CA1061536A

CA1061536A - Sprayable material changer apparatus

Info

Publication number: CA1061536A
Application number: CA235,195A
Authority: CA
Inventors: Charles H. Otterstetter
Original assignee: Ford Motor Company of Canada Ltd
Current assignee: Ford Motor Company of Canada Ltd
Priority date: 1974-11-04
Filing date: 1975-09-10
Publication date: 1979-09-04
Also published as: GB1475046A; US3924810A; JPS5941784B2; DE2548463A1; JPS5168647A; DE2548463C2

Abstract

SPRAYABLE MATERIAL CHANGER APPARATUS
ABSTRACT OF THE DISCLOSURE
Apparatus is disclosed for communicating a plurality of fluidized sources with a spray apparatus. A
plurality of sources are communicated to individual ones of a plurality of ports extending through a stationary plate member. A rotary and longitudinally displaceable plate member is arranged in alignment with the stationary plate member and is provided with a single orifice which commun-icates with the spray apparatus. The rotary plate is further provided with means forming a sealing member which are arranged to cooperate with gasket means provided for each of the source orifices on the stationary plate member so as to sealingly close the non-selected orifices and to provide for contamination free communication between the selected source orifice and the single orifice on the rotary plate member.

Description

~0~1S~6 I'he present invention relates to the field of spray apparatus in general and more particularly to tha~ por-tion of the above-noted field which is concerned with the spray-ing of material such as for coatings. The present invention is more par-ticularly directed to that portion of the above-noted field wherein a plurality of ma-terials must be intermittently sprayed in a random sequence fashion and wherein it-is highly desirable to avoid any cross contamina-tion of the material. More particularly still, the present invention is directed to apparatus for use in association with an electrostatic powder spray apparatus for providing that powder spray apparatus with communication to a plurality of dry powder sources in a manner which will allow rapid change of powder communication from a first selected powder to a second selected powder and which will avoid any cross contamination of the powder being sprayèd with residue from a previous spray operation.
In the spraying o~ dry powder materials such as ~ film forming coatings on, for example, automotive body panels, it is frequently necessary to have a single spray station spray a different powder coating on each of a succession of body panels. A single spray station may ~have one~or more spray apparatus, typically referred to as spray g~lns, arranged to spray the material in unison.
In order to maintain the speed of the spray assembly :
operation at a smooth and economically rapid level, it is necessary~that the spray apparatus be capable of changing from one sprayable~material~to another sprayable material in approximately the same amount of time as that required ~ for~the succes~sive;body~panel~to come lnto the range of the spray apparatus.

~6:~LS36 One way in which this may be achieved is to provide each spray material with separate spray apparatus and to automa-tically change be-tween successive spray apparatus for each successive body panel. However, this is an expensive and awkward solution to the problem in view of the fact that powder coating materials are normally sprayed with an electrostatic charge to facilitate uni~orm deposition of the uni~orm coating and the provision o~ a plurality of spray apparatus would necessitate the provision of a plurality of electrostatic charging devices. Such a solution would also be cumbersome in the sheer bulk of equipment required to be maintained at any one spray station. Furthermore, a safety hazard would be introduced by the additional machinery required to switch between successive spray apparatus and by the necessity of maintain-ing a large number of electrostatically charged pieces of spray apparatus.
One mechanism which has been successfully used in the past has been to provide a plurality of powder manifolds each havlng a spray channel and a powder channel. The manifolds are interconnected to align the spray channel so as to provide a common passage through the manifold. Each powder channel intersects the spray or common p~ssage and communicates with a single material source. Such an apparatus is thereafter controlled by sequential valvlng situated in the powder channel upstream from th~ junction of that channel with the spray passage. This valving may open individual powder~channels and will concomit-tently close all other powder channels to prevent any cross contamination. However, such valving apparatus, si-tua-ted as it must be within the powder channels slightly upstream ~ `

