EP0499100B1 - Manufacturing process of ready-made resistors - Google Patents

Abstract

In order to manufacture completely ready-made (that is to say provided with connecting wires) self-stabilising resistors having PTC elements as active parts, such as those resistors especially on coil windings, such as those used by electric motors, the invention provides a method according to which bearing surfaces and covering surfaces for the PTC elements are stamped out on a metallic supporting strip, a PTC element is placed on each bearing surface and is attached, the covering surface being bent over the PTC element, the bearing surfaces and covering surfaces being provided with connecting wires, and the covering surfaces and bearing surfaces being separated from the remaining supporting strip.

Description

The invention relates to a method for producing assembled resistors, in particular for use on coil windings, such as for electric motors, two opposite side faces of a PTC element being electrically connected to connecting wires.

In this context, it is known from document JP-A-59 063 536 to manufacture a temperature measuring component in which a carrier tape with a bearing surface and a cover surface is used, between which the temperature measuring element is received.

Resistors with PTC elements are used to monitor electrotechnical devices, in particular to monitor coil windings, such as those of electric motors or the like. with which electrical connection wires are connected. The resistors are partially wrapped in close thermal contact with the electrical device, such as the coil, for example by the coil winding wire. In order to be able to determine temperature changes over a larger area of the coil, such resistors are provided connected in series and attached to different points of the winding. As a rule, the connecting wires are soldered directly to the PTC elements, which are provided with a solderable metallic contact surface, such as a vapor-deposited silver coating. The connecting wires are usually soldered by hand. This is complex, especially when extremely small PTC elements are used, which have heights of less than 2 mm and also diameters of less than 5 mm down to only 3 mm. Further assembly is also done by hand; so shrink sleeves are made by hand. The creation costs are therefore considerable.

The invention is therefore based on the object of providing a method of the type mentioned at the outset which enables economical and inexpensive manufacture of such assembled resistors.

According to the invention, this object is achieved by a method of the type mentioned at the outset, which is characterized in that support and cover surfaces for the PTC elements are punched out on a metallic carrier tape, that a PTC element is placed and fastened on each support surface in such a way that the cover surface is bent over the PTC element, the support and cover surfaces are provided with connecting wires, and the cover and support surfaces are separated from the rest of the carrier tape. A Resistor assembled in this way differs from the known resistors in that, on opposite end faces of the PTC element, metal plates (support and cover surfaces) are soldered, which have protruding approaches to the PTC element, to which the connecting wires are fastened.

With the invention, a method is created which enables a largely automated and therefore mechanical production of such assembled resistors and thus reduces or almost eliminates the use of manual labor.

For this purpose, the method according to the invention provides that the PTC elements, which form individual parts which are difficult to handle by hand, are held and conveyed by a quasi-endless carrier tape during the assembly process - at least until the PTC elements are connected to connecting wires, which then can in turn be strapped in a manner known per se, whereupon the further automatic conveying can take place in a defined form and with a defined relative spacing of the PTC elements through the straps engaging on the connecting wires.

As a result, the PTC elements are kept defined and all machining and processing operations in stations of a processing device can be carried out fully automatically. However, the PTC elements can be fed to the endless carrier belt from a vibrating pot either via a slide with a locking slide. The slide ends immediately in front of the support surface for a PTC element on the carrier tape. If such a support surface has been conveyed in front of the slide, the locking slide can release a PTC element so that it can slide onto the support surface. The others are then held back by the slide or corresponding slide. Positioning pins can be provided which center the PTC element on the support surface. Or, alternatively, grippers can be provided, which grip the PTC elements and place them on the support surface. After a PTC element has been placed on a receiving or support surface, a cover surface is brought over it, so that the PTC element is delimited in a sandwich-like manner by the support surface and cover surface. If solder was previously applied to the support and cover surface, the PTC elements can now be soldered to the support and cover surface. PTC elements are also used here, which are provided with a metallic contact. The soldering can be done by high frequency. The PTC elements are then firmly connected to the carrier tape and are therefore conveyed through this to the further processing and processing stations.

In a preferred embodiment, it can be provided that protruding approaches for fixing the connecting wires are punched out from the support and cover surface. This facilitates the attachment, preferably welding, of the connection wires to the support and cover surface for the production of electrical connection contacts to the PTC element. In order to position the connecting wires in front of the fixed connection to the support and cover surface, in particular at their approaches, it can be provided in a preferred further embodiment that edges of the approaches are bent perpendicular to them.

