Reach truck

Abstract

A reach truck 1, comprising a main body 10, at least one load arm 70, which protrudes from the main body 10, a mast trolley 20, which is supported at the at least one load arm 70, wherein the mast trolley 20 is shift-able along a longitudinal axis 100 of the reach truck 1 relative to the main body 10, a mast 30, which is attached to the mast trolley 20, a linear actuator 50, for shifting the mast trolley 20 along the longitudinal axis 100 relative to the main body 10, wherein the linear actuator 50 is attached at a first end 52, A thereof to the main body 10 and at a second end 54, C thereof to the mast trolley 20, and the linear actuator 50 is arranged inclined to the longitudinal axis 100 of the reach truck 1 and defines a first angle between the extension direction of the linear actuator 50 and the longitudinal axis 100, wherein the first angle changes depending on the position of the mast trolley 20 relative to the main body 10, and the reach truck 1 further comprises a sensor 60, for determining the angular position of the linear actuator 50.

Claims

1. A reach truck, comprising: a main body; at least one load arm that protrudes from the main body; a mast trolley that is supported at the at least one load arm, wherein the mast trolley is shift-able along a longitudinal axis of the reach truck relative to the main body; a mast that is attached to the mast trolley; a linear actuator configured to shift the mast trolley along the longitudinal axis of the reach truck relative to the main body; wherein the linear actuator is attached at a first end thereof to the main body and at a second end thereof to the mast trolley; and the linear actuator is arranged inclined to the longitudinal axis of the reach truck and defines a first angle between the extension direction of the linear actuator and the longitudinal axis of the reach truck, wherein the first angle changes depending on the position of the mast trolley relative to the main body; and the reach truck further comprises a sensor communicating with a control unit, wherein the control unit is configured to determine the angular position of the linear actuator.

2. A reach truck according to claim 1, wherein the linear actuator comprises a hydraulic piston that is controlled by an electronic proportional hydraulic valve.

3. A reach truck according to claim 2, wherein the sensor comprises a length measuring device that is hinged at a first end thereof to the main body and at a second end thereof to the linear actuator.

4. A reach truck according to claim 1, wherein the sensor comprises a length measuring device that is hinged at a first end thereof to the main body and at a second end thereof to the linear actuator.

5. A reach truck according to claim 4, wherein the measuring direction of the length measuring device differs from the extension direction of the linear actuator.

6. A reach truck according to claim 1, wherein the position of the mast trolley along the longitudinal axis of the reach truck relative to the main body is calculated as follows: $d=\frac{a}{\tan },$ wherein a is a distance between the longitudinal axis that goes through the first end of the linear actuator and the second end of the linear actuator, and a is the angle between the extension direction of the linear actuator and the longitudinal axis of the reach truck.

7. A reach truck according to claim 1, wherein the first angle is calculated as follows: $=\arccos \left(\frac{x^2+z^2-y^2}{2\mathrm{xz}}\right)-$ wherein is the angle between the extension direction of the linear actuator and the longitudinal axis of the reach truck; x is a distance between the first end of the linear actuator and the first end of a length measuring device; y is a length, which is detected by the length measuring device, and which is a distance between the first end of the measuring device and the second end of the measuring device; z is a distance between the first end of the linear actuator and the second end of the length measuring device in the extension direction of the linear actuator; and is a second angle, which is the angle between the longitudinal axis of the reach truck, which goes through the first end of the linear actuator, and x.

8. A reach truck according to claim 1, wherein the control unit controls a movement speed of the mast trolley based on the position of the mast trolley along the longitudinal axis of the reach truck relative to the main body.

9. A reach truck according to claim 8, wherein the control unit calculates the position of the mast trolley along the longitudinal axis of the reach truck relative to the main body from information received from the sensor.

10. A reach truck according to claim 9, wherein the control unit automatically controls a maximum movement speed of the mast trolley based on the position of the mast trolley along the longitudinal axis of the reach truck relative to the main body according to a predetermined profile.

11. A reach truck according to claim 1, wherein the sensor is an angle sensor.

12. A reach truck according to claim 11, wherein the angle sensor is attached near to the first end or near to the second end of the linear actuator.

13. A reach truck according to claim 1, wherein the angular position of the linear actuator and/or the position of the mast trolley along the longitudinal axis of the reach truck relative to the main body is continuously detected during movement of the mast trolley.

14. A reach truck according to claim 13, wherein the control unit continuously controls the maximum movement speed of the mast trolley based on the continuously detected position of the mast trolley along the longitudinal axis of the reach truck.

