Abstract:
A walking stick with a flexure spring to store energy from compression during the user&#39;s step, and release of the energy to aid in propelling the user forward, thereby reducing fatigue and enabling longer and faster walks.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application, excluding claims  10  and  20 , claims the benefit of U.S. Provisional Application No. 60/477,913 filed Jun. 13, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates in general to walking aid sticks and, more specifically, to a walking stick with a built in flexure spring to return energy into each step to help propel the user forward.  
         BACKGROUND OF THE INVENTION  
         [0003]    Walkers and climbers can benefit from walking sticks that have the feature of returning kinetic energy that is acquired as the walking stick compresses in contact with the ground. This retained energy has the benefit that the users have to expend less of their own energy moving their legs forward, thus allowing them to walk or climb further and faster more comfortably and with less fatigue. Experiencing this advantage, the user will increase their interest in the activity and become a more active person.  
           [0004]    The use of a walking stick with an energy storage spring for returning energy to the walker is well known to those familiar with the art. An example is the use of energy storage springs in foot prosthesis; particularly those used for athletic purposes. Designs include that of U.S. Pat. No. 6,007,582 or that in use in the Flex-foot®, manufactured by Ossur hf of Reykjavik, Iceland. Examples where a spring mechanism stores and then sequentially dissipates energy for the sole purpose of cushioning a walking stick are described in U.S. Pat. No. 6,131,592, U.S. Pat. No. 5,720,474, and FR2617023. These walking sticks utilize a mechanical device such as a coil spring or cylinder for a spring and do not make use of the compression of a flexure to return the energy from the material compressing as a step is taken.  
           [0005]    A published paper entitled “The design of a compliant composite crutch” by D. Shortell et al. discloses two designs of crutches using composite materials. The first design utilizes a metal coil spring embedded in a single unit composite material crutch. The coil spring compresses under the weight of the user with a spring force in the range of 90 to 170 lbs. The spring force, which acts in the vertical direction, is for shock absorption, not as a forward propelling aid. A second crutch design utilizes the flexure of the S curve in the shaft of the crutch in place of the coil spring. The effective springs that are designed using the composite material in place of the coil spring also operate in the vertical direction for shock absorption, not as a forward propelling aid. Another feature of the crutches that are the subject of the Shortell et al. publication is a rigid armrest with a grip. These armrests are oriented in the vertical direction for the purpose of providing the user with more support.  
         SUMMARY OF THE INVENTION  
         [0006]    In light of the above, the object of the present invention is to provide a walking stick that absorbs energy in the downward first motion of a walking stride and then returns the stored energy to aid in propelling the walker forward in the final forward motion of the walking stride.  
           [0007]    The walking stick that is the subject of this patent application utilizes a flexure spring as an extension of the straight shaft of the stick. The shape and location of the flexure spring are such that the spring force helps propel the walker forward. The spring constant of the flexure spring is in the range of 5 to 50 lbs. per inch of deflection. In the preferred embodiment the flexure spring is fabricated using composite materials.  
           [0008]    The walking stick of the present invention may be used in a wide number of applications. Examples include a walking and climbing stick for hikers, an ambulatory aid for a person recovering from surgery or otherwise limited in ability to walk, a substitute for a ski pole for cross country skiing, a pole for use in roller blading, a hiking stick that will also function as a canoe paddle, or a walking stick for snow shoeing. It may be a molded single unit or assembled out of multiple components. As a molded single unit the flexure spring is integral to the molded stick. As a stick built of multiple components, the flexure spring is attached to the straight shaft of the stick and may be interchangable depending upon the size and weight of the user, or depending on one of the specific uses listed above.  
           [0009]    The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in some of which the relative relationships of the various components are illustrated, it being understood that orientation of the apparatus may be modified. For clarity of understanding of the drawings, relative proportions depicted or indicated of the various elements of which disclosed members are comprised may not be representative of the actual proportions, and some of the dimensions may be selectively exaggerated.  
         [0011]    [0011]FIG. 1 illustrates a single-piece walking stick.  
         [0012]    [0012]FIG. 2 illustrates a multi-piece walking stick.  
         [0013]    [0013]FIG. 3 illustrates a multi-piece walking stick with adjustable length.  
         [0014]    [0014]FIG. 4 illustrates a walking stick with a horizontal arm support.  
