WO2000066937A1

WO2000066937A1 - Locking mechanism having improved retention characteristics

Info

Publication number: WO2000066937A1
Application number: PCT/US2000/011950
Authority: WO
Inventors: Harry J. Kuhlen; Thomas E. Tauber
Original assignee: Vibro-Meter S.A.
Priority date: 1999-05-03
Filing date: 2000-05-03
Publication date: 2000-11-09
Also published as: AU4981000A

Abstract

A chip detector for use in a lubrication system comprises a probe (1) and a lower housing (3). The probe (1) includes a threaded surface (7), a collar (22), and a chip-detection element (16). The collar (22) is slidably coupled to a remainder of the probe. The lower housing (3) comprises a threaded surface (6). The collar slidably engages the lower housing when the threaded surface of the probe fully engages the threaded surface of the lower housing. The engagement of the collar and the lower housing prevents the threaded surfaces from disengaging, thereby securing the probe to the lower housing.

Description

LOCKING MECHANISM HAVING IMPROVED RETENTION

CHARACTERISTICS

Field of the Invention

The present invention relates generally to chip detectors, and more particularly to an improved quick-disconnect locking mechanism that is particularly well suited (although not limited) for use with chip-detectors.

Background of the Invention

Gas-turbine engines, helicopter transmissions, aircraft auxiliary drive systems, gear boxes, and many other types of machines commonly incorporate wear- particle sensors such as chip detectors. Wear-particle sensors are utilized to detect incipient failures of the bearings and gears within such machinery. In particular, wear- particle sensors detect the presence of wear debris that is typically produced by a bearing or a gear experiencing a mechanical failure. Wear debris is typically generated well before the point at which a failing gear or bearing ceases to function. Lubricating oil usually carries wear-debris from the failing gear or bearing toward a sump or a filter within the machine. . The wear debris can be intercepted and collected by a chip detector or other type of wear-particle sensor as the debris is transported in this manner.

Two types of chip detectors are currently used on a widespread basis. One common type of chip detector is the magnetic plug, or chip collector. Chip collectors comprise a magnetic probe mounted inside a self-closing valve. Chip collectors are usually inspected at regular intervals, e.g., every 50 to 200 operating hours. The inspection interval is typically reduced when wear-debris particles are detected, thereby allowing the progressing component failure to be closely monitored.

Another type of commonly-used chip detector is the electric chip detector. Electric chip detectors collect wear debris. In addition, electric chip detectors provide an external, electrically-generated indication of the presence of such debris. Although electric chip detectors do not require regular, routine inspections, such detectors must be removed and inspected each time an external signal (a so-called "chip light") has been activated. Many gas turbine engines and helicopter transmissions have separate bearing compartments, auxiliary gear boxes, or gear modules. These systems often incorporate several chip detectors to allow the location of an impending bearing or gear failure to be identified. In particular, the use of multiple chip detectors allows wear debris to be traced to a specific component module, thereby allowing the affected module to be removed and replaced without replacing the entire engine or transmission. The regular inspection of multiple chip detectors can be a time-consuming maintenance requirement if the chip detectors are not specifically designed for quick removal and reinstallation.

Chip-detector probes are frequently mounted by means of quick-disconnect, bayonet-type locking mechanisms. These mechanisms permit the chip-detector probe to be removed and replaced relatively quickly. Bayonet locking mechanisms typically comprise two or three locking pins that engage an equal number of helical grooves. The chip-detector probe is secured by simultaneously pushing and twisting the probe against a spring force while the pins engage the helical grooves. The spring eventually locks the probe into place by pushing the pins into detents located at the ends of the helical grooves Bayonet locking mechanisms have a number of serious shortcomings that have caused in-flight engine shutdowns and other costly and dangerous service disruptions in aircraft. Specifically, bayonet locking mechanisms are subject to vibration-induced wear. Such wear can cause a failure of the bayonet pins and the helical grooves, leading to ejection of the probe, loss of lubricating oil, and a forced shut down the machine in which the probe is utilized. Bayonet locking mechanisms are also subject to improper installation. Specifically, a mechanic installing a chip-detector probe equipped with a bayonet locking mechanism may fail to impart the twist-and-push motion needed to lock the probe in place. Such improper installation can result in an inadvertent ejection of the probe and an ensuing loss of engine oil.

