U.S. patent number RE28,590 [Application Number 05/494,074] was granted by the patent office on 1975-10-28 for apparatus for aligning the couplings on separate vehicles.
Invention is credited to Melvin I. Salmi.
United States Patent |
RE28,590 |
Salmi |
October 28, 1975 |
Apparatus for aligning the couplings on separate vehicles
Abstract
Disclosed is an indicating apparatus for attachment to a trailer
or the like for use in aligning the couplings between the trailer
and a towing vehicle, said apparatus being mounted on the trailer
and having a spring loaded extendible and retractable guide line
which releasably attaches to the rear of the towing vehicle
adjacent the coupling. Sensing means are included in the apparatus
for sensing deflection of the guide line in horizontal and vertical
directions and for sensing the separation of the vehicles and
indicator means in the vehicle to indicate said deflections and
separation to the operator of the towing vehicle. Variable
sensitivity means for increasing the sensitivity of the apparatus
as the towing vehicle approaches the trailer and means for allowing
the towing vehicle to approach the trailer from various angles are
also provided.
Inventors: |
Salmi; Melvin I. (Dallas,
TX) |
Family
ID: |
26890848 |
Appl.
No.: |
05/494,074 |
Filed: |
August 3, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
195263 |
Nov 3, 1971 |
03734539 |
May 22, 1973 |
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Current U.S.
Class: |
280/477; 340/431;
340/687; 342/458 |
Current CPC
Class: |
B60D
1/38 (20130101) |
Current International
Class: |
B60D
1/38 (20060101); B60D 1/00 (20060101); B60q
001/00 () |
Field of
Search: |
;280/477 ;340/282,52R
;343/112R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Friaglia; Leo
Attorney, Agent or Firm: Glaser; Kenneth R.
Claims
What is claimed and desired to be secured by United States Letters
Patent is:
1. An apparatus for guiding the approach of a towing vehicle to
align the hitch on the towing vehicle with the hitch on a trailer
comprising:
a. a guide line detachably connected between said trailer and said
towing vehicle;
b. means for maintaining a tension in said guide line as said
towing vehicle is moved with respect to said trailer;
c. sensing means operatively associated with said guide line for
sensing the relative vertical and horizontal positions of the
hitches on said towing vehicle and said trailer, during the
approach of said towing vehicle to said trailer; and
d. indication means operatively connected to said sensing means for
indicating the relative vertical and horizontal positions of the
hitches on said trailer and said towing vehicle.
2. An apparatus as defined in claim 1 wherein additional means are
provided for sensing and indicating the relative separation of said
towing vehicle and said trailer.
3. An apparatus as defined in claim 1, additionally comprising
automatic jack means on said trailer for variably adjusting the
height of said hitch on said trailer, and control means operatively
associated with said sensing means and said jack means for
automatically maintaining a fixed, relative vertical separation
between said hitch on said towing vehicle and said hitch and said
trailer during the approach of said towing vehicle to said
trailer.
4. An apparatus as defined in claim 1 wherein, said sensing means
additionally comprises variable sensitivity means for increasing
the sensitivity of said sensing means to sense the relative
horizontal positions of said trailer and said towing vehicle as
said towing vehicle approaches said trailer.
5. An apparatus as defined in claim 1 wherein said sensing means
additionally comprises adjustment means for guiding the approach of
said towing vehicle to said trailer from various directions of
approach.
6. An apparatus for guiding the approach of a towing vehicle to
align the hitch on the towing vehicle with the hitch on a trailer
comprising:
a. a guide line detachably connected between said trailer and said
towing vehicle;
b. sensing means operatively associated with said guide line for
sensing the relative vertical and horizontal positions of the
hitches on said towing vehicle and said trailer, during the
approach of said towing vehicle to said trailer; and
c. indication means operatively connected to said sensing means for
indicating the relative vertical and horizontal positions of the
hitches on said trailer and said towing vehicle.
