Method to manufacture sealing nipples or plugs

Abstract: The method to manufacture sealing nipples or plugs comprises a cutting process of a disk-shaped element (1) from a metal sheet followed by drawing of the disk (1) to obtain a hollow element (2) of cylindrical shape, closed at one end by a cap (2a), and then pressing the hollow element to form an annular crown (10) on the outer peripheral surface of it. Lastly the threading of at least a portion (12) of the outer peripheral surface starting from the open end, is carried out.

Description: This invention relates to the technical field concerning the manufacture of sealing nipples or plugs, particularly for radiators. It is known that the radiators of the common thermosiphons are fitted with plugs and metal nipples, used to close at one end the hydraulic circuit formed by the heating elements associated together and at the other end for connection with the hot- water delivery pipe. Said plugs are threaded externally, to be screwed on the radiators, and are shaped in such a way as to allow the mounting of a suitable seal gasket, matching an external annular shoulder. The screwing of the plugs may be carried out by means of a special wrench tool, catching an end of the same plugs shaped with a prismatic contour. At present, said plugs are made by die-casting or other equivalent methods. Said manufacturing methods provide a product certainly reliable, but relatively expensive, in proportion to its use. The object of the present invention is to provide a method which allows to manufacture sealing nipples or plugs starting from a metal sheet. A further object of this invention is to provide a method to manufacture sealing nipples or plugs through a technical solution which turns out to be simple, certainly functional and reliable, as well as relatively cheap. The above-mentioned objects are achieved through a method to manufacture sealing nipples or plugs that comprises a cutting process of a disk-shaped element from a metal sheet followed by drawing of the disk to obtain a hollow element of cylindrical shape, closed at one end by a cap, and then pressing the hollow element to form an annular crown on the outer peripheral surface of it. Lastly the threading of at least a portion of the outer peripheral surface starting from the open end, is carried out. In conclusion, the method described above makes it possible to manufacture sealing plugs, e.g. for radiators and the like, starting from a metal sheet, with an apparent reduction of production costs. Furthermore, the plugs are manufactured with a limited number of simple mechanical workings. In particular, said workings make it possible to obtain, on the outer surface of the plugs, an annular crown designed to match, on assembly, a conventional seal gasket. The present invention will be described further, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a perspective view of a disk obtained by said cutting process; Fig. 2 is an axial cutaway view of the hollow element obtained by said drawing process; Figs. 3a and 3b are axial cutaway views of successive phases of said pressing process; Fig. 4 is a perspective view of a plug manufactured through the method conforming to the invention; Figs. 5 and 6 are respectively axial cutaway views of different embodiments of a nipple made by said method. Referring to said figures, the method conforming to the invention provides, first of all, for cutting a disk-shaped element 1 from a metal sheet (fig. 1). Subsequently, the disk 1 undergoes a drawing process by which is obtained a hollow element 2 of cylindrical shape closed at one end by a cap 2a, basically spherical (fig.2). The hollow element 2 is then suitably trimmed along its circular edge, through known techniques. Then, the hollow element 2 undergoes a pressing process inside a die made up of a movable part 3 and of a stationary counter-die 4. The counter-die 4 features a hole 5 housing a punch 6, stationary with respect to the same counter-die. The punch 6 presents, starting from a shoulder 7, a head 6a of smaller diameter. Between the head 6a of the punch 6 and the peripheral surface of the hole 5 is defined an annular seating into which may be inserted the hollow element 2 to be pressed, matching the shoulder 7 and with the cap 2a turned outwards. The head 6a of the punch 6 is partially projecting from the upper surface of the counter-die 4, and it is suited to cooperate with a hollow 8 correspondingly provided in the movable die 3; the hollow 8 has the same diameter as the hole 5 and has the peripheral surface suitably faceted, as pointed out hereinafter. Furthermore, the hole 5 is edged with a step-shaped annular groove 9, on its outer edge. Therefore, when the movable die 3 is shut against the counter-die 4, the cap 2a of the hollow element 2 is progressively forced into the hollow 8, as shown in fig. 3a. At the same time, the axial compression of the hollow element 2 brings about a fold 2b of the outer peripheral surface of the same hollow element 2, in the zone where said surface is not locked in the seating defined between the hole 5 and the punch head 6a. At the end of the pressing process, the punch 6 fits with its head 6a into the inner surface of the cap 2a, completing its forming inside the hollow 8, as shown in fig. 3b. At the same time, the fold 2b is shut into the groove 9 by the movable die 3, so as to form, on the peripheral surface of the hollow element 2, an annular crown, designated by the numeral 10 for the sake of clarity. The pressing stage also produces, on the peripheral surface at the rear of the crown 10, a series of facets 11, visible in fig. 4, which shows the plug made according to the method conforming to the invention. Said facets 11, corresponding to the internal profile of the hollow 8, provide a prismatic profile which is suited to be caught by a special tool for screwing the plug. After the extraction from the die, the plug undergoes a threading of the portion 12 of the peripheral surface between the crown 10 and the free end. Starting from the plug described above, it is also possible to make nipples, as illustrated in figs. 5 and 6. The manufacture of the nipple shown in fig. 5 provides for forming an inward folded portion 13, starting from a hole made in the bottom 14 of the plug. The folded portion 13 is coaxial to the outer peripheral surface and presents, made subsequently, an inner threading 15. Therefore, the nipple makes it possible to join a pipe, screwed in the inner threading 15, with the element on which the outer threading 12 is screwed. According to the embodiment illustrated in fig. 6, the portion bearing the inner threading, for the sake of clarity designated by the numeral 16, is folded inwards close to the peripheral surface of the nipple. In that case, the inner threading of the nipple allows the screwing to a pipe of larger diameter than in the previous case.