from -the junction cf the respective powder channel with -the spray channel, prGvides a small pocket area where residue spray ma-terial may accumulate. While it is normally the custom to provide for a flushing operation of the spray channel and of the spray apparatus between successive applications of material by the spray apparatus, the pockets of accumulated s~ray material are difficult to thoroughly flush and frequently result in contamination of the material being sprayed by a residue of material from a previous spray operation.
Still another attempt to solve the above noted problem has been to provide the spray apparatus with a plurality of material supply conduits. The supply conduits are arranged to have each of their exhaust ports aimed or focussed to deliver streams of material to be sprayed to the centre of a vorte~ nozzle. This a single material may be supplied from a selected supply conduit and may be sprayed by the apparatus. The spray nozzle may be subsequently communicated to a different supply. This arrangement is size limited in that only a small number of conduits may be arranged to be focussed toward the center of the vortex and is further complicated by the fact that the vortex aiming is critical.
The present invention is directed to appara-tus for communicating a powder spray gun with a plurality of fluidized powder sources while avoiding cross contamination ofpouders which overcomes the prior art problems noted above.
In accordance with the present invention, the apparatus comprises, in combination: apparatus for ~
~ communicating a powder spray gun with a plurality of ~ ~B

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fluidized powder sources while a~oiding cross contam:ination of powders comprising in combina-tion: a stationary plate member having a powder side and a sealing side, a pluralit~
of powder passages and at least one flushing passage, the passages extending through the plate from the powder side to the sealing side; hose means coupled to the powder passages on -the powder side of the plate for fluid-tight communication of the powder passages with the plurality of powder sources; further hose means coupled to the at least one flushing passage on the powder side of the plate;
means coupled to the further hose means for flowing a flushing medium therethrough; plate valve means supported in closely spaced relation to the stationary plate member and having a flow passage means extending through the plate valve means and aligned for fluid communication with the powder passages and the at least one flushing passage;
hose means coupled to the flow passage means for communicating the flow passage means with the spray gun;
means connected to the valve plate means for varying the spatial relation between the valve plate means and the stationary pLate member; indexing means operative to align the flow passage with a selected one of the powder and ~ flushing passages; and seal means interposed between the ~stationary plate member and the valve plate means operative to provide sealed communication between the :Elow passage and the selected one of the powder and flushing passages.
.~'he lnvention is described further, by way of illustration,:with reference to the accompanying drawings, ~ in which:

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Figure 1 illustrates a side sectional view of the changer appara-tus according to the present invention;
Figure 2 illustrates an end view of the apparatus of Figure l;
Figure 3 illustrates in a schematic diagram form the present invention as applied to an electrostatic powder coating spray operation;
Figure 4 illustrates a block diagram for one form of a control system for controlling the material changer apparatus according to the present invention and useful in a system according to Figure 3; and Figure 5 illustrates an alternate embodiment o-f the valve sealing for the changer accoxding to the present invention.
Referring now to the drawings, Figure 1 i~lustrates the material changer apparatus 10 according to the present invention. For purposes of illustration, the present invention will be described hereinbelow with reEerence to the application of various colour fluidized powder film forming materials by electrostatic spray deposition methods to automotive vehicle body panels. It will be appreciate~.
that the present invention is applicable to spray apparatus other electrostatic spray apparatus and with sprayable materiaLs other than dry powder fi.lm-forming coating .:
material. ~ ~:
Powder changer apparatus 10 i.s comprised of a stationary plate member 12 and a movable plate member 14 ::
which is supported for rotation about axis 16O Plate member 12 has a powder supply side 18 and a sealing surface ~ side 20. Plate member 12 is provided with a plurality of : ~ . passages 2Z which extend therethrough ~rom the powder ~6~LS3~i su~ply side 18 to the sealing sllrface side 20. Each of the ~assages 22 may be communicated, fox example,,by means of hoses 24 with a source of fluidized powder and by means of hose 26 with a source of a Elushing agent as will be described hereinbelow.
Sta-tionary plate member 12 is connected to the movable plate member 14 by cylinder means 28 which is illustrated as being at-tached to the powder supply side 18 of the stationary pla-te member 12. Cylinder means 28 includes a double acting piston member 30 situated within the cylinder cavity 32. Piston 30 is arranged for reciprocating movement within cylinder means 28 and is provided with stub shaft member 34 which extends through the stationary member 12 and is fixedly attached to movable plate member 14. It will be appreciated that stuh shaft member 34 should be provided with some form of pressure retaining sealing between it and stationary plate member 12. Piston member 30 is arranged to be actuated in the first dlrection by fluid pressure provided to cylinder cavity 32 through fluid conduit 36 and is arranged to be actuated in a second or opposite direction by fluid pressure provided to cylinder aavity 32 through fluid conduit 38. Piston 30 is further provided with a pair of seal members 40 which operate to seal each end of the piston 30. As illustrated, seal members 40 may be, ~
for example, flexible O-rings or such other seal ~eans as are convenient.
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~The application of fluid pressure through fluid conduit 36 and fluia passage 42 to face 46 of piston 30 is operative to displace piston 30 rightward relative to Figure 1, and~through its connection to t~e movable plate ~ B ~ - 7 ~

