Reducing elongation of roping or belting of an elevator by pretensioning the roping or belting of the elevator

Abstract

Example embodiments relate to an elevator. The elevator may include a car of the elevator and a counterweight that are to be moved reciprocally, at least one roping or belting traveling via a top pulley assembly for connecting the car of the elevator and the counterweight to each other via the top pulley assembly, and at least one roping or belting traveling via a bottom pulley assembly for connecting the car of the elevator and the counterweight to each other via the bottom pulley assembly.

Claims

1. An elevator, comprising: an elevator car configured to transport a load; a counterweight; at least one roping or belting travelling over a top pulley assembly so as to connect the elevator car and the counterweight to each other via the top pulley assembly; at least one roping or belting travelling over a bottom pulley assembly so as to connect the elevator car and the counterweight to each other via the bottom pulley assembly; a tensioning device configured to pretension the at least one roping or belting travelling over the bottom pulley assembly to a force equal to or greater than a weight of a nominal load of the elevator car such that the at least one roping or belting is pretensioned prior to loading the elevator car; and at least one brake configured to increase a spring constant associated with at least one of the at least one roping or belting travelling over the top pulley assembly and the at least one roping or belting travelling over the bottom pulley assembly while loading the elevator car by preventing a rotation of the at least one of the top pulley assembly and the bottom pulley assembly while the tensioning device pretensions the at least one roping or belting travelling over the bottom pulley assembly.

2. The elevator according to claim 1, wherein the tensioning device includes a lock and a spring.

3. An improvement for reducing movement of the elevator car incident to elongation of the at least one roping or belting of the elevator during loading of the elevator car, wherein the elevator according to claim 1 is used so that the pretensioned at least one roping or belting traveling via the bottom pulley assembly and the at least one roping or belting traveling via the top pulley assembly interact with each other and provide a reduction of the movement of the elevator car during the loading of the elevator car incident to elasticities of the at least one roping or belting travelling via the top pulley assembly and the at least one roping or belting traveling via the bottom pulley assembly as compared to when the at least one roping or belting traveling via the bottom pulley assembly is not pretensioned.

4. The elevator according to claim 1, wherein, for different loads, the pretensioning of the at least one roping or belting traveling via the bottom pulley assembly is pretensioned to different forces based on the different loads.

5. The elevator according to claim 1, wherein the pretensioning of the at least one roping or belting is configured to act on a section of the at least one roping or belting between the elevator car and the bottom pulley assembly.

6. The elevator of claim 1, wherein the at least one brake comprises: a top brake configured to prevent the rotation of the top pulley assembly while loading the elevator car; and a bottom brake configured to prevent the rotation of the bottom pulley assembly while loading the weight of the load into the elevator car.

7. The elevator of claim 1, wherein, while the tensioning device pretensions the at least one roping or belting travelling over the bottom pulley assembly, the at least one brake is configured to, increase a spring constant associated with the top pulley assembly while loading the elevator car, when the at least one brake prevents the rotation of the top pulley assembly, increase a spring constant associated with bottom top pulley assembly while loading the elevator car, when the at least one brake prevents the rotation of the bottom pulley assembly, and increase spring constants associated with the top pulley assembly and the bottom pulley assembly while loading the elevator car, when the at least one brake prevents the rotation of both the top pulley assembly and the bottom pulley assembly.

8. A method of pretensioning of at least one roping or belting traveling over a bottom pulley assembly, the method comprising: moving reciprocally an elevator car and a counterweight; connecting the elevator car and the counterweight to each other via a top pulley assembly; connecting the elevator car and the counterweight to each other via the bottom pulley assembly; pretensioning the at least one roping or belting travelling over the bottom pulley assembly using a tensioning device, such that the pretensioning pretensions to a force equal to or greater than a weight of a nominal load of the elevator car such that the at least one roping or belting is pretensioned prior to loading the elevator car; and increasing a spring constant associated with at least one of the at least one roping or belting travelling over the top pulley assembly and the at least one roping or belting travelling over the bottom pulley assembly while loading the elevator car by preventing a rotation, using at least one brake, of the at least one of the top pulley assembly and the bottom pulley assembly of the at least one roping or belting while the elevator car is loaded.

