GB2116459A

GB2116459A - Tubular stem for electric hand soldering iron

Info

Publication number: GB2116459A
Application number: GB08301511A
Authority: GB
Inventors: Enrico Loewenthal
Original assignee: ELETREX SpA
Current assignee: ELETREX SpA
Priority date: 1982-03-01
Filing date: 1983-01-20
Publication date: 1983-09-28
Also published as: GB8301511D0; IT1154493B; IT8267227A0

Abstract

A sheared plane blank (1) is provided with configurations (2) desired for reducing heat transmission and in addition, along its two opposite longitudinal edges (9), two or more complementary configurations (5, 6; 7, 8) provided with undercuts. The blank (1) is then wound to a tubular shape, and during this operation the complementary configuration 5, 6; 7, 8) are mutually coupled. Thus, a tubular stem is obtained whose production cost is equal to that of a stem having edges simply approached to one another, but in which the mutual engagement of the complementary configurations provided with undercuts positively acts to prevent the approached edges from moving away from one another, and thus allows supporting, without any deformation, stresses even directed from the inside to the outside of the tubular stem. <IMAGE>

Description

SPECIFICATION A tubular stem for an electric hand soldering iron, and a process of manufacturing the same The present invention concerns the manufacture of electric hand soldering irons, and relates to a tubular stem for this type of soldering irons and to the process of manufacturing the same.

In the electric hand soldering irons, the soldering tip, provided with a heating electric resistance, is mechanically connected to the handle or handgrip of the soldering iron by means of a tubular stem in which a plurality of transversal slits is formed whose purpose is to hinder the transmission of heat from the heated tip towards the handle of the soldering iron. The manufacture of these stems by means of a tube section is economically little convenient because the tube section has to be milled to provide the transversal slits therein, which is a relatively expensive operation. Therefore, it is preferred to provide this tubular stem by shearing a plane blank thereof and then binding it to form the tube section.However, in this way, the two edges of the curved blank approached to one another define a longitudinal slit which seriously weakens the tubular stem and renders it unable to support radial stresses directed from the inside to the outside, as they are exerted by certain soldering tips. Accordingly, in many cases the tubular stem thus obtained must be welded along said longitudinal slit, or should be provided with an outer reinforcing ring nut neat its end. Either these provisions generate further costs of production.

It is an object of the present invention to improve the production of tubular stems for electric hand soldering irons so as to render possible an economical manufacture of tubular stems having per se a sufficient resistance even against radial stresses, without requiring further workings or the use of fittings.

This object is attained according to the invention by the fact that the tubular stem is first provided in the form of a plane blank having along its opposite longitudinal edges complementary configurations provided with undercuts, and is then completed by bending this blank and winding it to a tubular shape and by mutually connecting, during this operation, said complementary configurations provided with undercuts.

By this process a tubular stem is obtained which has a longitudinal slit whose edges are mutually connected by the mutual engagement of the coupled complementary configurations with undercuts.

Therefore, by a simple blanking operation by means of suitably designed dies it is possible to form the plane blank having the desired transversal slits, the complementary configurations with undercuts and any other configuration, such as anchorage tabs, bores for screws and so on, which may be desired for the tubular stem. By the bending operation a finished tubular stem is then obtained, whose production cost substantially corresponds to that of a normal tubular stem with an open longitudinal slit, but in which the mutual engag#ement of the complementary configurations prevents the tube from yielding under possible radial stresses acting from the inside, so that the provision of a welding along the longitudinal slit of the tubular stem or the application of a ring nut near the end of this latter are no more necessary.

The said complementary configurations provided with undercuts, for example, be in the form of dovetail joints with rounded corners, thus allowing to obtain an optimum mechanical strength without giving rise to blanking difficulties.

The number and arrangement of said complementary configurations depend on the total desired strength against radial stresses and on the location of the expected stresses. A substantially uniform strength all over the length of the stem can generally be obtained by providing two complementary configurations with undercuts in positions situated near the two ends of the tubular stem, but in certain cases even a single complementary configuration on each edge may be sufficient, whilst there is no impediment to provide more than two complementary configurations on each side of the slit in case a higher strength is desirable.

