US 3705687 A
A membrane gun for spraying abrasive liquids has a membrane supported around its full periphery in a chamber in the body of the membrane gun, a first surface of the membrane forming a wall of this chamber. A tubular member is supported in the chamber with a free end facing the membrane. A second surface of the membrane is acted on variably by a composite plunger of a single-acting pneumatic cylinder. The liquid is admitted to the chamber and must pass over the free end of the tubular member to enter the interior of their member and be expelled from the gun through a nozzle. Regulation of the plunger regulates the distance of the membrane from the tubular member and thus the flow through the gun. The pneumatic cylinder is arranged coaxially with the body of the gun to occupy the minimum lateral space.
Claims available in
Description (OCR text may contain errors)
United States Patent Vicentini et al.
 SPRAYING DEVICE, MORE PARTICULARLY FOR ABRASIVE LIQUID COMPOSITIONS  lnventorsz'Giorgio Vicentini; Giulio Console, both of Turin, Italy  Assignee: Boeri di A.G. Boeri & C., Turin,
Italy  Filed: June 18, 1971  Appl. No.: 154,375
 Foreign Application Priority Data June 25, 1970 ltaly "69198 A/70  us. Cl. ..239/92,239/296,'239/412 s11 rm. Cl. ..-B05b 1/30  Field of Search ..239/88, 92, 410, 41 1, 412, Y 239/296; 251/6l.1, 62, 331
 I References Cited UNITED STATES PATENTS 3,622,078 11/1971 Gronert ..239/412 X [451 Dec. 12,1972
3,424,385 1/1969 Gutermann eta] ..239/4l2 3,194,502 7/1965 West ..239/411 Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar Attorney-Richard C. Sughrue et a].
[5 7] ABSTRACT A membrane gun for spraying abrasive liquids has a membrane supported around its full periphery in a chamber in the body of the membrane gun, a first surface of the membrane forming a wall of this chamber. A tubular member is supported in the chamber with a free end facing the membrane. A second surface of the membrane is acted on variably by a composite plunger of a single-acting pneumatic cylinder. The liquid is admitted to the chamber and must pass over the free end of the tubular member to enter the interior of their member and be expelled from the gun through a nozzle. Regulation of the plunger regulates the distance of the membrane from the tubular member and thus the flow through the gun. The pneumatic cylinder is arranged coaxially with the body of the gun to occupy the minimum lateral space.
4 Claims, 4 Draiving Figures PAIENTED E 12 I972 3.705.687
- SHEET 3 0F 3 Fig. 5
This invention relates to a spraying device for abrasive liquid compositions.
The use of abrasive liquid compositions for polishing has become common. These compositions differ greatly from one another in their characteristics, and their viscosity, which is a very important factor as regards spraying, varies from 6,000 to 180,000 cps.
Spray guns of the type used for spraying paints and the like were at first used for spraying abrasive liquid compositions. In these guns a needle valve capable of being actuated from outside is provided in a duct through which the material to be sprayed is supplied, and the supply of material is regulated by means of this valve. When this material consists of an abrasive liquid composition the excessive wear to which the needle valve is subjected makes the gun unserviceable in a short time, and it is therefore clear that the gun is unsuitable for this purpose.
, The guns described above were thus of little practical utility, and were soon replaced by spraying devices more suitable for abrasive liquid compositions and known as membrane guns. The membrane gun generally comprises an elongated substantially cylindrical body having inside it a duct which communicates at one end with the supply system and at the other end with an ejector nozzle. The body is also provided with a generally radial connector incorporating a duct through which compressed air is supplied. Inside the duct through which the abrasive composition is supplied there is usually a transverse diaphragm which cooperates qt its edge with the surface of a membrane. The membrane when in contact with this diaphragm closes the supply duct, whereas the membrane when separated from the diaphragm permits the abrasive composition to pass between the membrane and the free edge of the diaphragm.
A device for controlling the open position of the membrane is arranged radially on the cylindrical body. This device is generally of the all or nothing type or, more rarely, consists of a pneumatic cylinder and regulating device, of very cumbersome structure and difficult to manipulate,-which is adapted to permit the membrane to assume more than one open position. The regulating device acts on the membrane so as to limit the displacement of the membrane, the arrangement being such that the membrane, when not displaced completely blocks the duct through which the abrasive material is supplied.
