Abstract:
An electroformed cornercube retroreflector, wherein a conductive mandrel locates within an electrolyte containing metallic solution and through charging of the mandrel located within the solution attains electrodepositing of the metallic solution on to the mandrel for the purpose of plating a thick coating of the metal upon the mandrel. When the coating has achieved sufficient structural integrity to form a cornercube retroreflector, it is removed from the electrolyte, the deposited metal is separated or stripped from the mandrel to provide a natural highly inner polished metallic cornercube that can be placed within a partial sphere or other supportive body for use as a retroreflector for application for laser tracking in industrial or other applications.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This non provisional patent application claims priority to the provisional patent application having Ser. No. 61/396,226 having filing date May 24, 2010. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to the forming of a cornercube retroreflector for use in laser tracking, and more particularly, provides both a method and article for forming a cornercube from the electroforming process, by depositing through electrolytic action a metallic layer upon a mandrel(s) until such time as sufficient metal thickness forms a cornercube of integral structural integrity when removed from the mandrel for locating within a partial spherical body to create a Spherically Mounted Retroreflector (SMR) or other supportive body mounting designs as required, for use in laser tracking in industrial applications. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cornercubes are applied or formed within a reflecting chamber normally have three mutually orthogonal surfaces, and are located within a cylinder, as an example, or within a partial spherical body, and have been manufactured and used for some time. For example, in the prior art, it has been known to place glass or related material reflecting surfaces, normally three blended surfaces into a triangular form within a sphere, to function as the reflective surface for diverting a laser beam back to its source for precision placement of machining components, tooling, or other parts to be worked or to inspect for quality. The efforts required to form that type of a retroreflector requires one highly skilled in the art, to attain the proper placement of reflective surfaces perpendicular to each other, and then to mount the glass assembly precisely within the sphere, having the inner apex of the three optically flat reflective surfaces located precisely at the center of the formed partial sphere. These types of spheres can readily be seen within the prior art patents obtained by one of the co inventors herein, such as to be seen in the U.S. Pat. No. 7,110,194, in addition to the SMR shown in his U.S. Pat. No. 7,204,024. 
         [0004]    Other patents showing related SMR&#39;S can be seen in the U.S. Pat. No. 6,299,122, disclosing a spherically mounted retroreflector edge adaptor. 
         [0005]    The co-inventor of this current invention has also designed a displacement process for forming a hollow surveying retroreflector reflecting chamber. This can be seen in the U.S. Pat. No. 7,014,325. In that patent, the malleable material is placed beneath a punch, and the punch itself is applied by pressure within the malleable material, in order to form a cubecorner configuration, that is used to form a reflecting chamber, by pressure, within the material, and having the three mutually orthogonal surfaces that are formed within the cylinder. Then, the reflecting chamber within the cylinder can be used for reflecting the laser, or it may be applied within a partial sphere, to form the Spherically Mounted Retroreflector for use for laser tracking purposes. 
         [0006]    The concept of electroforming has been around for over a century. For example, as known, electroforming has been used for precision replication of fine-featured items, such as coins and bank note printing plates, along with other jewelry, and artistic products. Usually, electroforming is done upon a conductive surface. If the surface to be coated is nonconductive, then usually some form of a conductive paint, or other conductive coating, is applied to the nonconductive surface, to provide a conductive surface. As noted, electroforming, as a process, adds metal, atom by atom, to the conductive surface, until it builds up to a sufficient layer, normally having sufficient structural integrity through the application of its thick layer of deposited metal, so that the finished item is self-supporting. 
         [0007]    The concept of this current invention is to combine the concept of forming a cornercube retroreflector, through the metal forming process, then to add it to a partial spherical body, in a precise manner, so that the partial sphere and cornercube assembly can be adapted for use and mounted for laser tracking purposes. 
       SUMMARY OF THE INVENTION 
       [0008]    The concept of this invention primarily relates to electroforming, and more specifically for use of a mandrel that has the male components for forming precisely a cornercube for use in a Spherically Mounted Retroreflector or other supportive body. 
         [0009]    Electroforming is a metal forming process that uses electrodeposition to plate the base form, know as the mandrel, which is removed after plating. Technically, it is a process of synthesizing a metal object by controlling the electrodeposition of metal passing through an electrolytic solution onto a metal or metallized form. More simply, a metal skin is built up on a metal surface, or any surface that has been rendered conductive through the application of a specialized paint, that contains metal particles, or metallic vapor deposition, to make the surface conductive. Essentially, a metal part is fabricated from the plating process itself. 
