US3248985A - Stall releases for presses - Google Patents

Stall releases for presses Download PDF

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Publication number
US3248985A
US3248985A US370818A US37081864A US3248985A US 3248985 A US3248985 A US 3248985A US 370818 A US370818 A US 370818A US 37081864 A US37081864 A US 37081864A US 3248985 A US3248985 A US 3248985A
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US
United States
Prior art keywords
motor
transistor
fluid pressure
pressure
pump
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
US370818A
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English (en)
Inventor
Richard W Hitchcock
Jr Ralph E Karcher
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.)
United Shoe Machinery Corp
Original Assignee
United Shoe Machinery 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 United Shoe Machinery Corp filed Critical United Shoe Machinery Corp
Priority to US370818A priority Critical patent/US3248985A/en
Priority to DE1965U0011696 priority patent/DE1660128A1/de
Priority to GB22503/65A priority patent/GB1110595A/en
Priority to FR18789A priority patent/FR1435469A/fr
Application granted granted Critical
Publication of US3248985A publication Critical patent/US3248985A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A43—FOOTWEAR
    • A43D—MACHINES, TOOLS, EQUIPMENT OR METHODS FOR MANUFACTURING OR REPAIRING FOOTWEAR
    • A43D8/00—Machines for cutting, ornamenting, marking or otherwise working up shoe part blanks
    • A43D8/02—Cutting-out
    • A43D8/04—Stamping-out
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
    • B23D36/00—Control arrangements specially adapted for machines for shearing or similar cutting, or for sawing, stock which the latter is travelling otherwise than in the direction of the cut
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B26—HAND CUTTING TOOLS; CUTTING; SEVERING
    • B26F—PERFORATING; PUNCHING; CUTTING-OUT; STAMPING-OUT; SEVERING BY MEANS OTHER THAN CUTTING
    • B26F1/00—Perforating; Punching; Cutting-out; Stamping-out; Apparatus therefor
    • B26F1/38—Cutting-out; Stamping-out
    • B26F1/40—Cutting-out; Stamping-out using a press, e.g. of the ram type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/28—Arrangements for preventing distortion of, or damage to, presses or parts thereof
    • B30B15/281—Arrangements for preventing distortion of, or damage to, presses or parts thereof overload limiting devices
    • C—CHEMISTRY; METALLURGY
    • C14—SKINS; HIDES; PELTS; LEATHER
    • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
    • C14B5/00—Clicking, perforating, or cutting leather
    • C—CHEMISTRY; METALLURGY
    • C14—SKINS; HIDES; PELTS; LEATHER
    • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
    • C14B2700/00—Mechanical treatment or processing of skins, hides or leather in general; Pelt-shearing machines; Making driving belts; Machines for splitting intestines
    • C14B2700/11—Machines or apparatus for cutting or milling leather or hides
    • C14B2700/113—Cutting presses
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T83/00—Cutting
    • Y10T83/869—Means to drive or to guide tool
    • Y10T83/8702—Clicker die press
    • Y10T83/8704—With reciprocating presser
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T83/00—Cutting
    • Y10T83/869—Means to drive or to guide tool
    • Y10T83/8702—Clicker die press
    • Y10T83/8704—With reciprocating presser
    • Y10T83/8716—With manually actuated control apparatus for reciprocation of presser member
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T83/00—Cutting
    • Y10T83/869—Means to drive or to guide tool
    • Y10T83/8821—With simple rectilinear reciprocating motion only
    • Y10T83/8858—Fluid pressure actuated

