Spring loaded drop foot trailer jack

An apparatus for adjustably supporting a portion of a wheeled vehicle, which apparatus may be retracted or disengaged from a supporting surface when the wheeled vehicle is put into use. A tubular outer housing is provided for attaching to the vehicle, with second and third tubular members slidably disposed therein. A locking mechanism is provided adjacent an aperture in a wall of the second tubular member for positioning a pin in selectively alignable apertures in a wall of the third tubular member, thereby preventing relative movement between the second and third tubular members. A tension spring engaging both second and third tubular members and located within the third tubular member is provided for biasing the third tubular member toward a retracted position with respect to the second tubular member. A cranking rod and threaded screw member are also disclosed for moving the second tubular member with respect to the tubular outer housing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This apparatus relates generally to apparatus for at least partially 
supporting a portion of a wheeled vehicle and more particularly, but not 
by way of limitation, to apparatus for adjustably supporting a trailer and 
which may be retracted or disengaged from the ground or other supporting 
surface when the trailer is put into use. 
2. Description of the Prior Art 
Supporting apparatus have utility in facilitating engagement and 
disengagement of a trailer from a ball or other type trailer hitch mounted 
on the rear of a truck or automobile. In practice, these apparatus 
typically provide some means to adjust the height of the trailer above the 
ground, as with a jack, and to thereby effect or close a vertical 
separation of the trailer and the usual ball-type trailer hitch. Several 
such apparatus are disclosed in the prior art. For example, U.S. Pat. No. 
2,939,679 to Ryan disclosed a jack mechanism, mounted on the tongue of a 
trailer-type vehicle, which is vertically retractable when not in use. The 
jack is disclosed as disposed within a housing member and as engaging a 
telescoping member slidably received within the housing member. A latch 
dog is pivotally attached to the housing member, and engages elongated 
slots in the housing member to bear against a nut which is threaded onto 
the jack and fits closely within the housing member. Extension of the 
telescoping member, and a tension spring which is attached to the base 
plate at the lower end of the telescoping member and to an external 
portion of the housing member, pass the nut downward past the latch dog 
and force the top of the nut against the latch dog, thus locking the latch 
dog into place. Further adjustment of the device is accomplished by 
rotation of the threaded shaft of the jack through the nut and by bearing 
of the shaft against a thrust bearing welded across the top of the 
telescoping member. 
Patents to Douglass, U.S. Pat. No. 3,595,527 and Osborne, et al., U.S. Pat. 
No. 4,216,601, disclose similar devices which employ a tubular support 
member, with openings disposed therein, attached to the frame of the 
trailer or other wheeled vehicle. Coarse adjustment of these apparatus is 
accomplished by positioning ears or radial supporting projections from a 
first tube slidably disposed in the tubular support member within openings 
in the tubular support member. Finer adjustments of the apparatus are 
accomplished by the relative rotation of a jack screw with respect to a 
second tube slidably disposed within the first tube. The patent to 
Osborne, et al. also discloses the use of a spring loaded locking 
mechanism, mounted on the tubular support member, for inserting a pin into 
selectively alignable openings in the first and second tubes, thereby 
fixing those tubes into place with respect to the tubular support member 
and to the frame of the trailer to which the support member is affixed. 
Patents to Richards, U.S. Pat. No. 2,205,436, and Vinther, et al., U.S. 
Pat. No. 3,281,160, disclose apparatus employing telescoping tubes and 
pins which are manually inserted into selectively alignable openings in 
the tubes. 
One of the problems associated with these apparatus as previously disclosed 
is the absence of convenient means for retracting the innermost 
telescoping tubular member when any locking means provided are disengaged, 
and which are durable and not jeopardized by the environment in which the 
apparatus is employed. For instance, the patents to Osborne et al. and 
Douglass which were previously discussed require that the user crank or 
twist something to retract this innermost member from an extended 
position. The patents to Ryan and to Richards appear to disclose spring 
means for accomplishing an automatic retraction of the apparatus from a 
supporting surface, but both spring means are exposed and therefore 
subject to the influences and interference of the environment. 
Such interference can be substantial. For example, an apparatus of the type 
disclosed in the patents to Ryan and to Richards could be used in a 
farming operation to support hay wagons or other tractor attachments, 
where dirt could become caked on the spring or otherwise interfere with 
the operation of the spring. Such apparatus could also be employed to 
support a boat trailer, where exposure to water, and particularly salt 
water, could quickly compromise the utility of such spring means as 
disclosed in the patents to Ryan and to Richards. The biasing means of the 
present invention, in contrast, is disclosed as protected from the 
environment within a third tubular support member, which is in turn 
slidably disposed within two other tubular members. 
Another need not met by the prior art is the provision of a locking 
mechanism which is variably positionable with respect to the frame or 
other portion of the vehicle to be supported and which further is 
conveniently actuated, though the patent to Vinther, et al. does disclose 
the use of a manually inserted pin which is variably positionable with 
respect to the frame or other portion of the vehicle to be supported. 
