Overload protection device for counterbalance vehicles

Claim 2

A vehicle comprising: a frame; a load member mounted on the frame for movement relative to the frame, a cylinder having first and second ends and defining a cavity; a piston within the cavity and dividing the cavity into first and second chambers partially bound by the first and second cylinder ends, the piston being movable through the cavity between the first and second cylinder ends; a first passage proximate the first cylinder end and communicating with the first chamber; a second passage proximate the second cylinder end and communicating with the second chamber; a rod connected to the piston and projecting out of the cavity through one of the cylinder ends; means connecting the rod and cylinder to the load member and frame to move the load member relative to the frame in response to movement of the piston relative to the cylinder; valve means responsive to a difference in pressure between the first and second chambers to prevent movement of the load member in one direction relative to the frame; means to add fluid to one chamber and remove fluid from the other chamber through the first and second passages to move the piston relative to the cylinder; and means operative to seal the first passage when the piston is a given distance from the first cylinder end.

Claim 3

A vehicle according to claim 1 further including means operative to seal the second passage when the piston is a given distance from the second end.

Claim 4

A piston-cylinder device for use on a vehicle having a frame, a load member connected to the frame and movable relative thereto, a circuit for the transfer of fluid, and a suitable device operable in response to a difference in fluid pressure between two sources to prevent movement of the load member relative to the frame, the piston-cylinder device comprising: a cylinder having first and second ends and defining a cavity; a piston located within and dividing the cavity into opposite chambers partially bounded by the first and second ends of the cylinder, the piston having first and second sides respectively facing the first and second ends of the cylinder; a rod connected to the piston and extending outwardly of the cylinder through one of the ends of the Cylinder; means adapted to interconnect the rod and the cylinder to the load member and the frame for movement of the load member relative to the frame in response to movement of the piston relative to the cylinder; means defining a passage at each of the ends of the cylinder communicating with each of the opposite chambers in the cylinder and adapted to ommunicate with the circuit whereby fluid may be introduced through one passage into one chamber and withdrawn through the other passage from the other chamber to move the piston relative to the cylinder; means operative to transmit a signal representative of the magnitude of the fluid pressure in each chamber to the suitable device; and means operative in response to movement of the piston to a position proximate the first end of the cylinder to seal the passage at the first end of the cylinder.

Claim 5

A piston-cylinder device for use on a vehicle having a frame, a load member connected to the frame and movable relative thereto, a circuit for the transfer of fluid, and a suitable device operable in response to a difference in fluid pressure between two sources to prevent movement of the load member relative to the frame, the piston-cylinder device comprising: a cylinder having first and second ends and defining a cavity; a piston located within and dividing the cavity into opposite chambers partially bounded by the first and second ends of the cylinder, the piston having first and second sides respectively facing the first and second ends of the cylinder; a rod connected to the piston and extending outwardly of the cylinder through one of the ends of the Cylinder; means adapted to interconnect the rod and the cylinder to the load member and the frame for movement of the load member relative to the frame in response to movement of the piston relative to the cylinder; means defining a passage at each of the ends of the cylinder communicating with each of the opposite chambers in the cylinder and adapted to ommunicate with the circuit whereby fluid may be introduced through one passage into one chamber and withdrawn through the other passage from the other chamber to move the piston relative to the cylinder; means operative to transmit a signal representative of the magnitude of the fluid pressure in each chamber to the suitable device; and means operative in response to movement of the piston to a position proximate the first end of the cylinder to seal the passage at the first end of the cylinder.

Claim 6

A piston-cylinder device according to claim 3 wherein the means operative in response to movement of the piston, seals the passage prior to contact of the first side of the piston with the first end of the cylinder to maintain a pressure in the chamber at the first end of the cylinder substantially equal to (F + P2A2)/A1 where: F is the force on the rod; P2 is the pressure of the fluid in the chamber at the second end of the cylinder, A2 is the area of the second side of the piston; and A1 is the area of the first side of the piston.

