Patent Application
20160082463
The present invention relates generally to devices, systems and methods for applying thermoplastic powder to fasteners and, in particular, to a combined spray and vacuum nozzle that fits within the bore of a fastener to apply thermoplastic powder to threads within the bore.
It is known to apply thermoplastic powders to the threads of pre-heated fasteners to form a locking patch or other element that prevents the fasteners from loosening. Such a patch or element is commonly referred to as a “retention patch.” The thermoplastic material is often a polyamide, but other thermoplastics or resins may be used instead.
The thermoplastic powder is typically sprayed onto the threads of a heated fastener using a spray nozzle. The spray nozzle is in communication with a source of pressurized air and thermoplastic material that is fluidized so as to spray from the nozzle. The sprayed powder that contacts the heated threads melts so as to adhere to the threads. Excess powder that does not melt and adhere to the threads is typically withdrawn from the fastener using a vacuum nozzle that communicates with a powder collection system.
It is desirable to combine the spray and vacuum functions into a single nozzle in situations where the space providing access to the threads is limited. Such is the case for internally threaded fasteners, where the fastener includes a bore containing the threads. Unitary nozzles developed for such applications include commonly assigned U.S. Pat. No. 6,454,504 to Duffy et al. and U.S. Pat. No. 6,797,320 to Sessa. The Duffy et al. '504 patent discloses a unitary nozzle where the spray and vacuum passages are concentric. The Sessa '320 patent discloses a unitary nozzle where the spray and vacuum passages are axially aligned in a stacked configuration with the spray port positioned adjacent to the vacuum port.
A need exists, however, for a unitary nozzle for applying thermoplastic powder to form a retention patch into the threads of a small closed end nut, such as a #10-32 closed end nut. The nozzle of the Sessa '320 patent, however, is not suitable for such an application because it requires that both ends of the threaded fastener bore be open and the coaxial nature of the spray and vacuum passages provide bore size constraints. The unitary nozzle of the Duffy et al. '504 patent is not suitable because the concentric orientation of the spray and vacuum passages does not allow the porting to be large enough for a sufficient amount of powder to move thru the nozzle without blocking the ports when the outside diameter of the nozzle is made small enough to enter the fastener bore with sufficient clearance.
A nozzle assembly including an embodiment of the combined spray and vacuum nozzle of the present invention is indicated in general at 10 in
A powder supply conduit 20 and a vacuum withdrawal conduit 22 are also connected to the base block 16 and, as described in greater detail below, communicate with side-by-side passages within the nozzle housing. As examples only, each conduit may have an outer diameter of 0.072 inches and an inner (channel) diameter of 0.065 inches.
As illustrated in
Base block 16 includes a powder supply passageway 30a and a vacuum withdrawal passageway 30b. Powder supply passageway 30a has a top opening that communicates with the powder supply passage 24a of the nozzle housing 12 and a bottom opening that communicates with channel 32 of the powder supply conduit 20. Vacuum withdrawal passageway 30b similarly has a top opening that communicates with the vacuum withdrawal passage 24b of the nozzle housing 12 and a bottom opening that communicates with the channel 34 of the vacuum withdrawal conduit 22.
When installed within machinery for use, the powder supply conduit 20 is connected to a source of aspirated thermoplastic powder and air, such as may be supplied, for example, by a venturi style powder pump. As an example only, the thermoplastic powder may be a polyamide. Of course alternative types and sources of aspirated powder and air may be used. The vacuum withdrawal conduit 22 is connected to a vacuum source and a powder collection arrangement. The vacuum source may be run continuously when the nozzle assembly is in use, or may be sequenced to operate only when the source of aspirated powder and air is activated so that powder is being supplied to the threads of a fastener by the nozzle assembly.
As illustrated in
The top end of the dividing wall 26 of the nozzle housing is provided with a curved distal end portion 50 (also shown in
As will be explained in greater detail below, powder not adhering to the heated threads of a fastener (powder overspray) is collected through a vacuum port 48 (
In use, with reference to
The nut 60 is preheated and positioned above the spray nozzle assembly 10 using a system such as the ones disclosed in commonly assigned U.S. Pat. No. 5,141,771 to DiMaio et al. and U.S. Pat. No. 6,454,504 to Duffy et al., the contents of both of which are hereby incorporated by reference. Of course alternative fastener heating and handling systems known in the art may be used.
When a spray cycle is initiated, the spray nozzle assembly 10 moves upward so that the distal end of the nozzle housing 12, and thus spray and vacuum nozzle window 14, travels into the bore 62 of the nut at a controlled rate. The aspirated powder and air supply system is activated to supply an aspirated thermoplastic powder and air stream (arrows 42 and 44) to the threads 66 of the pre-heated nut so that a patch 70 of thermoplastic material is formed. As the powder exits the spray port 46 (
The spray nozzle extends and retracts, as illustrated by arrows 68 of
Therefore, in the embodiment described above, a combined spray and vacuum nozzle features powder supply and vacuum withdrawal passages that reside side-by-side or bilaterally, instead of being coaxial or collinear. This construction allows for close placement of the passages. This construction also allows the passages to be large enough so that a sufficient amount of powder can move thru the system without blocking the passages. The outside diameter of the nozzle housing can also be made small enough to enter the bore of the nut with sufficient clearance. This construction provides the ability to make a patch inside a closed end internally-threaded fastener. It should also be understood that this construction method can be used on a dual open-ended fastener as well.
While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.
