Continuously energized electrostatic coating voltage block

A continuously energized electrostatic spray coating system sends measured masses of highly conductive coating material across an insulating air space from a grounded pulser to a high voltage container. A series of such continuously energized voltage blocks have their output connected to a manifold which is alternately supplied paint from one of the voltage blocks by remote control.

BACKGROUND OF THE INVENTION 
1. Field Of The Invention 
The present invention relates to an electrostatic spray coating system and 
more particularly to electrostatic spray coating systems for applying 
conductive coating materials such as water base paints. 
2. Description Of The Prior Art 
In the past years the applicant of the invention herein described designed 
and placed on the market automatic electrostatic spray coating systems for 
spraying high conductive coatings such as porcelain enamel frit in a water 
carrier wherein the entire spray coating system including the entire 
supply system was electrically isolated from ground. 
Such a system is disclosed in U.S. Pat. No. 3,463,121 issued Aug. 26, 1969, 
U.S. Pat. No. 3,621,815 issued Nov. 23, 1971, and U.S. Pat. No. 3,637,420 
issued Jan. 25, 1972. Although such a system advanced the art, it could 
not have its main coating material supply reservoir filled while the high 
voltage was being applied to the system and it could not be utilized for 
manual spray systems for the operator would be touching components charged 
to the high voltage utilized in such systems. 
Voltage blocks have been developed which consists of a jain supply source 
or first continaer which is used to fill a second container. A third 
container at high voltage receives conductive coating material from the 
second container at times when no material is flowing fro the first to the 
second container. These systems have the disadvantage that arcing will 
occur if insulated conduit is used between the first and second containers 
because of residual material on the conduit surfaces. Pouring from a 
transportation drum or container as the grounded first container 
eliminates this arcing, but there still remains three required sub-systems 
which are the first at ground, the second or intermediate alternately at 
ground or high voltage, and the third at high voltage. Further, these 
three container or three sub-system supply systems can not be utilized for 
manual electrostatic spray systems for the operator would be touching 
components charged to high voltage. 
SUMMARY OF THE INVENTION 
The present invention overcomes these difficulties by providing an 
electrostatic spray coating system wherein highly conductive spray coating 
material is transferred from a grounded container or circulating system 
across an air space to a high voltage supply sub-system which in turn 
delivers coating material which has now become highly charged to one or 
more electrostatic spray coating spray guns. The closest spacing between 
the two sub-systems and the intermediate masses of coating material are so 
adjusted that the high voltage is prevented from arcing across the air 
insulation space through the individual masses to the grounded supply 
sub-system. 
It is therefore an object of the present invention to provide a new and 
improved spray coating system for spraying highly conductive coating 
material. 
Another object is to provide an electrostatic spray coating system which 
has two coating supply sub-systems separated from each other by an air 
space through which masses of conductive coating materials are ejected, 
the masses being small enough in comparison to the air space to prevent 
arcing between the grounded sub-system and the high voltage supply 
sub-system. 
An additional object is to provide a selected multicolor supply system 
having a voltage block for each color in the system wherein the high 
voltage components are all continuously charged to high voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
While this invention is susceptible of embodiment in many different forms, 
there will be described herein in detail embodiments of the invention with 
the understanding that the present disclosures are to be considered as 
exemplifications of the principles of the invention and are not intended 
to limit the invention to the embodiments illustrated. The scope of the 
invention will be pointed out in the appended claims. 
Referring to FIG. 1 the paint supply and mix area 10 has five paint 
containers 11-15 mounted therein and electrically grounded. The containers 
may be tanks of any size which are compatible with the needs of a 
particular system. Each container has a pump 16-20 connected thereto to 
receive paint or other coating material. An electrically grounded paint 
circulating line 21-25 is connected to the output of each respective pump 
16-20. When no paint is being removed from the respective lines 21-25 the 
pumps 16-20 continuously circulate paint through the lines. When paint is 
being removed from the lines the respective pump replenishes the paint in 
the line from the respective containers 11-15. In a typical operation, 
tanks 11-14 and therefore lines 21-24 respectively each contain a 
difficult color of highly conductive paint or coating material. Container 
15 and therefore line 25 contains a paint solvent. The pumps 16-20 are of 
any suitable design well known to those skilled in the art. 
