Abstract:
The ski pole has normal strength when the pole is normally gripped at its handle and reduced strength when not gripped. The poles permanently deform when a predetermined level of excessive bending force is applied. The pole shaft is hollow with a short circumferential segment having reduced cross-section. When the handle is gripped, a plug slideable within the shaft spans the reduced cross-section and reinforces the pole at that region. When the handle is not gripped, the plug slides away from the reduced wall segment and reduces pole strength. A button on the handle connects to the plug by a rod, cable, hydraulics, pneumatics, etc. Alternatively, button actuation electrically drives a magnetic solenoid to move the plug. The weakened portion is replaceable so the pole is reusable.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to ski poles of the type used in downhill and cross-country skiing by both amateurs and skilled athletes, and more particularly to a ski pole having features intended to reduce the hazards of injury to the thumbs of the skier. Gamekeeper fracture of the thumb and Stener lesion are the second most common trauma of skiers. The ulnar collateral ligament is torn and the ends distracted allowing an aponeurosis to interpose itself between the torn ends of the ulnar collateral ligaments. This interposition prevents the normal healing of the ulnar collateral ligament and causes long term disability with disorders of pinch and grip. The damage occurs upon high impact collision between the ski pole and the thumb where the skier normally grips the pole. The damage occurs most frequently during falls or loss of balance events, when the ski pole is loosely held and is suddenly accelerated relative to the hand that holds it. Extension of the thumb occurs when there is loss of grip on the ski pole. 
     The Stener lesion is believed to be avoidable if the pole is firmly gripped by the skier&#39;s hand when the fall or loss of balance occurs, and/or if the direction of the kinetic energy can be directed along a vector that is different from that which causes hyperabduction of the thumb. An important condition in the development of a situation that leads to such a hand injury is that the ski pole has become fixed at its pointed tip, either in the snow, under the ski blades, or in any other obstacle that may present itself on the skier&#39;s path. While losing his balance and falling, the skier generally loses the tight grip on the pole handle, which is normal during skiing and thus creates the conditions for violent hyperabduction of the thumb. 
     The problem was recognized and a solution proposed in U.S. Pat. No. 4,229,016 to Wolf. Therein a mechanism allows the handle to pivot relative to the extended shaft of the ski pole when a certain force is applied to the handle relative to the pole shaft. The forces required to cause the handle to pivot may be pre-selected such that the handle hopefully pivots before the thumb is injured. The handle may later be restored to its longitudinal position and the pole is again in condition for use. 
     Three patents to Bujold, U.S. Pat. Nos. 6,070,907; 6,082,767; and 6,203,063, disclose a ski or hiking pole having an articulated handle. The handle pivots relative to the shaft under high bending stress. An internal spring mechanism restores the pole to its normal configuration when the stress is no longer present. 
     Fuji, U.S. Pat. No. 4,597,589, provides a handle that is pivotable to a right angle with the shaft so that a skier may push off with a greater force at the start of a downhill run. The handle pivots when the user presses a button on the handle and a spring returns the handle to its normal position when the button is released. 
     Kepple, U.S. Pat. No. 4,332,399, provides a ski pole with a shaft in two portions. The upper portion is connected to the lower portion by a coil spring that bends only under high bending forces. The handle may also be spring-connected to the top of the shaft. 
     Kepka, U.S. Pat. No. 3,797,845, provides an extended history of ski poles designed to lessen the dangers of injury. His particular construction provides a shaft in two portions that telescope on each other when axial force on either end exceeds a preselected value. The pointed tip can also telescope. The primary concern is with skier impalement by the pole, and bending and thumb injuries are not considered. In all embodiments, the pole returns to its original condition when axial forces are removed. 
     In spite of prior recognition of the problem, thumb injuries, as stated, remain as the second most common skier injury. It is suspected that many thumb injuries go unreported although the consequences can be serious and at times permanent. 
     Mechanisms proposed for incorporation in ski poles in the earlier patents were complex and presumably costly to produce. Applicant is unaware of any commercially available ski pole that incorporates safety features to protect against thumb injury. What is needed is a protective ski pole that reduces the likelihood of thumb injury in those situations as described above where the skier momentarily loosens his grip on the ski handle while the tip of the ski pole is fixedly engaged in the snow or in some unexpected obstacle. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the invention, a ski pole less likely to cause thumb injuries to a skier is provided. The ski pole has normal strength when the pole is normally gripped at its handle and has reduced strength, is weakened, when the handle is not gripped. It should be understood that the pole is not so weak as to impair its utility when the handles are not gripped. A skier skis normally and does not have to continuously squeeze the pole handles to prevent failure of the poles. The poles are intended to break or permanently bend when a pre-determined level of excessive force is applied, as may happen in the emergency situations described above. 
