Mining or in situ disintegration of hard material – Cutter tooth or tooth head – Cleansing fluid passage
Patent
1992-09-22
1993-08-10
Bagnell, David J.
Mining or in situ disintegration of hard material
Cutter tooth or tooth head
Cleansing fluid passage
175424, E21C 3518, E21C 3522
Patent
active
052342581
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a cutter for extraction machines.
The German patent 39 20 205 describes an arrangement of a nozzle on a chisel holder in which the nozzle insert is stepped. A small annular sealing element is provided at the foot of the nozzle insert and the nozzle insert is pressed onto the sealing element by application of a holding device. This small sealing element has been found to be inadequate.
A chisel of the type to which the invention relates is disclosed, for example, in the German Offenlegungsschrift 40 15 022.
In this known chisel, a pressure seal is provided in the channel of the chisel holder and projects beyond the upper edge of the chisel holder. However, in the assembled condition of the chisel holder and the chisel head, the pressure seal projects into a matching bore in the support flange of the chisel head. The pressure seal acts as a gap bridging component and has a water guide channel which leads to the actual nozzle.
Thus, in this known arrangement, the small but unavoidable gap between the upper edge of the chisel holder and the lower side of the support flange of the chisel head is bridged by the pressure seal. To provide adequate sealing, the pressure seal must consist of a relatively elastic material and it has been found that this arrangement has certain drawbacks.
One drawback is that the pressure seal does not resist a high water pressure such as, for instance, of the order of 200 bars, but pushes into the gap where it bursts.
When the chisel is changed, the pressure seal projects significantly beyond the upper edge of the chisel holder, i.e., the sealing is exposed. The upper side of the sealing element can here be damaged by scratches or the like so that, upon reinsertion of a new chisel, the entire seal comes into question.
In the known arrangement, the nozzle opens at the upper side of the foot portion of the chisel head and here, during operation, this nozzle is constantly damaged. Thus, the nozzle must be frequently changed if, indeed, it is not so badly damaged that the chisel must be changed also.
Since the pressure seal must engage in a corresponding receiving bore of the chisel and, in assembled condition, must here also seal by means of pressure, difficult sealing surface machining of a bulk part such as constituted by the actual wear chisel is required. As a result, the known arrangement is costly.
That the actual nozzle in the known arrangement is installed via a thread is likewise disadvantageous since substantial costs are involved in production of the thread and the thread can be readily damaged.
It is an object of the invention to provide a cutter for extraction machines, i.e., a chisel with nozzle, in which the actual nozzle insert is arranged within the chisel holder or the chisel head such that, notwithstanding a change of the chisel, damage to the seal is no longer possible, and such that bursting of the pressure seal is prevented even at high pressures.
This object of the invention is achieved by the teaching of the main claim.
Advantageous embodiments are described in the subclaims.
In other words, it is proposed that a receiving bore be arranged in the actual chisel holder, i.e., a longer-lived component, and that the receiving bore accommodate a pressure seal which, however, does not project beyond the upper edge of the chisel holder when the chisel is inserted. A tubular portion of a gap bridging component made from a relatively rigid, i.e., relatively inelastic, plastic engages in the pressure seal which has an annular configuration. This plastic absorbs the pressures acting in the region of the gap without difficulty and, upon insertion in the pressure seal, presses the pressure seal tightly into the receiving chamber of the chisel holder. This gap bridging component then projects beyond the foot of the chisel head and this gap bridging component receives the actual nozzle. The nozzle is now located at a distance from the upper side of the foot portion of the chisel head. Consequently, damage during operation of the chisel is virtually elim
REFERENCES:
patent: 4705321 (1987-11-01), Hedlvnd
Bagnell David J.
Komotzki Michael
Kontler Peter K.
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