For very low operating pressures, the side of the membrane remote from the diaphragm is provided with a projection adapted to connect the membrane with the control device. In this case the abrasive liquid composition is supplied at a pressure which does not permit resilient deformation of the membrane itself.
During the polishing operations the membrane guns are generally mounted on a casing known as a hood which covers one or more polishing drums. These drums are rotatably mounted on a shaft and are disposed tangentially to the surface to be polished.
, The membrane guns described above have numerous disadvantages. Above all, the abrasive composition feed is generally axial, whereas the atomizing air feed and the device for controlling the position of the membrane are arranged radially and spaced apart from one another. As a consequence, the group of supply ducts connected to the gun is very bulky and does not permit easy and convenient arrangement of this gun on the hood.
Another disadvantage of the known membrane guns is that, because of the bulk of thedevice for controlling the position of the membrane, the diaphragm is located at a relatively great distance from the ejector nozzle. Consequently, when the membrane blocks the supply duct at the end of the spraying operation there is a considerable quantity of abrasive composition downstream of the diaphragm, and if the viscosity of the abrasive composition is below a certain value this abrasive composition drips out.
Since the diaphragm is arranged transversely in the supply duct, it is also subjected to heavy wear. In membrane guns the diaphragm is generally formed integrally with the cylindrical body, and therefore rapid wear of the diaphragm leads to rapid wear of the gun itself, so that the costs are high.
Known membrane guns'are generally employed in automatic polishing plants in which a plurality of guns are used and are fed simultaneously by one pressure system and in which the consumption of the abrasive composition is controlled by two timing devices which set the beginning and'the end of the spraying process. Since all the guns are connected to the same supply system and since the pressure drops in the connections leading to each individual gun differ from one gun to another, each gun consumes a larger or smaller quantity of abrasive composition according to whether the pressure at which it is fed is larger or smaller. The consequences of this fact map be very serious inthat they may cause non-uniform polishing of a workpiece.
In order to avoid this disadvantage in the known membrane guns it would be necessary to regulate the rates of consumption of the abrasive composition in accordance with the pressure drops in the supply system on each of the guns used so as to obtain uniform consumption of the abrasive material and therefore uniform polishing. In order to obtain this it would be necessary to adopt the expensive solution of providing each gun with two timing devices adapted to regulate the beginning and the end of the period of consumption of the abrasive composition.
In order to eliminate this disadvantage, in one known membrane gun the position of the membrane is controlled by single-acting pneumatic cylinder, and the projecting length of the rod of this cylinder is regulable from outside. In this way, by varying the aperture through which the abrasive composition passes it is possible to regulate the quantity of material sprayed, thus compensating for the non-uniformities of feed pressure which are found in the various guns mounted on the same protective cap. But because of the position of the pneumatic control cylinder; this regulation of the projecting length of the rod is very difficult and not very accurate. It must also be noted that when a pneumatic control cylinder of the type described above is used, the times which the membrane takes to return to the closed position are very long and do not permit compositions of very high viscosity to be sprayed under the best conditions.
than!" [nun The invention provides a spraying device for an abrasive liquid composition, comprising an elongated body having a longitudinal axis, a nozzle for ejecting abrasive compositions and atomizing air, the nozzle being connected longitudinally to one end of the body, a passage leading from the exterior into the body and communicating with the nozzle, the abrasive composition being adapted to be admitted through such passage and expelled through the nozzle, a membrane located in such passage, and regulating means for varying the position of the membrane in order to vary the flow of abrasive composition through the passage; with the improvement that the regulating means includes a longitudinally arranged single-acting pneumatic cylinder having a plunger adapted to co-operate with the membrane, and a pin member arranged longitudinally and being adjustable from outside the body to limit the permissible movement of the plunger.
FIG. 1 is a diagrammatic cross section through a protective hood provided with a spraying device of the invention,
FIG. 2 is a front elevation view on an enlarged scale of the spraying device of FIG. 1, partly broken away to show interior construction;
FIG. 3 is a view on line III III of FIG. 2, and
FIG. 4 is a side view in elevation of part of the spraying device of FIGS. 1 to 3.
