Water resistant seal for watch case

An improvement in a water resistant seal for a watch case with a bezel having a peripheral wall and a lens having a peripheral edge. The wall has an inwardly protruding flange and the lens edge has an outwardly protruding flange, the flanges being diagonally offset from one another. An elastomeric gasket of L-shaped cross section is clamped between the lens and the bezel. The gasket has an upstanding leg deformed in opposite lateral directions, by the flanges with a shearing force across the gasket leg, and is dimensioned to provide clearances which allow for manufacturing variations in size of the lens and bezel, while still maintaining a water resistant seal.

BACKGROUND OF THE INVENTION 
This invention relates to an improved water reisitant seal for a watch case 
of the type having a lens with a peripheral edge to be sealed within a 
peripheral wall on the watch case bezel. More particularly, the invention 
relates to an improved water resistant seal using an elastomeric gasket. 
Water resistant seals are well known which employ an elastomeric, or 
yielding, gasket which is forced between the peripheral edge of the watch 
lens or crystal and a groove in the bezel of the watch case to prevent 
moisture from entering the inside of the watch case. When the lens is 
circular, sealing is relatively easy to accomplish. However, sealing is 
much more difficult when the lens is rectangular or other non-circular 
shape. Variations in size due to normal manufacturing tolerances 
permissible in the lens or in the bezel become magnified in the event that 
a slightly oversized lens is assembled into a slightly undersized bezel 
opening, and vice versa. Watch designers have used a yieldable gasket to 
accomodate the variations. However, the compressive force on the gasket 
will also vary, leading to a leaking seal when an undersized lens is used 
with an oversized bezel opening. With very thin lenses of mineral glass or 
plastic, excessive pressures on the gasket to prevent leaking can lead to 
damage or breakage of the lens. 
Prior art seals have been known which use elastomeric rings of circular 
cross section, which are squeezed in grooves between the edge of the lens 
and the bezel, sometimes being arranged to provide a downward force 
component on the lens to assist in the sealing. L-shaped gaskets are also 
known in which one leg of the "L" is compressed or squeezed radially or 
laterally between the bezel and the edge of the lens. The foregoing 
arrangements, however, are highly susceptible to variations in their 
effectiveness when the parts vary in size due to manufacturing tolerances. 
Accordingly, one object of the present invention is to provide an improved 
water resistant seal which permits variations in component size due to 
manufacturing tolerances, while yet providing an effective seal. 
Another object of the invention is to provide an improved water resistant 
seal using an L-shaped elastomeric gasket.

SUMMARY OF THE INVENTION 
The invention comprises an improvement in a water resistant seal for a 
timepiece of the type including a lens with a peripheral edge having a 
first major transverse dimension, to be sealed inside a bezel with a 
peripheral wall having a second larger major transverse dimension, the 
major transverse dimensions being subject to variations due to 
manufacturing tolerances, wherein the improvement comprises a first 
peripheral flange on the lower edge of the lens protruding outwardly 
toward the peripheral wall, a second peripheral flange on the bezel wall 
protruding inward toward the edge of the lens, the peripheral flanges 
being offset in a diagonal direction from one another, and an L-shaped 
elastomeric gasket with an upstanding leg deformed by the flanges in 
opposite lateral directions with a shearing force across the gasket leg 
whereby manufacturing variations in the major transverse dimensions are 
accommodated. 
DESCRIPTION OF THE PRIOR ART 
FIGS. 1a through FIG. 1d depict typical constructions known in the art. In 
FIG. 1a, an L-shaped gasket 10 of synthetic resin, soft metal or synthetic 
rubber of radial elasticity is compressed between the peripheral edge of 
lens 11 and a peripheral wall of bezel 12. This seal is illustrated in 
U.S. Pat. No. 4,312,062 of Fujimori issued Jan. 2, 1979. 
