Electric lamp

Abstract: The electric lamp comprises a light source (5), a printed-circuit board (2) having an electric circuit (3, 4) for operating the lamp, and a lamp cap (7). A synthetic resin (11) in which the circuit (3, 4) is embedded also constitutes a housing (1) to which the light source (5) and the lamp cap (7) are attached and in which the printed circuit board (2) and the electric circuit (3, 4) are accommodated. There is a rigid connection between the printed-circuit board (2) and the shell (8) of the cap (7). The electric lamp is of a simple construction that allows for an easy manufacture.

Description: The invention relates to an electric lamp comprising a housing in which an electric circuit for operating the lamp is accommodated, a light source fastened to the housing and connected electrically to the circuit, a lamp cap having a shell and a base and provided with contacts, which lamp cap is fastened to the housing and whose contacts are connected to the circuit, the circuit being embedded in a synthetic resin which at the same time constitutes the housing. Such a lamp is known from WO-A-83/04139. The manufacture of the lamp is comparatively time-consuming owing to the large number of components that have to be assembled. This is also true for the lamp disclosed in DE-U-8 701 424. In this lamp the circuit is present on a printed-circuit board which is accommodated in a separate housing and subsequently united therewith in that the housing is filled with a synthetic resin. It is an object of the invention to provide a lamp of the kind described in the opening paragraph which is of a simple construction which can be easily realized. This object is realised in that the circuit comprises a printed-circuit board and the shell of the lamp cap is connected to the said printed-circuit board by means of a rigid conductor. The lamp may be obtained in a very simple manner in that the assembly of light source, circuit, and lamp cap, in which all electrical connections have been made, is introduced into a mould which is filled with the synthetic resin. Handling of the assembly before the lamp has been finished by the application of the synthetic resins facilitated in that the shell of the lamp cap is connected to the printed circuit board by means of a rigid conductor. Also in the case of a bayonet lamp cap, where the shell does not form a contact, this construction can be used in that the conductor is connected mechanically to the board, but not electrically to the circuit thereon. The construction and the simple method of manufacture which is made possible by the construction have a number of important advantages. Electrical connections between components of the circuit, between the circuit and the contacts of the lamp cap, and between the circuit and the light source can be made simultaneously or in immediate succession. If an Edison lamp cap is used, a connection with the circuit at the inside of the shell of the lamp cap may have been made, for example with solder. The result is that a major defect cannot arise. This defect, for which conventional lamps are specially inspected, consists in that the conductor, which is normally fastened at the outside of an Edison lamp cap to its shell, extends to beyond this fastening, for example alongside the light source. It is then possible to touch this conductor while it carries the mains voltage. Other intermediate manufacturing steps, such as the mounting of the circuit in the housing and fastening of the lamp cap to the housing, are avoided. Other steps which are avoided are the manufacture, supply, and use of a separate housing, and also the fastening of the lamp cap to the housing, for example with glue, or through local deformation of the lamp cap after assembly. The construction of the lamp according to the invention renders a very compact lamp possible. It may be advantageous to use two or more of such rigid conductors connecting the lamp cap shell to the board. The conductors may then be integral with the shell, or in the form of pins or strips be fastened thereto, for example with a weld. In an advantageous embodiment, the synthetic resin in which the circuit is embedded and which also forms the housing is at the same time the base of the lamp cap. A contact at this base is electrically insulated from the shell in this way. An advantage of this embodiment is that an inexpensive lamp cap is used, the shell being without a previously formed vitrite base. Furthermore, the absence of the vitrite means that more space is available inside the lamp cap, for example for an electrolytic capacitor. In a favourable modification of this embodiment, a contact of the base portion is connected to the circuit by a rigid conductor. Two such contacts may be connected to the circuit in this way in lamps having a bayonet lamp cap. This modification avoids the use of wires for making the said connection which wires are to be guided through narrow openings. Examples of synthetic resins, which may be used are epoxy resin, polyurethane resin, polyether imide, and polyether sulfon. They may contain, for example, up to 50% by weight of filler, powder or fibres, for example, SiO₂, CaCO₃, Al₂O₃. An embodiment of the lamp according to the invention is shown in the drawing in side elevation, partly in longitudinal section. In the drawing, the electric lamp has a housing 1 in which a printed-circuit board 2 comprising a circuit for operating the lamp is included. A transformer 3 and an electrolytic capacitor 4 of the circuit are visible. The printed-circuit board 2 consists of two parts. The parts are interconnected by rigid conductors 14. A light source 5 is fastened to the housing and electrically connected to the circuit 3, 4, in the drawing by means of conductors 6. The light source drawn is a compact low-pressure mercury discharge lamp with a quadruple lamp vessel which has a fluorescent powder coating. A lamp cap 7 having a shell 8 and a base 9 and provided with contacts, is fastened to the housing 1. The lamp cap 7 has a first contact 10 at the base 9 and, in the Edison lamp cap drawn, the shell itself as a second contact. The contacts 8, 10 are connected to the circuit 3, 4. The circuit 3, 4 is embedded in a synthetic resin 11 which fills the housing 1, at the same time constituting the housing 1 itself. The shell 8 of the lamp cap 7 is connected to the printed-circuit board 2 by a rigid conductor 12. The conductor 12 is fastened to the inside of the shell 8 by means of welding. The conductor 12 is fastened to the board 2, electrically connected to the circuit 3, 4. The synthetic resin 11 in which the circuit 3, 4 is embedded and which at the same time constitutes the housing 1, also forms the base 9 of the lamp cap in the drawing. The contact 10 at the base 9 is electrically connected to the circuit 3, 4 by a rigid conductor 13, two such conductors being visible in the lamp drawn. During manufacture of the lamp, all electrical connections are made first. Owing to the construction as drawn, rigid connections between the printed-circuit board 2, the shell 8 of the lamp cap 7, and the contact 10 at its base 9 were thus created at the same time. The substantially rigid assembly is then placed in a mould, after which the synthetic resin is introduced.

Claims: An electric lamp comprising a housing (1) in which an electric circuit (3, 4) for operating the lamp is accommodated, a light source (5) fastened to the housing (1) and connected electrically to the circuit (3, 4), a lamp cap (7) having a shell (8) and a base (9) and provided with contacts (8, 10), which lamp cap is fastened to the housing (1) and whose contacts are connected to the circuit (3, 4), the circuit (3, 4) being embedded in a synthetic resin (11) which at the same time constitutes the housing (1), characterized in that the circuit (3, 4) comprises a printed circuit board (2) and the shell (8) of the lamp cap (7) is connected to the said printed-circuit board (2) by means of a rigid conductor (12). An electric lamp as claimed in Claim 1, characterized in that a conductor (12) connecting the circuit (3, 4) to the shell (8) of an Edison lamp cap is fastened to the inside thereof. An electric lamp as claimed in Claim 1 or 2, characterized in that the synthetic resin (11) at the same time forms the base (9) of the lamp cap (7). An electric lamp as claimed in Claim 3, characterized in that the contact (10) at the base (9) of the lamp cap is connected to the circuit (3, 4) by means of a rigid conductor (13).

Inventors: DE JONG NICOLAAS JOHANNES, STOMMEN THEODOOR HUBERT, DE JONG, NICOLAAS JOHANNES, STOMMEN, THEODOOR HUBERT
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1991
Main classification: H01J61
IPC codes: H01J5, H01J61, H01K1, F21S2