# US 5,703,569 A · Retrofit hydraulic fluid leak detection system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,569 A - Document ID: US5703569A - Status: Granted - Kind: A - Application number: 08/481,910 - Filed: 1995-06-07 - Granted: 1997-12-30 - Earliest claimed: 1984-02-03 - Assignees: Ransomes America Corporation - Inventors: Joseph J. Oliver; Christopher L. Young; Richard D. Bednar - Web page: https://patentgrep.com/patent/US5703569A ## CPC - G01F 25/20: of apparatus for measuring liquid level - A01D 69/03: fluid - G01F 23/72: using magnetically actuated indicating means - G01F 23/74: for sensing changes in level only at discrete points - G01M 3/3245: {using a level monitoring device (G01M3/3272 takes precedence)} - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - A01D: HARVESTING; MOWING - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract Provided is a self-calibrating system which self-calibrates for operation regardless of the particular reservoir or expansion tank, which further detects when a hydraulic fluid system adapted to a turf care machine has developed a leak and which warns the machine operator of such a leak before an appreciable amount of hydraulic fluid is allowed to leak from the system. The system includes a reservoir for holding a quantity of hydraulic fluid. The reservoir is connected via a connecting tube or hose located at the upper-most portion of the reservoir and connected to an expansion tank mounted substantially adjacent to the reservoir. The expansion tank includes a fitting having an elongated tube extending down into the expansion tank. The end of this tube is maintained substantially below the level of hydraulic fluid in the expansion tank during operation of the turf care machine to which it is attached. As the machine is operated, the hydraulic fluid expands with rising temperatures, and the connecting tube communicates the expanding fluid to the expansion tank. When operation of the machine is discontinued the hydraulic fluid contracts as it cools. As the hydraulic fluid contracts, the hydraulic fluid in the expansion tank is automatically drawn by a siphoning action through the elongated tube within the expansion tank through the connecting tube and back into the reservoir. The self-calibrating leak detection system is adaptable to a variety of self propelled machines having hydraulically actuated devices. In particular, significant savings could be gained by the early detection of hydraulic system leaks on large, earth-moving equipment and the like. Further, the self-calibrating hydraulic fluid leak detection system may be retrofit onto existing hydraulic systems by the addition of an expansion tank to the hydraulic system reservoir. ## Claims ### Claim 1 A hydraulic fluid leak detection system for a self-propelled vehicle or self-propelled machine including a hydraulic system having a hydraulically actuated device and a reservoir of hydraulic fluid, the leak detection system comprising: an expansion tank in fluid communication with the reservoir; a first sensor disposed within the expansion tank and operable for sensing the hydraulic fluid level in the expansion tank over a range of possible fluid levels in the expansion tank and for producing a first signal varying in accordance with the hydraulic fluid level; a second sensor operable for sensing the temperature level of the hydraulic fluid in the reservoir and for producing a second electronic signal corresponding thereto; electronic processing means for receiving the first and second signals and for determining from the first and second signals if a leak exists in the hydraulic system; and means for indicating to an operator that a leak exists in the hydraulic system. ### Claim 2 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the expansion tank is formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within the expansion tank. ### Claim 3 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the expansion tank and reservoir are formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within each of the expansion tank and reservoir. ### Claim 4 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the reservoir and the expansion tank are integrally formed to define one tank having a reservoir portion and an expansion portion. ### Claim 5 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the reservoir and the expansion tank define two discreet tanks and a conduit communicates fluid between the reservoir and the expansion tank. ### Claim 6 (depends on 1) The hydraulic fluid leak detection system of claim 1 further comprising a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck. ### Claim 7 (depends on 1) The hydraulic fluid leak detection system of claim 1 further comprising: a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck; and a filler neck adaptor for interconnecting the filler neck of the reservoir to the expansion tank. ### Claim 8 (depends on 7) The hydraulic fluid leak detection system of claim 7 wherein the adaptor may be of varying sizes and shapes to suitably connect filler necks of corresponding sizes and shapes to an expansion tank having a predetermined size and shape. ### Claim 9 (depends on 7) The hydraulic fluid leak detection system of claim 7 wherein the filler neck and adaptor threadably interconnect. ### Claim 10 (depends on 7) The hydraulic fluid leak detection system of claim 7 wherein the adaptor and the expansion tank are shaped to form a substantially fluidic seal when interconnected. ### Claim 11 (depends on 1) The hydraulic fluid leak detection system of claim 1 further comprising an expansion tank support positioned upon the reservoir, the expansion tank being substantially seated upon the expansion tank support to support the expansion tank above the reservoir. ### Claim 12 (depends on 11) The hydraulic fluid leak detection system of claim 11 wherein the expansion tank support is a generally annular support. ### Claim 13 (depends on 11) The hydraulic fluid leak detection system of claim 11 wherein the expansion tank support includes a plurality of