A MULTIPLE-STEP GEAR DRIVE

Abstract: In a multiple-step gear drive there are two stationary toothed wheels, a driving wheel (4) and a driven wheel (5). For each gear step there is a gear train, each train consisting of one gear-wheel or of several gear-wheels (8, 11; 9; 10 and 12) in engagement with each other, all these gear-wheels being rotatably journalled in a housing (6). The housing is movable substantially parallel to a plane running perpendicular to the shafts (1, 2) of the stationary toothed wheels, to be brought into a specific engagement position for each gear step in which the gear train is in engagement with both stationary toothed wheels (4, 5). The housing (6) and gear wheels (8, 11; 9; 10, 12) are thus arranged so that in at least one gear step the housing (6) can be disengaged from its engaged position in two substantially opposite directions, thus moving the corresponding gear train in the selected direction and thereby breaking the driving connection between the two stationary toothed wheels (4, 5).

Description: A multiple-step gear drive The invention relates to a multiple step gear drive com¬ prising a first stationary toothed wheel rotatable about a first shaft, a second stationary toothed wheel spaced from the first toothed wheel and rotatable about a second shaft, one gear train for each gear step, each gear train consisting of a gear-wheel or of several drive-connected gear-wheels, all the gear-wheels being rotatably journalled in a housing movable substantially perpendicular to said first and second shafts to be brought into a specific enga- gement position for each gear step in which the gear train is in engagement with the first and second toothed wheels. Conventional gear drives permitting multiple step gear changing generally comprise a plurality of parallel , rota¬ table shafts on which a number of toothed wheels are mount- ed to transmit driving torque. Some shafts are provided with axially displaceable gear-wheels, secured by splines, for instance, to prevent relative rotation. When changing gear, the gear-wheels are displaced along the shafts and brought into or out of engagement with axially immovable toothed wheels. Such gear drives require considerable space in all directions since there must be space both for the toothed wheels and for the above-mentioned displacement of the gear-wheels perpendicular to the main extension of the toothed wheels. It is therefore impossible to use such gear drives when the available space is relatively limited. Furthermore, this arrangement is rather complicated and ex¬ pensive. The mechanism for moving the gear-wheels, for in¬ stance, must be executed with great precision, and the de¬ gree of complexity increases the more gear steps are in- eluded. A multiple step gear drive is already known through SE-C-118 558. This is composed of a plurality of small gear drives, each corresponding to the gear defined in the introduction. This known gear thus comprises a drive and two gear-wheels housed in a housing pivotable about the pivot shaft of the drive. Rotation of the housing enables the gear-wheels to be brought into engagement with a toothed wheel secured on the driven shaft so that it cannot rotate. The gear-wheels engage one on each side of the con¬ necting plane between the turning shaft of the housing and the pivot shaft of the driven shaft. When one of the gear¬ wheels is turned to engage, the other will be disengaged and vice versa. Only two gear changes are possible with a fixed axial position of the housing. In this known gear drive, the number of gear steps is increased by the housing and the gear-wheels also being displaceable parallel to the turning shaft and pivot shafts respectively. This type of gear drive with more than two steps thus takes up a con- siderable amount of space even in the axial direction of the toothed wheels and cannot therefore be used when the space available is limited. The object of the present invention is to effect a multip¬ le step gear drive comprising several gear steps but which takes up little space in one direction, while at the same time having a simple construction and consequently low ma¬ nufacturing cost. This is achieved in a gear drive of the type described in the introduction in that in at least one gear step the housing can be disengaged from its engaged position in two substantially opposite directions, thus moving the corre¬ sponding gear train in the selected direction and thereby breaking the driving connection between the first and second toothed wheels, established in said engagement po- sition. The invention will be described in more detail in the following with the aid of two embodiments and with refe- . rence to the accompanying drawings in which Figure 1 shows schematically from above a first embodi¬ ment of a gear drive according to the invention, with certain components removed for the sake of clarity, Figure 2 shows a longitudinal section along the line II-II in Figure 1, with a first gear-wheel in engage¬ ment position, Figure 3 shows a londitudinal section corresponding to tha in Figure 2, with a second gear-wheel in engage¬ ment position. Figure 4 shows a longitudinal section corresponding to tha shown in Figures 2 and 3, with a third gear-wheel in engagement position, and Figure 5 shows schematically from above a second embodi- ent of a gear drive