Note: Descriptions are shown in the official language in which they were submitted.
WO 96/08428 PCT/US95/12371
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021 99 X52
Description
Caulking Gun and Cartridge With Afterflow Prevention
Technical Field:
The invention relates to caulking guns and to
dispensing cartridges, and more particularly to the type
of composition dispensers in which a cartridge is placed
into a gun structure and a piston urges a plunger
forwardly from the rear of the cartridge, thus reducing a
volume available for the composition inside the cartridge
and forcing the composition from an open tip at the front
of the cartridge.
These types of caulking guns have been the subject of
undesireable afterflow, i.e. the interior of the cartridge
is still subject to overpressure after the plunger is no
longer actively urged forward and, as a result, additional
amounts of composition are forced from the cartridge.
Two primary reasons for the afterflow phenomenon are
recognized. Firstly, the usually thin-walled cartridge
expands during the plunger actuation and, according to the
physical law that systems always attempt to return to the
relaxed state, the cartridge wall relaxes after the
plunger actuation. Due to the fact that prior art
backwalls of the cartridges have been devised to retain
their forward-most position and that the plunger of the
caulking gun is typically locked against a return
movement, the relaxation of the cartridge wall leads to
afterflow, i.e. to oozing at the dispensing tip. Secondly,
most caulking compositions have a high degree of viscosity
and are at least marginally compressible, which, upon
plunger actuation, causes a substantial internal pressure
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buildup which, after the plunger is no longer forced
forward, also leads to oozing at the dispensing tip.
Backcrround Art
The afore-described afterflow problem is often
answered in the context of conventional prior art
structures by quickly releasing and moving back the gun
plunger as soon a sufficient amount of composition has
been dispensed.
U.S. Patent No. 5,236,105 to Galex describes a novel
system for preventing over-ejection. In that system,
conventional caulking guns are retrofitted with several
members, namely a female element, male element, a return
spring, and a stop. The spring is utilized as an active
biassing element which actively pulls back the backwall in
the cartridge and thus introduces a relative vacuum inside
the cartridge.
U.S. Patent No. 4,834,268 to Keller describes a
plunger system in which an elastic sealing ring is urged
towards the inner wall surface of the cartridge by a
radial component of the force which urged to plunger
forwardly in the dispensing mode. When the plunger is no
longer actuated, the sealing ring relaxes slightly and
allows the plunger to relax the inside cartridge pressure.
The first of the above-noted methods of preventing
afterflow is clearly unsatisfactory. The systems described
in the two afore-mentioned patents are quite complicated
and thus rather expensive.
Disclosure of Invention:
It is accordingly an object of the invention to
provide a caulking gun and cartridge with afterflow
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prevention, which overcomes the above-mentioned disadvantages
of the prior art devices and methods of this general type. The
primary object is to provide a simple and inexpensive system
which is applicable to ~~ wide array of cartridges and caulking
guns and which safely prevents overflow or over-ejection.
With the foregoing and other objects in view there is
provided, in accordance with the invention, an improved
caulking cartridge, of t:he type having a substantially tubular
body, a forward dispens_Lng opening at a forward end of the
tubular body, a backwall movably disposed within the tubular
body, the tubular body having a wall with an inner wall surface
defining an inner diameter of the tubular body, and the tubular
body defining a chamber therein bounded by the inner wall
surface, the forward end and the backwall. The improvement is
defined in that the backwall has a diameter which is less than
the inner diameter of the tubular body and there is defined a
substantially contact-free spacing distance between the inner
wall surface and a periphery of the backwall.
In accordance with the present invention, there is
provided an improved cau:Lking cartridge, of the type having a
substantially tubular body, a forward dispensing opening at a
forward end of the tubular body, a backwall movably disposed
within the tubular body,, the tubular body having a wall with an
inner wall surface defining an inner diameter of the tubular
body, and the tubular body defining a chamber therein bounded
by the inner wall surface, the forward end and the backwall,
the improvement which comprises: the backwall having a
diameter less than the :inner diameter of the tubular body and
defining a substantially contact-free spacing distance between
the inner wall surface and a periphery of the backwall such
that the backwall moves backwardly away from the forward end of
the tubular body when a pressure inside the chamber is greater
than a pressure outside the chamber.
