US2519558A - Thermostatic switch - Google Patents
Thermostatic switch Download PDFInfo
- Publication number
- US2519558A US2519558A US64326A US6432648A US2519558A US 2519558 A US2519558 A US 2519558A US 64326 A US64326 A US 64326A US 6432648 A US6432648 A US 6432648A US 2519558 A US2519558 A US 2519558A
- Authority
- US
- United States
- Prior art keywords
- lever
- switch
- resilient
- contact
- plate
- 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
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H37/00—Thermally-actuated switches
- H01H37/02—Details
- H01H37/64—Contacts
- H01H37/66—Magnetic reinforcement of contact pressure; Magnet causing snap action
-
- 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
- This invention relates to thermostats embodying a magnetic snap action switch and in which the thermally sensitive member actuating the switch comprises a tube or rod of relatively high thermal expansion material associated with a rod or'tube of low coeificient of expansion, and more particularly to thermostatic switches embodying a magnetic snap action switch of the type described in the specification of our copending application No. 39,276, filed July-17, 1948.
- thermostats of this type are to control electric water heaters, and in such apparatus the space available for the switch head of the thermostat is very limited. It is also required that the temperature adjustment provided on the thermostat be in the form of a rotatable knob in the switch head located concentrically with the stem of the instrument.
- the magnetic snap action switch of this invention consists of a resilient switch member carrying two iron armatures positioned one on each side of a permanent magnet, and so adjusted for movement that one armature remains closer to the magnet than the other in both the open and closed positions of the switch.
- This adjustment of armatures produces a magnetic bias acting as a closing force between switch contacts, one of which is carried by the resilient switch member, the co-acting contact being arranged with screw adjustment in a supporting plate.
- FIG. 2 showing a thermostat constructed in accordance with this invention
- Fig. 2 is a plan view with the casing broken away
- Fig. 3 an isometric view of the resilient switch lever with its attached armatures and contact.
- Figures 4 and 5 show an elevation and plan of another embodiment of this invention. Similar parts in Figures 1, 2, 4 and 5 are indicated by the same reference numerals.
- a thermally sensitive stem comprising a tube 2 of brass or similar metal of high thermal expansion into which is screwed at the end remote from the base i a nickel iron rod 3, having a low expansion coefficient.
- Clamping posts 4, i screwed into the base i carry spacing washers 5, between which washers are held the magnet support plate 6, the resilient switch lever l, and fixed contact plate 8.
- the position of the armatures i2, i3 relative to magnet H, and the travel of the moving contact [4 is set by adjustment of contact i5 and back stop 2 I.
- Figure 4 shows an embodiment of the invention in'which the metal base i, the insulation 9 and the metal parts 5 below-the switch lever l in the first embodiment are replaced by a block 25 of insulating material such as steatite. Short posts 26, 26', fixed into the base block 25, clamp the switch parts to the base.
- the terminals (not shown in Figure l) but actually carried on the outside of the case are, in the embodiment shown in Figures 4 and 5, disposed within the cover as shown at 28, 28, access being obtained to the terminals through suitably placed holes in the outer enclosing cover.
- Rod 3 has mounted at its upper end a collar i3 adapted to move within a chamber as in a rigid lever l6.
- Chamber has contact risers BB at its lower end which are contacted by shoulder l9 during downward movement of rod 3 in response to temperature increase.
- Rigid lever it is iulcrumed at point on contact plate 8 and has a pip i! at its lower side to impart pressure to switch lever '5.
- Rigid lever E5 is of electrical insulating material to avoid making permanent electrical connection between contact plate 8 and resilient switch lever 1.
- the effective fulcrum of the spring switch lever l is at a point 7' where lines drawn as extensions to slots 21, 27 and shown dotted in Fig 3 intersect the centre line of the lever, taken through the contact M.
- the point of application of pressure under pip H is, therefore, between the contactsv and the fulcrum and acts to open the contacts with increasing temperature.
- knob l8 accessible from the outside of the thermostat casing to adjust the operating temperature of the thermostat. Rotation of knob It causes rotation of rod 3 and, because of the threaded engagement between rod 3 and tube 2, a relative longitudinal movement therebetween. By rotating knob I8 in such direction as to cause movement of rod 3 and hence shoulder 59 downwardly toward the switch pack, the temperature at which the switch opens is decreased, and by rotating knob H3 in the opposite direction the temperature at which the switch opens is increased.
