RELEASE BINDING FOR TELEMARK AND
CROSS-COUNTRY SKIS
TECHNICAL FIELD
The present invention relates generally to the field of ski bindings, and more particularly to a release binding for telemark and cross-country skis.
BACKGROUND ART
10
A downhill ski binding for holding a boot to the ski has releases at both the toe and heel which release the boot from the ski when predetermined forces have been reached. The toe binding releases when the fall or force is to the side. The heel binding releases when the fall or force is toward the 15 front. The toe and heel bindings are at a fixed distance from each other and operate with a stiff downhill boot having a rigid sole. The stiff boot rigidly attached to the ski provides the control necessary for the skier to manipulate the ski. But the rigid attachment between the boot and the ski can cause 20 trouble during a fall when forces are magnified by the leverage of the long ski. And, the chances for the skier getting into trouble are enhanced in downhill skiing by the fast speeds, which increase the forces encountered in falls, and crowded slopes where the skier is surrounded by skiers 25 and snowboarders of varying skill levels, which increase the likelihood of collisions and need for sudden evasive action to avoid collisions. Release bindings are therefore essential to protect the legs of the skier.
In contrast, cross-country skiing is more gentle because 30 the speeds are usually slower, the terrain is usually gently sloping, and there are fewer other skiers in the vicinity. The cross-country boot is not rigidly attached to the ski. It is only attached at the toe allowing the heel to rise off the ski as the skier strides along. The boot is flexible and usually has a sole 35 with three holes across the toe which couple to three pins on the ski. This arrangement is flexible and provides some protection for the skier during a fall. Instead of the ski being rigidly attached to the boot as on a downhill ski, the heel of the boot can move away from the ski during a fall thereby 40 substantially lessening the chances for injury to the leg.
A similar arrangement is found on a telemark ski which is similar to a cross-country ski but is also useful on downhill slopes. The telemark ski is shorter for a given skier than a cross-country ski making it easier to turn. Because the skier requires a given surface area to support his weight, the telemark ski is slightly wider than the cross-country ski to compensate for the decrease in length. The binding and boot arrangement of the telemark ski are similar to the crosscountry ski with the three pin system being common.
Even though cross-country and telemark skis may be considered safer than downhill skis, injuries still occur. The increasing use of plastic boots instead of leather boots has helped reduce the injury rate somewhat. Some releasable 55 bindings have become available but they are not widely used. An improved releasable binding for cross-country and telemark skiers would therefore be of value.
A release ski binding for downhill and cross-country skis is shown in U.S. Pat. No. 3,877,712 utilizing torsion bars on go each side of the boot to control levers engaging the heel of the boot. The entire ski binding assembly rotates up around the toe when the skier desires to raise the heel for crosscountry use.
U.S. Pat. No. 4,348,036 shows a safety binding for nordic 65 skis which features a cylindrical structure mounted across the front of a boot having cupped rotation surfaces at each
end. A releasable binding is mounted on the ski having two arms each with a ball member on the end facing the cupped rotation surfaces on the ski. The boot rotates up and down around its toe on the ball members. When unusual forces are encountered, a spring which holds the arms in place allows them to spread apart thereby releasing the ball members from the ends of the cylinder on the boot.
A similar arrangement is seen in U.S. Pat. No. 4,621,828 which shows a safety binding for nordic skis. Instead of moving arms, a rigid bracket is mounted on the ski having the cupped rotation members. A cylinder mounted transverse to the toe of the boot has a spring which pushes out two ball ends into the cupped rotation members. As in U.S. Pat. No. 4,348,036, the boot rotates up and down around its toe on the ball members. When unusual forces are encountered, the ball ends push in against the spring releasing the boot from the ski.
U.S. Pat. No. 5,518,264 discloses a free heel/anterior release binding utilizing a cable. A rocker means at the heel of the boot rotates under sufficient stress to cause the effective lengthening of the cable relative to the length of the boot allowing the boot to slip free.
