Apparatus and method for determining the thickness of insulated glass

A light source projects a light beam through an insulating multiple glass sheet insulating unit. The size of the beam spot on a target indicates unit thickness.

BACKGROUND OF THE INVENTION 
This invention is directed to the measurement of thicknesses of insulating 
glass units. 
Thicknesses of installed glass units are the most perplexing problem to 
glass replacements specialists and estimators. 
When estimating replacement of insulated glass units having broken or 
damaged glass or seals, cost may vary widely according to the thicknesses 
of the glass units. Fixed estimates may result in reduction or loss of 
profits, or in actual negative profits. Overestimations may result in loss 
of contract awards and reduction of jobs. 
When a job is awarded based on an estimate, the estimators measurements of 
thickness and areas may be accepted, or a skilled glass installer may 
remeasure the job for precise requirements when ordering materials. While 
the square areas may be measured with precision, it is often difficult to 
measure glass thicknesses with the same precision. If the thickness is 
miscalculated, losses may be incurred when ordering nonreturnable special 
sizes, or when ordering wrong standard sizes. Delays are encountered and 
installation expenses are increased when insulating units of the wrong 
thickness are assembled and delivered to job sites. 
Calipers have been available to measure glass thickness, but the calipers 
are limited in lateral expanse. Many buildings with insulated glass do not 
have windows that open to permit insertion and engagement of the calipers, 
and thus the calipers are useless. Many doors are separated from windows 
by greater dimensions than the length of the calipers, again rendering the 
calipers useless. 
Devices with mirrors on opposite sides of the window and viewing scopes for 
looking through the window toward a mirror at predetermined angles and 
lining up marks on the angular devices have been offered with mixed 
reception. Difficulties of seeing images in the devices and understanding 
the use of the devices sufficiently to avoid mistakes in their use have 
prevented widespread acceptance or use of such devices. 
A need persists for a simple device with simple indications that can be 
easily and assuredly read for measuring thicknesses of insulating glass 
units. 
SUMMARY OF THE INVENTION 
The present invention is directed to providing a simple, easily readable 
device. The present invention uses a standardized light source on a first 
outer glass surface, and a standardized target on a second opposite outer 
glass surface. 
Readings are taken directly from the light source or directly from the 
target, which indicate the thickness of the insulating glass unit between 
the first and second outer glass surfaces. 
One of the problems in measuring unit thickness of the insulating glass 
units is that individual sheets of glass within the units have varied 
thicknesses. Usually both sheets are of equal thickness, but the sheets 
may be of single strength, double strength, 3/16" or 1/4" glass sheet 
thicknesses. The exact thicknesses of the glass sheets may be determined 
using a thickness card held at a 45.degree. angle against the glass sheet. 
The thickness of the glass sheet is not indicative of the distance between 
the glass sheets. Distance between the sheets is independent of the 
thicknesses of the individual sheets. 
One of the problems encountered in the measurement of total unit thickness 
is the different refraction in units having glass of different thickness. 
The present invention solves the problem of varied refraction, and uses 
the varied refraction in the total unit thickness measurement. 
A light source projects a light beam through an insulating multiple glass 
sheet insulating unit. The size of the beam spot on a target indicates 
unit thickness. 
The glass thickness measurement apparatus is a target having plural 
parallel lines for mounting on an outer glass surface of an insulated 
glass unit. A standard light source having a hood is positioned on a 
second outer surface of the insulated glass unit opposite the target. A 
scale is provided either on the hood or target, wherein variations in the 
thickness between the first and second outer glass surfaces of the 
insulated unit are noted by comparing the dispersion and refraction of 
light from the light source through the glass and onto the target. 
In one embodiment, the target includes at least one base line and plural 
boxes for bracketing a light spot projected from the light source through 
the glass to the target. Alternatively, the target can incorporate plural 
parallel base lines, each being associated with a particular thickness of 
glass sheets within the insulated unit. In cooperation with the plural 
base lines, the target has a plurality of parallel rectangular boxes, each 
associated with a particular thickness between outer surfaces of the glass 
in the insulated unit. The base lines can be straight lines, which are 
placed relatively far from the rectangles, wherein the base lines for 
thicker glass are placed closer to the rectangles associated with the 
respective unit thicknesses. 
The light source and shroud project a circular light spot through the glass 
to the target, wherein a light spot is projected from the light source 
through the glass to the target. A first edge of the spot rests on a base 
line of the target and a second edge rests within an area circumscribed by 
target lines indicative of unit thickness between the first and second 
opposite surfaces of the glass unit. 
