generally freely slidable within the gas cylinder  23 . This arrangement of the gas cylinder and piston in the crutch is important with regards to the functional aspects and other structural features of the crutch in that it provides a safe and easy to operate device as will be discussed in detail below.  
         [0025]     The crutch  1  also includes an adjustable handle  11  which is moveably, slidably attached to the upper crutch tube  3  so as to be grasped by the user to support themselves and operate the crutch  1  in a conventional manner well known to anyone who has had to use a crutch. The handle  11  can be slidably moved relative to the upper crutch tube  3  and the shoulder support  7  and is adjusted independently of the length of the crutch  1  so that varying arm lengths of different user&#39;s can be accommodated by the crutch  1 . Also, as will be discussed in further detail below, the handle  11  can be provided with a manually operated valve control device to permit the user to actuate the gas spring  21  so as to lengthen or shorten the crutch  1 . The shoulder support  7  for engaging underneath the arm and shoulder of the user as generally known is provided on the upper tube at the upper most end of the crutch  1 . At the lower most end of the crutch  1 , a rubber, plastic or similar non-slip material is applied as a ground engaging butt end  9  to ensure that the crutch  1  does not slip on any ground surface. It is to be appreciated that while a user usually utilizes two crutches, one with each arm for the appropriate balance and ease of movement, for purposes of brevity and clarity in this application only a single crutch and the operation thereof will be discussed.  
         [0026]     In order to understand the operation of the above discussed crutch  1  in conjunction with the locking gas spring  41 , the general construction and function of the gas spring  21  will now be discussed. As shown generally in  FIG. 4  where like numbers of the gas spring represent the same elements in each disclosed embodiment, a gas spring  21 ′ includes; a gas cylinder  23 ′, a piston  25 ′ contained within the cylinder  23 ′, a piston rod  27 ′ connected to the piston  25 ′, and a seal  29 ′ between the edge of the piston  25 ′ and the cylinder wall. To understand how a gas spring works it is imperative to understand that in a steady state, i.e. before compressive forces are applied, the cylinder  23 ′ is of course charged with some desired gas pressure P, and the gas pressures P 1  and P 2  on both sides of the piston  25 ′ adjust themselves to a state according to the equation F=P×A. Importantly, because the area of the face side  31 ′ of the piston  25 ′ is larger than the area of rod side  33 ′ of the piston  25 ′ due to the area taken up by the piston rod  27 ′, the pressures P 1  and P 2  on either side will adjust so that P 2  is larger to accordingly cause equal forces F 1 , F 2  acting on the face side  31 ′, and the rod side  33 ′ of the piston  25 ′ respectively, essentially maintaining the piston  25 ′ in an initial steady state position.  
         [0027]     A force F A  applied to the gas spring  21 ′, for purposes of example through the piston rod  27 ′, causes the piston  25 ′ to move within the cylinder  23 ′ reducing the volume on one side of the cylinder  23 ′ thus causing a higher pressure P 1  on the respective side of the cylinder  23 ′. Because the face side  31 ′ area remains the same, the increased pressure causes a corresponding increase in force F 1 , thus acting to return the piston  25 ′ to its initial steady state position once the applied force F A  is removed. It is well known that as the volume of a gas cylinder  23 ′ decreases, the mass of the gas remains constant, creating a higher pressure as is well known in the art.  
         [0028]     Turning to  FIG. 5 , different from the simple gas spring described above, in a locking gas spring  21 ′, a hole or valve  35 ′ is located in the piston  25 ′ to allow the pressure on both sides of the piston  25 ′ to equalize as the piston  25 ′ is compressed into the cylinder  23 ′. The valve through the piston  25 ′ is controllable via a valve control device  37 ′ to attain an open position allowing an equalization of the pressure on both sides of the piston  25 ′ within the cylinder  23 ′ as the piston  25 ′ is compressed, and a closed position where such equalization is not permitted. Understanding basic gas theory as described above, where force is equal to a pressure multiplied over an area (F=P×A), where there is a larger area defined by the face side  31 ′ of the piston  25 ′ and the pressures P 1  and P 2  are the same because of the open valve, a higher force F 2  will be generated to act on the face side  31 ′ of the piston  25 ′. The magnitude of the higher force F 2  is dependant upon the pressure level inside the cylinder  23 ′, the cross-sectional area of the cylinder  23 ′ and piston  25 ′, and the cross-sectional area of the piston rod  27 ′.  
