Note: Descriptions are shown in the official language in which they were submitted.
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DOUBLE-ACTING TRAILER HITCH
FIELD OF THE INVENTION
This invention relates to a double-acting trailer hitch that requires the use
of
significantly less tongue weight than is required in previously known trailer
hitches and
which may be used effectively with trailers having various tongue weights and
with tow
vehicles having various frame strengths.
BACKGROUND OF THE INVENTION
During the 1920s and 1930s, trailer hitches began incorporating a hitch ball
attached to an extension of the tow vehicle and a ball coupler carried by the
forward
end of the trailer. The coupler was engaged with the ball so that the tow
vehicle could
pull the trailer along the highway.
A number of developments, including improved highways, more powerful
automobiles and trucks, and the advent of electromagnetic trailer brakes
allowed the
vehicles and attached trailer to achieve greatly increased highway speeds.
These
developments also permitted much heavier trailers to be towed. The traditional
ball
hitch was soon found to be unacceptable for handling such increased speeds and
trailer weights. In particular, the rig tended to be very unstable. The most
significant
source of instability was the upward hinging and toggling that occurred
between the tow
vehicle and the trailer at the point of the coupling ball. This was especially
noticeable
during braking. At such times, a portion of the linear momentum of the tow
vehicle is
converted to angular momentum. This causes the front of the tow vehicle to dip
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downwardly and the rear of the vehicle to pitch upwardly. In the case of the
original ball
hitch, the delay in activation of the trailer's electromagnetic brakes caused
the
significant weight of the trailer to push against the trailer ball. This
tended to push the
rear of the tow vehicle upwardly with even greater force. The height of the
ball at the
top of the hinge point effectively formed a toggle with front axle of the tow
vehicle and
the rear axle of the trailer. Accordingly, the linear momentum of the trailer
was also
converted into upward force on the ball. The toggle effect was exacerbated
when the
rig encountered bumps or dips on the highway. All of this made the traditional
ball
coupling highly unstable and contributed to serious highway accidents.
To counteract the instabilities of the original ball hitch, the weight-
distributing
hitch was introduced during the 1950s. Initially, the upward hinging exhibited
between
the tow vehicle and trailer was addressed by adding weight to the tongue of
the trailer
proximate the ball. It was determined that "a tongue weight" of approximately
10 to 15
percent of the gross trailer weight was generally adequate to prevent
excessive upward
hinging about the trailer ball. However, simply adding tongue weight was and
still is, by
itself, an inadequate remedy. This weight must be effectively distributed
among the
axles of the tow vehicle and the trailer so that the rear of the tow vehicle
does not sag
and a level, stable ride is maintained. Weight distributing trailer hitches
that perform
this function have been available for many years.
Notwithstanding their current widespread use, conventional weight distributing
hitches still exhibit a number of disadvantages. The forces that these hitches
generate
to counteract the heavy tongue weight of the trailer tend to exert significant
stress on
the suspension of the tow vehicle. As a result, trucks, sport utility vehicles
and full
frame automobiles normally must be used as the tow vehicle. Smaller
automobiles
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without a full frame are generally inadequate to support the force produced by
the
weight-distributing hitch. Such smaller vehicles normally cannot be used to
pull a large
trailer, which is equal to or heavier than the tow vehicle.
Moreover, the heavy tongue weights exhibited in present weight distributing
hitches can create serious instabilities when the rig is driven at highway
speeds. In
particular, during a sudden lane change, which may result when the driver
takes
evasive action, the tongue weight carried by the overhang of the trailer
behind the rear
axle of the tow vehicle often creates a large X-axis moment transverse to the
direction
of travel. This moment can cause the tow vehicle and trailer to jackknife or
flip.
Serious accidents often result from such instability.
Trailer instabilities are inherent at all speeds of travel. At speeds below 40
mph
they are usually not yet of such sign~cance as to create unsafe travel.
Instability
increases as a function of speed of travel. At 50 mph some kind of control
must be
introduced or it is simply so unsafe that the speed cannot be maintained.