supports which support the expansion tank above the reservoir at a plurality of points. ### Claim 14 (depends on 1) The hydraulic fluid leak detection system of claim 1 further comprising: a first visible marking on the expansion tank to indicate a minimum fill level at a first temperature; and a second visible marking on the expansion tank to indicate a maximum fill level at a second temperature. ### Claim 15 (depends on 14) The hydraulic fluid leak detection system of claim 14 wherein the first temperature indicates a cold fluid level, and the second temperature is associated with a hot fluid level. ### Claim 16 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the fluid passage connects the reservoir and the expansion tank, and the fluid passage is located in proximity to a center of the expansion tank. ### Claim 17 (depends on 16) The hydraulic fluid leak detection system of claim 16 wherein the expansion tank is cylindrically shaped and the fluid passage is substantially in the center of the expansion tank in order to limit sloshing of the hydraulic fluid in the expansion tank. ### Claim 18 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein: the first and second signals are electronic signals; and the processing means is further operable for determining if the hydraulic fluid level within the system is below a predefined normal operating level. ### Claim 19 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the processing means is further operable for determining if the hydraulic fluid level within the system is above a predefined normal operating level. ### Claim 20 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the processing means is further operable for determining if the hydraulic fluid temperature within the system is above a predefined normal operating range. ### Claim 21 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the processing means is operable to determine an estimated level of fluid within the expansion tank and for comparing the estimated level of fluid to an actual fluid level determined by the first sensor for signalling the presence of a leak. ### Claim 22 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the processing means is operable to determine a rate of change of the fluid level within the expansion tank and for comparing the determined rate of change to an allowable rate of change for signalling the presence of a leak. ### Claim 23 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the first sensor comprises a float sensor. ### Claim 24 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the first sensor comprises a plurality of float sensors, the float sensors being disposed in an offset relationship with respect to each other. ### Claim 25 (depends on 1) The hydraulic fluid leak detection system of claim 1 wherein the second sensor is disposed within the reservoir. ### Claim 26 (depends on 5) The hydraulic fluid leak detection system as in claim 5 wherein the conduit includes an elongated tube structure. ### Claim 27 (depends on 26) The hydraulic fluid leak detecting system as in claim 26 wherein the reservoir, expansion tank and tube structure are cooperatively arranged and positioned such that the fluid is siphoned from the expansion tank through the tube structure to the reservoir when the fluid in the reservoir cools. ### Claim 28 A hydraulic fluid leak detection system for a self-propelled land vehicle or self-propelled machine including a hydraulic system having a hydraulically actuated device and a reservoir of hydraulic fluid, the system comprising: an expansion tank disposed adjacent and in communication with the reservoir; a first sensor disposed within the expansion tank, the first sensor operable for sensing the level of hydraulic fluid in the expansion tank and for producing a first electronic signal corresponding thereto; a second sensor operable for sensing the temperature of the hydraulic fluid in the reservoir and for producing a second electronic signal corresponding thereto; memory for storing the level of hydraulic fluid in the expansion tank and for storing the temperature of the hydraulic fluid in the reservoir, the memory storing a map which associates the hydraulic fluid level with a corresponding hydraulic fluid temperature; processing means for receiving the electronic signals and for determining from the first and second electronic signals if a leak exists in the hydraulic system; and means for indicating to an operator that a leak exists in the hydraulic system. ### Claim 29 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the expansion tank is formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within the expansion tank. ### Claim 30 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the expansion tank and reservoir are formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within each of the expansion tank and reservoir. ### Claim 31 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the reservoir and the expansion tank are integrally formed to define one tank having a reservoir portion and an expansion portion. ### Claim 32 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the reservoir and the expansion tank define two discreet tanks and a conduit communicates fluid between the reservoir and the expansion tank. ### Claim 33 (depends on 28) The hydraulic fluid leak detection system of claim 28 further comprising a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck. ### Claim 34 (depends on 28) The hydraulic fluid leak detection system of claim 28 further comprising: a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck; and a filler neck adaptor for interconnecting the filler neck of the reservoir to the expansion tank. ### Claim 35 (depends on 34) The hydraulic fluid leak detection system of claim 34 wherein the adaptor may be of varying sizes and shapes to suitably connect filler necks of corresponding sizes and shapes to an expansion tank having a predetermined size and shape. ### Claim 36 (depends on 34) The hydraulic fluid leak detection system of claim 34 wherein the filler neck and adaptor