Sealing strips

Abstract: A sealing strip for sealing between a flange (22) defining a door opening, such as in a motor vehicle body, and the door (24) of the opening, comprises a channel-shaped gripping part (12) for gripping the flange (22) and supporting a hollow tubular sealing part (14), preferably made of sponge rubber. The latter is partially compressed between the flange (22) and the closing door (24) so as to provide a barrier seal against ingress of moisture and draught. In order to provide improved blocking of acoustic energy, so as to reduce the amount of exterior noise (road noise, aerodynamic noise) transmitted into the interior of the vehicle, the sealing part (14) also carries an acoustic screen (30) which is made of material having increased acoustic energy attenuating properties as compared with the sponge rubber of the sealing part (14). The acoustic screen (30) carries notches (32) to increase its flexibility, and is positioned substantially clear of the door (24) and the bodywork (23) adjacent the frame, so as to minimise any increased effort required for closing the door and to maximise its acoustic energy blocking action.

Description: The invention relates to a sealing strip for sealing around at least part of the frame of an opening closable by a closure member, comprising compressible material positioned to be compressed between the frame and the closing closure member to provide a barrier seal. Such a sealing strip is known, for example, from DE-A-3 527 094 or from US-A-4 143 497. However, although the compressible material, such as foamed or low density elastomeric material, used in such sealing strips provides good sealing characteristics against water, moisture or draughts, it may be less satisfactory as an acoustic screen - that is, it may provide low resistance to the transmission of exterior noise into the interior of the vehicle. The invention aims to deal with this problem. The known sealing strip is therefore characterised, in accordance with the invention, in that the sealing strip comprises, in combination with the compressible material, additional material having a higher acoustic impedance than that of the compressible material and being so positioned in relation to the compressible material as to attenuate acoustic wave energy tending to pass between the frame and the closed closure member. Sealing strips embodying the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a known form of sealing strip; Figure 2 is a cross-section through the sealing strip of Figure 1, but showing it mounted on a bodywork flange surrounding a door opening in a vehicle body; Figure 3 corresponds to Figure 2 but shows the configuration which the sealing strip adopts when the door closes in the opening; Figure 4 is a cross-section corresponding to Figure 2 but showing a sealing strip embodying the invention; Figure 5 corresponds to Figure 4 but shows the configuration which the sealing strip adopts when the door closes into the opening; Figures 6 and 7 correspond respectively to Figures 4 and 5 but show a different form of sealing strip embodying the invention; Figures 8 and 9 correspond to Figures 4 and 5 but show a further form of sealing strip embodying the invention; and Figure 10 corresponds to Figure 4 and shows yet a further form of sealing strip embodying the invention. In all the Figures, corresponding parts are indicated by the same reference numerals. The sealing strip of Figures 1,2 and 3 comprises a longitudinally extending channel-shaped gripping part 12 on one outside wall of which is mounted a co-extending tubular sealing part 14. The gripping part 12 comprises extruded material, such as plastics or rubber material 16, in which is embedded a reinforcing core or carrier 18. The carrier 18 may take any suitable form. It may be made of metal which may be apertured at intervals along its length. In one form, the carrier comprises U-shaped elements arranged side by side along the length of the carrier to define a channel and either completely disconnected from each other or connected together by short integral connecting links. Instead, wire looped to and fro around the channel and along its length can be used. However, other forms of carrier construction are possible. The gripping part 12 is preferably produced by a cross-head extrusion process. The sealing part 14 is preferably made of soft rubber, such as sponge or cellular rubber. The sealing part 14 may again be made by an extrusion process. It may be made separately from the gripping part, and then adhesively attached to the gripping part in a separate operation. Instead, however, the whole sealing strip may be made by simultaneous extrusion. The extruded material 16 of the gripping part 12 is preferably extruded with integral gripping lips 20 mounted on the inside facing walls of the channel. The extrusion process may be arranged so that the material of these gripping lips is softer than the remainder of the extruded material 18. In use, the sealing