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

Elevators are generally provided with a separate machine room placed at the upper end of the elevator shaft. The machine room can also be located below, immediately be¬ side the elevator shaft, in which case the system is known as "side drive elevator with machine room below" . A drawback with a machine room placed at the upper end of the elevator shaft is the high cost of a separate ma¬ chine room; the machine room may account for approx. 15 % of the total costs of the elevator. Moreover, such a machine room is often placed on the roof of the build¬ ing, where it forms an unaesthetic structure in the en¬ vironment, especially in the case of low buildings. In certain countries, placing the machine room on the roof is even forbidden for aesthetic reasons, e.g. old, pro- tected buildings. Furthermore, the shadowing effect of the machine room may be a problem and thus an obstacle to building a machine room at all.

A side drive elevator with machine room below has the drawback that it requires a large number or diverting pulleys. In addition to the high price due to the large number of pulleys and the drawbacks regarding space and installation, the large number of pulleys and rope bends also reduces the useful life of the ropes. Moreover, due to the rope lengths involved, the elastic extension of the elevator ropes tends to become too large.

Because of the above drawbacks, elevator rope solutions have been developed which require only a small machine room or no machine room at all. A solution of this type is presented in French patent specification no. FR2640604, in which the machinery unit is placed either

on the elevator car or on the counterweight. However, the machinery unit is so large that it does not leave any room for maintenance purposes on the top of elevator car. In addition, the rope pulleys are so arranged that the elevator ropes undergo bends in opposite directions, involving fast rope wear. However, the worst drawback is that the angle of contact of the rope on the traction sheave e.g. in a solution as presented in Fig. 2 in the aforesaid French patent specification is much less than 180° when the suspension ratio is 1:1. Even if the larg¬ est undercut β=105° allowed by the elevator standard were to be used, it will not be economical to build an elevator car heavy enough to provide a sufficient fric¬ tion.

The object of the present invention is to eliminate the drawbacks described above and to achieve an economical and reliable elevator system. The traction sheave eleva¬ tor of the invention is characterized by what is pre- sented in the characterization part of claim 1. Other embodiments of the invention are characterized by what is presented in the other claims.

An important advantage achieved by the traction sheave elevator of the present invention is that, due to the placement of the drive machine and diverting pulleys, more space is available on the top of the elevator car and that the useful life of the hoisting ropes is pro¬ longed because the ropes do not undergo any bends in op- posite directions when passing around the traction sheave and the diverting pulleys closest to it, but in¬ stead the ropes turn in the same direction around the traction sheave and the diverting pulleys closest to it. This arrangement, where successive bends of the rope oc- cur in the same direction, is termed "forward bending".

Another significant additional advantage is that, al¬ though the rope coming to the traction sheave and the rope leaving it are subjected to a diagonal pull, an equal diagonal pull is applied to both rope portions from opposite sides of the plane of rotation of the traction sheave, so these diagonal forces cancel each other. Besides, the angle of diagonal pull is very small, only about 1.2°. Consequently, no axial forces are applied to the traction sheave and its axle. A fur- ther advantage is a prolonged useful life of the rope and traction sheave, because the wear of the rope and the rope groove on the traction sheave is more uniform and occurs on both sides and not on one side only, which would be the case if there were a diagonal pull to only one side of the plane of rotation of the traction sheave.

An additional advantage is that the ropes go to the traction sheave and leave the traction sheave in the di- rection of the planes of rotation of the diverting pul¬ leys, so these can have parallel axles. This means con¬ siderably easier and simpler installation of the hoist¬ ing machinery and ropes.

A very important advantage is the fact that the solution of the invention requires no machine room at all, which is a considerable improvement in respect of both cost and utilization of space. It is also possible to build an elevator even where a machine room placed on the roof is, for aesthetic or other reasons, forbidden.

In the following, the invention is described by the aid of an application example by referring to the attached drawings, in which

Fig. 1 presents a prior-art traction sheave elevator in side view,

Fig. 2 presents a simplified view of a rope arrange¬ ment according to the invention in a traction sheave elevator, seen obliquely from above,

Fig. 3 presents a simplified view of another rope ar¬ rangement according to the invention in a traction sheave elevator, seen obliquely from above,

Fig. 4 presents a simplified view of a third xrope arrangement according to the invention in a traction sheave elevator, seen obliquely from above,

Fig. 5 presents a simplified view of yet another rope arrangement according to the invention in a traction sheave elevator, seen obliquely from above, and

Fig. 6 presents a solution as illustrated by Fig. 5, seen from above the elevator car.

