Field of the invention

The present invention relates to an elevator without counterweight and related drive assembly. The invention relates in particular to the tensioning system for the traction member of such elevator.

Prior art

Elevators without counterweight have a self-supporting construction separated from the structure of the building, providing a significant cost reduction and making them attractive for installation in small or old buildings The hoisting system can be arranged on one side or both sides of the cabin. For example, the elevator comprises a cabin, a frame structure with two vertical guide elements, and a drive system comprising a motor and a traction member such as a hoisting rope. A problem of this kind of elevators is to maintain a suitable tension of the traction member, due to lack of the counterweight. There is the need of a tensioning and compensation system to maintain the suitable tension of the traction member, e.g. taking into account the thermal expansion.

WO 2008/056026 discloses an elevator without counterweight wherein an elevator car is suspended on hoisting ropes, and comprising rope pulley modules, each pulley modules comprising a plurality of diverting pulleys. Basically, the plurality of diverting pulleys serves to reduce - according to the well known principle of multiple pulleys or sheaves - the power required to operate the elevator. To provide the tensioning of the hoisting ropes, a bottom pulley module comprises a rope compensation mechanism.

This prior art has the following disadvantages: the compensation system is not able to provide accurate adjustment of the tension; the disclosed system is not suitable to use of a belt as the traction member, due to the fact that the pulleys are coaxial and require a lateral deviation of the traction member, which however is not permitted by belts unless specific guide elements are provided, leading to a more complicated arrangement; moreover, the coaxially arranged pulleys generate an overturning momentum on the cabin, which results in major abrasion on the guide elements and increase of the need of traction power.

Summary of the invention

The aim of the invention is to overcome the above drawbacks of the prior art. An object of the invention, in particular, is a drive arrangement suitable for a belt-driven elevator without counterweight, and a related tensioning and compensation device.

The underlying idea of the invention is to provide a drive system with at least one belt, running over stationary pulleys fixed to the frame structure of the elevator, and moving pulleys associated with the cabin, said moving pulleys being arranged in at least a first assembly fixed to the cabin, and a second assembly connected to the first assembly by a compensation device of the tension of said drive belt.

For example, moving pulleys comprises a set of pulleys associated with a support firmly fixed to the cabin, and a further set of pulleys associated with a floating support, elastically suspended to t h e f i xed s u p po rt by t h e compensation device. The second assembly is suitably distanced from the first assembly, by tensioning the compensation device, e.g. compressing one or more spring(s).

Hence, an object of the invention is an elevator without counterweight comprising: a cabin and a frame structure, the cabin being movable relative to the frame structure in a vertical direction; a drive system comprising at least one drive belt running over a respective plurality of pulleys; the pulleys of said drive belt being grouped in at least one group of stationary pulleys associated with the frame structure, and at least one group of moving pulleys associated with the cabin; wherein said moving pulleys are arranged in at least a first assembly fixed to the cabin, and a second assembly distanced from said first assembly in the vertical direction, the second assembly being connected to the first assembly by a compensation device of the tension of said drive belt. Accord ing to one aspect of the invention, the pulleys are coplanar. In a preferred embodiment, the pulleys are substantially aligned on the vertical direction so that also their axes lie on a same plane.

For example, each group of pulleys comprises a plurality of substantially coplanar pulleys, the pulleys of each group being arranged vertically one above the other and having a diameter progressively decreasing from a first pulley of the group having a maximum diameter, to a last pulley of the group having a minimum diameter. Each of the groups of pulleys can be composed of any number of vertically aligned pulleys, with a diameter progressively decreasing from a first larger pulley to a last and smaller pulley. In common embodiments of the invention, each group is composed of two or three pulleys. At least one of the pulleys is driven by a suitable motor. In some embodiments, a disc-like motor can be used to save space.

In a preferred embodiment, the first assembly of moving pulleys comprises a first plurality of pulleys associated to a first support fixed to the cabin, and the second assembly of moving pulleys comprises a second plurality of pulleys associated to a floating support, the floating support being elastical ly connected to the fixed support by said compensation device. Preferably, the compensation device comprises at least a spring which, in use, is compressed.

