Sound deadening dual sleeve sealing arrangement
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a sealing sleeve for masking the aperture between a positionally stable wall and a shaft penetrating a bore through the wall, which sleeve includes a bellows for compensating offset positions of the shaft. 
     A sealing sleeve is known from a publication of Daimler-Benz Aktiengesellschaft of Stuttgart, Federal Republic of Germany, assignee of this application, illustrated in technical drawing FG 21 90, which masks the interstice between a vehicle body end wall of a passenger compartment of a motor car and a steering spindle protruding through a bore in this wall and seals the bore against passage of dirt. So that the installation dimensions, which differ due to tolerances, do no jeopardize the tight fit of the sleeve, the latter exhibits a thin-walled flexible bellows compensating any offset of the steering spindle which occurs. 
     Because the smallest possible wall thicknesses are aimed at for the sealing sleeve as a whole due to the required resilience, it is unfortunately also necessary to accept that the passage of sound into the passenger compartment, emanating from the units of the engine compartment, occurs particularly strongly at such a sealing point. 
     This does not appear justifiable, particularly when one considers what outlay is undertaken in vehicles for the desired sound insulation of the engine compartment relative to the passenger compartment, by additional vehicle body partition walls for example, which are intended to achieve better sound insulation. 
     An object of the invention is therefore to construct a flexible sealing sleeve with improved sound insulation. 
     This object is achieved by providing a second sleeve which is anchored together with the first sleeve and is disposed to form a sound insulating air chamber between the first and second sleeves at least in the area of the bellows. 
     The sealing sleeve, which is flexible by virtue of bellows, seals the wall aperture against dirt, dust and spray water, whereas conjointly with the second sleeve connected thereto an air chamber is formed which conjointly with the walls, which are now double-acting, largely prevents the sound waves from penetrating the wall aperture. 
     It is sufficient in certain preferred embodiments to cover only the bellows when they are made thinner-walled and more sound-permeable than an adjacent more stable sleeve wall by a drawing operation in production. 
     In certain advantageous preferred embodiments, the second sleeve exhibits externally a cylindrical external circumference, whereby the overall volume is only slightly increased compared to a single sealing sleeve, but due to the interval between the sleeve walls the compensating movement of the bellows of the sealing sleeve is not obstructed. 
     In certain preferred embodiments a combination of the two sleeves which is favorable for production is provided, wherein the second sleeve is molded integrally onto the sealing sleeve at one end, and by inversion round the latter and clipping in of a free end forms a sound-insulating air chamber conjointly therewith. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial schematic, part sectional view of a sealing sleeve between a wall aperture and a steering spindle shaft with a second sleeve connected thereon, constructed in accordance with a first preferred embodiment of the invention; and 
     FIG. 2 is a partial view of another preferred embodiment of the invention with a sealing sleeve with a second sleeve molded on integrally at one end. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In FIG. 1, a sealing sleeve 3 is arranged to mask an aperture between a vehicle body end wall 1 of a passenger compartment of a motor car, not further shown, and a steering spindle 2 penetrating a bore in the end wall 1. Sealing sleeve 3 abuts the end wall 1 with one end region and the steering spindle 2 at the other end via a sealing part 4 accommodated rotationally stably thereby. In a median region, the sealing sleeve 3 exhibits a bellows 5 by which an accurate seating of the sealing sleeve 3 is ensured even in the event of a steering spindle 2 offset out of the center, within the values of the installation tolerances, because it compensates such an offset by modification of its form. 
     This sealing sleeve 3 has attached to it externally a second sleeve 6, which is clipped to the ends of the sealing sleeve 3 at two connection points 7, 8. 
     Because the second sleeve 6 is less resilient than the sealing sleeve 3 with the bellows 5, the interval between its walls is determined by its configuration so that during the movement of the bellows 5 compensating an offset of the steering spindle 2, sleeve 3 and 6 can execute a corresponding relative movement between their connection points 7, 8. 
     The sound can no longer pass unobstructed through the closed double-walled air chamber 9 constructed in this manner, but is attenuated. 
     The second sleeve 6 exhibits a cylindrical external circumference, whereby the overall volume of the combined sleeves 3 and 6 does not substantially exceed that of a single sealing sleeve 3, so that the use of the combined sleeves 3 and 6 creates no installation problems. 
     In FIG. 2, a second sleeve 6&#39; is molded integrally onto a sealing sleeve 3&#39; at one end 7&#39;, and can be inverted over the region of a thin-walled bellows 5&#39; and then clipped in an all-round notch 10 of the sealing sleeve 3&#39; by its appropriately shaped loose end 11 at connection 8&#39;. By this means, in this case again an air chamber 9&#39; is created which reduces the passage of sound in the region of the bellows 5&#39;. 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.