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In accordance with the present invention, there is
provided in combination, a caulking gun and a cartridge, said
cartridge having a subst<~ntially tubular body, a forward
dispensing nozzle at a forward end of said tubular body, a
backwall movably disposed within said tubular body, said
tubular body defining a ~~hamber therein between said forward
end and said backwall; said caulking gun comprising a body
forming a trough for receiving said cartridge, and a piston
movable parallel to said trough for pushing said backwall
forward within said tubular body and causing a reduction of
volume within said chamber in said cartridge; said tubular body
having a wall with an inner wall surface defining an inner
diameter of said tubular body, and said backwall having a
diameter less than said inner diameter of said tubular body and
defining a substantially contact-free spacing distance between
said inner wall surface and said backwall such that the
backwall moves backwardl.y away from the forward end of the
tubular body when a pressure inside the chamber is greater than
a pressure outside the chamber.
In accordance with an added feature of the invention,
the distance is at least: 0.2 mm, and it may be up to more than
1.0 mm.
In accordance with another feature of the invention,
there are provided spacer ridges formed on a circumference of
the backwall, the spacer ridges being in contact with the inner
wall surface of the tubular body and defining the spacing
distance.
With the above and other objects in view there is
also provided, in accordance with the invention, a combination
caulking gun and cartridge. The cartridge has
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a substantially tubular body, a forward dispensing nozzle
at a forward end of the tubular body, a backwall movably
disposed within the tubular body, the tubular body
defining a chamber therein between the forward end and the
backwall. The caulking gun thereby comprises a body
forming a trough for receiving the cartridge, and a piston
movable parallel to the trough for pushing the backwall
forward within the tubular body and causing a reduction of
volume within the chamber in the cartridge. The tubular
body has a wall with an inner wall surface defining an
inner diameter of the tubular body, and the backwall
having a diameter less than the inner diameter of the
tubular body and defining a substantially contact-free
spacing distance between the inner wall surface and the
backwall.
In accordance with a further feature of the
invention, there are provided means operatively associated
with the tubular body of the cartridge for preventing a
radial expansion of the tubular body while the piston
forces the backwall forward. These prevention means may be
in the form of a rigid tubular sleeve tightly fit on the
tubular body, for instance by slipping the cartridge into
the sleeve.
In accordance with again another feature of the
invention, the tubular sleeve is formed of a hard material
selected from the group consisting of PVC,
fiber-reinforced plastic, and metal.
In accordance with again a further feature of the
invention, the prevention means is a clamp device disposed
at the trough of the caulking gun for selectively
squeezing the tubular body of the cartridge.
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In accordance with a concomitant feature of the
invention, the caulking gun has a trigger handle pushing
the piston forward for dispensing caulking composition,
and the clamp device is connected to the trigger handle of
the caulking gun such that the tubular body is squeezed
simultaneously with the piston forcing the backwall
forward.
Other features which are considered as characteristic
for the invention are set forth in the appended claims.
Although the invention is illustrated and described
herein as embodied in a caulking gun and cartridge with
afterflow prevention, it is nevertheless not intended to
be limited to the details shown, since various
modifications and structural changes may be made therein
without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
The construction of the invention, however, together
with additional objects and advantages thereof will be
best understood from the following description of the
specific embodiment when read in connection with the
accompanying drawings.
