GB2065375A - Plunger solenoid construction - Google Patents

Abstract

A plunger solenoid comprises a bobbin 6 having a bore 11 formed therethrough, flanges 8, 9 on both end portions thereof, and a coil 10 wound thereon; a first iron core 13 inserted into the bore 11 from one end, a movable iron core 12 inserted into the bore 11 from the other end, a yoke 1 having plates 2, 4 on both end portions thereof, and a stop 14 formed on the inner surface of the bore 11 at a predetermined location for positioning the first iron core 13 within the bore 11. <IMAGE>

Description

SPECIFICATION Plunger solenoids This invention relates to plunger solenoids.

A previously proposed plunger solenoid is shown in Figs. 1 A and 1 B of the accompanying drawings, where Fig. 1A is a cross-sectional view of the plunger solenoid and Fig.

1 B is a front view thereof. A U-shaped yoke 1 made of a pressed metal plate comprises a front plate 2, a bottom plate 3 and a rear plate 4. A U-shaped recess 5 is cut in the front plate 2 to extend from its upper edge to a predetermined middle position. A coil bobbin 6 made of moulded resin comprises a cylinder 7 and front and rear flanges 8 and 9 at the front and rear ends of the cylinder 7.

On the cylinder 7 of the bobbin 6 between the flanges 8 and 9 is a coil 10. The front end of the cylinder 7 projects a little from the front flange 8 in the forward direction (to the right in Fig. 1A) and engages with the Ushaped recess 5 to be supported thereby. A movable iron core 1 2 is inserted into a bore 11 in the cylinder 7 from the front open end of the bore 11, a fixed iron core 1 3 having previously been inserted from the rear open end. A rear end portion 13' of the core 13, which is smaller than the remainder of the core 1 3 in diameter, is inserted into a bore 4' formed through the rear plate 4 of the yoke 1, and is caulked thereto.

This plunger solenoid is assembled as follows. The bobbin 6 having the coil 10 wound thereon is positioned in the yoke 1, then the fixed iron core 1 3 is inserted into the bore 11 of the cylinder 7 from its front end sufficiently for the rear portion 13' to engage with the bore 4' in the rear plate 4 of the yoke 1.

Then, the rear end portion 13' is caulked against the bore 4' or the rear plate 4 using a suitable jig and a tool securely to fix the bobbin 6 to the yoke 1. This caulking is however troublesome.

When the plunger solenoid is attached to a chassis or the like, threaded bores 3' are formed through the bottom plate 3 of the yoke 1 as shown in Fig. 1A and bolts (not shown) are screwed through the bores 3' to the chassis to attach the plunger solenoid to the chassis.

According to the present invention there is provided a plunger solenoid comprising: a bobbin having a bore formed therethrough, flanges on both end portions thereof, and a winding wound thereon; a first iron core inserted into said bore from one end thereof; a movable iron core inserted into said bore from the other end thereof; a yoke having plates on two end portions thereof; and a stop formed on the inner surface of said bore at a predetermined location for positioning said first iron core within said bore; said first iron core being fixedly supported in position within said bore by the cooperation of said stop and the inner surface of one of said plates of said yoke when said bobbin is assembled with said yoke.

The invention will now be described by way of example with reference to the accompanying drawings, throughout which like references designate like elements, and in which: Figures 1A and 1B are a cross-sectional view and a front view of a previously proposed plunger solenoid; Figure 2 is a cross-sectional view of an embodiment of plunger solenoid according to the invention; Figure 3 is an exploded perspective view of the embodiment of Fig. 2; Figure 4 is a side view showing an example of the manner of attaching the embodiment to a chassis; and Figures 5 and 6 are perspective views of the main parts of respective other embodiments of plunger solenoid according to the invention.

Figs. 2 and 3 show the first embodiment, and parts corresponding to those of Figs. 1A and 1 B are marked with the same reference numerals and their detailed description will be omitted.

In the embodiment of Figs. 2 and 3, a coil bobbin 6 is made of resilient moulded resin, and a stop 14 is formed on the inner surface of a bore 11 of a cylinder 7 of the bobbin 6 at a position near the rear end (left end in Fig.

2) of the bore 11 to abut against a fixed iron core 1 3 when it is inserted into the bore 11.

The respective elements are so designed and dimensioned that when a yoke 1 and the bobbin 6 are assembled, the core 1 3 can be previously inserted into the bore 11 from its rear end (left end in Fig. 2) to a position where the right-hand end of the bore 1 3 abuts against the stop 1 4 and the left end surface of the core 1 3 is flush with the rear surface of a rear plate 4.

As shown in Fig. 3, the lower portions of front and rear flanges 8 and 9 are of correspondingly positioned semicircular shapes and their upper portions have respective portions 8' and 9' extending in the forward and rearward directions. Thus the respective flanges 8 and 9 are each of L-shape viewed from the side. A bore 9" extends through the portion 9', and an engaging projection 1 5 is formed on the front surface of the front flange 8 at its centre portion, with a contour coincident with the shape of a U-shaped recess 5 formed in a front plate 2 of the yoke 1.

The yoke 1 and the bobbin 6 are elastically engaged, and the core 1 3 is then inserted into the bore 11 of the bobbin 6 from its rear end and located in the bore 11 by the stop 14 formed on the inner surface of the bore 11 and the inner or front surface of a rear plate 4 of the yoke 1, whereby the yoke 1 and the bobbin 6 are secured together.

