Hammer mill

Details Hammer mill Hammer mill

1999-05-12

2001-12-18

Rosenbaum, York (Department: 3725)

Solid material comminution or disintegration

Apparatus

With separation or classification of material

C241S189100

Reexamination Certificate

active

06330982

ABSTRACT:

TECHNOLOGY FIELD
This invention relates to a type of hammer mill, especially a rotary hammer mill generally used in the areas of feed processing, food processing and chemical industries.
BACKGROUND TECHNOLOGY
Nowadays, a variety of recognized existing types of mills generally include screens, hammers, rotors, machine body and motors. During operation, the motor drives the rotors, on which the hammers are rotating and crushing the material so that acceptable sizes of pulverized particles are discharged from the screen sieve.
Such hammer mills usually have the deficiency as described below:
1. They only produce coarse material (e.g., poultry feed with screen sieves of 1, 2, 3 and 4 mm in diameters) and are incapable of producing fine material (e.g., aquatic feed with screen sieves of 40, 50, 60, 70, 80, 90, 100, 120, and 140 meshes, or more.)
2. They may cause the finished material to be uneven in particle size.
3. These types of hammer mills are inefficient.
The major reasons for inefficiency include:
A. The screening and crushing capability of the hammer mills is relatively inadequate so pulverized particles will not be discharged promptly and may cause repeated cycling of the material for processing to the acceptable sizes, with a result that the fine particle ratio is increased, uneven sizes of finished material are produced and the power consumption is more.
B. Generally, the blades of the screened hammer mill have dual functions of crushing and serving as a power source to discharge the particles through the screen sieves. The hammer blades, as the sole power source in the screening process, may be blocked by multi-layers of the material cycling near the surface, thereby limiting the push and extruding forces that are applied to the material through the screen. For coarse material with greater sizes and less layers of material cycling required, the acting forces of the hammer blades are effected on the surface of the screen, resulting in smooth discharge of the pulverized particles of the feed material whereas for the fine material, the diameters are far smaller than the clearance between the screen and the hammer and more material cycling is required, it is more difficult for the acting force of the hammer blades to reach the surfaces of the screen, thus retaining the material on the screen surface, such retention state of the material may cause blockage of the finished material. Hence such screened hammer mills are not able to process fine particles of the material with 40 to 140 meshes.
Previous improvement mades always focused the improvement on the physical factors such as screen shape design, screen construction, clearance between the hammer and the screen, aspirating system and the hammer configuration and so on, without considering the active power source with the screen and studing further. Several examples of the previous improvement are given below:
a. Improvement on shapes of the screen sieves—such as fish scaled sieves type of screens (refer to the article “Preliminary Report on the Effect of Scaled Screen Plate” as published on “Shanghai Feed” magazine Jan. 1994 in China.).
b. Improvement on extended screen surfaces—such as axially fed widening screen type of the hammer mill (refer to the article “Application on Improved Process of Model 91940-40 Economic Feed Hammer Mill” as published on “China Feed” magazine, Issue 1, 1995); and also the type of the hammer mill is shown in FIG. 4 of U.S. Pat. No. 4,114,817 (Harris) (Sep. 19, 1978) with such a feature that the surface area of the screen is increased by extending the axially screen width.
c. Further improvements are by having an increasingly rounded screen comer, increasing of screen surface and mounting method, such as vertical rotor type hammer mill with no aspiration installation (refer to the article “Application on Improved Process of Vertical Rotor Hammer Mill” as published on “China Feed” Issue 1, 1991; various axially feed designs of hammer mills; dipping type hammer mills; and also a type of hammer mill disclosed in FIG. 2 of U.S. Pat. No. 3,790,093 (Mcintyre) (May 2, 1974) has a screen development on the left side, which increases the surface areas, but the screen is considered liable to be blocked by larger size material at a section of the left side, thus failing to achieve the anticipated result. Moreover, this improvement is an eccentric feed design which fails to make full use of the forward and reverse rotation of the hammer, resulting in non-uniform wear of the hammers and the screen.
d. Improvement on aspirating system of the hammer—refer to the article “Design Improvement and Study on the Aspirating System of Hammer Mills—Non-aspirating Vertical Rotor Hammer Mill” as published on “China Feed” Issue 17, 1995.
e. Improvement on mounting with roll chain end-connected spring and hammer mill aspirating system with holes at the axial wall and air blow blades patented in China, China Patent No. CN 2156931 (Li Dayan) (Feb. 23, 1994) describes a type of vibrating screen. However, it is not a vibrating screen with an active power source, but the vibration is induced by material impacting screen surfaces with no control of vibrating parameters.
f. Improvement on clearance between the hammer and the screen—the improved clearance between the hammer and the screen of the mill is adjustable (in two steps), which is capable of processing the feed material with feed sizes of 0.8 to 4.0 mm in diameters. This improvement of hammer mill has extended the range of the material to be processed as compared to conventional mills, but is not applicable for the sizes of 60 to 140 meshes fine material.
In short, lots of improvements have been made on the hammer mills and have achieved certain results, yet no hammer mills in the world by then are capable of processing both coarse material (sieves 1 to 4 mm in diameters) and fine material sizes (40 to 140 meshes).
Abundant experiments have indicated that the improvement made on the active power source to the screen and proper selection of mounting of the special vibrating source and the vibrating parameters, e.g., vibrating direction, frequency, amplitude, etc., are the keys to solve the material blockage problems so that the screen will be no more solely effected by the acting force of the hammer blades, but rely on its independent discharging capability, which will have enough capability for screening the fine material particles.
SUMMARY OF THE INVENTION
The invention provides a screened hammer mill that is capable of processing both coarse pulverized particles (screen sieves 1 to 4 mm in diameters) and fine pulverized particles sizes (40 to 140 meshes) and also produces relatively even sizes of the material with higher efficiency.
The invention pinpoints a major design improvement given below based on the existing technical deficiency mentioned in the above paragraphs. The improvement of this invention is described as follows:
1. A hammer mill screen is enhanced with an additionally independent source for vibrating. The said vibrating source is attached to the screen, which includes the functions of motor, etc. The improved mounting is to install the vibrator at the center of the gravity of the screen apart from the machine body and the other reaction force of the vibrating source is suspended (free) so that no effect is made to the machine body by the vibrating energy produced in the processing. The vibrational direction of the screen of the rotor is upward and downward as well as leftward and rightward on the radial plane relative to the rotor with vibrating frequency and amplitude controllable.
Generally speaking, the screen and machine body of the conventional hammer mills may produce resonance and residual vibration when the motor is operating and screen vibration may be caused when the material is impacting the screen surfaces, yet hardly results in desired effect as it is essentially an inactive and passive vibration, of which the vibrating parameters are not able to be controlled. With an additional vibrating source, the passive vibration is turned out to be

Affiliated with

Also associated with

Rating

Hammer mill does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Hammer mill, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hammer mill will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2595159