# US 9,038,378 B2 · Hydrostatic transmission apparatus making improved braking possible > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,378 B2 - Document ID: US9038378B2 - Status: Granted - Kind: B2 - Application number: 13/503,207 - Filed: 2010-10-20 - Published: 2012-10-11 - Granted: 2015-05-26 - Earliest claimed: 2009-10-22 - Assignees: Poclain Hydraulics Industries - Applicants: Jean Heren; Julien Viard - Inventors: Jean Heren; Julien Viard - Web page: https://patentgrep.com/patent/US9038378B2 ## CPC - F16H 61/448: Control circuits for tandem pumps or motors - F16H 61/4052: by using a variable restriction, e.g. an orifice valve - F16H 61/4157: Control of braking, e.g. preventing pump over-speeding when motor acts as a pump - F16H: GEARING ## Abstract Hydrostatic transmission apparatus having an elementary motor with a feed enclosure and a discharge enclosure; a displacement selector suitable for taking up a bypass position, in which the feed and discharge enclosures are interconnected via a bypass link; and constriction means for constricting said bypass link. When the selector is in the bypass position, the constriction means can be activated to restrict the flow of fluid through the bypass link when the discharge pressure in the discharge enclosure exceeds a constriction threshold, said threshold being a function of a control pressure prevailing in a control chamber. ## Claims ### Claim 1 Hydrostatic transmission apparatus comprising at least a first elementary motor fed via a feed enclosure and from which fluid is discharged via a discharge enclosure, and a displacement selector, the displacement selector being suitable for taking up a bypass position, in which said feed enclosure is put into communication with said discharge enclosure via a bypass link, the apparatus further comprising constriction means for constricting said bypass link, and wherein, when the selector is in the bypass position, said constriction means are suitable for being activated to restrict the flow of fluid through the bypass link when a discharge pressure prevailing in the discharge enclosure exceeds a constriction threshold, said threshold being a function of a control pressure prevailing in a control chamber, and said constriction means are suitable for being deactivated to enable fluid to flow substantially freely through the bypass link when the discharge pressure is less than said constriction threshold. ### Claim 2 (depends on 1) Hydrostatic transmission apparatus according to claim 1, wherein, when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is a function of the control pressure. ### Claim 3 (depends on 1) Hydrostatic transmission apparatus according to claim 1, wherein, when they are activated, the constriction means make it possible to vary a through section of the bypass link, in such a manner that an increase in the feed pressure of the first motor tends to cause a decrease of said through section. ### Claim 4 (depends on 1) Hydrostatic transmission apparatus according to claim 1, further comprising a fluid distributor, the selector being disposed inside the distributor on an axis of rotation of the first elementary motor. ### Claim 5 (depends on 1) Hydrostatic transmission apparatus according to claim 1, wherein the selector includes a moving part having an outside surface that constitutes a wall of the control chamber, the pressure that is exerted on said surface inside the control chamber being suitable for causing the moving part to move, thereby causing the displacement to change. ### Claim 6 (depends on 1) Hydrostatic transmission apparatus according to claim 1, wherein the selector has a body, and the constriction means are disposed in the body of the selector. ### Claim 7 (depends on 1) Hydrostatic transmission apparatus according to claim 1, wherein the selector has a body, and a slide that is disposed in a bore in said body; and, inside said control chamber for controlling the constriction means, the control pressure is applied on the slide, making it possible to cause said slide to go into said bypass position or not to cause said slide to go into said bypass position. ### Claim 8 (depends on 7) Hydrostatic transmission apparatus according to claim 7, further comprising a main pump, and wherein: the body of the selector is provided with at least three grooves; the first groove and the second groove respectively form at least part of the discharge enclosure and at least part of the feed enclosure of the first elementary motor; the first groove is suitable for being connected to a fluid feed or fluid discharge circuit, the second groove is suitable for being connected to the first groove or to the third groove respectively when the slide of the selector is in a first position and when said slide is in a second position, the first position thus constituting the bypass position; the third groove is suitable for being connected to a fluid feed or fluid discharge circuit, e.g. to a main orifice of the main pump; the constriction means comprise a moving constriction part; and in the bypass position; when the constriction part is in a first position, the