CA1107326A

CA1107326A - Automatic magnetic switch

Info

Publication number: CA1107326A
Application number: CA302,175A
Authority: CA
Inventors: Wen-Fong Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-27
Filing date: 1978-04-27
Publication date: 1981-08-18
Also published as: AU527719B2; ZA785603B; IT7828740A0; AU4025378A; DK438778A; IT1099741B; SE7810139L; BR7806828A

Abstract

AUTOMATIC MAGNETIC SWITCH
ABSTRACT
An automatic magnetic switch comprises a switch casing and a cover, an over-load or short-circuit protection means and a manual magnetic switch installed in the switch casing, and a magnetic control means contained in a sub-casing of the switch.
The manual magnetic switch has a substantially closed casing. A conductive plate with an electrical contact is fixedly mounted in the casing. Another conductive plate, generally rigid and inflexible, has an electrical contact mounted thereon and is mounted inside the casing for pivoting or sliding movement. Magnetic members, such as permanent magnets, one on the movable plate and one outside the casing urge the movable plate to a contact engaging position when the outside magnetic member is brought proximate to the casing, and a spring is used to restore the movable plate to its non-engaging position when the outside magnetic member is moved away from the casing.
The magnetic control means has a T lever to be actuated by the protection means, a control lever having a second magnet mounted thereon corresponding to a first magnet on the T lever, a pair of first and second control slots mounted on the couple arm of the control lever to lock in the first and second stop recesses of a control rod thereby to control the outside magnet moving away from or bringing approximate to the switch casing.

Description

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BACKGROUND OF THE INVENTION
The present invention relates to an automatic magnetic switch for utilization in common or specialized applica-tions.
In conventional electric switches especially in power circuits, the contacts are exposed to the air whether the contacts are of the knife or magnetic type. These kinds of switches are not fit for utilization in a dusty, moist, easily explosive or combustible environmentO Several different types of switch contacts for proventing explosions have been developed, such as oil switches, safty switches, etc. However, due to the complex constructions of these switches, they are not practical from a manufacturing or econamic point of view.
BRIEF SUMMARY OF T~IE INVENTION
An object of the present invention is to overcome the above limitations by providing a very simple magnetic switch. By adjusting the distance between a permanent magnet or an electromagnet and a plurality of moving contacts to attract or release -the same for contacting corresponding ~ixed contacts, the goal of closing an ` electric circuit is achieved.
Another objec-t of the present invention is to provide a switch wherein a chamber is filled with ins~ lating oil~ or a vacuum is maintained therein so as to minimize the arc which is produced during changes in states of thle switch from ON-OFF or OFF-ONc Th~e present invention also provides an electro-magnetic control means to automatically switch off the

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power circuit when it is over loaded.
Another object of the present invention is to provide -the switch with a safety guard. Once the power circuit is off, one can only manually restart the guard to recover the circuit to an ON state.
A still another object of the present invention is to reduce the maintenance cost, elevate reliability and increase the li~e time of the switch.
A skill further object of the present invention is to provide a magnetic switch which is particularly adapted for use in power circul-ts.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will be apparent from the following detailed descrlption of the preferred embodiment with reference to the accompanying drawings where:
Fig. 1 is a vertical sectional view of an automatic magnetic switch according to the present invention;
Fig. 2 is a perspective view of a manual switch using permanent magnet according to the present invention with part of the casing cut away;
Fig. 3 is a vertical sectional view of a switch according to the present invention along arrows A-A' in Fig, 2 showing a closed state of the contacts;
Fig. 4 is a sec-tional view along arrows B-B' in Fig. 3 showing a magnetic metal blocks disposed in a cover of the~switch casing;
Fig. 5 ~1S a vertical sectional view of an example~
of a~manual~switch using an electromagnet according to the ~: :
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preserlt inven-tion showing an open state o~ the contac-ts;
` ~ig. 6 is a ver-tical sectional view o~ an example of a manual switch showing a spring for restoring -the contacting plate;
~ig. 7 is a vertical sectional view o~ an example of a switch wherein the spring-operated contacting plate is cen-trally pivoted;
Fig. 8 is a vertical sectional view o~ other example of a switch showing a spring-operated contac-ting plate with parallel contacts;
Fig. 9 is a sectional view along arrow C-C' in Fig. 8 showing the construction of the contacting plate;
Fig. 10 is a vertical sectional view of another-example of a switch using a horizontally sliding con-tact;
Fig. 11 is a sectional view along arrows D-D' in Fig. 10;
Fig. 12 is a sectional view o- the switch in Fig. 10 showing a closed state of the horizontally sliding contacts;
Fig. 13 is a perspective view of the over-load or short-circuit protection means shown in Fig. 1 of the present inventlon;
Fig. 14 is a perspective view of the electromagnetic control means in an automatic magnetic switch according to the present invention;
Fig. 15 is a vertical sectional view o~ the automatic magnetic switch in Fig. 1 according to the present invention showing the power circuit is at an OFF
state;

