U.S. patent application number 13/159131 was filed with the patent office on 2011-10-27 for trailer tongue weight measurement system.
Invention is credited to Michael M. CLEARY.
Application Number | 20110259651 13/159131 |
Document ID | / |
Family ID | 40581368 |
Filed Date | 2011-10-27 |
United States Patent
Application |
20110259651 |
Kind Code |
A1 |
CLEARY; Michael M. |
October 27, 2011 |
TRAILER TONGUE WEIGHT MEASUREMENT SYSTEM
Abstract
A trailer tongue weight measurement system is provided to ensure
proper loading and safe handling of a trailer being towed by a
vehicle. The weight measurement system includes a two part or split
housing having a operating shaft, a spring and a scale. The weight
measurement system may be incorporated into the trailer tongue, the
tongue jack, or the hitch. Deflection of the spring in response to
a load on the trailer is converted to a weight measurement that may
be read on a calibrated scale.
Inventors: |
CLEARY; Michael M.;
(Carpinteria, CA) |
Family ID: |
40581368 |
Appl. No.: |
13/159131 |
Filed: |
June 13, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12260142 |
Oct 29, 2008 |
7960659 |
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13159131 |
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60983624 |
Oct 30, 2007 |
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Current U.S.
Class: |
177/136 |
Current CPC
Class: |
G01G 19/08 20130101 |
Class at
Publication: |
177/136 |
International
Class: |
G01G 19/08 20060101
G01G019/08 |
Claims
1. A trailer weight measurement system comprising: a split housing,
wherein one part of the split housing may move relative to another
part of the split housing; a shaft rotatably disposed within the
housing, the shaft comprising: a non-threaded portion; a distal end
of the non-threaded portion of the shaft extending through a shaft
opening in one part of the split housing; a threaded portion, the
threaded portion being threaded into a threaded hole in the other
part of the split housing; a shoulder separating the non-threaded
portion and the threaded portion of the shaft; a spring located
within the split housing and concentrically around the shaft
between the shaft shoulder and an inside surface of one part of the
split housing; a handle located external to the split housing and
connected to the distal end of the shaft; and a scale having a zero
point and a series of indicators corresponding to a weight being
measured by the weight measurement system.
2. The trailer weight measurement system of claim 1, wherein the
split housing further comprises a tube-like housing comprising a
main housing and a jack housing, the jack housing slidably disposed
within the main housing and extending through an open bottom end of
the main housing.
3. The trailer weight measurement system of claim 2, wherein: the
main housing further comprising: a top end having the shaft
opening; the open bottom end; a side wall extending between the top
end and the open bottom end; the jack housing further comprising: a
top end; the threaded hole in a center of the top end; a bottom
end; a foot plate at the bottom end of the jack housing for
engaging a support surface; the shaft further comprising: the
distal end of the non-threaded portion of the shaft extending
through the shaft opening in the top end of the main housing; the
threaded portion being threaded into the threaded hole in the top
end of the jack housing; a thrust bearing disposed concentrically
about the non-threaded portion of the shaft, a first side of the
thrust bearing contacting the shaft shoulder; the spring disposed
concentrically about the non-threaded portion of the shaft, a first
end of the spring contacting a second side of the thrust bearing,
and a second end of the spring contacting an inside surface of the
top end of the main housing, the spring acting to urge the main
housing and the jack housing apart; and the scale located on the
non-threaded portion of the shaft proximate the shaft opening, the
scale having a zero point and a series of indicators corresponding
to a weight being measured by the weight measurement system.
4. The trailer weight measurement system of claim 3, wherein the
weight measurement system may be calibrated so that the zero point
of the scale is at the shaft opening with no load on the system,
and wherein the shaft moves upward out through the shaft opening as
a load is applied to the system and the spring compresses thereby
revealing the series of indicators on the scale on the shaft.
5. The trailer weight measurement system of claim 2, wherein: the
main housing further comprising: a top end having the shaft
opening; the open bottom end; a side wall extending between the top
end and the open bottom end; the jack housing further comprising: a
top end; the threaded hole in a center of the top end; a bottom
end; a foot plate at the bottom end of the jack housing for
engaging a support surface; a gear housing slidably disposed over
the top end of the main housing and the distal end of the shaft,
the gear housing comprising: a right angle gear set connected to
the non-threaded portion of the shaft extending through the shaft
opening, the gear set for transitioning the shaft output 90
degrees; an upper portion of the gear housing extending above the
main housing and enclosing the gear set; a lower portion of the
gear housing extending over and about an upper portion of the main
housing to a lower edge; the shaft further comprising: the distal
end of the non-threaded portion of the shaft extending through the
shaft opening in the top end of the main housing; the threaded
portion being threaded into the threaded hole in the top end of the
jack housing; a thrust bearing disposed concentrically about the
non-threaded portion of the shaft, a first side of the thrust
bearing contacting the shaft shoulder; the spring disposed
concentrically about the non-threaded portion of the shaft, a first
end of the spring contacting a second side of the thrust bearing,
and a second end of the spring contacting an inside surface of the
top end of the main housing, the spring acting to urge the main
housing and the jack housing apart; and the scale located on upper
portion of the main housing, the scale having a zero point and a
series of indicators corresponding to a weight being measured by
the weight measurement system.
6. The trailer weight measurement system of claim 5, wherein the
weight measurement system may be calibrated so that the zero point
of the scale is at the lower edge of the gear housing with no load
on the system, and wherein the gear housing moves upward with the
shaft as a load is applied to the system and the spring compresses
thereby revealing the series of indicators on the scale on the main
housing.
7. The trailer weight measurement system of claim 2, further
comprising a flange plate extending from the main housing and
having one or more holes for connecting the trailer weight
measurement system to a coupler of a trailer.
8. The trailer weight measurement system of claim 2, further
comprising a pin for securing the shaft in place relative to the
main housing, the pin holding the shaft, spring, thrust bearing,
and jack housing from falling out the bottom of the main
housing.
9. The trailer weight measurement system of claim 2, further
comprising a crank shaft connected to the non-threaded portion of
the shaft extending through the opening in the top end of the main
housing, wherein rotation of the crank shaft causes rotation of the
shaft and sliding movement of the jack housing relative to the main
housing.
10. The trailer weight measurement system of claim 2, further
comprising a tongue and groove formed between the main housing and
the jack housing, the tongue and groove constraining rotational
movement between the main housing and the jack housing.
11. The trailer weight measurement system of claim 2, further
comprising a gage read out for amplifying the spring deflection to
make it easier to read.