Claim 7

A piston-cylinder device according to claim 4 further comprising means operative in response to movement of the piston to a position proximate the second end of the cylinder to seal the passage at the second end of the cylinder prior to contact of the second side of the piston with the second end of the cylinder to maintain a pressure in the chamber at the second end of the cylinder equal to (F + P1A1)/A2 where P1 is the pressure of the fluid in the chamber at the first end of the cylinder.

Claim 8

A piston-cylinder device according to claim 3 wherein the means operative in response to movement of the piston includes a resilient member secured to and projecting away from the first side of the piston toward the first end of the cylinder and wherein the leading surface of the resilient member seals the passage at the first end of the cylinder when the first side of the piston is a predetermined distance away from the first end of the cylinder.

Claim 9

A piston-cylinder device according to claim 3 wherein the means operative in response to movement of the piston includes: a cover at the first end of the cylinder adapted to seal the passage at the first end of the cylinder; means secured to the cover and the cylinder to bias the cover away from the passage at the first end of the cylinder; and resilient means secured to the cover intermediate the cover and the first side of the piston and adapted to be compressed by the first side of the piston to force the cover to seal the passage at the first end of the cylinder when the piston is a predetermined distance away from the first end of the cylinder.

Claim 10

A piston-cylinder device according to claim 3 wherein: the passage at the first end of the cylinder includes an enlarged tubular portion communicating with the passage at the first end and with the chamber at the first end; and the means operative in response to movement of the piston includes: a plunger operative to move within and relative to the tubular portion between a first and a second position and having an end portion projecting into the chamber at the first end of the cylinder and a passage communicating with the chamber at the first end of the cylinder and with the passage at the first end of the cylinder when the plunger is in the first position and spaced from the passage at the first end of the cylinder when the plunger is in the second position; and means biasing the plunger to the first position.

Claim 11

A pIston-cylinder device according to claim 8 further including a one-way check valve operative to provide a path for a flow of fluid from the passage at the first end of the cylinder to the chamber at the first end.

Claim 12

An overload protection device for use on a vehicle having a primary load member movably mounted on a frame and a secondary load member movably mounted on the primary load member and adapted to receive a load which creates a moment about a point on the frame, the device comprising: first means responsive to a given magnitude of the moment to prevent movement of the primary load member in a given direction relative to the frame; and second means operative in response to positioning of the secondary load member in a given position with respect to the primary load member to override the first means and release the primary load member for movement in the given direction.

Claim 13

An overload protection device for use on a vehicle having a primary load member movably mounted on a frame and a secondary load member movably mounted on the primary load member and adapted to receive a load which creates a moment about a point on the frame, the device comprising: first means responsive to a given magnitude of the moment to prevent movement of the primary load member in a given direction relative to the frame; and second means operative in response to positioning of the secondary load member in a given position with respect to the primary load member to override the first means and release the primary load member for movement in the given direction.

Claim 14

An overload protection device for use on a vehicle having a primary load member mounted on a frame for movement relative to the frame, a first piston-cylinder device for moving the primary load member relative to the frame in response to the introduction of fluid through a first passage into the first cylinder at one side of the first piston and the removal of fluid through a second passage into the first cylinder at the other side of the first piston, a secondary load member mounted for movement relative to the primary load member, and a second piston-cylinder device for moving the secondary load member relative to the primary load member in response to the introduction of fluid through a third passage into the second cylinder at one side of the second piston, the overload protection device comprising: first means responsive to a difference in fluid pressure at the opposite sides of the first piston to move between a first position and a second position; second means adapted to prevent movement of the primary load member relative to the frame in one direction when the first means is in the second position; third means responsive to a given fluid pressure on one side of the second piston to move between a first position and a second position; and fourth means operative in response to the positioning of the third means in the first position to override the second means and enable the primary load member to move in said direction relative to the frame.