7. An apparatus as defined in claim 6 wherein additional means are
provided for sensing and indicating the relative separation of said
towing vehicle and said trailer.
8. An apparatus as defined in claim 6, additionally comprising
automatic jack means on said trailer for variably adjusting the
height of said hitch on said trailer, and control means operatively
associated with said sensing means and said jack means for
automatically maintaining a fixed, relative vertical separation
between said hitch on said towing vehicle and said hitch and said
trailer during the approach of said towing vehicle to said
trailer.
9. An apparatus as defined in claim 6 wherein, said sensing means
additionally comprises variable sensitivity means for increasing
the sensitivity of said sensing means to sense the relative
horizontal positions of said trailer and said towing vehicle as
said towing vehicle approaches said trailer.
10. An apparatus as defined in claim 6 wherein said sensing means
additionally comprises adjustment means for guiding the approach of
said towing vehicle to said trailer from various directions of
approach. .Iadd. 11. Apparatus for aiding in the hitching of a
towing vehicle with a vehicle to be towed, comprising:
a. guide means defining a preferred path of vertical alignment
between the respective areas of said towing vehicle and of said
vehicle to be towed where said hitching is to occur;
b. electrical sensing means operatively associated with said guide
means for continuously monitoring the relative vertical positions
of said respective areas during the approach of said towing vehicle
and said vehicle to be towed and producing a signal indicative of
the misalignment of said respective areas from said preferred path
of vertical alignment; and
c. indication means operatively connected to said electrical
sensing means for receiving said signal and indicating the relative
vertical alignment or misalignment of said areas during said
approach. .Iaddend..Iadd. 12. The apparatus as defined by claim 11
wherein means are provided for sensing and indicating the relative
separation of said towing vehicle and said vehicle to be towed
during said approach. .Iaddend. .Iadd. 13. The apparatus as defined
by claim 11 wherein said guide means additionally defines a
preferred path of horizontal alignment between said respective
areas; said electrical sensing means additionally continuously
monitors the relative horizontal positions of said respective areas
and produces a signal indicative of the misalignment of said
respective areas from said preferred path of horizontal alignment;
and said indication means additionally indicates the relative
horizontal alignment or misalignment of said respective areas
during said approach. .Iaddend..Iadd. 14. The apparatus as defined
by claim 13 wherein the said signals produced by said electrical
sensing means are respectively indicative of the direction of
vertical and horizontal misalignment of said respective areas from
said preferred paths of vertical and horizontal alignment.
.Iaddend..Iadd. 15. An apparatus for guiding the approach of a
towing vehicle to align the hitch on the towing vehicle with the
hitch on a trailer, comprising:
a. preferred path of alignment guide means between said trailer and
said towing vehicle;
b. sensing means operatively associated with said preferred path of
alignment guide means for sensing the relative vertical and
horizontal positions of the hitches of said towing vehicle and said
trailer, during the approach of said towing vehicle to said
trailer; and
c. indication means operatively connected with said sensing means
for indicating the relative vertical and horizontal positions of
the hitches of said trailer and said towing vehicle. .Iaddend.
Description
The present invention relates to an apparatus for aligning, from
various approach angles, the couplings between a trailer and a
towing vehicle and more particularly to an apparatus which is
provided with horizontal, vertical, and relative distance sensors
for the two couplings and indicator means for displaying the output
of these sensors.
One of the problems that has long faced the owners of recreational
trailer vehicles, such as house trailers, boats, and the like, has
been the difficulty encountered in hitching a trailer to a towing
vehicle, such as a station wagon, truck, or automobile. This
difficulty is due to the fact that many of the trailers to which
the car must be coupled are large and are so heavy that it is
difficult, if not impossible, for a single individual to shift the
position of the trailer by hand, therefore, it becomes important
for the towing vehicle to be brought into exact position for
attachment of couplings of the trailer and towing vehicle. In this
regard, it is additionally difficult during the backing to exactly
position the coupling of the towing vehicle into proper alignment
with the trailer coupling because, in most cases, it is impossible
to see the couplings from the driver's position, and therefore, the
hitching is accomplished on a hit-or-miss basis or with the
guidance of a helper viewing the relative position of the
couplings.
