US3281551A - Mechanical oscillatory switch - Google Patents

Mechanical oscillatory switch Download PDF

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Publication number
US3281551A
US3281551A US347188A US34718864A US3281551A US 3281551 A US3281551 A US 3281551A US 347188 A US347188 A US 347188A US 34718864 A US34718864 A US 34718864A US 3281551 A US3281551 A US 3281551A
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United States
Prior art keywords
mass
lever
magnet
contacts
base plate
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Expired - Lifetime
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US347188A
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English (en)
Inventor
Becke Ludwig
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BBC Brown Boveri AG Germany
BBC Brown Boveri France SA
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BBC Brown Boveri France SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/14—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch
    • H01H35/144—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch operated by vibration
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H5/00—Snap-action arrangements, i.e. in which during a single opening operation or a single closing operation energy is first stored and then released to produce or assist the contact movement
    • H01H5/02—Energy stored by the attraction or repulsion of magnetic parts

Definitions

  • Safety switches of this type are in common use on machinery to protect the latter against strong vibrations.
  • they are used on rotating machinery such as turbines, generators, etc. to protect the same in the event any strong vibrations are produced which could cause damage to the foundation for the machine or its bearings.
  • Such machines are normally mounted and so balanced that normal vibrations incident to normal running are very small and cause no damage.
  • damage occur within the rotor element of the machine such as failure of one or more blades of a gas or steam turbine, the unbalance which results creates very strong virbations which'may have dangerous consequences for the machine and in particular its bearing suspensions.
  • vibration-responsive switches of the general type mentioned are mounted on the machine in any suitable position such as on the bearing housing and in the event strong vibrations arise, the switch contacts are closed and either give a warning signal or cause the'machine to be stopped.
  • Vibration-responsive switches which have so far been developed have the disadvantage that they respond to only very strong vibrations and are not sufficiently sensitive.
  • the mass member attractable to the magnet is loaded in the direction away from the magnet by compression of a helical spring, and in addition the mass is fastened through a flexible joint to the base plate.
  • the mass In the event of a strong vibration or impact, the mass is broken away from the magnet as the acceleration forces exceed the magnetic attractive forces and strikes against a pin which in turn actuates the electrical switch contacts to a closed position.
  • a screw is usually provided to effect an adjustment of the loading force exerted by the spring and hence makes it possible to set the response point at which the mass breaks away from the magnet.
  • the improved construction in accordance with the present invention eliminates many of the disadvantages inherent in the prior known arrangements and is characterized by an improved mounting arrangement for the mass and the magnet. More particularly, the mass is mounted on a cantilever type spring and the magnet is mounted on an adjustable double reduction dual lever system. With 3,281,551 Patented Oct. 25, 1966 this construction, adjustment of the response point for the mass is made, not on the spring, but rather on the double lever system.
  • FIG. 1 is a view in side elevation of the switch with certain parts shown in section;
  • FIG. 2 is an electrical schematic view of one suitable circuit arrangement incorporating the switch and which enables the protective system to distinguish between sustained vibration forces which characterize actual imbalance conditions within the machine and occasional vibrations or impacts which have a rather long interval therebetween and hence indicate occasional extraneous forces not harmful to the machine; and
  • FIG. 3 is also an electrical schematic view of another circuit arrangement similar to FIG. 2 in that it is enabled to discriminate between harmful and non-harmful forces.
  • the improved switch construction includes a base plate 1 which is adapted to be mounted on 'a suitable surface of the machine for which it is to protect against severe vibrational forces.
  • a base plate 1 which is adapted to be mounted on 'a suitable surface of the machine for which it is to protect against severe vibrational forces.
  • it can be mounted in a force-transmitting relation to the bearing housing whose vibration is to be monitored.
  • a block 2 Upstanding at one end of plate 1 is a block 2 in which is anchored, by insertion, one end of a cantilever spring leaf 3.
  • a mass 4 of magnetic material is mounted at the opposite, free end of spring 3 and this mass normally rests upon a spacer ring 5 which in turn is supported on the base plate 1.
  • magnet 6 preferably of the permanent type, which is arranged for vertical adjustment to an extremely fine degree by means of a double reduction effect established by a dual lever system.
  • magnet 6 is supported on the flat upper face of a first lever 7 that is provided with depending feet at the front and rear ends thereof and which terminate in knife edges 7a and 7b, respectively.
  • the rear knife edge 7b rests upon the flat upper face of base plate 1, and since lever 7 is located above a second lever 8, the contact between knife edge 7b and the upper face of base plate 1 is established in any suitable manner such as by passing the rear foot of lever 7 through a slot 8b in the lower lever 8.
  • the front knife edge 7a rests upon the flat upper face of the second lever 8.
  • lever 8 The front end of lever 8 is provided with a depending foot which terminates in a knife edge 8a that rests upon the upper face of the base plate 1 and the rear end portion of lever 8 is provided with a vertical threaded hole 9 which receives a vertically disposed adjusting screw 10, the lower end of which also engages the upper face of base plate 1.
  • adjustment screw 10 By turning adjustment screw 10 in one direction or the other, one is able to make a corresponding adjustment in the height of the magnet 6 and hence effect a similar adjustment in the spacing and hence the degree of magnetic attraction maintained between the upper face of magnet 6 and the lower face of the mass 4. It is preferred to always maintain a certain spacing as between mass 4 and magnet 6 to prevent the mass from sticking to the magnet which, if it occurred, would result in faulty operation of the safety switch.
