Felt needle

A transition part is provided for a felt needle between the clamping part and the working part, which transition part is designed as elongated, narrow truncated cone. The length of this transition part is at least as long as twice the length of the working part. As a result, a very narrow transition region is formed, which has little tendency to pull out and accumulate fibers from the fibrous web. Should fiber deposits still form, these can be removed easily.

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 needles. The
 needle according to the invention can replace felt needles with single,
 double or triple diameter reduction. As a result of this, the type variety
 that must be offered by the needle manufacturer is reduced.
 Another advantage is the fact that the shank region, which enters the
 working region between stripper plate and base plate during the
 needle-punching operation, has a smaller diameter than the traditional
 needles. Consequently, the openings caused by the shank region in the
 produced felt have a smaller diameter, which improves the surface quality
 of the felt.
 The transition region preferably is designed as one piece with a conical
 shape. The cone can be a straight truncated circular cone, meaning a
 surface line generatrix on this region is a straight line. Alternatively,
 the cone can also be a non-straight cone. In that case, the transition
 part has a curved surface line.
 The working part and the clamping part for the needle according to the
 invention are preferably arranged coaxially to each other. However, it is
 possible to deviate from this if necessary. The working part furthermore
 preferably has a constant diameter and adjoins the transition part
 smoothly, preferably without a change in diameter.
 According to a further embodiment, the transition part occupies the
 complete space between the needle board and the working part. The total
 length of the transition part can be less than twice the working part
 length owing to the needle dimensions. In that case, the needle consists
 of three regions: working part, transition part and shank part, which is
 embedded completely in the needle board.
 It is advantageous in this case if the transition part is longer than the
 thickness of the needle board provided for fastening the needles.
 Regardless of the total length of the transition part, the transition part
 for the inventive embodiment starts directly at the needle board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 illustrates a device 1 for needle-punching a fibrous web. The device
 1 includes a needle board 2, which is driven, for example, via an
 eccentric cam plate and performs a back and forth movement in a direction
 illustrated by an arrow 3. The needle board 2 contains openings 4 for
 holding and storing the needles 5. The needles 5 extend outward from the
 needle board 2 parallel to and spaced from each other. They project
 through stripping openings 6 that are formed in a stripper plate 7. This
 plate is arranged at some distance to a base plate 8 and together with
 this plate defines an intermediate space 9 through which loose and
 randomly distributed fibers are guided in a direction indicated by arrow
 11. During the subsequent process, these fibers are compacted to form a
 fibrous web, as a result of the up and down movement of the needles 5.
 The base plate 8 is provided with openings 12, wherein respectively one
 opening 12 in the base plate 8 is aligned with one opening 6 in the
 stripper plate 7.
 The needles 5 are designed identically. Each needle comprises a clamping
 part 14 that is held in the needle board 2, as well as a working part 16,
 which is provided with barbs or hooks 15. A transition part 17 is arranged
 between the clamping part 14 and the working part 16. The transition part
 17 extends from the clamping part 14 to the working part 16 and starts
 immediately adjacent to the needle board 2.
 In FIG. 2, a needle 5 is shown in order to demonstrate the proportions. The
 cylinder-shaped clamping part 14 changes at a transition location 18 to
 the transition part 17, which has the form of a narrow cone. In the
 transition part 17, the size of the diameter changes from a larger size at
 the transition location 18 to a smaller size at a transition location 19
 where the working part 16 begins. The transition part 17 is arranged
 coaxially to a longitudinal axis 21 of needle 5 and, on the whole, forms a
 coherent region for the diameter adaptation. The clamping part 14 and the
 working part 16 are also arranged coaxially to the longitudinal axis 21.
 The diameter of the transition part 17 decreases continuously and linearly
 along the longitudinal axis 21. The length of the transition part 17
 measured between transition locations 18 and 19, is at least twice as long
 as the length of the working part 16, meaning the distance of transition
 location 19 to a tip 22, formed at the free end of needle 5. As a result,
 the transition part becomes very narrow and long and has no steps or
 projections whatsoever.
 The device 1 operates as follows:
 During the operation, loose fibers are guided through the intermediate
 space 9. In the process, the needle board 2 is moved in quick succession
 back and forth in the direction of arrow 3, in such a way that the needles
 5 periodically release and puncture the intermediate space 9. The hooks 15
 of the working parts 16 in the process compact the individual fibers to
 form a fibrous web. The danger that individual fiber filaments are carried
 along, are pulled through the stripping openings 6 and are then deposited
 on the needle 5 exists during this process especially for the first
 needles, which come in contact with the as yet non-compacted fibers. The
 long and narrow design of the transition parts 17 for the needles 5
 according to the invention counteracts this tendency. The needles 5 pull
 fewer fibers through the stripping openings 6, especially with some
 fibrous web materials and in particular with recycled fibers. As a result
 of this, less lint if any at all will accumulate between the needle board
 2 and the stripper plate 7. However, if fibers should nevertheless
 accumulate on the needles 5, between the needle board 2 and the stripper
 plate 7, these can be stripped relatively easily from the narrow
 transition regions 17. This is particularly true if the transition
 location 18 is immediately adjacent to the underside of the needle board
 2, in contrast to the location shown in FIG. 1.
 FIG. 3 shows a somewhat modified embodiment of the needle 5. The region
 formed by the transition part 17 is divided into two partial regions 17a,
 17b in which the diameter of needle 5 is reduced from the shank diameter
 to the working part diameter. The partial region 17a in this case borders
 on the transition location 19, while the partial region 17b borders on the
 transition location 18. A cylindrical intermediate section 17c is formed
 between the partial regions 17a, 17b. It is true for this embodiment as
 well that the transition part 17 advantageously starts immediately
 following the needle board 2, meaning the transition location 18 is
 aligned with the underside of the needle board 2. The partial regions 17a,
 17b, in which a tapering of the needle 5 occurs, together have a length
 that is equal to or longer than twice the length of the working part 16,
 meaning the distance between the transition location 19 and the tip 22.
 The latter applies correspondingly to the embodiment of needle 5 that is
 illustrated in FIGS. 4 and 5. The above description applies
 correspondingly, but with one exception. The partial regions 17a, 17b
 respectively are located on the surface shell of a small cone, meaning the
 diameter is reduced in these partial regions 17a, 17b in the direction of
 the tip 22. The diameter reduction for the embodiment according to FIG. 4
 is linear for the partial region 17a, but not for the partial region 17b.
 In the embodiment according to FIG. 4, this is true for the partial region
 17a, but not the partial region 17b. Starting with the transition location
 18, the diameter in this region initially tapers off more strongly and
 then less strongly. Thus, the outline for the cone that forms is a curved
 line. Such a cone can also be formed in place of the cone in the partial
 region 17a or, for the embodiment according to FIG. 2, in place of the
 straight, narrow truncated cone in the transition region 17.
 It will be understood that the above description of the present invention
 is susceptible to various modifications, changes and adaptations, and the
 same are intended to be comprehended within the meaning and range of
 equivalents of the appended claims.
 LIST OF REFERENCE NUMBERS
 1 device
 2 needle board
 3 arrow
 4 openings
 5 needles
 6 stripping openings
 7 stripper plate
 8 base plate
 9 intermediate space
 10 arrow
 11 openings
 14 clamping part
 15 hook
 16 working part
 17 transition part
 17a partial region
 17b partial region
 17c intermediate section
 18 transition location
 19 transition location
 21 longitudinal axis
 22 tip