_ 4 : , ~73~j Fig. 16 is a ver-tical sectional view of other example of an automatic magnetic switch using an electric magnet;
Fig. 17 is a vertical sectional view of another example of an automatic magnetic switch using a solenoid to indirectly control the magnet; and Fig. 18 is a vertical sectional view of still another example of an automatic magnetic switch USillg a manual switch shown in Fig. 10.
DETAILED DESCRIPTION OF TXE PREFERRED EMBODIMENT
Referring to Fig. 1, there is shown a vertical sectional view of an automatic magnetic switch according to the present invention. The automatic magnetic switch (1) includes a switch casing (2) and a cover (3) securred to the switch casing (2) by screws (4). The switch casing (2) - substantially includes two adjacent chambers (5) and (6) for the installation of an over-load or short-circuit . ~ .
protection means (7) and a magnetic contacting plates means 8 (actually a manual magnetic switch) respectively.
: 20 A sub-casing ~9~ is integrally moulded on the cover (3) forming a housing for the installation of a maenetic . ~
control means (10).
The magnetic contaoting plates means (8~
hereinafter~eferred as a manual magnetic switch i8 one of the important ~eatures according to the present invent~ion.
The manual swltch (8)~mainly includes a conductive plate (11) with~an electrical contact; another conductive plate (123, gene;rally rigid and inflexible havlng an electrical contact mounted théreon~ and being~mounted inside the casing (2) ~or pivoting or sliding movement; and magnetic member ~
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(13), such as peramen-t magnet, ~ixed on the movable conductive plate (12) for urging the later to a contact engaging position when an outside magnet (14) is brought proximate to the casing (2)o The manual switch (8) with various embodiments or examp:les is detailed descripted with reference to figures 2 to 12.
Re~erring to Figs. 2 and 3, there are shown perspective and vertical sectional views of a manual magnetic switch according to the present invention, which includes a switch casing 15 made o~ insulating and non-magnetic materials such as wood, plastics, etc.
The casing 15 has two protrusive plates or ~langes 16 with a plurality of holes 17 formed thereon for mounting the switch on a surface by screws. Block seats 18 and 19 are molded on a base 20 o~ the casing 15 and against the side walls 21. The block seats 18, 19 have a plurality of recesses 22 ~or receiving en electrically conductive plates 23 or a Z-shaped electrically conductive plate 24 which plates are fixed on the seats 18 and 19 by screws 25~ On the ~langes 16, a plurality o~ wire seats 25 are provided ~or permitting the lead wires 27 to lead away ~rom the caslng 15, the wires being connected to the electrically conductive plates 23 or Z-shaped plates 24 .
and connected to the same by screws 28. The construction of the electrically conductive plates~23 and Z-shaped ; plates is~suitable for single phase or three phase power applications. : : : ' The Z-shaped plates 24 are made of rigid conductive metals~with~platinum~or alloy electrical~
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con-tacts 29 formed thereon as :fixed contacts. Where the contacting pla-tes 23 are made of ~lexible eondueting metals, platinum contacts 30 are ~ormed on their ends as moving contacts. Additionally, a block 31 made o-f insulating and non-magnetie materials is mount and ~ixed on the eontaeting plate 23 by serew 32 as shown with a magnet 33 being mounted on the bloek 310 The block 31 is relatively thiek in dimension so that -the magnetie ~ield indueed by the eurrent in the contacting plate 23 does not interfere wi-th the iield o~ the magnet 33 to thereby isolate the same.
The switch casing 15 also eon-tains anlaccessible wall or a cover 34~attached to the side walls o~ the casing by serews 35. Actuatable means in the nature o~ a -shaped ~rame eonstruction 36 is hinged pivotally mounted on the eover 34 by a hinge 37 at the ends o~ supports 38 by pins 39. The -shaped ~rame eonstruction 36 also includes a ; hollow beam or cross member 40 with a permanent magnet 41 eontained in the hollow portion thereo~. The permanent magnet 41 is positionable above the magnetie 33 and can be positioned to be away or near the same when the -shaped ~rame eonstruction rotates about the pin 39.
Referring to Fig. 3, when the permanent magnet 41 is near the magnetie 33j an attraetive ~oree will eause the~
later to move upward eausing the pla-te 23 and ~he CODtaCt 30 to move to an engaging position and~eontaet the ~ixed eontaet 29 and thus elose the eireuit. On the other hand, when the pêrmanent magnet 41 is mo~ved away from said ~ ~ magnetie 33, the elastie or restoring foree of the eontaeting : : ~ : ~ ~ ; : .
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~ ~ ~ 3 ~9 plate 23 w:ill overcome the attractive ~orce therebetween causing the later to move downward to a disengaging position thus breaking the circuit between contact 30 and fixed contact 29. It is not necessary to use the above~
mentioned -shaped frame structure. Any method or apparatus which can adjust the attractive force between the permanent magnets 41 and 33 can be used such as arrangements which use horizontal motion or rotation of the permanent magnet 41 along the surface of the casing cover 34. Furthermore, -the chamber in the switch casing 15 is advantageously hermetically sealed and filled with inert gas or insulating oil or a vacuum maintained therein to minimize arcs which are produced during switching or changes in the ON-OFF states.
- Referring to Fig. 4 which is a sectional view along arrow B-B' in Fig. 2, there is shown a pair of magnetic blocks 42 which are disposed in the cover 34 of the casing as shown under the beam 40 and the permenent :;
~ magnet 41 to bridge the space between the latter and ;~ 20 magnet 33 and concentrate the magnetic flux and thus enhance the attractive force. The magnetic flux path is shown by the arrow and dash line.~
Referring to Fig. 5, which shows a verticle sectional view of a switch according to the present , ~
2~5 invention, an electro magnet 43 is fixed on the cover 34 o~ the caslng 15 replacing the permanent magnet 41. The operation of the rest of the parts of the switch is the same as described for the switch in Figs. 1 and 2.
Referring to Fig. 6, the contacting plate 44 lS

