Abstract:
An apparatus and method for producing a solid product such as orthopedic appliances, dental splint mouthpieces, dentures, lined dentures and the like from flowable materials such as silicones, acrylics, polyurethanes and dental casting investments. The container in which an article is treated will develop 80-100 psi and has opposed curved surfaces between which a seal is formed without leakage.

Description:
TECHNICAL FIELD 
   This invention relates to product production and more particularly a method and apparatus for producing a solid product that is particularly suitable for dental appliance usage. 
   BACKGROUND ART 
   There are a number of dental applications including orthopedic appliances, dental splints, mouthpieces, dentures, and lined dentures that utilize a flowable material that is changed to a solid product. Typical flowable materials are silicones, acrylics, polyurethanes and dental casting investments. 
   For making a denture a dental acrylic begins as a two-part liquid and powder (flowable material) and then is changed to a solid denture product. Undesirable air bubbles usually of microscopic size form in the solid product when done at atmospheric pressure or at pressures below 50 psi. A further example of the use of two of the above flowable materials are the acrylic denture to which is applied a liner of silicone. A good bond between the denture and liner without the formation of air bubbles in or between the materials is desirable. 
   Prior known pressurized containers heretofore provided for similar purposes use pressures of about 20 psi to 35 psi. These containers were not effective for some materials particularly silicones because micro-bubbles tend to form in the solid product. Another deficiency in the prior art containers is that a seal was formed between opposed flat surfaces and these tend to leak when pressures increase to above 50 psi. 
   SUMMARY OF THE INVENTION 
   A method and apparatus has a body of flowable material with air bubbles that is pressurized at a higher pressure and during a selected time interval to drive out the air bubbles as the material changes from a flowable state to a solid state. The time interval varies according to the material and may range from about 20 minutes to 13 hours. The apparatus disclosed includes a container preferably of elliptical shape having a domical top wall with an opening and a lid inside the container with the curvature of the top wall and the lid complementary so that a flexible seal between the two curved surfaces causes an effective sealing under pressure. The container is pressurized to a pressure above 50 psi and preferably to a pressure between about 80 psi and 100 psi to drive out air bubbles from the material as the material changes from a flowable state to a solid state. The flowable materials are silicones, acrylics, polyurethanes and dental casting investments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Details of this invention are described in connection with the accompanying drawings that bear similar reference numerals in which: 
       FIG. 1  is a top perspective view of a pressurizing container embodying features of the present invention. 
       FIG. 2  is an exploded view of a portion of the lid and clamp for the lid. 
       FIG. 3  is a top plan view of  FIG. 1  with the lid in a closed position. 
       FIG. 4  is a top plan view of the container without the lid. 
       FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 3 . 
       FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIGS. 1-6  there is shown a pressurizing container  12  embodying features of the present invention having a dished bottom wall  13 , a pair of opposed, spaced, curved end wall portions  14  and a pair of opposed, spaced, curved side wall portions  15  arranged in an elliptical shape and extending up from the bottom wall  13 , a domical top wall  16  extending in and up from the top of wall portions  14  and  15  and provided with an elliptical top opening  17 . A curved lid  18  of elliptical shape is provided inside the container that is removable from the container. The lid  18  has a step or notch  19  inwardly of the outer peripheral edge providing a domical curved top surface  18   a  that is opposite and complementary in shape with the curved undersurface  16   a  of the top wall  16 . A ring shaped or endless flexible seal  20  flexes to fit in the notch  19  and rests on the top surface  18   a  of lid  18 . 
   A lid clamping assembly includes a clamping bracket  24  with a bow shaped main body  25  and flared end portions  26 , a through hole  27  centered in the top, an externally threaded bolt  28  in and spaced from the main body to be slidable therein with a turning knob  29  affixed to the top end of bolt  28 . The lid  18  has an internally threaded center hole  30  into which the bolt  28  is threaded. The bracket  24  straddles the lid  18  with end portions  26  resting on the top wall outside the center opening  17 . Once the articles to be treated are place in the container the knob is turned to draw the lid up and compress the seal  20  between surfaces  16   a  and  18   a . A threading in the opposite direction will release the lid for removal. The elliptical shape of the hole  17  and lid  18  allows the lid to be readily removed from and put back inside the container  12 . The seal  20  is further compressed between the lid top surface  18   a  and container undersurface  16   a  when the container is pressurized. 
   A pair of opposed handles  21  extend out from opposite sides of the end wall portions. Three feet  22  are mounted at circumferentially spaced intervals of 120 degrees extend down than the outside of the bottom wall  13  to support the container  12  upright. The container and lid are preferably formed from cast aluminum. 
   An air control valve  32  is mounted to the container  12  which includes a housing  33  attached to the top wall  16  in flow communication with the inside of the container, an air input valve coupling  34  extending up from the housing to releasable couple with a female coupling head  35  connected for an air source  36  such as a compressor. A pressure relief valve  37  is at one end of the housing  33  and a manual on-off valve  38  is connected at the opposite end with an air discharge outlet  39  with a control lever  41  to enable air to flow through the valve and to the atmosphere to depressurize the container. A pressure gauge  42  is mounted on the top wall  16  opposite the air valve to indicate the pressure inside the container. 
   A flat support plate  45  is shown resting on the bottom wall  13  to provide a horizontal surface for the articles to be pressurized. The articles to be pressurized according to the present invention are shown disposed on plate  45  as an acrylic and denture  46  as well as a similar denture with a lining  48  of silicone. The container is shown as containing a quantity of water  49  in which the plate  45  and treated articles  46  and  48  are submerged. The water in the container serves to equalize the pressure around the article being treated. For heating purposes, if desired, there is provided a heating device  51  shown as an electric coil in the bottom of the container below plate  45  having a pair of electric lines  52  and an electric plug  53  connected to electric power input lines shown as a means to heat the container and the contents therein for some applications. 
   The time interval for the treatment will vary according to the material being treated. Typical time intervals for acrylics is about 20 minutes to 30 minutes for silicones about 12 hours to 13 hours for polyurethanes about 6 hours to 8 hours and for dental casting investments about 30 minutes to 60 minutes. 
   In a full sequence of operation the product to be treated is placed in the container on the support plate  45  and water is added, the clamp assembly is tightened so that the seal  20  is slightly compressed between the lid and container. The control valve  32  is operated to pressurize the container to a select pressure. Heat is applied, if desirable, and at the end of the selected time interval the container is depressurized by activating the lever  41 . The handle  29  is turned to open the lid so the product treated may be removed. 
   Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.