GB2176449A - Trailer unit security lock - Google Patents

Abstract

A security lock is disclosed for mounting upon a trailer unit of an articulated vehicle, for use in obstructing access to the connecting means of the unit, the trailer unit connecting means being of the type which includes a king pin which in use is gripped by the connecting means associated with a tractor unit for the vehicle. The security lock includes a metal pin 35 normally retained within a casing 28 having an opening adjacent one end of the pin, means 44 on the end of the pin for drawing the pin out of the casing against the force of a coil spring and means for locking the pin in the extended position where it projects from the casing, for example a padlock passing through a hole 41 in the pin. <IMAGE>

Description

SPECIFICATION Trailer unit security lock This invention relates to articulated vehicles. Articulated vehicles consist essentially of a tractor unit, comprising a driving cab, engine, driven rear wheels and steerable front wheels, and a trailer unit, typically comprising a container or other loadcarrying body, having one or more road wheel axles towards the rear and temporary supporting wheels towards the front. The present invention provides an improved security lock, which can be fitted to the trailer unit of an articulated vehicle and can be used, when the trailer unit has been detached, to prevent unauthorised attachment of the trailer unit to that or another tractor unit.The security lock of the invention includes a removable key, which allows the lock to be operated, both so that unauthorised removal of a trailer unit, by attachment of a tractor unit, can be prevented and also so that the security lock can be easily returned to an out-of-use position, e.g. for authorised attachment of a tractor unit to it, when the trailer unit is to be driven away.

In articulated vehicles, the arrangements for coupling trailer units to tractor units are generally standardized and consist of a level or inclined hard metal plate attached to the rear part of the tractor unit. This plate includes a rearwardly/ facing Vslot, with the base of the V forming the foremost part of the slot, positioned at the centre of the plate. A corresponding hard metal plate is attached to the underside of the trailer near the front and includes at its centre a dependent king-pin, usually having an enlarged head at its lower end. The plate or table on the tractor unit includes springoperated claws or other attachment means.

When the tractor unit is to be coupled to a trailer unit, the latter is supported on its rear wheels and its temporary front wheels and is kept stationary, its wheels being held by brakes or chocks, for instance. The driver reverses the tractor unit into position, so that the rearmost parts of the plate on the tractor unit, either side of the slot, slide under the plate on the other unit, the plates come into face-to-face contact and the king pin moves into the slot until it reaches its forward extremity. The spring-operated claws or other attachment means on the tractor unit then close round the king pin, so that the trailer unit becomes properly attached to the tractor unit. The articulated vehicle can then be driven away.

When it is necessary to detach the trailer unit from the tractor unit, for instance when the load in the container body is to be left for a period of time, the claw methanism on the tractor unit is opened, so that when the tractor unit is driven forward it becomes detached from the stationary trailer unit, which remains supported on its rear wheels and also rests upon its front wheels, which are lowered to the ground as the tractor unit moves forward.

Because the load in an articulated vehicle can be extremely valuable and the trailer unit itself is valuable, it is highly desirable, when a trailer unit has to be parked for a period of time, to prevent it from being stolen. For this purpose, it is common practice for articulated vehicles to be provided with some form of security lock, which can be attached to a parked trailer unit, so that it cannot then be connected to another tractor unit. When a tractor unit has been detached from a trailer unit, therefore, correct practice is for the security lock, which is usually stored with its key in the driver's cab, to be attached to the king pin or some other part of the connecting mechanism on the trailer unit and then locked in place. When this has been done, the original or another tractor unit cannot then be connected to it.When the trailer unit is to be taken from where it has been parked, this is usually done by using the same tractor unit, the driver being provided with the key of the security lock, which he must first remove from the trailer unit.