9. The method according to claim 8, wherein, the preventing the rotation is performed at least in part by a brake device.

10. The method according to claim 8, wherein, the preventing the rotation includes preventing a rotation of two or more pulleys of the top pulley assembly or the bottom pulley assembly at least in part by the at least one brake.

11. The method according to claim 10, wherein, the preventing the rotation includes preventing a rotation of at least one pulley of the top pulley assembly and a rotation of at least one pulley of the bottom pulley assembly.

12. A method of operating an elevator, the elevator including an elevator car connected to a counterweight via a top pulley assembly using a first rope, and a bottom pulley assembly using a second rope and a tensioning device, the method comprising: pretentioning, using the tensioning device, the second rope, to a force equal to or greater than a nominal weight of the elevator car such that the second rope is pretensioned prior to loading the elevator car; and increasing a spring constant associated with at least one of the first rope and the second rope while loading the elevator car by preventing a rotation, using at least one brake, of at least one of the top pulley assembly and the bottom pulley assembly while the elevator car is loaded.

13. The method according to claim 12, wherein the increasing the spring constant includes preventing the rotation of both the top pulley assembly and the bottom pulley assembly while loading the elevator car.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention will be presented in more detail by the aid of some embodiments described by FIGS. 1 and 2.

(2) FIG. 1 illustrates a schematic view of the car of an elevator and a counterweight, which are connected to each other by the aid of ropings traveling via both a top pulley assembly and a bottom pulley assembly;

(3) FIG. 2 illustrates a schematic view of an elevator corresponding to FIG. 1, in which is also marked to be visible a motor and tensioning means.

(4) The same reference numbers refer to the same parts in both FIGS.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(5) The displacement during loading of the car 10 of the elevator 1 according to FIG. 1 can be reduced, or the displacement can be minimized or even totally eliminated, by pretensioning the displacement ropes 51, 52 of the supporter force.

(6) In a conventional elevator, the elasticity of the displacement ropes causes a displacement of the car during loading. The supporter is the rope between the car and the machine. The displacement is at its maximum when the car is at the bottommost level. In a conventional elevator, the supporters between the machine and the traction sheave participate in supporting the load coming into the car.

(7) In the elevator 1, the car 10 and the counterweight 11 are connected in such a way that the displacement rope 51 passes around a pulley assembly (pulley 12 and shafting 13) that is rigidly fixed in the top end of the elevator hoistway and the displacement rope 52 passes around a pulley assembly (pulley 14 and shafting 15) that is rigidly fixed in the bottom end of the elevator hoistway in such a way that the length of the supporter loop thus produced remains constant and pretensioning is performed on this loop. The displacement during loading of the car 10 essentially decreases because the displacement ropes 51, 52, i.e. the whole loop, support the car 10.

(8) One of the two pulleys 12, 14 is the traction sheave of the machine of the elevator 1. During the loading the brake of the machine prevents rotation of the traction sheave 12, 14 (the brake acts at the point of the supporter 18, 19 on the side of the traction sheave). The elevator 1 can also comprise a second brake, which prevents the rotation of the second pulley 12, 14 and the movement of the supporters (the brake acts at the point of the supporter 18, 19 of the pulley on the opposite side to the traction sheave).

(9) The system thus produced is significantly stiffer than a conventional elevator system. The amount of leveling starts of the electric drive of the drive machinery of the elevator 1 can be essentially reduced and comfort in the car 10 improved when the movement of the car 10, particularly on the bottommost floor (which is in most cases the main floor) can be reduced to somewhere around one one-hundredth of what is conventional.

