ELECTRIC LAMP HAVING A LAMP CAP OF SYNTHETIC MATERIAL

Abstract: The electric lamp has a lamp vessel (1) received by an opening (8) in a lamp cap (5) of synthetic material. The lamp cap (5) has a first set of projections (9, 10) with contact surfaces (11, 12), over which current conductors (3) extend, and a second set of projections (13, 14) with contact surfaces (15, 16). The first projections (9, 10) are tongues, which extend at a certain distance along the circumference of the lamp cap (5) and have their contact surfaces (11, 12) at their free ends. The lamp is suitable to be used in a printed circuit board with wide tolerances with respect to its thickness.

Description: The invention relates to an electric lamp having a lamp cap of synthetic material for use in a printed circuit board comprising a tubular translucent lamp vessel, an electric element in the lamp vessel, current conductors extending from the electric element through a first end of the lamp vessel to the exterior, the lamp cap of synthetic material having a longitudinal axis and comprising a sleeve-shaped portion having an opening for receiving the lamp vessel, on the sleeve-shaped portion a first pair of outwardly directed projections with each a first contact surface and a second pair of outwardly directed projections each with a second contact surface, these second contact surfaces facing the first contact surfaces and lying in the direction of the longitudinal axis at a certain distance therefrom, the first end of the lamp vessel being received by the opening of the lamp cap and the current conductors extending over a respective contact surface of a pair of projections. Such a lamp is known from DE 1589314 A1. A disadvantage of the known lamp is that the current conductors of the lamp are themselves the contacts which have to establish an electrical connection with tracks of a printed circuit board. The current conductors are generally fairly thin and slack so that they have little resilience. This results in that stringent requirements have to be imposed on the thickness of a board and of the printed circuit thereon, so that a good contact is guaranteed between the current conductors and tracks of the said printed circuit when the lamp is arranged in a printed circuit board. These stringent requirements cause a printed circuit board to be expensive. A possibility of preventing the necessity of these stringent requirements is to provide the lamp cap with metal springs, which on the one hand are in contact with the current conductors and on the other hand can establish in a reliable manner contact with tracks of a printed circuit. However, this possibility is expensive because a larger number of parts to be assembled are required for the lamp. The invention has for its object to provide an electric lamp of the kind mentioned in the opening paragraph, which has a simple construction and nevertheless is capable of establishing reliable contacts with tracks of a printed circuit with tolerances with respect to the thickness of the board carrying the printed circuit and with respect to the thickness of the tracks. This object is achieved in an electric lamp of the kind mentioned in the opening paragraph in that the projections of the first pair are tongues, which extend at a certain distance from the sleeve-shaped portion along its circumference and have the first contact surfaces at their free ends. Due to their shape, the first projections are resilient. The current conductors are consequently brought into reliable contact and held in reliable contact with tracks of a printed circuit board, for which the lamp is intended, in spite of tolerances with respect to the thickness thereof. It is particularly favourable if the current conductors extend over a respective first contact surface, but they may alternatively extend over a second contact surface. In a favourable embodiment, the contact surfaces over which the current conductors extend have a guide for these conductors, for example a grove, by which the relevant conductor is received, or openings through which the conductor extends. The conductor may also be bent around the free end of the projection, e.g. of the tongue, for additional fixing. The synthetic material of the lamp cap may be, for example, a thermoplast, for example a polyether imide or a polyether sulphone that may be filled with, for example, powder or fibres, such as glass powder or glass fibres. The electric element in the lamp vessel may be a filament, but may alternatively be a pair of electrodes. An embodiment of the electric lamp according to the invention is shown in the drawing. In the drawing: Figure 1 is a side elevation of an electric lamp having a lamp cap of synthetic material, Figure 2 is a front elevation of the lamp cap shown in Figure 1, Figure 3 is a rear view of the lamp cap shown in Figure 1. The electric lamp having a lamp cap of synthetic material shown in Figure 1 is suitable for use in a printed circuit board. The lamp has a tubular translucent lamp vessel 1, in which an electric element 2, i.e. a filament, is arranged. Current supply conductors 3 extend from the electric element 2 through a first end 4 of the lamp vessel 1 to the exterior. A lamp cap 5 of synthetic material has a longitudinal axis 6 and a sleeve-shaped portion 7 provided with an opening 8 for receiving the lamp vessel 1. At the sleeve-shaped portion 7 (cf. also Figures 2 and 3) is formed a first set of projections 9, 10 extending laterally outwards with each a first contact surface 11 and 12, respectively, and a second set of projections 13, 14 extending laterally outwards with each a second contact surface 15 and 16, respectively. The second contact surfaces 15, 16 are directed towards the first contact surfaces 11, 12 and are arranged in the direction of the longitudinal axis 6 at a certain distance therefrom. The first end 4 of the lamp vessel 1 is received by the opening 8 of the lamp cap 5 and the current conductors 3 extend over a respective contact surface 11, 12. The projections 9, 10 of the first set are tongues, which extend at a certain distance from the sleeve-shaped part 7 along its circumference and have at their free ends the first contact surface 11 and 12, respectively. The embodiment shown is suitable to be inserted, the lamp vessel 1 direct forwards, through an opening intended for this purpose in a printed circuit board and then to be rotated in the direction of the arrow P (cf. Figure 3). For this purpose, a slot 17 for a screw-driver is provided. The second contact surfaces 15, 16 are then located on one side and the first contact surfaces 11, 12 are located on the other side against the board. The distance in the axial direction between the second contact surfaces 15, 16 and the current conductors 3 on the first contact surfaces 11, 12 is chosen so that this distance is at most equal to the smallest thickness that a printed circuit board for which the electric lamp is intended together with a track thereon can have. If the board with a track on it has a thickness larger than the minimum permissible thickness, the lamp can nevertheless be arranged due to the fact that the projections of the first set are then bent away in axial direction. Whilst maintaining good electrical contacts, the electric lamp according to the invention permits a wide tolerance with respect to the thickness of the printed circuit board. In a modification of the electric lamp of Figure 1, in which the opening 8 receiving the end 4 of the lamp vessel 1 is located on the lefthand side of Figure 1, the lamp can be inserted, the lamp cap 5 directed forwards, into the same printed circuit board. Figures 2 and 3 show clearly the shape of a tongue of the projections 9, 10 of the first set and their course along the circumference of the sleeve-shaped portion 7 at a certain distance and so as to be free therefrom. As a result, the projections 9, 10 have a high resilience and the lamp cap 5 consequently has a high adaptability to the thickness of a board. Due to the fact that the contact surfaces 11, 12 have a smaller axial distance from the second contact surfaces 15, 16 than other portions of the projections 9, 10 of the first set, they retain their function as contact surfaces, i.e. regions in which contact is established by the lamp cap 5 with a board, if a comparatively thick board gives rise to displacement of these surfaces in the axial direction. The first contact surfaces 11, 12 have a guide for the current conductors 3 in the form of a groove of small depth, i.e. smaller than the thickness of the current conductors 3, by which these current conductors are received. For additional fixing, the current conductors 3 are bent around the free end of the projections 9, 10.

