Implement attaching to a forward motion-producing machine for elevating an edge encountering an immovable object

1. An implement attaching to a forward motion-producing machine, comprising:

a work assembly having an edge and a heel;

a linkage assembly attachable as a sole attachment between said work assembly and said forward motion-producing machine and having first and second configurations,

said first configuration providing said heel to contact a prevailing ground surface, and said edge to move in a forward direction as determined by said forward motion-producing machine and to move along a path generally parallel with path,

said second configuration providing said heel to maintain contact with said prevailing ground surface, and said edge to be elevated above said prevailing ground surface in order to pass over an obstruction encountered by said edge as said edge moves in the forward direction,

said edge moving about said heel as said linkage assembly goes from said first configuration to said second configuration.

2. The implement in accordance with claim 1 , wherein the attachment of said linkage assembly is in front of said forward motion-producing machine.

3. The implement in accordance with claim 1 , wherein the attachment of said linkage assembly is behind said forward motion-producing machine.

4. An implement attaching to a forward motion-producing machine, comprising:

work means for cutting or scraping, said work means having an edge and a heel;

linkage means, attachable as a sole attachment between said work means and said forward motion-producing machine and having first and second configurations, for supporting said edge in the first configuration along a path generally parallel with prevailing ground surface as said edge moves in a forward direction as determined by said forward motion-producing machine and for elevating said edge in the second configuration above said prevailing ground surface in order to pass over an obstruction encountered by said edge as said edge moves in the forward direction, said edge moving about said heel as said linkage means moves from said first configuration to said second configuration, wherein said heel maintains contact with said prevailing ground surface in said first configuration and in said second configuration.

5. An implement attaching to a forward motion-producing machine, comprising:

a work assembly having an edge and a heel; and

a linkage assembly attachable between the motion-producing machine and said work assembly having first and second pivot axes pivotally connecting with said work assembly, said first pivot axis being beneath said second pivot axis, said linkage assembly having first and second configurations, said first configuration including said first axis located in a first position horizontally relative to said second axis, said second configuration including said first axis located in a second position horizontally relative to said second axis, said second position being horizontally separated in a direction toward said work assembly relative to said first position,

wherein when the edge of the work assembly strikes an immovable object, the linkage assembly moves from the first to the second configuration,

wherein when said linkage assembly is in said first configuration, the edge and the heel of the work assembly are both resting on ground, and

wherein when said linkage assembly is in said second configuration, the heel of the work assembly is on the ground and the edge is elevated to allow the edge to ride over the immovable object.

6. The implement in accordance with claim 5 , wherein the first pivot axis is located in a brace attaching to said work assembly, said brace having an end located facing the ground and so that said brace end is less than an inch from the ground when said linkage assembly is in the second configuration, said pivot axis being less than an inch from the brace end.

7. The implement in accordance with claim 5 , wherein the linkage assembly further includes third and fourth pivot axes and first, second, third and fourth inextensible members, said first inextensible member connecting said first and second pivot axes, said second inextensible member connecting said second and third pivot axes, said third inextensible member connecting said third and fourth pivot axes, said fourth inextensible member connecting said fourth and first pivot axes, said second and fourth inextensible members being nonparallel so that said first pivot axis moves from said first to said second position when said first work assembly strikes the immovable object, said fourth inextensible member including a frame assembly attachable to said motion-producing machine and having a pair of downwardly projecting legs pivotally attached to said work assembly at said first pivot axis, said downwardly projecting legs each including a hinged joint, said downwardly projecting legs of said frame assembly having upper portions and lower portions separated at break locations, said lower portions comprising top and bottom lower portions slideably attached to one another, a fluid filled cylinder attached between said top and bottom lower portions for reversibly elongating said lower portion, and a control circuit for controlling said fluid filled cylinder when said edge of said work assembly strikes the immovable object.

8. The implement in accordance with claim 5 , wherein the linkage assembly further includes third and fourth pivot axes and first, second, third and fourth inextensible members, said first inextensible member connecting said first and second pivot axes, said second inextensible member connecting said second and third pivot axes, said third inextensible member connecting said third and fourth pivot axes, said fourth inextensible member connecting said fourth and first pivot axes, said second and fourth inextensible members being nonparallel so that said first pivot axis moves from said first to said second position when said first work assembly strikes the immovable object, said fourth inextensible member being inclined about 70 degrees from horizontal when said linkage assembly is in the first configuration and about 90 degrees from horizontal when said linkage assembly is in the second configuration.