- An electric thermostat comprising a base, a clamping post extending from the base, a first rigid plate and a resilient lever clamped on said post in spaced superposed relation, a permanent magnet fixed to said plate, an armature assembly including a pair of spaced armatures mounted on said lever and disposed in fixed relation to each other respectively on opposite sides of said permanent magnet and spaced therefrom, a second rigid plate clamped on said post on the side of said lever opposite said first rigid plate, a rigid lever having a point at one end bearing on said second plate and a point at its other end bearing on said resilient lever, a contact fixed to said second rigid plate, a contact actuated by the resilient lever and adapted to engage the contact fixed to said second plate, an actuating member engaging said rigid lever intermediate said points and adapted to move said rigid lever to actuate said resilient lever and the contact actuated thereby, and means for limiting the movement of the armature assembly with respect to the permanent magnet so that one ar- 4 mature remains closer to the magnet than the other armature in
- An electric thermostat comprising a base, a pair of spaced clamping posts extending from the base, a first rigid plate and a resilient lever clamped on said posts in spaced superposed relation, a permanent magnet fixed to said plate, an armature assembly including a pair of spaced armatures mounted on said lever and disposed in fixed relation to each other respectively on 0pposite sides of said permanent magnet and spaced therefrom, a second rigid plate clamped on said posts on the side of said lever opposite said first rigid plate, a rigid lever having a point at one end bearing on said second plate and a point at its other end bearing on said resilient lever, a
- An electric thermostat comprising a magnet, a movable resilient lever, a pair of armatures carried by said resilient lever for movement therewith and disposed on opposite sides of said magnet at unequal distances therefrom in switchclosed position, a fixed contact, a cooperating contact carried by said resilient lever, a, second lever fulcrumed at one point fixed with respect to said contact and at another point on said resilient lever, a thermostatically-controlled member positioned to engage said second lever,
Landscapes
- Thermally Actuated Switches (AREA)
Description
g- 1950 T. N. FLIGHT ETAL 2,51
THERMOSTATIC SWITCH Filed Dec. 9, 1948 2 Sheets-Sheet 1 Aug. 22, 1950 T. N. FLIGHT ETAL THERMOSTATIC SWITCH Filed Dec. 9, 1948 2 Sheets-Sheet 2 mu e/1734s Mar a I) a Patented Aug. 22, 1950 UNITED STATES PATENT OFFICE THERMOSTATIC SWITCH company Application December 9', 1948, Serial No. 64,326 In- Great Britain December 9, 1947 3 Claims. 1
This invention relates to thermostats embodying a magnetic snap action switch and in which the thermally sensitive member actuating the switch comprises a tube or rod of relatively high thermal expansion material associated with a rod or'tube of low coeificient of expansion, and more particularly to thermostatic switches embodying a magnetic snap action switch of the type described in the specification of our copending application No. 39,276, filed July-17, 1948.
One use of thermostats of this type is to control electric water heaters, and in such apparatus the space available for the switch head of the thermostat is very limited. It is also required that the temperature adjustment provided on the thermostat be in the form of a rotatable knob in the switch head located concentrically with the stem of the instrument.
It is the object of this invention to embody an improved magnetic snap action switch of the type referred to within a switch head of minimum dimensions and to provide adjustment for the temperature setting concentric with the stem.
As disclosed in the specification of application No. 39,276 the magnetic snap action switch of this invention consists of a resilient switch member carrying two iron armatures positioned one on each side of a permanent magnet, and so adjusted for movement that one armature remains closer to the magnet than the other in both the open and closed positions of the switch. This adjustment of armatures produces a magnetic bias acting as a closing force between switch contacts, one of which is carried by the resilient switch member, the co-acting contact being arranged with screw adjustment in a supporting plate.
By the use of this arrangement of magnet and twin armatures the force needed for switch operation is limited to the adjusted difference in pull of the magnet on the two armatures, which force can be of such low value relative to the strength of the resilient switch member that consistent and reliable action can be obtained within a switch head of minimum dimensions.
Thermal movement consequent on a temperature change of the stem of the thermostat is transmitted to the resilient switch member through a non-resilient lever rigidlyisupported at one end and pressing the switch member at its opposite end, the movement being applied at approximately the centre of the non-resilient lever member to press the switch to open position with a rising temperature.
In the accompanying drawings Figure 1 is 'apart section in elevation on the line I-I'of Fig. 2
2 showing a thermostat constructed in accordance with this invention, Fig. 2 is a plan view with the casing broken away and Fig. 3 an isometric view of the resilient switch lever with its attached armatures and contact. Figures 4 and 5 show an elevation and plan of another embodiment of this invention. Similar parts in Figures 1, 2, 4 and 5 are indicated by the same reference numerals.
Referring to the drawings, in the base I is fixed a thermally sensitive stem comprising a tube 2 of brass or similar metal of high thermal expansion into which is screwed at the end remote from the base i a nickel iron rod 3, having a low expansion coefficient. Clamping posts 4, i screwed into the base i carry spacing washers 5, between which washers are held the magnet support plate 6, the resilient switch lever l, and fixed contact plate 8.
