CA979786A - Power transmission - Google Patents

Power transmission

Info

Publication number
CA979786A
CA979786A CA166,460A CA166460A CA979786A CA 979786 A CA979786 A CA 979786A CA 166460 A CA166460 A CA 166460A CA 979786 A CA979786 A CA 979786A
Authority
CA
Canada
Prior art keywords
power transmission
transmission
power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA166,460A
Other languages
English (en)
Inventor
Robert G. Farrell
Carl R. Binkley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sperry Corp
Original Assignee
Sperry Rand Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sperry Rand Corp filed Critical Sperry Rand Corp
Priority to IN2141/CAL/73A priority Critical patent/IN138725B/en
Application granted granted Critical
Publication of CA979786A publication Critical patent/CA979786A/en
Expired legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/163Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/0416Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor with means or adapted for load sensing
    • F15B13/0417Load sensing elements; Internal fluid connections therefor; Anti-saturation or pressure-compensation valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/06Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with two or more servomotors
    • F15B13/08Assemblies of units, each for the control of a single servomotor only
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/20Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205Systems with pumps
    • F15B2211/2053Type of pump
    • F15B2211/20546Type of pump variable capacity
    • F15B2211/20553Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/30525Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053In combination with a pressure compensating valve
    • F15B2211/30535In combination with a pressure compensating valve the pressure compensating valve is arranged between pressure source and directional control valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/30525Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053In combination with a pressure compensating valve
    • F15B2211/3055In combination with a pressure compensating valve the pressure compensating valve is arranged between directional control valve and return line
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/31Directional control characterised by the positions of the valve element
    • F15B2211/3105Neutral or centre positions
    • F15B2211/3111Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/505Pressure control characterised by the type of pressure control means
    • F15B2211/50509Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/505Pressure control characterised by the type of pressure control means
    • F15B2211/50509Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50536Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using unloading valves controlling the supply pressure by diverting fluid to the return line
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/515Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5157Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source and a return line
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/515Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5159Pressure control characterised by the connections of the pressure control means in the circuit being connected to an output member and a return line
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/55Pressure control for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/57Control of a differential pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71Multiple output members, e.g. multiple hydraulic motors or cylinders
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/86493Multi-way valve unit
    • Y10T137/86574Supply and exhaust
    • Y10T137/8667Reciprocating valve
    • Y10T137/86694Piston valve
    • Y10T137/86702With internal flow passage
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87169Supply and exhaust
    • Y10T137/87177With bypass
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/877With flow control means for branched passages
    • Y10T137/87829Biased valve
    • Y10T137/87837Spring bias
    • Y10T137/87845For valve having a ball head
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/877With flow control means for branched passages
    • Y10T137/87885Sectional block structure
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87917Flow path with serial valves and/or closures
    • Y10T137/88054Direct response normally closed valve limits direction of flow

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Multiple-Way Valves (AREA)
  • Valve Housings (AREA)
  • Safety Valves (AREA)
CA166,460A 1972-04-18 1973-03-20 Power transmission Expired CA979786A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
IN2141/CAL/73A IN138725B (fr) 1973-03-20 1973-09-20

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US24510372A 1972-04-18 1972-04-18

Publications (1)

Publication Number Publication Date
CA979786A true CA979786A (en) 1975-12-16

Family

ID=22925300

Family Applications (1)

Application Number Title Priority Date Filing Date
CA166,460A Expired CA979786A (en) 1972-04-18 1973-03-20 Power transmission

Country Status (9)

Country Link
US (1) US3774635A (fr)
JP (1) JPS5316527B2 (fr)
AU (1) AU476156B2 (fr)
CA (1) CA979786A (fr)
DE (1) DE2319018C3 (fr)
FR (1) FR2180912B1 (fr)
GB (1) GB1424574A (fr)
IT (1) IT979832B (fr)
SE (1) SE392750B (fr)