FIG. 1 shows a workpiece 1 to be polished. A plurality of polishing drums 2 rotatably supported by a shaft 3 are disposed tangentially to the surface of the workpiece. The polishing drums are protected by a protective hood 4 which consists of a cylindrically curved sheet 5 connected to a suction device (not shown in the drawing) through a connecting duct 6. The protective hood 4 has a plurality of radial holes 7 each provided externally with an inlet funnel 8 rigid with the sheet 5.
The end part of a spraying device 9 is arranged in each hole 7 and inside the funnel 8. This device comprises an elongated cylindrical body 11 located outside the hood 4 and an ejector nozzle 10 extending axially from the body 11 and projecting into the funnel 8.
The hood 4 is provided externally with a bracket 12 adjacent each hole 7, the bracket connecting one end of a support bar 13 pivotally to the hood. The other end of the bar 13 is mounted in a hole 14 in a bracket 15 extending radially from the cylindrical body 11 and rigid with this body. Inside the bracket 15 there is an internally screw-threaded hole 16 (FIG.2) accommodating a screw 17 adjustable from outside to secure the cylindrical body 1 l in a predetermined position with respect to the hood 4. As is best seen in FIG. 3, the cylindrical body 11 comprises a plurality of parts, the first of which is a body 18 located at the end remote from the nozzle 10. The body 18 is substantially cylindrical and has a flat end surface 19, a cylindrical cavity 20 being formed coaxially in the body 18 and ending at the surface 19. On its end opposite the surface 19, the body 18 has a flat annular surface 21 from which a cylindrical projection 22 extends axially. Inside the projection 22 is a coaxial bore 23, that communicates with the cavity 20.
A cylindrical rod 24 is slidably mounted inside the hole 23 and extends into the cavity 20 where it is integrally connected to an end wall 25 of a cup-shaped body 26. The free end of this body is provided with a flange 27 bounded externally by a cylindrical surface disposed in sealing contact with the cylindrical surface of the cavity 20. The length of the rod 24 is such that when the end wall of the body 26 touches the end surface'of the cavity 20, a short section at the free end of the rod 24 extends outside the projection 22.
The open end of the cavity 20 is closed by a disc 28 which is prevented from leaving the cavity 20 by a circlip 29 mounted inside this cavity 20. The disc 28 is provided with a central threaded hole 30 into which a threaded pin 31 is screwed. The end of this pin outside the cavity 20 is provided with a knurled'head 32, and the end of the pin inside the cavity 20 is adapted in certain conditions to engage the end wall 25 of the body 26. A knurled locking ring 33 screwed on to the pin 31 is located between the head 32 and the disc 28.
The disc 28 is provided internally with an annular groove 34 which is coaxial with the pin 31 and accommodates the end of a helical spring 35. The other end of the spring 35 is introduced into the body 26 and bears against the end wall 25. The end portion of the cavity 20, together with the flange 27 and the external cylindrical surface of the body 26, define an annular chamber 36 which is sealed by means of a seal 37. The chamber 36 communicates with the exterior through a radial duct (not shown in the drawing) formed inside the body 18 and communicating with a connector 38 (FIGS. 1, 2, 4, 5) adapted to permit a compressed air supply tube 39 to be connected to the body 18. The compressed air supplied through the tube 39 will be referred to as control air.
The cylindrical body 11 also includes an annular body 40 (FIG. 3) fitting around the cylindrical projection 22 and having an external diameter equal to the external diameter of the body 18, and a cylindrical body 41 of which the external diameter is equal to that of the body 18. The cylindrical body 41 is bounded at its ends by two flat surfaces 42 and 43 and is arranged in contact with the annular body 40.
For interconnecting the bodies 18, 40 and 41, holes 44 and 45 are formed in the bodies 40 and 41 and extend through these bodies coaxially with blind screwthreaded holes 46 formed in the surface 21 of the body 18, to accommodate screw-threaded bolts 47.
A cylindrical cavity 48 formed in the surface of the body 41 has a diameter equal to the external diameter of the projection 22 and is partly occupied by the end portion of this projection 22. The cavity 48 has a flat end surface 49. A membrane 50 of disc shape is arranged against this surface and is adapted to come into contact centrally with the free end of the rod 24.