12. The trailer weight measurement system of claim 11, wherein the
gage read out further comprises: a gage housing disposed over the
top end of the main housing, wherein the shaft extends through the
gage housing; a circular gear rack formed on the portion of the
shaft extending through the gage housing; a pinion gear engaged
with the circular gear rack; a shaft extending from the pinion gear
through an opening in the gage housing to an exterior of the gage
housing; and an indicator needle connected to the shaft and
extending over the scale, the scale being formed on an exterior
surface of the gage housing.
13. The trailer weight measurement system of claim 2, wherein the
weight measurement system is retrofit into an existing trailer
tongue jack by replacing at least the shaft and adding the
spring.
14. The trailer weight measurement system of claim 2, wherein the
weight measurement system is formed integral with a new trailer
tongue jack.
15. The trailer weight measurement system of claim 1, wherein the
spring further comprises a coil spring.
16. A trailer weight measurement system comprising: a main housing
comprising: a top end having a shaft opening; an open bottom end;
and a side wall extending between the top end and the open bottom
end; a jack housing slidably disposed within the main housing and
extending from the open bottom end, the jack housing comprising: a
top end having a threaded hole; a foot plate at a bottom end of the
jack housing for engaging a support surface; a side wall extending
between the top end of the jack housing and the foot plate; a shaft
rotatably disposed within the main housing, the shaft comprising: a
non-threaded upper portion; a distal end of the non-threaded upper
portion of the shaft extending through the shaft opening in the top
end of the main housing; a threaded lower portion, the threaded
lower portion being threaded into the threaded hole in the top end
of the jack housing; a thrust bearing disposed concentric about the
non-threaded portion of the shaft, a first side of the thrust
bearing contacting the threaded portion; a spring disposed
concentrically about the non-threaded portion of the shaft, a first
end of the spring contacting a second side of the thrust bearing,
and a second end of the spring contacting the main housing; and a
scale having a series of indicators corresponding to a weight being
measured by the weight measurement system, wherein a deflection of
the spring and movement of the shaft corresponds to a weight being
measured that is displayed on the scale.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application in a continuation of U.S. application Ser.
No. 12/260,142 filed Oct. 29, 2008 which claims priority to U.S.
provisional application Ser. No. 60/983,624 filed Oct. 30, 2007,
which is incorporated herein by reference in its entirety.
TECHNOLOGY FIELD
[0002] The present invention relates generally to a trailer safety
system, and more particularly to safety systems and methods for
measuring the weight on the tongue of a trailer. This technology is
particularly suited, but by no means limited, for use with trailers
designed to be towed behind a motor vehicle.
BACKGROUND
[0003] In the use of typical automotive utility trailers such as
boat, cargo, camping, horse, race car, or work trailers it is
critical for safe towing to have the proper distribution of weight
between the hitch on the towing vehicle and the axle[s] of the
trailer. If the weight on the hitch is too small, the trailer will
shimmy and sway possibly causing loss of control and an accident.
If the weight is too high on the hitch, then the rear of the tow
vehicle is over loaded and the steering wheels and brakes are less
effective, which will lead to control and stopping problems. Proper
trailer loading and weight distribution helps ensure proper and
safe trailer handling.
[0004] At the present time there are no convenient and accurate
ways for a user to determine whether the trailer is properly
loaded. For example, one conventional way to measure this weight
distribution is for the user to guesstimate it themselves. This is
particularly true in the case of all rental style cargo trailers
where untrained people who are not familiar with the requirements
of towing are doing the loading. Even in the case of travel and
boat trailers where the manufacturer has provided the trailer and
properly balanced it, the user can upset that balance by how they
load additional equipment into the boat or trailer.
[0005] Another conventional means for obtaining the tongue weight
on trailers is a separate weight scale that may be placed under the
trailer tongue. One example includes the Sherline Trailer Tongue
Weight Scale (see. e.g., http://www.sherline.com/lm.htm). The
Sherline scale uses a hydraulic principle to convert weight into a
direct reading on a hydraulic pressure gauge.
[0006] An accurate measurement of tongue weight may be achieved by
measuring right where the hitch actually rests on the ball or
alternatively at the tongue jack. The Sherline scale uses an
extension that screws into the top of the cylinder so that the
trailer hitch may be supported. The Sherline scale teaches that it
is best practice to measure the hitch weight with the trailer level
(trailer wheels blocked to prevent movement) and the hitch at the
approximate height it will be when installed on the tow
vehicle.
[0007] The trailer tongue may be supported with the tongue jack.
Blocks are required to be used with the Sherline scale to block the
Sherline scale into position under the hitch. The Sherline scale
teaches that, alternatively, a hydraulic floor jack may be used and
the Sherline scale may be placed on the jack and jacked into
position. The tongue jack may be raised until the full weight of
the hitch is on the Sherline scale and the weight in pounds may be
read directly from the gauge on the Sherline scale.
[0008] As such the Sherline scale suffers from the drawbacks that
it is a standalone device that must be separately carried around
and also from the fact that separate and ancillary devices (e.g.,
wood blocks or a hydraulic floor jack) are required to properly
place and use the Sherline scale.
[0009] Thus, there is a need for a trailer weight measurement
system that is accurate and easy to use. What is needed is a simple
and effective means for determining whether a trailer is properly
loaded for safe handling when being towed by a tow vehicle. What is
needed is a simple and effective means of determining the weight on
the trailer tongue without having to carry and use separate
devices.
SUMMARY
[0010] Embodiments of the present invention are directed to a
trailer weight measurement system including a split housing,
wherein one part of the split housing may move relative to another
part of the split housing. A shaft may be rotatably disposed within
the housing. The shaft may include a non-threaded portion and a
threaded portion. A distal end of the non-threaded portion of the
shaft extends through a shaft opening in one part of the split
housing. The threaded portion of the shaft may be threaded into a
threaded hole in the other part of the split housing. The shaft may
include a shoulder separating the non-threaded portion and the
threaded portion. A spring may be located within the split housing
and positioned concentrically around the shaft between the shaft
shoulder and a surface of one part of the split housing. A handle
may be located external to the split housing and connected to the
distal end of the shaft. The weight measurement system includes a
scale having a zero point and a series of indicators corresponding
to a weight being measured by the weight measurement system.
[0011] In one embodiment, the split housing includes a tongue jack
unit having a tube-like housing comprising a main housing and a
jack housing. The jack housing may be slidably disposed within the
main housing and may extend through an open bottom end of the main
housing.
[0012] In this embodiment, the main housing further includes a top
end having a shaft opening, an open bottom end, and a side wall
extending between the top end and the open bottom end. In this
embodiment, the jack housing further includes a top end, a threaded
hole in a center of the top end, a bottom end, and a foot plate at
the bottom end of the jack housing for engaging a support surface,
such as the ground.
