Process and machine for coating ophthalmic lenses

Details Process and machine for coating ophthalmic lenses Process and machine for coating ophthalmic lenses

2000-04-04

2001-12-04

Beck, Shrive P. (Department: 1762)

Coating processes

Optical element produced

Transparent base

C427S164000, C427S240000

Reexamination Certificate

active

06326054

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to the coating of ophthalmic lenses and more particularly concerns the automation of the lens coating process.
Present ophthalmic lens coating procedures include manual insertion of the lens into a washing chamber to be washed by hand or by use of a high pressure wash pump, drying the washed lens by manually holding the lens over a filtered compressed air jet, manually moving the dried lens to a coating apparatus in which the lens coating material is not recycled and then manually transferring the coated lens to a curing oven which is generally inaccurately controlled by use of a stop watch and potentiometer control.
These independent steps and the manner in which they are performed result in a slow, labor intensive process which wastes coating material and produces greater volume of hazardous waste material for disposal. The room in which these steps are performed must be environmentally controlled to minimize the risk of contamination during the process.
It is, therefore, an object of this invention to provide a process and machine for the automatic cleaning, coating and curing necessary to apply a scratch resistant coating to an ophthalmic lens. Another object of this invention is to provide a process and machine for coating ophthalmic lenses in a self-contained environment, eliminating the need for a “clean” room. A further object of this invention is to provide a process and machine for coating ophthalmic lenses which minimizes the use of hazardous or flammable solvents. Yet another object of this invention is to provide a process and machine for coating ophthalmic lenses that minimizes coating waste by recirculating coating. Still another object of this invention is to provide a process and machine for coating ophthalmic lenses that reduces operator exposure to coating by encapsulating the coating. Another object of the invention is to provide a process and machine for coating ophthalmic lenses that reduces operator decisions by use of computer control to instruct lens processing parameters. Yet another object of this invention is to provide a process and machine for coating ophthalmic lenses which eliminates process steps by automatically replenishing the coating supply and prompting the operator when the available coating has been exhausted. Still another object of this invention is to provide a process and machine for coating ophthalmic lenses which minimizes manual handling of the lens. Another object of this invention is to provide a process and machine for coating ophthalmic lenses that affords accurate control of the curing phase of the process. A further object of this invention is to provide a process and machine for coating ophthalmic lenses that facilitates operator adjustment of curing times in accordance with the strength of the curing device.
SUMMARY OF THE INVENTION
In accordance with the invention, a lens coater is provided which automatically controls the lens coating process from the insertion of the lens into the washer to the removal of the lens from the curer.
The back or concave portion of the ophthalmic lens is coated in a software controlled coating machine. The lens is attached to a rotating shaft on a slide conveyor having both lateral and vertical transfer paths. At the insertion end of the machine, the lens is mounted on the slide conveyor and above the washing and drying basin which is substantially cylindrical.
The lens is washed by a high pressure jet of deionized water directed at the radius of the concave lens surface while the lens is rotated at a preselected spin speed. As the lens rotates, the nozzle directing the water jet at the concave surface of the lens is rotated over an approximately 28 degree arc from the center of the lens toward the outer perimeter of the lens. The arc movement of the nozzle is controlled by a stepper motor with a cam linkage that causes the nozzle to shift outwardly at a slow rate of speed and inwardly at a high rate of speed so as to minimize operating time. In one wash cycle, the nozzle rotates outwardly twice and inwardly once.
The basin also includes one air nozzle directed upwardly at the concave surface of the lens and a second air nozzle directed inwardly toward the edge of the lens to apply breathable air from a tank at high pressure to the lens while the lens is spinning at a preselected lens drying speed. In the drying process, the air nozzle directed at the concave surface of the lens is twice outwardly and once inwardly pivoted over the 28 degree arc by the cam linked stepper motor.
When the drying cycle is completed, the lens is vertically transferred out of the washing/drying basin and horizontally transferred to a position above the coating basin. It is then vertically lowered into the coating basin for the coating process. The coating is applied by another nozzle under the control of the cammed stepper motor. In the coating process, the lens is caused to rotate at predetermined coating speeds. A low coating speed is used to dispense the coating from the nozzle to the concave surface of the lens. A high speed rotation of the lens is used when dispensing is complete to thin the coating. The operating speed of the cam is coordinated to the rotational speed of the lens so as to permit appropriate distribution of the coating material.
A coating material injection system distributes a specified quantity of coating material into the coating basin for a preselected number of lenses to be coated. That is, for one density of coating material, the unit may typically add 25 milliliters of coating material to the coating basin for every 588 lenses that are coated. For another density of coating material, 25 milliliters of coating material may be injected into the coating basin for every 392 lenses to be coated. These numbers have been found suitable in the preferred embodiment of the device hereinafter described, but they could vary considerably. A cartridge injection system which meters the use of the machine by the quantity of coating applied is preferred. The cartridge injection system allows the coating process to be changed by simply flushing the former coating out of the system and changing the cartridge. The cartridge contains a software pack which controls the operation of the system and thus provides the user the ability to change the operating parameters of the machine by merely changing a cartridge. This is especially beneficial to the user because upgrades to the machine can be made by simply providing to the user new cartridges containing the upgrade in the cartridge software. An additional advantage is that, since the unit automatically times the injection of coating from the cartridge into the basin in specified small doses, preferably in the 25 milliliter range, if the coating basin becomes tainted, only 25 milliliters of coating material need be replaced. Also, since the dosages are metered, the unit can give warning to the operator as to when the machine is low in coating material and can even shut the machine down automatically to prevent the dry operation of the device if coating reaches a predetermined minimal level. The injector includes a sensor for determining the level. Since the lens coater process is controlled by a stepper motor, preferably involving 200 steps per revolution, the timing of the coating operation is extremely accurate.
The injection system employs a fluid containing tube which dispenses fluid in response to the drive of a plunger. An information pack is disposed at the rear of the plunger with a probe at the rear of the information pack. A screw driven by the stepper motor drives the probe, information pack and plunger into the fluid cartridge on demand. The probe is electrically connected to the lens coater computer to provide the necessary data for system operation.
During the washing process, as the lens spins about the axis extending approximately through its center and transverse to the lens face, water is applied to the concave face of the lens through the nozzle orifice, the pressure being deter

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