Abstract:
A method and apparatus for transferring a wet object, such as a contact lens, from a first station to a second station includes a probe having a barrel with a passage for communication with a vacuum source and a pressurized gas source, a nozzle at the end of the passage, and a hood around the nozzle in communication with a vacuum source. The barrel is moved in a first direction to place the nozzle adjacent the object in the first station and the vacuum from the nozzle attaches the object to the nozzle. Moving the barrel in a second direction removes the nozzle with the object attached from the first station. The probe is moved to the second station with the object attached. The barrel is moved in the first direction to place the object at the second station, the vacuum is removed from the nozzle and pressurized gas is applied through the barrel passage to remove the object from the nozzle and deposit it at the second station and, at the same time, blow off matter from the object. Vacuum is applied to the hood when the probe is at the second station for the hood to collect the matter blown the object by the compressed gas.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for transferring wet plastic objects, such as contact lenses, from one station to another. 
     BACKGROUND OF THE INVENTION 
     The molding of hydrophilic contact lenses is known. Various processes are disclosed in U.S. Pat. No. 4,495,313 to Larsen; U.S. Pat. No. 4,640,489 to Larsen, et al.; U.S. Pat. No. 4,680,336 to Larsen et al.; U.S. Pat. No. 4,889,664 to Larsen et al.; and U.S. Pat. No. 5,039,459 to Larsen et al., all of which are assigned to the assignee of the present invention. 
     These prior art references disclose a contact lens production process wherein each lens is formed by molding a reactive mixture between a front curve (lower mold section) and back curve (upper mold section). Typically, the lenses are carried in a mold array or pallet, such as a two-by-four array. While in between the front and back curves, the monomer is polymerized to form the lens. In one type of process, the lens is removed from the front curve mold during a hydration step and then washed by the application of a hydrating deionized (DI) water to remove processing chemicals, e.g. diluents, from the lens. 
     Sometimes, when deionized water is used in the hydration, the final step of the process is to introduce a buffered saline solution into the final package holding the lens, and then seal the lens within the package so that the final lens equilibrium (ionic neutralization, final hydration and final lens dimensioning) is accomplished in the package at room temperature or during sterilization. U.S. Pat. No. 4,961,820, also assigned to the assignee of the present invention, discloses a final package for a contact lens, wherein the package is formed from a transparent plastic material such as polypropylene and a foil laminate that is heat sealed thereto. 
     The transfer of soft contact lenses during manufacture has been a significant problem. The lenses are small, are nearly invisible and are particularly hard to handle when immersed in the fluids commonly used in the manufacturing process. Accurate and reliable transfer of the wet lenses from one location to another or to a final package is often necessary during the manufacturing process. 
     As apparent from the foregoing, a need exists for an apparatus to transfer wet lenses from one station, such as a mold or hydrating bath, to another station, such as a package, and at the same time to remove or reduce the amount of the hydrating liquid and other material present on the lens from the hydrating process. 
     U.S. Pat. No. 5,578,331, entitled “Automated Apparatus and Method for Preparing Contact Lenses for Inspection and Packaging”, also assigned to the assignee of the present invention, discloses a robotic arm for transferring a plurality of soft contact lenses from a first processing station to a second processing station. The robotic device includes an adjustable array of convex contact lens carriers. The specification of U.S. Pat. No. 5,578,331 is herein incorporated by reference. 
     U.S. Pat. No. 5,561,970, which also is owned by the assignee of this application, discloses an automatic contact lens transfer system, comprising robotic arms to contact and transfer soft contact lenses. The &#39;970 patent is hereby incorporated by reference. U.S. Pat. No. 5,706,634, which also is owned by the assignee of this application, discloses a contact lens transfer device which comprises a convex lens transfer surface onto which the lens is secured via surface tension. The device then transports the lens to a second location. The lens is removed from the convex lens transfer surface when an amount of deionized water is ejected from the device. The &#39;634 patent is hereby incorporated by reference. However, neither of these patents teach the removal of the hydrating solution or other matter, nor are they capable of performing the function of transfer and controlled matter removal. In addition, prior contact lens transfer systems fail to address splatter of liquid from a lens onto the packaging during lens transfer. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is concerned with the withdrawal of excess or foreign matter from a wet object, such as a contact lens, and/or its packaging prior to being sealed in a package. In preferred embodiments, this is achieved by providing a hood around a probe which is used to pick up and later release the wet object. The probe preferably handles the wet object using positive and negative pressure. The hood encompassing the probe creates suction to control matter during deposition and matter withdrawal or removal. 