Accordingly, it is the general purpose of the present invention to
provide an improved alignment apparatus, which is fully automatic,
to quickly and simply align the trailer and the towing vehicle from
various approach angles without the necessity of additional
assistance from a person not located in the towing vehicle. To
obtain this, the present invention contemplates the use of a unique
arrangement in which a retractable guide line extends between the
trailer and the towing vehicle. Sensing means are appropriately
positioned so that deflections of the guide line will produce an
error signal on an indicator means located in the vehicle in the
view of the operator of the vehicle so that correct alignment of
the towing vehicle can be accomplished by viewing the error
signal.
It is therefore an object of the present invention to provide an
improved alignment apparatus for aligning the couplings on a
trailer and a towing vehicle.
Another object of the present invention is to provide an improved
alignment apparatus which senses and indicates the relative
vertical position of the couplings on the trailer and the towing
vehicle.
A further object of the present invention is the provision of an
improved alignment apparatus which senses and indicates the
relative horizontal position of the couplings on the trailer and
the towing vehicle.
A further object of the present invention is the provision of an
improved alignment apparatus which senses and indicates the
relative distance between the couplings on the towing vehicle and
the trailer.
Yet another object of the present invention is the provision of an
improved alignment apparatus which has a variable sensitivity as
the coupling of the towing vehicle and the trailer vary in
separation distance.
Another object of the present invention is the provision of an
improved alignment apparatus which allows the towing vehicle to
approach the trailer from various angles.
Still a further object of the present invention is the provision of
an improved alignment apparatus which is simple and inexpensive to
manufacture and use.
Other objects and many of the attendant advantages of the present
invention may be readily appreciated by those of ordinary skill in
the art as the same becomes better understood by reference to the
following detailed description when considered in connection with
the accompanying drawings, in which:
FIG. 1 illustrates a plan view of a towing vehicle and trailer with
the improved coupling alignment apparatus of the present invention
attached thereto;
FIG. 2 illustrates an elevational view of a towing vehicle and
trailer with the improved coupling alignment apparatus of the
present invention attached thereto;
FIG. 3 illustrates an enlarged elevated view similar to FIG. 2;
FIG. 4 illustrates an enlarged partial plan view of the towing
vehicle coupling with an anchor of the present invention attached
thereto looking in the direction of arrows 4--4 of FIG. 2;
FIG. 5 is a perspective view of the vertical sensor assembly;
FIG. 6 is a sectional view taken on line 6--6 of FIG. 3 looking in
the direction of the arrows;
FIG. 7 is a sectional view taken on line 7--7 of FIG. 8 looking in
the direction of the arrows;
FIG. 8 is a sectional view taken on line 8--8 of FIG. 6 looking in
the direction of the arrows and
FIG. 9 is a schematic wiring diagram.
Referring now to the drawings wherein like reference characters
designate like or corresponding parts throughout the several views,
there is shown in FIGS. 1 and 2, a towing vehicle 12 and trailer 16
shown prior to the towing vehicle being guided up to and attached
to the trailer 16. The towing vehicle 12 has a hitch 14 and trailer
16 has hitch assembly 18 which can be attached together when the
two hitches are appropriately positioned. The trailer 16 is
provided with a conventional jack 20 which is preferably of the
auxiliary power type to enable the relative height of the hitch
assembly 18 to be remotely adjusted as required during the hitching
procedure. As will be subsequently described in more detail, an
alignment apparatus 22 is attached to the trailer 16 in the
vicinity of the hitch assembly 18. This apparatus 22 is provided
with a guide line 24 which is attached to the towing vehicle 12 in
the vicinity of the hitch 14 to assist in guiding the approach of
the towing vehicle to the trailer 16. The alignment apparatus 22 is
electrically connected to an electrical display panel (not shown)
located within the towing vehicle 12 within view of the operator to
display directional signals to the operator, and to assist the
operator in backing the towing vehicle into vertical and horizontal
alignment so that hitch 14 and hitch assembly 18 can be aligned and
connected without additional assistance and guidance during
relative positioning of the two vehicles. The indicator means can
be of numerous types, but for purposes of description, a panel
having a plurality of identified lights which can be selectively
illuminated by use of sensor means to be hereinafter described. As
will be explained, the alignment apparatus 22 can be adjusted to
allow for the approach of the towing vehicle 12 to the trailer 16
from a variety of angles.
