The present application is based on International Application No. PCT/IB2006/000314 filed Feb. 16, 2006, and claims priority from, German Application Number 10 2005 007 242.9, filed Feb. 17, 2005.
The present invention relates to a compressed air throttle apparatus in particular used for powder spraycoating equipment. Moreover the present invention relates to powder spraycoating equipment containing at least one such throttle apparatus.
Powder spraycoating equipment comprising a throttle apparatus of the above kind is known from the European patent document EP 1 156 882 B1. It comprises an electrical stepping motor which rotates a valve element by the intermediary of a bellows connection. The valve element is fitted with a thread engaging a housing thread whereby, during its rotation, said valve element is axially displaced relative to a valve seat in order to change the aperture of a throttling duct present in the valve seat. Said patent also shows a throttle apparatus having two throttle valve s configured in mutually opposite manner and being driven by the same stepping motor, as a result of which, during opening one throttle valve, the other throttle valve shall close or, vice-versa depending on the direction of rotation of said stepping motor. The stepping motor shall be rotated by a given number of steps from its reference position to a predetermined aperture of the minimum of one throttling duct.
In practice, the known throttle apparatus valve is at its minimum aperture in the reference position, said minimum aperture being at least completely closed or at most a slightly open one to a compressed air leakage flow that is measured before operating the throttle apparatus and that is taken into account when the stepping motor is electrically controlled to adjust a desired operational, compressed air flow. On account of manufacturing tolerances and the need to take into account the motor shaft angular position at the end of a rotational step, It is exceedingly difficult in practice to make use of the completely closed position of the throttle apparatus as the reference position from which the number of steps of said stepping motor shall be counted in order to allow a given airflow through the throttle apparatus valve.
The objective of the present invention is to create a way to fine-adjust the throttle apparatus in a simpler way than possible in the state of the art.
The throttle apparatus of the present invention is especially advantageous when applied to powder spraycoating equipment because therein good coating quality and good efficiency relating to the needed quantity/rate of coating powder do depend on the pertinent flows of compressed air being accurately adjustable, hence in fine steps or continuously. All these requirements are now met by the present invention.
Moreover the present invention is applicable to more than powder spraycoating equipment, namely where finely adjusted flows of compressed air or liquids are required.
The compressed air throttle apparatus 21 of the invention shown in
Moreover the invention provides an electrical circuit 44 fitted with at least two, illustratively three electrically conducting contacting elements 46, 48, 50 to alternatively open and close the electrical circuit 44 as a function of the setting of the throttle valve 22.
In a special embodiment of the invention, at least one of the contacting elements, for instance the contacting element 50, is mounted on an axially displaceable valve part 52 and jointly with same is displaceable by the motor 24 relative to at least one of the other contacting elements, for instance relative to the two other contacting elements 46 and 48 and thereby at the same time relative to a valve seat 54 of the throttle apparatus valve 22, for the purpose of changing the aperture of a throttle apparatus duct 56 in the valve seat 54 using the valve head 58 of a valve element, preferably a valve needle, which is a part of the adjustable valve part 52.
The valve needle 60 is linked in such manner to the motor shaft 26 that it shall be axially displaceable by rotating the motor shaft 26 without said needle 60 itself being rotated. For that purpose the valve needle 60 is guided axially in a passage 64 of the valve case 34. At least over part of its length, the passage 64 is non-circular, preferably it shall be polygonal, for instance being square/rectangular, to preclude rotating the valve needle 60. In accordance with the shown preferred embodiment mode of the drawings, a threaded bush 62 is affixed to the rear end of the valve needle 60, said bush preferably being made by injection molding and comprising a polygonal outer periphery portion 66 which is guided axially along a polygonal inner peripheral portion 68 of the passage 64. The threaded bush 62 is fitted with an inside thread 70 engaging an outside thread 72 of a second threaded bush 74 that is irrotationally affixed on the motor shaft 26.
The electrically conductive contacting elements 46, 48 and 50 of the electric circuit 44 are configured around the valve needle 60 in the passage 64 between a forward-pointing end face 76 and a rearward-pointing end face 78 of a spacer 80. The spacer 80 rests axially against a rearward-pointing end face 82 of an offset of the passage 64.
An aperture portion 84 of the passage 64 is constricted by the offset 82 and is sealed by a seal 86 relative to a first valve chamber 88. The throttle valve 22 is situated between the first valve chamber 88 and a second valve chamber 90.