     In one respect, the invention is directed to a method and apparatus for transferring a wet object, such as a contact lens, during and between various steps of manufacture and packaging. One set of these manufacturing steps is disclosed in U.S. Ser. No. 09/252,307, filed herewith in which transfer is necessary from a station at which washing and hydration of the lens takes place, in a front curve mold, to a final package designed for customer use. Alternatively, this apparatus could be used to transfer a lens from a reusable mold to a contact lens package, or from a mold to a container for inspection of the contact lens, or from any other first position to a second position. 
     In a preferred embodiment, the invention comprises a probe with a perforated hemispherical nozzle head having a diameter and shape corresponding to the contact lens shape. The probe is moved into close proximity, and more preferably into contact with the lens&#39; concave surface while in a carrier or holder, such as a front curve mold, and picks up the contact lens from the holder by vacuum force, which creates suction at the nozzle which draws the lens from the holder onto the probe hemispherical nozzle. 
     A hood assembly encompasses the lower end of the probe and is resiliently biased to exert downward pressure preferably via holding pins on the carrier or holder, e.g., front curve, from which the lens is being removed to hold it in place against the vacuum force as the lens is being removed from the front curve mold 
     The probe is then relocated over the carrier or package into which the lens is to be deposited. In a preferred mode, once the lens is lifted by the probe out of the front curve mold, the vacuum is shut off, with the lens being held by surface tension while the probe is relocated over the carrier or package. Alternatively, the vacuum force supply can be shut off after the probe has been positioned over the carrier or package. Preferably, the hood is pressed against the carrier or package, holding it in place, and if a package, the hood is designed to protect the sealing area from splashing. Once in the proper location, one or more short, controlled pressure pulses of liquid or gas, preferably air, are supplied. At the same time, preferably a vacuum is applied within more than one passage designed within an opening from the hood assembly. As a result, the contact lens is ejected from the probe into the package by at least one pressure pulse, and any residual washing solution or other material on the lens or packaging which is displaced from the contact lens by the pressure pulse(s) or movement of the lens off the probe is drawn into the passage of the hood by the vacuum. This results in rapid placement of the contact lens into the final package without excess matter on the lens or the package. The vacuum draws away any excess matter which becomes airborne during the ejecting step, and preferably the vacuum also removes any matter in the heat seal area of the package to provide for successful package closure. 
     Presence of the lens during transfer can be detected by measurement of the vacuum that is achieved. A low vacuum indicates that there is no lens carried by the probe. 
     In one respect, the invention provides a method for transferring a wet object from a first position to a second position. The method includes the steps of picking up an object from a first position with a nozzle, ejecting the object from the nozzle with a pressurized fluid to a second position, and drawing away any excess matter from the object which becomes airborne during the ejecting step. In a preferred mode, the drawing step commences before the ejecting step with the excess matter being drawn away from and external to the nozzle. The method may further include the step of providing a coating material to the object during the transfer process, with excess coating material being drawn away the same as any other excess matter. The object being transferred can be relocated to a different position by moving the nozzle after it is picked up, or the object can be relocated by moving a new container, for example, product packaging, under the nozzle while the nozzle remains stationary. 
     In another respect, the method of the invention transfers a wet object from a first container to a second container. This process includes the steps of locating a probe having a nozzle adjacent the object in the first container, creating a vacuum in the nozzle to draw the object to the nozzle, deactivating the vacuum, providing a pressurized fluid in the nozzle to release the object and to displace any excess matter from the object, and creating a vacuum within a hood disposed about the nozzle to draw away the any excess matter. 
     According to another aspect of the invention, an apparatus for transferring a wet object from a first station to a second station is disclosed. The apparatus includes a probe having a reciprocating barrel with a passage for communication with a positively or negatively pressurized fluid. A nozzle is affixed at one end of the probe for transferring the wet object from the first station to the second station, the nozzle being in communication with the passage. A variety of nozzles of different sizes and shapes can be affixed to the probe. A hood is disposed about the nozzle and is connectable to a vacuum source. Upon application of the pressurized fluid, e.g. gas or liquid, the wet object is released from the nozzle, thereby causing excess matter to be ejected from the wet object which is drawn away within the hood. In a preferred form, the hood includes spacers which depend therefrom and space the hood from the station that it contacts, for example, a front curve mold for a contact lens or a contact lens package. The spacers limit movement of the hood and ensure that an inflow passageway is available to cause air to rush over the station (e.g., the seal area of a package) and thereby dry the area surrounding the hood or maintain that area dry during the transfer of the wet object. The apparatus may further include a controller programmed to control the vacuum connection to the hood and the application of pressurized fluid to the probe, and control the movement of the assembly. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the invention to provide a method and apparatus for transferring wet flexible objects, such as contact lenses, from one station to another. 
