Power shovel with variable pitch braces

A power shovel comprising

• a frame,
• a dipper handle mounted on said frame for pivotal movement relative thereto about a generally horizontal dipper handle axis such that said dipper handle has a variable pivotal position relative to said frame,
• a dipper connected to said handle for pivotal movement relative thereto about a generally horizontal dipper axis such that said dipper has a variable pivotal position relative to said handle, said dipper having external forces exerted thereon during normal operation of said power shovel, and
• a variable pitch brace connected between said handle and said dipper at a point spaced from said dipper axis, said variable pitch brace including a spring biasing said dipper in one rotational direction relative to said handle and about said dipper axis, such that said pivotal position of said dipper automatically varies depending on said pivotal position of said handle and on external forces on said dipper.

A power shovel comprising

• a frame,
• a winch mounted on said frame,
• a boom having a lower end mounted on said frame and having an upper end,
• a sheave rotatably mounted on said boom adjacent said upper end thereof,
• a dipper handle mounted on said boom for pivotal movement relative thereto and for translational movement relative thereto,
• a dipper connected to said handle for pivotal movement relative thereto about a generally horizontal lower dipper axis, and
• a variable pitch brace connected between said handle and said dipper, said variable pitch brace including a first link connected to said handle for pivotal movement relative thereto about a generally horizontal upper handle axis spaced from said lower dipper axis, and a second link which is connected to said dipper for pivotal movement relative thereto about a generally horizontal upper dipper axis spaced from said lower dipper axis, and which is connected to said first link for pivotal movement relative thereto about a link axis spaced from said upper handle axis and from said upper dipper axis, and a gas spring extending between said links such that said spring biases said links so as to increase the angle between said links, thereby increasing the distance between said upper handle axis and said upper dipper axis.

A method of operating a power shovel including a frame, a dipper handle mounted on said frame for pivotal movement relative thereto about a generally horizontal dipper handle axis such that said dipper handle has a variable pivotal position relative to said frame, said dipper handle having a centerline, and said dipper handle being mounted on said frame for translational movement relative thereto such that said handle has a translational position relative to said frame, a dipper connected to said handle for pivotal movement relative thereto about a generally horizontal dipper axis such that said dipper has a variable pivotal position relative to said handle and such that said dipper can be crowded by moving said dipper handle translationally, said dipper having thereon digging teeth defining a tooth cutting angle relative to said dipper handle centerline, said dipper being pivotable upwardly from a tucked position, and said dipper having external forces exerted thereon during normal operation of said power shovel, and a variable pitch brace connected between said handle and said dipper at a point spaced from said dipper axis, said variable pitch brace including an extendable and contractible spring biasing said dipper in a rotational direction, relative to said handle and about said dipper axis, decreasing said tooth cutting angle, such that said pivotal position of said dipper automatically varies depending on said pivotal position of said handle, on said translational position of said handle, and on external forces on said dipper, said method comprising the steps of

• (a) locating said dipper in said tucked position with said spring extended to minimize said tooth cutting angle,
• (b) pivoting said dipper upwardly from said tucked position to contact material to be excavated,
• (c) pivoting said dipper further upwardly and crowding said dipper to cause said spring to contract to increase said tooth cutting angle, and
• (d) pivoting said dipper further upwardly to cause said spring to extend to decrease said tooth cutting angle.