SYSTEM, WORKSTATION AND METHOD FOR DENTAL AND JEWELRY MANUFACTURING FIELD OF THE INVENTION The present invention relates to the field of dental restorations and more particularly to the preparation of dental crowns with a system and method that easily separates contaminates from precious metal scrap generated in the making of the crowns and facilitates a high rate of recovery thereof. The present invention is also useful in the jewelry and like industries where noble and high noble metal items are made. The present invention also relates to a workstation for use with the system.

BACKGROUND OF THE INVENTION A number of fields of manufacturing require the production of small one-of-a-kind items. Examples include the production of metal dental restorations, such as crowns, and jewelry. Production of these items is typically done at a workstation designed specifically for the task, which protect the technician from exposure to the materials used in the production of the items, provides convenient and comfortable work conditions and permits the retention and recovery of waste materials.

Some of these items are made of a significant amount of precious metals as well as other materials. For example, with respect to the production of dental restorations, the most prevalent crown construction is the porcelain veneered cast metal crown and full contour metal crowns. The cast metal crown is fabricated using a relatively thin metal understructure formed from casting noble and high noble metals into an investment mold of a wax or plastic pattern of the metal understructure or full contour crown. Dental porcelain is then applied in layers over part or all of the understructure and fired at high temperature to form a veneer layer. The metal understructure may be formed from a base ally (non-precious) noble based metal or a noble

based alloy with varying quantities of gold, platinum, palladium, silver, nickel, and an array of"trace elements".

The crown typically is made in a process where a model or pattern of the patient's teeth is made. The pattern of the crown is made of out of wax.

The pattern is sprued, invested, burned out and a metal casting is made therefrom in the classic lost wax technique. Each metal unit is cut off from the base (or button) with a disk, typically made of carborundum. The button is saved and reused. The scrap, from grinding or cutting and typically collected by vacuum, is not readily reusable and is saved for processing at an off-site refiner. Unusable, contaminated scrap is generated at most or all the subsequent steps as well. For example, scrap is generated when the units are separated from the sprues. Scrap is generated when the inside and outside surfaces of the units are prepared with stones. The scrap contains at least contaminates from the stone cutting and surface preparation devices.

Significantly, the expense of sending the scrap to be processed by an outside refiner yields a low rate of recovery of the value of the material, on the order of about sixty percent. Similar disadvantages exist in the jewelry industry, where lost wax casting techniques, and the like, are employed to make small precious metal items.

Heretofore, the cutting and grinding steps may have taken place in a device resembling a miniature"clean room", which typically includes a fully or partially enclosed housing. The housing may include fixtures to attach to either a source of vacuum (negative pressure) or positive pressure airflow.

The negative pressure is used to vacuum grindings and finer dust-like material from the production of the crown, or like item, into a filter or collection receptacle of some type. Positive pressure airflow has been used to knock grindings and dust into a filter apparatus. In either case, the housing is permanently or semi-permanently attached to the source of vacuum or positive pressure airflow. Since many different metal materials may be used in the production of dental and other items, such housing are necessarily cleaned during changeovers between production runs of different materials.

This is necessary to reduce cross-contamination and the cost of refining the materials into a reusable form.

Therefore, there is a demand for an improved system, workstation and method for preparing crown understructures and like items that overcomes at least these disadvantages. The present invention satisfies the demand.

SUMMARY OF THE INVENTION In broad overview, one aspect of the present invention relates to a system which includes a modular base and grinding enclosure or collection unit to form a workstation assembly for preparing metal items, such as precious metal items, e. g., dental crown understructures and full contour metal crowns, with respect to recovering noble and high noble material from scrap or waste generated in the making of the items. The base is designed to receive an enclosure, which enclosure may be quickly and easily substituted with another enclosure. In this way, a single base may be used with a plurality of enclosures. Each of the plurality of enclosures is usable with a single metal type, which avoids contamination of the scrap collected therein and thus avoids expensive refining processes, avoids cross-contamination of alloy types and provides an efficient and effective collection chamber.

As used herein, the noble material or metal referred to specifically may be gold, silver, platinum and palladium or an alloy thereof used in making the desired unit, such as a crown understructure or full contour metal crown. The workstation may be used for other material preparation, and not limited by the examples given herein. The term scrap, as used herein, will refer to a waste material that has been generated during the preparation of the units. Some or all of the contaminate may be magnetic and is thus capable of being magnetically separated from a noble metal portion of the waste or other non- magnetic waste by exposure to a magnetic field, from for example a magnet.

It will be understood that the embodiments of the present invention illustrated herein are scaled to be more cost effective when used by a small or limited sized laboratory or business.

