Information
-
Patent Grant
-
6257445
-
Patent Number
6,257,445
-
Date Filed
Thursday, March 23, 200024 years ago
-
Date Issued
Tuesday, July 10, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Shaver; Kevin
- Cartagena; M A
Agents
- Wood, Herron & Evans, L.L.P.
-
CPC
-
US Classifications
Field of Search
US
- 222 1
- 222 504
- 222 510
- 222 518
- 222 61
- 222 333
- 222 399
- 251 12902
- 137 61411
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International Classifications
-
Abstract
A fluid dispensing apparatus for dispensing a viscous fluid from a source of viscous fluid onto a substrate. The dispensing apparatus includes an electrically operated, normally-opened, dispensing valve having an inlet in fluid communication with the source of fluid and a shut-off valve fluidly connected between the inlet of the dispensing valve and the source of viscous fluid. The shut-off valve has a normally-closed state interrupting fluid communication between the source of fluid and the inlet of the dispenser body, thereby inhibiting the normally-opened dispensing valve from dispensing fluid when power is removed from the dispensing apparatus.
Description
FIELD OF THE INVENTION
The present invention generally relates to an apparatus for dispensing viscous fluids and more specifically, to an electrically operated apparatus for dispensing viscous liquids, such as hot melt adhesives.
BACKGROUND OF THE INVENTION
Various viscous fluid dispensers have been developed for the precise placement of viscous fluid such as a hot melt adhesive. Generally, viscous fluid dispensers have a valve stem with a valve body on its distal end which is disposed on an upstream side of a valve seat and moved in an upstream direction to open the valve and in a downstream direction to close the valve. For purposes of this document, the term “upstream” refers to a direction or location that is toward or closer to the source or fluid inlet and away or further from the fluid outlet of the dispenser; and “downstream” refers to a direction or location that is toward or closer to a fluid outlet and away or further from a source or fluid inlet of the dispenser. Many viscous fluid dispensing applications require that the viscous fluid be applied to the substrate with sharply defined boundaries, that is, the leading and trailing edges of the applied pattern of fluid on the substrate fluid be sharply defined or delimited. Thus, it is necessary that the motion of the valve body be very fast, and the flow of viscous fluid be abruptly started and stopped. With the valve construction described above, when the valve opens, the valve body is moving in an upstream direction against the direction of flow of the fluid and has a tendency to delay and disrupt the flow of fluid out of the dispensing nozzle. Similarly, when the valve closes, the valve body is moving in the downstream direction with the direction of fluid flow and has a tendency to cause a small additional quantity of fluid to be dispensed.
To provide a sharper initiation and cut-off of fluid flow, a “snuff back” valve construction is known. With this construction, the valve body is disposed on a downstream side of a valve seat and moved in the downstream direction away from the valve seat to open the valve and in the upstream direction toward the valve seat to close the valve. Consequently, as the valve opens, the valve body is moving in the same downstream direction as the viscous fluid; and the viscous fluid begins to be dispensed simultaneously with the opening of the valve body. When the valve closes, the valve body is moving in the upstream direction and is effective to sharply cut-off the flow of viscous fluid. While such valves are operated by electric-pneumatic solenoids, due to the relatively short useful life of pneumatic solenoids and their inability to be precisely and repeatably controlled over the long term, it is desirable to provide an electrically operated viscous fluid dispenser of the above-described “snuff-back” design.
Such “snuff-back” electric fluid dispensers are known and are generally of the structure illustrated in FIG.
4
. An electrically operated viscous fluid dispenser or dispensing gun
20
comprises one or more dispensing modules or valves
22
mounted on a fluid distribution manifold plate
24
in a known manner. The dispensing valve
22
includes a dispenser body
26
and a fluid dispensing nozzle body
28
having a nozzle
30
through which droplets
32
of the viscous fluid are dispensed onto a substrate
34
. Relative motion between the substrate
34
and dispenser
20
is provided in a known manner.
