US3918213A - Overspeed safety control mechanism for rotary tools - Google Patents

Overspeed safety control mechanism for rotary tools Download PDF

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Publication number
US3918213A
US3918213A US484719A US48471974A US3918213A US 3918213 A US3918213 A US 3918213A US 484719 A US484719 A US 484719A US 48471974 A US48471974 A US 48471974A US 3918213 A US3918213 A US 3918213A
Authority
US
United States
Prior art keywords
counterbalancing
diaphragm
motor
chamber
valve
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 - Lifetime
Application number
US484719A
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English (en)
Inventor
Emmet E Stout
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.)
Chicago Pneumatic Tool Co LLC
Original Assignee
Chicago Pneumatic Tool Co LLC
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 Chicago Pneumatic Tool Co LLC filed Critical Chicago Pneumatic Tool Co LLC
Priority to US484719A priority Critical patent/US3918213A/en
Priority to GB20883/75A priority patent/GB1485906A/en
Priority to IN1004/CAL/1975A priority patent/IN143466B/en
Priority to IT49804/75A priority patent/IT1035854B/it
Priority to CA227,979A priority patent/CA1025738A/en
Priority to FR7518470A priority patent/FR2276901A1/fr
Priority to JP50072801A priority patent/JPS5115288A/ja
Priority to NL7507746A priority patent/NL7507746A/xx
Priority to SE7507473A priority patent/SE7507473L/xx
Application granted granted Critical
Publication of US3918213A publication Critical patent/US3918213A/en
Assigned to NATIONAL WESTMINSTER BANK USA reassignment NATIONAL WESTMINSTER BANK USA SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CHICAGO PNEUMATIC TOOL COMPANY
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B55/00—Safety devices for grinding or polishing machines; Accessories fitted to grinding or polishing machines for keeping tools or parts of the machine in good working condition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
    • F01B25/00—Regulating, controlling or safety means
    • F01B25/02—Regulating or controlling by varying working-fluid admission or exhaust, e.g. by varying pressure or quantity
    • F01B25/04—Sensing elements
    • F01B25/06—Sensing elements responsive to speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
    • F01B25/00—Regulating, controlling or safety means
    • F01B25/16—Safety means responsive to specific conditions
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
    • G05D13/02—Details
    • G05D13/04—Details providing for emergency tripping of an engine in case of exceeding maximum speed

