US3327955A - Pulverizing mill - Google Patents

Description

June 27, 1967 w. s. TYLER PULVERIZING MILL 2 Sheets-Sheet 1 Filed June 15, 1964 W. J. Ty/er I INVENTOR. BY 4 M w/ June 27, 1967 W. S. TYLER PULVERIZING MILL 2 Sheets-Sheet 2 Filed June 15, 1964 a N f 0 e m m w M v A Jr W W m 7 1 NM a mum/ WU 4 Q u flw a M WU WU WU MU W United States Patent 3,327,955 PULVERIZIN G MILL William S. Tyler, 614 Oak Ave., Sulphur Springs, Tex. 75482 Filed June 15, 1964, Ser. No. 375,220 1 Claim. (Cl. 241-187) This invention relates to an improved pulverizing mill using counter-rotating members or rotors. More particularly this invention relates to a mill having a pa1r of spaced apart rotors each of which is provided with flails, such as lengths of chain, and which rotors are turned in counter-rotational directions to provide improved grinding or pulverizing results.

In the grinding and/or pulverizing art, it is important to have an apparatus which will provide the maximum amount of grinding with a minimum amount of power requirements and which will have a minimum of operation problems such as clogging or the like. In some instances it is desirable to have a grinder which will be so efiicient in this grinding operation that no screen or grate is required to retain the material being ground in the grinding zone, since such a screen or grate might clog with some materials. Moreover, the greater the efilciency of the mill, the less will be the re-run, thereby speeding production flow and eliminating re-run problems.

The prior art teaches many types of hammer mills wherein hammers are mounted about a single rotor or shaft and in which the material to be ground is directed against these hammers during rotation of the shaft. Thls is typical of hammer mills which have been in use for many years. Those mills, utilizing swing-typehammers have many shortcomings, one of which is that 1f, for example, a tramp piece of metal is run through the mill, quite often the swing hammer is knocked in a rearward position where it often times freezes such that the centrifugal force will not overcome the frozen conditlon, with the result that the grinder is not always operating at top efficiency. This diificulty was overcome by the use of attaching a plurality of lengths of chain about a rotor to replace the above referred to swing hammers. The chains are much less susceptible to being knocked back in a frozen position and also accomplish a much more efiic1ent grinding operation in most instances.

However, even the use of a single rotor mill with chaln flails was not fully satisfactory in all instances and often times required the use of screens or baffles against which the particles could be batted during the grinding thereof.

It is therefore an object of the present invention to provide an improved double-opposed pulverizing mill which will overcome the foregoing problems and which will provide improved grinding results without the need of screens or grates.

- Other objects of this invention will be obvious to those skilled in the art by reference to the description herein and the drawings which form a part of this application.

Briefly stated, this invention comprises a grinding or pulverizing mill having a housing mounted on suitable supports. The housing is provided with inlet means for receiving material to be ground and outlet means for discharging the material after the grinding thereof. A pair of spaced apart rotors is mounted for rotation in this housing. These rotors each have a plurality of flails, such as lengths of chain or the like, attached in spaced apart relationship thereabout. The lengths of these flails or lengths of chain are so selected that the flails attached to one rotor do not interlace with the flails of the other rotor during rotation of the rotors.

Means are also provided for rotating these rotors in counter-rotational directions and in the direction of the outlet means. During this rotational movement, there is 3,327,955 Patented June 27, 1967 established an impact area between the two rotors wherein the material received through the inlet means of the housing is subjected to repeated impaction with the par ticles being batted back and forth therein during the grinding operation.

Reference to the drawings will further teach the invention, wherein like numerals refer to like parts and in which:

FIG. 1 is a central sectional view of one embodiment of the invention herein.

FIG. 2 is a side elevation view of a disassembled portion of the rotor showing the arrangement of the chain flails.

FIG. 3 is a fragmentary view of a disassembled portion of the rotor showing the arrangement of the discs in relation to the shaft of the rotor.

