DE1208387B - Electrical bimetal snap switch - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

HOIh

German class: 21 c - 40/05

Number: 1208 387

File number: M 52665 VIII d / 21 c

Filing date: April 28, 1962

Opened on: January 5, 1966

The invention relates to an electrical bimetal snap switch with a one-sided clamped, at its free end the movable contact-carrying bimetallic strip, which is an elongated one has a curvature that cannot be developed and that extends from the clamping to the movable contact, which is partially surrounded by a rigid support plate with lateral projections near the clamping point is.

In the case of the known switch from which the invention is based, the curvature that cannot be developed is sufficient not across the entire width of the strip. This creates additional resistance when snapping over of the bimetal strip in itself. In addition, the support plate has only very short lateral projections. Between the ends of the projections of the transverse axis tier not developable curvature and the edge this curvature itself are therefore located in the known snap-action switch with gusset-shaped surfaces of the Bimetal strips that are not covered by the support plate. If in the bimetal strip as a result Heat generation Tensions arise, these cause the strip to bend slightly, namely due to the presence of the flat surfaces of the bimetal strip not covered by the support plate. There is thus a considerable reduction in contact pressure between the stationary and the movable switching contact, In the borderline case, creeping occurs, which should be avoided at all costs.

Snap switches are also known, but they are also part of the subject matter of the invention. at In these known switches, the support plate engages over half of the curvature that cannot be developed. In other words, the support plate supports the bimetallic strip over the curvature, since it is on the arch itself rests on.

It is also known for snap switches to use a narrow tongue as a support plate, which extends to the middle of the bulge that cannot be developed.

In these snap switches, which are further away from the subject matter of the invention, their bimetallic strips has a non-developable bulge of circular outline also occurs before snapping over a contact pressure reduction on the switching contacts, which is caused by a correspondingly strong mechanical bias must be counteracted. In contrast, the unresolvable Curvature of the subject invention be elongated. The length of the bimetal strip from the clamping point to the movable switch contact is usually larger than the width of the strip. counter Electrical bimetal snap switch

Applicant:

Mechanical Products, Inc.,

Jackson, me. (V. St. A.)

Representative:

Dr.-Ing. H. Negendank, patent attorney,

Hamburg 36, Neuer Wall 41

Named as inventor:
Homer Freeman Malone,
Robert William Filchak,
Jackson, me. (V. St. A.)

Claimed priority:

V. St. v. America May 1, 1961 (106 701)

with a circular curvature, d. H. a curvature of spherical cap shape, can therefore not differ from the Clamping to extend to the switching contact, so that parts of the strip remain, which are due to can bend from thermal stresses. This in turn causes a significant decrease in pressure to the Switch contacts. In all cases it is non-bifurcated support plates, which, however, like continue to show known snap switches that must rest on the non-developable bulge. this however, it is disadvantageous because it affects the sensitivity of the switch.

With the invention, a bimetallic snap switch of the type mentioned is to be created at the disadvantages inherent in the known snap-action switch are avoided, the switch In particular, it should be designed so that it can be snapped over more easily than was previously possible can, so that the sensitivity of the switch is increased, with the known switches existing considerable contact pressure reduction immediately before switching off practically avoided will. The mechanical preload can therefore be kept much smaller in order to achieve the required Maintain contact pressure until it snaps.

This is achieved according to the invention in that the curvature is approximately pointed in the longitudinal direction Ends that the width of the bulge in at

509 777/307

is known to be equal to the width of the bimetal strip and that the elongated, by a approximately V-shaped section of the support plate formed projections the flat clamping end of the Cover the bimetallic strip up to close to the transverse axis of the bulge.

In the snap switch designed according to the invention, the bimetallic strip is snapped over only on internal stresses of the bulge, while with the known switches still thermal Forces that occur outside of this zone act significantly. The snapping of the invention trained switch only takes place if the switch contacts are still in contact, because the strip tries to bend due to the internal stresses, which is prevented by the support plate will. In other words, as the bimetal strip heats up, the support plate presses more and more Measure to the zone near the bulge. When snapping from the unlocked position to the On position, this additional external force does not occur.

