GB2057377A - Anti jack-knifing coupling system - Google Patents

Abstract

The invention relates to an anti jack-knifing coupling system for coupling a trailer to a towing vehicle, the coupling having a pivot spindle 3 which is rotationally fixed to the trailer 9 and is joined to the towing vehicle 1 by a locking device 2 which can be activated to brake or lock the spindle 3 by a control system which responds to a control signal supplied by a sensing means 15 which detects the condition of operation of the braking system 14 of the vehicle. <IMAGE>

Description

SPECIFICATION Coupling system for coupling a trailer to a towing unit This invention relates to a coupling system for coupling a trailer to a towing unit.

In a known form of coupling of this kind, it is provided that the coupling shaft which is fixed by way of one of its ends to one of the pivotally connected units, namely the towing unit or the trailer, is joined to the other unit way way of a locking device which is activated, so as to assume a locked condition, when the steering mechanism stops or is held stationary in a given position, which may be either the position for travelling in a straight line or any position for turning in one direction or the other. The purpose of this arrangement is to provide a control over the pivotal connection for the purpose of preventing the known phenomena of 'jackknifing', namely, when the pivot connection folds up under the inertia forces of the trailer when the vehicle is braked when in a turning position.

It has been found that, with this system, it may happen that, particularly when leaving a bend, the steering of the towing vehicle may have resumed the rest position for travelling in a straight line, when the longitudinal axis of the trailer is still at a substantial angle to that of the towing vehicle, so that the remaining turning movement of the pivotal connection has to be carried out while subjected to the locking force, which gives rise to corresponding problems in regard to stresses on and damage to the components of the device.

According to the present invention there is provided a coupling for coupling a trailer to a towing vehicle comprising a pivot spindle which is fixed at one end to one of the pivotally connected units of the towing vehicle or the trailer, and which is joined to the other unit by way of a locking device which can be activated so as to assume a condition of braking or locking said spindle in dependence on given operating conditions of the vehicle, the device for braking or locking said spindle being controlled by a control system which responds to a control signal supplied by a sensing means which detects the condition of operation of the braking system of vehicle.

Preferably, the locking device is energised electrically or by pressure fluid from a suitable supply source, by way of a servo control device which responds to the presence of pressure in the braking circuit of the vehicle in order to cause locking ofthe coupling. In both cases, the responses of the servo control device to the presence of pressure in the braking circuit may be based on the 'all-or-nothing' principle, so as totally to lock the pivotal connection when braking begins, or it may act progressively, in accordance with any predetermined law of variation.

Since under given conditions of braking, there may be a reaction by the trailer on the towing vehicle, this effect may also be considered as an error parameter which provides for activation of the locking device so that, in an alternative form of the invention, the servo control device is regulated by a device or means for detecting such a reaction, for the purpose of causing total or gradual actuation of the pivotal connection in response to the presence of such a reaction. Moreover, it is possible to use a combination of these two forms of control action as referred to above. The braking reaction of the trailer on the towing vehicle may also be used in order to modify the braking action on the latter, for example by making it act on the braking circuit of the trailer.In this connection, it may also be necessary to modify the response of the pressure multiplying device in dependence on the load carried by the trailer, by means of the provision of a load-sensing device which is associated with the pressure multiplying device in order to increase the multiplication coefficient proportionately, and in accordance with a predetermined law, with respect to the load on the trailer.

It will be appreciated that this system may be completed by any suitable or necessary additional characteristics which are currently employed in the braking systems in large vehicles, such as deceleration-measuring control means, balancing means or compensating means, skid sensing means, and the like.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawing, in which: Figure 1 shows in elevation a coupling with a pivotal connection between a towing vehicle and a trailer and a locking device based on a rotary hydraulic or pneumatic cylinder, which is mounted on the towing vehicle, the drawing also showing a block diagram which represents a fluid contol system in accordance with the invention, and Figure 2 is a similar view to Figure 1 showing the possibility of installing the locking device in the trailer unit.

Disposed on the chassis or frame 1 of the towing unit (Figure 1) is a locking device 2 for pneumatic or hydraulic braking of the connecting shaft 3 of the trailer 9. Disposed on the chassis or frame 1 is a plate 4 with support members 5 which, by means of bolts members 6, permit rocking movement of the plate 7.

The plate 8 of the trailer 9 is pivotally mounted on the plate 7, with the possibility of being able to rotate about the spindle 3. Fixed to the plate 8 is the spindle 10 while, in addition to the normal safety members which are provided in any trailer of this type, that is to say, the coupling and retaining members, this arrangement also has a special assembly so that the spindle 10 can remain connected without any possibility of turning with respect to the spindle 3. This angular coupling between the members 3 and 10 may be effected in various known way; in the embodiment illustrated, this is achieved by engagement between a square hole in the block 11 and the square base of the end 12 of the spindle 3.

The braking mechanism 2 is subjected to the control actions for locking and unlocking by way of conduits 13 of the system which is shown in the form of a block diagram in the lower part of Figure 1.

