FI113017B - Air-free target sprayer intake dampers and suction valve spring - Google Patents

Abstract

An airless paint sprayer (10) includes a dampener to lessen cavitation and loss of pressure in the paint sprayer (10). The dampener comprises a generally T-shaped fitting (36) in which one leg (46) is capped and includes a trapped volume of air (52) to dampen acceleration/deceleration forces and acceleration spikes being transmitted from the pump (20) to the fluid being pumped through the fitting (36).

Description

113017 Airless Spray Inlet Damper and Suction Valve Spring

The present invention relates to airless spray guns according to the preambles of claims 1, 6, 7 and 8 5, and more particularly to a mechanism for providing a more uniform spray gun without loss of pressure by various operating parameters.

In a typical airless spray gun, the plunger-driven film draws the paint from the feed tube to the paint storage or diaphragm container. The paint syringe has a trigger which, when pressed, opens the valve to allow the pressurized paint in the chamber to flow into the spray nozzle and decompose as it exits the paint hole to be sprayed onto the surface to be painted.

FR-A-1 405 442 describes a syringe device in which a reservoir is provided near its nozzle to control the heart rate generated by its pump.

US-A-4,524,947 relates to a solenoid valve comprising double springs in a serial arrangement.

Airless spray guns usually include a suction tube that is inserted into the paint can, through which the paint is distributed to the film chamber. The suction is created in the suction tube by means of a deformable film which is secured around its 20 circumference. The center portion of the diaphragm is vibrated by a piston driven hydraulic system, for example between a convex and a concave shape, thereby drawing the paint toward the diaphragm and thereby forcing it outward into the spray gun.

•: In another model, the rotating cam cam uses a bearing which: 25 uses a piston. The piston is coupled to the diaphragm, and rotation of the cam drives the piston and thereby moves the diaphragm between convex and concave shapes. The paint is drawn from the vessel through the suction tube and inlet valve toward the membrane and into the membrane chamber to be discharged through the spray gun.

; · ·, Despite previous attempts, the use of such systems • »30 paint spraying has been prone to inconsistent results and * ': · * unexplained, undesirable variations. For example, on a given day, the system may not work well with one paint, failing to: · · *: completely disintegrate it and “spray” it on the surface while it works: efficiently with the same paint at another time or another.

* »· 35 Other problems commonly encountered with such airless *" * 'paint spray guns are ineffective spraying of the first type of paint 2 113017 but effective spraying of the second type of paint. A number of possible causes for these types of problems have been suggested, such as lack of uniform start-up, paint buildup, clogged filters, paint viscosity, humidity and so on. However, these problems occur even when the problem paint is thinned to the overall water composition, the filters are clean or the paint flow path is not clogged. These symptoms may occur when one paint is used but not another, although the paint has the same viscosities.

Thus, the efficient and consistent use of an airless paint system 10 sometimes appears to depend on fluctuations of parameters that are constantly changing.

Therefore, it is obvious that there is a need for an airless paint spray, which does not exhibit pressure loss during spraying and is capable of spraying all types of paint reliably, efficiently and efficiently under a wide range of operating conditions without the above problems and non-conformities.

Thus, the main object of the present invention is to provide an improved airless spray gun according to the characterizing parts of claims 1, 6, 7 and 8, which does not lose pressure when spraying.

It is a further object of the present invention to provide a paint sprayer that can be used efficiently and effectively with a variety of paint types without losing pressure when spraying.

It is a further object of the present invention to provide a paint syringe that can be used with a variety of paints and coatings viscosities to uniformly disperse paint and spray into a desired homogeneous pattern.

To achieve these objectives, a preferred embodiment of the invention provides the use of a suppressant on the spray liquid or paint suction side. In a still further preferred embodiment, the double-spring shut-off valve is used at the paint inlet together; 30 with silencer.

One aspect of the invention is the discovery of the underlying problem which is responsible for varying paint spray performance. According to the invention: *: The problem is the inconsistency of the system for distributing paint from an open container to a pumping or diaphragm chamber of an injection device.

