Paint spraying unit

Abstract

A paint spraying unit for generating a shaped paint jet, including a paint nozzle positioned in a gap, wherein the paint nozzle includes a needle with a needle head that deviates from a rotationally symmetrical cross sectional design and a paint outlet opening that deviates from a rotationally symmetrical cross sectional design. The needle head is displaceable in relation to the paint outlet opening along a longitudinal axis of the needle for controlling a needle valve formed by the paint outlet opening and the needle head. The needle head, with the paint nozzle in a closed position with reference to the longitudinal axis, closes the paint outlet opening in a positive locking manner. In this connection, the needle head and/or the paint outlet opening is/are formed by a material with elastic properties at least in a surface region with which the two components come in contact.

Claims

1. A paint spraying unit for generating a shaped paint jet, comprising a paint nozzle that is positioned in a gap, wherein the paint nozzle includes a needle with a needle head that deviates from a rotationally symmetrical cross section thereof and a paint outlet opening that deviates from a rotationally symmetrical cross section thereof, wherein the needle head is displaceable in relation to the paint outlet opening along a longitudinal axis of the needle for controlling a needle valve formed by the paint outlet opening and the needle head, wherein the needle head, which has an abutting end surface, with the paint nozzle in a closed position with reference to the longitudinal axis, closes the paint outlet opening in a positive locking manner, and wherein the needle head and the paint outlet opening are formed by a material with elastic properties at least in a surface region with which two components come into contact; wherein the needle is a plastic material part comprising a first component of the two components and a second component of the two components, wherein the needle head comprises the first component and wherein a needle shank comprises the second component, with the needle shank, which extends in the longitudinal axis toward the needle head, comprising a shank outer surface that has an undercut formed in the shank outer surface at a spaced distance from an outermost end of the needle shank along the longitudinal axis, and an end portion of the needle head, which is opposite to the abutting end surface of the needle head, has an inner shape corresponding to the undercut on the needle shank that is engaged and held in the undercut on the needle shank along the longitudinal axis, such that an interlocked connection, which is configured to transmit tensile and compressive forces between the needle head and the needle shank, is formed between the end portion of the needle head and the undercut on the needle shank, and the needle head is fully rotatable about the longitudinal axis in relation to the needle shank; wherein the needle shank comprises a plastics material having a melting point of greater than 200 degrees C., and less than 240 degrees C., wherein the material forming the needle head is a plastic having a melting point of less than 200 degrees C., wherein the needle head is softer than a nozzle body that forms the paint outlet opening, and wherein the needle head is softer than the needle shank.

2. The paint spraying unit as claimed in claim 1, wherein the paint outlet opening is rotatable about the longitudinal axis together with the needle head in order to rotate the shaped paint jet in its orientation with reference to the longitudinal axis.

3. The paint spraying unit as claimed in claim 1, wherein the needle head is connected to the needle shank so as to be separable in a damage-free manner.

4. The paint spraying unit as claimed in claim 1, wherein one of the needle head or the entire needle has a Rockwell hardness of between 65 and 95.

5. The paint spraying unit as claimed in claim 1, wherein the needle shank has a Rockwell hardness of between 100 and 130.

6. The paint spraying unit as claimed in claim 1, wherein a nozzle body has a Rockwell hardness of more than 100.

7. The paint spraying unit as claimed in claim 1, wherein the needle head is also formed by the material with elastic properties in a core region which connects directly to its surface region.

8. The paint spraying unit as claimed in claim 1, wherein the entire needle is softer than the nozzle body that forms the paint outlet opening.

9. The paint spraying unit as claimed in claim 1, wherein the nozzle body is softer than the entire needle.

10. The paint spraying unit as claimed in claim 4, wherein the Rockwell hardness of the one of the needle head or the entire needle is 80.

11. The paint spraying unit as claimed in claim 5, wherein the Rockwell hardness of the needle shank is 115.

12. The paint spraying unit as claimed in claim 6, wherein the Rockwell hardness of the nozzle body is more than 115.

13. The paint spraying unit as claimed in claim 1, wherein the needle shank is produced from a plastics material having a melting point of greater than 215° C. and the needle head is produced from a plastics material having a melting point greater than 170° C.