The full periphery of the membrane 50 is kept in contact with the surface 49 by means of a raised rim 52 of a disc 51 arranged inside the cavity 48. The disc 51 bears against the end surface of the projection 22; a central tubular projection 53 integral with the disc fits round the rod 24 and is located inside an enlarged end part 54 of the bore 23. By means of its projection 53 the disc 51 closes the cavity 54 and forms the outer boundary of an annular chamber 55 which communicates with the annular chamber 36 through the gap between the rod 24 and the cylindrical surface of the bore 23. The chamber 55 is sealed at its end nearest the membrane 50 by means of a seal 56.
' A substantially cylindrical projection 57 coaxial with the cylindrical body 11 extends from the surface 43 of the cylindrical body 41. A coaxial cavity formed inside theprojection 57 is provided with two annular grooves 58 and 59 separated from one another by an internally screw-threaded annular projection 60. At its inner end the cavity in the projection 57 terminates in a frustoconical hole 61 communicating with a cylindrical hole 62 in the body 41, the other end of this hole 41 communicating with a cylindrical cavity 63 closed at one end by the membrane 50. A tubular body 64 is fixed in the hole 62, and projects into the cavity 63. It is adapted to contact with the membrane 50 when the pressure on both sides of the membrane is equal. 7
A seal 65 is arranged at the end of the cavity defined by the groove 58' inside the projection 57, and cooperates with a frusto-conical section 66 of an internal body 67 of the nozzle 10. The body 67 extends into the interior of the projection 57 and ends in a frusto-conical section 68 that co-operates with the surface of the hole 61. The body 67 also has a screw-threaded section 69'that co-operates with the screw-threaded projection 60'so as to secure the body 67 against axial-movement with respect to the cylindrical body 41. The outer surface of'the body 67 inside the projection 57 bounds two annular chambers 70 and 71 defined by the grooves 58 and 59. r
In addition to the body 67, the nozzle includes a cap 72 secured to the end of the projection 57 of the cylindrical body 41 by means of a ring 73 screwed on to a screw-threaded end of this projection 57. The cap 72 has two internal frusto-conical surfaces adapted to cooperate with two annular frusto-conical projections 74 and 75 of the internal body 67 which are separated from one another by a cylindrical section 76.
At its free end the internal body 67 terminates in a conical section 77. This section projects outside through a hole 78 formed centrally in the end of the cap 72. The projections 74 and 75, the section 76 of the body 67 and the internal surface of the cap 72 bound an annular chamber 79 which communicates with the chamber 70 through an axial duct 80 formed inside the body 67. An axial duct 81 formed inside the cylindrical body 41 provides communication between the chambers 70 and 71 and between these chambers and a duct 82 perpendicular to the axis of the cylindrical body 41. The duct 82 leads to the outside and is connected through a connector 83 (FIG. 2) to an external tube 84 through which atomizing air is supplied.
Two axial projections 85 extending from the end wall of the cap 72 are located outwardly of the hole 78 in diametrically opposite positions with respect to this hole and inclined outwards.
Each of the projections 85 has a generally radial hole 86 (FIG. 3) communicating with the annular chamber 79 through a duct 87. The cap 72 has a frusto-conical surface 88 round the conical section 77 of the body 67. This surface is spaced away from the surface of the section 77 and in conjunction with that section, with the annular projection 75 and with the end wall of the cap 72, bounds an annular chamber 89 communicating with the atmosphere through a plurality of holes 90. The annular chamber 89 communicates with the annular chamber 71 through an axial duct 91.
A duct 92 of conical shape formed inside the body 67 is coaxial with and passes through t'his body. The duct. 92 ends in an outlet hole 93 of small cross-sectionalarea and communicates at the other end with the interior of the tubular body 64.
The'outside surface of the tubular body 64 located inside the cylindrical cavity 63, together with the surface of this cavity and the membrane 50, bound an an- 'nular chamber 94. This chamber is adapted to be placed in communication with the interior of the tubular body 64 by axial deformation of the membrane 50.
The annular chamber 94 also communicates with the exterior through a radial duct 95 (FIGS) and a duct 96 perpendicular to the axis of the cylindrical body 41 and formed inside this body. The duct 96 is connected through a connector 97 with a tube 98 adapted to supply the abrasive composition to the interior of the annular chamber 94.
OPERATION OF THE DEVICE 4 The device 9 described above operates in the followingway. When the device is not in operation, neither the atomizing air nor the control air are supplied to the device. whereas on the other hand theabrasive composition fills the annular chamber 94. This chamber is closed by the membrane 50 which is forced by the rod 24 to close the end of the tubular body 64. The rod 24 is pressed against the membrane 50 by the spring 35.
