Grommet structure
BACKGROUND OF THE INVENTION 
     The present invention generally relates to a structure of a grommet consisting of a soft grommet body and a resinous lock member, and more particularly, to a grommet having a structure for preventing the grommet body fitted to the resinous lock member from being released therefrom. 
     FIG. 1 is a perspective view illustrating parts of a conventional grommet, FIG. 2 is a vertical sectional view illustrating the assembly thereof, and FIG. 3 a rear elevation. The conventional grommet shown is composed of a soft grommet body A and a hard resinous lock member B. The grommet body A has a protrusively provided tube 2 serving as an electric wire insertion hole formed in an inner periphery of a base 1 assuming a hollow disc-like configuration. A peripheral wall 3 is crookedly formed along an outer periphery of the base 1; and the tip portion of the peripheral wall 3 is further bent inwards, thus providing an annular supporting portion 4. 
     An inner peripheral surface of the tube 2 is provided with a plurality of lips 5 by which an electric wire inserted into the tube 2 is sealed. For waterproofing, tapes T are wound both on the electric wire and on the tube 2. 
     The base 1, the peripheral wall 3 and the supporting portion 4 of the grommet body A cooperate to internally form an annular recess 7 to which a substrate 8 of the resinous lock member B is attached. 
     The resinous lock member B includes the hollow disc-like substrate 8 on which a square pillar 9 is mounted. A bottom wall 10 assuming a hollow disc-like shape is fitted to the square pillar 9. 
     Four stop members 11 each having a stop stepped-portion 11a are vertically provided on the outer periphery of the bottom wall 10 so as to be directed to the substrate 8. 
     The stop members 11 are fitted in, creating elastic flexure, when the resinous lock member B is inserted into a hole of a pannel P, resulting in elastic enagement of the stop stepped-portions 11a. The resinous lock member B is thus .seized by the pannel P. Accordingly, the square pillar 9 is formed to have four angular portions 9a middled between the contiguous stop members 11 so as not to interfere with the flexural deformation of the stop members 11. 
     The supporting portion 4 of the grommet body A, as depicted in FIG. 1, serves to support, with a dimension l 1  an entire outer periphery of the substrate 8, thus keeping the engagement of the resinous lock member B with the grommet body A (see FIGS. 4 and 5). The reference numeral 12 designates an annular outer peripheral lip, provided along the peripheral wall 3, for protecting the hole of the pannel P from the permeation of water by virtue of its close-contact with the pannel P. 
     The thus constructed grommet is installed in the following manner. 
     The grommet body A is, as illustrated in FIG. 2, fitted in the resinous lock member B, and the electric wire (wire harness) 6 penetrates the bottom wall 10 and the substrate 8 and is inserted into the tube 2. 
     Next, the resinous lock member B is inserted into the hole P 1  formed in the pannel P while being guided by the square pillar 9. At this time, each of the stop members 11 impinges upon an edge of the hole P 1 , thereby producing flexure. Just when the stop stepped-portion 11a is overlapped with the hole P 1 , the stop stepped-portion 11a is brought into press-contact with the edge of the hole P 1  by pint of elastic force of the stop member 11, whereby the resinous lock member B is seized by the pannel P. The outer peripheral lip 12 of the grommet body A fitted in the resinous member B is tightly secured to the pannel P, causing elastic deformation. 
     In this way, the grommet functions to provide the waterproofing between the electric wire 6 and the pannel P. 
     The resinous lock member B fitted in the annular recess 7 formed in the grommet body A is held in a fitstate by the supporting portion 4. For instance, however, where a tensile force acts on the electric wire, the grommet body A is stretched together with the electric wire 6, thereby causing elastic deformation of the grommet body A. Then, the periphery of the supporting portion 4 is lifted with the result that the seizing force of the substrate 8 is lost. Hence, there arises such a problem that the grommet body A comes off the substrate 8. 
     The present invention has been made to obviate such problems. 
     SUMMARY OF THE INVENTION 
     A grommet according to the present invention comprises: a soft grommet body including a supporting portion arranged such that an electric wire insertion hole is formed in an inner peripheral portion of a hollow disclike base, a peripheral wall is crookedly formed along an outer periphery thereof, and tip portion thereof is further bent inwards; a square pillar having a substrate fitted in an annular recess constituted by a combination of the base, the peripheral wall and the supporting portion, and a plurality of angular portions each fitted in a hole of a pannel; and a hard resinous lock member having stop members for providing locking in the hole. In this construction, an inner periphery of the supporting portion assumes an angular configuration having corners close to the plurality of angular portions. 