So that when the cover surface is bent over, which, like the support surface, has been punched out of the carrier tape but is still firmly connected to it by tabs, the cover surface comes to lie flat on the PTC element can be provided in advance that the cover surface is first bent from the plane of the carrier tape, while maintaining its parallel extension to it, before it is bent over the PTC element. The offset of the top surface to the level of the carrier tape essentially corresponds to the thickness of the PTC element.

According to a development, it is provided that after the PTC element has been firmly connected to the support and cover surface, only the latter is initially separated from the rest of the carrier tape. Despite separating the top surface from the carrier tape, this is still held because it is firmly connected to the PTC element. This procedure electrically separates the contact surface and the top surface. It can then be provided in a further preferred embodiment that an electrical test of the PTC element is carried out after an electrical separation of the support and cover surfaces. An essential test of the PTC elements used is that they are checked under operating temperature conditions with regard to their conductivity or their electrical resistance. It is therefore provided that the PTC element is checked on the carrier tape by a tempered bath, in particular an oil bath. For electrical contacting, contact pins are brought against the top and contact surfaces. Here, too, the approaches to which the connecting wires are later attached show their usefulness, in particular if they are aligned parallel to one another, but are arranged offset from one another in plan view. In this case, contact pins can be pressed against the lugs in parallel from top to bottom. This makes it possible to guide the carrier tape through the thermal bath in a horizontal orientation. It is not necessary for a contact pin to pass through the bottom of the temperature bath tub from below is performed, which would require difficult sealing. Furthermore, it is also not necessary to connect the carrier tape in any way in order to bring it in a vertical direction, so that contact pins could run in a horizontal direction from both sides against the support surface and the top surface. A connection of the carrier tape or vertical conveyance of the carrier tape at least over partial areas would also be associated with problems, among other things due to the inherent rigidity of the carrier tape.

PTC elements identified as faulty in the above checking step can then be removed from the carrier tape and thus eliminated by providing a punching device at a corresponding clock step distance from the testing device and the number of conveying cycles corresponding to the distance later the corresponding PTC element by punching the connecting tab from the carrier tape is eliminated.

In a simple manner, a single connecting wire can be attached to each of the approaches on the support and top surface. However, two or more PTC elements can also be connected in series. For this purpose, it is provided that one end of a piece of wire is connected to the top surface of the first PTC element and the other end of the piece of wire is connected to the contact surface of the immediately following PTC element and that the contact surface of the first PTC element and the top surface of the second PTC element are each provided with individual wires or that for the series connection of three PTC elements in each case the first end of a connecting wire with the top surface of a preceding PTC element and the second end of the connecting wire in each case with the immediately following PTC element. element are connected and that the contact surface of the first PTC element and the top surface of the third PTC element are provided with individual connecting wires.

As said, it can be provided in a subsequent work step that after the connecting wires are fastened, they are taped.

On the belt, the ready-made resistors are conveyed for further processing, which may consist in that the PTC elements connected to the support and cover surface and provided with connecting wires are provided with an insulation layer, in particular by the fact that the PTC elements connected to the support and cover surface Elements can be provided with a powder coating. Furthermore, a shrink sleeve can be pushed on and shrunk on.

Fig. 1

eine schematische Darstellung der ersten Arbeitsschritte des erfindungsgemäßen Verfahrens, wobei Figur 1a eine Seitenansicht auf den Eintauchvorgang des Trägerbandes darstellt;

Fig. 2a u. b

Ansichten auf PTC-Element und Auflage- und Deckfläche vor dem Abtrennen der Deckfläche vom Trägerband;

Fig. 3

weitere Verfahrensschritte des erfindungsgemäßen Verfahrens; und

Fig. 4

die Endkonfektionierung gemäß dem erfindungsgemäßen Verfahren.

Further advantages and features of the invention result from the claims from the following description in which an embodiment of the invention is explained in detail with reference to the drawing. It shows:

Fig. 1

is a schematic representation of the first steps of the method according to the invention, wherein Figure 1a is a side view of the immersion process of the carrier tape;

Fig. 2a u. b

Views of the PTC element and the support and cover surface before the cover surface has been separated from the carrier tape;

Fig. 3

further process steps of the method according to the invention; and

Fig. 4

the final assembly according to the method according to the invention.

The method according to the invention for producing assembled resistors for use on coil windings, such as for electric motors, is based on an endless carrier tape 1 made of thin sheet metal. Support surfaces 2 and cover surfaces 3 for PTC elements 4 are punched out of the carrier tape, the surfaces 2.3 still being held on a narrow holding strip 6 via connecting sections 7, 8 extending therefrom (method step A). On the cover and support surface 2, 3 extend essentially tangentially lugs 9, 11 for the later reception and fixing of connecting wires.