[0013] In this embodiment, a shaft extends between the main housing
and the jack housing. The shaft further includes a distal end of
the non-threaded portion that may extend through the shaft opening
in the top end of the main housing. The threaded portion of the
shaft may be threaded into the threaded hole in the top end of the
jack housing.
[0014] A thrust bearing may be disposed concentrically about the
non-threaded portion of the shaft. A first side of the thrust
bearing may contact the shaft shoulder. A spring may be disposed
concentrically about the non-threaded portion of the shaft. A first
end of the spring may contact a second side of the thrust bearing
and a second end of the spring may contact an inside surface of the
top end of the main housing. The spring acts to urge the main
housing and the jack housing apart. In some embodiments, the spring
may be a coil spring.
[0015] According to another aspect of the invention, a crank shaft
may be connected to the non-threaded portion of the shaft extending
through the opening in the top end of the main housing. Rotation of
the crank shaft may cause rotation of the shaft and sliding
movement of the jack housing relative to the main housing. The
crank handle may be used to raise and lower the tongue jack.
[0016] According to another aspect of the invention, a scale may be
located on the non-threaded portion of the shaft proximate the
shaft opening. The scale may include a zero point and a series of
indicators corresponding to a weight being measured by the weight
measurement system.
[0017] According to another aspect of the invention, the weight
measurement system may be calibrated so that the zero point of the
scale is at the shaft opening with no load on the system. When a
load is applied, the spring compresses and the shaft may move
upward out through the shaft opening thereby revealing the series
of indicators on the scale on the shaft.
[0018] According to another embodiment of the invention, a gear
housing may be slidably disposed over the top end of the main
housing and the distal end of the shaft. The gear housing may
include a right angle gear set connected to the non-threaded
portion of the shaft extending through the shaft opening. The gear
set may provide for transitioning the shaft output 90 degrees
(e.g., from substantially vertical to substantially horizontal). An
upper portion of the gear housing may extend above the main housing
and enclose the gear set. A lower portion of the gear housing may
extend over and about an upper portion of the main housing to a
lower edge.
[0019] In this embodiment, the scale may be located on an upper
portion of the main housing. The weight measurement system may be
calibrated so that the zero point of the scale is at the lower edge
of the gear housing with no load on the system. When a load is
applied to the system, the spring compresses and the shaft and gear
housing move upward with the shaft thereby revealing the series of
indicators on the scale on the main housing.
[0020] According to another embodiment of the invention, the
trailer weight measurement system may include a gage read out for
amplifying the spring deflection to make it easier to read. The
gage read out may include a gage housing disposed over the top end
of the main housing where the shaft extends through the gage
housing. A circular gear rack may be formed on the portion of the
shaft extending through the gage housing and a pinion gear may
engage the circular gear rack. A shaft may extend from the pinion
gear through an opening in the gage housing to an exterior of the
gage housing. An indicator needle may be connected to the shaft and
may extend over the scale formed on an exterior surface of the gage
housing. The gage read out for amplifying the spring deflection may
be used for heavier trailer loads.
[0021] According to some embodiments of the invention, the weight
measurement system may be retrofit into an existing trailer tongue
jack by replacing at least the shaft and adding the spring. In
another embodiment, the thrust bearing may also be added. According
to some embodiments of the invention, the weight measurement system
may be formed integral with a new trailer tongue jack. According to
some embodiments of the invention, the weight measurement system
may be formed as a replacement part and may be retrofitted onto an
existing trailer.
[0022] According to another aspect of the invention, a crank shaft
may be connected to the gear set, the crank shaft having a
horizontal output. Rotation of the crank shaft may cause rotation
of the shaft and sliding movement of the jack housing and gear
housing relative to the main housing.
[0023] According to another aspect of the invention, the trailer
tongue weight measurement system may be calibrated such that, in an
unloaded condition, the zero point on the scale is located at the
bottom edge of the gear housing.
[0024] According to another embodiment of the invention, the
trailer tongue weight measurement system may comprise a trailer
tongue or coupler unit--i.e., the trailer tongue weight measurement
system that is connected to or formed integral with the trailer
tongue or coupler. In this embodiment, the trailer tongue weight
measurement system includes a first plate connected to the ball
receptacle and a second plate connected to the tongue coupler. A
pivot pin may pivotally connect the first plate and the second
plate proximate a bottom edge of the first and second plates.
[0025] In this embodiment, the a first plate includes: a shaft
opening located proximate a center of the first plate; and one or
more threaded holes. The second plate includes: a shaft opening
located proximate a center of the second plate, wherein the shaft
opening in the second plate corresponds in location (i.e., is
in-line) to the shaft opening in the first plate; a threaded hole
concentric with the shaft opening of the second plate; one or more
through holes, wherein the through holes on the second plate
correspond in number and location to the one or more threaded holes
on the first plate.
[0026] In this embodiment, one or more shoulder bolts may be
inserted through one of the through holes in the second plate and
threaded into one of the threaded holes in the first plate. Each
shoulder bolt may include a head, a shoulder, and a threaded
shaft.
[0027] One or more clearance indicators may be disposed between the
first plate and the second plate. Each clearance indicator may
include an opening surrounded by a body portion. A shoulder bolt
may be inserted through the opening in the clearance indicator.
[0028] A shaft may be rotatably disposed between the first plate
and the second plate. In this embodiment, the shaft includes: a
non-threaded portion that extends through the shaft opening in the
first plate; a threaded portion that is threaded into the threaded
hole in the second plate; a shoulder between the non-threaded
portion and the threaded portion of the shaft.
[0029] A spring may be disposed concentrically about the
non-threaded portion of the shaft. In this embodiment, a first end
of the spring may contact a rear surface of the first plate and a
second end of the spring may contact the shaft shoulder. The spring
acts to urge the plates apart. The spring may include one or more
spring washers.
[0030] A scale may be located on a rear surface of the second plate
(or whatever side the shaft extends out of). The scale may include
a zero point and a series of indicators corresponding to a weight
being measured by the weight measurement system.
[0031] According to another embodiment of the invention, the
trailer tongue weight measurement system may comprise a trailer
hitch unit--i.e., the trailer tongue weight measurement system that
is connected to or formed integral with the trailer hitch. In this
embodiment, the trailer tongue weight measurement system includes a
first plate connected to the ball and a second plate connected to
the hitch tubing. A pivot pin may pivotally connect the first plate
and the second plate proximate a bottom edge of the first and
second plates.