     Another object is to provide a method and apparatus for pickup and transfer of wet flexible molded parts and removing the liquid and other matter, particularly from the surface of the molded parts, during the transfer. 
     An additional object is to provide a method and apparatus for transferring a wet object, such as a contact lens, from one station to another which uses a probe to remove the lens from the first station by vacuum pressure and transfer it to the second station where it is deposited by applying a pressurized stream or pulse of air or liquid through the probe to the object. 
     A further object is to provide a probe to transfer a wet lens from one position to another and to remove excess liquid or other matter from the lens surface during the transfer. 
     Yet a further object is to provide a method and apparatus for transferring a wet object which prevents contamination of the heat seal area of the package. In this design, the hood fits over the package to prevent contamination of the heat seal area. 
     Another object is to provide a probe which has a hood which prevents the pickup of the containers at the first and second stations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent upon reference to the following specification and annexed drawings in which: 
     FIG. 1A is an elevational, cross-sectional view showing a lens being picked up by a probe; 
     FIG. 1B is an elevational, cross-sectional view of the probe shown depositing the lens into a package; 
     FIG. 2A is a front view of the front end of the probe nozzle; 
     FIG. 2B is a cross-sectional view of the probe nozzle of FIG. 2A; 
     FIG. 3 is a detailed view of FIGS. 1A and 1B; and 
     FIG. 4 is a schematic diagram of a system in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, in the preferred embodiment, the probe  10  has a tubular barrel  12  having a central passage  14  which is controllably connected to sources of a vacuum A and compressed gas C, such as air (see FIG.  4 ). The probe is of any suitable material, for example, a high density , polyetheretherketone (PEEK). The probe barrel  12  is spring loaded by spring  35 . The probe barrel  12  is controllably driven by a suitable mechanism, such as a pneumatic or electromagnetic driven piston, to move it laterally and/or to reciprocate it up and down. Once the probe contacts a contact lens, any additional downward movement of the probe causes the spring  35  to compress until the probe assembly is moved back up (reciprocated). The probe is preferably resiliently biased when it contacts a contact lens. The barrel  12  is surrounded by and slides in a sleeve  31  whose lower enlarged end defines a hood  28 , which surrounds the lower end of the barrel  12 . The barrel  12  and sleeve  31  reciprocate in a stationary mounting block  20 . 
     The hood  28  defines a passage  30  for a vacuum. The hood  28  is connected to a vacuum B. The hood  28  surrounds the sides of the nozzle  40  attached to the lower end of the probe  10 . The hood  28  and sleeve  31  are spring loaded by a spring  16  within a casing  17 . The casing  17  preferably provides equal distribution of the vacuum within the hood and around the probe  10 . The spring&#39;s  16  upper end engages the mounting block  20 , and its lower end engages a seat  19  on of the hood  28 . As the probe barrel  12  moves down under control of the external mechanism, the hood  28  also moves with it by the action of the spring load provided by spring  16 . There are opposing stops  29   a  on the hood sleeve and  12   a  on the barrel to limit motion of the two relative to each other. 
     The nozzle  40  at the lower end of the probe barrel  12  is in communication with the central passage  14 . As shown in FIGS. 2A and 2B, the nozzle  40  is of generally semi-spherical shape (although other shapes can be provided) and has a plurality of perforations  42 , preferably 0.28 mm to 0.41 mm in diameter, and more preferably closer to about 0.41 mm in diameter. The nozzle perforations  42  preferably are arranged in concentric rings, as shown in FIG. 2A, over the entire nozzle surface area including having holes which permit the vacuum to engage the edges of the lenses  52  for optimum pick-up. The nozzle  40  preferably is of a hard material. It is of a size and shape to generally conform to the object to be transferred, here the inner concave surface of the lens. The nozzle may be made interchangeable so as to accommodate objects of different sizes and shapes. Generally the nozzle is about 12 to 15 mm in diameter, depending on the size of the object, e.g. lens, being transferred. Vacuum is achieved or compressed air is supplied through the perforations  42  in the nozzle  40  via the barrel  12  and the central passage  14 . 
     In alternative embodiments, the hood  28  can be used with the nozzles described in the aforementioned U.S. Pat. Nos. 5,561,970 and 5,706,634. 
