# US 2025/0146549 A1 · Drum brake assembly and wear sensor device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0146549 A1 - Document ID: US20250146549A1 - Status: Published application - Kind: A1 - Application number: 18/503,331 - Filed: 2023-11-07 - Published: 2025-05-08 - Earliest claimed: 2023-11-07 - Assignees: ArvinMeritor Technology, LLC - Applicants: ArvinMeritor Technology, LLC - Inventors: Prathap Babu - Web page: https://patentgrep.com/patent/US20250146549A1 ## CPC - F16D 65/22: adapted for pressing members apart {, e.g. for drum brakes} - F16D 66/024: {Sensors mounted on braking members adapted to contact the brake disc or drum, e.g. wire loops severed on contact} - F16D 51/20: extending in opposite directions from their pivots - F16D 51/22: mechanically actuated - F16D 66/023: {directly sensing the position of braking members} - F16D 66/026: {indicating different degrees of lining wear} - F16D 66/027: {Sensors therefor} - F16D 2125/30: acting on two or more cam followers, e.g. S-cams - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## Abstract A drum brake assembly comprising first and second brake pad assemblies and a wear sensor device. The wear sensor device comprises a sleeve, a plunger, and a sensor. The sleeve is coupled to the first brake pad assembly. The plunger is coupled to the second brake pad assembly. The sensor provides a signal indicative of a position of the plunger with respect to the sleeve. ## Claims ### Claim 1 A drum brake assembly comprising: first and second brake pad assemblies; and a wear sensor device that comprises: a plunger that is coupled to the first brake pad assembly; a sleeve that is coupled to the second brake pad assembly, wherein the plunger is moveable with respect to the sleeve; and a sensor that provides a signal indicative of a position of the plunger with respect to the sleeve. ### Claim 2 (depends on 1) The drum brake assembly of claim 1 wherein the sensor is disposed on the sleeve and the plunger is moveable with respect to the sensor. ### Claim 3 (depends on 1) The drum brake assembly of claim 1 wherein the sleeve further comprises a sleeve hole and the plunger is at least partially disposed inside the sleeve hole. ### Claim 4 (depends on 1) The drum brake assembly of claim 1 wherein the plunger is moveable with respect to the sleeve when the first and second brake pad assemblies are actuated away from each other. ### Claim 5 (depends on 1) The drum brake assembly of claim 1 wherein the plunger does not move with respect to the sleeve when the first and second brake pad assemblies are retracted toward each other. ### Claim 6 (depends on 1) The drum brake assembly of claim 1 wherein the wear sensor device further comprises a first mount that extends from the first brake pad assembly, wherein the first mount further comprises a first mount hole, and the plunger extends through the first mount hole. ### Claim 7 (depends on 6) The drum brake assembly of claim 6 wherein the plunger further comprises an enlarged head that is sized to not pass through the first mount hole, wherein the enlarged head is engageable with a side of the first mount that faces away from the sleeve. ### Claim 8 (depends on 7) The drum brake assembly of claim 7 wherein the plunger extends along a wear sensor device axis, the enlarged head is disposed at a first end of the plunger, and the first mount hole is axially positioned between the enlarged head and the sleeve. ### Claim 9 (depends on 1) The drum brake assembly of claim 1 wherein the sleeve further comprises a sleeve hole, the plunger further comprises a core that is received in the sleeve hole, and the signal generated by the sensor is indicative of a position of the core with respect to the sensor. ### Claim 10 (depends on 9) The drum brake assembly of claim 9 wherein the core further comprises a body, first and second arms that extend from the body, and first and second pads that extend from the first and second arms, respectively, wherein the first and second pads engage the sleeve. ### Claim 11 (depends on 10) The drum brake assembly of claim 10 wherein the body and the first and second arms do not contact the sleeve. ### Claim 12 (depends on 10) The drum brake assembly of claim 10 wherein a gap extends between the first and second pads. ### Claim 13 (depends on 12) The drum brake assembly of claim 12 wherein the gap extends between the first and second arms. ### Claim 14 (depends on 10) The drum brake assembly of claim 10 wherein the first and second arms bias the first and second pads, respectively, against the sleeve. ### Claim 15 (depends on 10) The drum brake assembly of claim 10 wherein the first pad further comprises material that is detectable by the sensor. ### Claim 16 (depends on 6) The drum brake assembly of claim 6 wherein the plunger further comprises a core that is received inside the sleeve, the wear sensor device further comprises a second mount that couples the sleeve to the second brake pad assembly, and the sleeve further comprises a free end that is disposed opposite the second mount, wherein the core is positioned closer to the free end of the sleeve as thickness of friction material of the first brake pad assembly decreases. ### Claim 17 (depends on 1) The drum brake assembly of claim 1 wherein the sensor comprises a linear variable differential transformer. ### Claim 18 (depends on 1) The drum brake assembly of claim 1 wherein the drum brake assembly further comprises a camshaft that is rotatable about a camshaft axis to actuate the first and second brake pad assemblies, wherein the camshaft axis intersects the wear sensor device. ### Claim 19 (depends on 1) The drum brake assembly of claim 1 further comprising first and second cam rollers that engage the first and second brake pad assemblies, respectively, and a camshaft that is rotatable about a camshaft axis to actuate the first and second brake pad assemblies, wherein the camshaft further comprises a cam that engages the first and second cam rollers, and the wear sensor device extends across the cam. ### Claim 20 (depends on 19) The drum brake assembly of claim 19 wherein the wear sensor device extends across the first and second cam rollers.