Patent Application
20140353413
This invention relates generally to a hammer mill apparatus and more particularly to one that uses a bushing that extends between adjacent plates of a hammer mill and has one or more hammers press fit onto the bushing.
Hammers such as those shown in U.S. Pat. No. 7,419,109 to Rondfelt et al. and U.S. Pat. No. 8,104,177 to Plumb need to be replaced periodically. Due to the impact nature of the grinding, the heat treatment of the entire hammer has historically been at low levels to avoid breakage of the hammer. This low level of heat treatment however leads to excessive wear at the hole where the hammer rotates on a hammer mill rod. This phenomenon is sometimes referred to as “hole elongation”. This will also cause excessive wear on the rod itself upon which the hammer rotates about especially once the hammer itself experiences some “hole elongation”.
Another problem is that small particles of the material being ground, such as corn, will tend to build up between the rod and that portion of the hammer forming the hole in the hammer, resulting in excessive premature wear.
Accordingly, there is a need for a solution to the aforementioned problems.
The present invention solves the aforementioned problem by using a two piece setup where the rod on which the hammers rotate is covered by a insert or bushing that is replaceable so that the entire hammer does not need to be replaced when the bushing becomes worn. Since the insert/bushing is separate from the hammer blade itself, the hammer blade can be heat treated to different specifications depending upon what it is being used to grind than it could otherwise be treated. For example it can be heat treated to extreme hardness for grinding certain softer materials, not heat treated at all if for application of high impact, or heat treating between very hard and no heating treating at all of the hammers.
The present invention results in a hammer mill hammer blades that do not directly touch the rods that rotate about the central rotational axis of the hammer mill, but instead have an insert bushing pressed into a hole in each hammer blade so that the hammerblade rotate with the bushing around the rods.
This arrangement also permits multiple hammer blades to be placed on one insert/bushing, which greatly decreases installation time for assembly or replacement of hammers onto a hammer mill. These multiple hammers can have spacers between them or can be installed without spacers if desired.
In one embodiment of the invention, an entire hammer rotor slot (the entire distance between two plates of a hammer mill) utilizes a hardened bushing which is pressed inside of multiple hammerblades which can optionally be of the same or of different thicknesses, varying thickness from the grinding end to bushing end allowing for increased/decreased surface area at bushing versus the striking end of the hammer, with or without spacers between adjacent hammers.
By using a bushing or insert that extends completely between (and thereby at least partially sealed) between adjacent plates of a hammer mill, small abrasive particles of the material being ground are kept from lodging between the rod and the bushing, thereby reducing wear on the bushing or insert, reduction in hammers sticking and not rotating on the rod and extending the life of the bushing and the hammer itself.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The above needs are at least partially met through provision of the apparatus described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.
Referring now to the drawings, where like reference numbers designate identical or corresponding views throughout the several views,
The hammer mill assembly 10 would be disposed for rotary movement inside of a perforated housing (not shown) of the type shown in
A screen (not shown) is formed by having a plurality of openings in the housing 11 radially outwardly of the rotor 14. The rotor 14 also includes a plurality of plates 18 rigidly attached thereto. Rods 19 are connected to each one of the plates 18 for rotatably attaching hammers 20 thereto via a bushing/insert structure.
The rotor 14 has a plurality of preferably forged hammers 20 disposed in a hammer mill style and also being disposed in groups spaced circumferentially of the rotor 14. The hammer mill assembly 17 of each group of hammers 20 has a common pivot axis 21 that extends transversely of the rotor 14. Each of the pivot axes 21 are spaced respectively equidistantly radially outwardly of the rotor axis 16. Each of the hammer assemblies 17 is proportioned lengthwise thereof for hammer mill style cooperation with the screen upon rotation of the rotor 14. The rotor 14 is rotatable about its journaling axis 16 for grinding and screening through the screen (not shown) for passage to the housing outlet (not shown) so that the material to be reduced in size can be introduced into the housing inlet (not shown). The material can be any material, but corn is a common material that is processed in a hammer mill of the type shown.
Referring now to
Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the spirit and scope of the invention, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept as expressed by the attached claims.