strip is mounted around the frame of a door or other closable opening in a motor vehicle body by fitting the gripping part 12 onto the flange 22 (Figure 2) which extends around the opening and is formed where the inner and outer panels of the bodywork are brought together at the opening and welded. The configuration of the gripping part is such that it tightly grips the flange 22, this gripping action being assisted by the lips 20. In this way, therefore, the gripping part 12 supports the sealing part 14 so that the latter runs around the periphery of the opening and faces towards the door 24 or other closure member for the opening. Figure 3 shows how the closing door 24 partially compresses the sealing part 14 to provide an effective seal around the opening against draught and water or moisture. Figure 4 corresponds to Figure 2 but shows one of the sealing strips embodying the invention. The sealing strip of Figures 4 and 5 differs from the sealing strip of Figures 1 to 3 in that at least part of the wall of its sealing part 14 is covered with or replaced by material 30 which is selected and constructed to form an acoustic screen. The normal material of the sealing part 14 (sponge or cellular rubber), although providing excellent sealing properties against ingress of draught, water or moisture, provides poor acoustic screening properties. Therefore, a sealing strip of the form shown in Figures 1 to 3 provides poor attenuation of external noise (such as road noise or aerodynamic noise), and thus provides low resistance to the transmission of such exterior noise into the interior of the vehicle. When an acoustic wave strikes the elastic material of the sealing part 14, part of the acoustic energy passes through the wall, another part is reflected and some is absorbed. The amount of energy passing through the wall and the amount reflected respectively depend on the acoustic impedance of the wall, that is, on its mass and rigidity. The greater the mass of the wall and its rigidity, the greater will be its acoustic impedance and, consequently, the lower will be the wave energy passing through the wall. In the case of the sealing strip shown in Figures 1 to 3, the material of the sealing part has a very low acoustic impedance and a significant part of the acoustic energy thus passes through the sealing part into the interior of the vehicle. In the case of the sealing strip shown in Figures 4 and 5, however, the amount of acoustic energy passing through the sealing part 14 when the door is closed (Figure 5) is greatly reduced by the acoustic screen 30. The acoustic screen comprises material of high acoustic impedance, for example a thermoplastic material or a compact elastomer. Because of the type of material from which it is constructed, the acoustic screen 30 will tend to decrease the flexibility of the sealing part 14, thus tending to increase the effort require for closing the door. Therefore, the acoustic screen 30 is positioned on the sealing part 14 so as to minimise its effect on the latter's compressibility. As shown in Figure 5, it is positioned on the sealing part so that, when the door 24 is closed, the acoustic screen 30 is neither in contact with the door nor with the bodywork 23 adjacent the opening. Advantageously, the acoustic screen 30 is formed with longitudinal notches 32 which facilitate deformation of the acoustic screen when the sealing part 14 is deformed by the closing door (see Fig. 5), thus offsetting the decreased flexibility of the acoustic screen material. The acoustic screen 30 can be secured to the material of the sealing part 14 by adhesive. Preferably, though, it is formed by co-extrusion with the remainder of the material of the sealing part. The acoustic screen 30 may be formed as a layer on the outside of the sealing part whose cross-section is otherwise unaffected. Instead, the thickness of the wall of the main material of the sealing part may be locally reduced in the region of the acoustic screen 30 or may be completely replaced in that region by the acoustic screen. In the sealing strip of Figures 4 and 5, the acoustic screen 30 is of course visible and it must therefore present an aesthetic appearance. Figures 6 and 7 correspond to Figures 4 and 5 but show an arrangement in which the acoustic screen 30 is provided on the inside of the hollow sealing part 14 instead of on its outside. The construction and operation is otherwise the same. In this case, the acoustic screen has to be formed by co-extrusion with the remainder of the sealing part 14. Although Figures 4 to 7 show the use of a sealing part 14 of hollow configuration, the sealing part may in certain circumstances take the form of a lip. In such a case, the acoustic screen 30 may be provided in the same way as described. Figures 8 and 9 show another form in which the sealing part 14 is provided with a dividing wall 34. Part or all of this wall is constituted by the acoustic screen 30. The construction and operation is otherwise the same as for