A valve stem
36
is mounted within the dispenser body
26
and has a valve body
38
on its lower, distal end below or downstream of a valve seat
40
. The valve body
38
sealingly engages with a valve seat
40
to inhibit the flow of fluid from the dispenser
20
. A fluid inlet passageway
42
intersects the interior portion
44
of the dispenser body
26
and is connected to a fluid passage
46
in the manifold
24
which, in turn, is fluidly connected to a pressurized source of viscous fluid
48
, such as a hot melt adhesive. Arrows
49
indicate the flow path of the fluid entering through the fluid inlet passageway
46
and through the interior portion
44
.
An armature
50
is disposed within the interior portion
44
and is coaxially aligned with, and is often formed integrally with, a proximal end of the valve stem
36
. An electromagnetic coil
52
is disposed about the armature
50
. A return spring
54
biases the valve stem
36
and valve body
38
in an upstream, upward direction to a closed position at which the valve body
38
sealingly contacts the valve seat
40
, thereby interrupting the flow of viscous fluid through the nozzle
30
. The return spring
54
is normally a compression spring which is placed under compression within the bore
60
through engagement with an electromagnetic pole
56
. When supplied with electrical current, the coil
52
generates an electromagnetic field. The electromagnetic coil
52
must generate an electromagnetic field between the armature
50
and the pole
56
of sufficient strength so as to attract the armature
52
and the pole
56
together. Since the pole
56
cannot move, the armature
52
moves downward against the force of the spring
54
, thereby moving the valve body
38
downstream away from the valve seat
40
to its open position.
The design of the dispensing valve
22
of
FIG. 4
is known as a normally-closed design for the reason that when the coil
52
is de-energized, the spring
54
maintains the valve body
38
sealingly against the valve seat
40
, thereby holding the valve
22
in the closed position. Thus, the valve
22
is normally in, or defaults to, a closed state or position. Therefore, in the event of any electrical power failure to the coil
52
, the valve
22
is always mechanically biased to the illustrated closed position. Thus, the valve
22
always defaults to the closed position.
However, to provide that desired normally-closed capability, the armature
50
must be located within the interior
44
above the pole
56
; and further, the valve stem
36
must extend through a bore
58
within the pole
56
. Those structural features introduce several disadvantages in the operation of the valve. First, the bore
58
in the pole
56
reduces the mass of the pole
56
, thereby reducing the effectiveness and strength of the electromagnetic field produced by the coil
52
and pole
56
, thereby reducing their capability to move the armature
50
. Further, the viscous fluid presents a greater resistance to motion of the portion of the valve stem
36
located within the bore
58
than the portion of the valve stem
36
located outside the bore
58
. In addition, the valve stem
36
is substantially elongated to be able to pass through the length of the pole
56
, thereby increasing the mass that must be moved by the electromagnetic field. Therefore, the viscous fluid dispenser
20
of
FIG. 4
requires that the coil
52
and pole
56
provide a greater electromagnetic force in order to move the armature
50
, valve stem
36
and valve body
38
between the open and closed positions.
Second, the interior portion
44
extends over the entire length of the valve body
38
, and there are wetted surfaces throughout the entire length of the interior portion
44
of the valve body
38
. That large area of wetted surfaces increases the probability of the accumulation of char over the operating life of the dispenser
30
. Char is a fluid residue that accumulates on wetted surfaces and is most generally caused by a long term degradation of the viscous fluid. To minimize the potential accumulation of char, the design of the valve of
FIG. 2
has a further disadvantage of providing the viscous fluid inlet at the upper end of the dispenser body
26
, thereby requiring the viscous fluid to pass through the entire length of the dispenser body
26
prior to being dispensed by the nozzle
30
. That long and tortuous fluid flow path not only adds resistance to motion of the armature
50
and valve stem
36
in the viscous fluid, but in addition, the flow rate of the viscous fluid through the dispenser
20
may also be adversely impacted.