member 14 by stub shaft 34, to cause movable pla-te member 14 to translate rightwards. The applica-tion of fl~id pressure through fluid conduit 38 and fluid passa~e 44 to the right hand face 48 of piston 30, relative to Fi~ure l, will be operative to cause piston 30 to translate leftward relative to the figure. Due to the interconnection of piston 30, stub shaft 34 and movable plate member 14, leftward movement of piston 30 will cause the movable plate member 14 to also translate leftward.
Each of the material supply hoses 24 and the flush-ing material supply hose 26 is arranged to extend through stationary plate member 12 from the supply side 18 to the sealing surface side 20. The hoses 24, 26 are terminated in an extending flange portion 50 which generally surrounds the passages 22 of the stationary plate member 12. Each flange portion 50 is provided with a gasket seat or ridge 52 which may be, for example, a ridge portion formed as a part of the flange portion 50. Ridge 52 may also be a separately enlbedded member or annulus of suitable material such as metal.
Movable plate member 14 is provided with means defining a single ~luid passage 54 whi.ch communicates on the one side with spray apparatus supply hose 56 and is arranged tG communicate on the other side with a similarly provided passage 58 which extends through cooperating seal element 60. In a preferred embodiment, cooperatiny seal element 60 is an annular band of natural rubber materlal which extends around the periphery of the inner ~ side of movable plate member 14. Coopera-ting seal element 60 is provided with a sinyle passage 58 and is therefore operative, when movable plate member 14 is in the extreme .

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~0~536 lef-tward position Lelative to Figure 1, to cooperate with -the gasket seats or ridges 52, and the flange por~ions 50, of each of the hoses 24, 26 to seal the hoses from the environment. In the case of the selected, here illustrated as hose 26, which is in fluid communication with spray apparatus supply hose 56, the sealing action of cooperating seal element 60 and gasket seat or ridge 52 will be to provide for fluid tight communication from the selected one hose 24 and the spray apparatus supply hose 56.
A second stub shaft 62 is attached to piston 30 so as to extend away from face 46 of piston 30. This stub.
shaft 62 extends through cylinder 28 and may be connected, for example, by a sliding spline connection, to a stepping motor 64. When energized, steppin~ motor 64 may be arranged to rotate stub shaft 62, piston 30, stub shaft 34, and movable plate member 14. Thus, when fluid pressure is applied to the face 46 of piStOIl 30 and piston 3Q has been displaced rightward so as to displace movable plate ;
member 14 rightward with respect to stationary plate member 12, energization of stepping motor 64 will be operative to rotatably displace movable plate member 14 with respect to stationary plate member 12. By arranging the spacing of the steps o:E the step motor 64 in any of the well known ways, the single passa~e means 54 of the movable plate member 14 may be aligned with selected ones of the~ . .
passages 22 so as to permit, upon leftward disp]acement of the piston 30, direct communication between the spray apparatus supply hose 56 ancl the selected one of the .:
materi.al suppl~ hoses 24, 2:6~ ~.
With reference now to Figures 1 and 2 it can be .
- seen~ that passage means. 5.~ of the movable plate member 14 and the passages 22 of the stat.ionary plate member 12 are g ~ ~) ~ , .