The present invention overcomes the shortcomings of the prior art by 
providing a novel and improved spring loaded drop foot trailer jack which 
permits coarse and fine adjustment for the height above a supporting 
surface, which may be locked into a desired position, and which provides 
means for automatically retracting the jacking apparatus from engagement 
with the supporting surface with minimal exposure to interference from the 
environment. 
SUMMARY OF THE INVENTION 
The trailer jack of the present invention comprises a tubular outer housing 
for attaching to the wheeled vehicle to be supported and having an upper 
end and an open lower end, a second tubular member slidably disposed 
within the tubular outer housing, a third tubular member slidably disposed 
within the second tubular member, biasing means located within the third 
tubular member for biasing the third member toward a retracted position 
with respect to the second member, locking means for preventing movement 
be-tween the second and third tubular members when actuated, and a vehicle 
support member attached to a lower portion of the third tubular member. 
The locking means comprises a pin case extending from a wall of the second 
tubular member adjacent an aperture in the wall, a pin which is slidably 
disposed in the pin case and which has a first portion and an enlarged 
second portion, and a plate, adjacent an end of the pin case, with an 
aperture defined in the plate for allowing passage of the first portion of 
the pin, but preventing the enlarged portion from passing from the pin 
case. The locking means of the apparatus also comprises a lever pivotally 
engaging the first portion of the pin and movable from a first position 
wherein the pin engages one of a series of spaced openings in the wall of 
the third tubular member, to a second position wherein the pin is removed 
from engagement with the opening, and includes a spring abutted against 
the plate and against the enlarged second portion of the pin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, and more particularly to FIGS. 1 and 2, the 
spring loaded drop foot trailer jack of the present invention is shown and 
generally designated by the numeral 10. In the preferred embodiment shown, 
the trailer jack 10 is adapted for supporting a portion of a wheeled 
vehicle, such as trailer 12, and comprises a tubular outer housing 14 
having an upper end 16 and an open lower end 18. Brackets 19 are used to 
attach outer housing 14 to trailer 12 in a manner known in the art. A 
second tubular member 20 is slidably disposed in the tubular outer housing 
14, and is extended from and retracted into the tubular outer housing 14 
through its open lower end 18. A third tubular member 22, having an upper 
portion 24 and a lower portion 26, is slidably disposed within the second 
tubular member 20. A vehicle support member such as a plate 28 is attached 
to the lower portion 26 of the third tubular member 22 for engaging a 
supporting surface 30 such as the ground when in use. 
The trailer jack 10 of the present invention is movable from a fully 
retracted state, as shown in FIG. 1, to a fully extended state, as shown 
in FIG. 3, by the use of a combination of biasing means and locking means 
for moving the third tubular member 22 with respect to the second tubular 
member 20, and of a combination of connecting means and extending means 
for moving the second tubular member 20 with respect to the tubular outer 
housing 14. Referring again to FIG. 1, the biasing means of the preferred 
embodiment comprises a tension spring 32 which is connected to a lower 
ring 34 connected to the lower portion 26 of the third tubular member 22. 
The tension spring 32 is connected also to an upper ring 36 which is 
connected to a plate 38 secured to an upper portion 40 of the second 
trailer member 20. Detailed discussion of the locking means of the 
preferred embodiment is deferred until a description of the operation of 
the jack can be undertaken in conjunction with FIGS. 4 and 5. 
The connecting means of the preferred embodiment comprises a screw support 
plate 41 having a hole 42 defined therein and which is secured to the 
tubular outer housing, a threaded screw member 44 having a unthreaded 
portion 46 rotatably received in hole 42 and a threaded portion 48 
threadingly received in a threaded hole 50 defined in a nut 51 held 
between plates 38 and 39, and the plates 38 and 39. The nut 51 is 
prevented from rotating with respect to the second tubular member 20 by a 
close fitting engagement with a hole 37 defined in the plate 39, which 
plate is secured also to an upper portion 40 of the second tubular member 
20. It will be seen that rotation of the threaded screw member 44 moves 
the plates 38 and 39 and thus the second tubular member 20 upwardly or 
downwardly with respect to the tubular outer housing 14. A bearing 52 and 
a ring 54 are provided also for guiding the rotation of the threaded screw 
member 44 in conjunction with the screw support plate 40. 
The extending means of the preferred embodiment shown in FIGS. 1 and 3 
accomplishes the rotation of the threaded screw member 44, as just 
discharged, and comprises a bushing 56 disposed adjacent each of a pair of 
opposing transverse openings 58 defined in the tubular outer housing 14 
adjacent its upper end 16, and a first bevel gear 60 attached to the 
threaded screw member 44. A second bevel gear 62 engages the first bevel 
gear 60 and has a hole 64 defined therein aligned with the bushings 56. A 
cranking rod 66 having first and second ends 68 and 70, respectively, is 
disposed through the bushings 56 and through the hole 64 defined in the 
second bevel gear 62, and is secured to the second bevel gear for 
preventing relative movement therebetween. 