14. The paint spraying unit as claimed in claim 13, wherein the needle shank is made from polybutylene and the needle head is made from polyamide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details of the present invention are described in the drawing by way of schematically shown exemplary embodiments, in which:

(2) FIG. 1 shows a first exploded representation of a paint spraying unit according to the present invention;

(3) FIG. 2 shows an assembled paint spray head;

(4) FIG. 3 shows a second exploded representation of a paint spray head with a needle;

(5) FIG. 4 shows a cross section through an assembled paint spraying unit;

(6) FIG. 5 shows a needle according to the invention for the paint spraying unit;

(7) FIG. 6 shows a sectional representation of the air link, control disk and air cap;

(8) FIG. 7 shows a representation of a detail of the two-part needle shown in the previous figures;

(9) FIG. 8 shows a schematic representation of a second realization variant of a two-part needle;

(10) FIG. 9 shows a schematic representation of a third realization variant of a two-part needle and

(11) FIG. 10 shows a schematic representation of a fourth realization variant of a two-part needle.

DETAILED DESCRIPTION OF THE INVENTION

(12) FIG. 1 specifically shows an exploded representation of a paint spraying unit 1. The paint spraying unit 1 is formed basically by a body 2, at the bottom end of which a receiving means 3 for a paint container is provided. An alternative embodiment which is not shown is conceivable by the receiving means 3 for the paint container being omitted and a paint supply line supplying the body 2 with paint from a remote receptacle. This is described, for example, in German patent application DE 10 2009 048 022 of the applicant.

(13) The body 2 has a trigger 4 which is freely suspended on a top side of the body 2 and entrains a coupling pin (shown in FIG. 4) via a blind hole, which is arranged at the side of the trigger lever 5, or a bore (hidden here by a cover cap 6). The coupling pin serves, as disclosed generally in the prior art, for pulling a needle 7 back against a spring ballast or the like in order to operate a needle valve 101 (see FIG. 2) for controlling a paint discharge.

(14) The paint spraying unit 1 according to the present invention includes, along with the body 2 and the needle 7, an air link 8, a control disk 9, an air cap 10, a union nut 11 and a rotary actuator 12 with an entrainment means 13 arranged thereon and, where applicable, a further entrainment means 14 arranged thereon. The arrangement of the designated components in the direction of the air flow, proceeding from the body 2, is shown in the realization shown in FIG. 1. The needle 7 is realized in two parts and includes a needle head 16 as the first component 7a and a needle shank 116 as the second component 7b.

(15) The air cap 10, the control disk 9, the air link 8 and the needle 7 form, in this case, a structural unit 15 which provides the technical prerequisites for the paint atomization process. In this case, the needle 7 engages with its needle head 16 in a paint outlet opening 17 which is arranged centrally in the air link 8. The needle head 16, in its wedge form, is adapted, in this case, to the form of the paint outlet opening 17 in such a manner that it closes the paint outlet opening in a paint-tight manner as a result of engagement in the completely pushed-in position. The technical principles of a needle valve, which, as a result of pulling back the needle, provides an opening gap in a paint outlet opening 17, through which paint can then emerge in a metered manner, are disclosed many times in the prior art for rotationally symmetrical needles and paint outlet openings.

(16) FIG. 2 shows an assembled realization of a spray head 20 of a paint spraying unit according to the present invention. The spray head 20, in this case, is formed by the air link 8, the control disk 9 arranged thereon, the air cap 10 covering the control disk 9, the union nut 11 arranged thereon as well as the rotary actuator 12 clamped thereon and the further entrainment means 14. The needle 7, proceeding from the side of the body 2, is not shown in the present case.

