GB2128710A - Transmissions - Google Patents

Abstract

A rigidly supported gearbox casing (1) houses a gear train (6/7/8/9/10) that interconnects an input shaft (4) and an output shaft (5). A gear (8) of the gear train is supported for pivoting relative to other gears (6,9) of the train by a subsidiary shaft (12). Pivoting of the shaft (12) is compliantly restrained, externally of the casing (1), so that compliant restraint is introduced into the transmission of power from the input shaft (4) to the output shaft (5). Thus fluctuations in power supplied to the input shaft (4) can be reduced at the output shaft (5). By siting the compliant restraint mechanism externally of the casing (1) large angular displacements of the gear (8) associated therewith within the casing (1) are possible, design of the compliant restraint mechanism is unhampered by space or weight considerations, and there is good access to all components. <IMAGE>

Description

SPECIFICATION Transmlssions Th-invention relates to transmissions and is particularl4icorlcerned with a transmission capable of reducing arthe Output side fluctuations in power supplied to thsinput side. Fluctuations in power supply is a partfcularprnblem in the use of winddriven turbines generate electricity.

Large, say 60m'diameter, wind-driven turbines, when connected to-etectricity supply grids through synchronous generatorsand rigidly-connected transmissions produce output powerfiuctuations which are generally unacceptabletothe grid. One way of reducing the fluctuations isto introduce mechanical compliance into the transmissions, for example by incorporating rotating compliant elements, such as flexible couplings or quill shafts, in the transmission; by shaft-mounting the gearbox and restraining rotation of its casing by compliant supports; or by using an epicyclicfirst-stage gearbox with internal compliant restraint of the normally fixed annulus or planet carrier.It is, however, difficult to engineer a rotating compliant element system of a sufficient degree of compliance within size, weight and cost constraints; a swinging gearbox system requires a separate shaft/ bearing arrangement which is heavy, and a co-axial high speed output which gives problems in obtaining access to the rotor; and in an epicyclic system internal compliance gives access problems and only limited displacement is possible.

According to the present invention there is provided a transmission comprising a gearbox casing that is rigidly supported in use, a transmission gear arrangementwithin the gearbox, an input shaft connected through the transmission gear arrangement to an output shaft, and at least one subsidiaryshaft that supports within the gearbox part ofthe transmission gear arrangementfor movement with this subsidiary shaft, the subsidiary shaft being. restrained externally of the gearbox so that said movementofsaid part of the transmission gear arrangement is compliantly restrained and thereby there is introduced compliant restraint into the transmission of powerfrom the input shaft to the output shaft via thetransmission gear arrangement.As a part ofthetransmission gear arrangement is supported such that compliance is introduced into the transmission of power from the input shaft to the outputshaft,fluctuations in power supplied to the input side can be reduced atthe output side. As the compliant restraint mechanism is located externally ofthe gearbox casing large angular displacements are possible,the design ofthe compliant restraint mechanism is unham pered by space or weight considerations,,and good access to all components can be achieved.

Fora better understanding of the invention and to show howthe:sa;Re may be carried into effect, reference-will now be made, by way of example, to the ,,cmpanvtngdrawing in which the single Figure shows schematically a transmission.

The transmission shown in the Figure consists of a casing 1 that is rigidly supported on a mount 2. Within the gearboxthere is a transmission arrangement3 that interconnects a low speed input shaft 4 and a high speed output shaft 5. The transmission arrangement includes a gear 6 on the input shaft 4that is meshed with a first gear7 of a gear pair7, 8. The second gear 8 of the gear pair 7,8 drives, through an idler pinion 9 a contrate gear 10 on the output shaft 5. As so far described the transmission gear arrangement 3 is a right-angle step-up drive whose ratio is determined by the pairs of gears 6/7, 819, 9/10 that make up a gear train between the input and output shafts.

The gear pair 7,8 is carried by a stepped support arm 11 that is an extension of a shaft 12 that can pivot ion a bearing 13. Externally of the casing 1 pivoting of the shaft 12 is compliantly restrained by mechanism, not shown, such asatorquebararrangement including linear springs and dampers if only a few degrees of displacement is to be accommodated, or a damped hydraulic system with a compressed air spring if larger displacements are to be restrained.

Other arrangements incorporating either elastic or damping elements, oF both, are of course possible.

The degree of movementto be restrained coutd be through an arc of asfew as, say, 20 degrees, or could through several rotations ofthe arm 11 and shaft 12 (in which case an alternative arrangement of the pairs of 617,819,9/lOis required to accommodate full rotation ofthearm 11).

In place ofthe single compliantly restrained arm 11 and shaft 12,two or more such arms and shafts supporting associated parts ofthegeararrangement can be provided, each such arm and shaft being compliantly restrained externally of the casing 1.

As the part ofthetransmission arrangement 3 that is carried bythe support arm 11 can move with the shaft 12,there is introduced into the transmission of power from the inputshaft4to the output shaft 5 compliant restraint,theextentofwhich is determined bythe characteristics ofthe restraining mechanism utilised.

1. Atransmission comprising a gearbox casing that is rigidly supported in use, a transmission gear arrangement within the gearbox, an input shaft connected through the transmission gear arrange menttoan output shaft, and at least one subsidiary shaftthat supports within the gearbox part ofthe transmission geararrangementfor movement with this subsidiary shaft, like subsidiary shaft being restrained externally of the gearbox so that said movement of said part of the transmission gear arrangement is compliantly restrained and thereby there is introduced compliant restraint into the transmission of power from the inputshaftto the output shaft via the transmission gear arrangement.