The elevator machinery 4 is normally a single-start self-braking worm gear. A feature characteristic of the solution of the invention is that the suspension is im¬ plemented using a large angle of contact on the traction sheave 28 and forward bending, so the elevator ropes 3 do not undergo any S-bends, i.e. bends in opposite di- rections, which cause fast wear. The angle of contact may be e.g. 270°. A large angle of contact allows a minimum car weight because the friction is sufficient, and therefore it is also possible to use a small machin¬ ery. In addition, as only a small undercut angle is needed and the rope arrangement is implemented using forward bending, a long rope life is achieved. As the machinery is placed in a separate supporting frame to

which the car 1 is also attached, it is possible to use damping elements between the car and the supporting frame, thus substantially reducing the vibrations trans¬ mitted from the machinery to the car.

The top of the car is of a construction rigid enough to safely support two installers and their tools. Moreover, it provides a sufficient working space for the servicing of the machinery, and likewise for bringing the elevator to a landing in the event of a power failure or malfunc¬ tion. In addition, the car can be locked in place by means of the safety gear to allow maintenance opera¬ tions .

In a suspension arrangement as illustrated by Fig. 2, one end 10 of the hoisting ropes 3 is fixed to the vault of the top floor 14. The fixing is done using a rope equalizer. From the equalizer, the ropes are passed up over a diverting pulley 8 on the upper end of a guide rail 12 and then down to a diverting pulley 5 on the top of the car. From diverting pulley 5, the ropes are passed around the traction sheave 28 of the machinery 4, which is placed on the roof of the elevator car, and further to a second diverting pulley 6 on the top of the car. From here, the ropes go up to a diverting pulley 7 mounted on the upper end of a second guide rail and then further down to the diverting pulley 9 of the counter¬ weight 2 , from where the ropes go up again to a rope an¬ chorage 11 on a supporting rail 15 at the upper end of the shaft. The diverting pulley 7 mounted on the end of the guide rail has been turned about its vertical axis approx. 22° towards the shaft wall so that the rope go¬ ing to the counterweight 2 meets the diverting pulley at an entering angle of ≤1.5°. The diverting pulley 9 on the counterweight has been turned by an equal amount in the opposite direction. Alternatively, the rope can also be fixed directly to a concrete shaft wall. The counter-

weight is placed on one side of the car, behind the guide rail, disposed between the guide rail and the shaft wall either centrically with respect to the verti¬ cal plane determined by the guide rails or aside of it. A centric arrangement has the advantage that the coun¬ terweight guide rails can easily be fixed to the same fixing rail with the car guide rails. In the case of 1:1 suspension as described above, a traction sheave under¬ cut angle of β=105°, the usual value, is used. In this case the minimum car weight is about 1.45 * rated load, which is very moderate, considering the effect of the weight of the machinery placed on the car.

Another preferred solution with suspension R=l:l is pre- sented in Fig. 3. This solution only differs from the previous one in that the diverting pulley 16 of the counterweight 2 is placed at the lower end of the coun¬ terweight. The diverting pulley 7 mounted on the end of the guide rail has been turned about its vertical axis approx. 22° towards the shaft wall so that the rope go¬ ing to the counterweight 2 meets the diverting pulley at an entering angle of ≤1.5°. The diverting pulley 16 of the counterweight has been turned by an equal amount in the opposite direction. The rope coming from the coun- terweight is fixed to a transverse beam 17 supported by the upper ends of the two guide rails.

Fig. 4 presents a third preferred solution, this time with suspension R=l:2. As a difference from the previous R=l:l solution (Fig. 2), it can be seen that the car side ends of the ropes are fixed by means of an equal¬ izer directly to an anchorage 10 on the car. The anchor¬ age is at the level of the floor joists of the car. In addition, the counterweight side ends of the ropes are passed from the diverting pulley 9 at the upper end of the counterweight to an additional diverting pulley 18 and then further down to an anchorage 11 on the axle of

the diverting pulley 9 of the counterweight. The addi¬ tional diverting pulley 18 is mounted on an anchorage 19 in the overhead beam 15.

A fourth preferred embodiment is presented in Fig. 5 and 6. The suspension ratio is 1:2, and the ropes 3 are fixed with an equalizer to an anchorage 10 on the car. From the equalizer, the ropes go up to a diverting pul¬ ley 25 mounted on the upper end of a guide rail and then down to a diverting pulley 5 on the roof of the car. Us¬ ing forward bending, the ropes are passed further around the traction sheave 28, under another diverting pulley 6 on the car roof, and then up to a diverting pulley 21 on the upper end of the other guide rail. From here, the rope goes further to a diverting pulley 22 on the upper end of a counterweight guide rail 27 and then down to diverting pulleys 23 and 24 on the upper edge of the counterweight 2, which is placed behind the car. After passing under the diverting pulleys of the counter- weight, the ropes go further up around a diverting pul¬ ley 26 on the upper end of the other counterweight guide rail and finally down to an anchorage 11 in the counter¬ weight. All the diverting pulleys 21, 22, 25 and 26 at the upper end of the shaft are mounted on a rectangular frame supported by the guide rails of the car and coun¬ terweight. For the sake of clarity, the frame is not shown in the drawings.

