Choke coil comprising a bead of a softmagnetic material

Abstract: The choke coil (1) comprises a bead (3) of a soft-magnetic material in which a number of ducts (6) extend in parallel. An electrically conductive wire (9) comprising fee ends (11) is accommodated in the ducts (6). The choke coil (2) comprises means for shielding a portion of the turn which extends outside the ducts (6). To this end, for example an electrically insulating housing (13) is arranged around the bead (3). The housing (13) consists of two approximately cylindrical portions (15, 17), each of which comprises a substantially closed end face (23, 25) which is situated on a first end portion (19, 21). The cylindrical portions are axially slid over the bead (3) with their second open end portion (27, 29) fitting one into the other. In each end face (23, 25) there is provided at least one opening (31) for feeding out the wire (9). When the choke coil is also provided with electrically insulating caps (35, 37) having a wire passage (39) in the prolongation of the axis (41) of the bead (13), the wire (9) fed out will be oriented along said axis (41).

Description: The invention relates to a choke coil, comprising a bead of a soft-magnetic material in which a number of ducts extend with mutually parallel axes from a first end face to a second end face in order to accommodate an electrically conductive wire having free ends, said wire forming a number of turns, each of which extends via at least two ducts and the free ends of the wire projecting from the first end face. A choke coil of the kind set forth is known from Philips Components and Materials Handbook C5, April 1986, Fig. 5, page 335. The English abstract of JP-A 55 - 1188 discloses a bead of ferrite material comprising a plurality of ducts extending parallel to the axis of the material. In the ducts a conductor is inserted. In the known choke coil there is a risk of short-circuiting between the portion of the turns which projects from the bead and other conductors, for example, the tracks on a printed circuit board (PCB) or the free ends of the wire itself whereby the bead can be mounted on a PCB. It is an object of the invention to provide a choke coil of the kind set forth in which the described drawback is mitigated. To achieve this, the choke coil in accordance with the invention is characterized in that in at least the first end face there is provided a recess between two ducts, which recess interconnects the two ducts and accommodates, a portion of the wire, the depth of the recess being greater than the transverse dimension of the wire. At the end face of the bead wherefrom the free ends of the wire project, the turns are situated in a recess, so that they remain fully within the bead and no longer give rise to short-circuiting. A preferred embodiment of the choke coil in accordance with the invention is characterized in that the bead is provided with two diametrically oppositely situated flat faces which extend parallel to the ducts. Because the bead comprises flat faces, it can be readily gripped for mounting on a PCB. It is to be noted that a choke coil comprising flat faces is known per se. A further embodiment in accordance with the invention is characterized in that the axes of the ducts wherethrough the free ends of the wire project from the bead are situated in a plane substantially parallel to the flat faces. Because the free ends of the wire are situated in a plane parallel to the flat faces of the bead, the choke coil can be positioned with respect to a PCB utilizing said flat faces so that the choke coil can be automatically positioned. The invention will be described in detail hereinafter with reference to the drawing. Figure 1 is a side elevation of an embodiment of a choke coil in accordance with the invention; Figures 2a and 2b are a bottom view and a plan view, respectively, of the choke coil shown in Figure 1; Figure 3 is a detailed, partial longitudinal sectional view of a recess in the bead of the choke coil as shown in Figure 1, and Figure 4 shows choke coils in accordance with the invention arranged on a tape. The choke coil 61 shown in Figure 1 comprises a bead 63 of a soft-magnetic material, for example ferrite, which serves as a core. The bead 63 comprises a first end face 65 and a second end face 67 wherebetween a number of ducts 69, 70 extend so as to accommodate an electrically conductive wire 71 having free ends 73. The free ends 73 of the wire 71 extend through the ducts 70 and project from the first end face 65 of the bead 63. In the first end face 65 of the bead 63 there is provided a recess 75 which interconnects the ducts 69. Figure 2a is a bottom view of the bead 63 and Figure 2b is a plan view of the bead 63. Figure 3 is a longitudinal sectional view at an increased scale of the recess 75 in the first end face 65, taken along the line III-III in Figure 2a. The recess is proportioned so that a winding which interconnects two ducts 69 wherebetween the recess 75 is provided is situated completely within the bead 63. The risk of short-circuiting is thus strongly mitigated. Figures 2a and 2b clearly show that the bead 63 comprises two flat faces 77 and 79 which are diametrically oppositely situated. The bead 63 can thus be readily gripped by an appropriate tool which, for example forms part of a machine for the automatic mounting of components on a PCB (not shown). The faces 77 and 79 extend parallel to the ducts 70. Moreover, the axes of the ducts 70 and the free ends 73 projecting from said ducts 70 are situated in a plane extending substantially parallel to the flat faces 77, 79. This allows for the choke coils 61 to be arranged on a tape 81 for packaging and transport as shown in Figure 4. Furthermore, for the mounting of choke coils on a PCB the fact that the flat faces 77, 79 and the plane in which the free ends 73 are situated extend in parallel can be used for positioning the choke coils 61 with respect to a PCB, so that this operation can be automatically performed. The described embodiment of the choke coil comprises two turns. Only one turn extends via the first end face 65 between two ducts 69. However, it is alternatively possible to manufacture choke coils comprising three or more turns. In that case the bead 63 must comprise four or more ducts 69 which are interconnnected two-by-two by recesses 75 in the first end face 65. These recesses 75 may be separated by ridges of the material used to manufacture the bead. Alternatively, however, the ducts 69 may also open into one large recess. In the described embodiment only the first end face 65 is provided with a recess 75. If desirable, recesses 75 can also be provided in the second end face 67 in order to prevent short-circuits also at that area.

Claims: A choke coil (61), comprising a bead (63) of a soft-magnetic material in which a number of ducts (69, 70) extend with mutually parallel axes from a first end face (65) to a second end face (67) in order to accommodate an electrically conductive wire (71) which has free ends (73) and which forms an integer number of at least two turns, each turn extending via two ducts (69, 70) and the free ends (73) of the wire (71) projecting from the first end face (65), characterized in that in at least the first end face (65) there is provided a recess (75) between two ducts (69), which recess (75) interconnects the two ducts (69) and accommodates a portion of the wire (71), the depth of the recess (75) being greater than the transverse dimension of the wire (71). A choke coil as claimed in Claim 1, characterized in that the bead (63) is provided with two diametrically oppositely situated flat faces (77, 79) which extend parallel to the ducts (70). A choke coil as claimed in Claim 2, characterized in that the axes of the ducts (70) wherethrough the free ends (73) of the wire (71) project from the bead (63) are situated in a plane substantially parallel to the flat faces (77, 79).

Inventors: CORTES MORALES PEDRO MIGUEL, ESTEBAN PICO JOSE MARIA, HERRERO GONZALEZ MARIA ISABEL, OTER MUNOZ MANUEL, CORTES MORALES, PEDRO MIGUEL, ESTEBAN PICO, JOSE MARIA, HERRERO GONZALEZ, MARIA ISABEL, OTER MUNOZ, MANUEL
Applicants: PHILIPS NV, N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1991
Main classification: H01F17
IPC codes: H01F27, H01F37, H01F17