GB2575808A

GB2575808A - Elevator car

Info

Publication number: GB2575808A
Application number: GB1811986.7A
Authority: GB
Inventors: Bennett Alister
Original assignee: Singapore Lift Co Pte Ltd
Current assignee: Singapore Lift Co Pte Ltd
Priority date: 2018-07-23
Filing date: 2018-07-23
Publication date: 2020-01-29
Also published as: GB201811986D0; WO2020021243A1

Abstract

An elevator car comprising a tubular shell 12 of thermoplastic material, at least a first rigid panel 14 bonded or otherwise affixed over an open end of the shell. Also disclosed is a method of manufacturing an elevator car 10. Comprising: forming a plug of a desired cross- sectional shape; heating a first sheet of thermoplastic material to its processing temperature and moulding said heated first sheet around said plug so as two opposing edges thereof meet and abut or overlap; subsequently allowing or causing said moulded first sheet to cool and harden into a generally tubular component 12 having a lateral cross-sectional shape corresponding to that of said plug, and removing said plug; cutting or otherwise forming a second sheet of rigid material 14, 16 into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component 12; and, bonding said second sheet over a first open end of said generally tubular component.

Description

ELEVATOR CAR

Field of the Invention

This invention relates generally to an elevator car, and a method of manufacturing an elevator car.

Background of the Invention

Elevators, otherwise known as lifts, are well known and there are a number of different types of such devices in common use today. In general, an elevator or lift comprises a vertical shaft and an elevator car located within the vertical shaft. The elevator car is coupled to a mechanism, such as a belt or chain mechanism, that enables its ascent and descent between upper and lower ends of the shaft corresponding to bottom and top floors of a building or other structure, and a control mechanism to cause the elevator car to move within the shaft to the top or bottom floor or, where applicable, intermediate floors therebetween. The elevator car is usually, essentially a rectangular container having four side walls, a ceiling and a floor, and includes an opening or door in one of the side walls to enable persons to enter and leave the car at their destination or floor. In order to meet the required strength and fire regulations, the lift car is often made primarily of rigid metal, such as steel sheet or similar material.

Another type of elevator system is known as a pneumatic vacuum elevator.

Referring to Figure 1 of the drawings, a typical pneumatic vacuum elevator comprises a tubular elevator car 100, which may be formed of aluminium and polycarbonate, having a floor 102 and a ceiling 104. A tubular housing 106, again formed of aluminium and polycarbonate, defines a vertical shaft 108 (when oriented for use) and the elevator car 100 is slidably mounted therein with a seal 2 between the outer wall of the ceiling 104 and the inner walls of the shaft 108. A vacuum pump 4 is provided at the top end 105 of the housing 106 and an atmospheric pressure zone 1 is maintained within the shaft 108, below the elevator car 100. A piston gear (not shown) is configured to selectively depressurise the top chamber 3 inside the shaft 108 above the elevator car 100, while the inside of the elevator car always remains at atmospheric pressure (A.P.). If the pressure within the top chamber 3 is lowered to below atmospheric pressure, the elevator car 100 will be lifted by the higher atmospheric pressure beneath it. A valve (not shown) regulates inflow of air in the top chamber 3 (low pressure zone) so as to control pneumatic depression and enable selective descent of the elevator car 100. It will be understood that, when the valve allows air at atmospheric pressure into the top chamber 3, the elevator car can be lowered to a desired level, the speed of air inlet controlling the speed of travel. The atmospheric pressure zone 1 is open to ensure it remains at atmospheric pressure. A simple suction process (using the piston gear and air inlet valve and limited by the side walls of the shaft 108 and the upper end of the housing 106) is used to set the difference in pressures between the top chamber 3 and the atmospheric pressure zone 1. Locking devices and a braking system are generally also included.

Elevator arrangements of this type have some advantages relative to conventional elevator devices. For example, they are simpler to install, have a smaller footprint and consume much less energy. However, with pneumatic vacuum elevators, as with conventional elevator devices, there are a number of issues.

