Abstract:
A grit blasting nozzle and nozzle fixture assembly provides for both rapid installation of the nozzle within the fixture, and precise alignment of the nozzle when installed in the fixture. Corresponding flat surfaces and shoulders on the nozzle and nozzle fixture orient the nozzle within the fixture, and a spring-biased pin engages an angled surface in the nozzle housing to fully seat the nozzle within the fixture. A proximity sensor facilitates consistent setting of the proper distance between the nozzle and the workpiece.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to grit-blasting nozzles and their support fixtures. More specifically, the invention provides a grit-blasting nozzle mating with a support fixture in a manner that provides precise, identical alignment every time it is installed, and a method for precisely setting the proximity of the nozzle to the workpiece. 
     2. Description of the Related Art 
     Grit blasting is presently utilized as a step in a variety of manufacturing processes. Typically, aluminum oxide particles of a selected size are directed against the surface to be grit-blasted by compressed air, or possibly by a fluid such as water. The goal of the grit-blasting process is often to create a surface having a roughness within a certain range, which is achieved by varying the size of the alumina grit, the air pressure, the size of the nozzle opening, and/or the distance of the nozzle from the workpiece. Additionally, grit blasting may be used to precisely cut holes, for example, in silicon wafers. It is therefore necessary to precisely control these variables during the grit blasting process. Additionally, the grit blasting nozzle and hose leading to the nozzle will typically be subject to a high degree of wear due to the highly abrasive alumina grit constantly passing through them at high pressure. Therefore, it is necessary to replace the nozzle and hoses not only to achieve different surface roughnesses and/or different holes with different manufacturing processes, but also to minize machine downtime when replacing worn out components. 
     The time necessary to replace presently available grit blasting nozzles reduces the overall productivity of the grit blasting operation. Additionally, lack of repeatability of adjustment settings may result in increased variation in the results of the grit blasting operation, and a corresponding decrease in overall component quality. Accordingly, there is a need for a grit blasting apparatus having a nozzle. capable of being quickly installed into its fixture, and precisely aligned when it is within the fixture. Additionally, there is a need for a grit blasting apparatus having means for precisely adjusting the distance between the nozzle and the workpiece. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for precisely aligning a grit blasting nozzle. The invention includes a movable bracket, a nozzle dimensioned and configured for rapid, precise installation within the movable bracket, and may also optionally include a fixed bracket with at least one proximity sensor. 
     The nozzle housing includes a flat surface and a shoulder, with each being dimensioned and configured to abut a corresponding surface on the movable fixture bracket. The nozzle also defines a means for being secured at exactly the same height with respect to the movable bracket each and every time it is utilized. Specifically, one preferred embodiment includes an angled surface on the nozzle housing dimensioned and configured to abut a spring-biased hinge within the movable bracket. When the nozzle. is inserted into the movable bracket, the pressure of the spring-biased pin against the angled surface will push the nozzle further into the bracket until the shoulder on the housing abuts the bracket, thereby precisely locating the nozzle in the same position relative to the bracket each and every time the nozzle is inserted into the bracket. 
     The movable bracket includes a first arm dimensioned and configured to removably secure the grit blasting nozzle, a second arm dimensioned and configured to removably secure a proximity sensor, and a grit blasting machine engaging portion dimensioned and configured for sliding motion within a desired range of distances from the workpiece. The movable bracket may, if desired, also include means for removably securing a light source dimensioned and configured to provide light to the target area of the workpiece. 
     If a proximity sensor is desired, then the fixed bracket will be used to support either the sensor or the sensor&#39;s target. The fixed bracket therefore include means for being secured to the grit blasting machine in close proximity to the movable bracket, and an arm dimensioned and configured to removably secure a proximity sensor or a sensor target. 
     A proximity sensor secured within one bracket may be utilized to detect the distance between the proximity sensor and the proximity sensor target on the opposing bracket, from which the distance between the nozzle and the workpiece target region can be calculated. One preferred proximity sensor is an inductive resistance proximity sensor, which is well known in the art of proximity sensors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a grit blasting nozzle and fixture assembly according to the present invention. 
     FIG. 2 is a back view of a grit blasting nozzle and fixture assembly according to the present invention. 
     FIG. 3 is a top view of a grit blasting nozzle and fixture assembly according to the present invention. 
     FIG. 4 is an exploded side view of a grit blasting nozzle and fixture assembly according to the present invention. 
     FIG. 5 is a side view of a nozzle housing according to the present invention. 
     FIG. 6 is a bottom view of a nozzle housing according to the present invention. 
     FIG. 7 is an end view of one of two mirror image, mating nozzle components according to the present invention. 
     FIG. 8 is a side view of one of two mirror image, mating nozzle components according to the present invention. 
     FIG. 9 is an end view of a proximity sensor target according to the present invention. 
     FIG. 10 is a side view of a proximity sensor target according to the present invention. 