35 Typically, the suction line between the pump chamber suction shut-off valve and the open ground a · '' auxiliary tank is perpendicular and can be 30 to 61 3 113017 cm (1 to 2 feet) long. Paint is sucked from the tank into this tube through an inlet shut-off valve and into the pumping chamber. To suck paint past the suction shut-off valve, the diaphragm must create a pressure drop in the chamber by means of an eccentric actuator or piston-driven hydraulic actuator. The nature of the membrane 5 is cyclic; the diaphragm accelerates and decelerates continuously with each suction and pumping direction.

For example, when the diaphragm is moved to enlarge the chamber to suck paint up the feed tube, it accelerates due to the eccentric action of the piston. It slows down when it reaches its maximum stroke, 10 and the shut-off valve closes. During this time, the paint in the tube is subjected to a pressure drop, which first accelerates and then decelerates near equilibrium as the suction shut-off valve closes. The film is then accelerated into the chamber to pump the paint into it. Once that stroke has ended, the diaphragm accelerates in the opposite direction to reopen the suction shut-off valve and suck paint 15 up the tube. Thus, eccentric rotation of the cam actuator, and acceleration / deceleration of the following arm of the cam generates acceleration peaks in the paint flow during each cycle. The acceleration peaks correspond to specific points or areas on the shaft cam, resulting in significant acceleration / deceleration of the shaft. These acceleration / deceleration forces are transferred from the shaft to the diaphragm, and as a result, the acceleration peaks occur in the paint stream drawn into the diaphragm chamber through the suction shut-off valve and the suction tube. The paint is accelerated and •; thus slowing down with each stroke of the membrane. The present invention is based on ** *: in part the realization that the force required to accelerate the paint was v; in many cases, greater than what the paint itself can support without cavernous or • · 25 boiling.

.. Thus, it has been found that the paint cavities or boils in the film chamber: * *; in many cases due to the sum of the various forces applied to the paint. Factors contributing to paint cavity in paint spray guns are the ambient temperature and barometric atmospheric pressure 30 (i.e., sea level) at which the spray gun is used. Other factors that may affect are suction tube dimensions, shapes and tolerances, as well as: paint viscosity. Thus, under certain circumstances, it has now been found that: the force required to overcome the paint's slowness and accelerate it: through the system was greater than what the paint could support. Such '·' 35 resulted in cavitation or boiling of some paint fluids and consequent interruption of full paint flow through the syringe, loss of pressure during spraying, and inconsistent spraying results such as "spraying" and non-uniform decomposition.

Thus, in one embodiment, the damper generally comprises a T-shaped connector connected to a suction line leading to the suction shut-off valve of the pump or diaphragm chamber 5. The T-shaped connector includes a first portion having a port through which paint is received from a suction tube inserted into a paint vessel or container, and a second portion perpendicular to the first portion through which the paint is discharged through a second port to the pump suction shut-off valve. The third part of the T-connector comprises a closed chamber 10 which is in line with the first part and perpendicular to the second part in the now preferred embodiment of the invention. Other formulations of the silencer for various injection shapes are possible and within the scope of the invention.

The foregoing aspect of the present invention solves a significant number of the pressure loss problems that occur partially due to acceleration peaks transferred to the paint during spray operation. This is initially accomplished by means of a T-shaped connector placed in line over the suction pipe on the suction side of the suction shut-off valve. The air that remains trapped in one of the parts of the T-connector dampens the acceleration peaks and thus smoothes the paint flow. Although some paint is still applied to the paint on the disassembly or other part of the T-20 connector. acceleration peaks and acceleration / deceleration forces, the volume of paint that remains at T- ·. »· • ;;; on the suction side of the first part of the connector, is isolated from the acceleration peaks.

