JPH0343200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lifting vehicle equipped with a pushing frame;
In particular, the present invention relates to a lifting and transporting device that can transfer a lifted load to a predetermined position at a predetermined speed without requiring any advanced skills from the driver.

Conventionally, when pushing a lifted load forward from a load supporting fork using a push frame, the load placed on the fork must be aligned and transferred on top of another load of the same size, or the load must be accurately placed in a predetermined position. The task of transferring the cargo to the truck was particularly difficult for the operator of the lift vehicle. This problem is due to the fact that it is most difficult to keep the load above the desired transfer position while pushing it forward from the fork, and the reason is that achieving this objective is This is because it is only possible to realize this by moving backward at the same speed as the advance of the push frame. Only a very skilled operator can synchronize these two control functions, namely the forward speed of the push frame and the reverse speed of the lifting vehicle, and most operators do not. I don't get it.

One technology that solves this problem is disclosed in U.S. Patent No.
It is proposed by specification No. 2709531. This specification discloses a lifting vehicle in which a clutch for driving a pushing frame advancing device with wheels is selectively engaged, so that the pushing frame is advanced when the lifting vehicle moves backward. ing. Since this pushing frame advancing means is driven by wheels, the pushing frame advancing speed corresponds to the backward moving speed of the carrier vehicle, and the advancing speed of the pushing frame corresponds to the backward moving speed of the carrier vehicle by a mechanical drive link mechanism from the wheels. can be matched. However, the basic operating principle of such a system, ie, synchronization by obtaining power for advancing the push frame from the wheels of the transport vehicle, has many drawbacks and is not practical for modern cargo handling applications.

The biggest drawback is that the pushing frame cannot be advanced separately from the backward movement of the transport vehicle. Cargo handling operations that require the push frame to advance independently in this way to bring cargo to the appropriate position (for example, when lifting and transporting cargo of various sizes, or when there is an obstacle that requires a lifting vehicle) Since there are many cargo handling operations in which it is not possible to approach the transfer position, the above-mentioned proposed lifting vehicle is not useful for such requests.

Furthermore, this carrier vehicle only matches the advancement speed of the push frame with its backward movement speed, but cannot control the loading and unloading speed of the cargo. Therefore, for example, when an unskilled driver is transporting fragile or heavy loads, the speed may be too high, causing damage to the load, mistakes in transferring the load, or damage to the stack. There is a risk of instability.

Additionally, a clutch engagement operation is required prior to the transfer operation. This extra operation is a waste of time, increases the working time in modern bulk material handling operations, and reduces the overall efficiency of the material handling operation. Furthermore, this extra operation may be inadvertently forgotten and the vehicle is moved backwards, in which case the vehicle must be repositioned and the same operation repeated.

Finally, many pushing frames are now equipped with slip-seat clamps whose clamping and releasing actions are correlated to the advancing and retracting means of the pushing frame, so that the pushing frame advancing operation of the means and the actual movement of the pushing frame can be controlled. Since various time delays are set between advance and advance, it is more difficult to synchronize the speed and movement of the push frame and the transport vehicle, even if the power sources for performing the two functions are not separated from each other, for example. becomes.

In the past, other types of agricultural machines with load pushing mechanisms driven synchronously by the wheels of the vehicle have been proposed, for example, in US Pat. No. 2,531,560 and US Pat. No. 3,110,148. However, these essentially operate on the same principle as the proposed technology,
The above problem cannot be solved.

Therefore, in addition to making the loading and unloading position of the cargo accurate by matching and synchronizing the advance speed of the push frame with the backward speed of the lifting vehicle, it is also possible to operate the carrier vehicle and the push frame using separate power sources. This allows the speeds of the transport vehicle and the pushing frame to match, and to make these speeds a constant scheduled speed. There is a need for an improved lift vehicle to provide the desired synchronization of the movement of the vehicle and pusher frame despite the inherent time delay in advancing the pusher frame due to the release action of the slip seat clamp.

