DRIVE UNIT FOR A RACK ELEVATOR

Abstract

The invention relates to a drive assembly (1) for raising or lowering a structure (4) on a mast (2), which drive assembly comprises a drive frame (5) movable along the mast and supporting said structure, a pair of pinions (4:1, 4:n), a rack (6) arranged on the mast (2), a transfer case (14) which comprises a planetary gear set (20) and drives a starting pinion (4:1), an additional gear set (30) which drives a final pinion (4:n) through a drive unit (7) connected to the planetary gear set (20).According to the invention, the planetary gear set (20) and the auxiliary gear set (30) are arranged in a transmission ladder (36) at different levels in height in the transfer case (14) and configured to rotate their respective pinions (4:1, 4:n) on parallel shafts (34:1, 34:n) in a series in a stack formation (17) in a vertical plane at different levels in height and, being in engagement with a tooth side of the rack (6) common to the pinions, maintain a balanced even load on the shafts (34:1, 34:n) regardless of instantaneous speed deviations between the starting pinion (4:1) and the final pinion (4:n) while the pinions (4:1, 4:n) are driven with the same direction of rotation.

Description

The invention relates to a drive unit for raising and lowering a structure on a mast according to the preamble of claim 1. The invention also relates to a rack-and-pinion driven elevator system according to claim 14, and to a distribution box included in a drive unit in a rack-and-pinion driven elevator according to claim 15.BACKGROUNDRack and pinion elevators used in the construction industry comprise a mast which is erected in sections and a lift cage or a work platform which, supported on a drive frame, can move up and down along the mast. A drive unit is attached to the drive frame of the rack and pinion elevator and with which drive unit the lift cage can move along the mast through the interaction between a rack extending along the mast and one or more motor-driven pinions whose gears engage the rack.A drive unit intended to carry only a relatively small payload, up to about 1 ton, can normally be driven satisfactorily by a single motor with a single pinion meshing with the rack. For drives with a larger required load capacity this arrangement is not satisfactory as the load on the teeth of the pinion becomes too great. If a single pinion is to be used it is necessary to increase the cross-sectional area of the rack in order to provide teeth of sufficient strength. Increasing the rack dimensions not only increases the material costs but also the cost of machining the teeth. Increasing the cross-section of the rack to enable the elevator to carry heavier loads therefore considerably increases the cost of the elevator as a whole.To avoid having to increase the cross-section of the rack for elevators carrying payloads over 1 ton, it has become common practice to provide drive units with two electric motors sharing the load, each with its own gearbox and output pinion meshing with the rack. The use of two electric motors has the advantage that the drive force is evenly balanced between the output shafts of the pinions and is forgiving of external factors such as tolerance deviations or defects in the respective gear meshing to the extent that the drive system allows for sporadic speed deviations between the pinions. However, using two or more electric motors is costly, cumbersome and creates extensive assembly problems. With two or more electric motors, significant assembly and space problems also arise, which often limit the available load space of the elevator car and also increase the dead weight of the elevator car very significantly, which limits the desired payload and energy efficiency of the elevator.The term pinion refers in the following to a gear wheel supported on a rotatable shaft that drives against a rack from a transfer case (gearbox). The term mast refers to a vertically elongated vertical standing and braced structure. The term gear mechanism refers to a device for power transmission that changes the rotational speed, torque and / or direction of rotation from one rotating shaft to another. The term planetary gear refers to a composite transmission system, whereby the term sun gear refers to the inner central gear of the planetary gear, the term planet carrier refers to the rotatable part that holds at least one, usually three or more, gear wheels and that rotates around the sun gear. The term outer ring refers to the outer gear ring with inward-facing teeth that interact with the teeth of the planet gear / gears. The term mono refers to one, tandem or pair = two and a group = three or more. The term planetary gear set with starting pinion refers to a planetary gear set that is located at a starting level in a transmission ladder and to which planetary gear set a drive unit is connected. The term additional gear set with final pinion refers to a gear that is located at a final level in the transmission ladder that is separate from the starting level. The term transmission ladder refers to one or more series-connected gear sets, of which an additional gear set is the gear that is furthest from the planetary gear set at the starting level. The term intermediate planetary gear set refers to one or