In the operation of an electric viscous fluid dispensing gun, the coupling between the coil and the armature is not efficient; and therefore, the electric coil of an electric dispensing valve normally is not capable of providing the same forces as a pneumatic solenoid. That fact in combination with the above described structural features in which the coil
52
and the pole
56
provide a weaker electromagnetic field and the armature
50
, valve stem
36
and valve body
38
experience a greater resistance to motion, makes the valve construction of
FIG. 4
unacceptable for many viscous fluid dispensing applications.
Therefore, there is a need to provide a more efficient and higher performance design for an electric dispensing gun of the “snuff-back” valve body design as described above.
SUMMARY OF INVENTION
The present invention provides an improved electric fluid dispenser for viscous fluids that is faster, more reliable and can be used in a wider range of fluid dispensing applications than known electrically operated viscous fluid dispensers. Further, the electrically operated fluid dispenser of the present invention is simpler in construction, less expensive to manufacture and has a longer useful life than known electrically operated viscous fluid dispensers.
In accordance with the principles of the present invention and the described embodiments, the invention in one embodiment provides a fluid dispensing apparatus for dispensing a viscous fluid from a source of viscous fluid onto a substrate. The dispensing apparatus includes an electrically operated, normally-opened, dispensing valve having an inlet in fluid communication with the source of fluid and a shut-off valve fluidly connected between the inlet of the dispensing valve and the source of viscous fluid. The shut-off valve has a normally-closed state interrupting fluid communication between the source of fluid and the inlet of the dispenser body. The shut-off valve is used to disconnect the dispensing valve from the source of viscous fluid when power is removed from the valves.
In one aspect of the invention, the dispensing valve has a valve body disposed downstream of a valve seat within a dispenser body. An armature is connected to the valve body, and an electrically operated coil is mounted adjacent the armature. The coil generates an electromagnetic field that moves the valve body into sealing contact against the valve seat, thereby preventing a flow of fluid from the dispensing valve. A biasing element biases the valve body in a downstream direction toward an open position; and in an absence of the electromagnetic field, the biasing element moves the valve body to an open position permitting the flow of viscous fluid from the dispensing apparatus.
In another aspect of the invention, a control provides a first signal to the dispensing valve to close the dispensing valve and a second signal to the shut-off valve to open the shut-off valve. In the absence of the first signal, the dispensing valve opens, and in the absence of the second signal, the shut-off valve closes. Thus, the dispensing valve is closed and opened by the control respectively applying and removing the first signal to the coil of the dispensing valve. The shut-off valve is opened by the second signal; however, if at any time power is removed from the control, the second signal is removed from the shut-off valve and the shut-off valve closes, thereby disconnecting the dispensing valve from the source of viscous fluid.
The electrically operated dispensing apparatus of the present invention has a substantially simpler structure that provides a stronger electromagnetic field and has less friction than known electric dispensing valves. Thus, the use of a normally-opened dispensing valve has the advantages of providing a more efficient, higher performance and higher quality fluid dispensing operation.
During a fluid dispensing cycle, the normally-opened dispensing valve is turned on and off at a frequency or rate that is appropriate for a particular application. In contrast, the shut-off valve is typically opened at the start of the fluid dispensing cycle and closed at the end of the fluid dispensing cycle. The shut-off valve is also closed in response to a user initiated or control initiated shut-down command. Thus, the shut-off valve is not required to be a high performance valve but instead, is a simple, inexpensive valve. Further, with its nominal performance requirements, the shut-off valve does not require a complex or expensive valve driver. Consequently, the addition of the simple shut-off valve and its valve driver in combination with the generally simpler structure of the normally-opened valve results in little, if any, additional cost to the dispensing apparatus.
The normally-opened valve of the present invention has a further advantage in those applications in which the valve, on average, is open more than it is closed. Energy is applied to the normally-opened valve only during the time that the valve is closed. Thus, heat dissipation in the normally-opened valve is limited and less than normally-closed valves, and the normally-opened valve has the advantage of being able to operate at a higher frequency without overheating. Therefore, the electrically operated dispensing valve of the present invention is simpler, less expensive and more reliable than known electric dispensing valves.