         [0010]    This differs from electroplating basically because the skin is much thicker and can exist as a self supporting structure if the original matrix, or mandrel, is removed. The object being electroformed on can be a permanent part of the end product or can be temporary, and removed later, leaving only the metal form, the “electroform”. 
         [0011]    New technologies have made it possible for mandrels to be very complex. In order to facilitate the removal of the electroformed article from the mandrel, a mandrel is often made of aluminum. Because aluminum can easily be chemically dissolved, a complex electroform can be produced with near exactness. 
         [0012]    In recent years, due to its ability to replicate a mandrel surface precisely atom-by-atom with practically no loss of fidelity, electroforming has taken on new importance in the fabrication of micro and nano scale metallic devices and in producing precision injection molds with micro and nano scale feature for production of nonmetallic micro molded objects. Electroforming tolerance of 1.5 to 3 nanometers has been reported by some precision fabricators. 
         [0013]    In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroplatable metal onto a conductive patterned surface, such as conductively coated glass or other non-conductive material that has been conductively coated, or normally conductive metallic materials such as stainless steel, nickel, carbide and the like or any combination of the previously suggested substrates. Once the plated material has been built up to the desired thickness, the electroformed part is separated from the master substrate. This process allows high-quality duplication of the master and therefore permits quality production, at low unit cost with high repeatability and excellent process control. 
         [0014]    The main advantage of electroforming is that it reproduces the external shape of the mandrel within 1 micrometer. Generally, forming an internal cavity accurately is more difficult than forming an external surface. 
         [0015]    More specifically, with respect to forming a cornercube for an item such as a Spherically Mounted Retroreflector, as noted in the background discussion, such cornercubes hereto for have been formed of usually glass prisms, three surfaces that mate in a triangular orientation, in order to furnish the type of precise reflective surface that allows for it to cooperate with the laser beam, when performing laser tracking for precision setting or measuring of various components or tooling. Then, the concept of pressing a metal, such as lead, into the configuration of a cornercube, was developed by one of the inventors herein, as to be seen from a review of his U.S. Pat. No. 7,014,325. 
         [0016]    If the mandrel used in the current invention is of metallic composition, then normally it will have conducting characteristics, and can be used in an electrolyte for achieving electroforming of a cornercube. If a non-conducting mandrel is utilized in the process, such as a glass, polymer, composite, ceramic or non-conductive base, then it must be coated in such a way as to become conductive. Nevertheless, regardless what type of mandrel is used, the process yields a mirror bright finish, which in turn is representative of the mirror bright finishes that are a part of the mandrel, particularly where nickel may be used as the coating composition, and which functions well in the formation of a cornercube, for application into a Spherically Mounted Retroreflector or other supportive body. 
         [0017]    More specifically, this invention comprehends the usage of an electroforming bath, and into which one or a plurality of mandrels may be applied, the proper conducting charges may be applied to each of these units, such as a positive connection to the bath, that may contain nickel, or other depositable metals in solution, and a negative charge may be applied to the mandrel, to allow for the metal forming deposition. The mandrel is then introduced into the bath, for some period of time, usually at least twenty-four hours of submersion, or even up to five days, at which time the metal forming process takes place, upon the tip of the mandrel, which provides for its formation into a coating upon the mandrel, for formation of the desired cornercubes. Usually, the desirable result is to built up a coating of approximately fifteen thousands of an inch, more or less, of nickel or other metal deposition, and when that is achieved, the mandrel may be removed from the bath, at which time one can readily observe the metal forming applied at the tip of the mandrel, through the electroplating process. At this point, the nickel alloy, that has been applied to the male formed mandrel tip, that has the appearance of a cornercube, with the metal formed nickel alloy being removed, from the tip, and provides a very precise cornercube, having a highly reflective and naturally polished inner three triangulated surface, that is ready for application to a partial sphere or other supportive body, for uses as a retroreflector, in laser tracking applications. And, where it is desired to form a series of the electroformed cornercubes, then a plurality of mandrels may be applied to the supporting base, for submersion within the electrolytic fluid, for creation of a series of cornercubes, of precision dimensions, that can be readily applied within their separate partial spheres to create a Spherically Mounted Retroreflector or other supportive body, in preparation for usage. 
         [0018]    These are examples of the summary of the concept of this invention, and how cornercubes can be formed by the identified process, to precision dimensions, and ready for usage and application in the further assembly of laser tracking equipment. 