more series-connected planetary gears that are located at an intermediate level in the transmission ladder, between the planetary gear set at the starting level and the final gear set at the final level. The term conventional gear mechanism refers to a gear mechanism that has a lack of gear wheels (planetary gears) that are fixed on a shaft and can move in an orbit around a central gear wheel (sun gear).In order to solve the above-mentioned problems with varying rotational speeds occurring when the pinions mesh, it is previously known to arrange drive units that include a single engine for tandem operation in which a transfer case allows reduced speed operation of a pair in the form of two pinions in combination with a tandem-type rack equipped with two tooth sides facing each other, whereby said pinion pairs are active on each side of the rack, i.e. on two sides of the rack facing each other. Thanks to the fact that the pinions are in mesh on each side of the rack, the pinions are allowed to rotate sporadically at different speeds without the driving force on the shafts being significantly affected.Such drive units which include a planetary gear set are known, for example, from WO2006079759 A1 and WO2017198464A1 . Manufacturing tandem-type racks with double rows of teeth, on either side of the rack along its length is expensive and involves significant difficulties and costs for implementing tandem-type drive units, since existing elevator installations are normally adapted for conventional single pinion drive on mono-type racks with only a single tooth side.It should be understood that in arrangements involving a single motor driving two pinions operating on a common side, it has been found that the load on the pinions will inevitably vary due to the difficulty of manufacturing the drive mechanism with sufficiently close tolerances to ensure that both gears engage the teeth of the respective rack precisely simultaneously and synchronously equally over the entire length of the rack, and due to wear and similar external factors.In this part, it should be understood that some of the problems with uneven loading on the pinions arise from the discontinuous running that due to tolerance deviations, as well as wear and similar external factors that can randomly and over time occur between the pinion and the rack.Accordingly, it is desired to overcome these disadvantages by providing a cost-effective drive unit for a rack and pinion elevator which comprises a single motor and which, via a transfer case, allows differential operation of at least two pinions in combination with a monotype rack which is only equipped with gear teeth on one of its long sides. In this part, the desire lies in the transfer case being designed so that the pinions strive to always spread and distribute the load equally between their respective shafts, i.e. in the case of a design with two pinions to 50 / 50 between them, regardless of the above-mentioned external factors.Another desire is to provide a cost-effective drive unit for a rack and pinion elevator which comprises a single drive unit and which, via a transfer case, allows the operation of a group of pinions which is equal to or exceeds three pinions and which, with a large payload, can operate in combination with a monotype rack which is only equipped with gear teeth on one of its long sides and which at the same time can thereby ensure that the load under all circumstances strives to be distributed evenly between the pinions which are jointly engaged with the rack. Another desire is that the transfer case should allow the pinions to rotate at different speeds in a forgiving manner, when necessary, such as when different loads occur on the pinions, but which automatically successively evens out and distributes the load equally between the shafts of the pinions.Another requirement is that the drive unit should be compact and lightweight.Another desire is to provide a drive unit with a distribution box that can be part of a flexible production system and that, through a modular design of the multiple gear sets that in the form of small, stackable parts can be manufactured in large series, and can be easily adapted to a variety of differential gears in a variety of designs that can meet every need for the desired payload of the elevator through a simple connection (series connection).An object of the present invention is therefore to provide a drive assembly for a rack and pinion elevator that allows operation of at least two pinions in combination with a monotype rack that is only equipped with gear teeth on one of its long sides.Another object of the invention is to provide a rack-and-pinion driven elevator system in a rack-and-pinion elevator which ensures that the load under all circumstances tends to be distributed evenly between the at least two pinions which are jointly engaged with the rack.Another object of the invention is to provide a transmission ladder included in a drive unit for raising or lowering a structure on a mast, a drive unit in a rack and pinion elevator which allows differential operation of a pair or a group of pinions equal to or exceeding three pinions and which can operate in combination with a monotype rack which is only equipped with gear teeth on one of its long sides.These