(10) In high-rise buildings the lateral swinging of the displacement ropes caused by swaying of the building is a problem. When the displacement ropes 51, 52 are pretensioned between two rigidly fixed pulleys 12, 14, the amplitude during lateral swinging of the displacement ropes 51, 52 is smaller than in a conventional solution, in which the pulley 14 of the bottom end of the hoistway is able to move in the vertical direction.

(11) In a conventional solution the own mass of the displacement ropes cannot be reduced by using displacement ropes of a high strength class, because the flexing of the displacement ropes would become too great. In the elevator 1 according to the invention the use of displacement ropes of a high strength class as the displacement ropes 51, 52 is possible owing to the increased load-bearing cross-section.

(12) There follows an example calculation for an elevator 1 comprising steel ropes as the displacement ropes 51, 52:

(13) According to our model, the bulk factor of the cable is 0.622 and the cable weighs 1.2 kg/m.

(14) According to our model, the elongation L.sub.i of each displacement rope 51, 52 is proportional to the change F.sub.i in the force acting at any given time on the displacement rope 51, 52 in question:
L.sub.i=k.sub.iL.sub.i(1.1)

(15) On the other hand, the change in the force is exerted on both ropes:
F.sub.1+F.sub.2=F(1.2).

(16) The change L.sub.i in the length of each displacement rope 51, 52 is equal
L.sub.1==L.sub.2(1.3).

(17) According to its definition, for the spring constant:

(18) $\begin{array}{cc}{k}_i=\frac{A_i{E}_i}{L_i}.& \left(1.4\right)\end{array}$

(19) On the basis of equations (1.4), (1.1) and (1.3), we can write:

(20) $\begin{array}{cc}\frac{F_1}{k_1}=\frac{F_2}{k_2}=\frac{F-F_1}{k_2}.& \left(1.5\right)\end{array}$

(21) From this we can solve F.sub.1:

(22) $\begin{array}{cc}{F}_1=\frac{k_1}{k_1+k_2}F.& \left(1.6\right)\end{array}$

(23) On the basis of equation (1.1) we can write:

(24) $\begin{array}{cc}{L}_1=\frac{F_1}{k_1}& \left(1.7\right)\end{array}$
in which k.sub.1, and k.sub.2 can be determined separately for each of the cases we want.

(25) The general parameters of our model can be seen in Table 1:

(26) TABLE-US-00001 TABLE 1 general parameters Pretensioning force .fwdarw. nominal load 0.00 0.25 0.50 0.75 1.00 Load of car (%) 100 100 100 100 100 Load (kg) 1800 1800 1800 1800 1800 Distance (m) 240 240 240 240 240 Nominal load (kg) 1800 1800 1800 1800 1800 Car + displacement 3450 3450 3450 3450 3450 ropes Average brake 149832 149832 149832 149832 149832 force (min.) E1 (N/mm.sup.2) 75000 75000 75000 75000 75000 E2 (N/mm.sup.2) 75000 75000 75000 75000 75000 A1 tot. (mm.sup.2) 841 841 841 841 841 A2 tot. (mm.sup.2) 803 803 803 803 803 k11 (N/m) 259585 344695 512839 1001257 21026394 k21 (N/m) 21026394 1001257 512839 344695 259585 k21 (N/m) 20072195 955819 489566 329052 247805 k21 (N/m) 247805 329052 489566 955819 20072195 k1a (N/m) 256419 256419 256419 256419 256419 k2a (N/m) 244783 244783 244783 244783 244783

(27) Case 1: The top pulley 12 is braked and the bottom pulley 14 is free to rotate.

(28) $k_1=k_{11}=\frac{A_1{E}_1}{L_{11}}$$k_{12}=\frac{A_1{E}_1}{L_{12}}$$k_{2a}=\frac{A_2{E}_2}{L_{12}+L_{22}}$$k_2=\frac{k_{12}{k}_{2a}}{k_{12}+k_{2a}}$

(29) The data for Case 1 are in Table 2.