Furthermore, bayonet locking mechanisms do not provide a readily- discernable visual indication that the mechanism has been secured in its locked position. Some existing bayonet locking mechanism include various visual identifiers that are intended to signal whether the mechanism is properly secured. In practice, however, these identifiers have proven inadequate.

The above-noted shortcomings of bayonet-type locking mechanisms often cause designers of jet engines, helicopter transmissions, and other critical machinery to specify the use of thread-in chip-detector probes. Thread-in chip-detector probes are tightened to a specific installation torque, and are subsequently secured against inadvertent loosening by means of lock wiring. This process locks the probe in position, and provides an unambiguous visual indication that the probe is secured. Lock wiring, however, must be removed and reinstalled each time the probe is inspected, thereby increasing the time needed to inspect the probe.

The above discussion highlights the currently-existing need for a secure and reliable quick-disconnect locking mechanism for elements that are adapted for installation in and removal from another structure or element. In particular, a need currently exists for a quick-disconnect locking mechanism that is subject to minimal vibration-induced wear, is difficult to install in an unsecured manner, and provides an unambiguous visual indication of whether the mechanism is securely locked.

Summary of the Invention

An object of the present invention is to provide a secure and reliable quick-disconnect locking mechanism for elements that are adapted for installation in and removal from another structure or element. In accordance with this object, a presently- preferred embodiment of the invention comprises a chip detector for use in a lubrication system. The chip detector includes a probe and a lower housing. The probe comprises a threaded surface, a collar, and a chip-detection element. The collar is slidably coupled to a remainder of the probe.

The lower housing comprises a threaded surface. The collar slidably engages the lower housing when the threaded surface of the probe fully engages the threaded surface of the lower housing. The engagement of the collar and the lower housing prevents the threaded surface of the probe and the threaded surface of the lower housing from disengaging, whereby the probe is secured to the lower housing. In one particular preferred embodiment, the collar cannot slidably engage the lower housing when the threaded surface of the probe and the threaded surface of the lower housing are not fully engaged.

Further in accordance with the above noted object, another presently- preferred embodiment of the invention comprises a system for locking a removable element in place. The system includes a housing and the removable element. The housing comprises a first surface and a second surface. The removable element comprises a first surface and a second surface. The second surface of the housing engages the second surface of the removable element when the first surface of the housing fully engages the first surface of the removable element. The engagement of the second surface of the housing and the second surface of the removable element prevents the first surface of the housing and the first surface of the removable element from disengaging. In one particular preferred embodiment, the second surface of the housing cannot engage the second surface of the removable element when the first surface of the housing and the first surface of the removable element are not fully engaged.

Another object of the present invention is to provide a method for securely and reliably installing a chip detector and locking the chip detector in place. In accordance with this object, a presently-preferred method for installing a chip detector in a lubrication system of a machine and locking the chip detector in place comprises the step of threadably engaging a first section of the chip detector and a first section of a housing on the machine. The presently-preferred method also includes the step of slidably engaging a second section of the housing and a collar on the chip detector when the first section of the chip detector and the first section of the housing are fully engaged. The engagement of the collar and the second section of the housing prevents disengagement of the first section of the chip detector and the first section of the housing.