objects of the invention are solved by a drive unit for a rack and pinion elevator that has obtained the features and characteristics stated in claim 1. A rack and pinion-driven elevator system according to claim 14 and a distribution box for a rack and pinion elevator according to claim 15.The insight underlying the invention is that a differential gear constructed of planetary gears connected in series will automatically be self-regulating in terms of its ability to divide driving torques between two or a group of even more shafts by dividing each input torque equally between the planetary gears. By suitable configuration, the transfer case will similarly divide and spread the load between a number of pinions and be self-regulating, in which case different torques occurring will automatically be distributed evenly between the pinions in a drive unit in a rack and pinion elevator. That is, the driving force will be distributed evenly between the output shafts of the pinions, which ensures that the load on the shafts is always balanced, regardless of whether the rotational speed between the shafts momentarily varies.More specifically, it has been found that since the load in a differential gear based on planetary gear technology will always choose the path of least resistance, it will also automatically distribute more load to all pinions that have less resistance than the others until the torque is again equal between the pinion shafts. This property, which has been taken into account in the invention, is based on the ability of a planetary gear to allow an asymmetrical speed distribution between driven pinions.It has further been somewhat surprisingly shown that this very property, of automatically distributing more load to pinions with less resistance, can effectively compensate for tolerance deviations between pinion and rack, wear and similar external circumstances so that load deviations can be avoided by sporadic speed variations in the pinions.According to the main idea of the invention, the drive unit uses a gearbox with one planetary gear per extra output pinion over one to achieve an optimal torque distribution between output gears and distribute the load equally on both shafts, regardless of the circumstances that may occur, which may relate to unevenly and or seriously worn racks, large occurring rack gaps, unforeseen damage to interacting tooth formations, etc. The drive unit thereby offers a differentiated drive that is self-regulating and that ensures that the torque is automatically distributed equally between the pinions. The gearbox works by having a sun gear at the starting level driven by the engine. The carrier of the planetary gear then directly drives one of the output shafts and the outer ring of the planetary gear drives the other output shaft via a secondary gear set, which is advantageously also of the planetary type. By selecting a suitable set of teeth in the gear sets of the gearbox in all stages, the torque is then divided 50 / 50 to each output pinion. Since the load will always choose the path of least resistance through differential distribution, the planetary gearbox will automatically distribute more load to all pinions that momentarily have less resistance (rotate at a higher speed) than the others until the torque is equal between the two shafts of the pinions. To achieve more than two output pinions, the outer ring of a planetary gear set should drive the sun gear of a subsequent planetary gear set and so on for each additional planetary gear set in the transmission stages per desired output pinion from the distribution box formed by series-connected planetary gear sets.The drive assembly according to the invention thus has good ability to adjust itself automatically so that the drive, regardless of external circumstances, is transmitted equally between the two pinions or the arbitrary (n) number of pinions included in the drive assembly driven by a single drive unit.FIGURE DESCRIPTIONIn the following, the invention will be described in more detail with reference to the accompanying drawings, in which;Fig. 1 shows a perspective view of a rack and pinion elevator incorporating a drive unit according to the invention.Fig. 2A shows a perspective view from the gear side of a transfer case in a first embodiment that drives a pair in the form of two output pinions in a drive assembly according to the invention.Fig. 2B shows a perspective view from the pinion side of the transfer case in Fig. 2AFig. 3 schematically shows a first embodiment of a transfer case that drives a pair in the form of two output pinions in a drive assembly according to the invention.Fig. 4 schematically shows a second embodiment of a transfer case which drives a series of an arbitrary "n" number of pinions which may but need not necessarily exceed a group of three or even more pinions.DESCRIPTION OF EMBODIMENTSIn Fig. 1 a rack-and-pinion driven elevator 1 is shown which is part of the type of elevator system used in the construction industry. The rack-and-pinion elevator 1 comprises a mast 2 of truss type constructed in the form of a number of stackable and mountable mast sections 3 and a structure in the form of an elevator car 4 which, through controlled interaction between a drive frame 5 included in the elevator car, can move