Patent Application
20060081730
This nonprovisional application claims priority under 35 U.S.C. ยง 119(a) on German Patent Application No. DE 2004051217, which was filed in Germany on Oct. 20, 2004, and which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to an apparatus and a cutting unit for comminuting large pieces of cuttable material
2. Description of the Background Art
The purpose of industrial comminuting of material is oftentimes the fabrication of an intermediate product of defined shape and size, which is subsequently used as source material for the production steps of another production process. The production of granulate is an example, which is further processed in extrusion devices. The uniformity in shape and size are thereby the determining factors for the quality of the intermediate product.
The operators of comminuting devices are regularly presented with a challenge, when large pieces of material, for example, bales of rubber, are to be reduced to a relatively small end size, for example, to granules. Generally, multi-step comminuting is used for applications of this kind, whereby several cutting mills of varying size, one behind the other, are provided. The end product of the previous cutting mill thereby serves as the source material for the next cutting mill. In this way, a step-by-step comminuting of the material to the desired end size takes place.
The advantage of this method is that it yields high-quality granulate material. The disadvantages, however, are economical because several cutting mills have to be on hand. Due to the need and operation of several comminuting machines, there are, apart from the expenditures for their acquisition, maintenance, and operation, additional costs for the required surge tank capacities, means of transportation, and the additional space requirement.
To circumvent these disadvantages, devices have been made for special applications, for example, the comminuting of bales of rubber, which make it possible to comminute inside a housing the original material to the desired fineness of the end product. Devices of this kind have a rotating, cylinder-shaped rotor provided with axially oriented knives, which are evenly distributed around its periphery moving in a mutual blade flight circle. For the purpose of comminuting, the knives interact with stator knives, which are tangent to the blade flight circle. A perforated strainer is arranged over a partial area of the blade flight circle, via which the sufficiently comminuted material is discharged. During comminuting, the material remains in the cutting area of the knife until the particles are small enough to pass through the perforations of the strainer. In other words, in devices of that kind, the pre and post comminuting is done simultaneously with one piece of equipment with the same comminuting tools.
One of the advantages thereof is the need for only one comminuting device, which in contrast with the previously described multi-step variation is a cost and space-saving way of comminuting. However, the consequence of the one-step comminuting is that the entire comminuting process, that is, coarse and fine comminuting, is done by the same comminuting tools. However, since the individual comminuting steps have different objectives due to different initial conditions, it would be desirable in view of quality improvement to adjust the respective comminuting tools to the specific requirements of each comminuting step by using particularly suitable comminuting tools. This would not be possible with one-step comminuting, which is the reason why, from a technical viewpoint, one-step comminuting is a compromise.
An additional factor in the comminuting of bales of rubber or extruded synthetic hollow sections is that for the initial cutting of the material, very high forces must be applied to make comminuting possible. During that process, high impact forces are applied to the material by the comminuting tools. These cause extremely high mechanical stress, which must be taken into consideration in regard to the dimensional design of the device. Furthermore, this way of comminuting characteristically generates considerable noise, which makes it necessary to encapsulate the device to protect the personnel.
Additionally, the resistance encountered at the initial cutting of the material by the comminuting tools causes a reduction of the rotational speed of the comminuting rotor. To offset this loss of rotational speed, a strong short-term power surge to the drive motor occurs. Since energy costs are calculated not by the average energy consumption but by peak demand, this leads to a superproportional increase in energy costs.
It is therefore an object of the present invention to comminute large pieces of material in an economical way, without having to make sacrifices with regard to the quality of the end product.
The invention is based on the idea to carry out the comminuting of the material in two steps, whereby a pre-comminuting device is arranged in a material delivery unit of the fine-particle comminuting device. In this way, it is possible to combine the benefits of two-step comminuting with the benefits of a one-step comminuting device.
As a result of the step-by-step comminuting of the material, the determining factors for each comminuting step remain constant for the most part during the comminuting process. By introducing material that is defined in shape and size, it is possible to adjust the comminuting tools for each comminuting step to the characteristics of the material and the specific requirements for the intermediate or end product to be fabricated.
The result is primarily a high-quality comminuted product, which both in shape and in size remains within narrow tolerances. This is critical for its usability as a source material in other production processes, for example, in extruding.
Furthermore, it makes it possible to always operate a comminuting device of the present invention at its optimal capacity. In this way, performance fluctuations are very considerably reduced, which is noticeable in the largely constant energy intake of the device. Peak consumptions, which are the basis for calculating energy costs, are mostly evened out, which makes an economical comminuting operation possible.
