DEBRIS DETECTION SYSTEM AND METHOD

Abstract: A debris detection system for detecting debris in a fluid flow in which both a primary and a secondary fluid flow (20, 22) from a fluid reservoir (10) are maintained. The fluid reservoir (10) is situated downstream of the system being served and receives the debris from the system being served. Within the reservoir (10) the primary fluid flow (20) is shielded from all but the colloidal debris received. All non-colloidal as well as col­ loidal debris is diverted to the secondary fluid flow (22) where the amount and rate of debris accumulation is detected.

Description: DEBRIS DETECTION SYSTEM AND METIIOD 4 BACKGROUND OF TIIE INVENTION 1. Field of the invention This invention relates to a system for detecting debris in a fluid flow and in particular to a system in which detection is achieved without disrupting the fluid flow. 2. Prior Art A popular means of determining incipient deterioration of a mechanical. sysLem is to monitor the fluid flow serving the mechanical system, and more specifically to monitor the quantity of debris in the fluid flow. Consider, for example, U.S. Patent Nos. 3,686,926, 3,878,103 and 4,070,660. The systems described in these patents are all located in the primary fluid flow path. See, for example, lig. 6 of U.S. Patent Nos. 3,686,926 and 3,878,103. In the circuit shown, the two screens and the filter are arranged in series in the oil line serving the transmission. Any detection system which is placed in the primary fluid flow path introduces an added risk, namely, a detection stem failure wholly apart from the mechanical system being served. Such a failure will disrupt the fluid flow to the mechanical system, and the consequences of such a disruption could be quite serious. or example, if in a transmission, and in particular the transmission of a helicopter, the detection system failed and lubricating fluid flow to the transmission were disrupted, the trallslllission could quickly seize, resulting in loss of the helicopter. OnJEC'VS AND SUMMARY Si)#flARY OF TIIE INVENTION An object of this invention therefore, is to provide the existing state-of-tlle-debris detection system art with a detection system which separates the detection function from the primary lubrication function, and is therefore safer for the system served. Another object of Chits invention is to provide the existing state-of-tl#e-debris detection system art with a detection system according to the previously stated object which permits optimization of debris monitoring without jeopardizing primary lubrication flow. Another object of this invention is to provide the existing state-of-tlle-alehris detection system art with a detection system including a rate of debris accumulation capa ability without jeopardizing primary lubrication flow. Another object of this invention is to provide the existing state-of-the-debris detection system art with a full flow monitoring detection system having the characteristics of the previously stated objects. Another object of this invention is to provide the existing state-of-the-debris detection system art with a detection system having the characteristics of the previously stated objects and in addition is easily inspectable without disruption to the primary fluid flow system. Another object of this invention is to provide the existing state-of-the-debris detection system art with a detection system having the characteristics of the previously stated objects and in addition has size discrimination capability. Another object of this invention is to provide the existing state-of-ti#e-d#'bris detection system art with a metllod of debris detection in a fluid stream without disrupting flow. Another object of this invention is to provide the existing state-of-thc-debris detection system art with a method of debris detection in a fluid stream having a primary and secondary flow in which a significant warning is rendered as a function of monitoring the debris accumulation in the secondary flow. According to tlle invention a secondary fluid flow is introduced into the circuit including the primary fluid flow and a fluid reservoir. The fluid reservoir is situated downstream of the system being served (transmission, for example) and serves as a fluid source for both fluid flows. Upstream of or within the reservoir the primary fluid flow is shielded from all but colloidal debris generated in the system being served and the debris is diverted to the secondary fluid flow. Within the secondary fluid flow there is situated a pump and detecting. apparatus located downstream of the pump for indica Ling amount of debris accumulation. The detecting apparatus in the secondary fluid flow also serves to provide verification for the presence of metallic debris. Implementation of the invention into the lubricating system of a system being served, such as a transmission, effects an added degree of safety to the system being served because the development of a failure in the system being served can be detected more reliably. BRIEF DESCRIPTION OF TIIE DRAWINGS Five figures have been selected to more fully explain the invention to tllc person skilled in the art. These relate tu a lubrication system for a