     FIG. 11 is a side view of a nozzle spacer according to the present invention. 
     FIG. 12 is an end view of a nozzle spacer according to the present invention. 
     FIG. 13 is a side view of a movable fixture bracket according to the present invention. 
     FIG. 14 is a top view of a movable fixture bracket according to the present invention. 
     FIG. 15 is a back view of a movable fixture bracket according to the present invention. 
     FIG. 16 is a top view of a fixed fixture bracket according to the present invention. 
     FIG. 17 is a back view of a fixed fixture bracket according to the present invention. 
     FIG. 18 is a side view of a fixed fixture bracket according to the present invention. 
     FIG. 19 is a schematic view of a sensor, microprocessor, and associated components for use with the present invention. 
     Like reference numbers denote like elements throughout the drawings. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides an improved grit blasting nozzle and fixture assembly  10 . Referring to FIGS. 1-4, a preferred embodiment of the grit blasting assembly  10  includes a nozzle assembly  12 , removably secured within a movable fixture assembly  14 . The movable fixture assembly  14  also includes a proximity sensor  16  working in conjunction with a proximity sensor target  18  removably secured to a fixed bracket  20 . 
     Referring to FIGS. 5-6, the nozzle assembly  12  includes a nozzle housing  22 , defining a channel dimensioned and configured to receive a spacer  24  and a pair of nozzle half-portions  26  (described below, FIGS. 7-8,  11 - 12 ). The nozzle receiving channel  28  includes an open lower end  30 , and an upper end  32  in communication with a grit passage channel  34 . The grit passage channel  34  includes an upper opening  36  at the top end  38  of the nozzle housing  22 . The nozzle housing  22  is preferably cylindrical, but includes an alignment guide surface  40  at its upper end. The alignment guide surface  40  is preferably flat. The bottom of the alignment guide surface  40  forms a shoulder  42 . The top section  38  of the housing  22  also preferably includes a taper portion  44 , thereby forming a camming surface. The bottom of the tapered portion or camming surface  44 , in conjunction with the cylindrical housing portion  46 , defines a concave corner  48 . 
     Referring to FIGS. 11 and 12, a spacer  24  is illustrated. The spacer  24  includes a mixing chamber  50 , having a pair of open ends  52 ,  54 . Referring briefly to FIG. 4, the spacer  24  is dimensioned and configured to fit within the upper end  32  of the nozzle receiving channel  28  of the nozzle housing  22 . 
     Referring to FIGS. 7 and 8, one of two mirror image nozzle half-portions  26  is illustrated. Each nozzle half-portion  26  has the form of one-half of a cylinder, including a tapered tip portion  56 . The interior surface  58  includes a half channel portion  60 , extending lengthwise down the nozzle half-portion  26 . Referring back to FIG. 4, two identical nozzle half-portions  26  will be placed together with their interior surfaces  58  abutting each other. Both nozzle half-portions  26  will then be inserted into the nozzle receiving channel  28  of the nozzle housing  22 . It will preferably be necessary to very slightly crush the two nozzle half-portions  26  to fit them within the channel  28 , thereby creating an interference fit between the channel  28  and nozzle half-portions  26  to retain the nozzle half-portions  26  within the nozzle housing  22 . The two half channel portions will thereby form a channel, which in the present example is substantially planar, having twice the width of each half channel portion  60 . 
     Referring to FIGS. 13-15, a movable bracket  14  is illustrated. The movable bracket  14  includes a grit blasting machine-engaging portion  62 , dimensioned and configured for sliding motion within a desired range of distances from the workpiece. Some preferred embodiments may include one or more channels  64 ,  66 ,  68 , for slidably mating with a rod (not shown and well understood in the art of grit blasting) attached to the grit blasting machine. A first arm  70  extends from the machine-engaging portion  62 , with the first arm  70  being dimensioned and configured to removably secure the nozzle assembly  12 . The first arm  70  preferably defines an aperature  72 , dimensioned and configured to receive the top end  38  of the nozzle housing  22 . The aperture  72  will therefore be generally cylindrical, with an alignment guide surface  74  dimensioned and configured to abut the alignment guide surface  40 . The alignment guide surface  74  is therefore preferably flat if a flat alignment guide surface  40  is used. A nozzle-securing aperture  76  is in communication with the aperture  72 . Referring briefly to FIG. 1, the nozzle-securing aperture  76  preferably contains a spring-biased cylindrical pin  78 , dimensioned and configured to abut the concave corner  48  of the nozzle housing  22 . Some preferred embodiments of the first arm  70  may also include a light source retaining aperture  80 , which may be angled to point a light source towards the target area of the workpiece, directly beneath the nozzle assembly  12 , and which may be either a fixed or an adjustable aperture. A light source securing aperture  82 , in communication with the light source retaining aperture  80 , permits insertion and/or installation of a means for securing a light source within the aperture  80 , for example, a spring-biased pin, or possibly a removable pin. The movable bracket  14  also includes a second arm  84 , dimensioned and configured to removably secure a proximity sensor  16 . The second arm  84  may include an aperture  86 , dimensioned and configured to receive the proximity sensor  16 . Referring briefly to FIGS. 1 and 4, one or more nuts  88  may be secured to the proximity sensor  16 , above and below the second arm  84 , thereby removably securing the proximity sensor  16  within the aperture  86 . 