Claim 15

An overload protection device for use on a vehicle having a primary load member mounted on a frame for movement relative to the frame, a first piston-cylinder device for moving the primary load member relative to the frame in response to the introduction of fluid through a first passage into the first cylinder at one side of the first piston and the removal of fluid through a second passage into the first cylinder at the other side of the first piston, a secondary load member mounted for movement relative to the primary load member, and a second piston-cylinder device for moving the secondary load member relative to the primary load member in response to the introduction of fluid through a third passage into the second cylinder at one side of the second piston, the overload protection device comprising: first means responsive to a difference in fluid pressure at the opposite sides of the first piston to move between a first position and a second position; second means adapted to prevent movement of the primary load member relative to the frame in one direction when the first means is in the second position; third means responsive to a given fluid pressure on one side of the second piston to move between a first position and a second position; and fourth means operative in response to the positioning of the third means in the first position to override the second means and enable the primary load member to move in said direction relative to the frame.

Claim 16

An overload protection device according to claim 11 wherein: the second means includes a fluid passage adapted to be located in series with one of the passages communicating with the first cylinder, the passage of the second means is open when the first means is in the first position and sealed when the first means is in the second position; and the fourth means includes a fluid passage in parallel with the passage of the second means, the passage of the fourth means is open when the third means is in the first position and sealed when the third means is in the second position.

Claim 17

An overload protection device according to claim 12 including a one-way check valve in parallel with the passage of the second means and bypassing the sealed portion of the passage of the second means, the check valve enables fluid to flow into the first cylinder and blocks fluid from flowing out of the first cylinder.

Claim 18

An overload protection device according to claim 11 including means to bias the first means to the first position, the biassing means has a relatively high biasing rate and a relatively low preload force.

Claim 19

An overload protection device according to claim 11 including dampening means to control the movement of the first means between the first and second positions at a relatively slow rate of travel in response to relatively rapid changes in the magnitude of the difference in pressure.

Claim 20

An overload protection device according to claim 11 including: fifth means responsive to a difference in fluid pressure at the opposite sides of the first piston to move between a first posItion and a second position; and sixth means adapted to prevent movement of the secondary load member in one direction relative to the primary load member when the fifth means is in the second position.

Claim 21

An overload protection device according to claim 16 wherein the sixth means includes a fluid passage adapted to be located in series with the third passage, the passage of the sixth means is open when the fifth means is in the first position and sealed when the fifth means is in the second position.

Claim 22

An overload protection device according to claim 17 including a one-way check valve in parallel with the passage of the sixth means which bypasses the sealed portion of the passage of the sixth means, the check valve enables fluid to flow out of the second cylinder and blocks fluid from flowing into the second cylinder.

Claim 23

An overload protection device according to claim 16 including means to bias the fifth means to the first position, the biasing means has a relatively low biasing rate and a relatively high preload force.

Claim 24

An overload protection device according to claim 16 including dampening means to control the movement of the fifth means between the first and second positions at a relatively slow rate of travel in response to relatively rapid changes in the magnitude of the difference in pressure.

Claim 25

An overload protection device according to claim 20 wherein the dampening means enables movement of the fifth means at a relatively slow rate of travel during relatively rapid decreases in the magnitude of the difference in pressure and at a relatively high rate of travel during relatively rapid increases in the magnitude of the difference in pressure.