the other examples shown in Figures 4 to 7. Again, the acoustic screen of the strip of Figures 8 and 9 can only be produced by co-extrusion. The sealing strip shown in Figure 10 is similar to that shown in Figures 8 and 9, except that the mass of the acoustic screen 30 is selected so as to increase the acoustic screening effect. Thus, if m is the mass of the acoustic screen 30 and k is the rigidity of the wall extending across the interior of the sealing part 14, the assembly comprising the acoustic screen and this wall will have a resonant frequency f , where f = 1 2 π √ k m Therefore, incident acoustic wave energy at the frequency f will cause the acoustic screen and its supporting wall to resonate at this frequency. However, incident acoustic wave energy at frequencies above f will cause the acoustic screen and the wall to vibrate in opposition to the incident energy. The acoustic impedance and thus the acoustic screening effect will be increased or reinforced. The amount of acoustic energy reflected by the acoustic screen will be increased by the resultant vibration of the mass m . Therefore, by selecting the mass m and the rigidity k in dependence on the primary frequency band of the acoustic energy to be attenuated, the attenuation effect can be considerably increased. The resonant frequency should be low relative to the passband of the human ear (which is from about 20 Hz to about 20 kHz). A value for the resonant frequency of about 30 to 50 Hz may be used, for example. It is necessary, though, to ensure that the mass m is not increased to such an extent that the resultant volume of the acoustic screen 30 causes the latter to come into contact with the internal wall of the sealing part 14 at maximum deformation. The optimum geometry for the acoustic screen 30 can be obtained by computer-aided design.

Claims: A sealing strip for sealing around at least part of the frame of an opening closable by a closure member (24), comprising compressible material (14) positioned to be compressed between the frame (22) and the closing closure member (24) to provide a barrier seal, characterised in that the sealing strip comprises, in combination with the compressible material (14), additional material (30) having a higher acoustic impedance than that of the compressible material (14) and being so positioned in relation to the compressible material (14) as to attenuate acoustic wave energy tending to pass between the frame (22) and the closed closure member (14). A sealing strip according to claim 1, characterised in that the additional material (30) is positioned so as to minimise its effect on the compressibility of the compressible material (14). A sealing strip according to claim 1, characterised in that the additional material (30) is connected to the compressible material (14) and is provided with longitudinally extending notches (32) to increase its flexibility in response to compression of the compressible material (14). A strip according to any preceding claim, characterised in that the compressible material is in the form of a hollow tube (14) which is partially collapsed by compression by the closing closure member (24), and in that the additional material (30) is mounted on a part of the wall of the tube (14) which is substantially clear of both the closing closure (24) member and the frame (22). A strip according to claim 4, characterised in that the additional material (30) is positioned on the outside of the wall of the tube (14). A strip according to claim 4, characterised in that the additional material (30) is positioned on the inside of the wall of the tube (14). A strip according to any one of claims 1 to 3, characterised in that the compressible material is in the form of a hollow tube (14) which is positioned to be partially collapsed by the closing closure member (24), the tube having an internal partition wall which carries or is partially formed by the additional material (30). A strip according to any preceding claim, characterised in that the compressible material (14) and the additional material (30) are produced by co-extrusion. A strip according to any preceding claim, characterised in that the mass of the additional material (30) and the rigidity with which it is supported are so selected in relation to the frequency of the acoustic wave energy to be attenuated as to provide dynamic attenuation of the acoustic energy. A strip according to any preceding claim, characterised in that it is mounted on a channel-shaped gripping part (12) adapted to engage the frame (22). A strip according to any preceding claim, characterised in that the compressible material (14) is soft rubber, such as sponge rubber. A strip according to claim 11, characterised in that the additional material (30) is a thermoplastic material or a compact elastomer.

Inventors: GALLAS GERARD, GALLAS, GERARD
Applicants: DRAFTEX IND LTD, DRAFTEX INDUSTRIES LIMITED
Application year: 1993
Main classification: B60J10
IPC codes: G10K11, B60R13, B60J10, E06B7