Trailer hitch alignment device

Apparatus for indicating axial alignment or deviation from alignment, and proximity between a tow vehicle and a trailer towards which the tow vehicle must be maneuvered. The apparatus comprises a storage reel mounted on the tow vehicle for storing and paying out a cord, a pulley having a magnet for mounting the pulley temporarily on the trailer hitch, and a take up reel mounted on the tow vehicle for applying tension to the cord. As the tow vehicle is maneuvered, changes in relative position between tow vehicle and trailer cause the cord to change length and angular orientation relative to the tow vehicle. These changes are sensed as one or both of the storage reel and take up reel rotate responsive to cord changes. A plurality of switches make or break contact to a matrix of indicating lamps located in the cabin of the tow vehicle, the indicating lamps indicating position of the tow vehicle relative to the trailer. The reels are permanently or temporarily mounted on the tow vehicle. The pulley has a magnet for temporary, readily removable attachment to the trailer hitch.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to apparatus for aligning a tow vehicle 
bearing a trailer hitch ball to a trailer bearing a hitch socket. More 
particularly, the invention provides indicating lamps for indicating 
relative locations of the ball and socket, switches for illuminating 
selected lamps, and a probe for activating appropriate switches. The probe 
comprises a cord paid out from a storage reel mounted on the tow vehicle, 
extending to and encircling a pulley adhered to the trailer hitch, and 
extending to a take up reel disposed upon the tow vehicle. The switches 
respond to length of cord paid out and to angle existing between the tow 
vehicle and the socket of the trailer. 
2. Description of the Prior Art 
Moving a tow vehicle towards a trailer to be towed and aligning a towing 
ball disposed upon the tow vehicle and a tow hitch disposed upon the 
trailer is a notoriously difficult undertaking. Because no direct line of 
sight exists between the operator of the tow vehicle and the ball and 
hitch, the operator must estimate relative locations of the socket of the 
hitch and the ball with which the socket must be vertically aligned. Even 
if the operator periodically leaves the cabin of the tow vehicle to 
observe directly critical proximity and alignment of the tow vehicle and 
trailer, estimating appropriate steering corrections and distances remains 
extremely difficult. 
The prior art has suggested many approaches to solving this problem. U.S. 
Pat. No. 3,825,921, issued to Louis J. Marus et al. on Jul. 23, 1974, 
describes an induction based sensor which controls a dial display located 
proximate the operator of the tow vehicle. By contrast with the device of 
Marus et al., the present invention makes physical connection to the 
trailer, and bases input signals on displacement of a probe physically 
connected to the trailer. The output of the present invention is a matrix 
of indicating lights rather than a dial indicator. The matrix of 
indicating lights indicate not only discrepancy in axial alignment of the 
two vehicles, as performed by Marus et al., but also indicates relative 
proximity, which information Marus et al. fails to report. Marus et al. 
requires careful and secure mounting of one of an induction coil and an 
emitter on the trailer. By contrast, the present invention provides 
convenient yet secure temporary mounting by magnetic attraction. 
Apparatus for improving the operator's view of components of the two 
vehicles as they approach one another is shown in U.S. Pat. Nos. 
5,180,182, issued to James R. Haworth on Jan. 19, 1993, and 5,269,554, 
issued to Benjamin J. Law et al. on Dec. 14, 1993. Haworth provides a 
mirror for mounting to the rear of the tow vehicle, thereby effectively 
putting the ball and hitch within line of sight of the operator. Law et 
al. provide masts attachable to the trailer hitch socket and to the ball. 
These masts extend sufficiently above their mountings as to be directly 
visible to the operator. The devices of Haworth and Law et al. depend upon 
restoring line of sight control to the operator rather than providing a 
visible indicator within the cabin, as seen in the present invention. 
These direct viewing arrangements are susceptible to distortions of 
perception, since depth perception may be distorted by either invention. 
Apparatus for mechanically aligning the two vehicles during maneuvering of 
the tow vehicle is shown in U.S. Pat. Nos. 4,854,604, issued to Bradley E. 
Stallsworth on Aug. 8, 1989, and 4,991,865, issued to Thomas E. Francisco 
on Feb. 12, 1991. In both cases, the apparatus lacks indicators audible or 
visible to the operator, therefore relying upon the operator to steer the 
tow vehicle without constant feedback, as provided by the present 
invention. 
None of the above inventions and patents, taken either singly or in 
combination, is seen to describe the instant invention as claimed. 
