US3833876A - Temperature compensated snap-beam actuator - Google Patents

Temperature compensated snap-beam actuator Download PDF

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Publication number
US3833876A
US3833876A US00417862A US41786273A US3833876A US 3833876 A US3833876 A US 3833876A US 00417862 A US00417862 A US 00417862A US 41786273 A US41786273 A US 41786273A US 3833876 A US3833876 A US 3833876A
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United States
Prior art keywords
beams
snap
loading
sequencer
heating
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Expired - Lifetime
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US00417862A
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English (en)
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W Bassett
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Honeywell Inc
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Honeywell Inc
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Priority to US00417862A priority Critical patent/US3833876A/en
Application granted granted Critical
Publication of US3833876A publication Critical patent/US3833876A/en
Priority to CA209,915A priority patent/CA1028301A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/10—Compensation for variation of ambient temperature or pressure

Definitions

  • ABSTRACT A snap acting thermal actuator apparatus and more particularly a temperature compensated snap beam actuator, one embodiment disclosing a snap beam thermal sequencer.
  • the thermal electric snap beam actuator apparatus is operable to either of two retained positions dependent on the temperature of the thermal snap beam element.
  • the bimetal snap beam element is ambient temperature compensated by another bimetal beam.
  • the end loading of the compensator beam is less than that of the snap beam, the compensator beam end loading preferably being barely equal to the buckling force of the beam, at which point the compensator beam presents a constant force at all displacement positions within the operating range and thus does not load down the snap beam.
  • the compensated snap beam is also disclosed in multiple in a sequencer switch arrangement. The plurality of snap beams are heated together and by biasing the snap beams with end loads differing from each other they will be caused to operate at different operating points, such as in sequential action.
  • thermoelectric compensating beam in addition to the snap beam has been a desirable feature, however, it has had one undesirable aspect in that it typically requires oversizing the driver bimetal snap beam since part of the energy will be absorbed by the compensator beam.
  • the specific beam arrangement described herein covers an embodiment of temperature compensation which requires no additional power from the driver by providing a critical compressive longitudinal loading on the compensator bimetal beam.
  • FIG. 1 is a diagrammatic representation of the compensated snap beam of this invention
  • FIG. 2 is a graphical representation of the effects of end loading of the bimetal beam
  • FIG. 3 is a top plan view of a sequencer using a multiple number of the compensated snap beams of FIG. 1;
  • FIG. 4 is a pictorial or perspective view of the heating oven portion of the sequencer
  • FIG. 5 shows more details of a stop plate which is also shown in FIGS. 3 and 4; and, FIG. 6 shows a preferred form of the bimetal beams of this invention.
  • FIG. 1 there is shown a compensated snap beam assembly comprising a snap beam 10 and a compensating beam 11 which are mechanically linked at a midpoint of each beam by an actuating arm 12.
  • the beams 10 and 11, which may be identical to one another if desired, are conventional thermally responsive bimetallic strips, and may be constructed as shown in FIG. 6.
  • the beams are shown as having a normal curvature at ambient room temperature for a purpose to be described later. The beam need not have the curvature.
  • the ends of the beams are fixed in position in the assembly, the central portion being free to move between stops.
  • the right hand ends of beams 10 and 11 seat in V-notches I3 and 14 of a support or frame 15.
  • Compression force or end loading force is applied to the opposite end of the snap beam 10 and also of the compensating beam 11 by loading means which here are shown as resilient means or springs 16 and 17, respectively.
  • the compressive loading force on each beam can be individually adjusted by adjusting screws 20 and 21 which are threaded into frame member 15'.
  • the screw, spring and beam are longitudinally or axially aligned.
  • a heating means for snap beam 10 is herein shown as an electrical heating coil 18 around the beam which is energized. when it is desired that beam 10 take the warm position 10'.
  • Ambient temperature compensation is regularly achieved in the prior art by using two bimetal elements back-to-back, i.e., oppositely arranged, such that the net force change is zero so long as both elements see the same ambient temperature.
  • This means of temperature compensation is effective but typically requires oversizing the driver bimetal since part of the driver bimetal energy is taken by the compensator because of lost motion or by compressing a spring member, i.e., the compensator.
  • the specific beam arrangement described herein covers a novel bimetal temperature compensation which requires no additional power from the driver.
  • the operation of the snap beam is largely dependent on the end load applied to the snap beam.
  • Three basic conditions can be established based on the amount of end loading. Referring now to the graph of FIG. 2 there are shown curves of force vs. displacement of bimetal beams under several end load conditions.
  • the critical end load which is the buckling load
  • Graph line A shows force vs. displacement when the end load to the beam is less than the critical or buckling load. Under this condition the beam has a positive spring gradient, as a force must be applied in order to move the beam.
  • Graph line B describes the condition when the end loading of the beam is equal to the critical load.
  • Graph line C shows the force vs. displacement when the end load exceeds the critical load.
  • the beam will be in a buckled position and it is necessary to apply an initial force which will be stored until such time as this energy is released.
  • the beam then snaps through center providing energy as it moves through a displacement.
  • the beam has a negative spring gradient characteristic.
  • the gradient characteristic in each case is determined by the end load on the beam.
  • the snap beam 10 is loaded with an end load exceeding the buckling load and operates in the manner of Graph line C.
  • the two stable positions of the beam 10 are shown in FIG. 1, the solid line 10 showing the cool (absence of heating) temperature position of the bimetal beam and the dashed line 10' showing the warm temperature position of the beam, the beam moving suddenly or snapping from one position to the other as the temperature of the beam 10 warrants.
  • compensator beam 11 is mechanically linked to snap beam 10 by arm 12, the two beams move together as one.
  • the thermally responsive beam 10 having its ends restrained, has a central portion movable in a first direction upon heating and in a second direction upon cooling.
  • the beam 10 by sufficient end loading is provided with a snap action from one to the other of two positions, one on either side of center.
  • the thermally responsive beam 10 may if desired, be made to have a curvature at ambient room temperatures (i.e., the cool temperature), as shown in FIG. 6, which curvature aids in returning the beam against the cool stop of stop plate 44 except during the time the beam is heated by the electrical heating means 18 or 35 and snaps over to the warm position against the warm stop.
