MXPA97010186A - Method and apparatus for coating recipien - Google Patents

Abstract

The present invention relates to an apparatus for forming a layer of a fluid coating material in a container, the apparatus comprising: a transport means for transporting the container through the apparatus, a distribution means for filling the container with a amount of the fluid coating material to cover the bottom of the container, a first suction means for sucking a portion of the coating material from the container and forming a uniform coating of the coating fluid material, and a dewatering means for dewatering the coating material to form a uniform, substantially dehydrated coating of the coating material in the container

Description

METHOD AND APPARATUS FOR COATING CONTAINERS Field of the Invention The present invention is directed to a method and apparatus for coating containers and in particular coating Petri dishes with an agent for inducing the gelation of a nutrient growth medium. The invention is particularly directed to the formation of a stable, substantially dry coating or a layer of a gel-inducing agent at the bottom of a container which is incorporated as part of a nutrient growth medium. BACKGROUND OF THE INVENTION Numerous devices are known in the art to fill containers with a predetermined amount of material. Other devices are known for coating the interior surfaces of containers. These devices can produce acceptable results for certain materials but do not produce universally good results for all coating materials. Producing a stable layer of gel-inducing agent or gel in a Petri dish is generally difficult and takes a long time. To obtain accurate results of the test a uniform and sterile layer of the gelling agent in the Petri dish is required. The commercial production of coated petri dishes often requires manual handling of the boxes which produces incompatible results and increased risk of contamination. An example of the above nutrient base medium is applied to a gelling agent consisting of a coating of calcium chloride and agar solution in the box followed by a liquid layer of gelling nutrients of, for example, low methoxyl pectin. This method requires a complete and uniform coating of the calcium chloride to avoid delayed or incomplete gelling of the pectin. This procedure often produced unsatisfactory results for general applications. For example, it is necessary to ensure that the total surface area of the plate is covered both with the pretreatment layer of the gelling agent, and with the growth medium. Not covering the plate completely results in incomplete gelification of the medium and inaccurate test data. Other methods for preparing Petri dishes use a pectin gel having a layer of agar gel containing calcium chloride. In this prior method, about six millimeters of a 1% agar solution containing about 100 milligrams of calcium chloride are distributed in a Petri dish which was previously sterilized. The petri dish is then swung by hand and swirls to spread the layer evenly over the bottom of the box. The box is then placed on a level surface and allowed to cool and gel. The cooled and gelled boxes are stacked in a clean room and left to cure and cure. After six to eight days of tempering, the treated boxes are examined to see if they are contaminated and classified for packing. The packed boxes are then stored in a cool, dry place for an additional period of seven to 14 days and then re-examined to see if they are contaminated. All contaminated boxes are discarded and the remaining boxes are packaged for transport. The above-mentioned procedure experiences numerous disadvantages in addition to the laborious nature of the process. For example, this procedure often results in condensation forming on the top of the newly stratified boxes which needs to be removed before storage. The repeated handling of the boxes and the static loading of plastic plates produces considerable contamination of molds of the gel layer despite efforts to maintain controlled temperature and clean and sterile rooms. The process also requires large amounts of storage space for the two-week tempering period, thereby increasing manufacturing costs. The above methods for producing coated petri dishes usually result in unacceptable moisture levels in the coating material rendering the layer susceptible to freezing temperatures during transport., thus destroying the layer. Temperature fluctuations during transport and storage result in the formation of condensation inside the boxes and sleeves that hold the boxes. The manual procedure for coating the box requires care to ensure complete coverage of the bottom of the box without spills or bubble formation in the layer. Not maintaining a level surface during the hardening of the coating or shaking the box during hardening produces a layer that is not smooth and flat. An irregular coating of the coating material causes deficient qualitative and quantitative results in the finished product. Various growth media and methods for preparing Petri dishes are known in the art. Examples of prior methods and devices are generally disclosed in U.S. Patent No. 4,170,861 to Snyder et al., U.S. Patent 4,565,787, U.S. Patent 3,928,136 to Launey, U.S. Patent 4,988,302 to Smith et al., U.S. Patent 5,089,413 to Nelson et al., U.S. Patent 4,656,130. from Shoshan and United States Patent 4,262,091 from Cox. These devices and methods have met with limited success and have not provided a completely satisfactory result. Accordingly, there is a continuing need in the art for a method and apparatus for efficiently producing a treated Petri dish containing a thin coating layer. Summary of the Invention The present invention is directed to a method and apparatus for forming a layer of a coating material in a container. In particular, the invention pertains to a method and apparatus for preparing a layer of a coating material at the bottom of a Petri dish. Accordingly, a main object of the invention is to produce a stable layer of a coating material in a Petri dish in an efficient and fast manner. A further aspect of the invention is to produce a fully automated apparatus for receiving a plurality of containers and producing a coating on the bottom surface of each container. A further object of the invention is to provide a thin and uniform coating of a gel-inducing agent capable of solidifying a gelling material containing nutrients in a Petri dish. The container, like a previously sterilized Petri dish, is initially separated from its lid and passed through a sterilization chamber to maintain sterility of the box. Typically, the sterilization chamber directs the filtered air to the container in combination with a sterilizing agent such as germicidal ultraviolet light. The box is then filled with a predetermined amount of a coating material, such as a base medium containing metal ions plus a gel-inducing agent. In embodiments, the box is tilted to distribute the material through the bottom of the container. The container is turned to one side and the overcoating material is removed, preferably by suction. After removing the excess material, the container is tilted in the opposite direction to evenly distribute the remaining coating material. The coated box is then cooled to form a gelled coating and then passed through a dehydration or drying chamber which directs the heated air to the container to dewater the coating material. In embodiments, the coating material is a gelling material that contains a gel-inducing agent and the drying air is heated to remove moisture from the coating material. The method of the invention produces a thin and uniform coating which is thinner than conventional coatings. The resulting coating is dry and stable and can be transported and stored for extended periods of time without the harmful formation of condensation or cracks and freezing danger, or growth of pollutants. The apparatus for use in the invention is preferably a fully automated apparatus capable of providing a continuous production of the coated containers. In the embodiments, the apparatus accepts a plurality of containers