Also disclosed is a method for measuring thickness between first and second 
outer surface of an insulated glass unit, wherein a light source having a 
shroud is positioned against a first outer glass surface of the light unit 
for projecting a light beam through glass sheets in the unit. The 
projected light falls upon a target positioned on the second outer glass 
surface of the unit, thus producing a spot on the target. The target has a 
plurality of graduated marks for indicating a size of the light spot, 
thereby indicating a thickness of the glass unit between the first and 
second surfaces. 
In an alternate embodiment, the shroud can include an adjustment for 
positioning the light source at variable positions from the first glass 
surface. 
The adjustment means incorporates marks related to a distance of the light 
source from the first glass surface for use with a measurement of the 
thickness between the first and second surfaces. The adjustable shroud 
varies the light beam passing from the shroud through the first and second 
glass surfaces and through the insulated unit, thus varying a size of the 
spot on the target. The shroud is adjustable perpendicularly with respect 
to the first glass surface. 
Specifically, the shroud can incorporate a fixed ring portion and a movable 
ring portion, wherein plural marks on at least one of the ring portions 
allow alignment as an indication of the adjustment of the ring portions to 
thereby measure distance of the light source from the first glass surface 
and further, the glass thickness. 
These and further and other objects and features of the invention are 
apparent in the disclosure, which includes the above and ongoing written 
specification, with the claims and the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring to FIG. 1, an insulating glass unit is often made with parallel 
sheets of glass with an intermediate dry air or gas filled space. The 
edges of the precut sheet are sealed and held together with polysulfide or 
silicone or hot butyl bonding material, and an aluminum spacer holds the 
glass sheets apart uniformly around the edges of the sheets. 
In FIG. 1, the insulating glass unit is generally indicated by the numeral 
1. Glass sheets 3 and 5 are uniformly spaced on opposite sides of an air 
space 7. An aluminum channel spacer 9 holds the sheets a precise distance 
apart and a peripheral seal 11 is formed of vinyl. The insulating glass 
unit has outer glass surfaces 13 and 15. The purpose of the present 
invention is to measure the difficult to determine distance 17 between the 
flat glass outer surfaces 13 and 15. Further the present invention makes 
it possible to measure the distance 18 between inner surface 13 and 15 
this distance is prescribed aluminum spacer 9 in FIG. 1. The system uses a 
target 21, which is adhered to one of the outer surfaces 13 with a bonding 
material 23 such as glue. The target preferably is a white thin plastic 
layer which is printed with offset printing indicia on a face 25 thereof, 
which is bonded to the glass surface. Alternatively, the target may be 
printed on a good quality paper which would adhere to the glass. Targets 
may be mounted on thin plexiglass. 
The particular bonding material 23 may be any suitable bonding material 
which will hold the target on the glass surface 13 for a time sufficiently 
long to make an accurate thickness reading. The bonding material 23 may be 
a permanent bonding material in the case where the particular measured 
window is intended to be removed from the structure and replaced by 
another window. 
In tall buildings the target may be applied with a long handled applicator 
27, which may reach to the second or third floor windows from outside of 
the building. The target may be held on the applicator by suction and 
removed from the applicator by moving the applicator laterally across the 
target, or by releasing the suction. Preferably the target is smooth on 
the window. 
In conventional high rise office buildings insulating glass units are 
constructed with uniform thickness throughout so that measuring the 
thickness of the glass on the ground floor or on the second floor is a 
valid indicator of the thickness of glass in other parts of the building. 
The target 21 may be placed on an interior outer glass surface such as 15, 
and the control light source 31 may be focused on the target from an 
exterior side of the unit. It is usual to place the target on the exterior 
and the light source 31 on the interior. The opposite may be true. The 
light source has a conventional flashlight body 33 with plural 11/2 volt 
cells 35, which illuminate a screwed-in lamp 37, to shine light through a 
focusing lens 39. Preferably lens 39 is selected so that the edges of the 
beam from the light source 31 are sharp at a distance from the light bulb 
37 equal to the distance between the lens 39 and the outer glass surface 
15 plus the general thickness range between outer glass surfaces 13 and 15 
in insulating glass units 1 to be measured. Light source 31 has a control 
shroud 41 with a generally straight walled usually cylindrical outer 
surface 43 and a slightly tapered inner surface 45 leading to a circular 
edge 47. 
Referring to FIG. 2, a preferred target is generally indicated by the 
numeral 21. The face of the target has a number of markings. 