up and down along the mast 2, which is illustrated by a double arrow. The drive frame 5 can, in a manner known per se and not shown in more detail, abut with guide rollers against longitudinal roller tracks of the mast and via one or a plurality of pinions 4:1, 4:n be supported on a rack 6 of monotype extending along the mast and thus only having a single tooth side along its length. Said pinions 4:1, 4:n are two in number and thus of tandem type. The pinions 4:1, 4:n are driven by an electric motor unit so that the drive frame 5 and thus the elevator car 4 can be driven up and down along the mast 2. The mast 2 is intended to be anchored at regular intervals to a nearby building structure such as a wall or the like (not shown).The drive frame 5 carries a drive assembly 10 with a drive unit 7 comprising a drive motor 11 and a gearbox 1 connected to the drive motor and housed in a housing 12, which as a unit forms a transfer case 14 for differential operation of the pinions 4:1, 4:n from the drive unit 7. The elevator car 4 thus carries its own drive assembly 10 and is guided on the mast 2 by interaction between the said guide rollers included in the drive frame 5 and the said guides in the form of roller tracks extending along the mast (not shown).The elevator car 4 is thus movable up and down along the mast 2 by interaction between the rack 6 extending along the mast and the said motor-driven pinions 4:1, 4:n which, starting from the distribution box 14, engage the rack 6. In the area opposite each of the said pinions 4:1, 4:n, an abutment member 8 is arranged in a known manner in abutment against the back side of the rack 6 (see Fig. 1). The abutment member 8, usually in the form of a steel roller rolling against the back side of the rack 6, is arranged to counteract the deflection of the rack 6 that would occur through the engagement of the pinions 4:1, 4:n if only the gearing of the pinions 4:1, 4:n acted against the rack 6.With reference to Fig. 2, a first embodiment of a drive unit 10 for raising and lowering the elevator car 4 along a mast 2 according to the invention is schematically shown.As mentioned above, the drive assembly 10 comprises a starting pinion 4:1 extending from the transfer case 14 housing 12 and an output final pinion 4:n which in tandem formation are in common engagement at a mutual distance C - C from each other along the length of the tooth side of the monotype rack 6 extending along the mast 2. The drive unit 7 is connected to the transfer case 14 for operating said pinions 4:1, 4:n from the drive unit 7 so that the driving force of the drive unit is distributed between the two pinions 4:1, 4:n. The transfer case 14 which in its function essentially forms part of said gearbox is shown schematically with a dotted contour line.The drive unit 7 comprises a motorized system of hydraulic or electric type whose output shaft 15 corresponds to the input shaft of a possibly present preparatory reduction gear 16 if necessary or a speed reduction stage which substantially reduces the input engine speed before it is transferred to the sun gear 21 of the planetary gear set 20 at starting level Z0 in the transfer case 14.In order to achieve desired automatic torque distribution between said output tandem formation of pinions 4:1, 4:n from the drive unit 7 which is connected to the transfer case 14, said transfer case comprises a planetary gear set 20 which drives a starting pinion 4:1 and an additional gear set 30 which drives a final pinion 4:n.As can be seen from Fig. 2A and 2B and Fig. 3, the planetary gear set 20 and the auxiliary gear set 30 are arranged in a sequence of transmission stages at different levels in height with respect to the longitudinal axis of the rack 6 and which gear sets 20, 30 are configured to rotate their respective pinions 4:1, 4:n with the same direction of rotation on parallel shafts 34:1, 34:n (see also Fig. 1) arranged in a series in stack formation 15 in a vertical plane at different levels in height with respect to the longitudinal axis of the rack 6 and in engagement along the single tooth side of the monotype rack 6. By means of the embodiment, a balanced even load will be maintained on the shafts 34:1, 34:n regardless of instantaneous speed deviations between the starting pinion 4:1 and final pinion 4:n while pinions 4:1, 4:n are driven with the same direction of rotation.It should thus be understood that even if the direction of rotation of the respective pinions 4:1, 4:n is the same, the speed of rotation will in practice differ sporadically, i.e. the pinions 4:1, 4:n do not necessarily have to rotate synchronously at the same speed, but through the influence of the differential gear effect offered by the planetary gear set, the pinions 4:1, 4:n will automatically search for the least resistance and rotate accordingly. It should be understood, however, that through the occurring tooth engagement, the joint will lock the pinions 4:1, 4:n to rotate alternately with the least resistance in the same direction.The planetary gear set 20, which is located at a starting level Z0 in the transmission stages 36, comprises a planetary gear set whose sun gear 21 is driven by the drive unit 7, whose planet carrier 22 drives the starting pinion 4:1 and whose outer ring 23 drives the final pinion 