The upper threshold of safe travel of a tow vehicle towing a heavy trailer by
means of a ball coupler alone is approximately 35 mph for the heavy trailers
to
approximately 45 mph for lighter trailers. These figures are approximate. The
greater
the trailer weight is in proportion to the tow vehicle's weight, the lower the
speed at
which the coupled vehicles can safely travel.
The free hinging movement at the trailer ball is also a factor in trailer
instability.
The height of the trailer ball is another factor, because the higher the ball
above the
axles of the vehicles, the greater is the upward thrust of the toggle at the
ball.
Where the ball pitches upward during tow car braking (and before trailer
braking
is effective due to the magnet delay) the toggle is increased significantly. A
heavy
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trailer thrusting forward on the rear arm of the toggle, and is pushing
upwardly on the
ball lifts the rear end of the tow vehicle which causes dangerous loss of
traction on the
road surface.
Conventional weight distributing trailer hitches also normally require that
the
trailer axles be positioned fairly close together and located a significant
distance from
the trailer tongue. This is needed in order to provide the trailer with the
necessary
tongue weight. If the trailer axles are positioned close together, optimal
trailer stability
may not be exhibited.
One known trailer hitch designed for use with relatively lightweight frameless
automobiles employs a dolly that is mounted beneath the hitch. The dolly
travels
along the roadway with the rig and supports the tongue weight without
distributing
the weight to the tow vehicle. This apparatus is unduly complicated and
introduces
additional wheels that must engage the highway. A failure of the dolly wheels
will
render the entire rig inoperable.
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SUMMARY OF INVENTION
It is therefore an object of the present invention to provide a trailer hitch
in which
tongue weight is not a factor in towing stability, thus permitting the use of
a significantly
reduced tongue weight.
It is a further object of this invention to provide a trailer hitch, which
joins the
frame of the tow vehicle and the frame of the trailer such that they behave as
a single
piece along an axis extending in the direction of travel.
It is a further object of this invention to provide a trailer hitch that
eliminates the
upward hinging and toggle action between the tow vehicle frame and the trailer
frame
so that significantly improved and more stable towing is achieved.
It is a further object of this invention to provide a trailer hitch that
permits the
tongue weight to be greatly reduced so that less stress is placed on the
springs and
suspension of the tow vehicle.
It is a further object of this invention to provide a trailer hitch that
reduces the
dangerous instability and risk of jackknifing often accompanying evasive
maneuvers
and sudden lane changes.
It is a further object of this invention to provide a trailer hitch, which
exhibits
extremely stable operation, but without requiring the use of a heavy tongue
weight.
It is a further object of this invention to provide a trailer hitch that
minimizes the
transverse moment at the trailer ball and resulting instability caused when a
tow vehicle
and trailer swerve on the highway.
It is a further object of this invention to provide a trailer hitch apparatus
that
reduces the tongue weight of the trailer so that additional accessories and/or
equipment are not required to be mounted to the forward end of the trailer.
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It is a further object of this invention to provide a weight distributing
trailer
hitch apparatus that employs an effective coil spring dampening system to
control
and reduce bounce and greatly improve ride stability.
It is a further object of this invention to provide a weight distributing
trailer hitch
employing an easy to operate cam that adjusts the hitchhead quickly and
reliably so
that the hitchhead and the drawbar can be coupled and the tongue weight is
properly
and evenly distributed to the tow vehicle.
It is a further object of this invention to provide a trailer hitch of both
the weight
distribution kind and the low weight kind which converts the toggling upward
force at
the trailer coupling (which force is generated by the trailer pushing against
the coupling
means such as during braking) into a downward force at the coupling and thus
causing
this force to become a force which increases stability, instead of being a
force which
increases instability as in previous practice.
It is a further object of this invention to provide control of the angular
forces of
momentum in the tow vehicle during the short period of early braking which
occurs
before the electric brakes of the trailer become effective.