The present invention attempts to solve all of the above-mentioned problems of the prior art by using a different principle to make the advance of the push frame and the backward motion of the carrier vehicle the same speed and synchronize them. When using such an alternative operating principle, there is the additional advantage that the invention can be easily applied to lifting vehicles known in the art with a push frame, requiring only relatively simple additions.

Lifting vehicles with a pusher frame are usually equipped with separate power systems for driving the carrier and for advancing the pusher frame (i.e., a motor for driving the wheels and a hydraulic cylinder for advancing and retracting the pusher frame). are completely individually controlled,
Since they are not mutually synchronized as a whole, these individual power systems and their respective control systems can easily be pushed by the actuation of the hydraulic cylinder for the pushing frame when the vehicle is not moving backwards. A moving frame can be advanced. A device for matching the advancing speed of the pushing frame and the backward moving speed of the carrier without relying on the principle of performing both of these functions with a single power system includes a pushing frame speed controller, which is correlated to the hydraulic cylinder. a vehicle speed controller associated with the vehicle drive motor so that the hydraulic cylinder can maintain a constant speed at which the pusher frame is advanced from the vehicle; This allows the variable transport vehicle reverse speed to be fixed at a constant predetermined speed approximately equal to the push frame advance speed. In this case, the matching of both speeds can be achieved very easily and precisely, and such a speed controller not only allows two separate power systems to survive, but also
To actually set the load transfer speed in advance so that a driver does not need to match the pushing frame speed and the transport vehicle speed with each other, and also eliminates the need to control these speeds. I can do it.
Further, the speed controller according to the present invention is adjustable, so that when carrying out special cargo handling work such as when the cargo is of a special type or heavy, the above-mentioned speed can be set to various values accordingly. be able to.

When using the speed setting and speed matching system according to the present invention, multiple operations are not required, and a synchronization device that responds to the actuation of a hydraulic cylinder that advances the pusher frame moves the carrier when the driver advances the pusher frame. Start reversing at the scheduled speed that is automatically set. Therefore,
Even if the system forgets to switch the truck to reverse,
The unloading position does not become haphazard as in the conventional case, and backward movement of the vehicle can be compensated for by the push frame advancing operation by the push frame hydraulic cylinder. If the push frame is not advanced, the system will not control the vehicle drive motor and the vehicle can be selectively advanced and reversed at various controlled speeds as usual.

The present invention also compensates for the normal time delay that occurs between the movement of the hydraulic cylinder to advance the pusher frame and the actual advance of the pusher frame, which is the time delay that most such pusher frame advancers use to advance the pusher frame. This occurs because it is necessary to release the slip seat clamp before advancing. To provide this compensation, a variable adjustable delay device is used which delays the operation of the speed matching and direction control system by a predetermined amount of time relative to the push frame advance movement of the hydraulic cylinder.

In order to enable the pushing frame to advance even when the transport vehicle is not moving backwards, the speed matching and direction control functions of the drive motor are separated from the pushing frame advancing function so that the drive motor automatically responds to the advancing of the pushing frame. Provide a device that is not subject to physical control.

Therefore, the first object of the present invention is to automatically control the advancing speed of the pushing frame and the reversing speed of the moving vehicle while maintaining independent and individually controllable power sources for advancing the pushing frame and driving the moving vehicle. To provide equipment for matching.

Another object of the present invention is to provide a device of this type that not only allows the advancing speed of the push frame and the backward moving speed of the transport vehicle to match each other, but also allows these speeds to be fixed at predetermined values.

A further object of the present invention is to enable such scheduled speed to be adjusted in accordance with various cargo handling conditions.

Another object of the present invention is to automatically operate the above-mentioned device in response to the advancing movement of the push frame.

Still another object of the present invention is to provide an apparatus in which such automatic operation is delayed by a predetermined amount of time from the advance movement of the push frame to compensate for the time required to release the slip seat clamp.

Yet another object of the present invention is to provide a device for selectively inhibiting such automatic activation if desired.

Furthermore, the present invention enables the above-mentioned device to be installed as an accessory on a lifting vehicle with a push frame, thereby achieving the above-mentioned object.

The invention will be explained below with reference to the drawings.