     With this arrangement, a seizing width of the supporting portion for seizing the substrate of the resinous lock member is widened. Even if the tensile force works on the grommet body to such an extent that the grommet body is deformed, it is hard for the substrate to be released from the annular recess because of the larger seizing width of the supporting portion. This results in improvement of reliability of a water proofing function of the grommet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a perspective view showing a grommet body and a resinous lock member according to the prior art; 
     FIG. 2 is a sectional view taken along the line II--II of FIG. 3; 
     FIG. 3 is a rear view of the grommet according to the prior art; 
     FIG. 4 is a sectional perspective view showing a portion in the vicinity of a stop member of the grommet shown in FIG. 1; 
     FIG. 5 is a sectional perspective view showing an angular portion of a square pillar of the grommet shown in FIG. 1; 
     FIG. 6 is a sectional view taken along the line VI--VI of FIG. 7; 
     FIG. 7 is a rear view of a grommet according to the present invention; 
     FIG. 8 is a sectional view showing a seizing area of the embodiment; 
     FIG. 9 is a perspective view showing a grommet body and a resinous local member according to the invention; 
     FIG. 10 is a sectional perspective view, taken along the line X--X of FIG. 6, showing a portion in the vicinity of a stop member of the grommet according to the invention; 
     FIG. 11 is a sectional view showing another embodiment of the invention; 
     FIGS. 12 to 14 show another embodiment of the invention; and 
     FIGS. 15 to 17 show still another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will hereinafter be described with reference to the accompanying drawings. 
     Note that the same components as those in the conventional example are marked with the like symbols. 
     FIG. 5 is a cross-sectional view of a grommet, FIG. 6 is a rear elevation thereof and FIG. 9 is a perspective view showing parts thereof. The grommet shown consists essentially of a soft grommet body A and a hard resinous lock member B. A substrate 8 is fitted in an annular recess 7, which arrangement is the same as that in the prior art. In addition, a configuration of the resinous lock member B is identical with that in the conventional example. 
     An inner periphery of a supporting portion 4, as depicted in FIGS. 6 and 8, assumes a substantially square shape. Namely, this square is shaped by connecting an inner periphery 4b with a rectilinear line. 
     In the prior art, the substrate 8 seizing width of the supporting portion 4 is uniformly l 1  (see FIGS. 4 and 5). In contrast with this, according to the present invention the seizing width is l 1  at a corner 4c but is l 2   in the intermediate portion between corners 4c (see FIG. 8). A seizing area increases by a range 13 defined by a dotted line of FIG. 7. 
     Therefore, the grommet body A is stretched together with an electric wire 6 undergoing outer tensile forces so that the grommet body A is subjected to distortion. Even under such a condition, it is difficult for the supporting portion 4 to come off the substrate 8. 
     Directing attention to FIG. 11, there is shown another embodiment of the present invention, wherein a polygonal pillar 9 includes three angular portions 9a, and the inner periphery 4d of the supporting portion 4 takes a substantially triangular configuration. 
     In such a case, the substrate 8 seizing area of the supporting portion 4 increments by a range 14 defined by the dotted line as compared with that in the conventional example, whereby it is hard for the supporting portion 4 to be released from the substrate 8. 
     Where the square pillar 9 has five pieces of angular portions 9a, the configuration of the inner periphery of the supporting portion 4 may be substantially pentagonal. 
     However, if the configuration of the inner periphery of the supporting portion 4 is arranged to be more polygonal, the substrate 8 seizing area of the supporting portion 4 will be stepwise shrunk. Therefore, the seizing force undesirably exhibits less effects. 
     As discussed above, the present invention provides the following effects. Since the inner periphery of the supporting portion of the grommet body assumes the angular configuration having corners contiguous to the plurality of angular portions, the area for seizing the substrate thereof increases. By virtue of this arrangement, it is difficult for the grommet body to come off the resinous lock member, thereby improving the reliability of a waterproofing function of the grommet. 
     Another embodiment of the present invention will now be described with reference to FIGS. 12 to 14 in which the same reference numerals are used to designate the like components or members. In FIGS. 13 and 14, a hard resinous lock member B is provided with a base plate 8 and a circumferential wall 90 integrally formed with the base plate 8. An inward peripheral edge 93 is directed centrally. A plurality of cutout stop members 11 are formed in the circumferential wall 90. In this embodiment, instead of the specific form of the supporting portion 4, an electric wire fixing portion 91 is formed integrally with the peripheral edge portion 93 of the resinous lock member B. The plate-like fixing portion 91 extends downwardly with a thickness being gradually decreased toward a distal end at which a projection 91a is provided. In this embodiment, the grommet structure may be installed on the pannel P substantially in the same manner as in the foregoing embodiment. A tape T is applied to the tube 2 and the wire fixing portion 91 as shown in FIG. 12. 
     FIGS. 15 to 17 show another embodiment of the invention, in which the same reference numerals are used to indicate the like components or members. As shown in FIG. 16, an electric wire fixing portion 150 that is substantially in the form of a planar member is integrally formed through a hinge portion 140 with the substrate 8 of one lock member B. It should be noted that the lock member 8 is divided into two halves to be assembled later. A stop 160 is formed on one side of the fixing portion 150 at a distance l 3  from the hinge portion 140. The distance l 3  is somewhat larger than a thickness l 4  of the resinous lock member C. Namely, the fixing portion 150 is turned through 180° with the projecting stop 160 being directed outwardly as shown in FIG. 16. In this case the stop 160 is positioned in contact with the peripheral edge 93 of the lock member B. The wire fixing portion has a projection 150a at its distal end around which the tape T is applied as in the foregoing embodiment. 
     It is apparent for those skilled in the art that the wire fixing means shown in FIGS. 12 to 14 and 15 to 17 may be applied to the square pillar structures shown in FIGS. 6 to 11.