Information
-
Patent Grant
-
6273345
-
Patent Number
6,273,345
-
Date Filed
Friday, February 11, 200025 years ago
-
Date Issued
Tuesday, August 14, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Scherbel; David A.
- Kim; Christopher S.
Agents
- Greer, Burns & Crain, Ltd.
- Lorenzen; John M.
- Janci; David F.
-
CPC
-
US Classifications
Field of Search
US
- 239 418
- 239 422
- 239 427
- 239 428
- 239 433
- 239 419
- 239 4193
- 239 424
- 239 4175
- 239 4233
- 239 4275
- 239 423
- 239 407
- 239 290
- 239 296
-
International Classifications
-
Abstract
A slurry spray machine for spraying a settable slurry includes a main passageway configured for receiving a supply of pressurized slurry and having a supply end and an outlet end opposite the supply end. A first compressed gas inlet is disposed intermediate the supply and outlet ends and in fluid communication with the passageway for introducing a first supply of pressurized gas into the slurry, and a second pressurized gas inlet is disposed closer to the outlet end than the first inlet and in fluid communication with the passageway for introducing a second supply of pressurized gas into the slurry. A pressurized supply of adjuvant is provided in fluid communication with the second pressurized gas inlet for providing a blended gas to the second gas inlet. At least one valve is provided for controlling the flow of slurry through the passageway and the flow of the first and second gases into the passageway. Prior to the pressurized ejection of the slurry from the outlet end, the first gas is injected into the slurry, and the blended gas is mixed with the slurry and the first pressurized gas between the first gas inlet and the outlet end.
Description
BACKGROUND OF THE INVENTION
The present invention relates to machines for spraying slurries of settable substances such as plaster or gypsum cement, and more specifically, to an improved spray machine suitable for spraying the slurry upon a vertical surface so that the slurry sets quickly.
In industrial, architectural and tooling applications, such as the fabrication of molds for the construction of large fiberglass or plastic items such as boat hulls, it has been contemplated to create a master form out of a sprayable plaster, also known as calcium sulfate hemihydrate composition. Unlike prior sprayable plaster slurries, the present slurry composition may have relatively high viscosity and/or high cohesiveness, and is preferably formulated to be readily machinable so that once sprayed and set upon the substrate, the form can be shaped using conventional machining tools.
However, in developing a suitable spray apparatus for achieving this goal, it has been found that conventional systems for spraying plaster are unsuitable for this application. Conventional plaster slurry spray machines utilize spray gun designs such as pole guns which are unwieldy and lack the necessary precision, are designed for spraying paint or resin and are typically internal mix designs.
More specifically, conventional spray machines employ simple peristaltic or progressive cavity pumps fed by a drum or other type of slurry storage/mixing container. The slurry is pumped and delivered to an atomizing device (“spray gun”) which range from an internally atomized to an externally atomized device which breaks up the slurry with compressed air. It is known in such devices to incorporate so-called chopper guns, which are fed a supply of rope-like fiberglass roving, and chop the roving into fibers which are then incorporated into the slurry to add strength.
It is also known in such devices to inject a stream of accelerant (also referred to herein as “accelerator”) into the slurry to reduce the set time once the slurry is sprayed on the substrate. If the accelerant is injected internally (within the gun), it has been found that the slurry begins to prematurely set inside the gun, causing clogging and interfering with cleaning of the spray apparatus. Such systems require frequent maintenance to remove any buildup of set particles. Externally supplied accelerants have been found to supply a non-uniform distribution of accelerant to the slurry stream, causing spotty plaster set times. In such cases, the resulting product has an uneven appearance and cannot be worked as rapidly as desired.
A design criterion of such systems is that peristaltic pumps are typically used. However, a drawback of such a system is that the slurry is delivered in a pulsating flow which is not uniform. This causes difficulties for both the operator and the uniform integration of accelerant or chopped fiberglass into the plaster slurry stream. Progressive cavity pumps deliver slurry at a constant rate, but are expensive and difficult to clean and maintain.
Further, conventional slurry spray systems are equipped with ball valves, which are prone to plaster build-up and premature failure. Lastly, conventional slurry spray systems do not provide the user with the ability to finely control slurry output.
Accordingly, there is a need for a spray apparatus configured for spraying a settable slurry such as a plaster slurry, which is relatively low maintenance, hinders clogging caused by premature setting of the slurry, yet provides for the incorporation of an accelerant into the slurry, which provides for a relatively uniform or constant output of slurry and which provides for a relatively finite output adjustability controlled by the user.
