Abstract:
A gearbox to be mounted on a turbomachine and driven by a radial drive shaft of the latter. The gearbox has a three-dimensional or sinuous shape, which can house a large quantity of equipment to be driven, without occupying a large amount of space in any dimension, since the gearbox remains close to the turbomachine and the equipment can be distributed over a large surface. The drive train of gears successively extends into several non-parallel planes and comprises an axial branch on the turbomachine and a branch forming an arc of circle around the turbomachine.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a drive gearbox on a turbomachine, intended to transmit the movement originating from the turbomachine by the intermediary of a radial shaft exiting from the latter, and to transmit it to various pieces of equipment annexed to the turbomachine, such as pumps, electricity generators, etc., which are indispensables for the operation of the turbomachine or to other devices of an aircraft propelled by this turbomachine. The transmission is carried out via a drive train comprised of successive gears; this train is here comprised of gear lines located in non-parallel planes. 
     Discussion of the Background 
     Gear lines here refers to a set of adjacent gears, meshing in principle between them, of which the gear wheels are located in the same plane or in parallel planes; in other terms, the axes of rotation of the gear wheels are all parallel (perpendicular to this plane or to its parallel planes), and it is considered that the gear wheels that mesh directly together extend into the same plane; the gear line can however continue into parallel planes if there are gear wheels aligned along the same axis of rotation or of the offsets of toothing in the same gearing. 
     The gearbox primarily comprises a drive train comprised of all of the gear wheels, meshing together in such a way as to transmit a movement, inside a casing. This train is connected to the radial shaft of the turbomachine and to drive shafts of the equipment. The gearbox is fixed to the turbomachine at the desired position and the equipment itself is fixed to the gearbox. A document describing a gearbox of known design is U.S. application Ser. No. 12/0006137. It succinctly represents therein the drive shaft 12 of the turbomachine, with the radial shaft 14 and the gearbox properly speaking, comprising a drive train comprised of gear wheels 16 with straight toothing in a casing 10. The equipment 22 is located on the box opposite the fastening to the turbomachine. As all of the axes of the gear wheels 16 are parallel, the gearbox of this document from prior art comprises a single gear line in the sense of the invention. 
     It is sought to decrease the space occupied of the assembly comprising the gearbox and the equipment on the turbomachine. The design described in the document or prior art is insufficient from these standpoints, since the drive train of the box is extended in a direction and therefore occupies a large amount of space. 
     More generally, the existing gearboxes belong to two different types: the single-face type, where the equipment is placed on a single face of the box, and the double-face type, wherein they are placed on two opposite faces. In the first design, the box must be of great length and the angular amount of space occupied around the turbomachine is generally substantial (often 200°), and, in the second design, it is the space occupied in the axial direction that is substantial. 
     SUMMARY OF THE INVENTION 
     This invention relates to a gearbox that is improved under these various aspects, and which in particular offers a large degree of design freedom, able to bring a reduction of the space occupied by the assembly comprised of the box and of all of the equipment that it carries. 
     Very generally, the conventional design is renounced wherein the drive train is comprised of a single gear line extending in a plane, possible in a single direction, or in parallel planes, as is the case in the document U.S. application Ser. No. 12/0006137, or in the parallel branches and in the secant planes as in EP-2 455 597-A. 
     In a general form, the invention relates to a gearbox to be fixed to a turbomachine in order to drive at least one piece of equipment annexed to the turbomachine, comprising a casing, a drive train internal to the casing and comprising a series of gears, as well as a drive member intended to mesh with a drive shaft of the turbomachine, with the casing comprising fastening points to the turbomachine and to the equipment, wherein the drive train comprises at least two gear lines located in non-parallel planes and connected together by a junction gear to a junction interface, comprised of a pair of gear wheels with non-parallel axes, of which, characteristically, at least one end line housed in a casing branch that has a main extension in a substantially axial direction of the turbomachine when the box is fixed to the turbomachine, and another line housed in an intermediate casing branch substantially in the portion of a circle, substantially perpendicular to the end branch and which surrounds a portion of circumference of the turbomachine when the box is fixed to the turbomachine. 