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generally rigid and inflexible and pivoted on the block seat 45 by a pin 46. Resilient means such as a spring 47 is connected to ~he contacting plate 44 and to the casing base 48 causing the plate 44 rest on a seat 49. A soft wire 50 is connected between the contactingpplate 44 rest on a seat 49. A soft wire 50 is connected between the contacting plate 44 and the lead-out wire 51. In this kind of switch, the contacting plate 44 can be made of a thicker and harder metal which can conduct larger currents and is thus more suitable for power applications. In addition, the ON-OFF operation is much more accurate as being spring-operated.
Referring to Fig. 7, the contacting plate 52 is centrally pivoted on a seat 53 by a pivot 54. This switch embodiment has the same operation mechanism as the switch in Fig. 6 except for the pivot position o~ the contacting plate 7 one being at the end at the end and the other being at the center.
Referring to Figs. 8 and 9, there is shown an example of a spring-operated switch. A apir of contacting plates 55 are fixed on the block seats 56 at the input and output sides. A moving contacting plate 57 slidably engaged the slot~58 of a vertical bar S9, and bîased by a sprlng 60. The moving contacting plate 57 together with the contacts 61 formed thereon move upward to close the circuit upon the establishment.of an attraction force , ;~; between the magnets 62 and 63. And Fig. 9 is a sec-tional view along arrows C-C' in Flg. 8 showing the construction of the moving contacting plate 57 and the slot 58.

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Referring to Figs. 10 and 11 there is shown a vertical sectional view of another examp]e of a switch.
A lever 64 pivoted on a support 65 by a pin 66 has a fork arm 67 adapting cooperating with a slipper 68 of a horizontally sliding contact 69. The sliding contac-t 69 is also biased by a spring 70 and can move right or left according to the attraction force between magnet 71 and 72 through the lever mechanism. The closed state of the horizontally sliding contacts with the fixed contact 73 is shown in Fig. 12, The over-load or short-circuit protection means (7) installed in the chamber (5) of the switch casing (2) is better shown in Fig. 13. This means (7) is a conventional one and includes a current conductive plate 74, a bi-me-tal 75 and a short-circuit protection electromagnet 76.
Referring to Fig. 13 with reference to Fig. 1, the current conductive plate 74 can be fixed to the switch casing 2 by screws. The bi-metal 75 will bend to a certain extent when power circuit is over current and the current conductive plate 74 raises in temperature. If any t~o of the three phase power circuit are short circuited, the large current variation on the current conductive plate74 will cause an induced magne-tic flux in the electromagnet 76 thus attract down the moving portion 77 of the electromagnet `~ 76.
Referring to Fig. 14, which is a perspect view of the magnetic con-trol means 10 accordlng to~the present invention.
This magnetic control means 10 is another important features of the present :invention. The magnetic control means 10 has a T
lever 78pivotally mounted to a support extending from side wall :