[0032] In this embodiment, the first plate may include: a shaft
opening located proximate a center of the first plate; a threaded
hole concentric with the shaft opening; and one or more threaded
holes. The second plate may include: a shaft opening located
proximate a center of the second plate, wherein the shaft opening
in the second plate corresponds in location (i.e., it in-line) to
the shaft opening in the first plate; one or more through holes,
wherein the through holes on the second plate correspond in number
and location to the one or more threaded holes on the first
plate.
[0033] In this embodiment, one or more shoulder bolts may be
inserted through one of the through hole in the second plate and
threaded into one of the threaded holes in the first plate. Each
shoulder bolt may include a head, a shoulder, and a threaded
shaft.
[0034] One or more clearance indicators may be disposed between the
first plate and the second plate. Each clearance indicator may
include an opening surrounded by a body portion. A shoulder bolt
may be inserted through the opening in the clearance indicator.
[0035] A shaft may be rotatably disposed between the first plate
and the second plate. In this embodiment, the shaft includes: a
non-threaded portion that extends through the shaft opening in the
second plate; a threaded portion that is threaded into the threaded
hole in the first plate; and a shoulder between the non-threaded
portion and the threaded portion of the shaft.
[0036] A spring may be disposed concentrically about the
non-threaded portion of the shaft. In this embodiment, a first end
of the spring may contact a front surface of the second plate and a
second end of the spring may contact the shaft shoulder. The spring
acts to urge the plates apart. The spring may include one or more
spring washers.
[0037] A scale may be located on a rear surface of the second
plate. The scale having a zero point and a series of indicators
corresponding to a weight being measured by the weight measurement
system.
[0038] According to another aspect of the invention, the shaft may
include a spindle portion and a second threaded portion. A handle
may be disposed over and may engage the spindle portion of the
shaft. A nut may be threaded onto the second threaded portion of
the shaft to secure the handle in place.
[0039] According to another aspect of the invention, the handle may
be placed on the shaft and over the zero point of the scale when
the trailer weight measurement system is unloaded. In a loaded
condition, the handle may be rotated by a user until the one or
more clearance indicators are free to move. At this time, a weight
measured by the trailer weight measurement system may be read from
the scale based on the position of the handle over the scale.
[0040] According to another aspect of the invention, the clearance
indicators may include double action stirrup clearance indicators.
When the handle is rotated too far, the double action stirrup
clearance indicators will be restrained by a clamping action
between a head of the shoulder bolt and the second plate to help
assure a proper weight is read on the scale.
[0041] According to another aspect of the invention, the one or
more clearance indicators may include stirrup type indicators. Each
stirrup indicator may include a U-shape body portion having two
washer portions and an opening in each washer portion. The U-shape
body portion may surround a top edge of the second plate and the
shoulder bolt may pass through the opening in each washer
portion.
[0042] According the another aspect of the invention, a handle may
be connected to the shaft and may be located over the scale.
Rotation of the handle causes rotation of the shaft and either
compression or release of the spring.
[0043] According the another aspect of the invention, the trailer
tongue weight measurement system may be calibrated such that in a
loaded condition, the zero point on the scale is located under the
handle and the handle is rotated until the one or more clearance
indicators are free to move. The position of the handle over the
scale when the clearance indicators are free to move indicating the
weight on the trailer tongue.
[0044] The scale may include a variety of forms, including
numerical, color, symbols, and the like.
[0045] Additional features and advantages of the invention will be
made apparent from the following detailed description of
illustrative embodiments that proceeds with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] The foregoing and other aspects of the present invention
will become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings. For the purpose of illustrating the invention, there is
shown in the drawings embodiments that are presently preferred, it
being understood, however, that the invention is not limited to the
specific instrumentalities disclosed. In the drawings:
[0047] FIGS. 1A and 1B are a side view of an exemplary tow vehicle
and trailer;
[0048] FIG. 2 is a top view showing an exemplary hitch on a tow
vehicle and coupler on a trailer;
[0049] FIG. 3 is a side sectional view of the exemplary tongue
weight measurement system incorporated in to an exemplary trailer
jack;
[0050] FIG. 4A is a side, partial sectional view of another
exemplary tongue weight measurement system incorporated in to an
exemplary trailer jack;
[0051] FIG. 4B is a detailed top, cross sectional view of the
tongue weight measurement system of FIG. 4A;
[0052] FIG. 5A is a side sectional view of another exemplary tongue
weight measurement system incorporated in to an exemplary trailer
jack;
[0053] FIG. 5B is a sectional view taken along section line A-A of
FIG. 5A;
[0054] FIG. 5C is an end view of the exemplary tongue weight
measurement system of FIG. 5A;
[0055] FIG. 6A is a side sectional view of another exemplary tongue
weight measurement system incorporated in to an exemplary trailer
tongue or coupler;
[0056] FIG. 6B is an end view of the exemplary tongue weight
measurement system of FIG. 6A;
[0057] FIG. 6C is a perspective view of an exemplary stirrup type
indicator of FIGS. 6A and 6B;
[0058] FIG. 7A is a side sectional view of another exemplary tongue
weight measurement system incorporated in to an exemplary hitch;
and
[0059] FIG. 7B is an end view of the exemplary tongue weight
measurement system of FIG. 7A.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0060] The present invention is directed to embodiments of trailer
tongue weight measurement systems and methods that overcome the
shortcomings of conventional methods of trying to determine a
trailer's tongue weight--e.g., user's guesstimating the trailer
tongue weight and also conventional stand-alone trailer tongue
weight scales. The trailer tongue weight measurement systems and
methods disclosed herein may be used, for example, for the safe
loading and proper handling of trailers being towed by a tow
vehicle. The weight measurement system may be formed integral with
the trailer or hitch to determine the weight on the trailer tongue
for proper loading and safety in trailer towing. The trailer tongue
weight measurement systems and methods provide a versatile system
of measuring the tongue weight which may be universally adaptable
to the needs of the trailer industry and user group. Embodiments of
the trailer tongue weight measurement systems and methods integrate
a simple spring scale device to measure the tongue weight of the
loaded trailer. As used herein, the term trailer includes typical
automotive utility trailers such as, for example: boat, cargo,
camping, horse, race car, work, and the like. The different
embodiments disclosed herein may be desirable to suit the different
requirements of the various trailer constituencies including, for
example: manufacturer, owner, user, Rental Company, an owner of
multiple trailers, and the like.
[0061] Embodiments of the trailer weight measurement system may
include a two part or split housing having a integral spring and
scale. The two parts or split housing may move relative to one
another in response to a load on the trailer ball and compress the
spring. The deflection of the spring may be converted to a weight
on the trailer using the scale. Preferably, the trailer weight
measurement system is located at or proximate the trailer ball or
tongue jack.