Claims: An electric lamp having a lamp cap (5) of synthetic material suitable for use in a printed circuit board comprising a tubular translucent lamp vessel (1), an electric element (2) in the lamp vessel, current conductors (3) extending from the electric element through a first end of the lamp vessel to the exterior, the lamp cap (5) of synthetic material having a longitudinal axis (6) and comprising a sleeve-shaped portion (7) having an opening (8) for receiving the lamp vessel, on the sleeve-shaped portion (7) a first pair of outwardly directed projections (9, 10) with each a first contact surface (11, 12) and a second pair of outwardly directed projections (13, 14), each with a second contact surface (15, 16), these second contact surfaces (15, 16) facing the first contact surfaces (11, 12) and being located in the direction of the longitudinal axis at a certain distance therefrom, the first end of the lamp vessel (1) being received by the opening (8) of the lamp cap (5) and the current conductors extending over a respective contact surface (11, 12) of a pair of projections, characterized in that the projections (9, 10) of the first pair are tongues, which extend at a certain distance from the sleeve-shaped portion (7) along its circumference and have the first contact surfaces (11, 12) at their free ends. An electric lamp as claimed in Claim 1, characterized in that the current conductors extend over a respective first contact surface. An electric lamp as claimed in Claim 1 or 2, characterized in that the contact surfaces over which a current conductor extends have a guide for it. An electric lamp as claimed in Claim 3, characterized in that the guide is a groove.

Inventors: WEENINK, LEON PIETER
Applicants: N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1988
Main classification: H01R33
IPC codes: F21V19, H01R33