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w.ith a first magnet 79 mounted on one end of the transverse lever arm 80 thereof. In the sub-casing 9, a seat 81 ex-tends from the cover 3 and a control lever ~2 is pivoted on said seat 81 by a pin 83. The control lever 82 includes a lower transverse arm 84 with a second magnet 85 mounted thereon;
a couple arm 86 with a first control slot 87 pivoted there-to by a pin 88 and a second control slot 89 slidably mounted to the adjacent end thereof by a bolt 90; and a spring 91 connect-ing the couple arm 86 to the case cover 3. The second control slot 89 has a vertical slot 92 engaging with said bolt ~0 and a pair of ear portions 93 to stop the spring 94 which normally causes the bolt 90 to rest at the lowest portion of the vertical slot 92. Both the first slot 87 and second control slot 89 have an inclined surface at the top portion thereof and pro-trude -through the wall 95. The sub-casing 9 also has slots 96 and 97 for containing a control rod 98 which has a first stop recess 99 and a second stop recess 100. The control rod 98 connects to the outside magnet 14 which is screwed to a non-magnetic plate 101 with a spring 102 connecting the same to the.sub-casing 9. The magnetic control means 10 also has a manual : swi.tch off means 103 which:has an arc--faced button 104, a forked body portion 105 and a pushing plate 106 installed between the wall 95 and the ear portions 93 of the second control slot 89.
The operation o~ the automatic magnetic switch accord-ing to the present invention will be described herein after with rePerence to Figs.. 1, 14 and 15. When power circuit is normal, the outside magnet 14 attracts the magnet 13 thus close the:contadts on the current con~uctive plate 11 and 12 and the se.cond control slot 89 locks in the second stop recess 100 of the .

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control rod 98 as that sho~n in Figs 1 and 14. Once the power circuit is over-load or short circuit, -the bi-metal 75 or protection electromagne-ts functions and the T lever 78 sta~ts -to rotate causing the first magnet 79 th attract the second magnet 85. Since the second magnet 86 is attracted by the first magnet 79 of the T lever 78, the control lever 82 begins to rotate clockwise thus the couple arm 86 drives the second control slot 89 to go downwarld and to slip off -the second stop recess 100. 'Irhe control rod 98 now moves to right due to the restoring force of the spring 102 and drives the outside magnet 14 -to be away from the cover 3. The control rod 98 will finally be locked by the first control slot'87 and the magnet 13 drops down to switch'off the contacts of the current conductive plates 11 and 12 as that shbwn in Fig. 15.
It is to be noted that the restoring force of the spring 102 must be larger than the magnetic attractive force between : magnets 13 ahd 14, And -the magnetic attractive ~orce between :
the first magnet 79 and second magnet 85 must be larger than the'restorlng force of the spring 91. Besides, once the power ~ 20 circuits is automatlca11y switched off, the first and second .~ ma~nets 79 and 85 remain attracted and the first control slot'87 remains to lock in.the'forst stop recess 99 of,the.control rod 98~ The outside magnet 14 can not recovered -to. its initial state except one manually liffl the~lower transverse arm 84 of the control lever 82.to cause the first control slot 87 to slip out of the'first stop recess 99 of the~control rod:
98. Therefore, the lower transverse~arm 84 serves as a safty guard to the automatic swi'tch . On the other hand~ one'can~
push'down thle manual switch'off means 103 from the button 1~4 .

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to ~anually switch of~ the circ-uit under emergency circum-st ances O
In the side wall of the sub-casing 9, there is provided a screw 116 ~or adJusting the position of the lower transverse arm 84. The sensitivity of the automatic magnetie switch can be adjusted by adjusting the screw 116. The lower the transverse arm 84, the higher the sensitivity of the switcho Referring to Fig. 16 which shows an embodiment according to the present invention. An electromagnet 107 has been employed and a contacts means 108 is installed in -the switch ca casing 2. A driving arm 109 is ~ormed to the right end of the transverse lever arm 80 of the T lever 78. A rod 110 with a second magnet 111 is instaled in sub-casing to serve as the safty guard to the automatic magnetic switch. When the power circuit is over-load or shbrt circuit~ the T lever 78 will be actuated by the bi-metal 75 or protection electromagnet 76 to rotate. The driving arm 109 will switch of~ the contacts of the contacts means 108 to-cut off the current of the electromagnet 107. And the magnet 103 will drop down to switch o~f the whole power circuit.
Referring to Fig. 17 which shows another emhodi-ment o~ an automatic magnetic switch according to the present inventionO The construction of the switch in Fig. 17 is similar to that shbwn in Fig. 16 except the former utilizes a solenoid 112 to indirectly control the outside magnet 113.
When the power circuit is over-load or short circuit~ the , ~ .
; current~w~ o~ the solenoid 112 will be switched off, the magnet 113 will rotate away ~rom ~he cover about a shaft 114 due to the restoring force o~ a spring 115. Again, the rod 110 .