Various additional advantages, objects and features of the invention will become more readily apparent to those of ordinary skill in the art upon consideration of the following detailed description of embodiments taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
is an axial cross-sectional view of an electrically operated fluid dispenser having a “snuff-back” valve body design in an opened position in accordance with the principles of the present invention.
FIG. 2
is an axial cross-sectional view of the electrically operated fluid dispenser of
FIG. 1
illustrating the “snuff-back” valve in a closed position.
FIG. 3
is an axial cross-sectional view of the electrically operated fluid dispenser of
FIG. 1
illustrating the “snuff-back” valve in the opened position and a check valve in a closed position.
FIG. 4
is an axial cross-sectional view of a known electrically operated fluid dispenser having a “snuff-back” body valve design.
DETAILED DESCRIPTION OF THE INVENTION
Referring to
FIG. 1
, an electrically operated viscous fluid dispenser or dispensing gun
120
of the “snuff-back” design is illustrated which has generally similar components to the dispenser
20
of FIG.
2
. The dispensing gun
120
of
FIG. 1
comprises one or more dispensing modules or valves
122
mounted on a fluid distribution manifold plate
124
. Each dispensing valve
122
includes a dispenser body
126
and a fluid dispensing nozzle body
128
with a nozzle
130
through which droplets
132
of the viscous fluid are dispensed onto a substrate
134
. Relative motion between the substrate
134
and dispenser
120
is provided in a known manner.
A fluid inlet passageway
142
intersects the interior portion
144
of the dispenser body
126
and is connected to a fluid passage
146
in the manifold
124
which, in turn, is in fluid communication with a pressurized source of hot melt adhesive
148
. Arrows
149
indicate the flow path of the fluid entering through the fluid inlet passageway
146
and through the interior portion
144
of the dispenser body
126
. The dispenser
120
dispenses high viscosity fluids, such as a hot melt adhesive, but other dispensed fluids can benefit from the invention as well. Such other fluids include soldering fluxes, thermal greases, heat transfer compounds and solder pastes. Furthermore, the dispenser
120
is mounted in a dispensing machine or system (not shown) in a known manner to dispense fluids in discrete amounts, preferably as droplets or dots, but alternatively in continuous beads.
An armature
150
is disposed within the interior portion
144
and is coaxially aligned with, and is often formed integrally with, a valve stem
136
. The valve stem
136
extends downward past the valve seat
140
and has a valve body
138
on its lower, distal end below or downstream of a valve seat
140
. An electromagnetic coil
152
is disposed about the armature
150
. A biasing element
154
, for example, a spring, is disposed in a bore
160
within the valve stem
132
. The biasing element
154
biases the valve stem
136
and valve body
138
in a downstream, downward direction away from the valve seat
140
to an open position as shown in
FIG. 1
, thereby opening the valve
122
and permitting the flow of viscous fluid through the nozzle
130
. The biasing element
154
is often a compression spring which is placed under compression within the bore
160
by the armature
150
. The downward stroke of the valve body
138
can be controlled one of several different ways. For example, a stop
155
is located in the lower interior portion of the nozzle body
128
and functions to limit the downward travel of the valve body
138
. Thus, as the biasing element
154
pushes the valve toward an open position away from the valve seat
140
, an end surface
139
strikes an upper portion of the stop
155
; and the stop
155
supports the valve body
138
in the open position. The viscous fluid then flows from the source
148
, past the valve seat
140
into the interior of the nozzle body
128
, through openings
157
in the stop
155
and out the nozzle
130
.
When supplied with electrical current, the coil
152
generates an electromagnetic field. The electromagnetic coil
152
must generate a sufficiently strong electromagnetic field between the armature
150
and the pole
156
so as to attract the armature
150
and the pole
156
together. Since the pole
156
cannot move, the armature
152
moves against the force of the biasing element
154
, thereby moving the valve body
138
in an upward, upstream direction to a closed position as illustrated in
FIG. 2
at which the valve body
138
sealingly contacts the valve seat
140
, thereby interrupting the flow of viscous fluid through the nozzle
130
.