~(J6~3~ii arranged to be equidistantly spaced fxom th~ axis 16.
Furtllermore, passages 22 may be arranged to be ~ngularly equidistantly spaced about the periphery of stationary pla~e member 12. As illustrated in Figure 2, there are six passages 22 arranged about the stationary plate member 14. It will be appreciated that the number of passages 22 is dependent only on the size of the passages 22 and the size of stationary plate member 12. It can also be~
seen that the stationary and movable plate members 12, 14 preferably are of circular configuration. It will be appreciated that, while reference is made herein to the passages 22 as being individual passages and passage 5~ .
has been referred to as a single passage, passage 54 could be a plurality of passages in any desired configura-tion, each of which could be communicated to one of a ::
plurality of spray apparatus supply hoses. The passages 22 of stationary member 12 could be similarly arranged and configured and could communicate with a plurality of hoses 24, 26 each of which would then communicate with a reservoir of sprayable material. The advantage of this arrangement would be to permit the supply of a single sprayable material to a plurality of spray nozzles as may be used ~or example to apply coatings to a large surface area when a single spray apparatus would not have sufficient delivery capability.
Referring now to Figure 3, the changer apparatus 10 according to the present in~Iention is illustrated as applied to a powder paint spray apparatus operation : utillzing an electrostatically charged powder spray 30 ~ apparatus 66. Po~der spray apparatus 66 is elec-trosta-t- -~
ical.ly charged from electrostatic charging means.68 through conductors 70.. Electrostatic charging apparatus 68 is , T~ 10 -~6~36 illustrated as being energized from a conventional AC
electrical source throu~h electric line cord 72. 1 Electrostatic powder spray appara-tus 6~ is operative to provide a spray of electrostatically char~ied powder coating material to the surface of a member to be coated, shown as 7~. As is well known, the powder paint material will be uniformly distributed and will adhere to member 74 through the action of the electrostatic charge. In the spray coating of automobile bodies, for example, as discussed hereinabove it is frequently necessary that successive spray applications of material to successive body panels be of differing colours. In order to facili-tate a rapid and contamination-free change of the powder being provided to the powder spray apparatus, the changer of the present invention is arranged to communicate with a plurality o~ reservoirs of fluidized powder coating material through a plurality of connecting hoses 24. For example, Figure 3 illustrates a pair of connecting hoses 24 being communicated to reservoirs 76,78 each of which contains a fluidized bed of powder material of differing colours and a venturi-type powder pump 80j 82. A pneumatic fluid line 90 extends from the control system 84 to each of the powder pumps 80, 82 for providing an energizing fluid flow for the selected material. In addition, hose 26 may ;;
be communicated to a source of flushing agent. One convenient flushing agent is shop air which may be used to purge the hoses and passages downstream from the changer apparatus between suocessive applications of powder coating material.
In operation, the present lnvention functions as follo~ls. A flushing agent such as shop air is communicated ~ ~ , ~6~L~3~;

