Abstract:
A hydraulic lift for a truck trailer, having a pair of hydraulic cylinders mounted to the under side of a semi-trailer. The bottom of the cylinder pistons are connected to a foot, which sits on the ground. A telescoping jackstand positioned between the two cylinders, and can be locked into its extended position with a locking pin. The jackstand acts as a safety device in case the hydraulic system looses pressure, and also acts to take the load off of the hydraulic cylinders when the trailer needs to sit for extended periods of time.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a trailer hydraulic lift for use in connection with hydraulically controlling land gear legs for commercial semi trailers. The trailer hydraulic lift has particular utility in connection with adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand. 
   2. Description of the Prior Art 
   Trailer hydraulic lifts are desirable for hydraulically controlling landing gear legs for commercial semi trailers. 
   The use of trailer hydraulic lifts is known in the prior art. For example, U.S. Pat. No. 5,217,209 to Anders discloses a trailer hydraulic lift with a hinged stowed position controlled by a positioning hydraulic cylinder. However, the Anders &#39;209 patent does not disclose the use of a telescoping jackstand positioned between the lifting cylinders. 
   U.S. Pat. No. 3,341,170 to Smith discloses a hydraulic jack trailer support that is held rigid by a bracing means. However, the Smith &#39;170 patent does not disclose the use of a telescoping jackstand for safety and provides no way to remove the load on the struts for long term positioning. 
   Lastly, U.S. Pat. No. 5,299,829 to Rivers, et al. discloses a pneumatic system for operating semi trailer landing gear that uses a pneumatic gear motor attached to a gear reduction box to control the landing gear. However, the &#39;829 patent does not provide for a jackstand, and does not provide a means to remove the load from the pneumatic struts. 
   While the above-described devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe a trailer hydraulic lift that allows adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand. The Anders patent makes no provision for any means to remove the load from the landing gear struts. 
   Therefore, a need exists for a new and improved trailer hydraulic lift that can be used for adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand. In this regard, the present invention substantially fulfills this, need. In this respect, the trailer hydraulic lift according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing disadvantages inherent in the known types of hydraulic landing gear lifts now present in the prior art, the present invention provides an improved trailer hydraulic lift, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new and improved trailer hydraulic lift which has all the advantages of the prior art mentioned heretofore and many novel features that result in a trailer hydraulic lift which is not anticipated, rendered obvious, suggested, or even implied by the prior art, either alone or in any combination thereof. 
   To attain this, the present invention essentially comprises a hydraulic lift having a pair of hydraulic cylinders mounted to the under side of a semi-trailer. The bottom of the cylinder pistons are connected to a foot, which sits on the ground. A telescoping jackstand positioned between the two cylinders, and can be locked into its extended position with a locking pin. The jackstand acts as a safety device in case the hydraulic system looses pressure, and also acts to take the load off of the hydraulic cylinders when the trailer needs to sit for extended periods of time. 
   Of course, the invention also includes a hydraulic pump and a hydraulic fluid reservoir to operate the cylinders. Also, the invention can have a control box, with an on/off switch, an up/down control lever, and a precise up/down control knob. Finally, the invention could be constructed with varying numbers and configurations of hydraulic cylinders, depending on the strength of the cylinders. 
   There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
   The invention may also include a hinged mounting to connect the trailer hydraulic lift to the trailer, so that it can fold up and sustain less damage while traveling. This configuration might also have a third hydraulic cylinder for raising and lowering the pair of hydraulic cylinders and the jackstand to and from a stowed position parallel to the bottom of said trailer. 
   There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached. 
   Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. In this respect, before explaining the current embodiment of the invention in detail, it is to be understood that the invention is not limited in its application&#39;to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
   It is therefore an object of the present invention to provide a new and improved trailer hydraulic lift that has all of the advantages of the prior art trailer hydraulic lifts and none of the disadvantages. 
   It is another object of the present invention to provide a new and improved trailer hydraulic lift that may be easily and efficiently manufactured and marketed. 
   An even further object of the present invention is to provide a new and improved trailer hydraulic lift that has a low cost of manufacture with regard to both materials and labor, and which accordingly is then susceptible of low prices of sale to the consuming public, thereby making such trailer hydraulic lift economically available to the buying public. 
   Still another object of the present invention is to provide a new trailer hydraulic lift that provides in the apparatuses and methods of the advantages thereof while simultaneously overcoming some of the disadvantages normally associated therewith. 
   Even still another object of the present invention is to provide a trailer hydraulic lift for adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand. This is a safety feature for protection in case of a hydraulic failure, and it also allows the trailer to be left supported on the lift for long periods of time without danger that the height will drop if pressure is lost in the hydraulic system. 