and associated caps. The caps are separated from the container and consecutively sorted through a number of processing stations and then reassembled. The containers are first passed through a sterilization station and then to a filling station. The overcoating material is then removed from the container in at least one and preferably two suction stations followed by a tilt station to uniformly tilt and distribute the remaining coating material. A gelling station directs cold air to the coated containers followed by air heated in a second sterilization chamber and dried to dry the coating. When the coating reaches the desired dryness, the lids are automatically returned to the container. These and other aspects of the invention are basically achieved by providing an apparatus for forming a layer of coating material in a container, the apparatus comprising a conveyor means for transporting the container through the apparatus.; a filling means for filling the container with a quantity of the coating material; a first suction means for sucking a portion of the coating material from the container; and a dehydration means for dehydrating the coating material to form a substantially uniform coating of the coating material in the container. These aspects of the invention are also achieved by a method for producing a coating of a coating material on the inner bottom surface of a container comprising the steps of filling the container with a quantity of a coating material in a filling station. of a conveyor; the removal of an excess of the coating material from the container to form a coating of the coating material and the dehydration of the coating the coating material in the container to form a uniform and stable coating. A thin layer of the coating material adheres over the entire surface due to the surface tension and cohesion properties of the coating material. These and other objects, advantages and salient features of the invention will be apparent from the following detailed description, which, taken in conjunction with the appended drawings, discloses the preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the drawings forming part of this original disclosure in which: Figure 1 is a side elevational view of the apparatus in accordance with a preferred embodiment of the invention; Figure 2 is a top plan view of the apparatus of Figure 1 showing the unstack device, sterilization chamber, filling station, aspiration station, drying and sterilization chamber and re-stacking device; Figure 3 is a partial cross-sectional view of the unstacking device taken along line 3-3 of Figure 2; Figure 4 is a partial top plan view of the unstack device as seen along line 4-4 of Figure 3; Figure 5 is a partial cross-sectional view of the filling station showing the dispensing nozzle and the pneumatic tilting device; Figure 6 is a partial cross-sectional view of the suction station showing the suction nozzle and the pneumatic tilt device; Figure 7 is a partial cross-sectional view of the tilting device; Figure 8 is a partial top plan view of the re-stacking device showing the parallel conveyors, thrust plate and stacking equipment; and Figure 9 is a partial side elevational view of the re-stacking device showing the lifting and stacking equipment. Detailed Description of the Invention The present invention relates to a method and apparatus for producing a uniform coating or layer of a material on the inner bottom surface of a plastic or glass container. The method and apparatus are particularly suitable for forming a uniform coating or layer of a cohesive material or gellable adhesive in a container. A preferred mode of the invention forms a thin coating or layer of gelled medium in a plastic or glass Petri dish. The method and apparatus are suitable for producing a thin layer of a coating material in a variety of containers. In preferred embodiments of the invention, the container being coated is a standard Petri dish normally used to propagate and quantify microbiological cultures. The coating material can be a solid support medium capable of supporting the growth of a biological sample. In preferred embodiments, the coating material is a material capable of forming a gel layer when it is cooled on the bottom surface of the Petri dish and includes a gel-inducing agent. In an embodiment, the gel layer contains a sufficient amount of calcium ions to cause a nutrient medium containing pectin to form a gel when placed in the container. The method and apparatus of the invention are particularly adapted to form a uniform layer of a gelled material comprising a uniform distribution of a metal cation, such as calcium cations. A material containing nutrients including, for example, a pectin gelling material low in methoxyl, is poured into the coated petri dish. The uniform distribution of the cation forms a uniform base layer of gelled nutrients.

In preferred embodiments, the coating material is a gelation solution containing calcium chloride as a gel-inducing agent as the composition disclosed in U.S. Patent 4,282,317 which is hereby incorporated by reference in its entirety. As discussed therein, a solid medium is made by first applying a coating of a material which contains a source of calcium ions such as calcium chloride. Next, a pectin solution containing essential nutrients that sustain the growth is poured over the first layer so that the calcium ions react with the pectin to form a gel layer. A suitable aqueous coating solution contains about 2% (2 grams per 100 millimeters of deionized or distilled water) of agar-agar and calcium chloride. Other compounds containing multivalent metal cations, well known in the art, can be used to provide sufficient gelling of the pectin. Generally, calcium compounds include, for example, calcium chloride, calcium nitrate and calcium phosphate. In preferred embodiments, the calcium compounds are soluble in water capable of providing a source of calcium ions for reaction with pectin and gelling. The concentration of the calcium chloride or other compound that provides multivalent metal cation is determined to provide the proper metal cation concentration to cause solidification of the nutrient and pectin composition when poured into the gel-containing metal ion-containing layer . Prepare a solution of 2% agar and material that provides metal cations through a suitable medium, such as by dissolving agar and metal salt in water heated to a pressure of 15 pounds and about 121 ° C in an autoclave. The sterile agar mixture can then be distributed to the Petri dish to cover the bottom of the box as discussed in detail hereinafter. In the embodiments of the invention, the coating material contains at least about 7 grams of calcium chloride per 100 milliliters of the water / agar mixture. Preferably, the coating material contains calcium chloride, agar and water. In alternative embodiments, the gelling component can be, for example, gelatin, silica gel, Carrageenan gum and other gums. Other materials can also be used as the carrier of the compound that provides multivalent cations. In one embodiment, the coating material is a plastic resin material dissolved or dispersed in a suitable solvent or mixture of solvents containing an effective amount of calcium ions for the mixture to adhere to the container. When a plastic container is used, the plastic resin of the selected coating material must be compatible with the container to adhere to the bottom wall of the container. The coating material includes a plastic resin and metal ion concentration so that a sufficient amount of the metal ions are available to gel a pectin-containing solution. In other embodiments, additional resins or types of carriers can be used to provide available calcium ions to gel a pectin material. The carriers are inert and non-toxic to living cells and should not be hydrolyzed during the process. Generally, the coating material does not include growing nutrients. However, in the embodiments of the invention, the coating material may contain various nutrients to support the biological growth known in the art. The liquid growth medium which is