Method of Manufacturing a Multi-Phase Thermal Circuit Breaker and Multi-Phase Thermal Circuit Breaker Produced Thereby

The present invention relates to a new and improved method of manufacturing a multi-phase thermal circuit breaker, and to a new and improved multi-phase thermal circuit breaker manufactured thereby.

In its more particular aspects, the method of manufacturing the multi-phase thermal circuit breaker comprises the steps of mounting each of a multiple number of bimetallic elements, each of which contains a bendable section which acts upon a common actuator member, at a support and mounting the supports in juxtaposition to each other at a retainer or holder member.

As to the circuit breaker of the present development such is of the type comprising a multiple number of bimetallic elements, each associated with one phase, and each bimetallic element comprises a bendable section or portion arranged to act upon a common actuator member. Each of the bimetallic elements is mounted at a support which, in turn, is secured to a retainer or holder member.

In multi-phase bimetallic circuit breakers of such type the bimetallic elements each associated with one respective phase act upon a common actuator member which, as a general rule, is designed as a slider. It must be ensured by appropriate measures that all bimetallic elements exert the same effect upon the actuator member when they are heated-up in the same manner. That is to say, the bending sections or portions of all the bimetallic elements must assume the same position relative to the actuator member at a defined ambient temperature and in the absence of current flow through the bimetallic elements.

In a prior art circuit breaker known, for example, from Swiss Pat. No. 558,593 there is measured for this purpose the mutual distances between the freely bendable end portions of the bimetallic elements after the bimetallic elements have been mounted in the housing. On the basis of the thus determined distances an individual slider is manufactured for this particular circuit breaker. Since, in addition to measuring the mentioned distances an individual slider or slide member has to be manufactured for each circuit breaker, this solution is rather expensive in respect of the work involved, something which is disadvantageous in terms of the manufacturing costs even in the case of automated production.

Furthermore, a bimetallic circuit breaker as known, for example, from Swiss Pat. No. 216,532, has bimetallic elements, each of which is secured to a support at one of its ends, and the support is pivotably mounted at a housing. Prior to the installation of the circuit breaker there is adjusted the position of each individual bimetallic element relative to the actuator member, which is designed as a controlling slider, by pivoting the individual supports in such a way that at a defined ambient temperature the distance between the bendable free ends of the bimetallic elements and abutting edges formed at the controlling slider is the same for all the bimetallic elements. This adjustment, which additionally requires some dexterity on the part of the installator, however, is very time-consuming and expensive and is unsuited for an automated manufacturing mode.

A further construction of circuit breaker is known from Swiss Pat. No. 400,319.

Therefore, with the foregoing in mind it is a primary object of the present invention to provide an improved method of manufacturing a multi-phase thermal circuit breaker which permits an automated manufacturing operation.

Another and more specific object of the present invention aims at the provision of a new and improved method of the aforementioned type which requires the least possible expense and is uncomplicated.

Also, it is a significant object of the present invention to provide a new and improved construction of a multi-phase thermal circuit breaker which may be rationally produced at the smallest possible expense in respect of time and apparatus.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the method of the present development is manifested by the features that, after mounting the bimetallic elements at least one supporting face is formed at each one of the supports, the supporting face lying in a plane which extends transversely relative to the bending direction of the bimetallic elements and at a distance from the bendable section which is essentially the same for all supports when the bimetallic elements are in the same heated-up state. Counter surfaces lying in a common plane are provided at a retainer or holder member, and the supports are supportingly connected to the retainer member with the support surfaces being supported at the counter surfaces.

The supporting surfaces can be formed at a predetermined distance from the related bendable section, which is preferably the end portion of the bimetallic elements, in a simple manner and in an automated operation. The same is true for manufacturing the counter surfaces at the retainer or holder member which, for example, may form part of a housing. Since, on the one hand, the distance between each of the bimetallic elements and the supporting surface formed at the associated support or support member is the same for all the bimetallic elements at a given temperature and since, on the other hand, the supports secured to the retainer member are mutually aligned due to their being supported at the counter surfaces which lie in a common plane, the bendable sections or portions of the bimetallic elements also assume a mutually aligned position. Due to the alignment of the bimetallic elements during the course of manufacture re-adjustment is thus no longer required.

As alluded to above, the invention is not only concerned with the aforementioned method aspects, but also relates to a novel construction of a multi-phase thermal circuit breaker. Generally speaking, the inventive circuit breaker comprises supports or support members each of which comprises at least one supporting surface lying in a plane which extends transversely relative to a bending direction of the bimetallic elements and at a distance from the bendable sections of the bimetallic elements which is the same for all supports when said bimetallic elements are in the same heated-up state. Counter surfaces are formed at a retainer or holder member, these counter surfaces lying in a common plane and supporting the supports at the supporting surfaces thereof.

