US 2849580 A
Description (OCR text may contain errors)
g 1958 KAZUMA TATElSHI 2,849,580
SNAP SWITCH FOR DIRECT CURRENT Filed April 7, 1954 INVENTOR )fagzzma. Z'afez'shi United States This invention relates to a snap switch for direct current.
It is an object of the invention to provide a switch of compact form especially adapted to be used for controlling direct current.
It is another object to construct a snap switch which can handle relatively large amount of direct current with safety.
A still further object of this invention is to protect the inner walls of the switch casing from high temperature of arcs.
The invention is illustrated in the accompanying drawings, in which:
Fig. l is a side sectional view of the snap switch according to this invention,
Fig. 2 is a plan view of the casing with the cover removed, and
Fig. 3 is the sectional view taken on line III-III of Fig. 2.
In said drawings, 2 is a casing of any suitable insulating material wherein a leaf spring 6 carrying contacts 7 and 7' at one end, is fixed at the other end by a screw 4 to an anchor 3. Said leaf spring 6 constitutes the central arm of a three-armed spring plate 13, the two remaining arms of which consisting of the compression spring members 6. Said spring members 6' are thus preferably formed as an integral part of the plate 13 and are integral with the leaf spring 6. The spring members 6' are shorter than the leaf spring 6 and are maintained in compression by being bowed downwardly as clearly shown in Fig. 1 by having their ends disposed in the notches 5 in the anchor 3.
Further, in the casing 2, an upper stationary contact 8 and a lower stationary contact 8 are so arranged at the opposite sides of the anchor 3 as to make contact with the contacts 7 and 7 respectively which are fixed at the end of the leaf spring 6.
1 is a cover in which a small permanent magnet block 9 is partially embedded just above the stationary contacts 3 and 8'.
Between the cover 1 and the casing 2, a push button 11 is placed with its plunger 12 protruding upwardly from the cover 1 while its lowest end rests on the leaf spring 6.
The drawings show the switch in its normal state wherein the contact 7 is in contact with the upper stationary contact 8 while the lower stationary contact 8 remains opened.
When the plunger 12 is depressed, the leaf spring 6 bends downwardly against the action of the compression members 6' until the dead point of the link is over when the contact between the contacts 7 and 8 is opened and the contact between the contacts 7 and 8 is closed quickly by the snap action of the spring plate 13. When the plunger 12 is released, the spring plate 1.3 snaps back quickly with the aid of the compression members 6' as well as the elasticity of the leaf spring 6, and the contact between the contacts 7' and 8' is opened and the contact between the contacts 7 and 8 is reestablished. The arcs generated between the moving contacts 7, 7' and stationary contacts 8, 8 during the opening of the circuits are both blown sidewards by the magnetic flux of the magnet 9 as it is arranged horizontally with longitilt 2 tudinal poles and quenched so quickly that the contacts are protected from burning out due to the immense heat of the arcs. Consequently, the switch becomes capable of handling relatively large amount of direct current safely.
In the switch shown here, as the magnet 9 is arranged horizontally with longitudinal poles, the arcs produced at the upper and lower stationary contacts are blown sidewards against the inner walls of the casing 2 where sheets 10 of metal with good heat conductivity such as copper and brass are attached to cool the heat of the are by distributing it quickly and evenly over the surfaces of said sheets when the arc reaches to them, whereby the breaking capacity of the direct current of this improved switch is adequately increased and moreover the walls of the casing 2 are effectively protected from the are.
To increase the cooling effect of the sheets 10, it is preferable to provide openings 14 in the casing 2 just behind said sheets.
In the present invention, as a small rectangular block of permanent magnet is used, the size of the whole switch can be made smaller than the switch which uses a horse shoe magnet.
It is further to be noted that the arrangement of the permanent magnet 9 wherein the line connecting the poles is longitudinal to the leaf spring 6, is one of the important features of the invention; because, if said magnet be placed with the line connecting the poles be vertical to the leaf spring, the arc will be blown along and onto the leaf spring whereby the quenching of the are will become difficult and the capability of the switch for cutting off direct current will be much reduced.
Having described my invention, I now claim:
A double-throw snap switch for direct current comprising a completely closed casing, an anchor mounted therein and having a notched end, a three-armed spring plate having a central spring arm secured at one end to the anchor, contacts carried by and movable with the other end of the spring arm, the two remaining arms of the plate being bowed under compression and maintained in such bowed condition by engagement with the notched end of the anchor, upper and lower stationary contacts mounted within the casing respectively above and below the contactcarrying end of the spring arm, a cover fitted on and closing the casing, a push button having a plunger operative through the cover and located above the spring arm and adapted when depressed to force the spring arm downwardly, a permanent magnet partially embedded in and carried by the cover and positioned above the upper stationary contact with its poles disposed longitudinally to the spring arm, whereby an are formed upon breaking of contacts is deflected transversely of said arm and sheets of heat-oonductive metal attached to the inner side wall surfaces of the casing adjacent to the contacts in the path of arc deflection, the walls of the casing overlying said sheets' being perforated for heat transfer directly to the atmosphere.
References Cited in the file of this patent UNITED STATES PATENTS 1,146,637 Massa A July 13, 1915 1,960,020 McGall May 22, 1934 2,096,502 Wetzel Oct. 19, 1937 2,133,158 Planck et al Oct. 11, 1938 2,250,016 Garner July 22, 1941 2,374,986 Fetter May 1, 1945 2,380,851 Lamb July 31, 1945 2,417,134 Scott Mar. 11, 1947 2,490,020 Enzler Dec. 6, 1949 2,627,754 Millard Feb. 10, 1953 2,639,352 Watson May 19, 1953