Description

4. BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, preferred embodiments of the present invention are disclosed by the use of the accompanying figures, in which shows:

(2) FIG. 1a is a schematic side view of a reach truck according to an embodiment of the invention, wherein the mast trolley is located near to a main body;

(3) FIG. 1b a schematic side view of the reach truck of FIG. 1a, wherein the mast trolley is located spaced apart from the main body;

(4) FIG. 2a a schematic top view of the arrangement of a linear actuator and a length measuring device according to an embodiment of the invention, when the mast trolley is located spaced apart from the main body;

(5) FIG. 2b a schematic top view of the arrangement of FIG. 2a, when the mast trolley is located near to the main body;

(6) FIG. 2c a schematic top view of another arrangement, when the mast trolley is located near to the main body;

(7) FIG. 3 a sketch, which describes the mathematic correlations of the length, which is determined by the length measuring device, with a first angle and a position of the mast trolley along the longitudinal axis relative to the main body of the reach truck;

(8) FIG. 4a a diagram of a first v/d-profile of the mast trolley; and

(9) FIG. 4b a diagram of a second v/d-profile of the mast trolley.

5. PREFERRED EMBODIMENTS OF THE INVENTION

(10) In the following, preferred embodiments of the invention are explained in detail with respect to the figures. However, it is obvious for the person skilled in the art that features of specific embodiments may be also provided to other embodiments, even if this is not explicitly shown in following explanations:

(11) FIG. 1a shows a schematic side view of a reach truck 1 according to the invention, wherein the mast trolley 20 is located near to a main body 10. In FIG. 1b the mast trolley 20 is located spaced apart from the main body 10. The reach truck 1 comprises a main body 10 comprising an overhead guard 12, a steering member 14, wheels 16, a control unit, an energy source and a drive for one or more of the wheels 16. In the embodiment of FIGS. 1a and 1b, a user sits on the main body 10, where he or she is protected by the overhead guard 12 in view of falling goods. The steering member 14 is connected to the control unit, wherein the user is able to control the reach truck 1 by the steering member 14. The steering member 14 may be any suitable steering device like a joystick, a keyboard, a mouse, a touchscreen, paddles and the like. The reach truck 1 furthermore comprises three or more wheels 16, wherein at least one wheel 16 is driven and may be rotated around a vertical axis, in order to change the driving direction of the reach truck.

(12) Moreover, the reach truck 1 comprises two load arms 70 protruding from the main body 10 to the front and thus defining a longitudinal axis 100 of the reach truck 1. However, it is obvious for the person skilled in the art, that the inventive concept of the present invention may be also realized in a reach truck 1 with a different configuration of the front. In the embodiment of the present invention, the load arms 70 are arranged symmetrically to each other. For the sake of stability and for the sake of handling convenience it is advantageous to maximize the distance between the two load arms 70 that support the front wheels 16 at their outermost end. In between the load arms 70 a base plate 80 is provided in order to provide further stability and in order to provide fixation members as desired. The base plate 80 and the load arms are members of and integral with the main body 10 of the reach truck 1.

(13) The reach truck 1 furthermore comprises a mast trolley 20, which is slide-able on the load arms 70, in particular on tracks (not shown), which are provided at the load arms 70. A mast 30 is attached to the mast trolley 20, wherein the mast provides a vertical actuator 42 for extending the mast and for shifting a fork 40 in the vertical direction.

(14) FIG. 2a shows a schematic top view of the arrangement of a linear actuator 50 and a length measuring device 60 according to one embodiment of the invention. In FIG. 2a the mast trolley 20 is located spaced apart from the main body 1 whereas in FIG. 2b the mast trolley 20 is located near to the main body 10. A first end 52, A of the linear actuator 50 is hinged to the main body, particularly to the base plate 80 by means of a hinge comprising a vertical hinge axis. A second end 54, C of the linear actuator is hinged to the mast trolley 20 by means of a hinge comprising a vertical hinge axis. When the linear actuator 50 extends the mast trolley 20 moves forward along the longitudinal axis 100. The linear actuator 50 is arranged inclined by an angle to the longitudinal axis 100 of the reach truck 1. During an extension movement of the linear actuator 50, the first angle between the extension direction of the linear actuator 50 and a longitudinal axis 100, which goes through the first end 52, A of the linear actuator 50, decreases. This angular movement of the linear actuator 50 corresponds to the movement of the mast trolley 20 along the longitudinal axis 100 of the reach truck 1 relative to the main body 10. Thus, the angular position of the linear actuator 50 can be used as a variable value for the determination of the actual position of the mast trolley 20 relative to the main body 10.

(15) In the embodiment of FIG. 2a the angular position of the linear actuator 50 is determined by a length measuring device 60, which is hinged at a first end 62, E thereof to the main body 10 by means of a hinge comprising a vertical hinge axis. At a second end 64, D of the length measuring device 60 it is hinged to the linear actuator 50 by means of a hinge comprising a vertical hinge axis.