Firstly, the weight of the elevator car is constrained by the materials that need to be used and the safety regulations that need to be adhered to, including fire safety regulations. The materials used to make the lift car must be appropriately fire rated, as well as needing to have sufficient strength and rigidity to comply with associated safety regulations and ensure durability. This, in turn, results in a relatively heavy elevator car, even if some parts are formed of a relatively light polycarbonate, it must be a of a minimum thickness, and the aluminium frame is required to secure the polycarbonate sheets and provide the required rigidity. It is clear that the weight of the elevator car determines the size of the pneumatic piston required and the overall energy consumption of the elevator device.

to There is a general desire to reduce energy consumption of elevator devices, and aspects of the present invention seek to address this issue.

Statements of Invention

In accordance with an aspect of the present invention, there is provided a method of manufacturing an elevator car, comprising the steps of: - forming, or otherwise obtaining, a plug of a desired cross-sectional shape; - heating a first sheet of thermoplastic material to its processing temperature and moulding said heated first sheet around said plug so as two opposing edges thereof meet and abut or overlap; subsequently allowing or causing said moulded first sheet to cool and harden into a generally tubular component having a lateral cross-sectional shape corresponding to that of said plug, and removing said plug; cutting or otherwise forming a second sheet of rigid material into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component; and bonding said second sheet over a first open end of said generally 5 tubular component.

In an exemplary embodiment, the method may further comprise cutting or otherwise forming an entrance opening in a portion of said generally tubular component.

The plug may be formed of metal material, such as aluminium.

The first sheet may advantageously comprise a thermoplastic composite, such as a reinforced thermoplastic composite material and more preferably a fire rated reinforced thermoplastic composite material, examples of which include polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

In an exemplary embodiment, the first sheet may comprise a laminated structure comprising a pair of thermoplastic skins having therebetween an intermediate layer of material having a foam, honeycomb or corrugated structure.

The thermoplastic skins may, advantageously, be formed of thermoplastic composite, such as a reinforced thermoplastic composite material and more preferably a fire rated reinforced thermoplastic composite material, examples of which include polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

The intermediate layer of material may comprise thermoplastic, thermoplastic composite, paper, pressboard or aluminium. In an exemplary embodiment, the intermediate layer may be bonded to adjacent surfaces of said skins by means of an adhesive, such as epoxy resin adhesive.

The method of the invention may further comprise: cutting or otherwise forming a third sheet of rigid material into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component; and bonding said third sheet over a second, longitudinally opposing open io end of said generally tubular component.

In an exemplary embodiment, the second and/or third sheets may comprise a thermoplastic material, and more advantageously a thermoplastic composite material, such as a fire rated reinforced thermoplastic composite material, examples of which include polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

In an exemplary embodiment, the second and/or third sheet may comprise a laminated structure comprising a pair of thermoplastic skins, having therebetween an intermediate layer of material having a foam, honeycomb or corrugated structure. The thermoplastic skins may, advantageously, be formed of a thermoplastic composite, such as a reinforced thermoplastic composite material and more preferably a fire rated reinforced thermoplastic composite material, examples of which include polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).

Once again, the intermediate layer of material may comprise a thermoplastic, thermoplastic composite, paper, pressboard or aluminium, and be bonded to adjacent surfaces of said skins by means of an adhesive, such as an epoxy resin adhesive.

The method of the present invention may further comprise printing, on an inner surface of said generally tubular component and/or on a surface of said second and/or third sheet, an electroluminescent film defining OLED elements.

In a first specific exemplary embodiment of the invention, the said bonding of io said second and/or third sheet to an open end of said generally tubular component may be performed before said step of cutting or otherwise forming it into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component; whereas in an alternative exemplary embodiment of the invention, the said bonding of said second and/or third sheet to an open end of said generally tubular component may be performed after said step of cutting or otherwise forming it into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component.

In accordance with another aspect of the present invention, there is provided an elevator car comprising a generally tubular shell formed of thermoplastic material, and at lease a first rigid panel bonded or otherwise affixed over an open end of said shell.