Brief Description of the Drawing:
Fig. 1 is a perspective view of a prior art caulking gun;
Fig. 2 is a longitudinal section of a prior art caulking
cartridge;
Fig. 3 is a similar section of a caulking cartridge
according to a first embodiment of the invention;
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Fig. 4 is rear elevational view of a backwall of a
caulking cartridge of a second embodiment;
Fig. 5 is a section thereof taken along the line V-V in
Fig. 4;
Fig. 6 is a front elevational view of a piston
corresponding to the embodiment of Figs. 4 and 5;
Fig. 7 is a longitudinal section of a rigid sleeve
according to a third embodiment of the invention;
Fig. 8 is a diagrammatic front view section of a trough of
a caulking gun; and
Fig. 9 is a side elevational view of a caulking gun with a
squeeze mechanism.
Description of the Preferred Embodiments:
Referring now to the figures of the drawing in detail
and first, particularly, to Fig. 1 thereof, there is seen
a conventional caulking gun. A forward body 1 is formed
with a trough 2, which receives a caulking cartridge. A
piston stem 3 pushes a plunger head 4 forward towards a
forward end wall 5 of the trough 2. A locking dog 6
prevents the stem 3 from moving backwards, and a spring 7
biasses the dog 6 into the locking position. The stem 3 is
released and allowed to move backwardly by swinging the
dog 6 forward into a substantially vertical release
position.
With reference to Fig. 2, a typical prior art
caulking tube has tubular body 8. Usually, the body is
formed as a cylindrical tube 8, which is formed of paper
laminate, fibrous plastics, rolled metal sheets, or the
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like. The cylindrical tube 8 is relatively soft and, in
response to increased pressure in the interior chamber
thereof, it expands radially. A nozzle tip 9 is formed on
a forward closure wall 10. The tube 8 is air-tightly
closed in the rear with a backplate 11. An outer
cylindrical flange 12 of the backplate 11 has an outer
radius which corresponds to an inner radius of the tube 8.
The flange 12 forms a sliding seal between the inner wall
surface of the tube 8 and the backwall 11. A reinforcing
ring 14 with a cylindrical seal flange 15 is clamped at
the rear edge of the tube 8. In storage, the backwall 11
is disposed directly adjacent the ring 14, such that the
flange 12 is clamped under the seal flange 15. Only after
the forward wall 10 is punctured and the nozzle tip 9 is
cut to form a dispenser opening is the backwall 11 pushed
forward for dispensing caulking composition 13.
As the backwall 11 is pushed forward and the flange
12 slides as along the inner wall surface of the tube 8,
the caulking composition 13 is forced from the dispensing
tip because of the increased pressure inside the tube
chamber. Besides pushing composition 13 out of the
dispensing tip, the increased pressure also causes the
tube body to expand radially. In fact, it can be shown
that the radial pressure on the cylindrical tube wall is
exactly twice the axially acting pressure towards the
dispensing opening. This radial "breathing" of the tube 8
causes afterflow when the piston 4 is no longer actuated
and the tube 8 resiliently relaxes its increased diameter
towards the relaxed position.
Referring now to Fig. 3, which illustrates a first
embodiment of the invention, an outer diameter OD of the
cylindrical flange 12 is smaller than an inner diameter ID
of the tube 8 by a spacing DD. The spacing OD is chosen in
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dependence on the caulking composition 13, i.e. on the
viscosity and its reaction rate with air. In other words,
the higher the viscosity of the composition, the greater
the spacing DD. Further, the more inert the composition is
relative to the atmosphere, the greater the spacing DD. In
general, tubes for typical silicones, glycerol esters,
resin and rosin acids, and the like may be provided with a
spacing of DD = 1 mm.
Tubes for compositions with a higher viscosity may be
provided with DD < 0.2 mm. Proper spacings may be chosen
by those of skill in the art.