Brief Description of the Drawings

Figure 1 is an perspective view of a chip detector that incorporates the present invention; Figure 2 is a cross-sectional view of the chip detector of Figure 1 taken along the line 2-2, with the chip detector installed in a host structure, and with a collar of the chip detector fully engaging a lower housing of the detector;

Figure 3 is a cross-sectional view of the chip detector of Figure 1 taken along the line 3-3 of Figure 2, with a collar of the chip detector fully engaging a lower housing of the detector;

Figure 4 is a cross-sectional view of the chip detector of Figure 1 taken along the line 2-2, with a collar of the chip detector about to engage a lower housing of the detector;

Figure 5 is a cross-sectional view of the chip detector of Figure 1 taken along the line 2-2, with a collar and a probe of the chip detector removed from a lower housing of the detector; and

Figure 6 is an perspective view of the chip detector of Figure 1, with an upper and a lower housing of the detector installed in a host structure, and with a collar and a probe of the detector removed from a lower housing of the detector.

Detailed Description of Preferred Embodiments

The present invention provides a locking mechanism having improved retention features. A preferred embodiment of the invention is described in connection with a magnetic chip detector installed in a lubrication system for a gas-turbine engine. This embodiment is presented for exemplary purposes only. Accordingly, the invention should not be limited to the particular embodiment shown, as the invention can be applied to other types of elements adapted for installation in and removal from another structure or element.

A preferred embodiment of the detector comprises a probe 1, a poppet housing 2, and a lower housing 3. Poppet housing 2 and lower housing 3 are mounted in a structure 4 surrounding a lubrication passage 5 in an engine, transmission, or other machine in which a lubricating fluid is circulated.

Lower housing 3 comprises a means for removably engaging probe 1. Preferably, the engagement means comprises female threads 6 disposed within housing 3. Female threads 6 engage a corresponding set of male threads 7 disposed on the outer surface of probe 1. Threads 6 and 7 are best shown in Figure 5. Threads 6 and 7 are preferably triple-lead threads with a square profile, similar to an ACME screw thread. This profile allows probe 1 to fully engage housing 3 with a relatively small twisting motion of less than 270 degrees. Housing 3 further comprises a lower section 8 and an upper section 9.

Lower section 8 has a non-circular cross-section. Preferably, the cross-section is hexagonally shaped, with the outer surface of section 8 comprising hexagonal flats 10. This configuration is best illustrated in Figure 6.

Upper section 9 of housing 3 has a circular cross-section. Section 9 mates with structure 4 of the host machine, i.e., the machine in which the chip detector is utilized. In the exemplary embodiment, the host machine is a gas turbine engine for use in a fixed or rotary- wing aircraft. Upper section 9 can be mated with structure 4 by way of an interference fit between an external surface of section 9 and machine structure 4. Alternatively, upper section 9 and machine structure 4 can be mated through the use of threads disposed on each component, as shown in the figures. An O-ring seal 11 is disposed on the outer surface of upper section 9 to prevent oil leakage between section 9 and machine structure 4. When housing 3 is installed, lower section 8 is externally disposed on an outer surface of the host machine.

Poppet housing 2 comprises a circular cross-section. Poppet housing 2 is mounted on an opposing side of lubrication passage 5 from lower housing 3. A poppet 12 is slidably disposed within housing 2, as shown in Figures 2, 4, and 5. Poppet 12 is biased toward lower housing 3 by a spring 13. Poppet 12 comprises an angled surface 14. When probe 1 is not installed in lower housing 3, spring 13 forces poppet 12 downward, until surface 14 engages a similarly-angled seating surface 15 on housing 3. (Throughout this specification, terms that make a directional reference, e.g., "downward," "uppermost," "vertical," etc., are used in reference to the component orientations depicted in Figure 2.) This configuration is shown in Figure 6. The engagement of surfaces 14 and 15 block the flow of lubricant between housings 2 and 3, thereby inhibiting the leakage of lubricant from the host machine when probe 1 is removed.