  • the compensating beam 11 is preferably loaded with an end load equal to the buckling load, as shown in Graph line B.
  • the force provided by the compensating beam will not be influenced by its position at 11 or 11 or inbetween since the beam has a zero gradient. Beam 11 thus does not provide a loading effect on snap beam 10'. A change in temperature, however, will cause the force to change since the bimetal beam 11 produces a force based on its internal moments.
  • the force produced by the compensator 11 is therefore responsive to temperature changes, but is independent of position.
  • This compensator is that it provides temperature compensation without absorbing any energy from the driving member, that is from snap beam 10, when it is displaced.
  • the snap beam 10 thus does not have to be oversized to provide the desired work output.
  • the temperature of the beam 10 at which it snaps from the cool position to the warm position 10 is controllable by changing the set screw 20 to increase or decrease the end force.
  • the end force on compensating beam 11 can be adjusted slightly above or slightly below the critical force if desired to provide further calibration.
  • the compensated snap beam of FIG. 1 is utilized in multiple in an electric sequencer apparatus shown in FIG. 3. It is desired to have apparatus for the switching of a plurality of electrical loads in which there is a time interval between the switching of the several loads. In the apparatus of FIG. 3 there may be four compensated snap beams to provide a time interval between the switching of each of four electrical loads. This precise number of sequencing switches is not significant and is illustrative only.
  • a heating chamber or oven having within mounted a plurality of snap beams of which 10 and 1 10 are shown. Two additional sets of beams may be located immediately below the shown members.
  • FIG. 4, which is a pictorial view of the oven 30, may be considered together with FIG. 3 during the description of the oven and the snap beams contained therein.
  • The-oven assembly comprises slotted end members 31 and 32 and top and bottom longitudinal connecting members 33 and 34.
  • the heating coil 35 a few turns of which are shown in FIG. 3, is wound around the members 33 and 34 to form an oven within for heating the snap beams when the coil terminals are energized.
  • In the end member 31 are a plurality of notches l3, 14, 113 and 114 to receive the ends of the beams.
  • the beams may be vertically retained in position by the small slots in the V-notch area into which the tab end 41 of the beam is inserted.
  • the other end member 32 has wider slots 42 through which the snap beams may pass and extend, and similar slots 43 through which the compensating beams may extend.
  • Stop plate 44 In the center of the oven assembly is a stop plate 44 which controls the amount of movement of the snap beam between the cold position and the warm position. Stop plate 44 is shown in its entirety in FIG. 5, and the slot areas 45 and 46 through which the snap beams pass are indicated as being the same for all of the several snap beams. The slot areas need not be the same for each snap beam and may be modified as desired, and two sample modifications as suggested by dashed lines 47 and 48 show how the cold stop can be changed at 47 and how the warm stop can be changed at 48. The operational graph of FIG. 2 indicates the operational changes as these stops are changed.
  • the springs 16, 116, 17 and 117 as shown in FIG. 3, which provide the end loading for the snap beams 10 and and the compensating beams 11 and 11 may have adjusting screws as described in FIG. 1 or the compensating springs 17 and 117 may be of a strength to apply the critical end load to the compensating beams 11 and 111, while the snap beam springs 16 and 116 apply an end force greater than the critical buckling force to the snap beams 10 and 110.
  • the snap beam springs 16, 116 etc. may be identical one to the other or may have a spring force which is slightly different one from the other. If snap beam springs are chosen which are slightly different, then the graph line C of FIG.
  • the switches 12a and 112a of FIG. 3 have been shown as conventional normally closed SPST leaf switches, however, it is obvious that any suitable switch can be used.
  • first loading means to provide a compressive loading throughout a first of said bimetal beams in excess of said critical value whereby said beam snaps from one to the other of two positions dependent upon the temperature of said beam;
  • second loading means to provide a compressive loading throughout the second of said bimetal beams to approximately said critical value at which loading said second beam can assume changes in displacement with no change in force whereby said second beam operates as a temperature compensator for said first snap beam without changing the loading on said first beam;
  • stop means positioned to constrain the movement of said beam.
  • a temperature compensated thermal actuator comprising:
  • first and second thermally responsive beam said beams having their end positions relatively fixed and having a central portion movable in a first direction upon heating and in a second direction when heating ceases, said first beam being provided with a snap action throughout a certain range of its movement;
  • first support means mechanically interconnecting and positioning one end of said first and second beams
  • second support means interconnecting and positioning the other end of said first and second beams so that said beams are positioned relatively parallel to one another, said beams being oppositely arranged to provide temperature compensation;
  • first spring means associated with said support means and positioned to apply compressive end loading to said first beam, said loading exceeding in magnitude that necessary to cause buckling of said beam to cause said snap action;
  • second spring means associated with said support means and positioned to apply a lesser magnitude of compressive end loading to said second beam which loading is approximately that necessary to cause buckling of said second beam;
  • heating means associated with said first beam to actuate said first beam when heated
  • adjustable means associated with at least one of said LII first and second beams for adjusting the magnitude of said compressive end loading.
  • a snap beam type thermal sequencer comprising:
  • loading means applying a compressive longitudinal loading on each of said plurality of thermally responsive snap beams, said means loading each said beam in excess of its buckling load so that said beams are biased to either of two positions, said snap beams having a central portion which snaps in a first direction upon heating and in a second direction when heating ceases and the beam cools;
  • electrical heating means positioned in heat transfer relation with said snap beams whereby said beams can be simultaneously heated
  • said means comprising an electrical heating chamber having first and second end member means and having longitudinal connecting member means extending between said end member means, the end member and connecting member means defining said chamber, said first and second end member means receiving and positioning said plurality of snap beams within said chamber, said chamber including power input terminals for connection to a controlled supply of power whereby said chamber can be heated to simultaneously heat said beams;
  • each of said beams is compressively loaded to a slightly different value to cause a sequential operation of said beams.
  • said first and second end member means also being adapted for receiving and positioning said plurality of compensator beams such that one compensator beam is substantially parallel to each snap beam.
  • stop means positioned to constrain the movements of said beams to define said two positions of each of said beams.

