GB1567038A

GB1567038A - Tow coupling assembly

Info

Publication number: GB1567038A
Application number: GB3362876A
Authority: GB
Original assignee: EEZION Ltd
Current assignee: EEZION Ltd
Priority date: 1977-11-10
Filing date: 1977-11-10
Publication date: 1980-05-08

Description

(54) TOW COUPLING ASSEMBLY (71) We, EEZION LIMITED, a British Company, of Stanley Works, Ampthill Road, Kempston Hardwick, Bedford, Bedfordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a towing assembly for coupling a towing vehicle to a trailer such as a caravan. In known towing assemblies it is normal to provide a spring damper in order to absorb the shocks to the vehicle and trailer chassis when accelerating or braking. Overrun braking devices are provided in the form of a master cylinder having an operating shaft actuated by the relative movement of the trailer towards the towing vehicle. Such an arrangement is described in Patent No.

1224491.

According to the present invention we provide a towing assembly for coupling a towing vehicle to a trailer, the towing assembly including damping cylinder, a piston assembly movable within the damping cylinder, a piston rod connected to piston assembly and extending out of the damping cylinder at each end thereof, means provided on one end of the piston rod for connecting a trailer to the towing assembly, a by-pass passage between the two sides of the piston assembly to permit fluid to pass from one side of the piston assembly to the other and back, a throttle in the by-pass passage to damp the movement of the piston assembly relative to the damping cylinder and a hydraulic master cylinder spaced from the damping cylinder and operated by the movement of the other end of the piston rod relative to the damping cylinder, which master cylinder is adapted to supply fluid under pressure for operation of the brakes of the trailer.

Constructional embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a longitudinal section through the towing assembly of the invention, Figure 2 is a part plan view, Figure 3 shows the towing assembly in part longitudinal section; Figure 4 shows an alternative towing assembly according to the invention; and Figure 5 is a cross section taken on the line V-V in Figure 4.

A pair of upper arms 1 are pivotally mounted on two parallel plates at the rear end of the chassis of the towing vehicle. Similarly, a pair of lower arms 2 are pivotally mounted on the vehicle chassis below the upper arms. The arms 1, 2 are cranked to give a wish-bone appearance in plan view and are pivotally connected by means of anchor pins 26 at their ends remote from the chassis mounting to a tow body housing 3.

The latter comprises a pair of parallel and spaced apart plates and upper and lower tubes connected between the plates and serving to receive bushes 10 through which pass the anchor pins 26.

The pivots of the arms are all arranged at the vertices of a parallelogram when viewed in side elevation (see Figure 1).

Mounted in the tow body housing 3 between the two plates thereof is a tow coupling 19 having at the rear end thereof a coupling means formed by a towing eye 31 to which the trailer is coupled.

The towing coupling comprises a damping cylinder 40 closed at each end by walls 41, 42 having openings therein to permit the passage of a shaft or piston rod 43 which carries a piston closely fitting within the cylinder 40.

The piston is formed in three parts; a steel collar 44 with an annular groove 45 in its cylindrical surface, and two cup-shaped piston heads 46 of a suitable plastics material or rubber fixed to the shaft 43 one on each side of said collar 44. The piston heads 46 are spaced from collar 44 so as to provide cham bers 47,48. The towing eye 31 is fixed to one end of the shaft 43.

At or near the ends of the cylinder there is connected a pipe 49 containing throttle valves 50 whereby fluid (oil) contained within the cylinder can pass from one end to the other and back. The chambers 47,48 are also filled with oil.

When relative movement between the shaft 43 and the cylinder 40 occurs, oil passes from one end of the cylinder via the pipe 49 to the other end, damping being effected by restriction through the throttle valves 50.

The groove 45 receives oil and air seepage which creates a seal between the chambers 47, 48 on each side of the collar 44. The groove 45 is dimensioned to permit the correct mixture of oil and air without frothing occurring.

The shaft 43 extends through the opneing in the end wall 42 and its end remote from the towing eye 31 actuates a hydraulic master cylinder shown generally at 51. The master cylinder 51 is connected between the tow body housing 3 and the towing eye, and pressurised by the towing eye in the event of over-run of the trailer during braking of the towing vehicle, which cylinder in turn feeds a hydraulic brake line to operate the brakes on the trailer. In order to render the master cylinder inoperable for the purpose of reversing the trailer there is provided fixed to the shaft a second collar 52 having an annular groove 53 therein engageable by a spring loaded pin 54 which passes through an opening in a casing 55 which serves to mount the master cylinder on the cylinder 40.When the pin 54 engages the groove 53, no movement of the shaft can take place relative to the master cylinder or the cylinder.