The uppermost portion of probe 1 comprises a cylindrically-shaped magnet 16. As probe 1 is installed in lower housing 3, magnet 16 impinges against a projection 17 disposed on the lower surface of poppet 12. Magnet 16 forces poppet 12 upward within housing 2, until poppet 12 reaches the position shown in Figure 2. At this point lubricant passage 5 is open, thereby allowing lubricant to flow between housings 2 and 3, and around magnet 16. Magnet 16 attracts wear-generated debris from the lubricant stream, and retains the debris for visual inspection when probe 1 is removed. Although the chip- detection function is performed by a magnet in this particular embodiment, the invention can also be used with electronic chip detectors (electronic chip detectors automatically detect the presence of debris and generate an electrical signal that so notifies the user of the host machine).

Probe 1 comprises a cylindrical section 18 disposed between threads 7 and magnet 16, as best shown in Figure 5. Section 18 slidably engages an inner surface of lower housing 3 when probe 1 is installed in housing 3. An O-ring seal 19 is disposed on the outer surface of probe section 18 to prevent leakage of lubricant past probe 1. An additional O-ring seal 20 is disposed on the lower end of section 18. Seal 20 furnishes additional protection against leakage, and provides a "soft" stop when probe 1 reaches the end of its travel within housing 3.

Probe 1 further comprises a shank 21 and a collar 22. Shank 21 is disposed below threads 7, as illustrated in Figures 2, 4, and 5. Collar 22 is slidably coupled to shank 21 in a manner that allows the collar to move axially (vertically) but not rotationally in relation to shank 21. Shank 21 preferably comprises a hexagonal cross-section. Any square, triangular, or other non-circular cross-section which couples shank 21 and collar 22 from a rotational standpoint may also be used. Because of this configuration, any rotational movement of collar 22 will be imparted to threads 7 via shank 21. A plate 23 is fixedly attached to the lower portion of shank 21. A spring 24 is disposed between plate 23 and collar 22. Spring 24 biases collar 22 in the position shown in Figures 1, 2, 5, and 6.

A lower section 25 of collar 22 has a circular cross-section. Preferably, the outer surface of section 25 is knurled to facilitate rotation by hand. A flange 26 is disposed along the lower portion of collar 22 Collar 22 further comprises one or more lobes 27 disposed along the upper portion of the collar. Preferably, collar 22 comprises three lobes. Each lobe 27 has a substantially flat inner surface 28, as best shown in Figure 6 As explained below, when probe 1 and lower housing 3 are fully engaged, lobes 27 engage lower-housing section 8 in the manner best shown in Figures 1 and 3. When probe 1 is not installed in housing 3, the uppermost portion of threads 7 is positioned higher than the upper surfaces of lobes 27, as best illustrated in Figure 5. Hence, when probe 1 is installed in lower housing 3, probe threads 7 initially engage housing threads 6 with no interference between lobes 27 and hexagonal flats 10 Furthermore, magnet 16 and section 18 of probe 1 are sized in such a manner that magnet 16 will not contact poppet 12 until threads 6 and 7 are partially engaged Hence, no axial force is required to begin the engagement of probe 1 and lower housing 3

As probe threads 7 continue to engage housing threads 6, collar 22 (and lobes 27) translate toward lower housing 3, until the upper surfaces of lobes 27 contact the lower surfaces of hexagonal flats 10 At this point, the individual installing probe 1 must apply a small amount of axial (vertical) force to collar 22 in a direction opposite the direction of engagement, i.e., away from housing 3 This force is necessary to move lobes 27 off of section 8 against the bias of spring 24, as shown in Figure 4 Because threads 6 and 7 are engaged at this point, further rotation of collar 22 will continue to drive probe 1 into lower housing 3, despite the application of force on collar 22 in the opposing direction.

