Airbrush

The present invention relates to airbrushes, and more particularly, to an improved airbrush of relatively small size of the type used by hobbyists and craftsmen for painting relatively large areas.

Airbrushes have long been used by artists, photographers, designers, illustrators and others for fine or delicate work. Over a long period of development, two general types of airbrushes have emerged, those having a single control lever for controlling the entry of air or other aeriform substance and the amount of paint flow, and the other having only a control for entry of air with no provision for adjusting the flow of paint during operation. A variety of both types are commercially available, the former being relatively more expensive and used for fine or delicate work, and the other type, because of the lack of control of paint flow, normally being used for less delicate work, such as the painting of models, touch-up work, and work on relatively large areas not requiring fine control of the paint spray. Indeed, some of the less expensive commercially available airbrushes of the latter type are hardly more than an atomizer in that air is blown over a dip tube to draw the paint from a receptacle and force it through a preset nozzle.

The present invention is directed to airbrushes of the less expensive type, the object being to provide an airbrush that can be sold at a price competitive with airbrushes in the low price category yet have a performance approaching that of more expensive airbrushes. A more specific object of the invention is to provide an airbrush having a minimum number of parts that can be manufactured and assembled at low cost, and which can be readily disassembled for cleaning of the jet and needle.

Briefly, the airbrush according to the invention has an elongated generally cylindrical body formed in one piece, as by molding from a suitable plastics material, and having a cylindrical internal bore for a portion of its length defining a cavity in which other elements are contained. In particular, a carrier member assembled within the cylindrical bore supports a needle that extends a predetermined distance from the open end of the bore and also defines a passageway for the paint. The bore is closed at its forward end by a cap inside which is threadably secured a jet, preferably molded from a suitable plastic material, through which the free end of the needle extends. By adjusting the longitudinal position of the cap on the body the jet is also moved with respect to the stationary needle, thereby providing regulation of the amount of paint through the jet. The body includes an integrally molded cap for receiving a threaded paint jar from which paint is delivered to the paint passageway by a dip tube. The carrier member is shaped to provide, in association with the cylindrical bore, a passage for air to the region of the jet.

Other objects, features and advantages of the invention will become apparent, and its construction and operation better understood, from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of the airbrush according to the invention;

FIG. 2 is an elevation cross-sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a greatly enlarged perspective view, partly cut away, of the left-hand portion of the airbrush, as viewed in FIG. 1; and

FIG. 4 is an enlarged perspective view of the jet element of the airbrush and a wrench provided for removal of the jet from the cap.

Referring to FIG. 1, the airbrush according to the invention, shown essentially full size, includes an elongated body 10 which when viewed from the top and sides appears to be cylindrical, and which is gradually tapered toward the rear end. Body 10 preferably is molded from a suitable plastics material, such as Delrin, and includes as an integral part a depending internally threaded cap 12 dimensioned to receive a standard size, commercially available glass jar 14 for containing the paint. The cover has an opening 16 formed therein communicating the interior of the jar to the atmosphere, and paint is drawn by aspiration into the body of the airbrush through a dip tube 18. Air or other aeriform substance under pressure is applied to the airbrush through a hose 20 to one end of which is secured a standard fitting 22 and the other end of which engages a connector and valve assembly 24, the barrel of which is integrally molded with the body 10. The contained valve mechanism (to be described) is actuated by a finger-operated push button 26 which extends upwardly from body 10 at a position approximately equidistant from its ends. The body 10, which, as will be seen, has an internal bore extending from just forward of button 26 to its forward end, is closed at its forward end by an internally threaded cap 28, preferably formed of metal, which engages threads molded on the front end portion of the body. The front end of cap 28 is flared at 28a and is provided with a small orifice from which paint emerges under control of a jet threadably and removably secured within cap 28, and a needle, the construction and action of which will be described shortly. A wrench 30 for removing the jet from cap 28 for cleaning or replacement, the construction of which will be described in more detail later, is provided with an opening 30a so that it can be placed over hose 20 to preclude its loss or misplacement so as to always be conveniently available for use when needed.

