CA1074100A - Airless spray apparatus - Google Patents

Abstract

ABSTRACT
A fluid spraying apparatus, such as for use in paint spraying and the like, including a high pressure diaphragm pump, a safety and pressure adjustment valve system, and a high pressure safety spray gun. The valve system includes a valve for maintaining a desired pressure relationship be-tween the sprayed fluid side of the system and the pumping fluid section of the high pressure diaphragm pump. The high pressure safety gun includes a pressure-responsive locking barrel portion which prevents access to the spray tip while the fluid being sprayed is under pressure.

Description

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This application is a division of application 265, 941, filed ~ovember 17, 1976.
The parent application is concerned with a high pressure diaphragm pump with a safety and pressure adjustment valve system. ~Iydraulic section pressure is used to control or unload the driven fluid side of the system.
In the past many injuries have occurred while the driven fluid section of an airless spraying unit was pressureized, even after the power to the motor was disconnected, from an operator attempting to perform maintenance on the unit, ana therefore there has been a need for means for automatically de-pressurizing the driven fluid section of the system.
The present invention relates to a spray gun apparatus suitablefor use with such a pump.
A fluid dispensing gun having some pressure-responsive valve stem movement is shown in United States Patent ~o. 3,410,491 to Malec. Malec, ho~ever, does not disclose a safety gun mechanism responsive to pressure as set forth herein.
According to the present invention there is provided a spray gun apparstus comprising: a spray gun body; means for coupling pressurized fluid to a spray chamber and sn auxiliary chsmber in communica~ion with the spray-ing chamber in the sprsy gun body; nozzle means for select:ively dispersingfluid from the spray chamber; a cover member, threadedly received on a nozzle end of the spray gun body, including a plurality of circumferentially arrayed recesses; a plunger member, slidably received within an end of said auxiliary chamber, having a rear portion acted upon by the pressure in the auxiliary chamber and having a front pin portion operable to be received within one of said recesses when the auxiliary chamber is pressurized moving the plunger to sn end of the auxiliary chamber; and return means for moving the plunger from the end of the chsmber and retracting the pin portion from said recess - 1 - ~ ';

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when the auxiliary and spraying chambers are depressurized.
In the accompanying drawings, which illustrate a diaphragm pump as well as an exemplary embodiment of the present invPntion:
Figure 1 is a diagrammatic vertical cross-sectional view through a pump apparatus;
Figure 2 is a side view of a portion of the apparatus of Figure l;
and Figure 3 is a diagrammatic cross-sect~onal view of a spray gun according to the present invention.
Referring in particular to Figure 1, there is shown a diaphragm pump 11. Pump ll comprises a casing 12 and an eccentric bearing 13 driven by shaft 14 and a motor (not shown). A pumping chamber 17 is defined between a diaphragm 16 and pump body member 19 which is rigidly attached to housing 12. A pumping chamber 18 for hydraulic fluid or the like is defined by dia-phragm 16 and cylinder 27 and piston 26.
Fluid to be sprayed such as paint is supplied from a container, positioned below pump 11, through inlet line 21. A check valve 22 is pro-vided in line 21 to permit flow of the liquid only into chamber 17. The pressurized paint is discharged through an outlet check valve 25 including checX b~ll 23 in line 24 to a supply hose (not shown) which couples the pressurized liquid to a connector such as 25 of the spray gun of Figure 3. -~
As shall be described hereinafter, the spray gun has a control val-.e ~^hrot-tling or completely stopping flow from the pumping chamber 17.
Diaphragm 16 is axially moveable with driving pressure intermit-tently applied and relieved by means of hydraulic ~luid in chamber 18. This driving pressure is provided by a piston pump generally identified as 28 and including a cylindrical chamber 27 slideably receiving a cylindrical piston 26 driven by eccentric drive bearing 13 rotated by a driving motor (not

