Method and apparatus for jackscrew with integral drive nut grease fitting

An improved device and method of lubrication for a tongue jack, 5th wheel jack, or other jack or other threaded positioning device. Ports are provided in the inner and outer tubes of the jack. The aligned ports provide access to a lubrication cavity in the jacknut. The lubrication cavity may include a grease fitting such as a zerk fitting. When the ports are in alignment, a grease gun can be inserted easily to the zerk fitting to apply grease to the interior structure of the nut as well as to the threads of the jackscrew. The lubricant may be introduced directly at a region of contact between a screw and the load bearing element. Applicant's test results show that this improved lubrication can increase the life cycle of the jack by more than 100%.

BACKGROUND

Field of Invention

The current invention relates to an apparatus and method for improving jack lubrication by providing a jack with external access to a grease fitting provided in a drive nut

Prior Art

Prior art jack designs typically require either partial disassembly of the jack in order to access parts for lubrication, or they attempt to provide grease fittings in proximity to a jack drive nut.

For example, U.S. Pat. No. 6,926,261 to Renshaw describes a trailer tongue jack includes a grease (or zerk) fitting for providing grease to internal parts The jack includes an outer tube and an inner telescoping tube. A threaded insert (or nut) is fixedly attached inside an upper end of the inner telescoping tube. A screw shaft threadedly cooperates with the insert to extend or retract the inner telescoping tube from a lower end of the outer tube. A crank or motor gear assembly is provided to turn the screw shaft either directly or through gears, and a thrust bearing carries a vertical load between the screw shaft and the outer tube.

SUMMARY OF INVENTION

The current invention provides improved devices and methods of lubrication of a tongue jack, 5th wheel jack, or other jack or other threaded positioning device. In one embodiment, the methods comprise positioning one or more grease fittings, such as a zerk fitting, within a jack nut, ball bearing nut, or other screw load bearing element so that a lubricant may be introduced directly at a region of contact between a screw and the load bearing element. Prior art grease fittings are typically provided at fixed external access points on a threaded positioning device. For example,FIG. 1is a prior art tongue jack with a lubrication fitting34provided in the outer tube of a jack screw.

In other embodiments, the methods comprise providing access to a lubrication port so that lubricants such as oil, dry graphite, or other lubricating agents may be introduced directly at a region of contact between a screw and the load bearing element.

The current invention extends the life cycle of tongue jacks, 5th wheel jacks, and other jack devices. One of the root causes for a tongue jack to fail is that the grease wears away from the jackscrew and nut resulting in too much friction for the motor to overcome. This increased friction can cause the jackscrew to jam in the jack drive nut or cause the motor to overheat and fail. Another cause for failure is that with repeated use, the grease used for lubrication will breakdown and no longer provide the lubrication necessary between the jackscrew and nut to allow the jackscrew to thread its way through the nut. This lubrication breakdown causes too much friction for the motor to overcome, and causes jackscrew freezing in the nut.

By applying grease directly to the interior threads of the nut through the zerk fitting, grease can be applied to both the interior threads of the nut and the jack screw threads. Applicant's test results show that this improved lubrication can increase the life cycle of the jack by more than 100%.

Ports are provided in the inner and outer tubes, and when the ports are in alignment, a grease gun can be inserted easily to the zerk fitting to apply grease to the interior structure of the nut as well as to the threads of the jackscrew.

The position of the port in the outer tube is preferably located in the area of the jackscrew that is used the most when lifting a trailer off the hitch ball or hitch pin as the jack is extending.

In one embodiment of the current invention, an electric jackscrew comprises a grease zerk provided in the jackscrew drive nut. The zerk fitting is accessed when a port in the jack's outer tube is aligned with a port in the jack's inner tube, thereby exposing a grease fitting which is provided in a recess in the jack nut. Grease introduced through this fitting is specifically applied to the inner nut and jack screw and directly lubricates the jackscrew at the region where it contacts the jack nut.

In another embodiment of the current invention, a manual jackscrew is provided with outer tube and inner tube access ports which provide access to a grease fitting which is provided in a recess in the jack nut.

In another embodiment of the current invention, a grease fitting is provided for a ball screw trailer jack so that grease may be introduced directly to the ball bearings.

DETAILED DESCRIPTION OF EMBODIMENT—JACKSCREW WITH GREASE FITTING IN JACK Drive Nut

The following example element list is provided for convenience in referencing the figures.

