Sealed meter assembly such as for a speedometer, tachometer, odometer or the like

A sealed display device comprises a case for encasing a meter such as a speedometer, tachometer, odometer and the like, viewable through a display window or opening formed in the case, with a transparent cover sealed over the opening. The case has an annular lip surrounding the opening and adapted to receive a peripheral edge of the transparent cover. A layer of sealant is placed between the lip and the cover to seal the cover to the case. A plurality of spaced support members support the cover in spaced relationship to the lip so that a sufficiently thick layer of sealant may be placed between the cover and the lip to prevent breakage of the seal due to differences in thermal expansion and contraction between the case and cover. Angled areas may be milled from the case in surrounding relationship to the lip to define areas for accommodating a thicker layer of sealant than could otherwise be accommodated.

FIELD OF THE INVENTION 
This invention relates to sealed display devices such as used on 
automobiles, motorcycles, and the like. 
BACKGROUND OF THE INVENTION 
Motorcycles, for example, are equipped with sealed meters or display 
devices such as tachometers, speedometers, odometers and trip odometers. 
These meters are sealed by a transparent member such as transparent glass 
or resin serving to keep water and dirt from getting inside the unit. FIG. 
7 shows a seal configuration of this type of display window. Transparent 
member 103 is set via sealant material 104 into the lip 102 which is 
formed in the display window unit 101 of the case 100. 
In the above-described unit, the transparent member 103 is tightly sealed 
in the display window 101 around the lip 102 of the display window 101 by 
means of sealant 104. However, because the assembly of these units 
requires that the edge of the transparent member 103 be positioned on the 
top surface of the lip 102 and that it be coated with sealant, it is 
impossible to use a sufficiently thick layer of sealant 104 and at the 
same time accurately position the transparent member 103 with respect to 
the lip. 
Accordingly, when the sealed display device is exposed to heat, the 
differences in the thermal expansion coefficients between the case 100 and 
the transparent member 103 can cause the seal of the sealant 104 to be 
broken between the upper surface of the lip 102 and the transparent member 
103. 
It would be possible to resolve this problem of seal breakage by increasing 
the thickness of the sealant, but since this would involve broadening the 
gap between the transparent member and the lip, this would make 
positioning during assembly all the more difficult and detract from 
assembly productivity. 
There is thus need for a means for covering the opening of an instrument 
such as a speedometer, tachometer and the like with a transparent member 
so that the transparent member is sealed to the housing of the instrument 
with a sufficiently thick layer of sealant to maintain a seal over a 
prolonged period of time, and which also facilitates production of the 
sealed unit. 
DISCLOSURE OF THE INVENTION 
The present invention was developed after consideration of the foregoing 
problem, and its primary object is to provide a sealed display device 
which prevents breakage of the seal while at the same time permitting good 
productivity. 
In order to resolve the foregoing problems, the present invention provides 
a sealed display device in which a transparent cover is sealed in place 
over a display window or opening to cover the display area of an encased 
meter, in which a lip surrounds the opening to receive a marginal edge of 
the transparent cover, and spaced support members on the lip engage the 
transparent cover to space it from the lip when the cover is set into 
place via sealant between the cover and the lip. 
The use of support members between the top surface of the lip of the 
display window case and the transparent member allows the transparent 
member to "float" above the lip. This arrangement assures sufficient 
thickness of the sealant which seals between the upper surface of the lip 
and the transparent member. Seal reliability is improved because even if 
the device is subjected to heat, the differences in the coefficients of 
thermal expansion between the case and the transparent member do not cause 
the seal to separate. Also, when applying the sealant, the position of the 
transparent member with respect to the lip is indexed by the support 
members for the transparent member.

BEST MODE OF CARRYING OUT THE INVENTION 
Referring more particularly to the drawings, one embodiment of the 
invention is depicted generally at 1 in FIGS. 1-5. The sealed display 
device 1 comprises a case 2 made from a material such as synthetic resin, 
and having a rectangular display window area 3. An instrument, not shown, 
such as a tachometer, speedometer, odometer or tip odometer would be 
displayed through the window 3. 
A lip 4 is molded in the display window area, along with support or 
indexing pillars 5, two on each of the sides of the rectangular window 
area. The indexing pillars are preferably formed integrally with the case 
during the molding process. In addition, there is an upper sloped or 
angled area 4a above the lip 4, and a lower angled area 4b below the lip, 
which were formed by milling around the perimeter of the display window 
area between the face of the case and an outer vertical wall section 4c, 
and between an inner diameter of the lip and an inner vertical wall 
section 4d. 
A transparent member or cover 6 made of transparent glass or synthetic 
resin, for example, is received in the lip 4 of the display window area 3. 
During assembly, the transparent member 6 is set atop supports 5, which 
indexes the position of the transparent member 6 with respect to the lip. 
Sealing material 7 between the transparent member and the lip seal the 
display window area 3. Silicone type resins may be used as the sealant 
material, and the resin may be applied so that it extends from the lower 
milled area 4b to the upper milled area 4a. 
When the transparent member 6 is assembled to the lip 4 of the display 
window area 2 in the manner described above, the support pillars 5 index 
the position of the transparent member with respect to the lip so that the 
transparent member 6 is "floated" or spaced above the lip 4. This 
maintains a sufficiently wide gap between the transparent member and the 
lip to assure a sufficiently thick seal 7. Even if the case is subjected 
to heat, the seal 7 will not break due to differences between the the 
thermal expansion coefficients of the case 2 and the transparent member 6 
because of the improved seal thus obtained. 
In addition, by establishing the angled milled areas 4a and 4b above and 
below the lip, respectively, increased seal thickness can be maintained 
between the transparent member 6 and the case 2. 
Further, since the indexing of the transparent member 6 with respect to the 
lip 4 is accomplished by means of setting the former atop the supports 5, 
the operational efficiency of the assembly operation is considerably 
improved. Even if some sealant 7 gets between the top of the support 
pillars 5 and the transparent member 6, there will be little effect and 
this will cause but small loss to the operational efficiency when compared 
to the case of not using the supports. 
FIG. 6 shows another embodiment of a sealed display device in a 
cross-sectional view in the same position as used in FIG. 2. In this 
embodiment, there is a lower angled area 4c which has been milled away, 
but there is no upper angled area corresponding to area 4a in the previous 
embodiment. This embodiment prevents over-exposure of the sealant on the 
exposed surface. 
The support pillars 5 are shown in the drawings as integrally formed with 
the case, but instead they could be formed integrally with the transparent 
cover, or separate from either of these structures. Also, there is no need 
from them to be pillar shaped, and they may have any desired shape so long 
as they allow the transparent member to "float" above the lip and provide 
space for a substantial thickness of sealant between the case and the 
cover. 
The invention therefore provides means to support a transparent instrument 
cover above a lip on the instrument case so that a sufficiently thick seal 
can be placed between the lip and the cover to prevent the seal from 
breaking due to differences in thermal coefficients between the case and 
the cover. 
Moreover, since the position of the transparent member is indexed by 
resting atop the support pillars in spaced relation to the lip when the 
sealant coating is applied, productivity is increased due to the ease in 
accurately positioning the cover on the case. 
While the invention has been shown and described in detail, it is to be 
understood that this invention is not to be considered as being limited to 
the exact form disclosed, and that changes in detail and construction may 
be made therein within the scope of the invention, without departing from 
the the spirit thereof.