WO2019180300A1

WO2019180300A1 - Traction sheave elevator

Info

Publication number: WO2019180300A1
Application number: PCT/FI2018/050218
Authority: WO
Inventors: Simo Mäkimattila
Original assignee: Kone Corporation
Priority date: 2018-03-22
Filing date: 2018-03-22
Publication date: 2019-09-26
Also published as: CN111699150A

Abstract

The invention relates to a traction sheave elevator comprising an elevator car (1), a hoisting machinery (4) with a traction sheave (5) and hoisting ropes (3) that are arranged to transmit driving force from the traction sheave (5) to the elevator car (1), and which traction sheave (5) comprises circumferential rope grooves (7) that have a coating (9) with a contact surface (10) for each hoisting rope (3) to contact. The coating (9) in the rope groove (7) is a metallic layer on the surface of the rope groove (7), and the con-tact surface (10) of the coating (9) of the rope grooves (7) is harder than the base material of the traction sheave (5).

Description

TRACTION SHEAVE ELEVATOR

The present invention relates to a traction sheave elevator as defined in the preamble of claim 1.

Typically elevators comprise a hoisting or drive machinery with a traction sheave and hoisting ropes to drive the ele vator car under the control of an elevator control system. The drive machinery usually comprises a hoisting motor that rotates the traction sheave engaging the hoisting ropes that are connected to the elevator car and advantageously also to a counterweight or balance weight. Thus, the driving force is transmitted from the hoisting motor to the elevator car through the traction sheave and hoisting ropes.

One problem in known elevator arrangements is the sliding of the hoisting ropes in the rope grooves of the traction sheave. The sliding of the ropes in the rope grooves of the traction sheave depends on both a load condition and a rope elasticity.

The transmission of the driving force is based on friction between the rope grooves of the traction sheave and the hoisting ropes made of twisted steel wires. The rope grooves of the traction sheave have a certain friction force on the hoisting ropes. The rope friction force is usually lower than the torque affected by the hoisting motor because the friction force has an upper limit above which the ropes slide on the rope grooves of the traction sheave. For that reason the mechanical efficiency of the elevator system can be improved by increasing the friction coefficient between the hoisting ropes and the rope grooves of the traction sheave. Usually this is done by making an undercut to the bottom of the rope grooves and selecting suitable materials and lubricants. Most common materials for the pairs of trac tion sheave and hoisting ropes are cast irons for the trac tion sheave and carbon steels for hoisting ropes.

If the traction force and friction coefficient can be made higher the elevator car and counterweight in relation to a car load can be made lighter. This is beneficial for the el evator layout and energy consumption. It is thus possible to reduce the moving masses, which means that less energy is needed to move the payload.

The hoisting ropes slide in the rope grooves also because of the elasticity of the system. The rope stress on different sides of the traction sheave is different, which leads to different elastic elongations of the ropes in different lo cations. When a highly stressed rope travels to a position where its stress is lower it contracts. To prevent sliding due to rope elasticity the ideal ropes have a high elastic coefficient .

The hoisting ropes slide due a to dynamic condition, too. The ropes have differences in diameter, groove contacts and elastic coefficients, which lead to uneven rope stresses, which during elevator car movements are compensated by slid ing .

The lifetime of the hoisting ropes is strongly dependent on wear between the ropes and the rope grooves of the traction sheave. Wear itself depends on the pressure and force be tween the ropes and the rope grooves of the traction sheave. The groove pressure and sliding in combination determine the wear rate. The more the ropes slide and the higher the con tact pressure the faster the ropes wear and at the same time the diameter of the ropes is reduced. Commonly, for example, the ropes must be discarded when the wear has reduced the rope diameter by 6 % below the nominal diameter. As to the power consumption and rope lifetime the optimum would be the highest friction, which leads to minimization of the rope sliding in the rope grooves of the traction sheave.

A rope wear is associated to the wear of the rope grooves of the traction sheave. If the material of the traction sheave is too soft the rope grooves often wear too fast. Typically rope wires are made from high-carbon pearlitic, cold drawn wires or ferritic stainless steel wires, which have a high hardness and a high wear resistance. The hardness of the rope grooves of the traction sheave is adjusted to the hard ness of the wires of the ropes so that the total system wear is minimized. Traction sheaves and deflection pulleys are usually made of cast irons having the hardness between 200 and 350 HB . Typical materials of traction sheaves are carbon steel, cast steel, cast irons like grey cast iron, spheroi- dized cast irons, and heat-treated austenitic hardening irons. Coatings of rope grooves have been used to increase the wear resistance and friction.

