Abstract:
In a device for spraying on pigmented liquids by means of an air flow comprising a base body, a spray nozzle disposed at the front side of the base body, wherein a needle is disposed centrally in the spray nozzle, a compressed air inlet and an adjacent compressed air duct, an outlet opening for a pigmented liquid, wherein a controllable compressed air flow is supplied via the compressed air duct and is guided past the outlet opening for the pigmented liquid where it is loaded with droplets of liquid, these droplets of liquid being discharged through the spray nozzle as long as the compressed air flow is maintained, wherein the nozzle and the needle are disposed in a nozzle head that is removable or replaceable, respectively, as a whole, it is provided that a receptacle for the pigmented liquid to be sprayed on is disposed in the nozzle head.

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for spraying on pigmented liquids by means of an air flow comprising a base body, a spray nozzle disposed at the front side of the base body, wherein a needle is disposed centrally in the spray nozzle, a compressed air inlet and an adjacent compressed air duct, an outlet opening for a pigmented liquid, wherein a controllable compressed air flow is supplied via the compressed air duct and is guided past the outlet opening for the pigmented liquid where it is loaded with droplets of liquid, these droplets of liquid being discharged through the spray nozzle as long as the compressed air flow is maintained, the nozzle and the needle being disposed in a nozzle head that is removable or replaceable, respectively, as a whole. 
     BACKGROUND ART 
     Such a device is described in DE 10 2005 038 162.6. 
     In the known device, it is provided that the pigmented liquid is supplied via an inlet opening from an external receptacle. 
     SUMMARY OF THE INVENTION 
     Based thereon, it is the object of the invention to develop a device of the generic type in a way as to achieve an even easier manipulation. 
     This object is attained according to the invention by disposing a receptacle for the pigmented liquid to be sprayed on in the nozzle head. The nozzle support will then be available with an already filled receptacle; alternatively, the receptacle may be individually filled or refilled, respectively. 
     To this end, a fill opening may be provided that is connected with the receptacle, the fill opening preferably being covered by a slit diaphragm that may consist of silicone. 
     The receptacle may be disposed about the needle so as to achieve a compact, symmetrical design. 
     According to another preferred embodiment, the receptacle has a hollow cylindrical basic shape with a conically tapering front end area forming the outlet opening and a rear end area, a sealing element being inserted into the rear end area of the receptacle. The two mentioned end areas are disposed at the front or at the back, respectively, in relation to the axial direction, i.e. the direction defined by the central longitudinal axis of the needle. Thus, a hollow space is formed inside the receptacle for receiving the pigmented liquid, the hollow space being sealed to the front and to the back. Sealing to the back is provided by the sealing element which in particular consists of Teflon. Sealing to the front is in particular performed by the needle which shuts off the outlet opening when in the rest position, i.e. in the inactive state. To this end, the needle may be force-fitted or pressed into a conically tapering seat of the outlet opening and/or be disposed in this seat in a closely-adhering manner. 
     According to another preferred embodiment, the sealing element closely adheres to an inner wall of the receptacle so as to provide a sealing effect. The sealing element furthermore has a passage opening through which the needle is guided in an axially movable manner, a contact between the sealing element and the needle in the passage opening being narrow enough to provide a sealing effect. The sealing element is in particular inserted into the receptacle by means of an interference fit. A form of an interference fit is preferably also provided between the needle and the sealing element, the contact force thereof advantageously being lower than between the sealing element and the inner wall of the receptacle, however, since the needle should be capable of reciprocating movement in the passage opening. This way, the two contact areas between the sealing element and the receptacle on the one hand and between the sealing element and the needle on the other hand are each designed in a tight manner, i.e. in particular so tight as to avoid a discharge of the pigmented liquid. 