FIG. 1 shows a typical electric lifting vehicle 10 having drive wheels 12 which are driven by an electric motor to be described later to enable forward and backward movement. A mast 14 for lifting a load is attached to the front side of a transport vehicle 10, and a load support stand 16 is attached to the mast 14 so as to be vertically movable. A load support 1 such as a platen or a pair of forks 18 (only one shown) is attached to the load support 16.
8 to support the cargo 20, and a push frame 22 that can selectively move forward and backward. In many cases, the pusher frame 22 includes a slip seat clamp extending laterally along its bottom edge, which slip seat clamp can automatically close upon retraction of the pusher frame to clamp the load and , can be opened automatically in response to the advance of the push frame. A pantograph link mechanism 24 (see FIG. 2) is used to push the load forward from the fork 18 by advancing the push frame 22, and to pull the load backward onto the fork 18 via the clamp by retracting the push frame 22. This is driven by a hydraulic cylinder that selectively expands and contracts as described below.

FIG. 3 shows the electrical drive circuit of a typical motorized lifting vehicle, such as shown at 10, and the electrical connection panel 2.
Since the entire circuit is well known except for the circuit portion indicated by the broken line below 6 and the line 112a, it will be briefly described. In order to best understand the operation of the present invention, the normal operation of the electric drive circuit for a lifting vehicle will first be described. The electric drive motor, generally indicated at 28, comprises a field winding 30 and an armature 32;
It is coupled to drive wheels 12 via a well-known mechanical drive train (not shown). The speed of the lift vehicle is controlled by a well-known silicon controlled rectifier (SCR) 34, which is connected between the on-board battery and the drive motor 28. An SCR is a solid-state rectifier with silicon as the primary semiconductor material, which operates as a high-speed switch and is capable of providing battery voltage to a motor in the form of variable pulses, thereby providing a variable average voltage to the motor to Speed and transport vehicle 1
You can change the speed of 0. Pulsing of the SCR is controlled by a variable resistor 36, which is controllably connected to the driver's accelerator pedal. If the driver requests full power, full depression of the accelerator pedal closes switch 38, bypassing variable resistor 36.

The direction of drive of the motor 28, and thus the direction of travel of the vehicle, is determined by a forward/reverse switch 40 controlled by the driver. When forward/reverse switch 40 is operated to the upper position, it closes a circuit through line 42 and energizes relay 44, thereby causing associated switches 46 and 48, respectively, to move to the right side as shown in FIG. position, and a current is applied to the field winding 30 in the direction of moving the carrier vehicle forward. Alternatively, if switch 40 is operated to the down position, the switch energizes relay 50 via line 52, causing switch 46,
48 to the left to apply a current in the opposite direction to the field winding 30, thereby allowing the vehicle to move backward. The switch 54 is controlled by an accelerator, and is closed while the accelerator is depressed, that is, as long as the driver desires to drive.
A circuit passing through can be closed.

FIG. 3 further shows a simplified part of the hydraulic circuit of the carrier 10 that advances and retreats the push frame 22, and this hydraulic circuit part is shown connected to the lower side of the hydraulic connection panel 56. . Such parts of the vehicle's hydraulic circuit are completely known, except for the interruption of the hydraulic line 62, which is shown in phantom. During normal operation, the pushing frame 22 is advanced by moving the spool of the manually controlled hydraulic valve 58 to the right in FIG. This activates a battery-powered electric pump 60 via a well-known switching circuit (not shown), which sucks fluid from a reservoir 61, pressurizes it, and discharges it into a circuit 62, which pumps fluid into a hydraulic cylinder. 64 is extended. The piston rod of cylinder 64 is connected by well known means to pantograph linkage 24, which linkage is then extended to advance pusher frame 22. If the transport vehicle 10 is equipped with a slip sheet clamp, right movement of the valve 58 causes the pressurized fluid initially supplied to the conduit 62 to be supplied through the conduit 66, causing the slip sheet clamp cylinder 68 to retract and clamp the slip sheet. Release the clamp. Since the pressure required to release the slip seat clamp is lower than the pressure required to advance the pusher frame 22, the initial contraction of the slip seat clamp cylinder 68 is limited to the pusher frame cylinder for only the amount of time necessary to cause complete contraction of the cylinder 68. 64 initial expansion. This time is the circuit 62
depends on the rate of flow of pressurized fluid through. Conversely, when the spool of valve 58 is operated to the left in FIG. The slip seat clamp is extended and closed.

