Patent Application
20080217107
The present invention relates to aircraft landing systems and more particularly to an apparatus for providing measured or continuous greasing of pin joints to reduce or eliminate scheduled maintenance.
Every retractable landing gear is, by necessity, composed of links that fold and rotate during stowage. The technology of these rotating joints has not progressed significantly over the years. They are essentially static joints which must take large loads during landing and ground manoeuvring operations, then rotate in an essentially unloaded state during retraction or extension once the aircraft is off the ground.
The standard solution for these joints is a steel pin (which may, for example, be coated with chrome or high velocity oxygen fuel (HVOF) applied WCCoCr) running in a bronze (or Aluminum-bronze or Beryllium-Bronze) bushing. These materials are merely examples of the type of interface materials that may be used. The bushing is pressed into a hole in the surrounding structure. The joint is greased manually and periodically to avoid excessive metal on metal contact. In addition to the lubrication function served by the grease, the greasing action helps displace moisture and dirt that may collect in the pin-bushing interface. Thus, regular greasing helps minimize corrosion and wear.
The pin joints typically used in landing gear applications employ pins that are hollow in order to optimize the strength while minimizing the weight (weight being a significant factor in all aircraft). The hollow pin is typically filled with a plastic ‘grease insert’ that has internal channels that act as grease distribution tubes, delivering grease from a grease fitting on the external edge of the insert, to holes in the interior of the grease insert. The grease exits from these points, and travels through holes in the pin to the pin/bushing interface.
One reason why these joints have not advanced significantly over the years is that they are a good solution to the problem. Although various material improvements may be made and tried, at its core, the design solution is solid. The primary drawback is that the joint must be thoroughly and regularly greased to ensure continued proper behaviour of the joint.
In today's operational environment, a regular maintenance requirement, i.e. greasing, is seen as a drawback because the industry demand is for maintenance free joints. Eliminating the maintenance requirement by eliminating greasing only results in increased corrosion and wear in components which jeopardizes safety and increases overhaul costs. Changing the material specifications to ‘self lubricating’ materials such as oil impregnated bushings or Teflon materials and the like increases the joint cost, but also has not shown sufficient performance in operation, both in strength and lubrication/corrosion protection.
The present invention provides a solution that not only works for new design components, but also may be retrofitted to existing joints to overcome some of the problems discussed above.
In one aspect, the present invention provides a lubricating pin insert for use in a hollow pin, the pin having at least one aperture within it. The lubricating pin insert includes a body having a chamber that is operable to receive a quantity of a lubricating agent, the body also includes at least one passageway in fluid communication with the chamber and configured to align with the at least one aperture of the pin when the insert is received in the pin. The pin insert also includes a dispensing means connected to the chamber that is operable to dispense a quantity of lubricating agent from the chamber through the at least one passageway.
In one embodiment the pin insert includes, as the dispensing means, a pressure producing means that is connected to the chamber and further a floating piston that is received within the chamber between the quantity of lubricating agent and the pressure producing means. The pin insert may also include at least one lubrication inlet connected to the chamber to allow for passage of the lubricating agent into the chamber.
In another aspect the present invention provides a pin assembly for use in a pin joint on an aircraft landing gear, comprising a pin having a hollow body and at least one aperture therein and a pin insert as described herein.
In an alternative aspect the present invention provides a pin for use in a pin joint on an aircraft landing gear, comprising a pin having a hollow body operable to receive a quantity of a lubricating agent and comprising at least one passageway that is operable to allow passage of the lubricating agent from the body out of the pin. The pin further includes dispensing means connected to the body and operable to dispense a quantity of lubricating agent therefrom. The pin may also include at least one lubrication inlet to allow for refilling of the pin with the lubricating agent.
The present invention will be described further below with reference to the following figures:
The present invention provides a pin assembly that is self lubricating. The present invention also provides an insert for a pin that may be used in a pin joint that contains an automatic lubrication dispensing mechanism. The pin insert stores in its hollow interior a quantity of grease that is dispensed into the joint over time. Maintenance of the joint is eliminated completely, or reduced to a grease reservoir refill which is required much less frequently than the current maintenance action. An additional benefit is that the joint stays properly greased at all times ensuring low corrosion risk and low wear to the mating surfaces.
