JPS5911519B2 - Overload protection device using differential pressure sensing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overload protection device for a vehicle having a load carrying member mounted for movement relative to a frame by two or more motors.

1 by a pair of motors in the form of double-acting, fluid-actuated piston-cylinders mounted on the frame and struts.
Strut lodging is a problem for vehicles such as lift trucks that have a load bearing member or strut rotatably mounted about an axis on a frame that moves back and forth in two vertical planes.

Attempts to solve this problem include overload protection devices that prevent further movement of the column relative to the frame when the moment created by the load on the column tends to cause the column to collapse. .

One such device is described and illustrated in U.S. Pat. No. 3,007,593.

The device of this patent includes a valve that engages when the difference in fluid pressure across one piston of a piston cylinder exceeds a predetermined value.

The action of this valve prevents further increase in forward lodging moment by preventing further forward movement of the strut.

The value of the fluid pressure difference corresponds to the force acting on the piston rod of the piston cylinder due to the load.

This force acting on the piston rod then corresponds to a forward moment that collapses the column.

Such overload protection devices are of great convenience, but they do not occur when there is a misaligned or improperly adjusted cylinder and piston rod, i.e. one piston contacts its cylinder end sooner than the other. If you do,
Problems arise when the piston cylinder providing the fluid pressure differential signal fails or when loads are applied unevenly to the struts.

The invention relates to any type of vehicle that includes a load-bearing member, such as a strut, spar, or arm, movable relative to the vehicle frame by at least two motors connecting the load-bearing member and the frame. Applicable.

A feature of this invention is that the forces acting on the two motors that attempt to move the load-bearing member are sensed, and a signal is generated indicating the magnitude of the force acting on each motor.

These signals are compared and the one exerting the greatest force is transmitted to the mounting device, which stops further movement of the load-carrying member when the transmitted signal exceeds a predetermined value. Operate.

Another feature of the invention is that the motor includes a double-acting fluid-actuated piston cylinder having a first and second end, sensing the fluid pressure at the first end of each cylinder and sensing the fluid pressure at the second end of each cylinder. An apparatus is provided for transmitting a maximum pressure hail signal to a valve receiving the hail signal.

This valve precludes further movement of the load-bearing member relative to the frame when this signal differs from the determined manner.

According to another feature of the invention, the signal from the second end of the cylinder indicates the maximum fluid pressure at the second end.

According to another feature of the invention, the fluid pressure at the first end of each cylinder is constantly monitored and this signal reflects only the highest existing pressure at any point at any given time.

An embodiment of the invention is shown in the drawings.

The industrial lift truck 10 of FIG. 1 includes a frame 12 supported on a pair of rear steering wheels 14 and a pair of front drive wheels 16. The industrial lift truck 10 of FIG.

Strut 18, which is mounted for pivotal movement about the axis of wheel 16, has a pair of stationary upright channel members 20 connected by support members 22.

A bracket 24 is coupled to the lateral portion of each channel member 20 to which is pivotally mounted one end of a motor piston rod 26 in the form of a double-acting, fluid-actuated piston cylinder 28, said piston cylinder being located at its bottom. It is pivotally coupled at the end to a bracket 30 of the frame 12.

The two piston cylinders 28 are identical in structure,
In addition, the column 18 is tilted back and forth from the vertical position.

A driver's cab is attached to the rear of the support column 18, and this driver's cab includes a driver's seat 32 attached to the frame 12 and a steering handle 3.
4 and a tilt selection control device 36 for controlling the operation of the piston cylinder 28.

The strut 18 is raised and lowered in a known manner by a double-acting lift piston cylinder 40 using a lift selection control 42 of known design.
including.

Briefly, the operation of the circuit shown in FIG.
This is based on the fact that the moment tending to collapse the piston rod 8 forward is proportional to the tensile force acting on the piston rod 26.

The tensile force acting on each piston rod is then shown as being related to the magnitude of the force exerted on each side of the piston by fluid pressure acting on both sides of the piston of each piston cylinder 28.

This concept is described in U.S. Pat. No. 3,007,593, as well as some of the construction and operation of the hydraulic circuit of FIG.

The circuit of FIG. 2 includes a pump (
(not shown).

Line 46 connects tilt selection control device 36 to piston rod 2.
6 and is connected to the full area side 48 of the tilting piston 50 disposed within the piston cylinder.

The entire area side of each piston 50 is connected to each line 5.
4t56 to both sides of a shutoff valve 58 of known design.

The line 60 connects the central outlet of the shutoff valve 58 to the tilt limit valve 6.
It is connected to the pressure chamber 62 in 4.

The block side 66 of the piston 50 is connected to the tilt limit valve 64 via lines 68,70.