As is clear from the above description of the known electric drive circuit and push frame hydraulic circuit of a lifting vehicle,
The two systems can be controlled independently as a whole.
That is, the speed and direction of the vehicle are controlled by depression of the accelerator pedal and manual operation of the switch 40, respectively, while the speed and control of the push frame 22 relative to the vehicle is manually controlled by selective movement and adjustment of the valve 58. . Independent operation of these two systems is highly desirable for the reasons discussed above, is useful in many situations, and should be retained. However, when the driving vehicle wants to place the baggage 20 on top of another baggage 21 as shown in FIGS. A high level of skill is required in the operator's department to place the baggage 21 straight and accurately on top of the baggage 21. Normally, the driver moves the carrier vehicle 10 forward so that the cargo 20 is in the position shown in FIG. will be transferred. This operation requires simultaneous operation of the valve 58 and the accelerator so that the retraction speed of the carrier and the advance speed of the pusher frame are equal.
Unfortunately, in most bulk material handling operations, the average lift vehicle driver does not have the level of experience to perform this maneuver successfully or efficiently.

Accordingly, in the present invention, accessories are added to the vehicle 10 to partially modify the well-known electric drive circuit and push frame hydraulic circuit described above with reference to FIG. The added circuit sections are connected above the electrical connection panel 26 and the hydraulic connection panel 56 as shown in a portion of FIG. The attachment includes three electrical circuit and hydraulic circuit breakers indicated by broken lines, and includes an additional electrical circuit 112a.

The hydraulic part of the attachment is preferably provided with a pressure-compensated flow control valve 72 of a known type which is adjustable in various ways and is inserted between the connections 74 and 76 formed by the interruption in the hydraulic circuit 62. However, this circuit 62 is used to supply fluid for extending the cylinder 64 and advancing the push frame 22. Valve 72 maintains fluid through circuit 62 at a predetermined rate of flow, regardless of the position of valve 58 and the load on cylinder 64, thereby setting the advance speed of the pusher frame to a predetermined value, and setting this setpoint to a predetermined value. This can be controlled by adjusting the flow rate control valve 72. Note that the advancement speed of the push frame 22 can also be determined by other methods. For this purpose, for example, a stop whose position can be adjusted is provided on the control handle of the valve 58 operated by the driver, and this stop determines the degree of opening when the valve is operated. 2
The advancing speed of 2 can be controlled. Also, instead of this,
The advancing speed of the pushing frame 22 can also be controlled by determining the pump 60 in various ways in advance so that the flow rate can be controlled. In this case, the valve 58 is made almost impossible to adjust. However, due to the ease of connection to the hydraulic circuit of the transport vehicle, the suitability of the equipment as part of the accessory used, and the insensitivity to changes in load, the flow rate control valve 72 is Suitable for use in control.

The attachment also includes a synchronization switch 7 that is hydraulically controlled.
8, which is biased to the open position by a spring, but which automatically closes in response to pressure within the pilot circuit 80. The circuit 80 leads to the inlet side of the flow control valve 72, and the pressure in this circuit indicates that the operator has operated the valve 58 in the pusher frame advancement direction. For this purpose, for example, a relay switch can be used instead, which is connected to switch 7.
The relay is actuated by another switch provided at position 8 and fixed to the valve 58, so that the relay is energized in response to the operation of the valve 58 in the advancing direction of the pushing frame. However, hydraulic synchronization by switch 78 requires no extra equipment and is therefore preferred when the advance speed of the pusher frame is controlled by a flow control valve such as 72 as part of the accessory.

