Patent Application
20050269423
The present invention relates to writing and drawing instruments. More particularly, the present invention relates to an airbrush and a method for producing an airbrush.
U.S. Pat. No. 5,687,886 discusses an apparatus for dispensing a fine spray of liquid particles. The apparatus apparently comprises a hollow tubular housing and a reservoir pen formed with a nib of absorbent material which is retained within and spaced from the inner wall of the housing. The tubular housing includes at one end a nozzle whose interior defines a converging path and at its other end a mouthpiece through which air can be caused to flow through the tubular housing and over the pen to the outlet orifice of the nozzle. An abutment is provided within the housing for locating the pen within the housing with its absorbent nib at least partially within the boundary of the outlet orifice of the nozzle.
U.S. Pat. No. 6,024,300 discusses an apparatus for dispensing a fine spray of liquid particles that apparently comprises a hollow tubular casing whose internal cross section is formed with at least one abutment surface. A tubular liquid source is positioned within the casing with the abutment surface in close contact with the outer surface of the source to provide support thereto. The casing includes a passageway for the flow of air from a mouthpiece positioned at one end of the casing to a nozzle positioned at the other end of the casing into which the discharge end of the liquid source protrudes.
The prior art references include felt tip pens and nibs of absorbent material. The references apparently disclose that the liquid is dispersed from the absorbent material into the flow of air. Additionally, the references apparently disclose the nib of material being within the boundary of the outlet nozzle.
Airbrushes utilizing nibs of material may have the disadvantage that the nib dries easily and may be difficult to operate. Also, nibs may be used in conjunction with a filter which holds the ink in a barrel. The combination of the filter and barrel may limit the amount of ink which may be accessed by the nib.
There is thus a need for an efficient method of drawing liquid and dispersing the liquid into an air stream, and for accessing more liquid ink with an airbrush.
An apparatus is provided for spraying an atomized liquid, which includes a hollow casing including an inlet and an outlet. The inlet is adapted to receive an airflow. The outlet includes a nozzle having an aperture. The apparatus also includes a liquid cartridge associated with the hollow casing and a tube having a tip and a source end. The source end of the tube is attached to the liquid cartridge. The tip of the tube is positioned in a region on a side of the nozzle outside of an interior of the hollow casing and the tube is adapted to draw liquid out of the liquid cartridge.
The airflow received into the inlet may pass through the hollow casing, may pass out of the nozzle, may creat a low pressure in the region, may draw the liquid out of the tip of the tube, and may atomize the liquid. The drawing of the liquid out of the tip of the tube by the low pressure region may be caused by a venturi effect.
The apparatus may further include an arrangement for attaching the liquid cartridge to the hollow casing, which may include welding two halves of the casing into a single unit. The two halves may sandwich a plurality of anchors of the cartridge. The anchors may extend into the interior of the hollow casing. The cartridge may be arranged flush to the exterior of the hollow casing. The welding may include an ultrasonic welding of the two halves of the hollow casing to each other and possibly to the anchors.
The hollow casing and/or the liquid cartridge may include plastic. The tip may be arranged perpendicular to the flow of air in the region. The liquid cartridge may include an air inlet arranged on the liquid cartridge opposite of the tube. An opening on the tip of the tube may have a diameter sufficiently small to prevent a flow of the liquid out of the tip due to surface tension absent a flow of low pressure air over the tip. The aperture of the nozzle may be one of equal to and slightly larger than the tip of the tube. The tip may include a short tube with a constricted throat. The inlet may be adapted to receive the airflow directly from a human mouth. The inlet may be adapted to receive the airflow from a flexible tube.
A method is provided for producing an airbrush, which includes providing two halves of an outlet end of a hollow casing and providing an inlet end of the hollow casing. The method further includes providing a liquid cartridge including anchors for attaching the liquid cartridge to the two halves of the outlet end and possibly providing a nozzle insert adapted to fit between the two halves of the outlet end near an outlet. The method further includes welding the two halves together to form an outlet component, thereby sandwiching between the two halves the liquid cartridge and possibly the nozzle insert.
The method may further include joining the outlet component and the inlet end, possibly by a friction fit. The two halves of the outlet end may include plastic. The joining of the two halves of the outlet end may include ultrasonic welding.