poured over the calcium cation layer may contain a low methoxyl pectin and various constituents. In general, the medium may correspond to a wide variety of known growth media for cell cultures and / or microbial tissues, except to the extent that the components which disintegrate or interfere with the pectin should be avoided. Normally, the culture medium includes various constituents including a carbon source such as glucose or other sugars, a source of nitrogen and other micronutrients in the form of natural products such as tryptone, peptone, beef extract, yeast extract, etc. or synthetic materials. The actual composition of the growth medium will depend in large part on the particular crop being treated. The carbon source is generally included in the amount of about two to 10 grams per liter of solution. The source of nitrogen is included in the amount of about two to 10 grams per liter of solution. The method and apparatus are particularly effective for applying a thin coating on the inner bottom surface of a container with a material capable of gelling at room temperature. The coating material is preferably heated to a liquid and applied to the bottom of the container as a solution and allowed to cool and gel. In a preferred mode of the invention, the coating material is an aqueous solution of a metal salt such as calcium chloride and a gelling material without nutrients. The gelling material without nutrients is preferably a low methoxyl pectin which can be solidified at room temperature. The metal salt is a gelling agent capable of gelling a nutrient base medium as a medium containing low methoxyl pectin. The method and apparatus of the invention are particularly adapted to form a stable layer of the source that provides metal ions and the gelling material without nutrients. A nutrient base medium is then poured into the gelling agent layer to solidify the nutrient base medium. Referring to the drawings, the method of the invention uses the apparatus 10 adapted to continuously handle a plurality of Petri dishes at the same time. The apparatus 10 is fully automated by a microprocessor control 11 for consecutively sorting the Petri dishes through the various treatment stations. The apparatus is capable of receiving a plurality of Petri dishes, automatically separating the covers, covering the inside bottom of the boxes and replacing the covers in the boxes. As shown in Figures 1-9, the apparatus essentially comprises a conveyor 12, an unstack unit 14, a first sterilization chamber 16, a dispensing station 18, a vacuum unit 20, a dehydration chamber, drying and sterilization 22 and a re-stacking unit 23. In operation, the apparatus 10 receives a plurality of petri dishes 44 stacked in the unstack unit 14. The petri dishes 44 are placed in the unstack unit 14 with the associated lid 46 The unstacking unit 14 separates the lid 46 from the box 44 at the bottom of the stack and places the box 44 and the lid 46 on the parallel sorting conveyors 24, 26, respectively. The box 44 and the cover 46 are passed through the apparatus 10 in a gradual manner to the various stations. Initially, the boxes 44 and covers 46 are passed through the sterilization chamber 16 which subjects the box 44 and lid 46 to sterile air and germicidal ultraviolet light. The box 44 is then transported to the distribution station 18 where the box 44 is stopped and a dispensing nozzle doses a predetermined amount of the coating material in the box 44. In the embodiments of the invention, the nozzle distributes the coating material to along a first side of the box while a pneumatic moving arm slowly raises the first side of the box to an inclined position thereby causing the material to flow through the bottom of the box. The pneumatic moving arm is retracted by means of which the box is returned to a level position and advanced to the vacuum unit 20. In the vacuum unit 20, the box 44 is inclined towards the first side to gather the coating material distributed by the distributor nozzle. A suction nozzle in a first suction station is lowered to the assembled material to remove excess material. In preferred embodiments, the box is sorted to a second suction station and a second suction nozzle is lowered into the box to remove any remaining stock while keeping the box in the inclined position. After removal of the overcoating material, the box is advanced to a tipping station where the box is tilted in the opposite direction to make the collected waste material not removed in the suction passage flow from the first side and spread uniformly on the bottom of the box. The box is then returned to the horizontal position, passed through the cooling fans 149 and advanced to the drying chamber 22. The dewatering chamber 22 directs hot air to the box to remove excess moisture. In preferred embodiments, the temperature of the drying air is below the recast temperature of the coating material. The dewatering chamber 22 further subjects the box and caps to ultraviolet light to maintain the box and the coating material in a sterile condition. The boxes leave the dehydration chamber 22 in a substantially dehydrated condition containing a solid layer with gel-inducing ions. The boxes 44 and covers 46 are then advanced to a re-assembly unit where the covers are placed in the respective box. The boxes and covers are then lifted to a stacking unit where the coated boxes are removed and packaged. As shown in Figure 2, the apparatus 10 includes a first parallel classifying conveyor and a second parallel classifying conveyor 24, 26 in the form of parallel strings passing over sprockets 28, 30 at an input end and drive sprockets 32, 34 at the discharge end. The sprockets 28, 30 are installed on a common rotating shaft 36. The drive sprockets 32, 34 are fitted with a common drive shaft 38 which is connected to a drive motor 40 by transmission or suitable gear connections. The drive motor 40 is preferably a stepping motor operated by a microprocessor to advance the chains 24, 26 in a sorting manner or in a gradual manner through each station as discussed in detail hereinafter. The sprockets 28, 30, 32, 34 are fixed to the shafts 36, 38 to rotate and advance the chains 24, 26 in an identical manner. As shown, the input sprockets 28, 30 are of the same size and the sprockets 32, 34 are the same size so that the chain conveyors 24, 26 move at the same speed and at the same distance with each revolution of the cogwheels. The chain conveyors 24, 26 advance along horizontal transport surfaces 25, 27, respectively, which extend the entire lh of the apparatus 10. The chain conveyors 24, 26 include a plurality of spaced push bars 29. , 31 extending upwards from the conveying surfaces 25, 27, respectively, to define a transport area and to fit the Petri dishes 44 and lids 46. The push rod 29 coupled to the chain conveyor 24 extends upwards a distance approximately equal to the upper edge of the Petri dish that is being transported along the transport surface 25. The chain conveyor 26 extends along a transport surface 27 parallel to the conveying surface 25 of the conveyor chain 24. As shown in Figure 3, the transport surface 27 of the chain conveyor 26 is elevated from the transport surface 25 of the chain conveyor 24 in such a way that the transport surfaces of the Petri dish and lid are parallel but in different planes. The push bar 31 of the chain conveyor 26 is longer than the push bar 29 of the chain conveyor to extend to the transport surface 27 a sufficient distance to transport the lid 46. The unstack device 14 as shown in FIGS. Figures 3 and 4 include a stacking frame 42 for receiving a plurality of Petri dishes 44 and associated covers 46. The stacking frame 42 in the preferred embodiments includes four vertical stacking rods 48 spaced apart to hold the boxes in a vertical frame. The rods 48 as shown in Figure 3 extend upwardly from an upper plate 50 having an opening 52 dimensioned to allow the boxes 44 and lids 46 to pass vertically therethrough. A lower sliding plate 54 is spaced below the upper plate 50 and parallel thereto. The sliding plate 54 is also provided with an opening 56.