In a further advantageous embodiment of the subject matter of the invention the curvature can be limited by two opposing circular arcs, the curvature of which corresponds to the length-width ratio of the Bimetal strip is adapted.

The invention will now be based on an exemplary embodiment which is shown in the drawings is to be described.

Fig. 1 shows a side view of a thermosensitive snap body in section, the is effectively built into a motor protection switch;

F i g. Fig. 2 shows a plan view of the support body and the thermosensitive body of Fig. 1;

F i g. Fig. 3 shows an exploded view of the superimposed parts of Fig. 1;

F i g. 4 shows a plan view of a modified motor protection, with part of an outer insulating Sleeve removed to show a conductive inner sleeve;

F i g. 5 shows a section essentially along line V-V of FIG. 4;

F i g. 6 shows a section essentially along line VI-VI in FIG. 5;

F i g. 7 shows a partial illustration of the tensioned portion of the temperature sensitive body according to the invention;

F i g. 8 shows a section essentially along line VIII-VIII of FIG. 7;

F i g. 9 shows a section essentially along line IX-IX in FIG. 7.

A temperature-sensitive snap-in body in the form of a bimetal strip 10 is exemplified in one Embodiment of the present invention operatively connected to a protective housing 12. That Housing 12 consists of an elongated conductive outer jacket 14 in which a fixed contact is inside 16 and is electrically connected to the housing 14. An insulating end plug 18, the For example, made of epoxy resin, the open end 19 of the jacket 14 seals off. That outer end 20 of a connector 22 is held by the plug 18, this connector 22 with a lead wire 24 is electrically connected, which is connected to a pole of an electrical energy source can be.

The connecting body 22 extends into the jacket 14 and has its inner end section 28 designed as a support body which is held in pressure contact with one end 30 of the bimetal 10. The bimetal 10 and the inner end 28 of the terminal 22 are. stacked between two insulating bodies 32 and 33 inserted, with a central section 34 of the insulating body 33 through openings 35, 36 and 37 in the bimetal 10, the terminal 22

ίο and the insulating body 33 is pushed through, to hold the kit of the stacked parts together.

A lead wire 40 having a terminal 42 on it is electrical to the jacket 14 of the switch 12 connected to the same with the other pole of an electrical, not shown Connect energy source. At the free end portion 52 of the bimetal strip 10 is, for example by welding, a movable contact 50

zo so that it is aligned for cooperation with the fixed contact 16 and with brought this to close an electrical circuit through the circuit breaker 12 in contact can be.

According to a feature of the invention, the inner end portion 28 of the end fitting 22 is fork-shaped formed and acts as a support or pressure plate, the edge portions 54 and 56 from the space between the stacked insulating bodies 32 and 33 up to Points extend substantially transversely with the minor axis one on the bimetal formed embossing or non-developable surface 60 are aligned, which as a dome of a flattened Spheroids can be called. Therefore, essentially all of the unembossed portion is of the bimetal body 10 between the outer end portion 30 and the contact thereon 50 rigidly mounted.

The main part of the embossing 60 extends in the longitudinal direction essentially over the entire, unprotected length of the bimetal strip 10 between the apex 62 of the fork-shaped end 28 the terminal 22 and the contact 50. Furthermore, the minor axis of the embossing 60 extends transversely across the entire width of the strip 10 near the ends of the edge portions 54 and 56. So is im substantially all of the unsupported area of the bimetal strip 10 between the fixed end 30 and the movable contact 50 is biased. This bias must be due to initial temperature changes of the bimetal are overcome before its snap action. Therefore effect proportionately small temperature changes caused by changes in current or heat fluctuations, just a change the bias of the arch and not a creep of the bimetal. Be that way disadvantageous creeping movements of the bimetal essentially excluded.

