Note: Descriptions are shown in the official language in which they were submitted.
~ 110094
This invention relates to liquid dispensing devices
and particularly to devices adapted for dispensing relatively
viscous sticky substances such as adhesives,. hot melts, sealing
compounds, etc.
There are many applications for dispensers in which
it is desirable or necessary to sharply cut off the flow of
liquid from the nozzle of the device without any droolîng, drip-
ping, or stringing of the liquid from the nozzle after closing
of the nozzle. To that end there has heen a long standing need
for a dispensing device which would sharply cut off the flow of
liquid from the nozzle when the valve of the nozzle is closed~
One such attempt at such sharp cut off of flow is disclosed
in U. S. Patent No. 3,~23,.252. According to the disclosure of
this patent, sharp cut off may be o~tained by maintaining the
conically shaped needle valve of the device centered within a
frustoconical.seat of.that device. To that end centering bush-
ings are located within the device through which the needle valve .
must pas.s.
Another patent which recognizes the desirability of
minimizing dripping or stringing from a nozzle orifice as a
desirable end is U. S. Patent No. 3,841,567. According to the
disclosure of this patent, dripping or stringing of viscous
liquid from the nozzle orifice after cut off of flow may be
minimized by maintaining a minimum volume cavity between the cut
off valve and the nozzle orifice of the device,
I have discovered and one aspect of this invention is
predicated upon the discovery that sharp cut off of flow without
stringing from a nozzle of a dispensing device may be achieved
by providing a small orifice in a very small radius semi-spherical
end surface of the nozzle. In the preferred embodiment, the
llSS094
nozzle orifice is only .020 inch in diameter and the nozzle tip
is semi-spherical in shape and only .084 inch in radius. A
nozzle thus configurated and having a frustoconical valve seat
located immediately adjacent the nozzle orifice has been found
to result in a nozzle which materially reduces the amount of
stringing of material between the nozzle and substrate upon
which the material is being deposited.
One consideration of th.is invention is that it
provides very sharp cut off of liquid flow from the nozzle
whenever the valve of the dispensing device is closed.
Consequently, there is no dripping of liquid from the device
after valve closing. If the device is used to dispense very
viscous substances such as adhesive or sealing compounds, this
unique nozzle and needle valve guide structure.materially reduces
stringing of the viscous substance between the nozzle orifice
and the substrate on which the viscous substance is deposited.
According to the present invention there is
provided a device for.dispensing viscous liquids comprising a
body having an axial bore therein, a liquid storage chamber
defined at least in part by the bore, a nozzle having an axial
bore therein, the bore of the nozzle being in fluid communica-
tion with the bore of the body, the nozzle bore having a
frustoconical valve seat terminating at a nozzle outl.et
o~ifice, an axially movable needle valve having a generally
conical section of the distal end thereof, the conical section
of the needle being engageablé with the frustoconical valve
seat to close the valve, and means for minimizing stringing of
viscous material from the nozzle orifice after closing of the
needle valve on the valve seat, the last named means comprising
a tip on the nozzle having an exterior surface which tapers
inwardly toward the nozzle orifice, the tip terminating in a
semi-spherical end surface having a radius of approximateiy .084
csm/f)~
l~SS094
inch and the distal end of the needle valve terminating at
the nozzle orifice so that there is no cavity between the
distal end of the needle valve and the nozzle orifice.
These and other objects and advantages of this
invention will be more readily apparent from the following
description of the drawings in which:
Figure 1 is a cross sectional view of a dispensing
device incorporating the invention of this application.
- 3a -
csm/~
~ 11550~4
Figure 2 is an enlarged cross sectional view of the
nozzle and nozzle orifice of the dispensing device illustrated
in Figure 1.
Figure 3 is a cross sectional view taken on line
3-3 of Figure 2.
Referring to Figures 1 and 2, the invention of this
application is illustrated as being being embodied in a dispensing
gun 10. This gun 10 includes a generally cylindrical bcdy 11,
an end cap 12, and a nozzle 13. The end cap 12, body 11, and
nozzle 13 all have a longitudinal bore extending therethrough
within which there is located an axially movable needle valve
14 for controlling flow of liquid from the orifice 16 of the
nozzle 13.
The valve body 11 contains a stepped axial bore 20, the
larger diameter section 21 of which is located at the forward
end of the body. This larger diameter sectio~ 21 is intersected
by a transverse passage 22 through which liquid is supplied to
the gun. AddLtionally, a vent port 23 intersects the smaller
diameter section 24 of the bore 20. There is also an air inlet
passage 25 which connects the rear end of the valve body with an
~- inlet air port 26.
A bushing 27 is located within the bore 20 of the body
11. This bushing supports seal assemblies 29 and 30 within a bore
28 which extends longitudinally through the bushing.
To prevent fluid flow around the bushing 27, there is
an annular groove in the surface of the bushing within which there
is an O-ring seal 31. Additionally, there is an O-ring seal 32
contained within an annular channel formed in the valve body 11.
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There is a piston assembly 35 mounted upon the needle
~alve 14 for controlling movement of the needle valve 14. This
piston assembly comprises a nut 36 threaded onto a threaded
section 37 of the needle valve and a piston retainer ring 38 seal-
ingly secured onto the periphery of the nut 36. This retainer
ring carries a pair of piston rings 39, 40 between which there i5
sandwiched a resilient gasket 41. Th outer edge of this gasket
41 contacts the interior surface of a cylinder 42 formed on th~
interior of the end cap so as to form a pneumatic seal between
the lower side of the piston and the surface of the cylinder 42.
The end cap 12 is bolted onto the upper end of the
body 11 by bolts (not shown). Preferably, a resilient gasket
seal 44 is located between the contacting surfaces of the end cap
and the body.