Claims: Method to manufacture sealing nipples or plugs comprising the steps of: cutting a disk-shaped element (1) from a metal sheet; drawing of said disk (1) so as to obtain a hollow element (2) of cylindrical shape, closed at one end by a cap (2a); pressing said hollow element (2) to form an annular crown (10) on the outer peripheral surface of said hollow element (2); and threading of at least a portion (12) of said outer peripheral surface starting from the open end of said hollow elemet (2). Method according to Claim 1, characterized in that the pressing of said hollow element (2) is carried out inside a die made up of a movable part (3) and of a stationary counter-die (4), which features a hole (5) housing a punch (6), stationary with respect to the counter-die itself and suited to cooperate with a hollow 8 correspondingly provided on said movable die (3). Method according to Claim 2, characterized in that said punch (6) features, starting from a shoulder (7), a head (6a) of smaller diameter, which is partially projecting from the upper surface of said counter-die (4) and it is suited to define, with respect to the peripheral surface of said hole (5), an annular seating into which may be inserted said hollow element (2) to be pressed, matching the shoulder (7) and with said cap (2a) turned outwards. Method according to Claim 1, characterized in that said pressing of said hollow element (2) provides for the engagement of the inner surface of said cap (2a) by a punch (6) which is suited to force the same cap (2a) into a hollow (8) having a shape complementary to the head (6a) of said punch. Method according to Claim 4, characterized in that said pressing of said hollow element (2) is suited to produce, on the peripheral surface at the rear of said crown (10), a series of facets (11), corresponding to an inner profile of said hollow (8) and suited to provide a prismatic profile designed to be caught by a special screwing tool. Method according to Claim 1, characterized in that said pressing of said hollow element (2) provides for an axial compression of said hollow element (2) suited to bring about a fold (2b) of the outer peripheral surface of the same hollow element (2), in a free zone of said surface, and the subsequent shutting of said fold (2b) into an annular groove (9) of the die, so to form said annular crown (10). Method according to Claim 1, characterized in that it provides for forming a portion (13,16) folded inwards, starting from a hole provided on the bottom (14), said portion (13) being coaxial to the outer peripheral surface and bearing, made subsequently, an inner threading (15). Method according to Claim 7, characterized in that said portion (16) bearing the inner threading is folded inwards close to the outer peripheral surface.

Inventors: BRUNO NICOLETTI, BRUNO, NICOLETTI
Applicants: LOLLI VALTER, LOLLI, VALTER
Application year: 1991
Main classification: B21D51
IPC codes: F28F9, B21D51, F24H9