# US 5,347,862 A · Fluid flow meter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,862 A - Document ID: US5347862A - Status: Granted - Kind: A - Application number: 07/979,996 - Filed: 1992-11-23 - Granted: 1994-09-20 - Earliest claimed: 1992-11-23 - Inventors: Dov Ingman - Web page: https://patentgrep.com/patent/US5347862A ## CPC - G01F 1/54: by means of chains, flexible bands or wires introduced into and moved by, the flow - G01F 3/20: having flexible movable walls, e.g. diaphragms, bellows - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME ## Abstract The fluid flow meter includes a flexible membrane clamped between upstream and downstream centering springs to enhance membrane behavior and extend the fluid flow measurement range by automatically adaptively moving the apparent clamping points in response to flow rate. Adaptation of the clamping span alters the relative effective excess membrane length within the clamping span to adapt membrane behavior to flow rate. The upstream centering spring includes a long leaf spring pair cantilevered into the clamping span from the clamping region. The long leaf spring pair is sandwiched within a shorter leaf spring pair active at higher flow rates and formed as part of a guide extending to the chamber surface. The membrane ends are narrowed upstream and downstream of the clamping span to reduce flutter while the upstream intake is split into even laminar flows. The fluid direction is substantially changed at the outlet to minimize membrane distortion. ## Claims ### Claim 1 A fluid flow meter, comprising: a long, flexible membrane; upstream clamping means for mounting a first end of said membrane in an upstream clamping region in a fluid flow path; downstream clamping means for mounting a second end of said membrane in a downstream clamping region in said fluid flow path at a clamping span distance downstream from said upstream clamping region, the length of said membrane between said first and second ends exceeding said clamping span distance by an excess membrane length to permit an undulating motion of said flexible membrane along said clamping span distance in response to a rate of flow of fluid in said path; sensor means responsive to said undulating motion for measuring said flow of fluid in said path; and centering spring means within said clamping span distance adjacent a first one of said clamping regions for resiliently resisting motion of said membrane from a central plane substantially parallel to said path. ### Claim 2 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: apparent clamping point means for creating an apparent clamping point whose location changes from said first one of said clamping regions by a distance responsive to said rate of flow of fluid in said path. ### Claim 3 (depends on 2) The invention of claim 2, wherein said apparent clamping point means further comprises: means for creating an apparent clamping point downstream of said upstream clamping region. ### Claim 4 (depends on 2) The invention of claim 2, wherein said apparent clamping point means further comprises: means for creating an apparent clamping point upstream of said downstream clamping region. ### Claim 5 (depends on 2) The invention of claim 2, wherein said apparent clamping point means further comprises: means for creating an apparent clamping point downstream of said upstream clamping region; and means for creating another apparent clamping point upstream of said downstream clamping region. ### Claim 6 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: adaptive clamping span means for changing an effective relative excess membrane length in response to said rate of flow of fluid in said path by creating an apparent clamping span different from said clamping span distance. ### Claim 7 (depends on 6) The invention of claim 6, wherein said adaptive clamping span means further comprises: apparent clamping point means for creating an apparent clamping point whose location changes from said first one of said clamping regions by a distance responsive to said rate of flow of fluid in said path. ### Claim 8 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: second spring means within said clamping span distance for resiliently resisting motion of said membrane adjacent a second one of said clamping regions from said central plane. ### Claim 9 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: upstream leaf spring means for applying a restoring force to said membrane beginning from and extending downstream of an apparent clamping point displaced downstream of said upstream clamping region to resist said motion of said membrane from said central plane. ### Claim 10 (depends on 9) The invention of claim 9, wherein said leaf spring means further comprises: adaptive restoring means for altering said displacement of said apparent clamping point from said upstream clamping region as a function of said rate of flow of said fluid in said path. ### Claim 11 (depends on 10) The invention of claim 10, wherein said restoring force is non-linearly related to said displacement of said apparent clamping point from said upstream clamping region. ### Claim 12 The invention of 1, wherein said centering spring means further comprises: downstream leaf spring means for applying a restoring force to said membrane beginning from and extending upstream of an apparent clamping point displaced upstream of said downstream clamping region to resist said motion of said membrane from said central plane. ### Claim 13 (depends on 12) The invention of claim 12, wherein said downstream leaf spring means further comprises: downstream adaptive restoring means for altering said displacement of said apparent clamping point from said downstream clamping region as a function of said rate of flow of said fluid in said path. ### Claim 14 (depends on 13) The invention of claim 13, wherein said restoring force is non-linearly related to said