Threads 6 and 7 are indexed in such a manner that inner surfaces 28 of lobes 27 align with hexagonal flats 10 when threads 6 and 7 have fully engaged This alignment is best shown in Figure 3 Alignment of the noted surfaces, combined with the bias of spring 24, causes lobes 27 to slidably engage hexagonal flats 10 Conversely, surfaces 28 will not align with hexagonal flats 10 when threads 6 and 7 and have not fully engaged, and lobes 27 will not slidably engage flats 10 Hence, the invention provides a - in conspicuous indication that probe 1 has or has not fully engaged lower housing 3. The indication can be made even more conspicuous by painting hexagonal flats 10 a color which provides a visual contrast with lobes 27 and the remainder of housing 3, e.g., red. Thus, if probe 1 has not fully engaged housing 3, lobes 27 will not cover hexagonal flats 10, and the contrast in color will furnish an additional indication of the incomplete engagement. This feature substantially reduces the possibility of an unintentional ejection of probe 1 due to improper or incomplete installation. The feature thus reduces the potential for a dangerous and costly failure or forced shut-down of the host machine.

Lobes 27 and hexagonal flats 10 furnish the contact surfaces that provide the locking action between probe 1 and housing 3. These surfaces are relatively large in comparison to the contact surfaces on typical bayonet-type locks. Hence, the forces associated with the locking action are distributed over relatively wide areas on probe 1 and housing 3. This feature reduces wear on the contact surfaces, and lowers contact-related stresses within probe 1 and housing 3. Hence, these components have improved reliability and life in relation to the equivalent components on a bayonet-type probe.

The invention provides the further benefit of locking probe 1 in place once probe 1 has been installed in lower housing 3. Specifically, the spring-loaded engagement of lobes 27 and hexagonal flats 10 prevents collar 22 (and probe 1) from rotating in relation to lower housing 3. Hence, once probe 1 has been properly installed in housing 3, probe 1 cannot "back out" of the housing due to factors such as vibration. This feature is particularly beneficial in machines that operate with relatively high levels of vibration, and to which a loss of lubricating fluid would likely prove catastrophic, e.g., engines and transmissions. Thus, the positive locking action provided by the invention further reduces the potential for an unintentional ejection of probe 1. Furthermore, the noted locking action is provided with virtually no additional labor on the part of the individual installing the chip detector. The invention thus furnishes a benefit in relation to locking systems that can only be engaged through the expenditure of additional labor, e.g., locking or safety wire. Hence, maintenance costs can be reduced through the use of the invention. Furthermore, the invention eliminates the possibility of an unintentional ejection of probe 1 due to a failure to properly install safety wire. Removal of probe 1 from housing 3 is accomplished by pulling collar 22 away from lower housing 3 until lobes 27 and hexagonal flats 10 no longer overlap. Collar 22 can then be rotated, thereby disengaging threads 6 and 7.

Although the present invention has been described with reference to a chip detector, the invention can readily be applied to other types of elements adapted to be installed in and removed from another structure or element. For example, the invention can be applied to electrical connectors, caps for fluid reservoirs and passages, sensors, fasteners, etc. Moreover, the present invention is not limited to the particular embodiment disclosed above. It is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of the parts, within the principles of the invention expressed above.

Claims

What is claimed is:

1. A chip detector for use in a lubrication system, comprising a probe and a lower housing, wherein: said probe comprises a threaded surface, a collar, and a chip- detection element, said collar being slidably coupled to a remainder of said probe; said lower housing comprises a threaded surface; said collar slidably engages said lower housing when said threaded surface of said probe fully engages said threaded surface of said lower housing; and said engagement of said collar and said lower housing prevents said threaded surface of said probe and said threaded surface of said lower housing from disengaging, whereby said probe is secured to said lower housing.

2. The chip detector of claim 1, wherein said collar cannot slidably engage said lower housing when said threaded surface of said probe and said threaded surface of said lower housing are not fully engaged.

