GB2436452A

GB2436452A - Fork-lift reach truck with vibration compensation

Info

Publication number: GB2436452A
Application number: GB0705153A
Authority: GB
Inventors: Paul John Eckersley; Stephen John Newton
Original assignee: Linde Material Handling UK Ltd
Current assignee: Linde Material Handling UK Ltd
Priority date: 2006-03-21
Filing date: 2007-03-19
Publication date: 2007-09-26
Anticipated expiration: 2027-03-19
Also published as: GB0705153D0; DE102006012982A1; GB2436452B

Abstract

A ground-level conveying vehicle, in particular a fork-lift reach truck, with a vehicle frame (1 fig 1), a lifting structure 7 and at least one movement device such as an actuator such as a linear actuator 16 (19 fig 5) for moving the lifting structure 7 in relation to the vehicle frame 1. An electrical control device is provided for activating the actuator 16 (or 19 fig 5). At least one sensor 20, 21 (or 22, 23, 25 figs 5 and 6) is provided to detect vibratory movement of the lifting structure 7, the sensor may be a force sensor, a relative movement sensor or a hydraulic pressure sensor. The sensor 20, 21 is operatively connected to the control device which activates the at least one actuator 16, (19 fig 5) as a function of the output signal from the sensor 20, 21 in such a way that the actuator 16 (19 fig 5) exerts on the lifting structure 7 a counterforce compensating for vibratory movement. The movement device may be formed by a pushing device for displacing the lifting structure 7 in relation to the vehicle frame 1 in an essentially horizontal direction (9 fig 1) or by an inclination device for movement about an essentially horizontal axis 12.

Description

* 2436452 * Fork-Lift Reach Truck With A Lifting Sfructure The invent

ion relates to a ground-level conveying vehicle, in particular a fork-lift reach truck, with a vehicle frame, with a lifting structure and with at least one movement device for moving the lifting structure in relation to the vehicle frame, the movement device comprising at least one actuator, and an electrical control device being provided for activating the actuator.

Ground-level conveying vehicles of the type mentioned, such as, for example, counterweight fork-lift trucks or fork-lift reach trucks, have a movement device for the lifting structure, by means of which the lifting structure can be moved in relation to a vehicle frame of the ground-level conveying vehicle. In the case of counterweight fork-lift trucks and fork-lift -reach trucks, the movement device provided is often an inclination device for inclining the lifting structure in relation to the vehicle frame about a horizontal axis. The fork-lift reach trucks have in any event, as a movement device, a pushing device, by means of which the lifting structure can be displaced in relation to the vehicle frame in a horizontal direction. In addition to the pushing device, in the case of fork-lift reach trucks, an inclination device for inclining the lift structure in relation to the vehicle frame may likewise be provided.

During the operation of a generic ground-level conveying vehicle, undesirable vibrations of the lifting structure often occur, in particular vibrations about a horizontal transverse axis of the ground-level conveying vehicle and about a vertical longitudinal axis of the lifting structure. These vibrations may impede and slow the handling of the ground-level conveying vehicle. Furthermore, the vibrations adversely influence the safety of the ground-level conveying vehicle, in particular ifs tilting stability and the stability of a picked-up load. These vibrations are caused, for example, by an acceleration or braking of the pushing movement of the lifting mast of a fork-lift reach truck, by cm acceleration or braking of the entire ground-level conveying vehicle or by a rotational movement of the entire ground-level conveying vehicle about a vertical axis. Factors influencing the amplitude and frequency of a vibration of the lifting structure are, for example, the instantaneous extension length of the lifting structure, the lifting height of the load raised by means of the lifting structure, the mass of the lifting structure and the load raised by means of the lifting structure, the rigidity of the lifting structure and also the spacing of the rollers with which the various masts of the lifting structure are guided in relation to one another.

In the prior art, arrangements are known which are aimed at damping vibrations occurring on the lifting structure, for example by means of hydraulic damping elements. It is also known to limit the extent of the vibrations occurring by in particular smoothly accelerating and smoothly braking the pushing movement of the lifting structure of a fork-lift reach truck.

These known measures, however, do not prove to be suitable, in practice, for persistently suppressing vibration of the lifting structure.

The object on which the present invention is based is, therefore, to make available a ground-level conveying vehicle, in which vibrations of the lifting structure can be largely prevented.