  • mass 4 will pull away from the magnet due to the related acceleration forces in combination with the constant force in such direction as represented by the loading of spring 3. This causes the upper face of mass 4 to strike against pin 11 which in turn causes the contacts, not shown in this view, of switch 12 to be actuated and raise the desired alarm or bring the machine to a stop before any damage can be caused.
  • a reset plunger 16a is provided for resetting the mass 4 so that the latter again comes under the influence of the attractive magnetic field of magnet 6 after normal conditions are restored.
  • This reset plunger can be actuated manually by pressing downwardly on the head part or it can be actuated electromagnetically by having it function as the core element of a solenoid 16. Solenoid 16 will be energized at the proper time to reset the mass 4 in accordance with the alternative circuit arrangernents shown in FIGS. 2 and 3.
  • FIG. 2 shows a circuit which includes a step-switch mechanism.
  • the spring 3, mass 4, switch 12 and reset solenoid 16 from FIG. 1 are depicted somewhat schematically.
  • the contacts of switch 12 serve, when closed, to close a circuit for energizing electromagnet 13 and also relay 14.
  • Magnet 13 then attracts its pivotally mounted armature and causes the toe of the latter to advance, by one step, the step wheel 151.
  • Relay 14 attracts its contact 143 which establishes a holding circuit for the relay coil.
  • Relay contact 141 of this relay also closes after a time delay 1 to energize magnet 18.
  • a further relay contact 142 of this relay also closes after a time delay t
  • the time delay t should be less than t Closure of relay contact 142 serves to complete a circuit for energizing the reset solenoid 16, which as previously explained, serves to reset mass 4 to its initial position on spacer ring 5.
  • step wheel 151 is advanced one step each time the contacts of switch 12 are closed. After time has expired, mass 4 will be reset by energization of reset solenoid 16. If a second mass-moving impact occurs immediately following the first one, wheel 151 will be advanced another step and this will be sutficient to bring the spring-mounted arm 152 rotated by step wheel 151 into such position as to actuate the contacts of switch 17 to a closed position and thereby energize the circuit A which actuates the alarm signal or shuts down the machine.
  • the details of the actuating circuit A have not been included since they are not considered to be essential to the present invention and moreover can take a wide variety of forms already known.
  • the time delay mechanism represented by relay 14 runs out after expiration of time t and effects closure of relay contacts 141.
  • the system remains passive and no alarm or machine shut-down takes place.
  • the system of FIG. 2 is thus able to discriminate as between actual faults arising within the machine which bring about a sustained vibration effect, and infrequent vibrations or shocks which may occur and which have no relation to the operating condition of the machine itself.
  • FIG. 3 The circuit arrangement illustrated in FIG. 3 is similar in final function to that shown in FIG. 2 but operates with electrical relays only.
  • the spring 3, mass 4, switch contacts 12 and reset solenoid 16 are shown schematically.
  • closure of switch contacts 12 serves to energize relay 19 having two sets of contacts 191 and 192 which are closed without any time delay.
  • Closure of contacts 191 serves to energize relay 20 which has two sets of contacts 201 and 202. Contacts 201 close immediately and contacts 202 close after expiration of a time delay period t Contacts 201 serve as hold-in contacts for the relay coil to keep the latter energized even after relay contacts 191 re-open.
  • Closure of contacts 192 serves to energize relay 21 which is a timing relay with a delay release characteristic. That is to say, this relay releases its contacts 211 after expiration of time period but pulls in without any deliberately introduced delay. Closure of relay contacts 192 also serves to energize relay 22 which closes its contacts 221 after expiration of time delay period t
  • the circuit of FIG. 3 operates in the following manner. As in the previous case, any impact force exceeding the critical value set on the safety switch will cause mass 4 to pull away and close the switch contacts 12. This serves to energize the auxiliary relay 19 to close its two sets of contacts 191, 192. Closure of contacts 192 energizes relay 21 which in turn immediately closes its contacts 211.
  • Closure of relay contacts 191 will now supply voltage to relay 20 which, since contacts 211 are already closed, immediately close its contacts 201 and thereby hold itself in. Contacts 202 will close only after time Closure of relay contacts 192 also serves to energize relay 22 but which does not yet effect closure of its contacts 221, the latter being closed only after expiration of time delay 1 which, incidentally must be shorter than 1;; and t and this serves to energize the reset solenoid 16 to thereby reset mass 4. If another shock follows immediately on the heels of the first one, relay 19 is thereby immediately energized again and relay 20 continues to run, so to speak, without having been released, as the circuit has remained closed through the relay contacts 211. If there occurs still another re-setting operation through relay 22 and if thereupon another shock occurs, relay 20 runs down with the time t closing its contacts 202 and thereby energizing the alarm or machine shut-down circuit A.
  • the improved safety switch construction which has been described operates in the prescribed discriminatory manner and also functions with a very fine degree of sensitivity as a result of the very fine adjustment obtainable through use of the double-lever magnet support mechanism and the leaf spring support for the mass which produces a rapid and definite switching.
  • a vibration responsive safety switch comprising a base plate adapted to be secured to a machine part whose vibration is to be monitored, a leaf spring mounted on said base plate, a mass of magnetic material mounted on said leaf spring, an adjustable double reduction dual lever system mounted on said base plate, said dual lever system comprising a first lever including a point of rest at the forward end thereof bearing on said base plate and an adjustable screw at the rear end thereof bearing against said base plate, and a second lever including a point of rest at its forward end bearing on the forward end of said first lever and another point of rest at its rear end bearing on said base plate, a magnet mounted on the rear end of said second lever, said rnagnet serving to attract and hold said mass against a counter biasing force exerted by said leaf spring only for vibration forces which do not exceed a critical magnitu-de selectable by the adjustment made on said double lever system to effect a corresponding variation in the spacing between said mass and magnet, and switch means including contacts actuated in response to a break-a-way of said mass from