This invention results from a realization that the normally high tongue
weights
used in weight-distributing trailer hitches may be sign~cantly reduced by
employing
preloaded, double-acting spring means for dampening the relative movement
befinreen
the tow vehicles and the trailer about a horizontal (X) axis transverse to the
direction of
travel. This invention results from the further realization that tongue weight
may be
reduced and stability improved by pivotably overlapping the forward end of the
trailer
and the X-axis coupling and joining the drawbar extension of the tow car hitch
to the
trailer at a point rearwardly of and below the hitch ball. This enables the
tow vehicle
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and trailer to act essentially as a unified beam, which is controlled by a
preloaded
double-acting spring so that hinging and toggling are eliminated when the rig
is driven
at highway speeds. Conversely, hinging is allowed to occur between the tow
vehicle
and trailer when bumps and dips are encountered at low speeds. The overlapping
of
the drawbar extension and the trailer frame, as well as the use of a preloaded
spring
assembly also helps to safety control the force of angular momentum normally
generated in the tow vehicle during braking. As used herein "double-acting"
means
that the spring assembly controls both upward and downward motion of the tow
vehicle
and trailer at their point of interconnection, which is located proximate the
rearward end
of the drawbar extension significantly behind and below the hitch ball.
This invention features a double-acting trailer hitch for interconnecting a
trailer to
a tow vehicle. The hitch includes a drawbar assembly that is selectively
attached to the
tow vehicle. A first coupling component is attached to a rearward end of the
drawbar.
A hitchhead assembly includes a ball element that carries a clevis and is
suspended by
a ball coupling supported by the trailer. The hitchhead also includes a yoke
that is
pivotally connected to the clevis by a first horizontal pivot that is axially
transverse to
the direction of travel. A drawbar extension is interengaged with and extends
generally
rearwardly from the horizontal pivot. A second coupling component is pivotally
connected to the yoke along a generally vertical axis. The second coupling
component
may include means for interengaging complementary means in the first coupling
component such that the first and second coupling components are coupled and
the
drawbar is held at a predetermined axial angle relative to the ground. There
are also
means for interconnecting a rearward portion of the drawbar extension to the
trailer.
Such means for interconnecting may include a horizontal pivot that is
substantially
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parallel to the horizontal axis and perpendicular to the direction of travel.
The means
for interconnecting further include preloaded double-acting spring means
connected to
the horizontal pivot for dampening upward and downward movement of the drawbar
extension relative to the trailer. While the tow vehicle and trailer travel in
a straight line
on a relatively level highway, the spring means resist pivoting of the drawbar
extension
and the tow vehicle and frame move forwardly as a single unified structure.
When the
tow vehicle engages bumps and dips in the roadway, the preloaded spring means
permit the drawbar extension to temporarily pivot relative to the trailer,
until the
undulation is crossed. The preloaded spring means then return the drawbar
extension
to its original condition.
In a preferred embodiment, the first coupling component is fixedly
interconnected to the drawbar. The first and second coupling components may
include
elements that prevent hinging or pivoting movement between the first and
second
coupling components. For example, the first coupling component may include an
upper and a lower hitchpin hole. The second coupling component may include a
horn
featuring an upper slot or recess and a lower hitchpin hole. The hom may also
include
a ramp that is connected to the upper slot. The drawbar assembly may be
directed
against the hom such that the upper hitchpin rides up the horn and drops into
the slot of
the second coupling component.
The second coupling component may include means for adjusting the height of
the second coupling component. Such means may include a vertical channel
element
that is slidably interengaged with the hom. Means may be provided for
interlocking the
hom in the channel element at a selected height. The height adjustment allows
the
user to fine-tune the hitch to accommodate differing tow vehicle heights.
Additionally,
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the drawbar assembty may be constructed so that the first coupling component
is
disposed at an angle to the drawbar. As a result, the drawbar assembly may be
inverted to position the first coupling component at differing heights
relative to the
hitchhead assembly. The drawbar assembly is selectively inverted, depending
upon
the height of the tow vehicle, so that the first coupling component is held at
a height
that conveniently interengages the second coupling component carried by the
hitchhead.