The invention is composed of four principle components: the body of the grease insert, a quantity of stored grease, an actuation mechanism to displace the grease through the lubrication holes, and a control mechanism to determine when the actuation mechanism should activate.
The present invention will now be described in detail with reference to the accompanying figures. The present invention will be described with reference to one embodiment in which the pin assembly comprises a pin insert. However, it will be understood that the present invention also provides a pin assembly in which the components that are described herein as being a pin insert are integral with the pin assembly, i.e. are formed within the pin assembly and not as a separate insert component.
Turning to
The pin 14 is a hollow pin typically used in pin joints in aircraft landing gear. A person skilled in the art will know the types of pins that are used and the preferred size and configuration for each application. An example of the dimensions of a pin that may be used is illustrated in
As illustrated in
As can be seen more clearly in
The pin insert 12 also includes a dispensing means 20 to dispense the grease out of the chamber 18 and control means 22 for controlling the dispensing means 20. These two components may be separate or may form a unitary component, seen in
The insert body 16 includes at least one insert aperture 24 that extends into the chamber 18 to allow for the passage of grease from the chamber 18 through the insert body 16 and out of the insert 12 and through at least one corresponding pin aperture 26, into the pin joint. It will be understood that the term apertures refers to either a hole in the wall/exterior surface of the insert that reaches the inner chamber or a passageway that passes through the exterior wall of the insert into the chamber 18. The terms aperture and passageway may be used interchangeably when describing either the pin insert aperture or the pin aperture.
As can be seen in
The pin insert 12 may be a plastic tube that is sized to be received within the pin 14. As an example, the pin insert 12 may be formed from a high strength thermoplastic material, for example Delrin™. However, it will be understood that the grease insert 12 is not limited to such material and may be formed from any suitable material, for example, such as metal or any composite material. In the illustrated embodiment (e.g. shown in
The stored lubricating agent/grease 32 may be of any type of lubricating agent that is suitable for the lubrication of the pin and of an appropriate viscosity to allow it to flow under effort from the actuation mechanism through the lubrication holes into the pin joint.
Located within, or connected to, the pin insert 12 is dispensing means 20. The dispensing means 20 is operable to provide the motive effort to move a quantity of lubricating agent 32 from the chamber 18 in the pin insert 12 through the insert aperture(s) 24. The dispensing means 20 may be, for example, a piston that is moved within the chamber 18 by a battery powered gas generator; or a piston that is moved within the chamber by a battery powered electrical actuator; or a piston that is moved within the chamber 18 by a mechanically actuated rotary to linear gear mechanism. It will be understood that these examples are not meant to be limiting. It will be understood that the piston and the means to move the piston, as described above, may be a unitary component or may be separate components that are connected.
Connected to the dispensing means 20 is control means 22, which may vary depending on the dispensing means 20. For example, in the case of the battery powered systems, a tilt switch and timer relay or tilt sensor and timer electronics may be configured to provide a timed amount of actuation following a gear retraction event. In this manner, a small amount of grease is dispensed each flight, and during non-loaded operation of the landing gear. This allows the grease to move freely. In the case of the mechanical actuation system, a linkage connects the rotating and non-rotating portions of the landing gear that the pin is connecting. The linkage drives a ratchet mechanism which turns a lead screw. The lead screw is attached to a piston head in such a manner that rotation of the landing gear component drives the piston head in one direction only—to compress and dispense the grease. The ratchet mechanism is selected such that flexure of the landing gear components during ground operations do not provide sufficient rotation to provide indexing of the ratchet and drive of the lead screw.
Different embodiments of the dispensing means and control means will now be discussed in reference to
Turning to
A quantity of lubricating agent/grease 32 is stored in the chamber 18 between the end of the insert 12 and a floating piston 20. The lubricating agent 32 is forced to exit from the insert aperture(s) 24 by the pressure of a gas 34 acting on the floating piston 20 and hence on the quantity of grease 32. The gas 34 is produced by a gas generation module 22 containing an electrochemical gas generator 36 and switch and timing circuit 38 and a battery 40. The gas generator module 22 is fixably attached to the end of the pin insert 12 using a pin end cap 42 which is threaded or otherwise allows a fixable attachment to the pin insert 12. The end cap 42 also contains an externally actuated check valve 44 which allows the pressurized gas 34 to be vented to atmosphere during the manual addition of new grease in to the chamber 18 through a lubrication fitting 46 located at the end of the chamber 18.