[0062] In one embodiment, the trailer tongue weight measurement
system comprises a tongue jack having a main housing and jack
housing that may move relative to one another and an integral
spring disposed concentrically about a shaft disposed within the
housings to urge the main housing and the jack housing apart. A
scale may be provided integral with the tongue jack weight
measurement system to convert the deflection of the spring
resulting from the trailer load to a weight measurement. In another
embodiment, the trailer tongue weight measurement system comprises
a hinge plate assembly having two plates and an integral spring
disposed concentrically about a shaft extending between the plate
to urge the plates apart. A scale may be provided integral with the
weight measurement system to convert the load on the spring
resulting from a spring loading device to a weight measurement. In
one embodiment, the trailer weight measurement system is on the
trailer coupler. In another embodiment, the trailer weight
measurement system is on the hitch. One advantage of the trailer
tongue weight measurement systems and methods disclosed herein are
that they are integral, meaning that a separate scale does not have
to be carried and used, and ancillary devices, such as blocks or a
floor jack are not required.
[0063] Other benefits and advantages of a tongue jack weight
measurement unit include: it may mount on any standard trailer; it
is inexpensive to manufacture and maintain; it is easy to use; it
is accurate; it includes a versatile jack design and may be used
when the trailer is connected or disconnected from the tow vehicle;
it may cover a relatively large weight span; etc. Other benefits
and advantages of a trailer coupler or tongue weight measurement
unit include: it may be built into the trailer; it is inexpensive
to manufacture and maintain; it is easy to use; it is accurate; no
un-hitching of the trailer is required; etc. Other benefits and
advantages of a hitch weight measurement unit include: it may be
built into the hitch; it is inexpensive to manufacture and
maintain; it is easy to use; it is accurate; no un-hitching of the
trailer is required; one hitch unit may be used for multiple
trailers; etc.
[0064] FIGS. 1A and 1B show an exemplary tow vehicle 10 and trailer
20. As shown in FIGS. 1A and 1B, the tow vehicle 10 may include a
hitch 12 and a ball and ball mount 14 at the rear of the tow
vehicle 10. The tow vehicle 10 may include any motor vehicle
suitable for towing a trailer 20. As shown, the tow vehicle 10 may
include an automobile having front and rear axles/wheels 15.
[0065] As shown in FIGS. 1A and 1B, the trailer 20 may include a
compartment 22 for holding goods and one or more axles/wheels 24.
The trailer 20 may also include a trailer tongue 26 and a tongue
jack 32. As shown, the trailer tongue may include a coupler 28 and
a ball receptacle 30. The ball receptacle 30 may be designed and
constructed to fit over the ball mount 14 of the hitch 12 on the
tow vehicle 10. As shown, the tongue jack 32 may include a handle
34 for activating the tongue jack 32 to raise or lower the trailer
tongue 26 and a footplate 36 for engaging a support surface 37,
such as the ground. As shown in FIG. 1A, the tongue jack 32 is in a
lowered position and the trailer 20 is not connected to the tow
vehicle 10. As shown in FIG. 1B, the tongue jack 32 is in a raised
position and the trailer 20 is connected to the tow vehicle 10.
Safety chains (not shown) may be used as a back-up system between
the tow vehicle 10 and the trailer 20.
[0066] The hitch 12 and ball 14 should be selected based on the
expected load of the trailer 20. Preferably, the hitch 12 and/or
ball 14 are removable from the vehicle and the properly rated
hitch/ball may be used to tow the expected load of the trailer. The
ball 14 is typically rated by its towing capacity. The hitch 12 is
typically rated not only by its towing capacity, but also by the
tongue weight.
[0067] FIG. 2 is a top view of the exemplary tow vehicle and
trailer 20 of FIG. 1A. As shown in FIG. 2, the hitch 12 and ball 14
may be connected to the tow vehicle 10. As shown, the hitch 12 may
include square tubing 16 which telescopes into the receiver 18 on
the hitch 12 and may be held in position by a pin 19 (see e.g.,
FIG. 7A).
[0068] The trailer tongue 26, coupler 28, and ball receptacle 30
are also shown in FIG. 2. As shown, the tongue jack 32 may be
connected to the coupler 28 of the trailer tongue 26 using, for
example, bolts 38 that extend through holes 40 in plate 42.
[0069] FIG. 3 shows one exemplary embodiment of the trailer tongue
weight measurement system. As shown in FIG. 3, the trailer tongue
weight measurement system may include a modification to a standard
trailer tongue jack. This modification may be designed into a new
tongue jack or retrofitted into an existing tongue jack.
Essentially all trailers have a tongue jack 32 that allows a user
to lift the trailer tongue 26 high enough so that the ball 14 of
the tow vehicle 10 may be positioned below the trailer ball
receptacle 30. Accordingly, the tongue jack unit may be used on any
standard trailer, either as a new or retrofit unit.
[0070] As shown, the trailer tongue weight measurement system may
include a main housing 44 that may be attached to the coupler 28 of
the trailer 20 at flange plate 42 by bolts 38. A jack housing or
jacking tube 56 may be slidably disposed within the main housing
44. A shaft 46 may be positioned in the center of the main housing
44 and may be threaded at its lower end 48. The shaft threaded
portion 52 may engage with a mating thread 54 on jacking tube 56. A
pin 45 may be used to hold the shaft assembly in place. A crank
handle 34 may be provided at a top end 50 of the shaft 46.
[0071] The jacking tube 56 may be constrained from rotating with
respect to the main housing 44 by a tongue and groove feature 58
(see e.g., FIG. 4B) on the two parts 44, 56, but may allow free
linear movement of the jacking tube 56 up and down relative to the
main housing 44. For example, turning the crank handle 34 may cause
the shaft 46 to rotate thereby causing movement of the jack housing
56 relative to the main housing 44. In this embodiment, turning of
the crank handle 34 causing up or down movement of the jack housing
56 relative to the main housing 44. The direction of travel may be
determined by the direction in which the crank handle 34 is
rotated.
[0072] A thrust bearing 60 may be located at the interface between
the threaded portion 52 and non-threaded portion 53 of the jack
screw shaft 46. The thrust bearing 60 may bear against a shoulder
62 on the shaft 46. In a conventional tongue jack (not shown), this
bearing would bear against the under side of the top of the main
housing and give free rotation of the shaft relative to the
housing. As shown in this embodiment of the trailer tongue weight
measurement system, a spring 64 may be introduced between the
bearing 60 and the inside top surface 66 of the main housing
44.
[0073] In addition to the spring 64, a calibrated scale 68 may be
provided to indicate a load (i.e., weight) on the tongue jack 32.