The design of the dispensing valve
122
of
FIGS. 1 and 2
is known as a normally-opened design for the reason that when the coil
152
is de-energized, the biasing element
154
functions to move the valve body
138
in a downstream direction out of contact with the valve seat
140
, thereby opening the valve
122
as shown in FIG.
1
. Thus, the valve
122
is normally in, or defaults to, an open state or position. Hence, in the event of any electrical failure, the valve
122
is mechanically biased to the open position and the viscous fluid is dispensed from the outlet nozzle
130
. Obviously any uncommanded or inadvertent dispensing of the viscous fluid is undesirable. To avoid such a condition, a normally-closed shut-off valve
164
is placed in fluid communication between the normally-opened dispensing solenoid valve
122
and the source of viscous fluid
148
. During normal operation of the normally-opened solenoid valve
122
, power is a applied to the normally-closed shut-off valve
164
, thereby maintaining the shut-off valve open. However, in the event of a loss of electrical power, as the dispensing valve
122
biases itself to the open position, the shut-off valve
164
is simultaneously biasing itself to its closed position, as shown in
FIG. 3
, thereby interrupting the flow of viscous liquid from the source
148
to the valve
122
. The shut-off valve
164
is often a solenoid valve in which a valve element
166
is biased against a valve seat
168
by a biasing element or spring
170
. Such a solenoid valve is commercially available as model no. E100AC from Slautterback Corporation of Monterey, Calif.
In use, whenever power is applied to a control
172
, the control
172
provides a signal over output line
171
to energize a solenoid
174
of the normally-closed shut-off valve
164
causing the solenoid
174
to electromagnetically move the valve element
166
away from the valve seat
168
as shown in FIG.
1
. When the valve element
166
moves away from the valve seat
168
, fluid from the source of fluid
148
flows through an inlet passage
176
, past the valve seat
168
, through an outlet passage
180
and into the inlet passages
146
,
142
of the manifold
124
and valve
122
, respectively. Thus, with the shut-off valve
164
open, the dispensing valve
122
is fluidly connected to the source of fluid
148
.
Upon power being applied to a control
172
, the control
172
further provides a signal over output line
173
to apply power to, and energize, the magnetic coil
152
. The electromagnetic field generated by the coil
152
secures the valve body
138
in sealing contact with the valve seat
140
, as shown in
FIG. 2
, thereby maintaining the valve
122
closed. In the closed state, viscous fluid is not dispensed from the source of fluid
148
to the substrate
134
via the nozzle
130
. When it is desired to dispense viscous fluid from the valve
122
, the control
172
terminates the signal on output
171
to the coil
152
, thereby causing the magnetic field to collapse. The biasing element
154
is then able to move the valve body
138
downward away from the valve seat
140
(FIG.
1
), and the viscous fluid is dispensed from the source of fluid
148
and through the outlet
130
onto the substrate
132
. Subsequently, when it is desired to terminate the viscous fluid dispensing operation, the control
172
again provides power to the coil
152
, thereby energizing the coil
152
and creating an electromagnetic field that pulls the valve body
138
back into contact with the valve seat
140
(FIG.
2
). That process continues in the process of dispensing fluid in a desired pattern onto the substrate. Thus, during a fluid dispensing cycle, the normally-opened dispensing valve
122
is turned on and off at a frequency or rate that is appropriate for a particular application.
Referring to
FIG. 3
, if at any time power is removed from the control
172
, either predictably, by turning off the power, or unpredictably, through a system component failure, a tripped circuit breaker, accident, storm, etc., the signals on the output lines
171
,
173
from the control
172
are terminated. Thus, power to the coil
152
is lost, and the electromagnetic field collapses, thereby permitting the biasing element
154
to move the valve body
138
to its open position (FIG.