(30) We observe that if the traction sheave 12 in the top end or the traction sheave 14 in the bottom end must be braked, the corresponding displacement in the top end or in the bottom end is 35.2 mm, i.e. approx. one-half compared to the conventional elevator system presented below.

(31) TABLE-US-00002 TABLE 2 Pretensioning force .fwdarw. nominal load 0.00 0.25 0.50 0.75 1.00 k1 (N/m) 259585 344695 512839 1001257 21026394 k2 (N/m) 241966 196696 165695 143136 125983 dF1 (kg) 932 1146 1360 1575 1789 dF2 (kg) 868 654 440 225 11 dL car (mm) 35.2 32.6 26.0 15.4 0.8 75 kg .fwdarw. dL car (mm) 1.5 1.4 1.1 0.6 0.0

(32) Case 2: the bottom pulley 14 is braked and the top pulley 12 is free to rotate:

(33) $k_1=\frac{k_{1a}{k}_{22}}{k_{1a}+k_{22}}$$k_{1a}=\frac{A_1{E}_1}{L_{11}+L_{12}}$$k_{22}=\frac{A_2{E}_2}{L_{22}}$$k_2=k_{21}=\frac{A_2{E}_2}{L_{21}}$

(34) The data for Case 2 are in Table 3.

(35) TABLE-US-00003 TABLE 3 Pretensioning force .fwdarw. nominal load 0.00 0.25 0.50 0.75 1.00 k1 (N/m) 126019 144115 168280 202180 253185 k2 (N/m) 20072195 955819 489566 329052 247805 dF1 (kg) 11 236 460 685 910 dF2 (kg) 1789 1564 1340 1115 890 dL car (mm) 0.9 16.1 26.8 33.2 35.2

(36) Case 3: the bottom pulley 14 is braked and the top pulley 12 is braked:

(37) $k_1=k_{11}=\frac{A_1{E}_1}{L_{11}}$$k_2=k_{21}=\frac{A_2{E}_2}{L_{21}}$

(38) The data for Case 3 are in Table 4. We observe that if the pulleys 12, 14 of both the top end and the bottom end are kept in their position with a brake, the displacement of the car 10 of our example case is 17.6 mm, i.e. approx. one-quarter of the displacement of a corresponding conventional solution.

(39) TABLE-US-00004 TABLE 4 Pretensioning force .fwdarw. nominal load 0.00 0.25 0.50 0.75 1.00 k1 (N/m) 259585 344695 512839 1001257 21026394 k2 (N/m) 20072195 955819 489566 329052 247805 dF1 (kg) 23 477 921 1355 1779 dF2 (kg) 1777 1323 879 445 21 dL car (mm) 0.9 13.6 17.6 13.3 0.8 75 kg .fwdarw. (mm) 1.5 1.4 1.1 0.6 0.0 dL car

(40) Data for the non-pretensioned elevator are presented in Table 5. As we observe, elongation of the displacement ropes of a conventionally designed elevator being implemented with the same dimensioning would produce with the nominal load a displacement of 68.0 mm of the car.

(41) TABLE-US-00005 TABLE 5 Pretensioning force .fwdarw. nominal load 0.00 0.25 0.50 0.75 1.00 k1 (N/m) 259585 344695 512839 1001257 21026394 dL car (mm) 68.0 51.2 34.4 17.6 0.8 75 kg .fwdarw. dL car (mm) 2.8 2.1 1.4 0.7 0.0

(42) FIG. 2 presents an elevator of the type of FIG. 1, wherein also marked to be visible are a motor 20 and a tensioning unit, which comprises a spring 21 and a lock 22. The lock 22 is installed in connection with the car 10.

(43) According to the markings presented in FIG. 2 we can write
L.sub.0=L.sub.1+L.sub.2(2.1)
and
F=F.sub.0+F.sub.2(2.2).