For example, a scale may be engraved or attached on the outside of
the upper part of the shaft 46, as shown in FIG. 3. Alternatively,
a series of color bands corresponding to a weight range may be
used. For example, a red, yellow, and green color band may be
provided to delineate proper weighing of the trailer. The scale 68
may include a zero point and a series on marks corresponding to a
load or weight measurement. As shown in FIG. 3, the tongue jack 32
is unloaded and the zero point of the scale 68 is at the top of the
housing 44.
[0074] In operation, the tongue 26 of the trailer 20 may be
supported by the tongue jack 32 and the trailer 20 may or may not
be attached to the hitch 12 of the tow vehicle 10. The spring 64 of
the tongue jack 32 will deflect (e.g., compress) in direct
proportion to the weight on the tongue jack 32. This deflection of
spring 64 will cause the shaft 46 to move upward relative to the
main housing 44 exposing the scale 68 on shaft 46. The weight on
the trailer tongue 26 can then be read off the scale 68.
[0075] FIG. 4A shows another exemplary embodiment of the trailer
tongue weight measurement system. As shown in FIG. 4A, the trailer
tongue weight measurement system may include a modification to a
standard trailer tongue jack. This embodiment of the weight
measurement system may be designed into a new tongue jack or
retrofitted into an existing tongue jack.
[0076] The second embodiment of trailer tongue weight measurement
system is a result of a design feature incorporated on many tongue
jacks now in production. That feature is at the top of the
operating shaft 46 there is a gear housing 70 having a pair of
bevel gears 72 so that instead of a vertical output shaft there is
a horizontal output shaft 74. This is done for ease of operation
and to facilitate a change in gear ratio between the crank handle
34 and the operating shaft 46. As such, the scale 68 on shaft 46 as
used in the first embodiment would be covered by the gear housing
70 and not visible.
[0077] FIG. 4A illustrates the second embodiment. As in the first
embodiment, the trailer weight measurement system may include a
main housing 44 and a jack housing 56. The main housing 44 may be
attached to the coupler 26 of the trailer 20 at flange plate 42
using bolts 38. A shaft 46 may be positioned in the center of the
main housing 44. The shaft 46 may include a threaded portion 52 at
its lower end 48 and a non-threaded portion 53 at its upper end
50.
[0078] Shaft 46 may be secured in place relative to the main
housing 44 by a pin 45 to prevent spring 64, shaft 46, and the
jacking tube 56 from falling out the bottom of the main housing 44.
The threaded portion 52 of shaft 46 may engage a mating thread 54
on the jacking tube 56. As shown in FIG. 4B, the jacking tube 56
may be constrained in rotation with the main housing by a tongue
and groove feature 58 on the two parts 44, 56, but is allowed free
linear movement up and down relative to the main housing 44.
[0079] A thrust bearing 60 may be provided at the interface between
the threaded portion of 52 and the non-threaded portion 53 of shaft
46. The thrust bearing 60 may bear against a shoulder 62 on the
shaft 46. Again, in a conventional tongue jack this thrust bearing
would bear against the under side of the top of the main housing
and give free rotation of the shaft relative to the housing. As in
the first embodiment described above, in this embodiment of a
tongue jack 32 having a weight measurement system a spring 64 may
be introduced between the bearing 60 and the inside top surface 66
of the main housing 44.
[0080] A gear housing 70 may be provided on an extension to shaft
46 and above pin 45 and the top of the main housing 44. This gear
housing 70 may also be restrained in rotation by a tongue and
groove feature 58 just like the main housing 44 to jacking tube 56
(see e.g., FIG. 4B). This gear housing 70 may house a right angle
gear set 72 and the operating handle 34. The lower portion 71 of
the gear housing 70 may overlap the main housing 44 to engage its
anti-rotation feature and to provide a read out location for the
weight scale 68. Preferably, the overlap is designed and
constructed to be more that the travel of the spring 64 or the
anti-rotation feature may disengage.
[0081] A scale 68 may be provided to indicate a load (i.e., weight)
on the tongue jack 32. For example, a calibrated scale may be
engraved or attached on the outside of the upper part of the main
housing 44, as shown in FIG. 4A. Alternatively, a series of color
bands corresponding to a weight range may be used. The scale 68 may
include a zero point and a series on marks corresponding to a load
or weight measurement. As shown in FIG. 4A, the tongue jack 32 is
unloaded and the zero point of the scale 68 is at the lower edge of
the lower portion 71 of gear housing 70. As such, with zero load
the scale 68 is mostly hidden by the skirt or lower portion 71 of
the gear housing 70.
[0082] In operation, the tongue 26 of the trailer 20 may be
supported by the tongue jack 32 and the trailer 20 may or may not
be attached to the hitch 12 of the tow vehicle 10. As weight is
applied, the spring 64 of the tongue jack 32 will deflect (e.g.,
compress) in direct proportion to the weight on the jack tongue 32.
This deflection of spring 68 will cause the shaft 46 and gear
housing 70 to move upward relative to the main housing 44 exposing
the scale 68 on housing 44. The weight on the tongue 26 of the
trailer 20 can then be read off the scale 68.
[0083] FIGS. 5A-5C show another exemplary embodiment of the trailer
tongue weight measurement system. The embodiment of the trailer
tongue weight measurement system shown in FIGS. 5A-5C results from
the need to adapt trailer tongue weight measurement system to the
needs of heavier classes of trailers. Since the outside diameter of
the standard tongue jacks and the holes to receive them in standard
couplers is a fixed size, there is a limit on the size of spring
and its available deflection that can be fit within this envelope.
What results in the case of stiffer springs required by heavier
loads is that when the spring is strong enough for the given load
the deflection of the spring may be so small that the scale would
be very difficult to read accurately. Therefore, the embodiment
shown in FIG. 5A-5C provides a gage read out of unique design to
amplify the movement of the spring to make it easier to read.
[0084] The tongue jack 32 illustrated in FIGS. 5A-5C is similar to
the tongue jack shown in FIG. 3. As before, the main housing 44 of
the tongue jack 32 may be attached to the coupler of the trailer at
flange 42 using bolts 38. A shaft 46 may be disposed in the center
of the housing 44. The shaft 46 may include a threaded portion 52
at its lower end 48 and a non-threaded portion 53 at its upper end
50. The top end of the shaft 46 may be located at the top of the
main housing 44 by a pin 45 to prevent spring 64, shaft 46, and the
jacking tube 56 from falling out the bottom of the main housing 44.
The threaded portion 52 of the shaft 46 may engage a mating thread
54 on the jacking tube 56.