The block-shaped side of each piston 50 further includes lines 72.74.
are respectively connected to opposite sides of a shutoff valve 76 of known design.

The central outlet of the shut-off valve 16 is connected via a line 80 to the pressure chamber 18 within the tilt limit valve 64 .

One type of shutoff valve that can be used is the one manufactured by KepnerProd Company of Summit, Illinois.
uct3 Co, Summit I 1lino
One example is the 2456C-1 type manufactured by IS).

The tilt limit valve 64 includes a piston 82 biased toward a full area side 84 by a helical compression spring 86 disposed within the pressure chamber 62 .

A full area side 84 of piston 82 communicates with chamber 62 .

A spool 88 defining an annular peripheral chamber 90 is coupled to piston 82 and slidably disposed within tilt limit valve 64 .

Pressure chamber 78 communicates with one side 92 of spool 88 .

The ratio of the area of side 92 to the total area of side 840 is equal to the ratio of the area of side 48 to the area of side 66 of each piston 50.

When spool 88 is in its normal position shown in FIG. 2, peripheral chamber 90 communicates with line 70 and line 94.

Another line 96 connects line 94 and slope selection control device 3.
6.

An outlet line 98 connects the slope selection control device 36 to a reservoir (not shown).

Bypass line 100 passes through line 68 to piston 5G
to the block-shaped side 66 of and connected to line 94.96.

Line 100 includes a non-return valve 102 through which fluid flows into line 100 only from lines 94,96.

Front and rear stops 104, 106 are provided on the block side 66 and full area side 48 of each piston, respectively.

In each piston cylinder 28, stops 104 and 106 respectively seal the lines 68, 46 as the piston 50 approaches the respective end of the cylinder.

When each line is sealed, it prevents contact with the piston's "bottoming" or cylinder end, and retains a volume of fluid under pressure between the piston and the cylinder end.

Lines 54,56°72.74 are not sealed by stops 104,106.

To tilt the strut 18 forward from the vertical position, the tilt selection control 36 is moved to a position where line 44 joins line 46 and line 96 joins line 98.

Fluid contacting full area side 48 of piston 50 moves the piston to the left in FIG.

Fluid on the block side 66 of the piston 50 is routed through line 68
, the line 70 passes through the peripheral chamber 90, and if the spool 88
If it is in the normal position, it flows into the storage tank through line 94, line 96, slope selection device 36, and line 98.

To move strut 18 rearward from the vertical position, tilt selection control 36 is moved so that lines 44 and 96 and 98 and 46 are connected.

Fluid flowing through line 96 flows through line 94, peripheral chamber 90 and line 10 if the spool is in the normal position.
through line 68 to the block side 66 of piston 50, and if not in the normal position, through non-return valve 102 and line 100, and so on.

Fluid is discharged from the full area side 48 of the piston 50 via line 46, slope selection control 36 and line 98 to a reservoir.

The pressure on the block side 66 of the piston 50 is in line 72.74.
The ball 1 acting on the shutoff valve 76 through the
Press 08 to seal the line transmitting the lowest fluid pressure,
and the line transmitting the highest fluid pressure to the central outlet, line 80 and the slope limit valve 640 to the spool 8 via the chamber 78.
It communicates with the side part 92 of 8.

The fluid pressure on the full area side 48 is transmitted to the shutoff valve 58 via lines 54,56.

The line with the highest fluid pressure pushes against the bulb 110 of the shutoff valve 58 to seal off the line with the lowest fluid pressure.

The highest fluid pressure present on side 48 is thereby transmitted to full area side 84 of piston 82 via central outlet, line 60 and chamber 62.

When the force acting on the spool 88 due to the fluid pressure in the chamber 78 exceeds the resultant force of the force acting on the spool 88 due to the fluid pressure in the chamber 62 and the force of the spring 86, the spool 88 is moved from its normal position to the outer peripheral chamber 90 in line. 70 and 94 to a blocking position.

The spring constant and preload of the spring 86 is such that the outer chamber 90 is aligned with the lines 70, 94 when the moment tending to topple the column 18 of the truck 10 is slightly less than the moment required to topple the column 18. selected so that it deviates from the

As the peripheral chamber 90 moves out of alignment with the lines 70, 94, fluid flow from the annular side 66 of the piston 50 is prevented, thereby causing further protrusion of the piston rod 26 of the piston cylinder 28 and the strut. 18 and thus prevents an increase in moment.

When spool 88 is in the blocking position, piston cylinder 28 is in line 44 and line 96 as well as line 46.
and from the traction and backward movement of the strut 18 due to the connection with the line 98.

Such line coupling results in fluid flowing through line 96 past one-way check valve 102 and then through line 100.68 to the annular side 66 of piston 50.