Openings 12 are also punched out of the holding strip 6, by means of which, during further processing, an exact positioning of the holding strip 6 and thus also of the cover and support surfaces 2, 3 can be effected.

Then embossing takes place out of the plane of the carrier tape 1 (step B). On the one hand, edges 13 (FIGS. 2a, b) of the projections 9, 11 are bent upward in the plan view of FIG. 1. On the other hand, the top surface 3 is displaced approximately as far from the plane of the carrier tape 6, but still lying parallel to it, as corresponds to the thickness of the PTC element 4. Cover and support surface 2, 3 can furthermore be plate-shaped or bowl-shaped, as can be seen in FIG. 2b, so that edges 14 are formed which can encompass and center the PTC element 4 around its circumference.

In a further step C, solder 16 is applied to the support and cover surface 2, 3.

Then a PTC element in the form of a PTC pill is placed on the soldered support surface. The PTC elements can be conveyed on a vibrating pot 17 and either taken over by a gripper and placed on the support surface 2 or conveyed to the support surfaces 2 by means of a slide and an exposed stop. To position the PTC elements 4, positioning pins 18 can be provided in addition to the contact surface 2, which, when a new contact surface 2 comes into their area, are moved upwards and hold the PTC element 4 between them. Then, in step E, the tab 7 carrying the top surface 3 is bent over in such a way that the top surface 3 is brought exactly over the PTC element 4. The result of this step is shown on the one hand in FIGS. 2a and b in plan view and on the other hand in enlarged view. In the subsequent step F, the PTC element 4 and the support and cover surface 2, 3 are soldered to the previously applied solder 16. The soldering is preferably carried out at high frequency, that is to say by means of a high-frequency generator. After the PTC element 4 has been fastened in this way to the support surface 2 and thus also the cover surface 3 has been fixed via the PTC element 4, its carrier tab 7 can be separated from the carrier tape 6, for example at the point indicated by 19 (FIG. 2b). This takes place in method step G. Subsequently, the support surface 2 with the carrier tape 6 and the cover surface 3 are electrically separated from one another, so they no longer form a short-circuit connection. In order to check the quality of the PTC element, the carrier tape 6 is now placed in an oil bath 22 over rollers 21 (FIG. 1a) for checking the resistance at a predetermined temperature deflected and the resistance is checked via contact pins 23, which are moved against the connecting lugs 9, 11. In the following step I degreasing and finally (step J) cutting off defective PTC elements, the deficiency being determined in the above-mentioned test process.

The lugs 9, 11 are then provided with corresponding connecting wires 23, 24 (FIG. 3). If a plurality of PTC elements 4 are to be interconnected in series, for example two PTC elements in a twin circuit or three PTC elements in a triplet circuit, as shown in FIG. 3, the connection ends 26, 27 of a U -shaped wire 23 connected on the one hand to the shoulder 11 of the cover part 3 of a PTC element (end 27) and on the other hand (end 26) to the shoulder 9 of the support part 2. The wire ends 26, 27 are preferably welded to the lugs 9, 11 (step K1). In step K1 'it can be seen how three successive PTC elements are connected in series with one another by two U-shaped connecting wires. In step K2, the individual connecting strands 24 are attached to the free lugs 9 and 11, respectively. The connecting wires 23 are prepared in such a way that they are pulled off a wire reel, first a sufficient stripping of the front wire end takes place at a front end in a stripping block 28, and then the wire is conveyed further along two aligned grippers 29 which can be pivoted relative to one another. After the required wire length has been reached, the wire piece 23 is separated from the remaining wire and stripping is also carried out at the rear end (26). The grippers 29 pivot against one another and thereby bend the piece of wire 23 into the U-shape shown at the beginning of FIG. 3, in which the start (27) and end 26 of the wire reach the parallel orientation shown.

After the connection wires 23, 24 have been attached, they are preferably taped, for example sandwiched between two adhesive tapes, which can be done in a conventional manner (step L). After the connecting wires 23, 24 and then the PTC elements are held by the belts 31, the PTC elements can be completely separated from the carrier tape 6 by a complete separation at 32 (FIG. 2b) (step M).

The resistors produced in this way can now be fed to further processing steps.