In preferred embodiments, the opening 56 has a slightly oval shape and is dimensioned to allow the box 44 to pass therethrough while the cover 46 remains in the slide plate 54. Below the slide plate 54 is placed the first chain conveyor 24 cooperating with the horizontal transport sliding surface and parallel lateral guide rails 60. As shown in Figure 3, the sliding plate 54 extends over both chain conveyors 24, 26 and is part of the transport surface of the chain conveyor 26. A sliding arm 62 is arranged for sliding movement in the sliding plate 54. The sliding arm 62 includes a connecting arm 64 coupled to a piston rod 66 extending axially of the piston 68. As shown in Figure 3, the piston 68 is installed in the bottom of the structure 70 of the conveyor 12. In alternative embodiments, the piston 68 can be installed by means of an independent support. In the structure 70 a second pneumatic piston 72 is also installed which has a piston rod 74 installed for vertical reciprocating movement. A reciprocal square plate 76 is coupled to the distal end of the piston rod 74. As shown in Figure 3, four upwardly extending rods 78 are installed in the four corners of the plate 76. Two of the rods 78 are installed on one side of the chain conveyor 24 while the other two rods are positioned on the opposite side of the chain conveyor 24. The plate 76 is installed perpendicular to the piston rod 74 while the rods 78 are perpendicular to the plate 76. As shown in Figure 4, the sliding arm 62 includes a narrow tongue portion 63 that extends forward to define the inlet end 65. The tongue portion 63 has a width less than the space of the rods 78. so that the rods 78 do not interfere with the sliding arm 62. In this way, the rods 78 can extend upwardly by the sliding arm 62 as shown in FIG. n the phantom lines of Figure 3 when the sliding arm 62 and the piston rod 66 are retracted. The pneumatic pistons 68 and 72 are connected to a central microprocessor 11 and are driven by it to activate the pistons 68, 72 in a controlled manner and in cooperation with the gradual advancing movement of the chain conveyor 24. In operation, a The plurality of Petri dishes and their associated covers are stacked in a stacking frame 42. The piston 42 extends the rod 74 upwards by means of which the rods 78 are in an upward position, as shown in the phantom lines, raising the petri dish 44 a slight distance from the surface of the sliding arm 62. The piston 68 is driven by the microprocessor 11 to extend the piston rod 66 by means of which the sliding arm 62 is withdrawn to the position shown in FIG. Figure 3. The piston 72 retracts, gently lowering the casing 44 through the hole 56 in the sliding plate 54 and to the surface 58 of the sliding plate 58. The chain conveyor 24. The lid 46 of the associated Petri dish 44 is retained in the slide plate 54 with the plurality of Petri dishes and covers in the stacking frame 42 resting on the lid 46. The piston 68 is after driven by the microprocessor to retract the piston rod 66 by means of which the sliding arm 62 pushes the cover 46 on the sliding plate 54 to a second sliding surface 80 of the chain conveyor 26 as shown in the phantom lines of Figure 3. When the lid 46 is pushed from below the plurality of Petri dishes and caps in the stacking frame 42, the plurality of Petri dishes fall on the surface of the sliding arm 62. The chains 24, 25 then advance forward an incremental amount so that the next transport area is placed below the unstack device. The piston 72 is then activated by means of which the rods 78 lift the next Petri box in the stack of the surface of the sliding arm 62. It is convenient to make the rods lift the stack of petri dishes of the sliding arm 62. before the sliding arm 62 moves to the position shown in Figure 3 to prevent the boxes from falling or twisting in the stack and lowering the plates through the hole in a level manner. The piston 68 is then activated to remove the sliding arm 62 from the stacking frame 42 to the position in Figure 3. The driving cycle of the pistons 68, 72 and the chain conveyors 24, 26 is performed again. Referring to Figures 1 and 2, the chain conveyors 24, 26 are advanced in incremental steps to transport the Petri dishes 44 and their associated covers 46 simultaneously from the unstack device 14 through the sterilization chamber 16 of a gradual way In this way, the lid 46 is parallel to the Petri dish 44 in all the forward movement as shown in Figure 2. The sterilization chamber 16 is a closed chamber having an inlet 82 where the chain conveyors 24, 26 and Petri dishes 44 and lids 46 enter an upstream end. An outlet 84 is provided at a downstream end where the chain conveyors 24, 26, Petri dishes 44 and covers 46 exit. The sterilization chamber 16 may include an observation window in the housing 88. A fan 90 is included for provide a constant flow of sterile air to the chamber in order to provide positive pressure inside the chamber. A source of ultraviolet light 94 floods the interior of the sterilization chamber 16 to provide sterilizing and germicidal treatment. The ultraviolet light source can be a standard UV source having sufficient intensity to provide a germicidal effect in the Petri dishes and their tops. The length of the sterilization chamber 16 is selected to provide sufficient sterilization effect for the operating speeds of the chain conveyors. In other embodiments, the intensity or amount of the UV source can be adjusted in relation to the forward speed of the chain conveyors 24, 26. In alternative embodiments, other sterilization devices can be used, such as, for example, gamma-ray treatments. or sterilizing gas. The outside air is drawn through a HEPA filter and introduced as sterile air into the chamber 16 to maintain a positive pressure inside the chamber 16. The positive pressure in the chamber 16 