WO1995024321A1

WO1995024321A1 - Guide-and-locking unit for use in two-coupling vehicles

Info

Publication number: WO1995024321A1
Application number: PCT/GB1995/000504
Authority: WO
Inventors: Shane Patrick Clarke
Original assignee: Clarke, Valerie, Dawn, Rose
Priority date: 1994-03-08
Filing date: 1995-03-08
Publication date: 1995-09-14
Also published as: GB9404442D0; GB2287232B; GB2287232A; AU1855795A

Abstract

A two-coupling assembly based upon conventional two-coupling parts e.g. cup (1) and ball (2) includes a guide and locking unit comprising a male member (3) and mating female member (4) interposed between the ball (2) and mounting bracket (5) on the tug-vehicle, the male member (3) being retracted into mating engagement with female member (4) by tensioning a cable (13) by operation of a winch mechanism (14, 15) and then locking the mated male and female members together by means of locking pins (17a and 17b).

Description

GUIDE-AND-LOCKING UNIT FOR USE IN TOW-COUPLING VEHICLES

This invention relates to a guide and locking unit for use in tow-coupling an automotive tug-vehicle to a trailer- vehicle .

Tow-couplings are well known two-part vehicle

5 accessories, one part of which can be either built into an automotive tug-vehicle during manufacture thereof, or subsequently attached thereto as an accessory, while the other part is also similarly built into or subsequently attached to a trailer-vehicle. As a

10 generalisation it is probably true to say that trailer- vehicles are usually purpose-built and thus tend to have one part of such a two-part tow-coupling already in-built during manufacture, but (while the same may be true of tug-vehicles intended for commercial,

15 agricultural &c. use) with tug-vehicles built for domestic-type use usually the other part of any two- part tow-coupling is a bolt-on accessory, not in-built during manufacture but fitted afterwards.

There are a number of existing forms of tow-

20 couplings, and so far as known all of them (with perhaps one exception, mentioned hereinafter) have to be manually connected up - that is to say the two vehicles have to be brought into close conjunction as accurately as possible, and thereafter coupled together

25 by physically lifting one of the tow-coupling parts into coupling engagement with the other by hand. Bringing the two vehicles into the correct relative conjunction can be very difficult and thus time- consuming, while the lifting of one tow-coupling part

30 onto the other is at best quite tiring and at worst may be beyond the physical strength of some people, especially when the trailer vehicle is heavily loaded.

Attempts have indeed been made to alleviate the vehicle-positioning problem by enabling one of the

35 vehicles, probably the trailer, to be winched under power into couplable conjunction with the other vehicle.

Arrangements of this nature have been disclosed in British Patent No. 2,092,536 B and International Publication No. WO 93/17886, both of which go some way to solve the problem of bringing the two vehicles into couplable conjunction, though not in an elegant and robust fashion... but neither of them even attempts to address the problem of thereafter actually coupling them together.

There are indeed other previously-suggested arrangements which seek to address the problem of not merely bringing the vehicles into conjunction but also actually coupling them together, see Australian Patent No. 553,313, United States Patent Nos . 5,005,852, 5,048,854, 4,807,899 and 4,466,632 British Patent Specification No. 2,252,290 A and European Publication No. EP 0,136,017 A, but none of these previous proposals guarantees the ease of attachment between tug and trailer which is needed if the use of this kind of device is to become widespread.

It is the object of this invention to devise a way of establishing a tow-coupling between a tug-vehicle and a trailer-vehicle which more nearly approaches the ideal inasmuch as it will simultaneously provide both ease of coupling up conventional two-part tow-couplings of various different kinds, and also avoid problems of vehicle-alignment. These and other desirable objectives are attained by the provision and use of the new or improved guide and locking unit as more fully described hereinafter.