FIG. 4 is a laid out plane view showing the pattern for attaching the chain flails to the rotor.

Referring now to FIG. 1, the housing for the grinder is generally comprised of base 11 having opening 12 therethrough with rectangular shaped lower hopper 13 supported thereabove, which generally forms the outlet means of the housing.

Upper housing 15 is supported on the top of lower hopper 13 and encloses the grinding rotors to be described hereinafter and has mounted thereon a pair of motor slide mounts 16 on either side thereof.

Each of the slide mounts 16 has mounted thereon motors 17 for driving the rotors as will be explained hereinafter. Slide mounts 16 are each provided with adjusting screws 18 for moving motors 17 for adjustment purposes.

The inlet means for directing material to the grinding or impact area is formed by upper hopper 19 mounted on the top of upper housing 15. Hopper guide 20 is supported in upper hopper 19 for directing the downward flow of material to be ground into two streams.

Upper housing 15 is provided with a pair of cross braces 21 which are suitably spaced apart for mounting the rotors as will now be described.

Each of the cross braces 21 is provided with two axle mountings 22 having suitable bearings therein and which support the ends of two generally parallel and spaced apart shafts 23, with shafts 23 being journaled for rotation in mounts 22.

Reference to FIG. 3 shows one suitable arrangement of the rotors of this invention. Shaft 23 has mounted thereabout and supported thereon in a spaced apart relationship a plurality of annular discs 24 suitably keyed thereon so that during rotation of shaft 23, discs 24 will rotate therewith.

Reference to FIG. 2 will show the method by which the flails, preferably flexible flails in the form of lengths of chain, are attached to the rotor. As explained above, FIG. 2 shows a side elevation View of a disassembled disc showing the arrangement of the chain flails in relation thereto. Thus, it will be seen that disc 24 has a central keyed aperture 25 which mounts on shaft 23 as shown in FIG. 3. Discs 24 are each provided with eight small threaded holes 26 through which threaded rods are passed, which rods (not shown) are adapted to extend through all the dis-cs 24- on one rotor to thereby give support to the peripheral edges of discs 24.

Discs 24 also have eight larger holes near the periphery thereof through which eight swing rods 27 are adapted to be passed and supported therein. Rods 27 also extend through all of the discs 24 and are for the purpose of attaching the chain flails, such as coil chains 28, each of which in this instance has five links.

Reference to FIG. 4 will show one preferred layout or alignment of coil chains 28 with respect to the rotor. There it will be seen that coil chains 28 are supported on swing rods 27 and positioned between discs 24 in staggered alignment, hence this particular embodiment shows 48 coil chains 28 secured about one of the rotors. It is to be understood that other arrangements would be satisfactory so long as there were a plurality of such chained flails attached to the rotor in a uniform manner.

During operation of the pulverizing mill, motors 17 are adapted to drive belts 30 which are supported on appropriate pulleys whereby shafts 23 are rotated. It is to be understood that motors 17 are so arranged that shafts 23 are turned in counter-rotational directions and in the direction of the outlet means of the grinder as illustrated by arrows 31 and 32.

During rotation of shafts 23 and discs 24 attached thereto, coil chains 28 are extended therefrom by centrifugal force. When the rotors, i.e. discs 24 and shafts 23, are so rotating there is established between the two rotors an impact area 33 where particles to be ground are subjected to repeated or multiple impaction. With the rotors so turning in counter-rotational directions the material to be ground is admitted through upper hopper 19 by gravity flow or the like such that the material is struck by the rotors and chains 28 with grinding taking place in impaction area 33, with the particles being batted back and forth therein. It is this repeated impaction established by the double-opposed rotors which provides this grinder with such great efiiciency. In the preferred embodiment, chain flails are utilized and provide the most efficient grinding.

Not only is the material being ground subjected to repeated impaction but it is also directed to the outlet means of the mill inasmuch as shafts 23 are rotated in the direction of the outlet means, as explained above, which thereby reduces the possibility of plug-up or clogging.