The spring means preferably include at least one generally helical coil or
compression spring and linkage that are interconnected between the harizontal
pivot,
located at a rearward portion of the drawbar extension, and the trailer. Each
spring
may be disposed in a housing that is mounted in the trailer frame. A single
spring may
be utilized for relatively low tongue weights; a pair of springs may be
employed for
medium tongue weights; and three springs may be used for heavy tongue weights.
The spring assemblies may be adjustably preloaded to dampen pivoting of the
drawbar
extension about the horizontal axis by a selected or predetermined amount. The
spring
assembly may include a connector link that is slidably mounted within the
housing and
resiliently engaged with each spring. The depending connector link may be
pivotably
interconnected to a distal portion of the drawbar extension. The spring means
minimize the hinging motion or toggle effect normally exhibited between the
trailer and
the town vehicle and thereby reduce the need for using heavy tongue weights to
counteract this effect.
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BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages will occur from the following
description
of preferred embodiments and the accompanying drawings, in which:
FIG. 1 is an elevational, side view of a preferred trailer hitch according to
this
invention with the hitchhead assembly suspended from the front end of a
trailer and the
drawbar assembly extending from a tow vehicle (not shown); the hitchhead
assembly
and the drawbar assembly are depicted prior to coupling in accordance with
this
invention;
FIG. 2 is a top plan view of the trailer hitch in an assembled condition;
FIG. 3 is an elevational, party cross sectional and partly cut away view of
the
drawbar extension, the yoke, the rearward end of the channel, and the ball
component
and clevis by which the foregoing components are suspended from the trailer,
FIG. 4 is a plan view of the drawbar extension, the yoke and the second
coupling component;
FIG. 5 is a rear, cross sectional view of the lower portion of a preferred
single
coil spring assembly used in the hitch of this invention;
FIG. 6 is a rear, cross sectional view of the upper portion of the spring
assembly;
and
FIG. 7 is an elevational side view of the hitch in a fully assembled and
operating
condition.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
There is shown in shown in FIGS. 1 and 2 a preferred double-acting, weight
distributing hitch apparatus 10. It should be understood that a number of the
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components featured in the hitch are analogous and constructed similarly to
corresponding features disclosed in commonly owned U.S. Patents Nos. 5,951,036
and
6,142,500. Components described herein may also be constructed in the manner
shown for analogous components and those referenced patents.
In particular, hitch 10 is designed for attaching an A-frame trailer 12 to a
tow
vehicle, not specifically shown. Hitch 10 is suited for use in connection with
various
types of trailers, as well as all types and sizes of tow vehicles. Neither the
type of tow
vehicle nor the type of trailer should be construed as a limitation of this
invention. It
should also be understood that the axles and wheels of both the trailer and
the tow
vehicle are not depicted. These are standard components that do not comprise a
part
of the invention. Their relative positioning and operation should be
understood to those
skilled in the art. Nonetheless, through the use of the invention disclosed
herein, the
axles of the trailer may be spaced further apart than in conventional
trailers. This is
possible because of the significantly reduced tongue weight required for this
trailer hitch.
Repositioning the forward trailer axle closer to the tongue reduces the
leverage of the
tongue and thereby the tongue weight. This shall become more evident from the
following description.
Hitch apparatus 10 includes a forward drawbar assembly 14 and a rearward
hitchhead assembly 16. The hitchhead assembly is attached to and suspended
from
trailer 12 in a manner described in the above-referenced applications and
further
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described below. The drawbar assembly is disposed beneath the tow vehicle
bumper
(not shown) and includes an elongate drawbar, 20 which preferably has a square
cross
sectional shape. Bar 20 is selectively inserted in a complementary shaped
receiver
tube 22. The receiver tube is secured to and extends from a transverse
mounting bar
24. This bar extends between and is attached to the longitudinal frame
components of
the tow vehicle. In tow vehicles not employing a frame, the transverse bar can
be
attached to various other structural components of the tow vehicle. Bar 20 is
secured
to tube 22 by a transverse pin 26. A first coupling component 30 is
permanently and
preferably unitarily fixed to drawbar 20. Component 30 comprises a shank that
extends
angularly from drawbar 20 and has a pair of spaced apart flanges 32 and 34,
best
shown in FIG. 2. These flanges include a pair of aligned upper holes and a
pair of
aligned lower holes. Each pair of aligned holes receives a respective hitchpin
40, 41.