second groove is put into communication with the first groove substantially without any constriction; and when the constriction part is in at least one other position, the second groove is put into communication with the first groove and the constriction part constricts a through passage between the first groove and the second groove. ### Claim 9 (depends on 8) Hydrostatic transmission apparatus according to claim 8, further comprising a second elementary motor having a discharge enclosure and a feed enclosure formed respectively, and at least in part, by the first groove and by the third groove. ### Claim 10 (depends on 8) Hydrostatic transmission apparatus according to claim 8, further comprising a second elementary motor having a discharge enclosure formed at least in part by the first groove, and a feed enclosure, which feed enclosure is suitable for being put into communication with a fluid feed or fluid discharge circuit by additional displacement selection means. ### Claim 11 (depends on 9) Hydrostatic transmission apparatus according to claim 9, wherein the two elementary motors are part of the same hydraulic motor and are suitable for driving a common outlet member of said hydraulic motor. ### Claim 12 (depends on 8) Hydrostatic transmission apparatus according to claim 8, wherein: when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is a function of the control pressure and the constriction part, is urged in opposite directions by the control pressure and by the feed pressure; moves in a first direction and reduces the section of said through passage when the feed pressure is tending to increase above the balancing pressure; and otherwise moves in a second direction and increases said section of said through passage; whereby said constriction part makes it possible to regulate the feed pressure to the balancing pressure. ### Claim 13 (depends on 8) Hydrostatic transmission apparatus according to claim 8, wherein the constriction part comprises a slidably mounted bushing disposed in the bore, said bushing making it possible, as a function of its position relative to the grooves, to close off in part said through passage between the first and the second groove. ### Claim 14 (depends on 13) Hydrostatic transmission apparatus according to claim 13, wherein the bushing and the slide have concentric surfaces and are disposed on an axis (D) of the bore of the selector. ### Claim 15 (depends on 1) Hydrostatic transmission apparatus according to claim 1, further comprising means for causing the control pressure to vary. ### Claim 16 (depends on 7) Hydrostatic transmission apparatus according to claim 7, wherein when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is a function of the control pressure. ### Claim 17 (depends on 16) Hydrostatic transmission apparatus according to claim 16, further comprising a main pump, and wherein: the body of the selector is provided with at least three grooves; the first groove and the second groove respectively form at least part of the discharge enclosure and at least part of the feed enclosure of the first elementary motor; the first groove is suitable for being connected to a fluid feed or fluid discharge circuit, e.g. to a main orifice of the main pump; the second groove is suitable for being connected to the first groove or to the third groove respectively when the slide of the selector is in a first position and when said slide is in a second position, the first position thus constituting the bypass position; the third groove is suitable for being connected to a fluid feed or fluid discharge circuit; the constriction means comprise a moving constriction part; and in the bypass position: when the constriction part is in a first position, the second groove is put into communication with the first groove substantially without any constriction; and when the constriction part is in at least one other position, the second groove is put into communication with the first groove and the constriction part constricts a through passage between the first groove and the second groove. ### Claim 18 (depends on 2) Hydrostatic transmission apparatus according to claim 2, wherein, when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is substantially proportional to the control pressure. ### Claim 19 (depends on 12) Hydrostatic transmission apparatus according to claim 12, wherein, when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is substantially proportional to the control pressure. ### Claim 20 (depends on 16) Hydrostatic transmission apparatus according to claim 16, wherein when they are activated, said constriction means are suitable for regulating the feed pressure of the first motor to a balancing pressure that is substantially proportional to the control pressure. ### Claim 21 (depends on 8) Hydrostatic transmission apparatus according to claim 8, wherein the first groove is suitable for being connected to a main orifice of the main pump. ### Claim 22 (depends on 17) Hydrostatic transmission apparatus according to claim 17, wherein the first groove is suitable for being connected to a main orifice of the main pump.