         [0029]     By way of further explanation, the locking gas piston is achieved by controlling the equalization of pressures on both sides of the piston  25 ′, in other words controlling the amount of gas which is permitted through the valve  35 ′ in the piston  25 ′ as the system attempts to equalize the pressures on both sides of the valve. Thus, it is to be appreciated that at any point during operation of the locking gas spring  21 ′ the valve  35 ′ can be closed whether or not the pressures have equalized. This closing of the valve essentially “locks” the piston  25 ′ in place in the cylinder  23 ′ because the pressures P 1  and P 2  remain unequal while the forces on each side are equal. With the valve  35 ′ closed, and the piston  25 ′ locked in the desired position, again applying an external force F A  to the piston rod  27 ′, still with the valve closed, will not permit the piston  25 ′ to move much, only as much as the compressibility of the gas will permit. Even where there is some slight movement of the piston  25 ′, the increased pressure caused by the reduction in volume will return the piston  25 ′ to the locked position.  
         [0030]     On the other hand, with the valve  35 ′ open, and the force F A  applied to the piston rod  27 ′ which in combination with force F 2  starts to equal or overcome the force F 1  pushing on the face of the piston  25 ′, and the piston  25 ′ now starts to slide down the cylinder  23 ′ with gas pressure accordingly rising on the rod side  33 ′ of the piston  25 ′ as the mass of the gas the piston face side  31 ′ of the piston  25 ′ is allowed to pass through the open valve  35 ′. At some given point the valve  35 ′ can again be closed, thus the differing pressures P 1  and P 2  and equal forces F 1 , F 2  on each side of the piston  25 ′ are now essentially “locked” into the respective sides of the piston  25 ′ and cylinder  23 ′. The higher pressure on the rod side  33 ′, along with the smaller area, now equals the lower pressure on the face side  31 ′ of the piston  25 ′ times the larger piston area, i.e. F 1 =F 2  and the piston  25 ′ is thus also locked in place.  
         [0031]     If the valve  35 ′ were merely to be opened at this point, with no force F A  applied, the higher pressure P 2  on the rod side  33 ′ would want to equalize and migrate through the valve  35 ′ thus again permitting the face side force F 1  to become higher and return the gas spring  21 ′ to an extended steady state position. The further structural and functional aspects of the locking gas spring  21  in combination with the crutch  1  are described in further detail below.  
         [0032]     Turning to  FIG. 6 , the main body of the gas spring  21  i.e. the cylinder  23  containing the gas and the slidable piston  25 , is located and essentially fixed within the lower crutch tube  5 , and the free end of the piston rod  27  extends into and is directly attached to the upper crutch tube  3 . Thus, as may be appreciated, movement of the piston  25  relative to the essentially fixed nature of the gas cylinder  23  in the lower crutch tube  5  which is essentially directly supported on the ground surface, causes the upper crutch tube  3  to be axially moved relative to the lower crutch tube  5  and the ground surface and thus to shorten and lengthen the crutch  1 . A further description of the relative movement and operation of the gas piston  25  and crutch  1  is provided below.  
         [0033]     The crutch length adjustment system works as follows. In an operative, i.e. a steady state position, wherein the crutch  1  is essentially fixed in length and the gas spring  21  is in a locked position, whether fully or partially extended, the forces F 1 , F 2  acting on both sides of the piston  25  are equal as described above, because the pressure P 2  in the upper portion of the gas cylinder  23  and the pressure P 1  in the lower portion of the gas cylinder  23  are unequal, yet the areas over which the pressures act are inversely proportional relative to the pressure difference. Therefore, as long as the piston valve  26  is closed, the piston  25  will remain in the steady state locked position because the force differential as applied by the weight of the crutch  1  user is not great enough to compress the air or gas in the lower portion  46  of cylinder  23  i.e. overcome the pressure P 1  in the lower portion of the gas cylinder  23 .  
         [0034]     In order to raise or lower, i.e. extend or compress the crutch  1 , the user must operate a pressure release assembly which opens the piston valve  26  via valve control device  37 . To extend the crutch  1 , the user removes their body weight, or a significant portion of their body weight, from the crutch  1  and operates the valve control device  37 . Once the valve  35  is open, the pressures P 1 , P 2  on both sides of the piston  25  begins to equalize, and the higher force F 1  acting upward overcomes the force F 2  acting downward and the piston  25  thus moves upward, i.e. extends the crutch  1  until a point at which the user releases the pressure relase assembly and closes the piston valve  26  or the piston  25  tops out at an upper end of the cylinder  23 .  
