Windshield repair device

A device for repairing windshield cracks. A cylinder includes a sealing mouth adapted to contain a quantity of filler material. The mouth with filler material therein is positioned over the crack opening. The cylinder includes a small cavity adjacent the mouth and a larger upper cavity. A plunger fitted to the cylinder carries a lower seal for the small cavity and an upper seal for the larger cavity. Moving the plunger from an initial fully depressed to a fully retracted position opens the small cavity to the upper cavity whereby the vacuum of the upper cavity enhances the evacuation of air from the crack. Subsequent depression of the plunger is assisted by a one-way exhaust valve. Such depression of the plunger produces injection of the filler material into the crack replacing the evacuated air.

FIELD OF INVENTION 
This invention relates to a device used to repair windshield cracks by 
injecting a liquid bonding material into the crack. 
BACKGROUND OF THE INVENTION 
Perhaps the most common of all damages to a vehicle is windshield damage. 
Stones and rocks from the roadway are kicked up by vehicle tires and 
strike the windshield, causing the glass to fracture. Windshields 
typically include an inner glass layer or plate and an outer glass layer 
or plate separated by a sheet of tough mylar or other transparent plastic 
material. Each of the glass layers are highly shatter resistent and even 
when the outer plate is pitted or cracked, the windshield may be quite 
serviceable except for the crack being visible. The visible fracture is 
annoying and can impair the driver's vision of the road. For these 
reasons, cracked and/or pitted windshields are commonly replaced at a very 
substantial cost, typically in the hundreds of dollars. (Whereas 
windshield fractures are of varying types and descriptions, they will 
often herein be collectively referred to as cracks.) 
Recently, developments have been made for repairing windshields having 
cracked outer glass layers. The concept is quite simple. The crack in the 
windshield is visible because of ambient air that resides in the openings 
of the crack. Because air has a different index of refraction than the 
glass, light is transmitted in a manner different than the glass and 
becomes visible. A liquid filler material injected into the crack so as to 
replace the air will make the crack invisible if that liquid has the same 
index of refraction as the glass. Such a liquid that will harden and bond 
securely to the glass provides the added benefit of reinstating the 
strength of the glass and inhibits any spreading of the crack. 
A filler material that satisfies the needs of the present invention is a 
transparent resin identified as "Crack Weld".TM. which is in liquid form 
until subjected to ultraviolet light. The liquid material is shielded from 
ultraviolet light (sunlight) until the air in the crack is replaced with 
the filler material so that the crack is no longer visible. Ultraviolet 
light is then applied and the filler material cures and hardens. 
The concept is simple and the filler material is available. Not so readily 
available, however, is the apparatus or device to accomplish the task of 
injecting the filler material into the crack so as to remove or replace 
the air. The present invention is directed to a device for serving that 
purpose. 
Before explaining devices that have been available heretofore and to which 
the present invention is an improvement, the reader needs to understand 
that there are two different kinds of cracks commonly considered for 
repair by the techniques that will be described. The first is what might 
be considered as a surface crack. The crack along its entire length is 
exposed to the atmosphere. By injecting the liquid filler material into 
the crack, the air is simply crowded out of the crack and thereby 
replaced. This type of crack does not create a very serious problem for 
prior devices. However, such damaged windshields are more likely not 
repairable. If the crack is of the second variety where it is largely 
formed under the surface with a small hole into the crack, as it 
frequently is when struck by a small object, simply injecting the filler 
material into the crack will not get rid of the air which becomes trapped 
under the surface. 
Devices that have been developed for repairing cracks incorporate a 
mechanism in some respects having the features of an air pump. The small 
opening into the crack is sealed by the device so as to communicate only 
with an air chamber or cylinder of the device. A vacuum is drawn to remove 
air from the crack. The filler material is injected into the device 
adjacent the opening to the subsurface crack (e.g. through a syringe) and 
the vacuum is released so that the filler material is drawn into the 
crack. Whereas the vacuum generating step does not remove all of the air, 
the process often must be repeated. Because of the relative properties of 
air versus the highly viscous filler material, air will be gradually 
withdrawn through the filler material until the air is totally replaced 
with the filler material and the crack becomes invisible. 
Prior patents that function in this manner are U.S. Pat. No. 3,562,366 Sohl 
02/09/71, U.S. Pat. No. 3,765,975 Hollingsworth 10/16/73, U.S. Pat. No. 
4,132,516 Storey 01/01/79, and U.S. Pat. No. 4,200,478 Jacino 04/29/80. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention is distinguished from all prior known devices in the 
manner by which the air is extracted and replaced by the filler material. 
The present device includes a stepped cylinder cavity or cavities with a 
dual acting plunger. The cavity adjacent the crack opening (the lower end 
of the cylinder) has a small cross section that is fitted with a first 
sealing disk carried by the plunger. A second or upper cavity portion is 
substantially larger in cross section and is fitted with a second sealing 
disk also carried by the plunger. A one-way air valve (it exhausts only) 
is provided between the two cylinder portions. As the plunger is 
retracted, two separated vacuum chambers are formed, one below the first 
disk and one below the second disk. 
