Metal working – Method of mechanical manufacture – Disassembling
Reexamination Certificate
1999-06-11
2001-11-20
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Disassembling
C029S252000, C254S0930VA, C254S0930VA, C254S13300A
Reexamination Certificate
active
06317956
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates generally to tools and more particularly to a method and an apparatus for removing landing gear struts from aircrafts having retractable landing gear.
2. Description of the Related Art
Retractable aircraft landing gear struts periodically need to be removed for maintenance. One reason is that retractable landing gear systems typically include hydraulic assemblies that, over time, require servicing to maintain proper fluid and pressure levels.
Maintenance of the hydraulic landing gear assemblies is required only once every few years. Other than servicing the strut to maintain the hydraulic retractable landing gear system, the struts are not usually removed. Accordingly, some struts are not removed from their aircraft for many years. While the aircraft strut is left untouched for many years, most aircraft are occasionally and sometimes frequently exposed to damp or wet environmental conditions. Some aircraft are even usually left out in the weather most of the time. Accordingly, without proper maintenance, some aircraft parts collect moisture that often causes corrosion and its undesirable effects.
The problem is especially acute for some small and older aircraft having a specific type of retractable landing gear strut. For these aircraft, corrosion often causes the landing gear strut to become bonded or seized to a pivoting landing gear support. The pivoting landing gear support is the device in a landing gear system that receives and holds the landing gear strut into place. By design, only removable retaining bolts, pins or springs (collectively “pins”) are used to hold a landing gear strut in place. With corrosion that commonly develops between the landing gear strut and the pivoting landing gear support, however, the retaining pins may not be solely responsible for holding the strut in place. Thus, the struts are very difficult to remove even after retaining bolts or pins are removed.
Whenever a landing gear strut becomes seized by corrosion and the strut must be removed for servicing, a challenge is presented for economically removing the strut without damaging it. Occasionally, extreme amounts of force are required to grip the strut and to break it free from the pivoting landing gear support. Sometimes, aircraft mechanics apply significant force to the strut for prolonged periods to try to break it free from the corrosive grip of the landing gear support.
Even if the mechanic is successful in removing the landing gear strut, a mechanic frequently spends as much as eight hours trying to remove the strut without damaging it or the aircraft. Moreover, given that aircraft repair labor rates can approach $100 per hour at the time of this application, the labor cost for merely removing a strut can exceed $800.
Damaging the strut or the airplane or its components is common for experienced aircraft repair mechanics while trying to remove a strut seized by corrosion. If the strut or aircraft is damaged as often happens, however, the cost of trying to remove the strut can exceed thousands of dollars in parts and labor. Consequentially, properly servicing an aircraft's landing gear assembly is unduly expensive.
Thus, there exists a need in the art for a tool that can quickly remove an aircraft strut, and in particular, a retractable aircraft landing gear strut for certain models having a pivoting landing gear support and mating strut that are subject to the aforementioned problems, without damaging either the strut or the airplane and without requiring significant levels of effort. In general, there is need for a tool and a method to economically remove the struts to facilitate and encourage proper maintenance of the aircraft landing gear systems.
SUMMARY OF THE INVENTION
The problems outlined above are in large part solved by the present invention in which a hydraulic aircraft strut removal tool is formed for integrally and matingly attaching to an aircraft strut of a specified aircraft and for urging the strut in an outward direction relative to the aircraft pivoting landing gear support that holds the strut in place. Moreover, the hydraulic tool is formed to distribute necessary force to free the strut from the corrosive grip of the landing gear support while, at the same time, applying significant force to free the strut.
More specifically, a first end of the tool system matingly and securely attaches to a distal end of the strut while a second end of the tool system loosely and slidingly attaches to a proximate end of the strut. The first end of the tool includes a stiffening anchor that securely grips and distributes force supplied by the hydraulic tool along a curved portion of the landing gear strut. The stiffening anchor, by distributing the pressure applied by the hydraulic tool, prevents excessive force from being applied to anyone point on the strut thereby avoiding damage to the strut.
The second end of the tool includes a press collar that not only slidingly attaches to and contains the strut, but also that engages a rigid aircraft portion to press against it to remove the strut. By way of example, the press collar presses against a pivoting landing gear support that is for receiving and holding the strut into place.
Between the stiffening anchor and the press collar is an urging mechanism to urge the stiffening anchor away from the press collar. Accordingly, the press collar slidingly applies pressure against the pivoting landing gear support whenever the urging mechanism provides urging pressure.
In the described embodiment of the invention, the urging mechanism comprises a hydraulic ram that receives hydraulic liquid from a hydraulic liquid source, by way of example, from a manual hydraulic pump. Upon receipt of the hydraulic liquid from the hydraulic liquid source, the urging mechanism expands creating an outward urging pressure of up to 20,000 pounds.
A method of the present invention includes fixedly attaching a first end of a hydraulic tool to a distal and curved end of a landing gear strut. Additionally, a second end of the hydraulic tool is slidingly attached against a proximate end of the landing gear strut. After that, hydraulic fluid is supplied to a hydraulic ram portion of the hydraulic tool to cause it to exert an outward pressure on the distal end of the landing gear strut relative to the pivoting landing gear support.
The method further includes continuing to supply hydraulic liquid from the hydraulic liquid source to continue increasing outward pressure until the strut is urged free or until twenty thousand pounds of outward pressure is applied to the strut. If the strut still does not come free, the strut is manipulated as known by those skilled in the art to cause the strut to break free.
While the described embodiment includes using a hydraulic ram that can provide up to twenty thousand pounds of pressure, the invention also includes using hydraulic rams that can provide greater or lesser amounts of urging pressure. For example, a thirty thousand pound (15 ton) hydraulic ram may be used instead of a twenty thousand pound (10 ton) hydraulic ram.
These and other aspects of the present invention will become apparent with further reference to the drawings and specification that follow.
REFERENCES:
patent: 2719695 (1955-10-01), McKee
patent: 3638887 (1972-02-01), Thurston
patent: 3710427 (1973-01-01), Doty
patent: 3797094 (1974-03-01), Combs et al.
patent: 3815202 (1974-06-01), Squires
patent: 5129136 (1992-07-01), Richardson
Compton Eric
Hughes S. Thomas
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