Referring now to FIG. 2 in addition to FIG. 1, each circulating lines 21-25 
has a solenoid valve 26-30 connected thereto to remove paint from each 
circulating line by line pressure and/or the force of gravity when the 
respective valve is opened. A plastic paint cannister 31-35 is mounted 
below each respective solenoid valve 26-30. The valves 26-30 and the 
cannisters 31-35 are mounted adjacent a spray booth generally indicated at 
100, which has a normal exhaust stack 101. The circulating lines 21-25 
together with the valves 26-30, the paint supply containers 11-15, and 
pumps 16-20 comprise an electrically grounded paint sub-supply system. The 
cannisters 31-35, each of which is separated by an air space from the 
respective valve 26-30, together with the elements which will presently be 
described, form a high voltage coating material supply sub-system which 
receives coating material through the air space and delivers it to one or 
more electrostatic spray guns. The cannisters 31-35 have conduits 36-40 
respective connected at their bottoms to be gravity fed. The conduits 
36-40 are each connected to an intake port of a coating material pump 
41-45, which may be of any conventional design well known in the art. A 
discharge port of each pump 41-45 is connected to a remote controlled 
three-way valve 81-85 respectively. The valves 81-85 are connected to a 
general supply manifold 102 having an output port 103. 
Level sensing devices 51-55 are electrically connected by respective leads 
56-60 to timers 61-65 respectively. The timers 61-65 are connected to 
actuating coils 66-70 of the solenoid valves 26-30 respectively by a pair 
of electrical leads 71-80 to alternatively energize and de-energize coils 
66-70. Timers 61-65 provides activation signals of a predetermined length 
to coils 66-70 spaced by de-energization of the coils 66-70 for a 
predetermined length as long as the timers 61-65 are energized by signals 
from the respective sensing devices 51-55. 
The level sensing devices 51-55 may be made of any conventional design well 
known to those skilled in the art which detects an upper or full level as 
indicated by the solid line on the cannister and a lower or refill level 
as indicated by the dashed lines in the cannisters 31-35. They may be of 
the float level switch type wherein a pair of electrical contacts are 
closed when the fluid in a cannister reaches the lower level to provide an 
energizing signal to the respective timers 61-65 until the upper level is 
reached, at which point the actuating signal is terminated. As a further 
example the two level sensing device which controls the respective timers 
can be of the weighing type wherein an electrical signal is set to a 
respective timer whenever the cannister becomes lighter than a 
predetermined low value and terminates said signals when the cannister 
reaches a heavier or predetermined full weight. 
Each three-way valve 81-85 has a port connected by a respective return line 
86-90 respectively to the respective cannisters 31-35. 
The cannisters 31-35, pumps 41-45, valves 81-85, and the manifold 102 are 
mounted on an electrically insulating support structure generally 
indicated at 104. A plastic shield generally indicated at 105 surrounds 
the structure to prevent operator contact. The manifold 102 has a flexible 
fluid hose 106 connected either to one or more manual or automatic spray 
guns, such as 107. A high voltage power supply 108 is connected by a lead 
109 to an electrode 110 on the gun 107. 
The operation of the preferred embodiment of the invention illustrated in 
FIGS. 1 and 2 will now be described. Highly conductive coating material of 
four different colors are placed in paint containers 11-14 respectively. 
Container 15 is filled with a solvent. These containers are part of the 
grounded sub-supply system. They may be refilled at any time regardless of 
whether high voltage is being applied to the electrode 110 and thereby to 
highly conductive coating material in the gun 107, the flexible hose 106, 
and the manifold 102. The pumps 16-20 are then turned on, filling the 
electrically grounded coating material recirculating lines 21-25 
respectively. When high voltage power supply 108 is energized, an 
actuation circuit for the timers 61-65 is also activated. The level 
sensing devices send electrical signals to start the timers 61-65. With 
timers 61-65 operating periodic activation of solenoid valves 26-30 are 
accomplished by the series of signals of predetermined length provided 
from the timers 61-65 respectively. Therefore valves 26-30 open long 
enough to emit a measured quantity of highly conductive coating material 
which transfers the air space to cannisters 31-35 by pressure and/or the 
force of gravity. The time between the actuation signals generated by 
timers 61-65 is of sufficient length that the space between the sequential 
measured masses of coating material from the valves 26-30 are sufficiently 
spaced that an arc will not traverse the air space through the coating 
material masses from the cannister or its contents, to the grounded valves 
26-30. The sensing devices 51-55 electrically isolate their operating 
elements from the respective electrical leads 56-60 so that the high 
voltage material supply sub-system does not short to ground. 
When the level of the coating material in any of the cannisters 31-35 
reaches the upper predetermined level, respective level sensing device 
terminates its signal deactivating and stopping the respective timers 
61-65. Since no actuation signals are now being sent from the timer to the 
respective solenoid coil, its valve remains closed. When the system is in 
operation the pumps 41-45 run continuously and the three-way valves 81-85 
are set to return the output of the pumps to the respective cannisters 
31-35 in order that there is a continual circulation of paint from the 
pump to the valve, to the cannister, and back to the pump. 