creates an air flow directed outward through the chamber. entrance 82 of the box to prevent outside air from entering the distribution station 18 which carries contaminants such as bacteria and spores. As shown in Figure 1, the chain conveyors 24, 26 and the Petri dishes 44 and covers 46 exit the sterilization chamber 16 and advance consecutively to the distribution station 18. The distribution station 18 includes a nozzle distributor 100 coupled to a support bracket 102. In the embodiments of the invention, the distributor nozzle 100 is in a fixed position a short distance above the Petri dish 44. An optional air cylinder 104 is connected to a microprocessor 11 and is operated by it to lower the nozzle 100 towards the Petri dishes by advancing and raising the nozzle 100 at the end of the filling cycle. The nozzle 100 is provided with fluid material 112 by a pump 116 and flexible supply tube 110 extending from a closed storage vessel 114. The storage vessel 114 may be a suitable flask or other container capable of storing fluid material in a sterile condition. Usually, the vessel 114 is provided with a suitable closure member to prevent contamination of the contents. In embodiments where the fluid material is a gelling material, a heating plate 118 is included to keep the material flowing constantly. In preferred embodiments, pump 116 is a standard peristaltic pump, although another pump may be used. The pump 116 is connected to a microprocessor 11 to control the amount of material that is being distributed and the timing of the distribution cycle. A second pneumatic cylinder 106 and a piston 108 are positioned below the chain conveyor 24 as shown in Figure 5. In operation, the Petri dishes 44 are advanced to the distribution station 18 and stopped below the distributor nozzle 100. As shown in Figure 1, the distribution station 18 and the aspiration station 20 are enclosed within a cabinet 21, of transparent plastic, to reduce the risk of contamination of the boxes 44 during filling. The nozzle 100 is preferably placed a slight distance above the Petri dish 44. The pump 116 is then operated to introduce a predetermined amount of the fluid material to the Petri dish 44. In an embodiment of the invention as shown in Figure 5, the dispenser nozzle 100 is positioned towards an edge of the Petri dish along the side wall. When the dispenser nozzle 100 introduces the fluid material to the Petri dish 44, the pneumatic cylinder 106 is actuated and the piston 108 lifts an edge of the Petri dish. As shown in Figure 5, the pneumatic cylinder 106 is positioned below the distributor nozzle 100 so that the piston 108 tilts the Petri dish 44 away from the point where the dispensing nozzle 100 introduces the fluid material. When the Petri dish 44 is tilted, the fluid material flows through the bottom of the Petri dish to ensure that the bottom surface is completely coated. The excess fluid material forms a puddle 119 on the opposite side of the distributor nozzle 100. When the desired amount of fluid material is introduced to the Petri dish 44, the pneumatic cylinder 106 is activated again and the piston 108 is retracted to lower the Petri dish 44 to the initial horizontal position by means of which the fluid material is spread through the bottom surface of the box. The chain conveyors 24, 26 are again driven to advance the filled petri dish to the suction station 20 and put a new Petri dish in the filling position. In alternative embodiments, the fluid material is distributed to the box 44 without tilting the box 44. The pump 116 is controlled by a microprocessor to distribute the amount of fluid material by a predetermined amount. The amount of fluid material distributed to the Petri dish 44 is the minimum amount necessary to completely cover the bottom surface of the box. In the preferred embodiments, more fluid material needed to cover the bottom of the box is distributed. The distribution of the fluid material is controlled by the microprocessor which determines the speed and duration of the pump cycle. Generally, the speed of the pump and the cycle of operation time are coordinated to distribute the selected amount of the fluid material. In alternative embodiments, the nozzle 100 includes a solenoid operated distribution valve with the supply line being supplied under constant pressure. In this embodiment, the distribution valve is operated by the microprocessor for a selected time cycle to distribute the fluid material. Once the Petri dish 44 is filled and the pneumatic cylinder 106 is retracted, the petri dish is advanced to the first suction station 120. The first suction nozzle 122 is lowered in contact with the fluid material for aspirating the excessive fluid material from the Petri dish 44 and returning the fluid material to the storage vessel 114. The horizontal sliding surface 25 of the conveyor 10 includes a bearing surface of the cam 124. The forward movement of the chain conveyor 24 causes an edge of the bottom face of the Petri dish 44 to fit and rise to the inclined surface 123 of the cam 124 thereby causing the Petri dish to tilt to one side as shown in Figure 6. In the preferred embodiments, the cam 124 tilts the Petri dish in the opposite direction of the inclination direction in the distribution station 18. In this way, the fluid material in the petri dish flows back to the initial feeding site to ensure coverage complete at the bottom of the Petri dish 44. The excess fluid material gathers in a puddle 126 on the opposite side of the cam 124. While the Petri dish 44 is in the inclined position shown in Figure 6, the suction nozzle 122 is lowered into the puddle 126 to remove the excess of the fluid-filled material. The suction nozzle 122 is operated by an air cylinder 128 which raises and lowers the nozzle 122 in contact with the Petri dish 44 and the fluid material 126 therein.