     According to another preferred embodiment, a contact force between the sealing element and the needle guided through the sealing element is defined such as to maintain a relative position between the sealing element and the needle as long as there is no effect of an external force. An effect of an external force is in particular to be understood as the force exerted by the actuating ram of the spraying device. Above all, this ensures that the needle cannot move away from its rest position on its own and without any external action, the rest position being the position in which the needle is disposed in the seat of the outlet opening in a closely adhering manner that is in particular narrow enough to provide a sealing effect. In particular, a passage diameter of the passage opening of the sealing element is approximately 1% to approximately 5%, in particular approximately 2%, smaller than a needle diameter of the needle in the area that is situated in the passage opening when in the assembled state. According to an alternative embodiment, it is however also possible to provide an additional spring to press the needle into the seat of the outlet opening, thereby preventing an accidental opening of the outlet opening and, consequently, an unwanted leakage of the pigmented liquid stored in the receptacle. 
     According to another preferred embodiment, the rear end of the needle is securely but detachably connected to an actuating ram by mechanical means. This enables the nozzle head to be replaced whilst ensuring a simple and secure manipulation of the spraying device. 
     According to another preferred embodiment, the connection between the rear end of the needle and the actuating ram is provided by means of a positive fit. For example, a form of a detachable bayonet coupling is provided between the rear end of the needle and the actuating ram. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The following is a more detailed description of the invention by means of a preferred embodiment, taken in conjunction with the drawing, in which 
         FIG. 1  shows a perspective, partially broken view of a device of the generic type as it is known from DE 10 2005 038 162.6; and 
         FIG. 2  shows a section through the nozzle support in accordance with the inventive solution. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An inventive device has a longitudinal base body  1  which may be handheld in a pencil-like manner, a colour-carrying nozzle part  2  being disposed at the front end thereof. 
     The colour-carrying nozzle part  2  comprises a conical nozzle cover  3  with a passage-and-guide bore  4  for a nozzle  5 , a safety cover  6  that overlaps with the nozzle cover  3  and a ring body  7 . 
     The ring body  7  has an annular, circumferential groove  8 , a guide collar  9  of the base body  1  engaging therewith so that the ring body is mounted for rotation through 360°. 
     Moreover, a nozzle support  10  forming a nozzle head is disposed in the colour-carrying nozzle part  2 , a nozzle pipe  11  extending away therefrom, wherein the nozzle  5  is formed on the front end of the nozzle pipe  11 . A needle  12  is positioned in the nozzle pipe  11 , the needle  12  being acted upon by a helical spring  13 . The helical spring  13  and the needle  12  are positioned in a longitudinal bore  14  of the nozzle support  10 , a longitudinally displaceable ram  15  acting into said longitudinal bore  14  as described below. 
     The nozzle support  10  has a substantially circular outer shape and may be form-fitted into the ring body  7 , a lateral projection  16  of the nozzle support  10  engaging with a slot—not shown in the drawing—of the ring body  7  so as to be non-rotational with respect to the ring body  7 , which in turn is rotatable relative to the base body  1 , however. 
     A colour inlet  17  in the shape of a recess is formed in the projection  16 , wherein either a connecting hose leading to a colour reservoir or the connecting plug of a small, directly attachable colour reservoir is insertable into the colour inlet  17 . 
     The ring body  7  has an external thread  18  over which the internal thread  19  of the safety cover  6  may be screwed. This way, the nozzle cover  3  may be attached to the ring body  7  via the safety cover  6  whilst at the same time axially fixing the nozzle support  10  which is positioned in the front-side recess of the base body  1 . 
     It is apparent from the above description that the entire colour-carrying nozzle part  2  is rotatable relative to the base body  1 , and that the nozzle support  10 , together with the colour inlet  17 , the nozzle  5 , the nozzle needle  12  and the helical spring  13 , is replaceable in a way that no colour-carrying parts are left behind so that work may continue with another colour, i.e. upon inserting a new nozzle support  10 , without any problems whatsoever. 
