GB2069208A

GB2069208A - Prevention of collisions of or between industrial trucks

Info

Publication number: GB2069208A
Application number: GB8103245A
Authority: GB
Original assignee: Jungheinrich Unternehmensverwaltung KG
Current assignee: Jungheinrich AG
Priority date: 1980-02-08
Filing date: 1981-02-03
Publication date: 1981-08-19
Also published as: DE3004671A1; FR2476355A1; GB2069208B; FR2476355B1

Abstract

An arrangement for preventing collisions of or between industrial trucks 2, 3 comprises at least one transmitter and at least one receiver 7, 8, 9, 10 at the front and/or rear ends of the trucks and functional links between the receivers and the drive means of the trucks, wherein the transmitters emit radiation to which the receivers are responsive. Optoelectronic transmitters and receivers are used in the arrangement. <IMAGE>

Description

SPECIFICATION Prevention of collisions of or between industrial trucks description This invention relates to an arrangement for preventing a collision of or between industrial trucks, comprising at least one transmitter and at least one receiver at the front and/or rear end and functional links between the receivers and the drive means of the truck, wherein the transmitters emit radiation to which the receivers are responsive. The invention relates also to an industrial truck provided with such arrangement.

Such vehicles, particularly industrial trucks, such as high-lift trucks, are desirably provided with means for preventing collision. It is known to prevent collision by the provision of transmitters which emit strobiscopicflashes in the direction of travel and receive the reflected flashes and convert them to a signal for controlling or de-energizing the travel drive means. Such arrangements are included.

Such means for preventing collision are particularly important for industrial trucks, such as high-lift trucks, whether these trucks travelling in a passage between shelves are directed by rails or are inductively directed and whether their direction is controlled automatically or by a driver. Means for preventing collision are important in such case because for an optimum utilization of storage shelves the trucks must follow each other in intervals which are as short as possible. Such short intervals between vehicles cannot be ensured by a driver because where a driver is employed, an additional margin of safety will always be required for the drive control to allow for the reaction time of the driver.Besides, the path of travel in straight passages between shelves can be overlooked but this is not possible in a system calling for curved paths of travel, which cannot be supervised by a driver.

The functional links provided between the receivers and the drive means of the vehicle ensure that a signal will be delivered to the control means of the vehicle in time before a safety distance has been reached which is determined by the stopping distance of the vehicle, possibly with an allowance for the load which is carried. Such signal will at least initiate a braking of the vehicle and may particularly de-energize the drive means of the vehicle.

It is an object of the invention so to design an arrangement or truck of the kind described hereinbefore that the distances required to prevent an accident due to a collision will be reliably maintained and particularly an influence of stray radiation will be avoided.

Whereas acoustic waves might be used in accordance with the echo sounding method or with utilization of the Doppler effect, this will not be successful because numerous reflections occur which introduce errors into the signal received by the receiver and because an acoustic coupler cannot generate a narrow radiation lobe. Besides, the velocity of sound in the airvaries highly with temperature.

A radar system might be used but is not included because it involves high costs and is not ready for mass production.

The object is accomplished in accordance with the invention in that an optoelectronic transmitter or transmitters and receiver or receivers are used. The use of optoelectronic transmitters and receivers results in a certain wavelength and an adequate directivity so that stray radiation due to undesired reflections is reduced to such a degree that a useful monitoring is permitted.

It is desirable to use optoelectronic transmitters and receivers which constitute reflected-light sensors, which consist of GaAs sensors for operation with pulsed light. Reflected-light sensors comprise a transmitter for emitting light and a receiver for receiving light that has been reflected by any object that has entered the light emitted by the transmitter and for generating a signal in response to the received light. Whereas reflected-light sensors are reponsive only to signals reflected from a distance up to 2 metres, this may be adequate for various uses and constitutes an application of the invention.

Such reflected-light sensors are commercially available, e.g., under the tradename Leuze Elektronik RK 784 R, and they have transistor and relay outputs and are rather insensitive to extraneous light. Particularly preferred is the use of reflected-light photoelectric detectors, which may consist of GaAs detectors for operation with pulsed light and are commercially available, e.g., under the tradename Leuze Elektronik RK 79 also for larger distances. In a reflected-light photoelectric detector, the reflecting object consists of a high-grade reflector which is secured on the correct level to the obstacle consisting of a vehicle or a wall. This results in a higher directivity.