If communication in line 70.94 is not closed by spool 88, fluid is forced through circumferential chamber 90 and line 68 into the annular side of piston 50.

By using shutoff valves 58 and 76 to sense fluid pressure on the annular side and/or full area side of series-acting piston cylinder 28 , the two from each respective side of piston 50 to tilt limit valve 64 The higher of the two fluid pressures is transmitted.

This effect can be caused by improper loading of the struts, failure of one of the stops 104, 106 of each piston cylinder 28, or failure of one of lines 54, 56 or line 72.
．． In the event of a failure of one of the lines 74, the spool 88 will work properly.

Although shutoff valves 58,76 are shown at each end of piston cylinder 28, shutoff valves 58 may be omitted if only strut 180 collapse is considered.

When a lodging moment exists in the strut 18, a relatively high fluid pressure exists on the annular side 66 of the piston 50 and a relatively low pressure exists on the full area side 48 of the piston.

The highest fluid pressure present on the annular side 66 of the piston must be delivered to the side 92 of the spool 88 at the same time as the lower pressure is delivered from the full area side of the piston to the side 84 of the piston 82 to prevent collapse.

If there is no pressure on the side 84, the spool 8
8 will start exercising earlier than planned.

Although this early movement will affect the workability of the vehicle, it will not cause the column 18 to collapse.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a lift truck having an embodiment of the invention, and FIG. 2 is a plan view of a portion of the fluid circuit used to tilt the column of the lift truck shown in FIG. 10... Lift truck, 12... Frame, 14... Steering wheel, 16...
Drive wheel, 18... Strut, 20... Groove-shaped member, 26... Piston rod, 28...
... Piston cylinder, 36 ... Inclination selection control device, 38 ... Fork stand, 40 ...
...Double acting lift piston cylinder, 42...Lift selection control device, 48...Piston full area side,
50...Tilt piston, 58...Shutoff valve, 62...Pressure chamber, 64...Tilt limit valve, 66... Piston annular side, 76...
...Shutoff valve, 78...Pressure chamber, 82...
... Piston, 84 ... Piston full area side, 88 ... Spool, 90 ... Annular outer peripheral chamber, 92 ... ... Side of spool, 100...
...Bypass line.

Claims (1)

[Claims] 1. A traveling frame, a load-bearing member attached to a column tiltably attached to the frame so as to be movable up and down,
A vehicle overload protection device having two laterally spaced motors that connect a frame and a column and operate the column to tilt the column relative to the frame, the device comprising: a member that generates a signal that indicates the amount of force required for each motor to maintain the motor in a predetermined position, and a member that transmits a signal that indicates the largest force by comparing the signals from each motor. , the transmission member receives the transmitted signal, and when the transmitted signal causes the force to become larger than the set force, the motor stops operating, and the support column changes the direction in which the force acts on the frame. An overload protection device using a differential pressure sensing method, characterized by comprising a member that suppresses tilting. 2. a traveling frame, a load-bearing member movably attached to a column tiltably attached to the frame,
a first having first and second ends coupled to a frame and a post;
, second piston cylinders, the cylinders being laterally spaced apart, and in response to fluid entering one chamber and fluid exiting the other chamber with respect to the piston of each cylinder. A vehicular overload protection device having a piston cylinder that operates to move a column against the piston, and a fluid circuit for flowing fluid to one chamber and collecting fluid from the other chamber with respect to the piston of each cylinder, the device comprising: first and second members transmitting a signal to the actuating member to detect the highest fluid pressure in the chambers at the first and second ends of the cylinder;
an overload protection device comprising: a member that operates to inhibit tilting of a support column in at least one direction due to movement of a piston in response to a difference between two signals; 3. An overload protection device having a running beam, a load carrying member attached to a column tiltably attached to the frame, and a fluid transmission circuit having a fluid outlet and a fluid inlet, the a first cylinder having an end and a chamber; a first piston disposed within the chamber of the first cylinder and movable between the first and second ends; and a first cylinder having first and second ends and the chamber;
a second cylinder disposed laterally apart from the first cylinder; and a second cylinder disposed within the chamber of the second cylinder;
a second piston movable between ends, the cylinder and the piston being coupled to the frame and the column for tilting the column relative to the frame in response to movement of the first and second pistons relative to the first and second cylinders; a connecting member for alternately connecting a fluid inlet and an outlet of the circuit to each end of each cylinder; and a first member for generating a signal indicative of maximum fluid pressure at the first and second ends of the cylinder. , a second transmitting member, and a member that operates to inhibit tilting of the column in at least one direction due to the movement of the first and second pistons depending on the difference between the two signals. Features overload protection device.