A preferred embodiment of the compensation device provides that a spring or a plurality of springs act(s) on corresponding pin(s) passing through guide elements of the fixed support and the floating support. For example, the compensation device comprises a left pin and a right pin passing through a first and a second coaxial sleeves of the fixed support and of the floating support respectively, each of said left and right pin having a spring compressed between the head of the pin and one of said first and second coaxial sleeves, and having an end opposite to said head abutting against the other coaxial sleeve.

In one embodiment, a first group of stationary pulleys are fixed to the top of the frame structure of the elevator, a second group of stationary pulleys are fixed to the bottom of said frame structure, and moving pulleys are associated with the cabin, the drive belt having opposite fixed ends located in correspondence of said first and second groups of stationary pulleys.

The drive belt is a belt comprising a coating e.g . of a plastic material , enveloping suitable tension members, according to known art. For example the tension members are steel wires. The drive belt may have an arcuate shape with a convex or concave surface, matching a corresponding concave or convex surface of the pulleys, with a self-centering capability.

According to different embodiments of the invention, the elevator may have one drive belts or multiple drive belts. The drive belt or drive belts may be arranged at the sides of the cabin or behind the cabin, for example.

In embodiments with a single drive belt, said compensation device may act also as a tensioning device.

In embodiments with multiple drive belts, i .e. two or more drive belts, the above described compensation device is preferably in common for all belts, and each drive belt has preferably its own tensioning device. The common compensation device also cooperates to tension the belts.

Each belt has two opposite terminations, where the belts is fixed e.g . to a suitable termination assembly. The termination assembly preferably provides adjustment of the tension of the respective belt. In those embodiments with multiple drive belts, it is preferred that the drive belts have first terminations fixed to a common termination assembly, and second terminations fixed to a respective termination assembly associated with a respective tensioning device. Hence, each belt has a first termination fixed to the common termination assembly, and a second, opposite termination fixed to a specific termination assembly of that belt, with a suitable tensioning device. The tensioning device of each belt preferably comprises a resilient member such as a spring.

In a particularly preferred embodiment, the termination of the belt is secured to an anchor bolt that can be rotated in order to adjust the tension of the belt. The head of said anchor bolt is fixed to a lever; a distal end of said lever is acting on a pin; the pin is movable axially in a slot, and is biased by a resilient member.

An advantage of the invention is that the compensation device is integrated with the moving cabin. Another advantage is that the adjustment of the tension of the drive belt is more accurate and stable during operation. For example the tension can be regulated by acting on one of the fixed ends of the belt, and the reduction factor between the end of the belt and the tensioning device allows a fine adjustment of the tension.

The invention permits application of pulleys of minimum diameter, requiring less lateral space and keeping all the functional advantages of belts over steel cords, in particular if applied in elevators without counterweight, which in the known art depend on the friction exerted onto the rope of the driving pulley for correct movement.

The coplanar pulleys placed on mutually parallel axes, located one above the other vertically, and of decreasing diameters, allow to obtain a course of the belt adapted to reduce the power requirements by a factor of four, six or more. The reduction of power requirements is obtained with the adoption of two, three pulleys per group, etc. in such manner that the single parallel vertical tracts of the belt are not contacting each other, and that the belt does not undergo any lateral deviation. The invention provides a higher coefficient of friction and the possibility of applying smaller pulleys without requiring lateral guide elements for the belt, which moves always in the same plane and do not induce any lateral excursion of the cabin. Further advantages are the silent and vibration-free operation.

The advantages of the invention, thanks to the fact that the belts are applied in arrangements requiring a minimum of space, and with a higher factor of reduction of the drive power required, allow realisation of elevators with or without counterweight under conditions of scarce availability of space, at limited cost, and securing efficient and reliable operation.

These and other advantages of the invention will be elucidated hereinbelow with reference to preferred and non-limiting embodiments.

Description of the figures

Fig. 1 is a view of an elevator according to a first embodiment of the invention with a single drive belt.