Thus, it is a first object of the present invention to provide an improved slurry spray apparatus which incorporates an accelerant into the slurry without internal clogging, and so that the accelerant is generally uniformly distributed in the slurry.
Another object of the present invention is to provide an improved slurry spray apparatus which emits or ejects the slurry at a relatively constant rate to achieve a more uniform sprayed substrate.
A further object of the present invention is to provide an improved slurry spray apparatus in which the component parts such as pumps and valves are designed to accommodate the unique characteristics of plaster slurries for efficient industrial applications.
A still further object of the present invention is to provide an improved slurry spray apparatus which features a pneumatically operated control and valve system for operator safety and for more controllable output of the sprayed slurry.
BRIEF SUMMARY OF THE INVENTION
The above-listed objects are met or exceeded by the present high performance slurry spray machine, which features an applicator or spray gun having two points of atomization by compressed air. The first atomization point introduces compressed air into the slurry to increase its spray ability. A second atomization point is preferably located at the slurry spray outlet of the spray gun, and achieves two goals. First, the slurry is still further atomized, for a more even application. Second, the accelerant is vaporized and blended with compressed air at the second atomization point to prevent in-gun clogging while providing a more uniform distribution of accelerant in the sprayed slurry. Specially designed manifolds and outlet nozzles are provided for atomizing the slurry and for mixing the vaporized and atomized accelerant with the main slurry flow. An open-topped slurry container coupled to a positive displacement pump provide constant feed flow of this type of slurry.
Another feature of the present spray apparatus is the inclusion of a dampening device in applications where a pulsating-type pump is employed. The dampener evens out the flow pulses, and is designed to be used with the somewhat abrasive and sometimes relatively viscous plaster slurries. Pneumatically controlled pinch valves are used throughout the apparatus to prevent the clogging through plaster buildup inherent with conventional ball valves.
More specifically, the present invention provides a slurry spray machine for spraying a settable slurry includes a main passageway configured for receiving a supply of pressurized slurry and having a supply end and an outlet end opposite the supply end. A first compressed gas inlet is disposed intermediate the supply and outlet ends and in fluid communication with the passageway for introducing a first supply of pressurized gas into the slurry, and a second pressurized gas inlet is disposed closer to the outlet end than the first inlet and in fluid communication with the passageway for introducing a second supply of pressurized gas into the slurry. A pressurized supply of adjuvant is provided in fluid communication with the second pressurized gas inlet for providing a blended gas to the second gas inlet.
At least one valve is provided for controlling the flow of slurry through the passageway and the flow of the first and second gases into the passageway. Prior to the pressurized ejection of the slurry from the outlet end, the first gas is injected into the slurry, and the blended gas is subsequently mixed with the combined slurry and the first pressurized gas.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1
is a partial schematic of the present high performance slurry spray system;
FIG. 2
is a partial schematic of the slurry spray system depicted in
FIG. 1
;
FIG. 3
is a diagrammatic side elevational view of the applicator or spray gun used in the system of
FIGS. 1 and 2
;
FIG. 4
is an end view of the nozzle used with the applicator of
FIG. 3
;
FIG. 5
is a vertical sectional view of the dampener depicted schematically in FIG.
1
.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to
FIG. 1
, the present high performance slurry spray system is generally designated
10
and is designed for spraying settable slurries, such as plaster or gypsum cement slurries in industrial applications. The present apparatus is particularly suitable for applying a thin coating of slurry upon a generally vertical substrate, and achieving a relatively uniform appearing and setting layer. The system
10
includes a slurry mixing and storage tank
12
suitably dimensioned for retaining a supply of slurry. In the present system, it is preferred that alpha or beta calcium sulfate hemihydrate or plaster slurry is used, however other compositions are contemplated, for example slurries containing a mixture of alpha and/or beta calcium sulfate hemihydrate and other non calcium sulfate hemihydrate slurries such as portland cement blends (sometimes referred to as a gypsum cement), or magnesium phosphate cement formulations, depending on the application. It is also preferred that the mixing and storage tank
12
be made of a lightweight, water and corrosion resistant, sturdy material such as rigid plastic. However, other equivalent materials are contemplated, including stainless steel, fiberglass and aluminum. It is also preferred that the tank
12
have an open top
13
to facilitate pouring of ingredients and for exposure to atmospheric pressure, and a conical or tapered bottom to facilitate complete drainage. It has been found that an open-topped tank facilitates uniform slurry flow rates, especially when coupled to a positive displacement pump, as described below.
