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BACKGROUND OF THE INVENTION 
     The present invention relates to a seal for a window in a motor vehicle, and in particular to a windshield seal for use in a large vehicle in which there may be flexing of the structure defining a window opening. 
     It is well known to utilize rubber seals to create a somewhat flexible support and provide a sealing interconnection between a glass pane and the relatively flexible body structure of a motor vehicle surrounding a windshield or other fixedly mounted window in a motor vehicle. 
     As shown in Eichner U.S. Pat. No. 2,189,138, a conventional seal for a windshield may include a rubber strip defining pair a of oppositely facing channels which receive, respectively, a margin of a body panel or the like defining a window opening and a margin of a pane of glass. A locking strip fits in a groove defined in the seal to keep the seal in place. 
     A somewhat similar seal structure is shown also in Isbell U.S. Pat. No. 2,770,487. 
     When the structure of a motor vehicle surrounding a large fixed window such as a windshield or rear window is even slightly flexible, as in the case of the window openings of the cab of a large truck, flexure may cause significant movement of surrounding body panels relative to a window pane. Relative movements of up to 3 mm may occur, resulting in relaxation of sealing pressure between a window pane and a conventional rubber seal&#39;s critical surface. When such a motor vehicle is operated on uneven surfaces, leakage may occur around a window pane if such a conventional seal is flexed and water enters into the channel surrounding the glass pane. With repeated cycles of flexure, repeated small amounts of water can enter into the channel surrounding the pane of glass and travel around the margin of the pane of glass and then be squeezed from the channel of the seal into the interior of the vehicle. Such “pumping” of water into the interior of a motor vehicle can result in significant costs, not only for repair of water-damaged interior materials, but also in terms of loss of use of the vehicle, if a commercial vehicle has to be taken out of service to accomplish repair of such a leaking condition. 
     In the past, repair of leaky windshield seals has often been accomplished by the use of a flexible adhesive sealant cement to create a better seal than can be obtained by only the elastic pressure of the rubber against the surfaces concerned. While this can provide a watertight seal, if a windshield sealed in this manner is damaged and must be replaced, replacement requires a significant amount of time because of the extra labor involved in dealing with the adhesive cement. Where an adhesive cement sealant is used to install a replacement windshield the motor vehicle may well be unavailable for commercial use for 48 hours to provide ample time for the adhesive material to cure properly. Since time utilized in such repair represents time when the motor vehicle is unavailable to generate revenue, not only is it desirable to provide a windshield seal which is effective in excluding water from the interior of the motor vehicle in which it is used, but it is also important to provide a seal which allows rapid and efficient replacement of the glass when that becomes necessary. It is therefore desirable to provide a window seal which is effective without the use of an adhesive sealant material in addition to the mechanical action of a glass-supporting seal assembly. 
     Window seals have previously been made of synthetic rubber materials such as ethylene-propylene diamene monomer (“EPDM”), or other rubber-like materials, which typically cure chemically after being manufactured and have a significant weight. It is desirable, however, for a seal to be manufactured of a material which is somewhat lighter, in order to reduce the total weight of a motor vehicle, and it is also desirable to make a seal of a material which is easily molded or extruded, yet which has the necessary strength, flexibility and resiliency. 
     SUMMARY OF THE INVENTION 
     The present invention provides an answer to some of the aforementioned shortcomings and disadvantages of the prior art window seal structures by providing a seal that is watertight despite significant window pane movement relative to the structure defining a window opening in a motor vehicle. Broadly, the present invention provides a flexible seal made of an elastomeric material, defining a channel receiving a margin of a pane of a window, and including a flexible, elastic sealing lip, located near the channel. The lip extends toward and continuously presses against the pane at a short distance away from an edge of the channel despite pane movement relative to the surrounding structure. 
     In one preferred embodiment of the invention a lip extends from a shoulder of an exterior wall that defines a channel in which a margin of a pane of a window is received and supported, and a narrow sealing surface along an outer margin of the sealing lip is pressed against an outer surface of the pane as a result of the elastic deformation of the lip by the pane. 
     In one preferred embodiment of the invention a first or outer channel is provided in an outer margin of an elastomeric main member of a seal, to receive a portion of a surrounding structure defining a window opening in a motor vehicle body, and a glass-holding channel is located opposite the outer channel in a generally coplanar arrangement, with the sealing lip extending from a shoulder of a wall defining the glass-holding channel. 
     In one preferred embodiment of the invention, a locking strip is engaged in a corresponding groove to keep the exterior walls of both the outer, or body panel-receiving, channel and the glass-holding channel properly located with respect to each other and with respect to the margins of a surrounding body structure defining a window opening and of a pane of the window being sealed. The locking strip thereby also helps to support the root of the sealing lip, urging the lip and, particularly, its sealing surface, into contact against an outer surface of the window pane. 