     The probe  10  is to transfer a wet object from a first station to a second station. Here, illustratively, the object is a wet, hydrogel contact lens  52 . In FIG. 1A, the lens  52  is shown in a concave mold  50 , called the front curve in the manufacture of contact lenses. The mold  50  can be of plastic or of a reusable mold material, e.g. quartz. The mold  50  also can represent a tray or other type of holder to hold the lens while being subjected to a hydration bath or other processing stage. The hydration bath also can be carried out while the lens is in the mold. 
     The wet lens  52  is to be removed from the mold  50  and transferred to a second station, which in FIG. 1B is a package  60  having a well  62  into which the lens  52  is to be placed, or deposited. This can be the final package which is to be opened by a consumer. The package well  62  has a surrounding lip  63  which defines the heat-seal area of the package. Also, before, during and/or after the deposition of the lens into the package well  62 , liquid and/or other residual material on the contact lens and/or within the package can be removed in a controlled and repeatable manner by the lens transfer device of this invention. 
     To remove the lens  52  from the mold  50 , the probe barrel  12  is preferably moved in register with the lens  52 , and downwardly moved to preferably contact the lens  52 , and to slightly compress the spring  35 . At this time, the vacuum is applied through the barrel central passage  14  to pick up the lens from the mold  50  to be engaged against the nozzle  40 . The pickup vacuum pressure can be in the range of about 0.06 to 0.15 bar, for example. At this time, the hood  28  is positioned above the front curve mold  50 . Preferably, the hood  28  is resiliantly biased by spring  19  against the front curve mold, and pins or spacers  70  on the hood  28  engage the front curve mold  50  to prevent the mold from being picked up by the suction from the nozzle  40  as it picks up the lens  52 , and as the barrel  12  with the attached lens  52  is raised by the external mechanism. In an alternative embodiment, the vacuum(s) within the barrel  12  and/or hood  28  can be used to remove all of the liquid from the first station from which the lens is removed. In particular, in a process in which the front curve molds  50  are reused for subsequent lenses, the vacuum assists in preparing such molds for reuse by withdrawing all of the liquid. 
     The addition of Tween 80, polysorbate 80NF, manufactured by ICI Specialty Chemicals, at 10 to 100 ppm, and preferably 20-30 ppm to the last liquid the contact lens contacts prior to transfer using the nozzle of this invention, may improve lens transfer performance. Other surfactants or other processing agents can be added to the liquid. 
     The wet lens  52  has now been removed from the first station and is to be deposited into the package well  62 . Either the mounting block  20  with the probe  10  is moved over the package  60 , or the package is moved under the probe. This is accomplished by any conventional mechanism. 
     The nozzle barrel  12  is moved downwardly onto the package  60  and is stopped when the nozzle with the lens and the package are at a fixed distance apart, preferably, defining a gap of 0.3-0.7 mm, and more preferably a gap of approximately 0.5 mm between the nozzle and the bottom of the package well  62 . The lower end of the hood  28  is resiliantly biased against the package positioned by the stop pins or spacers  70 , as shown in FIG. 3, which also provides a space between the lower end of the hood and the package lip  63 . The stop pins  70  fix the distance between the nozzle  40  and the bottom of the package well  62  (FIG. 1B) and the mold  50  (FIG.  1 A). 
     At this stage, the vacuum flow in probe passage  14  is stopped, if not stopped earlier. Preferably, compressed gas is then blown, for example, as one or a series of several jets or pulses, through the probe central passage  14 . The jets or pulses may range in duration from 0.3 to 2.5 seconds, preferably 0.3 to 0.7 seconds, with a 0.5 second off-time therebetween, and may be pulsed one to three times, for example. The pressurized pulses can be, for example, 20 lb/in 2  to 1.5 bar. In and around this time, including shortly before and shortly after, a vacuum is drawn around the perimeter of the probe barel  12  through the hood  28  within the passage  30 . Preferably, the vacuum is drawn in the passage  30  before the vacuum in the passage  14  is stopped, and more preferably, just before the vacuum is stopped, for example, 0.5 second before. The vacuum within the passage  30  can be, for example, 0.12 to 0.20 bar. The compressed air drives the lens  52  off of the nozzle  40  into the package well  62 . It also drives liquid, and any other material, from the lens surface, and the vacuum drawn through the hood passage  30  captures this blown off material. Preferably, the strength of the vacuum in the passage  30 , under the hood  28 , is greater than that of the jets or pulses conveyed through the nozzle  40  from the passage  14 . Because the hood and the package lip  63  are spaced from one another by the stop-pins  70  with inflow passageways  74  therebetween, the vacuum in the passage  30  not only draws liquid from the lens  52 , it also draws air across the package lip  63  or seal area of the package through the inflow passageways  74  and into the passage  30  to dry or maintain this area dry to better ensure that the package  60  is effectively heat sealed with a lidstock, if this is needed. Importantly, the lens is not drawn into the passage  30 , partially due to the in-rush of air or other ambient gas from outside the hood  28  and the package  60  through the inflow passageways  74 , and also due to the pulses/stream of positive pressure applied to the lens from the passage  14 . Preferably, after the transfer is complete, the well is filled with a buffered solution, such as saline, before the package is sealed. 
