Device for detecting edge of transparent sheet of laminated transparent and translucent sheet assembly

A device for detecting an edge of a transparent sheet of a laminated transparent and translucent sheet assembly, is provided which includes a light source for producing a shadow of the edge of the transparent sheet on a translucent sheet, a photosensor operative to produce an electrical output which varies depending upon variation of intensity of light supplied thereto, and a lens for producing a clear image of the shadow on the photosensor. A picture processing unit determines the position of the edge of the transparent sheet on the basis of a variation of the output of the photosensor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for detecting an edge of a 
transparent sheet of a laminated transparent and translucent sheet 
assembly as an assembly of two transparent glass sheets between which a 
translucent interlayer is sandwiched. The present invention further 
relates to laminated safety glass for an automobile windshield, etc. and 
to an apparatus for cutting off, in production of laminated safety glass, 
a protruding end portion of an interlayer sandwiched between two glass 
sheets. 
2. Description of the Prior Art 
Generally, an automobile windshield is formed from laminated safety glass 
which consists of two glass sheets and an interlayer of polyvinyl butyral 
or the like sandwiched between the glass sheets and bonded to same. 
In production of laminated safety glass, the interlayer is first sized a 
little larger than the glass sheets and then cut to size after sandwiched 
between the glass sheets by cutting off its end portion protruding from 
the glass sheets. After that, the glass sheet and interlayer assembly is 
processed by tacking rolls for initial adhesion and then by an autoclave 
for permanent fastening. 
In order to cut off the protruding end portion of the interlayer, it has 
been practiced to first locate the glass sheet and interlayer assembly in 
place, i.e., in a predetermined base position by means of locating tools 
adapted for abutment upon the corresponding edges of one of the glass 
sheets which are nearly rectangular and then cut off the protruding end 
portion of the interlayer by means of a cutter adapted to move along a 
predetermined path which is fixedly set on the basis of the base position 
of the assembly. 
With the prior art cutting apparatus, cutting of the protruding end portion 
of the interlayer is carried out without detecting the edges of the glass 
sheets and thereby knowing whether the glass sheet and interlayer assembly 
is located in place. 
A problem of the prior apparatus is that the protruding end portion of the 
interlayer may possibly be turned up and sandwiched between some locating 
tool or tools and the corresponding edge or edges of the glass sheet, 
causing the assembly to be largely moved out of place, i.e., out of the 
base position and therefore variations in cutting off of the interlayer 
and, in some cases, causing damage of the cutter and the edges of the 
glass sheets. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a device for 
detecting an edge of a transparent sheet of a laminated transparent and 
translucent sheet assembly, which comprises a light source disposed on one 
side of the laminated sheet assembly for throwing light toward an edge 
portion of the laminated sheet assembly and thereby producing a shadow of 
an edge of the transparent sheet on a translucent sheet of the laminated 
sheet assembly, a photosensor disposed on the other side of the laminated 
sheet assembly for detecting intensity of light transmitted through the 
edge portion of the laminated sheet assembly and producing an electrical 
output which varies depending upon a variation of intensity of light 
supplied thereto, lens means for forming a clear image of the shadow on 
the photosensor, and picture processing means for determining the location 
of the edge of the transparent sheet on the basis of a change of the 
electrical output of the photosensor. 
In accordance with the present invention, there is also provided an 
apparatus for cutting off a protruding edge of an interlayer sandwiched 
between two glass sheets, which comprises means for optically detecting 
edges of the glass sheets and producing signals representative thereof, 
means for computing an amount of movement of the glass sheets out of a 
predetermined base position thereof in response to signals from said 
detecting means and producing a signal representative thereof, and means 
for cutting off the protruding end portion of the interlayer through 
adjustment in position in response to the signal from the computing means. 
The above device makes it possible to detect an edge of a transparent sheet 
of a laminated sheet assembly of the described kind accurately and 
assuredly. Further, the above apparatus is effective for overcoming the 
above noted problems inherent in the prior art. 
