Anti-jackknifing control system, apparatus and method

A system including an anti-jackknifing abutment apparatus (FIGS. 1-4, 7, 8) and electrical (FIG. 5) and hydraulic (FIG. 6) controls provides system control which controls limited relative angular movement between an articulated tractor 10 and trailer 20. An engagement driver in the form of cylinder 36 mounted within a rigid frame 23 is mounted by a mounting bar 25 to a forward beam member 22 of the trailer 20 for moving a abutment element 28, 128 into and out of an engagement zone within the longitudinal V-slot 17 of the fifth wheel 14. The abutment element in position on a rotational swing of the articulated vehicle is contacted by ears 18 of the V-slot, where due to the structure of the apparatus, the further rotational movement may be arrested or controlled to permit adjustment of the rotational limit of further angular movement under control of the driver. The system can be adjusted and controlled to permit adaption of the moving vehicle to various road and rig movement conditions, acting to prevent dangerous jackknifing from occurring.

BACKGROUND OF THE INVENTION 
The field of devices of the inventions are those designed for preventing 
jackknifing between a truck and trailer and the method of operation of the 
system. 
Jackknifing has been ranked as the third most hazardous type of truck 
accident, accounting in the United States of America for approximately 
$20,000,000 of property damage and more than 5% of the fatal truck-trailer 
accidents. Safe driving practices such as keeping speed down to a safe 
speed for road conditions, avoidance of sudden decelerations and slippery 
surfaces or loose dirt, safe easy stops and smooth steering substantially 
improve the risk of a jackknife occurrence. Nevertheless the jackknife 
accident continues to occur thousands of times a year. 
Trucks pull a trailer through a fifth wheel-kingpin connection which allows 
the tractor and trailer to pivot about the axis of this connection. The 
huge tractor rigs on the highway are guided by the small front tire 
footprint on the road. When braking, even at slow speeds, the inertia 
forces push at an angle against the pivot point connection and the trailer 
swings around pulling the tractor out of position, breaking the front tire 
contact, and causing a complete loss of control and a "jackknife" occurs 
as the trailer and tractor pivot on the kingpin connection toward each 
other to close like a knife blade enters the handle in a camper's 
jackknife. Uneven braking can trigger the phenomena, as well as side 
winds, sudden engine deceleration and loss of braking. The trailer can 
override the tractor pushing it into jackknife or the tractor can 
underride the trailer and cause the jackknife. These variable causes make 
a practical solution to the problem difficult. 
This problem has long been known. It has been known for at least a decade 
that corrective action needs to be taken before the angle between a 
tractor and trailer exceeds 15 degrees. Over the years many "solutions" to 
this problem have been suggested. In the last decade electrical brakes 
were suggested as a means to reduce the jackknife occurrence, and these 
were employed on many trailers. However, this system did not effectively 
work and few vehicles use this "solution". Since 1975 so called anti-lock 
systems known as 121 brakes required by U.S. Federal Motor Vehicle Safety 
Standard 121 have been employed to automatically release brakes on an axle 
or tandem if any wheel locks up more than momentarily. Still sudden brake 
applications can cause wheel lock-up. Hand valves to cause trailer wheels 
to lock to prevent jackknifes have been proposed, but the U.S. National 
Safety Council found this solution could actually induce trailer 
jackknifes. Drivers who over-accelerate in a effort to pull out of such an 
induced jackknife may induce a tractor jackknife by spin-out. 
While there are only six fundamental machines the field of mechanisms and 
structures may be unlimited. However, in this art here have been numerous 
suggestions in prior art attempts. An effective solution needs to be cost 
effective and safe and reliable. The many prior art devices suggested by 
the patent literature are not seen on the vehicles on the road today and 
jackknife accidents continue to occur. If an effective solution had been 
achieved, in view of the clear need, one of the prior art devices should 
have been adopted widely prior to this time. With such a number of prior 
devices available, without the use of hindsight, a description of relevant 
background prior art applicable to the present invention would not be 
readily apparent. In the prior art there does exist many attempts to limit 
the amount of pivotal movement of the fifth wheel and kingpin of a 
tractor-semitrailer combination and other various arrangements to prevent 
or minimize the tendencies of tractor-trailers to jackknife. However, 
these arrangements do not provide apparatus which are adjustable to road 
conditions as does the present apparatus and they do not provide a control 
system for continuous monitoring of an anti-jackknifing apparatus which 
limits swing to a anti-jackknifing controlling arc and which allow the 
driver to control the vehicle and control apparatus in accordance with 
varying road conditions and rig movement and which has the other features 
which will be described. A representative sample of the prior art granted 
over many years may be listed as follows: 
U.S. Pat. No. 2,462,211, filed Feb. 24, 1947 to C. L. Moore 
U.S. Pat. No. 2,553,959, issued May 22, 1951 to H. F. Cook et al. 