In accordance with a further aspect of the present invention, there is provided an elevator car manufactured in accordance with the method defined above, comprising a generally tubular component formed of a first sheet of fire rated reinforced thermoplastic composite material and a floor and/or ceiling formed of a respective second sheet of fire rated reinforced thermoplastic composite material, said floor and/or ceiling being bonded over a respective open end of said generally tubular component by a non-metallic weld and having a shape and size corresponding to the lateral cross-sectional shape and size of the generally tubular component.

Optionally, an inner surface of said generally tubular component and/or a surface of said floor and/or ceiling may have printed thereon an electroluminescent io layer defining a plurality of OLED elements.

Aspects of the invention extend to an elevator system, such as a pneumatic vacuum elevator system, incorporating an elevator car substantially as defined above.

The elevator system may, in some exemplary embodiments, comprise an electromechanical mechanism for effecting selective ascent and descent of said elevator car within an elevator shaft, said electromechanical system being electrically coupled to an energy supply unit, said energy supply unit comprising an AC to DC conversion module having an input communicably couplable to an AC power supply, and a DC power output, said DC power output being communicably coupled to said electromechanical mechanism for driving said elevator car.

Brief Description of the Drawings

Embodiments of the present invention will now be described, by way of examples only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram illustrating a pneumatic vacuum elevator in accordance with the prior art; Figure 2 is a schematic perspective view of an elevator car according to an exemplary embodiment of the present invention; s Figure 2A is a schematic bottom view of the elevator car of Figure 2; Figure2B is a schematic plan view of the elevator car of Figure 2; and Figure 3 is a schematic cross-sectional view of a laminate RTC including a honeycomb core, suitable for use in a method of manufacturing an elevator car according to an exemplary embodiment of the present invention.

Detailed Description

Referring to Figure 2 of the drawings, an elevator car 10 in accordance with an exemplary embodiment of the present invention comprises a generally tubular shell 12, a floor panel 14 and a ceiling panel 16. The shell 12, the floor panel 14 and the ceiling panel 16, together, form a transport 'container' for transporting people or cargo between floors of an elevator system such as, but not necessarily limited to, a pneumatic vacuum elevator system of the general type described above. Referring additionally to Figures 2A and 2B of the drawings, it can be seen that the peripheral profile of the tubular shell 12 is not circular, but instead it has an irregular peripheral profile.

An opening 18 is provided in the side wall of the elevator car, defined by the shell 12, to enable access to the inside of the elevator car 10 by which a person may enter or leave the elevator car 10 when it is stationary and located at a floor of the building or structure in which the elevator system is installed. A door (not shown), for example, a circumferential sliding door, may be provided adjacent the opening 18 to open and close the access means as required.

The outer shell 12 is formed of a fire-rated thermoplastic (to be discussed in more detail hereinafter) by means of a hot moulding process. First, a mould is created, using any known method, which has an outer profile matching that required for the peripheral profile of the shelll2. The mould or "plug" may be formed of any material able to withstand the temperature at which the thermoplastic being used softens or melts. For example, aluminium is known to be a highly suitable material for use in a mould or "plug" for a thermoplastic hot moulding process, although the io present invention is not intended to be limited in this regard.

A suitably sized sheet of the fire-rated thermoplastic is heated, in an oven or other suitable heating apparatus, to its "processing temperature namely the temperature at which the thermoplastic melts and softens sufficiently to be readily manipulated. Processing plants for manufacturing thermoplastic components are known in the art, and this aspect will not be described in any further detail herein.

The softened thermoplastic sheet is then moulded around the aluminium plug, and the opposing side (longitudinal) edges are pushed together. The moulded sheet is then cooled so that it hardens into the shape defined by the mould and the abutting opposing edges from a strong bond with each other. The plug is removed, and the exposed lateral edges can be finished in any known manner, as required. Any known form of cutting the thermoplastic shell, such as laser cutting, may be used to form an opening therein to serve as an access opening for entering and leaving the elevator car.