It is accordingly an object of the present invention to provide a device 
for detecting an edge of a transparent sheet of a laminated transparent 
and translucent sheet assembly, which is accurate and reliable in 
operation. 
It is another object of the present invention to provide a device of the 
above described character which is useful for detecting relative movement 
of laminated transparent sheets and thereby knowing whether the laminated 
sheet assembly is defective. 
It is a further object of the present invention to provide an apparatus for 
cutting off a protruding edge of an interlayer sandwiched between two 
glass sheets, which is accurate and reliable in operation. 
It is a further object of the present invention to provide an apparatus of 
the above described character which can prevent damages of a cutting tool 
and of edges of glass sheets assuredly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, a laminated sheet assembly 10 consists of nearly 
rectangular transparent sheets 12, 14 as glass sheets for a laminated 
safety glass, etc. and a translucent interlayer 16 as an interlayer of 
polyvinyl butyral or the like prior to being processed by an autoclave, 
which is sandwiched between the transparent sheets 12, 14 and bonded to 
same. 
A device for detecting an edge of the laminated sheet assembly 10 is 
generally indicated by the reference numeral 18 and includes a light 
source 20 as a tungsten halogen lamp, a convex lens 22 and a photosensor 
24 which are joined to constitute an integral unit as an ITV camera, and a 
picture processing unit 26. Though not shown, a hood formed with a 
circular hole of 10 mm in diameter is attached to the ITV camera so as to 
shut off light disturbance. The light source 20 is disposed at a distance 
of 1.0 to 2.0 m from the laminated sheet assembly 10, and the ITV camera 
is at a distance of about 10 cm. An air source may additionally be 
provided to blow air toward the protruding end portion of the interlayer 
16 when the protruding end portion is so large as to bend downwardly and 
disable edge detection by the device 18. 
In operation, the light source 20 throws light toward an edge and its 
adjacent part of the laminated sheet assembly 10 so that a shade Sl is 
produced in a beveled or chamferred edge portion, i.e., a so-called 
seaming portion of the transparent sheet 12, which is one of the 
transparent sheets nearer to the light source 20, and is cast as a dark 
image S2 on the translucent sheet 16. On the other hand, since the 
translucent sheet 16 transmits light though to a certain reduced extent, a 
shade or dark image S' is produced in a seaming portion of the transparent 
sheet 14, which is one of the transparent sheets remoter from the light 
source 20. The images S2 and S' are clearly formed on the photosensor 24 
through adjustment of the position of the convex lens 22, i.e., through 
adjustment of the focus of the ITV camera. Since the photosensor 24 
increases its output current with increase of intensity of light supplied 
thereto, the portions where the output current of the photosensor 24 are 
reduced extremely are regarded as representing the edges of the 
transparent sheets 12, 14. That is, by turning on the light source 20 and 
focusing the ITV camera on the translucent interlayer 16, the edges of the 
transparent sheets 12, 14 are represented by the two extremely small 
output portions M, M' of the photosensor 24. By processing the output of 
the o photosensor 24 by the picture processing unit 26, the edges of the 
transparent sheets 12, 14, i.e., an edge of the laminated sheet assembly 
10 can be detected. 
In the above, it will be noted that with the edge detecting device 18 not 
only the edge of the transparent sheet 12 nearer to the light source 20 
but the edge of the transparent sheet 14 remoter from the light source 20 
can be detected. Accordingly, with the edge detecting device 18 relative 
movement between the transparent sheets 12, 14 can be detected to know 
whether the relative movement is within an allowable range. 
It is further to be noted that while it is desirable for the transparent 
sheet to be provided with a so-called seaming edge (i.e., a beveled or 
chamferred edge), the similar detection of the edge of the transparent 
sheet can be attained by making the light from the light source 20 be 
incident on the edge of the transparent sheet at a predetermined angle so 
that the shadow of the edge which is perpendicular to the opposed surfaces 
of the transparent sheet, is cast on the interlayer 16 even if the 
transparent sheet is not provided with a seaming edge. 