This object is achieved, according to the invention, in that at least one sensor is provided, by means of which a vibratory movement of the lifting structure can be detected, the sensor being operatively connected to the control device which activates the at least one actuator as a function of the output signal from the sensor, in such a way that the actuator exerts on the lifting structure a counterforce compensating for vibratory movement. Action is taken actively on the vibratory behaviour of the lifting structure by means of the actuator. For this purpose, the sensor detects any vibration of the lifting structure. The detected measurement values are evaluated in the control device, the magnitude, direction and time profile of the force being determined, this force then being exerted on the lifting structure by the actuator in order to counteract the vibration of the lifting structure.

The invention can be employed particularly advantageously when the movement device is formed by a pushing device for displacing the lifting structure in relation to the vehicle frame in an essentially horizontal direction.

Ground-level conveying vehicles designed in this way are commonly designated as fork-lift reach trucks.

The invention may likewise be employed when the movement device is formed by an inclination device for inclining the lifting structure in relation to the vehicle frame about an essentially horizontal axis of inclination. An inclination device for the lifting structure is normally present in counterweight fork-lift trucks, but often also in fork-lift reach trucks. Fork-list reach trucks may also be equipped with an inclination device in addition to the pushing device, both being movement devices within the meaning of the present invention.

Expediently, the actuator is formed by a linear actuator. For example, an electrically driven threaded spindle or hydraulic cylinder may be considered as a linear actuator.

According to an expedient embodiment of the invention, the at least one sensor is provided for detecting a force acting between the lifting structure and the vehicle frame. The sensor by means of which a vibratory movement of the lifting structure is detected is in this case designed as a force sensor. The force sensor may be arranged, for example. at a bearing point at which the lifting structure is connected to the vehicle frame.

Particularly advantageously, the sensor for detecting a force acting between the lifting structure and the vehicle frame is arranged in the region of the actuator. The forces occurring during a vibration of the lifting structure are transmitted to the vehicle frame via the actuator. Since the counterforces for compensating this vibration are exerted on the lifting structure by the same actuator at the same point, the calculations to be carried out in the electrical control device become particularly simple.

* Vibrations about a vertical longitudinal axis of the lifting structure can be detected and compensated when two actuators are provided, which are arranged parallel to one another, spaced apart from one another in a horizontal direction, each actuator being assigned a sensor for detecting a force acting between the lifting structure and the vehicle frame.

A simple structural arrangement is obtained when the sensor for detecting a force acting between the lifting structure and the vehicle frame is formed by a sensor element arranged between the actuator and the lifting structure or between the actuator and the vehicle frame. The sensor element may in this case be formed by a separate component or may be integrated into a pivoting bearing present in any case at the point mentioned.

If the at least one actuator is formed by an electrical actuator, the sensor for detecting a force acting between the lifting structure and the vehicle frame may be formed by an electric drive motor of the actuator. In particular, a threaded spindle may be considered as an electrical actuator.

The forces supported by the threaded spindle are transmitted directly to the electric drive motor of the threaded spindle and supported by the said drive motor. For example, the force supported on the threaded spindle can then be measured via the motor current of the drive motor, as a result of which the drive motor assumes the function of a sensor.

If the at least one actuator is formed by a hydraulic actuator, the sensor for defecting a force acting between the lifting structure and the vehicle frame may be formed by a hydraulic pressure sensor. The pressure sensor detects the hydraulic pressure which is present in the pressure chamber of the hydraulic actuator and which is directly proportional to the force supported on the actuator.

According to a second embodiment of the invention, the at least one sensor is provided for detecting a relative movement present between the lifting structure and the vehicle frame. In this case, instead of the force acting * between the lifting structure and the vehicle frame, a movement of the lifting structure in relation to the vehicle frame is detected by the sensor.

A torsional vibration of the lifting structure about a vertical longitudinal axis of the lifting structure can be detected when two sensors for detecting a relative movement present between the lifting structure and the vehicle frame are provided, which are arranged spaced apart from one another in a horizontal direction.

Expediently, the at least one sensor is spaced apart from the axis of inclination in a vertical direction. The further the sensor is spaced apart from the axis of inclination, the greater is the relative movement to be measured between the lifting structure and the vehicle frame.

The control device is designed in such a way that the at least one actuator exerts on the lifting structure a counterforce directed counter to a vibration of the lifting structure about a horizontal transverse axis. The actuator or actuators is or are activated correspondingly by the control device. In this case, a vibration of the lifting structure about a horizontal transverse axis is prevented, and, in ground-level conveying vehicles with a inclinable lifting structure, the transverse axis may be formed, for example, by the axis of inclination of the lifting structure.

For this purpose, the control device is designed in such a way that the counterforce has a periodic profile, preferably at least approximately at the frequency of the vibratory movement of the lifting structure. The periodic profile of the counterforce may in this case be in-phase or out-of-phase with respect to the vibratory movement of the lifting structure. The amount of the exerted counterforce may correspond to the force determined by means of the sensor and acting between the lifting structure and the vehicle frame.