[0085] The jacking tube 56 may be constrained in rotation with the
main housing 44 by a tongue and groove feature 58 between the two
parts 44, 56, but is allowed free movement up and down relative to
the main housing 44. A thrust bearing my be disposed at the
interface between the threaded portion of 52 and the non-threaded
or cylindrical portion 53 of shaft 46. The thrust bearing 60 may
bear against a shoulder 62 on the shaft 46. The thrust bearing 60
allows free rotation of the shaft 46 relative to the housing 44. A
spring 64 may be disposed between the bearing 60 and the inside top
66 of the main housing 44.
[0086] A gage housing 80 may be provided on the top of the main
housing 44. For example, an inverted U shaped gage housing 80 may
be formed integral with the main housing 44. Alternatively, the
gage housing 80 may be formed separate from and connected to the
main housing 44. As shown, the shaft 46 may extend through the gage
housing 80 and the operating handle 34 may be attached to shaft 46.
The portion of the shaft 46 that is within the gage housing 60 may
be machined with a circular gear rack 82. This gage rack 82 may
engage with a pinion gear 84. An indicator needle 86 may be
connected to the pinion gear 84 via a shaft which may extend
through an opening in the gage housing 80. A scale may be provided
on the outside of the gear housing 80 for the read out of the
weight on the tongue of the trailer.
[0087] The amplifier system of FIGS. 5A-5C may also be used with
other types of tongue jacks, including the tongue jack shown in
FIG. 4A.
[0088] FIGS. 6A and 6B show another embodiment of the trailer
tongue weight measurement system. The trailer tongue weight
measurement system embodiment illustrated in FIGS. 6A and 6B is
located at the trailer tongue coupler 28. The trailer tongue weight
measurement system may be formed integral with the trailer tongue
26 or may be formed as a separate unit and attached to the trailer
tongue 26.
[0089] As shown, the weight measuring system may be integral to the
coupler 28 and ball receptacle 30 on the tongue 26 of the trailer
20. When a load is applied to the trailer it bears down on the
hitch and the force on the ball receptacle is pushed up. One
advantage of this embodiment is that the trailer tongue weight
measuring system may be built directly into the trailer. Another
advantage of an integral trailer tongue weight measuring system is
that it may be a permanent part of the trailer. Yet another
advantage is that the trailer tongue weight may be measured with
the trailer attached to the tow vehicle. In order to retrofit this
unit onto existing trailers, the unit would have to be formed as a
separate unit and the trailer tongue may have to be modified to
receive the unit. As shown in FIG. 6A, the trailer tongue weight
measuring system may be used with a standard type hitch.
[0090] Also as shown in FIG. 6A, this embodiment of the tongue
weight measuring system may be based on a normal type hinge plate
assembly 90 having a front plate 90a and a rear plate 90b that may
be pivotally connected using a hinge pin 92. Plates 90a and 90b are
hinged together such that when there is load on the weight
measurement system the plates 90a, 90b are pressed together. As
shown, the front of the trailer tongue 26 or coupler 28 may be
connected (e.g., welded) to the rear plate 90b of the hinge plate
assembly 90. The front plate 90a of the hinge plate assembly 90 may
be attached to the rear plate 90b by hinge pin 92 and a series of
four shoulder bolts 96. The front plate 90a may also be connected
(e.g., welded) to the ball receptacle 30 and its ball retention
hardware (not shown).
[0091] In operation, the weight of the trailer 20 on the ball 14
causes the hinge plate 90b to close against hinge plate 90a. To
limit the opening motion of the hinge plate assembly 90, four
shoulder bolts 96 may pass through hinge plate 90b and may be
screwed into hinge plate 90a. In an alternate embodiment, the
orientation of the shoulder bolts may be reversed.
[0092] As shown in FIGS. 6A-6C, one or more clearance indicators 98
may be provided and captured by the upper shoulder bolts 96. As
shown, the clearance indicators may comprise stirrups 98 that may
surround an upper edge of hinge plate 90b. These stirrups 98 may
act as indicators of when the tongue weight has been properly
measured (i.e., not too high or too low). For example, the stirrups
98 may include a tolerance such that the total thickness of the two
washers 99 plus the thickness of hinge plate 90b is between about
0.010 inch and about 0.020 inch less than the height of the
shoulder of the shoulder bolts 9. Alternative devices may be placed
between plates 90a and 90b to be used as indicators. When an
indicator device is free to move, a weight of the trailer may be
read.
[0093] As shown in FIG. 6A, two openings 100, 102 may be provided
in the center of the two hinge plates 90a, 90b. As shown, the
openings may be concentric to each other and may include a smaller
opening 102 in the front plate 90a and a larger opening 100 in the
rear plate 90b. A nut 104 may be connected (e.g., welded) to the
rear of the rear plate 90b. The nut 104 may be concentric to the
opening 100 and the nut 104 may include a right hand threaded
portion 106.
[0094] Shaft 108 may be threaded into the nut 104 and may protrude
through the opening 102 in front hinge plate 90a. As shown, shaft
108 has several features including a forward cylindrical portion
140, a central threaded section 142, a tapered spline 144, and a
small diameter threaded section 146.
[0095] A spring 118 may be provided between the hinge plates 90a
and 90b to urge the hinge plates 90a, 90b apart. As shown, spring
118 may be place over shaft 108 between the two hinge plates 90a
and 90b. In one embodiment, the spring 118 may include one or more
spring washers, such as Belleville spring washers, that surround
the cylindrical section 140 of the shaft 108 and are captured
between a shoulder 109 on the large threaded section 142 and the
front hinge plate 90a. With the two hinge plates 90a and 90b held
tight together, shaft 108 may be turned counterclockwise until it
is snug against spring 118 and then the handle 120 may be placed
over the spline section 114 on shaft 108 such that the knob 122 on
the handle 120 is located over the zero location on the weight
scale 130 on the rear face 132 of hinge plate 90b. The handle 120
may be secured to the shaft 108 with nut 124.
[0096] In operational use, the trailer mount unit having the weight
measuring system may be connected to the towing vehicle 10 by
placing the trailer ball receptacle 30 over the hitch ball 14. The
trailer load pushing down on ball 14 and the weight of the trailer
20 will firmly clamp the indicator stirrups 98 between hinge plates
90a and 90b.
[0097] To determine the tongue weight, the operator may grasp one
of the stirrups 98 and rotate the handle 120, for example
clockwise, from the zero position until the stirrup indicator 98 is
free to move. This freedom of movement being caused by the rotation
of shaft 108 into nut 104 by the handle 120 and the resultant axial
movement of shaft shoulder 109 against spring 118. The load in
spring 118 will increase until at some point it will balance the
opposing load on the ball 14 and cause the two hinge plates 90a and
90b to move apart, thereby freeing the stirrup indicator(s) 98 to
move/rotate.