The lower pin should be removable. The upper pin may be permanently or
removably
carried by component 30. The operation of the coupling component 30 and the
hitchpins is described more fully below. Each pin is secured in its respective
hole by a
spring clip 44. The axis 50 of drawbar 20 is perpendicular to the line
interconnecting
the centers of the holes receiving pins 40 and 41. In alternative embodiments
a
pivotably adjustable first coupling component may be used as shown in United
States
Patent No. 5,951,036 and PCT International Publication No. W000/01546.
Hitchhead assembly 16, also shown in FIGS. 3 and 4, includes a standard ball
element 46 that is threadably attached to a clevis 64. Alternatively, the ball
may be
welded or otherwise secured to the clevis. The ball element comprises the Y-
axis
coupling about which the rig rotates when one of the wheels strike a curb, for
example.
The ball is mounted in and suspended from ball coupler 60 (FIGS. 1 and 2) in a
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conventional swiveling manner and, more particularly, in the manner shown and
described in the above-referenced applications. The Y-axis is in the line of
travel. The
hitchhead further includes a yoke device 72 that is pivotally connected to the
lower end
of clevis 64 by a horizontal pivot or bolt 68. Yoke 72 includes a forward
bearing 65 and
a generally rearwardly extending shank 69.
As shown in FIGS. 1, 3 and 4, a drawbar extension 66 is pivotally
interconnected
to pivot 68 at the lower end of clevis 64. More particularly, drawbar
extension 66
includes a pair of elongate spaced apart elements 71 and 73 interconnected by
transverse struts. A hole is formed proximate the forward end of each elongate
element
71, 73. These holes, which are aligned interengage clevis pivot 68 such that
drawbar
extension 66 is pivotably connected to clevis 64 as shown in FIGS. 3 and 4. As
best
shown in FIG. 4, elements 71 and 73 are sandwiched about shank 69 of yoke 72.
Threaded connector element 79 extends between elements 71 and 73 and through
shank 69. By tightening component 79 elements 71 and 73 of drawbar extension
66 are
tightened against the shank. Horizontal pivot 68 permits the drawbar extension
and the
yoke to pivot or rotate about a horizontal axis that is generally transverse
to the direction
of travel. As a result, the drawbar extension is permitted to pivot relative
to the hitch ball
in the manner indicated by doubleheaded arrow 70 in FIG. 1.
A channel member 80, FIGS. 1 - 7, is pivotally connected to yoke 72 by a
generally vertical pin or shaft 82. More particularly, channel 80 is attached
integrally to
a pair of spaced apart bearings 84, 85 that are sandwiched about the forward
bearing
65 of yoke 72. See the analogous construction disclosed in United States
Patent
Application Serial No. 5,951,036 and PCT International Publication No.
W000/01546.
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The bearings have aligned holes that receive pin 82. As a result, channel
member 80
is pivotal about a Z-axis defined by pin 82 relative to hitchhead 16 and
drawbar
extension 66, in the manner indicated by doubleheaded arrow 86 in FIG. 2. The
pin 82
effected forms a Z-axis coupling.
A horn 88, best shown in FIGS. 1 and 2, is slidably mounted in channel 80 in
the
manner described in the previously referenced applications. As a result, horn
88 may
be adjusted vertically within channel 80 as indicated by doubleheaded arrow 90
in FIG.
1. Horn 88 includes an upper recess or slot 92 and a lower hitchpin hole. An
incline or
ramp 96 extends from the forward end of the horn to a point adjacent recess
92. The
channel member and its adjustable attached horn comprise a second coupling
component that is interengaged with the first coupling component in a manner
more fully
described below.
Drawbar extension 66 is interconnected to trailer frame 52 proximate the
rearward distal end of the drawbar extension. More particularly, drawbar
extension 66
is interconnected to the trailer frame by a vertically disposed dampening
spring
assembly 300, FIGS. 1, 2 and 5 - 7. The distal end of the drawbar extension is
pivotally
connected to a connecting link 301 of spring assembly 300 at X-axis pivot 302.