More specifically, according to the invention, a damping chamber, for example v; such as the T-connector illustrated, is operatively connected upstream of the 4-t: 25-inlet of the suction shut-off valve. At start-up, the pump will beep i. normally, however, it is accelerated so that a slight negative pressure is created in the damping chamber. In use, when the diaphragm is inserted into the pump blow chamber and the suction shut-off valve is closed, the pressure drop in the suction shut-off -; **. the supply side of the valve is reduced. A slight negative pressure in the damping chamber draws a certain amount of paint into it.

When the diaphragm starts its reciprocating motion and begins to accelerate, the suction shut-off valve is open. As the amount of pressure drop increases, the suction in the paint supply increases to a peak. However, according to the invention, not only *. the paint in the suction pipe is subject to that drop, but the paint in the damping chamber is sufficient to feed the increased need for paint. The incoming paint thus consists not only of the feed pan and the paint above it 5113017, but also of the paint in the damping chamber.

During operation, the pressure in the damping chamber is greater than the pressure at the inlet side of the connector connected to the suction shut-off valve. As a consequence, paint at higher pressure in the damping chamber feeds the supply side of the connector during extreme film acceleration. Thus, the supply side of the targeted acceleration peaks falling into the match, and are not lavish enough to cause cavitation and kick-pumppaussäi reservoir incomplete fulfillment.

Thereafter, during the pressure stroke, the pumping chamber is full and the designed pressure drop at the nozzle mouth is maintained sufficiently to support uniform paint jet disintegration and performance. At the same time, the suction shut-off valve now permits a slight negative pressure in the damping chamber to suck a small amount on the manufacturing site from the suction pipe 15 ready for another damping cycle.

The suppressor of the present invention thus solves a significant number of the problems identified herein with respect to airless film-coated spray guns. The suppressor of the present invention achieves a steady flow of paint from the tube to the spray gun without cavities, loss of pressure or other problems associated with airless film paint spraying.

The spring of the suction shut-off valve of the present invention also largely solves the problem of paint cavity and pressure loss in the paint jet, and very often more instances than the muffler connector described above. Prior to this invention, only about 10% to 15% of the maximum paint flow went through the paint gun into the paint cavity ·. due. For example, a spray pump capable of operating at a peak flow of approximately 4.5 liters per minute (Ipm) [1.2 gallons per minute (gpm)] operated at a flow rate of only about 0.53-0, 72 Ipm 30 (0.14 - 0.19 gpm). It was found that if the passage or distance that the suction shut-off valve moved to allow paint to flow from the suction inlet tube through the suction shut-off valve to the diaphragm chamber was increased, the paint volumetric flow *: ··· could also be increased.

.- \ t Increasing the passage of the suction shut-off valve caused another 35 problems. As the passage of the suction shut-off valve is increased, the reaction time * "'of the valve drops below an acceptable minimum level. The valve response time is the time it takes the 6113017 valve to return from open to closed. One way to increase the valve response time and maintain a longer travel distance was to increase the return spring preload or spring depression depth per load unit. However, increasing the spring bias or depression depth 5 adversely affects the vacuum and start-up filling functions of the pump.

One way to increase the spring preload is to use a spring that has a higher spring deflection per load unit (i.e., a spring that requires more force for the same amount of deflection). However, the sensitivity of the valve and parts to wear increases with the use of a spring having a sufficiently high spring depression depth to maintain sufficient reaction time for the system, while providing a greater inlet passage distance to avoid paint cavity.

The suction shut-off valve of the present invention was invented with consideration of the sea level, temperature and pressure conditions that could occur at any particular operating site, and the boiling points of the paints and / or liquids to be pumped. At maximum probable operating altitudes, barometric pressures and temperatures, pressure drop for the airless spray gun and the entire suction system was used to calculate the maximum pressure drop on the suction shut-off valve without paint cavity. For example, in one currently preferred embodiment of an airless spray gun, a pressure drop of approximately 2400 Pa (3.5 pounds / square inch) with a non-cavity suction valve is possible with a minimum of 6 900 Pa (10 pounds / square inch): The design pressure.

The suction shut-off valve of the present invention includes dual springs which, in combination, provide the maximum passage of the suction shut-off valve to avoid cavity, sufficient reaction time of the suction shut-off valve to maintain system performance without increased wear or dimensional fluctuation of valve components. The suction shut-off valve-spring assembly * «30 includes a primary spring with a very shallow spring depression depth, approximately 180 N / m (1 lb. of force) in the presently preferred embodiment, and a secondary spring with a much higher spring depression: ··: depth, approximately 1,050 N / m (6 lb. inches):! ·. 'in the preferred embodiment. The primary spring is always combined with * »· 35 suction shut-off valves and reduces the sensitivity of the valve to wear and dimensional variability due to its low spring depression depth. The secondary spring, 7113017, depending on the tolerance conditions, can either be nominally biased or disconnected from the valve when not in use. If the secondary spring is coupled due to tolerance conditions, the combined preload of the secondary and primary spring will not exceed that of the current single suction 5 suction shut-off valve. As a result, the dual suction shut-off valve spring can be used on products now available with a standard single spring without causing damage to the vacuum or starter fill function.

The secondary spring allows increased reaction time for valve 10 due to the higher spring depression value. The primary spring maintains low bias during start-up refill operations. The secondary spring provides little, if any, preload during the start-up operation, but provides a large, if not all, of the preload during normal operation. The dual-suction spring of the suction shut-off valve of the present invention avoids paint cavity and associated problems in an airless syringe by allowing a greater flow of liquid to pass through the suction shut-off valve. The dual spring facilitates higher flow without the drawbacks of reduced reaction time, increased sensitivity to component wear and loss of boot fill performance.

The silencer and suction shut-off valve of the present invention solve most, if not all, of the problems previously encountered in airless film paint spray guns. By means of a damper having a T-connector of the present invention and a spring in the suction shut-off valve, a steady flow of paint from the tube is achieved: to the spray gun without cavities, pressure loss or other problems with airless film paint sprayers.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: * * The objects and features of the present invention will be more readily apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of the airless air gun of the present invention::: * * Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1 of the T-shaped muffler connector and suction shut-off valve in accordance with this invention; is an enlarged cross-sectional view of the suction shut-off valve assembly having the double spring I · '· · · * in Figure 2.

3, 113017

The airless paint sprayer 10 shown in Fig. 1 includes moving hand carts 12 supported on the ground by wheels 14 mounted on a shaft 16 for rotation. The hand trolleys 12 include a frame 18 to support a pump 20 and a motor 22 which draws paint from a vessel 24 or other container 5 mounted on a generally L-shaped carriage 26 mounted on the lower portion of the frame 18. The spray gun 10 can be moved from one place to another by grasping the generally U-shaped handle 28 and tilting the unit backwards, thereby lifting the carriage 26 and the paint receptacle 24 supported thereon to balance the syringe 10 on the wheels 14. Any other structure for transporting and supporting the pump and motor 10 20, 22 over the paint canister or injection fluid canister may be used.

In use, paint is drawn from vessel 24 through a generally cup-shaped suction device 30 having a plurality of cuts 32 through which the paint enters the suction device 30 supported on the bottom wall of vessel 24. The paint is drawn from the receptacle 24 through the suction device 30 and into the suction tube 34. The paint flows through the suction tube 34 and the pump 20 to distribute pressure to the feed tube 35 and spray gun 37 through which the pressurized paint is sprayed out The paint path from vessel 24 through pump 20 is illustrated as paint path P in Figure 2.

A generally T-shaped connector 36 is attached to the upper end of the suction tube 34.

In one embodiment, the T-shaped connector includes a first portion ··: 38 inserted into the upper end of the suction tube 34, as shown in Figure 2, and •! A first port 40 through which paint is drawn from the suction pipe 34. The second portion 42 of the TV-shaped connector 36 is generally perpendicular to the first portion 38 and includes a second port 44 through which the paint exits the connector 36. Perpendicular to the second portion 42 and generally in line with the first portion 38 of the connector 36 is a third portion 46 which extends upward and includes a third port 48.

The third gate 48 is closed by a lid 50 secured to the upper end of the third portion 30 by a matching thread or other appropriate fastening mechanism on the surface 50 and the outer surface of the third portion 46. The lid 50 secured to the third portion 46 closes the third gate 48 and *: ** : delimits the volume or attenuation chamber 52 inside the third portion 46.

: * ·. In the preferred form of the T-shaped connector 36, the first portion 38 is approximately 25 mm (one inch) long and the first port 40 has an inside diameter of approximately 12 mm (0.48 inch). The second portion 42 is approximately 53 113017 g mm (2.1 inches) long as measured from the center line of the first portion 38, and the second port 44 has an inside diameter of 20 mm (0.78 inches). The third portion 46 is approximately 53 mm (2.1 inches) long as measured from the center line of the second portion 42 and the third port 48 has an internal diameter of approximately 23 mm (0.9 inches). Preferably, the T-5 shaped connector 36 is made of 10% glass-filled nylon.

The second portion 42 of the T-shaped connector 36 is connected to the suction valve cartridge 54 by a connector 56 or other mechanism known in the art. The suction valve cartridge 54 is mounted on the housing 58 of the pump housing 10 of the pump 20. The housing 58 is secured to the pump 20 as shown in Figure 2 by bolts 60 or other mechanical fasteners. Positioned inside the end of the suction valve cartridge 54 and mounted in the housing 58, there is a suction shut-off valve assembly 62 having an elongated valve stem 64 projecting axially inside the suction valve cartridge 54 and having a plate-shaped valve end 66,15 secured to its other end shifts between open and closed positions to allow paint flow through the suction valve cartridge 54 to the hose 35 and the spray gun after actuation by a trigger 39 or other appropriate mechanism well known to those skilled in the art.

The valve end 66 is disposed near the diaphragm chamber or pumping chamber 70 and separated from the deformable diaphragm 72. The diaphragm 72 is secured around its circumference such that the central portion of the diaphragm 72 may oscillate between a convex and: concave shape. When pulled to the left as shown in Figure 2: Γ: it pulls the paint suction valve cartridge 54 and the open suction shut-off valves · 25 through assembly 62 toward diaphragm 72. As it moves to the right, it pressurizes the chamber of “.i # 70 and pumps the paint. through an orifice 73 with a shut-off valve 75, and into an injection tube 35 and a spray gun 37. The deformable diaphragm 72 has »* i spindle 74 attached to center portion 76. Spindle 74 is used indirectly from: piston and eccentric cam (not shown), as is well known in airless spray guns of the type described above.

As best shown in Figure 3, the suction shut-off valve assembly 62 ·: * ·: is prestressed in the closed position with the valve end 66 in sealing contact with the surface 78 of the annular seat 81. The seat 81 is positioned parallel to the stop 80. The suction shut-off valve assembly 62 is shown in Figures 2 and 3 in the closed position 35 with the valve end 66 in contact with the | therein, valve seat 64 protrudes through hole 82 in the center of stop 1010. Valve 62 is biased toward the closed position by a pair of nested helical compression springs 84, 86 in accordance with the presently preferred embodiment of the present invention. The outer primary spring 84 is mounted between the stop 80 and the opposing retainer 88. The end windings of the primary spring 5 84 rest on the flanges over the retainer 88 and the stop 80, as shown in Figure 3. The retainer 88 is placed in parallel with the annular overhanging retainer 94 near the end 68 of the valve stem 64. .

The secondary spring 86 is disposed inside the primary spring 84 and around the valve stem 64. The secondary spring 86 sits inside the sleeves 96 formed by the retainer 88 and the restraint 80 within the central portions 15 as shown in Figure 3. According to the present invention, the secondary spring 86 may promote biasing of the valve 64 in closed form, or the secondary spring 86 may be disposed sideways inside the sleeves 96 either or both of the retainer 88 and the stop 80 so that it is not compressed when the valve stem 64 is closed.

According to the now preferred embodiment of the present invention, the primary spring 84 has a relatively low spring depression value, and the secondary spring 86 has a significantly higher spring value. In one embodiment of the airless spray gun 10 of this invention:] i ': the primary spring 84 has a value of approximately 180 N / m (1 pound force 25 per inch), and the secondary spring 86 has a value of 1050 N / m (6 · * .. nail force per inch). The primary spring 84 maintains engagement with both the retainer 88 and the stop 80, and thereby remains at least partially compressed. The relatively low spring v # value of primary spring 84 reduces valve wear and dimensional sensitivity of parts of suction shut-off valve assembly 62. When valve 64 is in the closed position, the secondary bias of its secondary spring "86", depending on tolerance conditions, may vary from approximately "0.25 mm (0.01 inch) to a deflection of 5.1 mm (0.20 inch) ·" : ·: A free field in a particular embodiment of the present invention. If. the secondary spring 86 is coupled to the closed position, the combined preload of the primary and 35 secondary springs 84, 86 should not exceed that of the standard, single spring suction shut-off valve assembly 11 113017. As a result, the suction shut-off valve assembly 62 of this invention can be used in many standard, airless spray guns without damaging the system, vacuum or start-up functions.

During operation of the airless spray gun 10, the deformable diaphragm 72 functions by pulling paint into the diaphragm chamber 70 with the suction shut-off valve assembly 62 open and the end 66 spaced from the surface 78 of the stop 80. In open form, the primary and secondary springs 84, 86 are being pulled closer to one another as a result of the travel or movement of the valve stem 64 10 so that the valve end 66 is spaced from the surface 78. The primary and secondary springs 84, 86 of the suction shut-off valve assembly 62 of the present invention allow increasing the valve travel relative to known one The increased travel distance of valve head 66 allows for a greater flow of liquid 15 through valve 62 without the paint being cavernous or boiling under highly variable operating conditions, barometric pressures, ambient temperatures and sea level elevations.

Specifically, for a pump with a peak flow rate of 4.5 liters per minute (1.2 gallons per minute), the maximum achievable fluid flow rate was increased from 0.53-0.71 Ipm (0.14-0.19 gpm). , to a value between 3.22 and 4.31 Ipm (0.85 to 1.14 gpm) through increased travel of the valve and dual spring assembly. This increased potential fluid flow was achieved due to the increased clearance of the valve. However, as the range of the valve is increased, the response time of the valve must be maintained so that the performance of the ·: 25 spray gun 10 is not impaired. Reaction time, as used herein, refers to the time used by the suction shut-off valve 62 as it moves when opened and:. between closed position. Preferably, the suction shut-off valve 62 should have a reaction faster than 30 Hz in one preferred embodiment of the airless spray gun of the present invention.

The suction shut-off valve assembly 62 having a double spring according to the present invention maintains a relatively low preload with the valve stem '64 in the closed position and system startup, and a much higher tension when the valve 62 is in the open position. In one of the primary airless spray guns of this invention, the optimum composite spring bias for the suction shutoff valve assembly 62, '·' with a maximum travel distance of the suction shutoff valve head 66 is 12113017 approximately 0.38 kg (0.83 lb). This value changes depending on the valve size, part geometry, maximum travel distance and other spray gun parameters. The optimum preload force for the valve in the closed position is approximately 0.059 kg (0.13 lb).

As a result of the double spring suction shutoff valve assembly 62, the travel distance of the valve head 66 can be increased and thereby allow greater fluid flow through the suction shutoff valve 62 without paint cavity while still maintaining appropriate response time to .

In addition to the suction shut-off valve assembly 62 of the present invention, the T-shaped connector 36 contributes to reducing paint cavity by damping the acceleration peaks transmitted by the fluid-deforming film 72. When the paint gun 10 is triggered and in action 15, the paint level The chamber 52 in the third portion 46 contains a sealed air volume, preferably in a partial vacuum greater than about 3,390 Pa [1.0 inches of mercury (in-Hg)] and about 10,200 Pa (3.0 in-Hg) in one of the primary embodiment. The closed air inside the chamber 52 in the third portion 46 of the T-shaped connector 20 will dampen the acceleration peaks transmitted from the diaphragm 72 through the paint ... into the cartridge 54 of the suction valve 36 and the second portion 42 of the T-shaped connector 36. Although the paint in the discharge portion of the T-shaped connector 36: the paint in the second portion 42 may be exposed to some of the acceleration peaks and 25 acceleration / deceleration forces generated by the deforming film 72, the paint I · volume remaining on the suction side or first portion of the T-shaped connector 38, is isolated from the acceleration peaks. The paint volume inside the chamber 52 in the third portion 46 is drawn to the second portion 42 along with the paint from the suction tube 34 and the first portion 38 while the suction shut-off valve 62 is open and pulls the paint through it. Increased paint '' * supply from chamber 52 overcomes acceleration peaks and prevents cavity in paint "" i track P. Therefore, the paint does not cavitate, boil or break, thus avoiding a significant amount of pressure drop in spray gun 10 and other problems previously encountered. airless film paint sprayers.

35 thanks to the T-shaped connector 36, which dampens the acceleration peaks i »'· * and acceleration / deceleration forces transmitted in the paint, and the 13113017 suction shut-off valve assembly 62, which allows increased fluid flow through the suction shut-off valve, most, and pressure loss in airless spray guns 10, corrected without significant paint spray reshaping or other system changes.

It should be noted that, although suction shut-off valve assemblies having a damper and a double spring are shown and explained herein, any of the features can be used alone to prevent paint cavity in the air path of the spray gun. Each of these features and the inventions individually contribute to solving the problems described above and should not be considered as interdependent in order to achieve the objects and objectives of the present invention. In addition, the use of the inventions of the suction shut-off valve with a damper and a double spring offers greater advantages by avoiding most of the cavity problems than using the invention individually. The invention has now been described and described with reference to a spray gun, but could easily be used in other systems.

i · t I t • · • t · (* · • • • I · •. 1 • · • • * ti »· * * · 5» * ·> II it II t · • · * · «·> ·. «• · • t * · t M» * · fa II ·

Claims (14)

14 113017 An airless paint syringe (10) diaphragm pump (20) inlet having a suction tube (34) for feeding paint from a paint source through the pump to a syringe nozzle inlet comprising a valve (62) biased toward a closed position to prevent paint from flowing through the inlet. when the paint is allowed to flow through the inlet when the valve is in the open position, a first spring (84) engaging said valve (62) in said closed position and biasing the valve toward said closed position, and a second spring (86), first and second springs (84). , 86) being combined to bias the valve (62) towards said closed position with greater force in said open position than said closed position, characterized in that the second spring (86) engages and biases the valve toward said closed position only in said open position. For 15 bricks (62) sufficient k an offset distance between said open and closed position to prevent cavity of the paint through the valve (62) without impairing the response time of the valve. Inlet according to claim 1, characterized in that the second spring (86) has a depth of depression of the spring per load unit 20 greater than that of the first spring (84). Inlet according to Claims 1 and 2, characterized in that the first and second springs (84, 86) are both helical pressure springs. An inlet according to claims 1 and 2, characterized in that the second spring (86) is within the first spring (84), and the first spring and the second spring have a common axis. An inlet according to any one of the preceding claims, characterized in that the first spring (84) engages the valve (62) in said open and closed positions and in intermediate positions between said open and closed positions. A syringe (10) for injecting filing material from a vessel (24), characterized in that the syringe comprises a connector (36) having a suction tube (34) having a first end immersed in a liquid inside said vessel. * having first and second ports (40, 44) and damping chamber (52), the first port (40) being operatively connected to the other * ··· * end of the suction pipe, flowing fluid said vessel (24) through the suction line (34) 15113017 and to the connector (36), being discharged through its second port (44), the chamber (52) being connected to the first and second ports (40, 44) and positioned near the first and second ports an interface, the suction opening of any preceding claim being operatively connected to a second port (44) of the connector (36) and downstream thereof, the diaphragm pump (20) operatively connected to and upstream of the suction valve (62) and the nozzle operatively connected a pump (20) such that during operation of the syringe (10) the pump draws fluid from said receptacle (24) into the suction pipe (34) and the connector (36) and pump 10 for injecting filing agent into the nozzle, the chamber (52) of the connector (36) having a closed volume of air from the vessel (24) through the connector (36) and into the pump (20) to prevent cavitation of the filing agent. An airless liquid diaphragm pump (20), characterized in that it comprises a pumping chamber (70), an inlet according to any one of claims 1 to 5, the fluid supply path being operatively connected to both the suction valve (62) and the first fluid supply (24). and the second fluid supply (52) operatively connected to the feed line upstream of the suction valve (62) and open to a pressure less than ambient pressure and greater than the pressure drop 20 applied to the first fluid supply (24) in the path of the pump (20). during the peak acceleration of the suction cycle, so that the liquid from the second supply (52) flows at least partially to the suction line while the suction shut-off valve (62) is open. j 8. An airless syringe (10) comprising a diaphragm pump (20) having a ·. : A pumping chamber (70), an 'inlet according to any one of claims 1 to 5, and an injection fluid inlet path operatively connected ... between the pump and the injection fluid, characterized in that the syringe (10)' comprises a damping chamber (52), functionally connected to the suction track to dampen pressure drops on the spraying fluid in the web. A syringe (10) according to claim 8, characterized in that: | comprising a suction tube (34) having a first end inserted into an injection fluid reservoir inside the vessel (24), the damping chamber (52) is delimited by a connector (36) having first and second ports (40, 44), the first port being: operatively connected to one end of the suction tube (34), a fluid flowing from the vessel (24) through the suction tube and the connector (36), discharging through its port (44) with the chamber (52) connected to the first and second ports (40, 44) and positioned near the junction of the first and second ports, the suction tube (54) having a first end pump (20) operably connected to the pump 5 (20) such that the syringe (10) ) during operation, the pump draws the injection liquid from the vessel (24) through the suction pipe (34) and the connector (36) and pumps the injection liquid into the nozzle for injection into the damping chamber (52) o of the connector (36). a closed volume of air from the vessel (24) through the connector (36) and to prevent cavitation of the fluid flowing into the pump (20). Syringe (10) according to Claim 9, characterized in that the axis of the second port (44) is generally parallel to the axis of the suction valve (62). A syringe (10) according to any one of claims 8 to 10, characterized in that the damping chamber (52) is arranged to maintain an air volume at a pressure sufficient to draw the injection fluid into the damping chamber when the suction shut-off valve (62) is closed. flow the injection fluid toward the suction shut-off valve when the suction shut-off valve is open. A syringe (10) according to any one of claims 6, 9, 10 or 11 added to claim 9, characterized in that the connector (36) 20 is T-shaped, the first portion (38) of the T-connector including a first port (40), the second portion (42) of the connector including the second port (44) and the third portion (46) of the T-connector: the chamber (52), the first and third portions (38, 46) being generally parallel and the second portion (42) in ol is generally perpendicular to the first and second portions. ; 25 A syringe according to any one of claims 6 or 8 to 12, characterized in that the volume of air enclosed in the damping chamber (52) is. in a vacuum greater than about 3,390 Pa [1 inches of mercury (in-Hg)]. A syringe (10) according to claim 13, characterized in that said air volume is in a vacuum of about 10 160 Pa (3 in-Hg). »» I · »* · '»> * · 17 113017