The connecting mechanisms of articulated vehicles naturally require heavy lubrication, so that all the parts where the security lock has to be attached are greasy and moreover are relatively difficult to reach, as they are under the forward part of the trailer unit. It is an awkward and dirty job to attach and detach a security lock to the connecting mechanism of the trailer unit of a conventional articulated vehicle. It is obviously much easier for a parked container, on a trailer unit, to be stolen or hi-jacked, if it can still be coupled up to a tractor unit, because the attachment of a security lock is awkward or difficult. It is an object of this invention therefore to provide an improved form of security lock for the purpose of protecting the trailer units of articulated vehicles.It is also an object of the invention to provide a security lock which can be fitted to an articulated vehicle, either as original equipment or as a later addition, which is inexpensive to make, easy to use and highly effective in preventing the theft of parked trailer units.

According to this invention, a security lock is provided, which can be installed in the connecting mechanism of a trailer unit of an articulated vehicle, near the king pin, and which includes a heavy metal pin mounted inside a casing and normally retracted into it, with one end exposed, by means of a coil spring located in the casing, means on the exposed end of the pin for attaching a key in order to draw the pin down from the casing against the compression of the spring and means associated with the pin for holding it in its extended position, where it projects down from the underside of the plate and so obstructs access to the king pin and so makes it impossible for the inclined table of an articulated vehicle tractor unit to be coupled up to the connecting mechanism on the trailer unit, until the security lock is operated so as to allow the spring to retract the pin into the casing. Preferably, the casing is made so that it can be welded to the inclined plate mounted on the trailer unit.

When a trailer unit is fitted with the security lock of the invention, the means for holding the pin in the extended position, preferably consisting of a padlock having its own key, must first be unlocked before the pin can retract into the casing, preferably being held by the security lock key as this is done. If an attempt is made to attach a tractor unit to the trailer unit without first unlocking the security lock, the pin moves into the V-slot in the plate on the tractor unit and reaches the extremity of the slot before the claws can become attached around the king pin.

In order that the present invention may be readily understood, a preferred embodiment of the trailer unit security lock of the invention is described below in conjunction with the accompanying drawings, in which: Figure 1 shows, in highly diagrammatic side view, the tractor unit and trailer unit of a typical articulated vehicle; Figure 2 shows in vertical cross-section, taken on the line Il-Il of Figure 3, the preferred form of the security lock of the invention; Figure 3 shows an underneath plan or end view of the security lock of Figure 2; Figure 4 is a view generally similar to Figure 2, but showing the security lock in the extended position, in use; Figure 5 shows a key for operating the security lock of Figures 2 to 4.

Referring to Figure 1, an articulated vehicle of conventional construction consists of a tractor unit 10, comprising a chassis carrying the engine and controls (not shown) in a driver's cab 11 in the usual way, together with steerable front wheels 12 and driven rear wheels 14. The means for connecting the tractor unit 10 to the remainder of an articulated vehicle consist essentially of a massive metal plate 15 located to the rear of the unit 10. At least the rearmost parts of the plate 15 are inclined to the horizontal in practice, so that these parts are at the lowest portion, although this is not shown.

The plate 15 includes a slot 16, typically of Vshape, directed to the rear. The slot 16 has a forward rounded corner 17 located at the centre of the plate 15. The remainder of the vehicle consists of a trailer unit 18, consisting e.g. of a container body 19 mounted on a chassis, which carries one or more axles with supporting wheels 20, towards the rear of the trailer unit 18, and small front wheels 21 which normally are not in use. These front wheels 21 allow the trailer unit 18 when detached from the tractor unit 10, to be supported, in conjunction with the rear wheels 20. The connecting means on the trailer unit 18 consist of a heavy metal plate 22, having generally the same shape and size as the plate 15 on the unit 10 and including at its centre a dependent king pin 24, with an enlarged head 25 at its lower end.When the trailer unit 18 is to be taken from where it has been parked, for instance to collect or deliver a load in the container body 19, the tractor unit 10 is carefully reversed into position, as shown in dotted lines in Figure 1. In this operation, the king pin 24 enters the slot 16 in the plate 15 and its head 25 comes to rest in the space below the plate 15. The tractor unit 10 is reversed until the king pin 24 reaches the front corner 17 of the slot 16, when spring-loaded mechanism (not shown) operates so as to move one or more curved claws around the king pin 24 and so attach the trailer unit 18 to the tractor unit 10. The latter can then tow the former.