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and -the second magnet 111 serve as a safty guard th the aotomatic magnetic switch. This switch embodiment has special advantages and values because a low power solenoid will be enough for switching a power circuit. Besides, it can obivate the disadvantages of a conven-tional magnetic switch, i.e. to avoid the iron-rust dropping into the switcho It is further to be noted that the automatic magnetic switch according to the present invention may have æ plurality o~ variations, e.g. the switch in Fig. 18 utilizes the manual switch construction ofFig. 10. As a matter of fact, the switch in Figo 7 may also be applied to the automatic magnetic switch.
It is stlll to be noted that the bridging magnet 42 as shbwn in Fig. 4 may also be applied to the cover be-tween the first magnet 79 and the second magnet 85 or the outside rnagnet 14 and magnet 13 to concentrate the magnetic flux thus enhance the attraction force therebetween.
The design of the switch ~ccoxding to the present invention provides a novel, sa~e, simple, econamic and practicall magnetic switch particularly suitable for hmgh power switching applications.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An automatic magnetic switch comprising a switch casing, a cover secured to the casing, an over-load and short-circuit protection means installed in a first chamber of said switch casing, a manual magnetic switch installed in a second chamber of said switch casing, and a magnetic control means contained in a sub-casing which is integrally molded on the cover wherein said manual magnetic switch has a first electrically conductive plate fixedly mounted within said casing; a first electrical contact on said first elec-trically conductive plate; a generally rigid and inflexible second electrically conductive plate mounted within said casing for movement between engaging and disengaging posi-tions; a second electrical contact on said second electrically conductive plate arranged to make and break contact with said first electrical contact in the respective engaging and dis-engaging positions of said second electrically conductive plate and leading out of said casing through the walls thereof;
resilient means for urging said second electrically conductive plate to one of said engaging and disengaging positions;
magnetic means cooperating with said second electrically conductive plate and including actuatable means movable proximate to and away from said casing cover on an outer surface thereof with respect to said second electrically con-ductive plate, movement of said actuatable means proximate to said casing cover moving said second electrically conductive plate to the other of said engaging and disengaging positions without flexure or deformation thereof.

2. An automatic magnetic switch as defined in claim 1, wherein said switch casing is hermetically sealed.

3. An automatic magnetic switch as defined in claim 1, wherein said second chamber of the casing is filled with an insulating oil.

4. An automatic magnetic switch as defined in claim 1, wherein vacuum is maintained within said casing.

5. An automatic magnetic switch as defined in claim 1, wherein said casing is filled with an inert gas.

6. An automatic magnetic switch as defined in claim 1, wherein said magnetic means comprises magnetizable members mounted on said second electrically conductive plate and on said actuatable means, at least one of said magnetizable members comprising a magnet.

7. An automatic magnetic switch as defined in claim 6, wherein said magnetizable member mounted on said second electrically conductive plate comprises a permanent magnet, and further comprising a non-magnetic block interposed between said second electrically conductive plate and permanent magnet to space and at least partially magnetically isolate the same.

8. An automatic magnetic switch as defined in claim 1 further comprising magnetizable blocks disposed in said accessible wall and arranged to bridge a substantial portion of the space between said second electrically conductive plate and said actuatable means to enhance the magnetic field in the proximate position of said actuatable means.

9. An automatic magnetic switch as defined in claim 6, wherein said second electrically conductive plate is pivotally mounted within said casing.

10. An automatic magnetic switch as defined in claim 6, wherein said second electrically conductive plate is slidably mounted for generally transverse movements.

11. An automatic magnetic switch as defined in claim 6, wherein said second electrically conductive plate comprises a slidably mounted shaft or rod, and a pivotally mounted lever or crank arm cooperating with one end of said shaft or rod to slide the same upon actuation of said lever or crank, whereby said shaft or rod only moves between engaging and disengaging positions along the longitudinal length thereof.