transmission of a helicopter, und are: Fig. 1 which scluematically illustrates a fluid reservoir with primary and secondary fluid flow-lines and cl#?lJris detection apparatus in accordance with one embodiment of the invention. Fig. 2 which schematically illustrates a fluid reservoir with primary and secondary fluid flow lines and debris detection apparatus in accordance with a second embodiment of the invention. Fig. 3 which schematically illustrates a variant of the second embodiment of Fig. 2. Fig. 4 which is a circuit diagram schematically illus trating the various components of the debris detection appara tus of the invention. Fig. 5 which illustrates a variant of the circuit of Fig. 4. DVl'A Ll,ED DESCRIPTION A debris detection system for use with a transmission, and in particular a helicopter transmission will be described in greater detail. The invention, however, has application in any fluid flow system subject to debris accumulation. The lubricating systems of many helicopter transmissions are now dual systems, i.e., they include a primary flow of lubricant and a seconelaly or auxilliary flow of lubricant. The second or auxiliary flow of lubricant is a lower capacity flow and is required only in the event of failure of the primary flow. This invention utilizes the dual system in a unique manner, in that the secondary flow serves an additional function, i.e., debris detection. If a failure occurs in the primary flow the secondary flow will be available for lubrication. In addition, the secondary flow serves to detect the amount and rate of debris accumulating in the whole lubricating system. Structurally, the invention is located at and utilizes tile lubricating system reservoir. The reservoir may be a but sump", i.e., the reservoir is corrected directly to the transmission housing, or a"dry sump", i.e., the reservoir is removed from the transmissioll housing. Figures 1 and 2 illustrate the debris deLectio:# system used with a"wet sump", while Figure 3 illustrates tulle debris detection system used with a'Ury sump". The reservoir 10 shown in Figure 1 is mounted directly to tiie bottom of the transmission 12 (not shown in further detail). The reservoir 10 includes a bottom wall with downwardly tapered sides 11 and 16. The tapered sides 14 and 16 can be representative Of oly a portion of the bottom wall. Alternatively, the entire wall can be shaped as a cone witii the sides 14 and 16 serving as side walls of the cone. In either case the sides 14 and 16 taper downwardly toward each other and meet at an opening 18. Connected to the reservoir 10 is a primary flow line 20 and a secondary or auxilliary flow line 22. An opening 21 in the bottom wall of the rescrvoir serves as the point of origin for the primary flow through the primary line 20. The opening 18 serves as the point of origin for the secontlar-y flow through the secondary line 22. Each line has its own pump for generating flow such as the ,ulnp 26 in the primary 3 ine and the pump 28 in the secondary line. The capacity of tie primary line is greater than the capacity of the sccondnlryy litre since the secondary line is intended to serve only as a backup in the event of an emergency. Lor example, in one helicoE)ter model manufactured by the assignee company the primary flow quantity is approximately 30 gallons per minute while the secondary flow quantity is only ae,proximately 1.5 gallons per minute. At the opening 24 to the primary flow line 20 a coarse mesh screen 30 is situated. The screen 30 is provided with a cap 32 having a flanged sicle 34 and a skirt 36. The cap 32 and skirt 36 can be sheeL metal plates. They should not be ,erforated. Downstream of the opening 18 in the secondary line 22 there is located a coarse screen 38 and a magnetic chip detector 40. Preferably, the screen 38 and magnetic chip detector 40 are assembled as a single unit with the magnetic plug situated at the bottom of the screen (when viewed in the direction of flow). Downstream of the pump 26 in the primary line 20 there is situated a large capacity fine mesh filter 42, while downstream of the pump 28 in the secondary line 22 there is situated a fine mesh screen filter 44. A differential pressure gauge 46 (AP) monitors the pressure drop across the filter 44. A pressure gauge 48 is located downstream of the filter 42 and indicates the pressure in the primary flow downstream of the filter 42. The differential pressure gauge 46 and the pressure gauge 48 are connected to a cockpit display panel 50, while the filter 38 and magnetic chip detector 40 are connected to a maintenance panel 52 which is located at a point in the helicopter remote from tEle cockpit. The cockpit display 50 and maintenance panel 52 are connected together so that a significant warning can be rendered. This point will be better understood in conjunction with the discussion of Figure 4. As previously no Led, the reservoir 10 is connected directly to the transmission housing 12 and the oil in the transmission is fed by gravity to the reservoir 10 where the oil forms a pool 54. Tie pumps 26 and 28 draw the lubricating fluid from the pool 54 through the openings 24 and 18, respec Lively. As a result, one can envision two streams being created in the pool 