Both designs constitute preferred embodiments which will prevent a collision. The radiation may be parallel to the longitudinal axis of the vehicle and the transmitter and receiver and, if desired, the reflector may be disposed opposite to each other near one side of a vehicle which precedes or succeeds the vehicle concerned. Such an arrangement involves certain disadvantages even when the distance is controlled by controlling or switching means which are responsive to a reflected signal which is in excess of an adjusted threshold value. The use of such controlling or switching means is included, also the use of such threshold values. The strength of the actually received signals may be strongly changed by external influences, e.g., when the light is travelling along a virtually straight line.

It is an important object of the invention to eliminate such influences and to deliver a control signal to the drive means of the vehicle in response to a certain proximity value, regardless of such influences.

This is accomplished in that at least the transmitter and receiver extend at an angle to the longitudinal axis of the vehicle. Particularly during a travel along a straight line, the angled arrangement will result in an incidence of a strongly increased reflected light flux when the transmitters and receivers and possibly reflectors carried by different vehicles are parallel to each other and their mid-perpendiculars are aligned with each other, which indicates that a certain distance has been reached. This represents a special embodiment of the invention, which permits a detection of a certain distance in dependence on the strength of a signal without need for additional means. A higher accuracy can be achieved in such case by a monitoring with reference to a threshold value. An angular arrangement of reflectors will not be required where corner reflectors are employed.

In a preferred embodiment, a transmitter and receiver are closely spaced apart and are provided at the front and rear ends of vehicles near different sides of the vehicle and an angle a is in each case an acute angle to the longitudinal axis of the vehicle.

This arrangement will result in a transmission of a signal along a diagonal path and a reflection of the signal through the longitudinal axis or the path of travel of the vehicle.

In another desirable embodiment a transmitter and receiver are spaced apart and provided at the front and/or rear end of the vehicle and arranged at the same acute angle P to the longitudinal centre line of the vehicle. A reflector may be included. A reflector for the optoelectronic radiaton may be provided at least at one end (front or rear end) of the vehicle. This arrangement will permit particularly a defined measurement of the distance from an obstacle which is provided with a reflector.

In a desirable embodiment, a reflector may be provided at that end of the vehicle which is opposite to that end of the vehicle where the latter is provided with an optoelectronic transmitter and receiver group and the reflector may be arranged at a suitable angle unless a corner reflector is used. If transmitters and receivers are arranged at an angle on both sides of the centre line of the vehicle in the preferred embodiment, a reflector which is parallel to an end face of the vehicle may be arranged in the central region of that end face. The angled arrangement of the transmitter and receiver will substantially eliminate any extraneous influence, such as of temperature, foreign matter.

In a particularly desirable embodiment applied to a vehicle which has a steering mechanism, at least some of the parts consisting of the transmitter and receiver and any reflector are pivoted and are adapted to be adjusted at an angle to the longitudinal axis of the vehicle in dependence on the position of the steering mechanism. In that case the described arrangement will be effective also when the vehicle is cornering. The angle may be adjusted about an axis that is at right angles to the longitudinal axis of the vehicle.

A preferred embodiment comprises a device which is adjustable about a transverse axis of the vehicle and serves to measure the angle of inclination of the vehicle and drive means for adjusting at least some of the parts consisting of the transmitter, receiver and reflector about a horizontal axis. This will ensure the operation also when the vehicle travels across a threshold or through depressions or the like. Said adjustability may be selected to suit the intended operations in a piant.

Because vehicles may travel at different velocities and may also travel towards each other, the adjust mentofan angle relative to a reflector or a lateral displacement may be used to ensure that the critical distance which will result in a switching of the drive means of the vehicle will be larger and particularly twice as large when vehicles are moving towards each other than when a vehicle is approaching a wall.

This invention relates also to an industrial truck provided with an arrangement as described, i.e., with a transmitter, receiver and reflector, particularly at both ends.

The invention will be described with reference to illustrative embodiments shown on the accompanying drawings, in which Figure 1 is a diagrammatic top plan view showing two vehicles in a passage between shelves; Figure2 shows an improvementovertheembo- diment of Figure 1; Figure 3 is a top plan view showing vehicles embodying a special design and disposed in a passage between shelves; Figure 4 shows a modification which constitutes an improvement over Figure 2; Figure 5 is a diagrammatic top plan view showing a vehicle with an illustration of a steering system of a certain kind; Figure 6 is a diagrammatic top plan view showing two vehicles in a passage between shelves and illustrates another special embodiment.

In all figures, like parts are designated with the same reference characters.

The invention is applicable to vehicles which are railbound or inductively directed or which are steered by a driver or which move in a plant under automatic electronic control. Where a driver is employed and the distances between vehicles are small, he may not always recognize the distance which must be kept in order to safely prevent a collision. The invention is also applicable to vehicles for use in shelf systems which have passages having dead ends, which must be recognized in time.