     In a preferred embodiment of the invention, when the main member of the seal is in a relaxed condition the lip extends curvingly toward the interior side of the main member, so that when a pane of glass is installed within the glass-holding channel the lip is elastically deformed, and a narrow sealing surface near an outer margin of the lip is elastically pressed against an outer surface of the window pane. 
     In a preferred embodiment of the invention the lip has a length from its root to its outer margin or tip that is at least two to four times the thickness of the lip so that the lip is resiliently flexible. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a front elevational view of a portion of a cab of a truck including a windshield equipped with a seal embodying the present invention to retain the glass panes of the windshield within the window opening defined by the cab of the truck. 
     FIG. 2 is a sectional view at an enlarged scale, taken in the direction indicated by the line  2 — 2  in FIG. 1, showing portions of two transparent panes of the windshield and a portion of the seal. 
     FIG. 3 is a sectional view at an enlarged scale, taken along line  3 — 3  in FIG. 1, showing a portion of the seal shown in FIG. 1 together with a pane of the windshield glass and a portion of the surrounding structure defining the window opening of the motor vehicle. 
     FIG. 4 is a sectional view of a portion of the main body of the seal such as that at the location shown in FIG. 3, but free from the window pane and surrounding structure shown in FIG.  3 . 
     FIG. 5 is a sectional view of a portion of the main body of the seal such as that shown in FIG. 2, but without the windshield glass in place. 
     FIG. 6 is an isometric view of a curved portion of a main body of a seal such as the one shown in FIG.  1 . 
     FIG. 7 is an isometric view of a “T” joint in a main body portion of a seal such as the one shown in FIG.  1 . 
     FIG. 8 is a view similar to FIG. 3, showing the manner in which the seal is flexed to accommodate displacement of a pane of the windshield in a first direction relative to the structure defining the window opening. 
     FIG. 9 is a view similar to FIG. 8, showing displacement of the windshield pane in the opposite direction from that shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings which form a part of the disclosure herein, in FIG. 1 a windshield  10  is mounted in a cab  12  of a large truck. The windshield  10  includes a pair of panes  14  and  16  of glass or other suitable transparent window pane material fixedly mounted to close a window opening  18 . The panes  14  and  16  are isolated and held in place by a seal  20  which accommodates the flexing of the cab  12  resulting from operation of the truck. The seal  20  permits enough relative movement between the cab  12  and each of the panes  14  and  16  to protect the panes  14  and  16  from excessive stresses, while also providing an efficient seal to exclude water from entering into the interior of the cab  12 . 
     The seal  20  has a configuration generally resembling a figure eight, with a center divider member  22  separating and engaging both of the panes  14  and  16 , as shown in sectional view in FIG. 2. A peripheral portion  24  engages the separate portions of the margins of each of the panes  14  and  16  and also engages the surrounding portion of the body structure of the cab  12  that defines the window opening  18 . In a modern semi-trailer truck tractor the shell of the cab  12  may be of laminated fiber-reinforced plastic construction including a margin  26  that is coplanar with each of the panes  14  and  16  along a respective margin of each, as shown in FIG.  3 . 
     The center divider member  22  and the peripheral portion  24  include respective main bodies  28  and  30 . The seal  20 , and thus each of the main bodies  28 ,  30  has an interior side  32 , corresponding to the interior of the motor vehicle in connection with which it is used, and an exterior side  34 . 
     The main bodies  28  and  30  are of an elastomeric material amply tough to support the weight of the panes  14  and  16  without being cut or torn, and strong enough to maintain the positions of the panes  14  and  16 . At the same time, the material should be soft enough to conform sealingly to the surfaces of the margin  26  and the panes  14  and  16 , and stable enough to retain its elastic restorative force after being deformed elastically for many months and in all weather conditions. For example, a thermoplastic synthetic polymeric rubber-like material is preferred, and one such material is a thermoplastic matrix filled with crosslinked rubber particles, having a 100% modulus of elasticity in the vicinity of 350 psi and a hardness of 64-65 on the Shore A scale, available from Advanced Elastomer Systems, L.P. of Akron, Ohio under the trademark and designator Santoprene 101-64. Other thermoplastic or thermosetting elastomeric materials with Shore A hardness in the range of 55-75 would also be acceptable. 