Also heat surface hardening treatments like flame hardening, induction hardening and laser hardening have been used to increase the hardness and wear resistance of traction sheaves. To protect traction sheaves and ropes from wear a suitable lubricant is used. The lubricant is generally in the rope. During the rope manufacturing the rope or its wires or strands pass through a lubrication bath. As a result the el evator hoisting ropes usually have 1, 0-2,0% grease lubricant in their surface wire strands.

One object of the present invention is to reduce and elimi nate the drawbacks and problems of the solutions of prior art and to achieve a traction sheave elevator with a trac tion sheave where the friction between the rope grooves of the traction sheave and hoisting ropes has been increased with a material harder than the base material of the trac tion sheave. Another object of the invention is to use in the rope grooves of the traction sheave a coating material which has better wear resistance than the base material of the traction sheave. Yet another object of the invention is to achieve a longer lifetime of the hoisting ropes and the traction sheave. The elevator with a traction sheave accord ing to the invention is characterized by what is presented in the characterization part of claim 1. Other embodiments of the invention are characterized by what is presented in the other claims .

The inventive content of the application can also be defined differently than in the claims presented below. The in ventive content may also consist of several separate inven tions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts. Likewise, the different details present ed in connection with each embodiment can also be applied in other embodiments. In addition, it can be stated that at least some of the subordinate claims can, in at least some situations, be deemed to be inventive in their own right.

In order to achieve the objectives mentioned above, the pre sent invention provides a traction sheave elevator compris ing an elevator car, a hoisting machinery with a traction sheave and hoisting ropes that are arranged to transmit driving force from the traction sheave to the elevator car, and which traction sheave comprises circumferential rope grooves that have a coating with a contact surface for each hoisting rope to contact. Advantageously, the contact sur face of the coating of the rope grooves is harder than the base material of the traction sheave. Advantageously rope groove coating is done by using metal spraying or thermal spraying, preferably by using a plasma spray process.

It is also advantageous that the coating in the rope grooves is a metallic layer on the surface of the rope groove and comprises a metal alloy sprayed onto the surface of the rope groove. Advantageously the surface of the base material is strengthened/made more firm by spraying coating on it. Preferably, the coating in the rope grooves has a martensit ic metallurgical microstructure, and has a bigger friction coefficient and a bigger wear resistance than the corre sponding characteristics of the base material of the trac tion sheave.

Additionally or alternatively parameters of spraying metal alloy onto the surface of the rope groove are selected so that the surface of the rope groove base material will be modified. For example in case of cast iron as a base materi al, in the surface layer of the base material at least some of the carbon and/or other particles of the base material fine structure deform and/or escape from the base material; some of such particles may move into the coating. Thus, the base material of the traction sheave has a reduced carbon content in the proximity of the coating. Additionally or alternatively the sprayed metal coating is partly mixed with the base material so, that there has been formed an intermediate layer or zone between the coating and the outer surface of the base material of the traction sheave groove. The intermediate layer may consist of several sublayers or composition and material characteristics of the intermediate layer may change gradually and/or several times stepwise .

The intermediate layer or zone could comprise material from the base material and coating material. Advantageously it consist a sublayer, which is treated or transformed base ma terial .

Advantageously the intermediate layer or zone consist a sub- layer, which is a mix of the material from the base material and the coating material.

One advantage of the intermediate layer or zone is improved bonding of the coating.

The solution according to the invention has an advantage among other things that it improves the friction coefficient and further the friction force between the hoisting ropes and the rope grooves of the traction sheave. The friction force is the force exerted to the hoisting ropes, which force is achieved by the combined effect of the friction of the material pair formed by the rope groove and the hoisting rope. A further advantage of the invention is that the high er friction coefficient makes is possible to achieve a big ger rope force at the same torque of the hoisting machinery. In practice, it is possible to make the relation between the weight of the elevator car and the weight of the payload smaller. Yet another advantage is that a better coefficient of efficiency is achieved. Yet a further advantage is that the wear of the sides of the rope grooves of the traction sheave decreases. Yet a further advantage is that thanks to the innovative coating of the rope grooves the base material of the traction sheave can be simple and inexpensive. One more advantage is that the variation of the friction coeffi cient of the coated rope grooves is more stable than with rope grooves without the coating. Yet a further advantage is that thanks to a narrow contact area between the hoisting rope and the rope groove it is possible to coat only the flanks of the rope grooves. That makes the manufacturing the traction sheave easier. Yet a further advantage is that hardness of the coating is in an area where the wear of the strand of the rope wire is not strong. Yet a further ad vantage is that hardness of the coating is in an area where its own wear is not strong. Yet one more advantage is that the coating efficiently resists corrosion, and therefore the protection of rope grooves against corrosion is not needed, for example during storage and transportation. In the following, the invention will be described in detail by the aid of embodiment examples by referring to the at tached simplified and diagrammatic drawings, wherein Fig. 1 presents in a simplified and diagrammatic side view a typical traction sheave elevator where the solu tion of the invention can be used,

