Overload protection device with differential pressure sensing

Claim 2

An overload protection device for a vehicle having a frame, load carriage mounted for substantially vertical movement on a mast which is pivotally mounted on said frame for tilting motion reLative thereto and two motors operatively connected between said frame and said mast to tilt said mast, the overload protection device comprising: means for generating a signal at each motor representative of the magnitude of the force on the motor needed to maintain the mast at its position relative to the frame; means for comparing the signals from each motor and for transmitting the signal representative of the greatest magnitude of force on the motors, means operative for receiving the transmitted signal and for preventing tilting of the mast in at least one direction relative to the frame by preventing operation of the two motors in at least their corresponding direction when the magnatude of the tramsitted signal is above a given preselected magnitude.

Claim 3

An overload protection device for a vehicle having a frame, a load carriage mounted for movement on a mast pivotally mounted on the frame, first and second piston-cylinder assemblies each having a respective first and second piston, each piston-cylinder assembly having first and second ends connected to the frame and the mast, the assemblies being operative in response to a flow of fluid into the chamber at one end of each cylinder and out of the chamber at the other end of each cylinder to pivotally move the mast relative to the frame, and a fluid circuit for providing a flow of fluid to the chamber at one end of each cylinder and for collecting fluid from the chamber at the other end of each cylinder, the overload protection device comprising: first means for transmitting a signal representative of the highest pressure of the fluids in the chambers at the first ends of the cylinders to the operative means; and second means for transmitting a signal representative of the pressure of the fluid in the chamber at the second end of at least one of the cylinders to the operative means and means operative in response to the magnitude of the difference between the two signals for preventing pivotal movement of the mast in at least one direction by preventing movement of the first and second pistons in the corresponding direction.

Claim 4

An overload protection device for a vehicle having a frame, a load carriage mounted for movement on a mast pivotally mounted on the frame, first and second piston-cylinder assemblies each having a respective first and second piston, each piston-cylinder assembly having first and second ends connected to the frame and the mast, the assemblies being operative in response to a flow of fluid into the chamber at one end of each cylinder and out of the chamber at the other end of each cylinder to pivotally move the mast relative to the frame, and a fluid circuit for providing a flow of fluid to the chamber at one end of each cylinder and for collecting fluid from the chamber at the other end of each cylinder, the overload protection device comprising: first means for transmitting a signal representative of the highest pressure of the fluids in the chambers at the first ends of the cylinders to the operative means; and second means for transmitting a signal representative of the pressure of the fluid in the chamber at the second end of at least one of the cylinders to the operative means and means operative in response to the magnitude of the difference between the two signals for preventing pivotal movement of the mast in at least one direction by preventing movement of the first and second pistons in the corresponding direction.

Claim 5

An overload protection device according to claim 2 wherein the first means continuously monitors the pressure of the fluids in the chambers at the first ends of the cylinders.

Claim 6

An overload protection device according to claim 2 wherein the second means transmits a signal representative of the highest pressure of the fluids in the chambers at the second ends of the cylinders to the operative means.

Claim 7

An overload protection device according to claim 4 wherein the first and second means continuously monitor the pressures of the fluids in the chambers respectively at the first and second ends of the cylinders.

Claim 8

An overload protection device for a vehicle having a frame, a load carriage mounted on a mast pivotally mounted on the frame, a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising: a first cylinder having first and second ends and a chamber; a first piston located within the chamber in the first cylinder and movable between the first and second ends; a second cylinder having first and second ends and a chamber; a second piston located within the chamber in the second cylinder and movable between the first and second ends; means adapted for connecting the cylinders and the pistons to the frame and the mast to pivotally move the mast relative to the frame in response to movement of the first and second pistons relative to the first and second cylinders; means adapted for connecting the fluid inlet of the circuit to the first end of each of the cylinders; means adapted for connecting the fluid outlet of the circuit to the second end of each of the cylinders; first means to produce a signal representative of highest pressure of the fluids at the first ends of the cylinders and second means to produce a signal from the second ends of the cylinders means opeRative in response to the magnitude of the difference between the two signals for preventing pivotal movement of the mast in at least one direction by preventing movement of the first and second pistons in the corresponding direction.

Claim 9

An overload protection device for a vehicle having a frame, a load carriage mounted on a mast pivotally mounted on the frame, a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising: a first cylinder having first and second ends and a chamber; a first piston located within the chamber in the first cylinder and movable between the first and second ends; a second cylinder having first and second ends and a chamber; a second piston located within the chamber in the second cylinder and movable between the first and second ends; means adapted for connecting the cylinders and the pistons to the frame and the mast to pivotally move the mast relative to the frame in response to movement of the first and second pistons relative to the first and second cylinders; means adapted for connecting the fluid inlet of the circuit to the first end of each of the cylinders; means adapted for connecting the fluid outlet of the circuit to the second end of each of the cylinders; first means to produce a signal representative of highest pressure of the fluids at the first ends of the cylinders and second means to produce a signal from the second ends of the cylinders means opeRative in response to the magnitude of the difference between the two signals for preventing pivotal movement of the mast in at least one direction by preventing movement of the first and second pistons in the corresponding direction.

Claim 10

An overload protection device according to claim 6 wherein the second means transmits the highest pressure of the fluids at the second ends of the cylinders to the operative means.