(17) A paint nozzle 21 is formed on the paint outlet side of the spray head 20 by a nozzle body 121 (see FIG. 6) with the paint outlet opening 17 and by the needle 7 (see, for example, FIG. 6). The paint nozzle 21, at the same time, forms the needle valve 101 which is closed or open in dependence on a position of the needle 7. The paint nozzle 21, which is slot-shaped in the present case, is arranged in the interior of an atomizer air opening 22 in the air cap 10. The edge of the atomizer air opening 22 and the edge of the paint outlet opening 17 define the ring gap 23 (see FIG. 2) which surrounds the paint nozzle 21 and through which the atomizer air flows for atomizing the paint emerging out of the paint outlet opening 17. A paint mist is generated in this way according to known atomization principles.

(18) Air horns 24 are arranged in the continuation of a longitudinal axis 27 of the slot-shaped paint outlet opening 17 in such a manner that they direct a directed shaped air jet onto the paint mist, which emerges from the paint outlet opening 17 and the ring gap 23, and consequently further reinforces the realization of a flat jet. This principle is also disclosed in the prior art of the applicant which is named in the introduction.

(19) The rotary actuator 12 is clamped on the union nut 11 via lateral clamping wings 25 (see FIG. 2), which rotary actuator is arranged so as to be rotatable about the longitudinal axis 27 by means of the positive closure 26 of the clamping wings 25 engaging behind the union nut 11 in this way. The rotary actuator 12 comprises entrainment means 13 which are arranged in each case corresponding to the air horns 24 and, as a result of the positive locking surrounding hold, ensure the air horns 24 are entrained when the rotary actuator 12 is rotated. In addition, the rotary actuator 12 comprises a caliper guide 30 in which the further entrainment means 14 is guided, the further entrainment means 14 once again being fastened on the rotary actuator 12 by means of a clamping wing 28 and a positive locking undercut 29 behind the rotary actuator 12 in such a manner that it is displaceable about the longitudinal axis 27 along a circular path along the caliper guide 27. The further entrainment means 14, in this case, controls a pin 31 which is arranged on the control disk 9. In this way, the control disk 9, located behind the air cap 10, is able to be rotated by the further entrainment means 14.

(20) FIG. 3 shows the exploded representation which is shown corresponding to FIG. 1, the pistol body 2 not being shown and the arrangement of the individual components having been rotated by 90° clockwise when viewed in the direction of the air flow.

(21) The needle 7 comprises a sealing arrangement on its side remote from the needle head 16. The sealing arrangement includes a pressing surface 40, in front of which at least one seal 41 is arranged (two seals are provided in the present case). The seal or the seals 41 is or are held as a result of a thread 42, which is arranged on the needle 7, by means of a clamping nut 43 screwed thereon and the sealing action thereof can be adjusted as a result of prestressing the clamping nut 43 in a corresponding manner.

(22) The passage 44 (see FIG. 3) for the coupling pin (shown in FIG. 4), which includes the pressure surfaces 45 for the transmission of energy for pulling back the needle 7, then follows the sealing arrangement in the rear direction of the needle 7.

(23) The passage 44 is realized as a substantially quadrant-shaped passage 44, the passage 44 also being provided symmetrically to the longitudinal axis 27 on the other side of the needle (not shown here). As a result of the substantially quadrant-shaped realization of the passage 44, it is possible for the needle to be rotatable about an angle of approximately 90° corresponding to the passage opening 44 without torsional stresses acting through the coupling pin, which passes through the needle, onto the needle 7.

(24) Along with the arrangement of the pressure surface 45 and of the seal, which will be described in more detail in subsequent FIG. 5, FIG. 3 shows the arrangement of the passage openings for the individual air guides. Along with the passage opening for the atomizer air 51, which subsequently passes through the ring gap 23 which is described in FIG. 2, the air link 8 includes passage openings for the horn air 50 and passage openings for the compensation air 52. The control disk 9 includes two control openings 53 and 54 which, when the control disk 9 is rotated about the longitudinal axis 27, can be made to coincide either with the passage openings for the horn air 50 or the passage openings for the compensation air 52. Corresponding air channels for the horn air and the compensation air are also present in the air cap 10.

