Method for production of an air jet nozzle

Method of forming a nozzle for use in air jet thread spinning processes, the nozzle comprising a body of selected steel material having a thread passage with an axis extending the longitudinal length of the body and one or more lateral bores entering tangentially into the passage, the method comprising the steps of selecting a raw unhardened steel material which is hardenable by heat or nitriding treatment; forming the body of the nozzle including the passage and the lateral bores out of the selected raw steel material; and hardening the formed body of raw steel material to a hardness of at least about 50 HRC.

BACKGROUND OF THE INVENTION 
The present invention relates to spinning nozzles and methods of making 
nozzles for a spinning machine and in particular to spinning nozzles 
having a passage extending the longitudinal direction of the nozzle and 
lateral bores leading tangentially into the passage. 
Nozzles for air jet spinning machines operating on the pneumatic spinning 
principle have long been known (for example see DE-A-32 37 990). This 
specification describes the invention in the context of a spinning machine 
having two twist nozzles, more particularly a first or injector nozzle and 
a second or twist nozzle. These nozzles have lateral bores which typically 
have a diameter of less than 1 mm. 
Air jet nozzles are increasingly complex in shape and require passage and 
bore diameters with increasingly accurate tolerances with as yet 
unsuitable production methods being available for producing same. It has 
been essentially impossible to satisfy such stringent requirements as 
dimensional tolerances while at the same time guaranteeing very high 
wear-resistance. 
SUMMARY OF THE INVENTION 
It is an object of the invention therefore to provide a method for 
producing a nozzle for a spinning machine which guarantees very high 
wear-resistance and very high dimensional and directional accuracy of the 
bores, the nozzles being adapted to particularly cost-effective 
manufacture by comparison with conventional production processes. A novel 
nozzle is also provided which may be produced according to the novel 
method herein. 
Bores to be formed in a hardened and wear resistant metal housing can be 
made only with very great difficulty; i.e., special jigs and specially 
hardened bits or special drilling methods are required to ensure that the 
direction of the bore is in any way accurate, and, even if the drilling 
fixtures are properly clamped, there is a risk of the drilling bit 
deviating such that the bore departs from an ideal geometry. For example, 
where a cylindrical bore is desired, an elliptical bore may be formed. In 
looking for suitable production methods for such nozzles it has been found 
particularly advantageous to make the bores before hardening of the nozzle 
material thus achieving high dimensional and directional accuracy of the 
bores. It has been found that such hardening process has practically no 
appreciable effect on the quality of the bores. 
It is an object of the invention to provide wear resistant nozzles for 
nozzle spinning machines cost effectively and with accurate dimensions. 
Manufacture of the bores is not restricted to conventional mechanical 
methods. Casting, powder metallurgy methods, ultrasonic machining or 
erosion, and electron or laser beam treatments can also be employed. 
Heat treatment of the nozzle material is preferably carried out at the 
material specific hardening temperature or at the nitriding temperature of 
the nozzle body material, typically steel, which is used. 
Mechanical or chemical polishing processes are typically used to finish the 
surfaces of the bores and passage. Suitable mechanical methods are shot 
blasting with glass beads or suspension blasting with corundum. Another 
suitable method is longitudinal polishing using a cord and polishing 
paste. 
Selection of steel material should primarily be governed by the fact that 
the steel should not excessively deform during heat treatment or 
hardening. Particularly suitable commercially available steels are, for 
example, those designated as X40Cr13, 100MnCrW4, 34CrAlMo5 or ETG 100 (all 
available from VEW, Vereinigte Edelstahlwenke AG, Vienna, Austria). 
The new production method has proved particularly suitable for nozzles in 
which the diameter to length ratio of the bores is between about 1:3 and 
about 1:8, most preferably about 1:5. The diameter of the bores is 
preferably between about 0.3 and about 1.0 mm, preferably about 0.5 mm and 
the passage preferably has a cross sectional diameter of between about 2.0 
and about 4.0 mm, most preferably about 2.5 mm. The angle of the bores 
with the longitudinal axis of the passage is typically between about 
30.degree. and about 90.degree., most preferably about 45.degree..

FIG. 1 shows a nozzle housing 1 comprising an injector nozzle 2 and a twist 
nozzle 3 having a coaxially aligned passage 4. The passage 4 of the twist 
nozzle 3 has a conically widened end 5. Each of the nozzles 2 and 3 is 
formed with three lateral tangential bores 6, only one of which is shown 
in each case. The bores 6 lead tangentially into the passage 4, the bore 6 
of nozzle 2 forming an angle .alpha. of 45.degree. with the longitudinal 
direction (or axis) of the passage 4 while the bore 6 of the twist nozzle 
3 forms an angle .beta. of 60.degree. with the longitudinal direction of 
the passage 4. The bores 6 of the injector nozzle 2 enter substantially 
into about the middle of the length of passage 4. Chamfers or surfaces 7 
are provided on the outsides of the nozzles 2 and 3 and are disposed 
perpendicularly to the longitudinal direction (or axis) of the bores 6. 
These chamfers 7 provide easy and accurate location of the drilling head 
so that the bores 6 can be readily formed to the accurate dimensions and 
direction. The injector nozzle 2 is screwed on the nozzle housing 1 by 
means of a cap 8 having a screwthread 9. The nozzle housing 1 is formed 
with two air inlets 10 intended for the air supply. In the case of the 
injector nozzle 2, the air passes via a continuous bore 11 extending 
parallel to the passage 4 into an air chamber 12 connected to the bores 6. 
In the case of the twist nozzle 3, an annular recess 13 is provided which 
communicates with the air inlet 10 and the bores 6. For sealing purposes, 
O-rings 14 are provided between the nozzles 2 and 3 and the nozzle housing 
1. For reasons associated with manufacturing and assembly techniques, air 
inlets 10 are typically formed in the nozzle housing 1 on both sides of 
the nozzles 2 and 3, the unused air inlets 10 being closed by a screw 15. 
The bores 6 most preferably have a diameter of 0.5 mm and a length of at 
least about 2.5 mm. It has proven particularly satisfactory for the length 
of the bores 6 to be about five times their diameter. 
The injector nozzle 2 and the twist nozzle 3 may be formed, in a preferred 
exemplary manner, as follows: 
In a first step, the nozzles 2 and 3 are formed from unhardened steel and 
the passage 4 and the bores 6 are formed therein. Typically, the passage 6 
and the bores 4 are formed by drilling with a drilling machine and a 
suitable steel bit. Other methods can be used however, such as ultrasonic 
drilling or erosion, or laser or electron beams. Alternatively, the 
nozzles can be made directly by casting or powder-metallurqical methods, 
such as hot pressing. Such alternative methods require a suitable casting 
or hot-pressing mould. 
In a second step, the nozzles 2 and 3, which now have the required rough 
form are surface treated by removing burrs and other irregularities by 
shot blasting or by suspension blasting. Such finishing operation is 
typically effected by shot blasting using glass shot of a diameter of 150 
to 250 .mu.m, and a blasting pressure of 3 to 7 bar, most typically 5 bar. 
Another suitable surface finishing operation may be effected by blasting 
with a suspension of corundum having a particle size of typically about 20 
to about 100 .mu.m, most preferably about 40 .mu.m, and water at a 
blasting pressure of 4 to 8 bar, most typically at about 6 bar. 
Similarly, the passage 4 and the bores 6 can be longitudinally (axially) 
polished by means of a cord and polishing paste. Another polishing method 
is of a chemical type and is explained in detail, for example, in an 
article by F H Wells, Electroplating and Metal Finishing, June 1960, pages 
241 et seq., the disclosure of which is incorporated herein by reference. 
In a third and last step, the nozzle 2 or 3 is preferably subjected to a 
heat treatment which is typically carried out in a buffer gas or in a 
vacuum depending on the particular composition of steel used (exemplary 
preferred heat treatments versus exemplary steel materials are set forth 
in Table 1.) The heat treatment of the unhardened raw steel nozzle is 
carried out in such a way and to such an extent as to achieve a nozzle 
body material hardness of at least about 50 HRC (HRC is also known as the 
Rockwell C hardness). More particular details as to preferred heat 
treatment operations are set forth in DIN Standard 17211 (nitriding 
steels; quality specifications) and DIN Standard 1651 (free cutting 
steels) and DIN Standard 17440 the disclosures of which are incorporated 
herein by reference. Nozzles 2 and 3 prepared in this way have a very low 
surface roughness of RA=0.1, i.e. the passage 4 and the bores 6 have a 
maximum deviation of 0.5 .mu.m. The heat treatment operation can 
alternatively be carried out by high-frequency hardening also known as 
induction hardening, as described for example in Dubbel, Taschenbuch fur 
den Maschinenbau, Springer Verlag (1987) p. E 32 and U.S. Pat. No. 
4,167,846, the disclosures of which are incorporated herein by reference. 
Nozzles 2 and 3 made in the above described manner have bores 6 leading 
tangentially into the passage 4 with a very high accuracy in respect of 
the dimensions and direction which were originally given the passage 4 and 
boxes 6 before the nozzle body was subjected to the hardening process. The 
production process proposed has proved particularly cost-effective, since 
the sequence of process steps to manufacture the nozzle can be 
substantially automated. 
TABLE 1 
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Type of Steel Hardening Method 
______________________________________ 
X40Cr13 Vacuum or buffer gas hardening 
Hardness HRC 54 .+-. 2 
Hardening temperature 1000- 
1050.degree. C. 
Annealing temperature 180.degree. C. 
100MnCrW4 Hardness HRC 62 .+-. 0.2 
Hardening temperature 780-830.degree. C. 
Quenching in oil 
Annealing temperature 180.degree. C. 
34CrAlMo5 Gas nitriding 
(Nitriding steel) 
Hardness HV3 1100 .+-. 100 
Hardness layer 0.3-0.4 mm 
ETG 100 Bath nitriding 
(Equivalent to 45S20) 
(Tenifer treatment) 
Thickness of nitride layer 10 to 
20 .mu.m 
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It will now be apparent to those skilled in the art that other embodiments, 
improvements, details and uses can be made consistent with the letter and 
spirit of the foregoing disclosure and within the scope of this patent, 
which is limited only by the following claims, construed in accordance 
with the patent law, including the doctrine of equivalents.