Other systems are contempaneld in view of the teachings below, which may be applied to larger facilities by providing numerous such workstations or applying the same principles to larger or automated apparatuses. One can see the benefit of such modular workstations. An operator using a workstation to form an item made of any first material such as, for example gold, can remove a first enclosure, which is expressly devoted to forming the gold items and install a second enclosure onto the base of the workstation, which is expressly devoted to forming items of, for example, platinum.

One aspect of the present invention provides such a modular workstation. In general, the workstation essentially includes two main portions. A first portion forms a base, which may stay fixed in position at a workplace desk, on a wall or other workplace fixture. The base is provided with a mechanism for providing a negative airflow. The mechanism may be a fan optionally enclosed within a fan housing attached to the base or a separate fixture attached to a remote vacuum-producing pump, or the like.

A grinding enclosure or collection unit, which is essentially a box-like housing is provided with openings for user arms, tools and venting in connection with the base. The enclosure is sized and shaped to be received and held by the base. The enclosure includes an opening with cooperates with the base to convey the negative airflow from the base to an interior of the enclosure. The base may be used with numerous enclosures by replacing a first enclosure with subsequent enclosures. In this manner, each separate enclosure may be used for a single species of material and need not be cleaned out between sessions.

Another aspect of the present invention provides a method for recovering noble and high noble metal from scrap generated during the manufacture of noble and high noble metal units including providing a cast metal unit. The unit is made of at least some noble metal. The surface of the unit is prepared with an abrading element. The preparing step further includes generating a magnetically attractive particulate contaminate and generating an amount of scrap thereby. The scrap includes noble metal and

a percentage of particulate contaminate. The noble metal is magnetically separated from the contaminate.

Another aspect of the method of the present provides removal of a casting button and sprue from an item. The method includes removing the button from the unit and removing the sprue from the unit with the abrading element before surface preparation of the unit, generating an additional amount of scrap thereby; and combining the generated amounts of scrap before magnetic separation thereof.

The unit may be a dental crown understructure. The unit may be a jewelry item. The abrading element may be a tungsten carbide bur operated at a speed of about 10,000 to about 300,000 RPM. The bur may be operated at about 40,000 RPM. The step of preparing the surface of the unit may take place in a substantially closed housing. The step of magnetically separating the noble metal may include transferring the scrap into a refining jar, wherein the refining jar comprises a magnet, and agitating the scrap therein.

Another aspect of the present invention provides a system for preparing noble metal units and recovering noble metal from scrap generated during the manufacture thereof, including at least one abrading element and means for operating the bur at a speed sufficient to prepare the surface of the units. The abrading element may be a stone abrading element, a tungsten carbide bur, a diamond bur or any other suitable abrading element. A substantially closed collection unit is provided for operation of the at least one bur therein, for collecting scrap generated during preparation of the unit by the bur, wherein the scrap includes a percentage of magnetically attractive contaminate. A refining unit is provided including a magnet positioned therein for magnetically removing the tungsten carbide contaminate from the scrap.

Other aspects of the system of the present invention provide a collection unit that may include a housing, at least a portion of the housing being transparent. The housing may include a metallic portion. The housing may include left and right sides, at least one of which includes a tool port formed therein through which a tool may be inserted therethrough. Each of the left and right sides may include an opening into whicn a panel is rotatably

positioned, each of the panels including an orifice formed therein through which a hand may be inserted therethrough. Each orifice may be eccentrically formed in each panel. The refining unit may include a glass portion and a lid portion, the lid portion being releasably positioned to close the glass portion. The magnet may be a rare earth magnet. The magnet may be affixed to the lid for positioning within the glass portion of the refining unit.

The invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will be further understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein : FIG. 1 shows a side view of one aspect of an embodiment of the present invention, and in particular, a collection device; FIG. 2 shows a side view of another aspect of an embodiment of the present invention, and in particular, a refining vessel ; FIG. 3 shows a flow chart of one embodiment of the method of the present invention ; FIG. 4 shows a perspective view of one embodiment of a base of the workstation of the present invention; FIG. 5 shows a side view of the base of FIG. 4; FIG. 6 shows a perspective view of one embodiment of a grinding enclosure of the workstation of the present invention ; FIG. 7 shows a side view of the grinding enclosure of FIG. 6; and

FIG. 8 shows a side view of the base and grinding enclosure operatively connected into the workstation of the present invention.