The machine bed 30, designed to act as a hoisting ele- ment, is fixed to the top of the car or to the car frame using elastic rubber elements. For the sake of clarity, the car frame is not shown in the figures. The machine bed has been turned into such a position that, seen from above, it crosses the car guide rail line 31 at an oblique angle. In Fig. 6, this can be clearly seen as an intersection between the centre line 32 of the machine bed and the guide rail line 31. Due to the oblique posi-

tion of the machine bed, the hoisting force is applied to the car in a fully centric manner.

Via the diverting pulleys on the ends of the guide rails, the forces resulting from the car and load weight are transmitted to the guide rails along the centroid axes of their cross-sections and further along said axes to the bottom structures 13 of the shaft. As the guide rails are placed symmetrically in the same line with re- spect to the corner points of the shaft, the shaft can be covered after the erection of the elevator by attach¬ ing the covering structures of the shaft, which may be of a net, sheet or glass construction, to the elevator and counterweight guide rails. The result is a self- supporting elevator, which needs only minimal connec¬ tions to the building; for the smallest loads (Q=320-400 kg) , it is sufficient to fix the guide rails to the floors of the building, so this type of elevator is par¬ ticularly well suited for old houses. The elevator solu- tion illustrated by Fig. 3 is like the one described above in respect of transmission of forces, covering of the shaft and adaptation for old houses.

Fig. 6 also shows a control cabinet 29 so disposed that it forms a part of the back wall of the elevator car. In this lay-out version, the control cabinet is placed be¬ tween the elevator car and the counterweight as seen in the depthwise direction. If the counterweight is placed by the side of the elevator, then the control cabinet is between the elevator car and the back wall of the eleva¬ tor shaft. This placement of the control cabinet has the advantage of simple installation and electrification of the elevator car. Moreover, this is a good solution with regard to maintenance, because servicing can be easily and safely performed from inside the elevator car by opening the door of the control cabinet from within the car.

One of the most important advantages of the traction sheave elevator is a small energy consumption when com¬ pared e.g. with the hydraulic elevator. This is due to the use of a counterweight, which compensates for the car weight and half the load weight so that when one half of the total load consists of passengers, the ele¬ vator car can remain stationary by itself. However, this brings the drawback that when the load is less than half the maximum load, the car may rush to the ceiling and damage the machinery. Rush down of the car is prevented by means of a normal safety gear mounted on the elevator car. In the solution of the invention, a characteristic feature is a large angle of contact on the traction sheave (<= =270 ^o ) as compared with a conventional traction sheave elevator, which has an angle of contact of the order of ∞=160°. This means that with the solution of the invention, a traction capacity of the traction sheave is achieved that is one and a half times the cor- responding value in a conventional solution when the normal undercut angle β=105° is used. This is indicated by the following formula:

In this formula, the number 0.2168 corresponds to the effective friction coefficient between the elevator rope and the traction sheave, achieved with 105° undercut and calculated as prescribed by the elevator standard.

The above discussion and the friction calculations indi- cate that, in the case of the structures according to the invention as illustrated by Figures 2-5, only the car weight can be counterbalanced and the counterbalanc¬ ing of the load portion of the weight can be omitted

without running the risk of an insufficient traction sheave friction for normal car weights. In elevators us¬ ing 1:1 suspension as illustrated by Fig. 2 and 3, in the most unfavourable case (maximum load, large guide rail friction) a car weight of 1.62*Q is required to en¬ sure a sufficient friction between the traction sheave and the elevator ropes. The term Q means the effective load of the elevator. Correspondingly, in elevators us¬ ing 1:2 suspension as illustrated by Fig. 4 and 5, a car weight of 1.21*Q is needed to provide a sufficient fric¬ tion. Thus, by only counterbalancing the weight of the elevator car, accidental rushing of the elevator car to the shaft top is eliminated, and no expensive extra braking device is needed on the secondary shaft.

With the arrangement described above, it also becomes advantageous to replace the conventional heavy worm gear with a light gear type having a good efficiency, such as a cylindrical gear, planet gear, cyclo gear or harmonic- drive gear. In this way, ordinary elevators for residen¬ tial buildings, e.g. elevators with values up to 8 per¬ sons, 0.63 m/s, can be implemented without load compen¬ sation and without the risk of the elevator rushing up, with the same connected load of about 4.5 kW as in the case of corresponding traction sheave elevators cur¬ rently used, because the worm gear has an efficiency only about half as good as the efficiency of the above¬ mentioned gear types (η _W orm = 0.45, whereas η _t0oth ≡ 0.95) . If load compensation is omitted, this would in principle require a stronger motor, because in this case the coun¬ terweight is lighter and does not "help" in the hoisting of a loaded elevator. Now, by using a gear with a better efficiency, the use of a larger motor can be eliminated.