4 via the additional gear set 30. In the embodiment shown, the additional gear set 30 at the final level Zn comprises a conventional gear set.The power transmission between the outer ring 23 of the planetary gear set 20 and the final pinion 4 of the additional gear set 30 following in the transmission stage 36 comprises a gear set 38 whose flow path for rotatable movement between coupled gears extends in a radial direction in relation to the 4:1 shaft 34:1 of the starting pinion. The gear set 38 comprises an intermediate gear 25 which, together with the outer ring 23 of the planetary gear set 20, rotates about the 4:1 shaft 34:1 of the starting pinion, and a connecting gear 36 which is torque-transmittingly supported on the 4:1 shaft 34 of the final pinion.As best seen in Fig. 2A and 2B, the planetary gear set 20 comprises a wheel-like structure 26 connected to the outer ring 23, which extends from the outer ring and further radially inward towards the 4:1 axis 34:1 of the starter pinion and terminates in a central hub 24 on which the intermediate gear 25 is mounted in a rotationally fixed manner for rotation together with the outer ring 23 about the 4:1 axis 34:1 of the starter pinion. The intermediate gear 25 supported on the hub 24 is freely mounted on the 4:1 axis of rotation 34:1 of the starter pinion via a rolling bearing 39. The rotation shaft 34:1 of the planetary gear set 20 and the rotation shaft 34:n of the additional gear set 30 project from an end piece 27, only indicated in Fig. 2B by dotted contour lines, which is part of the transfer case 14. Said respective rotation shafts 34:1, 34:n each comprise a first and a second rolling bearing 40, 40' with which the rotation shafts are held in said end piece (27) in the transfer case (14).The gear set 38 of the auxiliary gear set 30, comprising said intermediate gear 25 and connecting gear 36, is located in a space between said end piece 27 and the wheel-like structure 26 of the planetary gear set 20. The wheel-like structure 26, the planetary gear set 20 and the auxiliary gear set 30 each constitute essentially a series of flat, plane-parallel and in a series, side-by-side units with very limited axial extension, which contributes to the essentially compact design of the transfer case 14.Referring to Fig. 4, a second embodiment of the invention is schematically shown, a series of an arbitrary "n" number of pinions 4:1, 4:2 - 4:n comprising a group consisting of at least three pinions 4:1, 4.2 - 4:n and configured to rotate said pinions with the same direction of rotation on parallel axes 34:1, 34.2 - 4:n in a series in stack formation 15 at different levels in height in a common vertical plane. Pinions 4:1, 4:2 - 4:n are in engagement with the tooth side of the rack 6 common to the pinions.In accordance with this second embodiment of the invention, between the planetary gear set 20 which is located at a starting level Z0 in the transmission stages 36 and drives the starting pinion 4:1 included in the group and the additional gear set 30 which is located at a final level Zn in the transmission stages 36 and drives the final pinion 4:n included in the group, an intermediate planetary gear set 20:2 is arranged which drives an intermediate pinion 4:2 at an intermediate level in height of the stack formation 15 on parallel axes 34:1, 34:2 - 34:n. Said intermediate planetary gear set 20:2 comprises on the one hand a sun gear (21) which is driven by the outer ring 23 of the planetary gear set 20 which is located at a starting level Z0 in the transmission stages 36, and on the other hand a planet carrier 22 which drives the intermediate pinion 4:2.In this second embodiment of the invention, there are two intermediate planetary gear sets 20:2, 20:3 which drive intermediate pinions 4:2, 4:3 at an intermediate level at different heights of the stack formation 15 on parallel axes 34:1, 34:2, 34:3 - 34:n in a common vertical plane. The parallel shafts 34:1, 34:2, 34:3 - 34:n project from an end piece 27 which is part of the transfer case 14. The pinions 4:1, 4:2, 4:3, 4:n are in engagement with the tooth side of the rack 6 common to the pinions, whereby the sun gear 21 of one intermediate planetary gear set 20:3 in the transmission stages 36 is driven by the outer ring 23 of the other intermediate planetary gear set 20:2 in the transmission stages 36.A characteristic of the invention is that a planet carrier 22 of each of said intermediate planetary gear sets 20:2, 20:3 drives the intermediate pinions 4:2, 4:3.However, it should be pointed out that the corresponding self-regulating and torque-spreading effect between the pinions would also be obtained if the inventive drive unit were driven in reverse, i.e. so that the planet carrier drives a second subsequent gear in a series and the outer ring the first in the series.In the latter embodiment, the sun gear 31 of the intermediate planetary gear set 20:3 in the transmission stages 36 is driven by the action of the outer ring 23 of a preceding intermediate planetary gear set 20:2 in the transmission stages 36. Alternatively, the sun gear 31 of an intermediate planetary gear set 20:3 in the transmission stages 36 is driven by the action of the outer ring 23 of a preceding intermediate planetary gear set 20:2 in the transmission stages 36.