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a section taken substantially along the line I--I in FIG. 2 of a bimetallic circuit breaker constructed according to the invention,

FIG. 2 is a side view, partially cut open of the bimetallic circuit breaker shown in FIG. 1 looking in the direction of the arrow A thereof; and

FIG. 3 is a side view of a bimetallic element mounted at a support or support member of the bimetallic circuit breaker shown in FIG. 1.

Describing now the drawings, it is to be understood that only enough of the structure of the multi-phase thermal circuit breaker has been shown as needed for those skilled in the art to readily understand the underlying principles and concepts of the present development. Turning attention now specifically to FIG. 1, there has been illustrated therein a three-phase bimetallic circuit breaker 1 comprising a housing 2 which is provided at one side thereof with a removable cover or cover member 3. Three bimetallic elements 4, 5 and 6 are accommodated in the interior of the housing 2. The bimetallic elements 4, 5 and 6 are arranged in juxtaposition to each other and each is associated with one phase (see FIG. 2). Each of the bimetallic elements 4, 5 and 6 is provided with a heater coil or winding 7, 8 and 9, respectively, one end of which is connected to the associated bimetallic element 4, 5 and 6, respectively, at an attachment spot or location designated by reference numeral 10, and the other end of which is fixed to a connecting element 11, 12 and 13, respectively. The connecting elements 11, 12 and 13 pass through the cover 3 and their free ends 11a, 12a and 13a, respectively, protrude from the housing 2.

One end 4a, 5a and 6a of the strip-like designed bimetallic elements 4, 5 and 6, respectively, is fixed to a related metallic support or support member 14, the construction of which will be evident from FIGS. 1 and 3. Each support or support member 14 comprises two protruding attachment or mounting arms 15 and 16 which pass through holes 17a and 17b, respectively, in a retainer or holder member 17 forming a housing wall. The supports 14 are additionally provided with a connecting member 18 to form a plug connection or junction, and such connecting member 18 extends in parallel to the attachment or mounting arms 15 and 16 and passes through a hole or opening 17c in the retainer member 17, so as to be freely accessible from the exterior of the housing 2. Furthermore, each support or support member 14 is provided with a second connecting member 19 to which an electric conductor or line may be connected by means of a terminal 20.

Two supporting surfaces 21 and 22 are provided at each support 14. The supporting surfaces 21 and 22 lie in a common plane which has been indicated by a dash-and-dot line in FIGS. 1 and 3 and which has been designated by reference character C. The plane C extends substantially at right angles to the bending direction B of the bendable sections or portions forming free ends or end portions 4b, 5b and 6b of the bimetallic elements 4, 5 and 6, respectively, mounted at the respective supports 14. Each support or support member 14 contacts a plate-shaped intermediate layer 23 by means of its supporting surfaces 21, 22, the intermediate layer 23 having a uniform thickness at least at the region of the supporting surfaces 21 and 22. On the side opposite to the supporting surfaces 21 and 22 the intermediate layer 23 contacts counter surfaces 24 and 25 formed at the retainer or holder member 17. Also the counter surfaces 24 and 25 lie in a common plane D which has been indicated by dash-and-dot lines in FIG. 1. This plane D also extends at right angles to the aforementioned bending direction B, and thus, is substantially parallel to the plane C.

A backing element 26 having spring or resilient properties is provided for each support 14 at the side of the retainer member 17 which is located opposite to the counter surfaces 24 and 25. The backing element 26 is pierced by the attachment or mounting arms 15 and 16. By twisting the ends or end portions 15a and 16a of these attachment or mounting arms 15 and 16, respectively, the supports or support members 14 are secured to the retainer or holder member 17 as shown in FIG. 1. The supports 14 and the intermediate layer 23 are urged against the retainer member 17 due to the backing element 26 which is supported at the retainer member 17 and which acts upon the twisted ends or end portions 15a, 16a of the attachment or mounting arms 15 and 16, respectively, in the manner of a compression or pressure spring. Consequently, the supports 14 which are supported at the counter surfaces 24 and 25, respectively, by means of their supporting surfaces 21 and 22 through the action of the intermediate layer 23 are held in an aligned position. Since the counter surfaces 24 and 25 lie in one and the same plane D for all three supports 14, these three supports 14 are thus, also, mutually aligned.