Fig . 2 presents in a simplified and diagrammatic cross- sectional view a periphery part of a traction sheave used in an elevator according to the inven tion,

Fig . 3 presents in a simplified and diagrammatic cross- sectional view a periphery part of a traction sheave according to Fig. 2 with hoisting ropes in the rope grooves,

Fig . 4 presents in an enlarged, simplified and diagrammat ic cross-sectional view a part of the surface layer of a rope groove of the traction sheave according to the invention,

Fig. 5 presents in an enlarged, simplified and diagrammat ic cross-sectional view an interface between the base material of the rope groove of figure 4 and the coating of the rope groove, and

Fig . 6 presents a chart of friction coefficients of an ad vantageous coating of the rope grooves according to the invention and the rope grooves of the original cast iron.

Figure 1 presents in a simplified and diagrammatic side view a typical traction sheave elevator where the solution of the invention can be used. The elevator comprises at least an elevator car 1 and a counterweight 2 that are connected to each other with one or more hoisting ropes 3, which form a hoisting roping. Preferably, the hoisting ropes 3 are metal wire ropes having metal wires forming at least a part of the outer surface of the rope 3. Advantageously, the hoisting ropes 3 are steel wire ropes. The first ends of the hoisting ropes 3 are fastened to the elevator car 1 and the second ends of the hoisting ropes 3 are fastened to the counter weight 2. The counterweight 2 can also be a balance weight. Later the both are meant when only the counterweight 2 is mentioned .

The elevator further comprises a hoisting machinery 4 with a traction sheave 5 and a hoisting motor 4a to rotate the traction sheave 5. In this embodiment the hoisting machinery

4 is placed above the elevator car 1 and the counterweight 2 but as well the hoisting machinery 4 could be below the ele vator car 1 and the counterweight 2, or in some other appro priate location in relation the elevator car 1 and the coun terweight 2. In this embodiment the hoisting ropes 3 are ar ranged to pass over the traction sheave 5 and a deflection pulley 6 so that the contact angle or wrap angle between the traction sheave 5 and the hoisting ropes 3 is long enough to provide a sufficient friction force to transmit the driving force from the hoisting motor 4a to the elevator car 2 through the traction sheave 5 and the hoisting ropes 3.

Figures 2 and 3 present in a simplified and diagrammatic cross-sectional view a periphery part of the traction sheave

5 according to the invention. Figure 2 presents the periph ery part of the traction sheave 5 without the hoisting ropes 3 and in figure 3 the contours of the hoisting ropes 3 are shown . In this embodiment the traction sheave 5 comprises on its periphery four similar circumferential grooves 7 for the hoisting ropes 3. The rope grooves 7 are parallel with each other and the cross-section of each groove 7 is formed as suitable as possible for the hoisting rope 3. The cross- section of the grooves 7 can be, for instance a semi-circle, i.e. a so-called U groove, or like a letter V, i.e. a so- called V groove. In order to improve the traction between the rope grooves 7 and the hoisting ropes 3 the grooves 7 are often undercut so that the rope 3 does not hit the bot tom of the rope groove 7. The rope grooves 7 in this embodi ment of the invention are undercut U grooves having an un dercut 8 at the bottom of the rope groove 7 as shown in fig- ures 2 and 3.

Each circumferential rope groove 7 of the traction sheave 5 comprises a metallic circumferential coating 9 that is ar ranged to cover at least the contact areas between the hoisting rope 3 and the coating 9. Advantageously, the coat ing 9 covers at least a part of each side of the rope groove 7 along the total circumferential length of the rope groove 7. Further, each coating 9 comprises a metallic circumferen tial contact surface 10 for each point of contact with the hoisting rope 3. Advantageously, the coating 9 comprises a metallic contact surface 10 at least on each flank of the rope groove 7.