In movement, the trailer unit 18 is prevented from moving forward relative to the tractor unit 10 by engagement of the king pin 24 in the corner 17, it is prevented from moving rearwardly by the claws (not shown) engaging the rear of the king pin, the head 25 prevents the front of the trailer unit 18 moving upwardly so as to separate the plate 22 from the plate 15 and, as the articulated vehicle moves from place to place, the trailer unit 18 hinges relative to the tractor unit 10 about a substantially vertical axis 26 through the king pin 24 at the centres of the plates 15 and 22.

According to the invention, a security lock 27 is attached to the unit 18, preferably by being attached to the upper side of the plate 22 forward of the king pin 24. When used, as explained below, a pin included in the lock 27 projects below the underside of the plate 22.

Referring to Figures 2 to 4, the security lock 27 of the invention is associated with the connecting mechanism, comprising the plate 22 and the king pin 24 on the trailer unit 18 of an articulated vehicle 10, 18. The lock 27 is mounted on the plate 22, above a hole made in the plate 22, forwardly of the king pin 24 and the axis 26, as shown in Figure 1.

If a vehicle 10, 18 is fitted with the lock 27 as original equipment, the plate 22 with the hole and the lock 27 are assembled together during construction; if the lock 27 is added to an existing vehicle 10, 18, the hole is drilled in the plate 22 and the lock 27 is welded in place. The lock 27, the detailed construction of which is described below, is thus positioned on the upper side of the plate 22 above the hole (not shown) formed in the plate 22, through which the lock 27 can operate, again as described below.

Referring to Figures 2 and 3, the lock 27 consists of an exterior housing 28 made for instance of steel, consisting of a cylindrical wall 29 having a heavy flange 30 at its lower end, by which the lock 27 is welded to the plate 22 when the lock is installed. At its upper end, the housing 28 includes an inturned lip or flange 31 surrounding a central aperture 32. The heavy flange 30 at the lower end of the casing 28 contains a central aperture 34. Inside the housing 28, a heavy hard steel pin 35 is located, consisting of a cylindrical shank 36 having a diameter such that it can slide easily through the aperture 34 in the flange 30. At its upper end, the pin 35 has an outwardly-projecting flange or head 3, the external diameter of which is an easy fit inside the internal diameter of the wall 29 of the housing 28. The underside of the head 37 and the upper surface of the interior of the flange 30, where the latter projects inwardly from the wall 29 to the perimeter of the aperture 34, form support surfaces for the ends of a heavy coil spring 38. In its out-of-use state, the lock 27 is thus constructed and arranged so that the spring 38 holds the head 37 of the pin 35 against the inturned lip or flange 31. The length of the shank of the pin 35 is such that in this condition the lower end 39 of the pin 35 is level with the underside 40 of the flange 30 of the housing 28. Near its lower end, the pin 35 in cludes a transverse hole 41 which preferably extends between recesses 42 made in the cylindrical surface of the shank 36.In its end surface 39, the pin 35 includes a keyhole 44, consisting of a central circular aperture 45 with opposite rectangular extensions 46, which gives access to a cylindrical chamber 47 in the end of the pin 35.

A key 48 for operating the security lock 37 is shown in Figure 5 and consists of a shank 49 having a ring-like handle 50 at one end. At the operative end of the shank 49, the key 48 consists of a cylindrical rod 51 of reduced diameter, compared with the shank 49, terminating in a cross-piece 51, the ends of which extend beyond the rod 51 at either side. The key 48 is so shaped, as will be readily understood, that the rod 51 can pass through the central hole 45 in the keyhole 4, when the cross-piece 51 is oriented so that its ends pass through the rectangular extensions 46. When the key 48 is then rotated about its axis 54 relative to the pin 35, the cross-piece 52 then lodges within the chamber 47. Downward force exerted on the key 48 then results in the pin 35 being pulled through the aperture 34, against the action of the spring 38.This continues until the transverse hole 41 in the pin 35 is below the under surface 40 of the flange 30 and, in practice, also below the underside of the plate 22, the pin 35 then extending from the casing 28 sufficiently to project through the hole in the plate 22, and allow the transverse hole 41 in the pin 35 to be clear of the plate 22.