displacement of said apparent clamping point from said downstream clamping region. ### Claim 15 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: upstream leaf spring means for applying a restoring force to said membrane beginning from and extending downstream of an apparent clamping point displaced downstream of said upstream clamping region to resist said motion of said membrane from said central plane; and downstream leaf spring means for applying a restoring force to said membrane beginning from and extending upstream of an apparent clamping point displaced upstream of said downstream clamping region to resist said motion of said membrane from said central plane. ### Claim 16 (depends on 15) The invention of claim 15 wherein said leaf spring means further comprise: adaptive restoring means for altering said displacements of said apparent clamping points as a function of said rate of flow of said fluid in said path. ### Claim 17 (depends on 15) The invention of claim 15 wherein said restoring forces are non-linearly related to said displacement of said apparent clamping points. ### Claim 18 (depends on 1) The invention of claim 1 wherein said centering spring means further comprises: leaf spring means for adaptively restoring elastic energy to said membrane in response to motion of said membrane from said central plane. ### Claim 19 (depends on 18) The invention of claim 18, wherein said leaf spring means further comprises: upstream leaf spring means for restoring elastic energy to said membrane in response to motion of said membrane adjacent said upstream clamping region. ### Claim 20 The invention of 18, wherein said leaf spring means further comprises: downstream leaf spring means for restoring elastic energy to said membrane in response to motion of said membrane adjacent said downstream clamping region. ### Claim 21 (depends on 18) The invention of claim 18, wherein said leaf spring means further comprises: upstream leaf spring means for restoring elastic energy to said membrane in response to motion of said membrane adjacent said upstream clamping region; and downstream leaf spring means for restoring elastic energy to said membrane in response to motion of said membrane adjacent said downstream clamping region. ### Claim 22 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: leaf spring means for modifying the behavior of said membrane to simulate the behavior of a membrane having a different length. ### Claim 23 (depends on 22) The invention of claim 22, wherein said leaf spring means further comprises: upstream leaf spring means for modifying the behavior of said membrane to simulate the behavior of a membrane extending upstream of said upstream clamping region. ### Claim 24 (depends on 22) The invention of claim 22, wherein said leaf spring means further comprises: downstream leaf spring means for modifying the behavior of said membrane to simulate the behavior of a membrane extending downstream of said downstream clamping region. ### Claim 25 (depends on 22) The invention of claim 22, wherein said leaf spring means further comprises: downstream leaf spring means for modifying the behavior of said membrane to simulate the behavior of a membrane extending downstream of said downstream clamping region; and upstream leaf spring means for modifying the behavior of said membrane to simulate the behavior of a membrane extending upstream of said upstream clamping region. ### Claim 26 (depends on 1) The invention of claim 1 wherein said centering spring means further comprises: leaf spring means for modifying the resonant frequency of said membrane. ### Claim 27 (depends on 1) The invention of claim 1, wherein said centering spring means further comprises: a pair of equal length inner leaf springs cantilever supported on either side of said membrane by said upstream clamping region and extending downstream therefrom a first flexure point distance along said central plane. ### Claim 28 (depends on 27) The invention of claim 27, wherein said centering spring means further comprises: a pair of equal length outer leaf springs cantilever supported on either side of said inner leaf springs by said upstream clamping region and extending downstream therefrom along said central plane to a second flexure point at a distance shorter than said first flexure point distance. ### Claim 29 (depends on 28) The invention of claim 28, wherein said outer leaf springs each further comprise: a permeable, flexible guide extending outward from said second flexure point away from said central plane. ### Claim 30 (depends on 29) The invention of claim 29 wherein each said flexible guide further comprises: a pair of outboard windows for directing substantially equal streams of fluid downstream to enhance membrane behavior. ### Claim 31 (depends on 1) The invention of claim 1, wherein said membrane further comprises: a clamping span width within said clamping span distance; and a first end width narrower than said clamping span width at a first one of said membrane ends. ### Claim 32 (depends on 31) The invention of claim 31, wherein said membrane further comprises: a second end width narrower than said clamping span width at a second one of said membrane ends. ### Claim 33 (depends on 1) The invention of claim 1, wherein said upstream clamping means further comprises: leading edge means for dividing said flow of said fluid in said path into a pair of streams of equal, rectangular cross sectional area to reduce turbulence downstream of said upstream clamping means. ### Claim 34 (depends on 1) The invention of claim 1, wherein said downstream clamping means further comprises: flow redirecting means for substantially altering said path downstream of said clamping span distance to enhance membrane behavior at said second end. ### Claim 35 (depends on 2) The invention of claim 2, wherein said apparent clamping point means further comprises: means for creating an apparent clamping