(1) Field of the Invention.
The present invention relates to the crushing or digesting of used fluorescent tubes. More particularly the present invention relates to an improved rotatable crushing blade and the method of using such blade for the effective crushing of used fluorescent tubes into substantially uniform sized pieces of glass or pieces of glass within a uniform range of sizes prior to separating the glass and various potentially toxic materials contained within the interior of the fluorescent tubes from each other. More particularly, the present invention relates to an improved shape of a fluorescent tube fracturing blade and a range of speeds for operation of such blade which provides the desired results, i.e. the desired separation of the fractured glass particulates and the toxic powder and other substances contained originally within the fluorescent tubes.
(2) Discussion of the Prior Art.
Fluorescent light tubes are formed from elongated, cylindrical or tubular glass receptacles which are charged with mercury or other conductive vapors. The inside surface of the tube is coated with a fluorescent coating of some form such as phosphorus itself or other phosphor powders such as antimony, beryllium, cadmium and strontium compounds plus in some cases, lead and the like. Mercury vapor as well as beryllium, strontium, lead and cadmium are well known as potentially toxic materials as are other phosphor powders with which the inside of the fluorescent tube may be coated. Older fluorescent tubes often use high concentrations of beryllium powders, but this has been in general superseded in more recent fluorescent tubes by cadmium-type powder.
Since fluorescent tubes are, in general, bulky and unsatisfactory for disposal without treatment, it has become customary to crush them into small pieces by various means and then dispose of the fractured pieces. Merely fracturing the tube itself into small pieces for disposal, however, is not very satisfactory because of the potentially toxic nature of the dust and vapor originally confined inside the fluorescent tube. Such potentially toxic particulates, which occur mostly in the form of small dust particles plus mercury vapor and small drops or beads of mercury, can be quite detrimental if they escape to the environment.
In previous applications filed by the present Applicant, methods and means for crushing fluorescent tubes and then separating the fractured glass particulates from the potentially toxic materials contained within the original tube have been disclosed. Such methods and apparatus are based on an air separation effected between the glass particulates and the smaller toxic powders and vapors contained within the original fluorescent tubes. In particular, in accordance with such previous inventions, the fractured fluorescent tube materials are exposed to a rapidly moving body of gas such as stripping air, preferably passing countercurrently with such particulates. In this way the smaller, lighter dust and mercury vapor is carried away to a recovery system while the glass particulates are removed from the system for recycling to glass manufacturers and the like. In order to provide such separation, it is important that the glass particulates not be crushed too small so that they will have sufficient weight such that they will not be carried away by the stripping gas together with the small toxic powder particles.
In Applicant's U.S. application Ser. No. 458,177 filed Dec. 28, 1989 a flat, rapidly rotating blade was disclosed for fracturing fluorescent tubes thrust down a feed chute into the path of the rotating blade. The blade, upon striking the fluorescent tube, fractured such tube into small particles and these were then conveyed by gravity and other means through a system while separating toxic powder from the surfaces both by gravity processes and particularly by countercurrent air flow or gas stripping processes. As indicated above, it is important in crushing the glass that the pieces not be too small such that they may be carried away with countercurrent stripping air, nor should such pieces of glass be too large or they will not only not pack efficiently, but will also not have their surfaces exposed efficiently for transportation through the stripping air for stripping away of the toxic powder normally adhering to the original inside surface of the fluorescent tube. It is highly desirable, therefore, that the glass particles be of fairly uniform size and shape. It is also desirable, since glass is a very hard substance which rapidly wears away even fairly hard steel, for the rotating crushing blade to have a configuration and composition which will be durable and wear-resistant.
It has long been known to provide apparatus for generally breaking or crushing glassware, and particularly glass bottles and the like to reduce their bulk and more recently, it has also been widely suggested that fluorescent tubes be fractured into their constituent pieces for more convenient disposal as well as, in some cases, recovery of the components of the tubes. Among apparatus provided for crushing glass, and, of late, particularly fluorescent tubes, may be mentioned the following:
U.S. Pat. No. 2,185,352 issued Jan. 2, 1940 to C. F. Peters discloses an early type of glass fracturing device for fracturing bottles. The fracturing device in the Peters patent is a pivoted hammer-type arrangement.
U.S. Pat. No. 2,538,255 issued Jun. 26, 1951 to N. E. Johnson et al. discloses a remote control glass breaking machine in which bottles in particular are slid down a tube where they intercept a horizontally rotating motor driven fracturing blade comprised essentially of a rotating backing having slightly curved forward hammer surfaces which rapidly strike the bottle, pulverizing it by repeated blows. The hammer surface shown has a sharp edge on one side and is somewhat like a cleaver blade.
U.S. Pat. No. 2,593,657 issued Apr. 22, 1952 to A. J. Coon et al. discloses a reciprocating-type crusher designed to crush fluorescent tubes and the like. The Coon et al. crusher involves reciprocating two opposed crushing surfaces relatively towards each other with a fluorescent tube between them, said reciprocating surfaces being moved by means of a rotating cam arrangement. There is no rotating fracture blade per se.