In the
version described herein, the spring assembly employs a single coil spring
assembly
300. Alternative embodiments may employ other numbers and types of spring
assemblies.
Spring assembly 300 is shown in detail in FIGS. 5 and 6. The spring assembly
is mounted by plates 297 and 315 to a spring assembly support component 299 of
trailer frame 52. See also FIG. 2. A linkage 316 depending from assembly 300
and
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extending through component 299 interconnects the spring assembly with a pivot
302
formed through drawbar extension 66 (FIGS. 5 and 6).
Spring assembly 300 comprises a vertically disposed helical coil spring 304
that
is arranged vertically and mounted within a cylindrical spring housing 306.
The housing
comprises a pair of telescopically interconnected cylindrical components 307
and 309.
The spring is wound about a central tube 308 and extends between a lower
movable
base 310 and an interior surtace at the top end of spring housing 306. The
lower end
of tube 308 is fixed to a drive block 314. Drive block 314 is received
slidably through a
central opening in a plate 315.
The distal end of drawbar extension 66 is pivotably connected by pivot 302 to
connecting link 301 of spring assembly linkage 316. Connector link 301 is
received in
the lower end of a generally cylindrical linking component 320 and is secured
therein by
appropriate means such as, for example, a threaded sleeve or bushing 322,
which is
fastened to link connector 301 and threadably engaged with interior threads of
link
component 320. Component 320 extends upwardly through a bottom bracket 324 and
into a vertical opening 326 in spring assembly support 299. The link component
carries
a projection 330 at its upper end. A pin 332 pivotably interconnects
projection 330 to
block 314.
As shown in FIG. 6, the upper end of tube 308 receives a threaded shaft 334
that carries a nut 338 that is welded to the upper end of tube 308. Shaft 334
extends
through a central opening in a movable cap 335 received in an opening at the
top of
cylindrical component 309. The upper end of shaft 334 carries a fixed head 339
that is
received in a clearance 341 of upper plate 340. That plate is supported above
housing
306 by vertical posts 342. The normal bias of spring 304 urges cap 335 against
the
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lower surface of plate 340, as shown in FIG. 6. As best shown in FIG. 6, the
lower
ends of posts 342 are fastened to plate 315.
Spring assembly 300 dampens relative movement between the trailer and the
rearward end of drawbar extension 66, located at the X-axis couple or pivot
302. When
the rig engages a bump in the road, connector link 301 urges link assembly 316
upwardly, as indicated by arrow 370 in FIG. 5. This urges block 314 upwardly.
The
block pushes movable base 310 upwardly to resiliently compress coil spring 304
within
housing 306. At the same time, block 314 drives tube 308 and attached shaft
334
upwardly such that the shaft slides through cap 335 and plate 340. The coil
spring
thereby dampens the upward hinging movement between the tow vehicle and the
trailer.
Conversely, when the rig engages a dip in the road, the connector link and
attached link assembly are pulled downwardly in the direction of arrow 374.
This pulls
tube 308 and shaft 334 downwardly. As a result, upper cap 335 pushes
cylindrical
component 309 resiliently downwardly against coil spring 304. Downward
movement
of the drawbar extension relative to the trailer and therefore dampened
hinging
between the tow vehicle and trailer are also dampened.
It should be noted that the spring may be selected and preloaded to accomplish
desired dampening. The preloaded compression spring largely replaces the
pressure
required by conventional heavy tongue weights and serves to significantly
reduce
bounce-related hinging and toggling effects. Various alternative types of dual
acting
spring constructions may be employed within the scope of this invention.
Preloading
the coil springs eliminates the tedious and often difficult task of preloading
conventional
trailer hitch spring bars.
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Spring assembly 300 is typically constructed to permit some degree of play or
movement in linkage 316 as the trailer is pulled. Lateral play is provided by
pivot 332.