Figs. 2 and 3 are details of Fig. 1 showing the top and bottom groups of pulleys.

Fig. 4 is a detail of Fig. 1 , showing the pulleys associated with the cabin and the tensioning device.

Fig. 5 is a scheme of the arrangement of the drive belt and pulleys of the drive system of the elevator of Fig. 1 . Fig. 6 relates to a second embodiment of the invention wherein the elevator comprises two drive belts, and is a detail of pulleys associated with the cabin and the tensioning device.

Fig. 7 is a detail of the top groups of pulleys of an elevator according to the second embodiment of Fig. 6. Fig. 8 is a detail of the bottom groups of pulleys of an elevator according to the second embodiment of Figs. 6 and 7. Detailed description of preferred embodiments First embodiment

Figs. 1 to 5 relate to an embodiment of the invention, wherein an elevator without counterweight comprises a cabin 1 and a frame structure 2 with guide rails 2a, 2b for said cabin 1 . The cabin 1 is moved relative to the frame structure 2 in a vertical direction when a drive system is operated . In this embodiment, the drive system comprises a sing le drive belt 3 which is arranged behind the cabin 1 .

The drive system comprises a number of stationary pulleys arranged in a group 4 fixed to a top element 5 of the frame structure (Fig. 2), and a group 6 fixed to a bottom element 7 of the frame structure (Fig. 3). The drive system also comprises moving pulleys arranged in groups 8, 9 associated with the cabin 1 .

The arrangement of the pulleys and the belt can be readily appreciated in Fig. 5. From a fixed termination around a first anchor bolt Pi, the belt 3 runs over pulleys 101 to 1 12 respectively, up to an opposite fixed termination of anchor bolt P ₂ . A drive motor 10 is also shown. The anchoring of the terminations of belt 3 at the anchor bolts Pi and P ₂ is realized according to a known technique. At least one of said anchor bolts allows to wrap around the belt 3 in order to regulate the overall tension of the belt itself.

Each group of pulleys comprises a plurality of coplanar pulleys, in the example there are three pulleys each group. The pulleys of each group have a diameter decreasing, from a larger pulley to a smaller one. Referring for example to group 4 of Fig. 2, the upper pulley 106 is larger than the intermediate pulley 104, and the intermediate pulley 104 is larger than the bottom pulley 102.

Pulleys 102, 104 and 106 are part of the group 4 of stationary pulleys and are rotatably supported on a plate 4a firmly screwed to the frame elements 5. The pulleys 107, 109 and 1 1 1 are part of the stationary group 6 and are rotatably supported on a plate 6a firmly screwed to the frame element 7. The pulleys 101 , 103 and 105 are part of the group 8 of moving pulleys; the pulleys 108, 1 10 and 1 12 are part of the group 9 of moving pulleys. It can be demonstrated that this arrangement of the belt 3 has a power factor of six, i.e. the lifting force is six times the tension of the belt.

The moving pulleys 101 , 1 03, 105 and 108, 1 10, 1 12 are associated to respective assemblies. One assembly is firmly fixed to the cabin 1 , while the other assembly is "floating", being elastically suspended to the fixed assembly by a tensioning device. In the example, the group 8 is associated to the fixed assem bly and the grou p 9 is associated with the suspended (floating) assembly.

A compensation device 30 is provided between said fixed assembly and said suspended assembly.

A preferred arrangement of the compensation device 30 is shown in Fig. 4. The three pulleys 1 01 , 1 03 and 1 05 are supported by a plate 20 which is screwed to the rear wall of the cabin 1 , while the three pulleys 108, 1 10 and 1 12 are supported by a plate 21 which is separate from the cabin 1 . The plate 21 is connected to the plate 20 by a left pin 22 and a right pin 23. Each of the left pin 22 and right pin 23 passes through a first guide sleeve 24 fixed to the plate 20, and a second guide sleeve 25 fixed to the plate 21 .

Said sleeves 24 and 25 may be realized with tubes welded to the plates 20 and 21 , respectively.