The floor 14 and ceiling 16 may also be formed of fire-rated thermoplastic material. For both components, a sheet of the selected thermoplastic material need only be cut into the same shape as the lateral cross-sectional profile of the shell 12. As stated above, methods of cutting thermoplastics into a required shape, such as laser cutting for example, are known in the art and need not be discussed in any further detail herein.

Next, the floor 14 and ceiling 16 must be attached over the bottom and top ends, respectively, of the shell 12. It will be clear to a person skilled in the art that the bond between the floor/ceiling and the lower/upper edges of the thermoplastic shell 12 need to be as strong as possible to ensure that they don't introduce significant regions of weakness in the finished elevator car, which would otherwise potentially cause a failure. A non-metallic bond is required, and many different methods of non-metallic bonding of thermoplastic components are known in the art. For example, the most commonly used form of bonding such components is known as induction welding, wherein the thermoplastic sheets are heated to melting point at their common interface and then allowed to cool. This forms a strong bond between the two surfaces, but the shape and size of the induction head limits the shapes and geometries of the thermoplastic components which can be welded together and, in the case of the present invention, would not always work in respect of the various non uniform and irregular shaped profiles that the elevator car could otherwise have.

Thus, a preferred method of non-metallic bonding of the thermoplastic shell to the floor/ceiling is resistance welding, wherein an electrically conductive carbon-fibre textile is positioned between two surfaces to be bonded to form a weldable assembly, and pressure is applied to the weldable assembly. Next, a voltage is applied to the carbon-fibre textile to heat it, thereby melting the thermoplastic at the adjoining surfaces. The melted thermoplastic fills the inter-fibre spaces in the carbon-fibre textile; and, when the voltage is removed and the carbon-fibre textile is allowed to cool, a weld is formed between the two adjoining surfaces of the thermoplastic components. This method of non-metallic welding is described in s more detail in US Patent Application Publication No. US2017/0043528A1. However, it will be appreciated that other types of non-metallic bonding or joining could, in some alternative exemplary embodiments, be used. For example, dove tail joints and bonding (adhesive or welding) could be used or, indeed, the components could be bolted together using metallic rods that run from floor to ceiling through channels in the wall sections so that they are hidden within the wall structures.

Many different thermoplastics are widely known in the art. Thermoplastic composites are becoming increasingly widely used due to their strength and other beneficial characteristics, and are readily available in sheet form for use in the above-described method of manufacture. Although the present invention is not necessarily intended to be limited with regard to the thermoplastic composite used, there are some considerations to be made when selecting a specific thermoplastic or thermoplastic composite for use in any application. Depending on where the elevator car is to be used, and to what purpose, there are likely to be strict statutory regulations to be adhered to, which dictate, for example, the strength of the elevator car (and the weight/force it can withstand without failing), power consumption, recyclability and fire, smoke and toxicity characteristics. Reinforced Thermoplastic Composites (RTCs) are, therefore, considered highly beneficial for use in a method according to the invention. RTCs comprise thermoplastic, otherwise known as thermsoftening plastic, integrated with one or more other materials. Examples of thermoplastics are polyvinyl chloride (PVC) and polyetrafluorethylene (PTFE).

Typically, the other material will be a fibrous compound, for instance carbon-fibre or fibreglass, thereby adding strength to the composite material. Specific examples of such RTCs include polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), which are inherently fire resistant and are finding increasing utility in, for example, aircraft interiors to meet stringent flame, smoke and toxicity (FST) standards. These, and similar materials, are thought to be highly beneficial for use in the exemplary method described above to produce the safety-and weight-critical components, namely the shell 12, the floor 14 and the ceiling 16 of an elevator car according to an exemplary embodiment of the present invention.