     The poles are provided with a weakened section along their length. Desirably, the pole will fail in bending at the weakened section in an emergency situation prior to injury of the thumb. Reinforcement is provided for the weakened section whenever the pole handle is conventionally gripped by the person, but there is no reinforcement when the grip is released. Thus the ski pole has available two levels of bending strength and the skier selects the operating level either by intent or instinct in an emergency by his/her grip on the ski pole handle. 
     In a preferred embodiment, the pole shaft is a hollow tube with a short circumferential segment of the tube wall having a reduced cross-section. When the handle is gripped, a piston or plug slidable within the tube is aligned to span the reduced cross-section and reinforce the pole at that region. When the handle is not gripped, the piston slides away from the reduced wall segment and reduces the strength of the pole. A button on the handle connects to the sliding piston by a rod, cable, hydraulics, pneumatics, etc. Alternatively, actuation of the button may initiate an electrical sequence that actuates a magnetic solenoid to move the reinforcing piston. The weakened portion of the pole may be a replaceable section so the pole is reusable, and a particular pole may be calibrated to fail in bending at a pre-selected force. 
     Accordingly, it is an object of the invention to provide an improved protective ski pole that is strong when in normal use and becomes weaker in bending in an emergency situation wherein the skier releases his tight grip on the pole handle. 
     A further object of the invention is to provide an improved protective ski pole that is simple in construction and has two states, a stronger state and a weaker state. 
     It is a further object of the invention to provide an improved protective ski pole that is maintained with readily replaceable parts so that it may quickly be returned to use after occurrence of an emergency event. 
     Still other objects and advantages of the invention will be apparent from the specification. The invention accordingly comprises the features of construction, combination of elements, an arrangement of parts, which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a conventional ski pole; 
     FIG. 2 is a segment in partial cross-section of an embodiment of a ski pole in accordance with the invention; 
     FIGS. 3 a-c  are variations of mechanical actuation components in accordance with the invention; 
     FIG. 4 is a segment in partial cross-section of an alternative embodiment of a ski pole in accordance with the invention; 
     FIGS. 5 a  and  b  are construction details of the embodiment FIG.  4 . 
     FIG. 6 is a segment in partial cross-section of another alternative embodiment of a ski pole in accordance with the invention; and 
     FIG. 7 is an electrical schematic associated with the ski pole of FIG.  6 . 
    
    
     The Figures are not drawn to any scale. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a conventional ski pole  10  includes a shaft  12  of extended length  14  connected to a handle  16  at one end of the shaft and to a tip assembly  18  at the other end of the shaft  12 . The tip assembly has a pointed tip  20  longitudinally aligned to the shaft axis  100  and a transverse web  22 , as is well known in the construction of ski poles. The tip assembly is used, for example, to limit penetration of the shaft into the snow during skiing, for example when turning, and the handle  16  is gripped by the skier when performing on skis. When the tip assembly  18  becomes fixed in place for reasons described in the Background of the Invention above, forces on the handle  16  and along the shaft length  14  tend to put the shaft in bending stress as in a cantilever beam. When a transverse force as indicated by the arrow  24  is applied to the handle  16 , the bending stresses within the shaft  12  increase and are maximum at the fixed end of the shaft where it joins the tip assembly  18 . Thus, as the force at  24  is increased, it would be expected that a shaft  12  of uniform cross-section along its length would fail at the fixed base proximate the web  22 . 
     Along the length of ski pole  26  (FIG. 2) in accordance with the invention, the shaft  28  has a safety element  30  generally of a diameter similar to that of the adjacent shaft portions. The safety element  30  has a narrowed cross-section  32 . A nipple  34  threads into the lower end  36  and a similar nipple  35  with a through opening  38  threads into the upper end  40  of the safety element  30 . Thus, a hollow space  42  is provided within the safety element  30 . In the hollow space, a strong cylindrical plug  44 , e.g. steel, is slidable between the nipples  34 ,  35 , with a close fit against the internal wall  46  of the hollow space  42 . A return spring  48  between the plug  44  and lower nipple  34 , biases the plug  44  toward the nipple  35 . A vent hole  50  through the wall of the safety element  30  ensures ambient pressure in the hollow space  42  regardless of the position of the plug  44 . Alternatively, an opening (not shown) is provided longitudinally through the nipple  34  and a vent passage is provided in the shaft  28  at a location below the safety element  30 . 