The invention will be more clearly apparent from the following description of an embodiment given by way of non limiting example and diagrammatically shown in the annexed drawing, in which: Figure 1 is a side view showing the tubular stem according to the invention and its relationship with other parts of a hand soldering iron which are indicated by chain lines; Figure 2 is another view of the tubular stem as seen in the direction of the arrow II of Fig. 1; Figure 3 is an axial view of the tubular stem as seen in the direction of the arrow III of Fig. 2; Figure 4 is a plan view of the sheared plane blank intended to form the tubular stem;; Figure 5 is an end view in the direction of arrow V of Fig. 4 The tubular stem according to the invention is formed by a metal sheet element 1 blanked in plane as shown in Figures 4 and 5 and subsequently would to a tubular shape. In the plane blank of the tubular stem 1 are to be remarked the transversal slits 2 intended to hinder the transmission of heat, holes 3 for fastening members A of a soldering tip B, and a tab 4 for the anchorage of the tubular stem 1 on a soldering handle C, all these configurations being usual in a soldering iron tubular stem. In the plane blank of the tubular stem are further to be remarked the characteristic elements of the invention, formed by the complementary configurations 5 and 6, 7 and 8, in this case in the form of dovetail joints with rounded corners, disposed along the longitudinal edges 9 of the blank.

During the operation of bending and winding the plane blank shown in Fig. 4 to form the tubular stem shown in Figures 1 and 3, the said complementary configurations 5 and 6, as well as 7 and 8, are made to engage one another, so that the opposite longitudinal edges 9 of the blank result in being approached to one another and define a longitudinal slit which, however, does not represent a line along which the tubular stem could be opened under a stress directed from the inside to the outside, because such event would be hindered by the complementary configurations 5 and 6, 7 and 8, owing to their mutual engagement and to the presence of the undercuts.

On the other hand, said complementary configurations are disposed at the same level along the cylindrical surface of the tubular stem and do not generate any projections which could in any way interfere with the use of the tubular stem or of the soldering iron to which the stem appertains.

In the embodiment shown, the complementary configurations 5 and 6 are disposed in those positions in which there may take place stresses directed towards the outside, applied from the portion of the soldering tip B engaged within the tubular stem 1 and subjected to thermal expansion which reaches its maximum value where the heating resistance is housed. The complementary configurations 7 and 8, which ensure the stability of the tubular stem 1 where it is inserted into the handgrip C, are disposed within the free space between the transversal slits 2 and the end of the tubular stem 1.

However, it is clear that various arrangements may be chosen in case it is deemed suitable to locate in another manner the points of maximum strength of the tubular stem, and at the same time it is possible to choose numbers of pairs of complementary configurations other than two.

Various modifications and any substitution of technical equivalents may be made to the configurations and processes described hereinabove and shown in the drawing, in order to reach particular objects, without departing from the scope of the invention.

Claims

1. A process for the manufacture of tubular stems for electric hand soldering irons, characterised in that it consists in first providing a sheared plane blank having the configurations desired for the tubular stem to be manufactured, as well as, along the opposite longitudinal edges of the blank, one or more pairs of complementary configurations provided with undercuts; and then bending the said plane blank and winding it to a tubular shape, and carrying out during this operation the mutual engagement of the complementary configurations provided with undercuts, disposed along the opposite longitudinal edges of the blank which are brought into contact with one another.

2. A tubular stem for an electric hand soldering iron, characterized in that it is formed by a plate element wound to a tubular shape with the opposite longitudinal edges substantially contacting on another and defining a longitudinal slit along which said longitudinal edges have one or more pairs of complementary configurations with undercuts, mutually coupled and suitable for positively preventing said longitudinal edges from being moved away from one another by stresses exerted onto the tubular stem from the inside to the outside.

3. A tubular stem as claimed in Claim 2, characterized in that said complementary configurations with undercuts are in number of two pairs and are disposed near the opposite ends of the tubular stem.

4. A tubular stem as claimed in Claim 2, characterized in that said complementary configurations with undercuts are substantially in the form of dovetail joints with rounded corners.

5. A tubular stem for an electric hand soldering iron, and a process for its manufacture, substantially as hereinbefore described with reference to the accompanying drawing.