The angle of contact of 215° - 270° on the traction sheave as provided by the invention is achieved by using

an arrangement where the rope 3 coming from above passes first under diverting pulley 5, clockwise and from right to left as seen e.g. in Fig. 2-5. After passing under diverting pulley 5, the rope goes in an oblique upward direction towards the traction sheave 28 and passes around the traction sheave in the clockwise direction by going up by the left side of the traction sheave, be¬ tween the traction sheave and diverting pulley 6. After passing over and around the traction sheave, the rope comes down by the right side of the traction sheave and goes between the traction sheave and diverting pulley 5 and further from under the traction sheave towards di¬ verting pulley 6. In other words, the rope, or rather the set of ropes (1 - 6 parallel ropes) , crosses itself under the traction sheave and then goes further in an oblique downward direction towards diverting pulley 6, passing under diverting pulley 6 and around it in the clockwise direction. From diverting pulley 6, the rope goes further up. In other words the set of ropes 3 crosses itself between the diverting pulleys 5,6 on the top of the car and the traction sheave 28. The individ¬ ual ropes in the rope set are prevented from touching each other or themselves at the crossing by suitably setting the planes of rotation of the diverting pulleys 5,6 and the traction sheave 28 and the directions of said planes relative to each other. This has been imple¬ mented by tilting the traction sheave 28 by about 1.2° from the horizontal plane and turning the whole machin¬ ery 4 in the horizontal plane by approx. 1.2° about the vertical axis passing through the centre of the traction sheave, so that the rope coming to the traction sheave and the rope leaving it form an angle of about 1.2° to the plane determined by the groove on the traction sheave on either side of said plane. The rope running in each rope groove of the traction sheave comes into the groove from one side of the plane determined by the groove and when leaving the groove it goes to the other

side of this plane. In this way, both the rope coming to the traction sheave and the rope leaving it are sub¬ jected to diagonal pulls that are preferably set to equal magnitudes so that the diagonal pulls cancel each other and do not produce any forces acting in the axial direction of the traction sheave. On the diverting pul¬ leys 5,6, the ropes run in the direction of the rope grooves both at entry and at exit, so there is no diago¬ nal pull on these pulleys. Naturally, the rope grooves on each diverting pulley and on the traction sheave are placed at a distance from each other such that the ropes in adjacent grooves are separated by a distance larger than the diameter of the ropes.

Each one of the ropes in the set of ropes runs in its own rope groove on the traction sheave so that the con¬ tinuous angle of contact on the traction sheave is within the range 215°-270°. A contact angle exceeding 270° produces on the traction sheave too large a diago- nal pull for the resulting fast wear of the ropes and traction sheave to be acceptable. With a contact angle of about 250°, fairly small distances between pulleys and a fairly small machinery can be used without a large diagonal pull. In the case of a traction sheave of ini- mum diameter (40*rope diameter) , a contact angle of 250° results in a diagonal pull of about 1.2° on the rope leaving the rope groove of a pulley. In most practical solutions, contact angles between 230°-260° are possi¬ ble, in which case neither the distance between pulleys nor the diagonal pull is very large. If a contact angle of 270° is used, this requires a traction sheave with a larger diameter. In this case, a diameter equal to 45*rope diameter results in a diagonal pull of about 1.2° as described above.

The distances between the diverting pulleys 5,6 and the traction sheave 28 in the lateral and vertical direc-

tions have been so adjusted that the desired angle of contact on the traction sheave is achieved. The traction sheave 28 is mounted above the level of the diverting pulleys 5,6, which again are generally at the same level relative to each other. The traction sheave can be placed at a level above the diverting pulleys such that one or both of the diverting pulleys 5,6 can go partly below the traction sheave, as shown in Fig. 6, in which diverting pulley 5 lies partly below the traction sheave 28. In this case, the point of crossing of the ropes un¬ der the traction sheave is not symmetrical with respect to the distance between the diverting pulleys.

It is obvious to a person skilled in the art that dif- ferent embodiments of the invention are not restricted to the application described above, but that they may instead be varied in the scope of the claims presented below. In the examples, the crossing between rope por¬ tions without the ropes touching each other or the - selves is achieved by turning the traction sheave through an angle in the horizontal plane and by tilting the traction sheave and via suitable placement of the diverting pulleys. However, it is obvious that the rope crossing can be implemented in other ways.