U.S. Pat. No. 2,652,262, filed Oct. 19, 1950 to W. G. Sherry 
U.S. Pat. No. 2,962,301, filed Oct. 15, 1959 and issued November, 1960 to 
W. J. Leinbach 
W. Ger. Pat. No. 960,696 issued Mar. 7, 1957 naming Hans Becker as inventor 
U.S. Pat. No. 3,031,205, issued Apr. 24, 1962 to P. Fox 
U.S. Pat. No. 3,063,739, issued Nov. 13, 1962 to P. M. Davies 
U.S. Pat. No. 3,420,548, filed Oct. 7, 1966 to C. M Wakeman 
U.S. Pat. No. 3,588,809, issued June 28, 1971 to A. S. Devlin 
U.S. Pat. No. 3,774,941, filed Feb. 14, 1972 to H. H. Durr 
U.S. Pat. No. 3,837,678, filed May 3, 1973 and issued September, 1974 to R. 
Cicero 
U.S. Pat. No. 3,856,329, issued Dec. 24, 1974 to M. A. Ordorica 
U.S. Pat. No. 3,895,827, issued July 22, 1975 to J. D. Padrick 
U.S. Pat. No. 3,972,542, issued Aug. 3, 1976 to Arthur A. Dirks 
U.S. Pat. No. 4,040,006, issued Aug. 2, 1977 to R. W. Kimmel 
U.S. Pat. No. 4,068,860, issued Jan. 17, 1978 to A. Dirks and W. Meyers 
U.S. Pat. No. 4,556,232 issued Dec. 3, 1985 to J. I. Sever 
Such a hindsight collection of patents can be developed after a review of 
the inventions herein. Prior art warning devices exist which warn drives 
of an oncoming jackknife, and which indicate fishtailing, principally 
relating to vehicles which do not employ a fifth wheel. A number of 
recognized prior art inventions recognized by their patents have disclosed 
the positioning of a device, such as a block or abutment member, within 
guide lugs in the entranceway or V-slot of the slide plate of a fifth 
wheel mounted on the tractor to prevent jackknifing. However, these 
inventions have not been widely adopted. Representative examples include 
U.S. Pat. Nos. 2,553,959; 2,962,301; 3,972,542 and 4,068,860. In the U.S. 
Patents to Dirks et al., this concept was employed and implemented by a 
generally horizontal longitudinally extending restraining tongue rigidly 
mounted on the trailer underside and terminating as a forward tapered 
tongue tip (or bracket) between the lugs in an extended station position. 
A remotely controlled cylinder attached to the tongue caused horizontal 
tongue reciptocation between the retracted and forward extending position 
to prevent jackknifes. After a review of the detailed description below it 
will be appreciated that none of the prior art attempts accomplish the 
results of the present inventions as detailed in the description. 
SUMMARY OF THE INVENTIONS 
The present control system functions in accordance with the described 
preferred embodiments of the present inventions normally in a position of 
actual or potential engagement with the fifth wheel and acts as an 
anti-jackknife control system and warning device which allows the driver 
to set the limits of swing of the trailer while driving in accordance with 
road conditions and rig movement. The present system allows the drive to 
set the control system by a control method implementing the functions of 
the apparatus. The control system provides for permissible swings of the 
articulated vehicles about a full swing arc, about a limited controlled 
arc lesser than the full swing, and free within a limited arc lesser than 
the controlled arc under supervision of a position control system. As such 
a jackknife is not permitted to occur when the control system is engaged, 
for system-fifth wheel engagement prevents rotation to the extent that a 
jackknife could occur. Instead, the system control the swing allowing the 
driver to continue to drive the vehicle and in the event a sever limit is 
reached the system causes the tractor to move into a controlled plow which 
averts the jackknife accident. 