2. Atransmission as claimed in claim 1,wherein said part ofthe transmission arrangement is a gear in a train of gears between the input and output shafts, the gear being supported for pivoting with the subsidiary shaft.

3. Atransmission substantially as hereinbefore The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Transmlssions Th-invention relates to transmissions and is particularl4icorlcerned with a transmission capable of reducing arthe Output side fluctuations in power supplied to thsinput side. Fluctuations in power supply is a partfcularprnblem in the use of winddriven turbines generate electricity. Large, say 60m'diameter, wind-driven turbines, when connected to-etectricity supply grids through synchronous generatorsand rigidly-connected transmissions produce output powerfiuctuations which are generally unacceptabletothe grid. One way of reducing the fluctuations isto introduce mechanical compliance into the transmissions, for example by incorporating rotating compliant elements, such as flexible couplings or quill shafts, in the transmission; by shaft-mounting the gearbox and restraining rotation of its casing by compliant supports; or by using an epicyclicfirst-stage gearbox with internal compliant restraint of the normally fixed annulus or planet carrier.It is, however, difficult to engineer a rotating compliant element system of a sufficient degree of compliance within size, weight and cost constraints; a swinging gearbox system requires a separate shaft/ bearing arrangement which is heavy, and a co-axial high speed output which gives problems in obtaining access to the rotor; and in an epicyclic system internal compliance gives access problems and only limited displacement is possible. According to the present invention there is provided a transmission comprising a gearbox casing that is rigidly supported in use, a transmission gear arrangementwithin the gearbox, an input shaft connected through the transmission gear arrangement to an output shaft, and at least one subsidiaryshaft that supports within the gearbox part ofthe transmission gear arrangementfor movement with this subsidiary shaft, the subsidiary shaft being. restrained externally of the gearbox so that said movementofsaid part of the transmission gear arrangement is compliantly restrained and thereby there is introduced compliant restraint into the transmission of powerfrom the input shaft to the output shaft via thetransmission gear arrangement.As a part ofthetransmission gear arrangement is supported such that compliance is introduced into the transmission of power from the input shaft to the outputshaft,fluctuations in power supplied to the input side can be reduced atthe output side. As the compliant restraint mechanism is located externally ofthe gearbox casing large angular displacements are possible,the design ofthe compliant restraint mechanism is unham pered by space or weight considerations,,and good access to all components can be achieved. Fora better understanding of the invention and to show howthe:sa;Re may be carried into effect, reference-will now be made, by way of example, to the ,,cmpanvtngdrawing in which the single Figure shows schematically a transmission. The transmission shown in the Figure consists of a casing 1 that is rigidly supported on a mount 2. Within the gearboxthere is a transmission arrangement3 that interconnects a low speed input shaft 4 and a high speed output shaft 5. The transmission arrangement includes a gear 6 on the input shaft 4that is meshed with a first gear7 of a gear pair7, 8. The second gear 8 of the gear pair 7,8 drives, through an idler pinion 9 a contrate gear 10 on the output shaft 5. As so far described the transmission gear arrangement 3 is a right-angle step-up drive whose ratio is determined by the pairs of gears 6/7, 819, 9/10 that make up a gear train between the input and output shafts. The gear pair 7,8 is carried by a stepped support arm 11 that is an extension of a shaft 12 that can pivot ion a bearing 13. Externally of the casing 1 pivoting of the shaft 12 is compliantly restrained by mechanism, not shown, such asatorquebararrangement including linear springs and dampers if only a few degrees of displacement is to be accommodated, or a damped hydraulic system with a compressed air spring if larger displacements are to be restrained. Other arrangements incorporating either elastic or damping elements, oF both, are of course possible. The degree of movementto be restrained coutd be through an arc of asfew as, say, 20 degrees, or could through several rotations ofthe arm 11 and shaft 12 (in which case an alternative arrangement of the pairs of 617,819,9/lOis required to accommodate full rotation ofthearm 11). In place ofthe single compliantly restrained arm 11 and shaft 12,two or more such arms and shafts supporting associated parts ofthegeararrangement can be provided, each such arm and shaft being compliantly restrained externally of the casing 1. As the part ofthetransmission arrangement 3 that is carried bythe support arm 11 can move with the shaft 12,there is introduced into the transmission of power from the inputshaft4to the output shaft 5 compliant restraint,theextentofwhich is determined bythe characteristics ofthe restraining mechanism utilised. CLAIMS

1. Atransmission comprising a gearbox casing that is rigidly supported in use, a transmission gear arrangement within the gearbox, an input shaft connected through the transmission gear arrange menttoan output shaft, and at least one subsidiary shaftthat supports within the gearbox part ofthe transmission geararrangementfor movement with this subsidiary shaft, like subsidiary shaft being restrained externally of the gearbox so that said movement of said part of the transmission gear arrangement is compliantly restrained and thereby there is introduced compliant restraint into the transmission of power from the inputshaftto the output shaft via the transmission gear arrangement.

2. Atransmission as claimed in claim 1,wherein said part ofthe transmission arrangement is a gear in a train of gears between the input and output shafts, the gear being supported for pivoting with the subsidiary shaft.

3. Atransmission substantially as hereinbefore The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

described with reference to the accompanying drawing.