Figures 4 and 5 present in an enlarged, simplified and dia- grammatic cross-sectional view a part of the surface layer of a rope groove 7 of the traction sheave 5 according to the invention. Figure 4 presents a part of an uncoated surface layer of the rope groove 7 of the traction sheave 5 and fig ure 5 presents the same part of the surface layer coated with the coating 9 used on the rope grooves 7 of the trac tion sheave 5 according to the invention.

Advantageously, the coating 9 is made onto the surface 7a of the rope groove 7 by metal spraying where, using various techniques, pulverized coating material is melted and sprayed to the surface 7a of the rope grooves 7. These kinds of metal spraying or thermal spraying techniques are not ex plained in a more detailed way in this context. The thick ness of the coating 9 on the flank of the rope groove 9 of the traction sheave 5 is preferably between 20-100 pm, ad vantageously between 25-80 pm. In that case the uneven sur face of the coating 9 and the thickness distribution of the coating 9 do not affect disadvantageously to the base sur face 7a of the rope groove 7 and to internal stresses of the coating 9.

Advantageously, the coating 9 is a metal alloy comprising one or more appropriate metals, metalloids and non-metals. Preferably, the metallurgical structure of the coating 9 substantially corresponds to martensitic stainless steel, such as 2Crl3 or stainless steel of grade 420. In an advan tageous embodiment of the invention the coating 9 comprises as alloying elements at least carbon, chromium, manganese and silicon. A preferable amount of the alloying elements is as follows (in wt%) :

C: 0, 16 ... 0, 25

Cr: 12,0 ... 14,0

Mn : 1 , 0 ... 1 , 5 Si: 0,0 ... 1,0

When sprayed onto the surface 7a of the rope grooves 7 the coating material is partially melted, and when cooling down, after the spraying, the coating material solidifies and forms a martensitic metallurgical microstructure. The micro hardness of the coating 9 is 430 ... 550 HV, but with an ap propriate mixture ratio of the alloying elements and suita ble hardening methods the microhardness can be increased to 700 ... 850 HV. Thus, the hardness of the coating 9 and pref erably the contact surface 10 of the coating 9 is bigger than the hardness of the base material of the traction sheave 5. The base material of the traction sheave 5 is, for example, cast iron or steel, and the surface 7a of the orig- inal rope grooves in the periphery of the base material is often the same material.

The pulverized metallic coating material is melted and sprayed onto the uncoated base surface 7a of the rope grooves 7 with a pressure and high speed so that at least a part of the hard coating material particles hits the base surface 7a with a great force and thereby cause deformation of the base surface 7a of the rope grooves 7. Thus, the traction sheave 5 according to the invention comprises rope grooves 7 which have the metallic coating 9 for the contact with the hoisting ropes 3, which coating 9 comprises an in termediate layer 12 between the base material of the trac tion sheave 5 and the contact surface 10 of the coating 9, which contact surface 10 forms an upper layer of the coating 9. The intermediate layer 12 comprises a mixture of the coating material and the base material in a gradually chang ing relation so that closer to the surface of the original base material of the traction sheave 5 the proportional amount of the base material is bigger than the proportional amount of the base material closer to the contact surface 10 of the coating 9.

Between the intermediate layer 12 and the base material of the traction sheave 5 the original surface 7a of the base material is at least partially deformed. That improves the fastness of the coating material. In figure 5 the intermedi ate layer 12 has an upper imaginary limit line 9a against the coating material and lower imaginary limit line 5a against the upper part of the base material of the rope groove 7 of the traction sheave 5. Clear limits lines like the imaginary lines 5a, 9a do not really exist but the com position of materials changes gradually from the base mate rial to the coating material or from the material of the traction sheave 5 to the material of the coating 9.

During the metal spraying phase also at least some of the carbon particles 11 deform and/or escape from the base mate rial of the traction sheave 5. Some of the carbon particles 11 move to the coating material, especially to the interme diate layer 12 of the coating 9 and some of the carbon par ticles 11 wear off totally. Thus, the base material of the traction sheave 5 has a reduced carbon content in the prox imity of the coating 9. However, the base material of the traction sheave 5 remains in its deeper areas unchanged.