In some applications, additional strength may be required. Of course, the thickness of the RTC sheet used to form a component will dictate, at least to some extent, its strength. However, it will be apparent to a person skilled in the art that it is highly preferable to minimise the thickness of the RTC layer, in order to minimise the weight of the elevator car. In cases such as this, it may be beneficial to utilise a laminated thermoplastic sheet, comprising relatively thin layers of thermoplastic material (or "thermoplastic skins") with a foam or honeycomb core therebetween. Referring to Figure 3 of the drawings, this is known as a 'sandwich structure' and may comprise, for example, a pair of RTC laminate skins 20 having a 'honeycomb' core 22.The core may be made of any suitable lightweight material having the required fire rating including, for example, Nomex paper, pressboard, thermoplastic composite foam, or Larcore ® aluminium honeycomb. The core 22 is typically bonded to the inner walls of the RTC skins 20 by a respective layer 24 of adhesive, such as epoxy resin adhesive. Sheets of such laminated RTC material, including the core 22, are available from various manufacturers, or they may be assembled specifically prior to commencing the above-described method, and the present invention is not necessarily limited in this regard. These laminated sheets can be manipulated (when heated to the temperature at which the RTC skins 20 melt and soften), cut and finished using similar techniques as are used in respect of single RTC sheets, and are therefore highly suitable for use in the method described above.

Thus, a method according to the invention results in the production of an elevator car for use in, for example, a pneumatic vacuum elevator system, having an outer profile, or footprint, of any desired shape, limited really only by the ability to shape the aluminium 'plug'. Given that the aluminium plug can be formed into a mould of almost any shape, the variations are substantially limitless. The weight of the resultant elevator car, if RTC is used for the shell, floor and ceiling, can be reduced relative to known (comparably sized and rated) elevator cars by 80-90%, whilst retaining or even exceeding current strength and fire, smoke and toxicity (FST) requirements and standards. This means that the power required to drive the elevator is significantly reduced. Indeed, it is thought that some elevator systems could, using an elevator car according to an exemplary embodiment of the invention, be run on DC, rather than AC, power. In addition, the materials used may be fully recyclable.

Another advantage of an elevator car according to an exemplary embodiment of the invention arises in relation to the interior walls thereof (i.e. the inner walls of the shell 12). The surface of the RTC skin lends itself to printing. Thus a portion, or even all, of the surface of the sheet or skin that will form the inner wall of the shell 12 can be printed (e.g. inkjet printed) with OLED emissive materials so as to form a screen on which any desired information or media can subsequently be displayed in a known manner. Because the electroluminescent film forming the OLEDs is able to flex, this can be done before the shell is moulded (although it can also be done after if required). Similarly, the OLEDs could be printed onto the inner surface of the floor or ceiling of the elevator car such that further display screens can be created, or s indeed OLED lighting can be used to light the interior of the elevator car. OLED technology is very low power and can be operated at very low voltages (-5V), thus further contributing to the overall low power solution and even the potential to run the whole elevator system on DC, rather than AC, power.

It will be appreciated by a person skilled in the art, from the foregoing description, that modifications and variations can be made to the described embodiment without departing from the scope of the invention as defined by the appended claims. In particular, it is to be understood that the present invention may not necessarily limited to use for elevator cars for pneumatic vacuum lifts. Indeed, it may be understood that the benefits afforded by aspects of the present invention may be equally effectively obtained in respect of elevator cars for other types of elevator devices.