     The handle  52  has an upper end with a socket  54  sunk therein. A push button  56  sits in the socket  54 . The push button  56  and socket  54  have corresponding cross-sectional contours to provide a sliding fit. A rod  58  of rigid material, for example, steel, connects between the push button  56  and the plug  44  by way of a hollow space  60  in the shaft  28  and handle  52  and passing through the opening  38  in the upper nipple  35 . 
     In use of the ski pole, the gloved skier tightly grips the handle  52  and depresses the button  56 , for example, with his thumb, such that the plug  44  is driven down (FIG. 2) by the rod  58  from its illustrated first position to a second position where the plug straddles the portion  32  of narrowed cross-section in the safety element  30 . Thus, the plug  44  reinforces the narrowed cross-section  32  while the skier depresses the button  56 . The coil spring  48  is compressed between the plug and the nipple  34  in the process. 
     In an emergency situation as described above, where the tip assembly of the ski pole  26  becomes undesirably fixed in place causing the skier to begin a fall, it is instinctive that the skier will release his tight grip on the handle  52  and button  56 . The skier may also release the button by intent in such a situation if he has the presence of mind. When the button  56  is released, whether or not the skier is still gripping the body of the handle  52 , the spring  48  expands and returns the plug to the first position, illustrated in FIG.  2 . Thereby the narrowed cross-section  32  is no longer reinforced, and the pole  26  is in a relatively weakened state, subject to failure more readily than when the button  56  is depressed. 
     The ski pole  26  and the safety element  30  may be made of metal or plastic or of a reinforced composition of plastic and, for example, fibers. A good sliding fit with low friction is provided between the plug  44  and the inner wall  46  as a result of the finish on the mating surfaces. Alternatively, the surfaces may be lubricated, or the plug may be coated with or fabricated from a self-lubricating material. The plug  44  may have a truncated, conical lower end to assure positive contact within the coils of the spring  48 . 
     In every embodiment of the invention, whether or not particularly disclosed herein, weakening the cross-section need not be provided by the necked-in portion  32  but may be produced instead by notches or grooves (not shown) circumferentially encircling the safety element  30  and recessed into the wall thereof. In place of the reduced cross-section  32 , the wall of the safety element  30  may be pierced radially by a series of holes (not shown) spaced circumferentially around the element. If the element  30  is fabricated from plastic or a reinforced composite, etc., a section may be weakened by a change in the plastic composition in that region or by a reduction of, for example, reinforcing fibers in a plastic matrix at that region. 
     In all of the variations, an inventive concept lies in a portion of the ski pole where there is a weakened segment that can be reinforced in normal use of the ski pole and that is weakened when the ski pole handle is not tightly gripped. 
     The safety element  30  may be disengaged in its entirety from the ski pole by unthreading it from the nipples  34 ,  35  and may be replaced by a new element  30  after an event that damages the present emergency element  30 . Or the element  30  may be replaced with another safety element that has a different degree of weakening in order to produce a protective response at another level of bending stress. Preferably, in removing a safety element  30  from a ski pole, the nipples  34 ,  35  are removed at the same time and the replacement unit includes new nipples  34 ,  35  such that possible contamination of the inner surfaces of the replacement safety element  30  is avoided. Flats (flat surfaces) may be provided on the outside of the safety element  30  near the ends  36 ,  40 , on the outer surfaces of the nipples  34 ,  35 , and on the outer surfaces of the adjacent portions of the ski pole  26  so that tight connections may readily be made using a simple wrench or pliers. 
     Although a rigid rod  58  was illustrated in FIG. 2 as the mechanical transmission element between the button  56  at the handle  52  and the plug  44  in the safety element  30 , other connections may be used. For example, a flexible control cable  62  whether twisted or woven, etc., may be used (FIG. 3 a ). A column of rigid balls  64  (FIG. 3 b ) may be used to fill the space  60  between the button  56  and the plug  44 . The force applied to depress the button  56  is transmitted through the contacting balls to move the plug. 