In accordance with the preferred embodiments of the inventions the 
apparatus is easily mounted on the trailer bed frame by bolting a control 
system frame to one of the horizontal trailer bed frame beam members. This 
mounting locates a pivotal engaging bar limit element which pivotally 
flips into and out of an engagement zone position between the ears of a 
tractor's conventional fifth wheel the under control of a switch 
accessible to the driver. The control system enables the position of the 
engaging bar limit element in the engagement zone to limit the trailer to 
approximately 12 to 14 (nominally 15) degrees of swing about a kin pin 
pivot point from the normal linear alignment of the tractor trailer, as 
well as swing through a wider controlled swing radius. Normally when the 
trailer turns it pivots completely around on the fifth wheel. When the 
limit element of the anti-jackknife control system is engaged, the hitch 
turns about 15 degrees in free swing before the fifth wheel contacts the 
engaging bar. At this point the trailer can proceed to swing an additional 
10 to 15 degrees in the same direction up to an end limit (preferred to be 
at 26 degrees). At the start of the additional swing an alarm sounds in 
the cab. This alarm tells the driver that the trailer is swinging towards 
the limit of turn and warns him that the transition point from permitted 
free swing is passed. At this point, the operator has the option of 
releasing the limit bar and by flipping a control switch inside the cab 
which releases the fifth wheel for free rotation, allowing full pivoting 
action of the fifth wheel, or he can leave the limit bar element in 
position and the limit bar element will continue to move sideways to the 
point of limit of lateral movement fixed by normal setting to a 10 to 14 
degree additional swing limit the tractor trailer movement, or to another 
angular (lateral) limit set by the driver. During this period of 
additional swing further lateral movement of the limit member is slowed 
(unless stopped by the driver), and a potential jackknife can be 
controlled by the driver who has been warned to steer in the direction 
that the rear of the trailer is sliding. If the tractor is sliding, the 
driver will steer in the direction that the rear of the tractor is 
sliding. 
When the limit element is in place, its fifth wheel control system 
interaction prevents further relative angular movement by the position of 
the limit element in a laterally stopped position, so that the tires of 
the tractor will plow sideways at an angle and the truck remains under 
control plowing down off of the tires like a plow. Tire plow will bring 
the rig to a halt, but the danger of turn over and jackknife has been 
prevented. 
In accordance with the invention, in operation the engaging bar limit 
element is to be normally in position between the ears of the fifth wheel. 
After coupling of the kingpin in the center of the fifth wheel V-slot the 
driver engages the engaging bar and the control system and limit element 
is engaged. The unit is adjustable to reasonable positions for speed, as 
it is in order to accomodate twisting mountain roads, (lower speeds permit 
a greater degree of swing without interial conditions causing a jackknife 
occurrence), between end limits of movement. These end limits of movement 
may be set by the driver before or after a time when the ears move the 
abutment limit element into the warning zone. Mechanically the system is 
designed so the the limit setting will be between an end limit of 
approximately 15 degrees to a total limit of a preferred 26 degrees (30 is 
the maximum range). Free swing between 12 and 16 degrees is permitted as 
being the the normal approximate 15 degree swing in either direction 
permitted before the anti-jackknife warning control signal is made 
noticeable. In the engaged position the unit feeds back to the driver the 
relative tractor position with the cab mounted control panel which 
contains the warning lights and audio alarm system, which, even when 
trailer angle is not being limited by throwing an auxiliary switch, serves 
as a safety feedback device notifying the driver that the trailer is 
moving toward its limits and approaching a position where it could 
jackknife if the system was not employed. 
This warning condition would occur should the driver momentarily doze and 
the truck becomes unstable, waking him and indicating corrective action 
when the engagement bar is in its normal active position. The driver can 
react to the warning. The bar can be disengaged by flipping the control 
and/or limit switch on a control panel on or off. When it is not needed 
and when the truck is under control, such as when the rig is going through 
city streets, pulling into filling stations and onto freeway ramps or 
backing to a loading dock the control switch may be switched off to 
disengage the bar control. Thus disengaged the control device allows the 
truck to negotiate such as easily as if the unit were not in place. 
In situations where when the engagement bar limit element is disengaged 
when the rig would reach an unstable condition, as when it went off onto 
the berm, switching on the control system would cause the engagement bar 
to move the limit element into position centered initially and then be 
permitted to move to the limit set by the driver where it is held until 
the rig has traction. 
The engaging bar of the control device in the present system is controlled 
by a panel control monitor, providing feedback to the driver as to the 
status of the engaging bar's position, whether it is engaged or not, and 
whether the relative movement is within or beyond normal free range. This 
panel signals the driver to engage the system if it is not but should be 
engaged. A fail-safe disengagement system is provided to prevent possibly 
dangerous feedback in the event of control failure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawings in greater detail, the preferred embodiment of 
the invention is illustrated in FIGS. 1-7, while alternate embodiments are 
shown in FIGS. 2A, 3A, 4A and a modified embodiment illustrated in FIG. 8. 
All embodiments are carried on a tractor-trailer rig illustrated generally 
in FIG. 1. 
A tractor 10 and a trailer 20 make up two intercoupled articulated 
vehicles, what is often called a rig, a tractor trailer coupled through a 
fifth wheel slide plate 14 of the tractor. For the purpose of illustration 
the tractor 10 of FIG. 1 has a cab 11 and a bed or platform 12 having 
mounted thereon a conventional fifth wheel assembly 13, 14, 15, including 
a disc shaped slide plate 14 pivotally secured at both sides thereof by a 
fifth wheel journal mount 15 to brackets 13 which are fixedly secured to 
the platform or bed of the tractor 10. 
