Felt needle

Textiles: manufacturing – Textile product fabrication or treatment – Fiber entangling and interlocking

Reexamination Certificate

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Reexamination Certificate

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06233797

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a felt needle to be fastened to a needle board and is of the type which has an elongated needle body that includes a clamping part and a working part which is provided with hooks along its length. The clamping part has a larger diameter than the working part. The felt needle further has a transitional part formed between the working part and the clamping part. The transitional part comprises a region whose diameter decreases from the size of the clamping part diameter to the size of the working part diameter.
For the production of felt, loose fibers that are arranged in a random order one above the other are guided through a machine, between a stripper plate having many holes and a base plate, which is also provided with holes. This fiber blend is repeatedly punctured with a larger number of special needles (felt needles). In the process, these felt needles cause a mutual bonding of the fibers, so that the fiber band gradually becomes more compact and, in the final analysis, a tight felt is produced. In addition to natural fibers and synthetic fibers, recycled fibers are also used. However, these generally have a higher tendency to adhere to the needles and form deposits.
Deposits are formed following a certain period of time during which the feltproducing machine is in operation. The deposits can accumulate on the needles, such that the needles can no longer penetrate the holes in the stripper plate. These deposits cause needle breaks and loss of production. As soon as the depositing process starts, the flow of air between the needles is negatively influenced, thereby causing the deposits to build up even faster. In order to clean the needles, the production must be interrupted. Needle breaks frequently occur during the cleaning.
The material is compacted during the needle-punching process. At the beginning, meaning prior to the needle-punching process, the material is relatively loose and voluminous. Once the needle with its shank region or the intermediate region penetrates the material, it produces holes with the diameter of the shank or the intermediate section, which is larger than the diameter of the working part. This results in a poor surface quality of the felt.
Felt needles with a long, straight shank are known from the German Patent 1760440 C3. The upper end of the shank is angled so that it can be clamped into a needle board. At the other end, the shank is tapered to form a reduced cross section and is furthermore provided with hooks. This section forms a working part, which is used for felting the fibrous web.
The transition between the working part and the remaining shank that serves as clamping part is relatively steep.
The German Published Patent Application 3704471 A1 discloses a device for needle-punching a mineral fiber web. The felt needles that are fastened to a needle board extend parallel to each other away from the needle board and through corresponding openings in a stripper plate. A gap forms between this plate and a base plate that is also provided with openings for the felt needles. The fibrous web is guided through this gap. The felt needles have a cylindrical shank that is angled at the top and is relatively thick. A section of this shank is held in the needle board. A transition region, which is barely longer than the diameter of the shank region, is formed between the clamping part and the toothed working part.
Deposits can form on the cylindrical shank.
German Published Patent Application 2222881 discloses a forked needle with a toothless working region. This working region is connected via a conical intermediate region to a cylindrical shank. The working part has a smooth finish on the outside and is provided with a mouth-shaped fork only at its free end. Depending on the embodiment, a more or less steep transition region in the form of a cone can be provided.
Forked needles are used for structuring compacted fibrous webs in a subsequent operation. Owing to the smooth, toothless flanks of the working part, they have little tendency to pull out fibers from the fibrous web and to carry these along.
Additional felt needles with toothed working parts are known from the U.S. Pat. No. 3,753,412. A relatively short transition part is arranged between the respectively toothed working part and a cylindrical shank.
Felt needles with toothed working parts have a tendency to accumulate fibers on their shanks, which are pulled from the compacted fiber material. During the needle punching of the fibers, the shank extends partially into the working space between stripper plate and base plate. The fibers pulled out from the material are deposited in the form of fiber rings, which are moved from the relatively narrow working part across the short transition region and onto the cylindrical shank region between needle board and stripper plate. In the process, they are expanded and pulled tight. If these deposits exceed a tolerable measure, the puncturing of the web by the needles is obstructed because the needle board no longer can be moved close enough to the stripper plate. Thus, cleaning actions are required from time to time, depending on the fibrous web material used. Owing to the high number of needles on a needle board, such a cleaning action is time-consuming and arduous.
SUMMARY OF THE INVENTION
It is an object of the invention to facilitate the cleaning of the needles and/or to reduce the tendency of the needles to accumulate fibers.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the felt needle includes a clamping length portion for securement to a needle board and a working length portion spaced from the clamping length portion and provided with hooks along its length. A transition length portion is formed between the clamping and working length portions. The transition length portion includes a length region having a diameter decreasing from the diameter of the clamping length portion down to the diameter of the working length portion. The length region of the transition length portion has a length which is at least twice the length of the working length portion.
The remarkable feature of the needle according to the invention is that a relatively narrow transition part or transition region is formed between the toothed working part and the toothless clamping part. This region has at least one segment in which the diameter decreases gradually from the shank diameter to the working part diameter. The length of this region, which can also be divided into several partial regions if necessary, on the whole is at least twice as long as the toothed working part. Thus, the length of the transition region for needle boards having a standard strength or thickness is longer than the respective thickness of the needle board.
In addition, the transition region preferably occupies the complete space between the needle board and the respective working part. A narrow transition region results, which leads to fewer deposits forming on the needle. The deposited fiber rings are expanded only slightly, which means they will not adhere as strongly in the transition region. However, whenever deposits are formed, the cleaning of the respective needles is made easier by the long transition part. It is easier to strip or remove lint rings on the needles, as well as fibers that have accumulated between the needles.
As a result of the gradual transition from the large shank diameter of the clamping part to the small diameter for the working part, the breaking characteristics and the flexibility of the needles are improved. Stress concentrations in the transition region are avoided.
From this it follows that the working part of the needle can have a narrower design than for traditional needles. The transition region preferably is longer than 11 mm and, even more preferable, longer than 20 mm.
Furthermore, it has proven to be advantageous that the needle according to the invention can replace many different types of existing

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