According to one aspect of this invention there is provided a guide and locking unit, primarily for use in conjunction with one part of a two-part tow-coupling capable of establishing a towing connection between a tug-vehicle and a trailer-vehicle, said guide and locking unit (in either assembled or kit form) comprising: a generally-concave female member, a generally convex, counterpart male member capable of self -alignment with said female member and when thus aligned being brought into mating engagement therewith, substantially all of the respective mating surfaces of the female and counterpart male members being convergent in the direction of mating engagement so that they are completely juxtaposed only when in full mating engagement, and so constructed as to be incapable of any significant mutual rotation with respect to each other about the axis of their engagement when the respective members are in full mating engagement, additional means, external of the female member and which do not mate with the male member, to facilitate self-alignment and mating engagement of the male and female members even when they are drawn together in a non-axial direction, locking means associated with both members operable when they are aligned and in full mating engagement with each other releasably to secure them together, one of said members being adapted to be attached both to one part of the two-part tow-coupling and also to a flexible tensor, and the other of said members being adapted to be attached to one of the respective vehicles and also apertured to accommodate passage of said flexible tensor aforesaid through said aperture so that such flexible tensor when attached to one of said members and passing through the aperture in the other said member may be utilized to draw the respective male and female members together, bringing them into alignment and finally into full mating engagement with each other, in order that they may then be locked together by said releasable locking means.

This invention is not primarily concerned with the vehicle-coupling device as such, which may be of any locally- or internationally-approved type. However in the United Kingdom there are at present three main types, namely those generally known as being of the cup-and-ball type, the pin-and-eye type and the military-hitch type, all of which can be used (perhaps with some slight modification) for the purposes of this invention.

It is preferred that it is the female member which is adapted for attachment to the tow-vehicle, and the male member which is adapted for attachment to one part of the two-part tow-coupling. It is likewise preferred that it is the member adapted for attachment to the tow-vehicle which is the apertured member that accommodates passage of the flexible tensor. While it is possible to envisage the use of virtually any such flexible tensor, it will normally take the form of the kind of multi-strand steel-wire cable already employed in vehicle towing winch mechanisms, and merely as a matter of brevity the flexible tensor will therefore hereinafter be referred to as "the cable".

While it is not impossible for the cable to be retracted in some other manner, clearly it will normally be associated with a winching mechanism operable to retract it through the aperture and thereby draw the respective members into full mating engagement with each other. Of course the winching mechanism could be hand-operable, but again it will normally be power-operable directly or indirectly from the prime- mover of an automotive tug-vehicle. The female member and the counterpart male member should be so constructed as to be incapable of any significant mutual rotation with respect to each other about the axis of their engagement when the respective members are in full mating engagement with each other. This is conveniently achieved by so constructing them that the female member and the counterpart male member share only a single plane of symmetry passing through the axis of the cable and normally (i.e. when mounted on a vehicle standing on an horizontal surface) lying in the vertical plane. A simple, effective and therefore desirable arrangement is one in which one of the members is adapted for attachment to the cable by abutment means provided within a bore therein which coacts with a stop member provided on the cable to prevent its withdrawal beyond the abutment means in one direction but leaves it free to be withdrawn in the other. It is a much preferred feature of the invention that the bore should be so constructed and located within said member relative to the tow-coupling part attachable thereto that the cable is capable of withdrawal from the bore and extension to serve in the manner of a conventional winching mechanism. In that event the free end of the cable will usually be equipped with a conventional attachment device, e.g. a hook. The releasable locking means can be of any convenient type, including e.g. spring-loaded latches and corresponding detents or the like, but a safe and effective arrangement which is therefore currently preferred comprises at least one keyhole bore (as herein defined) through each of the members which respective bores are aligned when the male and female members are in full mating engagement, and one or more corresponding pin(s) removably insertable through the aligned bore(s) transverse to the axial direction of mating engagement so as thereby to lock the male and female members against disengagement during use of the unit in the tow-coupling of two vehicles.