As is shown in detail in FIG. 3, the alignment apparatus 22 has a
guide line 24 which retractably extends therefrom. This guide line
24 is preferably constructed from a multi-element conductor, but
could be constructed from standard cable, rope, or the like. The
desirability of using a conductor for the guide line 24 can be
appreciated when it is considered that the conductor provides
convenient means by which the indicator means in the towing vehicle
can be electrically connected to the various sensor elements in the
alignment apparatus to be hereinafter described. An attachment loop
(or hook) 26 is connected to the extending end of the guide line 24
for attaching the guide line 24 to an anchor 28 on the towing
vehicle 12.
As can be seen in FIG. 4, anchor 28 is pivotally attached to the
hitch 14 at 30 so that it may pivot between the position shown in
solid lines and the position 28' shown in phantom lines. This
pivoting allows the anchor 28 to swing back on contact to prevent
damage thereto. Also, as shown, an anchor 28 can be attached to
either or both sides of the hitch 14 so that the guide line 24 may
be attached as desired. Thus, by attaching the loop 26 to the
anchor 28, the guide line 24 will extend between the alignment
apparatus 22 on the trailer 16 and the towing vehicle 12 as shown
in FIGS. 1 and 2.
As is best shown in FIG. 1, the apparatus 22 and anchor 28 are so
positioned to one side of the hitches that the guide line when
extended between the towing vehicle and the trailer will be
parallel to imaginary lines 25 passing through the centers of the
hitch 14 and hitch assembly 18. The guide line 24 will be displaced
a distance A from the line 25 with the guide line 24 extending in
the direction the towing vehicle must travel to correctly align the
hitches. As will be described in detail, the apparatus 22 is
provided with means to sense deflections of the guide line 24 from
the correct angle of approach and will indicate the deflections to
the operator of the towing vehicle so that he may make appropriate
corrections while backing of the towing vehicle up to the
trailer.
In solid lines in FIG. 1, the direct approach for aligning the
vehicles and attaching the hitches is shown. In phantom lines other
examples of approach directions that can be used by adjusting the
position of the alignment apparatus 22 are shown. These other
approach directions are accomplished by mounting the alignment
apparatus 22 on the towing vehicle 16 so that it can rotate through
various angles, yet keep the same parallel spacing A from the line
25. In the illustrated embodiment, the apparatus 22 is mounted on a
support 23 which is provided with an arcuate groove 27. The groove
27 is shaped so that guides (not shown) on the trailer 16 will mate
with groove 27 and allow the alignment apparatus to move between
position 22 shown in solid lines and 22a shown in phantom lines. It
is also apparent that the alignment apparatus can be located on the
opposite side of the hitch assembly 18 and moved as shown in
phantom lines to position 22b.
As can be seen in detail in FIGS. 3 and 5, a vertical sensor
assembly 32 is supported by guide line 24 adjacent to the loop 26.
This vertical sensor assembly 32 is designed to sense the relative
position between the hitch 14 and hitch assembly 18 and actuate an
indicator means located in the interior of the vehicle 12 or
automatically control the height of jack 20 during the hitching
operation. This vertical sensor assembly 32 is constructed from a
transverse member 34, which is attached to the guide line 24 to
extend perpendicularly therefrom. This transverse member 34 is
provided with a referencing socket 36 which will removably attach
to a mating referencing socket 38 on the alignment apparatus 22.