through hose 26 and thxouyh the appropriate passages of the chan~er apparatus 10 -to the spray apparatus supply hose 56 and the spray apparatus 66. After a sufficient period of time has elapsed to assure that all residue powders have been exhausted ~rom the spray apparatus supply passa~e 56 and from the spray apparatus 66, the control sy.stem 84 will command t~e application of ~luid pressure, which may also be shop air, to fluid conduit 36 and the face 46 of piston 30 to cause movable plate member 14 to translate ri~htward, relative to Figures 1 and 3~ away from the stationary plate member 12. Proximity sensor switch 86 will respond to plate 14 reaching the extreme rightward position so that steppin~ motor 64 may be actuated to rotatably displace movable plate member lai.
Step motor 64 may be arranged to rotate clockwise and/or counterclockwise a predetermined angular distance to align passage 54 with a selected one of the passages 22 so that upon application of fluid pressure to passage 38 and face 48 of piston 30 and leftward displacement of rotatably plate member 14, the spray apparatus supply hose 56 will be placed in fluid communication with the selected one o~
thè powder hoses 24 and its associated material reservoir so that the application of the appropriate powder coating material to the next successive body panel 74 ma~ be achieved. Upon le~tward displacement of movable plate member 14, proximity sensor switch 86 will inform the control system 84 t~at leftward displacement has been achleved and the~material reservoir powder pump ~or the ; selected material may be ener~ized. Due -to the ~iual sealing action of the inter-plate sealin~ means 50, 60 powder supplied ~rom the one se~ected powder reservoir S36i 76, 78 which comm~micates directly with the spray appara-tus supply hose 56 will be preven-ted ~rom entering and accumulating in the passages 22 which communic~-te with the nonselected reservoirsO After the passage of an amount o~ time selected to correspond with the rate of travel o~ the body panel 74 on the conveyor apparatus pas-t the nozzle 88 of spray apparatus 66, the control system 84 will depressurize the powder pump in the reservoir o~
the selected material and the movable plate member 14 will be automatically indexed to place the spray apparatus supply hose 56 in communication with -the flushing agen-t supply hose 26 so that residue powders may be exhausted from supply hose 56 and from the spray apparatus 66. In ~he preferred embodiment, the flushing agent may be pressurized shop air but alternatively~ the spray appar~tus 66 and s~1pply hose 56 may be flushed by a vacuum operation in which the powders which act as residue within the spray apparatus and the spray apparatus supply hose may be collected and returned to the respective fluid supply reservoirs 76 t 7~- .
Referring now to Figure ~, a representative control system 84 for controlling the sequence of operation ..
of the changer apparatus 10 according to the present invention is illustrated. In the illustrated control system, the principal element of the control is the memory and electrical sequence signaller 90 which may be, for example, an Edon Memo~Chain control mechani.sm having memory capability. This cen~ral processing unit 90 receives material selection indications from the powder selectro 30 ~. 92 and applies suitable control signals to the pneumatic :
control means 94. Unit 90 aLso applies suitable electri.cal ~ - 13 --"r~
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signals to indexer 64 to accomplish clockwise or counter-clockwise stepping motion when switching from one.of the selected passages 22 of statio:nary plate member 12, to the flushiny position, and to a second selected passage 22 of the stationary plate member 12. Pneumatic control means 94 receives pneumatic fluid, which may also be shop air, under pressure from pneumatic source 96. Pneumatic control means 94 may be comprised, for example, of suitab.le electromechanical valve means for controlling the application of pneumatic pressure to a selected pumping means 80, 82, for example and to control actuation of the cylinder means 28. Material to be sprayed would therefore be pumped by pump means 80, 82 through the associated material supply hose 24 to changer 10. This material would be delivered to spray apparatus supply hose 56 to be sprayed from nozzle 88. The lateral position of movable plate member 14 relative to stationary plate member may be communicated from switch member 86 to central processing unit 90 by conductor means 9~.
Referring now to Figure 5, a fragmentar~ view of a portion of~the stationary and rotary plate members 12 14 according:to the present invention and showing an alternate valving and se.aling mechanism is illustrated.
According to the structure of Figure 5, each of the passages 2a of the stat.i.onary plate member 12 is provided with a displaceable check valve means 100 and a separate sealing means 102. In the illu~.trated embodiment, the check:valve:means is comprised of a ball member 104 which is urged:toward a seat 106 by resilient means 108. Valve : 30 seat 106 is provided in combined valve seat and s~al member ~ 110 which may be formed of a re:silient material. ~ovable :~ . ~ 14 -~6~36 plate member 14 is similarly provided with ? complementary seal forming member 112 which is arranged -to ccact with the member 110 to provide a fluid tight seal betwe~n the passage 122 of stationary member 12 and the passage means 54 of the ro-tary member 14. As illustrated in the Figure 5 embodiment, cooperating sealing member 12 is provided with a central aperture 158 which is aligned with the similarly provided aperture within the seal mernber 110.
Passage 54 is further provided with means defining a check valve displacing element, finger 114, which is-situated within passage means 54 and arranged to project outwardly from the movable mernber 14 so as to engage, and displace, the ball member 104 of the check valve means 100. In the illustrated embodiment, each o~
the passages 122 of the stationary member l2 is provided -with a combined valve seat and seal member 110. The cooperating seal mer~er 112 is here illustrated as being an annular member arranged about the periphery of movable plate member 14 and which is radially spaced so~as to engage the cooperating seat forming member 110. As i71ustrated, seal member 112~possesses but a single aperture 158.
By providing structure which is situated between the confronting faces of the stationary and rotary plate members, double sealing is provided to 1) provide a fluid .
tight seal between the spray apparatus supply hose 56 and the selected supply passage of the stationary plate rnemher in communication with hose 56 while 2) sealing the non- .
selected supply passages of the stationary plate member from~any contamin:ation which mlght be inadvertently introduced into the region between the plate members 12, 14 from the operation of:changer 10. Furthermore, the - ' ' "' ~,~r~ : ~ ~ 15 -~1536 presen-t inventi.on provides a mechanism by which any residual powders remaining within the spray appar~tus supply structure may be exhausted so as to avoid any contamination forming residues when switching from a spray operation involving a first sprayable material to a spray operation involving a second sprayable ma-terial which may be incompatible with the first sp:rayable material because of colour or other differences. By the rather direct expedient of enlarging the diameter of the stationary and rotary plate members and by suitably arranging the indexing means 64 to accommodate for different sizes and different angular spacings between the stationary plate member passages, an indefinitely large number of different sprayable materials may be communicated to a single spray apparatus while avoiding the risk of contamination between different sprayable materials and assuring the availability of a ~lushing action when switching between two dissimilar and incompatible sprayable materials. Furthermore; multiple spray apparatus may be provided by utilizing multiple porting and multiple supply hoses.
While the invention has been described with reference to a particular utilization and specific exemplary structure has been described, the practitioner will recognize that certain modi~ications mày readily be made. For example, the changer apparatus may be used with material supplies which are not fluidized and need not be limited to use with powders. The translatory and indexing structure may be con.structed to provide a ~ nonro.tary piston member sealingly coupled to a single . through.shaft with the shaft being sl.idingly splined to either the movable pIate or the indexer, or the shaft may 53~i be fixedly attached to both wi-t~ the indexer being slidingly and nonrotarily coup:Led to the stationary plate member.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for communicating a powder spray gun with a plurality of fluidized powder sources while avoiding cross contamination of powders comprising in combination:
a stationary plate member having a powder side and a sealing side, a plurality of powder passages and at least one flushing passage, said passages extending through said plate from the powder side to the sealing side;
hose means coupled to said powder passages on the powder side of said plate for fluid-tight communication of said powder passages with the plurality of powder sources;
further hose means coupled to said at least one flushing passage on the powder side of said plate;
means coupled to said further hose means for flowing a flushing medium therethrough;
plate valve means supported in closely spaced relation to said stationary plate member and having a flow passage means extending through said plate valve means and aligned for fluid communication with said powder .
passages and said at least one flushing passage, hose means coupled to said flow passage means for communicating said flow passage means with the spray gun;
means connected to said valve plate means for varying the spatial relation between said valve plate means and said stationary plate member;
indexing means operative to align said flow passage with a selected one of said powder and flushing passages; and seal means interposed between said stationary plate member and said valve plate means operative to provide sealed communication between said flow passage and said selected one of said powder and flushing passages.