When the switch 78 closes in response to the operation of the valve 58 in the direction in which the push frame 22 is advanced, a circuit is closed that passes through the normally closed switches 82 and 84 and the line 86, and further passes through the double switch delay relay 88. Ru. Relay 88 may be a well-known solid state delay relay, such as the National Controls Corporation Model TIK-10-462 relay, which can vary in delay time from 0.1 to 10 seconds.
A switch 90 on one side of the relay 88 is interposed between connections 92 and 94 formed by a break in line 96 of the vehicle drive speed control circuit. This switch 90 is herein referred to as a speed selection switch.
The other switch 98 of the relay 88 is inserted between the connections 100 and 102 formed by the interruption in the line 104 of the vehicle forward and backward movement control circuit. This switch 98 is here assumed to be a direction selection switch.

Both switches 90 and 98 are synchronized switch 78
When the vehicle speed and direction control circuit line 96,1 is inactivated as shown in FIG.
The normal circuit through 04 is closed and the speed and direction of the vehicle is controlled normally by the driver. However, when the driver controls the push frame control valve 58 using the cylinder 64,
When operating the pushing frame in the extension direction, the synchronizing switch 78 is closed in response to the supply of pressurized fluid to the circuit 62. This closes the circuit through delay relay 88, which, after an initial time delay preset in relay 88, causes both relay switches 90, 98 to move to the left in FIG. 96,104. Alternatively, the speed selection switch 90 can be set to line 1.
06 to ground through panel 26 and SCR 34 via a variably configurable resistor 108 in line 110.
control. As a result, the variable resistor 36 controlled by the accelerator is replaced by the resistor 108 as means for controlling the speed of the motor 28 via the SCR 34 to a speed corresponding to the resistance value.

Simultaneously with the above-described operation of the speed selection switch 90, the direction selection switch 98 is also moved to the left in FIG.
This interrupts the current flowing through the line 104 of the vehicle direction control circuit. and the current is instead in line 11
2, 112a, bypasses the switches 40, 54 as drive direction control means, and is led to the circuit 52. This current causes the motor switches 46 and 48 to move to the left in FIG. 3, causing the transport vehicle to move backward.
The speed is determined by the setting value of variable resistor 108.

In order to properly adjust and synchronize the speed and direction control functions described above, the rate of flow passing through the variable flow rate control valve 72 must be appropriately set so that the advancing speed of the push frame 22 relative to the carrier vehicle is at a predetermined value. so that it becomes When setting the flow rate control valve 72,
The push frame 22 is actually advanced and the time delay between the actual start of advance of the push frame 22 and the operation of the valve 58 due to the contraction of the cylinder 68 which releases the slip seat clamp is measured. Then, the time delay of the relay 88 is set equal to the measured time delay. Then attached variable resistor 108
is set appropriately so that the backward speed of the transport vehicle becomes equal to the preset advance speed of the push frame 22 with respect to the transport vehicle. Therefore, the driver simply operates the valve 58 in the direction that causes the push frame 22 to move forward, and the entire system is automatically activated to synchronize the transport vehicle with the advance of the push frame 22 and move backward. At the same time, this backward movement speed can be made to match the pushing frame advancement speed.

Appendage switches 82 and 84 are both override switches that selectively allow or disable appendage speed selection and directional control actions. Switch 82 is simply a manual control switch that can be opened by the operator to prevent the system from operating if it is desired to advance the pusher frame regardless of any movement of the vehicle. Switch 84 is controlled by relay 114 which is responsive to the current flowing through switch 54 and line 104 of the vehicle control circuit. If such current is detected, relay 114
opens switch 84 to prevent system operation. This condition occurs, for example, when the valve 58 is inadvertently activated and the push frame is advanced while the driver is depressing the accelerator. When the driver steps on the accelerator, the truck will run during the delay time set in the relay 88, so the truck will move forward even though the relay switch 98 is causing the drive motor to move the truck backwards. will be done.
However, relay 114 and switch 84 sense any such possible conflict and interrupt the automatic synchronization operation before such a conflict occurs. The attached switch 116 selectively connects the relay 8.
Voltage step-down resistor 1 from the operating circuit of 8 and 114
18 can be omitted, and the switch 116 allows attachments to be installed on vehicles with various battery voltages. For example, switch 116 can bypass resistor 118 (as shown in FIG. 3) if the truck has a 36 volt battery, and switch 116 can bypass resistor 118 (as shown in FIG. 3) if the truck has a 48 volt battery. switches to non-bypass position.