(25) The diameter of the control disk 9 is realized slightly smaller than the diameter of the air link 8. On its surface facing the control disk 9, the air link 8 comprises springs 60 and 61, between which the control disk 9 is inserted and guided when rotating about the longitudinal axis 27. At least one of the springs 60, 61, in this case, projects beyond the control disk 9 in the mounted state such that it engages in a groove 62, which is arranged in the air cap 10 on the contact side to the air link 8 and control disk 9, for the defined arrangement and fixing of the rotational position of the air cap 10.

(26) The technical function of the described reversible air paths between an air passage through the horns 24 and an air passage through the compensation bores 65 is the avoidance of an increase in the inside air pressure inside the paint spraying unit. As fans are used for providing the working air in the majority of cases in the units and they utilize a certain volume flow for their own cooling purposes, it is disadvantageous to reduce the volume flow which can pass through a spray head. Consequently, as soon as the air horns 24, which form the spray jet, are switched off by means of the pin 31 as a result of the movement of the control disk 9 to influence the spray jet output, a reduced overall air volume flow would be provided without the compensation bores 65. This would have to be tolerated by the fan. Insofar as the fan relies on the volume flow for cooling purposes, the corresponding volume must be blown through the compensation bores in order to avoid increased backlog and to continue to cool the fan adequately. This technique is described in prior art EP 0 596 939 B1 for another genus of spray guns.

(27) FIG. 4 shows a cross section through a paint spraying unit 1 according to the present invention. The individual component parts are characterized corresponding to the above-described reference symbols.

(28) Proceeding from a paint conveying tube (not shown) in a paint container, which is screwed to the receiving means 3, paint is transported through a rising tube 70 via the paint chamber 71 to the paint nozzle 21. The paint chamber 71, in this case, is realized substantially as a sleeve which receives the needle 7 completely and has a passage opening for the coupling pin 72 and the access of the rising tube 70. In operation, only the front part of the paint chamber 71 is filled with paint.

(29) In the interior of the paint chamber, the needle 7 is arranged so as to be displaceable along the longitudinal axis 27 for opening the paint outlet opening 17. The needle can be provided as a two-part realization when, for example, a front portion 75 is to be produced with the needle head 16 from a different material to a rear portion 76. This is to be provided, for example, for the realization of the needle head as a wear part which is to be replaced more frequently compared to the rest of the arrangement. In principle, it would also be possible to realize a simple rotary joint by means of the parts of the front and rear portion 75, 76, which are pushed into one another, in order to mount the needle head 16 with the paint outlet opening 17 so as to be rotatable. In this case, the above-described semicircular passage could be omitted. A problem of the rather impaired embodiment could be the components sticking together as a result of the paint.

(30) FIG. 5 shows a needle 7 according to the invention in detail. In contrast to the conventional implementations of the needle disclosed in the prior art where a sealing package is arranged fixedly in the housing, which is expensive and structurally elaborate, in the present case the sealing arrangement is fixed on the needle 7. Whether the needle is realized, in this case, as a two-part realization, as shown in the present case, or is present as a one-part needle, is not important to the sealing arrangement nor to the functionality described below.

(31) Especially in the professional tools sector, sealing packages where the tension is able to be adjusted are often of great advantage. The adjustment or readjustment of a sealing tension brings about access to the optimum trigger pressure point which is determined by the sliding friction of the needle 7 in the seal, or in the present case by that of the seal 41 in the paint chamber 71.

(32) The adjustability is provided in the present case as a result of the tension which is exerted by way of the clamping nut 43 on the sealing package, consisting of the two sealing rings 41. The clamping nut 43 is screwed on the thread 42 for this purpose against the seals 41 and presses them onto the pressing surface 40. Depending on the pressing force, a sealing bead, which brings about the sealing action in relation to the wall of the paint chamber 71, is generated radially outward from the longitudinal axis 27.

(33) As an alternative to this, it is also possible for a coupling means of the needle trigger 4, 5 to abut against a, with reference to the longitudinal axis 27, radial broadening or radial constriction of the needle 7 and to move this consequently in the manner of a disk entrainment means.

(34) The present invention consequently also includes a paint spraying unit for generating a paint jet with a needle 7 which is received so as to be displaceable in a channel, a paint-conducting portion of the channel being sealed by a seal which encases the needle, and the seal being fixed in the axial direction to the needle.