         [0015]    [0015]FIG. 5 is plot of force versus deflection for two embodiments of walking sticks of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring to FIG. 1, therein is shown a preferred embodiment of the invention. This walking stick, generally designated by numeral  10 , is molded as a single unit of fiberglass, carbon, or other composite material. Walking stick  10  includes a straight shaft  28  terminated at the upper end with a handgrip  14  and at the lower end with a flexure spring  16 . Walking stick  10  may be constructed of laminated linear fiberglass or other composite material. In a preferred embodiment walking stick  10  is constructed of a fiberglass tape such as that manufactured by the Fibreglast Development Corp. of Brookville, Ohio, USA. Attached to flexure spring  16 , at the point where flexure spring  16  would contact the walking surface, is a foot  24 . The purpose of foot  24  is to prevent flexure spring  16  from sliding on the walking surface. Foot  24  may be made from rubber, such as, for example, a section of rubber tubing, or any other material with a suitable coefficient of friction with the walking surface.  
         [0017]    Another embodiment of the walking stick of the present invention is shown in FIG. 2 and designated generally as numeral  30 . Walking stick  30  in FIG. 2 includes similar sections as walking stick  10  in FIG. 1, that is, a straight shaft  26 , a handgrip  15 , and a flexure spring  18 , but the sections of walking stick  30  are separate assembled parts instead of molded as a single unit. In the walking stick  30  embodiment flexure spring  18  is constructed of laminated linear fiberglass or other composite material. Straight shaft  26  may also be constructed of laminated linear fiberglass or other composite material or of any other rigid material such as, for example, aluminum, steel, stainless steel, or the like. Handgrip  15  is constructed of hard rubber, wood, or any other similar material. Flexure spring  18  and handgrip  15  are connected to opposite ends of straight shaft  26  by pins  19  and  17  respectively. Flexure spring  18  of the walking stick  30  embodiment also has attached to it a foot  24 , the same as in the walking stick  10  embodiment.  
         [0018]    For some sports applications an adjustable length walking stick is preferred. Referring to FIG. 3, therein is shown a design of an adjustable length walking stick  40 . The walking stick  40  embodiment has the same flexure spring  18  with pin  19 , and handgrip  15  with pin  17  as the walking stick  30  embodiment of FIG. 2. The straight shaft of the walking stick  40  embodiment includes two telescoping sections  25  and  27 . Several means for locking the adjusted length of sections  25  and  27  are known in the art, one of which is shown in FIG. 3. Section  25  contains a spring-loaded pin  32  that is pushed into one of a series of holes  34  in section  26  to secure the desired length of walking stick  40 . Other adjustable means can be used such as the mechanism cited in U.S. Pat. No. 5,769,104.  
         [0019]    [0019]FIG. 4 shows another embodiment of the walking stick of the present invention generally designated by numeral  50 . Walking stick  50  embodiment is distinguished by an arm support section  52  at an approximate 90° angle to the vertical straight shaft  28 . Arm support section  52  has a semi-cylindrical arm support  54  and a handgrip  56 . AA is a cross-section view of semi-cylindrical arm support  54 . Straight vertical shaft  28  and flexure spring  16  with foot  24  in the walking stick  50  embodiment are the same is in the walking stick embodiment  10  of FIG. 1. Arm support section  52 , with semi-cylindrical arm support  54 , of the walking stick  50  embodiment is positioned in the horizontal direction, in line with the natural arm and hand posture used when walking or hiking and helps reduce arm fatigue on long hikes and especially climbing. Arm support section  52  with semi-cylindrical arm support  54  and handgrip  56  may also replace handgrip  15  of the walking stick embodiments of FIGS. 2 and 3, and be molded from plastic. To provide protection for the walker&#39;s hands, handgrip  56  of the walking stick  50  embodiment may also be surrounded by a molded hand guard.  
         [0020]    [0020]FIG. 5 illustrates, for two preferred embodiments of the walking stick of the present invention, the amount of spring force as a function of the amount of deflection of the flexure spring. Curve  50  represents the result for a preferred embodiment walking stick for a person weighing in the range of 175 to 225 lbs. Curve  52  represents the characteristics of a preferred embodiment hiking stick for a person weighing in the range of approximately 100 lbs. Curve  50  indicates that a deflection of 1 inch produces a spring force of 19 lbs. Similarly curve  52  indicates that a deflection of 1 inch produces a spring force of 10 to 11 lbs. These curves show that with a deflection greater than 4 inches, the relationship between deflection and force increases nonlinearly so that when the walking stick is heavily compressed, large spring forces result. When the transition to a higher spring force is reached, it is a signal to the athlete to push off or, in other words, to transfer his/her weight to the other stick.  
         [0021]    The multi-part embodiments of the walking stick of the present invention, as illustrated in FIGS. 2 and 3, enable the use of interchangable flexure springs with different spring force constants for different weight users, or with different shaped feet for use on different surfaces. For example, the foot shown in FIGS.  14  may be optimum for use on hard packed or paved surfaces, whereas a flared, higher surface area foot may be better for use in snow or mud. An extremely flared foot with very high surface area may serve double duty as a walking stick and as a canoe paddle.  
         [0022]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.