In the preferred embodiment of the invention, the two immovable contacting elements 44 and 46 are configured apart from each other in stationary manner at the rearward-pointing end face 78 of the spacer 80 in a transverse plane which is perpendicular to the center line 39. The displaceable contacting element 50 is displaceable jointly with the displaceable valve part 52 and is designed as a contact shunt to shunt the two contacting elements 44, 46, as a result of which the electrical contacting elements constitute a sensor. The contacting element 50 designed as a contacting element shunt makes contact with and shunts the two stationary contacting elements 44 and 46 only when the valve needle 60 has assumed a predetermined reference position, preferably when the valve needle 60 closes the throttling duct 56 almost completely or preferably completely as shown in
When the electric contacting elements 46, 48, 50 are closed, a reference signal is generated in an electric control 89 indicated only schematically, said signal corresponding to a reference setting (reference position) of the throttle valve 22, and said setting/position preferably being the completely or nearly complete closed throttle valve closed position. When this reference position is only the partly closed position of the throttle valve 22, the ensuing leakage of compressed air flowing through the throttle valve 22 can be measured. With each step of the stepping motor 24, the throttle valve 22 is opened a little more so that a slight increment of compressed air is passing through the throttle valve 22. Accordingly each rotational step constrained by the control 89 on the motor 24 relates to a predetermined and measurable quantity/rate of measurable, compressed air through the throttle valve 22. As a result a desired quantity/rate of compressed air is reproducible at any time.
The throttle valve is designed in a manner that at the beginning of a displacement opening the valve needle 60, the contacting element 50, which is also displaceable jointly with the valve needle shall be moved away from the contacting elements 46 and 48 and thereby the electrical circuit 44 shall be interrupted.
As shown by
The invention also may be implemented when the said preferred valve needle's reference position is replaced by another reference position.
The two stationary contacting elements 44 and 46 are respectively fitted with an electrical terminal 46-1 and 48-1 shown in
The displaceable contacting element 50 is connected to the displaceable valve element 52, preferably to the valve needle 60, for the purpose of joint motion and preferably is an electrically conductive contacting annulus enclosing the valve needle 60 and is supported in tipping manner on a forward-pointing rest surface 92 which is constituted at the valve needle 60 or preferably, as indicated in the drawings, at a forward-projecting annular collar 94 of the threaded bush 62. Because the contacting annulus 50 is able to tip, it ensures it will rest not only against one, but against both stationary contacting elements 46 and 48 and connect electrically the latter to each other when contacting surfaces of these contacting elements 46 and 48 do not run parallel to the contacting annulus 50 acting as a contacting shunt.
A helical compression spring 96 is axially stressed between the displaceable contacting element 50 (contacting shunt, contacting annulus) and the spacer 80 in order to keep the contacting element 50 resting against the support surface 92 in all axial settings of the adjustable valve part 52. Moreover the compression spring 96 ensures that the teeth of the threads 70 and 72 always shall rest against each other in the same axial direction, as a result of which neither play between these teeth nor tolerances shall affect the adjustment accuracy of the throttle valve 22.
In another, omitted embodiment mode of the invention, none of the electrically conductive contacting elements is a shunting element, instead this design of the invention provides only one of the two stationary contacting elements 46 or 48, and the displaceable contacting element 50 is fitted with an (electrical) terminal connected to the electrical control 89, as a result of which a signal shall be generated in said control when the two contacting elements 50 and 46 (or, in other embodiment modes, 50 and 48) make contact with each other in the reference position shown in
The first valve chamber 88 of the first throttle valve 22 is fitted with an external compressed air port 88-1. The second valve chamber 90 of the first throttle valve 22 communicates through a valve connecting duct 94 with a second valve chamber 190 of the second throttle valve 122. The throttling duct 156 of the second throttle valve 122 is situated between this second valve chamber 190 and a first valve chamber 188 which is fitted with an external compressed air port 188-1. The valve connecting duct 94 is fitted with an external compressed air port 94-1. When the external compressed air port 94-1 of the valve connecting duct 94 is connected to a source of compressed air, compressed air 96 from said source is able to flow in relation to the settings of the throttle valve s 22 and 122 by means of the single motor 24 either only through the first throttle valve 22 or through both throttle valve s 22 and 122 or only through the second throttle valve 122, each time at defined ratio of quantity/rate as schematically indicated in
A preferred application of the throttle apparatus of the invention are powder spraycoating equipment because in that application the powder coating and the coating quality depend very much on accurately set flows of compressed air.
In all throttle valve embodiments, the valve needle tip preferably is conical whereby, for a needle displacement in the initial aperture range of the throttle duct, the quantity/rate of compressed air flowing through this duct shall be changed only slightly, and also opening the throttle valve from the completely closed valve position into a minutely open valve position shall entail only a very slight increase in air flow.
In the preferred embodiment modes of the invention, the throttle valve when in its reference position shall be completely or nearly completely closed.
The threads 70, 72 of the bushes 62 and 74 preferably are trapezoidal.
The components adjoining the electrically conductive contacting elements are made of electrically con-conductive materials.
Number | Date | Country | Kind |
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10 2005 007 242 | Feb 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB2006/000314 | 2/16/2006 | WO | 00 | 6/3/2008 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2006/087625 | 8/24/2006 | WO | A |
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Entry |
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ISR for PCT/IB2006/00314 mailed May 30, 2006. |
Notice of Reasons for Rejection for JP2007-555722 mailed Jul. 12, 2011. |
Number | Date | Country | |
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20090121051 A1 | May 2009 | US |