     In another variation, articulated links  66  (FIG. 3 c ), hinged with pins  67 , extend between the button  56  and the plug  44 . In each variation, pressing on the push button  56  causes the plug  44  to move to span the weakened region  32  (or its equivalent as discussed above). When pressure is no longer applied to the button  56 , the return spring  48  restores the original positions of the actuation mechanism and the pole reverts to its weakened state. The linkages of FIGS. 3 a-c  are attractive when the ski pole has some curvature to it. These mechanisms operate effectively around curves although excessive slack in these mechanisms that might allow kinking is to be avoided. 
     The actuation mechanism may be simplified by locating the safety element  30  close to the handle  52 . However, stresses induced by bending when the ski tip is fixed by an obstacle, are greatest near the ski tip. Thus, location of the safety element  30  along the length  14  of the shaft  28  is only determinable when the shaft materials, diameter, shaft length, etc., are known. Then, safety elements  30  may be produced having a range of forces that will result in mechanical failure of the ski pole at the safety element  30 . 
     In alternative embodiments of a completely mechanical construction as shown in FIGS. 2 and 3 a-c , variations may be provided. For example, a lock (not shown) may be provided so that the button  56  is maintained in the selected out or in position permanently or until released by the user. A retaining cap may be provided so that the push button  56  is never separated (as illustrated in FIG. 4 for another embodiment hereinafter) from the handle. The rod  58  need not be of rigid material but may be flexible and resilient so long as it is stiff enough to transmit the desired forces from the push button  56  to the plug  44 , for example, hard rubber. 
     In another embodiment of a ski pole according to the invention (FIGS. 4,  5   a,b ), the mechanical actuation mechanism of FIG. 2 is replaced by a fluid linkage. The button  70  on the handle  72  is connected to a piston  74  that slides within the handle  72  with a sealed fit that is effected by “O” rings  76  that fit within grooves  78  provided on the piston  74 . The plug  80  is also a piston sealed to the inner walls of the ski pole shaft by means of “O” rings  76 ′ and grooves  78 ′. The otherwise hollow space within the shaft and handle between the piston  74  and plug  80  is filled with fluid  82 . The nipple  35  provides leak tight connections. 
     When the fluid  82  is incompressible, for example, an automotive coolant for below freezing temperature operation, depressing the button  70  causes the piston  80  to move down (FIG. 4) while compressing the spring  84 , as described in relation to FIG.  2 . The spring  84  operates in a vented space  86  having the opening  50 . The distance that the piston  74  travels relative to the distance that the plug  80  travels depends inversely upon the diameters of the two pistons. 
     When the fluid  82  is a gas, for example, air, the operating results are substantially the same except that the response to actuation of the button  70  may be slightly delayed and spongy due to compression of the gas. 
     To assure a good seal for the pistons and to prevent damage to the “O” rings, the inside wall surface and any contact between the walls and pistons (“O” rings) must have smooth surfaces and lubrication may be desirable. Where a good sliding fit is provided by including lubricant or surface coatings as necessary, it is possible to eliminate the “O” rings  76  and grooves  78  on one or both pistons. A fluid refill port (not shown) may be provided to allow addition and removal of fluid  82  between the pistons. 
     A flange  88  on the button  70  rests against the shoulder  90  in the handle  72  when the button is fully depressed thereby limiting travel of the button in driving the piston  74 . A cap  92  with a central opening  94  is threaded to the handle  72 . The periphery  96  of the opening  94  also engages the flange  88  to prevent inadvertent escape of the button  70  and piston  74  from the handle  72 . Thus, travel of the button  70  is limited between the shoulder  90  and periphery  96  of the central opening  94 . A return spring (not shown) may be used between the flange  88  and the shoulder  90  to facilitate release of the button and change in the operating state of the ski pole  68 . 
     FIG. 6 illustrates a ski pole  110  in accordance with the invention, which operates electrically/electronically to provide the two safety states of the device. Similar to the embodiments described above, the narrowed section  112  is straddled by the plug  116  and reinforced thereby from within the shaft  114  during normal skiing conditions. In an emergency where the skier releases his grip on the handle  118 , the plug is moved and the ski shaft is no longer reinforced at section  112 . In the present construction, the plug  116  connects to the plunger  120  of the linear actuator/electrical solenoid  122 . 
     When the button  124  on the handle  118  is depressed by the skier, a switch  126  is closed and a circuit between a battery pack  128  and the handle  118  is completed through conductors  130  to the linear actuator  122 . Motion of the button  124  is limited in both directions by a flange  132  on the button  124  and a cap  134  with a construction similar to that described above and shown in FIGS. 4 and 5 a, b.    