In FIG. 1b, a lens 13 has a peripheral rectangular groove 13a, and a bezel 
14 has an opposed peripheral groove 14a. An elastomeric ring 15 of the 
circular cross section is compressed into groove 13a with an assembly 
tool, and allowed to expand into an ellipsoidal shape when the lens is 
assembled. This construction is illustrated in U.S. Pat. No. 3,505,807 of 
Piquerez issued Apr. 14, 1970. 
FIG. 1c illustrates a similar arrangement, wherein a lens 16 has a 
peripheral groove 16a in its edge and a bezel 17 has a peripheral 
frustoconical wall 17a. A deformable elastomeric ring 18 is compressed and 
flattened between wall 17a and the edge of the crystal, forcing it 
downward against a dial 19 and holding it in place. This construction is 
illustrated in U.S. Pat. No. 3,545,197 of Fischer issued Dec. 8, 1970. 
Lastly, FIG. 1d is shown in U.S. Pat. No. 3,676,997 issued July 18, 1972 to 
Fujimori. An L-shaped hard gasket, made of synthetic resin or soft metal, 
has a leg 20, which forms an acute angle with its other leg 21 in the 
unassembled state. The gasket is first stretched to the shape shown by 
inserting the peripheral edge of watch lens 22. Next, the gasket and 
crystal are deformed into position into a frustoconical groove 23a in the 
bezel 23. 
The foregoing constructions serve to seal the edge of the crystal to the 
bezel by compressive force between two opposed surfaces. Therefore, 
variations in the major transverse dimensions of the bezel wall or the 
lens edge will vary the effectiveness of the seal. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 2 of the drawing, a watch case includes a bezel 24 having 
a peripheral wall 25 and a shelf 26 upon which rests the edge of a watch 
dial 27. A transparent lens or crystal 28 has a peripheral surface 
designated as peripheral edge 29 which generally follows the contours of 
peripheral wall 25. In other words, if wall 25 is cylindrical, then 
peripheral edge 29 of the lens is also cylindrical, as would be the case 
in a circular lens. However, the invention is particularly useful for 
sealing a rectangular lens, in which case it is understood that wall 25 
and wall 29 extend around the periphery of the lens at equal distances 
from one another. 
At any location around the watch case, such as the one shown in the cross 
section of FIG. 2, the peripheral edge 29 of the lens has a first major 
transverse dimension E taken from the center of the lens, and the wall 25 
has a second major transverse larger dimension W taken from the center of 
the bezel. These major transverse dimensions are subject to variations due 
to manufacturing tolerances. For example, a major transverse lens 
dimension might be allowed to vary +0.01 mm and a major transverse bezel 
wall dimension might be allowed to vary +0.02 mm, giving a worst case 
condition of 0.06 mm between large lens and small opening, or vice-versa. 
The bezel 24 is provided with a peripheral flange 30 protruding directly 
inwardly toward wall 29. Lens 28 is provided with a peripheral flange 31 
extending directly outwardly adjacent the base surface 28a of the lens 
toward the bezel peripheral wall 25. The flanges are diagonally offset as 
shown, rather than opposing one another. Flange 31 is provided with a 
frustoconical guide surface 31a for consisting in guiding the lens into 
position during assembly. 
Disposed between the lens and bezel is an L-shaped elastomeric gasket 32 
which is deformed into the shape shown during assembly. Gasket 32 includes 
a base leg 33 disposed between the lower edge 28a of the lens and the dial 
27. However, it is understood that the leg 33 could equally well be 
disposed directly upon shelf 26 of the bezel. The thickness of base leg 33 
is such that it positions lens peripheral flange 31 opposite the wall 25 
of the bezel, and accordingly also locates the peripheral flange 30 of the 
bezel opposite the major transverse dimension of the lens, and offset 
diagonally from the peripheral flange of the lens. 