Claims

1. Drive assembly (1) for raising or lowering a structure (4) on a mast (2), which drive assembly comprises a drive frame (5) movable along the mast and supporting said structure, a pair of pinions (4:1, 4:n), a rack (6) arranged on the mast (2) with which said pinions are in common engagement, a transfer case (14) which, for common operation of each pinion, comprises a planetary gear set (20) which drives a starting pinion (4:1) and an additional gear set (30) connected to the planetary gear set and which drives a final pinion (4:n) through a single drive unit (7) connected to the planetary gear set (20), characterised in that the planetary gear set (20) and the additional gear set (30) are arranged in a sequence of transmission stages (36) at different levels in height in the transfer case (14) and configured to be on parallel shafts (34:1, 34:n) rotate their respective pinions (4:1, 4:n) in a series in a stack formation (15) in a vertical plane at different levels in height and, being in engagement with a tooth side of the rack (6) common to the pinions, through the action of the planetary gear set (20) maintain a balanced even load on the shafts (34:1, 34:n) regardless of sporadically occurring speed deviations between the starting pinion (4:1) and the final pinion (4:n) at the same time as the pinions (4:1, 4:n) are driven with the same direction of rotation.

2. Drive assembly (1) according to claim 1, wherein the planetary gear set (20) is located at a starting level (Z0) in the transmission stages (36) and comprises a sun gear (21) driven by the drive unit (7), a planet carrier (22) driving the starting pinion (4:1) included in the pair, an outer ring (23) which, via the additional gear set (30), drives the final pinion (4:n) included in the pair, located at a final level in the height direction of the stack formation (15) and where said additional gear set (30) is located at a final level (Zn) in the transmission stages (36).

3. A drive assembly according to claim 2, wherein the auxiliary gear set (30) comprises a gear set (38) whose flow path for rotatable movement between coupled gears extends in a radial direction relative to the shaft (34:1) of the starting pinion (4:1) and which gear set (38) comprises an intermediate gear (25) which, together with the outer ring (23) of the planetary gear set (20), rotates about the shaft (34:1) of the starting pinion (4:1), a connecting gear (36) which is torque-transmittingly supported on the shaft (34:1) of rotation of the final pinion (4:n).

4. Drive assembly (1) according to claim 3, wherein the planetary gear set (20) comprises a wheel-like structure (26) connected to the outer ring (23) which extends from the outer ring and further radially inwards towards the shaft (34:1) of the starter pinion (4:1) and terminates in a central hub (24) on which the intermediate gear (25) is mounted in a rotationally fixed manner for rotation together with the outer ring (23) around the shaft (34:1) of the starter pinion (4:1).

5. Drive assembly (1) according to claim 4, wherein the intermediate gear (25) supported on the central hub (24) is freely mounted on the rotation axis (34:1) of the first pinion (4:1) via a rolling bearing (39).

6. Drive assembly (1) according to any one of claims 1 - 5, wherein the rotation shaft (34:1) of the planetary gear set (20) and the rotation shaft (34:n) of the additional gear set (30) protrude from an end piece (27) that is part of the transfer case (14) and which rotation shafts each comprise a first and a second rolling bearing (40, 40') with which the rotation shafts are held in said end piece (27) in the transfer case (14).

7. Drive assembly (1) according to any one of claims 3 - 6, wherein the gear set (38) of the auxiliary gear set (30), comprising said intermediate gear (25) and connecting gear (36), is located in a space between said end piece (27) and the wheel-like structure (26) of the planetary gear set (20).