     Preferably, the hood  28  has a circumferential size which generally matches the well in the package  60  and the lip  53  around the concave mold  50 . When sized in this way, the stop pins  70  will readily engage the heat-seal area  63  of the package  60  and the lip  53  of the mold  50 , yet permit an in-rush of air through the inflow passageways  74  between the pins  70 . The hood is designed to prevent contamination of the heat-seal area of the package, by making the circumference of the hood substantially match the shape of the heat-seal area of the package. 
     In an alternative embodiment, the front curve mold  50  can be sucked clear of its contents, the lens  24  transferred, and the mold cleaned (e.g., by injecting mold cleaning solution delivered by the nozzle or other device, with the solution removed simultaneously). The vacuum established within the passage  30  and compressed gas pulses from passage  40  can then be used to dry and clean the front curve mold  50  once the lens has been transferred. 
     FIG. 4 is a schematic diagram of the air/gas control system for the probe/hood assembly. These are two vacuum sources A, and B and one compressed gas source C. Vacuum source A and compressed gas source C communicate with the probe central passage  14 , either to apply suction or gas pressure. Vacuum source B comprises a high-mass regenerative blower  88 , which applies a vacuum to the hood  28  through passage  30 . Vacuum source A is controlled by a two-way valve  80  which regulates the compressed air source  85  feeding the vacuum ejector  86 . Alternatively, an alternate source of vacuum could be used, e.g. a regenerative blower. Compressed gas C is provided by a compressed air source  87  controlled by a two-way valve  81 . The vacuum in the hood  28  is controlled by a two-way valve  82 . A Programmable Logic Controller (PLC) can control each valve and the assembly movement in a properly timed sequence as described previously. Two gauges monitor pressures applied to passages  14  and  30  of the probe  10 /hood  28  assembly. Gauge  83  monitors both pressure and vacuum that is applied to the wet lens  52 , preferably supplying feedback to the PLC. Gauge  84  monitors vacuum to the hood, preferably supplying feedback to the PLC. Gauge  83  has the capability of monitoring the system to determine if a lens  52  is present on the nozzle  40  of the probe. 
     The PLC can be programmed in a conventional manner to control and ensure that the process is operating within prescribed parameters and that the valves and vacuum/pressure sources are operating correctly. Operation outside of the range of prescribed parameters can be noted by the PLC to identify one or more lenses  52 , molds  50 , or trays  20  to be marked for removal. 
     A mechanical, electrical or computer operated controller controls valves  80 ,  81  and  82 , as well as an electromagnetic, cam, or pneumatic driver (not shown) that reciprocates the probe. The controller is programmed to perform the operation described above in the properly timed sequence. 
     The pressurized fluid can be air, an inert gas, a buffered saline solution or distilled water as a liquid or vapor, and may include a coating material for the surface of the contact lens, for example, a coating material which makes the lens more hydrophilic. In one embodiment, such coating can be added to the lens as an aerosol spray or part of a liquid which emanates from the nozzle  40  with a gas during release of the lens from the probe  10 . Alternatively, the coating or another additive can be added as part of a separate processing step, for example, after the lens has been placed in the package  60 . 
     The lens transfer method and apparatus of the invention works effectively over a wide range of lens designs, including monofocal, multifocal, and toric lenses. In addition, the lens transfer method and apparatus of the invention provide a highly efficient controlled method over previous techniques with the ability to successfully transfer up to and exceeding 99% of the contact lenses. 
     All patents, applications, publications, and the method mentioned herein are hereby incorporated by reference. 
     As used herein, the term “excess matter” refers to any foreign matter or material which has not been prescribed or specified for a particular object such as a contact lens or contact lens package. For example, “excess matter” in the case of a hydrogel contact lens having a hydrophilic coating includes any water, saline solution, leachable diluent or processing chemical or the like which may be on the lens at a particular stage of processing. 
     Specific features of the invention are shown in one or more of the drawings for convenience only, as each feature may be combined with other features in accordance with the invention. Alternative embodiments will be recognized by those skilled in the art and are intended to be included within the scope of the claims.