The attachment of the yoke 1 and the bobbin 6 will now be described. A laterallyextending U-shaped groove 1 6 is formed on the inner surface of each of the front and rear plates 21 and 4 of the yoke 1 near the upper edge thereof by pressing or the like, while a U-shaped projection 1 7 is formed on the outer surface of each of the front and rear flanges 8 and 9 of the bobbin 6 integrally therewith at locations such that when the bobbin 6 is engaged with the yoke 1, the U-shaped projections 1 7 engage with the U-shaped grooves 1 6 in a click manner.At the final stage of assembling, the U-shaped projections 1 7 and the grooves 1 6 are resiliently engaged to support the core 1 3 and to fix the bobbin 6 to the yoke 1.

As will be apparent from the above description, since the fixed iron core 1 3 is located within the bore 11 of the coil bobbin 6 by the stop 14 and the back plate 4 of the yoke 1, the embodiment does not require the caulking required in the previously proposed plunger solenoid and moreover the working of the parts is simplified.

Turning to Fig. 4, a method of attaching the embodiment when assembled as described above to a chassis or the like will now be described. The completed plunger solenoid shown in Fig. 2 is turned upside-down, the projecting portion 8' provided on the front flange 8 of the bobbin 6 is urged by a bent portion 18' extending from a chassis 1 8 against the chassis 18, and the projecting portion 9' provided on the rear flange 9 of the bobbin 6 is fixed to the chassis 1 8 by screwing a bolt 9"' through a bore 9" to the chassis 1 8.

If the plunger solenoid is attached to the chassis in this way the threaded bores 3' in the yoke 1 of the previously proposed plunger solenoid are not necessary.

Another embodiment will now be described with reference to Fig. 5. In this embodiment a part of the chassis 1 8 is used as the yoke 1 of the plunger solenoid described above. That is, front and rear plates 2 and 4 are respectively cut and bent up from the chassis 1 8 at predetermined positions, and have sizes and shapes corresponding to those of the front and rear plates 2 and 4 of the yoke 1 of the plunger solenoid of Fig. 2. The other elements of this embodiment which are assembled to the front and rear plates 2 and 4 are not shown in Fig. 5, because they are substantially the same as those of the plunger solenoid of Fig. 2.

With the embodiment of Fig. 5 it is not necessary to provide a separate yoke. Also, it is not necessary to provide the portions 8' and 9' on the flanges 8 and 9 of the bobbin 6 which are necessary in the embodiment of Fig. 2.

A further embodiment will now be described with reference to Fig. 6, which shows the main parts of the embodiment on an enlarged scale.

A cylindrical hole 1 3a with a cone-shaped bottom is formed on a rear surface 1 3b of the fixed iron core 1 3 substantially at the centre, and the length of the core 1 3 in the axial direction of the bore 11 is located in position within the bore 11, between a front surface 4a of the rear plate 4 and the rear surface 1 3b of the core 1 3, so a small clearance 1 9 is defined as shown in Fig. 6.An elastic body 20 made, for example, of polyurethane resin or butyl rubber and having an approximately spherical shape is located in the clearance 1 9 and the hole 1 3a so as to be slightly compressed by the front surface 4a of the rear plate 4 and the hole 1 3a, so that when the respective parts are assembled to complete the plunger solenoid, the core 1 3 is firmly but resiliently supported in position within the bore 11 by the stop 1 4 and the elastic body 20.

With the embodiment of Fig. 6, when current is supplied to the coil 10 and the movable iron core 1 2 (see Fig. 2) is moved towards the fixed iron core 1 3 to impinge against the latter, the impact thereupon can be absorbed by the elastic body 20. Thus, impact sound can be reduced.

In the embodiment of Fig. 6, the elastic body is approximately spherical, but it is of course possible for the elastic body 20 to be of other shapes such as a cylindrical post, a ring or a plate. The hole 1 3a partially receiving the elastic body 20 is then of course formed to have a corresponding shape.

Claims (6)

1. A plunger solenoid comprising: a bobbin having a core formed therethrough, flanges on both end portions thereof, and a winding wound thereon; a first iron core inserted into said bore from one end thereof; a movable iron core inserted into said bore from the other end thereof; a yoke having plates on two end portions thereof; and a stop formed on the inner surface of said bore at a predetermined location for positioning said first iron core within said bore; said first iron core being fixedly supported in position within said bore by the cooperation of said stop and the inner surface of one of said plates of said yoke when said bobbin is assembled with said yoke.

2. A plunger solenoid according to claim 1 wherein first engaging members are respectively formed on outer surfaces of said flanges of said bobbin, and second engaging members are respectively formed on inner surfaces of said plates of said yoke, said first and second engaging members being elasti cally engaged with one another when said bobbin is assembled with said yoke.

3. A plunger solenoid according to claim 2 wherein said yoke is formed integrally with a chassis.

4. A plunger solenoid substantially as hereinbefore described with reference to Figs.

2 and 3 of the accompanying drawings.

5. A plunger solenoid substantially as hereinbefore described with reference to Figs.

2 and 3 as modified by Fig. 5 of the accompanying drawings.

6. A plunger solenoid substantially as herein before described with reference to Figs.

2 and 3 as modified by Fig. 6 of the accompanying drawings.