A mixing motor
14
with an impeller
16
is provided and mounted relative to the tank
12
so that the impeller can engage the slurry in the tank. In the preferred embodiment, the impeller has two sets of blades,
17
and
17
a
. The first set
17
is located at a tip of the impeller, and the second set
17
a
is located approximately midway up the length of the impeller, and preferably about 4 to 5 inches below the level of liquid in the tank
12
. It is preferred that the mixing motor
14
be at least of 5 HP capacity, and that the motor and the impeller
16
are mounted to a powered lift
18
for easy loading of the slurry ingredients, and easy cleaning of the tank
12
. The lift
18
is configured so that the mixing motor
14
and the impeller
16
may be vertically withdrawn from, or inserted into, the tank
12
.
Plaster or gypsum cement slurry is mixed in a plastic tank by means of either an automated weighing process (i.e. load cells), or by a manual batching process, as is known in the art. Also, using known technology, automated mixing/cleaning cycles are also controlled via electromechanical methods.
An outlet
20
of the tank
12
is in fluid communication with a valve
22
, which in the preferred embodiment is a pneumatically operated pinch valve. While other types of slurry control valves are also contemplated for use with the present system
10
, pinch valves are preferred because they do not become clogged with set plaster. Instead, upon entering the valve, the slurry flows through a rubber tube which is surrounded by a pressurized canister. By selective application of pressure, in the preferred embodiment pneumatic pressure, the flow of slurry through the hose can be controlled. Such valves are known in the art, and because of their superior qualities for the present application, have been incorporated into all valving locations of the present system
10
which are potentially exposed to the slurry.
Downstream of the valve
22
is a pump
24
, which is in fluid communication with the valve
22
and the tank
12
. While a variety of pumps are contemplated for use with the present system, including, but not limited to gear pumps, piston pumps, diaphragm pumps, and progressive cavity pumps, the preferred type of pump in the system
10
is a positive displacement pump, specifically a peristaltic pump, and particularly a high-pressure type using a lubricating bath of glycerin to the internal stator hose. A variable speed DC motor (not shown) supplies power to the pump. Although it emits a pulsating output flow, the moving parts of the peristaltic pump do not become exposed to the settable slurry. A suitable commercial example of a preferred type of pump is the DL Series of pumps manufactured by PCM POMPES, 17 rue Ernest Laval —BP 35, 972173 Vanves Cedex, France. The preferred pump
24
has a minimum flow rate of 84 tons/hr, a maximum flow rate of 20 m3/hr and a speed of between 5 to 133 rpm. In the preferred embodiment, an outlet
25
of the pump is configured as a quick connect fitting which is easily disconnected and allows the connection of a garden hose into the system for flushing purposes. Another suitable pump is a progressive cavity positive displacement pump manufactured by Moyno Products, Fluids Handling Division, Robbins & Meyers, Inc., Springfield Ohio. It has been found that the combination of the tank
12
with the open top
13
, and the positive displacement pump
24
provided with a dampener as described below has resulted in a generally uniform flow rate of plaster slurry.
The purpose of the pump
24
is to pressurize the slurry in the system, and as acknowledged above, a drawback of peristaltic pumps is the pulsating output flow. If left untreated, this type of flow would result in an uneven flow of slurry upon the substrate, which would be undesirable in the type of targeted industrial application, i.e., the fabrication of large forms for fiberglass or other types of plastic molding. Accordingly, one feature of the present system is to provide a mechanism for dampening the pulses generated by the pump
24
in a way which will be suitable for use with the present type of settable slurry.
Referring now to
FIGS. 1 and 5
, an accumulator, surge suppressor or dampening device
26
which is suitable for use with the present system
10
operates under a similar principle as a pinch valve, and includes an inner flexible or rubber-like bladder or tube
28
which is in fluid communication with the pump
24
, the valve
22
and the tank
12
. A rigid, elongate cylindrical jacket
30
surrounds the tube
28
, and is provided with flanged ends
32
,
34
which are also sealingly coupled to ends of the tube. It is contemplated that the ends of the tube
28
may be sealingly secured to the flanged ends
32
,
34
by chemical adhesive, threaded fasteners and clamps, combinations of the above, or other known fastening technologies. In this manner, a chamber
35
is created about the tube
28
. This sealed coupling allows for the introduction of pressurized gas (preferably air) through a pressurized air inlet
36
into the sealed chamber
35
. Sufficient pressurized air is introduced from a compressor
38
into the cylindrical jacket
30
to regulate the flow pulses generated by the pump
24
. The compressor
38
is preferably capable of providing 100 psi of air @ 30 CFM.