Claim 11

An overload protection device according to claim 6 wherein the first means for transmitting continuously monitors the pressure of the fluids at the first ends of the cylinders.

Claim 12

An overload protection device according to claim 8 wherein the first means for transmitting includes: means defining first and second passages each having one end communicating with the first end respectively of the first and second cylinders and another end; a valve having first and second ends respectively communicating with the other end of the first and second passages; means in the valve operative in response to a difference in the pressure of the fluids in the first and second passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure with an exit passage; and means defining a passage communicating with the exit passage and the operative means.

Claim 13

An overload protection device according to claim 9 further including a second means for continuously monitoring the highest pressure of the fluids at the second ends of the cylinders and transmitting it to the operative means comprising: means defining third and fourth passages each having one end communicating with the second end respectively of the first and second cylinders and another end; a valve having first and second ends respectively communicating with the other end of the third and fourth passages; means in the valve operative in response to a difference in pressure of the fluids in the third and fourth passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure to an exit passage; and means defining a passage communicating with the exit passage and the operative means.

Claim 14

An overload protection device for a vehicle having a frame, a load carriage mounted on the frame for substantially vertical movement on a mast which is pivotally mounted on the -frame, a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising: a first cylinder having first and second ends and a chamber; a first piston located within the chamber in the first cylinder and movable between the first and second ends; a second cylinder having first and second ends and a chamber; a second piston located within the chamber in the second cylinder and movable between the first and second ends; means adapted for connecting the cylinders and the pistons to the frame and the mast to move the mast relative to the frame in response to movement of the pistons relative to the cylinders; means adapted for connecting the fluid inlet of the circuit to the first end of each of the cylinders; means adapted for connecting the fluid outlet of the circuit to the second end of each of the cylinders; means operative in response to a given difference in pressure between two sources representative of the pressure differential across the first and second cylinders for preventing at least certain tilting movement of the mast relative to the frame; first means for continuously monitoring the highest pressure of the fluids at the first ends of the cylinders and transmitting it to the operative means including: a. means defining first and second passages each having one end communicating with the first end respectively of the first and second cylinders and another end; b. a first valve having first and second ends respectively communicating with the other end of the first and second passages; c. means defining a first exit passage communicating the first valve with the operative means; d. means in the first valve operative in response to a difference in the pressure of the fluids in the first and second passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure with the first exit passage; and e. means disposed on the first and second pistons preventing movement of the pistons to axial positions effecting the sealing of the first and second passages at the first ends of the cylinders; and second means for continuously monitoring the highest pressure of the fluids at the second ends of the cylinders and transmitting it to the operative means including: a. means defining third and fourth passages each having one end communicating with the second end respectively of the first and second cylinders and another end; b. a second valve having first and second ends respectively communicating with the other end of the third and fourth passages; c. means defining a second exit passage communicating with the second valve and the operative means; d. means in the second valve operative in response to a difference in pressure of the fluids in the third and fourth passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure to the second exit passage; and e. means disposed on the first and second pistons preventing movement of the pistons to axial positions effecting the sealing of the third and fourth passages at the second ends of the cylinders.

Claim 15

An overload protection device for a vehicle having a frame, a load carriage mounted on the frame for substantially vertical movement on a mast which is pivotally mounted on the -frame, a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising: a first cylinder having first and second ends and a chamber; a first piston located within the chamber in the first cylinder and movable between the first and second ends; a second cylinder having first and second ends and a chamber; a second piston located within the chamber in the second cylinder and movable between the first and second ends; means adapted for connecting the cylinders and the pistons to the frame and the mast to move the mast relative to the frame in response to movement of the pistons relative to the cylinders; means adapted for connecting the fluid inlet of the circuit to the first end of each of the cylinders; means adapted for connecting the fluid outlet of the circuit to the second end of each of the cylinders; means operative in response to a given difference in pressure between two sources representative of the pressure differential across the first and second cylinders for preventing at least certain tilting movement of the mast relative to the frame; first means for continuously monitoring the highest pressure of the fluids at the first ends of the cylinders and transmitting it to the operative means including: a. means defining first and second passages each having one end communicating with the first end respectively of the first and second cylinders and another end; b. a first valve having first and second ends respectively communicating with the other end of the first and second passages; c. means defining a first exit passage communicating the first valve with the operative means; d. means in the first valve operative in response to a difference in the pressure of the fluids in the first and second passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure with the first exit passage; and e. means disposed on the first and second pistons preventing movement of the pistons to axial positions effecting the sealing of the first and second passages at the first ends of the cylinders; and second means for continuously monitoring the highest pressure of the fluids at the second ends of the cylinders and transmitting it to the operative means including: a. means defining third and fourth passages each having one end communicating with the second end respectively of the first and second cylinders and another end; b. a second valve having first and second ends respectively communicating with the other end of the third and fourth passages; c. means defining a second exit passage communicating with the second valve and the operative means; d. means in the second valve operative in response to a difference in pressure of the fluids in the third and fourth passages for sealing the passage having the lowest pressure and communicating the passage having the highest pressure to the second exit passage; and e. means disposed on the first and second pistons preventing movement of the pistons to axial positions effecting the sealing of the third and fourth passages at the second ends of the cylinders.