Page 2 - us2875959

United States Patent Office 2,875,959
Patented Mar. 3, 1959

1 2
a tilted axis, that. is, an axis passing obliquely from the
muller pan over its upper edge to bearings located at
one side of the muller pan, i. e., not over it. More-
1,875,959 over, if such a muller wheel and its shaft and bearing are
6 carried in the tiltable cradle, it is possible to lift the
TILTED AXIS MULLER
entire assembly clear of the pan when it is desired to
Charles W. Calkins, Newhall, Calif., assignor to Bermite remove the pan and a completed batch therein. How-
Powder Comp:my, a corporation of California ever, any such muller construction presents certain diffi-
Application May 10, 1957, Serial No. 658,260 culties. In the first place, the usual method of driving
10 the muller wheel by means of power on the muller wheel
6 Claims. (Cl. 241-103) shaft becomes extremely cumbersome and complex. Even
if this problem is avoided by driving the pan or its
supporting table, and causing the muller wheel to rotate
by engagement with the bottom of the pan, there remain
This invention relates generally to mullers of the 15 problems of lifting the muller wheel assembly clear of the
horizontal turntable type, and more particularly to such pan for removal at the end of the grinding of a batch.
a muller in which a muller wheel, together with its shaft It is a major object of the present invention to provide
and bearings, can be tilted out of operating position to a muller suitable for explosives. However, it will be
permit removal of ground materials. Also, the axis understood that the utility of the muller disclosed herein
of the muller wheel is obliquely disposed when the wheel 20 is not restricted to the grinding of explosive materials.
is in operating position so that its bearings can be iso- Wherever a muller, capable of grinding under exception-
lated from the muller pan and to one side of it. ally fine control of purity and cleanliness, is required,
In the manufacture of many explosives, it is neces- for example, in manufacture of certain foods, drugs,
sary to reduce a granular material to some predeter- cosmetics, and chemicals, the present invention will have
mined mesh fineness. Those familiar with the art of 25 particular application. In addition, the muller construe-
explosives manufacture know that the grinding of such tion shown is susceptible to modification even for crude
materials is often accompanied by serious hazards of work that will provide an exceedingly reliable muller in
explosion. For example, certain explosive components which the moving parts are well protected from the se-
can be ground safely as long as they are in pure form vere wearing conditions usually prevailing in the en-
and are shielded from any sparks in the environment. 30 vironment of a muller, because of the tendency of pow-
The lightest trace of impurity, however, serves as a dered materials to find their way into the bearings of the
potential detonating agent which can be ignited fairly apparatus.
easily, and will serve as a primer for the entire batch It is another major object to provide a muller in which
contained within the muller. The total quantity of .the the muller wheel bearings are located to one side and
impurity need not be large; on the contrary, it niay be 35 not over the pan in which grinding is taking place. It
very minute indeed, since a batch which is almost en- is an associated object to provide a muller in which oil
tirely pure may be exploded by a relatively small, local drippings fall outside the pan, and in which a pan cover
primer explosion of the impure portion. with a packed opening in the side thereof for the muller
An obvious and common source of trouble in such wheel shaft can be used to seal the muller bearing from
mullers is the oil used to lubricate the moving parts 40 the pan and its contents. Another important object of
thereof. A drop or two of oil, which is inadvertently the present invention is to provide a muller construction
permitted to flow down a shaft or the like into the ma- well suited to isolation of the electric motor from the
terial being subjected to grinding, may have disastrous apparatus or the room in which it is operated.
consequences. On the other hand, it is dangerous to, 45 It is still another object of the present invention to
risk the heating of machine parts which may occur if provide a muller pan which can be completely sealed by
they are allowed to run continuously without proper packing means during operation of the muller. ·
lubrication. Still another object of the invention is to provide a re-
In addition to lubrication oil and grease, other stray liable muller apparatus extremely resistant to excessive
impurities which· may be present in the air, or may be 50 bearing wear from the powdered material in the muller.
dropped from the hands or clothing of an operator, Finally, an important object of the invention is to pro-
may fall into the muller apparatus and produce a dan- vide a muller in which the muller wheel and pan and
gerous mixture with the explosive granular material. cover assembly can be readily lifted completely clear
Most mullers are so constructed that it is very difficult of the pan in order to facilitate removal of the pan and.
to cover them while they are in motion, and to shield the 55 the batch of ground material contained therein.
muller pan from all contaminants. . The foregoing and other objects are accomplished by
Another requirement for any muller which is to op~r- means of a muller wheel, which is in tum rotatably
ate satisfactorily for the purposes of explosives· rilanil- mounted in a bearing-carrying cradle which can be tilted
facture is that it be completely isolated from the electric about a horizontal axis. Complexities of drive for the
motor providing the power for the muller drive. . Sparks 60 muller are avoided by driving the table upon which the
from the motor would produce an obvious explosion haz- muller pan is carried and causing the muller wheel to
ard. rotate by engagement of its grinding surface with the
An objectionable feature found not only in mullers bottom of the muller pan. The general principles of
for explosives, but in other mullers also, is the difficulty the invention will best be understood from a detailed
of removing a heavy batch of ground material. Many 65 and specific description of one specific embodiment, which
mullers are so constructed that the pan cannot be re- is illustrated in the accompanying drawings in which:
moved from the muller apparatus when it is. full; in- Figure 1 is a plan view of a muller apparatus built
stead, the material must be shoveled out by manual means; according to the invention, but with the pan cover re-
This type of handling is particularly unsuited for ex- moved in order to reveal in plan the interior of the muller
plosives. 70 pan and various apparatus therein; and
Many of the foregoing objectional features can be Figure 2 is a side elevational view, partly in section, of
overcome by using a muller wheel which is rotated about the apparatus of Figure 1.