It will be seen in FIG. 2 that the underside of that portion of body 10 that extends rearwardly from button 26 and valve assembly 24 is hollow and closed at 10a. This construction serves to reduce the weight of the device with an attendant reduction in the cost of the molding material required for fabrication of the body. Immediately forward of the hollow portion body 10 has a vertically oriented bore 40 formed therein, the upper end of which is surrounded by a boss 42. The bore 40 is of uniform diameter throughout its length and at its lower end is partially closed by a circumferential shoulder 40a which has a tapered central opening 44. Below the shoulder is formed a second colinear bore 48 enclosed by a short hollow tube 46. A barb member 50, preferably formed of metal, such as aluminum, and having an axial internal passage 50a and having barbs 50b on its external surface, is received by and firmly held in bore 48 and serves as a retainer for a small ball 52, and also facilitates the attachment of hose 20 to tube 46. In the non-operated condition of the airbrush, illustrated in FIG. 2, air under pressure within hose 20 forces ball 52 upwardly against the underside of shoulder 40a thereby to close opening 44 and prevent air from entering the airbrush. The valve is opened by a valve stem 54 integrally molded with button 26 from a suitable plastic material, such as Delrin, which has a tapered section 54a near its lower end dimensioned to be received in tapered opening 44 and terminating in a reduced diameter stem 54b. As best seen in the enlarged illustration of FIG. 3, where the valve is shown in its operated position, the diameter of the upper portion of the valve stem is slightly smaller than the diameter of bore 40, and at a position thereon to be contained within bore 40 at both the operated and non-operated positions of the valve has a circumferential groove 54c for retaining an "O-ring" 56, which provides an air seal between stem 54 and bore 40. From a point 54d immediately below the "O-ring" to a point 54e the stem is of reduced diameter and has a longitudinally extending slot 54f formed in its outer surface, the purpose for which will shortly become evident. Between point 54e and the tapered portion 54a the diameter of the stem is again substantially equal to the diameter of bore 40. This short section has a pair of diametrically opposite, axially extending slots formed therein, one of which is visible at 54g in FIG. 3, which provide passages for air to enter the region surrounding the reduced diameter portion when the valve is open.

From a point immediately forward of the valve assembly, body 10 has an internal cylindrical bore 60 of uniform diameter throughout a major portion of the remaining length of the body, the diameter increasing at point 60a with a slight flare to the front end of the body. The interior end of bore 60 communicates, through an opening 62, with the volume surrounding the reduced diameter portion of valve stem 54 to provide an entry for air into bore 60.

Separated passageways for air and paint, and fixed support for a needle 70, is provided by a carrier member 72 contained within bore 60. Carrier member 72 is a unitary molded plastic part, formed of Delrin for example, having an overall length somewhat greater than the length of bore 60. The front end of the carrier has a cylindrical portion 72a which, except for a small portion at the forward end, has a uniform outside diameter somewhat smaller than the diameter of bore 60 to a point 72b. A short portion at the front end has a slightly larger outer diameter and has a circumferential slot 72c formed therein for receiving and retaining an "O-ring" 74, the function of which will subsequently be described. The cylindrical portion 72a has a circular cross-section bore 72d extending rearwardly from the front end and terminating in a hollow compartment 72e of generally cubical shape, one face of which is open and confronts an opening 10b in the wall of body 10; the opening is surrounded by a cylindrical boss 10c having an opening dimensioned to receive the dip tube 18 with a snug fit. That portion of the carrier in which compartment 72e is formed is of generally inverted "U"-shape in cross-section, as best seen in FIG. 3, and is dimensioned to be received with a press fit in bore 60 to provide a paint-to-air seal at points 72f and 72g between the lower ends of the "U" and bore 60, around opening 10c. Thus, paint drawn up the dip tube by aspiration (to be described) enters compartment 72e and passes through and exits from the forward open end of bore 72d. The exterior surface of the "U"-shaped portion is curved to conform to bore 60 and is in sealing engagement therewith, and the exterior surface of the "legs" of the "U" each have an axial cutout, one of which is visible at 72h in FIG. 3, which cooperate with bore 60 to define passages through which air can pass from the rear portion of bore 60 into the annular passageway defined by cylindrical portion 72a of the carrier and bore 60. Integral with the "U"-shaped portion and extending rearwardly therefrom substantially along the axis of bore 60 is a slightly tapered tang 72j of generally rectangular cross-section, which extends through opening 62 with its rearmost end received in slot 54f in the valve stem. Thus, the tang 72j retains the valve stem in bore 40 and determines its rotational position therein. Carrier 72 is inserted into bore 60 from the forward end, preferably when cold but with the body 10 still hot from the molding process, such that upon cooling of body 10 the "U"-shaped portion of the carrier and the bore are jammed together with heavy interference to ensure a tight seal.

A needle 70, which may be formed of 0.020 inch diameter stainless steel spring wire, is removably supported within bore 72d. It is retained in the bore by shaping the wire by crimping it at three places: at 70a and 70b at such angles that when the rearmost end is received in compartment 72e, bend 70a drops into opening 10b, bend 70b engages the upper surface of bore 72d and the section between bends 70a and 70b engage a point on the circumference of the open rear end of bore 72d; and with a flattened "S" curve at 70c such that the wire engages the lower surface of bore 72d near its forward end and positions the free end of the needle substantially on the longitudinal axis of bore 72d. The forward end of the needle is tapered at 70d to a sharp point, the length of the taper being of the order of 0.08 inch. The wire is sufficiently flexible as to be insertable after carrier 70 is in place, and to be removable for replacement, if necessary. It will be evident that the described construction locates the tip of needle 70 at a predetermined distance from the forward open end of bore 60.