Definitions

  • the invention is particularly applicable to pneumatically powered tools such as rotary surface grinders.
  • Such tools are usually equipped with a speed governor.
  • Speed governors are at times for various reasons subject to failure or faulty operation. Since tools of this nature are usually designed to operate at high speed, an undesirable and hazardous condition could develop should the governor fail to properly function.
  • an object of this invention is to provide mechanism to supplement the governor which will automatically operate to discontinue operation of the motor should the governor fail tooperate.
  • Another object of the invention is -to provide in a pneumatically powered rotary ,tool, such as a surface grinder, .overspeed safety control mechanism which will respond automatically to development of a predetermined speed condition of the motor to shut off flow of operating air so as to cause the motor to come to a stop.
  • a further object of this invention is to provide improved and efficiently operating overspeed safety control mechanism for pneumatically powered rotary tools, particularly high speed surface grinders.
  • a rotary tool including a rotary air motor, an inlet passage for admitting live air to the motor, a manipulative throttle valve in the passage for initiating live air flow through the passage, a diaphragm operable control valve in the inlet passage between the throttle valve and the motor normally pneumatically balanced in open condition under pressure of air flowing through the passage, the passage having communication with the front and rear faces of the diaphragm, the control valve'being responsive to releasing of the pressure of air communicated to the rear face of the diaphragm to move to a closed condition in the passage blocking flow of air to the motor, and means responsive to a predetermined value of centrifugal force developed by the motor to release the pressure of air communicated to the rear face-of the diaphragm.
  • a vertical pneumatically powered surface grinding tool having a housing 10 in which is housed a rotary air driven motor 11 having a rotor 12, here of the slidable vane type.
  • the rotor is operable in a chamber 13 defined by a surrounding liner l4 closedover at opposite ends by end plates 15 and 16.
  • the usual guard 22 protectively skirts the wheel.
  • a cup 23 formed on the upper surface of the upper end plate 15 is fitted with a bearing in which an upper end 24 of the shaft is supported.
  • Shaft end 24 carries the supporting body 25 of a speed governor unit 26 located in a governorchamber 27 defined by'a crowncap section 28 of the housing, only half of the governor unit being shown for clarity of illustration.
  • An operating air inlet port 29 opening into the governor chamber communicates through the latter with a passage 31 leading through the upper end plate 15 to the motor chamber.
  • Governor flyweights 32 pivoted in the governor body are centrifugally responsive, accordingly as the speed of the motor varies relative to a predetermined rate, to slide a governor valve 33 against the bias of a return spring in restricting relation to the inlet port 29, whereby flow of inlet air to operate the motor is regulated and the speed of the motor is maintained at a substantially constant rate.
  • the housing 10 includes a pairof laterally projecting handles, a portion of one being shown at 30 which are adapted to be held by the operator when applying the grinding wheel to the work surface.
  • An air passage 34 extending through handle 30 is connectible at its inlet end to an external source of operating air.
  • the opposite end of the handle passage connects through a safety air shut-off control valve unit 35 with a passage 36 leading through the housing to the inlet port 29.
  • the usual lever operated throttle valve (generally indicated at 20) which is subject to the control of the operator, is incorporated in the handle passage. When the throttle valve is actuated to its open condition, source air flows through the handle and connecting passages to operate the motor.
  • the governor should fail to effectively operate and as a result the motor should develop an overspeeding condition; that is, a rate of speed at a predetermined level above that controlled by the governor, the control valve unit will be automatically actuated to effectively shut off further flow of operating air to the motor and disable the latter from being further operated until the operator intervenes and makes any required repairs.
  • the controlvalve unit 35 includes a valve bushing 37 fitted in the housing having a valve seat opening 38 communicating upstream through a valve chamber 39 with the handle inlet passage 34, and communicating downstream through radial ports 41 in the bushing with the housing passage 36 leading to the inlet port 29.
  • a diaphragm actuable control valve 42 is connected by a pilot or stem with an actuating diaphragm 44 sandwiched in the housing.
  • Valve 42 is normally held by the diaphragm in a condition suspended in the valve chamber clear of the walls of the latter and in open relation to the valve seat, as in FIG. 1.
  • the counterbalancing chamber has a pressure relief passage 46 which is normally sealed by means of a hollow frangible air releaase plug 47.
  • a hollow frangible air releaase plug 47 When the plug is ruptured, the pneumatically balanced condition of the valve will be upset as pressure air is dumped from chamber 45, and the valve will abruptly close upon its seat.
  • the plug is supported in the housing by means of a head 48 which is threadedly engaged in the housing.
  • the plug passes slidably and radially through the side wall of the lower bearing cup 17 into an annular vented space 51 above the lower bearing 18.
  • the interior of the plug communicates by radial ports 52 in the head of the plug with the relief passage 46 and is sealed at its outer end by means of a frangible tip 53 (FIG. 2).
  • An annular groove adjacent the tip provides a weakened area permitting the tip to be sheared off when struck a sharp blow so as to allow the pressure air to be dumped from the counterbalancing chamber.
  • the tip 53 of the plug is located in close radially spaced relationship to the periphery of a collar portion 54 of the rotor shaft.
  • a flyweight 55 carried by the collar is responsive to centrifugal forces developed by an overspeedin g condition of the motor to strike and shear off the tip of the plug.
  • the flyweight is riveted to the outer face of a resilient curved spring 56 (FIG. 2).
  • the latter is anchored at its opposite end 57 to the periphery of the collar 54.
  • the spring extends for about 90 about the collar lying upon the peripheral surface of the latter.
  • a rotary grinding tool including a grinding wheel and a pneumatically powered motor having a spindle carrying the wheel, a live air inlet chamber having an inlet connecting with a supply passage and an outlet communicating with the motor, a valve controlling air flow through the inlet, a diaphragm dividing the inlet chamber off from a pressure counterbalancing chamber, an axially extending stem operatively connecting the diaphragm with the valve, the diaphragm being responsive to inlet air pressure over a front face thereof exposed to the inlet chamber to draw the valve to a closed condition and being responsive to a counterbalancing air pressure over a rear face of the diaphragm exposed to the counterbalancing chamber to hold the valve in a normal open condition, a passage in the stem communicating the inlet chamber with the counterbalancing chamber so as to develop the counterbalancing air pressure over the rear face of the diaphragm, a relief passage connected with the counterbalancing chamber for relieving the latter of the counterbalancing pressure and as a consequence allowing
  • the plug has an internal passage communicating with the relief passage
  • the flyweight means includes a curved spring fixed at one end to the spindle and carrying a flyweight at its other end
  • the plug has an externally projecting frangible closure tip disposed on a level with the flyweight and in a predetermined centrifugally projected orbit of the flyweight.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Grinding-Machine Dressing And Accessory Apparatuses (AREA)
US484719A 1974-07-01 1974-07-01 Overspeed safety control mechanism for rotary tools Expired - Lifetime US3918213A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US484719A US3918213A (en) 1974-07-01 1974-07-01 Overspeed safety control mechanism for rotary tools
GB20883/75A GB1485906A (en) 1974-07-01 1975-05-16 Overspeed safety control mechanism for rotary tools
IN1004/CAL/1975A IN143466B (enExample) 1974-07-01 1975-05-20
IT49804/75A IT1035854B (it) 1974-07-01 1975-05-27 Perfezionamento nei sistemi di sicurezza contro eccessi divelocita per utensili rotanti
CA227,979A CA1025738A (en) 1974-07-01 1975-05-28 Overspeed safety control mechanism for rotary tools
FR7518470A FR2276901A1 (fr) 1974-07-01 1975-06-12 Outil pneumatique rotatif equipe d'un dispositif de protection contre les survitesses
JP50072801A JPS5115288A (en) 1974-07-01 1975-06-17 Kaitenkoguno kakaitenboshisochi
NL7507746A NL7507746A (nl) 1974-07-01 1975-06-30 Veiligheidsregelmechanisme voor te grote snelheid van draaiwerktuigen.
SE7507473A SE7507473L (sv) 1974-07-01 1975-06-30 Sekerhetsregleranordning for att forhindra overhastighet hos roterande verktyg.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US484719A US3918213A (en) 1974-07-01 1974-07-01 Overspeed safety control mechanism for rotary tools