         [0019]    It is, therefore, the principal object of this invention to provide a means for electroforming of cornercubes for use and installation within partial spheres to create Spherically Mounted Retroreflectors or other supportive bodies, for application within laser tracking procedures. 
         [0020]    Still another object of this invention is to provide the formation of cornercubes, that are of very precise and close tolerances, so that they can be simply fitted within their respective partial spheres to create Spherically Mounted Retroreflectors or other supportive bodies, in preparation for their usage. 
         [0021]    A further object of this invention is to provide the formation of cornercubes by the electroforming process. 
         [0022]    Still another object of this invention is to provide a means for forming, simultaneously, a series of cornercubes by the electroforming process. 
         [0023]    Furthermore, another object of the invention is to provide a means of re-producing accurate male cornercube mandrel portions, inversely, using the electroforming process, by replicating from an electroformed female cornercube, thus allowing for the production of mandrels using the electroforming process and thereby multiplying production tooling using the same process. 
         [0024]    These and other objects may become more apparent to those skilled in the art upon review of the summary of the invention as provided herein, and upon undertaking a study of the description of its preferred embodiments, in view of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    In referring to the drawings, 
           [0026]      FIG. 1  provides a view of the electroforming reservoir, containing its electrolyte, and showing its mounted mandrel ready for submersion into the electrolyte for electroforming of a cornercube; 
           [0027]      FIG. 2  shows the mounted mandrel submerged within the electrolytic solution during the electroforming process; 
           [0028]      FIG. 3  shows the mounted mandrel elevated from the solution, disclosing upon its tip an electroformed cornercube; 
           [0029]      FIG. 4  shows the supported mandrel with its electroformed cornercube having been separated from formed tip of the shown mandrel; 
           [0030]      FIG. 5  shows a formed cornercube of this invention, in this particular instance, being fabricated of a nickel metal; 
           [0031]      FIG. 6  shows another view of the formed cornercube; 
           [0032]      FIG. 7  shows a plurality of mandrels being supported by its upper mount and being positioned within the solution of the container, during performance of an electroforming process; 
           [0033]      FIG. 8  shows the mounted mandrels elevated, at the completion of an electroforming process, having a series of cornercubes formed upon the tips of the mandrels; 
           [0034]      FIG. 9  shows a formed cornercube that has been located within a partial sphere to create a spherically mounted retroreflector, in preparation for laser tracking usage; and 
           [0035]      FIG. 10  shows the cornercube of this invention mounted within a Spherically Mounted Retroreflector, and resting upon its sphere mount as during usage and application. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0036]    In referring to the drawings, and in particular  FIG. 1 , the equipment utilized in electroforming of the cornercubes of the current invention is readily disclosed. As to be seen, it includes a vessel  1  that contains a supply of the electrolyte  2 , which, as is well know, forms a liquid ionic conductor that provides for the movement of ions, which in the preferred case, a solution of nickel that transmits by electrolysis to the precisely formed tip  3  of the mandrel  4  that is supported by its mount  5  when ready for performing the electroforming process. Obviously, other electrolytes can be used, in the electroforming process, and it could use such metals as copper, gold, and other decorative metals such as platinum, rhodium, or even silver, but in this particular industrial application, nickel plating has been found most effective. The liquid ionic conductor utilized may include any substance such as a salt, or acid, when dissolved in a suitable solvent, such as water, and which functions as a carrier for the metallic ions, which when subjected to electrical charge, produces the electroforming upon the tip  3  of the mandrel, as can be understood. 
         [0037]    Usually, in the electroforming process, it may take approximately one to five days to achieve the thickness of electroforming as desired for the cornercube, and it has been found that a cornercube formed of approximately fifteen thousands of an inch, more or less, has sufficient structural integrity to allow its use within a Spherically Mounted Retroreflector or other supportive body, for laser tracking purposes. 
         [0038]    While the mandrel of this invention may be formed of a metal, and therefore is receptive to conductive charge, and for achieving electroforming thereon, other types of materials could be used, such as glass, polymer, or the like, and which may be coated with a conductive paint, or metallic vapor deposition, in order to attain the electroforming attributes of this invention. 
         [0039]    More specifically, in the basic electroforming process, an electrolytic bath is used to deposit the nickel, or other electroplatable metal, onto a conductive patterned surface, such as the tip  3  of the mandrel herein, or it may be coated onto glass, or stainless steel, the former including a coating of metallized paint, or metallic vapor deposition. Once the plated material has built up to its desired and required thickness, such as the fifteen thousands of an inch, as a forth set, the electroformed part is stripped off of the master substrate, in this instance, being the tip of the mandrel  4 . This process allows high quality duplication of the master, and therefore permits quality production of the cornercube, at low unit cost, with high repeatability and excellent process control, in the performance of its process. 