The operation of the pneumatic cylinder 128 is controlled by the microprocessor to coordinate the suction operation with the forward movement of each Petri dish 44. A suitable pump 130, like a standard peristaltic pump, is connected to the nozzle 22 to suck the material fluid from the Petri dish and returning the fluid material through a return line 132 to the supply container 114. The pump 130 is also connected to the microprocessor 11 and is operated by the same to coordinate the aspiration with the advance of the box Petri 44. In the preferred embodiments of the invention, a second suction station is provided downstream of the first suction station 120. Preferably, the surface of the cam 124 extends the length of the first station and second suction station 120, 134 so that the Petri dish is advanced by the chain conveyor in the inclined position similar to that shown in Fig. Figure 6. A second suction nozzle 122 'connected to a pneumatic cylinder 128' and a return line 132 'are provided in a similar arrangement as in the first suction station 120. The suction nozzle 122' is also connected to a pump 130. ' The pump 130 'and pneumatic cylinder 128' are similarly connected to a microprocessor to coordinate the suction of the fluid material with the forward movement of the Petri dish 44. Since the Petri dish 44 advances to the second suction station 134 in the inclined position, the excessive fluid material not removed in the first suction station remains encharcado in the lower portion of the Petri dish. The second suction nozzle 122 'is lowered in contact with a fluid material remaining in the Petri dish 44 by means of which the pump 130' is operated to suck the fluid material from the Petri dish 44 into the supply vessel 114. As shown, the downstream end of the cam 124 has a declining surface 125 which gently lowers the Petri dish 44 to the horizontal position on the transport surface 25 when the chain conveyor 24 advances the Petri dish forward . Immediately thereafter, the Petri dish 44 is advanced to a tilt station 136. The Petri dish 44 engages a surface of the cam 138 having an inclination 137 positioned on the horizontal sliding surface 25 of the conveyor 24. The surface of the cam 138 is positioned to fit the bottom of the Petri dish 44 along an edge to tilt the Petri dish 44 as shown in Figure 7. In the preferred embodiments, the cam 138 tilts the Petri dish in a direction opposite to the direction of inclination during the suction steps. In this way, the remaining fluid material in the Petri dish 44 flows back through the bottom of the surface to produce a thin and uniform layer of the fluid material. The Petri dish 44 is held in the inclined position for a selected period of time to ensure uniform coverage of the fluid material in the bottom. The cam 138 includes a declining surface 139 at the downstream end to return the Petri dish 44 to the horizontal position on the transport surface 25. The inclination provided by the cam 138 can alternatively be provided by a pneumatic lift at that station. Before entering the heated drying chamber 22, a cold sterile air flow is directed to the cooled Petri dish 44 to gel the fluid material when the gellable material is present. The cold air is directed downstream of the blower 149 as shown in Figure 2. The Petri dish 44 and the coordinated cover 46 are then advanced through the dehydration chamber 22. As shown in Figure 1, the chamber Dehydration is a closed housing 140 having an inlet opening 142 and an outlet opening 144. The housing 140 includes a heating device 146 having a fan or blower for forcing the heated air through the housing 140 and the boxes for heating. Petri. An adequate filter system can be included to maintain a sterile environment, free of dust inside the housing. An ultraviolet light source 148 is included within the housing. An ultraviolet light source 148 is included within the housing to emit germicidal UV rays in order to avoid contamination of the Petri dish during the drying step. The housing is of sufficient length to ensure that the Petri dishes leave the housing in a substantially dehydrated condition. In the embodiment shown in Figure 1, the sterile air introduced by the sterilization chamber 16 passes through the cabinet 21 of the distribution and aspiration stations 18, 20 in a rotating direction. The air continues to flow through the inlet opening 142 of the dewatering chamber 22 and finally exits through the outlet 144 of the dewatering chamber 22. The amount of fluid material remaining in the Petri dish after aspiration is determined by the amount of aspiration, the viscosity of the fluid material, the amount of gellable material in the fluid material, the gelation temperature of the fluid material, the temperature of the fluid and the amount of gelation that has occurred. Generally, about 0.5 to 2.0 ml of the fluid material remains in the Petri dish and preferably about 1.5 ml after aspiration. In embodiments, the fluid material is distributed as a hot aqueous solution containing 1-2% agar, low methoxyl pectin, or gellan gum. Alternatively, the fluid material is a plastic resin in a suitable solvent or carrier. The solution begins to solidify as soon as the solution touches the cold surface of the Petri dish. After the fluid material in the Petri dish is dehydrated, the Petri dish leaves the drying chamber and is advanced to the re-stacking device 150. Referring to Figures 8 and 9, the re-stacking device 150 includes a plate upper 152 which is parallel to the chain conveyor 26 and the sliding rails so that the lid 46 slides on the upper plate 152. The upper sliding plate 152 is positioned above the first chain conveyor 24 a distance sufficient to allow the Petri dish 44 slides down from the top plate 152. A lower slide plate 154 is positioned in the same plane as the first chain conveyor 24 to receive the Petri dish 44 from the chain conveyor 24. The upper plate of Sliding 152 includes an opening 156 above the lower sliding plate 154. The opening 156 is dimensioned to allow the cover 46 to be positioned in the upper sliding plate 152 on the opening 156 without falling off while being large enough to allow the Petri dish 44 to pass therethrough. A push plate 158 is positioned adjacent to the upper sliding plate 152. The push plate 158 is coupled to the rod 160 of the pneumatic cylinder 162 which is driven by the microprocessor 11. The pneumatic cylinder 162 is driven to extend the rod 160 and push plate 158 away from cylinder 162 to fit cap 46. Push plate 158 pushes cap 46 through upper plate 152 until cap 46 is substantially centered on opening 156 directly above the Petri dish 44. The push plate 158 is then retracted to the initial position shown in Figure 8. A lifting device 166 is provided below the lower slide plate 154 and the Petri dish 44. A frame is provided. stacking 168 immediately above the lifting device 166. The lifting device 166 includes a pneumatic cylinder 170 coupled to a mounting plate 174 and rod piston 172 cooperating for reciprocal vertical movement. A substantially square horizontal plate 176 is coupled to the distal end of the piston rod 172 and positioned parallel to the lower sliding plate 154. Four rods 178 engage the upper surface of the plate 176 and extend upward in shape perpendicular to plate 176. In preferred embodiments, the rods 178 are positioned at the corners of the plate 176 and are spaced in a uniform manner a distance to support the Petri dish 44. The piston rod 172 and the plate 176 are normally in the retracted position shown in Figure 9. The cylinder 170 is activated by the microprocessor 11 to extend the piston rod 172 and the plate 176 upwards