Tool changing – Process
Reexamination Certificate
2003-05-15
2004-06-29
Wellington, A. L. (Department: 3722)
Tool changing
Process
C483S031000, C483S057000, C029S426100, C144S172000, C144S373000
Reexamination Certificate
active
06755772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method, an arrangement, and a device for automatically changing knife units of a knife ring of a knife ring slicing device, wherein a knife changing magazine provided with resharpened knife units is moved into a defined knife changing position relative to the knife ring in which at least some of the knife receptacles in the knife changing magazine are axially aligned with at least some of the knife receptacles in the knife ring. In particular, the invention relates also to a device for comminuting material especially in the form of a knife ring slicing device, comprising a tool ring, which has uniformly distributed about its circumference tool receptacle for the comminution tools, and comprising a unit for pushing out the comminution tools, arranged on the periphery of the device, wherein the unit for pushing the comminution tools comprises several pushing elements which are axially aligned with the comminution tools to be pushed out and are advanced and retracted axially into and out of the tool receiving units of the tool ring by means of an advancing drive. The invention furthermore relates to a knife changing magazine for automatically changing the knife units of a knife ring, wherein the knife changing magazine has areas with receptacles for the knife units of a knife group to be exchanged at once.
2. Description of the Related Art
For producing wood strands as the starting material for manufacturing board-shaped structural components, slicing machines are known whose comminution tools are arranged in a stationary or rotating knife ring and operate relative to a stationary or rotating abutment. The strands produced in this way pass in the radial direction through the knife ring. The quality of the final product is greatly affected by the quality of the strands used as the starting material. The strands should have cut surfaces as smooth as possible and also identical dimensions. In order to ensure a constantly high quality of the strands, it must be ensured that the comminution tools always have sharp cutting edges in order to achieve comminution by means of cutting and, to a lesser degree, by squeezing or breaking or grinding. Sharp comminution tools have also the advantageous side effect of a reduced electric energy consumption of the comminution machine.
During operation of a comminution machine, the comminution tools are subjected to natural wear. The degree of wear depends on various factors, for example, the type of wood and moisture contents of the wood of the starting materials as well as the advancing speed and circumferential speed of the cutting tools as well as on constructive parameters such as the cutting angle and the material properties of the comminution tools. The strongest wear effect can be observed on the cutting edges of the comminution tools which become more and more blunt with increasing service life so that during the generation of wood strands a smooth cut can no longer be ensured. This causes at the same time a decrease of the strand quality, an increase of the undesirable proportion of fine particles in the wood strands and, as a result of this, an increase of the required amount of bonding agent as well as an increase of energy consumption of the slicing machine.
In order to avoid these disadvantages, it is required to perform a knife exchange in regular intervals wherein the worn or spent comminution tools are replaced by resharpened ones. Under regular conditions such a knife exchange is carried out in time intervals of three to eight hours. Since all comminution tools of a knife ring must be exchanged in such a knife exchange operation, this requires a considerable temporal expenditure which causes long downtimes of a comminution machine. In connection with known methods and devices for exchanging the comminution tools, which are performed manually or semi-automatically, a knife exchange takes approximately 20 to 40 minutes. For an average service life of the comminution tools of four hours, this causes a production loss of three hours per day. Accordingly, the resulting product loss relative to a nominal strand production output makes it necessary to design the comminution device for higher comminution output in order to ensure the continuous further processing of the produced strands in the subsequent processing steps. This entails providing larger bunker capacities as a buffer for bridging the production loss caused by the knife exchange.
In order to circumvent these disadvantages, attempts have been made to shorten the duration for a knife exchange. From German patent application 199 21 383 A1 and U.S. Pat. No. 5,313,696, a method and a device for changing the comminution tools of comminution devices are known in which the complete knife ring of the comminution device is removed and replaced by a second knife ring furnished with resharpened comminution pools.
For removing the worn or spent knife ring according to German patent application 199 21 383 A1, a tool exchange carriage is used which is moved in front of the end face of the comminution device and provides together with attachments of the comminution device a path on which the knife ring, detached from its fastening means, can be pulled axially out of the housing of the comminution device onto the carriage.
For demounting the knife ring, U.S. Pat. No. 5,313,696 suggests to arrange it, including its attachment components, its positioning components, and its drive components, on a support whose path, extending parallel to the axis of rotation, enables an axial movement of the complete comminution unit before the knife ring is removed by means of a crane and replaced by a newly furnished knife ring.
The disadvantage of these solutions is that for a knife exchange the complete knife ring must be exchanged. In addition to requiring an additional knife ring, this results in a great technical expenditure, for example, for a tool change carriage and the elements connected thereto for coupling the carriage or for a support for axially pushing out the complete comminution unit. The labor expenditure for mounting and demounting the knife ring must be added to the time required for exchanging the knives of the knife ring so that this solution is not satisfactory with respect to economic efficiency.
How the actual change of the comminution tools, i.e., their mounting in and demounting from the knife ring is carried out, is not disclosed in these prior art references.
Suggestions in this respect can be taken from German patent 41 14 840 C2 describing a method and a device for exchanging the knives of a knife ring wherein here the knife ring must first be demounted from the comminution device and must be placed into a knife changing device. In this knife changing device an automatic knife exchange takes place by means of a magazine in which the knives arranged in the knife ring, after having been released from their fastening means, are first pushed out individually and sequentially from the knife ring and are then transported on a carriage axially to the magazine where they are placed in the radial direction into the magazine.
In comparison to the prior art known at the time the invention according to 41 14 840 C2 was made, this method and this device provided a significant technological advance. However, this type of knife exchange is also possible only with the knife rings being removed from the comminution device wherein the individual knives are successively exchanged. The simultaneous exchange of several knives is not possible with this method and this device.
From German patent 33 09 517 C1 a knife exchange is known which is possible with the knife ring mounted in the comminution device. For this purpose, magazines are arranged at the end face of the knife ring which are in the form of a roll for steel strip knives or a cassette for disposable (single-use) knives, wherein the knives are moved by means of an axially acting advancing device into the knife ring. These solutions are said to enable a knife exch
Kueffner Friedrich
Pallmann Maschinenfabrik GmbH & Co. KG
Ross Dana
Wellington A. L.
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