FIG. 2Ais a side view of a jackscrew assembly200comprising an outer tube assembly220and an inner tube assembly240. An outer tube access port232is provided in the outer tube assembly for applying a lubricant to the jacknut, such as by greasing a zerk fitting254.

FIG. 2Bis a cross section view of the upper portion of the jackscrew assembly200ofFIG. 2Ashowing a jackscrew260.

FIG. 2Cis a detailed cross section view of the outer tube230, an inner tube242, a jack drive nut250with a grease fitting254, such as a zerk fitting, provided in a lubrication cavity252. In this embodiment, the nut grease fitting recess252is fixed relative to an inner tube access port244. When the inner tube access port244is aligned with the outer tube assembly access port232, the orientation permits grease or other lubricant to be applied directly to the jacknut. In this example, the lubricant is grease which is applied through the grease fitting254at the region of maximum stress and wear in the jackscrew assembly.

FIG. 3Ais a side view of the inner tube assembly240of the jackscrew assembly200ofFIG. 2A.FIG. 3Ashows the inner tube242, inner tube access port244, and the top251of the jack drive nut250.

FIG. 3Bis a cross section view of the upper portion of the inner tube242and jack nut250.

FIG. 3Cis a detailed view of the top of the inner tube242and the jack nut250showing the inner tube access port244and the grease fitting254. In other examples, the grease fitting254may be omitted, and the drive nut includes a lubrication cavity252where oil, dry graphite, or other lubricant may be introduced to lubricate the jack nut. This lubrication cavity is in communication with the jackscrew, such as with an orifice or lubrication channel that permits the lubricant to reach the jackscrew.

FIG. 4Ais a front view of an electric tongue jack101with a motor gear assembly400and the jackscrew assembly200ofFIG. 2A.

FIG. 4Bis a side view of the electric tongue jack ofFIG. 2A.

Example—Electric Tongue Jack with Grease Fitting in Jack Drive Nut

FIG. 5is a side perspective view of an electric tongue jack102for a trailer comprising a motor gear assembly400and a lower stem assembly300.

FIG. 6is an exploded view of the motor gear assembly400of the electric tongue jack ofFIG. 5.

FIG. 7is an exploded view of the lower stem assembly300of the electric tongue jack ofFIG. 5.

In this example, the jackscrew is lubricated by extending the jack until the zerk grease fitting is aligned with the access port in the outer tube. Using a standard grease gun, one or more pumps of grease are applied through the grease fitting.

Example—Manual Tongue Jack with Grease Fitting in Jack Drive Nut

In this example, the electric drive of the previous example is replaced with a manual crank. Lubrication is provided as described above by aligning the outside tube access port with the grease fitting.

Example—5th Wheel Jack

FIG. 8Ais an exploded view of a 5th wheel jackscrew assembly201for a 5th wheel jack. The outer tube assembly221comprises an outer tube231with an outer tube access port233. The inner tube assembly241comprises inner tube245with an inner tube access port248which provides access to grease fitting259positioned in lubrication cavity256. Other elements in the 5th wheel jackscrew assembly include washer510, ball bearings520, shaft pin522, support540, clip542, and pin544.

FIG. 8Bis a cross sectional view of the inner tube245, jackscrew261, jack drive nut255, and inner tube access port248for the 5th wheel jackscrew assembly ofFIG. 8A.

In this example, a grease fitting259is provided in lubrication cavity256. When the inner tube access port248is aligned with the outer tube access port233, the grease fitting is accessible.

Method of Lubrication

In one example, a jack is lubricated before leaving the factory. Under normal conditions, lubrication will be needed periodically, such as annually.

A lubricant can be applied to the jackscrew by extending the inner tube by means of operating the motor or manually rotating crank until the port in the outer tube is aligned with the port in the inner tube. This alignment exposes the grease fitting or lubrication cavity.

Once the ports are in alignment, grease or other lubricant can be applied through a grease gun or other lubricant application device directly to the inner threads of the threaded nut and the jackscrew threads. One means of lubricant application can be accomplished by use of a standard grease gun through a grease fitting or zerk in the threaded nut by one or more pumps of the grease gun.

It is to be understood that the specific embodiments and examples described above are by way of illustration, and not limitation. Various modifications may be made by one of ordinary skill, and the scope of the invention is as defined in the appended claims.