Abstract:
A mechanism that steers a high energy density output(s) in a shaking motion other than a rotating motion that when translated across a surface evenly affects the surface. One application can be used as an end effector. A pivot on the mechanism induces an angular motion that eliminates the tops and bottoms of the pattern produced by the shaking motion. As a waterjet stripping mechanism which may be an end effector, a nozzle or output manifold with one or more orifices or outputs is attached to a non-rotating tube eccentrically mounted within a rotating tube that shakes the nozzle or output manifold so as to direct the stream of water to the target in a skewed circular pattern.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to mechanism that is designed to steer or maneuver one or more small high energy density outputs across a surface to evenly affect the surface.  
         BACKGROUND OF THE INVENTION  
         [0002]    As one skilled in this art will appreciate there are sundry mechanisms that are commercially available that are intended to “work” the surface of a substrate, such as to remove paint, coatings, and oxides, or to affect the material or change its mechanical characteristics such as peening, heating, annealing, tempering or hard surfacing and the like. These mechanisms typically utilize mediums for these purposes such as waterjets (with or without abrasives or additives), fluid jets (with or without abrasives or additives), lasers, white light, or other mediums. This invention contemplates mechanism for providing an oscillating pattern of the medium being utilized that is applied to the surface of the item intended to be targeted.  
           [0003]    High energy density output mechanisms of the waterjet nozzle types that are utilized for removing coatings, paints and the like from substrates, for example, which are currently in practice are exemplified by the following patents:  
           [0004]    U.S. Pat. No 5,421, 517 granted to Knudson et al on Jun. 6, 1995 entitled “High Pressure Waterjet Nozzle” describes a prior art waterjet system that is typically employed to remove for example the coatings applied to aircraft components, space vehicles used in outer space missions and the like. The high power waterjet nozzle of the type depicted in this patent includes mechanism for rotating a nozzle and when translated across a surface creates an array of jet streams discharging from orifices in a nozzle that defines a swath that is intended to uniformly strip the coating from the substrate. In particular an array of radially extended orifices located in the nozzle are dimensioned and located to define the amount of energy of the jet that provides the uniform stripping without incurring damage to the substrate.  
           [0005]    U.S. Pat. No. 5,577,293 granted to Meredith et al on Nov. 26, 1996 entitled “Full Recovery Stripping System” discloses another high pressure waterjet nozzle capable of use for stripping coatings, paint and the like from substrates or components. The nozzle in the structure depicted in this patent includes radially spaced orifices that communicate with a source of high pressure water and the end effector supporting the nozzle is gimbal mounted to provide the desired motion of the nozzle and hence, the swath of highly energized jet stream developed by the nozzle.  
           [0006]    High energy density output mechanism for “working” the surface of a substrate by peening is disclosed in the following patent.  
           [0007]    U.S. Pat. No. 5,778,713 granted to Butler et al on Jul. 14, 1998 entitled “Method And Apparatus For Ultra High Pressure Water Jet Peening” discloses a nozzle with a single orifice that serves to discharge ultrahigh velocity waterjet that is utilized for peening the outer surface of an object so as to alter the properties of the material by localized compression and altering the crystal structure.  
           [0008]    The first two identified patents in the immediate above paragraphs are owned by United Technologies Corporation by virtue of a direct assignment thereto or by ownership of the subsidiary noted directly in the patent. The latter patent is assigned to Waterjet Technology, Inc. which has no affiliation with the assignee of the present patent application. All of these patents are incorporated herein by reference and details to waterjet technology may be referred to these documents for additional information.  
           [0009]    While this invention can be utilized in any of the applications described in the above paragraphs, the preferred embodiment of this invention relates to the technology that deals with high pressure and high velocity fluid flow that is utilized to remove paint or coatings from the substrate and is directly concerned with the pattern of the jetstream directed to the target. As one skilled in the art will appreciate, the heretofore waterjet nozzles are either fixed or movable in a rotational direction. The problem with these types of nozzles is that they have the propensity of cutting into or scaring the substrate unevenly and/or are less efficient than the invention to be described hereinbelow.  
           [0010]    Rather than rotating the nozzle, this invention provides a shaking motion to the nozzle that could be linear in one or more directions, thus, allowing any combination of two dimensional motions from straight lines to circles to any Lissajous figure pattern. In accordance with this invention, the shake motion can be angular in one or more directions to achieve the same motion on the work surface or a combination of linear and angular motions.  