     FIG. 7 illustrates schematically the linear actuator  122  and plunger  120  connected by leads  130  to the battery pack  128 , with the skiing switch  126  in position to make and break a complete circuit. Additionally, an on/off switch  136  is in circuit so that the battery  128  is not inadvertently drained when the skis are not in use or are in storage. The batteries  128  would be a rechargeable type preferably, and contacts for recharging the battery  128  while it is in the handle  118  may be provided. When on the slopes, a skier would place the switch  136  in the On position. A LED  140 , placed in parallel with the battery  128 , lights up to indicate the strength of the battery when the user presses the button  142 . A safety LED  148 , placed in parallel with the input to the linear actuator  122 , provides an indication when voltage is actually On at the linear actuator  122 . 
     A time delay circuit (not shown) may operate between the battery  128  and linear actuator  122  so that response of the plunger  120  is not instantaneous, and every momentary nervous actuation of the button  124  by the skier does not result in operation of the linear actuator  122 . Such a circuit may be beneficial in reducing unnecessary drain on the battery, and the time between recharging and replacing the battery may be extended. 
     In alternative embodiments in accordance with the invention, the hard-wired construction of FIGS. 6 and 7 may be replaced with more sophisticated signal transmission systems. For example, actuation of the button  124  by the skier may produce an optical, acoustic, or radio frequency signal at the handle  118 . The signal travels through the hollow space of the ski pole  114  and is detected by an appropriate sensor connected to circuitry that energizes the linear actuator  122 . Such techniques are now used frequently, for example, in the home in television remote controls, appliance remote controls, controls for automatic garage doors, etc., and implementation would present no obstacle to those skilled in the electronic arts. 
     Further, it should be understood that the battery pack  128  may be external to the ski pole shaft and handle and may also be located in the gloves of the skier with provision of proper electrical connection to the linear actuator. 
     In alternative embodiments, the nipples  34 ,  35  used as connections to provide a replaceable safety element, may be replaced by bayonet type connectors conventionally used in electronic devices. Thus, a simple twisting action can provide a strong and releasable connection. 
     Although all of the above described embodiments include a button on the handle that is pressed by the skier in order to change the operating state of the ski pole, it should be understood that actuation of the safety feature in the ski pole is not limited to a push button. For example, a lever type triggering mechanism may be used for operating with a handle in a manner similar to that found on handlebar brakes of a bicycle. The skier would squeeze the brake handle relative to the ski pole handle to provide actuation. Release of the safety handle would place the ski pole in its weaker condition. 
     In the embodiments relying entirely on mechanical mechanisms (FIGS. 2,  3   a-c ), the plug  44  may be eliminated and the column of balls  64  and articulated links  66  in respective embodiments may extend to span the reduced cross-section  32  continuously during operation. When the button  56  is not depressed, the balls  64  or links  66  easily move relative to each other and provide little resistance to bending of the pole. However, when the button  56  is depressed, the balls  64  and the links  66  become rigidized reinforcing columns in compression (when the lower end of the chain of balls or links is fixed by an internal stop) within the ski pole shaft  30 . 
     Similarly, a column of balls (not shown) that are on a flexible cable that threads through a hole in each ball (like pop-it beads), can be placed in compression by putting tension on the cable. This rigidizes the string of pop-it-like balls. 
     When the balls and links provide a close fit within the ski pole shaft, they provide reinforcement for the ski pole wall when the balls or links are in compression to form a rigidized element. 
     In other embodiments of the invention the weaker portion may be reinforced by actuation of the handle trigger mechanism to internally pressurize the weakened portion. The piston construction of FIG. 4 when depressed, may pressurize the pole interior when the hollow space is leak tight. Alternatively a balloon located at the weakened portion of the shaft may be inflated when the handle button is depressed to provide only a local reinforcement. 
     In each of the above embodiments, a relaxed grip at the handle provides the weakened state of the pole. It should be readily understood that this type of operation can be reversed such that a relaxed grip provides a stronger condition of the pole. This reversed operation can be accomplished in further alternative embodiments (not shown) that position the reinforcement at the weakened section of the pole when the normal grip at the handle is relaxed. For example, such a construction may be used in a fishing pole where the person desires a more flexible pole when firmly gripping the handle and casting his line. Then, a more rigid pole can be provided when reeling in the catch. 
     As stated above in all embodiments, a pole is provided that operates in one of two available states, namely the weaker or stronger state. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.