At this point it should be noted that the term "keyhole bore" is here used to embrace not only fully- circular (or other cross-section) bores passing wholly through one member and then through the other but also semi-circular (or other cross-section) channels formed simultaneously in opposed faces of the respective members when they are in full mating engagement, and indeed the latter arrangement is currently recommended. For reasons of safety and in order to equilibrate the stresses on the unit it is very desirable for there to be a pair of parallel keyhole bores through each of the male and female members, axially spaced apart equidistant one on either side of the axis of mating engagement of the male and female members but in a plane substantially normal thereto, and for the releasable locking means to comprise two pins, each adapted for insertion and removal from one of said keyhole bores when the respective male and female full mating engagement.

For ease of handling, it may be advantageous for the two pins to be integrated together via a handle into a dual-pin arrangement which facilitates their insertion and removal. Also, in order to provide a degree of flexibility in the way in which the unit is employed (bearing in mind the need to accommodate the unit to use upon a variety of different vehicles) it may be preferable to provide two separate pairs of parallel keyhole bores through each of the male and female members, one such pair being arranged in the horizontal plane and the other in the vertical plane. In that event, the spacing between the bore-axes in each pair of bores can advantageously be the same as each other and the same as that between the pin-axes, so that when employing an integrated dual-pin arrangement as mentioned above it can be inserted and withdrawn at will either horizontally or vertically.

As so far described the invention is centred on a new or improved guide and locking unit, but seeking now to set that unit in a wider context (as it will be used) there are also provided, according to other aspects of the invention, a variety of tow-coupling assemblies for establishing a towing interconnection between an automotive tug-vehicle and a trailer- vehicle, all of these assemblies including a guide and locking unit as hereinbefore generally or specifically described, in conjunction with:

-a mounting for normally-fixed attachment to one of said vehicles; and/or

-the other part of a two-part tow-coupling, with or without an associated mounting for normally fixed attachment to the other of said vehicles; and/or

-a flexible tensor in the form of a multiple- strand steel-wire cable passing through one of the respective male and female members in their mating direction and in use being attached to the other; and/or

-winch mechanism mounted on or adjacent the automotive tug-vehicle and power-operable at will directly or indirectly from the prime mover of the automotive tug vehicle.

Conveniently the winch will be powered by a D.C. electric motor adapted to run off the tug vehicle's normal electric system and under the command of controls remote from the immediate vicinity of the motor and external to the tug vehicle. For reasons of operator-safety it is best if the controls are connected to the electric motor via a cable of such length as to permit the operator to stand clear of both the tug and trailer vehicles as they are coupled together.

In order that the invention shall be better understood some preferred embodiments thereof will now be described in more detail, though by way of illustration only, with reference to the accompanying drawings, in which: Figure 1 is a schematic, part-sectional, part- elevational side-view of one preferred embodiment of the entire tow-coupling assembly of this invention, based upon a conventional cup-and-ball tow-coupling, the assembly being shown in place between a tug-vehicle and a trailer-vehicle and with the guide and locking unit held in full mating engagement by horizontally- disposed locking pins;

Figure 2 is a rather diagrammatic side-view of part of the embodiment of tow-coupling assembly of Figure 1, though on a larger scale, but now with the guide and locking unit no longer mated but instead separated and inter-linked only by an extended cable;

Figure 3 is a part-sectional, part-elevational side-view on an enlarged scale of another generally similar but alternative embodiment of the guide and locking unit, still based upon the conventional cup-and-ball tow-coupling but now with the locking pins disposed vertically;

Figure 4 is a part-elevational, part-sectional view, generally similar to that shown in Figure 3, of yet another embodiment based however here on the conventional pin-and-eye tow-coupling;

Figure 5 is cross-sectional view, in the horizontal plane, through the guide and locking unit illustrated in Figure 3, in a near-mated posture;