     The rear end of the nozzle needle  12  is attached to the helical spring  13 , while the front end of the helical spring  13  rests against the tapered nozzle  5  in a way that a forward movement of the actuating ram  15  causes the helical spring  13  to be compressed and a backward movement of the actuating ram  15  causes the helical spring  13  to retract the nozzle needle  12 . 
     At its inner end  20 , the actuating ram  15  is attached to an actuating lever H that is operable in the direction of the arrow P and is mounted for rotation about a pivot axis  21 , the actuating lever H causing the actuating ram  15  to be moved to the right or backwards, respectively, when moved in the direction of the arrow P against the force of a return spring  22 , thereby enabling the helical spring  13  to move the needle  12  in the drawing to the right so that the size of the passage opening of the nozzle  5  is steadily increased when moving further to the right or backwards, respectively, thus allowing a correspondingly larger amount of colour to be delivered. 
     An air inlet  23  is provided at the rear end of the base body  1 . An air duct  24  of a hose-like, flexible material adjoins the air inlet  23  towards the inside. A guide  25  for an adjusting wheel  26  with a knurled surface extends at an angle with respect to the air duct  24 , the adjusting wheel  26  engaging with the compressed air duct  24 , thus opening the latter when moved forward and closing the same when moved backward, thereby allowing the throughput of compressed air to be adjusted. 
     The compressed air duct  24  opens into the conically tapered nozzle cover  3 , causing the air flow to be accelerated and to flow past the nozzle  5 , thereby entraining the colour from a colour duct  27  adjoining the colour inlet  17  due to the low pressure generated by the Venturi effect so that a colour-air mixture is discharged through the nozzle  5 . 
     The compressed air may for example be generated by means of a compressor. The maximum operating pressure amounts to 3 bar. 
     The air duct  24  is guided past the actuating lever H and is squeezed closed at  28  when the actuating lever H is in the front locking position. When the actuating lever H is moved in the direction of the arrow P, this causes the nozzle  5  to be opened due to the backward movement of the needle, thereby simultaneously opening the compressed air duct  24  as already described. 
     The travel of the actuating lever H may be limited or adjusted, respectively, by means of a knurled nut  29 , enabling a constant thickness of the sprayed line to be maintained over a longer period of time. The knurled nut  29  is positioned on a threaded rod  30  which is axially displaced by a rotary movement of the knurled nut  29 , thereby forming a displaceable stop for the actuating lever H. 
     In the above described device of the generic type, it is provided that the pigmented liquid is supplied from the outside via a colour inlet  17 . 
     In the embodiment of an inventive spraying device shown in  FIG. 2 , on the other hand, a replaceable nozzle head  10   a  is provided in which a needle  12   a  and a helical spring  13   a  are directly disposed in a substantially hollow cylindrical receptacle  31  for the pigmented liquid to be sprayed on. At an axial front end, the receptacle  31  tapers conically and has an outlet opening  32  whose inner wall forms a seat  32   a  that also tapers conically in the forward direction. At its front end, the needle  12   a  tapers to form a needle tip  12   b  with which the needle  12   a  passes through the outlet opening  32 . In the rest position of the needle  12   a  shown in  FIG. 2 , the needle tip  12   b  is disposed in the seat  32   a  in a closely-adhering manner so as to prevent a leakage of liquid. The inner wall of the seat  32   a  and the outer contour of the needle tip  12   b  are matched to each other. In particular, they each have the same conicity, i.e. the same inclination angle with respect to the central longitudinal axis  36  of the needle  12   a  or the entire spraying device, respectively. 
     In the vicinity of the outlet opening  32 , a nozzle-head air duct  24   a  ends on the outside of the receptacle tapering conically at the front end, the nozzle-head air duct  24   a  being in connection with the compressed air duct  24  shown in  FIG. 1 . The nozzle-head air duct  24   a  extends between the receptacle  31  and an outer nozzle cap  37  of the replaceable nozzle head  10   a.    