The average comminuting efficiency of the pre-comminuting is not higher than the average comminuting efficiency of the fineness comminuting. At continuous feeding, the comminuting devices of both comminuting steps thus manage the same material throughput. The fluctuation-deficient comminuting thus achieved results in an evenness of the mechanical stress and makes it possible for the designer of devices of the present invention to avoid overdimensioning on account of load peaks. Thus, devices of the present invention can be constructed smaller and more compact at comparable machine capacities with the benefit of lower production costs and fewer spatial requirements for installation.
In a further embodiment of the present invention, the machine performance of the pre-comminuting device is regulated in dependence from the machine performance of the fine comminuting device, for example, in dependence from the power intake of the drive motor. In this instance, the pre-comminuting device not only has a comminuting function but also a feeder function to assure that the device for fine comminuting operates at optimal capacity.
In a further embodiment of the invention, the fine-comminuting device is preferably provided with a knife that cuts the material in the supply channel into pieces of defined size by linear form-feeding. In contrast to the rotating knives of a cutting mill, this method allows comminuting at a low cutting speed. The beneficial result is that noise emissions occur only to a marginal degree. Furthermore, the knife cutting into the material does not subject the material to impact energy, which due to heat transfer would otherwise lead to a heating of the material and high wear and tear.
Preferred is also the arrangement of the knife inside a slidable frame. The frame stabilizes the knife while cutting through the material, thus assuring a precise cut even at high cutting frequency.
In a further embodiment of the invention, the cutting unit is provided with a frame-shaped knife guide for the knife, that is, for the knife frame. The knife guide can be thereby inserted into the supply channel, which it replaces in this segment. In this way, even existing comminuting devices can be retrofitted in a simple way with a pre-comminuting device.
It is thereby beneficial if part of the knife guide, against which the knife moves, also forms a back stop for the knife blade. The back stop can be a self-contained, replaceable component that is manufactured with high precision and is mounted to the knife guide without tolerance. This assures a precise interaction between the knife and the back stop and thus a total severance of the material.
To operate the knife, a spindle drive or a hydraulic-driven cylinder piston unit is preferred, as this allows a power or path/direction-dependent control of the knife. Beneficially, the power to activate the cutting motion of the knife is derived from two asymmetrically arranged cylinder piston units. The symmetrical loading averts a tilting of the knife, that is, the knife frame during the form-feeding, thus increasing operational safety.
In a particularly beneficial embodiment of the invention, a retaining element for the material is provided below the knife. The retaining element thereby assumes two functions. On the one hand, it keeps the material in a cutting position during the comminuting process. On the other hand, by setting the distance to the knife, it determines the size of the parts to be cut off the material. In order to make the size of the parts to be cut adjustable, the distance between retaining element and knife is adjustable, according to an embodiment of the invention.
Furthermore, it is preferable to couple the activation of the retaining element to the motion of the knife. With a linearly slidable retaining element, this can be achieved by arrangement within the same frame that also serves for the mounting of the knife. Thus, both the knife and the retaining element can be actuated with only one drive in a most simple way.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
The comminuting of the material is carried out via two stator knives 7, which are mounted to the housing 2 and are positioned diametrically opposed to one another in relation to the axis of rotation, the cutting edges of which are tangent to the blade flight circle 6. The lower area of the blade flight circle 6 is covered by a perforated strainer 8, through which the sufficiently comminuted material exits the cutting area of the cutting mill 1. Downward from the housing 2, a funnel-shaped material discharge 9 is connected, via which the comminuted material is conveyed from the cutting mill 1 for further processing.
The upper circumference of the cutting rotor 3 is enclosed by a funnel-shaped housing part 10, which is adjacent to the supply system 11 for the material.
The upper segment of the supply system 11 is formed by an intake chute 12, which has a lateral opening 13. The material can be fed to the supply system 11 via the opening 13. The preferred material in
The intake chute 12 extends downward toward the cutting mill 1 in the shape of a rectangular supply channel 15 and connects with a cap-shaped end piece 16 to the housing part 10 that is open on the top. Via flange connections, a cutting unit 17 is interposed in the supply channel 15 and is thus integrated in the supply system 11.
The detailed construction of the cutting unit 17 is illustrated in
Inside the knife guide 18, a knife frame 22 is slidably mounted. The knife frame 22 includes lateral longitudinal spars 23, the ends of which are connected to one another via a crossbeam 24 and a yoke member 25. The yoke member 25 thereby extends beyond the longitudinal spars 23 thus forming a projecting length on both sides.