DETAILED DESCRIPTION OF A PRESENTLY PREFERRED EMBODIMENT In broad overview, the present invention relates to a system, workstation and method of preparing precious metal items, like dental crown understructures and full contour metal crowns for recovering noble and high noble material from scrap or waste generated in the making of the items. As used herein, the noble material or metal referred to specifically is gold, silver, platinum and palladium or an alloy thereof used in making the desired unit, such as a crown understructure or full contour metal crown. For purposes of the present description, reference to noble metal will include high noble metal materials. The noble material is non-magnetic. The term scrap, as used herein, will refer to a noble material that has been contaminated with other materials. Some or all of the contaminate is magnetic and is thus capable of being magnetically separated from the noble metal by exposure to a magnetic field from, for example, a magnet. It will be understood that the embodiments of the present invention illustrated herein are scaled to be cost effective when used by a small or limited sized laboratory or business. Other systems are contemplated in view of the teachings below, which may be applied to larger facilities by providing numerous such systems and workstations or applying the same principles to larger or automated apparatuses.

Beginning with the invention shown in FIG. 1, a collection unit or box is illustrated generally at 100. The collection box 100 includes a housing portion 110, which in one embodiment may be made of a clear Plexiglas material, or other suitable material. In another embodiment, the housing 110 may be made of a metal material. It may be preferable to construct the housing 110 of a material that is not capable of retaining static electricity. The collection box 100 is used to collect the scrap material, typically in the form of fine shavings, filings and dust and the like during the process of manufacturing a cast unit into a finished product. Manufacturing includes applying a tungsten

carbide bur to the unit and the scrap thus generated is retained in the unit 100.

The housing portion 110 includes top and bottom panels 112,114 and four sides. In one embodiment, the housing 110 is about a foot square. The front and back side panels 116, 118 and one example of a left side panel 120 being shown. The top panel 112 of the housing portion 110 may include a removable clear plastic viewing panel 122 through which the technician may easily observe the operation. The top panel 112 of the housing portion 110 may further include a handle 124 for transporting the unit 100. Further, the top panel 112 of the housing portion 110 may include a bracket (not shown) for stacking a number of identical or similar units 100. The housing portion 110 may include a slot 126 formed along a bottom area of one of the side panels, such as the front side panel 116, for inserting and removing a collection pan 128. During use of the unit 100 the collection pan 128 is normally positioned along the bottom of the unit 100 positioned to catch any materials generated inside the unit. The pan 128 is preferably a material with non-static properties, such as stainless steel in order to not statically retain any of the scrap material.

A back side panel 118 of the unit 100 may include a port 130 with an attaching portion 132, which is provided for attaching a vacuum hose (not shown) thereto in a conventional manner, by interference fit or threaded connection, for example. The port 130 opens to the interior 134 of the housing 110. The interior 134 of the housing 110 may preferably include an angled skirt 136 formed around the periphery thereof, which directs any materials generated inside to the collecting pan 128 residing at the bottom of the interior of the housing. Further, a downward angled member 138 may be provided in the interior of the housing 110, which extends over the port opening 130 to deflect any materials away from the port. The top surface 140 of the angled member 138 may include a plurality of openings 142 formed therein for inserting and storing various tools such as carbide burs or similar tools and tool bits (not shown). The openings 142 are sized to receive the shaft of each bur.

The left and right sides of the housing 110 are similar, and thus, only one will be discussed herein. One or more tool ports 144 may be provided, through which a drill (high or low speed), or similar tool may be inserted. The one or more tool ports 144 may be sealed by a cap member or plug (not shown).

Each of the left and right side panels of the housing 110 may be provided with a circular panel 146, which is held in place in a suitable opening 148 formed in each side. The opening 148 and panel 149 may be any suitable compatible shape, such as rectangular, hexagonal and so on. Each circular panel 146 contains an orifice 150, which may be eccentrically positioned relative to the center of the panel 146, through which the technician may insert a hand. The orifice may be about four inches in diameter, or sized to receive a technician's hand and wrist. Furthermore, the orifice 150 may be provided with a sleeve (not shown) to reduce loss of generated scrap through the orifice. In another embodiment of the invention, the orifice may be provided with a sealed glove or sleeve (not shown) to further enclose or seal the housing 110 from loss of scrap.

In the illustrated embodiment shown, a number of retaining devices 152 are provided to hold the circular panels 146 in the openings 148.

Retaining devices 152 may be a pair of spaced washers 154 held together by a screw 156 or suitable fastener. Loosening the retaining devices 152 permits the circular panel 146 to rotate in the opening 148. Tightening the retainers 152 fix the panel 146 in position. In this manner, the orifice 150 can be adjusted as to height and front to back positioning and thus permit the user to adapt the unit to each user and to different working conditions. Use of the collecting unit 100 will be explained more fully below with reference to FIG. 3.

