Cutting drum with percussive bits

Details Cutting drum with percussive bits Cutting drum with percussive bits

1998-11-25

2001-03-20

Lillis, Eileen D. (Department: 3673)

Mining or in situ disintegration of hard material

Cutter tooth or tooth head

Percussive tooth or bit

C299S039400, C299S037300, C299S069000

Reexamination Certificate

active

06203113

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a rotating milling machine for use in processing rocky materials, especially concrete, asphalt, and masonry.
Machines of this type are used, among other things, for milling off walls, floors, or roadways, or for milling grooves into such structures.
An acceptable degree of progress in milling, particularly in harder materials such as concrete, can generally be achieved only via the use of very heavyweight machinery, having a high level of driving power and a high rate of advance, and producing a severe vibration of the machines and a high degree of abrasion of the milling chisels.
For this reason, attempts have long been made to provide these chisels with a percussion effect similar to that of a percussion drill or a jackhammer. In the patents DE 196 31 659 and DE 196 34 514 this was achieved for the first time. Here, in the case of the compressed air design of the former patent, the cost of producing the compressed air, and thereby the overall costs, are still relatively high, the force of impact, especially in the case of smaller dimensions, is limited, and a high level of power is required for generation of the compressed air, due to a low level of efficiency in the generation of compressed air and losses through leakage in the milling cylinder.
In the latter patent, the force of impact is very limited, and the cams are eroded relatively rapidly, or they become overheated due to friction losses. The percussion principle in this patent is more like that of a percussion drill than that of the more effective jack hammer.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a substantially higher level of percussion force with a lower level of impact driving power, and with a more simple, and thus more cost-efficient, lighter, and more fail-safe design.
The object is attained in accordance with the invention in that in some or all of the chisels a percussion effect is induced via pendulums rotating on the inside of the milling cylinder.
This design provides the following advantages over state-of-the-art designs:
(a) Impact force and frequency levels that are many times higher can be realized with the same structural dimensions, and at a lower production cost, and thereby at a lower overall cost. With a milling diameter of 550 mm and a milling width of 25 mm, this new design easily achieves an impact speed of 27 m/s with an impact mass of 1 kg. The impact frequency thus also easily reaches 4,000 beats per minute or more. This corresponds to a force of impact of 47 kw, probably too great for this width. Known-in-the-art systems allow an impact mass of approximately 0.3 kg at an impact speed of 7 m/s and a driving force of more than twice the force of impact.
(b) The percussion drive mechanism alone is more than twice as efficient, while the impact force directly supports the rotating power of the milling cylinder, and thus enables a lower level of driving power for the entire machine. This means smaller dimensions, and lower weights mean less in transportation costs, and enable expanded applications. Lower power and weight requirements mean less damage to the environment and lower operating costs.
(c) With a simpler design, a higher level of impact power and, more importantly, a safer, more trouble-free operation are achieved.
(d) The system is also substantially less susceptible to contamination, since it is not dependent upon narrow fits and practically particle-free guide borings, as known-in-the-art designs are.
In accordance with the invention, a milling cylinder
5
equipped with chisels that lie on the outside of the cylinder is rotated, while on the inside of the milling cylinder, a shaft that is equipped with pendulums rotates at a different rpm and/or direction of rotation.
The frequency of impact is derived from the relative rpm of the milling cylinder
5
and the pendulum shaft
4
, and from the number of pendulums.
Aside from when they are in contact with the material being milled, no percussion effect is induced in the chisels, which serves to limit wear and tear on the parts of the machine. If the acceleration due to centrifugal force of the chisels in accordance with claim
14
is substantially higher than the acceleration due to gravity of approximately 9.81 m/s{circumflex over ( )}2, then the chisels are pushed to their outer stop points, where they cannot come into contact with the pendulums.
Only when the chisels are embedded in the material being milled
9
are they pressed against their inside stop devices, causing the pendulums to strike against the chisels.
In accordance with claim
7
, the point of impact of the pendulum, relative to the direction of rotation, lies behind the line that connects the point of rotation of the shaft and the point of rotation of the pendulum. Thus determined, the pendulum turns, at the same pendulum angle, farther toward the inside, away from the chisel, to smaller radii. The advantage of this is that only smaller pendulum angles must be allowed in order that the pendulums, after the striking the chisels, can rotate past the chisels more rapidly and safely and will also reach their initial outer position more rapidly, and thereby will strike the outer stop device at a lower speed, thereby causing less wear and tear on the outer stop device for the pendulum.
To better understand claim
12
, it is helpful to consider the concept of the game of billiards. Depending upon the angle of impact, the ball that is impacted is struck in a direction
10
that differs from the direction
11
of the approaching ball.
Further details and advantages of the object of the invention are provided in the following description of the attached diagrams, in which preferred exemplary embodiments are illustrated, with the key details and individual components indicated. These show:


REFERENCES:
patent: 3743033 (1973-07-01), Taylor
patent: 3778106 (1973-12-01), Taylor et al.
patent: 3778113 (1973-12-01), Taylor
patent: 4366991 (1983-01-01), Hilshorst
patent: 5335977 (1994-08-01), Morrell et al.
patent: 672 659 A5 (1989-12-01), None
patent: 32 32 985 A1 (1984-03-01), None
patent: 32 46 118 (1984-06-01), None
patent: 33 01 671 C2 (1984-07-01), None
patent: 30 22 317 C2 (1985-09-01), None
patent: 32 49 690 (1986-08-01), None
patent: 19634514 (1997-07-01), None
patent: 0825003A2 (1998-02-01), None

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