Definitions

  • This invention relates to improvements in die cutting presses and more particularly to improvements in controls for hydraulic die cutting presses having electric motor driven pumps for providing the operating fluid pressure.
  • Such a press has a work support and a beam movable toward and away from the work support for pressing dies through sheet material on the support.
  • Such presses commonly also include a control for the hydraulic motor of the press which control is actuatable by the operator to initiate a stroke of the beam and which operates automatically, suitably in response to the actuation of a limit switch or by conductive engagement of the die with a conductive surface of the work support, to effect reversal of the movement of the beam.
  • the maximum hydraulic system pressure is determined by a relief valve suitably set to open at a pressure which will not unduly strain the hydraulic and mechanical portions of the press.
  • a relief valve suitably set to open at a pressure which will not unduly strain the hydraulic and mechanical portions of the press.
  • the power output of the pump at normal speed is several times that of the motor so that the pump is stalling the motor, slowing it and the flywheel.
  • their rotational inertia provides an energy reservoir so that in the brief period of a normal cutting stroke, even where the hydraulic pressure may approach the maximum system pressure, conversion of rotational energy prevents complete stall of the motor.
  • the motor will shortly stall and protective heater switches therein will open the motor circuit. Resetting of these switches may involve a delay of from about two to ten minutes.
  • Another object of the present invention is to provide in a beam stroke return control means for providing an over-pressure return function which means is less costly and more reliable than a pressure switch of adequate reliability.
  • a stroke terminating control comprising means operative in response to slowing of the electric motor to a predetermined speed for effecting return of the beam.
  • the means comprises a transducer associated with a motor lead and transistorized relay means controlled thereby in response to rise in the current in said motor lead above a predetermined value for effecting termination of a press stroke.
  • one of the leads of a three 1 phase motor employed to drive the pump has in circuit therewith a current transformer for providing an output voltage proportional to the motor current.
  • the output of the transformer is connected in circuit with the stroke control of the press so that when the output voltage exceeds a predetermined value it is operative to cause the control to effect termination of the downward current as the criterion of the beam control function of pressure of the beam and to effect return movement of the beam to an upper position.
  • FIG. 1 is a diagrammatic view partly in section of a cutting press provided with an embodiment of the present invention, showing details of the hydraulic control mechanism;
  • FIG. 2 is a circuit diagram of electric control apparatus embodying the present invention.
  • the press shown in FIG. 1 comprises a work support supporting a cutting pad 12 made of conductive plastic material.
  • a work piece of sheet material 14 is disposed with a cutting die 16 superimposed on top of the work piece.
  • a beam 18, carrying in insulated relation on its lower surface a striking plate 20, is attached to a post 22 mounted in bearings, not shown, for vertical movement toward and away from the support 10. Such movement is imparted to the beam 18 by a hydraulic motor 24 connected to the post 22 by a rod 26.
  • the motor 24 is supplied with hydraulic fluid from a sump 28 by a pump P driven by a three phase motor M which also drives a flywheel F, the pump P supplying hydraulic fluid through a solenoid valve having a movable spool 30 and a winding S energiza'ble to cause the spool 30 to be moved downwardly.
  • a solenoid valve having a movable spool 30 and a winding S energiza'ble to cause the spool 30 to be moved downwardly.
  • a relief valve R limits the maximum hydraulic system pressure.
  • a movable handle 40 is mounted, controlling a switch 42 so that downward movement of the handle 40 causes an armature 44 of the switch to transfer from a contact 46 to a contact 48.
  • a switch 42 so that downward movement of the handle 40 causes an armature 44 of the switch to transfer from a contact 46 to a contact 48.
  • the solenoid S be de-energized to terminate the downward movement of the beam and to cause it to return to an upper position.
  • the control for providing the foregoing functions comprises a transformer 60 having a primary 62 with means for connecting it to a power line, and three secondary windings 64, 66 and 68.
  • Each of the secondary windings is center-tapped and provided with rectifying diodes and capacitor filter means to provide direct current, respectively at 30 volts across the leads 70, 72, at 8 volts for bias across the leads 74 and 70, and at 30 volts across the leads 78 and 80.
  • a transistorized delay circuit comprising a transistor 82 which prevents current from passing until a capacitor 84 has charged, for the purpose of preventing the application of voltage to transistors of the circuit before the bias voltage has been built up.
  • a PNP power transistor 90 For controlling the energization of the solenoid winding S from the leads 70 and 72, a PNP power transistor 90 has its emitter connected to the lead 70 and its collector connected to a lead 92 so that the winding S is connected across the leads 70 and 72 in series relation with the emitter and collector of the transistor 90.
  • the base of the transistor 90 is connected through a resistor 94 to the lead 74, thereby applying a reverse bias of 8 volts to the emitter-base junction of the transistor.
  • a control transistor 100 has its emitter and collector connected in series in a circuit extending between the lead 72 and the base of the transistor while the latter has its emitter and collector connected in series in a circuit extending between the lead 70 and the base of the transistor 100.