according to the invention with certain components removed for the sake of clarity. The gear drive shown in Figures 1 - 4 comprises an ingoing stationary shaft 1 and an outgoing stationary shaft 2, rota tably journalled in a gearbox 3. A gear drive 4 is immovab¬ ly secured on the driving shaft 1 and a driven wheel is si¬ milarly arranged on the driven shaft 2. A housing 6 is pi- votably journalled in the gearbox 3. The turning shaft of the housing 6 coincides with the pivot shaft 7 of the driving wheel 4. Three gear-wheels 8, 9, 10 are rotatably journalled in the housing 6 and by turning the housing 6 they can be brought into or out of engagement with the driven wheel 5. In this embodiment the gear-wheels 8, 9, 10 are constantly in connection with the driving wheel 4, either directly like the gear-wheel 9 or via one or more intermediate gear-wheels 11, 12. The toothed wheels 11, 9 and 12, respectively, which are constantly in engagement with the driving wheel 4, describe a planetary movement about the driving wheel 4 when the housing 6 is turned. The gear-wheels 8, 9, 10 are so arranged in the housing 6 that when they are in engagement with the driven wheel 5, the pivot shafts of the gear-wheels 8, 9, 10 are in approxi¬ mately the same plane as the pivot shaft 13 of the driven wheel 5 and the turning shaft 7 of the housing 6, i.e. in each individual gear train, the gear-wheel 8, 9, 10 which is moved into engagement with the driven wheel is arranged in the housing so that the sum of the distance between the turning shaft 7 of the housing 6, here coinciding with the pivot shaft of the driving-wheel 4, and the pivot shafts of the gear-wheels 8, 9, 10 and the pitch radius of the gear-wheel, is equal to the distance between the turning shaft 7 of the housing 6 and the pitch circle of the driven wheel 5, so that the gear-wheel 8, 9, 10 which is in enga¬ gement can be turned out of its engagement position in either of the two possible turning directions of the housing 6. If the housing is turned further in the selected direc¬ tion, the gear-wheel will be moved from contact with the driven wheel 5 and if turning is continued, the adjacent gear train will come into engagement with the driven wheel 5. Figure 2 shows a sectional view of a gear step in which the gear wheel 9 is in direct communication with the driving wheel 4. The toothed rim of the driving wheel is approxi¬ mately twice the width of the toothed rim 14 of the wheel 9 and above the toothed wheel 4 is a free space of approxi- mately half the width of the toothed wheel 4. The gear-wheel 9 is rotatably journalled in the housing 6 pivotable about the pivot shaft 7 of the driving wheel 4 and is arranged to engage with the upper half of the toothed rim of the driving wheel 4. There is thus a free space on either side* of the gear-wheel 9, this space being approximately as high as the toothed rim 14 is wide. The toothed wheel 9 engages on the lower half of the toothed rim of the driven wheel 5, this rim being approximately twice as wide as the rim 14. Below the driven wheel 5 is a free space approximately half as high as the width of the rim of the driven wheel 5. The driven wheel 5 is secured to a driven shaft projecting into the gearbox and is unable to pivot on this shaft. In the position shown in Figure 2, torque is transmitted from the driving shaft 1 to the upper half of the driving wheel 4, over the gear-wheel 9, on to the lower half of the driven wheel 5 and finally to the driven shaft 2. In the position shown in Figure 3 the gear-wheel 11 engages with the upper half of the driving wheel 4. The width of th gear-wheel 11 is approximately half that of the rim of the driving wheel 4. The gear-wheel 11 is secured so that it cannot turn on a shaft 15 journalled in the pivotable housi 6. Gear-wheel 8 is arranged above gear-wheel 11 and is also secured to the shaft 15 so that it cannot turn. Gear-wheel is approximately the same width as gear-wheel 11 but its di meter is considerably larger. In the position shown gear¬ wheel 8 engages in the upper half of driven wheel 5 and partially overlaps both the directly coupled gear-wheel 9 and the driving wheel 4. The various elements are of course spaced to allow movement without friction. The torque is transmitted from the upper half of the toothed rim of driving wheel 4 to gear-wheel 11, via shaft 15 to gear¬ wheel 8, from this to the upper half of the rim of driven wheel 5 and finally to the driven shaft 13. In the third gear step shown in Figure 4 a gear-wheel 12, approximately half as wide as the driving wheel 4, engages in the lower half of the driving wheel 4. The gear-wheel 12 is secured in a manner preventing it from turning, to a shaft 16 rotatably journalled in the housing 6. A gear-whee 10, approximately the same width as the gear-wheel 12 but considerably smaller in diameter, is also arranged on the shaft 16. Gear-wheel 10 engages with the lower half of driven wheel 5. Gear-wheel 12 is then below the driven wheel 5 and the gear-wheel 9 and is partially overlapped by these but without being touched by them. The torque is transmitted from the lower part of driving wheel 4 to gear-wheel 12, over to shaft 16 and then to gear-wheel 10 from where it is transmitted to driven shaft 13 via the lower part of the toothed rim of driven wheel 5. The gear drive shown in this first embodiment comprises