Prior to the device being placed over the crack opening, the liquid filler 
material is placed at the mouth of the small cavity, i.e. with the device 
inverted. The device is then turned upright and the mouth of the device 
with the filler material therein, is fit over the crack opening. Because 
the mouth is very small, e.g. one-eighth of an inch in diameter, the 
filler material clings to the mouth of the device due to surface tension 
of the filler material. 
As vacuum is drawn, the filler material remains positioned over the crack 
opening but allows passage of the air from the crack into the cavities. 
Initially the crack is exposed only to the vacuum of the small cavity. 
However, after a short distance the first disk enters the stepped portion 
of the cylinder and the crack opening is exposed to the greater vacuum 
created under the second sealing disk. 
Reversal of the plunger has the effect of allowing the filler material to 
be injected into the crack. It is desirable, however, not to generate a 
high positive pressure but rather to simply encourage flow of the liquid 
material into the crack. As the pressure is increased to the point of 
exceeding ambient pressure, the one-way exhaust valve opens and pressure 
from the upper chamber is exhausted to atmosphere. The lower sealing disk 
takes over to eject some positive pressure as it again seals against the 
cross section of the small cavity.

Reference is first made to FIGS. 1 and 3 illustrating a windshield 10 
consisting of an outer glass layer or plate 12, an inner glass layer 14 
and center layer of a thin tough transparent plastic layer 16, e.g. mylar. 
This combination is typical of the safety glass construction used for 
windshields in vehicles. The fracture illustrated includes an opening 
(resulting from the impact of a stone or intentionally drilled) and 
radiating cracks extending down into the outer glass layer 12 and 
constituting a subsurface crack as previously described. The fracture in 
total will generally hereafter simply be referred to as a crack 20 in the 
windshield 12. 
Generally, the windshield will not be considered repairable if the center 
layer 16 is damaged. The opening to the crack 20 is necessary and in those 
cases where the crack is totally subsurface, a hole is drilled down to the 
crack. In other instances, the opening may be too large for the mouth of 
the tool and in such instances a sealing ring or donut will be provided. 
The ring fits over the opening and reduces the size of the opening so as 
to fit the mouth of the tool. Such adaptations to oversized crack 
configurations are known to the industry and it will suffice to state that 
they are accommodated for the present tool in the conventional manner. 
Referring now FIGS. 1, 3 and 4, the various components of the device will 
be explained. A tripod support 22 consists of three legs 24 radiating from 
a center ring 26 with downwardly directed suction cups 28 fitted to the 
outer extremities of the legs 24. The center ring 26 is threaded and is 
threadedly engaged with screw threads 30 provided on the lower body 
portion of cylinder 32. It will be understood that the bottom end of the 
threaded portion of cylinder 32 forms a mouth 34 that includes an O-ring 
seal 36 seated in an inset 38 at the bottom end of a lower cavity 40. It 
is the mouth of the device as defined by the O-ring seal 36 that is placed 
over the opening of crack 20 as illustrated in the drawings. 
The cylinder 32 is comprised of an upper body portion 48 and a lower body 
portion 42 (on which screw threads 30 are provided). A cavity extends 
through the body portions 48,42 and includes a large diameter cavity 44 in 
the upper body portion 48, an intermediate cavity 46 in the upper region 
between the lower and upper body portions 48,42, and a small cavity 
portion 40 that extends upwardly from the mouth 34 to the intermediate 
cavity portion 46. The transition from the cavity 46 to the cavity 40 
includes a tapered wall portion 50. 
Residing in the cylinder 32 and extending through the cavities therein is a 
plunger 52. The plunger 52 includes a handle 54 and a shaft 56 protruded 
through an opening 58 in a cap 80 that is screwed onto the upper body 
portion 48 of the cylinder (note screw threads 86). The handle is exposed 
for manual manipulation of the plunger as will be later explained. The 
shaft 56 extends down through the opening 58 of cap 80 and is joined to an 
inner shaft 60, by screw threads 62. Shaft 60 includes a large sealing disk 
64 at the top of inner shaft 60, and small sealing disk 66 provided at the 
bottom end of inner shaft 60. Gaskets or O-rings provided on the periphery 
of the sealing disks provide air seals, the larger disk 64 being sealed 
against the wall of the large cavity 44 and the smaller disk 66 against 
the wall of the lower cavity 40. 
The relationship of the plunger configuration and that of the cavity 
portions are such that with the handle 54 and shafts 56,60 fully depressed 
as viewed in FIGS. 4 and 7, the large sealing disk 64 is positioned at the 
bottom of the large cavity 44 and the small sealing disk is positioned in 
the mouth 34 of the lower cavity 40. With the handle 54 and shaft 56 fully 
retracted as shown in FIG. 5, the large disk is positioned at the top of 
the large cavity 44 and the small disk is positioned in the intermediate 
cavity portion 46. 