Between the upper arms 1 there is provided a cross tie 13 which supports a suspension anchor 6 on a pin 9 passing through brackets 12 mounted on the cross-tie 13. A screw 5 passes through the anchor 6 and engages in an internally screw-threaded sleeve 4 mounted at one end of a leaf spring 20 carried by the trailer chassis and fixed there by means of a bolt 21 and a nut 30.

The sleeve is pivotally connected to the leaf spring by a pin 11. The upper end of the screw 5 is provided with a handle 7 which carries a screw lock 8 which in its locking position is between the brackets 12 carrying the suspension anchor 6. The height of the towing assembly can be adjusted by means of the screw jack according to the height of the trailer as it is loaded.

A second embodiment of the towing assembly according to the invention is shown in Figures 4 and 5. This towing assembly includes a cylinder 60 having a piston rod 62 passing out of one end thereof. The piston rod carries a piston head 64, dividing the interior of the cylinder 60 into two chambers 66, 68. The two cylinder chambers are interconnected by means of a flow passage 70 formed in the piston head 64. One end of the flow passage is of increased diameter and is internally threaded to accept a replaceable throttle valve 72.

The chambers 66 and 68 are filled with hydraulic fluid or oil under pressure by way of a filling port 74, normally closed off by a tight fitting stopper 76. The oil ensures that axial movement of the piston head in the cylinder is damped, the degree of damping being determined by the oil used and by the size of the opening in the throttle valve 72.

With conventional hydraulic oils, a throttle valve opening diameter of 1/16 inch has been found suitable.

The piston head 64 is provided with a circumferential groove 78 accommodating an o-ring 80 which prevents flow of hydraulic oil from one cylinder chamber to the other between the internal cylinder wall and the piston head.

Piston rod bushings 82, 84 close off the ends of the cylinder and escape of hydraulic oil from the cylinder between the bushings and the piston rod 62 is prevented by seals 86 and 88 respectively.

Each end of the piston rod 62 extends out of the cylinder 60. One of those ends is provided with a threading 90 whereby it may be connected to a towing eye, such as 31 shown in Figures 1 to 3.

The other end of the piston rod 62 is provided with a narrowed portion 92 which passes through a housing 94 bolted to the cylinder 60. In an annular space 96 between the narrow piston rod portion 92 and the inner surface of the housing 94, a shoe 98 is provided. The shoe is movable in a radial direction between an inner position in which movement of the piston rod 62 is prevented by abutment of the faces 100 and 102 on the shoe and piston rod respectively and an outer position in which movement of the piston rod is possible. A pin 104 connected to the shoe 98 extends out of the housing 94 by way of a sleeve 105. A spring 106 biases the pin and shoe assembly into the radially innermost position. That part of the pin 104 which extends out of the housing 94 carries a cross-piece 108 while the outer face of the sleeve 105 is provided with a cross-groove 110. The pin 104 is rotatable about its longitudinal axis and can therefore occupy two positions, namely a first position, as shown in Figures 4 and 5, in which the cross-piece 108 is engaged in the cross-groove 110 and in which position therefore movement of the piston rod is prevented, i.e. the piston rod is locked, and a second position in which the cross-piece 108 lies perpendicular to the cross-groove 110 against the end face of the sleeve 105 and in which position therefore the piston rod is unlocked. To make it easier for the pin 104 to be rotated, a further cross-piece 112 is provided at its free end.

The housing 94 is provided with an access hole 114 which enables the pin and shoe construction to be assembled.

The end of the piston rod 62 opposite to that to which the towing eye 31 is to be secured, is coupled to the hydraulic master cylinder 51 in the same manner as the towing assembly shown in Figure 3. The towing assembly shown in Figures 4 and 5 therefore operates as follows: In use, the tow coupling shown in Figures 4 and 5 is mounted on the tow body housing 3 (see Figure 1), and a trailer is coupled to a towing eye 31 screwed and pinned to the end of the piston rod 62. When, during towing, the towing vehicle slows down a force is applied to the piston rod 62 relative to the cylinder 60.Provided the locking shoe 98 is in the unlocked position, the piston rod therefore moves axially along the cylinder at a rate which is dependant upon the force applied, i.e. the weight of the trailer and the degree of acceleration, and also upon the nature of the hydraulic oil and the size of the throttle valve opening. Movement of the piston rod 62 causes the master cylinder 51 to operate thereby applying the trailer brakes.

When reversing, the locking shoe 98 is placed in the locked position which prevents movement of the piston rod 62 relative to the cylinder 60. Therefore the trailer can be reversed without the trailer brakes being actuated.