The functional principle of the present invention is based on the Venturi effect of spraying. Air escaping from end of one tube at a certain minimal speed and pressure creates a zone of low pressure. Another tube positioned below the zone of low pressure is connected to a reservoir of a liquid. The zone of low pressure forces liquid to move into the air flow where particles of liquid are broken down and dispersed as a mist. The quality of the spraying effect and the amount of minimum air pressure may depend on several factors, including: the diameter of the tubes; the positioning of the tube ends against, or adjacent to, each other; the angle of the tube ends with respect to each other; and the viscosity of the sprayed liquid. As a general rule, the tubes must be either of equal diameter or the air tube may be slightly larger than the ink tube.
An airbrush according to an exemplary embodiment of the present invention may be a simple, effective, plastic spraying tool for children and/or adults to spray washable inks in their artwork. The airbrush may be designed as a single use tool or a refillable/reusable tool. As a single use tool, the airbrush may be used as long as there is a supply of ink in the ink tank. After all the ink in the tank has been used, the whole tool may discarded. A modification to the design may allow the ink reservoir to be replaceable using ink replacement kits.
An exemplary embodiment of the present invention may include two major components: a back-end air tube (also referred to herein as inlet housing 11) and a front-end assembly (also referred to herein as outlet assembly 13). The back-end tube may be a single plastic piece. The front-end assembly may include two housing halves (also referred to herein as outlet assembly halves 14) that may be assembled together in an ultrasonic plastic welding process to ensure an airtight fit around the seam line. An ink tank (also referred to herein as liquid cartridge 15) may have two or three anchoring details (also referred to herein as anchors 64) that are adapted to lock the ink tank onto the housing assembly between the two halves, possibly making it a permanent assembly. There may also be an air nozzle insert (also referred to herein as nozzle 62), which is a small part with a hole in the middle that is positioned at the outlet nozzle between the two halves during ultrasonic assembly. Air may be blown through the length of the tool and may escape through the short tubular extension of the air nozzle insert. After passing through the air nozzle insert, air may flow above the end of an ink tube (also referred to herein as ink tank tube 40) that extends from the ink tank to the nozzle area.
The back-end air tube may be a simple, thin-wall tubular piece injected in polypropylene plastic. The user may put the rear section in his/her mouth and blow through it. Two halves of the front-end housing may be thin-wall plastic components that may be injected in either polyprolylene or polystyrene. The back-end air tube and/or the two halves of the front-end housing may be assembled onto each other with ultrasonic welding to provide an airtight seal on the joint line. During assembly, the sections may lock an ink tank using anchoring elements (also referred to herein as anchors 64) in between the two halves of the front-end housing and may also lock the nozzle insert between the two halves of the front end housing.
Liquid cartridge 15 may have a small diameter venting tube 70 of metal, plastic, or any other appropriate material. Venting tube 70 may enter the ink reservoir at an end opposite to ink tank tube 40. Venting tube 70 may provide air venting, which may be necessary to replace the volume of used ink inside liquid cartridge 15 with the same volume of air and to equalize atmospheric pressure inside and outside liquid cartridge 15. Venting tube 70 may be of a very small diameter to provide air passage and to ensure by liquid surface tension that ink does not flow freely out of liquid cartridge 15.
The principle of an airbrush according to an exemplary embodiment of the present invention is based on the Venturi effect of spraying. A possible advantage of this design is its simplicity and, thus, its low production and retail cost. A user may provide the necessary airflow and pressure by blowing by the mouth into a rear section of the pen. Alternatively, a flexible tube may be adapted to secure to the end of the airbrush. Pressurized air may be supplied to the flexible tube by either a human mouth, a hand-powered pump, an electric pump, or by any other appropriate method of supplying pressurized air. Air may then flow through the mouthpiece and through the mostly empty cavity of a front-end assembly. Then the air may pass through a small hole of the nozzle insert and escape directly above an end of a thin ink tube, thereby creating a lower pressure area there. The low pressure area above the end of the thin ink tube may draw ink out of the ink tube and disperse it into the airflow.
While the present invention has been described in connection with the foregoing representative embodiment, it should be readily apparent to those of ordinary skill in the art that the representative embodiment is exemplary in nature and is not to be construed as limiting the scope of protection for the invention as set forth in the appended claims.