     Referring to FIGS. 16-18, a fixed bracket  20  is illustrated. The fixed bracket  20  includes a grit blasting machine-engaging portion  90  having one or more channels  98 ,  100 , for mating with a rod (not shown and well understood in the art of grit blasting) attached to the grit blasting machine, thereby securing the bracket  20  to the grit blasting machine, and an arm  92  having means for removably securing a target  18  for a proximity sensor  16 , for example, the aperture  94 . The fixed bracket  20  may optionally include channels  96 , for aligning the fixed bracket  20  with the movable bracket  14 . Referring to FIGS. 9 and 10, a proximity sensor target  18  is illustrated. The proximity sensor target  18  is preferably made from ferromagnetic material, and includes means for being secured to the arm  92  of the fixed bracket  20 . These means may include an aperture  102 , for receiving a pin  106  passing through the apertures  102 ,  94 , thereby securing the proximity sensor target  18  to the arm  92 . 
     Referring to FIGS. 1-4, a preferred proximity sensor  16  may be a presently known inductive proximity sensor. Such a sensor typically includes a coil within the sensor head or tip  108  which, when brought in close proximity to the proximity sensor target  18 , the presence of the metal within the high frequency field radiated from the sensor head increases the electrical resistance within the sensor head, thereby decreasing the amount of current permitted to pass through the sensor head for a given voltage. Therefore, current can be correlated with the distance between the proximity sensor  16  and proximity sensor target  18 , and therefore also with the distance between the nozzle assembly  12  and the workpiece. As will be known to those skilled in the art, a microprocessor with stored data correlating various current values to the corresponding distance between the sensor  16  and sensor target  18  will be used to compare the output of the sensor with these stored values, to determine when the desired distance has been reached. When the desired distance is reached, the microprocessor may either display an audible or visible signal (if the distance D is manually set) or may transmit an electronic system to the controller of the grit blasting machine to stop movement of the movable bracket  14  (if an automated system, such as a computer-numerically-controlled (CNC) system, is used to move the movable bracket  14 ) 
     Referring to FIG. 19, the sensor  16  is illustrated in communication with a microprocessor  200 . As the sensor  16  is brought towards the desired distance D from the sensor target  18 , information about the amount of current within the sensor  16  is transmitted to the microprocessor  200  on an ongoing basis. The microprocessor  200  will then compare the current measurement with the known current measurements and corresponding distances D stored within the microprocessor  200 . Once the desired distance D is reached, the microprocessor  200  will signal that movement of the movable bracket  14  should stop moving. If the movement of the movable bracket  14  is automated, then the microprocessor  200  will send a signal to stop the controller  202  from moving the movable bracket  14 . If the movement of the movable bracket  14  is manual, than the microprocessor  200  will send a signal to the visual signal device  204 , such as a light, or an audio signal device  206 , such as a speaker, so that the signal device  204 , 206  will signal the operator to stop moving the movable bracket  14 . 
     Referring back to FIGS. 1-4, the top end  38  of the nozzle assembly  12  will be inserted into the aperture  72 , with the corresponding surfaces  40 ,  74  ensuring that the two channel halves  60  form a channel having the proper orientation. The spring-biased pin  78  pushes against the tapered portion or camming surface  44  pushes the nozzle assembly  12  upward within the aperture  74 , until the shoulder  42  abuts the bottom surface  104  of the first arm  70 . The nozzle assembly  12  is thereby precisely and repeatably secured in a constant orientation within the movable bracket  14 . The hose carrying the grit and compressed air may then be connected to the top end  38  of the nozzle assembly  12  using means well known in the art of grit blasting. 
     With the position of the nozzle  12  with respect to the movable bracket  14  precisely set, the distance D between the nozzle assembly  12  and the target area of the workpiece  110  can be controlled by setting the appropriate distance between the proximity sensor  16  and proximity sensor target  18 , accomplished by moving the movable bracket  14  relative to the fixed bracket  20 . The movable bracket  14  is therefore raised and/or lowered until the desired amount of electrical current is flowing through the proximity sensor  16 , indicating that the movable bracket  14  is the proper distance from the fixed bracket  20 , and the nozzle assembly  12  is therefore the proper distance D from the target area of the workpiece  110 . Grit blasting of the workpiece  110  may then be conducted in a conventional manner. 
     While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. For example, the location of the proximity sensor and sensor target may be reversed, or indicia denoting various distances D may be used as an alternative to a proximity sensor for positioning the movable bracket at a desired distance D from the workpiece. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.