Before spraying commences, the ring 33 is unscrewed and by means of the head 32 the pin 31 is rotated so as to be located in the required axial position inside the cavity 20. The axial position of the pin 31 depends on the quantity of abrasive composition which it is required to spray and on the pressure at which this composition is supplied. When the required axial position is reached, the pin 31, is locked by retightening the ring 33. This defines the possible movement of the "rod 24, .of the cup-shaped body 26, and therefore of the membrane 50, and so adjusts the size of the passage which establishes communication between the annular chamber 94 and the abrasive composition outlet duct 92. This passage is formed between the membrane 50 and the free end of the tubular body 64 when the membrane 50 is axially deformed under the pressure of the abrasive composition and comes into contact with the free end of the rod 24. t
This adjustment makes it possible to compensate for any load losses in the ducts through which the abrasive composition is supplied to the various devices 9 mounted on the same hood 4, so as to equalize the delivery of all the device 9.
When the spraying begins, the tubes 39 and 84 (FIG. 2) supply the device 9 with control air and atomizing air at the same time. The atomizing air passes through the tube 84 and the connector 83 to the interior of the duct 82, from which it passes through the duct 81 (FIG. 3) into the annular chamber 71. Same of the atomizing air passes from these along the passage 91 to reach the interior of the annular chamber 89. From there it passes out through the holes 90 and mixes with the abrasive composition emerging through the hole 93.
The other atomizing air inside the chamber 71 passes through the duct 80 into the annular chambers and 79 and from the second of these it passes through the ducts 87 to the outlet holes 86 formed in the projections 85.
The control air, on the other hand, passes through the Connector 38 (FIG. 2) into the annular chamber 36 (FIG. 3) and exerts a pressure on the cup-shaped body 26, forcing this body to slide inside the cavity 20 against the action of the spring 35 until the free end of the pin 31 is in contact with the internal surface of the end wall 25 of the body 26.
The sliding movement of the body 26 and therefore of the rod 24 axially frees the membrane 50 so that, under the thrust due to the abrasive composition under pressure inside the chamber 94, the membrane is deformed so as to move away from the end of the tubular body 64. The deformation of the membrane 50 thus permits the abrasive composition to pass into the duct 92 and escape through the outlet holes 93.
The volume of abrasive composition contained inside the duct 92 and inside the tubular body 64 is very small, so that the disadvantage of dripping of the abrasive material when the device is not in operation is practically eliminated.
The tubular body 64, beinga separate member mounted in the cylindrical body 41, can easily be replaced when worn out by the abrasive material passing through it.
What I claim is:
l. A spraying device for an abrasive liquid composition, comprising an elongated body having a longitudinal axis, a nozzle for ejecting abrasive composition and atomizing air, the nozzle being connected longitudinally to one end of the body, a passage leading from the exterior into the body and communicating with the nozzle, the abrasive composition being adapted to be admitted through such passage and expelled through the nozzle, a membrane located in such passage, and
regulating means for varying the position of the membrane in order to vary the flow of abrasive composition through the passage; said regulating means including a longitudinally arranged single-acting pneumatic cylinder having a-plunger adapted to co-operate with the membrane, and a pin member arranged longitudinally and being adjustable from outside the body to limit the permissible movement of the plunger, said passage including a chamber in which is secured a tubular member having a free end exposed in said chamber, said abrasive composition being adapted to flow over said free end before reaching the nozzle, the membrane being supported around its full periphery in the body with a first of its surfaces defining a wall of said chamber facing the free end of the tubular member, the plunger of the pneumatic cylinder being adapted to bear on a portion of the second surface of the membrane opposite the free end of the tubular member to regulate the distance of the membrane from the free end of the tubular member and thus regulate the flow of abrasive composition.
2. The spraying device of claim 1, in which the body has a duct connecting the chamber outside the tubular member to the exterior, this duct being adapted to be connected to a source of abrasive composition.
3. The spraying device of claim 1, in which the tubular member is replaceably mounted in the body.
4. The spraying device of claim 1, including resilient means biasing the plunger of the pneumatic cylinder towards a position in which the plunger presses the membrane against the free end of the tubular member to preven flow of abrasive composition and including means a apted to a mu compressed air to sue cylinder to overcome the resilient means.