The flange 12 and the inner wall surface of the tube
8 form a contact-less seal by virtue of a small amount of
caulking composition which is allowed to seep
therebetween. Due to the fact that the dispensing opening
is substantially larger in area than the area defined
(approximately) by the spacing DD times the circumference,
only a negligible amount of caulking composition is
allowed to escape through that route. As soon as the
pressure on the piston is relaxed and the piston is moved
back, the backwall 11 follows suit as the tube wall
attains its relaxed position. As the caulking composition
within the spacing between the flange 12 and the tube is
still fresh (its viscosity is at its maximum), the
backwall 11 slides easily. Shortly after the backwall has
reached its relaxed postion (i.e. the tube body is
relaxed), the remaining caulking composition which is
exposed to air is allowed to harden and thus form a proper
seal. The remaining composition within the cartridge
chamber is sealed against the atmosphere.
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After manufacture, i.e. during shelf storage before
initial use, the backwall 11 is sealed similarly to
conventional prior art systems.
The caulking tube system with a spacing DD > 0.0 mm
may at first appear illogical because the compositions
contained in such tubes cure upon contact with the air and
any such opening rather goes against common sense.
However, the inventor has been able to ascertain that,
after actuation, a sealing ring of dried composition forms
between the flange 12 and the inner wall surface of the
tube 8. As the piston 4 pushes the backwall 11 forward
during the next dispensing operation, that temporary seal
is broken and the slide seal between the flange 12 and the
inner wall surface of the tube 8 is effected by soft
composition. When the pressure on the piston 4 by the
piston stem 3 is relaxed immediately after dispensing, the
contracting tube 8 is able to push the backwall 11 back,
instead of causing undesireable afterflow.
With reference to Fig. 4, a second embodiment, which
may be combined with the first embodiment, is defined with
an active pull-back feature. The flange 12 is provided
with two mutually opposite latches 16. As the piston 4 is
pushed into the opening defined by the flange 12, it
engages behind the latches 16. When the backwall 11 is
thus engaged, it is possible to actively retract the
backwall 11 by pulling back on the stem 3. In a preferred
embodiment (Fig. 6), the piston plunger 4 may be provided
with cutouts 17, which allow selective engagement of the
piston 4 with the latches 16.
Referring again to Fig. 4, the spacing between the
r
inner tube wall surface and the flange 12 may be defined
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by ridges 19 integrally formed on the circumference on the
backwall 11, i.e. on the flange 12.
In a third embodiment, the radial expansion of the
tube 8 is prevented altogether in that a non-elastic
sleeve 18 is slipped over the tube 8. The sleeve 18 may be
formed of hard PVC, fiber reinforced plastic, metal, or
similar material. The inner diameter of the sleeve 18 is
chosen such that it corresponds with the outer diameter of
the tube 8. Further- more, the sleeve 18 is made as thin
as possible, so that it still fits into the trough 2 of
the caulking gun.
With reference to Fig. 8, the rigid sleeve may be
replaced with a top lid 20 which is articulated at an edge
of the trough 1 of the caulking gun body. As the lid 20 is
closed and latched into a latch hook 21, a rigid sleeve is
formed for the caulking tube.
Finally, in a fourth embodiment, the tube 8 is
squeezed in addition to dispensing by forwarding the
backwall 11. When dispensing is no longer desired, the
squeeze on the tube 8 is relaxed. Accordingly, in a
preferred structural embodiment of the invention, the
caulking gun is provided with a clamp device which
squeezes the tube simultaneously to forwarding the
backwall 11. As illustrated in Figs. 8 and 9, the lid 20
is braced with two strips 22 connected between the latch
21 and, with the opposite ends thereof, the trough body 1.
As the trigger handle 23 is pulled for advancing the
piston 4, wedges 24 are pulled below the strips 22. This
causes the strips 22 to clamp down the lid 20 and thus to
actively compress the caulking tube 8. The lid 20 is
preferably formed with a slightly larger diameter than the
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trough. This leads to a slightly elliptical cross section
of the space which is occupied by the caulking cartridge.
While we have herein referred to "caulking guns" and
"caulking compositions", it should be understood that the
terms are to be understood as commonly used in the art,
namely any such dispenser with piston actuated volume
reduction in tubular containers and with compositions of
any type which are subject to the afore-mentioned
afterflow problem.
