Coating system using tape encapsulated particulate coating material

#This invention relates to systems for coating a work piece with particulate material, and more particularly relates to apparatus for packaging, storing and applying the particulate material in a more controlled manner to produce a superior quality coating.

#Co-pending application Ser. No. 198,806, entitled "Method and Apparatus for Applying Particulate Coating Material to a Piece of Work", filed on Nov. 15, 1971 on behalf of Melton, et al, now U.S. Pat. No. 3,801,346, and assigned to the assignee of the present invention, and U.S. Pat. No. 2,972,550 disclose systems for applying particulate coating material, such as tungsten carbide, to a work piece in a series of pulses.

#The system disclosed in the former utilizes a combustible fuel-air mixture which is introduced to a combustion chamber having a restricted outlet nozzle at a sufficient rate to increase the pressure substantially above atmospheric pressure. The inlet valve is then closed and the mixture ignited while the pressure is still at a high level. The resulting combustion produces a still higher pressure as a result of confinement by the restricted outlet nozzle, and the hot gases of combustion then exit through the restricted outlet nozzle at a high velocity during a blow-down period. The particulate material is injected into the combustion chamber, preferably near the end of combustion, and before the peak pressure has been materially reduced. As a result, the particulate material is both heated and propelled from the nozzle against the work piece at a high velocity where the particulate material flattens and adheres to the work piece to form the coating.

#The novel features believed characteristic of this invention are set forth in the appended claims. The invention itself, however, as well as other objects and advantages thereof, may best be understood by reference to the following detailed description of illustrative embodiments, when read in conjunction with the accompanying drawings, wherein:

#FIG. 1 is a schematic block diagram illustrating a method and apparatus in accordance with the present invention;

#FIG. 2 is a perspective view of an elongated tape encapsulating particulate material in accordance with the present invention;

#A system in accordance with the present invention is indicated generally by the reference numeral 10 in FIG. 1. The system 10 includes a generally spherical combustion chamber 12, having an elongated, restricted outlet nozzle 14 which directs hot gases of combustion and particulate material entrained therein against a work piece. An inlet valve 16, which is relatively large compared to the outlet nozzle, admits a fuel-air mixture to the chamber. An air supply 18 provides compressed air at a relatively high pressure, typically 1,000 p.s.i., through a pressure regulator 20 which provides 100 p.s.i. to a carburation system 22, where a gaseous fuel is mixed with the air and the mixture fed through the inlet valve into the combustion chamber. The high pressure air is also directed to an injection system 24 which will presently be described in greater detail. An injector tube 26 extends from the injection system 24 into the combustion chamber 12. A conventional ignition system 28 ignites the combustible mixture supplied to the chamber 12 by means of a spark plug 30. A timing system 32 controls the inlet valve 16, the ignition system 28 and the injector 24, in a sequence which will be presently described in connection with the timing diagram of FIG. 4.

#Referring now to FIG. 2, an encapsulated tape in accordance with the present invention is indicated generally by the reference numeral 40. The encapsulating tape 40 includes a relatively thick tape member 42 in which are formed a series of pockets 44 at uniformly spaced intervals. Each pocket 44 is filled level full with a measured quantity of particulate coating material 46. The particulate coating material is sealed in the pockets 44 by a relatively thin sheet of material 48. The sheets 42 and 48 are preferably a plastic material, such as polyethylene, but may be a moisture-proof material where such a seal is desired. The relatively thick sheet 42 may be on the order of 0.004 inches thick, while the relatively thin sheet 48 may be on the order of 0.0005 inches thick. Each pocket is typically on the order of 1/8 inch to 1/4 inch in diameter, depending upon the particular application. A series of perforations 50 may be provided along either or both edges of the laminated tape structure to provide a positive indexing system, as will be described in connection with FIG. 3.

#An alternative embodiment of the encapsulating tape in accordance with the present invention is indicated generally by the reference numeral 40a in FIGS. 2a and 2b. The tape 40a includes a relatively thick carrier strip 41 having aperatures 41a at each capsule site. Particulate material 46a is encapsulated between a pair of relatively thin film strips 43 and 45 and each capsule is disposed within an opening 41a. The film strips 41, 43 and 45 may be any suitable plastic material, such as polyethylene, and are bonded together at the common points by heat or other suitable means. The relatively thick sheet 41 may be of the same thickness as sheet 42 in FIG. 2 and the relatively thin sheets 43 and 45 of approximately the same thickness as the thin sheet 48 of FIG. 2. The tape 40a increases the ease and efficiency with which the capsules may be burst by pneumatic pressure, yet provides sufficient strength for high speed indexing and handling.