It is contemplated that the volume of pressurized air retained by the jacket
30
may vary with the application. It is also contemplated that other types of apparatus may be provided which employ pneumatic pressure to equivalently dampen the pulses of pressure in the pump output line, as does the dampener
26
. It is further contemplated that the cylindrical jacket
30
will be of sufficient length to enable the pneumatic pressure to sufficiently dampen the pressure surges produced by the pump
24
. A spray applicator or spray gun
40
(best seen in
FIG. 3
) is placed in fluid communication with the flow of slurry emitted from the dampener
26
, preferably through a braided or otherwise reinforced plastic hose
41
connected to a main pinch valve
42
.
Another main component of the system
10
is a pressurized accelerant holding tank
44
into which is inserted a supply of accelerant for accelerating or hastening the setting time of the gypsum plaster slurry. Although a variety of known accelerants are contemplated, a preferred accelerant in the present system
10
is liquid aluminum sulfate and water. For other accelerants, see copending application U.S. Ser. No. 09/502,609 filed concurrently herewith for Efficient Catalyst for the Set Acceleration of Spray Applied Plaster, which is incorporated by reference herein. Also, depending on the application of the system
10
, other adjuvants beside accelerant can be introduced into the slurry flow.
Known slurry spray systems inject accelerant in the interior of the spray gun, which leads to premature setting of at least some slurry particles, and clogging of the gun. Another known system injects accelerant fluid externally into the slurry. However, an undesirable result of this approach is uneven setting of the plaster on the substrate through uneven distribution of the accelerant into the slurry.
In the present system, the accelerant is pressurized in the tank
44
, passed through a regulator
46
and is in fluid communication with an accelerant pinch valve
48
located in close operational proximity to the spray gun
40
. As will be described in further detail below, the pressurized accelerant is mixed with additional pressurized gas (preferably compressed air) to the point where the accelerant is vaporized. The vaporized accelerant is then introduced to the slurry, preferably at the point where the slurry is emitted from the spray gun
40
. Thus, a uniform distribution of accelerant is obtained, and its introduction adjacent the outlet of the spray gun
40
solves both of the problems of prior systems. It is also contemplated that the accelerant may be alternately introduced in pressurized form through a liquid pressure pot or through an open tank with a mechanical pump, both of which are considered to be equivalent to the pressurized holding tank
44
.
Referring to
FIGS. 1 and 2
, for operator safety and simplified maintenance, the present system
10
is pneumatically controlled through a main pneumatic control box
49
. Included in the control box
49
is a manifold
50
to which is connected the main supply of compressed air from the compressor
38
through a conventional ball valve
52
. Also connected to the manifold
50
is a pressure regulator
54
which is connected, through a pilot valve
56
to a first air supply inlet
58
on the spray gun
40
. The inlet
58
is also known as the pre-atomization air inlet.
A second regulator
60
is connected through the pilot controlled pinch valve
48
to an air inlet
64
known as the atomization inlet of the spray gun
40
. If the accelerant is provided from a paint-type pressure tank, as the holding tank
44
, then the pinch valve
48
is preferably a fine pitched needle valve for regulating the flow of pressurized accelerant fluid. Also connected to the manifold
50
is a check valve
66
which is connected to a pilot valve
68
operating the pinch valve
48
, and also connected to an accumulator
70
through a flow control valve
72
. The pilot valve
68
is also connected through a flow control valve
72
a
to a main slurry control pinch valve
42
on the spray gun
40
. The accumulator
70
maintains a designated pressure on the pilot valve
56
as is known in the art, and also is connected through the pilot valve
68
, to the pump
24
through a shuttle valve
74
, and to a FROM port
76
on a trigger valve
78
located on the spray gun
40
.
If desired, a third pilot valve
80
may be connected to an optional fiberglass roving chopper
82
for providing a source of ground fiberglass fibers to the slurry. A push button valve
84
is connected to the shuttle valve
74
to allow the operator to manually operate the pump
24
during clean-out or purging cycles. Otherwise, the pump would only be activated when the trigger valve
78
on the spray gun was actuated. Also connected to the manifold
50
is a third pressure regulator
86
which is connected to an IN port
87
on the trigger valve
78
. A toggle valve
88
is connected to the tank pinch valve
22
,
A fourth pressure regulator
90
is connected to the pulse dampener
26
, and a fifth regulator
92
is connected to the accelerator holding tank
44
to maintain pressure on the accelerant. Lastly, a toggle valve
94
controls the lift mechanism
18
for the mixer motor
14
. In this manner, the manifold
50
controls operational pneumatic flow throughout the system
10
.