Pivotally attached at 40 to the upper end of the transverse member
34 is a level assembly 42. This level assembly 42 can be of the
ordinary carpenter-type level which physically indicates the
horizontal inclination of the assembly 42.
Pivotally attached at 44 to the lower end of the transverse member
34 is a mercury switch assembly 46. This mercury switch assembly 46
has electrical conductors 48 extending therefrom, which conductors
are selectively connected and disconnected in the mercury switch
assembly 46 due to the orientation of the assembly 32. A second
transverse member 50 is pivotally connected between the level
assembly 42 and mercury switch assembly 46, respectively, at pivots
52 and 54. A groove 56 is provided in the second transverse member
50 to allow the guide lines 24 to extend therethrough without
contacting the member 50. The pivots 40, 44, 52, and 54 are each
provided with locking apparatus, which are not shown, but are well
known in the art, for releasably holding the parallelogram formed
by the transverse member 34, level assembly 42, second transverse
member 50, and mercury switch assembly 46, in the desired
orientation. This locking apparatus could be in the form of a thumb
screw or the like which could be rotated to clamp the adjacent
members together and prevent relative rotation therebetween.
The desired orientation of the parallelogram is determined
initially by engaging the sockets 36 and 38 to hold the transverse
member 34 in a position perpendicular to the pitch axis of the
tongue of trailer 16 and the ground surface. The locking apparatus
is released, and the pivots 40, 44, 52, and 54 allow the
parallelogram to be manually adjusted until the bubble of level
assembly 42 is centered to indicate that the assembly 32 is in a
position with level assembly 42 and mercury switch assembly 46
perpendicular to the force of gravity, whereupon the locking
apparatus are again engaged. By adjusting the parallelogram as
described above the extension of the guide line 24 will be parallel
to the pitch angle of the tongue of the trailer 16 and will tend to
guide the approach of the hitch of the towing vehicle 12 along the
line 24. Thereafter guide line 24 is extended until the loop 26 is
attached to the anchor 28 and the conductors 48 are releasably
connected to the indicator means inside the towing vehicle 12. In
this manner the relative position of the hitch 18 on the towing
vehicle 12 and the hitch 14 on the trailer 16 will be indicated by
the output of the mercury switch assembly 46 on the indicator means
in the towing vehicle 12 and/or can be connected to the control
mechanism of the jack 20 to operate the jack 20, lift or lower the
trailer 16 until the mercury switch assembly 46 is level. This
automatic leveling can continue during the approach of the towing
vehicle 12 to the trailer 16. In this manner, the correct relative
position of the hitches 14 and 18 can be maintained.
Referring now to FIGS. 6, 7, and 8, the details of the construction
of the alignment apparatus 22 will be described. In FIGS. 6 and 8,
it can be seen that the alignment apparatus 22 is divided into a
sensor portion 58 and a guide line storage portion 60. The portion
60 is provided with a shaft 62 which is mounted to rotate about a
vertical axis and carries a storage pulley 64 of a sufficient
capacity to store the guide line 24 thereon. Attached to the
opposite end of shaft 62 from storage pulley 64 is a torque spring
assembly 66 mounted to exert a continuous force on the shaft 62
which tends to rotate the storage pulley 64 in a direction to pull
the guide line 24 into the alignment apparatus 22 and wrap it
around the pulley 64. It thus can be seen by extending the guide
line 24 until the loop 26 is hooked on the anchor 28, that the
guide line 24 will be tensioned by the spring assembly 66 and will
be reeled onto the storage pulley 64 as the towing vehicle 12
approaches the trailer 16.
A pulley 68 is attached to the shaft 62 between the spring assembly
66 and storage pulley 64 to rotate with the shaft 62. An endless
belt 70 is entrained upon the pulley 68 and an additional pulley 72
which is mounted on a vertical shaft 74. This pulley 72 is mounted
so that it will axially slide with respect to the shaft 74 and is
provided with a set screw 75 which rides in an axial groove 77 in
the shaft 74. The shaft 74 is mounted to rotate about a vertical
axis in the sensor portion 58 of the alignment apparatus 22 with
the lower end of the shaft 74 in threaded engagement with the
threads 76 in the body of the apparatus 22, so that when the shaft
74 is rotated, it will be axially translated in the direction of
arrow 78 due to the engagement of the threads 76. A sensitivity
member 80 is slidably mounted in a vertically extending groove 82.
