Patent Application
20120091411
The present invention relates generally to the art of hydraulic jacks. More particularly, the present invention pertains to hydraulic jack assemblies of virtually any size and capacity with power extension and self-retracting capabilities.
It has heretofore been well known to utilize various mechanical and power-operated support jack assemblies to facilitate coupling and decoupling of a trailer apparatus from a towing vehicle, and as necessary, for supporting and leveling such a trailer. Such jack assemblies are typically mounted upon the tongue of a trailer and oftentimes require manual manipulation to raise and lower the trailer tongue. Manual screw jacks are generally commonplace with smaller load-bearing trailers, where manual rotation of a crank handle turns a vertical screw to effect the lifting and lowering of the trailer's tongue. Other hydraulically powered jacks incorporating a cylinder and ram system are oftentimes utilized for jacking heavier load-bearing trailers and the like. These devices usually comprise a series of telescoping upper and lower leg sections that slide relative to one another in response to a change in hydraulic pressure applied to the system. The hydraulic fluid may be pumped into the system through manual manipulation of a hand crank or via the use of a separate hydraulic power source.
While such prior lifting devices have been mildly successful in accomplishing their intended purpose, there are a number of deficiencies in their operation which make them less than satisfactory. For instance, some hydraulic jack assemblies incorporate a set of return springs connected between the telescoping legs to cause such legs to retract or collapse upon release of hydraulic pressure. These are typically tension springs, the ends of which are connected to the exterior of the telescoping legs. Such connections are subject to extensive wear and tear through repeated manipulation and long-term exposure to adverse weather conditions. Moreover, such devices are usually quite bulky, unsightly to look at, and offer limited options for mounting the jack due to design constraints.
Jacking devices equipped with a manual rotating crank or hand-operated pump handle are typically quite slow and tedious to operate, and suffer from similar mounting constraints due to the required operational design of the crank or pump, retraction springs, etc. One such exemplary hydraulic jack assembly can be found in U.S. Pat. No. 5,011,119, entitled: Conveniently Attached Hydraulic Trailer Jack. As noted, numerous working components of such manually operated devices are subject to premature aging and failure due to repeated manual manipulation and exposure to adverse weather conditions, and are bulky and unsightly in appearance. Particularly in situations where time is of the essence and large load-bearing capacities are required, such deficiencies in the prior art jacking devices can lead to significant and costly downtime, and possible catastrophic failure in the field.
It is therefore evident that there is a distinct need in the industry for a jacking device that is capable of full integration with existing trailer power/hydraulics; which minimizes premature failure due to repeated manual manipulation and/or exposure of critical working components to weather elements; and which is otherwise designed to prevent the wear and tear typically associated with conventional jacks. It is further desirable that such jack assembly be compact in design; provide maximum flexibility in mounting options to a trailer or the like; and be simple and pleasing in appearance.
One principal object of the present invention is therefore to overcome the deficiencies of prior art jacking devices by providing a self-retracting hydraulic jack assembly that enables full retraction of the jack's telescoping legs with no use of tension springs; reduces the overall number of required mechanical working components; and is more compact, reliable and durable functionally.
Another object of the present invention is to incorporate the critical working components of the jack assembly within a compact housing, thereby minimizing potential damage from exposure to the outside elements of nature and/or adverse weather conditions.
Still a further object of the present invention is to provide an improved hydraulic jack assembly of any desired size or capacity that incorporates such aforementioned design features and benefits, and is capable of full integration with existing trailer power/hydraulics.