The most widely used telemark release bindings commercially available are the CRB 3-pin cable and the CRB classic cable models available from Voile of Salt Lake City, Utah. Both feature a release plate on which either the 3-pin cable or classic cable mounts are attached. The boot is secured in either of these arrangements around the heel by a cable. The mount and release plate remain with the boot. The rear of the release plate features a semicircular indentation which abuts a semicircular friction pad that is permanently attached to the ski. The front of the release plate has a shallow ball type socket perpendicular to the bottom of the release plate and facing toward the front of the ski. Mounted on the ski in front of the ball type socket is a spring in a barrel having a ball end facing the ball socket. The skier engages the ski by placing the rear of the release plate against the friction pad on the ski and then pushing the toe down against the barrel forcing the ball end into the barrel until the ball end engages the ball type socket. When unusual backward forces are encountered, the release plate pushes the ball end against the spring releasing the binding. Unusual forward forces do not insure release in this release mechanism because the release plate remains engaged with the semicircular friction pad.
DISCLOSURE OF INVENTION
The present invention is directed to an improved release binding for telemark and cross-country skis. Instead of fastening the toe plate directly to the ski, a release plate is positioned between a toe plate and the ski. Inside the release plate is a planar load spring having two sides forming an elongated central aperture which is accessible through a top hole. A load spool having a circumferential groove is attached to the bottom of the toe plate. To install the toe plate on the ski, the skier positions the load spool in the hole in the release plate and pushes down with his weight to engage the groove of the load spool in the spring. The resulting release binding thereby securely holds the toe plate to the ski during normal skiing conditions while adding very little weight or height to the position of the boot above the ski.
If the skier falls down or otherwise subjects the release binding to unusual conditions, the load spool is pulled up against the resilience of the load spring. If the force is not sufficient to entirely displace the groove in the load spool from the spring, the resilience of the spring returns the toe plate to a secure position on the ski. If, however, the force
pulls the load spool entirely out of the load spring, the skier is released from the ski thereby avoiding injury.
In accordance with a preferred embodiment of the invention, an adapter plate is provided for adapting unmodified toe plates for use with the release plate. 5
In accordance with an important aspect of the invention, a pilot surface is provided on the load spool which has increasing diameters as the groove is approached for pushing the sides of the load spring apart as the load spool is inserted in the spring. 10
In accordance with a preferred embodiment of the invention, three conical guides nest in three coaxial countersinks to provide a means for orienting the toe plate on the ski. The conical guides provide a camming action aiding in the release of the load spool from the load spring during a fall.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying 2o drawings, which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an exploded top front left side perspective view 25 of a release binding in accordance with the present invention above a central portion of a ski;
FIG. 2 is bottom plan view of the release plate;
FIG. 3 is a sectional view of the release binding of FIG. 3Q 1 assembled on the ski substantially along line 3—3 of FIG. 2;
FIG. 4 is an exploded top front left side perspective view of a second embodiment having an adapter plate;
FIG. 5 is a sectional view similar to FIG. 3 of the release 35 binding and adapter plate of FIG. 4 assembled on the ski;
FIG. 6 is an exploded top front left side perspective view of a third embodiment having the conical guides riveted to the toe plate;
FIG. 7 is a sectional view similar to FIGS. 3 and 5 of the release binding of FIG. 6 assembled on the ski; and,
FIG. 8 is a sectional view similar to FIG. 7 showing a variation of the toe plate.
MODES FOR CARRYING OUT THE INVENTION
Referring initially to FIG. 1, there is illustrated an exploded top front left side perspective view of a release binding in accordance with the present invention, generally 50 designated as 20, above a central portion of a cross-country or telemark ski 22. Toe plate 24 has a standard three pin telemark mount for use with a boot having three pin holes in its toe. After the toe of the boot is inserted on the three pins 26, clamp 28 is rotated down around rivets 30 against the 55 flange of the toe of the boot until tongue 32 engages catch 34 which is mounted on axle 36 thereby securing the boot on the toe plate 24 in a manner well known in the art. Prior to the present invention, toe plate 24 was attached directly to the ski 22 by screws such as the three wood screws 38 go passing through three mounting holes at the positions shown by the countersinks 80.