Figure 6 shows elevational views of alternative types of locking pins, Figure 6A being a single pin and associated retaining clip while Figure 6B illustrates a dual-pin device; Figure 7 is a perspective view of a modified but otherwise conventional slider-plate assembly for interposition between the guide and locking unit of this invention and the normal tow-bracket on a tow- vehicle, so as to permit height adjustment when this is desirable; Figure 8 is a perspective view of the pin-and-jaw part of the pin-and-eye tow-coupling already part- illustrated in Figure 4;

Figure 9 is a perspective view of another conventional tow-coupling part, of the so-called "military-hitch" type of tow-coupling; and

Figure 10 is a perspective view of a preferred kind of tow-coupling part for use in the guide and locking unit, which combines both the pin and jaws of a pin-and-eye tow-coupling and also the towball of a cup- and-ball tow-coupling, further modified to permit the whole assembly of the present invention (when not in use for tow-coupling tug and trailer vehicles) to be employed in the manner of a conventional vehicle- mounted winch. Referring to Figure 1, it will be seen that on a trailer vehicle (not shown) there is the cup unit 1 of a conventional cup-and-ball tow-coupling, in the already-engaged position with the towball unit 2 of that type of tow-coupling. The ball unit 2 is fixedly attached (by bolts, not shown) to the rear of a male member generally indicated 3 which (as shown in Figure 1) is in full mating engagement with a female member generally indicated 4 which in turn is fixedly attached by retaining bolts (not shown) onto the rear of mounting bracket 5, which in turn is affixed in any conventional manner e.g. by a bolt 6 to the underside of the chassis-member carrying the rear-bumper (fender) 7 of a tug-vehicle (shown in part only, and generally indicated 8) and elsewhere to another chassis-member (not shown) of that vehicle.

The female member 4 (as seen better in Figure 3) includes a basal flange 9 around its periphery with apertures 10a, 10b &c to accommodate the retaining bolts (not shown), and also outwardly splayed lips 11 around its orifice which is open to admit the male member 3, and when they are in full mating engagement (as shown) the mating surfaces of the respective male and female members are closely juxtaposed. At its other end and centrally of flange 9 the female member 4 has an aperture 12a which communicates with a corresponding aperture 12b provided in the bracket 5, and through these aligned apertures 12a and 12b there passes a multi-strand steel-wire cable 13.

The inner end of cable 13 is wound on to the drum 14 of a conventional winch mechanism generally indicated 15 which is (as shown in Figure 1) bolted onto a forward part of the mounting bracket 5, in such a position that the cable 13 extends from the drum 14 in a straight line through apertures 12b and 12a (the latter being fitted with a phosphor-bronze or like bush 16 (see Figure 3) and is then secured to the male member 3 in a manner which will be described in more detail subsequently.

The fully-mated male member 3 and female member 4 in the embodiment of Figure 1 are locked together by horizontally-disposed pins 17a and 17b. However, in the slightly-modified, alternative embodiment shown in Figure 3 (and indeed also Figure 4) the pin(s), there denoted 18, are disposed vertically (as currently preferred) rather than horizontally. In the embodiment of Figures 3 and 4, the vertically-disposed pin(s) 18 is/are retained in locking position against accidental removal by means of one or more spring clip(s) 19.

In the embodiment of Figure 4, although the construction is otherwise identical the towball coupling part of Figure 3 has been exchanged for the pin-and-jaws tow-coupling part generally indicated 20, of a largely-conventional pin-and-eye tow-coupling, which however is modified as compared with the conventional one by provision of an aperture 21 through which the cable 13 can pass. In all Figures 1-4 above the male member 3 is shown in vertical cross-section, but referring now to Figure 5 both the male member 3 and the female member 4 are there shown in horizontal cross-section... and indeed on a larger scale, so that it can more readily be seen that the cable 13 is provided with a crimp or other stop member 22 disposed within a larger-diameter "wide" bore 23 formed in the rearward face of the male member 3 and communicating with a smaller-diameter "narrow" bore 24 in the forward edge of the male member 3, which narrow bore 24 is aligned and communicates with the aperture 12 in the female member 3, thus enabling the cable 13 to pass through aperture 12, narrow bore 24 and into wide bore 23, within which is accommodated the stop member 22 crimped to cable 13. Thus cable 13 is prevented from being withdrawn in the forward direction by abutment between stop member 22 and the constriction at the point at which wide bore 23 meets up with narrow bore 24. In this way tension applied to cable 13 by drum 14 of winch mechanism 15 draws stop member 22 and thus the male member 3 into full mating engagement with female member 4.