Referring to FIGS. 2 and 3, a glass sheet and interlayer assembly is 
generally indicated by the reference numeral 30 and consists of nearly 
rectangular transparent glass sheets 32, 34 and an interlayer 36 of 
polyvinyl butyral or the like, sandwiched between the glass sheets 32, 34 
and bonded to same. The assembly is in the state prior to being processed 
by tacking rolls for initial adhesion. The interlayer 36 is so sized as to 
protrude 50 to 100 mm from the respective edges of the glass sheets 32, 
34. 
The protruding end portion of the interlayer 36 is cut off in the following 
manner by means of an apparatus 38 of this invention. 
The glass sheet and interlayer assembly 30 is conveyed by a belt conveyor 
40 to vertically movable free rolls 42 where it is elevated by the free 
rolls 42 and freely movably supported on same above the conveyor 40. Under 
this condition, a plurality of locating tools 44, though only one is 
shown, are brought into contact with the corresponding edges of the glass 
sheet and interlayer assembly 30 for thereby roughly locating the assembly 
30 in place, i.e., locating the assembly 30 adjacent a predetermined base 
position. A suction cup unit 46 having a plurality of suction cups 46a is 
moved upwardly so as to support the assembly 30 in the located position, 
while on the other hand the 
locating tools 44 and the free rolls 42 are returned to their rest 
positions. 
Under the condition where the glass sheet and interlayer assembly 30 is 
stationarily supported by the suction cup unit 46, detection of the edges 
of the laminated glass sheets 32, 34 and computation of the amount of 
movement of the assembly 30 out of the base position are performed in the 
following manner. 
The detection of the edges of the glass sheets 32, 34 is performed by an 
edge detecting device 48 including three sets of light sources 50A, 50B, 
50C and ITV cameras 52A, 52B, 52C, and a picture processing unit 54. 
While the interlayer 36 at this production process is translucent, the 
shadows of seaming portions of the glass sheet 32 are cast on the surface 
of the interlayer 36. By focusing the ITV cameras 52A, 52B, 52C on the 
shadows, the edges of the glass sheet 32 can o be detected. 
In this connection, a plane cartesian coordinate system shown in FIG. 3 is 
used for computing the amount of movement of the assembly 30 out of place, 
i.e., of a predetermined base position. 
In the plane coordinate system in FIG. 3, the laminated glass sheets 32, 34 
of the assembly 30 accurately located in place, i.e., located in a 
predetermined base position is depicted by the solid line. The ITV cameras 
52A, 52B, 52C have windows elongated in parallel to the y-axis, y-axis and 
x-axis, respectively and are disposed so that their base positions are 
P.sub.A (x.sub.A, y.sub.A). P.sub.B (x.sub.B, y.sub.B), P.sub.c (x.sub.c, 
y.sub.c), respectively. The base positions P.sub.A, P.sub.B, P.sub.c of 
the ITV cameras 52A, 52B, 52C are stored in a memory 56 together with the 
angles .psi..sub.A, .psi..sub.B, .psi..sub.c. The angles .psi..sub.A, 
.psi..sub.B, .psi..sub.c respectively indicate inclinations of the 
peripheral portions adjacent to the points P.sub.A, P.sub.B, P.sub.C with 
respect to the x-axis, x-axis, y-axis when the peripheral portions 
adjacent to the points P4, P8, Pc are approximated to straight lines. 