(44) For the spring constant k.sub.i the following still holds true:

(45) $\begin{array}{cc}{k}_i=\frac{A_i{E}_i}{L_i}& \left(2.3\right)\end{array}$
likewise for the forces
F.sub.1=F.sub.2(2.4).

(46) Also in the case of FIG. 2 we can write:

(47) $\begin{array}{cc}{F}_i=k_i{L}_i\mathrm{and}& \left(2.5\right)\\ L_i=\frac{F_i}{k_i}.& \left(2.6\right)\end{array}$

(48) By inserting and solving we obtain:

(49) 0$\begin{array}{cc}\frac{F_0}{k_0}=\frac{F_1}{k_1}+\frac{F_2}{k_2}=F_2\left(\frac{1}{k_1}+\frac{1}{k_2}\right)& \left(2.7\right)\\ \frac{F-F_2}{k_0}=\frac{F_2}{k_1}+\frac{F_2}{k_2}\mathrm{and}& \left(2.8\right)\\ F_2=\frac{F}{\frac{1}{k_0}+\frac{1}{k_1}+\frac{1}{k_2}}.& \left(2.9\right)\end{array}$

(50) When the pretensioning force of the roping is marked F.sub.pr we obtain:

(51) When F.sub.pr>F.sub.0 in a situation in which the length of the roping is L.sub.0, minimum,

(52) in a situation in which the change in force is estimated to be maximal, we obtain:

(53) $\begin{array}{cc}{F}_0=\frac{F\left(\frac{1}{k_1}+\frac{1}{k_2}\right)}{\frac{1}{k_0}+\frac{1}{k_1}+\frac{1}{k_2}}& \left(2.10\right)\end{array}$
from this it follows that

(54) $\begin{array}{cc}{L}_{0,p}=F_2\left(\frac{1}{k_1}+\frac{1}{k_2}\right)& \left(2.11\right)\end{array}$
because the roping 51, 52 can be regarded as springs installed in parallel. When friction forces are ignored,
F.sub.1F.sub.2F.sub.3(2.12)

(55) From which it follows that

(56) $\begin{array}{cc}{L}_{0,s}=L_1+L_2=F\left(\frac{1}{k_1}+\frac{1}{k_2}\right),& \left(2.13\right)\end{array}$
in which case for the relative change in length we obtain

(57) $\frac{L_{0,p}}{L_{0,s}}=\frac{1/k_0/\left(\frac{1}{k_0}+\frac{1}{k_1}+\frac{1}{k_2}\right)}{\frac{1}{k_1}+\frac{1}{k_2}}$

(58) For example, in a case in which
L.sub.0=L.sub.1,L.sub.1=2L.sub.0,A.sub.0=A.sub.1=0.5A.sub.2 and E.sub.0=E.sub.1=E.sub.2
we obtain

(59) $\begin{array}{c}\frac{L_{0,p}}{L_{0,s}}=\frac{L_0/A_0/\left(\frac{L_0}{A_0}+\frac{L_0}{A_0}+\frac{2L_0}{A_0}\right)}{\frac{L_0}{A_0}+\frac{2L_0}{2A_0}}\\ =\frac{1/\left(1+1+1\right)}{1+1}\\ =\frac{1}{6}.\end{array}$

(60) If, correspondingly, there were not pretensioning in the fabricated elevator, the elasticity, or the relative change in length, would be much larger because the ropings 51, 52 would behave as springs installed in series and not as springs installed in parallel.

(61) In an example embodiment, the elevator must not be regarded as being limited only to the claims below but instead should be understood to include all legal equivalents of said claims and combinations of the embodiments presented.

(62) More particularly, instead of, or in addition to, the displacement ropes 51, 52 above, belts can be used. In the lattermost case, it is called displacement belting.

(63) A person skilled in the art will also understand that use of the pretensioning of an elevator according to the invention for bracing the roping could also be expressed as a method wherein the roping is braced by the aid of pretensioning.