The foregoing objects and others are achieved through use of the present invention, where a self-retracting hydraulic jack is provided which includes a leg retraction mechanism that is incorporated within and forms an integral part of the hydraulic extension cylinder of the jack. In general, the hydraulic jack is comprised of a plurality of telescoping tubular leg members that are extensible relative to one another in response to the introduction of hydraulic fluid into the extension cylinder. A first tubular leg member constitutes the outer structural body of the jack assembly, and is adapted for mounting in an upright position on the tongue of a trailer or the like. A second tubular leg member is telescopically received within the lower end of the first tubular leg and is hydraulically coupled thereto via the hydraulic extension cylinder. The second tubular leg surrounds and is fixedly secured to the outer casing of the hydraulic extension cylinder, and the first tubular leg is connected to the piston rod assembly thereof. Consequently, upon actuation of the hydraulic extension cylinder, the first and second tubular legs are displaced longitudinally relative to one another, thereby facilitating elevation of the attached load.
An optional third tubular leg member is telescopically received within the second tubular leg through a pull-pin casting that is secured to the lower end of the second leg. This third leg is freely adjustable longitudinally within the second tubular leg, and the pull-pin casting includes a spring-loaded locking pin configured to mate with any one of a plurality of openings in the side of the third tubular leg. As such, this third tubular leg constitutes a mechanically adjustable drop-leg assembly that may be freely adjusted and locked in any desired position relative to the second tubular leg. A foot or base plate is affixed to the bottom of the third leg for support of the jack assembly against a load-bearing surface, such as the ground. In the absence of the third leg, the base plate attaches to the bottom of the second leg.
The extension cylinder is comprised generally of an outer cylindrical casing within which an elongated piston rod assembly is housed for reciprocatory movement. A leg retraction mechanism, comprised of an elongated compression spring, is carried by the piston rod assembly within the piston extension cylinder. This compression spring is configured to slide over the piston rod in surrounding relation thereto, and is confined between the piston and the upper end cap of the extension cylinder.
Upon introduction of hydraulic fluid into the extension cylinder, the piston is caused to move upward within the extension cylinder, thereby simultaneously compressing the retraction spring as the hydraulically coupled legs of the jack assembly are extended. Upon release of the hydraulic fluid pressure, the force of the compression spring will cause the extension cylinder to automatically retract to its original position, drawing the first and second tubular legs back together.
By positioning a single compression spring over the piston rod in the above manner, retraction of the jack legs is accomplished swiftly and automatically with a minimum of required moving mechanical components. The maximum amount of energy from the compression spring is transferred directly in line with the piston rod assembly. Consequently, unlike conventional jack assemblies, the use of multiple extension springs to effect leg retraction has been eliminated. The compression spring utilized remains completely sealed within the extension cylinder, and there are no mechanical connections required to secure the ends of tension springs, as with conventional jack assemblies. This avoids the potential for localized structural damage at the spring joint connections due to metal fatigue from repeated cyclic loadings, as well as the potential for premature failure due to constant exposure to the elements of nature, such the sun, rain and snow, or dirt and gravel, etc.
These and other objects and advantages of the invention will more fully appear from the following description, made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:
With reference to
As shown, the second tubular leg member 5 is constructed of slightly smaller dimensions and with the same cross-sectional configuration as the first tubular leg 3 such that it is capable of being telescopically received within leg 3 through the lower open end 11 thereof. This second tubular leg 5 surrounds the hydraulic extension cylinder 9, and is secured at its upper end 19 to the upper end cap 21 of the extension cylinder 9. As shown in
The first and second tubular leg members 3 and 5 of the jack assembly 1 are hydraulically coupled via extension cylinder 9 to affect extensible movement of one relative to the other. As shown best in
As shown further in
As seen best in
The upper portion 57 of piston rod 35 is fixedly secured to the bolster cap 15 of the first outer leg 3. As shown best in
More specifically, hydraulic fluid introduced into the extension cylinder 9 through the piston rod 35 will flow into the hydraulic fluid storage chamber 53, thereby increasing fluid pressure and causing the piston rod assembly 33 to move upwardly within the extension cylinder 9. With the first tubular leg 3 fixedly secured to the piston rod 35 and the second tubular leg 5 rigidly connected to the outer casing 31 of the extension cylinder 9, such movement of the piston rod assembly 33 within extension cylinder 9 in response to the introduction of hydraulic fluid will cause the first and second tubular members 3 and 5 to extend longitudinally relative to one another.
