Swing hammers

Prater Industries, Inc., manufactures narrow swing-hammer screened mills for oilseeds and fibrous materials. 

Figure 12.5. Jaw, roll, impact, and tumbling equipment for size reduction, (a) Blake-type jaw crusher operates at 200-300 strokes/min (Allis-Chalmers Co.), (b) Smooth roll crusher, for which operating data are in Table 12.8(b). (c) Swing hammer mill operating data in Table 12.7(a). (d) View of a conical ball mill, showing distributions of balls and material and crusting ranges data in Table 12.6(b) (Hardinge Co.). (e) Tube mill with three compartments, length to diameter ratio 3-5. (f) Rod mill in a cylindrical tumbler, LID = 1.2-1.6 data in Table 12.6(d).

Depending on the design of the impactor, these mills can be divided into subclasses such as pinned disc mills, baffle plate mills, beater mills, hammer mills or swing hammer mills. 

In addition to the gyratory and jaw types for crushing, there are others that are very largely used, among these may be mentioned the swing-hammer type, the roll type and other specially designed machines. 

Granulating.—In many industries, it is necessary to produce material in granular form—a form in which the particles are considerably smaller than is ordinarily produced by secondary crushing, and not so small as when a pulverulent product is required. The requirements may be such that the product wanted is anything from 40 mesh to 10 mesh, the mesh meaning the number of apertures per lineal inch. Reduction of this character can be performed in any one of many different ways, but according to usual practice, is accomphshed by swing-hammer machines, rolls or ball tube mills. 

When the swing-hammer mill is used for this purpose, a fine grid screen is used, and the product of the machine is screened to secure the classification desired. Mills of this type do not produce a uniform material, in-so-far as size is concerned, and for that reason they are not popular for use where uniform particles are desired with a minimum of both oversize and undersize. 

During early operations of the secondary shredder, several configurations of swing hammers and fixed stators were tried to reduce the particle size of the product, particularly random textile pieces, to a level that minimized jamming and stalling of the densifier. 

Impact mills like the hammer mill use swinging hammers (typically running at 750-1800 rpm) to pulverize the solid feed by impact and attrition. As shown in Fig. 5, these hammers are mounted by pins on the periphery of a number of disks mounted on a horizontal rotating shaft and are free to swing. The hammers force the product against a rugged breaker plate. The... 

Hammer Mills. These are very effective for size reduction of brittle materials. Hammer mills for shredding refuse are available with fixed or swing hammers, bolted on the high-speed rotating shaft (700-1,200 RPM). Major and minor variations exist in the design of each manufacturer s hammer mill. 

Impact Crushers One type of impact crusher is the hammer mill. This consists of swinging hammers rotating at high speed on either a vertical or horizontal axis inside of a lined crushing chamber. Ore is broken by impact with the hammers and breakage plates that reside on the periphery of the crusher. Reduction ratios as high as 40 1 can be obtained however, because of their very high reduction ratios, they have a tendency to produce more fines than other crushers. 

Several rotor disks, 150 to 450 mm (6 to 18 in.) in diameter and each carrying four to eight swing hammers, are often mounted on the same shaft. The hammers may be straight bars of metal with plain or enlarged ends or with ends sharpened to a cutting edge. Intermediate hammer mills yield a product 25 mm (1 in.) to... 

Impactor crushers consist of a lined crushing chamber inside which a rotor revolves on a horizontal axis. Attached to the rotor are either swing hammers or fixed blow-bars (Fig. 5.4). Stone enters the crushing chamber down the feed chute and is broken by impact with the hammers/blow-bar and with the breaking plates. Reduction ratios of up to 20 1 can be obtained. More complex crushers with double rotors can give ratios of 40 1. 

Fixed blow-bar crushers are used as primary crushers and can accept lumps up to 1 m in size. Swing hammer mills are generally used for producing smaller sizes and are effective down to 3 mm. When crushing hard rocks, impactor crushers are generally operated in open circuit (i.e., without recycling of oversized lumps). 

Hammer Mills. The swinging hammer mill (instead of having teeth as on a single-roll crusher) has hammers that are mounted on a rotating shaft so that they have a swinging movement. 

In a rolling crusher, swing-hammer pulverizer, cutting mill, pinned disk mill, etc. In stirrers, drum mixers, paddle mixers, vortex mixers, screw mixers, etc. 

For the size reduction of smaller particles, hammer mills are often employed. In these machines, free-swinging, hammers are rotated at high speed so that they are thrown out by the centrifugal force, hit the feed, and break it down by the force of impact. In many cases the discharge from this mill is through a sieve or screen to control the output particle size. 

Test specimens are 10 mm x 10 mm x 55 mm long with a 2 mm deep 45 degree groove or notch cut into the specimen. Provisions are made in the ASME Code for thinner materials where sub-size specimens are used. The specimens are cooled in liquid nitrogen and allowed to warm to the exact temperature required for testing. At this point the specimen is placed in the swinging hammer device for testing. The hammer is pre-loaded to a certain... 

A hammer mill for ultrafine grinding vith intermediate classification is known as the Mikro-Atomizer. In this model, a set of swing hammers is mounted between two rotor discs in the same fashion used in conventional hammer mills. In addition to the hammers, the rotor shaft carries two fans in... 

Moving-tire Kiln. See annular kiln. Mud Hog. A US machine for the disintegration of dry or moist plastic clay. It consists of a rotating swing hammer operating close to a series of anvils linked together to form a steeply inclined slat conveyor. 

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