Referring now to
FIG. 3
, the spray gun
40
is depicted, and in the preferred embodiment, is based on a prior design produced by ES Manufacturing, Inc. of St. Petersburg, Fla., in which the plaster slurry was merely externally atomized by compressed air. The present spray gun
40
is designed to be used with all slurry viscosities, but most particularly, with very low viscosities, and at high volume outputs, especially when the slurry is cohesive (sticky). Included on the spray gun
40
is a handle
100
having a vertically extending chopper bracket
102
onto which is clamped a main slurry passageway or tube
104
by at least one U-clamp
106
. In the preferred embodiment, the U-clamp
106
is fastened to the bracket
102
by threaded fasteners such as hex nuts (not shown), however other types of conventional fastening technologies are contemplated.
The main slurry tube
104
has an inlet or supply end
108
to which is connected, and in fluid communication with, the main slurry pinch valve
42
. Opposite the supply end
108
is an outlet end
1
10
, to which is secured a nozzle
112
. It is contemplated that the outlet end
110
may have many configurations, including straight and in line with the passageway
104
, in the preferred embodiment, the outlet end
1
10
gradually and slightly narrows toward the nozzle
112
to facilitate the creation of a uniform spray pattern.
Downstream of the main pinch valve
42
is the air supply inlet
58
, which is configured as a halo fitting configured for circumscribing the main passageway
104
. In addition, the inlet
58
is in fluid communication with the main passageway
104
via a ring of accurately spaced forwardly angled (toward the outlet end
110
), first compressed gas inlet openings
116
for introducing a flow of compressed gas (preferably air from the compressor
38
) into the main passageway. This fitting
58
is also known as the preatomizing point, because the compressed air that is introduced here is forced into the main slurry flow to atomize it and make it easier to spray. To seal the air flow into the passageway
104
, a pair of O-rings
118
are disposed on either side of the ring of openings
116
. As will be seen from
FIG. 3
, the halo fitting
58
is disposed generally intermediate the supply end
108
and the outlet end
110
. The compressed air that is introduced into the halo fitting
58
is controlled by the pneumatic pilot pinch valve
56
(best seen in FIG.
2
).
Another feature of the present spray gun
40
is that it introduces two sources of compressed gas (air) into the slurry to properly atomize the slurry for improved spray performance. As described above, the first introduction of compressed gas occurs at the halo fitting
58
. A second pressurized gas inlet
120
is disposed closer to the outlet end
110
than is the halo fitting
58
and is placed in relation to the passageway
104
for introducing a second supply of pressurized gas into the slurry. In the preferred embodiment, the second gas inlet
120
is linearly displaced from the halo fitting
58
, however other dispositions are contemplated.
Yet another feature of the present system
10
is that the second inlet
120
is also the point at which the accelerant from the accelerant holding tank
44
is introduced in vaporized form, into the slurry. By introducing the accelerant adjacent the nozzle
112
, the accelerant does not actually enter the passageway
104
, and thus the clogging problem of prior art spray applicators is solved. While the preferred position of the second inlet
120
is adjacent the outlet end
110
and the nozzle
112
, it is contemplated that, if the problem of premature slurry setting can be addressed, the second inlet may be positioned along the passageway
104
and closer to the halo fitting
58
so that the blended gas (accelerant and compressed air) is mixed with the combination of the slurry and the pressurized gas between the first inlet and the outlet end.
In shape, the second inlet
120
is preferably integrally cast, molded or formed with the handle
100
, and is configured to circumscribe the passageway
104
, and provides a second attachment point of the passageway
104
to the spray gun
40
. In the preferred embodiment, a threaded fastener
122
is provided for anchoring the outlet end
110
of the passageway
104
to the spray gun
40
.
The second pressurized air inlet
120
is placed in fluid communication with a supply of pressurized, so-called external preatomization air from the compressor
38
. An inlet
124
in the spray gun
40
is in fluid communication with the air supply from the compressor
38
. An air passageway
126
in the handle
100
provides a fluid conduit between the inlet
124
and the second inlet
120
. Intermediate the inlet
124
and the second inlet
120
is the accelerant inlet
64
which receives pressurized accelerant from the holding tank
44
and is controlled by the pneumatic pinch valve
48
(best seen in FIG.
2
). Thus, prior to reaching the second inlet
120
, the compressed air and accelerant from the holding tank
44
is mixed or blended with additional external atomization air from the compressor
38
. In this manner, the accelerant is vaporized so that it is more uniformly dispersible in the slurry.