In the embodiment illustrated, the desired locking effect between the pivotal connecting members 3 and 10 is produced in dependence on whether there is or is not a pneumatic or hydraulic fluid pressure in the braking circuit 14 of the vehicle, that is to say, the part of the circuit which is directly connected to the means for actuating the brakes on the wheels. For that purposes, a pressure-detecting device or pressure sensor 15 is connected to the circuit 14 and is arranged to supply an electrical or fluid pressure signal which is characterised by two different states, in each one of which it corresponds to one of the operating states, namely the rest state of the braking state, of the braking installation.This signal is produced, by the means which will be described hereinafter, in order to supply the conduits 13 with a locking pressure when there is braking presure in the circuit 14.

Figure 1 shows a hydraulic embodiment of the system. The conduits 13 are connected to the outlet of a change-over valve 16 which has a central rest position for maintaining any operating condition of the system, and two end positions, in one of which the conduit 13 is connected to a supply 17 of oil under pressure, for example by way of a filter 19 from a gear-type or vane-type pump 20 which is actuated by a drive means 21 which may be an independent motor or a coupling device whose input shaft is connected to the engine of the vehicle, and in the other end position of valve 16 the conduit 13 is connected to discharge conduit 18 for pressure oil.

Accordingly, when there is no fluid pressure in the circuit 14the system is in the condition shown, wherein the valve 16 is in its central position and the locking device is unpressurized, or else with a given permanent pressure when it is desired that any tendency of the trailer to swing during travel in a straight line is to be damped.

The valve 16 is controlled by a conventional actuating means 22, which is electromagnetic or fluidic and which is subjected to the control of a control device indicated generally by the block 23, whose internal characteristics may be chosen from those which are usually found in the automation art in accordance with the type of control which is to be provided in each case.

The simplest form would be that of a lifting device for actuating the actuator 22 in the direction of locking under a pressure signal detected by the sensor 15; in that case it is possible to omit the central position of the valve 16 so that the discharge position would correspond to the rest position, or else by providing conventional means, for example, which respond to the transition edge 10 of the pressure signal so as to maintain the discharge position for a predetermined time. Nonetheless, the control device 23 may be designed using conventional arrangements for carrying out other desired functions; for example, by means of line 24 it may control the operation of the drive means 21 so as to maintain in a service accumulator25 a given working pressure controlled by a pressure-detecting means 26 which is connected to the control device 23 by the line 27.It may also be sensitive to other control signal inputs; for example, an input 28 may receive a signal corresponding to the forward thrust force which is applied to the towing vehicle by the trailer under given braking conditions, and another input 29 may introduce in the form of a control a signal which depends on the load condition of the trailer, so as correspondingly to modulate the strength or the slope of the locking and/or unlocking signal applied to the locking device 2. It may also comprise other outputs for modifying the braking operation in other aspects, for example in order to establish a given priority in respect of actuation of the brakes of the trailer; these other outputs which are not shown in the drawing can easily be envisaged by the man skilled in the art.

The system may be completed with other accessories which are conventionally used in the fluid art, for example a damper chamber 30 for damping possible thrust-induced surges on applying the locking action.

Figure 2 shows the same mechanical components of Figure 1 where the locking device 2 is applied to the trailer unit 9. The hydraulic circuit in this embodiment is the same as that described hereinbefore. Moreover, although a hydraulic system was chosen for the purposes of description, it will be appreciated that the system described may be embodied or constructed in an equivalent pneumatic or electrical form, using the corresponding components which are likewise available on the market.

Apart from this, the additional details and other non-essential structural characteristics used in putting the invention into practice will be independent of the subject of the present patent of invention, thereby fully remaining within the scope of the accompanying claims.

Claims (9)

1. A coupling for coupling a trailer to a towing vehicle comprising a pivot spindle which is fixed at one end to one of the pivotally connected units of the towing vehicle or the trailer, and which is joined to the other unit byway of a locking device which can be activated so as to assume a condition of braking or locking said spindle in dependence on given operating conditions of the vehicle, the device for braking or locking said spindle being controlled by a control system which corresponds to a control signal supplied by a sensing means which detects the condition of operation of the braking system of the vehicle.

2. A coupling as claimed in claim 1, in which the sensing means detects the fluid pressure in the braking circuit of the vehicle during braking, and the arrangement in such that the locking device is actuated when the braking action is produced and unlocked when the braking action is terminated.

3. A coupling as claimed in claim 1 or claim 2, in which the locking device is energised with electric current or pressure fluid from a corresponding supply source, by way of a servo control device which responds to the presence of pressure in the braking circuit of the vehicle to produce locking of the pivotal connection.

4. A coupling as claimed in any of claims 1 to 3, including modulating means for modulating the slope of at least the leading edge of the power signal which actuates the device for braking or locking the pivotal connection.

5. A coupling as claimed in any preceding claim, in which the servo control device is controlled by a device or member for detecting a braking reaction of thetowed unit on the towing unit, for causing partial or total activation of the device for locking the pivotal connection, in response to the presence of such a reaction.

6. A coupling as claimed in any of claims 1,2 and 5, in which the braking reaction of the towed unit on the towing unit is used to modify the general braking action of the vehicle.

7. A coupling as claimed in any of claims 1,2,5 and 6, including means which give actuating priority to the brake circuit of the trailer, in response to detection of a braking reaction of the trailer on the towing unit.

8. A coupling as claimed in claim 1, including means for modulating the power signal applied to the device from braking or locking the pivotal connection, in dependence on other operating parameters of the vehicle.

9. A coupling for coupling a trailer to a towing vehicle, substantially as herein before described with reference to and as illustrated in the accompanying drawing.