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  • Thermally Actuated Switches (AREA)
US00417862A 1973-11-21 1973-11-21 Temperature compensated snap-beam actuator Expired - Lifetime US3833876A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US00417862A US3833876A (en) 1973-11-21 1973-11-21 Temperature compensated snap-beam actuator
CA209,915A CA1028301A (fr) 1973-11-21 1974-09-24 Dispositif de commande a declic a compensation thermique

Applications Claiming Priority (1)

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US00417862A US3833876A (en) 1973-11-21 1973-11-21 Temperature compensated snap-beam actuator

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US3833876A true US3833876A (en) 1974-09-03

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CA (1) CA1028301A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339740A (en) * 1980-06-06 1982-07-13 The General Electric Company Limited Thermally responsive switches
US6438954B1 (en) * 2001-04-27 2002-08-27 3M Innovative Properties Company Multi-directional thermal actuator
US20060034562A1 (en) * 2004-08-13 2006-02-16 Xerox Corporation Beam switch structures and methods
US20120237375A1 (en) * 2009-12-07 2012-09-20 Niklaus Schneeberger Flexible element for micropump

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339740A (en) * 1980-06-06 1982-07-13 The General Electric Company Limited Thermally responsive switches
US6438954B1 (en) * 2001-04-27 2002-08-27 3M Innovative Properties Company Multi-directional thermal actuator
US20060034562A1 (en) * 2004-08-13 2006-02-16 Xerox Corporation Beam switch structures and methods
JP2006051598A (ja) * 2004-08-13 2006-02-23 Xerox Corp ビーム・スイッチ構造及び方法
US7221817B2 (en) * 2004-08-13 2007-05-22 Xerox Corporation Beam switch structures and methods
US20080002930A1 (en) * 2004-08-13 2008-01-03 German Kristine A Beam switch structures and methods
US20120237375A1 (en) * 2009-12-07 2012-09-20 Niklaus Schneeberger Flexible element for micropump
US9822774B2 (en) * 2009-12-07 2017-11-21 Debiotech S.A. Diaphragm pump having a strip connector

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Publication number Publication date
CA1028301A (fr) 1978-03-21

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