         [0035]     On the other hand, in order to compress the crutch  1 , the larger force F 1  acting upward can be overcome by adding to the force F 2  generally by application of the crutch user&#39;s own body weight. It is to be appreciated that by specific design assuming equal pressures P 1 , P 2  the upward force F 1  can be designed to be just larger than F 2  such that the piston  25 , and thus the upper crutch tube  3 , rise or extend in a controlled manner. Therefore in order to compress the crutch  1 , i.e. lower the piston  25 , the user can apply a portion of their body weight to the upper crutch via the shoulder support  7  and overcome the upward force F 1 . In other words, the piston  25  can be lowered by a now greater force F 2+ F A &gt;F 1 , F A  being the user&#39;s own body weight or a portion thereof acting downward on the piston  25  and/or upper crutch tube  3 . Thus, the orientation of the gas spring  21  is optimized with the cylinder  23  essentially fixed to the lower crutch tube  5  and with the piston rod  27  extending upwards and fixed to the upper crutch tube  3 .  
         [0036]     It should be noted that the amount of force F 2  supplied by the crutch  1  and the force F A  required to overcome the upward force F 1  can be controlled by the size of the piston valve  26  and the piston rod  27 . The cross-sectional area of the piston rod  27  relative to the cross-sectional area of the piston  25  will determine the amount of net force F 1  acting upward on the piston  25 . Furthermore, as the piston  25  is moving up or down in the shaft, air or gas is being forced through the valve of the piston  25  in an attempt to equalize the pressure. The diameter of the piston valve  26  determines how quickly and easily the air will move through the valve. A larger valve will allow more air to pass through the piston  25  quickly than a smaller valve.  
         [0037]     The operation of the piston valve  35  and the valve control device  37  which opens and closes the piston valve  35  is now described. In one embodiment of the present invention the piston rod  27  includes a throughbore  28  which communicates with a passage through the piston  25 . The passage through the piston  25  essentially defines the piston valve  35  which in turn provides communication between the upper cylinder chamber  44  and the lower cylinder chamber  46  as shown in  FIG. 6  to permit the passage of gas or fluid therebetween. A valve stem  39  is inserted in the through bore of the piston  25  and extends into and substantially through the piston valve  26 . The valve stem  39  is moveable relative to the piston  25  and piston rod  27  between an open position, permitting the passage of gas or similar fluid through the piston valve  26  and between the upper and lower cylinder chambers, and a closed position wherein the passage of gas or fluid through valve  35  between the upper and lower cylinder chambers is blocked. It is also to be appreciated that other known structures of valves and locking gas pistons could be utilized as well.  
         [0038]     The opening and closing of the piston valve  26  is controlled by the valve stem  39  which is in turn controlled by the valve actuator  37  actuated by the crutch user. A manually operated button or lever  61  may be located on the handle  11  of the crutch  1  to facilitate the actuation of the valve. Communication between the valve stem  37  and the button  61  to open and close the piston valve  26  can be done through a hydraulic valve stem operation mechanism  63  as seen in  FIG. 7 . The hydraulic valve stem operation mechanism  63  can include a first hydraulic cylinder piston  65  associated with the button  61  or lever located on the handle  11  of the crutch  1 . The first hydraulic cylinder piston  65  is connected via a link, for example a hydraulic line, to a second cylinder piston  67  that cooperatively operates the valve stem  37  to move into the open and closed positions relative to the hollow piston rod  27  and the piston  25 . For example actuation of the button  61  or lever on the crutch handle  11  would open the valve  35  via the hydraulic valve stem operation mechanism  63  to permit relative extension or compression of the upper and lower crutch tubes  3 ,  5 .  
         [0039]     Thus, assuming that the crutch  1  is in an initial steady state at a length which accommodates a particular user traveling or walking with the crutch  1  along the ground, when the crutch user finds it necessary to sit down, the user will maintain, or apply a sufficient portion of their body weight to the upper crutch tube  3  via the handle  13  or the shoulder support  7  and simultaneously actuate button  61  of the piston valve actuator  63  located in the clutch handle  11 . Actuation thus opens the piston valve  35  via the first and second cylinder pistons  65 ,  67  of the hydraulic valve stem operation mechanism  63 , biasing the piston valve  35  into the open position. The user&#39;s weight F A , added to the force F 2  thus overcomes force F 1  acting upward and causes the piston  25  to travel downwards through the cylinder  23  with the upper crutch tube  3  correspondingly traveling downwards over the lower crutch tube  5  until either the user closes the piston valve  26 , or the piston  25  bottoms out in the cylinder  23 . Now the crutch user has been lowered closer to the ground and thus closer to for example a sitting position which they desire to attain.  