[0098] When the stirrup indicator 98 becomes free, the weight under
the knob 122 on handle 120 may be read as the weight on the tongue
26 of the trailer 20. If the handle 120 is turned too far, then the
stirrup 98 will be restrained by being clamped between the head of
the shoulder bolt 96 and hinge plate 90b. This double action of the
stirrup 98 helps assure a proper weight is read on the scale
130.
[0099] FIGS. 7A and 7B show another embodiment of the trailer
tongue weight measurement system. In this embodiment, the trailer
tongue weight measurement system is on the hitch 12. As
illustrated, this embodiment is similar to the embodiment of FIGS.
6A and 6B in that the principles of operation are similar even
though some of the parts are in effect reversed because the forces
are in the opposite direction between the two embodiments. In the
embodiment of FIGS. 6A and 6B the force on the unit was pushing up
on the ball receptacle 30, and in the embodiment of FIGS. 7A and 7B
the forces are pushing down on the ball mount 14.
[0100] The embodiment illustrated in FIGS. 7A and 7B is based on a
scissor type hinge plate assembly 90, including front plate 90a and
rear plate 90b. As shown, the trailer tongue weight measurement
system hinge plate assembly 90 may be connected (e.g., welded) to
the hitch 12. In the embodiment illustrated in FIGS. 7A and 7B, the
rear hinge plate 90b may be attached (e.g., welded) to the tubing
16 of the ball mount 14. The bottom of this hinge plate 90 may
include a hinge pin 92 that allows the hinge plates 90a, 90b to
pivot relative to one another. As shown, the forward half 90a of
the hinge plate assembly 90 may be L-shaped and may surround the
tubing 16. In addition, the forward plate 90a of the hinge plate
assembly 90 (the lower portion 90c of the L-shaped plate) may also
protrude rearward to support the hitch ball 14 and its fixing nut
14a.
[0101] In operation, the weight of the trailer 20 on the ball 14
causes the hinge plate 90a to close against hinge plate 90b (in the
direction of arrow 94). To limit the opening motion of the hinge,
four shoulder bolts 96 may pass through hinge plate 90b and may be
screwed into hinge plate 90a. In an alternate embodiment, the
orientation of the shoulder bolts may be reversed.
[0102] Stirrup indicators 98 may be provided and captured by the
upper two shoulder bolts 96. As shown, the stirrups 98 may surround
plate 90b. These stirrups 98 may act as indicators of when the
tongue weight has been properly measured (i.e., when the operating
handle 120 has loaded the spring 118 to counter balance the weight
on the tongue of the trailer 20). For example, the stirrups 98 may
include a tolerance such that the total thickness of the two washer
portions 99 plus the thickness of hinge plate 90b is between about
0.010 inch to about 0.020 inch less than the height of the shoulder
of the shoulder bolts 96.
[0103] As shown in FIG. 7A, two openings 100, 102 may be provided
in the center of the two hinge plates 90a, 90b. As shown, the
openings may be concentric to each other and may include a smaller
opening 100 in the rear plate 90b and a larger opening 102 in the
front plate 90a. A nut 104 may be connected (e.g., welded) to the
front of the front plate 90a. The nut 104 may be concentric to the
opening 102 and the nut 104 may include a left hand threaded
portion 106. Shaft 108a may be threaded into the nut 104 and may
protrude through the opening 100 in rear hinge plate 90b. As shown,
shaft 108a has several features including a forward threaded
portion 110, a cylindrical portion 112, a tapered spline portion
114, and finally a small diameter threaded section 116.
[0104] A spring 118 may be provided between the hinge plates 90a
and 90b to urge the hinge plates 90a, 90b apart. As shown, spring
118 may be place over shaft 108a between the two hinge plates 90a
and 90b. In one embodiment, the spring 118 may include one or more
spring washers, such as Belleville spring washers, that surround
the cylindrical section 112 of the shaft 108a and are captured
between a shoulder 109 on the large/raised threaded section 110 and
the rear hinge plate 90b. With the two hinge plates 90a and 90b
held tight together, shaft 108a may be turned counterclockwise
until it is snug against spring 118 and then the handle 120 may be
placed over the spline section 114 on shaft 108a such that the knob
122 on the handle 120 is located over the zero location on the
weight scale 130 on the rear face 132 of hinge plate 90b. The
handle 120 may be secured to the shaft 108a with a nut 124.
[0105] In operational use, the hitch mount unit having the weight
measurement system may be connected to the tow vehicle 10 by
sliding the square tubing 16 into the receiver 18 on the hitch 12
and securing it in place with pin 19, as shown in FIG. 7A. With the
hitch 12 secured to the towing vehicle 10, the trailer tongue 26
may be connected to the hitch 12 by placing the trailer ball
receptacle 30 over the hitch ball mount 14. The load pushing down
on ball 14 also pushes down on the lower portion 90c of the L-shape
hinge plate 90a. This causes the L-shape hinge plate 90a to pivot
or rotate about hinge pin 92 (in the direction of arrow 93) and
causes the hinge half 90a to close against hinge half 90b (in the
direction of arrow 94). This movement captures the spring 118
between hinge plates 90a and 90b. The weight of the trailer 20 will
then firmly clamps the indicator stirrups 98 between hinge plates
90a and 90b.
[0106] To determine the tongue weight, the operator may grasp one
of the stirrup indicators 98 and rotate the handle 120, for example
clockwise, from the zero position until the stirrup indicator 98 is
free to move. This freedom of movement being caused by the rotation
of shaft 108a into nut 104 by the handle 120 and the resultant
axial movement of shaft shoulder 109 against spring 118. The load
in spring 118 will increase until at some point it will balance the
opposing load on the ball 14 and cause the two hinge plates 90a and
90b to move apart, thereby freeing the stirrup indicator(s) 98 to
move/rotate.
[0107] When a stirrup indicator 98 becomes free, the weight under
the knob 122 on the handle 120 can be read as the weight on the
tongue 26 of the trailer 20. If the handle 120 is turned too far,
then the stirrup indicator(s) 98 will be restrained by being
clamped between the head of the shoulder bolt 96 and plate 90b
indicating to the user that he or she has not adjusted it properly.
This double action of the stirrup 98 helps assure a proper weight
is read on scale 130.
[0108] Those skilled in the art will appreciate that numerous
changes and modifications may be made to the preferred embodiments
of the invention and that such changes and modifications may be
made without departing from the spirit of the invention. It is
therefore intended that the appended claims cover all such
equivalent variations as fall within the true spirit of the
invention.
* * * * *
References