SUMMARY OF THE INVENTION 
The present invention provides a visual display to the operator of a tow 
vehicle maneuvering the tow vehicle into alignment with a trailer. The 
display comprises a matrix of indicating lamps which indicate axial 
alignment of the respective vehicles and also proximity between the two 
vehicles. This display is conveniently located in the cabin of the tow 
vehicle, so that the operator is not obliged periodically to exit the 
vehicle to visually observe progress. 
The display is driven by a plurality of switches which are operated by a 
cord or the like which is paid out from a storage reel mounted on the tow 
vehicle. The cord passes over a rotatable pulley magnetically adhered to 
the hitch of the trailer and then extends to a take up reel mounted on the 
tow vehicle. Length of paid out cord operates switches indicating 
proximity between the vehicles. Angular orientation of components of the 
storage and take up reel operate switches indicating deviation from axial 
alignment between the tow vehicle and the trailer. 
Accordingly, it is a principal object of the invention to provide apparatus 
for indicating to the operator of a tow vehicle relative positions of the 
tow vehicle and an associated trailer. 
It is another object of the invention to provide a visual display within 
the cabin of the tow vehicle. 
It is a further object of the invention to utilize mechanical connection to 
or engagement of both the tow vehicle and the trailer to provide inputs to 
the indicator. 
Still another object of the invention is to enable secure yet readily 
removable temporary mounting of apparatus to at least one of the tow 
vehicle and the trailer. 
An additional object of the invention is to indicate both relative axial 
alignment between the tow vehicle and the trailer, and also proximity 
between tow vehicle and trailer. 
It is an object of the invention to provide improved elements and 
arrangements thereof in an apparatus for the purposes described which is 
inexpensive, dependable and fully effective in accomplishing its intended 
purposes. 
These and other objects of the present invention will become readily 
apparent upon further review of the following specification and drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 of the drawings shows novel apparatus 100 mounted on a tow vehicle 2 
and to the tongue 4 of a trailer (not shown in its entirety). Apparatus 
100 indicates relative axial alignment and proximity existing between tow 
vehicle 2 and the trailer. As employed herein, axial alignment signifies 
alignment of the longitudinal axis 6 of tow vehicle 2 and the socket 8 
formed in tongue 4 for receiving a ball 10. It is not necessary that the 
trailer be aligned along its longitudinal axis with respect to tow vehicle 
2. 
Apparatus 100 includes a plurality of visual indicators, preferably in the 
form of a matrix of illuminable lamps or indicating lights 102. Indicating 
lights 102 are located in the cabin (not shown) of tow vehicle 2, where 
they will be in ready view of the operator of tow vehicle 2. The matrix 
preferably includes a row 104 of indicating lights 102 and a column 106 of 
additional indicating lights 102 arranged perpendicularly to row 104. The 
matrix is positioned by the driver so that row 104 indicates angular 
deviation of socket 8 of tongue 4 from longitudinal axis 6 of tow vehicle 
2, column 106 representing proximity between socket 8 and ball 10. 
A probe of variable geometry for sensing relative axial alignment and 
proximity between tow vehicle 2 and the trailer by physical contact with 
both the tow vehicle and the trailer is provided by a flexible cord 108 
stored on and paid out by a storage reel 110. Cord 108 engages a pulley 
112 mounted on tongue 4, preferably at socket 8. Slack which would 
otherwise exist in cord 108 is taken up by take up reel 114 which is also 
mounted on tow vehicle 2. Storage and take up reels 110, 114 are mounted 
on a base plate 116 which is fastened to bumper 12 of tow vehicle 2 by 
bolts 118. 
Operative positions of the probe are shown in FIG. 2. Storage reel 110 is 
seen to have a guide 120 which constrains the housing 122 of storage reel 
110 to rotate in accordance with the direction of cord 108 as cord 108 
stretches in a straight line to pulley 112. Switches (see FIG. 3) are 
dependent upon this rotation for proper indication of axial alignment, as 
will be explained hereinafter. 
Pulley 112 has a mounting element 124 for mounting to tongue 4 of the 
trailer. Preferably, mounting element 124 is a magnet, which enables 
pulley 112 to be both securely temporarily installed on and readily 
removed from the trailer. 
Storage reel 110 and take up reel 114 are each associated with switches 126 
(see FIG. 3), 182 (see FIG. 5) for selectively rendering each visual 
indicator active. In the embodiment depicted, the matrix of illuminable 
lamps 102 are connected to power by these switches 126, 182. Storage reel 
110 and take up reel 114 house switch actuating apparatus for respectively 
operating switch 126 to signal sensed alignment between the tow vehicle 
and the trailer and deviation from alignment, and switch 182 to signal 
sensed proximity between tow vehicle 2 and the trailer. 