In accordance with Figure 1, two vehicles 2,3 are disposed in a passage between shelves. Each of said vehicles comprises, e.g., a control section 4 and a load-carrying section 5. An obstacle 6 indicated by a dotted line may be disposed in the passage 1 between the shelves. Each of the vehicles 2, 3 is provided at one end near one side with a reflectedlight sensor, which consists of an optoelectronic transmitter-receiver unit 7,8 or 9, 10. Radiation emitted in the direction of the arrow shown on the drawing will be reflected by an obstacle or by the end of another vehicle and a functional signal derived from the reflected radiation will be delivered to the drive means of the vehicle. A particularly high safety is afforded because the reflected-light sensors 7 to 10 or reflected-light photoelectric detectors are provided at the front and rear ends of the vehicle on different sides of the vehicle so that they will not influence each other. Particularly where reflectedlight photoelectric detectors are employed, a reflector 11,12 or 13, 14 will be provided on the front and rear ends of the vehicle near the other side of the vehicle and a reflector 16 which is responsive to a transmitter-receiver unit 17 may be provided, e.g., on one end wall 15 of the passage between shelves.

The other transmitter-receiver units are designated 18to20.

This arrangement affords a considerable safety because reflected-light photoelectric detectors have a high directivity. A further improvement can be obtained in accordance with Figures 3 and 4, which show an angular arrangement. The embodiment shown in Figure 1 has the disadvantage that the control will be influenced by coefficients of the reflecting object. Whereas this will be prevented in some degree in the embodiment shown in Figure 2, certain influences will also be exerted in the latter embodiment by temperatures, a soiling of the optical systems, etc. In contrast thereto, the embodiments shown in Figures 3 and 4 afford the advantage that the distance which initiates a switching can be detected in an improved manner particularly when the transmitters and receivers and any reflectors employed have a higher directivity.In accordance with Figure 3 the transmitters 21, 22, 23, 24, on the one hand, and the receivers 25, 26, 27, 28, on the other hand, are provided on the end faces near different sides of the vehicle and at the same angle in such a manner that their main directions of transmission and reception cross each other with a predetermined spacing and at an angle a, which means that each transmitter and receiver is arranged at an angle ss to the longitudinal axis of the vehicle. If this embodiment is used in a straight passage 1 between shelves, a reflector 29,30 or 31,32 may be disposed at the center of each end face of the vehicle. A signal beam emitted by a transmitter and deflected by the angle a will be incident on the associated receiver.

Obstacles such as are indicated at 6 in Figure 1 and may be present in a passage between shelves, or the end wall 15 of the passage between shelves, are provided with a centrally disposed reflector 33, which will then also initiate a warning or braking signal.

In the described embodiment, the critical distance will be determined by the angles a and ss and will thus be definite and reproducible.

In accordance with Figure 4, transmitter and receiver groups 34, 35 and 36, 37 are provided at opposite ends of the vehicle on different sides of the longitudinal axis of the vehicle and respective adjacent reflectors 38, 39 and 40, 41 are provided on the end face of the vehicle and may be arranged at a suitable angle or consist of flat corner reflectors. If the transmitter and receiver groups 34 to 37 approach vehicles or an end wall 15 of a passage between shelves so that they will assume such a position relative to a reflector 42 that the reflection takes place substantially along the main direction of light transmission, the receiver will deliver a stronger signal to the drive control means.

In consideration of the angle a it is mentioned with reference to Figure 4 that a signal that is capable of initiating a switching operation can be generated if the distance between two vehicles 2, 3 amounts to 43 orb or if the distance from an end wall 15 of a passage between shelves amounts to 44 or d. In view of the angle a, the transmitter 34 or receiver 35 is spaced from the associated reflector 39 or 40 by the distance a or cat right angles to the longitudinal direction of the passage between shelves. For this reason the critical distance can be determined by the selection of the angle of the transmitter-receiver set on the vehicle and the distance by which the reflector on the vehicle is lateraily offset.This may be expressed by the functions b = arans or d = c/tana For a given angle a, such distance a or c can be selected so that the critical distance 43 or 44 will be twice as large under given conditions, particularly when two vehicles approach each other in opposite directions of travel, as during an approach of a vehicle to a wall 15.

The invention has been described thus far with reference to straight paths of travel. From Figure 5 showing a vehicle 45 it will be apparent that the invention is applicable also to curved paths of travel.