The L-shaped gasket 32 has an upstanding leg 34 which is deformed outward 
near the base leg and inward near its free end, with a shearing force 
created by the diagonally offset flanges 30, 31. It remains to note that 
gasket 32 also includes a beveled surface 32a to provide clearance at the 
juncture of the legs 33, 34, and to facilitate assembly, and a beveled 
guide surface 32b to facilitate assembly and deformation of the gasket. 
Reference to FIG. 3 of the drawing illustrates the components prior to 
assembly and the shape of the L-shaped gasket prior to deformation. The 
term "lateral" is used herein rather than "radial" and denotes a 
horizontal direction on the drawing. The lateral clearance between the 
peripheral flanges 30, 31 is shown at A. The larger lateral clearance 
between bezel wall and lens edge, (difference between the major transverse 
dimensions of the lens peripheral edge 29 and the bezel peripheral wall 
25) is shown at C. Dimension A is preferably about half as great as 
dimension C. The axial space between bezel flange 30 and the dial 27 is 
indicated by B, while the axial dimension of the flange 31 on the lens is 
shown as F. Dimension B is preferably around twice as great as dimension 
F. The uncompressed thickness of the upstanding leg 34 of gasket 32 is 
shown as T, which is preferably selected so that it is slightly less than 
dimension C, but greater than the lateral clearance A between flanges. The 
outer dimension of gasket 32 in its undeformed condition may form a 
clearance space 35 with peripheral wall 25. The guide surfaces 31a on the 
lens and 32b on the gasket are dimensioned such that they engage when the 
lens 28 is forced downward and cause to exert an outward and downward 
force on the gasket into the clearance space 35. Gasket 32 is shown in 
phantom lines to illustrate the overlap of leg 34 with the bezel flange 
30. 
By way of illustration, and without intending to be in any way limiting, 
the following table gives typical dimensions for a rectangular watch lens 
approximately 25.times.27 mm. 
A=0.30 mm 
B=0.69 mm 
C=0.51 mm 
F=0.31 mm 
T=0.48 mm 
OPERATION 
The operation of the invention will be apparent by reference to FIGS. 2, 3 
and 4. Starting with the components as shown in FIG. 3, the gasket 32 is 
positioned, which due to the interference with flange 30 will commence to 
deform the upper end of leg 34 inward and the middle of leg 34 outward 
into clearance 35. As the lens 28 is pressed into position, the surfaces 
31a, 32b engage and further distort gasket 32 into space 35. This action 
continues as flanges 30, 31 pass one another and as they clear one 
another, the upper end of leg 34 expands radially inward with a definite 
snap action engagement. This retains the lens in position and results in 
the configuration of upper leg 34 illustrated in FIG. 2. The lens flange 
31 is positioned by the base leg 33 so as to be approximately centered on 
dimension B and a tight seal is maintained between flange 31 and wall 25, 
between flange 30 and wall 29, and between the diagonally offset sharp 
corners of the flanges by the opposed lateral shearing force exerted by 
the flanges. 
FIG. 4 of the drawing illustrates a "worst case" condition where an 
undersized lens with major transverse dimensiion E' is assembled with an 
oversized bezel opening having major transverse dimension W'. The 
reference numerals correspond to those of FIG. 2. As can be seen, a 
clearance space 36 can exist between the gasket leg 34 and lens edge 29, 
and a clearance space 37 can exist between gasket leg 34 and bezel wall 25 
on the other side. Yet, because of the diagonally offset peripheral 
flanges 30, 31 exerting an opposing shearing force on the gasket leg, the 
water resistance seal maintains its integrity. 
Due to the diagonally offset flanges 30, 31 the assembly is much more 
tolerant of variations in major transverse dimensions of the lens and the 
bezel. Clearances can exist at several places as shown in FIG. 4. An 
improved seal results without the necessity of trying to compress the full 
thickness of the gasket between the parts as in the prior art. 
While there has been described what is considered to be the preferred 
embodiment of the invention, other modifications will occur to those 
skilled in the art, and it is desired to cure in the appended claims all 
such modifications as fall within the true spirit and scope of the 
invention.