Solid material comminution or disintegration – Processes – Miscellaneous
Reexamination Certificate
2001-08-29
2004-05-18
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
Miscellaneous
C241S036000, C241S073000, C241S082000, C241S243000, C241S285300
Reexamination Certificate
active
06736342
ABSTRACT:
DESCRIPTION
The invention relates to a method for comminuting chips in a comminuting space between a driven horizontal shaft, which can be rotated in both directions and is fitted with shearing elements, and assigned counter-shearing elements, with chips introduced from above being comminuted and discharged downwards via a perforated screening plate and blocking constituents, which cause the shaft to come to a standstill, being segregated after reversing the shaft. The invention also relates to two apparatuses for carrying out the method according to the invention.
The comminuting of chips in horizontal chip breakers is known from DE 94 18 904 U1. In this case, chips which are generated during the machining of workpieces made of metal, plastic or wood are comminuted in a comminuting space between two electrically driven shafts, the shearing cutters of which engage in one another during rotation, and are discharged via a perforated plate. If a coarse part becomes lodged between the two shafts, and consequently causes a standstill of the shafts, the shafts can be moved in the opposite direction of rotation by means of a corresponding controller. A blocking coarse part can then generally be removed by hand or magnetic parts can be removed by magnets from the comminuting space. Each time coarse parts are removed, standstills and consequently reduced throughput rates occur. Moreover, the use of personnel is necessary for this.
A vertical chip breaker for steel or metal chips with a coarse-part ejecting element is known from EP 0 717 663 B1. This single-shaft breaker comprises a receiving hopper and a downwardly adjoining grinding hopper with circumferentially distributed tearing blocks, past the tearing edges of which the tearing cutters attached to a rotating cutter head can be moved. Underneath the grinding hopper there adjoins a grinding mechanism. Provided in the lower region of the grinding hopper is a discharge channel for coarse parts, which can be opened by means of a powered channel slide. If there is a coarse part among the chip material, it lies on the grinding mechanism and is moved by the cutter head together with the chips in a rotating manner until blocking of the cutter head occurs. To eliminate the blockage, a slow reversing operation is initiated and the coarse-part ejecting element is opened, in order that the disruptive elements can be transported from the cutter head towards the discharge and through the latter.
A disadvantage of this configuration is that it cannot be used for horizontal chip breakers. Furthermore, if there is an impairment of the rotational movement of the cutter head, there is no differentiation here between dense clumps of chips and coarse parts or combinations of the two. Experience has shown that dense clumps of chips can also often lead to a blockage. These clumps are likewise removed here via the discharge and are consequently extracted from the comminuting operation.
The object of the present invention is consequently to provide a method and two apparatuses of the type mentioned at the beginning, including a horizontal chip breaker which differentiates the blocking constituents according to groups, for example dense clumps of chips or purely coarse parts, and assigns to each group a defined reversing operation and, if appropriate, discharge from the comminuting space by means of a coarse-part ejecting element.
To achieve the object, the invention provides a method in which the rate of change of the loading of the driven shaft fitted with shearing elements is sensed, the presence of blocking constituents being established on the basis of the sensed rate of change of the loading while taking into account the type, quantity and/or size of chip, and then the non-comminuted blocking constituents being ejected after one or more reversals of the shaft. When sensing the rate of change of the loading of the shaft fitted with shearing elements due to blocking constituents it is found that each type of constituent brings about a different rate of change of the loading. Hard, one-piece coarse parts, for example fragments of machined workpieces, produce a high rate of change of the loading. Very dense clumps of chips bring about a lower rate of change of the loading. For less dense clumps of chips, the value is lower still. At the same time, the various chip parameters have to be taken into account, since chips break more or less easily, depending for example on the material from which they are produced. If there is an operational disruption as a result of a blocking part, it can be automatically discharged by means of a coarse-part ejecting element by one or more reversing operations. Intervention by the operator is not necessary. The comminuting operation is continued again after the removal. For configurations in which the counter-shearing elements are attached on a second shaft, it may be advantageous to program the controllers of the shaft and countershaft in such a way that during the reversing operation one shaft is stationary or is reversed much more slowly than the other shaft. This counteracts any throwing out of the previously blocking constituents. Furthermore, it is more probable in such a sequence of movements that the blocking constituents are taken along by the faster shaft, and consequently are taken to the same side of the comminuting space.
The method according to the invention may be carried out in an advantageous way by sensing the acceleration of the shaft to sense the rate of change of the loading of the driven shaft fitted with shearing elements. Hard, one-piece coarse parts, for example fragments of machined workpieces, produce a high negative acceleration. Very dense clumps of chips bring about a lower negative acceleration. For less dense clumps of chips, the value is lower still. It goes without saying that the rate of change of the loading can also be sensed for example via the change in torque of the shaft by means of strain gauges. Depending on the load, in this case the rate of speed of deformation of the shaft would vary. Vibration-measuring instruments are also conceivable, since a blockage due to coarse parts would cause greater vibration than dense clumps of chips.
The method according to the invention may be carried out in such a way that, on the basis of the established acceleration profile, the constituents causing a blockage are subdivided into at least two categories, the constituents being moved more or less frequently by reversing of the shaft, and either passed on in a comminuted state or thrown back in an uncomminuted state, according to the relevant category.
Subdivision into categories allows an optimized program sequence to be devised for each type of constituent in the case of blocking constituents. For instance, compacted clumps of chips which cause blocking can be recognized as such on the basis of the relatively low negative acceleration caused by them. Sustained repeated reversing with a closed coarse-part ejecting element may follow, intended to comminute the compacted clump of chips. At the end of the reversing operation, however, still existing dense remains of clumps can be discharged by means of the openable coarse-part ejecting element. Blocking coarse parts form another category. Coarse parts may be, for example, fragments of machined workpieces or screws. These coarse parts abruptly bring about a high negative acceleration when there is a blockage. Since it is not possible for constituents of this type to be comminuted by the shearing elements, a short reversing operation with the coarse-part ejecting element open is initiated in order to eject the coarse part as quickly as possible.
It may be advantageous in the case of the method according to the invention to arrange the categories according to increasing negative acceleration, the frequency of reversal decreasing from category to category with increasing negative acceleration. The more solid a blocking constituent is, the higher the negative acceleration in the case of a blockage and the lower the probability of this constituent being
Calfee Halter & Griswold LLP
Mayfran International B.V.
Rosenbaum Mark
LandOfFree
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