Locking Mechanism

1. Field of the Invention

The present invention relates generally to a locking mechanism suitable for use with a body and a lid which are arranged to lock into each other and, more particularly, to a locking mechanism of the type which is used with a protector for wire harnesses so as to secure the lid of the protector to the body thereof.

2. Description of the Related Art

FIGS. 5 and 6 show a conventional example of such a locking mechanism which is provided in a protector for protecting wire harnesses used for wiring electrical equipment in an automobile or the like. This kind of locking mechanism is described in, for example, the specification of Japanese Utility Model Laid-open No. 13931310-1988. In the figures, a protector body 1 has a bottom la and side walls 1b formed on the opposite sides thereof, forming a U-shaped configuration in cross section, and a space for accommodating a plurality of wire harnesses 7 is formed in the protector body 1. A lid 2 has a lid portion 2a and side portions 2b whose height is small compared with that of the side walls 1b, and forms a U-shaped configuration in cross section. Engagement projections 3 are formed in the vicinity of the engagement edge portion of each of the side walls 1b of the protector body 1, while engagement holes 4 are formed in the lid 2 at locations corresponding to the engagement projections 3 so that the engagement projections 3 can be fit into the corresponding engagement holes 4. The wire harnesses 7 are accommodated in the protector body 1, and the lid 2 is secured to the protector body 1 by a tape 8.

FIG. 5 is a perspective view showing the essential portion of the locking mechanism composed of the engagement projections 3 formed on the protector body 1 and the engagement holes 4 formed in the lid 2. Holding plates 6 are fixed to the lid portion 2a of the lid 2 so as to force the engagement projections 3, formed on the side walls 1b of the protector body 1, toward the corresponding engagement holes 4 by way of the adjacent side walls 1b.

Since such a protector usually accommodates a multiplicity of wire harnesses 7 which are heavy compared with the protector, there is a tendency for a force derived from the weight of the wire harnesses 7 to be applied to locking portions at which the protector body 1 and the lid 2 are engaged with each other. FIG. 6 is a cross-sectional view, taken along line VI--VI of FIG. 5, showing one of the locking portions. As illustrated, if a force as indicated by an arrow F is applied to the lid 2 when the body 1 is engaged with the lid 2, the lid portion 2a and the holding plate 6 tend to be displaced toward the position shown by phantom lines. As a result, a gap is formed at a point A' at which the lid 2 should be kept in contact with the inner edge of the side wall 1b. It follows, therefore, that the engagement projection, 3 of the side wall 1b of the protector body 1 is engaged with the lid 2 at a hook 3' alone. In consequence, it is likely that the engagement projection 3 is disengaged from the engagement hole 4.

To eliminate the likelihood of such disengagement, as shown in FIG. 5, it has been necessary to engage the lid 2 with the protector body 1 and then to fix them by winding the tape 8 therearound.

It is an object of the present invention to provide a locking mechanism which is capable of eliminating the above-described problems and which can lock a body and a lid in a state wherein they are not easily disengaged from each other.

To achieve the above object, in accordance with the present invention, there is provided a locking mechanism comprising an engagement hole formed in each side portion of a lid, an engagement projection formed on each side wall of a body for engagement with the corresponding engagement hole, holding plates disposed on a lid portion so as to hold the corresponding engagement projections toward the engagement holes in the adjacent side portions, and projections projecting from the edge surfaces of the respective side walls for engagement with corresponding holes formed in the lid portion.

In the arrangement of the present invention, if a force acting to open the lid is externally applied, the surfaces of the respective engagement holes formed in the lid portion act to force the corresponding projecting portions, particularly edge portions of the projections which project from the edge surfaces of the respective side walls of the body, thereby pressing the engagement projections toward the respective engagement holes. Accordingly, the engagement projections are not only engaged with the corresponding engagement holes but also the pressing forces of the engagement holes act upon the corresponding engagement projections by way of the respective side walls of the body. Accordingly, the side walls of the body are positively engaged with the side portions of the lid, respectively.

FIG. 1 is an exploded perspective view of the body and lid of a protector to which is applied a locking mechanism according to an embodiment of the present invention;

FIG. 2 is a perspective view of a locking mechanism portion of FIG. 1;

FIG. 3 is a cross-sectional view taken along line III--III of FIG. 1;

FIG. 4 is a view similar to FIG. 3, and serves to illustrate the function of the locking mechanism according to the embodiment of the present invention;

FIG. 5 is a perspective view of a protector provided with a locking mechanism of the conventional type; and

FIG. 6 is a cross-sectional view taken along line VI--VI of FIG. 5.

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 through 4.