Alternatively, it is also contemplated that the accelerant fluid may be introduced to the slurry spray at the nozzle
112
using a device known in the industry as a “catalyst injection device”, a suitable example of which is manufactured by ITW-Binks Manufacturing Co. of Franklin Park, Ill. Such a device includes an accelerator tank holding accelerator fluid, which may be pressurized, like the holding tank
44
. Compressed air, which will be used as the external air of atomization to be fed to the halo fitting
58
, passes over a venturi, creating a vacuum which draws accelerator fluid from the tank. Flow from the venturi is monitored by a metering device as is known in the art.
The accelerator is vaporized into the stream of compressed air, after which it is carried through a reinforced hose to the spray gun
40
entering at point
124
(FIG.
3
). This alternative construction is considered substantially equivalent to the preferred system described above, and is preferred when using viscous accelerants. Yet another alternative is to introduce a relatively viscous accelerant, such as described in commonly assigned, co-pending U.S. patent application Ser. No. 09/502,609 filed concurrently herewith entitled Efficient Catalyst for the Set Acceleration of Spray Applied Plaster and incorporated by reference, through a mechanical pump, such as a piston, diaphragm or other type of metering pump directly to the spray gun
40
at point
64
. It is also contemplated that, when slurries of other constituents, such as portland cement or magnesium phosphate products, it could be introduced at the first air supply inlet
58
.
Referring now to
FIGS. 3 and 4
, the second inlet
120
is provided with a plurality of diametrically spaced, inclined air jets
130
which receive the vaporized accelerant and dispense it from the nozzle
112
adjacent a main slurry outlet
132
. In the preferred embodiment, the main slurry outlet
132
is located at the outlet end
110
of the passageway
104
. The air jets
130
are preferably disposed in spaced, surrounding relationship to the main slurry outlet
132
, which is of a relatively larger diameter than the jets
130
. In this manner, the vaporized accelerant can be more evenly distributed in the slurry. In the preferred embodiment, the nozzle
112
is configured with a pair of inclined walls
134
so that the air jets
130
impact the slurry flow on an angle. As is the case with the inlet
58
, the inlet
120
is provided on either side with an O-ring
136
.
The trigger valve
78
is provided on the handle
100
of the spray gun
40
and is placed in fluid communication with the pneumatic control manifold
50
(best seen in FIG.
2
). In the preferred embodiment, the trigger valve
78
is a plunger or piston type known in the art, and a suitable model is No. G
300-001
produced by E.S. Manufacturing of St. Petersburg, Fla. The trigger valve
78
has a knurled outer boss
138
integrally affixed to a threaded nipple portion
140
which threadably engages a threaded bore (not shown) in the handle
100
. An O-ring
142
maintains an air seal at that connection. A main body
144
of the valve
138
defines an axial chamber (not shown) in which reciprocates a poppet
146
. An outer end
148
of the poppet
146
serves as the trigger which is actuated by the operator. In combination with the O-ring
142
, a relatively smaller O-ring
150
on the main body
144
isolates the outlet
76
. Two additional O-rings
154
on the poppet
146
pneumatically isolate the poppet. In a normally closed position, air pressure from the compressor
38
forces a small end
156
of the poppet against the valve body
144
where it is pneumatically sealed by the adjacent small O-ring
154
.
To emit slurry, the incoming air
87
from the pressure regulator
86
and the air exiting from the regulator
86
provides the pneumatic pressure to operate the pilot valve
68
. Upon depression of the trigger
148
, the regulator
86
is placed in fluid communication with the pilot valve
68
. Air is fed to the trigger valve
78
through an air inlet
158
located on the handle
100
of the spray gun
40
, and is emitted from the outlet port
76
to a gun outlet
160
and into the manifold
50
to initiate flow of slurry.
Referring to
FIG. 3
, if desired, the system
10
may be equipped with the chopper attachment or chopper gun
82
for introducing chopped fiberglass roving fibers into the slurry stream. The incorporation of such fibers is intended to increase the strength of the set plaster. Such attachments are known in the art, and are pneumatically operated. In the system
10
, the chopper attachment
82
is preferably mounted to the chopper bracket
102
, and is connected to the pneumatic control box
48
so that it is operated by the pilot valve
80
. Once mounted, the chopped fiberglass fibers are combined with the slurry externally of the passageway
104
as is known in the art.
Referring now to Table 1, a list of actual system performance parameters is provided, along with physical slurry data. The plaster mixture entry is a mixture of calcium sulfate hemihydrate, an internal binder which is preferably a free flowing, water redispersable polymer powder such as polyethylene glycol and an adhesive binder, A more detailed disclosure of the plaster mixture is found in copending application U.S. Ser. No. 09/502,740 filed concurrently herewith for Machinable Plaster Composition, which is incorporated by reference herein.