Coating can be carried out, for example casting or powder coating. In the latter case, in step N the initially horizontally conveyed resistors 33 are pivoted through 90 °, so that the connecting wires point upwards. This takes place in that the belt 31 is passed between rollers 34, 36 which are provided in pairs and are perpendicular to one another. The resistors 33 are passed through a powder bath. The adherence of the powder is then melted by heat that can be generated by a radiator 37, cools down again and forms a tight coating (step O). Finally, a shrink cap 38 can be pushed over the resistors 33. This is separated from an endless hose 39 (step P), possibly closed in its free end and provided with a label (step Q). It can be promoted on a circular conveyor 39. Then she is simply on the Resistors 33 pushed on (step R), whereupon a shrinking process can finally follow in step S, so that the shrink cap 38 tightly envelops the resistor 33. Finally, the connecting wires 23, 24 can be shortened.

Claims (18)

1. Method for manufacturing finished resistors (33), particularly for use on coil windings such as for electric motors, whereby two opposing lateral faces of a PTC element (4) are electrically connected to leads (23, 24), characterized in that on a metallic carrier strip bearing and top surfaces (2, 3) for the PTC elements (4) are being punched out, that on each bearing surface (2) a PTC element (4) is being placed and fixed, that the top surface (3) is being bent over the PTC element (4), that the bearing and contact surfaces (2, 3) are being provided with leads (23, 24), and that the top and bearing surfaces (2, 3) are being separated from the remaining carrier strip (1).
2. Method according to claim 1, characterized by the step of punching lugs (9, 11) extending from the bearing and top surfaces (2, 3) for fixing the leads (23, 24).
3. Method according to claim 1 or 2, characterized by the step of bending edges (13) of the lugs (9, 11) away perpendicular thereto.
4. Method according to any of claims 1 - 3, characterized by the step of bending the top surface (3), before being bent over the PTC element (4), out of the plane of the carrier strip (1) while maintaining the parallel orientation thereto.
5. Method according to any of claims 1 - 4, characterized by the step of connecting the PTC elements (4) to the bearing and top surfaces (2, 3) by soldering.
6. Method according to claim 5, characterized by the step of applying prior to the placement of the PTC elements (4) on the bearing surface (2) solder (16) to the latter and to the top surface (3).
7. Method according to any of the preceding claims, characterized by the step of after having fixedly connected the PTC element (4) to the bearing and top surfaces (2, 3) separating initially only the latter from the remaining carrier strip (1).
8. Method according to any of the preceding claims, characterized by the step of electrical checking of the PTC element (4) after electrical separation of bearing and top surfaces (2, 3).
9. Method according to claim 8, characterized by the step of passing the PTC element (4) on the carrier strip (1) through a thermostatic bath, particularly an oil bath (22), for testing the PTC element (4).
10. Method according to claim 8 or 9, characterized by the step of eliminating faulty PTC elements (4) by separating them from the carrier strip (1).
11. Method according to any of the preceding claims, characterized by the step of connecting the leads (23, 24) to the bearing and top surfaces (2, 3), particulary to the lugs (9, 11), by welding.
12. Method according to any of the preceding claims, characterized in that for a serial connection of two PTC elements (4) one end (26) of a wire portion is being connected to the top surface (3) of the first PTC element (4) and the other end (27) of the wire portion is being connected with the bearing surface (2) of the directly following PTC element (4) and that the bearing surface (2) of the first PTC element (4) and the top surface (3) of the second PTC element (4) are each being provided with single wires (23, 24).
13. Method according to any of the preceding claims, characterized in that for a serial connection of three PTC elements (4) each the first end (26) of a lead is being connected with the top surface (3) of the immediately preceding PTC element (4) and the second end (27) of the lead is each being connected to the bearing surface (2) of the subsequently following PTC element (4) and that the bearing surface (2) of the first PTC element (4) and the top surface (3) of the third PTC element (4) are being provided with single wires (23, 24).
14. Method according to any of the preceding claims, characterized by the step of connecting the leads (23, 24) to a belt after fixing the leads.
15. Method according to claim 14, characterized by the step of separating the resistors (33) produced thus far completely from the carrier strip (1).
16. Method according to any of the preceding claims, characterized by the step of providing the PTC elements (4) connected to the bearing and top surfaces (2, 3) and provided with leads (23, 24) with an insulating layer.
17. Method according to claim 16, characterized by the step of providing the PTC elements (4) connected to the bearing and top surfaces (2, 3) with a powder coating.
18. Method according to any of the preceding claims, characterized by the step of engaging and shrunking a shrink-on sleeve (38, 39) onto the PTC elements (4) connected to the bearing and top surfaces (2, 3) and provided with leads (23, 24).

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