(35) The seal, in this case, is fixed between a first stop and a second stop, at least one stop preferably being adjustable in the axial direction along the needle.

(36) For improved guiding of the seal, the seal is fixed to the needle in the circumferential direction, for example, by a positive locking tongue-groove rotary fixing or a rough structure on the pressing surface 40, e.g. a lock washer structure.

(37) Insofar as the needle 7 is provided in two parts or multiple parts, the front needle portion 75 and the rear needle portion 76 can be realized so as to be rotatable with respect to one another about a common longitudinal axis 27. It is advantageous, in this case, that the first material of the front portion 75 is a plastics material (for example, polyoxymethylene material) and that the second material of the rear portion 76 is a metal material (for example, cast zinc). During production, in this case, the front portion 75 can be connected to the rear portion 76 as a result of overmolding the rear portion.

(38) It is furthermore advantageous for the paint outlet opening 17 to be realized from a third material which is harder than the material of the front needle portion 75 and for the third material to be, in particular, ceramic and, in particular, sintered ceramic.

(39) FIG. 6 shows a sectional representation of the already disclosed components air link 8, control disk 9 and air cap 10, the needle head 16 also being shown. The paint outlet opening 17, which is realized in the air link 8, together with the needle head 16 forms the paint nozzle 21. In this connection, the needle head 16 is in a retracted position such that the paint nozzle 21 is open. In this connection, a nozzle body 121, which forms the paint outlet opening 17, is formed from an elastic material 201 in a circular shape with respect to its inside 121a around the paint nozzle 21 such that, with the needle valve 101 in the closed position, the needle head 16 abuts against a surface region 201a of the elastic material 201 and in so doing deforms the surface region elastically.

(40) FIG. 7 shows the needle 7 disclosed in the preceding figures in a view of a detail of its needle head 16. A tip 16a of the needle head 16 is formed from an elastic material 202 such that the needle head 16, with the needle valve in the closed position, abuts with a surface region 202a, which is formed by the elastic material 202, against the nozzle body in the region of the paint outlet opening thereof, in so doing the needle head 16 or the tip 16a of the needle head 16 being elastically deformed. The elastic material 202 is symbolized in FIG. 7 by cross hatching.

(41) According to a realization variant that is not shown, it is also provided to realize either only the nozzle body or only the needle head with an elastic surface region such that, with the needle valve in the closed position, in each case only the nozzle body or the needle head is elastically deformed. The respectively other surface region in these cases is then realized from a less elastic or non-elastic material such as, for example, a hard plastics material or a metal.

(42) FIG. 8 shows a schematic representation of a partially sectioned view of a detail of a second realization variant of a needle 301. The needle 301 is realized in two parts and includes a needle head 302 and a needle shank 303, the needle head 302 forming a first component 301a of the needle 301 and a needle shank 303 forming a second component 301b of the needle 301. The needle head 302 is received by a rotationally symmetrical lug 304 with a bead 305 in a bore 306 of the needle shank 303. In this connection, the bore 306 includes a recess 307 which is adapted to the bead 305 in such a manner that the bead, with the needle head 302 and the needle shank 303 plugged together, is held in such a manner in the bore 306 that tensile and compressive forces are able to be transmitted largely without play in the direction of the longitudinal axis 308 of the needle 301 and that the needle head 302 is infinitely rotatable about the longitudinal axis 308 in relation to the needle shank 303. As a result of a correspondingly elastic realization of the bead 305 and/or of the needle shank 303, the needle head 302 and the needle shank 303 are separable and connectable in a damage-free manner. As a result, it is also possible to replace the needle head 302 or the needle shank 303.