The trailer 20 is coupled to the fifth wheel assembly by a kingpin 19 which 
projects rigidly downwardly from the bolster baseplate 16 underlying the 
mainframe or underframe 21 of the trailer 20, and generally crossing two 
or more cross frame beam members 22 of the mainframe 21. As the tractor or 
truck 10 is backed beneath the trailer 20 the bolsterplate 16 contacts the 
slanting slide plate surface of the fifth wheel and the kingpin 19 enters 
V-slot 17 (FIG. 2) of the slide plate 14. The V-slot of the preferred 
embodiments is a conventional V-slot having therein a relatively straight 
longitudinal portion 17a and a diverging portion 17b forming the angular 
V-slot and defining the ear portions 18. 
As shown in FIG. 2 and FIG. 2A this V-slot 17 acts as a guide for the 
kingpin coupling. In the present inventions these V-slot ears act as a 
feedback mechanism input for the control of the articulation of the 
vehicles. This coupling of the tractor trailer is the conventional 
interconnection of the tractor with the trailer. The kingpin is usually 
clamped in the center of the disc slide plate 14 by a locking mechanism. 
There the kingpin is able to rotate about the vertical axis 19a of the 
kingpin as the trailer moves angularly relative to the tractor. 
The control apparatus of the preferred embodiment of the inventions, as 
illustrated in FIGS. 1, 2, 7 and 2A is preferably mounted beneath the 
trailer. A cross frame beam 22 is located above and crossing the position 
of the V-slot 17 when the tractor is coupled to the trailer. Above this 
V-slot position a mounting bar 25 is positioned. Lugs or bolts 25' secure 
the mounting bar 25 to the crossframe beam 22 of the trailer. In some 
trailers when mounting the control apparatus after trailer manufacture it 
is necessary to remove a cross frame member, or to cut out a section 
thereof. Sometime the bolster plate 16 extends rearwardly of the kingpin a 
distance which exceeds the distance of rearward ear extension of the slide 
plate 14, in which case the bolster plate has to be partially removed or 
an aperture cut therein to accommodate the control apparatus. 
The anti-jackknife control apparatus comprises an anti-jackknife apparatus 
mounted beneath the trailer and the system controls which are illustrated 
and described herein. 
The present apparatus is easily mounted on the trailer bed frame by bolting 
a control system support frame 23 to one of the horizontal trailer bed 
frame 21 beam members 22 to which the mounting bar 25 is attached. In the 
preferred embodiment the mounting bar 25 is a bar with projecting studs 
which is welded to the frame with the studs projecting rearwardly, and the 
support frame is placed with the studs projecting through beveled 
apertures in the front portion of the support frame 23, where lugs 25' 
lock the support frame tightly on the mounting bar. In an alternate 
embodiment shown in FIG. 2A the mounting bar 125 is part of the support 
frame which is bolted to the frame by bolts 125'. 
In the preferred embodiments the support frame 23 is horizontally and 
longitudinally mounted. Generally it may be considered substantially 
rectangular; however, as seen from the drawings the front engagement bar 
bracing section is wider than the rear cylinder mounting section of the 
support frame. This frame portion has side members 24 which extend around 
the control apparatus and protect it. The sides have rear portions 23a and 
outwardly flaring portions 23b as well as forwardly aligned bracing 
portions 23c and a front mounting bar 25, 125. 
The support frame when mounted within the protective bed frame 21 of the 
trailer surrounds the control apparatus and protects it from above, from 
the side, and from below. The mounting bar section and side of the frame 
is wide enough that the slide bar won't accidently penetrate the 
protecting frame as it is protected by the bolster plate and wide enough 
to slide up on the plate itself. As will be understood, when disconnected 
from fluid, the engagement bar 29 limit element member 28 will be 
retracted protecting it and the fluid operated cylinder 26 from damage. 
The forward limit member 28 may have a bifrucated end portion 127 or 
preferably the end of the piston rod 26 may be bifrucated to pivotally 
connect to the abutment means limit element link 28. 
In the preferred embodiment the movable members of the control apparatus 
are the engagement bar elements indicated generally at 29 with their 
abutment limit element member 28 mounted thereon, is moveable into and out 
of engagement position between the ear portions of the V-slot 17 by the 
extensible piston rod member 26' of the fluid actuation cylinder 26. It 
will be understood that the support frame when horizontally mounted 
underneath the trailer bed locates the engagement bar elements 29 in a 
position generally above the V-slot. The shaft 30 of the engagement bar 
elements 29 is journaled in a pair of lateral support housings 36. The 
lateral orientation of the engagement bar elements 29 in relation to the 
support frame and thus to the frame of the trailer and V-slot of the fifth 
wheel is determined such that the limit member 28 may be pivotally moved 
by shaft 30 rotation caused by linear movement of said extensible piston 
rod member 26' connected thereto by abutment pivot connection 27 down into 
position in the engagement zone within the V-slot. There the ear portions 
of the slide plate 14 may contact the limit member 28. 