The bendable sections forming free ends or end portions 4b, 5b and 6b of the bimetallic elements 4, 5 and 6, respectively, bend in the direction of the arrow B when the bimetallic elements 4, 5 and 6 are heated-up. The bendable sections forming such free ends or end portions 4b, 5b and 6b act upon a common slider 27, defining an actuation member, which is journaled in the housing 2 for displacement in the direction of the arrow B. The slider or slide member 27 actuates a lever 28 of a circuit-breaking mechanism which is disposed in the lower portion of the housing 2 and which is not here shown in greater detail. When no electric current flows through the bimetallic elements 4, 5 and 6 and when these bimetallic elements 4, 5 and 6 are at ambient temperature, that is to say, when all of the bimetallic elements are at the same heated-up state, then the bendable sections i.e., the free ends or end portions 4b, 5b and 6b of the bimetallic elements 4, 5 and 6, respectively, are mutually aligned for the reasons already explained and contact the slider 27 as illustrated in FIG. 1.

The aligned state of the bendable sections forming the free end or end portions 4b, 5b and 6b of the bimetallic elements 4, 5 and 6, respectively, is ensured by a corresponding mode of manufacture which will now be considered with reference to FIG. 3 of the drawings:

During a first step of the manufacturing operation the supports or support members 14 are produced with the exception of the supporting surfaces 21 and 22, for example, by performing appropriate punching and bending operations. During this manufacturing operation all supports 14 are provided at the same location with a circular hole 29 having a defined diameter. In the next step of the manufacturing operation the bimetallic elements 4, 5 and 6 already equipped with the heater coils 7, 8 and 9, respectively, and the connecting elements 11, 12 and 13, respectively, are secured at one end 4a, 5a and 6a, respectively, at a related support 14, for example by welding.

The supports or support members 14 are, then, placed on a mandrel or spike or the like by means of their related hole 29 and are pivoted about an axis 29a until the bendable sections forming the free ends or end portions 4b, 5b, and 6b of the bimetallic elements 4, 5 and 6, respectively, abut an abutment surface 30a of a stationary stop 30 which is indicated by broken lines in FIG. 3. By means of an appropriate tool, such as for instance, a punching tool, operating in a plane C at a fixed distance a from the abutment surface 30a of the stationary stop 30 and at right angles to the bending direction B of the bimetallic elements 4, 5 and 6 the supporting surfaces 21 and 22 are now formed at the supports or support members 14. The material sections or portions thus removed are shown in broken lines in FIG. 3 and are designated by reference numerals 31 and 32. The supporting surfaces 21 and 22 lying in this plane C thus possess the aforementioned given distance a from the bendable sections forming the ends or end portions 4b, 5b and 6b of the corresponding bimetallic elements 4, 5 and 6, respectively. Since the same temperature prevails during manufacture of the supporting surfaces 21 and 22, i.e., since all of the bimetallic elements 4, 5 and 6 are in the same heated-up state, the distance a is the same for all of the bimetallic elements 4, 5 and 6. During the next step of the manufacturing operation the supports 14 including the bimetallic elements 4, 5 and 6 are fitted to the housing 2 and secured to the housing wall i.e., the retainer or holder member 17 by twisting the ends or end portions 15a and 16a of the attachment or mounting arms 15 and 16, respectively. During a preceding step of the operation the counter surfaces 24 and 25 were produced at the housing wall or retainer member 17. As already mentioned heretofore, all of the counter surfaces 24 and 25 provided for the three supports 14 lie in one and the same plane D. Since the supports 14 are urged against the retainer or holder member 17 by the action of the backing element 26 and since the intermediate layers 23 have the same thickness, there is obtained a precise mutual alignment of the three supports 14 when the supports 14 are assembled. Thus the distance between the counter surfaces 24 and 25, that is between the plane D and the bending or bendable sections forming the ends or end portions 4b, 5b and 6b of the bimetallic elements 4, 5 and 6, respectively, is the same for all of the bimetallic elements. Therefore, the bendable sections forming the ends or end portions 4b, 5b and 6b are mutually aligned and capable of acting upon the slider 27 in the same manner when heated-up in the same way. After securing the supports 14 to the housing wall or retainer member 17, therefore, no re-adjustment of the bimetallic elements 4, 5 and 6 is required. The precise placement of the supporting surfaces 21 and 22 at the supports 14 as well as of the counter surfaces 24 and 25 at the retainer member 17 can occur without significant additional expense during the course of the manufacturing process which may be automated without any difficulties. Thus, the expense necessarily connected with re-adjustment work can be beneficially saved.

The circuit breaker 1 as described hereinbefore is connected by means of the terminal or connecting elements 11, 12, 13 and 18 or 19, respectively, into the circuit to be protected. When the bimetallic elements 4, 5 and 6 are heated-up, the bendable sections forming the respective ends or end portions 4b, 5b and 6b, thereof will bend in the direction of the arrow B and effect a displacement of the slider 27 which, in turn, acts upon the lever 28. When the latter is pivoted to a certain extent, the circuit-breaking mechanism will respond in conventional manner.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,