Electrical insulation is provided on the clamping posts by steatite bushes (not shown), and mica washers as at 5, provide the insulation between the switch parts. Nuts it, til, screwing on to the end of the clamping posts i, d clamp the switch pack rigidly to base I. A permanent magnet ll fixed into its carrying plate 6, is embraced by a twin armature unit l2, #3 attached to the centre limb of the resilient switch arm I, by riveting with the shank of the moving contact i l. Fixed contact [5 is screwed into plate 8.
The position of the armatures i2, i3 relative to magnet H, and the travel of the moving contact [4 is set by adjustment of contact i5 and back stop 2 I.
Figure 4 shows an embodiment of the invention in'which the metal base i, the insulation 9 and the metal parts 5 below-the switch lever l in the first embodiment are replaced by a block 25 of insulating material such as steatite. Short posts 26, 26', fixed into the base block 25, clamp the switch parts to the base. The terminals (not shown in Figure l) but actually carried on the outside of the case are, in the embodiment shown in Figures 4 and 5, disposed within the cover as shown at 28, 28, access being obtained to the terminals through suitably placed holes in the outer enclosing cover.
Rod 3 has mounted at its upper end a collar i3 adapted to move within a chamber as in a rigid lever l6. Chamber has contact risers BB at its lower end which are contacted by shoulder l9 during downward movement of rod 3 in response to temperature increase. Rigid lever it is iulcrumed at point on contact plate 8 and has a pip i! at its lower side to impart pressure to switch lever '5. Rigid lever E5 is of electrical insulating material to avoid making permanent electrical connection between contact plate 8 and resilient switch lever 1. The effective fulcrum of the spring switch lever l is at a point 7' where lines drawn as extensions to slots 21, 27 and shown dotted in Fig 3 intersect the centre line of the lever, taken through the contact M. The point of application of pressure under pip H is, therefore, between the contactsv and the fulcrum and acts to open the contacts with increasing temperature.
At the upper end of rod 3 is attached a knob l8 accessible from the outside of the thermostat casing to adjust the operating temperature of the thermostat. Rotation of knob It causes rotation of rod 3 and, because of the threaded engagement between rod 3 and tube 2, a relative longitudinal movement therebetween. By rotating knob I8 in such direction as to cause movement of rod 3 and hence shoulder 59 downwardly toward the switch pack, the temperature at which the switch opens is decreased, and by rotating knob H3 in the opposite direction the temperature at which the switch opens is increased.
Rising temperature on the stem tube 2 gives gradual increase of the length of this tube, which by its screw engagement takes with it rod 3. This movement transmitted to rigid lever Hi from pressure collar I9 gives gradual movement to that part of the resilient lever immediately beneath the pip ll, this movement causing force to be generated in the resilient'lever in opposition to the resultant magnetic pull on the twin armature unit l2, l3.
When this force exceeds this resultant pull,-
contact [4 moves with a snap action away from contact I5, thus interrupting the circuit through the thermostat.
With the heating means switched off falling temperature on the stem tube 2 results in contraction of this tube giving movement of the rod 3 and collar I 9 away from the base' of the switch, thus reducin the pressure of rigid lever is on the resilient lever until the magnet pull is able to overcome the spring tension of the resilient lever, and re-close contacts l4, 15.
In co-pending application Serial No. 718,635, filed December 27, 1946, there is disclosed and claimed a somewhat similar magnetic snap action switch in which the armature-carrying lever is non-resilient and is actuated by a resilient member.
We claim:
1. An electric thermostat comprising a base, a clamping post extending from the base, a first rigid plate and a resilient lever clamped on said post in spaced superposed relation, a permanent magnet fixed to said plate, an armature assembly including a pair of spaced armatures mounted on said lever and disposed in fixed relation to each other respectively on opposite sides of said permanent magnet and spaced therefrom, a second rigid plate clamped on said post on the side of said lever opposite said first rigid plate, a rigid lever having a point at one end bearing on said second plate and a point at its other end bearing on said resilient lever, a contact fixed to said second rigid plate, a contact actuated by the resilient lever and adapted to engage the contact fixed to said second plate, an actuating member engaging said rigid lever intermediate said points and adapted to move said rigid lever to actuate said resilient lever and the contact actuated thereby, and means for limiting the movement of the armature assembly with respect to the permanent magnet so that one ar- 4 mature remains closer to the magnet than the other armature in both the closed and open posi tions of the contacts, whereby said magnet continuously applies a force in one direction to the armature assembly which in turn maintains a tension between the resilient lever and the rigid lever in opposition to said actuating member.