1
). Without the shut-off valve
164
, fluid would immediately begin dispensing from the valve nozzle
130
. Any such uncommanded and unintentional dispensing of viscous fluid is very undesirable; however, such is prevented by the operation of the shut-off valve
164
. When power is lost to the control
172
, the electrical signal from the control
172
to the shut-off valve
164
is also lost. Therefore, the electromagnetic field produced by the solenoid
174
within the shut-off valve
164
collapses; and the biasing element
170
moves the valve element
166
into sealing contact with the valve seat
180
, thereby closing the shut-off valve
164
. Thus, as the dispensing valve
122
is being biased to an open position by its biasing element
154
, the valve element
166
within the shut-off valve
164
is simultaneously being biased to its closed position by its biasing element
170
. The operation of the normally-closed valve
164
moving to its default closed position interrupts the flow of viscous fluid from the source of fluid
148
to the valve
122
and limits or eliminates any flow of viscous fluid from the nozzle
130
.
The structure of the electric dispensing valve
122
of
FIGS. 1-3
has many advantages over the design of the known electric dispensing valve shown in FIG.
2
. First, the structure is substantially simpler in that the armature
150
is disposed below the pole
156
. Such a construction permits the use of a larger pole, thereby increasing the strength of the electromagnetic field over the cored pole
56
of FIG.
4
. The valve stem
136
and armature
150
of the dispensing valve
122
experience less friction from the viscous fluid than similar components in the design of FIG.
4
. Further, with the dispensing valve
122
of
FIGS. 1-3
, the flow path of the viscous fluid within the dispensing valve
122
is shorter, thereby further reducing the frictional effect of the viscous fluid. In addition, with the dispensing valve
122
of
FIGS. 1-3
, there is less wetted area, and the formation of char is less likely. Finally, the mass of the valve stem
136
is less and requires less electromagnetic force to move than the dispensing valve stem
36
of FIG.
4
. Thus, the use of a normally-opened dispensing valve has the advantages of providing a more efficient, higher performance and higher quality fluid dispensing operation.
In contrast to the higher performance, normally-opened valve
122
, the shut-off valve
164
is typically opened at the start of the fluid dispensing cycle and closed at the end of the fluid dispensing cycle or in response to a user or control initiated shut-down command. Thus, the shut-off valve is a simple, inexpensive valve. Further, with its nominal performance requirements, the shut-off valve does not require a complex or expensive valve driver. Consequently, the addition of the simple shut-off valve and valve driver in combination with the generally simpler structure of the normally-opened valve results in little, if any, additional cost to the dispensing apparatus.
The normally-opened valve of the present invention has a further advantage in those applications in which the valve, on average, is open more than it is closed. Energy is applied to the normally-opened valve only during the time that the valve is closed. Thus, heat dissipation in the normally-opened valve is limited and less than normally-closed valves, and the normally-opened valve has the advantage of being able to operate at a higher frequency without overheating. Therefore, the electrically operated dispensing valve of the present invention is simpler, less expensive and more reliable than known electric dispensing valves.
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail in order to describe a mode of practicing the invention, it is not the intention of Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. For example, the shut-off valve
164
is shown as a normally-closed valve located between the manifold
124
and the source of fluid
148
. As will be appreciated, the shut-off valve
164
can be located anywhere that permits it to perform its shut-off operation. For example, the shut-off valve
164
may alternatively be built into the valve
122
, the manifold
124
or the source of fluid
148
.
Further, while the shut-off valve
164
is shown and described as an electric solenoid valve, a pneumatically actuated valve may alternatively be used. In fact, any valve may be used that provides a normally-closed valve action in the event that electrical power to the system is turned off or lost. In addition, the relative orientation of the shut-off valve
164
can be reversed over that shown in
FIGS. 1-3
, so that the passage
180
is an inlet connected to the source of fluid
148
and the passage
176
is an outlet connected to the passage
146
.