That pivot may be disposed on a tapered, fulcrum-like surface (not shown) of
projection
330 so that play is also provided in forward and rearward directions. In such
embodiments, a slight gap should be formed between link component 320 and
surrounding brackets or structure carried by the trailer (e.g, lower bracket
324, FIG. 6).
Hitch apparatus 10 is installed in the following manner. Initially, drawbar 20
is
inserted into receiver tube 22. The trailer is then leveled with respect to
the ground
using conventional leveling means. Next, the installer selects the orientation
of the
drawbar. This will depend upon the height of the tow vehicle. Normally, the
receiver
tube is mounted to the tow vehicle such that its axis is positioned anywhere
from 10" to
17" above the ground. For low heights (e.g. 10" to 13.5") the drawbar assembly
is
orientated in the manner shown in FIG. 1. Coupling component 30 is angled
upwardly
and positioned proximate hitchhead assembly 16. Alternatively, in cases where
a
larger tow vehicle and a higher positioned receiver tube are used, the drawbar
assembly may be inverted so that the coupling component is angled downwardly
to
meet the hitchhead assembly 16. It should be noted that in most cases the
hitchhead
assembly is positioned such that there is a distance of approximately 17" to
19" from
the ground to the center of the ball. After the drawbar assembly is oriented
properly,
the bar 20 is inserted into receiver tube 22 and the pin 26 is connected to
secure the
drawbar assembly to the tow vehicle. The user then installs an upper hitchpin
40
through the aligned holes in component 30 and secures that hitchpin in place
with an
appropriate hitchpin clip 44.
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Hitchhead assembly 16 is mounted to trailer 12 by suspending the ball element
from the ball coupler. The drawbar extension 66 is interconnected to spring
assembly
300 by pivot 302. A connecting strap is installed to connect trailer frame 52
and shank
69.
Horn 88 is vertically adjusted within channel 80 so that the center of recess
92
is approximately equal to the height of the center of the upper holes (i.e.
hitchpin 40) in
coupling component 30. The horn is then locked in place in the manner
described in the
referenced application. In some cases, the horn may be tack welded so that it
is
permanently fixed in the channel. At this point, the hitch installer's task is
normally
completed. In some cases, skilled laymen or homeowners may be able to
undertake
the above referenced installation procedures.
To complete installation and coupling of the tow vehicle and trailer, the user
operates jack 56, FIG. 1, so that the center of recess 92 is positioned
approximately .75
inches above the center of the aligned upper holes in component 30. The
apparatus
is then coupled by simply driving the tow vehicle rearwardly toward the
trailer. The
upper hitchpin 40 interengages ramp 96 and rides up the ramp until it drops
into horn
recess 92. At this point, the aligned lower holes of component 30 and the
lower hole of
horn 88 are separated by an angle of approximately 1 °. This amount is
determined
because the center of the lower horn hole 94 is disposed approximately 1
° rearwardly
(i.e. toward the trailer) of the center of recess 92. The user then raises
jack 56 until
holes 39 and 94 are aligned. A lower hitchpin 41, FIG. 1, is then inserted
through the
aligned lower holes and coupling is completed. The jack is then used to lower
the trailer
and removed. At this point, the apparatus is attached to and is fully coupled
as
illustrated in FIGS. 2 and 7. Due to the offset construction between the upper
recess
and the lower hole of horn 88, the
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19
drawbar of assembly 14 is tilted 1 °. This imparts the necessary
torsion to the tow bar
assembly. It has been determined that 1 ° provides more than sufficient
weight
distribution because of the reduced amount of tongue weight needed by this
apparatus.