Claim 26

A valve responsive to a difference in pressure at opposite sides of a first piston movable in a first cylinder between opposite ends of the cylinder to prevent movement of the first piston relative to one end of the first cylinder when the difference in pressure exceeds a predetermined value and when the pressure exerted at one side of a second piston in a second cylinder is above a predetermined value, the valve comprising: a casing defining first and second cavities; a first spool movable in the first cavity between a first position and a second position; means biasing the first spool to the first position when the difference in pressure is below the predetermined value and to the second position when the difference in pressure is above the predetermined value; a second spool movable in the second cavity between a first position and a second position; means biasing the second spool to the first position when the pressure exerted at the one side of the second piston is below the predetermined value and to the second position when the pressure exerted at the one side of the second piston is above the predetermined value; means defining first and second passages communicating with one another through the first cavity when the first spool is in the first position and sealed from one another through the first cavity when the first spool is in the second position; and means defining third and fourth passages communicating with one another through the second cavity when the second spool is in the first position and sealed from one another through the second cavity when the second spool is in the second position, the first and third passages communicate with one another, the second and fourth passages communicate with one another, the third passage is adapted to communicate with the space between the first piston and the one end of the first cylinder, and the fourth passage is adapted to communicate with a fluid transfer circuit.

Claim 27

A valve responsive to a difference in pressure at opposite sides of a first piston movable in a first cylinder between opposite ends of the cylinder to prevent movement of the first piston relative to one end of the first cylinder when the difference in pressure exceeds a predetermined value and when the pressure exerted at one side of a second piston in a second cylinder is above a predetermined value, the valve comprising: a casing defining first and second cavities; a first spool movable in the first cavity between a first position and a second position; means biasing the first spool to the first position when the difference in pressure is below the predetermined value and to the second position when the difference in pressure is above the predetermined value; a second spool movable in the second cavity between a first position and a second position; means biasing the second spool to the first position when the pressure exerted at the one side of the second piston is below the predetermined value and to the second position when the pressure exerted at the one side of the second piston is above the predetermined value; means defining first and second passages communicating with one another through the first cavity when the first spool is in the first position and sealed from one another through the first cavity when the first spool is in the second position; and means defining third and fourth passages communicating with one another through the second cavity when the second spool is in the first position and sealed from one another through the second cavity when the second spool is in the second position, the first and third passages communicate with one another, the second and fourth passages communicate with one another, the third passage is adapted to communicate with the space between the first piston and the one end of the first cylinder, and the fourth passage is adapted to communicate with a fluid transfer circuit.

Claim 28

A valve according to claim 22 wherein the means biasing the first spool includes: a spring biasing the first spool to the first position; first means adapted for exerting a force on the first spool proportional to the pressure within the first cylinder at the one end to move the first spool to the second position; and second means adapted for exerting a force on the first spool proportional to the pressure within the first cylinder at the other end to move the first spool to the first position.

Claim 29

A valve according to claim 23 wherein the spring has a relatively low preload force and a relatively high rate.

Claim 30

A valve according to claim 23 wherein: the first spool has a first end located relative to the first position and a second end opposite the first end and located relative to the second position; the first means includes means defining a passage communicating with the first end of the first spool and adapted to communicate with the space at the one end of the first cylinder; and the second means includes means defining a passage communicating with the second end of the first spool and adapted to communicate with the space at the other end of the first cylinder.

Claim 31

A valve according to claim 25 wherein: the first cavity includes first and second enlarged annular spaces respectively communicating with the first and second passages; the first spool includes first and second enlarged portions respectively defining the first and second ends and in sliding engagement with the first cavity, and a necked-down center action intermediate and connected to the enlarged portions and aligned with the enlarged annular spaces when the first spool is in the first position and spaced from the enlarged annular spaces when the first spool is in the second position whereby fluid may flow from one enlarged annular space to the other enlarged annular space around the necked-down center section when the first spool is in the first position and fluid will be blocked from flowing from one enlarged annular space to the other enlarged annular space when the first spool is in the second position by the first enlarged portions; and means are provided on the first enlarged portion to regulate the fluid flow from one enlarged annular space to the other enlarged annular space when the first spool is proximate the second position.

Claim 32

A valve according to claim 22 wherein the means biasing the second spool includes: a spring biasing the second spool to the first position; and means adapted for exerting a force on the second spool proportional to the pressure within the second cylinder at the one side of the second piston to move the second spool to the second position.