           [0011]    The motion provided by the structure of this invention allows a much larger angular deviation from the normal to the surface than a rotating waterjet. The shaking motion eliminates the high pressure water swivel which is a relatively complicated structure requiring higher cost and requires higher maintenance. While the working pattern of rotated nozzles are always round, the pattern of the present invention could be square which simplifies the cleanup problem and reduces the over lap at the end of the process positions. The working head of the present invention lends itself to be smaller than the heretofore known rotating heads which is abundantly important in installations that utilize a vacuum recovery system of the type described in the 5,577,293 patent, supra.  
         SUMMARY OF THE INVENTION  
         [0012]    An object of this invention is to provide improved mechanism which steers or maneuvers one or more high energy density outputs as they are translated across a surface.  
           [0013]    A still further object of this invention is to provide a waterjet system that provides a shaking motion to the nozzle rather than a rotational motion.  
           [0014]    A feature of this invention is to mount the nozzle to the end of the non-rotating water transfer tube which is mounted in a housing that is pulley connected to a drive motor for rotating a cylindrical mass (rotating tube) which is offset from the centerline non-rotating eccentric tube. A pivot supports the housing at a judicious location and affects the motion of the non-rotating nozzle which in the present configuration moves in an oscillating fashion which is a circular motion. The assembly provides an angular motion limited by opposing bumpers to deform the circular motion of the nozzle.  
           [0015]    A further feature of this invention is to provide structure which is characterized as easy to manufacture, assemble, operate and maintain, that is capable of being steered or maneuvered yet capable of utilizing several different mediums that guide small high energy density outputs in a pattern that when translated across a surface will evenly affect the surface.  
           [0016]    The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a view partly in schematic and partly in elevation illustrating the invention;  
         [0018]    [0018]FIG. 2 is a view partly in section and partly in schematic of the embodiment depicted in FIG. 1;  
         [0019]    [0019]FIG. 3 is a plan end view of the embodiment of FIG. 1; and  
         [0020]    [0020]FIG. 4 is a graphical illustration of the motion across a surface produced from a simulation of a single orifice nozzle motion pattern with linear translation, and is illustrative of one of the many patterns that can be created by the present invention.  
         [0021]    These figures merely serve to further clarify and illustrate the present invention and are not intended to limit the scope thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    While this invention can be utilized for maneuvering or steering high energy density output(s) of different mediums the invention will describe in the preferred embodiment, mechanism with a non-rotating nozzle designed to have imparted thereto a small circular type oscillating motion (a very special case of linear, two dimensional motion) defining an arbitrary pattern with a pivot that allows small angular motion. The mechanism in this preferred embodiment is typically mounted on a robot and in industry this mechanism is often referred to as an “end effector”. As one skilled in the art will appreciate, the position of the eccentric mounted pulley and rotating tube serves to change the pattern of the end effector and hence, nozzle or other output manifold. While the invention is particularly concerned with the removal of paint and/or coatings from the substrate, it will be appreciated that this invention can be employed to perform other functions, such as peening, surface hardening, to name but a few.  
         [0023]    For the purpose of understanding the description of the invention the term small refers to the dimension of the swath of the output when the mechanism is in a stationary position when viewed relative to the total surface being worked. The term high energy density refers to the force or intensity of the medium wherein its interaction on the surface is such that if remained stationary at a given period of time the interaction would cut into the surface of the item being worked on or damage said surface.  
         [0024]    As best shown in FIGS.  1 - 3 , the invention comprises the end-effector generally illustrated by reference numeral  10  having a main generally rectangular shaped housing or block  12  having a central bore  13 . Housing  12  may be formed from two parts, fore portion  16  and aft portion  18  that are affixed by suitable bolts  19  and together the housing  12  supports the rotating tube  20  mounted in the central bore  13 . As noted, rotating tube  20  is rotatably supported by the commercially available needle bearings  26  and  28 . A flange  30  formed intermediate the ends of rotating tube  20  extending radially in the enlarged diameter portion  32  of bore  13  serves to form opposing shoulders for thrust bearings  33 . Obviously, the assembly is lubricated and suitable commercially available seals are suitably located to prevent lubricant leakage, which are the end seals  44  and  46  and O-ring  50 . Mounted and affixed to the rotating tube  20  are the pulley  52  and the hand-wheel  54 . The pulley serves to rotate the rotating tube  20  and is suitably attached to the drive wheel  56  of a suitable motor  58  shown in schematic and a suitable commercially available rubber or elastomeric belt  54  connected to the drive wheel  56  and pulley  52  which will be described in further detail hereinbelow. As one skilled in this art appreciates the pulley arrangement can be easily replaced by a gearing arrangement without departing from the scope of this invention. The commercially available motor  58  may be any of the well known types such as air or fluid driven or electric and serves to drive the rotating tube  20  at say, between 300 to 600 revolutions per minute (RPM) which speed is predicated on the particular task for the end effector.  