In the F i g. 4 to 6 a modified motor protection switch is shown, which consists of an elongated conductive housing 114, which is enclosed within a plastic sleeve 115. Within this housing 114 is a fixed contact 116 is arranged, which with a connecting strip 117 electrically connected is. An end portion 118 of the sleeve 115 closes an open end 119 of the housing 114

sealing. An outer end portion 120 of the connecting tape 117 is electrically connected to a lead wire 124 which can be connected to one pole of an electrical energy source.

As best seen in Fig. 5, a temperature-sensitive bimetal strip 125 is inserted with its one end section 126 between an insulating body 128 and a conductive body 130 in the manner of a stack. Through the openings 133, 134, 136, 138 and 139 in the conductive body 130, the bimetal 125, the insulating body 128, the connecting tape 117 and a lower insulating body 140 a, an insulating body 132 is pushed to hold the layered structure of the parts together.

With the housing 114, a lead wire 140 is electrically connected (not shown) to the other side of this housing 114 to the other pole of an electrical power source to be connected.

A movable contact 150 is attached to the free end portion 151 of the bimetal 125 , for example by welding, which is oriented so that it can interact with the fixed contact 116 and, through the motor protection switch, closes an electrical circuit from the conductor 124 to the connecting tape 117, the fixed contact 116, the movable contact 150, the bimetal 125, the conductive body 130, the housing 114 and to the conductor 140 leads.

In accordance with a feature of the invention, an inner end portion 152 of the conductive body 130 is fork-shaped and acts as a support or pressure plate, the outer edge portions 154 and J 56 of which extend on the bimetal 125 along to the minor axis of an embossing or non-developable surface 160 . The embossing 160 can be referred to as the dome of a flattened spheroid. Therefore, essentially the entire unembossed portion of the bimetal is rigidly supported between the end portion 126 and the contact 150 thereon. The main axis of the embossing 160 extends in the longitudinal direction essentially over the entire unsupported section of the bimetal 125 between an apex 162 of the fork-shaped end section 152 of the body 130 and the contact 150 on the bimetal strip 125. Furthermore, the minor axis of the embossing 160 extends across the full width of the strip 125 near the ends 152 of the edge portions 154 and 156 of the conductive body 130.

This switch corresponds in its function of the snap link to the switch according to FIGS. 1 to 3. It differs from the first exemplary embodiment essentially only in that the clamped end of the bimetal strip is in direct contact with the metallic housing 114 with regard to thermal output, while the mating contact 116 is insulated from this housing.
Figs. 7 and 9 show a hemispherical one

ίο Embossing 160, which is embossed into the bimetal by a pair of mold jaws 200 and 202 with convex or concave profiles 204, 206 . It should be noted that according to FIG. 8 the sections of the bimetal on the major and minor axes of the embossing 160 are arcuate and are determined by the radii 208 and 210 . It has been found that the embossment 160 when embodied in this manner has the most beneficial snap-in characteristics.

Claims (2)

Patent claims: 1.Electric bimetallic snap-action switch with a bimetallic strip clamped on one side and carrying the movable contact at its free end, which has an elongated curvature that extends from the clamping to the movable contact and that cannot be developed near the clamping point by a rigid support plate with lateral projections Part is included, characterized in that the curvature runs out in the longitudinal direction in approximately pointed ends, that the width of the curvature (60; 160) in a known manner is equal to the width of the bimetal strip (10; 125) and that the elongated, through an approximately V-shaped section of the support plate (22) formed projections (54, 56; 154, 156) cover the flat clamping end of the bimetal strip up to close to the transverse axis of the curvature. 2. Switch according to claim 1, characterized in that the curvature (60; 160) is limited by two opposing circular arcs, the curvature of which is adapted to the length-width ratio of the bimetal strip (10). Considered publications:
German Patent Nos. 639 496, 1000094; French Patent No. 1251469;
U.S. Patent Nos. 2,767,284, 2,820,870. For this purpose, 1 sheet of drawings