         [0040]      FIG. 2  shows the performance of the process of this invention wherein the base supported mandrel  4  has its precisely formed tip immersed within the electrolyte  2 , during the procedure of electroforming of the cornercubes of this invention. As previously stated, it may take as many as three to five days to build up the integrity of the forming cornercube, so that attains that desired structural thickness within the range of about that fifteen thousands of an inch, more or less. 
         [0041]    When it has been determined that the formed cornercube has achieved its desired thickness, and strength, the base supported mandrel  4  is removed from the bath. As to be seen in  FIG. 3 , the electroformed tip  6  is deposited onto the contoured lowered tip of the shown mandrel, and is ready to be separated in a linear motion, as to be noted in  FIG. 4 , and is ready for its preparation for application to a partial sphere to create a Spherically Mounted Retroreflector or other supportive body. Since the precision electroforming has formed the cornercube to precise dimensions, and its critical internal mirror like surfaces will be formed to micro dimensions, the entire formed cube is ready for application into the counterbore of a partial sphere or other supportive body, which may be adhesively applied therein, and ready for usage in the laser tracking process. 
         [0042]      FIG. 5 , in addition to  FIG. 6 , shows the electroformed cornercube  6 , and it can be seen that its peripheral thickness is formed of some degree of structural strength, as noted at  7 , and which may be within that range of approximately fifteen thousands of an inch, more or less as required which provides sufficient structural integrity against its bending or warping, as it is adhesively or otherwise applied or connected into the sphere, in preparation for its usage. As can also be seen, and due to the nickel plating of the formed cornercube upon the mandrel, the three internal surfaces  8 ,  9 , and the third surface (not shown) forms a triangulated series of surfaces that are highly polished simply due to their electroforming, and ready for use for reflective purposes, for the transmission of the laser beam, as applied during the laser tracking process, in industrial applications.  FIG. 6  shows the relative size of this particular formed cornercube  6 , although there are size options, after it has been separated in a linear motion from the mandrel  4 . 
         [0043]    As to be noted in  FIG. 7 , a plurality of mandrels  10  can be stably supported from its mount  11  and ready for deposition within the electrolyte  12  of the vessel  13 . This shows how a plurality of the cornercubes can be formed, simultaneously, during the manufacturing process, and immediately ready for application, once formed, into their respective spheres, when the Spherically Mounted Retroreflectors are prepared for marketing and industrial applications.  FIG. 8  shows the plurality of mandrels  10  as elevated from the electrolytic bath, and showing how their lower tips contain the formed cornercubes  14  ready for stripping and further processing when applied to partial spheres to create a Spherically Mounted Retroreflector. The only really time consuming feature of forming cornercube retroreflectors in this manner is the time delay in the electroforming process, but since the procedure is extremely accurate in forming very close tolerance cornercubes, and since no man power is necessary during the electroforming process, this does not add any significant cost to the construction of the structured spheres, for use for laser tracking purposes. 
         [0044]      FIGS. 9 and 10  show a Spherically Mounted Retroreflector (SMR)  15  where the electroformed cornercube  16  has been applied within a counterbore within the sphere, which is now readied for application within the sphere mount, as at  17 , when applied in a laser tracking operation. See  FIG. 10 . The naturally formed reflective surfaces  18  can be readily seen within the cornercube, and these are simply formed through the electroforming process, they are a highly reflective, mirror like surface without any further polishing procedure being necessary, simply because of the electroforming method, that applies the nickel metal to the surface of the tip of the mandrel, during and through usage of the electroplating and electroforming process. The naturally formed surfaces, 3 places, 19 that lie in sequence between the 3 reflective mirrors like surfaces, are dull and non-reflective. These 3 surfaces are also minimally tapered to assist in the separation of the electroformed cornercube from the mandrel tip. The formed cornercubes  16  are immediately ready for application and usage, for connection within the counterbore of the partial spherical body, immediately after they are stripped from the mandrel. 
         [0045]    Variations or modifications to the subject matter of this electroforming invention may occur to those skilled in the art upon review of the summary of the invention as provided herein, and upon undertaking a study of the description of its preferred embodiment. Such variations, within the spirit of this invention, are intended to be encompassed within the scope of any claims to patent protection issuing hereon. The description of the preferred embodiment, and the disclosure of the invention within the drawings, is done so for illustrative purposes only.