Commencing at the yoke member 25, the upper side of the knife frame 22 is covered by a knife 26, the blade 27 of which ends approximately at half-length of the knife frame 22. Likewise, commencing at the crossbeam 24, the lower side of the knife frame 22 is covered by a retaining element 28, which with its free edge 29 also ends in the middle of the knife frame 22. Thus, the knife 26 and the retaining element 28 are arranged in plane-parallel planes on top of one another, and the free edge 29 and the blade 27 are aligned with one another in a vertical projection to the frame plane. In this way, the knife frame 22 forms a kind of sled, the one frame half of which is solely taken up by the knife 26, and the other frame half is occupied in a parallel plane and at a distance by the retaining element 28.
The knife frame 22 is slidably arranged within the linear guides of the knife guide 18 via its longitudinal spars 23. To drive the motion of the knife frame 22, two hydraulic cylinder piston units 30 are provided. Their cylinders are fixedly attached to the outer sides of the longitudinal sides 19, whereas their slidable pistons are attached to the projecting segments of the yoke member 25. By activating the cylinder piston units 30, the knife frame 22 can be moved linearly to and from, as indicated by arrow 31. As an alternative, it is also possible to swivel the knife 26 in the knife plane around an axis of rotation that is vertical for this purpose.
a to 4c are greatly simplified illustrations of the above-described invention, with the aid of which the method of operation of the cutting unit 17 is therebelow described.
As indicated by the arrow 32, a bale of rubber 14 is conveyed lengthwise through the supply channel 17 to the area of the cutting unit 17 until it comes to rest on the retaining element 28.
b shows the start of the comminuting process. By running in the cylinder piston units 30, a movement of the knife frame 22 in the direction of the arrow 33 takes place. The knife 26 thereby penetrates the bale of rubber 14. Simultaneously, the retaining element 28 begins to clear the opening 20.
By sustained advance of the knife 26, the cutting unit 17 is put into a second end position. This position, which is achieved by completely running in the cylinder piston units 30, is illustrated in
Once a cutting cycle is completed, the cutting unit 17 is returned to its first end position by extending the cylinder piston units 30, and thus to the starting position for the next cutting cycle. Shifting between two end positions, the knife frame 22 thus executes a sled-like linear movement transversely to the supply channel 15 during the comminuting process, whereby for the feeding of the cutting unit 17, the opening 20 is cleared by the knife 26 and closed by the retaining element 28, and for cutting and further conveying of the material, the opening 20 is closed by the knife 26 and opened by the retaining element 28.
Further, the relation movement between the knife 26 and the retaining element 28 forms a shield. Thus, during the commuting process by the cutting mill 1, the material 14 is substantially prevented from entering the supply channel 15 above the cutting unit 17. Therefore, supplemental filters or retaining systems are not required in order to prevent the material 14 from escaping the supply channel 15 through the opening 13.
Lastly,
The free end of the cantilever 42 supports a console 43, on which a stepping motor 54 is arranged, with the aid of which the spindle 45 is relocatable during rotation. A knife holder 47 having a threaded bore is positioned on the spindle 45 and is movable along the spindle 45 during its rotation. The knife holder 47 supports the knife 48 in a parallel orientation to the cross section plane of the supply channel 15. At the level of the knife 48, a suitable opening 55 is provided in the knife guide 41 for the passage of the knife 48. In addition, a rigid lever 49 extends from the bottom side of the knife holder 47.
On the side of the cutting unit 40 that is opposite the cantilever 42, there is a stationary horizontal pivot bearing 50, which extends vertically to the plan view. A retaining element 51 is pivotably mounted thereon, with a triangular shank 52 attached to its bottom side. The rigid lever 49 and the triangular shank 52 are flexibly attached to one another via a push rod 53.
The illustration in
By activating the stepping motor 54, the knife holder 47 is moved along the spindle 45 in the direction of the bale of rubber 14, whereby the knife 48 cuts into the bale of rubber 14. Simultaneously, a force is applied to the shank 52 via the push rod 53, which causes a gradual pivoting up of the retaining element 51. When the bale of rubber 14 is completely severed by the knife 48, the retaining element 51 opens up the entire cross section of the supply channel 15 so that the severed part of the bale of rubber 14 can pass on to the second comminuting step.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| DE102004051217.5 | Oct 2004 | DE | national |