Making up the remaining components of the cylinder 32 is a one-way exhaust 
valve 68 including an orifice 70 into the intermediate cavity, and a 
sealing ball 72 that normally is biased by compression spring 74 to close 
the orifice 70 and thereby prevent atmospheric air from entering the 
cavity portions through orifice 70. In the event of a pressure imbalance, 
i.e. with the cavity pressure higher than atmospheric air pressure, the 
spring 74 will be compressed to open orifice 70 to outlet 76 and thus to 
the atmosphere. 
Finally a lock screw 78 extends through the cap 80 and is exposed to manual 
manipulation for screwing the lock screw 78 against or away from shaft 56 
to lock or unlock the plunger in a desired position. 
OPERATION 
Having explained the various components of the device, its operation will 
now be explained. 
Reference is first made to FIGS. 1 through 3. As previously explained when 
dealing with a subsurface crack, it is necessary to provide communication 
to the crack, i.e. through an opening as at center of crack 20. It may be 
necessary to drill a hole of, e.g. one-eighth inch, into the outer plate 
12. In instances where the opening 20 is too large, a sealing ring or 
donut can be provided. These are well known to the art and need not be 
described. For the purposes of this explanation, hole or opening 20 is 
assumed to be of the proper size, e.g. one-eighth inch in diameter. 
The first step following determination of the proper hole size is to 
unscrew tripod 22 from cylinder 32 and align the center of support ring 26 
over the opening in crack 20. The suction cups 28 are pressed down onto the 
glass. This assures placement of the mouth of the cylinder over the crack 
opening when the cylinder is screwed into the support ring 26. 
Next the filler material 82 is deposited inside the O-ring 36 as 
illustrated in FIG. 2, e.g. with a syringelike device. As shown, the 
plunger is in a near fully depressed position with the cylinder inverted. 
After receiving the filler material, the cylinder is turned over and 
screwed down into the tripod as illustrated by arrow 84 in FIG. 3. The 
filler material clings to the O-ring mouth 34 of the cylinder due to 
surface tension. The cylinder is screwed down onto the plate 12 with 
O-ring 34 sealing the opening of crack 20 so that the crack is sealed 
except for communication with the cylinder cavities. This is shown in FIG. 
The lock screw 78 is unscrewed and the plunger is fully retracted as 
illustrated in FIG. 5. In the initial stage of retraction, the lower 
cavity 40 is sealed by sealing disk 66 and the drawing of air from the 
crack 20 is very slight. As the sealing disk 66 crosses the transition 
area 50 in the upper end of cavity 40 (or the lower end of cavity 46) the 
cavity 40 and the crack in the plate 12 are exposed to the larger cavity 
44. The substantially greater vacuum effected by disk 64 in cavity 44 (the 
exhaust valve maintained in its closed position by spring biased ball 72) 
is thus exposed to the crack and a much greater evacuation of air from the 
crack is accomplished (as compared to prior devices). 
During the evacuation of air from the crack as described above, the air 
from the crack simply filters through the liquid filler material 82. FIGS. 
6 and 7 illustrate the process of injecting the filler material into the 
crack. The filler material is liquid and even though contained in a 
vacuum, will tend to flow downwardly due to gravity. Upon depression of 
the plunger, a pressure differential is created above the filler material 
which, added to the gravity effect, causes the filler material to flow 
into the crack. Note, however, that as a positive pressure is achieved in 
cavity 44, ball 72 will be unseated and air will be exhausted out the 
valve as illustrated in FIG. 6. Upon full depression as shown in FIG. 7, 
the crack simply disappears, as previously explained, because the filler 
material has the same index of refraction as the glass plate 12. 
In certain instances, some air may still remain in the crack, trapped by 
the filler material. The plunger action can be recycled in such event. In 
the recycling process, with the plunger fully retracted as shown in FIG. 
5, lock screw 78 may be tightened to lock the plunger for a short time and 
thereby effect a holding of the vacuum. Such a vacuum creates a drawing 
effect on any air bubbles in the crack and they simply are caused to 
"float" or filter through to the surface of the filler material. Movement 
of the air bubbles can be observed by the operator. When the crack 
visually disappears, the operator knows he has a good bond and he simply 
exposes the filler material to sunlight or to artificial ultraviolet rays, 
causing the filler material to cure or harden. The device is then removed. 
Those skilled in the art will readily appreciate the advantages of the 
invention. Sizes and shapes of the various components will be readily 
determined. Such sizes and shapes can be modified for a variety of repair 
projects without departing from the inventive concept. The inventive 
concept, at least in part, consists of a multiple cavity vacuum chamber 
that enables the filler material to be deposited in a small diameter mouth 
of the device, with the drawing of air primarily affected as the larger 
cavity is opened. The exhaust port is important to the pumping action and 
the device in general has been found to substantially improve on the 
repairing process of cracks in vehicle windshields.