point downstream of said downstream clamping region. ### Claim 36 (depends on 2) The invention of claim 2, wherein said apparent clamping point means further comprises: means for creating an apparent clamping point downstream of said upstream clamping region; and means for creating another apparent clamping point downstream of said downstream clamping region. ### Claim 37 A fluid flow meter, comprising: a flexible membrane having a first length; a fluid flow chamber including a fluid flow inlet port and a fluid flow exit port and a fluid flow path defined therebetween; a first pair of flexible leaf springs; inlet clamping means for clamping said pair of leaf springs to lie flat along either side of a first end of said membrane adjacent said fluid flow inlet port in a central plane in said fluid flow chamber; and exit clamping means for clamping a second end of said membrane in said central plane adjacent said fluid flow exit port at a distance from said first end less than said first length, whereby undulation of said membrane at said first end is resisted by said pair of leaf springs. ### Claim 38 (depends on 37) The invention of claim 37, wherein said first pair of leaf springs further comprises: a second pair of equal length leaf springs. ### Claim 39 (depends on 37) The invention of claim 37, further comprising: a second pair of equal length leaf springs, shorter than said first pair, said second pair of leaf springs being clamped by said inlet clamping means to lie flat along either side of said first pair of leaf springs in said fluid flow chamber. ### Claim 40 (depends on 38) The invention of claim 38, further comprising: a third pair of equal length leaf springs, said third pair of leaf springs being clamped by said exit clamping means to lie flat along said second end of said membrane in said central plane in said fluid flow chamber, whereby said undulation of said membrane at said second end is resisted by said third pair of leaf springs. ### Claim 41 (depends on 38) The invention of claim 38, wherein each of said leaf springs in said second pair of leaf springs further comprises: a permeable, flexible guide extending outward a downstream end thereof toward an inner surface of said fluid flow chamber. ### Claim 42 (depends on 41) The invention of claim 41 wherein each said flexible guide further comprises: a pair of outboard windows for directing substantially equal streams of fluid in said fluid flow chamber to enhance membrane behavior. ### Claim 43 (depends on 37) The invention of claim 37, wherein said membrane further comprises: a first width within said fluid flow chamber; and a second width narrower than said first width at a first one of said first and second ends of said membrane. ### Claim 44 (depends on 43) The invention of claim 43, wherein said membrane further comprises: a third width narrower than said first width at a second one of said membrane ends. ### Claim 45 (depends on 37) The invention of claim 37, wherein said inlet clamping means further comprises: leading edge means for dividing said flow of said fluid in said fluid flow path into a pair of streams of equal, rectangular cross sectional area to reduce turbulence downstream of said inlet clamping means. ### Claim 46 (depends on 37) The invention of claim 37, wherein said exit clamping means further comprises: flow redirecting means for substantially altering said fluid flow path downstream of said exit clamping means. ### Claim 47 A method for enhancing the behavior of a flexible membrane in a fluid flow meter, comprising the steps of: mounting a flexible membrane in a fluid flow chamber; clamping a first pair of leaf springs to lie against said membrane along either side of a first end of said membrane in a central plane in said fluid flow chamber; and clamping a second end of said membrane in said central plane, whereby undulation of said membrane at said first end is resisted by said pair of leaf springs. ### Claim 48 (depends on 47) The invention of claim 47, wherein the step of clamping said first pair of leaf springs further comprises the step of: clamping a second pair of leaf springs, shorter than said first pair, to lie along either side of said first pair of leaf springs in said fluid flow chamber. ### Claim 49 (depends on 48) The invention of claim 48, wherein the step of clamping said second end of said membrane further comprises the step of: clamping a third pair of leaf springs to lie along said central plane at said second end of said membrane. ### Claim 50 (depends on 48) The invention of claim 48, wherein the step of clamping said second end of said membrane further comprises the step of: mounting a permeable guide extending outward from each of said second pair of leaf springs toward an inner surface of said fluid flow chamber. ### Claim 51 (depends on 48) The invention of claim 48, further comprising the step of: directing a pair of equal streams of fluid in said fluid flow chamber on each side of said membrane. ### Claim 52 (depends on 47) The invention of claim 47, further comprising the step of: reducing the width of said membrane within said fluid flow chamber adjacent one end of said membrane. ### Claim 53 (depends on 52) The invention of claim 52, wherein said step of reducing the width of the membrane further comprises the step of: reducing the width of said membrane at the other end of said membrane. ### Claim 54 (depends on 47) The invention of claim 47, wherein said step of mounting said first pair of leaf springs further comprises: dividing said flow of said fluid in said chamber into a pair of streams of equal, rectangular cross-section, one of said streams flowing above and one of said streams flowing below said membrane. ### Claim 55 (depends on 47) The invention of claim 47, wherein said step of clamping said second end of said membrane further comprises the step of: substantially altering said fluid flow path downstream of said second end.