Claim 33

A valve according to claim 27 wherein the spring has a relatively low preload force and a relatively low rate.

Claim 34

A valve according to claim 27 wherein: the second spool has a first end located relative to the first position; and the means adapted for exerting a force includes means defining a passage communicating with the first end of the second spool and adapted to communicate with the space at the one side of the second piston.

Claim 35

A valve for use on a vehicle having a load member mounted on a frame for movement by a piston located within a cylinder, the valve comprising: a spool movable between a first and a second position; means to decrease the rate of movement of the load member relative to the frame substantially in proportion to the amount of movement of the spool from the first position to the second position and to prevent movement of the load member relative to the frame in one direction when the spool is in the second position; means operative to create a force on the spool to move the spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the load member about a point on the frame; and a spring acting on the spool and yieldably biasing the spool to its first position, the spring having a relatively high rate and a relatively low preload to counteract the force and to allow movement of the spool to given locations between the first and the second positions that correspond to given magnitudes of the moment.

Claim 36

A valve for use on a vehicle having a load member mounted on a frame for movement by a piston located within a cylinder, the valve comprising: a spool movable between a first and a second position; means to decrease the rate of movement of the load member relative to the frame substantially in proportion to the amount of movement of the spool from the first position to the second position and to prevent movement of the load member relative to the frame in one direction when the spool is in the second position; means operative to create a force on the spool to move the spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the load member about a point on the frame; and a spring acting on the spool and yieldably biasing the spool to its first position, the spring having a relatively high rate and a relatively low preload to counteract the force and to allow movement of the spool to given locations between the first and the second positions that correspond to given magnitudes of the moment.

Claim 37

A valve according to claim 30 whereIn the means to decrease the rate of movement is operative to decrease the rate of movement of the load member at one rate during a given portion of the movement of the spool from the first position to the second position and at another rate during the remaining portion of the movement of the spool from the first position to the second position.

Claim 38

A valve for use on a vehicle having a primary load member mounted on a frame for movement by a first piston located within a first cylinder, and a secondary load member mounted on the primary load member for movement relative to the primary load member by a second piston located within a second cylinder, the valve comprising: a first spool movable between a first and a second position; means to decrease the rate of movement of the primary load member relative to the frame in proportion to the amount of movement of the first spool from the first position to the second position and to retain the primary load member relative to the frame when the first spool is in the second position; means operative to create a force on the first spool to move the first spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the primary load member about a point on the frame; a first spring acting on the first spool and yieldably biasing the first spool to its first position, the first spring having a relatively high rate and a relatively low preload to counteract the force and to allow movement of the first spool to given locations between the first and the second positions that correspond to given magnitudes of the moment; a second spool movable between a first and a second position; means to prevent movement of the secondary load member in one direction relative to the primary load member when the second spool is in the second position; means operative to create a force on the second spool to move the second spool from the first position to the second position, the magnitude of the force being related to the magnitude of the moment; and a second spring acting on the second spool and yieldably biasing the second spool to its first position, the second spring having a relatively high preload and a relatively low rate to counteract the force and to allow movement of the second spool from the first position to the second position at a relatively fast rate when the magnitude of the moment exceeds a predetermined value.

Claim 39

A valve for use on a vehicle having a primary load member mounted on a frame for movement by a first piston located within a first cylinder, and a secondary load member mounted on the primary load member for movement relative to the primary load member by a second piston located within a second cylinder, the valve comprising: a first spool movable between a first and a second position; means to decrease the rate of movement of the primary load member relative to the frame in proportion to the amount of movement of the first spool from the first position to the second position and to retain the primary load member relative to the frame when the first spool is in the second position; means operative to create a force on the first spool to move the first spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the primary load member about a point on the frame; a first spring acting on the first spool and yieldably biasing the first spool to its first position, the first spring having a relatively high rate and a relatively low preload to counteract the force and to allow movement of the first spool to given locations between the first and the second positions that correspond to given magnitudes of the moment; a second spool movable between a first and a second position; means to prevent movement of the secondary load member in one direction relative to the primary load member when the second spool is in the second position; means operative to create a force on the second spool to move the second spool from the first position to the second position, the magnitude of the force being related to the magnitude of the moment; and a second spring acting on the second spool and yieldably biasing the second spool to its first position, the second spring having a relatively high preload and a relatively low rate to counteract the force and to allow movement of the second spool from the first position to the second position at a relatively fast rate when the magnitude of the moment exceeds a predetermined value.