2. An electric thermostat comprising a base, a pair of spaced clamping posts extending from the base, a first rigid plate and a resilient lever clamped on said posts in spaced superposed relation, a permanent magnet fixed to said plate, an armature assembly including a pair of spaced armatures mounted on said lever and disposed in fixed relation to each other respectively on 0pposite sides of said permanent magnet and spaced therefrom, a second rigid plate clamped on said posts on the side of said lever opposite said first rigid plate, a rigid lever having a point at one end bearing on said second plate and a point at its other end bearing on said resilient lever, a
contact fixed to said second rigid plate, a con-.
tact actuated by the resilient lever and adapted to engage the contact fixed to said second plate,
a member responsive to a thermostat engaging said rigid lever intermediate said points and adapted to move said rigid lever to actuate said resilient lever and the contact actuated thereby,
and means including an adjustable stop carried by said first plate for limiting the movement of the armature assembly with respect to the permanent magnet so that on armature remainsv closer to the magnet than the other armature in both the closed and open positions of the contacts, whereby said magnet continuously applies a force in one direction to the armature assembly which in turn maintains a tension between the resilient lever and the rigid lever in opposition to said actuating member.
3. An electric thermostat comprising a magnet, a movable resilient lever, a pair of armatures carried by said resilient lever for movement therewith and disposed on opposite sides of said magnet at unequal distances therefrom in switchclosed position, a fixed contact, a cooperating contact carried by said resilient lever, a, second lever fulcrumed at one point fixed with respect to said contact and at another point on said resilient lever, a thermostatically-controlled member positioned to engage said second lever,
between said fulcrum points and to cause movement of said second lever to move said resilient lever in response to change in temperature, andmeans for so limiting the movement of said resilient lever in switch-opening direction that the one of said armatures which is the nearer to ,the'
magnet in switch-closed position remains the nearer to the magnet in all positions of the resilient lever.
THEODORE NICHOLAS WILLIAM HARRY WILSON, ARTHUR JOHN CHINNL REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB32489/47A GB632904A (en) | 1947-12-09 | 1947-12-09 | Improvements in electric thermostats |
Publications (1)
Publication Number | Publication Date |
---|---|
US2519558A true US2519558A (en) | 1950-08-22 |
Family
ID=10339374
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US64326A Expired - Lifetime US2519558A (en) | 1947-12-09 | 1948-12-09 | Thermostatic switch |
Country Status (5)
Country | Link |
---|---|
US (1) | US2519558A (en) |
BE (1) | BE486196A (en) |
CH (1) | CH271496A (en) |
FR (1) | FR976366A (en) |
GB (1) | GB632904A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2707215A (en) * | 1951-10-18 | 1955-04-26 | Rheostatic Co Ltd | Safety cut-outs for electrically heated appliances |
US3207877A (en) * | 1959-03-02 | 1965-09-21 | Satchwell Controls Ltd | Thermostatic switch with permanent magnet induced snap action |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB882876A (en) * | 1959-03-02 | 1961-11-22 | Rheostatic Co Ltd | Improvements in temperature responsive magnetic snap-action switches |
DE1195852B (en) * | 1960-12-09 | 1965-07-01 | Christian Buerkert | Temperature limiter |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB437826A (en) * | 1934-05-26 | 1935-11-06 | Harold Curtice Sanders | Improvements in thermally-operated electric switches |
US2183745A (en) * | 1936-07-31 | 1939-12-19 | Landis & Gyr Ag | Thermostatic temperature regulator |
US2291501A (en) * | 1936-05-14 | 1942-07-28 | Automatic Control Corp | Differential adjuster |
-
0
- BE BE486196D patent/BE486196A/fr unknown
-
1947
- 1947-12-09 GB GB32489/47A patent/GB632904A/en not_active Expired
-
1948
- 1948-12-06 CH CH271496D patent/CH271496A/en unknown
- 1948-12-09 FR FR976366D patent/FR976366A/en not_active Expired
- 1948-12-09 US US64326A patent/US2519558A/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB437826A (en) * | 1934-05-26 | 1935-11-06 | Harold Curtice Sanders | Improvements in thermally-operated electric switches |
US2291501A (en) * | 1936-05-14 | 1942-07-28 | Automatic Control Corp | Differential adjuster |
US2183745A (en) * | 1936-07-31 | 1939-12-19 | Landis & Gyr Ag | Thermostatic temperature regulator |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2707215A (en) * | 1951-10-18 | 1955-04-26 | Rheostatic Co Ltd | Safety cut-outs for electrically heated appliances |
US3207877A (en) * | 1959-03-02 | 1965-09-21 | Satchwell Controls Ltd | Thermostatic switch with permanent magnet induced snap action |
Also Published As
Publication number | Publication date |
---|---|
GB632904A (en) | 1949-12-05 |
BE486196A (en) | |
FR976366A (en) | 1951-03-16 |
CH271496A (en) | 1950-10-31 |
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