Publications (1)

Publication Number Publication Date
US3918213A true US3918213A (en) 1975-11-11

Family

ID=23925320

Family Applications (1)

Application Number Title Priority Date Filing Date
US484719A Expired - Lifetime US3918213A (en) 1974-07-01 1974-07-01 Overspeed safety control mechanism for rotary tools

Country Status (9)

Country Link
US (1) US3918213A (enExample)
JP (1) JPS5115288A (enExample)
CA (1) CA1025738A (enExample)
FR (1) FR2276901A1 (enExample)
GB (1) GB1485906A (enExample)
IN (1) IN143466B (enExample)
IT (1) IT1035854B (enExample)
NL (1) NL7507746A (enExample)
SE (1) SE7507473L (enExample)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1066920A3 (en) * 1999-06-29 2003-06-04 Fuji Air Tools Co., Ltd. Air tool provided with safety device
US20060067800A1 (en) * 2004-09-30 2006-03-30 Ati Industrial Automation, Inc. Force-balanced air supply for pneumatic tools

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5363109U (enExample) * 1976-10-30 1978-05-27

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3369328A (en) * 1965-02-08 1968-02-20 Minnesota Mining & Mfg Abrading machinery
US3910030A (en) * 1973-09-12 1975-10-07 Ise Electronics Corp Digital clocks

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2291101A (en) * 1939-08-05 1942-07-28 Armstrong Machine Works Electromagnetic valve
US2314218A (en) * 1942-09-03 1943-03-16 Ingersoll Rand Co Safety device
GB1109800A (en) * 1965-11-18 1968-04-18 Broom & Wade Ltd Improvements in or relating to rotary air motors
US3410030A (en) * 1966-01-11 1968-11-12 Chicago Pneumatic Tool Co Safety overspeed control mechanism for rotary tools
GB1366482A (en) * 1971-11-03 1974-09-11 Broom & Wade Ltd Rotary air motors
US3923429A (en) * 1974-06-03 1975-12-02 Chicago Pneumatic Tool Co Overspeed safety device for rotary tools

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3369328A (en) * 1965-02-08 1968-02-20 Minnesota Mining & Mfg Abrading machinery
US3910030A (en) * 1973-09-12 1975-10-07 Ise Electronics Corp Digital clocks

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1066920A3 (en) * 1999-06-29 2003-06-04 Fuji Air Tools Co., Ltd. Air tool provided with safety device
US20060067800A1 (en) * 2004-09-30 2006-03-30 Ati Industrial Automation, Inc. Force-balanced air supply for pneumatic tools
US7396197B2 (en) * 2004-09-30 2008-07-08 Ati Industrial Automation, Inc. Force-balanced air supply for pneumatic tools

Also Published As

Publication number Publication date
IT1035854B (it) 1979-10-20
GB1485906A (en) 1977-09-14
IN143466B (enExample) 1977-12-03
JPS5115288A (en) 1976-02-06
NL7507746A (nl) 1976-01-05
FR2276901A1 (fr) 1976-01-30
SE7507473L (sv) 1976-01-02
CA1025738A (en) 1978-02-07

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Legal Events

Date Code Title Description
AS Assignment

Owner name: NATIONAL WESTMINSTER BANK USA, 175 WATER STREET, N

Free format text: SECURITY INTEREST;ASSIGNOR:CHICAGO PNEUMATIC TOOL COMPANY;REEL/FRAME:004681/0047

Effective date: 19861230