EP1471030B1 - Drive pulley for elevators and it's manufacturing process - Google Patents

Description

The invention relates to a traction sheave for elevators and their manufacturing method.

It is known that traction sheaves for elevators are currently made of lamellar graphite-containing cast iron (ÖV 200, or ÖV 250). For this purpose, hematite gray cast iron with a surcharge of ferrosilicon is used as the basic material for production. After pouring, ie after cooling of the casting follows a relaxing Normalisierbehandlung. Thereafter, the traction sheave from the casting is completed by relaxation (See, for example, the book of Dr. Vero and Dr. Käldor: "Metallurgy of Iron Alloys", Technical Book Publishing, Budapest, 1966, page 282-299 ; or the textbook of Dr. Gillemot: The Technology of Construction Materials. "Vol. I., Lehrbuch-Verlag, Budapest, 1954 ).

According to the operating experience, the traction sheaves produced by the above technology can not reach an acceptable service life, even under very careful operating conditions, because the too rapid wear of the cast-iron cable grooves through the steel cable necessitates premature wire replacement. As a result, however, the cost of maintaining the system is considerably increased, quite apart from the inevitable downtime costs of the elevators, which provide especially for multi-storey residential buildings for the residents difficult tolerable inconvenience, loss of time and annoyances. It would be acceptable for the operators of such facilities if the lifetime of the "traction sheave - steel rope" combination would permit at least one use cycle of about 10 years. Unfortunately, this desirable characteristic today, not even approximated with the pulleys made of lamellar graphite cast iron can be achieved.

For the traction sheaves, the maximum permissible groove pressure depends on the hardness of the groove material. An enlargement of the conventional material hardness of the rope groove produced from lamellar graphite cast iron piece of HB = 180 kp / mm ² would also be desirable because, according to the valid today basic principles of the traction sheave rope as a continuous surface, but the groove pressure as evenly distributed load must be assumed. But this does not quite correspond to the actual situation, since the load on the steel cable is by no means to be considered as "evenly distributed", so that in the points of contact (the disk groove - steel cable) "cardiac stresses" occur.

Further, the wear of the traction sheave groove - with otherwise correct planning, production, installation and proper operation - crucial depends on occurring rope sliding or Seilschlüpfen. The relative speed of sliding between the groove and the cable could, in principle, be prevented by an increase in the driving ability, but the maximum permissible groove pressure value sets this limit, which in turn is a function of the traction sheave hardness.

The patent document DE 1120702 discloses a traction sheave with two sectors (2, 3), wherein the sector (2) consists of a cast alloy G Al Si and the sector (3) consists of a softer leather-like thermoplastic. Task for the introduction of the thermoplastic material is the improvement of Seilmitnahmefähigkeit.

From the patent EP 279896 A method for producing traction sheaves of elevator installations is known, wherein the outer surface of the traction sheave, at least the cable-guiding groove surfaces, is subjected to a hardening process.

According to a feature of this patent, it is advantageous for larger loads, if after the finishing of the rope-receiving groove surfaces, they are subjected to a curing process, preferably a flame process. This measure is e.g. Thanks to traction sheaves of the same dimensions and the same casting technology - corresponding to the different loads - rope grooves of different surface hardness can be designed, and at a relatively low cost.

That in the patent EP 279896 described hardening of the traction sheave increases the traction, however, the material can become brittle and feed cracking. These irregularities lead to a shortened life of the traction sheave. Thus, although the wear resistance of the traction sheave is increased by the hardening, the life of the traction sheave is shortened by the spread of the cracks on the other hand.

Object of the present invention is to overcome this drawback and to propose a traction sheave for lifts and their manufacturing process, which traction sheave is hardened and is not prone to cracking or does not tend to crack.

This object is achieved according to the invention by a traction sheave, which traction sheave has at least two sectors, wherein at least one sector is hardened and at least one sector is not hardened.

Advantageously, the traction sheave is cast or manufactured in one piece. By hardening the traction sheave in sectors, hardening during hardening is easier to solve and the likelihood of cracking is therefore reduced.

Hardness is understood to mean any mechanical, thermal or chemical process which modifies the microstructure of a material and thereby increases its hardness.

With the surface of the traction sheave is here meant the outer cylindrical surface of the traction sheave, which carries the cables and which is worn during the elevator operation.

The sectors of the traction sheave are defined here as the cylindrical circular cut-outs of the traction sheave, which are delimited and measured in an angular range from the center of the traction sheave. The angle of the sector is limited by the two sector sides and.

Hardening of a sector means both the formation of a thin hardened layer on the surface of the traction sheave, which is subject to the angular range of the sector, or the hardening of the material of this sector below the surface of the traction sheave.

The invention will be apparent from the following FIG. 1 explained in more detail.

Fig. 1 shows a hardened traction sheave 1 for lifts according to a preferred embodiment of the present invention.

For normal use, ie as a lift for a residential building of medium height, a six-furled traction sheave of 638 mm nominal diameter is fabricated. As base material is based in a known manner from the hematite Grundroheisen, the 4.3 - 4.6% coal, 0.0015 - 0.05% manganese; 2.26 - 2.75% silicon and 0.035 - 0.11% phosphorus.

In the present case, ferrosilicon is added to the molten base pig iron as alloying material containing 73% silicon, 0.7% manganese, 0.1% phosphorus and 0.08% sulfur.

As the next step of the process, the sulfur content of the molten bath is reduced below 0.01%, in this case to 0.008%, or adjusted. For this purpose, magnesium coke is used, which reaches the molten bath at 1480 ° C temperature. The introduction of the magnesium coke into the molten bath takes place in such a way that this aggregate is introduced below the level of the molten bath.

Immediately before casting, the secondary modification with ferrosilicon is carried out to improve the homogeneity of the base fabric.

This is followed by casting into the mold at 1320 ° C temperature. The complete cooling takes place in the sand mold in approx. 9 hours.

Thereafter, the cooled cast piece is normalized for relaxation. First, the cast piece is preheated in the oven in a known manner to 920 ° C, and - after 4 hours keeping warm at this temperature in the oven - cooled to 900 ° C. Thereafter, the cooled casting is finished in a known manner to the nominal dimensions.

According to the results of the tests carried out with the traction sheaves prepared in the above manner, hardness values: HB = 210-260 kp / mm ^{2 are} measured on the rope guide sheath (with a ball of 10 mm diameter, with a load of 30 kN). The material test shows that the material of the casting has a ferritic - perlitic base (with about 30% ferrite, material grade: F 30, the fineness of the pearlite: Pf = 1.4), thus a spheroidal graphite cast iron with a constant graphite shape and Graphite distribution is (the characteristic values for the graphite form are: Ga 9-10, graphite size: Gm 45, (whose strength properties exceed the standard requirements on GÖV 500, ie R _{p 0.2} = 406-459 MPa, R _m = 602-658 MPa A ₅ = 2.3 - 3.6%).

The spheroidal graphite iron contains: 2.8 to 3.15% coal; 2.8-3.1 silicon; Max. 0.3% manganese; Max. 0.2% phosphate; as well as 0.008% sulfur.

Such a cast piece can be easily broken, as the conventional cast iron from lamellar graphite, which is for the cutting tools z. B. gives a 30% longer life. As a result, the cost of a longer life of the tools is further reduced.

The workpiece is subjected to a subsequent heat treatment with subsequent hardening after finishing. This heat treatment aims to further increase the hardness of the surface 2 of the traction sheave, and in particular the hardness of the surface of the grooves while avoiding cracking.

This heat treatment of the groove surface is carried out by hardening, or by one, done at 850 ° C flame hardening. At the same time, the traction sheave, which rotates at an adjustable speed, or its grooves are simultaneously heated with a special gas burner head. The heat-treated groove area is then immediately cooled, for example by rotating the traction sheave. By the rotational speed, d. H. by the speed of the traction sheave, the thickness of the hardened layer 5 of the groove surface can be regulated, which in the preferred embodiment is 1 - 1.5 mm. The desired Glühwärmegrad can be determined and identified on the basis of the color (sour cherry red) in practice.

The hardening takes place sectorally. Fig. 1 shows, for example, the hardened layer 5 of a sector with an angular range α. The angle α is limited by the sector sides 5a and 5b.

A sector 3 of the traction sheave subject to an angular range α of 25 ° measured by the center is first hardened. The adjacent sector 4 of the traction sheave, which is subject to an angular range of 5 ° measured by the center, is then not hardened. The sectoral hardening of the angular ranges is carried out over the entire circle of the traction sheave, ie 12 times 25 ° hardened separated by 12 times 5 ° uncured. Finally, the traction sheave consists of a regular series of hardened and non-hardened sectors. The sectors of the traction sheave are the preferred present embodiment of the invention sequentially hardened around the entire circumference of the surface of the traction sheave and not hardened. A simultaneous hardening of all sectors is also conceivable in principle. Irregular consequences of hardened and unhardened sectors are also possible.

The measured groove hardness values are given by HB = 480-500 kp / mm ² for the hardened sectors. Such values give the operators a satisfying, long service life and the assurance of economical operation.

In addition to their advantages already mentioned in the above, another important advantage of this invention is that traction sheaves can be produced for the different loading conditions with the same, universally applicable technology, which then, if necessary, can be subjected to the above-described surface hardening process after finishing. However, the respective optimum surface hardness and wear resistance can be adjusted, since the spheroidal graphite material structure achieved with the method according to the invention offers the possibility for this purpose. As a result of the use of a traction sheave according to the invention with a longer service life and improved wear resistance, a weight saving is achieved.

According to the operating results, the elevator pulleys produced by the above method have been subjected to normal stress, i. in a medium-high residential building of eight floors a - compared to the conventional elevator pulleys - significantly increased wear resistance and can therefore be operated much longer. As a result, however, the sum of forced downtime can be significantly reduced.

Instead of flame hardening, it is also possible to use induction hardening of the surface of the traction sheave, which leads to similar results.

The depth of the cured material can be varied as desired. In the minimum case, only a thin layer of the traction sheave surface is hardened, which is a few microns. In the extreme case, an entire sector of the traction sheave is hardened, with the hardened zone reaching the center of the traction sheave.

The sectorally hardened traction sheaves of elevator drives find use regardless of the type of drive, i. with gearbox, gearless or Riemenvorgelege.

All geometry variants of the sectoral hardening, number of segments, angular distribution, etc. are conceivable and lead to positive results, regardless of the production process of the traction sheave and the hardening process respectively their conditions and means.

For all possible groove shapes of the traction sheave there is a reduction of cracking.

Regardless of the choice of material of the traction sheave, which may also be a non-casting material, both the sectoral hardening over the peripheral surface of the traction sheave as well as a segment-wise hardening of the traction sheave has a positive effect.

Also, the hardened segments may be perpendicular to the rope groove or they may be at an angle, so diagonal to the traction sheave surface. The same hardening is also possible with split sheaves, with post-processing, i. a regrinding of the grooves, necessary to ensure the smoothness of high-speed elevators.

Claims (8)

1. Drive pulley (1) for lifts, with at least two sectors (3, 4), wherein the sectors (3, 4) are defined as cylindrical sectors of the drive pulley, which are bounded in an angular range (α) by the centre of the drive pulley (1), characterised in that the sectors (3, 4) consist of the same metallic alloy, wherein at least one of the sectors (3) is hardened and at least one other one of the sectors (4) is not hardened.
2. Drive pulley for lifts according to claim 1, characterised in that at least one sector is hardened in the angular range (α) of 15° to 35° and at least one sector is not hardened in the angular range of 1° to 15°.
3. Drive pulley for lifts according to claim 1 to 2, characterised in that at least one sector is hardened by induction hardening and/or by flame hardening.
4. Drive pulley for lifts according to claim 1 to 3, characterised in that the drive pulley consists of a regular sequence of hardened and non-hardened sectors.
5. Method of producing drive pulleys (1) for lifts, with at least two sectors (3, 4), wherein the sectors (3, 4) are defined as cylindrical sectors of the drive pulley, which are bounded in an angular range (α) by the centre of the drive pulley (1), characterised in that the sectors (3, 4) consist of the same metallic alloy, wherein at least one of the sectors (3) is hardened and at least one other one of the sectors (4) is not hardened.
6. Method according to claim 5, characterised in that at least one sector is hardened in the angular range of 15° to 35° and at least one sector is not hardened in the angular range of 1° to 15°.
7. Method according to claim 5 to 6, characterised in that at least one sector is hardened by induction hardening and/or by flame hardening.
8. Method according to claim 5 to 7, characterised in that the sectors of the drive pulley are hardened and not hardened sequentially around the entire circumference of the surface of the drive pulley.

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