Although the system of the present invention is illustrated as being suitably applied to an electric lifting vehicle, the operating principle of the system is equally applicable to a lifting vehicle driven by an internal combustion engine. Such vehicles are equipped, for example, with a presettable engine speed governor as a hydraulically or electrically actuated speed controller, which fixes the engine speed and the vehicle speed, and with a hydraulically or electrically actuated transmission. is provided as a direction controller, and as described above, this is configured to fully automatically move to the backward position in response to the advance of the push frame.

[Brief explanation of drawings]

Figure 1 is a side view of a lifting vehicle with a push frame, with a load lifted by the vehicle in a position where it is to be transferred onto another load, and Figure 2 is a side view of the vehicle shown in Figure 1. FIG. 3 is a partial side view showing a state in which the pushing frame has finished transferring a load onto another cargo. FIG. It is a circuit diagram shown together with accessories to be provided. 10... Lifting vehicle, 12... Drive wheel, 14
... Mast, 16 ... Luggage support stand, 18 ... Fork, 20 ... Luggage, 22 ... Pushing frame, 24 ...
Pantograph link mechanism, 26... Electrical connection panel, 28... Electric motor, 30... Field winding, 3
2... Armature, 34... Silicon controlled rectifier (SCR), 36... Variable resistor, 38... Switch, 40... Forward/forward switch, 42... Line, 44
...Relay, 46,48...Switch, 50...
Relay, 52... line, 54... switch, 56...
... Hydraulic connection panel, 58 ... Manually controlled hydraulic valve, 60 ... Electric pump, 61 ... Reservoir, 6
2... Circuit, 64... Hydraulic cylinder, 66... Conduit, 68... Slip seat clamp cylinder,
72...Pressure compensation type flow control valve, 74, 76...
Connection part, 78...Synchronization switch, 80...Pilot circuit, 82, 84...Normally closed switch, 86...
... line, 88 ... delay relay, 90, 98 ... relay switch, 92, 94 ... connection part, 96 ...
Line, 100, 102... Connection part, 104, 10
6, 110, 112, 112a... line, 108...
...Resistor, 114...Relay, 116...Switch, 118...Voltage step-down resistor.

Claims (1)