Therefore, the invention in its broadest aspects is not limited to the specific detail shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.
Claims
- 1. A fluid dispensing apparatus for receiving a viscous fluid from a source and dispensing the viscous fluid onto a substrate comprising:an electrically operated, normally-opened dispensing valve having an inlet for receiving the viscous fluid and an outlet for dispensing the viscous fluid onto a substrate; and a shut-off valve fluidly connected between said inlet of said dispensing valve and the source of viscous fluid, said shut-off valve having a normally-closed state interrupting fluid communication between the source of the viscous fluid and said inlet of said dispensing valve.
- 2. The fluid dispensing apparatus of claim 1 wherein said dispensing valve comprises:a dispenser body having a valve seat; a valve body positioned downstream of said valve seat; an armature connected to said valve body; an electrically operated coil mounted adjacent said armature and generating an electromagnetic field capable of moving said valve body into sealing contact against said valve seat, thereby preventing a flow of fluid from said outlet; and a biasing element for biasing said valve body to an open position in an absence of the electromagnetic field, thereby permitting the flow of viscous fluid from the dispensing apparatus.
- 3. The fluid dispensing apparatus of claim 2 wherein said shut-off valve comprises:a body having a valve seat, an inlet for receiving the viscous fluid from the source and an outlet in fluid communication with said inlet of said dispensing valve; a valve stem positioned upstream of said valve seat; an electrically operated coil mounted adjacent said valve stem and generating an electromagnetic field capable of moving said valve stem to an open position, thereby providing a flow of the viscous fluid from the source to said dispensing valve; a biasing element for biasing said valve stem to a closed position in an absence of the electromagnetic field, thereby preventing a flow of the viscous fluid from said shut-off valve and said dispensing valve; and a control providing a first signal to said dispensing valve to close said dispensing valve, and a second signal to said shut-off valve to open said shut-off valve, wherein, in the absence of the first signal, said dispensing valve opens and, in the absence of the second signal, said shut-off valve closes.
- 4. The fluid dispensing apparatus of claim 1 wherein said shut-off valve comprises:a body having a valve seat, an inlet for receiving the viscous fluid from the source and an outlet in fluid communication with said inlet of said dispensing valve; a valve stem positioned upstream of said valve seat; an electrically operated coil mounted adjacent said valve stem and generating an electromagnetic field capable of moving said valve stem to an open position, thereby providing a flow of the viscous fluid from the source to said dispensing valve; and a biasing element for biasing said valve stem to a closed position in an absence of the electromagnetic field, thereby preventing a flow of the viscous fluid from said shut-off valve and said dispensing valve.
- 5. The fluid dispensing apparatus of claim 4 further comprising a control providinga first signal to said dispensing valve to close said dispensing valve; and a second signal to said shut-off valve to open said shut-off valve, wherein, in the absence of the first signal, said dispensing valve opens and, in the absence of the second signal, said shut-of valve closes.
- 6. The fluid dispensing apparatus of claim 1 further comprising a control providinga first signal to said dispensing valve to close said dispensing valve; and a second signal to said shut-off valve to open said shut-off valve, wherein, in the absence of the first signal, said dispensing valve opens and, in the absence of the second signal, said shut-off valve closes.
- 7. A fluid dispensing apparatus for receiving a viscous fluid from a source and dispensing the viscous fluid onto a substrate comprising:a dispenser body having a valve seat, an inlet for receiving the viscous fluid and an outlet for dispensing the viscous fluid onto a substrate; a valve body positioned downstream of said valve seat; an armature connected to said valve body; an electrically operated coil mounted adjacent said armature and generating an electromagnetic field capable of moving said valve body in an upstream direction into sealing contact against said valve seat, thereby preventing a flow of fluid from said outlet; a biasing element for biasing said valve body in a downstream direction to an open position in an absence of the electromagnetic field, thereby permitting the flow of the viscous fluid from the dispensing apparatus; and a shut-off valve fluidly connected between said inlet of said dispenser body and the source of fluid, said shut-off valve having a normally-closed position interrupting fluid communication between the source of fluid and said inlet of said dispenser body.