Families Citing this family (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3976098A (en) * 1974-01-02 1976-08-24 International Basic Economy Corporation Hydraulic motor control apparatus
US4187877A (en) * 1975-01-13 1980-02-12 Commercial Shearing Inc. Compensated work port fluid valves
US4087972A (en) * 1976-08-02 1978-05-09 The Weatherhead Company Brake booster with spring type ratio changer
DE2943256A1 (de) * 1979-10-26 1981-05-07 Erwin Hengstler Hydraulik GmbH, 7613 Hausach Elektrohydraulische steuerung
SE450516B (sv) * 1980-11-27 1987-06-29 Vapormatic Co Ltd Fordelningsventil for hydraulsystemet pa en lantbrukstraktor
US4555766A (en) * 1981-10-09 1985-11-26 General Signal Corporation Brake control system for vehicles
US4519419A (en) * 1982-06-15 1985-05-28 Commercial Shearing, Inc. Hydraulic valves
US4520841A (en) * 1983-12-27 1985-06-04 Glen Brand Four-way valve
FR2562632B1 (fr) * 1984-04-18 1986-12-12 Bennes Marrel Distributeur hydraulique du type proportionnel, avec prise d'informations concernant les plus fortes pressions dans les circuits d'utilisation
JPS62151403U (fr) * 1986-03-18 1987-09-25
US4724673A (en) * 1986-06-30 1988-02-16 Vickers, Incorporated Power transmission
US4665801A (en) * 1986-07-21 1987-05-19 Caterpillar Inc. Compensated fluid flow control valve
US4688470A (en) * 1986-07-21 1987-08-25 Caterpillar Inc. Compensated fluid flow control valve
US4679492A (en) * 1986-07-21 1987-07-14 Caterpillar Inc. Compensated fluid flow control valve
US4694731A (en) * 1986-12-22 1987-09-22 Caterpillar Inc. Load compensated valve
US4741248A (en) * 1987-05-08 1988-05-03 Caterpillar Inc. Load responsive system having synchronizing systems between positive and negative load compensation
JPH01145401A (ja) * 1987-10-02 1989-06-07 Applied Power Inc 流れ調整弁
DE3833999A1 (de) * 1988-10-06 1990-04-12 Bosch Gmbh Robert Hydraulische steuereinrichtung
DE69015118T2 (de) * 1989-03-24 1995-05-04 Hitachi Construction Machinery Co., Ltd., Tokio/Tokyo Ventilanordnung und hydraulisches antriebssystem.
FR2694964B1 (fr) * 1992-08-21 1994-11-04 Rexroth Sigma Circuit hydraulique de commande d'un distributeur du type à division de débit indépendant de la charge.
US6148856A (en) * 1998-03-19 2000-11-21 Linde Aktiengesellschaft Control valve
DE19829530B4 (de) * 1998-07-02 2005-01-20 Hoerbiger Micro Fluid Gmbh Ventilanordnung
FR2857704B1 (fr) * 2003-07-16 2007-12-28 Bosch Rexroth Dsi Sas Distributeur hydraulique a fentes de couple
JP4719450B2 (ja) * 2004-11-08 2011-07-06 株式会社豊田自動織機 油圧制御装置、及び油圧回路
KR20160040581A (ko) * 2013-08-13 2016-04-14 볼보 컨스트럭션 이큅먼트 에이비 건설기계용 유량 제어밸브
CN104197046B (zh) * 2014-09-11 2016-10-05 宁波市博尔法液压有限公司 一种带卸荷保护的多路阀
CN110778555B (zh) * 2019-10-31 2021-03-05 徐州阿马凯液压技术有限公司 一种嵌入式压力补偿阀杆

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586932A (en) * 1949-07-25 1952-02-26 Vickers Inc Power transmission
US2980136A (en) * 1959-06-25 1961-04-18 Cessna Aircraft Co Hydraulic flow control system and valve with anti-cavitation feature
NL123239C (fr) * 1962-03-30 1900-01-01
US3266520A (en) * 1964-07-15 1966-08-16 Fluid Power Accessories Inc Hydraulic valves
FR1545439A (fr) * 1966-12-13 1968-11-08 Beringer Hydraulik Gmbh Dispositif de commande pour installations fonctionnant par voie hydraulique
US3506031A (en) * 1967-10-06 1970-04-14 Parker Hannifin Corp Relief-makeup check assembly for directional control valves
FR1585677A (fr) * 1968-09-10 1970-01-30
US3557824A (en) * 1968-11-01 1971-01-26 Cessna Aircraft Co Spool control valve

Also Published As

Publication number Publication date
DE2319018B2 (de) 1978-09-21
IT979832B (it) 1974-09-30
DE2319018C3 (de) 1982-10-28
JPS4919282A (fr) 1974-02-20
FR2180912A1 (fr) 1973-11-30
SE392750B (sv) 1977-04-18
AU5301973A (en) 1974-09-12
US3774635A (en) 1973-11-27
JPS5316527B2 (fr) 1978-06-01
AU476156B2 (en) 1976-09-16
DE2319018A1 (de) 1973-10-25
GB1424574A (en) 1976-02-11
FR2180912B1 (fr) 1978-12-01

Similar Documents

Publication Publication Date Title
CA994250A (en) Power transmission
CA979786A (en) Power transmission
AU469183B2 (en) Power transmission
AU467692B2 (en) Power transmission
AU463815B2 (en) Power transmission
CA962163A (en) Power transmission
AU4376272A (en) Power transmission
CA982022A (en) Power transmission
AU6029173A (en) Power transmission
AU4376172A (en) Power transmission
CA982019A (en) Power transmission
AU464393B2 (en) Power transmission
AU453431B2 (en) Transmission assembly
AU4105472A (en) Power transmission
AU3698071A (en) Power transmission
AU4369672A (en) Power transmission
CA911768A (en) Power transmission
CA892363A (en) Power transmission
CA894561A (en) Power transmission
AU463218B2 (en) Power transmission
CA975581A (en) Power transmission belts
CA906258A (en) Split power transmission
CA892896A (en) Variable power transmission
CA911767A (en) Power transmission mechanism
CA911205A (en) Power transmission mechanism