In this instance, assuming that the movement of the assembly 30 from the 
solid line position to the dotted line position causes the points P.sub.A, 
P.sub.B, P.sub.c to be moved into R.sub.A, R.sub.B, R.sub.c, respectively, 
the edges of the thus moved assembly 30 are detected by the ITV cameras 
52A, 52B, 52C. On the basis of this detection, the coordinates of the 
points P.sub.A (x.sub.A, y.sub.A). P.sub.B (x.sub.B, y.sub.B). P.sub.C 
(x.sub.c, y.sub.c) are translated into the coordinates of Q.sub.A 
(X.sub.A, y'.sub.A), Q.sub.B (X.sub.B, y'.sub.BB) Q.sub.c (X'.sub.c, 
y.sub.c) by means of the picture processing unit 54, respectively and the 
apparent movements .DELTA.Y.sub.A, .DELTA.Y.sub.B, .DELTA.X.sub.c at the 
ITV cameras 52A, 52B, 52C are computed from y'.sub.A -Y.sub.A, y'.sub.B 
-Y.sub.B, x'.sub.C -x.sub.c by means of an arithmetic processing unit 58, 
respectively. 
On the other hand, true movement of the glass sheet and interlayer assembly 
30 represented by movement of the points from P.sub.A, P.sub.B, P.sub.C to 
R.sub.A, R.sub.B, R.sub.C. is expressed by the angle of rotation 
.DELTA..theta. and parallel movements .DELTA.x, .DELTA.y. That is, in 
response to the movement of the assembly 30, the point P.sub.A is moved 
into the point P'.sub.a through turning of an angle .DELTA..theta. about 
the origin 0 and with a distance 0-PA for a radius. The o coordinates of 
the point P'.sub.A can be approximated to x.sub.A -Y.sub.A 
.multidot..DELTA..theta., Y.sub.A +x.sub.A .multidot..DELTA..theta.) since 
the true movement is actually quite small, and the coordinates of the 
point R.sub.A is expressed by (x.sub.A +.DELTA.x-y.sub.A 
.multidot..DELTA..theta., y.sub.A +.DELTA.y+x.sub.A 
.multidot..DELTA..theta.), by the arithmetic processing unit 58. 
In this instance, since .DELTA..theta., .DELTA.x, .DELTA.y are actually 
quite small, a peripheral portion of the assembly 30 adjacent to the point 
R.sub.a can be approximated to a straight line, and the inclination of the 
straight line Q.sub.A -R.sub.A can be approximated to tan .psi..sub.A, the 
following relational expression is obtained. 
EQU tan.psi..sub.A ={(Y.sub.A +.DELTA.y.sub.a)-(y.sub.a +.DELTA.y+x.sub.A 
.multidot..DELTA..theta.)}{x.sub.A 
-(x.sub.A +.DELTA.x-Y.sub.A .multidot..DELTA..theta.)}, that is, 
EQU .DELTA.Y.sub.A =-tan.psi..sub.A .multidot..DELTA.x+.DELTA.y+(x.sub.A 
+y.sub.A tan.psi.A).multidot..DELTA..theta. (1) 
Then, from the movement of the point P.sub.B to the point R8. The following 
relational expression is obtained. 
EQU .DELTA.y.sub.B =-tan.psi..sub.B .multidot..DELTA.x+.DELTA.y+(x.sub.B 
+y.sub.B tan.psi.B).multidot..DELTA..theta. (2) 
From the movement of the point P to the point R , the following relational 
expression is obtained. 
##EQU1## 
From the relational expressions (1), (2), (3), the true movements .DELTA.x 
.DELTA.y, .DELTA..theta. are obtained by the operation of the arithmetic 
processing unit 11. 
A cutter unit 60 consists of a cutter 60a and a carrier 60b as a robot, and 
is movable so as to offset movement of the assembly 30 out of the base 
position in response to signals representative of the movement .DELTA.x, 
.DELTA.y, .DELTA..theta. and supplied to the carrier 60b from the 
arithmetic processing unit 58 and thereby be capable of accurately cutting 
the protruded end portion of the interlayer 30 to a predetermined size, 
i.e., to such a size that the amount of protrusion on the short edge side 
of the assembly 1 is within the range from 0.5 to 1.0 mm and on the long 
edge side within the range from 1 to 10 mm. 
Thereafter, the glass sheet and interlayer assembly 30 is processed by 
tacking rolls for initial adhesion and by an autoclave for permanent 
fastening, whereby to be formed into a laminated safety glass.