In this embodiment the battery 40 is preferably of a lithium thionyl chloride chemistry allowing long service life and operation at temperatures as low as −55° C. However, other batteries may be used that allow for long service life and are operable within the temperature ranges to which the component will be exposed. The switch and timing circuit 38 may be of electronic or electromechanical means containing a tilt switch, timing circuit, and control switch such that upon movement of the pin insert from one orientation (landing gear extended) to another orientation (landing gear retracted), the tilt switch will close, enabling the timing circuit. The timing circuit will be energized by the battery 40 through the tilt switch and will turn on the control switch for a suitable period of time to activate the electrochemical gas generator 36 and create sufficient gas volume to displace the desired quantity of grease. Following this time the timing circuit will open the control switch, curtailing gas production.
In another embodiment, mechanical force generated by a lead screw (ball screw) is used to displace the grease. The gas generator is not used. In this embodiment, illustrated in
In this embodiment the battery 40 is preferably of a lithium thionyl chloride chemistry allowing long service life and operation at temperatures as low as −55° C. The switch and timing circuit 38 may be of electronic or electromechanical means containing a tilt switch, timing circuit, and control switch such that upon movement of the pin insert from one orientation (landing gear extended) to another orientation (landing gear retracted), the tilt switch will close, enabling the timing circuit. The timing circuit will be energized by the battery 40 through the tilt switch and will turn on the control switch for a suitable period of time to activate the electric motor 56 for a sufficient time to displace the desired quantity of grease. Following this time the timing circuit will open the control switch, curtailing motor operation.
In a further embodiment, illustrated in
A mechanism represented in this instance by a simple lever arm 66 may be connected to the drive shaft 64 in such a manner that relative movement between the pin insert 12 and the surrounding structure during retraction and extension of the landing gear will drive the drive shaft 64. In this manner, the system shall be configured such that during retraction of the landing gear, the drive shaft 64 will rotate, engaging the ratchet 62 and turning the gear reduction unit 58. The output of the gear reduction unit 58 will be tailored to turn the lead screw 48 a sufficient amount to dispense the required quantity of grease 32. During the opposite motion of the landing gear, the drive shaft 64 will freely turn without dispensing grease 32. The ratchet mechanism 62 shall be configured such that relative movement of the pin insert and the surrounding structure during ground manoeuvring of the aircraft will not sufficiently advance the ratchet and pawl mechanism to drive the gear reduction unit 58. This will ensure that grease is only dispensed during unloaded operation of the landing gear and will keep undo loads from the grease dispensing mechanism.
To facilitate reloading of the grease 32, a lubrication fitting 46 is attached into the body of the pin insert 12 and the lead screw shaft 48 is extended through the end of the pin insert 12 and made to form a shape drivable by standard tools, such as a hex driver. The ratchet mechanism 62 shall accept the lead screw 48 being backdriven without rotating the drive shaft 64. Refill of the grease 32 is accomplished by driving the external portion of the lead screw 48 and filling with a grease gun through the lubrication fitting 46.
While the illustrated embodiments show the pin insert 12 having two insert apertures 24 it will be understood that the pin insert 12 may include one or more than two apertures depending on the amount of grease required to lubricate the pin joint. Similarly the size of the apertures 24 may also vary provided that they allow sufficient quantity of lubricating agent to pass through to lubricate the pin joint. The position of the apertures 24 may also vary provided that they will align with pin apertures 26 and are positioned within the part of the chamber that the lubricating agent is in so that the action of the dispensing means forces the lubricating agent through the apertures.
While the present invention has been described relative to its use in a pin joint on an aircraft landing gear, it will be understood that the pin assembly and pin insert are not limited to this application and may be used in other applications that require the use of a pin assembly with the properties of that described herein.
Further it will be understood that any dimensions shown in the accompanying drawings are merely examples of the size of pin and pin insert that may be used and are not meant to be limiting in any way.
While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments. Further, all of the claims are hereby incorporated by reference into the description of the preferred embodiments.
Any publications, patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.
The present application claims the benefit under 35 U.S.C. §119(e) of provisional patent application Ser. No. 60/899,006 filed Feb. 2, 2007, the contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60899006 | Feb 2007 | US |