Thus, it may be said that the rotors of this particular embodiment are generally parallel and spaced apart a sufficient distance such that chains 28 on each of the rotors do not mesh or entangle with each other. This is important in order to insure continued and troublefree operation.

It will also be observed that in this particular embodiment the rotors, i.e. shafts 23 and discs 24, are horizontally spaced apart from each other such that the material to be ground may be gravity-fed from above with the discharge being through the outlet means at the bottom. This particular arrangement eliminates the need for blower equipment that might otherwise be needed in some types of mills to propel the material to be ground through the mill. However, it is to be understood that shafts 23 could be vertically spaced apart with the feeding of material to be ground passing therethrough in a horizontal direction.

It will be observed that no screen is required to enclose the material to be ground in the impact area until reduced to a specified size. This is particularly important when grinding material which would ordinarily clog the screen because of its physical characteristics.

In describing the proper length of chains 28, it may be said that the length of such flails is selected so that during rotation the peripheral arcs of each of the flails on one rotor are spaced apart a small distance from the peripheral arcs of the flails of the other rotor. Stated another way, and in the preferred embodiment, the length of chains 28 are all uniform such that the peripheral arcs of all of the chains 28 on each rotor define a curved plane during rotation thereof which curved plane is in the form of a cylinder. The curved plane of the peripheral arcs of the chains on each rotor are spaced apart a small distance so that the chains 28 on one rotor do not strike the chains 28 of another rotor.

There are many advantages of this particular mill. For example, the double-opposed arrangement of the rotors with the flails thereon provides an unsually good and efficient grinding zone or impact area whereby material can be ground more efficiently than single rotor mills using either swing hammers or chains. This mill does not clog up as easily as a single rotor mill, and tramp metal passing through the grinding zone does not disrupt the operation of the mill to the extent that it would in a single rotor swing hammer type mill. There is a greater degree of pulverization with one pass through the mill thereby reducing the amount of re-run. In fact, the grinding is so efficient that no screen is required to maintain the material in the grinding zone until reduced to a specified size. The elimination of a screen permits the grinding of many materials which would otherwise clog such a screen, and thereby promote malfunctioning. This is particularly true in the fertilizer industry, for example, where it is practically impossible to use sizing screens or grates in the mill because of the clogging and choking up. The grinding operation of this mill is so eflicient that a small unit will normally perform a grinding operation which would ordinarily require a much larger and more expensive mill of the single rotor type.

Modifications may be made in the invention as particularly described without departing from the scope of the invention. Accordingly, the foregoing description is to be construed illustratively only, and is not to be construed as a limitation upon the invention as defined in the following claim.

What is claimed is:

A pulverizing mill for pulverizing material by impact,

said mill comprising:

a housing having upper inlet means for receiving material to be pulverized downwardly thereinto and lower unobstructed outlet means for discharging said material after pulverization thereof, said inlet and outlet means being generally vertically aligned with respect to each other,

a pair of generally parallel and generally horizontally spaced apart rotors mounted for rotation in said housing between said inlet and outlet means, with the axes of rotation of said rotors being in a common generally horizontal plane,

each of said rotors having a plurality of. axially extending and circumferentially spaced apart rows of chain flails attached thereto, with the flails in each row being in staggered alignment with the flails of adjacent rows, and with the length of said flails being uniform and the same length and selected such that the flails of one of said rotors do not contact the flails of the other of said rotors during rotation thereof, and

means for simultaneously rotating said rotors in counter-rotational directions and in the direction of said outlet means and thereby creating a single impact zone between said rotors, with said zone being spaced directly above said outlet means, and with the discharge of said material being directly from said zone to said outlet means.

References Cited UNITED STATES PATENTS 359,630 3/1887 Pratt 2.4l193 X 811,671 2/1906 Simpson 241-187 X 1,893,030 1/1933 Kingsley 241193 X 2,958,530 11/1960 Kucera et al 241-194 X ANDREW R. JUHASZ, Primary Examiner.

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