Claim 40

A valve for use on a vehicle having a load member mounted for movement relative to a frame by a piston located within a cylinder, the valve comprising: a spool movable between a first and a second position; means to prevent movement of the load member in one direction relative to the frame when the spool is in the second position; means operative to create a force on the spool to move the spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the load member about a point on the frame; and a spring acting on the spool and yieldably biasing the spool to its first position, the spring having a relatively high preload and a relatively low rate to counteract the force and to allow movement of the spool from the first position to the second position at a relatively fast rate when the magnitude of the force on the spool exceeds a predetermined value.

Claim 41

A valve for use on a vehicle having a load member mounted for movement relative to a frame by a piston located within a cylinder, the valve comprising: a spool movable between a first and a second position; means to prevent movement of the load member in one direction relative to the frame when the spool is in the second position; means operative to create a force on the spool to move the spool from the first position to the second position, the magnitude of the force being related to the magnitude of a moment acting on the load member about a point on the frame; and a spring acting on the spool and yieldably biasing the spool to its first position, the spring having a relatively high preload and a relatively low rate to counteract the force and to allow movement of the spool from the first position to the second position at a relatively fast rate when the magnitude of the force on the spool exceeds a predetermined value.

Claim 42

A valve for use on a vehicle having a frame, a primary load member which is movable away from the frame by movement of a first piston within a first cylinder, having first and second ends, toward the first end of the first cylinder, and a secondary load member which is movable relative to the primary load member by movement of a second piston within a second cylinder, having first and second ends, toward the first end of the second cylinder, the movement of the pistons being caused by a flow of fluid into the second end of each of the cylinders and out of the first end of the respective cylinders, the valve comprising: a first spool having first and second ends and being movable from a first position to a second position when the force on the first end is greater than the force on the second end; means yieldably retaining the first spool in the first position; means adapted to prevent movement of the first piston toward the first end of the first cylinder when the first spool is in the second position; a second spool having first and second ends and being movable from a first to a second position when the force on the first end is greater than the force on the second end; means yieldably retaining the second spool in the first position; means adapted to prevent movement of the second piston toward the first end of the second cylinder when the second spool is in the second position; means defining first and second passages adapted to be connected respectively to the spaces at the first and second ends of the first cylinder, the first and second passages respectively communicating with the first and second ends of each of the spools to transmit fluid between the first end of the first cylinder and the first end of each spool, and between the second end of the first cylinder and the second end of each spool; and means located within one of the passages to one of the spools to restrict the flow of fluid through the one passage to prevent rapid oscillation of the spool in response to rapid changes in the pressure of the fluid in the spaces at the first and second ends of the first cylinder.