2. The apparatus of claim 1 wherein said plate valve means comprise a plate member mounted for rotation about an axis, said rotation axis being arranged to extend through the stationary plate member, and said spatial relation varying means comprise cylinder means inter-connecting said stationary plate member and said plate valve means actuable to increase the spatial relation to a first predetermined amount and to decrease the spatial relation to a second predetermined amount.

3. The apparatus of claim 2 wherein said indexing means comprise step motor means operative when the spatial relation between the stationary plate member and the valve plate means is at the first predetermined amount to rotate said valve plate means about said axis until said flow passages is aligned with the selected one of the powder and flushing passages and to actuate said piston means to establish a spatial relation of the second predetermined amount.

4. The apparatus of claim 3 including control means to automatically and sequentially operate the piston means and the indexing means to communicate different selected ones of the powder passages with the flow passage and to communicate the flow passage with the flushing passage between successive different powder passage commun-ications.

5. The apparatus of claim 1 including further seal means interposed between said stationary plate member and said plate valve means operative to seal closed the nonselected ones of the powder and flushing passages.

6. The apparatus of claim 5 wherein said seal means comprise:
a plurality of first seal element means situated on said stationary plate member in proximity to the sealing side thereof and arranged to be in surrounding relation to the sealing side orifice of each of the powder and flushing passages; and means defining second seal element means positioned on said plate valve member in juxtaposed relation to the plurality of first seal element means, the second seal element means including a passage means aligned with the flow passage means of the plate valve means to provide unrestricted material flow through from a selected one of the powder and flushing passages to said flow passage means.

7. The apparatus of claim 6 including further a plurality of check valve means situated in the powder passages and having orifices extending from the seal side of the stationary plate member toward the valve plate means, and valve operating means extending from the flow passage, operative to engage and open the check valve means situated in the selected one of the powder and flushing passages.

8. The apparatus of claim 7 wherein each of said check valve means comprise displaceable ball valve member, means resiliently biasing said ball valve member toward a valve seat and said valve operating means comprise a projecting finger element situated in the flow passage means of said plate valve means.