When held in this extended position by the downward force exerted with the aid of the key 48, the pin 35 is locked in the extended position. Any strong rod-like object can be passed through the hole 41, as the force of the spring 38 forces it against the underside of the plate 22 and a key or other tool like the key 48 is then needed before the pin 35 can be pulled down so as to allow the rodlike object to be removed. In practice, the object used to hold the pin 35 in the extended position is preferably the hasp 55 of a padlbck 56, which is shaped so as to pass through the hole 41. When the downward force on the key 48 and therefore on the pin 35 is released, the spring 38 urges the pin 35 upwardly, but it is prevented from retracting into the housing 28 as the hasp 55 of the padlock 56 contacts the underside of the plate 22.The padlock 56 can then be snapped shut. When in this extended position, the lower end of the pin 35 with the attached padlock 56 projects below the undersurface of the plate 22, so that a tractor unit 10 could not be connected to the trailer unit 18, because the pin 35 would enter the slot 16 and pass into the corner 17 before the tractor unit 10 had been reversed relative to the trailer unit 18 sufficiently to enable the king pin 24 to be seized by the claws of the interconnecting mechanism.Since the padlock 56 can only be released by using its own key (not shown), typically after it has been tilted into the inclined position shown in broken lines in Figure 4, and when downward force is exerted on the pin 35 again with the key 48 in order to enable the padlock 56 and its hasp 55 to be removed, the trailer unit 18 cannot be coupled to a tractor unit 10 until an authorised person, such as the driver of a tractor unit having the padlock key, returns to the place where the trailer unit 18 has been parked.

It is a simple matter to use the key 48 to operate the security lock 27, after a trailer unit 18 has been detached in order to be parked, and it is also a very simple operation to remove the padlock 56 and allow the pin 35 to return into the housing 28 under the action of the spring 38, when it is again desired to attach the trailer unit 18 to a tractor unit 10 and remove the articulated vehicle 10,18. The key 48 and the padlock 56 can remain free from grease and dirt during these operations. The security lock 27 of the invention thus provides an inexpensive and effective means for preventing unauthorised removal of the trailer units of articulated vehicles and the valuable loads which they often contain when they are left in a lorry park or other area.

Claims (12)

1. A security lock for mounting upon a trailer unit of an articulated vehicle, for use in obstructing access to the connecting means of the unit, the trailer unit connecting means including a king-pin which in use is gripped by connecting means associated with a tractor unit for the vehicle, in which the security lock includes a metal pin normally retained within a casing having an opening adjacent one end of the pin, means on that end of the pin for drawing the pin out of the casing against the action of a coil spring and means for locking the pin in the extended position where it projects from the casing.

2. A security lock as claimed in claim 1, in which a recess is provided in the end of the pin and is engageable by means of a key, for drawing the pin out of the casing by pulling on the key.

3. A security lock as claimed in claim 2, in which the recess comprises a circular aperture which has opposite rectangular extensions and gives access to a cylindrical chamber within the end of the pin.

4. A security lock as claimed in claim 1, 2 or 3, in which a transverse hole is provided in the pin, for receiving a rod or bar for locking the pin in a projecting position while being retained, under the action of the spring, against the part of the casing surrounding the opening.

5. A security lock as claimed in claim 4, in which the rod or bar is the hasp of a padlock.

6. A security lock as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawing.

7. A trailer unit of an articulated vehicle, provided with a security lock as claimed in any preceding claim.

8. A trailer unit as claimed in claim 7, wherein the security lock is mounted forwardly of the kingpin of the connecting means of the trailer unit.

9. A trailer unit as claimed in claim 7 or 8, in which the casing of the security lock is mounted wholly within the trailer unit.

10. A trailer unit as claimed in claim 7, 8 or 9, in which the opening in the casing registers with an aperture in a metal plate which forms part of the connecting means of the trailer unit.

11. A trailer unit as claimed in claim 10, wherein the casing of the security lock is welded to the plate.

12. A trailer unit as claimed in any of claims 7 to 11, substantially as described with reference to the accompanying drawing.