In operation as the tow vehicle is driven, drawbar extension 66 pulls trailer
at a
point located behind and below the trailer ball. The towing force is applied
to the trailer
at the distal end of the drawbar extension and not at the hitch ball. The
trailer and
drawbar extension overlap and effectively act as a unified beam. There is
significantly
less need to use a heavy tongue weight because a toggle or hinge effect is not
exhibited at the hitch ball. Instead the toggle is formed at pivot 302, behind
and below
the ball and is level or directed downwardly. The rear end of the tow vehicle,
therefore,
resists being lifted upwardly. Moreover, because a double-acting spring is
used, a
heavy tongue weight is not required to offset trailer bounce. Instead, the
unique form of
interconnection between the trailer and the hitch, as well as the spring force
of
assembly 300 accomplishes this. During normal operation on a level surface,
virtually
no hinging is permitted. If a bump or dip is struck, the spring assembly
allows the
drawbar extension to pivot (about pivots 68 and 302) and this permits the
requisite
hinging between the tow vehicle and the trailer. Preloaded spring assembly 300
then
quickly returns the drawbar extension to its original position {i.e. the
spring assembly
restricts pivoting of the drawbar extension about pivots 68 and 302) after the
bump or
dip is traversed and thereby serves to dampen hinging movement between the tow
vehicle and the trailer. An improved, stable ride is achieved. At the same
time, the
resulting tongue weight normally needed is reduced substantially.
The new hitch eliminates the free hinging in every direction and the toggling
by
extending the drawbar back under the trailer frame and providing the
application of the
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towing force at a coupling joint which is below the line joining the axles of
the tow
vehicles and the trailer. This means that any toggle force generated by the
trailer is
downward and increases traction on the tow vehicle.
Reducing the tongue weight yields several important advantages. Less stress is
exerted on the suspension and springs of the tow vehicle. Additionally, the
transverse
moment that is otherwise generated when the rig swerves, such as during lane
changes or when taking evasive action, is significantly reduced. The risk of
jackknifing
and flipping is therefore minimized. Moreover, reducing the tongue weight
reduces the
need for additional items, such as propane tanks and tools, to be stored
proximate the
tongue. The precise reduction in tongue weight that is possible through the
use of the
invention may vary. However, the spring assembly is typically preloaded to
reduce
hinging sufficiently so that the tongue weight may be reduced to a level not
exceeding
1.5 times the average weight per foot of the trailer. Ideally, the tongue
weight that is
required is between 'h and 1 '/2 times the average weight per foot. This means
that the
tongue weight should ideally be approximately 120 to 300 pounds. One half of
that
weight is transmitted to the tow vehicle. Accordingly, through the use of this
hitch, only
60 to 180 pounds of tongue weight acting on the tow vehicle. This is less than
the
average weight per foot of virtually all trailers. This is a negligible force,
which should
have virtually no effect on the tow vehicle or its suspension. Such a low
force also
permits the hitch of this invention to be utilized on vehicles that do not
have a frame.
The dolly required in the prior art is eliminated. By reducing the tongue
weight
required, the forward axial of the trailer may be moved forwardly along the
trailer, which
increases further the stability of the trailer.
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It should be noted that in alternative embodiments of this invention, a
plurality of
coil springs may be utilized to dampen upward and downward movement of
trailers
having even heavier tongue weights. Alternative spring assemblies and means
for
mounting those assemblies to the trailer may also be employed. For example,
one or
more stacks of disc springs may be utilized. See the above referenced United
States
applications. Such assemblies are particularly effective for heavier tongue
weights. In
either version, the double-acting spring assembly serves to dampen both upward
and
downward hinging movement between the tow vehicle and the trailer. The forward
end
of the trailer overhangs the rearward end of the drawbar extension. As a
result, the
vehicles act essentially as a unified beam while traveling down the highway. A
heavy
tongue weight is therefore not needed to offset a hinge or toggle effect.
Instead, the
unique form of interconnection between the trailer and the hitch, as well as
the spring
force of assembly 300 accomplishes this. The hitch of this invention provides
an
improved stable ride. The tongue weight may be reduced to a level between 'h
and 1
times the average gross weight per foot of the trailer. This translates to a
tongue
weight of approximately 300 pounds or less. A force comparable to only '/Z of
this
weight is transmitted to the tow vehicle. A significantly improved, stable
ride is
achieved.
Although specific features of the invention are shown in some of the drawings
and not others, this is for convenience only, as each feature may be combined
with any
and all of the other features in accordance with this invention.
Other embodiments will occur to those skilled in the art and are within the
following claims:
