BRIEF DESCRIPTION OF THE DRAWINGS
For the purposes of exemplifications, an embodiment of the invention will now be further described with reference to the following figures in which:
FIG. 1 shows a longitudinal cross section through an embodiment of a pressure monitoring device in accordance with the invention.
FIG. 2 shows a transverse cross section through the embodiment of FIG. 1.
FIGS. 3
a-3d show in various views the embodiment of FIGS. 1 and 2.
FIGS. 4
a-4g show in more detail views of the housing of the embodiment of FIGS. 1 to 3.
FIG. 5 shows in more detail, the valve and valve adjusting means of the embodiment of FIGS. 1 to 4.
FIG. 6 shows in isometric projection the shape of the combined air inlet, air outlet and air passage of the embodiment of the invention, in longitudinal cross section.
FIG. 7 illustrates how the shape of FIG. 6 may be formed from a die cast or injection moulded air inlet and outlet and a later added bore.
FIG. 8 shows a longitudinal cross section through an alternative embodiment of a pressure monitoring device wherein the direction of air flow is reversed.
FIG. 9 shows generally a paint spray gun retro fitted with the embodiment of FIGS. 1 to 4.
DETAILED DESCRIPTION OF THE EMBODIMENTS
As can be seen from FIGS. 1 and 2, a pressure monitoring device in accordance with the present invention comprises a housing 1 within which are provided an air inlet 2 and an air outlet 3. Connecting the air inlet 2 and the air outlet 3 is an air passageway 4 which includes a pressure take off point 9. The air inlet 2 includes a threaded bore section 2a into which is screwed a coupling device 7 for coupling with the air outlet of a compressed air supply. The air outlet 3 is also configured to receive a coupling device 8 for coupling with the air inlet of a paint spray gun. As is clear from FIG. 1 an end of the air outlet cavity terminates in a taper extending from the chord to the arc of the segment of the cavity. The pressure take off point 9 is located in the tapered end portion of the air outlet
A digital pressure gauge 5 is housed in a top surface of the housing 1 as shown in the figures. The gauge samples air pressure at the pressure take off point 9 through conduit 9a.
Screw threaded into a bore 11 in the housing is a needle valve 6 which can be adjusted by means of valve adjustment means 10a, 10b to move further towards or away from the pressure take off 9. The operation of the valve adjustment means is discussed in more detail in relation to FIG. 5.
FIG. 3 shows various views of the device illustrated in FIGS. 1 and 2. FIG. 3a shows an isometric view. FIG. 3b shows a plan view of the device with the gauge 5 present. It can be seen that the gauge includes a display 5a visible through a window in the housing 1. FIG. 3c illustrates a front view of the device and FIG. 3d illustrates a right end view.
FIG. 4 illustrates in various views the housing with the couplings 7, 8, gauge 5, valve 6 and valve adjusting means 10a, 10b removed. FIG. 4a shows an isometric view of the housing, FIG. 4b a plan view, FIG. 4c a front view, FIG. 4d a bottom view, FIG. 4e a left end view and FIG. 4f a right end view. FIG. 4g illustrates the view of FIG. 4c in cross section.
FIG. 5 shows in more detail the valve 6 and valve adjustment means 10a, 10b. The arrangement comprises a main valve body 18 which carries a threaded member 14 having an external, left hand thread 17 onto which is screwed a valve closure member 6a. At an opposing end of the threaded member 14, the threaded member is provided with a bore 13 having an internal screw thread 13a into which is screwed an adjustment screw 10b. which secures adjustable knob 10a to the threaded member 14 and main valve body 18. an O-ring 15 seals the valve. As can be seen in FIG. 1, the assembled valve 6 and valve adjustment means 10a, 10b can be screwed into a bore 11 of the housing 1 by means of complementary screw threads provided in the bore and on the main valve body 18.
It will be appreciated that turning of knob 10a will cause turning of screw 10b which in turn will travel along the screw thread 13a of the threaded member 14 causing the valve closure member 6a to extend from or be withdrawn into (depending on the direction in which the knob 10a is turned) the main valve body 18.