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shown).
The eccentric bearing 13 rotates in housing 12 for the driving fluid ?9, Driving fluid 29 communicates with the driving fluid pressure chamber 18 behind the diaphragm 16 by means of an overflow passage 31 con-taining an adjustable pressure limiting valve 35 and also by means of a re-fill passage 36. Adjusting valve 35 has a threadedly received control knob which determines the spring force with which needle 33 is held in the end of passageway 31. A return opening 34 to the sump is provided for hydraulic fluid flowing from pumping chamber 18 through passage 31 and past needle 33.
When the pumping chamber pressure exceeds that set by knob 32, hydraulic fluid returns to the sump by way of passages 31 and 34.
A refill passage 36 and a refill slot 37 in the cylindrical chamber 27 are provided. The slot 37 is uncovered by the piston 26 only at the end of the suction stroke of the piston and is otherwise closed by the piston 26.
Any loss of driving fluid by leakage past the piston 26 is replenished on each driving stroke through the refill slot 37 and refill passage 36 commu-icating with the liquid 2S in the sump. The housing 12 is partially filled with the driving fluid 29 to a~ldriving level as indicated at 38, and the top of the chamber is vented to the atmosphere by means of a relief valve 39.
A spring 41 urges the piston 26 against the eccentric bearing 13.
The eccentric bearing 13 drives the piston 26 through a predetermined dis-tance, and this reciprocation of the piston drives the fluid 29 in pumping fluid chamber 18 ahead of the piston forcing the diaphragm 16 to flex. This results in the pumping of the driven fluid in chamber 17 with liquid being drawn in through line 21 and check valve 22 on an upstroke of piston 26 and with liquid being forced out through line 42, check valve 25 and line 24 on a down stroke of piston 26.
Also during operation of the pump, fluid flows through a groove 20 .: . .

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and passage 43 unseating ball 44 of check valve 46. Pumping ~luid then flows through line 4~, tube 48 (Figure 2), and to plunger 49 which contains seal 51 to prevent further passage of the hydraulic fluid. The pl-mger is balanced by a spring 52, and if the hydraulic pressure exceeds the spring force of spring 52, the plunger 49 moves toward seat 54, needle 53 of plung-er 49 closing the opening in seat 54. The opening in seat 54 communicates with the pumped fluid output line 24 and with the pumped fluid container through a bypass line 56, which allows pumped fluid moving past the opening in seat 54 to return to the driven fluid container. When needle 53 closes the opening in seat 54, pressure builds up proportionally, and the difference in area (between the head of needle 53 in the opening in seat 54 being acted upon by the pumped fluid pressure and the rear portion of plunger 49 being acted upon by the hydraulic fluid pressure) prevents the unseating of needle 53 of plunger 49 from the opening in seat 54 during normal operation of the pump.
Only if the pressure is adjusted at adjustable valve 35 to the minus side, lowering the hydraulic fluid pressure, will the needle of the plunger disengage from seat 54 to release enough liquid from line 24 to keep the pressure in proportion. In operation, the operating pressure for the hydraulic fluid section is determinea by the setting of valve 35. Once the pressure in pumping fluid chamber 18 exceeds the pressure that is set with ad~ustable valve 35, needle 33 unseats providing a return path for the hydraulic fluid to the sump through opening 34. If the pressure at valve 35 is aajusted toward the minus side, the force exerted on plunger 49 from out-let line 24 becomes greater than the force on the back side of the plunger from the hydraulic fluid side, and the plunger moves briefly to the left un-seating needle portion 53 of the plunger equalizing the forces on both sides of the plunger.

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~` ~C37~ 3 If the power to the motor driving shaft 14 is shut off, the com-pressed fluid in line 48 is free to discharge through an adjustable re-stricted orifice valve 57 which is located in the pump housing 12 and com-municates directly between the check valve 46 and the fluid 29 in the reser-voir within housing 12. As the hydraulic! fluid seeps off through the re-stricted orifice valve 57, the spring force of spring 52 and pressure in line 24 starts to move the plunger 49 ancl its needle portion 53 away from the seat 54 and creates a free communication between line 24 and the liquid container through line 56. All pressure in the complete system is released and will remain so until the motor is once again turned on. During normal opera~ion, restricted orifice valve 57 does not pass a significant amount of fluid at operating pressures due to its small passage size.
At the time the motor is reactivated, the spring force of spring 52 is great enough to allow the pump to prime itself. Once recirculation of the driven fluid by the pump occurs, the pressure builds up in lines 47 and 48 and overcomes the spring force of spring 52. At this time, the system is once again pressurized. Thus, the pump is self-priming as well as automat-ically unloading the driven and driving fluid lines and permitting pressure adjustments from the hydraulic side.
Referring now to Figure 3, there is shown a spray gun 61 which receives the output of fluid to be sprayed from line 24 at connector 25.
The driven fluid is tnereupon conveyed through tube 62, through inlet passage 63 and into safety piston chamber 64. The pumped fluid also enters spray chamber 66 through passage 67. The pressurized fluid such as paint in pres-sure chamber 64 acts at the back side of spring returned piston 68, overcomes the spring force of spring 69, and moves the piston 68 toward the front of the pressure chamber 64. The front part of the pressure chamber is sealed off from liquid flo~r by an O ring seal 71`which is mounted on piston 68, l~t7~