threadably interconnect. ### Claim 37 (depends on 34) The hydraulic fluid leak detection system of claim 34 wherein the adaptor and the expansion tank are shaped to form a substantially fluidic seal when interconnected. ### Claim 38 (depends on 28) The hydraulic fluid leak detection system of claim 28 further comprising an expansion tank support positioned upon the reservoir, the expansion tank being substantially seated upon the expansion tank support to support the expansion tank above the reservoir. ### Claim 39 (depends on 38) The hydraulic fluid leak detection system of claim 38 wherein the expansion tank support is a generally annular support. ### Claim 40 (depends on 38) The hydraulic fluid leak detection system of claim 38 wherein the expansion tank support includes a plurality of supports which support the expansion tank above the reservoir at a plurality of points. ### Claim 41 (depends on 28) The hydraulic fluid leak detection system of claim 28 further comprising: a first visible marking on the expansion tank to indicate a minimum fill level at a first temperature; and a second visible marking on the expansion tank to indicate a maximum fill level at a second temperature. ### Claim 42 (depends on 41) The hydraulic fluid leak detection system of claim 41 wherein the first temperature indicates a cold fluid level, and the second temperature is associated with a hot fluid level. ### Claim 43 (depends on 42) The hydraulic fluid leak detection system of claim 42 wherein the fluid passage connects the reservoir and the expansion tank and the fluid passage is located in proximity to a center of the expansion tank. ### Claim 44 (depends on 43) The hydraulic fluid leak detection system of claim 43 wherein the expansion tank is cylindrically shaped and the fluid passage is substantially in the center of the expansion tank in order to limit sloshing of the hydraulic fluid in the expansion tank. ### Claim 45 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the vehicle or machine is a turf care machine. ### Claim 46 (depends on 45) The hydraulic fluid leak detection system of claim 45 wherein the fluid temperature and a corresponding fluid level are stored while performing leak detection. ### Claim 47 (depends on 46) The hydraulic fluid leak detection system of claim 46 wherein the map is stored in memory and is reset in response to a request to recalibrate the system. ### Claim 48 (depends on 47) The hydraulic fluid leak detection system of claim 47 wherein an operator initiates the calibration process. ### Claim 49 (depends on 48) The hydraulic fluid leak detection system of claim 48 wherein the processing means detects leaks during the operation of the hydraulic system and during transport of the vehicle or machine. ### Claim 50 (depends on 49) The hydraulic fluid leak, detection system of claim 49 wherein an operator may compensate for a change of shape of the expansion tank by recalibrating the system. ### Claim 51 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the expansion tank covers a first horizontal area and the reservoir covers a second horizontal area, and the first horizontal area is less than the second horizontal area to effect a multiplication of the change in fluid level of the reservoir in accordance with a ratio of the horizontal areas. ### Claim 52 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the expansion tank includes a flared section at the top to accommodate fluid overflow. ### Claim 53 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the processing means is further operable for determining if the hydraulic fluid level within the system is below a predefined normal operating level. ### Claim 54 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the processing means is further operable for determining if the hydraulic fluid level within the system is above a predefined normal operating level. ### Claim 55 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the processing means is further operable for determining if the hydraulic fluid temperature within the system is above a predefined normal operating range. ### Claim 56 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the processing means is operable to determine a rate of change of the fluid level within the expansion tank and for comparing the determined rate of change to an allowable rate of change for signalling the presence of a leak. ### Claim 57 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the first sensor comprises a float sensor. ### Claim 58 (depends on 57) The hydraulic fluid leak detection system of claim 57 wherein the float sensor is centrally located within the expansion tank. ### Claim 59 (depends on 28) The hydraulic fluid leak detection system of claim 28 wherein the first sensor comprises a plurality of float sensors, the float sensors being disposed in an offset relationship with respect to each other. ### Claim 60 A self-propelled land vehicle or self-propelled machine, comprising: a hydraulically operated device; a reservoir for hydraulic fluid for operating the hydraulically operated device; an expansion tank in fluid communication with the reservoir; a first sensor disposed within the expansion tank, the first sensor operable for sensing the level of hydraulic fluid in the expansion tank and for producing a first electronic signal corresponding thereto; a second sensor operable for sensing the temperature of the hydraulic fluid in the reservoir and for producing a second electronic signal corresponding thereto; electronic processing means for receiving the electronic signals and for determining from the first and second electronic signals if a leak exists in the hydraulic fluid system. ### Claim 61 (depends on 60) The vehicle of claim 60 further comprising a memory for storing the level of hydraulic fluid in the expansion tank and for storing the temperature of the hydraulic fluid in the reservoir. ### Claim 62 (depends on 60) The vehicle of claim 60 further comprising means for indicating to an operator that a leak exists in the hydraulic fluid system, thereby effecting a