If Iwo actuators of variable length are provided, the control device is designed in such a way that the two actuators exert on the lifting structure a countermoment directed counter to a vibration of the lifting structure about a vertical axis. Vibration about the vertical axis occurs in the case of a torsional vibration of the lifting structure. The two actuators are activated correspondingly by the control device.

The control device is designed in such a way that the countermoment has a periodic profile, preferably at least approximately at the frequency of the vibratory movement of the lifting structure. The periodic profile of the countermoment is in this case likewise in-phase or out-of-phase with respect to the torsional vibration of the lifting structure. The amount of the exerted countermoment may correspond to the moment which acts between the lifting structure and the vehicle frame and which is determined by means of Iwo force sensors.

Further advantages and particulars of the invention are explained in more detail by means of the exemplary embodiments illustrated in the diagrammatic figures. in which: Figure 1 shows a side view of a fork-lift reach truck; Figure 2 shows a device for a horizontal displacement of a lifting structure; Figure 3 shows a fork-lift reach truck with a lifting structure vibrating about a horizontal transverse axis; Figure 4 shows a fork-lift reach truck with a lifting structure vibrating about a vertical axis; Figure 5 shows a device for inclining a lifting structure; and Figure 6 shows a fork-lift reach truck with sensors for detecting a relative movement between the lifting structure and the vehicle frame.

Figure 1 shows a side view of a fork-lift reach truck. The vehicle frame 1, on which a driver's stand 2 and a battery block 3 are arranged, can be seen.

The vehicle frame 2 stands with two load beams 4 and one driving wheel 5 on a runway 6. A lifting structure 7 is guided displaceably in a horizontal direction 9 on the vehicle frame 1 by means of a pushing slide 8. The lifting structure 7 has a non-raisable stand mast 7a and two telescopically extendable extension masts 7b, 7c. The lifting structure 7 is illustrated by * unbroken lines in its position displaced completely towards the driver's stand 2. The broken lines show the position 10 of the lifting structure 7 when the latter is displaced completely to the left in the drawing.

During the operation of the fork-lift reach truck, undesirable vibrations of the lifting structure 7 may occur, in particular vibrations in the direction 1 1 about a horizontal transverse axis 12 of the fork-lift reach truck and torsional vibrations in the direction 13 about a vertical longitudinal axis 14 of the lifting structure 7.

Figure 2 illustrates a device for the horizontal displacement of a lifting structure 7. The lower part of the stand mast 7a of the lifting structure 7, the said lower part being mounted pivofably about the transverse axis 12 on a pushing slide 15, can be seen. The pushing slide 15 is guided on guide rails of the vehicle frame 1 by means of guide rollers, not illustrated. The pushing movement of the pushing slide 15 is generated by means of a linear actuator 16 which is connected in an articulated manner, on the one hand, to the pushing slide 15 and, on the other hand, to the vehicle frame 1. The actuator 16 may be formed, for example, by a hydraulic cylinder or a threaded spindle. Sensors for defecting a force acting between the lifting structure 7 and the vehicle frame 1 may be arranged, for example, at the points 20 or 21. The counferforce with which vibrations of the lifting structure 7 are compensated may be exerted on the lifting structure 7 be means of the actuator 16 in accordance with an electrical control device, not illustrated.

In order to detect torsional vibrations of the lifting structure 7 and to counteract them, two actuators 16 are provided, which are arranged in such a way that they conceal one another in the present view.

Figure 3 illustrates a top view of the fork-lift reach truck. In particular, the vehicle frame 1, the load wheels 4, the driving wheel 5 and the lifting structure 7 can be seen. The amplitude of the top side of the lifting structure 7 in the event of a vibration about the horizontal axis 12 is illustrated, exaggerated, by dotted lines 17.

* Figure 4 shows the view according to Fig. 3, the vibration of the lifting structure 7 about the horizontal axis 12 having superposed on it a torsional vibration of the lifting structure 7 about the vertical axis 14. The amplitude of the topside of the lifting structure 7 is illustrated, likewise exaggerated, by dot-and-dash lines 18.

Figure 5 shows, in the view according to Fig. 2. a device for inclining a lifting structure 7. The stand mast 7a of the lifting structure 7 is mounted on the pushing slide 15 inclinably about the transverse axis 12. The force required for inclining the lifting structure 7 is generated by means of a linear actuator 19 which is connected in an articulated manner, on the one hand, to the pushing slide 15 and, on the other hand, to the stand mast 7a. Sensors for detecting a force acting between the lifting structure 7 and the vehicle frame 1 may be arranged, for example, at the points 22 or 23. The counterforce with which vibrations of the lifting structure 7 are compensated may also be exerted on the lifting structure 7 by means of the actuator 19 in accordance with an electrical control device, not illustrated. In order to detect torsional vibrations of the lifting structure 7 and to counteract them, two actuators 19 are provided, which are arranged in such a way that they conceal one another in the present view.