while the rear side of the pressure chamber 64 is sealed off by a plug 72.
The front part 73 of piston 68 is shaped so as to act as an en-gagement plunger. ~en the piston 68 moves forward, end 73 engages with a safety cap 74 in which is mounted the spraying tip 76 and a washer 77. Also mounted on cap 74 is a safety extension 78 which is free to be rotated.
I~hen chamber 64 is pressurized, piston 68 moves forward in the chamber and end portion 73 is engaged within one of a plurality of notches or recesses 79 circumferentially arrayed in cap 74. Cap 74 is threadedly received on gun body 81 and therefore with piston portion 73 retained within recess 79, it is impossible to remove the cap from the gun. If a recess 79 is not initially aligned with end 73, the first rotation of cap 74 to unscrew it results in end 73 moving into a recess.
When chambers 64 and 66 are pressurized and filled with the fluid to be sprayed, not only is the front portion 73 of piston 68 engaged within one of recesses 79, but also ball 82 blocks the outlet passage preventing the spraying of the fluid unless trigger 83 is depressed, moving ball 82 to the right as is well known. The safety piston 68 prevents removal of the spray tip while the interior of chamber 66 is pressurized so that access to the end of the spray gun body in the vicinity of ball 82 is prevented.
Therefore, a user of the gun will not be exposed to an accidental high pres-sure discharge of sprayed liquid in atte~pting to, for example, clean an obstruction from the gun tip.
When the sprayer is deactivated, as has been described above, the pressure quickly unloads on the sprayed fluid side of the system, and cham-bers 64 and 66 consequently depressurize. With thedepressurization of cham-ber 64, the action of spring 69 retracts locking end 73 of piston 68 from recess 79, permitting the removal of the spray tip from the spray gun 61.
; This is now safe since chamber 66 is consequently also depressurized at this - ' .: . - , . ' ' ~ ' . -. - . ~, ; . .: - : .

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time, and cleaning or other manipulation of the spraying end of gun 61 may be performed safely.
Referring back to Figure 1, additional pumps of higher or lower pressure may additionally be operated from eccentrically mounted bearing 13 such as by mounting within either side wall of housing 12. A set of valves such as 22, 23, 35, 46 and 57 associated with the above-described pump may be provided for each of such additional pumps. Further, the unloading mech~
anism illustrated in Figure 2, may be made a part of each of the additional pump systems. For example, a high volume utility pump may be added to appa-ratus 10 along the right side wall for use in pumping washing liquids.
While there have been described above the principles of this invention in connection with specif'ic apparatus, it is to be clearly under-stood that this description is made only by way of example and not as a limitation in the scope of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A spray gun apparatus comprising: a spray gun body; means for coupling pressurized fluid to a spray chamber and an auxiliary chamber in communication with the spraying chamber in the spray gun body; nozzle means for selectively dispersing fluid from the spray chamber; a cover member, threadedly received on a nozzle end of the spray gun body, including a plurality of circumferentially arrayed recesses; a plunger member, slidably received within an end of said auxiliary chamber, having a rear portion acted upon by the pressure in the auxiliary chamber and having a front pin portion operable to be received within one of said recesses when the auxil-iary chamber is pressurized moving the plunger to an end of the auxiliary chamber; and return means for moving the plunger from the end of the chamber and retracting the pin portion from said recess when the auxiliary and spray-ing chambers are depressurized.