In the present invention, a release plate 40 is added between the toe plate 24 and the ski 22. The release plate is secured to the ski by the wood screws 38 instead of the toe 65 plate of the prior method. The toe plate is held on the release plate by a load spool 50 added to the substantially planar
bottom surface of the toe plate using a machine screw 52. The load spool is mounted with its longitudinal axis 66 (FIG. 3) substantially perpendicular to the bottom surface of the toe plate. Inside the release plate is a load spring 44 which grabs onto the load spool to retain the toe plate on the ski. The release plate is preferably only one-quarter inch thick which is an additional height not usually noticeable by a skier.
FIG. 2 is a bottom view of release plate 40. A hollow 42 is created for holding the load spring 44 and a plastic spacer 46 (FIG. 1). The spring and spacer surround a hole 48 in the top of the release plate through which the load spool passes. The spacer is provided with a clearance hole 54 for the bottom end of the spool as shown in FIG. 3. Two aft mounting holes 47 and a fore mounting hole 49 spaced 64 mm. from the aft holes provide mounting holes for the plate in the standard three screw telemark norm. An additional fore mounting hole 51 spaced 47 mm. from the aft screw holes 47 allows a standard three screw cross-country pattern if desired. Two end holes with notches 53 in the release plate are for the attachment of an anchor cord 82 (FIG. 1) discussed below. The overall arrangement of the release binding 20 allows it to be substituted on a telemark or cross-country ski by removing the old binding and installing the release binding on the ski without changing the original screw holes.
FIG. 3 is a sectional view of the release binding 20 of FIG. 1 assembled on the ski 22 substantially along line 3—3 of the release plate 40 of FIG. 2. The load spool 50 is engaged in the load spring 44 retaining the toe plate 24 on the ski. The load spool is mounted with its longitudinal axis 66 perpendicular to the planar bottom surface of the toe plate 24. The release plate 40 holds the load spring 44 so that the plane of the load spring is perpendicular to the longitudinal axis 66 of the load spool.
When the skier wants to install the toe plate 24 on the ski 22 as shown in FIG. 3, he first clamps his boot in the toe plate in the manner described above. He then inserts the load spool 50 into the hole 48 (FIG. 1) in the release plate 40 and steps down in the direction of arrow 55 against the load spring 44. In the process, the pilot surface 60 of the load spool pushes apart the two sides 62 and 64 of the load spring 44 in the directions of the arrows 72 and 74, respectively, allowing the load spool to pass through the spring. The sides of the spring then resiliently snap into the groove 56 of the load spool 50 to retain the toe plate 24 on the ski 22. The load spool passes into the hole 54 (FIG. 1) in the plastic spacer 46 without touching the ski 22. The force required to push the load spool into the spring is dependent upon the strength of the spring and the shape of the pilot surface 60 of the spool.
The load spring 44 is made of hardened stainless steel, preferably type 410 heat treated to hardness C-45, having a spring constant greater than 1000 pounds per square inch and preferably 2500 pounds per inch. It is substantially planar being about 3.5 inches long and 1.0 inch wide and has a constant thickness except in the engagement area 58. It is free to displace horizontally interior to the release plate as shown by the arrows 72 and 74 and is held from vertical movement inside the release plate 40 by the release plate on the top and the plastic spacer 46 on the bottom. The load spring is split into two opposing sides 62 and 64 coupled together at both ends (FIG. 1) defining an elongated central aperture so that when the spool is inserted, each side displaces equally. When the spring is unflexed as shown in FIG. 1, the two opposing sides in the engagement area 58 are spaced a distance less than the second distance 59 of the
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