Figure 6 illustrates the fork-lift reach truck in the view according to Figure 1.

The spots depicted identify the possible installation locations for a sensor 25 for defecting a relative movement present between the lifting structure and the vehicle frame. Each sensor 25 may have, for example, a potentiometer which converts the movements of the lifting structure occurring during a vibration of the lifting structure into an electrical signal.

Claims

O Claims 1. A ground-level conveying vehicle, in particular a fork-lift

reach truck, with a vehicle frame, with a lifting structure and with at least one movement device for moving the lifting structure in relation to the vehicle frame, the movement device comprising at least one actuator, and an electrical control device being provided for activating the actuator, characterised in that at least one sensor is provided, by means of which a vibratory movement of the lifting structure can be detected, the sensor being operatively connected to the control device which activates the at least one actuator as a function of the output signal from the sensor, in such a way that the actuator exerts on the lifting structure a counterforce compensating for * vibratory movement.

2. A ground-level conveying vehicle according to Claim 1, characterised in that the movement device is formed by a pushing device for displacing the lifting structure in relation to the vehicle frame in an essentially horizontal direction.

3. A ground-level conveying vehicle according to Claim 1 or 2, characterised in that the movement device is formed by an inclination device for inclining the lifting structure in relation to the vehicle frame about an essentially horizontal axis of inclination.

4. A ground-level conveying vehicle according to one of Claims 1 to 3, characterised in that the actuator is formed by a linear actuator.

5. A ground-level conveying vehicle according to one of Claims 1 to 4, characterised in that the at least one sensor is provided for detecting a force acting between the lifting structure and the vehicle frame.

6. A ground-level conveying vehicle according to Claim 5, characterised in that the sensor for detecting a force acting between the lifting structure and the vehicle frame is arranged in the region of the actuator.

7. A ground-level conveying vehicle according to Claim 5 or 6, characterised in that Iwo actuators are provided, which are arranged parallel to one another, spaced apart from one another in a horizontal direction, each actuator being assigned a sensor for detecting a force acting between the lifting structure and the vehicle frame.

8. A ground-level conveying vehicle according to one of Claims 5 to 7, characterised in that the sensor for detecting a force acting between the lifting structure and the vehicle frame is formed by a sensor element arranged between the actuator and the lifting structure or between the actuator and the vehicle frame.

9. A ground-level conveying vehicle according to one of Claims 5 to 7, characterised in that the at least one actuator is formed by an electrical actuator, and the sensor for detecting a force acting between the lifting structure and the vehicle frame is formed by an electric drive motor of the actuator.

10. A ground-level conveying vehicle according to one of Claims 5 to 7, characterised in that the at least one actuator is formed by a hydraulic actuator, and the sensor for detecting a force acting between the lifting structure and the vehicle frame is formed by a hydraulic pressure sensor.

11. A ground-level conveying vehicle according to one of Claims 1 to 10, characterised in that the at least one sensor is provided for detecting a relative movement present between the lifting structure and the vehicle frame.

12. A ground-level conveying vehicle according to Claim 11, characterised in that Iwo sensors for detecting a relative movement present between the lifting structure and the vehicle frame are provided, which are arranged spaced apart from one another in a horizontal direction.

13. A ground-level conveying vehicle according to Claim 11 or 12, characterised in that the at least one sensor is spaced apart from the axis of inclination in a vertical direction.

14. A ground-level conveying vehicle according to one of Claims ito 13, characterised in that the control device is designed in such a way that the at least one actuator exerts on the lifting structure a counterforce directed counter to a vibration of the lifting structure about a horizontal transverse axis.

15. A ground-level conveying vehicle according to Claim 14.

characterised in that the control device is designed in such a way that the counterforce has a periodic profile, preferably at least approximately at the frequency of the vibratory movement of the lifting structure.

16. A ground-level conveying vehicle according to one of Claims I to 15, characterised in that two actuators of variable length are provided, and the control device is designed in such a way that the two actuators exert on the lifting structure a countermoment directed counter to a vibration of the lifting structure about a vertical axis.

17. A ground-level conveying vehicle according to Claim 16, characterised in that the control device is designed in such a way that the counfermoment has a periodic profile, preferably at least approximately at the frequency of the vibratory movement of the lifting structure.