The purpose and operation of the sensitivity member 80 will be
explained hereinafter, it only being important to note that the
sensitivity member 80 will be moved in a direction of arrow 78 as
the shaft 74 is rotated.
A pair of limit switches 84 and 86 are illustrated in FIG. 6,
mounted with their sensor members 88 and 90, respectively,
extending into the storage pulley 64. Sensor 88 extends further
radially into the pulley 64 than does the sensor 90. The limit
switches 84 and 86 are each electrically connected to the indicator
means so that when the cable stored on the pulley 64 extends a
sufficient distance radially to contact either of the sensors 88 or
90, the indicator means will be actuated to indicate this condition
to the operator of the towing vehicle. The purpose of these
switches 84 and 86 is to sense the relative separation of the
trailer and the towing vehicle by sensing the amount of guide line
24 stored on the pulley 64, and to indicate this relative
separation to the operator by means of the indicator means. In
operation the sensors are so positioned that when the guide line 24
stored on the pulley contacts the sensor 88, it in turn actuates a
caution signal on the indicator means to inform the operator that
the hitches are nearing each other. The sensor 90 is so positioned
to cause a stop signal on the indicator means to inform the
operator that the two hitches are in vertical alignment for
coupling. These switches 84 and 86 and the other switches, within
the apparatus 22, can be connected to the conductors in line 24
through suitable brushes or the like (not shown) on the shaft
62.
Mounted in the sensor portion 58 is a pair of sensor fingers 92 and
94 for sensing the horizontal deflection of the guide line 24. As
can be seen in FIG. 6, the guide line 24 is positioned between the
two sensing fingers 92 and 94 and is held in position therebetween
by pins 96, 98, 100, 102, and 104. The sensor fingers 92 and 94 are
each mounted to rotate about vertically extending shifts 106 and
108, respectively, and are provided with guide line engaging
portions 110 and 112, respectively.
A pair of limit switches 114 and 116, are mounted with their
sensors 118 and 120, respectively, contacting a portion of the
fingers 92 and 94, respectively. By mounting the switches in this
manner, switch 114 will be operated by the rotation or movement of
finger 92 about shaft 106 and switch 116 will be operated by the
rotation or movement of finger 94 about shaft 108. These switches
114 and 116 are electrically connected to the indicator means so
that when the finger 92 is caused to rotate about shaft 106 in the
direction of arrow 122, switch 114 will be closed to energize the
indicator means and inform the operator that the trailer and towing
vehicle are out of alignment. Likewise, rotation of finger 94 about
shaft 108 in the direction of arrow 124 will close switch 116 and
energize the indicator means.
Thus, it can be seen that sufficient deflections of the guide line
24 will cause contact between the guide line 24 and one of the
fingers, thus operating either switch 114 or 116. By observing the
display means during backing of the towing vehicle 12, the operator
can determine the correct angle of approach and guide the vehicle
therealong.
As is best illustrated in FIGS. 7 and 8, the sensitivity member 80
is shown slidably mounted in a groove 82 and is vertically
positioned in said groove by a separate shaft 74. The sensitivity
member 80 is of a smaller width than the groove 82 and is mounted
so that it may slide back and forth in a horizontal direction, as
seen in FIG. 7, across the width of the groove 82. As was pointed
out previously, the rotation of the shaft 62 causes a rotation of
the shaft 74 which in turn causes the shaft 74 to move in an
axially upward direction as the guide line 24 is reeled onto the
storage reel 64 by the torque spring assembly 66. The relative
geometrical size of the sensitivity member 80 and the shaft 74 is
arranged so that as the hitch 14 on the towing vehicle 12
approaches the hitch assembly 18 on the trailer 16, the sensitivity
member 80 will be moved in an upward direction into the path of the
deflection of the guide line 24. The upper end of the sensitivity
member 80 is provided with a V-shaped groove 126 which slides up
between the sensor fingers 92 and 94 as the sensitivity member 80
is moved in an upward direction. It thus can be seen, the further
the sensitivity member 80 is moved in the upward direction the
narrower is the effective spacing between the two sensor fingers 92
and 94, thus increasing the sensitivity of the device in that
contact of the guide line 24 on the surfaces of the V-shaped groove
26 will in turn cause the engagement of member 80 with the sensor
fingers 92 or 94.