51, one flowing toward the opening 24. these streams carry with them some of the debris generated in the transmission itself, i.e., debris in suspension or colloidal debris. This type of debris tends to be very fine having an average size of 0.00001 to 0.000001 inches. It is generated mostly by wear, for example, in the gears and hearing. Another ta)e of debris is not retained in suspen ion because of its size and consequent weight, and simply falls to the surfaces 14 and 16. This type of debris can also lJc due to wear, but it can, and frequently is, due to the early stages of failure in, for example, the bearings or gears. When this latter debris reaches the surfaces 14 and 16, it falls, by gravity and the sloping orientation of the surfaces, toward the opening 18. Only colloidal debris passes the screen 30 as it is shielded from the other debris by the cap 32 and skirt 36. Ttie cap 32 is provided witty a flange(s) 34 sloped downwardly arid outwardly relative to the screen 30. The skirt 36 has a similar flange(s) slopc#d upwardly and outwardly relative to Llic screen 30. llle colloitlal debris which does pass through¯ tile secreen 30 is not suficinly large to damage the pump 26 and is filtered out by the filter 42. The screen 30 therefore serves the primary function of protecting the pump 26 from tEle large debris particles. The debris, botll colloidal and otherwise, is collected at the opening 18 and for tile most part, simultaneously encounters the coarse screen 38 and magnetic chip detector 40. The screen 38 can be constructed similar to that disclosed in U.S. Patent No. 3,686,926, while the magnetic chip detector 40 can be constructed similar to that disclosed in U.S. Patent No. 4,070,660. Physically, they can be assembled as a unit, as noted above. If tlle colloidal debris is of a ferrous nature it will be magnetically attracted to the magnetic chip detector 40. Ferrous debris which is larger than colloidal debris will be magnetically attracted to the magnetic chip detector. When a sufficient quantity of this debris is deposited on detector 40, an indication is relayed to panel 52. The larger particles of debris, i.e., those of sufficient size relative to the mesh size of the screen 38, that is metallic in nature, will impinge on tile screen 38 and an indication will be relayed to panel 52. Del)ris of any kind which passes through opening 18 past the magnetic chip detector 40 and through screen 38 will be collected by tulle fine screen filter 44. When a sufficient quantity of this debris is collected a pressure change occurs across tiie filter and the gauge 46 will provide a reading at the panel 50 for pilot observation. The purpose for the various indications can be better understood by reference to Fig. 4. Figure 4 illustrates a circuit including: Lile screen 38; the magnetic chip detector 40; the cockpit display panel 50 including light indicator 58; the differential pressure gauge contact 60; a switch 62 and control coil 64; a blink function generator 66; and the maintenance panel 52, including !lCludjnglight indicator 56. The circuit of Fig. 4 is connected to a DC source, such as 28VDC, and has Liiree modes of opelatioo: mode (1), a particle or particles impinge on screen 38 and/or sufficient ferrous particles accumulate on the magnetic chip detector 40, a circuit is completed to the light indicator 5G and an indication is rendered on the sllaintenace panel 52; mode (2), a sufficient pressure drop occurs across the filter 44 that contact 60 is closed and a circuit is completed to tlle light indicator 58 and an indication is rendered in the cockpit; mode (3), indicator 46 causes contact 60 to close; if either or both of indicators 38 and 40 are activated the coil 64 is energized tllrowing switch 62 to its opposite position (in dashed lines) causing thereby a pulsing of light indicator 58. A pulsing of light indicator 58 signifies that a dangerous condition is developing in the system being served (transmission, for example), and that therefore appropriate action should be taken with respect to tlie system being served. For example, iE the system being served is a helicopter trasmission, the transmission should be slit down and inspected. A pulsing of light indicator 58 therefore represents a significant warning. Since tile indication giving by the differential pressure gauge 46 is significant, it is displayed in the cockpit. Since Lhe indications given by the screen 38 and the detector 40 may not be as significant, i.e., a dangerous condition is not rapidly developing, they are only displayed in the maintenance panel 52. During routine mainteiiance, the panel 52 can be checked and if either the screen 38 or the detector 40 have been active, an appropriate indication will be visible (for example, the light 56, or even a mechanical indicator) then a manual check can le performed. The unit including the screen 38 and tlse detec Lor 40 can be easily removed for inspection, without tulle need to interrupt the primary lubricating system. When the pulsing of light indicator 58 is combined with a rate of debris accumulation indication at the filter 44, a dangerous condition exists in the system being served and immediate action is re'jiiired. The rate