3. The chip detector of claim 2, wherein: said collar comprises a plurality of lobes, each of said lobes comprising a substantially flat inner surface; said lower housing further comprises a plurality of substantially flat surfaces; said collar is biased so that said substantially flat inner surfaces of said lobes slidably engage said substantially flat surfaces of said lower housing when said substantially flat inner surfaces of said lobes substantially align with said substantially flat surfaces of said lower housing; said substantially flat inner surfaces of said lobes and said substantially flat surfaces of said lower housing substantially align when said threaded surface of said probe fully engages said threaded surface of said lower housing; and said engagement of said substantially flat inner surfaces of said lobes and said substantially flat surfaces of said lower housing prevents said threaded surface of said probe and said threaded surface of said lower housing from disengaging.

4. The chip detector of claim 3, wherein said substantially flat inner surfaces of said lobes and said substantially flat surfaces of said lower housing do not substantially align when said threaded surface of said probe and said threaded surface of said lower housing are not fully engaged.

5. The chip detector of claim 3, wherein said substantially flat surfaces of said lower housing are colored a first color, at least a portion of an outer surface of said lower housing is colored a second color, and a least a portion of an outer surface of said collar is colored at least one of said second color and a third color.

6. The chip detector of claim 5, wherein said first color is red.

7. The chip detector of claim 1, wherein said chip-detection element comprises a magnet.

8. The chip detector of claim 1 , further comprising a poppet and a poppet housing, wherein: said lower housing further comprises a seat for said poppet; said poppet is biased in said seat when said threaded surface of said probe and said threaded surface of said lower housing are not fully engaged; and said chip-detection element forces a substantial portion of said poppet into said poppet housing when said threaded section of said probe fully engages said threaded section of said lower housing.

9. A system for locking a removable element in place, comprising a housing and said removable element, wherein: said housing comprises a first surface and a second surface; said removable element comprises a first surface and a second surface; said second surface of said housing engages said second surface of said removable element when said first surface of said housing fully engages said first surface of said removable element; and said engagement of said second surface of said housing and said second surface of said removable element prevents said first surface of said housing and said first surface of said removable element from disengaging.

10. The system of claim 9, wherein said second surface of said housing cannot engage said second surface of said removable element when said first surface of said housing and said first surface of said removable element are not fully engaged.

11. The system of claim 10, wherein said first surface of said housing and said first surface of said removable element comprise threads.

12. The system of claim 11, wherein said threads comprise triple-lead, square-profile threads.

13. The system of claim 11 , wherein said engagement of said second surface of said housing and said second surface of said removable element prevents said removable element from rotating in relation to said housing.

14. The system of claim 10, wherein: said second surface of said housing is substantially flat; said second surface of said removable element is substantially flat; said second surface of said housing and said second surface of said removable element substantially align when said first surface of said housing fully engages said first surface of said removable element; and said second surface of said housing engages said second surface of said removable element when said second surface of said housing and said second surface of said removable element substantially align.

15. The system of claim 14, wherein said second surface of said housing and said second surface of said removable element do not substantially align when said first surface of said housing and said first surface of said removable element are not fully engaged.

16. The system of claim 15, wherein said removable element further comprises a collar, said collar comprises a lobe, and said second surface of said removable element comprises an inner surface of said lobe.

17. The system of claim 16, wherein said collar is slidably coupled to a remainder of said removable element and said collar is biased so that said inner surface of said lobe engages said second surface of said housing when said inner surface of said lobe and said second surface of said housing substantially align.

18. The system of claim 17, wherein said collar comprises three of said lobes.

19. The system of claim 17, wherein said second surface of said housing is colored a first color, at least a portion of an outer surface of said housing is colored a second color, and at least a portion of an outer surface of said collar is colored at least one of said second color and a third color.

20. The system of claim 19, wherein said first color is red.

21. A method for installing a chip detector in a lubrication system of a machine and locking said chip detector in place, comprising the steps of: threadably engaging a first section of said chip detector and a first section of a housing on said machine; and slidably engaging a second section of said housing and a collar on said chip detector when said first section of said chip detector and said first section of said housing are fully engaged, wherein said engagement of said collar and said second section of said housing prevents disengagement of said first section of said chip detector and said first section of said housing.