The operator through the remote controls (not shown) turns on valve 81 
filling the manifold 102 and the flexible hose 106 with the highly 
conductive coating material received from container 11. Spray gun 107 is 
now operated in the normal manner receiving highly conductive coating 
material through the flexible hose 106. Since the coating material as it 
is sprayed is in contact with electrode 110 the entire body of coating 
material contained in the gun 107, the hose 106, the manifold 102, valve 
81, pump 41, and cannister 31, are all charged to high voltage. As the 
coating material in cannister 31 is used up the level will fall to the 
lower predetermined level and the level sensing device 51 will start timer 
61 ejecting measured masses of conductive coating material sequentially 
from valve 26 under pressure and/or the force of gravity. If the pressure 
in the circulating lines is extremely low the force of gravity may be a 
significant factor in the size of the sequential masses of coating 
material relative to the time the valve is open. As the operating pressure 
is increased, the pressure provided by the respective pumps 16-20 will be 
the significant factor in the time the valve is open to eject each mass. 
The pumps 41-45 could be energized only when their respective valves are 
open to manifold 102, but it has been found desirable to continually 
recirculate coating material by such recirculating methods. 
When it is desirable to change to another color, valve 51 is closed to 
manifold 102 and valve 55 is opened to allow solvent to enter the manifold 
102, the hose 106, and the gun 107. After the solvent has cleared the 
coating material from these elements, valve 55 is closed and another valve 
is opened to manifold 102 to provide a new color for spraying the next 
group of work. Thus there is a continual flow of coating material of any 
given selected color without turning off the high voltage. Further colors 
can be varied and solvents may be utilized to flush the high voltage 
supply sub-system without turning off the high voltage power supply. 
Referring now to FIG. 3 a modified form of the invention illustrated in 
FIGS. 1 and 2 utilizes a single pump in the high voltage sub-system and 
eliminates the individual cannisters recirculating system. While this 
modification is relatively economical in original construction and its use 
of electrical power for the pumps, it does have the relative disadvantage 
of lacking continuous recirculation through the valves. The portion of the 
grounded sub-system which is not shown is similar to that illustrated in 
FIG. 1. Similar elements to those illustrated in FIGS. 1 and 2 which 
perform the same functions are identified by the same number prime ('). 
Grounded recirculating lines 21'-25' are connected to solenoid valves 
26'-30' and operating in the same manner as its corresponding components 
illustrated in FIG. 1. A set of tanks 31'-35' perform the same functions 
as the cannisters 31-35 in receiving masses of coating material ejected 
from the valves 26'-30' by the circulating line pressure aided the force 
of gravity. A set of level sensing devices 51'-55', a set of electrical 
leads 56'-60', a set of timers 61'-65' and electrical leads 71'-81' are 
connected and operate in the same manner as the corresponding elements in 
FIGS. 1 and 2. The tanks 31'-35' are connected directly to a set of valves 
81'-85' which are gravity fed by a set of conduits 46'-50'. Instead of 
having the pumps between the tanks or cannisters and the manifold valves 
in the high voltage sub-system, the tanks are connected directly to the 
valves and a single pump 120 is connected to the discharge of valves 
81'-85' as illustrated in FIGS. 1 and 2. Thus when one of the valves 
81'-85' is opened, material will flow from one of the tanks 31'-35' into 
the manifold 102', which, being connected to the suction side of pump 120, 
will have coating material transferred through the flexible conduit 106' 
to the gun 107'. The gun 107' like the gun 107 may be of the film 
electrode type described in detail in U.S. Pat. No. 3,774,844 issued Nov. 
27, 1973, or described in U.S. Pat. No. 3,746,253 issued July 17, 1973. In 
addition it may be of any one of the types commonly known in the art which 
has a metal electrode. If the gun is a manual gun rather than an automatic 
electrostatic spray gun, then the gun and the connecting cables should be 
of the protective construction fully described in the two aforementioned 
U.S. Patents. A high voltage power supply 108' is connected to ground by 
a lead 111' and has its high voltage terminal connected by a lead 109' 
directly to the highly conductive coating material in the tanks 31'-35'. 
The high voltage is then carried to the electrode, whether it be the 
atomizing fluid edge or a separate metallic electrode through the coating 
material flowing through the valves 81'-85', the manifold 102', and the 
flexible conduit 106'. 
The valves 81'-85' are actuated by remote control (not shown), which may be 
of any conventional mechanical or electrical design, to select a 
particular color or a washing solvent as before described without the 
necessity of securing the high voltage system. It will be understood by 
those skilled in the art that various combinations of automatic or manual 
electrostatic spray guns, various combinations of protective flexible 
conduit and various points of connection of the high voltage power supply 
may be made in the high voltage supply sub-system without departing from 
the scope of the present invention. 
Many other modifications may be made by those skilled in the art without 
departing from the basic invention disclosed herein. For example, the 
solenoid valve 26 could be replaced by a pump which delivers measured 
quantities of coating material through an output port and timer 61 could 
be replaced by a clock which merely issues spaced signals to the measuring 
pump. Under such circumstances, each measured mass of coating material 
will be propelled under pressure and may be propelled not only vertically, 
but horizontally, or at any angle therebetween through the air space to 
the receiving cannister.