As shown in FIG. 2, the refining vessel is shown generally at 200. As will be explained more fully below, scrap material 202 obtained from the unit 100 described in FIG. 1 is transferred to the refining unit 200 and separated magnetically. The refining unit 200 includes glass container 204, which is sealed by a lid 208, after the scrap 200 is placed inside. In one embodiment,

the glass container 204 may be about six inches in length and about two inches in diameter. The container 200 may be an eight-ounce container. A magnet 210 is centrally positioned inside the glass container 204. A fastener 212 may be used to fix the magnet 210 to the inside surface of the lid 208. A large diameter washer 214 may be used to stabilize the magnet 210 with respect to the lid 208 due to the large mass of the magnet 210.

The magnet 210 may be a rare earth magnet. It will be appreciated that a strong magnet is preferred and that any suitable magnet may be used with magnetic properties sufficient to separate magnetic material from non- magnetic material. The magnet 210 may be a single large magnet or a plurality of spaced magnets, preferably housed in a single casing. The surface of the magnet should be finished such that magnetic particles adhering thereon can be easily seen. It has been found that a sand blasted finish is preferable to that end.

FIG. 3 is a flowchart 300 generally illustrating one embodiment of the method of the present invention.

The process 300 may begin with block 310, wherein a desired unit is prepared by casting using a conventional lost wax or equivalent technique.

The unit may be a metal understructure for a crown, full contour metal crown or a piece of jewelry, or the like, made of gold alloy, for example, or including any suitable noble metal material.

The metal unit is removed from the casting button (block 320) with a cutting disk or the like. The disk is typically a stone, like carborundum, which is turned at a relatively slow speed in a tool, i. e. a drill or"laith". The button material is saved and may be reused, as it will typically contain little or no contamination from the disk. The scrap from the cutting operation is collected, by brushing or vacuum, for example, and due to being contaminated by material from the carborundum disk, is not reusable without refining as has been done conventionally outside the dental laboratory.

The remaining metal sprue is cut off of the metal unit (which will be eventually cemented in the mouth, for example) (block 330) with a tungsten carbide bur inside the collection box 100. The bur may preferably be turned

at a speed, for instance, on the order of about from 10,000 to 300,000 revolutions per minute (RPM). Due to the speed of the bur, it is advantageous to perform the sprue-removing operation in the collection box 100 of the present system. Use of the collection box 100 thus reduces or eliminates loss of the scrap material generated by scattering by rotation of the bur. The collection box 100 may be provided with a low volume vacuum to reduce humidity build up from the technician's hands. In order to prevent the vacuuming of the metal filings, it will be appreciated that the vacuum should not be applied at a rate that will prevent the metal alloy from landing in the collection pan 128 in the bottom of the box. Similarly, it can be seen that use of the deflector 138 between the vacuum orifice 130 and the box interior 134 during the operation will be advantageous in this and subsequent steps.

All of the subsequent seating and surface preparation steps (block 340) are also preferably performed in the collection box 100 with a carbide bur. In a presently preferred embodiment all or almost all (about ninety-eight percent) of the surface preparation can be done with such a bur. During this operation, all of the scrap material collected in the collection box 100 can be reused after refining in the inventive refining device 200.

The scrap 202 thus generated includes a major portion of noble metal and a minor portion of tungsten carbide bur contaminant. The scrap 202 is collected (block 350) and transferred to the refining device 200 (block 360).

A minor portion (about two percent) of the finishing or surface preparation of the unit may be done with a conventional stone. The scrap material from this portion of the operation must be collected separately from the scrap containing tungsten carbide and must be refined conventionally.

It will be appreciated that tungsten carbide is magnetic and the noble metal is not. As set out above, the refining jar 200 includes a magnet 210. It has been found that due to the moderate magnetic properties of the tungsten carbide, a magnet with strong magnetic properties is preferable for efficient magnetic separation of the carbide and the noble metal or high noble metal.

Thus, in one embodiment of the present invention a rare earth magnet is

preferred. It will be appreciated that other magnets may be suitable for separation purposes, such as an electromagnet or ceramic magnet.