(16) In the embodiment of FIG. 2a the linear actuator 50 is a hydraulic piston. Supply tubes (not shown) supply hydraulic liquid from a pump assembly (not shown) for extending and retracting the hydraulic piston 50.

(17) As it can be seen from a comparison of FIGS. 2a and 2b the length of the length measuring device 60 changes. Particularly, the distance between a reference point of the base plate (namely the position of 62, E of the length measuring device 60) and a reference point at the linear actuator 50 (namely the second end 64, D of the length measuring device 60) changes, when the mast trolley 20 is moved. In this preferred embodiment, the length measuring device 60 is arranged on the base plate 80 of the main body 10 and below the mast trolley 20, so that the mast trolley is able to move freely above the length measuring device 60.

(18) In the embodiment of FIG. 2c, the angular position of the linear actuator 50 is directly determined by an angle sensor 53, attached at first end 52, A. In other embodiments, the angle sensor 53 may be attached at or near second end 54, C. Angle sensor 53 is in communication with a control unit. Angle sensor 53 is configured to directly measure the angle .

(19) FIG. 3 shows a sketch, which describes the mathematic correlations of a length y, which is measured by the length measuring device 60, with a first angle and a position d of the mast trolley along the longitudinal axis 100 relative to the main body 10 of the reach truck 1. A designates the first end 52 of the linear actuator 50. B designates a point, which is the projection of A along the longitudinal axis 100 to the mast trolley 20. C designates the position of the second end 54 of the linear actuator 50, which is attached to the mast trolley 20. D designates the position of the second end 64 of the length measuring device, which is hinged at the linear actuator 50, preferably at the cylinder of the piston. E designates the first end 62 of the length measuring device 60, which is hinged to the base plate 80. a marks the distance between B and C. The distance a is defined during the design of the reach truck 1 and does not change during movement. d designates the distance between A and B, wherein d also characterizes the position of the mast trolley 20 relative to the main body 10. d is perpendicular to a. x designates the distance between A and E. x is defined during the design of the reach truck 1 and does not change during movement. y is the length, which is detected by the length measuring device 60. y is the distance between the first end 62 of the measuring device 60 and the second end 64 of the measuring device 60. z designates the distance between A and D. z is defined during the design of the reach truck 1 and does not change during movement. designates the first angle between the line segment AC and the line segment AB. varies depending on d, i. e. the position of the mast trolley along the longitudinal axis 100. designates a second angle between the line segment AB and the line segment AE, wherein is also defined during the design of the reach truck 1 and does not change during movement. designates a third angle between the line segment AC and line segment AE, so that
=+
results. is calculated from y by the following equation:

(20) $=\arccos \left(\frac{x^2+z^2-y^2}{2\mathrm{xz}}\right)-.$

(21) The position d of the mast trolley 20 along the longitudinal axis 100 is calculated from as follows:

(22) $d=\frac{a}{\tan }.$

(23) The above-mentioned calculations are carried out by the control unit (not shown), which is preferably arranged in the main body 10. The result of the calculations, i.e. the values or d, are preferably used for a position control and/or a speed control of the mast trolley 20.

(24) FIGS. 4a and 4b show diagrams of a first and a second v/d-profile of the mast trolley 20, wherein v designates the speed of the mast trolley 20 during its movement relative to the main body 10 and d is the position of the mast trolley 20 along the longitudinal axis 100. FIG. 4a shows a speed profile 90, wherein the maximum allowable speed increases linearly in a range from 0 to a position d.sub.1 up to a maximum speed V.sub.1 and wherein the speed of the mast trolley 20 also decreases linearly from a position d.sub.2 when the end of the admissible range of movement d.sub.3 is reached. This speed profile limits the maximum allowable speed of the mast trolley at both ends of the movement ranges and provides a soft stop of the movements at the end positions.

(25) FIG. 4b shows another speed profile 92, wherein the maximum speed of a mast trolley 20 increases exponentially up to the maximum speed V.sub.1. At the end of the admissible range of movement d.sub.3 of the mast trolley 20, the speed of the mast trolley 20 decreases exponentially down to zero. Such a speed profile again limits the maximum allowable speed of the mast trolley at both ends of the movement ranges and provides a soft stop of the movements at the end positions but provides an overall faster movement of the mast trolley from one end position to the other end position.

LIST OF REFERENCE SIGNS

(26) 1 reach truck 10 main body 12 overhead guard 14 steering member 16 wheels 20 mast trolley 30 mast 40 fork 42 vertical actuator 50 linear actuator 52, A first end of the linear actuator 54, C second end of the linear actuator 60 length measuring device 62, E first end of length measuring device 64, D second end of length measuring device 70 load arms 80 base plate 90 speed profile 92 speed profile 100 longitudinal axis