  • the base of the transistor is substantially at the potential of the lead 72 by connection thereto through a resistor 110, and resistor 112, the lead 92, and the winding S.
  • the emitter base function of the transistor 1% is given a reverse bias of a substantial fraction of a volt by connection of the emitter through a resistor 114 to the junction of a resistor 116 and a diode 118 polarized for conduction from the lead 70 to the lead 72 so that the forward voltage drop of the diode 118 provides a bias holding the transistor 100 normally non-conducting.
  • a capacitor 120 is charging through a resistor 122 so that the armature 44 is at about 30 volts negative with respect to the lead 70.
  • the handle 40 is moved downwardly until the armature 44 engages the contact 48.
  • the base of the transistor 90 is thus brought substantially negative with respect to its emitter, permitting the transistor to conduct current from the lead 70 through the solenoid winding S while at the same time the potential of the collector of the transistor 90 rises substantially, causing current to flow from the base of the transistor 100 to its emitter, thereby turning on the transistor 100.
  • This causes the collector of the transistor 100 and the base of the transistor 90 to go negative to a value approaching the potential of the lead 72, thus locking both transistors in conductive condition.
  • the solenoid winding will remain in energized condition until the circuit is unlocked. If the handle is held down, the diode 124 prevents the capacitor 120 from being recharged from current passing through the collector of the transistor 100. Thus holding down the handle does not prevent the circuit from being properly unlocked, nor will it result in recycling the stroke.
  • Unlocking the control circuit is accomplished by applying to the base of the transistor 100 a voltage which is negative with respect to its emitter, for example, by closure of a switch LS which suitably may determine the lower extent of movement of the platen.
  • a voltage which is negative with respect to its emitter
  • the voltage may be applied across the resistor 112.
  • Application of cut-off voltage to the transistor 100 permits the bias supply comprising the secondary 66 to apply turnoff reverse bias to the transistor 90, thus de-energizing the solenoid S.
  • a beam contact sensing circuit comprises two stages of amplification and one stage providing a variable time delay.
  • a transistor connected in the grounded collector configuration has an emitter resistor 162 connected between its emitter and the lead 78.
  • the base of the transistor 160 is connected to the lead 78 through a resistor 164 and through a resistor 166 to the striking plate 20.
  • the base of the transistor 160 is connected through a capacitor 168 to the ground line 170.
  • Emitter-base reverse bias is provided substantially entirely by leakage current which provides a fraction of a volt biasing the transistor against conduction.
  • the potential at the base of the transistor 160 will swing negative. Thereby the transistor 160 will be caused to conduct and, in turn, cause the second stage transistor to become,
  • This transistor connected in the grounded emitted configuration has a resistor 182 connected between the collector and the ground lead 170.
  • the voltage produced across the resistor 182 is applied to a time delay stage of conventional configuration comprising a transistor 100. After a time delay, determined by a variable resistor 192, the voltage across the resistor 182 is applied across the resistor 112 polarized to cut off the transistor 100, as previously described, to de-energize the winding S.
  • means for operating the solenoid valve to effect beam return in response to slowing of the pump to a predetermined speed. Because of characteristics of electric motors, this is indicated by the presence of current above a predetermined value in a lead of the electric motor.
  • Such means could be a speed responsive switch suitably operated by centrifugal force or a magnetic switch connected to cut olf the supply of energy to the solenoid when the current in a lead rises sufliciently.
  • the present invention is embodied in a control utilizing the previously described transistor lock-up switching circuit together with a transducer in the form of a current transformer connected in circuit with a motor lead for providing a voltage proportional to current and elements which suitably polarize the voltage for application to the transistor circuit and prevent the application of any voltage from the transducer to the circuit and isolate the circuits until the voltage exceeds a predetermined value.
  • a control utilizing the previously described transistor lock-up switching circuit together with a transducer in the form of a current transformer connected in circuit with a motor lead for providing a voltage proportional to current and elements which suitably polarize the voltage for application to the transistor circuit and prevent the application of any voltage from the transducer to the circuit and isolate the circuits until the voltage exceeds a predetermined value.
  • Such isolation not only prevents interference with the other functions of the control but improves the definiteness of the new control function as no signal comes through until a threshhold is exceeded.
  • a current transformer 200 is connected with its primary in series with a lead 202 comprising a supply lead to the motor M, the current in which reflects the speed and load of the motor as previously described.
  • the secondary 204 of the transformer is connected in a circuit extending between the base of the transistor 100 and the lead 72 through a neon tube 206, a diode 208 and the primary in series relation.
  • the diode is poled so that a negative voltage only is applied to the neon tube 206 which, when it exceeds the breakdown voltage of the tube, is applied to the base of the transistor 100 to turn it off.