The tip of needle 70 extends into a jet 80, preferably molded from a suitable plastics material, such as Delrin, having a cylindrical bore 80a for a portion of its back-to-front length, which tapers down at 80b into a small tapered opening 80c having a diameter at its forward end slightly less than the diameter of the needle wire, so as to be closed when the tapered portion 70d of the needle is jammed into the jet. The bore 80a has a diameter and is of a depth to receive the front end of portion 72a of the carrier, the O-ring 74 providing an air seal between the forward end of carrier 72 and the interior of jet 80.

The jet has a one-turn thread 80d formed on its external surface which engages internal threads 28b in cap 28, whereby the jet is removably secured in the cap with its forward end lying essentially in the plane of opening in the cap. As best seen in FIG. 4, the external surface of the jet is tapered forwardly at 80e, this tapered portion having four circumferentially distributed, axially extending slots, one of which is visible at 80f which serve as passages for air to flow forwardly toward the tip of the jet, which passages are further defined by a similarly tapered bore 28d internally of the forward end of the cap. The outer diameter of the jet tapers rearwardly at 80g from thread 80d and with the flared outer end of bore 60 in body 10 defines an annular passageway for air up to the thread 80d. A pair of diametrically opposed axial cutouts 80j and 80k extending through the thread serve as passageways for air to flow from the annular passageway into the tapered jet-cap region. Cap 28 is threadedly secured to threads formed, during molding, on the forward end of body 10 and extends rearwardly beyond an "O-ring" 82 retained in an external circumferential groove in body 10 to provide an air seal between the atmosphere and air under pressure within the cap.

From the description thus far it will be seen that when the air valve is opened by depression of stem 54, air from the source passes through slot 54g, through opening 62 into the rear portion of bore 60 through cutout 72h in the outer surface of the "U"-shaped member, into the annular passage defined by bore 60 and the external surface of portion 72a of the carrier, into the annular passageway defined by the tapered rear cylindrical portion of jet 80 and the tapered forward end of bore 60, through axial cutouts 80h and 80k, in the jet and finally through the grooves 80f formed in the tapered outer surface of jet 80 and exits through the opening in cap 28. The described air flow causes a vacuum at the forward tip end of the jet, causing paint to be drawn from jar 14 through dip tube 18 and opening 10b into compartment 72e and into bore 72d in the cylindrical front portion of the carrier and thence into the tapered annular passageway defined by the internal tapered bore 80c of the jet and needle 70. By virtue of the jet being secured to and movable with cap 28, and needle 70 being fixedly secured to body 10, the amount of paint flow is determined by the longitudinal position of cap 28 on body 10; thus a desired flow can be preset, or adjusted during operation of the airbrush, by rotating cap 28 relative to the body to change the degree to which the tapered portion 70d of the needle penetrates the orifice in the forward end of the jet.

To facilitate removal of jet 80 from cap 28 for cleaning and/or replacement, the previously mentioned wrench 30 is provided, the construction of which will be apparent from FIGS. 1 and 4. It consists essentially of a hollow tube having an outer diameter slightly smaller than the inside diameter of cap 28 and an inner diameter slightly larger than the tapered rear portion 80g of jet 80, and is formed with a pair of diametrically opposed axially extending ears 30a and 30b dimensioned to be received by the axial slots in the jet, and with a ring 30c at the other end. With the wrench attached to hose 20, as shown in FIG. 1, the wrench is simply inserted into the open end of the cap, and the cap turned relative to the wrench until the single thread 80b on the jet is free of the threads in the cap.

As best seen in FIG. 3, the paint jar cap 12, which is integrally molded with the body 10, has a single thread 12a molded therein of a pitch and size to engage the threads of a standard jar, and the top surface is formed with a pair of closely spaced circular ribs of a diameter and so oriented as to be engaged by the lip of the jar when in place in the cap, these ribs improving the seal between the jar and its cap.

It will be evident from the foregoing description that there is provided an airbrush having a minimum number of relatively inexpensive parts that are easily assembled, and which when assembled automatically preset certain dimensional inter-relationships, while at the same time providing adjustment of paint flow by simple adjustment of the longitudinal position of cap 28 on body 10. Also, by adjustment of cap 28 the jet may be completely closed to minimize drying of paint in the nozzle region, and when cleaning is required, cap 28 is easily removable from the body, the jet is easily removable from the cap, and the needle can be readily removed from the carrier for thorough cleaning and/or replacement.