Fluid motor control circuit with overspeed limiting means

Claim 2

A fluid motor control circuit for interconnecting a source of fluid under pressure and drain means and a reversible fluid motor having first and second fluid ports, comprising: a valve assembly having an inlet passage for receiving fluid from said source and having a first and second exhaust passages for returning fluid to said drain means and having first and second motor fluid passages respectively communicating with said first and second ports of said motor, and having motor control valve means shiftable to a forward drive position at which said first motor fluid passage is communicated with said inlet passage while said second motor fluid passage is communicated with said second exhaust passage, said motor control valve means being shiftable to a reverse drive position at which said second motor fluid passage is communicated with said inlet passage while said first motor fluid passage is communicated with said first exhaust passage, and first and second overspeed valves situated in the fluid exhaust flow path between said control valve means and said drain, said first overspeed valve having a fluid inlet means and fluid outlet means forming a portion of said first exhaust passage for transmitting exhaust flow from said motor control valve means to said drain means, said second overspeed valve having a fluid inlet means and fluid outlet means forming a portion of said second exhaust passage for transmitting exhaust flow from said motor control valve means to said drain means, each of said overspeed valves having pilot means for restricting the flow passage therethrough in response to pressure changes at said motor ports which accompany incipient overspeeding of said motor.

Claim 3

The combination defined in claim 1 wherein each of said overspeed valves has a spool and spring means urging said spool toward a position at which said inlet means of each overspeed valve is isolated from said outlet means thereof and wherein said pilot means comprises means for causing fluid pressure from said second motor fluid passage to act against said spool of said first overspeed valve in opposition to the force of said spring thereof and for causing fluid pressure from said first motor fluid passage to act against said spool of said second overspeed valve in opposition to the force of said spring thereof.

Claim 4

The combination defined in claim 2 wherein said means for causing fluid prEssure to act against said spools of said first and second overspeed valves comprises means forming a first pressure signal passage between said spool of said first overspeed valve and said second motor fluid passage and having a flow restriction, and means forming a second pressure signal passage between said spool of said second overspeed valve and said first motor fluid passage and having a flow restriction.

Claim 5

A fluid motor control valve assembly for interconnection to a source of pressurized fluid and to drain means and to a reversible fluid motor having forward and reverse fluid ports comprising: valve housing means having a fluid inlet passage for connection to said source of pressurized fluid and having an outlet passage for connection to said drain means, said outlet passage having branches extending adjacent each side of said inlet passage in spaced relation therefrom, said housing means having a service fluid passage communicating with said inlet passage and extending adjacent both branches of said outlet passage in spaced relation therefrom and having a pair of motor fluid passages for connection to separate ones of said motor ports and extending adjacent said service passage at opposite sides thereof in spaced relation therefrom, said housing further having a pair of overspeed valve inlet passages each extending adjacent a separate one of said motor fluid passages in spaced relation therefrom and having a pair of exhaust passages for connection to said drain means and each extending adjacent a separate one of said overspeed valve inlet passages in spaced relation therefrom, said housing being further provided with a motor control valve bore transecting each of said above named passages and being provided with a pair of overspeed valve bores each transecting a separate one of said overspeed valve inlet passages and the adjacent one of said exhaust passages, an axially movable motor control valve spool disposed in said motor control valve bore and having an intermediate position therein and a forward drive position and a reverse position, said motor control valve spool having groove means thereon for communicating said inlet passage with said branches of said outlet passage while blocking said motor fluid passages while said spool is at said intermediate position, said spool having land means for blocking said inlet passage from said branches of said outlet passage at either of said forward and reverse positions, said motor control valve spool having additional groove means for communicating said service passage with one of said motor fluid passages while communicating the other of said motor fluid passage with the adjacent one of said overspeed valve inlet passages when said spool is at said forward drive position and for communicating said other motor fluid passage with said service passage while communicating said one motor fluid passage with the adjacent one of said overspeed valve inlet passages when said spool is at said reverse drive position, a pair of overspeed valve spools each disposed in a separate one of said overspeed valve bores, each of said overspeed valve spools being spring biased to a position at which the adjacent exhaust passage is isolated from the adjacent overspeed valve inlet passage and each having a groove for communicating said adjacent passages upon being moved against said spring biasing, and pilot means for causing fluid pressure from the most remote one of said pair of motor fluid passages to act against each of said overspeed valve spools in opposition to the force of said spring biasing thereon.

Claim 6

A fluid motor control valve assembly for interconnection to a source of pressurized fluid and to drain means and to a reversible fluid motor having forward and reverse fluid ports comprising: valve housing means having a fluid inlet passage for connection to said source of pressurized fluid and having an outlet passage for connection to said drain means, said outlet passage having branches extending adjacent each side of said inlet passage in spaced relation therefrom, said housing means having a service fluid passage communicating with said inlet passage and extending adjacent both branches of said outlet passage in spaced relation therefrom and having a pair of motor fluid passages for connection to separate ones of said motor ports and extending adjacent said service passage at opposite sides thereof in spaced relation therefrom, said housing further having a pair of overspeed valve inlet passages each extending adjacent a separate one of said motor fluid passages in spaced relation therefrom and having a pair of exhaust passages for connection to said drain means and each extending adjacent a separate one of said overspeed valve inlet passages in spaced relation therefrom, said housing being further provided with a motor control valve bore transecting each of said above named passages and being provided with a pair of overspeed valve bores each transecting a separate one of said overspeed valve inlet passages and the adjacent one of said exhaust passages, an axially movable motor control valve spool disposed in said motor control valve bore and having an intermediate position therein and a forward drive position and a reverse position, said motor control valve spool having groove means thereon for communicating said inlet passage with said branches of said outlet passage while blocking said motor fluid passages while said spool is at said intermediate position, said spool having land means for blocking said inlet passage from said branches of said outlet passage at either of said forward and reverse positions, said motor control valve spool having additional groove means for communicating said service passage with one of said motor fluid passages while communicating the other of said motor fluid passage with the adjacent one of said overspeed valve inlet passages when said spool is at said forward drive position and for communicating said other motor fluid passage with said service passage while communicating said one motor fluid passage with the adjacent one of said overspeed valve inlet passages when said spool is at said reverse drive position, a pair of overspeed valve spools each disposed in a separate one of said overspeed valve bores, each of said overspeed valve spools being spring biased to a position at which the adjacent exhaust passage is isolated from the adjacent overspeed valve inlet passage and each having a groove for communicating said adjacent passages upon being moved against said spring biasing, and pilot means for causing fluid pressure from the most remote one of said pair of motor fluid passages to act against each of said overspeed valve spools in opposition to the force of said spring biasing thereon.

Claim 7

The combination defined in claim 4 further comprising an inlet check valve disposed in said housing between said inlet passage and said service passage, a pair of line relief valve means disposed in said housing each being between a separate one of said exhaust passages and the adjacent one of said motor fluid passages, and a pair of make up valves disposed in said housing each being between a separate One of said motor fluid passages and the adjacent one of said exhaust passages.