12. An automatic magnetic switch as defined in claim 1, wherein said magnetic control means comprises a T lever pivotally mounted to the side wall of the casing with a first magnet mounted on a transverse lever arm thereof; a control lever pivoted on a seat mounted on a transverse arm thereof; a first control slot and a second control slot are pivoted on the couple arm of said control lever; a control rod having a first and a second stop recesses formed thereon to connect the outside magnet; the magnetic control means is actuated by the over-load and short-circuit protection means to switch off the power circuit.

13. An automatic magnetic switch as defined in claim 12, wherein said second control slot has a pair of ear portions to stop a spring, a vertical slot formed on the second control slot and a bolt passes through said vertical slot;
said spring causes the bolt to rest at the lowest portion of the vertical slot.

14. An automatic magnetic switch as defined in claim 12 or 13 wherein said magnetic control means further com-prises a manual switch off means having an arcfaced button, a forked body portion and a pushing plate adapted between the wall of said sub-casing and the ear portions of the second control slot for manually switching off the power circuit.

15. An automatic magnetic switch as defined in claim 1, wherein said magnetic control means includes a contacts means fixed in the switch casing for switching off the circuit of an outside electromagnet.

16. An automatic magnetic switch as defined in claim 12, wherein said magnetic control means further includes a driving arm formed to the end of the transverse lever arm of the T lever for switching off the contacts of said contacts means when the T lever is actuated by the over-load and short-circuit protection means.

17. An automatic magnetic switch as defined in claim 1, wherein said magnetic control means further comprises a solenoid secured on the sub-casing, a contacts means fixed in the switch easing to switch off the circuit of said solenoid, and an outside magnet connected to a spring to rotate away from the cover of the switch easing when the current in said solenoid is switched off.

18. An automatic magnetic switch as defined in claim 1, wherein said switch contains bridging magnets in the cover at a position between a first magnet and a second magnet or an outside magnet and the magnet in the manual magnetic switch to concentrate the magnetic flux thus enhancing the attraction force therebetween.

19. An automatic magnetic switch as defined in claim 12, wherein said magnetic control means further comprises an adjusting screw for adjusting the position of the lower transverse arm of the control lever whereby to adjust the sensitivity of the switch.

20. A manual magnetic switch comprising a substantially closed casing having a cover; a first electrically conductive plate fixedly mounted within said casing; a first electrical contact on said first electrically conductive plate; a generally rigid and inflexible second electrically conductive plate mounted within said casing for movement between engaging and disengaging positions, said second electrically conductive plate being slidably mounted for generally transverse move-ments; a second electrical contact on said second electrically conductive plate and leading out of said casing through the walls thereof; resilient means for urging said second electri-cally conductive plate to one of said engaging and disengaging positions; magnetic means cooperating with said second electrically conductive plate and including actuatable means movable proximate to and away from said casing cover on an outer surface thereof with respect to said second electrically conductive plate, said magnetic means comprising magnetizable members mounted on said second electrically conductive plate and on said actuatable means, at least one of said magnetizable members comprising a magnet; movement of said actuatable means proximate to said casing cover moving said second electrically conductive plate to the other of said engaging and dis-engaging positions without flexure or deformation thereof.

21. A manual magnetic switch comprising a substantially closed casing having a cover, a first electrically conductive plate fixedly mounted within said casing; a first electrical contact on said first electrically conductive plate; a generally rigid and inflexible second electrically conductive plate mounted within said casing for movement between engaging and disengaging positions, said second electrically conductive plate comprising a slidably mounted shaft or rod, and a pivotally mounted lever or crank arm cooperating with one end of said shaft or rod to slide the same, upon actuation of said lever or crank, whereby said shaft or rod only moves between engaging and disengaging positions along the longi-tudinal length thereof, and a second electrical contact on said second electrically conductive plate and leading out of said casing through the walls thereof; resilient means for urging said second electrically conductive plate to one of said engaging and disengaging positions; magnetic means cooperating with said second electrically conductive plate and including actuatable means movable proximate to and away from said casing cover on an outer surface thereof with respect to said second electrically conductive plate, said magnetic means comprising magnetizable members mounted on said second electrically conductive plate and on said actuatable means, at least one of said magnetizable members comprising a magnet; movement of said actuatable means proximate to said casing cover moving said second electri-cally conductive plate to the other of said engaging and dis-engaging positions without flexure or deformation thereof.