Claim 43

A valve for use on a vehicle having a frame, a primary load member which is movable away from the frame by movement of a first piston within a first cylinder, having first and second ends, toward the first end of the first cylinder, and a secondary load member which is movable relative to the primary load member by movement of a second piston within a second cylinder, having first and second ends, toward the first end of the second cylinder, the movement of the pistons being caused by a flow of fluid into the second end of each of the cylinders and out of the first end of the respective cylinders, the valve comprising: a first spool having first and second ends and being movable from a first position to a second position when the force on the first end is greater than the force on the second end; means yieldably retaining the first spool in the first position; means adapted to prevent movement of the first piston toward the first end of the first cylinder when the first spool is in the second position; a second spool having first and second ends and being movable from a first to a second position when the force on the first end is greater than the force on the second end; means yieldably retaining the second spool in the first position; means adapted to prevent movement of the second piston toward the first end of the second cylinder when the second spool is in the second position; means defining first and second passages adapted to be connected respectively to the spaces at the first and second ends of the first cylinder, the first and second passages respectively communicating with the first and second ends of each of the spools to transmit fluid between the first end of the first cylinder and the first end of each spool, and between the second end of the first cylinder and the second end of each spool; and means located within one of the passages to one of the spools to restrict the flow of fluid through the one passage to prevent rapid oscillation of the spool in response to rapid changes in the pressure of the fluid in the spaces at the first and second ends of the first cylinder.

Claim 44

A valve according to claim 34 wherein: the one of the passages is the first passage; the first passage includes first and second branch passages, the first branch passage communicates with the first end of the first spool and is adapted to communicate with the first end of the first cylinder and the second branch passage communicates with the first end of the second spool and is adapted to communicate with the first end of the first cylinder; and the means to restrict includes a first orifice located within the second branch passage in the path of the flow of fluid from the space at the first end of the first cylinder to the first end of the second spool, a second orifice in parallel with the first orifice, and a check valve in series with the second orifice, the check valve being open when the flow of fluid is toward the first end of the second spool and closed when the flow of fluid is away from the first end of the second spool.

Claim 45

A valve according to claim 34 wherein: the one of the passages is the first passage; the first passage includes first and second branch passages, the first branch passage communicates with the first end of the first spool and is adapted to communicate with the first end of the first cylinder and the second branch passage communicates with the first end of the second spool and is adapted to communicate with the first end of the first cylinder; and the means to restrict includes a first orifice located within the first branch passage in the path of the flow of fluid from the space at the first end of the first cylinder to the first end of the first spool.

Claim 46

A fluid actuated piston-cylinder assembly adapted to be connected to a circuit used for the transfer of fluid, the piston-cylinder assembly comprising: a cylinder having opposite ends and defining a cavity; a piston located within and dividing the cavity into opposite chambers partially bounded by the piston; means for defining a passage at each end of the cylinder communicating with each of the opposite chambers and adapted to communicate with the circuit whereby fluid may be introduced through one passage into one chamber and withdrawn through the other passage from the other chamber to move the piston relative to the cylinder; and means operative in response to arrival of the piston to a position proximate to but spaced from one end of the cyLinder for sealing the passage at the one end to maintain a quantity of fluid between the piston and the one end and thereby preclude further movement of the piston toward the one end of the cylinder.

Claim 47

A fluid actuated piston-cylinder assembly adapted to be connected to a circuit used for the transfer of fluid, the piston-cylinder assembly comprising: a cylinder having opposite ends and defining a cavity; a piston located within and dividing the cavity into opposite chambers partially bounded by the piston; means for defining a passage at each end of the cylinder communicating with each of the opposite chambers and adapted to communicate with the circuit whereby fluid may be introduced through one passage into one chamber and withdrawn through the other passage from the other chamber to move the piston relative to the cylinder; and means operative in response to arrival of the piston to a position proximate to but spaced from one end of the cyLinder for sealing the passage at the one end to maintain a quantity of fluid between the piston and the one end and thereby preclude further movement of the piston toward the one end of the cylinder.

Claim 48

A fluid actuated piston-cylinder assembly according to claim 37 wherein the operative means is located within the cylinder and is interposed between the piston and the one end of the cylinder.

Claim 49

A fluid actuated piston-cylinder assembly according to claim 38 wherein the operative means includes a resilient member secured to and projecting away from the piston toward the one end of the cylinder, the resilient member having a leading edge that encompasses and seals the passage at the one end when the piston is a predetermined distance away from the one end of the cylinder.