A schematic wiring diagram showing connection of the various
switches is shown in FIG. 9. Point 130 is a terminal point to which
+12 volt power can be supplied while terminal point 132 is
connected to ground. This power can be obtained from the power
system of either the towing vehicle 12, trailer 16 or a separate
battery can be provided as desired.
The terminal 130 can be connected through an off-on power switch
134 to a positive bus 136. Terminal 132 is in turn connected to bus
138. This switch 134 can be mounted in the towing vehicle and is
used to supply power to the system.
The previously described switch 116 is connected in series with
indicator light 140 between bus 136 and bus 138. This indicator
light 140 is located in the towing vehicle on the previously
mentioned control panel and will be energized when switch 116 is
closed.
In a similar manner indicator lights 142, 144 and 146 are connected
in series with previously described switches 114, 84 and 86,
respectively. Each of these indicator lights are located on the
control panel and are energized when their respective switch is
closed.
As the switches 116 and 114 are selectively closed as previously
described, indicator lights 140 and 142 will indicate respectively
right and left deflection of the towing vehicle from the desired
line of approach. As switches 84 and 86 are selectively closed as
previously described indicator lights 144 and 146 will indicate the
relative separation of the towing vehicle and the trailer.
Mercury switch 46 has its center contact 148 connected to bus 136.
This switch has contacts 150 and 151, each of which can be
selectively connected to contact 148. Indicator light 152 is
connected between contact 150 and center terminal 154 of a single
pole double throw switch. This switch can selectively engage either
contact 156 or 158. Contact 158 is connected to bus 138 while
contact 156 is connected to terminal point 160. A relay coil 162 is
connected between point 160 and bus 138. A normally opened switch
164 is connected between point 160 and bus 136. The relay coil 162
closes normally closed contacts (not shown) which electrically
energize a motor to cause the trailer jack 20 to elevate the
trailer hitch 14. The mercury switch 46 is oriented as previously
described so that when the trailer hitch 14 is low, contacts 148
and 150 will be connected thus energizing indicator light 152 and
if switch terminal 154 is connected to contact 156, relay coil 162
will be energized. If the switch terminal 154 is connected to
contact 158, the coil 162 will not be energized. In addition, when
switch 164 is closed relay coil 162 can be manually energized.
In a similar manner contact 151 is connected to a down indicator
light 166 which is in turn connected to terminal 168 of a single
pole double throw switch. Contact 170 is connected to bus 138 while
contact 172 is connected to terminal point 174. Relay coil 176 is
connected between point 174 and bus 138. A normally open push
button switch 178 is connected between bus 136 and point 174. Thus
it can be seen that when the trailer hitch 14 is high, contacts 148
and 151 will be connected, energizing indicator light 166 and if
switch terminal 168 is connected to contact 172, relay coil 176
will be energized. This relay coil 176 when energized will close
normally opened contacts (not shown) to supply power to the motor
of jack 20, to in turn lower the hitch 18. If it is desired to
manually lower the hitch 18, switch 178 can be closed to energize
coil 176.
It should be understood, of course, that the foregoing disclosure
relates to only a preferred embodiment of the invention in that
numerous modifications or alterations may be made by those of
ordinary skill in the art without departing from the spirit and
scope of the invention as set forth in the appended claims.
* * * * *