Although not shown in the drawing it is possible to construct the locking device in such a manner that it automatically assumes the locked position when the trailer is reversed.

WHAT WE CLAIM IS: 1. A towing assembly for coupling a towing vehicle to a trailer, the towing assembly including a damping cylinder, a piston assembly movable within the damping cylinder, a piston rod connected to the piston assembly and extending out of the damping cylinder at each end thereof, means provided on one end of the piston rod for connecting a trailer to the towing assembly, a by-pass passage between the two sides of the piston assembly to permit fluid to pass from one side of the piston assembly to the other and back, a throttle in the by-pass passage to damp the movement of the piston assembly relative to the damping cylinder and a hydraulic master cylinder spaced from the damping cylinder and operated by the movement of the other end of the piston rod relative to the damping cylinder, which master cylinder is adapted to supply fluid under pressure for operation of the brakes of the trailer.

2. A towing assembly as claimed in Claim 1, wherein the by-pass passage is formed by a pipe connected at or near to the ends of the cylinder.

3. A towing assembly as claimed in Claim 2, wherein said pipe has provided along its length one or more throttle valves thereby constituting said throttle.

4. A towing assembly as claimed in Claim 1, 2 or 3, wherein the piston assembly is formed by a collar attached to the piston rod and closely fitting within the cylinder and piston heads attached to the piston rod disposed one on each side of the collar and spaced therefrom to define a chamber on each side of the collar.

5. A towing assembly as claimed in Claim 4, wherein the collar is provided on its peripheral surface with an annular groove which allows limited passage of oil and air from one side of said collar to the other without frothing occurring.

6. A towing assembly as claimed in Claim 1, wherein the piston assembly comprises a piston carried by the piston rod and having a passage therethrough to constitute said by-pass passage.

7. A towing assembly as claimed in Claim 6, wherein said throttle is constituted by a removable throttle valve inserted in said passage.

8. A towing assembly as claimed in any preceding claim, wherein locking means are provided which, when operated, serve to prevent movement of the piston rod relative to the cylinder, whereby reversing of the trailer is possible without the trailer brakes being actuated.

9. A towing assembly as claimed in Claim 8, wherein said locking means operate automatically when the trailer is reversed.

10. A towing assembly as claimed in Claim 1, substantially as hereinbefore described.

11. A towing assembly substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 together with Figure 3 or Figures 4 and 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. for the pin 104 to be rotated, a further cross-piece 112 is provided at its free end. The housing 94 is provided with an access hole 114 which enables the pin and shoe construction to be assembled. The end of the piston rod 62 opposite to that to which the towing eye 31 is to be secured, is coupled to the hydraulic master cylinder 51 in the same manner as the towing assembly shown in Figure 3. The towing assembly shown in Figures 4 and 5 therefore operates as follows: In use, the tow coupling shown in Figures 4 and 5 is mounted on the tow body housing 3 (see Figure 1), and a trailer is coupled to a towing eye 31 screwed and pinned to the end of the piston rod 62. When, during towing, the towing vehicle slows down a force is applied to the piston rod 62 relative to the cylinder 60.Provided the locking shoe 98 is in the unlocked position, the piston rod therefore moves axially along the cylinder at a rate which is dependant upon the force applied, i.e. the weight of the trailer and the degree of acceleration, and also upon the nature of the hydraulic oil and the size of the throttle valve opening. Movement of the piston rod 62 causes the master cylinder 51 to operate thereby applying the trailer brakes. When reversing, the locking shoe 98 is placed in the locked position which prevents movement of the piston rod 62 relative to the cylinder 60. Therefore the trailer can be reversed without the trailer brakes being actuated. Although not shown in the drawing it is possible to construct the locking device in such a manner that it automatically assumes the locked position when the trailer is reversed. WHAT WE CLAIM IS:

1. A towing assembly for coupling a towing vehicle to a trailer, the towing assembly including a damping cylinder, a piston assembly movable within the damping cylinder, a piston rod connected to the piston assembly and extending out of the damping cylinder at each end thereof, means provided on one end of the piston rod for connecting a trailer to the towing assembly, a by-pass passage between the two sides of the piston assembly to permit fluid to pass from one side of the piston assembly to the other and back, a throttle in the by-pass passage to damp the movement of the piston assembly relative to the damping cylinder and a hydraulic master cylinder spaced from the damping cylinder and operated by the movement of the other end of the piston rod relative to the damping cylinder, which master cylinder is adapted to supply fluid under pressure for operation of the brakes of the trailer.