In the preferred embodiments the rotatable shaft 30 is journaled so as to 
permit lateral (linear) movement in the shaft housing. Also in the 
preferred embodiments of the invention rotatable shaft 30 includes a 
bushing which is an integral casting with the link of the limit element 28 
(or element 28 may be welded thereon) so as to form a pivotal engaging bar 
limit element which pivotally rotates into and out of an engagement 
position between the ears of a tractor's conventional fifth wheel the 
under control of a master control switch 70 on control monitor panel 68 
accessible to the driver in the cab 11. The position of the engaging bar 
limit element 28 in the engagement zone normally limits the trailer to 12 
to 16 degrees (nominally 15) of free articulation or swing to either side 
about a kinpin pivot axis point 19a from the normal linear alignment of 
the tractor trailer before a warning beeper or horn 65 sounds. The 
ultimate lateral linear movement of shaft 30 may be set so as to be 
stopped by an limit stop 133 set by lock nut 135 in FIG. 2A (or by nipple 
33 in FIG. 2) so that the angular relative swing about axis 19' from a 
line interconecting the front of the tractor and rear of the trailer will 
not be more than approximately 26 to 30 degrees in either direction 
allowing for a normal 15 (or 12 or 16) degree swing, plus an additional 
preferred 10 or 14 degrees. Normally, when the trailer turns it pivots 
completely around on the fifth wheel. When the limit element of the 
anti-jackknife control system is engaged and the hitch turns "15" degrees 
the hitch ear portion 18 contacts the engaging bar limit element 28. At 
this point the ear 18 drives the abutment limit element 28 linearly in the 
housing in the direction of its own travel and the trailer can proceed to 
swing an additional amount in the same direction (up to the preferred 
limit of 26 degrees). But, shortly after the start of this additional 
lateral movement occurs, an alarm sounds in the cab. This alarm 65, which 
may include a flashing light 64, tells the driver that the trailer is 
swinging in engagement toward its 26 (up to 30) degree limit. 
At this point, the operator has the option of releasing the limit bar 28 by 
flipping the control switch 70 inside the cab which releases the fifth 
wheel for rotation by causing retraction of the piston rod of cylinder 26 
allowing full pivoting action of the fifth wheel, or he can leave the 
limit bar element in position in the engagement zone of the V-slot 17 and 
the limit bar element will continue to slide laterally. As it moves 
sideways the fluid in chamber 32 will cushion and retard further lateral 
swinging movement as the chamber bleed orifice 32' (a 60/1000ths drilled 
line) will allow the further lateral swing. This provides the driver an 
additional 10 degrees of swinging movement and time to react to the 
signal. This also allows the element 28 to be released from engagement 
with the fifth wheel ear. 
At any point the lateral movement of the abutment whether while being 
driven sideways by the ear or in the center position where the limit 
element is normally initially placed, the point of actual limit of lateral 
movement may be placed, the point of actual limit of lateral movement may 
be fixed by the driver. Further swing movement from the 15 or 16 degree 
danger point of articulation of the tractor trailer movement which causes 
more lateral traverse of the shaft 30 in the housing 36 may be adjustably 
set under control of the driver by throwing the limit switch 71 in the 
cab. In function limit switch 71 causes a check valve actuator (not shown) 
to close the dash pot chamber checkvalves 72 and 73 in the hydraulic 
system and limit expression of fluid from the dash pot fluid pressure and 
compression chamber 32 of housing 36. This acts to freeze the lateral 
shaft movement to one allowed solely by the centered position of the 
abutment limit element, or to another angular (lateral) limit where is is 
driven by the ear 18 of the slide plate 14 as set under control of the 
driver at the time he activates limit switch 71. When the dash pot is 
frozen only further compression of fluid between the shaft 30 and the 
check valves 72 and 73 is possible. This provides little lateral movement. 
During the period when the shaft is sliding laterally in the housing and 
compressing the fluid, the audible horn or speaker 65 warns the driver to 
steer in the direction that the rear of the trailer is sliding. If the 
tractor is sliding, the driver understanding the feel of the tractor 
movement and alerted by the signal will steer in the direction that the 
rear of the tractor is sliding. 
When the limit element is in place in the engagement zone in the V-slot 17 
of the slide plate 14 the engaging abutment of the engaging bar and the 
ears 18 of the slide plate of the fifth wheel control system interaction. 
When the engaging bar is locked in the center position it prevents further 
relative angular movement greater than about 15 degrees by maintaining the 
fixed position of the limit element in a laterally stopped position, and 
the tires of the tractor will move at an angle and plow sideways as the 
Tire plow will bring the rig to a halt, but the danger of turn over and 
jackknife has been prevented. 