The data indicates that approximately 21-23 pounds of slurry are sprayed per minute at a pump speed of about 40-45%. The pump speed is controlled by a variable speed DC motor (not shown) which in turn is controlled by an AC to DC converter/controller (not shown). Since the converter/controller provides variable DC output to the pump motor in increments measured as a percentage, that is why the speed is indicated as a percentage in Table 1. In Table 1, the dampener
26
is pressurized to 20 psi, the accelerator holding tank
44
is pressurized to about 40-42 psi, the accelerator flow rate is approximately 3 lbs./min, and is proportional to a slurry flow rate of 21 lbs./min. For these examples, the gun nozzle pressure at the inlet
120
was between 68 and 80 psi and the pre-atomization pressure at the first inlet
58
was approximately 100 psi.
In one example, prior to being sprayed the slurry had a consistency of 30 cc, referring to 100 parts by weight of plaster mixture in 30 parts by weight of clean, potable water. In actuality, the slurry mix resulted from a mixture of 150 lbs of sprayable, machinable plaster mixture, 45 lbs of water and a mix time of 10 minutes. In the second example, 250 lbs of plaster mixture, 75 lbs of water and a mix time of 12.5 minutes was employed.
TABLE 1
|
|
Trial 1
Trial 2
|
|
|
Pump Speed (%)
40.00
45.00
|
Slurry Delivery Rate (lbs./min.)
21.00
23.00
|
Pulse Dampener Pressure (PSI)
20.00
20.00
|
Accelerator Tank Pressure (PSI)
40.00
42.00
|
Accelerator Flow Rate (%)
50.00
50.00
|
Gun Nozzle Aspiration (PSI)
80.00
68.00
|
Gun Pre-atomization [Burp] (PSI)
100.00
100.00
|
Slurry Consistency (CC)
30.00
30.00
|
Plaster mixture 200 (lbs.)
150.00
250.00
|
Water (lbs.)
45.00
75.00
|
Mix Time (min.)
10.00
0.52
|
|
Referring now to Table 2, pump speed vs. slurry output is indicated, and demonstrates that as pump speed is increased, slurry output generally increased, however at higher speeds, the slurry output did not increase as dramatically.
TABLE 2
|
|
PUMP SPEED VS. SLURRY OUTPUT
|
Pump Speed
Slurry Delivery
Pulse Dampener
|
(%)
Rate (lbs./min.)
Pressure (PSI)
|
|
40.00
21.00
20.00
|
60.00
30.00
20.00
|
80.00
37.50
20.00
|
100.00
42.00
20.00
|
|
In operation, a supply of slurry is provided to the mixing tank
12
and stirred by the impeller
16
. When the operator wants to initiate slurry and accelerator flow, the trigger
148
is depressed axially against the system pressure, placing the air flow to the trigger valve
138
in communication with the outlet
152
. The outlet
152
is then in fluid communication with the manifold
50
, and will operate the various pinch valves commence the flow of slurry through the pump
24
, the dampener
26
and to the spray gun. Simultaneously, compressed air is fed from the compressor
38
to the halo fitting
58
, to the accelerator holding tank
44
, and to the gun inlet
124
for blending with the accelerant.
Thus, the slurry is first mixed with a preatomizing air at the halo fitting
58
to initially increase flowability. Next, the vaporized accelerant is blended into a second source of compressed air prior to ejection or emission as a blended gas into the slurry. In the preferred embodiment, this blended gas is introduced into the slurry at the nozzle
112
. In this manner, the accelerant is more evenly distributed in the slurry, and spray gun clogging is prevented. The present system
10
also features the use of the dampener
26
with the positive displacement peristaltic pump
24
to provide a relatively uniform flow of slurry. The open-topped tank
12
also provides an atmospheric pressure environment for slurry mixing and loading, which further facilitates relatively uniform flow rates. Upon completion of the spraying process, the tank
12
can be filled with water and flushed through the system
10
.
While a particular embodiment of the present high performance slurry spray machine has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.
Claims
- 1. A slurry spray applicator for spraying a settable slurry, comprising:a main slurry passageway configured for receiving a supply of pressurized slurry and having a supply end and an outlet end opposite said supply end; a first compressed gas inlet disposed intermediate said supply and outlet ends and in fluid communication with said slurry passageway for introducing a first supply of pressurized gas into the slurry, said inlet includes a fitting with a plurality of apertures connected to said slurry passageway for introducing said first pressurized gas into said passageway; a second pressurized gas inlet disposed closer to said outlet end than said first inlet and disposed in relation to said slurry passageway for introducing a second supply of pressurized gas into the slurry; a pressurized supply of adjuvant in fluid communication with said second pressurized gas inlet for providing a blended gas to said second gas inlet; valve means for controlling the flow of slurry through said passageway and the flow of said first and second gases into said slurry passageway; said applicator being constructed and arranged so that prior to the pressurized ejection of the slurry from said outlet end, said first gas is injected into the slurry, and said blended gas is subsequently mixed with the combined slurry and said first pressurized gas.