so that the rods 178 pass through the opening in the lower plate 154 to fit the bottom of the Petri dish as shown in FIG. discussed in detail later in the present. The stacking frame 168 includes two support members 180 that extend upward from the upper sliding plate 152 at the opposite edges of the opening 156 as shown in Figure 9. At the upper end of each support member 180 there is a finger 182 pivotally connected thereto by a pivot pin 184. A finger stop member 186 is also coupled to the upper part of the support member 180 to limit pivotal movement of the finger 182. As shown in Figure 9, the finger 182 is in a normal horizontal rest position with the rear end 188 engaging the finger stop member 186 and the front end 190 extending upwardly to the opening 156. The finger 182 is pivotable from the horizontal position shown in the Figure 2 up to the position shown in the phantom lines. A plurality of support rod 192 extend upwardly from the upper sliding plate to receive a stack of the Petri dishes. As shown in Figure 8, four rods 192 are generally provided and spaced around the opening in the upper slide plate 152 to allow stacking of the Petri dishes 44. In operation, the Petri dish 44 and the Associated cap 46 is advanced to the lower sliding plate 154 and the upper sliding plate 152, respectively, by the parallel chain conveyors. The cylinder 162 is then actuated by means of which the pushing plate 158 pushes the lid 46 through the upper sliding plate 152 and over the opening 156. The pushing plate 158 is then retracted to the original position. The cylinder 170 is then actuated by means of which the lifting rods 178 move upwardly fitting the bottom of the Petri dish 44. The lifting rods 178 continue the upward movement, lifting the Petri dish 44 through the opening 156 to cover 46 to the rearming position. The lifting rods 178 move upwards in addition to lifting the Petri dish 44 and the lid by the fingers 182. The fingers 182 pivot upward to allow passage of the Petri dish 44 and the lid 46, after which the fingers return to the original horizontal position. The lifting rods 178 are then retracted so that the petri dish and lid are retained in the re-assembly frame 168 by the fingers 182. The cycle is then repeated with the Petri dishes 44 and the caps 46 that are stacked between the rods 192. As can be seen, the method and apparatus provide an efficient means for coating Petri dishes or other containers with a coating material without the need to handle the boxes. The covers are separated from the boxes and are filled in a sterile environment. The filled and dried containers are closed with lids and stacked in the re-stacking device where they can be removed and packaged as needed. In the illustrated embodiment, the apparatus includes a single unstack unit with a pair of parallel chain conveyors for transporting the Petri dish and the caps. It will be understood that the apparatus can include more than one unstacking unit, a transport system and a re-stacking unit which can be operated by a single microprocessor control and a single energy source. The, the control unit shown in Figure 1 is positioned in the upper part of the drying chamber although in practice it can be placed in any suitable place. The preference control unit contains the necessary microprocessors to control and monitor the device. The speed of the chain conveyors and the gradual advance of the same are coordinated with the steps of unstacking, filling, aspiration and re-stacking so that the container is correctly classified at each station and advanced to the next station when the various cycle cycles are completed. distribution, aspiration and drying. Although several convenient embodiments have been selected to illustrate the invention, those skilled in the art will understand that various changes and modifications may be made thereto without departing from the scope of the invention as defined in the appended claims.

Claims (41)

1. CLAIMS 1. An apparatus for forming a layer of a fluid coating material in a container, the apparatus comprising: a transport means for transporting the container through the apparatus; a dispensing means for filling the container with a quantity of the fluid coating material to cover the bottom of the container; a first suction means for sucking a portion of the coating material from the container and forming a uniform coating of the coating fluid material; and a dehydrating means for dehydrating the coating material to form a uniform, substantially dehydrated coating of the coating material in the container. The apparatus of claim 1, further comprising a first tilting means for simultaneously tilting the container while being filled with the coating material and for gathering the excess coating material along a first side of the container. 3. The apparatus according to claim 2, wherein the first tilt means is a pneumatically driven piston for fitting a bottom corner of the container and lifting it. The apparatus according to claim 2, wherein the dispensing means is a dispensing nozzle placed above the container for filling the container adjacent to a second side of the container. The apparatus according to claim 2, further comprising the second tilt means downstream of the first tilt means, for tilting the container and flooding the coating material along a second side of the container, the first means of suction being positioned to suck the coated material along the second side. The apparatus according to claim 5, wherein the second tilting means is a surface of the cam which cooperates with the conveying means to fit a bottom face of the container and lifting a side edge of the bottom face with advance movement of the container. The apparatus according to claim 2, wherein the second inclining means tilts the container for flooding the coating material on a second opposite side of the first side. The apparatus according to claim 7, further comprising a second suction means for removing the coated coating material from the container, the second suction means being placed downstream of the first suction means. The apparatus according to claim 8, wherein the second tilting means is a surface of the cam which cooperates with the second suction means for tilting the container for flooding the coating material on the second side of the container, the second suction means being placed on top of the second side to remove the puddled material. The apparatus according to claim 5, further comprising a third tilt means placed downstream of the first suction means for tilting the container towards the first side after sucking the material. The apparatus according to claim 1, wherein the dewatering means comprises a heated chamber for directing heated air to the fluid coating material. The apparatus according to claim 11, wherein the coating material includes a gel-inducing agent and the distribution means includes a heating means for maintaining the coating material fluid. 13. The apparatus according to claim 12, wherein the dehydrating means comprises a heating element and a blower. The apparatus according to claim 1, further comprising the sterilization means upstream of the dispensing means for directing sterile air to the container. 15. The apparatus according to claim 14, wherein the sterilization means consists of a chamber having a source of ultraviolet light. 16. The apparatus according to claim 1, the transport means comprising a first parallel conveyor and a second parallel conveyor operatively connected to each other and a motor means for advancing the conveyors in predetermined incremental steps. The apparatus according to claim 16, further comprising an unstack device for receiving a plurality of containers and a plurality of caps for the containers, the unstacking device including a means for separating the caps from the containers and positioning the containers in the first conveyor and the lid in the second conveyor. 