  • the relation of the secondary voltage to the motor current is controllable by a variable resistor 210 connected across the secondary of the transformer 200.
  • the illustrative circuit provides no output signal and isolates the circuit until the magnitude of the output voltage from the transformer exceeds a predetermined breakdown value. This step function operation also promotes stability against spurious voltage transients which might affect operation at, or near, the critical input voltage for switching.
  • the operator In operation of the illustrative apparatus with the circuits energized and the motor M running, the operator locates a work piece 14 on the work support and locates a die 16 on the work where a cut is to be made. The operator then swings the beam 18 over the work and depresses the handle 40 to initiate a stroke. Normally, this stroke would be terminated and the beam caused to return by a conductive path formed between the striking plate 20 through the die 16 to the pad 12, as described above. However, should the work piece resist the cutting force of the die and stop the beam, this termination signal will not take place and the hydraulic motor 24 will still be urging the beam downwardly.
  • the fluid-output of the pump is bypassed through the valve R at the maximum system pressure which exceeds that at which the motor M can drive the pump. Accordingly, the motor M is slowed progressively and the current in its lead 202 rises accordingly.
  • the voltage of the winding 204 exceeds the breakdown of voltage of the tube 206 and a large negative voltage is supplied to the base of the transistor 100, turning 01f the solenoid current, as previously described.
  • variable resistor 210 The value of motor current at which cutting off occurs is controlled by the variable resistor 210.
  • This resistor may be set to effect stroke termination at the motor current corresponding to a suitably low motor speed, for example, about 500 rpm, at which speed most of the energy of the flywheel has been expended in keeping the pump rotating. With a flywheel of reasonable size, this provides a delay in stroke termination, during which the beam is applying maximum pressure to the die and which is sufficient in many instances to allow the. cut to be completed where, without such delay, the stroke would be terminated. At the same time, if the press beam is truly checked in its downward movement, the stroke will definitely be terminated at the end of the brief delay period.
  • a fluid pressure operated motor for moving the movable presser member
  • a pump driven by an electric motor for providing fluid under pressure for operating the fluid pressure operated motor
  • valve means connected with said pump means and the fluid pressure operated motor for controlling the fluid flow to and from the fluid pressure operated motor and operative selectively to cause said last motor to move said movable member toward or away from the other member and manually actuatable means for operating said valve means to cause said fluid pressure operated motor to move the movable member toward the other, in combination therewith, means operative in response to slowing of the pump to a predetermined speed for operating the valve means to effect movement of the movable member away from the other.
  • fluid pressure motor means operative to effect such movement
  • fluid pressure supply means comprising an electric motor and a pump driven thereby
  • a control for said fluid pressure motor means comprising valve means controlling the flow of fluid to and from said motor means and operable selectively to cause the motor means to urge said one member toward or away from the other, and means manually actuatable by the operator for operating the valve means to initiate movement of the one member toward the other member, in combination therewith, means including an electric circuit operative in response to the flow of current in excess of a predetermined value in a lead of said electric motor for operating said valve means to cause the motor means to urge said one member away from the other member.
  • fluid pressure operated motor means operative to effect such movement
  • fluid pressure supply means comprising an electric motor and a pump driven thereby
  • a control for said fluid pressure motor means comprising valve means controlling the flow of fluid to and from said motor and operable selectively to cause the motor means to force said one member toward or away from the other member, and means comprising a manual trip element for operating the valve means in response to actuation of said trip element to cause the motor means to force the movable presser member toward the other member, in combination therewith
  • transducer means operatively associated with the supply circuit of said electric motor and valve operating means controlled by said transducer for etfectiug reversal of the motor means in response to flow of a predetermined current in said motor circuit occasioned by slowing of said electric motor under load.
  • a fluid pressure operated motor for providing such movement
  • fluid pressure supply means comprising an electric motor and a pump driven thereby
  • a control for said fluid motor means comprising solenoid valve means controlling the flow of fluid to and from said motor and energizable selectively to cause the motor means to force the movable member toward or away from the other member
  • a transistor switching circuit for selectively energizing said solenoid valve means, said switching circuit having input means responsive to a first predetermined electric signal for causing operation of the solenoid valve means to effect movement of the movable member toward the other member and responsive to a second electric signal of predetermined voltage and polarity for causing operation of said valve means to elfect reversal of the movement of the movable member, in combination therewith, means for providing to the input means of said switching circuit a voltage corresponding to said second signal in response to slowing of the pump to a