Communicating with the cylinder 42 formed in the end
cap 12, there is a stepped axial bore 45 which extends through
the end cap. The upper smaller diameter section 46 of this
stepped bore is threaded and receives an adjustment stud 47. A
lock nut 48 secures the stud 47 in a position of axial adjust-
ment~
Between the bottom surface of the stud 47 and the top
of the piston assembly 35, there is a compression spring 5Q.
The upper end of this compression spring 50 contacts the bottom
surface of the stud 47 and the lower end of the spring 50 contacts
the top surface of a spring retainer 51. This spring retainer
is supported upon the top surface of the piston assembly nut
36. By adjusting the axial position of the stud 47 within the
bore 46, the closing force for retaining the needle valve closed
may be adjusted or varied.
1155094
The dispensing device heretofore described except for
the configuration of the needle valve 14 and the nozzle 13, is
conventional and per se, forms no part of the invention of this
application. Otherwise expressed, the invention of this applicat-
ion resides in the construction of the needle valve 14 and the
nozzle 13.
With particular reference to Figures 2 and 3, it will
be seen that the nozzle 13 contains a generally cylindrical
. axial bore 60 which extends forwardly from the rear of the nozzle
until it intersects a frustoconical valve seat 61 at the forward
end of the nozzle. This frustoconical valve seat 61 in turn
communicates with a small cylindrical nozzle orifice 16 through
which li~uid exits from the nozzle. In a preferred embodiment,thi 3
orifice is approximately .020 inch in diameter and the valve seat
61 defines an included angle of 34.
Press fit into the bore 60 there is a guide bushing
90, This bùshing 90 has a central axial bore 91 through which a .
needle valve 14 passes. Additionally, it has four equidistantly
spaced longitudinal channels or grooves 92 in its peripheral
surface through which liquid may flow from the interior of the
gun body 11 to the nozzle orifice 16 as is explained more fully
hereinafter.
At its forward end the needle valve 14 has a cylindrical
section 65 slideably received within the bore 91 of the guide
bushing 90. This sliding fit requires that the bore 91 be slight-
ly larger than the cylindrical section 65 of the needle, but that
there be no more than approximately .002 inch clearance between
the bore and the needle valve~ Preferably, the clearance is
approximat y .00 inch.
~50~
At its forward end the needle valve 14 terminates in a
frustoconical shaped valve section 66 engageable with the frusto-
conical shaped valve seat 61 in the nozzle 13. The frustoconical
shaped end section 66 of the needle valve defines an included angl ,
of approximately 30 while the valve seat 61 defines an in-
cluded angle B of approximately 34. The exterior surface 67
of the nozzle tip is also tapered at approximately 34. Con-
sequently, there is some slight clearance between the frustoconica 1
shaped section of the needle valve 65 and the valve seat 61 at the
rearward end of the valve seat.
The nozzle 13 has a cylindrical hub section 70 which is
tightly fitted within the large diameter section 21 of cylindri-
cal bore 20 in the body 11. Forwardly of the hub section 70, therl ,
is a flange 71 which is bolted to the forward end of the body 11
by conventional threaded connectors 73. Preferably, there is an
O-ring seal 74 contained within a channel 75 formed in the for~ard
end of the dispenser body 11. This seal 74 prevents any leakage
of liquid between the nozzle 13 and the body 11.
To prevent any movement of the bushing 27 within the borl ,
20, there is a spring 76 located between the rearward end of the
nozzle 13 and the forward end of the bush~ing seal assembly 29.
This spring 76 biases the bushing rearwardly and maintains a flang~
77 of the bushing engaged with a shoulder 78 formed in the bore
20.
In operation, liquid under pressure is supplied to
the liquid inlet port 80 of the device. This port communicates
via passage 22 with the bore 20 of the body 10 such that liquid
supplied to the port 80 flows into a liquid storage chamber 81
contained within the device. This chamber 81 is in turn open to
~the longit ~inal passages 92 within the guide oushing 9~.
_ 7 _
1155094
Whenever the device is to be actuated so as to permit
liquid to flow from the storage cham~er 81 through the passages
92 and past the valve seat 61 to the orifice 61, high pressure
air is supplied to the port 26. This high pressure air overcomes
the bias of the spring 50 and causes the piston assembly 35 to
move upwardly, carrying with it needle valve 14. This upward move _
ment of the needle valve results in the lifting of the conical
section 66 of the valve off of the seat 61 and, results in flow
of liquid from the storage chamber 81 through the passages 92
via the valve tQ the orifice 16. This flow continues so long as
the air pressure is maintained to the port-26. When that air
pressure is relieved, as for example by actuation of a controlling
pneumatic valve (not shown) the spring 5~ effects closing movement
of the valve.
The most important advantage of this invention resides
in the fact that when it is used to dispense high viscosity
liquids such as adhesives or sealing gasket material compounds,
etc., it materially eliminates or reduces stringing of material
~from the nozzle orifice after valve closing. This advantage
is apparently partially attributable to the needle valve guide
surface being in close proximity to the nozzle valve seat and
partially attributable to the small radius semi-spherical tip on
the nozzle. The needle valve guide surfaces on the guide bushing
apparently maintains the needle valve concentric to the valve seat
with the result that sharp cut off of flow and the reduction
or elimination of stringing is enhanced and apparently the small
radius semi-spherical tip on the nozzle also contributes
to this reduction.
1~55094
While I have described only a single preferred embodi-
ment of my invention, persons skilled in this art will appreciate
changes and modifications which may be made without departing
. from the spirit of my invention. Therefore, I do not intend to
be limited except by the scope of the following appended claims:
