Apparatus for needling a felt from one side

In order to ensure a desirable withdrawal of the felt in an apparatus for needling a felt from one side, the stripper plate (3) is provided on that side which faces the support (2) for the felt with guide ribs (7), which extend between the longitudinal rows of holes (4) and protrude from the underside surface of the plate and have a height amounting to 0.2 to 2 times the diameter of the holes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for needling a felt from one side, 
comprising at least one needle board, which is movable up and down, and a 
stripper plate, which is provided between a support for the felt and the 
needle board and is formed with holes for the passage of the needles, 
which are arranged in longitudinal rows extending in the direction of 
travel of the felt. 
2. Description of the Prior Art 
As the needles penetrate into the felt, fibers will be forced against the 
needle shanks and part of said fibers may be carried along by the needles 
as they are pulled out of the felt. As a result, that surface portion of 
the felt which is adjacent to the holes in the stripper plate may be 
bulged into said holes. Owing to the large number of needles this will 
considerably increase the resistance to the withdrawl of the felt so that 
excessively high loads will be incurred and the penetration frequency 
which can be achieved will be limited particularly if an operation at a 
high penetration frequency will result in vibration of the stripper plate 
and the take-off rollers. 
If spaced apart blades extending in the direction of travel of the felt are 
used instead of a perforate stripper plate and the needles move between 
said blades, it will be possible to avoid an increase of the resistance to 
the withdrawal of the felt. But such stripper blades cannot take up such 
high loads as perforate stripper plates. 
For an operation in which loop-forming needles penetrate into a non-woven 
web from mutually opposite sides it is known (Austrian Patent 
Specification No. 351,280) to associate a perforate guide plate with each 
side of the web and to provide said guide plate with grooves, which extend 
in the direction of travel of the web. The needles are bifurcate and are 
received by said grooves when said needles have penetrated through the web 
to form loops. That known apparatus cannot be used to needle a non-woven 
web only from one side but can be used to process only a preneedled web 
and the provision of the known grooves will result in the critical 
disadvantage that said needles will be soiled very quickly so that they 
become clogged and this may adversely affect the operability of the 
apparatus. 
SUMMARY OF THE INVENTION 
It is an object of the invention to avoid these disadvantages and to 
provide an apparatus which is of the kind described first hereinbefore and 
which is so improved with simple means that the penetration frequency can 
be increased without a risk of an excessively high load. 
The object set forth is accomplished in accordance with the invention in 
that the stripper plate is provided on that side which faces the support 
for the felt with guide ribs, which extend between the longitudinal rows 
of holes and protrude from the underside surface of the plate and have a 
height amounting to 0.2 to 2 times the diameter of the holes. 
Because the felt is held back by the guide ribes of the stripper plate and 
said guide ribs protrude from the surface of the plate by an adequate 
distance, the surface of the felt which bulges between the guide ribs as 
the needles are pulled out of the felt cannot enter the holes through 
which the needles pass. As a result, the felt can be moved between the 
support for the felt and the stripper plate by means of withdrawing 
rollers and the resistance to the withdrawal of the felt will not 
periodically be increased because the guide ribs extend between the rows 
of holes along the longitudinal rows of needles in the direction of travel 
of the felt and do not resist the withdrawal of the felt portions disposed 
between the guide ribs. In dependence on the possible bulging of the 
surface of the felt the height of said guide ribs must be so large that an 
entrance of fibers into the opening of the holes through which the needles 
pass will be avoided. Because the needle density should be as high as 
possible and the guide ribs should be sufficiently strong, the spacing of 
the guide ribs will generally correspond to the diameter of the holes. The 
height of the possible bulge of the surface of the felt will depend on the 
diameter of the holes and on the spacing of the guide ribs. It has been 
found in practice that a lower limit of the height of the guide ribs is 
0.2 times the hole diameter and that said height will be sufficient to 
ensure that the resistance to the withdrawal of the felt will be 
substantially constant. But the height of the ribs cannot be increased as 
much as desired because this may result in a soiling of the recesses 
formed between the ribs. If the height of the ribs is at an upper limit 
corresponding to twice the hole diameter, an adequate cleaning action of 
the felt in the recesses between the guide ribs will be ensured. For that 
purpose a design in which the height of the guide ribs is one-half to one 
diameter of the holes will be particularly advantageous. 
Because guide ribs having a defined height are arranged between adjacent 
rows of holes in the stripper plate, the penetration frequency will not be 
limited by the inevitable bulging of the surface of the felt as the 
needles are pulled out of the felt. Nevertheless, the penetration 
frequency will not be limited by the inevitable bulging of the surface of 
the felt as the needles are pulled out of the felt. Nevertheless the risk 
of a damage to the stripper plate by needles which have been broken out or 
bent will be low because the guide ribs have a comparatively small height 
and owing to the stripper plate have an adequate strength, which would not 
be achieved if individual guide blades were provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An illustrative embodiment of the invention will now be described in detail 
with reference to the drawing. 
As is apparent from FIG. 1 the illustrated apparatus essentially consists 
of a needle board 1, which is driven to move up and down, e.g., by an 
eccentric drive, a support 2 for the felt, which support consists of a bed 
plate composed of blades, and a stripper plate 3, which is disposed 
between the needle board 1 and the felt support 2 and is formed with holes 
4 for the passage of respective needles 5 of the needle board 1. The 
needles 5 of the needle board 1 are arranged in longitudinal rows, which 
extend in the direction of travel 6 of the felt. During the working stroke 
of the needle board 1 the needles 5 penetrate through the felt, which is 
moved by withdrawing rollers, not shown, between the felt support 2 and 
the stripper plate 3. As a result of said penetration, fiber loops are 
formed in the fibrous structure to increase the coherence of the fibers. 
As the needles 5 are pulled out, the felt is held back relative to the 
needles 5 by the stripper plate 3. As a result of said penetration, fiber 
loops are formed in the fibrous structure to increase the coherence of the 
fibers. As the needles 5 are pulled out, the felt is held back relative to 
the needles 5 by the stripper plate 3. 
As the needles are pulled out, the surface of the felt is bulged. To 
prevent that bulging surface of the felt from entering the mouths of the 
holes 4 in the stripper plate 3, the stripper plate 3 is provided on its 
underside surface, which faces the support 2 for the felt with parallel 
guide ribs 7, which are disposed between adjacent longitudinal rows of 
holes 4 and extend in the direction of travel 6 of the felt. As a result, 
as the needles 5 are pulled out the felt will be substantially held back 
by said guide ribs rather than by the entire underside surface of the 
stripper plate 3, which surface is set back from said guide ribs. The 
height h of the guide ribs 7 is about 0.2 to 2 times the diameter d and 
preferably to one-half of one diameter d of the holes 4. Owing to said 
size relations the surface of the felt which bulges at least close to the 
needles 5 as they are pulled out cannot enter the mouths of the holes 4 so 
that the resistance to the withdrawal of the felt will remain constant. 
But the height of the guide ribs 7 is not so large that the recesses 
formed between the guide ribs 7 may be soiled. This will be prevented by 
the fact that the bulging surface of the felt will clean the recesses as 
far as to the underside surface of the perforate plate. For that purpose, 
ribs having a height between 2.5 and 3.5 mm have proved satisfactory in 
conjunction with usual hole diameters.