         [0040]     In order to return the crutch  1  to the extended travel or walking position the user need only operate the release assembly without their body weight, i.e. force F A , or a significantly reduced body weight portion, applied to the upper crutch tube  3  whereby the valve is opened again and the pressures P 1  and P 2  begin to equalize and the correspondingly larger force F 1  pushes the piston rod  27  back to what is generally a user defined crutch height corresponding to the user&#39;s comfort and physical size.  
         [0041]     The crutch adjustment system is required to accommodate as many human body types as possible. The system is design to adjust easily to essentially two common physical proportions. First, the user&#39;s height determines a user defined maximum height ie. a maximum extension for the crutch  1 . Secondly the handle  11  may be adjusted to accommodate the user&#39;s arm length. For example, a person six-foot-one-inch tall of typical proportions will have an arm-length in a range which is of course generally different than a person who may be five-foot-one-inch tall. A change in height can therefore be expected to have a change in arm length. Importantly, this individual or personal user adjustment of the handle height is essentially an independent function from that previously described regarding the relative adjustability of the upper and lower crutch tubes for the reason that the handle  11  does not move relative to the upper crutch tube  3  to which it is connected when the upper and lower crutch tubes are extended or compressed. Although the handle is adjustable, once set for a specific user, the handle  11  of the crutch  1  should remain fixed relative to the upper crutch tube  3  and the shoulder support  7 .  
         [0042]     However the two adjustments are not entirely independent functions as the user defined maximum height of the crutch  1  which is of course defined individually by each user acts in a manner to automatically restrain the extension of the piston rod  27  in conjunction with the piston valve actuator  61  and the handle  11 .  
         [0043]     In  FIGS. 6, 7  and  8 , the intersection of the upper crutch tube  3 , lower crutch tube  5 , and handle assembly are shown in different views. The handle assembly is comprised of a hollow cylinder body  13  for slidably engaging the upper crutch tube  3 , a protruding handle support  15  and a handle  11 . Also, a wedge  19  which is threaded and dogged is designed to be inserted into a lower slightly flared lower portion of the cylinder body. Inside the handle  11 , is a portion of the hydraulic valve stem operation mechanism  63 , more specifically the first hydraulic cylinder piston  65  associated with the button or lever located on the handle  11  of the crutch  1 . Best seen in  FIGS. 6 and 8 , the first hydraulic cylinder piston  65  is filled with hydraulic fluid and the button  61  compresses the hydraulic fluid to actuate the hydraulic valve stem operation mechanism  63 . The cylinder piston  65  is generally fixed in the handle  13  by a locking pin  73  engaging a radial groove  69  or detent in the wall of the cylinder piston  65 . The hydraulic button  61 , cylinder piston  65 , locking pin  73  and a cylinder position follower  75  in the handle assembly play an essential role as a safety mechanism for automatically disengaging the hydraulic valve stem operation mechanism  63  to stop the crutch extension when the crutch  1  reaches a user-defined maximum height.  
         [0044]     The first hydraulic cylinder piston  65  located in the handle body has the radial groove  69  which receives one end of the locking pin  73  as seen in  FIG. 8 . The hydraulic button assembly also has the manually operated external button  61  and a button return spring  71 , both of which will be discussed in greater detail later. Observing  FIGS. 6-11 , the locking pin  73  is also attached to the cam-like cylinder position follower  75  which is rotatably fixed to the inside of the handle  11 . Although the cam follower  75  is shown in  FIG. 6  having passed or fallen, over the top of the gas cylinder, under normal operation the cam follower is in contact with the side of the gas spring cylinder  23 . In this condition with the cam follower  75  in contact with the side of the gas spring cylinder  23  the locking pin  73  is pushed outwards to intersect the button body groove  69 , thus preventing the button assembly from moving along its centerline, regardless of force applied by a user pressing the button  61 .  
         [0045]     During the course of operation, the cam-like cylinder piston follower  75 , which is attached via a pin to the inside of the handle body, will be in contact with the outer wall of the gas spring cylinder  23 . As the crutch  1  is extended and the piston  25  is forced upward, thus also moving the upper crutch tube  3  upward relative to the lower crutch tube  5 , the handle  11  and the associated cam-like cylinder piston  25  rides upwards along the side of the gas cylinder  23 . Once the cam-like cylinder piston  25  reaches the top of the gas cylinder  23 , the follower will fall over the top of the gas cylinder  23 , withdrawing the locking pin from the hydraulic cylinder piston  65  and activating the automatic disengagement system as shown in  FIG. 6 .  