     As seen in FIG. 3, the margin  26  of the cab structure defining the window opening  18  is located within a body panel channel  36  defined in an outer margin portion  37  of the main body  30 . The body panel channel  36  has a bottom  38  with a width  40  that is at least as great and preferably greater than the thickness  42  of the cab structure margin  26 . An interior wall  44  and an exterior wall  46  defining the channel  36  include respective planar interior wall surfaces  45 ,  46  that converge toward each other as they extend from the bottom  38  and approach respective edges  48  and  50 , which press against the opposite interior and exterior surfaces of the margin  26  of the body structure of the motor vehicle. The edges  48 ,  50  are separated from the channel bottom  38  by a channel depth  52  (FIG.  4 ), which may be, for example, about 0.445 inch. It will be recognized that the seal  20  could also be fastened to the structure surrounding a window opening in other ways, depending on the form of such surrounding structure. 
     Aligned generally coplanar with the body panel channel  36  and directed oppositely away from it is a glass-receiving channel  56  in which a margin  58  of the pane  14  or  16  is received, as shown in FIG.  3 . The glass-receiving channel  56  has a bottom  60  with a width  62  which is at least as great as, and preferably slightly greater than, the thickness  64  of the pane  14  or  16 . 
     An interior wall  66  and an exterior wall  68  of the channel  56  have, respectively, an interior wall edge  70  and an exterior wall outer or upper edge  72  defining a depth  73  of 0.331 inch, for example, to the bottom  60 . The interior wall  66  includes a shoulder  74  extending outwardly from the interior wall edge  70 , and a planar interior surface  76  of the interior channel wall  66  extends from the interior wall edge  70  to the bottom  68  of the glass-receiving channel  56 . Similarly, a planar interior surface  78  of the exterior channel wall  68  extends from the exterior wall edge  72  to the bottom  68  of the glass-receiving channel  56 , and an exterior wall shoulder  80  extends along and away from the exterior wall edge  72 , outside the channel  56 . 
     A sealing lip  82  has a root  84  adjacent the exterior wall shoulder  80  and extends obliquely upward from the root  84  to an outer tip or margin  85  that includes a narrow sealing or contact surface area  86  that presses against the outer face of the pane  14 , as seen in FIG.  3 . The distance along the shoulder  80  between the edge  72  and the root  84  is in the range of 0.09 inch to 0.16 inch, and preferably about 0.12 inch, in the seal  20 , to allow for flexing of the lip  82 . It is important that the lip  82  be long and thin enough to be flexible yet be thick enough and strong enough to reliably press the contact area  86  against the pane  14 . For example, in the seal  20  as shown, for panes  14  and  16  having a thickness  64  of 6.75 mm ±0.80 mm, the sealing lip  82  has a length  87  of about 0.350-0.385 inch, and a thickness  89  of about 0.095 inch, and thus the ratio of length to thickness of the sealing lip  82  is in the range of 3:1 to 5:1 and more precisely is about 4:1. 
     A locking strip  88 , which may be of a harder, less compressible, elastomeric material than that of the main body  24 , is located within a locking strip groove  90 , and supports the exterior wall  46  and exterior wall  68  firmly. It also urges their edges  50  and  72 , respectively, against the margin  26  of the structure defining the window opening  18  and against the pane  14  or  16  of the window. 
     Referring also to FIG. 4, it may be seen that in a relaxed condition the main body  30  of the peripheral portion  24  has the edges  48  and  50  of the body panel channel  36  closer together than the width  40  of that channel&#39;s bottom  38 . Similarly, the interior wall edge  70  and exterior wall edge  72  are located closer together, at 0.178 inch, for example, than the width  62  (0.307 inch, for example), of the bottom  60  of the glass-receiving channel  56 . Preferably, the distance between the edges  48  and  50  with the main body  30  relaxed is, for example, considerably less than the thickness  42  (for example, 0.236 inch) of the margin portion  26  of the structure defining the window opening  18 . Similarly, the distance between the edges  70  and  72  of the relaxed seal  20  is thus significantly less than the thickness  64  (for example, 0.265 inch) of the pane  14  or  16  of glass to be held in place and sealed by the seal  20 . 
     In FIG. 4 it may also be seen that in its relaxed condition, the sealing lip  82  has a convex outer surface  92  and a concave inner surface  94 , and its outer margin  85  is located approximately in line with the middle of the glass-receiving channel  56 . When the pane  14  or  16  is installed in the channel  56  the channel edges  70  and  72  press against opposite faces of the pane, while the sealing surface  86  also presses against the outer face of the pane  14  or  16 , bending the lip  82  elastically to the form shown in FIG. 3, with the result that the sealing surface  86  is pressed against the outer face of the pane  14  by the elastic restorative force of the lip  82 . 
     Referring again to FIG.  2  and also to FIG. 5, it will be seen that the structure of the main body  28  of the center divider member  22  consists essentially of a pair of mirror opposite portions arranged substantially back-to-back. Each of these portions is similar to the portion of the main body  30  defining the glass-receiving channel  56 , and thus the main body  28  defines glass-receiving channels  56  and  56 ′ and associated sealing lips  82  and  82 ′. A locking strip  96  is similar to the locking strip  88  and is similarly fitted into a locking strip groove  98  between the bases of the two exterior wall portions  68  and  68 ′. 
