Anti-jack-knifing apparatus for articulated vehicles, wherein the anti-jack-knifing force is exerted independently of the operation of the vehicle braking system by the provision of a hydraulic pressure source including two working chambers communicating via a throttling bore in a piston, the moving part of the pressure source being connected to the trailer while the stationary part is fixedly connected to the tractor, and the working spaces of the pressure source are connected with the brake cylinder of the anti-jack-knifing brake construction to actuate the latter, via throttle valve units including by-pass ducts and non-return valves.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention concerns anti-jack-knifing apparatus for articulated 
vehicles, primarily for tractor-type vehicles and articulated buses or 
coaches; hereafter, for simplicity, the driven and towed units of the 
articulated vehicle will be referred to as "tractor" and "trailer". 
2. Discussion of the Prior Art 
Anti-jack-knifing devices are known which exert a braking moment around a 
king-pin, that articulates a tractor and a trailer together, against the 
moment of forces tending to cause jack-knifing of the tractor when the 
tractor or the trailer is braked. Thus for instance British Pat. No. 
1,256,947 discloses anti-jack-knifing apparatus wherein the braking moment 
is provided by a disc brake comprising a plurality of plates. The 
stationary part of the brake is fixed to the base or rubbing plate of the 
trailer while the rotary part is connected with the king-pin. 
In deviation from conventional constructions, the king-pin is not fixed 
rigidly to the rubbing surface of the trailer, but instead has a tongue 
which fits into an appropriately formed part of the coupling on the 
tractor and thus rotates with the tractor. The plates of the brake are 
clamped together by a compressed air-operated piston. The air supply is 
taken from the emergency air brake system of the trailer and is controlled 
by a special valve which is built into the air brake system of the 
trailer. 
In another known construction disclosed in British Pat. No. 1,240,554 the 
anti-jack-knifing brake device is located at the steered front shaft of 
the trailer and is operated by a brake chamber connected with the brake 
system of the trailer. 
In the construction known from British Pat. No. 1,295,045, the 
anti-jack-knifing device includes pistons for a disc brake which also 
receive pressure from the wheel brake system of the vehicle, but only when 
a predetermined pressure in the brake system of the vehicle has been 
exceeded. 
In the construction disclosed in British Pat. No. 1,243,005 the 
anti-jack-knifing brake device is installed in the trailer and is 
air-operated. A special valve, controlled by wheel slip sensing means, 
permits air to pass from a tank into the brake system. 
The main disadvantage of the above-mentioned known constructions, except 
for that of the above-mentioned British Pat. No. 1,243,005, is that the 
control of the anti-jack-knifing braking system is coupled to the 
operation of the braking system of the vehicle. These known control 
systems start from the premise that the lateral supporting force of the 
tires decreases and thus the possibility of jack-knifing arises when the 
wheels at the rear tractor shaft lock on breaking. 
However, there is no necessary logical connection between braking locking 
and jack-knifing, since there can be factors other than wheel locking to 
cause a decrease or elimination of the lateral support forces on the tires 
mounted on the rear shaft, and if jack-knifing results from a circumstance 
other than braking, the known anti-jack-knifing devices are ineffective. 
In the known devices, the anti-jack-knifing brake construction exerts a 
braking force the magnitude of which depends on the controlling pressure 
of the brake valve. In this way the upper limit of the braking effort that 
can be exerted is limited since the anti-jack-knifing braking construction 
is unable to render the articulated vehicle rigid when braking occurs 
during the negotiation of a bend. 
SUMMARY OF THE PRESENT INVENTION 
The present invention seeks to provide an anti-jack-knifing braking system 
which eliminates, or at least reduces, the disadvantages of known 
constructions, and which makes the generation and actual magnitude of 
anti-jack-knifing forces independent of the operation of the main vehicle 
braking system. It is not necessary to alter the customary construction of 
the king-pin and the coupling. 
In the construction proposed in the present invention the anti-jack-knifing 
force is exerted independently of the operation of the vehicle braking 
system by the provision of a hydraulic pressure source having a piston 
actuated by a rotary vane or a rack-and-pinion device with a constriction 
or a throttling bore, provided in the rotary vane or piston the moving 
part of the pressure source being connected to the trailer while the 
stationary part is fixedly connected to the tractor. The working spaces or 
chambers of the pressure source are connected with the brake cylinder of 
the anti-jack-knifing brake construction and actuate the latter. 
The present invention accordingly consists in an anti-jack-knifing 
mechanism for articulated vehicles, primarily for tractors wherein the 
king-pin connecting the tractor and the trailer is arranged coaxially with 
a disc brake mechanism, having elements braked relative to each other and 
respectively secured to the tractor and to the trailer, characterized in 
that one member of the articulated vehicle is connected to a stationary 
part of a hydraulic pressure source while its other member is connected to 
a moving part of the hydraulic pressure source. The two working spaces of 
the pressure source communicating by way of a throttled opening, are 
connected to the working cylinder of the brake mechanism by way of a 
controllable throttling valve provided with a by-pass duct having a 
respective non-return valve. 
In a preferred, exemplary embodiment of the present invention the 
anti-jack-knifing brake mechanism is a disc brake the disc of which is 
connected to the trailer while a calliper part is floatingly connected to 
the tractor, the floating calliper being provided with an adjusting 
mechanism. 
According to a further preferred embodiment of the present invention, the 
brake adjusting mechanism has a spring-loaded roller fitting into a 
groove, preferably V-shaped, disposed at the inner diameter of the 
segment-shaped brake disc; the roller is axially fixed on a pin guided on 
the floating brake calliper and a split plate spring is loosely fitted on 
the pin and fitted in a pre-tensioned manner in a bore of the floating 
disc calliper with axial play. Brake adjustment takes place when the 
floating brake calliper is displaced by an amount exceeding the axial play 
relative to the brake disc.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings a coupling 4 of a tractor 1 is connected to a 
trailer 2 by way of a king-pin 3. The anti-jack-knifing brake construction 
is formed as a disc brake having a brake disc 5 in the form of an arcuate 
segment fixed to the trailer 2 and floating brake callipers 6 fixed in a 
V-shaped groove 7 of the coupling 4 of the tractor 1. A hydraulic pressure 
source 8 has a moving part 9 connected to a shoulder 10 welded to the 
bottom surface of the king-pin 3 by way of an intermediate member 11. A 
stationary part of the hydraulic source 8 is connected to the coupling 4. 
The hydraulic pressure source 8 has two working chambers or spaces 14, 15 
(FIG. 3) respectively connected with a hydraulic reservoir 21 by way of 
non-return valves 20a, 20b. Small bores 13 permit flow communication 
between the working chambers or spaces 14, 15. 
The reservoir 21 and the working chambers 14, 15 are connected to a common 
feed line of a plurality of (here, six) brake cylinders 19 by way of 
controllable throttle valve units 18a, 18b arranged in parallel. Each 
valve unit includes a by-pass duct 17a, 17b provided with a non-return 
valve 16a, 16b respectively. 
FIG. 4 illustrates an automatic gap adjusting device. On the inner 
cylindrical surface of the brake disc 5, formed as an arcuate segment, 
there is a generally V-shaped groove 22; a roller 24 loaded by a 
pre-tensioned spring 23 engages this groove. A bolt or pin 26 guided in a 
bore 25 of the floating brake calliper 6 serves axially to stop or abut 
the roller 24. A pre-tensioned spring 27 guides the bolt 26 in the bore 
25. Relative axial movement between the bolt 26 and the plate spring 27 is 
possible to the extent permitted by a predetermined clearance or gap 28 
but this axial displacement takes place against the biasing force of a 
pre-tensioned spring 29. A spring 31 bearing against a plate or disc 30 
ensures that the roller 24 at all times engages a shoulder or collar 32 of 
the bolt 26. 
The apparatus operates as follows: When the articulated vehicle tends to 
jack-knife or if the trailer "hunts", i.e. sways, the angle included 
between the longitudinal axes of the tractor and trailer changes. This 
change in angle causes a relative angular displacement between the 
coupling mechanism 4 fixed to the tractor and the king-pin 3. With the 
moving part 9 of the hydraulic pressure source 8 being fixed to the 
king-pin 3 while its stationary part is fixed to the coupling mechanism 4, 
then depending on the angular sense of the rotation, in one or other of 
the working chambers 14, 15 of the source 8 the pressure changes 
proportionally to the angular velocity of the angular displacement. 
As the working chambers 14, 15 are connected with the brake cylinders 19, 
there will be a braking force exerted which is proportional to the angular 
velocity of the angular displacement, and the brake linings 33 will be 
pressed to the brake disc 5. As the angular velocity decreases, so the 
pressure decreases in the working chambers 14, 15 of the hydraulic 
pressure source 8 and this pressure decrease is transmitted by way of the 
throttle valves 18a, 18b to decrease the pressure in the brake cylinders 
19. 
The automatic gap adjusting mechanism operates as follows: The floating 
brake calliper 6 is guided relative to the brake disc 5 by the roller 24 
clamped in the groove 22 by the spring 23. The bolt or pin 26 bears 
against the upper end surface of the roller 24. The bolt 26 is guided 
radially and axially in the bore 25 of the brake calliper 6 by the 
pretensioned spring 27. The pre-tensioning in a radial direction of the 
spring 27 in the bore 25 is such that the frictional force generated in 
the axial direction is greater than the weight of the brake calliper 6 but 
smaller than the pressing or clamping force exerted by the brake cylinders 
19. 
Thus when the brake linings or pads 33 exhibit wear, the clamping force 
causes the spring 27 to abut the bolt or pin 26 and the brake calliper 6 
slips relative to the bolt or pin 26 in an axial direction. 
When the hydraulic clamping force ceases, the pre-tensioned spring 29 
axially displaces the spring 27 on the bolt 26 in accordance with the 
value of the desired gap until abutment takes place and the spring 27 
entrains the brake calliper 6.