U.S. Pat. No. 2,620,988 issued Dec. 9, 1952 to E. H. Telier discloses a fluorescent tube chopping device including a rotating fracture blade or "star shaped breaking wheel" which progressively breaks off the end of a fluorescent tube during the fracturing operation. Each arm of the fracture blade appears to have a substantially flat striking face.
U.S. Pat. No. 2,628,036 issued Feb. 10, 1953 to J. B. Hall discloses a fluorescent lamp disposal arrangement including a rotating hammer-type arrangement for fracturing the fluorescent tubes. The rotating hammers, which are contained in a circular fracture chamber, are pivoted upon the outer circumference of a rotating disk.
U.S. Pat. No. 2,866,604 issued Dec. 30, 1958 to J. B. Hall discloses a fluorescent tube disposal device including a rotating breaker arm.
U.S. Pat. No. 3,333,777 issued Aug. 1, 1967 to C. W. Highfill et al. discloses a grinding mill which, although it is not designed for the fracturing of glass or fluorescent tubes, does disclose a series of flat blades arranged for progressively striking rocks and the like within a grinding chamber and in which fine dust is carried away.
U.S. Pat. No. 3,353,756 issued Nov. 21, 1967 to D. J. Morgenson discloses a horizontally rotating hammer blade, into the path of which glassware such as bottles are dropped. The blade is rotated at a high speed such as 1700 rpm's so that a bottle dropped into the spinning blades may be struck as many as sixty times for each second the bottle remains in the contact zone. The blades of Morgenson are more like chopping blades than impact blades since they strike the bottles on their edge rather than on their flat side.
U.S. Pat. No. 3,655,138 issued Apr. 11, 1972 to G. A. Luscombe discloses a multi-blade bottle or other glassware breaking device. The chopping blades comprise a series of fairly thin blades mounted in a stack, flat against each other to form a composite blade having in effect a number of knife blades sticking out from a central core at various points, which blades upon rotation of the central core strike anything passing by.
U.S. Pat. No. 3,889,886 issued Jun. 17, 1975 to J. D. Spivey discloses a bottle breaking device including a series of edgewise rotating blades journaled on a transverse shaft. There are also a series of transverse stationary blades extending across the chopper and forming a grating between which the rotating blades pass during rotation. In effect, glass material has to be chopped within a size range which will slip down through the grating before it can pass beyond the chopping blades.
U.S. Pat. No. 3,913,849 issued Oct. 21, 1975 to I. M. Atanasoff et al. discloses a fluorescent tube digester or breaker in which the breaking of the fluorescent tubes is accomplished by a double bladed knife rotating horizontally next to the tube inlet.
U.S. Pat. No. 4,545,540 issued Oct. 8, 1985 to A. Nakamura discloses a fluorescent tube breaking device in which the tubes are broken by rotating fracture blades which rotate edgewise on a shaft in cooperation with a number of other blades and catch the fluorescent tube against a series of stationary blades mounted effectively between the rotating blades. The arrangement is substantially similar to the Spivey patent cited above.
U.S. Pat. No. 4,579,287 issued Apr. 1, 1986 to W. E. Brown discloses a fluorescent tube fracturing device including a pair or plurality of flailing chains attached to a rotating disk. Both the disk and the chains rotate horizontally and intercept a vertically inserted fluorescent tube.
U.S. Pat. No. 4,607,798 issued Aug. 26, 1986 to K. F. Odlin discloses a lamp crushing apparatus having a special allegedly non-jamming crushing blade which takes the form of a plurality of surface compartments in a drum section into which compartments or pockets formed between vanes at the surface of the drum the lamps are inserted, crushing said lamps into more or less equal, discrete quantities of fractured glass.
U.S. Pat. No. 4,655,404 issued Apr. 7, 1987 to J. W. Deklerow discloses a fluorescent tub chopping apparatus in which the tubes are inserted into the path of a rotating chopping means formed from a pair of flails comprised of rectangularly shaped bars secured to a central rotating plate by hooks. The tube to be fractured is inserted past the horizontally rotating flails.
U.S. Pat. No. 4,786,000 issued Nov. 22, 1988 to E. P. Weil et al. discloses a bottle breaking apparatus comprising a pneumatic ram with a central punch and a following plate which fractures the bottle against a V-shaped supporting wall. It is said the device does not form as many small particles of glass which may be difficult to recycle. The plate is deliberately not completely advanced against the bottle to avoid crushing said bottle into small pieces.
U.S. Pat. No. 4,819,883 issued Apr. 11, 1989 to E. P. Weil et al. uses the same pneumatic punch and following plate to crush glass bottles as the prior Weil patent and in addition provides an angular support wall in the rear that does not support the bottle in the center and increases its shattering.
While the above devices have generally been effective to fracture fluorescent tubes as well as other glass materials and other compositions of materials into small pieces, such blades generally have not been effective to provide a uniform fracturing of the tubes.