FIG. 6 shows generally the shape of the space defined by the air inlet 2, air outlet 3, connecting air passage 4 and bore 11 within the housing 1. FIG. 7 shows how the shape can be formed from a pair of cavities 72, 73 of substantially the same size and shape, each cavity having a substantially circular cross sectioned portion adjacent the entry of the air inlet and exit of the air outlet and a substantially segmental cross sectioned portion 72a, 73a adjacent to the pressure take off point and passing through a plane which includes the pressure take off point, the substantially circular and segmental cross-sectioned portions being separated by a tapered section 72b, 73b tapering from the circumference of the circular cross sectioned portion to the chord of the segmental cross sectioned portion.
As illustrated, the air passage is formed by the introduction of a bore 74 (which extends from bore 711) having a central axis Y aligned orthogonally with respect to both the common axis X of the air inlet and air outlet and the chords of the segmental cross sectioned portions.
It will be appreciated that the general shape of the air inlet, outlet and connecting passage may have applications in other gas flow devices, for example but not strictly limited to pneumatic component valves. In another aspect, therefore, the invention comprises a gas flow passage comprising a pair of cavities of substantially the same size and shape, each cavity having a substantially circular cross sectioned portion adjacent the points of entry and exit to the passage and a substantially segmental cross sectioned portion, the substantially circular and segmental cross-sectioned portions being separated by a tapered section tapering from the circumference of the circular cross sectioned portion to the chord of the segmental cross sectioned portion, the pair of cavities being connected by a bore having a central axis aligned orthogonally with respect to both the common axis of the two cavities and the chords of the segmental cross sectioned portions.
The taper is desirably at an angle of from about 30° to about 80° with respect to the common axis, more desirably between about 55° and 80°. In a preferred embodiment, the angle of the taper of the inlet is about 60° and that of the outlet is about 75°.
In an alternative embodiment the air flow direction through the valve is reversed. As shown in FIG. 8, the air flows in direction A from air inlet 2 to air outlet 3. Air passageway 4 includes an alternative pressure take off point 9 at which the gauge samples air pressure. The shape of the pair of cavities 72, 73 forming the shape of the air passageway 4 is the same as in previously described embodiments but the air flow direction is reversed.
The reversal of air flow direction enables an accurate pressure reading to be taken even when the valve closure member 6a is screwed to a position close to the valve seat 6b. This arrangement leaves only a very small annulus in air passageway 4 and produces a high pressure drop from the air inlet 2 to the air outlet 3. The pressure take off point 9 is located in a cavity downstream of the valve, where the high pressure drop does not affect the pressure of the air sampled. As in previous embodiments, a digital pressure gauge 5 is housed in a top surface of the housing 1 as shown in FIG. 8.
As is shown in FIG. 9, a paint spray gun 81 generally comprises a gun body 87 having a trigger 86 mounted thereon. At the top end of the gun is an air cap 84 which surrounds a nozzle (not shown) through which atomised paint is delivered. Air flow to the nozzle 84 can be adjusted by means of spreader valve 83. Near to the nozzle is a paint inlet port 85 to which a supply of paint (not shown) can be connected. Situated just below the spreader valve 83 is a fluid flow valve 82 which can be adjusted to control the flow rate of paint being delivered to the gun 81. Supply of fluid to the gun 81 is generally controlled by operation of the trigger 86. At the bottom of the gun 81 is an air inlet port 88 and adjacent to the air inlet port 88 is an air flow valve 89 operable to adjust the flow rate of air entering the inlet port 88. Connected to the air inlet port 88 by means of coupling 8 is a pressure monitoring device 80 as previously described. It will be appreciated that with the pressure monitoring device 80 in place, the air flow valve 89 becomes redundant, as air flow can be adjusted by means of the valve 6 embodied and valve adjustment means 10a, 10b embodied in the pressure monitoring device
It is to be understood that the foregoing is merely exemplary of just one embodiment of the invention, others of which will readily occur to the skilled addressee without departing from the scope of the invention as defined by the appended claims. The illustrations and specific description are not intended strictly to limit the scope of the invention as claimed.
Patent Application
20080029615