of debris accumulation indication can be accomplished in several ways. It could be accomplished by manual inspection of the filter 44 prior to activating the fluid system. For example, if the system being served is a helicopter transmission, the filter 44 can be visually inspected before commencing the mission. If, for example, the filter 44 is clean at inspection, and a pulsing of the light indicator 58 occurs during flight, the pilot is on notice that the rate of debris accumulation is such that the mission should be aborted. Another means of indicating the rate of debris accumulation would be by utilizing the timing apparatus disclosed in U.S. Patent 3,686,926. Still another means of indicating tile rate of debris accumulation would be by the alternate embodiment of Fig. 4, i.e., the embodiment of Fig. 5. In Fig. 5, the differential pressure gauge 46 and its contact 60 are replaced by a pressure transducer 96 and a microprocessor 98 connected as shown. The pressure transducer 96 feeds pressure data detected across the filter 44 and feeds this pressure data to the microprocessor 98 which checks the rate of pressure change. IJIlen an acceptable rate of change is exceeded,a circuit is closed through the switch 62 result ing in pulsing of tlie ligllt indicator 58. In the alternate embodiment illustrated in Figure 2 the reservoir 68 is a modification of the reservoir 10. Within the reservoir 68 downwardly sloping surfaces 70 and 72 are situated. These surfaces serve a purpose similar to that of surfaces 14 and 16. The surfaces 70 and 72 converge at an opening 74 to which a perforated sleet or screen 76 is connected. A secondary fluid reservoir or sump 80 is provided concentric with the screen 76. The sump 80 includes an upper wall defining a downwardly directed flange 82, and downwardly sloping surfaces 84 and 86. In operation the lubricant drains through the opening 74 and develops a pool 88 within the sump 80. It then overflows the sump 80 forming the pool 90 which serves as a source of lubricating fluid for the primary flow. Debris, both colloidal and otherwise, are carried through the opening 74 itito the sump 80. Within tile sump 80 the surfaces 84 and 86 direct the heavy debris to tile opening 18. The colloidal debris is carried with the fluid through the opening 18. The colloidal debris is also carried with the fluid as it spills over to form the pool 90. This debris is passed through the screen 30 and collected at the filter 47. The flange 82 ensures that the Irrlcr and hcavier debris is not carried with the spill over fluid into the pool 90. Since the pool 90 is relatively free of any large debris, the screen 30 need not have tlic cap and skirt as does the screen 30 of the embodiment of figure 1. with the LXCt?1)t #on noted, the system operates in a manner similar to that of the embodiment of Figure 1. In the alternate embodiment illustrated in Figure 3, the modification lies in tile delivery of the lubricating fluid to the reservoir 68. Figure 3 illustrates a so-called dry ump, i.e., one which is removed from the system being served. fubricating fluid is drawn by a pump 92 through a line 94 and delivered to the reservoir 68. The screen 38 and magnetic clump detector 40 are located immediately upstream of the pump 92. While this location is preferred, it can also be located as shown in Figure 2 but this would require a protecting screen ahead of pump 92. Tiie location of Figure 3 in this type of system is preferred since inspection would not require reservoir draining or the use of self-closing devices. With the excep Lions noted, the embodiment of Figure 3 operates in a manner similar to that of Figures 1 alld 2. The screen 38 has openings dimensioned within the range 0.10 inches x 0.10 includes to 0.03 inches x 0.03 inches. The fine mesh screen filters 42 and 44 can have an opening size of 0.03 inches x 0.03 inclles to 15 microns. 'rhe microprocessor 9u call Le any 8 bit processor, such as, for example, the Intel 8085 or the Motorola 6502. With the present: invention delivery of all accessible debris to one area, the secondary flow inlet, is accomplished. aphis is accomplished by Eunneling the generated debris to the secondary flow inlet. Contoured sumps sloping to a single collection point can be used. Also, funnel-like baffles can be used. All but colloidal debris is shielded from the primary flow and a single easily removable unit is provided in the secondary flow for capturing both small and larger sized debris. Also a screen/ filter unit functions with a pressure differential switch downstream of the secondary flow pump to provide significant warning of impending failure. The system of tie invention is designed to provide a lligh degree of flexibility and implicit in detecting and Iglonitoring failure debris in an oil circulating system. For example, in the transmission of a helicopter, pilot warning is given for only significant conditions. Thus, pilots are relieved from monitoring inciluiellt failure conditions and abortive flights for such conditions are avoided. On the other hand, pilot confidence and safety is enhanced by providing pilot warning for those rare conditions of deterioration which produce failure debris at a rapid rate.