[Scope of Claims] 1. A prime mover capable of selectively moving the transport vehicle forward or backward, and a motor provided in association with the prime mover, the drive direction of which can be selectively moved forward or backward by the driver. a first direction control means for controlling the direction; a first speed control means provided in association with the prime mover and allowing the driver to control the forward and backward speed of the prime mover; and a cargo support protruding forward from the transport vehicle. a member, a push frame which is provided on the carrier vehicle so as to be selectively advanced and retractable so as to push the cargo from the cargo support member to the front of the carrier vehicle by advancing from the carrier vehicle; a lifting frame drive means that is connected to and selectively operates so as to move the frame forward and backward; a pushing frame advance detection means that detects a push frame advance operation by the push frame drive means; a second direction control means for driving the prime mover only in a direction in which the transport vehicle moves backward; and a second direction control means for driving the prime mover in the direction in which the prime mover is driven while the pushing frame advancing detection means does not detect advancement of the pushing frame. direction selection means for switching the driving direction of the prime mover to be controlled by the second direction control means while detecting advancement of the push frame; a second speed control means for controlling the speed of the prime mover so that the driving vehicle is moved backward at approximately the same speed as the advancing speed of the pushing frame, and a period during which the pushing frame advancing detection means does not detect advancement of the pushing frame; Speed selection in which the first speed control means controls the backward speed of the transport vehicle by the prime mover, and the second speed control means switches to control the backward speed of the transport vehicle by the prime mover while detecting advancement of the pushing frame. A lifting vehicle characterized by being provided with means. 2. The speed selection means is configured to switch and use a second speed control means in place of the first speed control means during advancement of the push frame in accordance with a detection result by the push frame advance detection means. Lifting vehicle as described. 3. The prime mover is an electric motor, and the first speed control means is a first speed control means that controls power supply to the electric motor.
the second speed control means comprises second electric circuit means for controlling the supply of electric power to the electric motor, and the selectively controlled speed selection means directs the current to the first electric circuit means. 2. A lifting vehicle as claimed in claim 1, further comprising switch means for selectively supplying power to the second electric circuit means. 4. The prime mover is an electric motor, the first direction control means is constituted by a first electric circuit means for controlling the supply of current to the electric motor so that the drive direction of the electric motor can be selected, and the second direction control means comprises second electrical circuit means for supplying current to the motor so as to drive the motor in only one direction;
The selectively controlled direction selection means is constituted by a switch means for selectively supplying current to the first electric circuit means or the second electric circuit means according to the detection result by the pushing frame advance detection means. A lifting vehicle according to claim 1. 5. The direction selection means is connected to and activated by the push frame drive means, and the second direction control means causes the transport vehicle to move backward while the push frame is advanced by the push frame drive means. Lifting vehicles as described in scope 1. 6. A prime mover capable of selectively moving the transport vehicle forward or backward, and a motor provided in connection with this prime mover for selectively setting the drive direction of the prime mover to the forward or reverse direction of the transport vehicle through operation by the driver. a one-way control means; a first speed control means provided in association with the prime mover and allowing the driver to control the forward and backward speed of the prime mover; a cargo support member protruding forward from the carrier; , a push frame that is selectively movable forward and backward so as to push the cargo from the cargo support member to the front of the carrier vehicle by advancing from the carrier vehicle; and a push frame connected to the push frame so that the push frame can advance and retreat the cargo. a pushing frame advancing speed fixing means for setting the advancing speed of the pushing frame by the pushing frame driving means to a constant scheduled speed; a pushing frame advancing detection means for detecting a pushing frame advancing operation by the pushing frame driving means; a second direction control means for driving the prime mover only in a direction in which the transport vehicle moves backward; and a pushing frame advancing detecting means. The first direction control means controls the drive direction of the prime mover while the means does not detect advancement of the push frame, and the second direction control means controls the drive direction of the prime mover while the means detects advance of the push frame. direction selection means for switching to the direction selected by the second direction control means; and a second direction selection means for controlling the prime mover so that while the prime mover is being driven in the direction selected by the second direction control means, the transport vehicle is reversed at approximately the same speed as the advancing speed of the pushing frame. speed control means, and while the pushing frame advancing detection means does not detect advancement of the pushing frame, the first speed control means controls the backward speed of the carrier vehicle by the prime mover, and while detecting advancement of the pushing frame; A lifting vehicle, characterized in that it is provided with speed selection means for switching so that the second speed control means controls the backward movement speed of the transport vehicle by the prime mover. 7. The pushing frame advancing speed fixing means is capable of variously adjusting a certain scheduled advancing speed of the pushing frame, and the second speed controlling means is configured to adjust the backward moving speed of the carrier vehicle to be equal to the pushing frame advancing speed. 7. A lifting vehicle according to claim 6, which can be fixed in various ways. 8. The speed selection means is provided with a synchronization means for switching and using a second speed control means instead of the first speed control means during advancement of the push frame in accordance with the detection result by the push frame advance detection means. range 6th
Lifting vehicle as described in section. 9. The synchronization means is provided with a delay means that delays the operation of the prime mover for moving the carrier vehicle backward in response to the advancing operation of the push frame by the push frame drive means by a scheduled time from the operation of the push frame drive means. A lifting vehicle according to claim 8. 10. The lifting vehicle according to claim 9, wherein said delay means comprises means for variously adjusting said scheduled time. 11. The lifting vehicle according to claim 9, wherein the synchronizing means selectively activates or deactivates the delay means in accordance with the operation of the pushing frame drive means. 12. The lifting vehicle according to claim 11, wherein the pushing frame driving means includes means for selectively advancing the pushing frame while the carrier is not being driven by the prime mover.