For instance, the vehicle 45 has four steerable wheels 46 to 49, which are adjustable in response to the operation of control or steering means, not shown in detail, by a steering mechanism 50.

Receivers 25 and 28 and transmitters 21 and 24 are coupled to the steering mechanism 50 of the vehicle by functional links 53, so that the direction of the receivers and transmitters is changed when the wheels are steered for cornering. This is shown in Figure 5 only for lateral turns, such as are performed on a level road. In that case the pivotal axes 55, 56, 57, 58 of the transmitters and receivers are vertical. It will be understood that a pivotal movement about horizontal axes can be provided for if a travel across thresholds, bridges or the like is called for in the programme.

Whereas it has been mentioned that the vehicle is to be stopped in order to prevent a collision, Figure 6 illustrates for the embodiment shown in Figure 4 that a switching to a creep speed may be included.

For instance, in accordance with Figure 6 the transmitter-receiver 59 are arranged on the vehicle 3 at an angle a and two reflectors 60,61 are carried by the vehicle 2 on the end face facing the vehicle 3. In that case, light will first fall on the reflector 60 and this will result in a switching to the creep speed. When a further approach then causes light to fall on the reflector 61,the travel drive means will be deenergized. The reflectors can also be arranged at the angle a unless corner reflectors are used but in that case too there will be two reflectors adjacent to each other so that there will be an interruption between the retroreflections at 60 and 61.

Claims

1. An arrangement for preventing a collision of or between industrial trucks, comprising at least one transmitter and at least one receiver at the front and/or rear end and functional links between the receivers and the drive means of the truck, wherein the transmitters emit radiation to which the receivers are responsive, characterized in that an optoelectronic transmitter or transmitters and receiver or receiv ers are used.

2. An arrangement according to claim 1, characterized in that the optoelectronic transmitter or transmitters and receiver or receivers constitute reflected-light sensors consisting of GaAs sensors for operation with pulsed light.

3. An arrangement according to claim 1, characterized in that the optoelectronic transmitter or transmitters and receiver or receivers constitute reflected-light photoelectric detectors, which consist of GaAs detectors for operation with pulsed light.

4. An arrangement according to any of claims 1 to 3, characterized in that at least the transmitter or transmitters and the receiver or receivers are arranged at an angle to the longitudinal axis of the vehicle.

5. An arrangement according to claim 4, characterized in that a transmitter and receiver are closely spaced apart and are provided at the front and rear ends of vehicles near different sides of the vehicle and an angle a is in each case an acute angle to the longitudinal axis of the vehicle.

6. An arrangement according to claim 4, characterized in that a transmitter and receiver are spaced apart and provided at the front and/or rear end of the vehicle and arranged at the same acute angle ss to the longitudinal centre line of the vehicle.

7. An arrangement according to any of claims 4 to 6, characterized in that a reflector for the optoelectronic radiation is provided at least at one end (front or rear end) of the vehicle.

8. An arrangement according to claim 7, characterized in that the reflector is provided on an obstacle, particularly an end of a passage between shelves.

9. An arrangement according to claims 5 and 7, characterized in that a reflector is arranged adjacent to a transmitter and receiver group and at the same angle a two the longitudinal axis of the vehicle.

10. An arrangement according to claim 7, characterized in that the reflector is provided at that end of the vehicle which is opposite to that end of the vehicle where the latter is provided with an optoelectronic transmitter and receiver group.

11. An arrangement according to any of claims 7 and 10, characterized in that a reflector is provided in the central portion of an end face of the vehicle and a transmitter and a receiver are arranged at an angle on both sides of the reflector.

12. An arrangement according to any of claims 1 to 11, for a vehicle comprising a steering mechanism, characterized in that at least some of the parts consisting of the transmitter and receiver and any reflector are pivoted and are adapted to be adjusted at an angle to the longitudinal axis of the vehicle in dependence on the position of the steering mechanism.

13. An arrangement according to claim 12, characterized in that an angular adjustment about an axis which is at right angles to the longitudinal axis of the vehicle is provided for.

14. An arrangement according to claim 12 or 13, characterized by the provision of a device which is adjustable about a transverse axis of the vehicle and serves to measure the angle of inclination of the vehicle and by the provision of drive means for adjusting at least some of the parts consisting of the transmitter, receiver and reflector about a horizontal axis.

15. An arrangement according to any of claims 7, 8, 10 and 12, characterized in that the reflectors comprise corner reflectors.

16. An industrial truck, characterized by an arrangement according to any of claims 1 to 15.

17. An arrangement for preventing a collision of or between industrial trucks substantially as herein described with reference to any of the accompanying drawings.