   These together with other objects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
       FIG. 1  is a side view of the present embodiment of the trailer hydraulic lift constructed in accordance with the principles of the present invention, installed on a trailer. 
       FIG. 2  is a close up side view of the trailer hydraulic lift of the present invention, in the area of the circle  2  in  FIG. 1 . 
       FIG. 3  is a perspective view of the trailer hydraulic lift of the present invention. 
   

   The same reference numerals refer to the same parts throughout the various figures. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, and particularly to  FIG. 2 , a present preferred embodiment of the trailer hydraulic lift of the present invention is shown and generally designated by the reference numeral  10 . 
   In  FIG. 1 , a new and improved trailer hydraulic lift  10  of the present invention for adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand is illustrated and will be described. More particularly, the trailer hydraulic lift  10  is shown attached to a trailer. The lift  10  would be attached toward the front of the trailer in the normal place for trailer landing gear. 
   Continuing to  FIG. 2 , where a close up view of the present embodiment of the invention is shown, the trailer hydraulic lift  10  has a pair of hydraulic cylinders  12 , each cylinder receiving a piston  14 . The cylinders  12  are connected at the tops thereof to a trailer, and at the bottoms to a foot  16 , which will rest on the ground as a normal trailer landing pad foot would rest. Between the cylinders is a jackstand  18 , said jackstand connected at the top thereof to the trailer. Next, the jackstand  18  has a telescoping member  20 , which is connected to the foot  16  between the two pistons  14 . The telescoping member  20  and the jackstand  18  are each provided with a set of matching holes  22  formed in the surfaces thereof. These holes provide a place to insert the locking pin  24 . There must be provided sufficient cylinder  12  and piston  14  lengths that the front end of the trailer can not only be leveled, but be lifted sufficiently to permit insertion of the working deck of a tractor under the trailer whereby to engage the trailer. 
   The cylinders  12  are supplied with hydraulic pressure by being connected to a hydraulic pressure line  34 , which is connected at the other end to the control box  26 . The control box  26  is provided with a an on/off switch, an up/down control switch, and a fine up/down control knob for precise control (not separately numbered). Also, the control box  26  contains control circuitry, valves, and connections needed to control the hydraulic pump (not shown in this FIGURE) and to control pressure in the hydraulic pressure line  34 . 
   Referring finally to  FIG. 3 , where a perspective view of another embodiment of the invention is shown not connected to a trailer, this embodiment is provided with two hydraulic lift units  32 , each of which comprise the elements shown in  FIG. 2 . These units are supplied by the hydraulic pressure lines  34 , which are controlled through the control box  26 , and supplied with pressure and fluid from the hydraulic pump and reservoir  28 . The pump and reservoir  28  is supplied with power from the tractor unit power system by a power line  30 . The pump and reservoir  28  must be of sufficient strength to provide lifting power to lift a fully loaded trailer. 
   In use, it can now be understood that the cylinders are the dollies that will raise or lower the trailer as desired and hold the trailer in place. The jackstand  18  can be engaged to hold weight in case of a rupture of a hydraulic line or fitting, and enable the trailer to be left for long periods without worry of leakage from a fitting. The user will use the hydraulic trailer lift  10  when they need to attach or detach a trailer from a tractor. The attachment is of course done by turning on the on/off switch, raising the lift  10  to a sufficient height that its lowest part clears the working deck of the tractor by operating the up/down control and up/down fine control, then backing the tractor underneath and lowering the trailer with the same controls. Detachment is exactly the reverse process. 
   While a preferred embodiment of the trailer hydraulic lift has been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. For example, any suitable material such as metal or composite may be used for the hydraulic lines described, and the control box could be made of any rugged material such as metal and could even be diamond plated for ruggedness. Also, the cylinder  12  and piston  14  will be made of metal as typically used in high load bearing hydraulic applications. And although adjusting the height of a trailer with a hydraulic lift and securing it with a telescoping jackstand have been described, it should be appreciated that the trailer hydraulic lift herein described is also suitable for many other lifting applications where a safety and load bearing feature is desirable. Furthermore, a wide variety of configurations may be used instead of the one described, either with one cylinder combined with a jackstand  18 , or with several lift units, each one comprising one or more cylinders and a jackstand. Or the invention could be hingedly attached to the trailer and lowered in place when needed, perhaps automatically with a lifting cylinder attached to the bottom of the trailer at one end and somewhere along the jackstand  18  at the other end. Finally changes could be made to achieve the same function as described. For example, the locking pin  24  can replaced with any of a variety of locking mechanisms, or the power line  30  can be replaced with a dedicated power system. 
   Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.