     The straight portions of the center divider member  22  and the peripheral portion  24  of the seal  20  may be manufactured as extrusions of thermoplastic rubber. It may be preferred, however, depending upon the particular material of which the seal  20  is to be manufactured, and also depending upon the radius of curvature in arcuate portions of the seal  20 , to provide curved sections  100  molded to fit the shape of a window opening  18  and panes  14  and  16 . Thus, the molded portion  100 , shown in FIG. 6, as seen in any radial plane including the axis of curvature of such a molded portion  100 , has the same sectional shape as the straight portions of the peripheral portion  24  of the seal  20 . As a result, the lip  82  in such molded sections  100  will provide the needed pressure to effect a seal on the pane  14  or  16 . 
     At locations where the center divider member  22  intersects with the peripheral portion  24  it is also preferred to have a specially molded T-joint element  102  as shown in FIG. 7, in which a portion  104  has the same sectional shape as the center divider member  22 , while a portion  106  has an outer margin  108  that resembles that of the peripheral portion  24  of the seal  20 . The portion  104  intersects with the glass-receiving channel portion  56  to form two right-angled inside corners  109  to receive the respective corners of the panes  14  and  16  at both the top and bottom of the windshield  10 . 
     As illustrated in FIGS. 8 and 9, the seal  20  accommodates a significant amount of relative movement between the margin  26  of the structure defining the window opening  18  and the pane  14  or  16  of the windshield  10 . The sealing surface  86  of the outer margin  85  of the sealing lip  82  remains in contact with the outer face of the pane  14  or  16  throughout all of a significant range of relative movement, from the position shown in FIG. 8, where the pane  14  or  16  is shown displaced relatively outward by a distance  110  with respect to the margin  26 , to the position shown in FIG. 9, where the margin of the pane  14  or  16  is shown displaced relatively inward by a distance  112  relative to the margin  26  of the structure defining the window opening  18 . In each position between the extremes shown in FIGS. 8 and 9 the lip  82  remains elastically deformed, with the result that there is always pressure exerted by the sealing surface  86  against the face of the pane  42 . 
     As a result, the sealing surface  86  remains always in sealing contact against the outer face of the pane  14  or  16  and maintains a watertight seal. 
     As in conventional window seals, the locking strip grooves  90  and  98  divide the main bodies  28  and  30  of the seal  20 , providing relatively thin and thus relatively flexible sections between the central portion of the main body and the exterior walls  46 ,  68 . The seal  20  can thus be installed in the conventional manner by installing the peripheral portion  24  into the window opening  18 , with the body panel channel  36  engaging the margin  26 , and by thereafter elastically flexing and moving the exterior wall  68  away from the glass-receiving channel  56  to provide ample space for insertion of the panes  14  and  16  one after the other. The elasticity of the material of which the seal  20  is made is sufficient to retain the panes  14  and  16  until both are in place with their margins safely located within the glass-receiving channel  56  the entire way around each pane  14  and  16 . Thereafter, the locking strips  88  and  96  are mounted in the locking strip grooves  90  and  98  in the conventional manner, and they thereafter urge the exterior wall  68 , and along with it urge the roots  84  of the sealing ribs  82 ,  82 ′, carrying respective sealing surfaces  86 ,  86 ′ toward the outer surfaces of the panes  14  and  16 . 
     As the direction of the flow of air and entrained water toward the seal  20  ordinarily does not urge water into the panel channel  36  around the margin  26  defining the window opening  18 , an adequate seal is maintained around the outer margin of the seal  20  without the need for a lip such as the sealing lip  82 . 
     While it may be desirable in some cases to use an adhesive sealant material between the seal  20  and the margin  26  defining a window opening  18 , this should not ordinarily be necessary, and it should ordinarily not be necessary to utilize any adhesive sealant material between the seal  20  and the panes  14  and  16  of glass of the windshield  10 , since relative movement between the margin  26  and the panes  14  and  16  will be accommodated by the available excess width in the bottom  38  of the body panel channel  36  and the excess width in the bottom  60  of the glass-receiving channel  56 . 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.

Summary:
A seal for a fixed window in a motor vehicle, including a pane-holding channel to receive and grip the opposite faces of a margin of a window pane. A sealing lip extending parallel with the pane-holding channel has a root located a small distance apart from the top edge of the pane-holding channel, and an outer margin of the lip extends to and presses sealingly against an outer surface of the window pane. In a preferred embodiment of the invention an outer margin of the main member of the seal defines a channel to receive and grip the opposite faces of a margin of the structure defining a window opening in the motor vehicle. A locking strip engaged in a locking strip groove keeps the seal in place after installation.