Claims

CLAIMS1. A method of manufacturing an elevator car, comprising the steps of: - forming, or otherwise obtaining, a plug of a desired cross-sectional shape; -heating a first sheet of thermoplastic material to its processing temperature and moulding said heated first sheet around said plug so as two opposing edges thereof meet and abut or overlap; - subsequently allowing or causing said moulded first sheet to cool and harden into a generally tubular component having a lateral cross-sectional shape corresponding to that of said plug, and removing said plug; - cutting or otherwise forming a second sheet of rigid material into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component; and -bonding said second sheet over a first open end of said generally tubular component.
2. A method according to claim 1, further comprising cutting or otherwise forming an entrance opening in a portion of said generally tubular component.
3. A method according to claim 1 or claim 2, wherein said plug is formed of metal material.
4. A method according to claim 3, wherein said metal material comprises aluminium.
5. A method according to any of the preceding claims, wherein said first sheet comprises a thermoplastic composite.
6. A method according to claim 5, wherein said thermoplastic composite comprises a reinforced thermoplastic composite.
7. A method according to claim 6, wherein said first sheet comprises a fire rated reinforced thermoplastic composite material.
8. A method according to claim 7, wherein said fire rated reinforced thermoplastic composite material comprises one of polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).
9. A method according to any of the preceding claims, wherein said first sheet comprises a laminated structure comprising a pair of thermoplastic skins having therebetween an intermediate layer of material having a foam, honeycomb or corrugated structure.
10.A method according to claim 9, wherein said thermoplastic skins are formed of a thermoplastic composite material, such as fire rated reinforced thermoplastic composite material, and said intermediate layer of material comprises thermoplastic, thermoplastic composite, paper, pressboard or aluminium.
11. A method according to claim 9 or claim 10, wherein said intermediate layer is bonded to adjacent surfaces of said skins by means of an adhesive.
12. A method according to any of the preceding claims, further comprising: - cutting or otherwise forming a third sheet of rigid material into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component; and - bonding said third sheet over a second, longitudinally opposing open end of said generally tubular component.
13. A method according to any of the preceding claims, wherein said second and/or third sheets comprise a thermoplastic material;
14.A method according to claim 13, wherein said second and/or third sheets comprise a thermoplastic composite material.
15.A method according to claim 14, wherein said thermoplastic composite material comprises a fire rated reinforced thermoplastic composite material.
16.A method according to claim 15, wherein said fire rated reinforced thermoplastic composite material comprises one of polyetherimide (PEI), Polyphenylene Sulfide (PPS), polyetheretherketone (PEEK) and polyetherketoneketone (PEKK).
17. A method according to any of the preceding claims, wherein said second and/or third sheet comprises a laminated structure comprising a pair of thermoplastic skins, having therebetween an intermediate layer of material having a foam, honeycomb or corrugated structure.
18. A method according to claim 17, wherein said thermoplastic skins are formed of a thermoplastic composite material, such as a fire rated reinforced thermoplastic composite material, and said intermediate layer of material comprises a thermoplastic, thermoplastic composite, paper, pressboard or aluminium.
19.A method according to claim 17 or claim 18, wherein said intermediate layer is bonded to adjacent surfaces of said skins by means of an adhesive.
20. A method according to any of the preceding claims, further comprising printing, on an inner surface of said generally tubular component and/or on a surface of said second and/or third sheet, an electroluminescent film defining OLED elements.
21. A method according to any of the preceding claims, wherein said bonding of said second and/or third sheet to an open end of said generally tubular component is performed before said step of cutting or otherwise forming it into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component.
22. A method according to any of claims 1 to 20, wherein said bonding of said second and/or third sheet to an open end of said generally tubular component is performed after said step of cutting or otherwise forming it into a shape and size matching the cross-sectional shape and size of the outer periphery of said generally tubular component.
23. An elevator car comprising a generally tubular shell formed of thermoplastic material, and at lease a first rigid panel bonded or otherwise affixed over an open end of said shell.
24. An elevator car manufactured in accordance with the method of any of claims 1 to 22, comprising a generally tubular component formed of a first sheet of fire rated reinforced thermoplastic composite material and a floor and/or ceiling formed of a respective second sheet of fire rated reinforced thermoplastic composite material, said floor and/or ceiling being bonded over a respective open end of said generally tubular component by a nonmetallic weld and having a shape and size corresponding to the lateral cross-sectional shape and size of the generally tubular component.
25. An elevator car according to claim 24, wherein an inner surface of said generally tubular component and/or a surface of said floor and/or ceiling has printed thereon an electroluminescent layer defining a plurality of OLED elements.26.An elevator system incorporating an elevator car according to any of claims 23 to 25.27.An elevator system according to claim 26 comprising a pneumatic vacuum elevator system.28.An elevator system according to claim 26 or claim 27, comprising an electromechanical mechanism for effecting selective ascent and descent of said elevator car within an elevator shaft, said electromechanical system being electrically coupled to an energy supply unit, said energy supply unit comprising an AC to DC conversion module having an input communicably couplable to an AC power supply, and a DC power output, said DC power output being communicably coupled to said electromechanical mechanism for driving said elevator car.