If the potential danger is due to a curve on mountanious terrain and no 
jackknife is probable driver judgment will control the limit by the 
setting made when the driver throws switch 71. 
The engaging bar limit element is retracted when the trailer is 
disconnected or when the control switch 70 is thrown to the disconnect 
position (up to the flasher pole in FIG. 5). The engaging bar is advanced 
by rotation of the shaft and link element 28 into the engagement position 
in position with the abutment limit element 28 in position between the 
ears of the fifth wheel by the action of the cylinder. When initially 
thrown the hydraulic system is powered to causes the shaft 30 which 
carries link element 28 to be centered between the housings 36. At this 
time the check valves 72 and 73 are open and equalized pressure exists in 
the dash pot fail-safe chambers 32, acting to center the shaft 
therebetween. 
Because of the ability to allow a variable overrun of the normal abutment 
position by throwing the variable check valve switch 71 only after the 
shaft has been moved sideways, the unit is adjustable to reasonable 
positions for speed, and to accomodate twisting mountain roads, (lower 
speeds permit a greater degree of swing without interial conditions 
causing a jackknife occurrence), between settable end limits of movement. 
The ultimate limit of movement beyond the 15 degree warning mark are 
usually set to an end limit of 26 degrees. However, even though the ear 
engages the abutment, throwing the check valve limit switch on and the 
control switch off allows retraction to allow free rotation. 
Normally the system should be engaged to permit the warning system to 
function. This warning condition would occur should the driver momentarily 
doze and the truck becomes unstable, waking him and indicating corrective 
action (which can include throwing the switch 71 and steering in the 
direction indicated by the audio system). 
When the driver is going over ice and snow, he can vary the limit of the 
amount of swing by turning on the extra limit switch 71 and hold the shaft 
at a specific point until he has traction and then may turn off this fluid 
lock and allow free swing of the tractor trailer. 
The engagement bar 29 bar can be disengaged by flipping the switch 70 on 
the control panel in cab 11 when it is not needed and when the truck is 
under control, such as when the rig is going through city streets, pulling 
into filling stations and onto freeway ramps or backing to a loading dock. 
In order to disengage the control engagement bar is rotated by cylinder 26 
retraction (under spring 60 bias, or preferably by air retraction bias 
caused when the control switch 70 is thrown, or a combination thereof) of 
the extensible member 26' rotating the link on which limit element 28 is 
fixed to allow the truck to negotiate such as easily as if the unit were 
not in place. 
When control switch 70 is thrown off, the switch is effectively moved up to 
the poles of the flasher signal light emitting diode 90 for the control 
monitor panel as shown in FIG. 5. This flashing LED is flashed by a 
flasher control element 91, such as the flip-flop LED flasher chip of 
National Semiconductor LM3903. This warning light may be yellow warning 
the driver to turn on the control system by throwing the switch 70 down. 
Thus engaged the switch 70 will activate cylinder solenoid valve system to 
move the engaging bar into position, as well as activate green operating 
signal, LED 92, on the control monitor when the piston of the cylinder 
causes the contact switch 63 to close. 
In situations where when the engagement bar limit element is disengaged 
when the rig would reach an unstable condition, as when it went off onto 
the berm, switching on the control system immediately causes the 
engagement bar to move the limit element into a centered position 
initially and then moved to the limit set by switch 71 where it is held 
until you have traction. Most of the time the driver will throw both 
switches at the same time. Accordingly, they are located together on the 
panel 68. 
The engagement bar 29,30 has a shaft section which is journaled in housing 
36. In the mode of the preferred embodiment of the invention illustrated 
by FIG. 4 a sealing ring 52 at each housing end is provided to position a 
O-Ring gasket 51 at the end and yet allow some fluid space to be 
maintained at the end of the chamber 32. Another O-ring gasket is provided 
on the shaft adjacent the bushing 36. A grease fitting is provided to 
allow introduction of grease so that the shaft can slide in housing 36 on 
a grease film, as shown in FIG. 4. 
In the best mode of the preferred embodiment the amount of fluid in this 
damping chamber may be fixed by closure of the normally open solenoid 
actuated dash pot check valve 73 and bleed control check valve 72 shown in 
FIG. 6 by switch 71. This switch locks fluid in the chamber 32 and allows 
no movement therefrom thus limiting with a fluid the further sliding 
movement of the shaft 30 toward the limit end 37 of housing 36. In the 
preferred embodiment the bolt 133 is replaced by the end of the hydraulic 
coupling 33 threaded into the housing 36. 
Normally the fluid used for control is air. The tractor is provided with a 
compressor and air reserve tank which maintains a pressure adequate to 
operate any air brakes and the control system. 