- 8. A fluid dispensing apparatus for dispensing viscous fluid from a source of fluid onto a substrate comprising:a dispenser body having a valve seat, an inlet in fluid communication with the source of fluid and an outlet downstream of said valve seat; a valve stem disposed within said dispenser body and having a valve body on its distal end positioned downstream of said valve seat; an armature disposed within said dispenser body and connected to a proximal end of said valve stem; an electrically operated coil mounted adjacent said armature and generating an electromagnetic field capable of moving said armature and said valve stem in an upstream direction to a closed position in which said valve body is sealingly engaged against said valve seat, thereby preventing a flow of fluid from said outlet; a biasing element disposed within said dispenser body for biasing said armature, valve stem and valve body in a downstream direction to an open position in an absence of the electromagnetic field, thereby permitting the flow of viscous fluid from said outlet; and an electrically operated shut-off valve fluidly connected between said inlet of said dispenser body and the source of fluid, said shut-off valve having a normally-closed state interrupting fluid communication between the source of the viscous fluid and said inlet of said dispenser body.
- 9. A method of operating a fluid dispensing apparatus to dispense a viscous fluid from a source onto a substrate comprising:applying electric power to a normally-closed shut-off valve receiving the viscous fluid from the source to open said shut-off valve and provide a path for the viscous fluid through said shut-off valve; removing electric power to a normally-opened dispensing valve receiving the viscous fluid from said shut-off valve to open said dispensing valve and dispense the viscous fluid onto the substrate; and closing said normally-closed shut-off valve in response to a loss of electric power to said dispensing valve, thereby interrupting a flow of the viscous fluid through said shut-off valve, through said dispensing valve and onto the substrate.
- 10. A method of operating a fluid dispensing apparatus receiving a viscous fluid from a source and dispensing the viscous fluid onto a substrate comprising:providing a first signal to a normally-closed shut-off valve fluidly connected to the source, thereby causing said shut-off valve to open; providing an electric signal to an electrically operated, normally-opened dispensing valve having an inlet receiving viscous fluid from said shut-off valve, thereby causing said normally-opened dispensing valve to close; removing the electric signal from said normally-opened dispensing valve, thereby causing said normally-opened dispensing valve to open; and removing the first signal from said normally-closed shut-off valve, in response to a loss of electric power to said normally-opened dispensing valve, thereby causing said normally-closed dispensing valve to close.
- 11. A method of operating a fluid dispensing apparatus to dispense a viscous fluid from a source onto a substrate comprising:opening a normally-closed shut-off valve having an input fluidly connected to the source in response to the application of a signal to said shut-off valve, thereby passing the viscous fluid to through said shut-off valve; selectively opening and closing a normally-opened dispensing valve having an input fluidly connected to an output of said shut-off valve in response to the removal and application, respectively, of an electric signal to said dispensing valve, thereby selectively dispensing the viscous fluid onto the substrate when said dispensing valve is open; closing said normally-closed shut-off valve in response to a loss of electric power to said dispensing valve, thereby terminating a flow of the viscous fluid through said shut-off valve and said dispensing valve.
- 12. The method of claim 11 further comprising:moving a valve body located downstream of a valve seat within said normally-opened dispensing valve in a downstream direction to an open position in response to a removal of the electric signal from said dispensing valve; and moving said valve body in an upstream direction to a closed position in response to an application of the electric signal from the dispensing valve.
- 13. The method of claim 11 further comprising:moving a valve stem located upstream of a valve seat within said normally-closed shut-off valve in an upstream direction to an open position in response to the application of the signal to said shut-off valve; and moving said valve stem in a downstream direction to a closed position in response to a removal of the signal from said shut-off valve.
- 14. The method of claim 11 further comprising opening said normally-closed shut-off valve in response to the application of a second electric signal to said shut-off valve.
US Referenced Citations (7)