To first determine the thickness of each glass sheet, edge 51 is held 
against a glass surface with the target at about a 45.degree. angle. An 
image is reflected by the glass showing the base line 53 and the thickness 
lines 55, 57, 59, 61 and 63. One of the latter lines 55-63 will be 
superimposed on the line 53 in the image. The particular line 55-63 that 
is superimposed on the base line 53 indicates the thickness of glass, 55 
single strength, 57 double strength, 59 5/32", 61 3/16" and 631/4" 
thickness. The reverse printed numbers are readable in the reflection. The 
target 21 is then adhered to the outer surface of the insulating glass 
unit. The flashlight 31 is held against the inner surface of the 
insulating glass unit 1, as shown in FIG. 1, and the circular spot of the 
flashlight which shines through the glass unit and falls on the target is 
moved by moving the flashlight so that the edge of the circular spot 
formed by the beam rests against one of the lines in the group of lines 65 
which corresponds to the measured single sheet thickness. Care is taken so 
that the lower edge of the circular spot rests upon or just contacts the 
selected line in the group of lines 65, but is not buried in that line. 
The diametrically opposite edge of the circular beam will fall on one of 
the group of lines generally indicated by the numeral 67. The edge of the 
spot falling on a particular line indicates the overall thickness of the 
glass insulating unit. For example, if the edge of the circular spot falls 
on the line labelled 3/4 or contacts the upper or lower surface of that 
line, the overall thickness between the outer surfaces 13 and 15 of the 
insulating glass unit 1 is 3/4". 
In an example, the target 21 is held at a 45.degree. angle with edge 51 
resting against a glass. The reflected image from the glass produces 
double images of each of the lines 53-63. It is found that one of the 
images of the line 57 overlies one of the images of the line 53. That 
alignment indicates that the glass is a double strength glass. Target 21 
is fixed to an outer surface 13 of the insulating glass unit 1, and the 
flashlight is pressed against the glass so that edge 47 rests upon the 
surface 15 of the glass. The flashlight is moved so that the beam touches 
line DS in the group of lines 65. The upper edge of the circular spot 
falls on a line opposite the 5/8 mark. That indicates that the total 
overall thickness between outer surfaces of the glass insulating unit is 
5/8". An estimator circles the reverse DD by line 57 and the DD at the 
right end of the group of lines 65, and circles the 5/8 in the group of 
lines 67 on a copy of the target 21, which is attached to the estimator's 
report. 
An alternate target 21B is shown in FIG. 2B, which shows a spot 70 of a 
flashlight beam having a lower edge aligned on the "SS line" corresponding 
to the predetermined glass thickness in group 65 of lines. An upper edge 
of the circular spot 70 falls on the line in the group of lines 67 
opposite the 3/8 notation, indicating that the thickness of the spacer is 
3/8". 
Gauge 21C is used with the adjustable light source shown in FIGS. 3 and 4. 
The group of lines 65 has been replaced by a single line 65C. 
The spaced parallel lines may be replaced by boxes, circles or other 
geometric shapes. 
A gauge embodiment shown in FIG. 3 uses a standard target 21C, which has 
spaced parallel lines. An insulated glass unit 1 has an outer surface 13 
on one side, and an outer surface 15 on another side. A light source 75 
has a bulb 77 and a lens 79. An outer end of the body 71 has external 
threads 73, and an inner surface of an adjustable sleeve 81 is threaded 
with complementary threads. Turning the adjustable sleeve 81 moves lens 79 
and light source 77 closer to or further away from edge 85 and surface 15. 
The sleeve 81 is turned until the lines 87 relating to the premeasured 
glass thickness using the edge 51 of target 21 aligns with the index line 
89 on body 71. The beam is shined through the unit 1 and the source is 
slid along face 15 until an edge of the light spot rests on line 65C. As 
shown in FIG. 4, marks 87 on the sleeve or collar 81 indicating the 
thickness of the glass are aligned with index 89 on the body 71 of the 
light source before shining the light beam on target 21C, as shown in FIG. 
2C. The overall thickness is read from the group of lines 67. 
In an alternate form of the invention, horizontal marks on body 71 align 
with an edge 83 of the sleeve 81 to provide an alternate form of a 
direct-reading thickness indication. 
As shown in FIG. 5, a target card 21 may be mounted on a glass surface 13 
using a spring clamp 91 with a leaf spring 93 held between two suction 
cups 95. 
Spring clamp 91 may be used with a rigid card stock target or may be used 
with a flexible film target when a backing plate is attached to the clamp 
spring 93. 
While the invention has been described with reference to specific 
embodiments, modifications and variations of the invention may be 
constructed without departing from the scope of the invention, which is 
defined in the following claims.