Claims: WL CLAIM: 1. In a fluid system having a reservoir from whicll a primary flow and a secondary flow originate for serving a common system, a system for detecting debris Qriginating in the common system being served, comprising: means for diverting debris from the common system being served to the secondary flow at its point of origin in the reservoir; monitoring means located in said secondary flow for detecting debris accumijiation within the secondary flow. 2. The system for detecting debris as defined in claim 1, wherein the means for diverting debris includes the bottom wall of the reservoir, said wall defining a downwardly sloping surface portion to the point of origin of the secondary flow. 3. The system for detecting debris as defined in claim 2, wherein the bottom wall of the reservoir slopes downwardly in the form of a cone to the point of origin of the secondary flow, said point of origin being located at the apex of said cone. 4. The system for detecting debris as defined in claim 2, wherein the means for diverting debris further includes shielding means for shielling the point of origin of the primary flow, thereby excluding debris from entering the primary flow. 5. The system for detecting debris as defined in claim 1, wherein the flow capacity of the primary flow is greater than the flow capacity of the secondary flow. 6. The system for ¯detecting debris as defined in claim further comprising: a pump for (Je:#erdLiilg the secondary flow. 7. TIle system for detecting debris as defined in claim 6, wherein the monitoring means includes a filter and a differential pressure sensor 1#oth located downstream of the pump, for detecting the amount of debris accumulated. 8. The system for detecting debris as defined in claim 7, wherein the monitoring means further includes a screen located upstream of the pump and at the point of origin of the secondary flow for detecting the presence of metallic debris of at least a predctcrinincd size. 9. The system for detecting debris as defined in claim 8, wherein the monitoring means further includes a magnetic chip detector located at the point of origin of the secondary flow, for detecting tiio presence of ferrous debris. 10. The system for detecting debris as defined in claim 1, wherein tile means for diverting debris includes a downwardly sloping surface within tile reservoir defining an opening and a perforated screen which extends from the opening in the downwardly sloping surface toward the point of origin of the secondary flow. 11. The system for detecting debris as defined in claim 10, wherein the means for diverting further includes a secondary flow container located within the reservoir and concentric with the perforated screen, the volume of said secondary flow container being less ìharl that of the reservoir. 12. The system for detecting debris as defined in claim 11, wherein the secondary flow container includes an inwardly directed flange about its upper periphery which serves to retain debris within the secondary flow container. 13. The system for detecting debris as defined in claim 1, further comprising: display means connected to said monitoring means for providing a visual display indicative of the debris accumulation. 14. In a lubricating system having a reservoir from which a primary flow and a secondary flow originate, said secondary flow serving as an auxilliary source of lubrication in the event of failure of the primary flow, a system for detecting debris, comprising: means for diverting debris to the secondary flow at its point of origin in tile reservoir; meals for shieldincj tha point oE oligin of the prilhaey flow, thereby excluding debris from entering the primary flow; tind monitoring means located in said secondary flow for detecting debris accumulation within the secondary flow. 15. The system for detecting debris as defined in claim 14, wherein the flow capacity of the primary flow is greater than the flow capacity of tile secondary flow. 16. The system for detecting debris as defined in claim 14, further comprising: a pump for generating tile secondary flow, and wherein the monitoring means includes: a filter and a differential pressure sensor both located downstream of the pump for detecting the amount of debris accu:nt:lated; a filter located upstream of the pup and at the point of origin of the secondary flow for detecting tile presence vL metallic debris of at least a predetermined size; and a magnetic chip detector located at the point of origin of the secondary flow for detecting the presence of ferrous debris. 17. The system for detecting debris as defined in claim 16, wherein the means for diverting debris includes the bottom wall of the reservoir, said wall defining a downwardly sloping surface portion to tlic point of origin of the secondary flow. 18. The system for detecting debris as defined in claim 17, wherein the bottom wall of the reservoir slopes downwardly in tile form of a cone to the point of origin of the secondary flow, said point of origin being located at the apex of said cone. 19. The system for detecting debris as defined in claim 16, wherein the means for diverting debris includes a downwardly sloping surface within the reservoir defining an opening, a perforated screen which extends from the opening in the downwardly sloping surface toward the point of origin of the secondary flow, and a secoxy flow container located within the reservoir and concentric witli the perforated screen, the volume of said secondary flow container being less than that of the reservoir. 20. The astern for detecting debris as defined in claim 19, wherein the secondary flow container includes an inwardly directed flange abotlt its upper periphery which serves to retain debris within the secondary flow container. 21. The system for detecting debris as defined in claim 20, further comprising: display means connected to said monitoring means for providing a visual display indicative of the debris accumulation. 22. A method for detecting debris within a fluid system, said system having a reservoir from which a primary flow and a secondary flow originate, the method comprising the steps of: diverting debris to the secondary flow at its point of origin in the reservoir; shielding the point of origin of the primary flow, thereby excluding debris from entering the primary flow; and detecting the debris accumulation within the secondary flow. 23. The method for detecting debris as defined in claim 22, wherein the rate of debris accumulation within the secondary flow is detected.

Inventors: RUMBERGER, WILLIAM E.
Applicants: THE BOEING COMPANY
Application year: 1983
Main classification: G01N15
IPC codes: G01N15, B01D35, F16N29