         [0046]     As the cylinder position follower  75  rotates over the top of the gas cylinder  23 , the locking pin  73  is pulled out of the radial groove  69  in the first hydraulic cylinder piston  65 . As a result, the first hydraulic cylinder piston  65 , which has an internal hydraulic spring constant greater than the button return spring  77  constant, is pushed into the hollow handle  11  by the force applied by the user to the external button  61 . As the hydraulic button  61  and the hydraulic cylinder piston  65  are pushed into the handle body, the pressure inside the first hydraulic cylinder piston  65  is released and the piston valve  35  is closed. This prevents any further movement of the piston  25  and thus prevents any further undesired extension of the crutch  1 .  
         [0047]     Should the user want to extend the crutch  1  past its preset maximum height, the user may override the automatic disengagement system by sticking a finger deeper inside the handle body and pressing the external button  61  until the button return spring  77  is fully compressed and the first hydraulic cylinder piston  65  resumes transmitting hydraulic fluid pressure and opening the piston valve  35 . This allows the user to only consciously extend the crutch  1  to a height higher than that imposed by the preset user defined maximum height.  
         [0048]     The handle vertical position adjustment and alignment feature relative to the upper crutch tube  3  is controlled by the manipulation of the wedge component of the handle system, shown in  FIGS. 9A, 9B  and  10 . The wedge  19  has two flexible tabs  90  with an outwardly protruding boss  85  on each arm. Once the wedge  19  is aligned in the appropriate position on the upper crutch tube  3  to accommodate the user&#39;s arm length, these bosses insert into the handle body to maintain the handle  11  in the specific alignment with the wedge  19  when this adjustment is completed.  
         [0049]     To adjust the wedge  19  into the appropriate position, the wedge  19  is provided with an inner wedge thread  87  that engages a corresponding upper crutch tube thread  89 . This permits the user to threadably adjust the wedge  19  along the length of the upper crutch tube  3  to the extent of the crutch  1  tube thread thereon. Additionally, the wedge  19  is provided with a dog  91  that engages at least a vertical slot in the upper crutch tube  3 . The wedge  19  is also segmented by a cut portion to allow the dog  91  to be disengaged out of the vertical slot while the thread features on the remainder of the wedge  19  remain engaged. The dog  91  can re-engage into the vertical slots in the upper crutch tube  3  every 180 degrees of rotation, or wherever the slots are provided around the circumference of the crutch tube, providing for the wedge  19  to be thus rotatably locked from rotation while the engaged threads maintain the vertical alignment of the wedge  19  and the upper crutch tube  3 .  
         [0050]     Once the wedge  19  has been manipulated into a desired position and the dogs and threads maintaining the wedge  19  in a desired position, the handle  11  may then be forced down over the wedge  19  until the wedge bosses align and engage respective receiving holes  93  in the handle  11 . This assembly provides for up/down position and proper orientation of the handle assembly, it also provides positive means against slipping up or down. The wedge shape is used to greatly reduce the loads that would be seen at the thread and wedge bosses if the wedge shape was not used. This reduction in loads at the thread and bosses allows for the wedge  19  to be manufactured out of a lightweight and flexible material such as plastic.  
         [0051]     Another embodiment of the invention shown in  FIGS. 10, 11  may have an additional pawl  95  to back up the cylinder follower system. This will allow for a preset normal height by halting the cylinder  23  if the button is not released before the maximum set height is attained. If additional height is required, the user can override the position by depressing the release button deep  61  into the handle  11  and adjusting the handle  11  accordingly.  
         [0052]     In one embodiment, the gas spring  21  has approximately a 20-30 inch, and more preferably about a 24 inch travel stroke. There is provided between about 60-100 lbs and preferably about 80 lbs pre-load and between about 90-130 lbs, preferably about 110 lb. full compression force requirement. On return, at full compression, about 100 lbs. are delivered, and about 70 lb. at full extension. The body diameter is approximately 22 mm, and the telescoping shaft diameter is about 10 mm. The overall length of the crutch  1  is approximately 52 inches. In general a gas spring of this or similar construction can accommodate a user with the approximately 24 inch travel stroke where the user is in a range of between about 6 foot 2 inch, and 5 feet 5 inches. It is to be appreciated that other lengths of crutches would permit persons of any size to utilize the full stroke as well.  
         [0053]     Since certain changes may be made in the above described improved, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.

Technology Classification (CPC): 0