(43) FIG. 9 shows a schematic representation of a partially sectioned view of a detail of a third realization variant of a needle 401. The needle 401 is realized in two parts and includes a needle head 402 and a needle shank 403, the needle head 402 forming a first component 401a of the needle 401 and a needle shank 403 forming a second component 401b of the needle 401. The needle head 402 is received by a rotationally symmetrical lug 404 with a journal 405 in a bore 406 of the needle shank 403. In this connection, the bore 406 includes a recess 407 which is adapted to the journal 405 in such a manner that the journal, with the needle head 402 and the needle shank 403 plugged together, is held in such manner in the bore 406 that tensile and compressive forces are able to be transmitted largely without play in the direction of a longitudinal axis 408 of the needle 401 and that the needle head 402 is infinitely rotatable about the longitudinal axis 408 in relation to the needle shank 403. As a result of orienting the contact surfaces of the journal 405 and the recess 407 transversely to the longitudinal axis 408, the needle 401, once the needle head 402 and the needle shank 403 have been plugged together, is no longer separable without destruction. The advantage here is that the needle is able to receive high tensile forces and consequently even a needle 401 which is stuck fast in the gap of the paint nozzle is able to be released again without there being any risk of separating the needle shank 403 from the needle head 402.

(44) FIG. 10 shows a schematic representation of a sectioned view of a detail of a fourth realization variant of a needle 501. The needle 501 is realized in two parts and includes a needle tip, which is designated as the needle head 502, and a needle shank 503, the needle head 502 forming a first component 501a of the needle 501 and a needle shank 503 forming a second component 501b of the needle 501. The needle 501 is realized as a two-component injection molded part. In this connection, the needle shank 503 is produced from a plastics material with a melting point which is greater than a melting point of a plastics material from which the needle head 502 is produced. The needle shank 503 is produced from a plastics material with a melting point of greater than 200° C. and preferably greater than 215° C. and less than 240° C., a polybutylene being used, in particular, as the material or first component. The needle head 502 is produced, in particular, from a plastics material with a melting point of less than 200° C. and preferably greater than 170° C., a polyamide being used, in particular, as the material or second component. According to a realization variant, it is also provided to configure the two-component injection molding process in such a manner that first of all a needle shank is produced and then the needle shank is placed in an injection mold as an insert part and there is injected around with a needle head. In this connection, the materials are selected such that the needle head does not melt or interlink with the needle shank. In principle, once the needle 501 has been produced, the needle head 502 is rotatable in relation to the needle shank 503 about a longitudinal axis 508 of the needle 501. However, the needle shank 503 comprises an undercut 509 which the needle head 502 engages over and by means of which the needle head is held on the needle shank 503 in the direction of the longitudinal axis 508.

LIST OF REFERENCES

(45) 1 Paint spraying device 2 Body 3 Receiving means 4 Trigger 5 Trigger lever 6 Cover cap 7 Needle 7a First component 7b Second component 8 Air link 9 Control disk 10 Air cap 11 Union nut 12 Rotary actuator 13 Entrainment means 14 Further entrainment means 15 Structural unit 16 Needle head 16a Tip of 16 17 Paint outlet opening 20 Spray head 21 Paint nozzle 22 Atomizer air opening 23 Ring gap 24 Air horn 25 Clamping wing 26 Positive locking closure 27 Longitudinal axis 28 Clamping wing 29 Positive locking undercut 30 Caliper guide 40 Pressing surface 41 Seal 42 Thread 43 Clamping nut 44 Passage 45 Pressure surface 50 Passage opening for the horn air 51 Passage opening for the atomizer air 52 Passage opening for the compensation air 53 Control opening 54 Control opening 60 Spring 61 Spring 62 Groove 65 Compensation bore 70 Rising tube 71 Paint chamber 72 Coupling pin 75 Front portion 76 Rear portion 101 Needle valve 116 Needle shank 121 Nozzle body 121a Inside 201 Elastic material 201a Surface region of 201 202 Elastic material 202a Surface region of 202 301 Needle 301a First component 301b Second component 302 Needle head 303 Needle shank 304 Rotationally symmetrical lug 305 Bead 306 Bore 307 Recess 308 Longitudinal axis 401 Needle 401a First component 401b Second component 402 Needle head 403 Needle shank 404 Rotationally symmetrical lug 405 Journal 406 Bore 407 Recess 408 Longitudinal axis 501 Needle 501a First component 501b Second component 502 Needle body 503 Needle shank 508 Longitudinal axis 509 Undercut on 503