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Forests & Forestry (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)
  • Control Of Presses (AREA)
  • Dc-Dc Converters (AREA)
US370818A 1964-05-28 1964-05-28 Stall releases for presses Expired - Lifetime US3248985A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US370818A US3248985A (en) 1964-05-28 1964-05-28 Stall releases for presses
DE1965U0011696 DE1660128A1 (de) 1964-05-28 1965-05-05 Stanze
GB22503/65A GB1110595A (en) 1964-05-28 1965-05-27 Improvements in or relating to presses suitable for use in performing cutting operations on sheet material
FR18789A FR1435469A (fr) 1964-05-28 1965-05-28 Dispositif de commande pour presse à découper

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US370818A US3248985A (en) 1964-05-28 1964-05-28 Stall releases for presses

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Publication Number Publication Date
US3248985A true US3248985A (en) 1966-05-03

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US370818A Expired - Lifetime US3248985A (en) 1964-05-28 1964-05-28 Stall releases for presses

Country Status (4)

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US (1) US3248985A (fr)
DE (1) DE1660128A1 (fr)
FR (1) FR1435469A (fr)
GB (1) GB1110595A (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3474695A (en) * 1967-06-13 1969-10-28 Usm Corp Control for cutting presses
US3854362A (en) * 1971-08-23 1974-12-17 Atom Cantella Deambrosis Hydraulic control system for hollow punching machines
US4015620A (en) * 1974-10-11 1977-04-05 Gulf & Western Manufacturing Company High response unloading valve
US4017235A (en) * 1974-10-30 1977-04-12 Edward Kusters Apparatus for avoiding an excess of pressure in a continuous press
US4412162A (en) * 1981-02-26 1983-10-25 Kitamura Machinery Co., Ltd. Protective system for automatic tool changing apparatus
US4520909A (en) * 1981-12-16 1985-06-04 Brewer Carl T Clutch actuator
US20080250762A1 (en) * 2007-04-10 2008-10-16 Midwesco Filter Resources, Inc. Dust Collector Tube Line Cleaner
CN115157717A (zh) * 2022-06-29 2022-10-11 中化工程沧州冷却技术有限公司 一种冷却塔用玻璃钢管道的生产工艺

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109567318A (zh) * 2018-11-13 2019-04-05 湖州黛丝娅鞋业有限公司 一种皮鞋加工用鞋底快速成型的冲压装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2735976A (en) * 1956-02-21 danly
US2777425A (en) * 1953-09-16 1957-01-15 American Brake Shoe Co Electronic control system for hydraulic motor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2735976A (en) * 1956-02-21 danly
US2777425A (en) * 1953-09-16 1957-01-15 American Brake Shoe Co Electronic control system for hydraulic motor

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3474695A (en) * 1967-06-13 1969-10-28 Usm Corp Control for cutting presses
US3854362A (en) * 1971-08-23 1974-12-17 Atom Cantella Deambrosis Hydraulic control system for hollow punching machines
US4015620A (en) * 1974-10-11 1977-04-05 Gulf & Western Manufacturing Company High response unloading valve
US4017235A (en) * 1974-10-30 1977-04-12 Edward Kusters Apparatus for avoiding an excess of pressure in a continuous press
US4412162A (en) * 1981-02-26 1983-10-25 Kitamura Machinery Co., Ltd. Protective system for automatic tool changing apparatus
US4520909A (en) * 1981-12-16 1985-06-04 Brewer Carl T Clutch actuator
US20080250762A1 (en) * 2007-04-10 2008-10-16 Midwesco Filter Resources, Inc. Dust Collector Tube Line Cleaner
CN115157717A (zh) * 2022-06-29 2022-10-11 中化工程沧州冷却技术有限公司 一种冷却塔用玻璃钢管道的生产工艺
CN115157717B (zh) * 2022-06-29 2024-02-09 中化工程沧州冷却技术有限公司 一种冷却塔用玻璃钢管道的生产工艺

Also Published As

Publication number Publication date
GB1110595A (en) 1968-04-18
FR1435469A (fr) 1966-04-15
DE1660128A1 (de) 1970-10-22

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