Power driven ski

Abstract

A power driven ski is divided by an aperture into anterior and posterior ski portions, which are held one to the other by a bridge so that their combined undersurfaces form a longitudinally smooth skiing undersurface throughout the length of the ski. A motor driven endless tread is circulateably supported around the posterior ski portion for thrusting against the snow over which the posterior ski portion slides.

I claim: 
     
       1. In a power driven ski for .[.attachment to a skier's foot and for.]. slidingly negotiating snow as with a conventional ski, said power driven ski having in combination; a. a ski with an aperture dividing it into an anterior ski portion having a longitudinally smooth anterior undersurface and a posterior ski portion,   b. a bridge holding said ski portions to each other,   .[.c. means for attaching said ski to a skier's foot,.].   .[.d..]. .Iadd.c. .Iaddend.an endless tread circulateably supported around said posterior ski portion having at least one tension carrying member and a plurality of cleats attached to said tension carrying member for thrusting against the snow.   .[.e..]. .Iadd.d. .Iaddend.means for circulateably supporting said tread around said posterior ski portion, and   .[.f..]. .Iadd.e. .Iaddend.motor means coupled to said tread for circulating said tread around said posterior ski portion, the improvement wherein the posterior ski portion has a longitudinally smooth, snow contacting stationary undersurface and said bridge holds said ski portions in position one relative to the other so that said undersurfaces jointly form a longitudinally smooth skiing undersurface substantially throughout the length of said ski.     
     
     
       2. A power driven ski as in claim 1 including a one way clutch coupling said motor means to said tread. 
     
     
       3. A power driven ski as in claim 1 wherein the engagement of one of said blades with snow near the front of said posterior undersurface is sequenced out of phase with the disengagement of another one of said blades from snow near the rear of said posterior undersurface. 
     
     
       4. A power driven ski as in claim 1 wherein said tread blades are outwardly protruding, and the tread circulates from above to below said posterior ski portion through said aperture, over a front sprocket having a first pitch-line radius and therafter over an arched ramp having a substantially larger pitch-line radius, said arched ramp being adapted to guide said cleats downwardly on an arc into gradual engagement with snow. 
     
     
       5. A power driven ski as in claim 1 wherein said posterior undersurface is stepped downwards relative to said anterior undersurface. 
     
     
       6. A power driven ski as in claim 1 wherein said blades are outwardly protruding and are adapted to erect into the snow on a bearing formed at their rear tip while engaging the snow and thereby cause said tension carrying member to assume a zig-zag configuration as viewed on a plane which is parallel to the chain and perpendicular to said posterior undersurface, said zig-zag configuration causing tension forces carried by said tension carrying member to negate bending moments imposed on it by said blades which are attached to it. 
     
     
       7. A power driven ski as in claim 6 wherein said tension carrying member is circulatebly supported on a drive sprocket which is coupled to said motor means, and on a rear sprocket which is mounted on said posterior ski portion by resilient means which permit said tension carrying member to assume said zig-zag configuration without becoming stretched. 
     
     
       8. A power driven ski as in claim 6 wherein said tension carrying member comprises a chain of links hinged one to the next to permit said links to pivot one relative to the next as viewed on a plane which is parallel to said chain and is perpendicular to said posterior undersurface, but resist such pivoting as viewed on a plane which is parallel to said posterior undersurface. 
     
     
       9. A power driven ski as in claim 8 wherein the part of said tension carrying member which is under said ski is longitudinally guided in a channel in said posterior undersurface to thereby shelter said tension carrying member from lateral movement between the ski and snow as well as for supporting the tread in its resistance to assume a zig-zag configuration on a plane that is parallel to said posterior undersurface due to asymetrical loading of the blades.