18. The apparatus according to claim 17, wherein the unstack device comprises a means for receiving a stack of containers and lids armed therein, a horizontal plate having an opening therein sized to allow the vessel to pass through. through the opening to the first conveyor while supporting the lid and a sliding means for sliding the lid of the horizontal plate to the second conveyor. 19. The apparatus according to claim 18, the unstacking device further comprising a vertically positioned pneumatic piston movable from an upper position for receiving the container to a lower position for lowering the container through the opening in the horizontal plate and to the first transporter. The apparatus according to claim 16, further comprising a re-stacking device positioned at a downstream end of the transport means, the re-stacking device having a horizontal plate with an aperture sized to allow the vessel to pass through. of the lid and the support, a sliding plate for sliding the lid to the horizontal plate around the opening and lifting means to lift the container of the first conveyor through the opening in the horizontal plate to engage with the lid and a retaining means for retaining the lid and the container in the re-stacking device. 21. A method for forming a coating on an inner bottom surface of a container, comprising the steps of: filling the container with an amount of a coating material at a distribution station at an upstream end of a transport device , removing a portion of the coating material from the container and forming a coating of the material on the inner bottom surface and dehydrating the coating of the material in the container. 22. The method of claim 21, wherein the container is a Petri dish and the coating material contains a gel-inducing agent. 23. The method of claim 21, comprising filling the container on a first side of the container and simultaneously tilting the container toward a second side of the container. The method of claim 21, further comprising tilting the container to a first side after the filling step to flood the coating material on the first side while removing the portion of the material. 25. The method of claim 21, wherein the removal step comprises suctioning the material from the container. 26. The method of claim 24, further comprising tilting the container toward the first side after the first step of removing and disposing of the puddled material from the container in a second elimination step. 27. The method of claim 24, further comprising the tilting of the container to a second side after the first removal step to uniformly distribute the remainder of the coating material on the inner bottom surface. 28. The method of claim 21, further comprising distributing a solution to the container, wherein the solution contains a gel-inducing agent. 29. The method of claim 21, further comprising passing the container through a sterilization chamber and subjecting the container to ultraviolet light. 30. The method of claim 21, wherein the dehydrating step comprises subjecting the container to a flow of heated air. 31. The method of claim 30, the drying step further comprising subjecting the container to ultraviolet light to maintain sterility. 32. The method of claim 21, the filling step further comprising delivering the material from a supply reservoir to the container and the elimination step consisting of returning a material removed from the container to the supply reservoir. 33. The method of claim 21, wherein the container includes a cap of complement and the method furthermore conspires to separate the lid of the container before filling the container and replacing the cap in the container after the dehydration step. 34. The method of claim 33, comprising placing the container in a first conveyor and the lid in a second conveyor parallel to the first conveyor and transporting the container through the filling station. 35. An apparatus for applying a substantially uniform layer of a coating material in a Petri dish, the coating material containing a gel-inducing agent, the apparatus comprising: filling means for filling a Petri dish with a predetermined amount of the coating material; first inclination means for tilting the Petri dish to flood the coating material to one side of the Petri dish; suction means for sucking a portion of the coated coating material from the Petri dish and forming a uniform coating of the coating material and dehydrating medium to dehydrate the remaining coating material in the Petri dish. 36. The apparatus of claim 35, further comprising tilt means for tilting the Petri dish simultaneously with the filling means while filling the Petri dish and wherein the filling means distributes the coating material adjacent to a wall. side of the Petri dish opposite the direction of inclination of the Petri dish. 37. The apparatus of claim 35, further comprising tilt means for tilting the Petri dish after the suction means removes the coating material to evenly distribute the coating material. 38. A method for forming a substantially uniform coating on an inner bottom surface of a Petri dish having a lid associated therewith consisting of the steps of: separating a Petri dish from the lid and distributing a predetermined amount of a solution containing a gel-inducing agent, wherein the distribution step distributes a necessary excess to cover the Petri dish, suck the excess solution from the Petri dish and form a substantially uniform coating of the solution in the box Petri, dehydrate the coating and replace the lid in the coated petri dish. 39. The method of claim 38, wherein the solution is a solution containing pectin including a metal cation as a gel-inducing agent, the method further comprising pouring a pectin-containing solution into the Petri dish and gelling the mentioned solution. 40. The method of claim 38, which consists of tilting the Petri dish to fill the excess solution on a first side and sucking the puddled solution from the Petri dish. 41. The method of claim 40, further comprising tilting the Petri dish to a second side opposite the first side to uniformly redistribute the remaining solution in the Petri dish. SUMMARY OF THE INVENTION A plurality of petri dishes or other glass or plastic containers are coated on the inner bottom surface of the containers by passing the containers through a coating or stratification apparatus. The apparatus includes a sorting conveyor for consecutively passing open containers through a filling station where a quantity of a coating material is applied while tilting the container to one side thereby distributing the material to the entire bottom surface of the container. The containers are transported to a suction station to suck the excess material while tilting the container towards the vacuum nozzle. After the passage of the aspiration, the containers are tilted in the opposite direction to distribute the material in the container. The material is then dried and the containers are stacked and packed. The coating material includes metal ions such as calcium ions or other divalent metal ions, in a suitable carrier that is capable of adhering to the inner bottom surface of the container. The coating material forms a dehydrated, solidified layer adhered to the bottom surface of the container. The coating material may be a water / agar solution or a plastic resin in a suitable solvent containing the calcium ions,