As shown in FIG. 6, the hydraulic system comprises a number of fluid 
connection lines running from a reserve surge tank 75. Should there be an 
electrical failure or a drop of pressure in the main air reserve normally 
closed failure switch 66 opens causing a series of shutdown actions. A 
fail-safe check valve 74 closes, along with the other normally open check 
valve 72. This traps fluid in the system dash pots 32 at enough pressure 
to allow for fail-safe staged control shutdown. The surge tank 75 can be 
used like the dash pots 32, in which case this is considered a fluid 
chamber which causes retraction of the cylinder when the check valve 74 is 
closed. In this alternative not shown, the check valve 74 would be located 
above the reservoir 75, and both valves 72 and preferably 73 would close. 
When check valve 74 closes it drops engaging bar operation pressure by 
opening the cylinder advance two way control valve 76 to exhaust 77 as 
well as coupling cylinder retraction two way control valve 78 to pressure. 
Normally these are in the engagement position shown in FIG. 6 due to the 
action of solenoid 67. However on shutdown, these valves being spring 
biased by the spring bias of solenoid 67, these valves move to the 
fail-safe mode, causing the remaining pressure in dash pots 32 to be used 
to retract the piston. Such a reaction will turn off the green operating 
light as the piston retracts and disconnects switch 63. 
Many of the features of the alternate preferred embodiment are common to 
the preferred embodiment and the alternate preferred embodiment, as well 
as the modified embodiment. These features have generally been given the 
same number and will not be separately discussed in redundant detail, 
however, some common important features will be discussed. 
The trailer is normally supplied with fluid to drive cylinder 36 by air 
lines 53 which pass through a distribution valve box 54 (some lines will 
pass to the brake system) and from there to the anti-jackknifing control 
system carried by support frame 23. From the box 54 the line (or lines) 
are distributed to the cylinder and other fluid devices by lines 55. The 
cylinder and dash pot control valves are preferably housed in a fluid 
distribution control box 56 from which they pass via fluid lines 58 (not 
shown in FIGS. 2A, 3A) to their controlled chambers (32 and 63) as shown 
in FIG. 6. 
In the alternate embodiment the dash pot pressure centering control is not 
used, but springs 32a bias the limit element 28 to a centered position. 
These springs have not been employed in the preferred embodiment, but, 
while redundant, they might be added. Similarly, in the alternate and 
modified embodiment, a spring 60 biases the piston 62 to the retracted 
position, as does first embodiment's auxilary spring 60 assist the 
preferred use of fluid pressure. 
In the alternate embodiment shown in FIGS. 2A and 3A adjustment means for 
setting the limit of end of lateral travel of the shaft 30 are provided by 
threaded bolt 133 having a head 34 and lock nut 35. The traverse shaft 
member 30 carries a ball 31 mounted within housing 36 which has a bracket 
for securement to the threaded member 38. The member 38 serves to mount 
the adjustable threaded bolt 133 on the frame. 
In all embodiments the rear of the cylinder is pivotally mounted on the 
frame 23 by a vertically pivotal connector 40. In the preferred 
embodiments this connector has a semi-universal connection 40 which allows 
the cylinder to move laterally as well as vertically, along with the 
lateral movement of the abutment link 28. The abutment is movable along 
with the cylinder as illustrated by the broken lines in FIG. 3 so as to 
prove support for the abutment in positions which are laterally adjustable 
to vary the angular relationship between the tractor and trailer. 
FIG. 7 is a modified section of the shaft housing 36 showing one half of 
the engaging bar shaft 30 and engaging bar limit member 28 in accodance 
with the best mode of this bar limit member 28 in accodance with the best 
mode of this feature as illustrated like a section taken along line 4--4 
of FIG. 3. In this embodiment the wall of the engaging bar shaft housing 
36 has inserted in the bore thereof a bushing 140 into which the shaft 30 
is journaled for rotational and sliding movement. A snap ring 141 
maintains the bushing in place. The shaft is not required to fit with a 
fluid seal to the sides of the bushing 140, and a small clearance is 
provided to ease movement and minimize maintainence. The position of the 
shaft is controlled by the position of the piston 142 (one in each of the 
dash pot fail safe chambers 32 located at either end of the shaft) which 
is provided with two O-rings 143 providing a fluid seal for dash pot 32. 
When the shaft contacts the piston 142 a contact switch (not shown here) 
pole is closed activating a warning signal. At the outer end of the dash 
pot fail safe chamber 32 is an O-ring 144 sealed end plug 145 held in 
place by a snap ring 146, as shown, or by a threaded adjustment nipple 
(not shown). The plug is provided with a threaded fitting aperature 146, 
and bleed aperature 147 having a fitting receptacle 148. As will be 
understood, the end of the shaft 30 is shown abutting the piston 142. 