However, on release of tension in cable 13 it may be extended in the opposite direction, thus allowing male member 3 to be withdrawn entirely from engagement with female member 4, and indeed much extended to serve other functions as will be hereinafter described.

Still referring to Figure 5, it will be noted that male member 3 is equipped with two keyhole bores 25a and 25b and that correspondingly female member 4 is equipped with keyhole bores 26a and 26b (shown in dotted outline) which come into alignment when male member 3 is fully mated with female member 4, and through which when thus aligned can be inserted locking pins 18 (see Figures 3 and 4) to hold the male and female members in fully-engaged and releasably locked condition.

Referring now to Figure 6, it will be seen that the separate pins which coact with the respective aligned bores 25a, 26a and 25b, 26b, can be two single pins 27 with a spring retaining clip 28 as shown in Figure 6a, or a dual-pin arrangement 29 wherein the two pins are integrated together via a single handle 30 and held in locking engagement by a single spring clip 31, as illustrated in Figure 6b.

For certain purposes it may be desirable for the bracket-mounted female member 4 to be adjustable in height relative to vehicle-mounting bracket 5. If so this may be achieved by means of the slider arrangement generally indicated 32 as shown in Figure 7, which comprises a bracket-attachment back-frame 33, which is to be bolted to bracket 5, and a vertically-slidable front-plate 34, adjustable in height relative to back- frame 33 but fixable relative thereto by means of locating pin 35, retained by split pin 36, onto which front-plate 34 in turn the female member 4 may be bolted. The arrangement as thus far described is essentially conventional, but for the purposes of the present invention the front-plate 34 must be slightly modified by the inclusion of an elongate slot 37, which is needed to accommodate passage of cable 13 therethrough, no matter at what level slider plate 34 is set. There is no need to modify back-frame 33, since this in the conventional construction will already accommodate passage of cable 13 between the upper and lower bars (not visible in Figure 7) which hold it together.

As already previously indicated, the guide and locking unit of this invention, and indeed the whole assembly including other components, have the advantage that they may be employed with any of the known two- part tow-couplings which are currently in widespread use. The application of this invention to the conventional cup-and-ball type of tow-coupling has already been illustrated in Figures 1-3, and the use of the pin-and-jaw part of the conventional pin-and-eye tow-coupling has been part-illustrated in Figure 4. However,in order to illustrate these possibilities still further it will be seen that Figure 8 shows the same pin-and-jaw arrangement as that already part- illustrated in Figure 4, but now showing a perhaps better view of the upper jaw 38 and lower jaw 39, with the vertical bore 40 (see Figure 4) and passing therethrough a pin 41, retained in situ by split pin 42... and which, incidentally, is safe-guarded against accidental loss by retaining chain 43. It will be noted that in Figure 8 the cable 13 is shown dangling out of the aperture 21 (see Figure 4) for purposes which will be further described below.

Figure 9 illustrates a third type of conventional tow-coupling part currently used in Britain and elsewhere, especially by the Military... and therefore often known as a "Military hitch" . Here the tow- coupling part comprises a back plate 44 (which can be bolted, if necessary through an adapter plate [not shown], to the rear face of male member 3) and on this back-plate 44 there is mounted a lower hook 45 into which the other part of the Military hitch tow-coupling (not shown) is lifted for engagement, and then held in place there by upper retaining member 46.