FIG. 3 illustrates operation of switch 126, for operating indicating lights 
102 of row 104 for signaling alignment and deviation therefrom. Housing 
122 of storage reel 110 rotates responsive to the direction of cord 108 as 
it stretches between storage reel 110 and pulley 112, as seen in FIG. 2. 
Housing 122 has a bridging conductor 128 disposed upon the lower surface 
thereof. Bridging conductor spans a grounded electrically conductive ring 
130 and an electrical contact 132, 134, 136, 138, 140, 142, or 144. Ring 
130 and contacts 132 . . . 144 are disposed upon base plate 116, which is 
electrically non-conductive, as seen in FIG. 4. Referring again to FIG. 3, 
each contact 132, 134, 136, 138, 140, 142, or 144 is connected by 
circuitry 146 to a single associated indicating light 102 of row 104. 
Indicating lights 102 of row 104 are connected to positive terminal 14 of 
battery 16 of tow vehicle 2, in vehicles in which negative terminal 18 is 
grounded. 
As housing 122 rotates responsive to cord 108 moving guide 120, bridging 
conductor 128 also rotates, progressively contacting a different contact 
132, 134, 136, 138, 140, 142, or 144, and thereby illuminating a 
respective corresponding indicating lamp 102 of row 104. It will be 
understood that the spool (not shown) of reel 110 rotates independently of 
housing 122. Cord 108, pulley 112, housing 122 and guide 120 of storage 
reel 110, and take up reel 114 thus combine to provide switch actuating 
apparatus without which switch 126 would be inoperative. 
Turning now to FIG. 5, it will be seen that take up reel 114 has a 
switching arrangement generally similar to that of storage reel 110, with 
an important exception. That is, bridging conductor 148 is fixed to spool 
150 of take up reel 114, rather than to housing 152. The switch 182 formed 
by grounded ring 154, bridging conductor 148, and contacts 156 . . . 178 
is thus responsive to the length of cord 108 taken up on spool 150, and 
thus indicates relative proximity between tow vehicle 2 and the trailer. 
Switch 182 thus illuminates appropriate indicating lights 102 of vertical 
column 106, and is connected to indicating lights 102 by circuitry 184. 
Switch actuating apparatus corresponding to that of switch 126 is thus 
also provided for switch 182. 
FIG. 5 illustrates a tensioning element acting on take up reel 114. A coil 
spring 180 is arranged to bias spool 150 to rotate in a direction winding 
in cord 108. Spring 180 is coiled around an axle (not shown) on which 
spool 150 is rotatably mounted. One end of spring 180 engages spool 150, 
and the other end engages base plate 116 or another component fixed 
relative to spool 150. This arrangement is well known and need not be set 
forth in greater detail. It is preferred that storage reel 110 be provided 
with a brake or other frictional resistance to rotation so that cord 108 
is maintained under just sufficient tension to constrain cord 108 to be 
stretched tight, while still being wound on spool 150 responsive to 
tension imposed by spring 180. 
The present invention is subject to modifications and variations which may 
be introduced thereto without departing from the inventive concept. 
Obviously, the order in which direction of maneuvering tow vehicle 2 
illuminates indicating lights 102 may be modified to suit individual 
preference. Also, the indicator could be other than indicating lights 102. 
For example, the indicator could comprise flags or pointers (not shown) 
indicating the active condition by their position, or arrows disposed 
movably upon a two dimensional display (not shown). 
The probe could be a telescoping rod (not shown), rather than comprising 
flexible cord 108. 
It is possible that switches 126, 182 and their respective contacts could 
be located in either storage reel 110 or take up reel 114, with 
appropriate modifications to the structure of each. 
In a further example, the tensioning element of take up reel 114 may be 
other than spring 180. 
It is also considered within the scope of this invention to use a single, 
vehicle mounted reel with angular and cord extension measurement 
capabilities. The trailer socket area would then only need to mount a 
single detachable cord and its proximity to the hitch ball would be 
electrically determined in polar coordinates by the reel on the tow 
vehicle. The reel also could be easily detachable from the tow vehicle 
with plugs for the wiring so as to form a completely portable unit. 
It is to be understood that the present invention is not limited to the 
embodiments described above, but encompasses any and all embodiments 
within the scope of the following claims.