However, the bushing is approximately 3.5 in. long, and the shaft may 
slide freely to the left so that its illustrated end is away from the 
piston 142 by a distance of about 1.34 in. before its other end contracts 
the piston (not shown) in the housing at the other end. Thereafter, if the 
engaging bar 28 is driven by the ear of the fifth wheel engagment it will 
move the piston and compress the fluid in the dash pot fail safe chamber 
32, expressing fluid through the bleed aperature 148 and/or the aperature 
146 until it reaches the end plug. This distance of travel is 
approximately 2 and 3/16 in. less the amount of the spacing of the end 
plug, a distance which will maintain the end of the shaft within the 
bushing at the other end of the shaft housing due to the axial dimensions 
of the piston and end plug. 
It will be understood that the axis of the shaft is aligned to lie within 
2-3 inches of and parallel to the mounting bar which places the apparatus 
against the beam of the trailer's frame. This close mounting places the 
shaft directly above the center of the V-slot, and provides maximum 
leverage for the engaging bar which itself is about 2 inches wide when it 
is moved into the V-slot engagement zone. It will be understood that the 
use of the bushing, piston and end plug allow (as well as any adjustment 
nipple if needed, allow an installer to vary the extent of lateral slide 
of the shaft to a specific amount, and thereby to permit the free swing of 
the vehicles to be limited to 12-16 degrees (the amount of slide of the 
shaft before it reaches the piston) and the controlled arc to be limited 
to the amount of the limited free swing arc plus an additional 10-14 
degrees (the controlled arc is determined by the amount of piston slide) 
simply by replacing one or more of these three elements with others that 
have different axial dimensions. The fluid pressure system is used to stop 
the axial movement of the piston and control its position (and thus the 
controlled arc) as in the above described system. 
When the fluid pressure in dash pot 32 is such as to hold the piston to the 
left, as it is when the engagement bar is engaged and during its movement 
into the V-slot, the piston causes the limit member 28 to be centered in a 
neutral position between the ends of its permissible travel. Because in 
the embodiment shown in FIG. 7 allows some free play, the member's 
movement in the vertical direction may cause engagement with the side of 
the V-slot, but this will only cause the shaft to slide slightly to permit 
the member to be fully positioned. The bar member centering may be aided 
by springs as shown in FIG. 3A. 
If the limit member is engaged at a loading dock in a position in which the 
bar member 28 comes down outside of the V-slot, due to a sharp 
articulation turn of the vehicle, when the tractor moves forward the slide 
plate will either lift the limit member up above it until it slides above 
the V-slot (as it will with most of the V-slot slide plates used on 
tractors today) or cause the shaft to contact the piston and sound a 
warning signal to the driver. 
FIG. 8 illustrated a modified embodiment of the invention which does not 
have the laterally movable and preferred features of the inventions 
illustrated by FIGS. 2 and 2A. In this embodiment, the abutment element 
128 is aligned vertically in relation to the longitudinal position of the 
frame and is carried by a slide 50 which is pivotally connected as at 51 
to the forward end of the extensible piston rod member 26. The slide in 
this modified embodiment is provided with anti-friction means 53 to assure 
ease of movement within a V-shaped groove 52 which is complementary to the 
V-shaped grooved sides 53 of the slide. This arrangement assures solid 
lateral support for the abutment 126 which projects downwardly from the 
slide 50, but does not allow lateral movement. The controls in such a 
system are along the lines of FIGS. 1-7 however the lateral movement 
controls are eliminated and the abutment member is moved into place only 
when needed to control the lateral movement of the abutment link 28 are 
eliminated. Instead, the switch 71 closes check valve 73' like valves 72 
and 73 to lock fluid in the rear of the chamber 63. In this embodiment the 
jackknifing movement will urge the abutment element 128 rearwardly upon 
contact with the ears. This movement is retarded by the forward pressure 
in the rear of the cylinder 36. Rearward movement is retarded and stopped 
by the switch 71 which checks further compression of the cylinder fluid. 
This arrangement allows some lateral movement, but the systems described 
in the preferred embodiment provides greater flexibility of control. 
The various valves illustrated in the drawings to explain the function of 
the hydraulic control may be combined into multi-function valves located 
in the distribution box 56. Similarly, the electrical controls may be 
altered by those skilled in the art to perform the described functions by 
different elements; however, the preferred described elements provide the 
control capability with simple, reliable and effective means. As shown in 
FIG. 6, the dash pot 32 can be alternatively supplied with hydraulic fluid 
160 through supply means 161, to lock hydraulic fluid in the dash pot in 
leiu of air normally used in the rest of the fluid system. 
Indeed, after review of the foregoing detailed disclosure of the preferred 
embodiments, as well as the alternate and modified embodiment, those 
skilled in the art will appreciate that further changes including 
modifications, rearrangements and alterations described elements may be 
made, both now and in the future, without departing from the spirit and 
scope of the following claims.