Elevator with traction sheave

An elevator has a drive mechanism connected to a traction sheave provided with grooves, over which run parallel suspension cables, and an elevator cage and an associated counterweight suspended from the suspension cables. The elevator is also provided with at least two diverting pulleys over which the suspension cables run and of which at least one diverting pulley is associated with the traction sheave in such manner that the suspension cables extending from the elevator cage to the counterweight have first and second wraps around the traction sheave and, between these wraps, a further wrap around the diverting pulley. Prior art traction sheave elevators exhibit insufficient friction between the traction sheave and the suspension cable, for which reason it is necessary, in the case of elevators of great heights, to use so-called compensating cables, which add to the weight of the elevator. With the present invention, this disadvantage is avoided by giving each of the first and second wraps an angle of wrap of at least 180.degree..

FIELD OF THE INVENTION 
The present invention relates to a traction sheave elevator comprising a 
drive mechanism, a traction sheave connected thereto and provided with 
cable grooves and parallel suspension cables running around the traction 
sheave, with an elevator cage suspended from the suspension cables and a 
counterweight therefor, the traction sheave elevator being provided, in 
addition to the traction sheave, with at least two diverting pulleys over 
which the suspension cables run and at least one of these diverting 
pulleys being associated with the traction sheave in such manner that the 
cables extending from the elevator cage to the counterweight have two 
wraps around the traction sheave and, between these two wraps, are wrapped 
one around that diverting pulley. 
DESCRIPTION OF THE PRIOR ART 
A suspension system similar to this has been disclosed in Finnish Pat. No. 
56,813, which discloses a so-called "ESW suspension" in which, in 
practice, the maximum angle of contact between the traction sheave and the 
cable running around it is 252.degree.. In more complex "double wrap" 
elevators, the angle of contact or wrap of the cable can be made 
300.degree. to 310.degree., and the cable usually runs in a semicircular 
groove. 
Elevators of this type have a high annular usage (about 400,000 to 800,000 
starts), for which reason cable grooves which help to support the cables 
are used in order to save the cables. A semicircular groove, for instance, 
is one such cable groove and has no undercutting. The friction grip is, 
however, reduced when such grooves are used, with the consequence that the 
masses of the cage and the counterweight have to be increased. From this 
it follows, further, that the diameter of the cables must also be 
increased, whereby their weight increases. A thicker cable also requires a 
larger traction sheave diameter, whereby a higher driving torque becomes 
necessary. Such elevators are normally employed when the velocities and 
elevating heights are great, in which case high accelerations are also 
employed in order to reduce the time intervals between floors. However, 
high accelerations imply high friction grippage and, owing to low 
friction, one is compelled, even for fairly small elevating heights, to 
use so-called compensating cables, which add to the linear mass of the 
elevator. A motor with even higher torque, and therefore commanding a 
higher price, is then required. 
BRIEF SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to achieve an 
improvement in a traction sheave elevator provided with a normal double 
wrap suspension. 
It is a further object of the present invention to provide a novel and 
improved traction sheave elevator which overcomes the above-discussed 
disadvantages of prior art elevators. 
The present invention provides a traction sheave elevator comprising an 
elevator cage, a counterweight for counterweighting the elevator cage and 
suspension cables extending between the counterweight and the elevator 
cage for suspending the elevator cage. A traction sheave drivingly engages 
the suspension cables, and has groove for receiving the suspension cables. 
The traction sheave is driven to thereby displace the elevator cage, at 
least two diverting pulleys being associated with the traction sheave for 
deflecting the suspension cables. The suspension cables have first and 
second wraps around the traction sheave and are wrapped, between the first 
and second wraps, about one of the diverting pulleys, the angles of wrap 
of each of the first and second wraps being greater than 180.degree.. 
Preferably, the first and second wraps have a total angle of wrap about the 
tractor sheave means of 400.degree. to 540.degree.. 
In an advantageous embodiment of the invention, the suspension cables are 
intercalated at locations where they cross themselves. For this purpose, 
the traction sheave is preferably inclined towards the diverting pulley 
and the latter is inclined about an axis passing through the centre of the 
sheave and the pulley. 
By means of the design of the present invention, a lower elevator cage 
weight than heretofore is achieved. Greater suspension heights than 
heretofore, without compensating cables, also become possible. The 
greatest savings are achieved with a so-called gearless elevator, which 
can be built without compensating cables for suspension heights up to 
about 60 m. Moreover, higher accelerations can be used in a elevator 
according to the invention. Likewise, thinner cables can be used and 
thereby the diameter of the traction sheave can also be reduced. As a 
result, the torque on the shaft of the gearless motor will be less and it 
also becomes possible to use a smaller motor.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 there is illustrated a elevator cage or car 5 disposed in guides 
(not shown) provided in a elevator shaft (not shown), this cage being 
suspended by parallel suspension cables 4, of which only one can be seen 
in FIG. 1. 
The drive mechanism 1 of the elevator is located at the top of the elevator 
shaft and comprises a traction sheave 3 provided with cable grooves. The 
suspension cables 4 coming from the elevator cage 5 have been conducted to 
the traction sheave 3 through a gap between a diverting pulley 2 and the 
traction sheave 3. The suspension cables are wrapped around the traction 
sheave 3 in such manner that the angle of contact or wrap between the 
suspension cables and the traction sheave is, in practice, about 
200.degree. to 250.degree.. The suspension cables are then directed 
obliquely downwardly and over the diverting pulley 2 back to the traction 
sheave 3 and wrapped once more around the traction sheave in such manner 
that the angle of contact or wrap between the suspension cables and the 
traction sheave 3 is again about 200.degree. to 250.degree.. 
The suspension cables then continue further over a diverting pulley 7 to a 
counterweight 6. The path of the suspension cables has been indicated by 
arrows 8-12 in FIG. 1, the numerical sequence of these arrows indicating 
the mode in which the cables run over the traction sheave and the 
diverting pulleys 2 and 7. In the embodiment of FIG. 1, directions of the 
arrows 8-12 have been selected on the assumption that the elevator cage 5 
is moving upwardly. With such an arrangement, the angle of contact or wrap 
between the traction sheave 3 and the suspension cables 4 is of the order 
of 400.degree.-500.degree. and may possibly be even more. 
As shown by FIG. 2, the suspension cables 4 are composed of three parallel 
cables. The number of cables may obviously be even greater. The cables 
have three crossing points 13, 14 and 15, at which points the cables are 
most advantageously disposed to run in intercalated fashion. In order to 
render such intercalation feasible the tractor sheave 3 has been 
appropriately inclined at an angle of 1.degree. to 1.5.degree. in the 
direction of the axis of the diverting pulley 2. similarly, the diverting 
pulley 2 has been inclined about the axis passing through the centres of 
traction sheave 3 and diverting pulley 2 (in FIG. 1 in the direction 
obliquely downward to the right). The diverting pulley 7 has also been 
tilted in order to obtain an appropriate cable angle. Likewise, the 
diverting pulley 7 has been displaced in its axial direction out of the 
plane defined by the traction sheave 3 and the diverting pulley 2, away 
from the viewer. It is to be understood that these tilts and axial shifts 
are in the nature of fine adjustment in the first place and that they can 
be accomplished in many other ways as well. 
It will be apparent to those skilled in the art that the invention is not 
confined to the embodiment given by way of example in the foregoing and 
that it may be varied within the scope of appended claims.