The cranking rod 66 is rotated by rotating means comprising a handle 72 
having an aperture 74 defined in a first end 76 thereof. This aperture 74 
is aligned with a hole 78 defined in the first end 68 of the cranking rod 
66, and a bolt 80 is disposed through the aperture 74 and hole 78. A nut 
82 located opposite the head portion 83 of the bolt 80 threadingly engages 
the bolt 80 and holds the handle 72 adjacent the first end 68 of the 
cranking rod 66. 
Alternatively, the handle 72 may be similarly disposed adjacent the second 
end 70 of the cranking rod 66 by alignment of the aperture 74 with the 
hole 78 in the second end 70. Whether attached to either end an extension 
(not shown) of a kind known in the art may be connected to rod 66 to clear 
trailer 12 as necessary with handle 72 mounted on the extension. 
In operation, the locking means of the present invention and the structure 
recited above make the trailer jack of the present invention amenable to 
coarse and fine height adjustments with respect to the supporting surface 
30. Referring specifically to FIGS. 4 and 5, coarse height adjustments of 
the preferred embodiment require first the movement of a lever 84 from a 
first position shown in FIG. 4, wherein a pin 86 engages one of a series 
of spaced openings 88 in a wall of third tubular member 22, to a second 
position shown in FIG. 5 wherein the pin 86 is removed from engagement 
with any of the openings 88. These positions and corresponding conditions 
are further illustrated in relation to the whole of the trailer jack 10 in 
FIGS. 1 and 3. 
Returning again to FIGS. 4 and 5, in the course of the movement of the 
lever 84 from the first position shown in FIG. 4 to the second position 
shown in FIG. 5, the lever 84 will pivot about a pivot pin 90 in a hole 92 
in a first portion 94 of the pin 86, to bring the ends 96 of the ears 98 
into abutment with a plate 100. The plate 100 is adjacent an end 102 of a 
pin case 104, which pin case 104 is in turn adjacent an aperture 106 
defined in a wall of the second tubular member 20. The plate 100 has an 
aperture 108 defined therein for passage of the first portion 94 
therethrough, but preventing passage of a second enlarged portion 110 of 
the pin 86, so that bringing the ends 96 of the ears 98 of the lever 84 
into abutment with the plate 44 pulls the first portion 94 of pin 86 
through the aperture 108. This action is resisted by a compression spring 
112, which bears against the second enlarged portion 110 of the pin 86 and 
against the plate 100. 
Extension of the third tubular member 22 with respect to the second tubular 
member 20 then requires the stretching of the tension spring 32, as by the 
placing of downward pressure on the plate 38. The pin 86 may then be moved 
into engagement once again with an opening 88 in the third tubular member 
22 which has been selectively aligned with the aperture 106 in the second 
tubular member 20, to secure the second and third tubular members 20 and 
22, respectively, from relative movement therebetween. Retraction of the 
third tubular member 22 with respect to the second tubular member 20 is 
automatically accomplished by the tension spring 32 located within the 
third tubular member 22 with a minimum of interference from the 
environment in which the trailer jack is used, when the pin 86 is removed 
from engagement with an opening 88 of the third tubular member 20 as 
described above. 
In making fine adjustments of the trailer jack, the user cranks the 
cranking rod 66 using the handle 72, thus rotating a second bevel gear 62, 
which rotates the first bevel gear 60 and the threaded screw member 44 to 
which the first bevel gear 60 is attached, which creates an upward or 
downward force on the plates 38 and 39 and on the second tubular member 20 
to which the plates 38 and 39 are secured. Downward movement of the second 
tubular member 20 with respect to the tubular outer housing 14 is limited 
by a pin 114 in the threaded portion 48 of the threaded screw member 44, 
as shown in FIG. 3. 
By the methods for coarse and fine adjustment just described, the user may 
easily retract the trailer jack completely, as shown in FIG. 1, or may 
with equal ease extend the trailer jack apparatus fully, as shown in FIG. 
3, with a minimum of interference from the environment in which the 
appar;atus is used. Contributing to the ease of operation is the provision 
of a locking mechanism which is variably positionable with respect to the 
frame or other portion of the vehicle to be supported, and which is 
conveniently actuated. Thus, the present invention is well adapted to 
carry out the objects and attain the ends and advantages mentioned above 
as well as those inherent therein. While a preferred embodiment of the 
invention has been described for the purpose of this disclosure, numerous 
changes in the construction and arrangement of parts may be made by those 
skilled in the art, which changes are encompassed within the spirit of 
this invention as defined by the appended claims.