- 2. The applicator as defined in claim 1 wherein said second gas inlet is adjacent said outlet end so that said blended gas contacts the slurry upon ejection from said outlet end.
- 3. The applicator as defined in claim 1 further including a nozzle at said outlet end of said passageway configured for defining a spray pattern of said ejected slurry.
- 4. The applicator as defined in claim 3 wherein said nozzle includes a main slurry aperture and at least one aperture of relatively smaller diameter surrounding said main slurry aperture configured for dispensing said blended gas and being in fluid communication with said second pressurized gas inlet.
- 5. The applicator as defined in claim 1 wherein said fitting is a halo fitting.
- 6. The applicator as defined in claim 1 further including a container for supplying the slurry, and a pump for receiving the slurry from said container and pumping the slurry to said inlet end of said passageway.
- 7. The applicator as defined in claim 6 further including a mixer in said container for mixing the slurry.
- 8. The applicator as defined in claim 6 wherein said pump generates a pulsating flow of the slurry, and said machine further includes a slurry dampener in fluid communication with said passageway and being located between said pump and said inlet end for dampening slurry flow surges produced by said pump.
- 9. The applicator as defined in claim 8 wherein said dampener includes a tubular flexible bladder surrounded by a jacket of compressed air.
- 10. The applicator as defined in claim 1 wherein said adjuvant is an accelerant for accelerating the setting of the slurry, and said blended gas is introduced into said passageway at a location near said outlet end so that the slurry will not set within said passageway.
- 11. The applicator as defined in claim 1 wherein said valve means includes a main valve for controlling the flow of the slurry in said passageway, a blended gas control valve for controlling the flow of said blended gas into said passageway and a main gas control valve for controlling the flow of said first gas into said passageway.
- 12. The applicator as defined in claim 11 wherein at least one of said valves is a pinch valve.
- 13. The applicator as defined in claim 1 further including control means for controlling said valve means for controlling the ejection of the slurry, said first gas and said blended gas from said outlet end.
- 14. The applicator as defined in claim 13 wherein said valve means controlled by said control means include a main valve, a main gas control valve, a blended gas control valve and a trigger valve.
- 15. The applicator as defined in claim 13 wherein said control means and said valve means are pneumatically operated.
- 16. A machine for spraying settable slurries, comprising:a container configured for storing a supply of a settable slurry; a pump in fluid communication with said container for pressurizing the slurry; an applicator with a main slurry passageway in fluid communication with said container for receiving a supply of the pressurized slurry and having a supply end and an outlet end opposite said supply end; a first compressed gas inlet disposed intermediate said supply and outlet ends and in fluid communication with said slurry passageway for introducing a first supply of pressurized gas into the slurry, said inlet includes a fitting with a plurality of apertures connected to said slurry passageway for introducing said first pressurized gas into said passageway; a second pressurized gas inlet disposed closer to said outlet end than said first inlet and disposed in relation to said passageway for introducing a second supply of pressurized gas into the slurry; a supply of accelerant in fluid communication with said second pressurized gas inlet for providing a blended gas to said second gas inlet; valve means for controlling the flow of slurry through said passageway and the flow of said first and second gases into said passageway; control means for controlling said valve means; said machine being constructed and arranged so that said first gas is injected into the slurry prior to the pressurized ejection of the slurry from said outlet end, and said blended gas is subsequently mixed with the slurry and said first pressurized gas.
- 17. The machine as defined in claim 16 wherein said container has an open top.
- 18. The machine as defined in claim 16 wherein said pump generates a pulsating flow of the slurry, and further including dampening means in fluid communication with said pump to dampen said pulsating flow.
- 19. The machine as defined in claim 18 wherein said dampener includes a tubular flexible bladder surrounded by a jacket of compressed air.
- 20. The machine as defined in claim 16 wherein said second gas inlet is adjacent said outlet end so that said blended gas contacts the slurry upon ejection from said outlet end.
- 21. The machine as defined in claim 16 further including a chopper attachment associated with said applicator for chopping a supply of fiberglass roving and injecting said fibers into the slurry.
US Referenced Citations (9)