US3923129A — Control for hydrostatic transmission and brake

Claim 1

Independent Claim 130 words

A speed control apparatus for controlling a hydrostatic transmission over a range of speed conditions including a zero speed condition comprising a hydrostatic drive and an output means, a braking circuit with a brake for applying braking pressure to said output means only upon said transmission attaining said zero speed condition characterized by said braking circuit having a mechanism comprising: a support, a lever pivotally mounted at one end on said support for movement between locking and unlocking positions; a recess in said lever; a follower on said drive having a position corresponding to each speed condition of said drive and being only engageable with said recess in the zero speed condition and an extendible and retractable plunger engageable with said lever and extendible for energization of said braking circuit.

Claim 2

Dependent Claim 130 words

A speed control apparatus for controlling a hydrostatic transmission over a range of speed conditions including a zero speed condition comprising a hydrostatic drive and an output means, a braking circuit with a brake for applying braking pressure to said output means only upon said transmission attaining said zero speed condition characterized by said braking circuit having a mechanism comprising: a support, a lever pivotally mounted at one end on said support for movement between locking and unlocking positions; a recess in said lever; a follower on said drive having a position corresponding to each speed condition of said drive and being only engageable with said recess in the zero speed condition and an extendible and retractable plunger engageable with said lever and extendible for energization of said braking circuit.

Claim 3

Dependent Claim 147 words

A speed control apparatus for controlling a hydrostatic transmission and over a range of speed conditions including a zero speed condition comprising a hydrostatic drive and, having an output means with a brake a braking circuit for applying braking pressure to said brake upon said transmission being at said zero speed condition, characterized by two stage relief valve coupled to said hydrostatic drive and comprising: a housing formed with a transverse partition intermediate the ends thereof; a relief port in said housing on one side of said partition, a hollow relief valve piston slidably mounted in said housing controlling said relief port; a spring seated between said partition and said relief valve piston and biasing said relief valve piston to close said relief port, and means responsive to energization of said braking circuit to reduce the force urging said relief valve piston to close said relief port.

Claim 4

Dependent Claim 147 words

A speed control apparatus for controlling a hydrostatic transmission and over a range of speed conditions including a zero speed condition comprising a hydrostatic drive and, having an output means with a brake a braking circuit for applying braking pressure to said brake upon said transmission being at said zero speed condition, characterized by two stage relief valve coupled to said hydrostatic drive and comprising: a housing formed with a transverse partition intermediate the ends thereof; a relief port in said housing on one side of said partition, a hollow relief valve piston slidably mounted in said housing controlling said relief port; a spring seated between said partition and said relief valve piston and biasing said relief valve piston to close said relief port, and means responsive to energization of said braking circuit to reduce the force urging said relief valve piston to close said relief port.

Claim 5

Dependent Claim 122 words

An apparatus as claimed in claim 2 characterized by said last named means comprising: a pilot port in said partition; a poppet valve received in said housing on the opposite side of said partition and controlling said pilot port; means biasing said poppet valve to a closed position with a predetermined maximum force when said braking circuit is deenergized and responsive to energization of saiD braking circuit to bias said poppet valve to a closed position with a force less than said predetermined maximum force and an orifice in the end wall of said relief valve piston for providing a pressure drop across said relief valve piston when said poppet valve is in an open position permitting flow through said pilot port.

Claim 6

Dependent Claim 113 words

An apparatus as claimed in claim 3 characterized bt said last named means comprising: a hollow piston slidably mounted in said housing; a spring seat mounted in said main housing; a first spring in said hollow piston biasing said poppet valve to a closed position against said pilot port; and a second spring in said housing seated between said annular spring seat member and said hollow piston biasing and hollow piston toward engagement with said partition and simultaneously compressing said first spring; said hollow piston being urged in the opposite direction by the pressure in said braking circuit to reduce the closing force on said poppet valve when said braking circuit is energized.

Claim 7

Dependent Claim 170 words

A speed control apparatus comprising a hydrostatic drive having a variable angle swash plate movable through a range of positions and a fluid source, a brake, a hydraulic line adapted to conduct hydraulic fluid from said source to said hydraulic brake, a mechanism having a normally inactive condition blocking flow through said hydraulic line and being operable to an active condition to permit flow through said line when said line is pressurized upstream of said mechanism when said swash plate is in a predetermined position characterized by said mechanism comprises; a support, a lever pivotally mounted at one end on said support for movement between locking and unlocking positions; a recess in said lever; a follower having a position corresponding to each speed condition of said hydrostatic drive and being engageable with said recess in the zero speed condition only; and an extendible and retractable plunger engageable with said lever and urged to extend inresponse to energization of said braking circuit to thereby urge said lever toward its locked position.

Claim 8

Dependent Claim 170 words

A speed control apparatus comprising a hydrostatic drive having a variable angle swash plate movable through a range of positions and a fluid source, a brake, a hydraulic line adapted to conduct hydraulic fluid from said source to said hydraulic brake, a mechanism having a normally inactive condition blocking flow through said hydraulic line and being operable to an active condition to permit flow through said line when said line is pressurized upstream of said mechanism when said swash plate is in a predetermined position characterized by said mechanism comprises; a support, a lever pivotally mounted at one end on said support for movement between locking and unlocking positions; a recess in said lever; a follower having a position corresponding to each speed condition of said hydrostatic drive and being engageable with said recess in the zero speed condition only; and an extendible and retractable plunger engageable with said lever and urged to extend inresponse to energization of said braking circuit to thereby urge said lever toward its locked position.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1978-12-01	1979-06-02	1979-12-02	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1982-12-01	1983-06-02	1983-12-02	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1986-12-01	1987-06-02	1987-12-02	$7700.00	Window Closed / Lapsed

Control for hydrostatic transmission and brake

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