The currently preferred tow-coupling part for use in the guide and locking unit of this invention, and indeed the whole assemblage as herein described, is illustrated in Figure 10. As will be seen, this essentially conventional but very flexible and therefore recommended device combines the features of both the cup-and-ball tow-coupling and the pin-and-jaw tow-coupling, having jaws 38 and 39 (as in Figure 8) with a vertically-disposed bore 40 (as in Figure 4) through which the pin (not here shown) can pass to establish a pin-and-eye connection; but it also, on upper jaw 38, has a towball 41 which enables it also to serve as part of a cup-and-ball tow- coupling. As indicated, this preferred device as so far described is already known, and may be obtained from Dixon Bate... .

However, for the purposes of this invention the known version of this device should best be slightly modified by provision of the aperture 22 (see also Figure 4) through which passes cable 13, carrying crimped stop member 22, and on the end of cable 13 a hook device 42.

Having thus described both the general assemblage and also various preferred embodiments of the guide and locking unit of this invention, its purposes and advantages should be already largely apparent, but some of the more significant ones of them can appreciated from a further consideration of the drawings, especially Figure 2 , and the following observations .

The guide and locking unit is suitable for use with any conventional two-part tow-coupling, so all existing fittings can be readily modified to operate in the manner now proposed. Thus , whether in-built during manufacture of the vehicle , added on afterwards as a bo l t -on f itment or mere ly incorporated as a modification into an existing fitment, the assemblage can be utilized for all normal existing purposes , e .g. in connecting/ disconnecting and towing of e . g . any towabl e s i z e s of 2 - and 4 -whee l open trai l ers , including boat trailers , caravans , sheep trailers , horse boxes and even car-transporters.

By declutching the winch drum from the winch mechanism and withdrawing the locking pins the cable can be run out - either for instance to launch a trailer-mounted boat without the need for the tug- vehicle to enter the water, or to retrieve it from the water. The extendibility of the cable, carrying on its end one part of the two-part tow-coupling, is of great utility not merely in boat-retrieval but for many other purposes.

By enabling the tow-coupling to be interconnected while one of its two parts is linked to the tow-vehicle only by the cable eliminates the difficulties of bringing the two vehicles into couplable conjunction with each other, and the exercise of strength to couple them together. The arrangement permits the trailer and tug vehicles to be winched into tow-coupling engagement with each other even when the respective vehicles are quite badly out of alignment with each other, so that no time need be wasted on the task of properly aligning the one with the other.

Normally it will be the trailer-vehicle which is winched towards the stationary type-vehicle, and besides the already-described advantage that this may be done without careful alignment of one vehicle with the other, this possibility is of great interest in off-road situations e.g. when a horsebox is parked in a field - since if the trailer-vehicle has become enmired in very soft ground instead of reversing the tug- vehicle into the same soft ground (with a danger that it too will become enmired) it becomes possible for the tug-vehicle to stand afar off on hard ground and to winch the trailer out of the mud. Or indeed the thing can be done the other way round - thus if the tug- vehicle itself gets enmired, provided the trailer is still on hard ground it can be chocked in position there, and the winch can then be used to drag the tug- vehicle itself out of the mire, provided only that its brakes are released and its gears put in neutral.

Nor is that the end of the useful possibilities achievable by means of this invention. If the winching mechanism, guide and locking unit and the rest of the assemblage is such as to enable the device when not in a tow-coupling situation to serve as a normal vehicle- mounted winch, then the end of the cable can be fitted with a hook for simple tasks such as tree-felling and timber-dragging, or it can be equipped with other suitable attachments for mountain and cliff rescue purposes, or in fact for any of the tasks in which vehicle-mounted winches already are employed. The type and size of winch employed in the assemblage of this invention is not limited except by availability and intended use, so it can be varied according to customer requirements. In the United Kingdom at present the smallest vehicle-mounted winch which is commercially available will pull up to 1/2 tons, and the largest up to 3 tons. All these winches will run off a normal vehicle 12-volt or 24-volt electric battery, and while the power-drain on the battery is of course considerable nevertheless by leaving the engine of the tug-vehicle running so that the battery is being charged by the engine at the same time as the winch is operated there should be no problem over the duration of operation of the winch.