         [0025]    The hand wheel  54  is also suitably affixed to the rotating tube  20  and rotates therewith and serves as a convenient way to set the end effector during set up at the initial start of the coating removal task.  
         [0026]    In accordance with this invention a through hole  25  is bored into rotating tube  20 , extends therethrough and is located off centerline A by an amount shown by letter B to define an eccentric as will be described hereinbelow. It is apparent from the foregoing that the centerline of non-rotating tube,  20  rotates in a circle of radius B about centerline A. The non-rotating tube  14  is supported by sleeve bearings  22  and  24  which are mounted at either end of the rotating tube  20  and disposed between outer diameter of the fixed high pressure tube  14  and inner diameter of the rotating tube  20 . Shaft collar  27  and thrust washer  29  surrounding the fixed tube  14  and at each end of tube  20  and serves to secure the fixed tube  14  into place and hold the fixed tube  14  inside the rotating tube  20 .  
         [0027]    Also, in accordance with this invention and to achieve the angular deflection of the nozzle, the main housing  12  is pivotally affixed to the bottom plate  59  by suitable bolts  66  and  68  via the trunnion supports  62  and  64 . Opposing cap screws are mounted in diametrically opposed bores formed in the trunnion supports  62  and  64  and form a pivot  65  for the main housing. As will be described in further detail hereinbelow the main housing by virtue of the relaxation and tension of the belt on pulley  52  as it drives the rotating tube  20  causes the housing to slightly pivot and bounce against the rubber or elastomeric members or bumpers  70 . The assembly provides four rubber or elastomeric bumpers  70  which are toroidally shaped to accommodate a screw  71  through the center thereof to affix the bumpers  70  on opposite sides of the inner face of bottom plate  59  attached by screws  60 . The housing engages the bumpers  70  in a timely fashion as will be described hereinbelow.  
         [0028]    In operation, a suitable nozzle  80  depicted schematically and may be the the type described in U.S. Pat. No 5,421,517, supra, or any other nozzle is attached to the end of the non-rotating tube  14  where the threads are formed and may include one or more outlets as is desired and is imparted the pattern dictated by the setting of the eccentric and pivot  65 . In this preferred embodiment, high pressure water at a ultra high velocity is fed thereto from the reservoir  76  through the suitable well known pump  81 , connecting line  78 , fitting  74  through the non-rotating tube  14  and ultimately through the orifices in the nozzle  80 . The motor is actuated and drives the drive pulley  56 , which in turn drives belt  54  and in turn, rotates pulley  52 . Because the fixed or non-rotating tube  14  and the rotating tube  20  are eccentric relative to each other as shown in FIG. 3 and the space depicted by the vertical lines B-B the nozzle will be imparted a shake pattern where the motion is in small circles.  
         [0029]    As described above the end effector of this invention also provides an angular motion. This is provided by the pivot  65 . The purpose of the angular motion is to eliminate the evenness of the tops and bottoms of the small circle or skew the small circles defined by the shake movement, so that the edges of the circle are smeared as the pattern is translated across the surface being treated. Without the pivot  65  we have found that the even edges of a perfectly circular pattern causes the stripped surface of the substrate to be overworked. In the preferred embodiment the driven pulley  52  has 48 teeth and the driving pulley  56  carries 19 teeth. The motor or driving pulley  52  is bored slightly center so that at each turn of the motor the toothed belt pulls the pivoted assembly into the front set of bumpers. As the driving pulley  52  moves away from the high spot the belt tension decreases and allows the bumpers  70  to move the pivoted housing  12  unforced in a nodding or rocking motion. Because of the differences in the number of teeth in the drive and driven pulleys there will be 48 such angular kicks in 19 rotations of the eccentric circular pattern before the pattern of angular kicks and eccentric positions repeats. This length makes the angular motion appear to be random.  
         [0030]    The housing  12  is implemented with a commercially available proximity sensor  83  that extends radially into housing  12  and is spaced relative to the peripheral surface of the flange  32  and serves to measure the speed of the rotating shaft  20 . This sensor is optional and does not constitute a part of this invention.  
         [0031]    [0031]FIG. 4 is a plot of the simulation of the center of a one orifice nozzle linearly translated across a flat surface. The pattern developed by this invention are small circles but with edges that are skewed. The smearing of the edges of a mostly circular pattern prevents the edges from becoming overworked.  
         [0032]    Obviously, this mechanism described in the above paragraphs can be simply modified to include additives or abrasives to the water or could substitute other fluid mediums. Moreover, it is contemplated by the scope of this invention that the mechanism can be employed for peening or surface hardening or other purposes and could use other mediums for “working” the surface, such as laser, white light and the like.  
         [0033]    Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.