Scrap material 202 including tungsten carbide contaminant from the above steps is transferred to the refining device or jar 200 and separated therein (block 370). In one embodiment, the jar is agitated for a period of time, manually or with the aid of an agitation device, which may hold the jar 200, for example, a period of time of one minute, ensuring that the scrap is evenly exposed to the magnet 210. The jar 200 is opened after agitation and the lid 208 and magnet 210 assemblies are lifted off of the glass jar 204. The carbide particles may be removed by wiping the magnet with an alcohol- soaked wipe. The alcohol is preferable to water, for example, due to the fact that alcohol evaporates relatively quickly. The wipe can be any suitable wipe, for example of cloth or paper. The carbide contaminant is removed from the magnet 210 with the wipe. After the magnet is dry, the magnet and lid assembly can be placed onto the jar containing the scrap and the agitation step repeated until no carbide particles are removed from the remaining material.

The remaining material can be melted and checked for purity as is conventional. The technician can then reuse the refined material immediately.

FIGS. 4 and 5 shows a base 400 of an embodiment of a workstation of the present invention. It will be understood that the description of the following drawings includes terms, such as left and right, which are used for orientation purposes in identifying the depicted elements of the invention.

These terms are for purposes of describing the invention as depicted in the drawings and are not intended to be limitations.

The base 400 may include a bottom panel 402. The bottom panel 402 may be any suitable shape, such as square or rectangular. The bottom panel preferably includes a pair of runners 404. The runners 404 may function as spacers and/or reduce sliding friction. The runners 404 may be strips of plastic or Teflon-like material disposed in a generally parallel configuration on an upper surface 406 of the bottom panel.

The base 400 includes a back panel 408, which may be joined perpendicular to the bottom panel 402 at a back edge 410 of the bottom panel 402. The current embodiment of the back panel 408 includes a fan 412, which is mounted over a fan opening 414 formed generally at the center of the back panel 408. A cowl or cowling 416, which may be rectangular, circular or any other suitable shape, is attached to the back panel 408 adjacent the fan opening 414 extending inwardly from the back panel 408. In a preferred embodiment, the fan 412 produces approximately seventy cubic feet per minute (CFM) of airflow.

A plurality of antiskid feet 418, made of a suitable elastomeric or similar material, is disposed on a bottom surface 420 of the bottom panel. In the illustrated embodiment there are four antiskid feet 418, which are positioned at the four corners of the rectangular bottom panel 402.

A pair of side brackets 422 is used for bracing the back panel 408 and bottom panel 402. The side brackets 422 include a right side bracket 422A and a left side bracket 422B. Each side bracket 422 includes a horizontal edge 424 positioned at an outside edge of the bottom panel 402 and a vertical edge 426 positioned at an outside edge of the back panel 408.

The bottom panel 402 may include a side extension 428 for attaching an optional light fixture 430. The light fixture 430 may be attached to the side extension 428 by way of a flexible gooseneck apparatus 432.

A grinding enclosure is illustrated generally at 500 at FIGS. 6 and 7. In a most general form the grinding enclosure 500 is a box. As such, the grinding enclosure 500 includes a bottom panel 502, four side panels 504, 506,508 and 510 attached to the bottom panel 502 and a top panel 512 with a lid 514 attached to upper edges of the side panels 504-510. For the grinding enclosure 502 to operate most effectively they should be relatively few passageways permitting the escape of scrap. In the illustrated embodiment, openings are necessarily formed to permit access to an interior 516 of the enclosure 500 of the operator's arms and at least one tool.

A rear vent 518 is formed in the back panel 506, which cooperates with the fan 412, fan opening 414 and cowl 416 (FIGS. 4 and 5) such that the

negative airflow produced by the fan is communicated to the interior 516 of the enclosure 500. The rear vent 518 is preferably shielded by a downward angled member 520, which extends over the vent 518 to deflect any materials away from the vent.

The left and right side panels 508,510 of the enclosure 500 are similar, and thus, only one will be discussed herein. One or more tool ports 522 may be provided, through which a drill (high or low speed), or similar tool may be inserted. A cap member or plug 524 may be used to seal the tool ports 522. Each of the left and right side panels 508,510 of box 500 may be provided with a suitable opening 526 formed in each side sized and shaped to receive a hand or forearm of an operator. Each opening 526 may be provided with a shield 528 to deflect material from exiting the opening. The shield 528 may be any suitable shape resembling a tab or flange.

FIG. 8 illustrates an enclosure 500 securely and operatively docked in a base 400 according to the present invention. The assembled base 400 and enclosure 500 form an assembly wherein airflow generated by the fan 412 is communicated to the enclosure interior 516. Also shown in the light 430 in position to illuminate the interior 516 workspace of the enclosure 500.

It should be appreciated that the embodiments described above are to be considered in all respects only illustrative and not restrictive. The scope of the invention is indicated by the following claims rather than by the foregoing description. All changes that come within the meaning and range of equivalents are to be embraced within their scope.