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  • Measurement Of Predetermined Time Intervals (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
US347188A 1963-03-01 1964-02-25 Mechanical oscillatory switch Expired - Lifetime US3281551A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH266863A CH404768A (de) 1963-03-01 1963-03-01 Mechanischer Schwingungsschalter

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US3281551A true US3281551A (en) 1966-10-25

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CH (1) CH404768A (de)
GB (1) GB1013027A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3710051A (en) * 1971-07-23 1973-01-09 Gen Motors Corp Acceleration responsive sensor
US3717732A (en) * 1971-06-30 1973-02-20 Gen Motors Corp Acceleration responsive sensor
US3717731A (en) * 1971-06-30 1973-02-20 Gen Motors Corp Acceleration responsive sensor
DE2412807A1 (de) * 1974-03-16 1975-09-18 Albert Steinmeier Beschleunigungsgrenzwertschalter
US5160876A (en) * 1988-09-09 1992-11-03 Yoshitaka Niinai Method of protecting rotating machine
CN115050606A (zh) * 2022-07-28 2022-09-13 清华大学 微机械振动开关与无人值守微***

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851995A (en) * 1973-08-06 1974-12-03 M Mills Pump-off control apparatus for a pump jack

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1529650A (en) * 1922-05-05 1925-03-17 Philip J Darlington Micrometer caliper
US1765479A (en) * 1927-04-07 1930-06-24 Adolph H Benson Electrical testing instrument
US2007371A (en) * 1932-02-24 1935-07-09 American District Telegraph Co Nonaccumulative bandit alarm retard device
US2030237A (en) * 1926-07-03 1936-02-11 Gen Motors Corp Gauging machine
CA623733A (en) * 1961-07-11 Edward V. Hardway, Jr. Acceleration responsive device
GB893170A (en) * 1958-10-16 1962-04-04 Robertshaw Fulton Controls Co Improvements in acceleration responsive device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA623733A (en) * 1961-07-11 Edward V. Hardway, Jr. Acceleration responsive device
US1529650A (en) * 1922-05-05 1925-03-17 Philip J Darlington Micrometer caliper
US2030237A (en) * 1926-07-03 1936-02-11 Gen Motors Corp Gauging machine
US1765479A (en) * 1927-04-07 1930-06-24 Adolph H Benson Electrical testing instrument
US2007371A (en) * 1932-02-24 1935-07-09 American District Telegraph Co Nonaccumulative bandit alarm retard device
GB893170A (en) * 1958-10-16 1962-04-04 Robertshaw Fulton Controls Co Improvements in acceleration responsive device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3717732A (en) * 1971-06-30 1973-02-20 Gen Motors Corp Acceleration responsive sensor
US3717731A (en) * 1971-06-30 1973-02-20 Gen Motors Corp Acceleration responsive sensor
US3710051A (en) * 1971-07-23 1973-01-09 Gen Motors Corp Acceleration responsive sensor
DE2412807A1 (de) * 1974-03-16 1975-09-18 Albert Steinmeier Beschleunigungsgrenzwertschalter
US5160876A (en) * 1988-09-09 1992-11-03 Yoshitaka Niinai Method of protecting rotating machine
CN115050606A (zh) * 2022-07-28 2022-09-13 清华大学 微机械振动开关与无人值守微***

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Publication number Publication date
CH404768A (de) 1965-12-31
GB1013027A (en) 1965-12-15

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