The kind of steel-wire cable used in the assemblage of this invention will be one of the standard items which are already available for use with vehicle-mounted winching mechanisms, and these have a range of breaking strains which are amply sufficient for any purpose currently envisaged. While the assemblage previously described herein involves mounting the winch drum externally of the tug-vehicle on the normal towball-bracket, if preferred the winch mechanism can be mounted elsewhere on the vehicle, e.g. in the boot (trunk) of the tow-vehicle, and fed from the winch drum into alignment with the guide and locking unit via tubing.

Thus it will be seen that the guide and locking unit of this invention, and indeed the general assemblage described herein, is a highly flexible one which achieves a range of advantages which far exceed anything available from prior proposals, and should encourage its widespread adoption in domestic, leisure, commercial and agricultural contexts.

Claims

CLAIMS 1. A guide and locking unit, for use together with one part of a two-part tow-coupling capable of establishing a towing-connection between a tug-vehicle and a trailer-vehicle, said guide and locking unit (in either assembled or kit form) comprising: a generally-concave female member, a generally-convex counterpart male member capable of self-alignment with said female member and when thus aligned being brought into mating engagement therewith, substantially all of the respective mating surfaces of the female and counterpart male members being convergent in the direction of mating engagement so that they are completely juxtaposed only when in full mating engagement, and so constructed as to be incapable of any significant mutual rotation with respect to each other about the axis of their engagement when the respective members are in full mating engagement, additional means, external of the female member and which do not mate with the male member, to facilitate self-alignment and mating engagement of the male and female members even when they are drawn together in a non-axial direction, locking means associated with both members operable when they are in full mating engagement with each other releasably to secure them together, one of said members being adapted to be attached both to one part of the two-part tow-coupling and also to a flexible tensor, and the other of said members being adapted to be attached to one of the respective vehicles and also apertured to accommodate passage of said flexible tensor aforesaid through said aperture, so that such flexible tensor when attached to one of said members and passing through the aperture in the other said member may be utilized to draw the respective male and female members together, bringing them into alignment and finally into full mating engagement with each other, in order that they may then be locked together by said releasable locking means.

2. A guide and locking unit as claimed in claim 1, which includes one part of the two-part tow-coupling, said one part being attached to that one of the male and female members which is adapted for attachment to the tug-vehicle, and in which said one part is or includes the towball of a cup-and-ball tow-coupling.

3. A guide and locking unit as claimed in claim 1 or claim 2, which includes one part of the two-part tow-coupling, said one part being attached to that one of the male and female members which is adapted for attachment to the tug-vehicle, and in which said one part is or includes the jaws, with or without the pin, of a pin-and-eye tow-coupling.

4. A guide and locking unit as claimed in claim 1, which includes one part of the two-part tow-coupling, said one part being attached to that one of the male and female members which is adapted for attachment to the tug-vehicle, and in which said one part is the hook-member of a military-hitch type of tow-coupling.

5. A guide and locking unit as claimed in any of the preceding claims, in which the female member is adapted for attachment to the tug-vehicle, and the male member is adapted for attachment to one part of the two-part tow-coupling.

6. A guide and locking unit as claimed in any of the preceding claims, in which the member adapted for attachment to the tug-vehicle is the apertured member adapted to accommodate passage of the flexible tensor.

7. A guide and locking unit as claimed in any of the preceding claims, in which the flexible tensor is associated with a winching mechanism operable to retract it through the aperture and thereby draw the respective members into full mating engagement with each other.

8. A guide and locking unit as claimed in claim 7, in which the winching mechanism is power-operable directly or indirectly from the prime-mover of an automotive tug-vehicle.

9. A guide and locking unit as claimed in any of the preceding claims, in which the female member and the counterpart male member share only a single, normally-vertical plane of symmetry passing through the axis of the flexible tensor.