As shown in
The function of pull pin casting 71 is best illustrated with reference to
In
In operation, when it is desired to decouple a trailer or similar device upon which jack assembly 1 is mounted from a towing vehicle, turning the locking pin 77 either clockwise or counterclockwise will cause the pin 77 to back out of its engaged opening 79 in leg 7. This causes leg 7 to become disengaged from leg 5 and drop to or near ground level, where it is then re-engaged in locking relation with leg 7. Extension cylinder 9 may then be actuated, causing hydraulic fluid to be pumped into the hydraulic storage chamber 53 thereof. This causes piston rod assembly 33 to move and leg 5 to extend relative to outer leg 3. In turn, foot 25 of leg 7 will engage the ground and the jack assembly 1 will raise the trailer, thereby decoupling it from the towing vehicle.
Upon release of hydraulic pressure within the jack assembly 1, it is desirable for the first and second tubular leg members 3 and 5 to retract to there original positions relative to one another. In order to cause legs 3 and 5 to retract, a leg retraction mechanism, comprised of an elongated compression spring 95, is carried by the piston rod assembly 33 within the extension cylinder 9. This compression spring 95 is configured to slide over the piston rod 35 in surrounding relation thereto, so as to be confined between the piston 39 and the upper end cap 21 of the extension cylinder 9. With this configuration, introduction of hydraulic fluid into the extension cylinder 9 will cause the piston 39 to move upward toward the end cap 21, thereby compressing the retraction spring 95 at the same time. Upon release of the hydraulic fluid pressure, the force of the compression spring 95 will cause the extension cylinder 9 to automatically retract to its original unextended position, thereby drawing the first and second tubular legs 3 and 5 back together.
By positioning a single compression spring 95 over the piston rod 35 in the above manner, retraction of legs 3 and 5 of the jack assembly 1 is accomplished swiftly and automatically with a minimum of required moving mechanical components. The maximum amount of energy from the compression spring 95 is transferred directly in line with the piston rod assembly 33. Consequently, unlike conventional jack assemblies, the use of multiple extension springs to effect leg retraction has been eliminated. The compression spring 95 utilized remains completely sealed within the extension cylinder 9, and there are no mechanical connections required to secure the spring ends to effect proper operation, as with conventional tension springs. Therefore, the spring 95 is free-floating within cylinder casing 31 of extension cylinder 9. As noted previously, this avoids the potential for localized structural damage at the spring joint connections due to metal fatigue from repeated cyclic loadings, as well as the potential for premature failure due to constant exposure to the elements of nature, such the sun, rain and snow, or dirt and gravel, etc.
In the illustrated embodiment herein, the telescoping tubular members 3, 5 and 7 are depicted as being square in cross section, which facilitates convenient mounting of the jack assembly 1 in multiple optional orientations upon a trailer or the like. However, it is certainly contemplated that such telescoping members could be configured differently without departing from the invention herein. For instance, the tubular leg members 3, 5 and 7 could be rectangular or circular in cross section, and still provide maximum flexibility, since the retraction compression spring 95 is sealed within the extension cylinder 9 and does not obstruct in any manner the outer mounting surface of tubular member 3.
Certain terminology used herein is for purposes of reference only, and is not intended to be limiting in any manner. For instance, terms such as “upper”, “lower”, “above”, “below”, “top”, “bottom”, “upward”, “downward”, “rearward”, and “forward” may refer to directions in the drawings to which reference is made. Similarly, terms such as “front”, “back”, “rear”, “bottom” and “side”, may describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and/or words of similar import. Also, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context.
Furthermore, when introducing elements or features and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It should be further understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of the invention which comprises the matter shown and described herein and set forth in the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 61392775 | Oct 2010 | US |