Springs 26 and 27 are mounted coaxially on each of said pins 22, 23, the spring 26 or 27 being then compressed between an end of the pin 22 or 23, and a guide sleeve. The connection between the plates 20 and 21 , by means of said pins 22, 23 and springs 26, 27 form said tensioning device 30 of the belt 3. More preferably, the spring 26 or 27 is compressed between a head portion of the pin and the guide sleeve of one of the fixed and floating supports. In the example of Fig. 4, the spring 26 is compressed between the head 22a of the pin 22, and the guide sleeve 24 fixed to the plate 20. The opposite end of the pin is abutting against the sleeve 25 of the plate 21 . In the shown embodiment, the pins have a threaded end and a nut is provided at the end of the pin. Fig. 4 shows the nut 22b at the end of the pin 22.

The system is adjusted so that the compensation device 30 induces a pretension of the belt 3. For example the distance y between the fixed plate 20 and the floating plate 21 is chosen to provide a given compression of the springs 26, 27 and a related pre-tension of the belt 3. Hence the device 30 acts also as a tensioning device of the belt 3 in a single-belt elevator.

In operation, the compensation device 30 reacts to change in length and/or tension of the belt 3, e.g. due to temperature, thermal expansion, maintaining the tension of the belt. Adjustment is possible by wrapping the belt around one of the anchor bolts. The system is designed so that the springs 26 and 27 operate always by compression.

Second embodiment

Figs. 6 to 8 relate to an embodiment with multiple drive belts. The items corresponding to those of the Figs. 1 to 5 are indicated with the same numerals.

In the example, the elevator has two drive belts 3a and 3b. Embodiments with more than two belts are also possible.

The compensation device 30 is in common between the two belts 3a and 3b, as seen in Fig. 6. Said belts 3a and 3b are wrapped around the moving groups of pulleys 8 and 9 associated to the cabin 1 (Fig. 6), having the compensation device 30 in common. The pulleys of first group 8 are rotatably supported on the plate 20, fixed behind the cabin 1 , and the pulleys of second group 9 are rotatably supported on the plate 21 , suspended to the plate 20 by means of pins 22, 23 and related springs 26, 27. Fig. 6 shows a different arrangement of the springs than that of Fig. 4, wherein the spring is abutting against the sleeve fixed to the floating plate. The arrangement of the springs of Fig. 4 or 6 are substantially equivalent.

Each drive belt 3a and 3b has two opposite fixed terminations connected to a respective termination assembly. One termination assembly is common to both the drive belts 3a and 3b; the other termination assembly is separate for belts 3a and 3b, and is associated to a respective tensioning device 30a, 30b.

Fig. 8 shows a common anchor belt P ₃ , which is common to a first termination of drive belt 3a and a first termination of drive belt 3b. In this example, the common termination assembly is at the lower stationary group of pulleys 6, where pulleys are supported by the plate 6a.

Fig. 7 shows that belts 3a and 3b have second terminations, opposite to said first terminations at the upper stationary group of pulleys 4, supported on the plate 4a. Said second terminations are fixed to separate anchor bolts P _4a and P ₄ b. The second termination of belt 3a is fixed to the anchor bolt P _a and the second termination of belt 3b is fixed to the anchor bolt P _b .

Each of said anchor bolts P _4a and P ₄ b is associated to a respective tensioning device 30a, 30b, comprising a lever 40, 41 fixed on the head of the anchor bolt, and having a distal end acting on a pin 42, 43; the pin 42, 43 is movable axially in a slot of a fixed member 46, 47, which in the example is a metal plate welded to the plate 4a; the displacement of the pin 42, 43 relative to said fixed member 46, 47 is biased by a spring 44, 45 coaxially mounted on the pin and compressed between the pin and the fixed member.

This arrangement provides separate regulation for the belts 3a and 3b, acting on the respective anchor bolt. The termination assemblies are preferably arranged in such a way that the belts 3a and 3b have the same tension when the levers 40 and 41 are parallel each other. Hence the levers 40, 41 give an immediate visual help for adjustment of the tension of the belts.