     At an axial rear or back end of the receptacle  31 , a sealing element in the shape of a Teflon seal  33  is inserted into the receptacle  31  by means of an interference fit so as to prevent a leakage of liquid. The Teflon seal  33  has a central passage opening  33   a  through which the needle  12   a  is guided. Guidance of the needle  12   a  through the passage opening  33   a  is designed such that on the one hand an axial reciprocating movement of the needle  12   a  is possible while on the other hand a tight sealing is ensured to prevent a leakage of liquid. 
     Thus, a receiving space  31   a  is formed in the receptacle  31  for receiving the pigmented liquid to be sprayed on. This receiving space  31   a  is defined laterally by the wall of the receptacle  31 , at the front end by the needle tip  12   b  that is tightly disposed in the seat  32   a  of the outlet opening  32  when in the rest position, and at the rear end by the Teflon seal  33 . 
     A refill opening  34  is disposed in the hollow cylindrical wall of the receptacle  31 , the refill opening  34  being shut off by a slit silicone diaphragm  35 . In the described embodiment, the silicone diaphragm  35  is inserted into another opening  34   a  provided in the nozzle cap  37  so as to be aligned with the refill opening  34   a , and has a slit  35   a  that has a pressure-compensating function. When pigmented liquid is discharged from the receiving space  31   a  of the receptacle  31  during the manipulation of the spraying device, the slit  35   a  allows air to enter the receiving space  31   a , thereby causing a pressure compensation to occur. Otherwise, the low pressure generated in the receiving space  31   a  could affect the functioning of the spraying device. On the other hand, the slit silicone diaphragm  35  is designed such that the pigmented liquid cannot be discharged through the slit  35   a . The silicone diaphragm  35  thus has a double function, on the one hand providing for the pressure compensation whilst preventing a leakage of liquid on the other. 
     In the receiving space  31   a , the needle  12   a  is provided with a stop washer  12   c  that is securely attached to the needle  12   a , for example by gluing, pressing or welding. The helical spring  13   a  is designed as a compression spring and is clamped between the stop washer  12   c  and the Teflon seal  33 , thus pressing the needle tip  12   b  of the needle  12   a  into the seat  32   a . When the spraying device is operated, the needle  12   a  is moved backwards in the axial direction against the spring force of the helical spring  13   a , causing the outlet opening  32   a  to open a bit. 
     The front of the needle  12   a  is guided by means of the conically tapering front end area of the receptacle  31 , in particular by the seat  32   a  provided therein, while the back of the needle  12   a  is guided by means of the Teflon seal  33 , in particular by the passage opening  33   a  thereof. 
     For operating the spraying device, the needle  12   a  is positively connected to an actuating ram  15   a  in a detachable manner. This connection is designed for the axial transmission of force from the actuating ram  15   a  to the needle  12   a . To this end, the needle  12   a  has a crimped or bent fixing end portion  12   d  at its rear axial end on the side of the Teflon seal  33  facing away from the receiving space  31   a , the fixing end portion  12   d  engaging with a corresponding radial bore  15   b  of the actuating ram  15   a  when in the assembled state. The connection is detachable, for example in the manner of a bayonet coupling, which allows the nozzle head  10   a  comprising the needle  12   a  to be replaced. 
     Along with the needle  12   a , the replaceable nozzle head  10   a  also comprises the receptacle  31  with the inserted Teflon seal  33 , the receptacle being more or less filled with pigmented liquid depending on the current filling state, the helical spring  13   a  and the outer nozzle cap  37  with the silicone diaphragm  35  inserted therein. The nozzle cap  37  is detachably connected to the base body  1  of the spraying device by means of suitable fixing means not shown in  FIG. 2 , such as a bayonet coupling. Due to the receptacle  31 , the nozzle head  10   a  is equipped with an integrated liquid container. Designed in particular as a hand-held device, the inventive spraying device may therefore be operated independently of an external liquid supply, in particular without requiring a large external liquid container attached separately to the nozzle head  10   a.