In the following description, the same reference numerals are used to denote the elements that are the same as shown in FIGS. 5 and 6.

Referring to FIG. 1, a protector body 1 made of a plastic has a bottom la and side walls 1b, and the side walls 1b respectively have edge surfaces 1c which define an opening on the side opposite to the bottom 1a. The edge surfaces 1c serve to form engagement surfaces which provide support for a lid 2 when the lid 2 is engaged with the protector body 1. The lid 2 is, therefore, adapted to engage with the protector body 1, and a locking mechanism is provided for securing the lid 2 to the protector body 1 when they are engaged with each other. As shown in FIGS. 2 and 3 which serve to illustrate a part of the locking mechanism in cross section, an engagement projection 3 is formed on the side of the side wall 1b which engages with the lid 2, and a projection 5 is formed on the edge surface 1c of the side wall 1b. A hole 4 for receiving and engaging with the engagement projection 3 and the projection 5 is formed in a side portion 2b of the lid 2, and a holding plate 6 extends from a lid portion 2a along the side portion 2b. When the protector body 1 is engaged with the lid 2, the holding plate 6 opposes the engagement hole 4 to hold the side wall 1b on which the engagement projection 3 is formed.

Although, in this embodiment, the engagement hole 4 for receiving the engagement projection 3 and the projection 5 is formed as a common hole, separate holes may be formed for the engagement projection 3 and the projection 5, respectively.

As shown in FIGS. 1 to 3, the engagement holes 4 are formed in the side portions 2b of the lid 2, and each of the engagement holes 4 is formed into a rectangular shape which has one side parallel to an inserting direction indicated at P in FIG. 3. Each of the engagement projections 3 formed on the side walls 1b of the protector body 1 has a hook 3' provided with an engagement surface 3", and an engagement surface 4' of each of the engagement holes 4 is adapted to engage with the engagement surface 3" of the corresponding engagement projection 3. As illustrated in FIG. 3, the engagement surface 4' of the engagement hole 4 is formed so as to face in the direction opposite to the inserting direction P, that is, the axis of inclination of the engagement surface 4' crosses the axis of the inserting direction P at an angle of approximately 80.degree. when the lid 2 is engaged with the protector body 1. The engagement surface 4' of the engagement hole 4 is engaged with the corresponding engagement surface 3" of the hook 3' of the engagement projection 3, formed on the side wall 1b, so that the engagement surfaces 4' and 3" lock into each other. Therefore, the engagement surface 3" of each of the engagement projections 3 is likewise formed such that the axis of inclination of the engagement surface 3" crosses the axis of the inserting direction P at a angle of approximately 80.degree. .

Projections 5 project from the edge surface 1c of each of the side walls lb of the protector body 1. Each of the projections 5 has a plate thickness which is approximately equal to that of the side wall 1b and a width which is approximately equal to that of the engagement hole 4 of the side wall 2b of the lid 2. The height of the projection 5 is at least not less than half the thickness of the lid portion 2a. More particularly, it is desirable that the height of the projection 5 be approximately equal to the thickness of the lid portion 2a.

The operation of the locking mechanism according to the emodiment of the present invention will be described below.

As shown in FIG. 4, if a force F is applied to the locking mechanism of the invention by means of which the body 1 and the lid 2 are engaged with each other, the engagement hole 4 formed in the lid portion 2a of the lid 2 acts to force an edge A of the projection 5 which projects from the edge surface 1c of the side wall 1b of the body 1, and thereby to press the projection 5 toward the engagement hole 4. As the projection 5 is pressed toward the engagement hole 4, the engagement projection 3 on the side wall of the body 1 is pressed toward the engagement hole 4. In this manner, the engagement projection 3 is not only engaged with the engagement hole 4 at the hook 3' but also the surface of the side wall 1b opposite to the engagement projection 3 is pressed toward the engagement hole 4. Accordingly, the engagement projection 3 is firmly engaged with the engagement hole 4 and it is therefore ensured that a positive locking function can be obtained.

As one example of application of the locking mechanism according to the present invention, a polypropylene protector for wire harnesses was prepared which comprised a protector body having a plate thickness of 1.5 mm, a lid having a plate thickness of 2.0 mm, engagement projections each having a height of 1.4 to 1.5 mm and a width of 12.00 mm, and projections each having a height of 1.5 mm. As compared with the conventional locking mechanism which was not able to bear a load of 10kg, the example of the locking mechanism according to the invention was able to bear a load of a maximum of 14-15 kg. This was an 50% improvement over the load level which could be borne by the conventional locking mechanism. In consequence, it became unnecessary to wind the tape 8 which was necessary in the related art described previously in conjunction with FIG. 5, and the efficiency of assembly working was improved.