10. A guide and locking unit as claimed in any of the preceding claims, in which one of the members is adapted for attachment to the flexible tensor by abutment means provided within a bore therein which coact with a stop member provided on the flexible tensor to prevent its retraction past the abutment means in the direction of mating engagement but to leave it free to be extended in the opposite direction.

11. A guide and locking unit as claimed in claim 10, in which the bore within said member and the tow- coupling part attachable thereto are both so constructed and located that the cable is capable of extension beyond said bore and tow-coupling part to serve in the manner of a conventional winching mechanism.

12. A guide and locking unit as claimed in claim 11, in which the free end of the extensible cable is equipped with a hook or other attachment device.

13. A guide and locking unit as claimed in claim 14, in which the alignment-facilitating means comprise splayed lips at least partly surrounding the female member orifice, and capable of funnelling the flexible tensor and thus the male member towards the female member.

14. A guide and locking unit as claimed in any of the preceding claims, in which the releasable locking means comprise one or more keyhole bore(s), each said keyhole bore passing at least partly through both of the respective female and counterpart male members, such bore(s) in the respective male and female members being aligned when they are in full mating engagement, and corresponding pin(s) removably insertable through the aligned bore(s) transverse to the axial direction of mating engagement, so as thereby to lock the male and female members against disengagement during use of the unit in the tow-coupling of two vehicles.

15. A guide and locking unit as claimed in claim 14, in which there are a pair of parallel keyhole bores through each of the male and female members, axially spaced apart equidistant one on either side of the axis of mating engagement of the male and female members but in a plane substantially normal thereto, and the releasable locking means comprises a pair of pins adapted for insertion and removal from said keyhole bores when the respective male and female members are in full mating engagement.

16. A guide and locking unit as claimed in claim 15, in which the pair of pins is integrated together via a handle which facilitates their insertion and removal.

17. A guide and locking unit as claimed in claim 15 or claim 16, in which two separate pairs of parallel keyhole bores are provided through each of the male and female members, one such pair being directed horizontally and the other directed vertically, the spacing between the bore-axes in each pair of bores being the same as each other and the same as that between the pin-axes .

18. A tow-coupling assembly (in either assembled or kit form) for the towing interconnection of an automotive tug vehicle with a trailer vehicle, said assembly comprising a guide and locking unit as claimed in any of the preceding claims together with a mounting for normally-fixed attachment to one of said vehicles.

19. A tow-coupling assembly (in either assembled or kit form) for the towing interconnection of an automotive tug-vehicle with a trailer vehicle, said assembly comprising a guide and locking unit as claimed in any of claims 1 to 17 together with the other part of a two-part tow-coupling, with or without an associated mounting for normally-fixed attachment to the other of said vehicles.

20. A tow-coupling assembly (in either assembled or kit form) for the towing interconnection of an automotive tug-vehicle with a trailer vehicle, said assembly comprising a guide and locking unit as claimed in any of claims 1 to 17 together with a flexible sensor in the form of a multiple-strand steel wire cable attached to one of the male and female members and passing through the aperture in the other.

21. A tow-coupling assembly (in either assembled or kit form) for the towing interconnection of an automotive tug-vehicle with a trailer vehicle, said assembly comprising a guide and locking unit as claimed in any of claim 1 to 17 together with winch mechanism mounted on or adjacent an automotive tug-vehicle and power-operable at will either directly or indirectly from the prime mover of said automotive tug-vehicle to retract the flexible tensor.

22. An assembly as claimed in claim 21, in which the winch mechanism is powered by a D.C. electric motor adapted to run off the tug vehicle's normal electric system and under the command of controls remote from the immediate vicinity of the motor and external to the tug vehicle.

23. An assembly as claimed in claim 22, in which the controls are connected to the electric motor via a cable of such length as to permit the operator to stand clear of both the tug and trailer vehicles as they are coupled together.