     The construction of the drive train in several gear lines located in non-parallel planes makes it possible to have a gearbox even of large dimensions entirely within the vicinity of the casing of the turbomachine, without occupying an excessive amount of space not in the radial direction or in the axial direction or in the angular direction, as the box is not rectilinear. There is in addition a large choice of faces of the gearbox, extending in very different directions, in order to place equipment therein, which also contributes in limiting the space taken up by the assembly. 
     In a particular embodiment, the gearbox comprises three of said gear lines of which two end lines that have directions of extension that are substantially parallel between each other and an intermediate line that joins these end lines; these end lines can be housed in substantially rectilinear branches of the casing and that have main extensions in a substantially axial direction of the turbomachine when the box is fixed to the turbomachine; the intermediate line can be housed in another branch of the carter which is an intermediate branch close to a portion of circle, primarily perpendicular to the end branches and which surrounds a portion of circumference of the turbomachine when the box is fixed to the latter. 
     Such an embodiment particularly shows how much the encumbrance of the gearbox can be limited with the invention: the axial extension of the gearbox is reduced thanks to the division of the drive train into two lines that can extend on either side of the turbomachine, while the intermediate branch itself has a very low axial encumbrance, and its angular encumbrance is advantageously equal to or less than a half-turn, which greatly facilitates the installation of the gearbox on the turbomachine, while the known single-face gear boxes often have a more substantial angular extension that makes the assembly more constraining. 
     In another design, which also exploits the division of the drive train into two lines extending in primarily parallel directions, these two lines belong however to secant planes, and the drive train has a junction portion with longitudinal ends of gear lines; the latter are housed in respective branches of the casing which are attached to one another at an edge and together have a v-shaped section according to cross-sections perpendicular to a main extension direction of the gearbox. 
     The angular space occupied by the gearbox is here further reduced; at the price of a moderate axial encumbrance, a casing is available that has a large surface for placing equipment, on faces that have orientations that are very different from one another. 
     The successive gear lines comprising the drive train can be connected by conical pinions to the ends of these gear lines and which define junction gears with non-parallel axes, which can be concurrent but not necessarily. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the invention shall now be described by means of the following figures; it is clear that other embodiments are possible and that this description is purely for the purposes of illustration: 
         FIGS. 1, 2, 3 and 4  show an embodiment of the invention; 
       and  FIG. 5 , a possible arrangement for this embodiment or others. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the invention is described by means of figures. The gearbox has the general shape shown in  FIG. 1 , with a three-dimensional shape comprising two end branches  1  and  2  that are substantially parallel and rectilinear (a slight curvature, shown in  FIG. 3 , being possible however) and an intermediate branch  3  that is substantially in the portion of a circle that connects the latter and which is substantially perpendicular to them.  FIG. 2  shows that this gearbox can be advantageously placed around a turbomachine  4 , for example in the location of a high-pressure body of the latter, by placing the end branches  1  and  2  in the axial direction of said turbomachine, with diametrically opposite cone distances, with the intermediate branch  3  then also next to the turbomachine  4  by making substantially a half-turn around it, or less. The gearbox can comprise a different number of branches extending in the axis of the turbomachine  4 , a single for example, or more than two, and the intermediate branch  3  can have an angular extension that is smaller than an approximate half-turn. A large choice is therefore available for the location of the drive chain of the turbomachine  4 , which can be done directly using a conventional radial shaft belonging to the turbomachine  4 , or by the intermediary of an intermediate shaft belonging to a separate box and meshing with the radial shaft. A radial shaft can as such extend up to an internal face  5  (directed towards the turbomachine  4 ) of any one of the branches  1 ,  2  and  3 , although an intermediate shaft can extend to one of the outside faces of one of the branches  1  to  3 . This can in particular be one of the upper faces  6  (substantially in the plane of the sector of the turbomachine  4 ) for the end branches  1  and  2 , one of the peripheral faces  7  (directed radially outwards) for the same branches, or a front face  8  (directed axially opposite the end branches  1  and  2 ) of the intermediate branch  3 . Some of the possibilities for the positions of the drive shaft (radial or intermediate) are indicated by reference  9 , in  FIG. 1 . 
     The equipment  10  can be mounted itself on the opposite upper  6 , peripheral  7  and axial  8  faces, as well as on radially external faces  11  of the intermediate branch  3 . There is again a large choice for the fastening of the gearbox to the turbomachine  4 , which can take place by bolting of the points of fastening  12  located on the casing  13 , using possibly wedges or other intermediate supports between the turbomachine  4  and, for example, some of the internal faces  5 . The pieces of equipment  10  are fixed to the casing  13  by other fastening points  12 . 
     This gearbox generally provides a very large choice in the possibilities for arrangement as well as the possibility to install a large number of piece of equipment  10 , while still retaining a moderate encumbrance in all directions (axial, radial and angular) of the turbomachine  4 . 
     This gearbox shall now be described in more detail.  FIG. 3  shows that it is substantially comprised of a casing  13  that defines the contour of the three branches  1 ,  2  and  3 , and of a drive train  14  contained in the casing  13  and wherein three gear lines  15 ,  16  and  17  can be distinguished, respectively housed in a respective branch  1 ,  2  and  3 . Each one of them comprises gear wheels  18  generally with a straight toothing meshing between them in order to form straight gears, with the axes  19  of some of these gear wheels  18  being used to drive in rotation the mobile portions of the equipment  10 , by passing through openings  20  of the casing  13 . The axes  19  are all parallel inside of the same gear line  15 ,  16  or  17 , but have directions that are different from one gear line  15 ,  16  or  17  to another. The number of gear wheels  18 , their diameters as well as the positions of the openings  20  defining the drive shafts  19  of the equipment  10  can of course be chosen freely, according to the rotation speeds the one wants to transmit and the positions of the equipment  10 . A particular opening  21  is intended at the inlet of the drive shaft  9 , which further comprises a drive pinion  22  meshing with any one of the gear wheels  18 . The drive pinion  22  is adjacent to the drive train  14 , which signifies that the latter would remain continuous in the absence of the former. It would however be possible for the drive pinion to be a gear wheel belonging to the drive train itself. 
       FIG. 4  shows the drive train  14  in an isolated manner. The connection between the three gear lines  15 ,  16  and  17  is carried out by junction gears  23  and  24  with concurrent or more generally non-parallel axes. Each one of them is comprised of a first conical pinion  25 , integral and coaxial with an end gear wheel  18  of the gear line  17 , and of a second conical pinion  26 , likewise integral and coaxial with a gear wheel  18 , of end of one of the gear line  15  or  16 . These junction gears  23  and  24  therefore provide the continuity of the drive train  14  and the faculty to move it entirely by the drive pinion  22  alone. They also make it possible to direct each one of the gear lines  15 ,  16  and  17  in the direction of the branch  1 ,  2  or  3  respective and in non-parallel planes. 
     An equivalent design from a kinematic standpoint would consist in replacing the conical pinions  25  and  26  with a straight pinion  48  and a ring gear  49  on a plane, which is shown in  FIG. 5 , without any other details of the embodiment being modified. 
     The gear lines  15  and  16  extending into the end branches  1  and  2  of primarily axial extensions also have roughly axial directions of extension and extend in primarily longitudinal planes with respect to the turbomachine  4 , while the gear line  17  housed in the intermediate branch  3  of the casing has a direction of extension that is primarily angular like it and belongs to an essential transversal plane of the turbomachine  4 .