Figure 6 presents a test result as a chart of a friction co efficient in relation to a sliding contact. In the test a lubricated high-strength steel rope was slid in various sliding speeds on the surface of spheroidal graphite cast iron, such as GJS 700 and the friction coefficients in the contact were determinated. The lubricant was a typical min eral based lubricant for elevator hoisting ropes. Curve 13 presents friction coefficients in different sliding speeds between the steel rope and the original cast iron surface. Correspondingly curve 14 presents friction coefficients in different sliding speeds between the steel rope and the coating 9 according to the invention, which coating 9 was sprayed onto the surface of the original cast iron surface using an appropriate metal spraying technique. The sliding speed of the steel rope in the test corresponds a normal slip of the rope on the traction sheave during the motion of the elevator car.

The friction coefficient stabilizes when the materials wear during the test. After that a stabilized friction coeffi cient can be determined. In the test the measured stabilized friction coefficient for the uncoated cast iron material was 0,130 whereas the measured stabilized friction coefficient for cast iron material coated with the coating 9 according to the invention was 0,175. In addition, the friction coef ficient and wear rate of the coating 9 proved to be more stable than the friction coefficient and wear rate of the surface of the original cast iron.

Also, a wear resistance of the coating 9 and the original uncoated cast iron surface were measured in the test. The measurement were made at the sliding speed of about 2,0 mm/s and with the contact pressure of 20-40 MPa. The measured wear volume of the uncoated cast iron material was 0,23 mm³ whereas the measured wear volume of the coating 9 according to the invention was 0,14 mm³. The test results clearly show that the coating 9 according to the invention on the surface of cast iron produces a higher friction coefficient for the rope grooves 7 of the traction sheave 5, and also the wear resistance of the coat ed rope grooves 7 is better than the wear resistance of the uncoated rope grooves 7 of the cast iron traction sheave. Also the hardness of the coating 9 according to the inven tion is bigger than the hardness of the base material of the traction sheave 5 as mentioned earlier.

All these characteristics above make it possible to achieve a traction sheave elevator where, thanks to the inventive solution in the traction sheave 5, the friction force be- tween the hoisting ropes 3 and the rope grooves 7 is im proved and where also the contact surfaces 10 or friction surfaces of the rope grooves 7 are harder than corresponding contact surfaces of uncoated rope grooves, and therefore al so wear resistance of the rope grooves 7 of the traction sheave 5 according to the invention is better than with the uncoated rope grooves of the prior art solutions.

It is obvious to the person skilled in the art that the in vention is not restricted to the example described above but that it may be varied within the scope of the claims pre sented below.

Claims

1. Traction sheave elevator comprising an elevator car (1), a hoisting machinery (4) with a traction sheave (5) and hoisting ropes (3) that are arranged to transmit driving force from the traction sheave (5) to the elevator car (1), and which traction sheave (5) comprises circumferential rope grooves (7) that have a coating (9) with a contact surface (10) for each hoisting rope (3) to contact, characterized in that the coating (9) in the rope groove (7) is a metallic layer on the surface of the rope groove (7), and the contact surface (10) of the coating (9) of the rope grooves (7) is harder than the base material of the traction sheave (5) .

2. Traction sheave elevator according to claim 1, characterized in that the coating (9) in the rope groove (7) is placed in the area where the wear of the string of the hoisting rope (3) is in its minimum.

3. Traction sheave elevator according to claim 2, characterized in that coating in the rope groove (7) is placed in the area where the wear of the coating (9) is in its minimum.

4. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) is placed in the side area of the rope groove

(7) .

5. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) has a bigger friction coefficient than the fric- tion coefficient of the base material of the traction sheave (5) .

6. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) has a bigger wear resistance than the wear re sistance of the base material of the traction sheave (5) .

7. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) comprises a metal alloy sprayed onto the surface of the rope groove (7) .

8. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) has a martensitic metallurgical microstructure.

9. Traction sheave elevator according to any of the claims above, characterized in that the coating (9) in the rope groove (7) comprises substantially 0,16 ... 0,25 wt% carbon; 12,0 ... 14,0 wt% chromium; 1,0 ... 1,5 wt% manganese and 0,0 ... 1 , 0 wt% silicon .

10. Traction sheave elevator according to any of the claims above, characterized in that the base material of the trac tion sheave (5) is of a reduced carbon content in the prox imity of the coating (9) .

11. Traction sheave elevator according to any of the claims above, characterized in that between the base material of the traction sheave (5) and the contact surface (10) of the coating (9) of the rope grooves (7) there is a zone in which composition and/or material characteristics change gradually and/or several times stepwise.