8. Drive assembly (1) according to any one of claims 1 - 7, wherein the planetary gear set (20) and the additional gear set (30) are arranged in a sequence in the transmission stages (36) at different levels in height with respect to the longitudinal axis of the rack (6).

9. Drive assembly (1) according to any one of claims 1 - 8, having a series of an arbitrary "n" number of pinions (4:1, 4:2 - 4:n) comprising a group consisting of at least three pinions (4:1, 4.2 - 4:n) and configured to rotate said pinions with the same direction of rotation on parallel axes (34:1, 34.2 - 4:n) in a series in a stack formation (15) at different levels in height in a common vertical plane and being in engagement with the tooth side of the rack (6) common to the pinions, whereby between the planetary gear set (20) which is located at a starting level (Z0) in the transmission stages (36) and drives the starting pinion (4:1) included in the group and the additional gear set (30) which is located at a final level (Zn) in the transmission stages (36) and drives the the input final pinion (4:n) is arranged an intermediate planetary gear set (20:2) which drives an intermediate pinion (4:2) at an intermediate level in height of the stack formation (15) on parallel axes (34:1, 34:2 - 34:n) and which intermediate planetary gear set (20:2) partly comprises a sun gear (21) which is driven by the outer ring (23) of the planetary gear set (20) which is located at a starting level (Z0) in the transmission stages (36), and partly a planet carrier (22) which drives the intermediate pinion (4:2).

10. Drive assembly according to claim 8, comprising at least two intermediate planetary gear sets (20:2, 20:3) which drive intermediate pinions (4:2, 4:3) at an intermediate level at different heights of the stack formation (15) on parallel shafts (34:1, 34:2, 34:3 - 34:n) in a common vertical plane and where said shafts project from a gable piece (27) which is part of the transfer case and the pinions are in engagement with the tooth side of the rack (6) common to the pinions, whereby the sun gear 21 of one intermediate planetary gear set (20:3) in the transmission stages (36) is driven by the outer ring (23) of the other intermediate planetary gear set (20:2) in the transmission stages (36).

11. The drive assembly of claim 10, wherein a planet carrier (22) of each of said intermediate planetary gear sets (20:2, 20:3) drives the intermediate pinions (4:2, 4:3).

12. Drive assembly (1) according to any one of claims 1 - 11, wherein the structure (4) comprises a lift car or a work platform.

13. Drive assembly (1) according to any one of claims 1 - 12, wherein the drive unit (7) comprises an electric motor (11) with an associated speed reduction stage (16).

14. Rack-and-pinion driven elevator system, characterized in that it comprises a drive unit (1) according to one or more of claims 1 - 13.

15. Transfer case (14) intended to be included in a drive assembly (1) for a rack-and-pinion elevator, said transfer case comprising a planetary gear set (20) driving a starting pinion (4:1) rotatable on a shaft (34:1), an additional gear set (30) connected to the planetary gear set (20) driving a final pinion (4:n) rotatable on a shaft (34:n), characterised in that the planetary gear set (20) and the additional gear set (30) are arranged in a sequence of transmission stages (36) at different levels in height in the transfer case (14) and configured to rotate their respective pinions (4:1, 4:n) with the same direction of rotation on parallel shafts (34:1, 34:n) in a series in a stack formation (15) in a vertical plane at different levels in height, the additional gear set (30) comprising a gear set (38) whose flow path for rotatable movement between coupled gears extends in a radial direction in relation to the shaft (34:1) of the starting pinion (4:1) and which gear set (38) comprises an intermediate gear (25) which together with an outer ring (23) included in the planetary gear set (20) rotates about the shaft (34:1) of the starting pinion (4:1), a connecting gear (36) which is torque-transmittingly supported on the shaft (34:1) of the final pinion (4:n), and that the planetary gear set (20) comprises a wheel-like structure (26) connected to the outer ring (23) which extends from the outer ring and further radially inwards towards the shaft (34:1) of the starting pinion (4:1) terminates in a central hub (24) on which the intermediate gear (25) is rotationally fixedly mounted for rotation together with the outer ring (23) around starter pinion (4:1) shaft (34:1).