hydraulic fluid leak detection system. ### Claim 63 (depends on 61) The hydraulic fluid leak detection system of claim 61 wherein the memory stores a map associating with each stored hydraulic fluid level a corresponding fluid temperature. ### Claim 64 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the expansion tank covers a first horizontal area and the reservoir covers a second horizontal area, and the first horizontal area is less than the second horizontal area to effect a multiplication of the change in fluid level of the reservoir in accordance with a ratio of the horizontal areas. ### Claim 65 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the expansion tank includes a flared section at the top to accommodate fluid overflow. ### Claim 66 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the processing means is further operable for determining if the hydraulic fluid level within the system is below a predefined normal operating level. ### Claim 67 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the processing means is further operable for determining if the hydraulic fluid level within the system is above a predefined normal operating level. ### Claim 68 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the processing means is further operable for determining if the hydraulic fluid temperature within the system is above a predefined normal operating range. ### Claim 69 (depends on 60) The hydraulic fluid leak detection system of claim 60 wherein the processing means is operable to determine a rate of change of the fluid level within the expansion tank and for comparing the determined rate of change to an allowable rate of change for signalling the presence of a leak. ### Claim 70 A retrofit hydraulic fluid leak detection system for installation on a self-propelled vehicle or self-propelled machine having a hydraulically actuated device and fluid reservoir for supplying fluid for operating the hydraulically actuated device, comprising: an expansion tank in fluid communication with the reservoir, the expansion tank being adaptable for installation on the vehicle; a first sensor disposed within the expansion tank and operable for sensing the hydraulic fluid level in the expansion tank over a range of possible fluid levels in the expansion tank and for producing a first signal varying in accordance with the hydraulic fluid level; a second sensor operable for sensing the temperature level of the hydraulic fluid in the reservoir and for producing a second electronic signal corresponding thereto; electronic processing means for receiving the first and second signals and for determining from the first and second signals if a leak exists in the hydraulic system; and means for indicating to an operator that a leak exists in the hydraulic system. ### Claim 71 (depends on 70) The vehicle of claim 70 wherein the expansion tank is formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within the expansion tank. ### Claim 72 (depends on 70) The vehicle of claim 70 wherein the expansion tank and reservoir are formed at least in part of a substantially translucent material so that an operator may inspect the hydraulic fluid within each of the expansion tank and reservoir. ### Claim 73 (depends on 70) The vehicle of claim 70 wherein the reservoir and the expansion tank are integrally formed to define one tank having a reservoir portion and an expansion portion. ### Claim 74 (depends on 70) The vehicle of claim 70 wherein the reservoir and the expansion tank define two discreet tanks and a conduit communicates fluid between the reservoir and the expansion tank. ### Claim 75 (depends on 70) The vehicle of claim 70 further comprising a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck. ### Claim 76 (depends on 70) The vehicle of claim 70 further comprising: a filler neck projecting from the reservoir, and the expansion tank is formed to fluidly communicate with the reservoir through the filler neck; and a filler neck adaptor for interconnecting the filler neck of the reservoir to the expansion tank. ### Claim 77 (depends on 76) The vehicle of claim 76 wherein the adaptor may be of varying sizes and shapes to suitably connect filler necks of corresponding sizes and shapes to an expansion tank having a predetermined size and shape. ### Claim 78 (depends on 76) The vehicle of claim 76 wherein the filler neck and adaptor threadably interconnect. ### Claim 79 (depends on 76) The vehicle of claim 76 wherein the adaptor and the expansion tank are shaped to form a substantially fluidic seal when interconnected. ### Claim 80 (depends on 70) The vehicle of claim 70 further comprising an expansion tank support positioned upon the reservoir, the expansion tank being substantially seated upon the expansion tank support to support the expansion tank above the reservoir. ### Claim 81 (depends on 80) The vehicle of claim 80 wherein the expansion tank support is a generally annular support. ### Claim 82 (depends on 80) The vehicle of claim 80 wherein the expansion tank support includes a plurality of supports which support the expansion tank above the reservoir at a plurality of points. ### Claim 83 (depends on 70) The vehicle of claim 70 further comprising: a first visible marking on the expansion tank to indicate a minimum fill level at a first temperature; and a second visible marking on the expansion tank to indicate a maximum fill level at a second temperature. ### Claim 84 (depends on 83) The vehicle of claim 83 wherein the first temperature indicates a cold fluid level, and the second temperature is associated with a hot fluid level. ### Claim 85 (depends on 70) The vehicle of claim 70 wherein the expansion tank includes a fluid passage between the reservoir and the expansion tank, and the fluid passage is located in proximity to a center of the expansion tank. ### Claim 86 (depends on 70) The vehicle of claim 70 wherein the expansion tank is cylindrically shaped and the fluid passage is substantially in the center of the expansion tank in order to limit sloshing of the hydraulic fluid in the expansion tank.