three steps. However, as should be evident from Figure 1, it takes up only about one third of the available space around the driving wheel 4 and could therefore be provided with considerably more steps. Furthermore, the three gear trains in Figure 1 are in per¬ manent engagement with the driving wheel 4. The gear trains are turned to their engagement positions by gear-wheels 11, 9, 12 which describe a planetary movement about the driving wheel 4. This arrangement gives an extremely compact, space- saving construction although at a cost of somewhat reduced efficiency. However, it is not necessary for the gear trains to be per¬ manently in engagement with the driving wheel. In the embo¬ diment shown in Figure 5 the gear trains consisting of gear- wheels 10a, 12a, 9a, 11a, 8a are turned with the aid of the housing 6a into and out of engagement simultaneously with both driving wheel 4a and driven wheel 5a. The turning shaft 17 of housing 6a is thus arranged in a line with the pivot shafts la and 2a of driving and driven wheel but spaced therefrom. In each gear train, therefore, the gear-wheel 8a, 9a or 10a which is moved into engagement with the driven wheel 5a is so arranged in the housing 6a that the * sum of the distance between the pivot shaft of this gear- wheel, the turning shaft 17 of the housing 6a and the pitch radius of the gear-wheel is equal to the distance between the turning shaft 17 of the housing 6a and the pitch circle of the driven wheel 5a. The gear-wheel 11a, 9a, 12a which is brought into engagement with the driving wheel 4a, is arranged so that the difference between the distance bet¬ ween the pivot shaft of this gear-wheel and the turning shaft 17 of the housing 6a and the pitch radius of the gear¬ wheel is equal to the distance between the turning shaft 17 and furthermost point of the pitch cicle of the driving wheel 4a. In engagement position parts of the gear-wheels 8a, 9a, and 12a overlap each other and also the stationa¬ ry wheels 4a, 5a in approximately the same way as in the first embodiment shown. The section through the engagement positions agrees substantially with the sections shown in Figures 2 - 4 for the first embodiment of the gear drive. Only the addition of "a" to the designations in Figures 2 - 4 is necessary for them to be applicable to the enga¬ gement positions shown in the second embodiment. The advantages of this latter arrangement is that it offers space for considerably more gear steps than in the first embodiment and that the losses will be low since only one gear train at a time engages with the driving wheel 4a in¬ stead of all of them. In both embodiments the housing 6, 6a is locked in the various engagement positions with the aid of a locking mechanism, not shown. When changing gear the locking mecha¬ nism is released and the housing 6 then turned so that the current gear train breaks the connection between driving wheel 4, 4a and driven wheel 5, 5a. The housing then con¬ tinues turning so that the desired gear train comes into engagement position and the housing is then locked in re¬ lation to the gearbox 3. In order to obtain reverse function in a torque-transmitting gear train, two or more intermediate shafts, provided with gear-wheels, may be rotatably journalled in the housing. Furthermore, the gear-wheels arranged on the same interme- diate shaft may be made in one piece in the form of a double gear-wheel, instead of as individual gear-wheels as shown in the example. Neither is it necessary for all gear trains to be able to be turned past their engagement positions. Instead, the firs and/or the last gear train may be arranged to engagement wit the driving wheel 4, 4a and driven wheel 5, 5a in an area located at the side of the connecting plane defined by the pivot shafts 1 , la and 2, 2a, respectively, of the statio¬ nary toothed wheels. it should be evident that torque transmission may be per¬ formed in the opposite direction to that described above, i.e. the toothed wheel 5, 5a constitutes the driving wheel from which torque is transmitted to the shaft 1, la which thus becomes the driven shaft.

Claims: C l a i m s 1. A multiple-step gear drive comprising a first sta¬ tionary toothed wheel (4, 4a) rotatable about a first shaft (1, la), a second stationary toothed wheel (5, 5a) spaced from the first toothed wheel (4, 4a) and rotatable about a second shaft (2, 2a) , one gear train for each gear step, each gear train consisting of a gear-wheel (9, 9a) or of several drive-connected gear-wheels (8, 11; 8a, 11a; 10, 12; 10a, 12a) , all the gear-wheels being ro- taLably journalled in a housing (6, 6a) movable substan- tially perpendicular to said first and second shafts (1, 2; la, 2a) to be brought into a specific engagement posi¬ tion for each gear step in which the gear train is in simultaneous contact with the first and second toothed wheels (4, 5; 4a, 5a) , w h e r e i n in at least one gear step the housing (6, 6a) can be disengaged from its engaged position in two substantially opposite directions, thus moving the corresponding gear train in the selected direction and thereby breaking the driving connection between the first and second toothed wheels (4, 5; 4a, 5a) established in said engagement position. 2. A gear drive according to claim 1, w h e r e i n the housing (6, 6a) is pivotable about the shaft (7, 17) parallel to the shafts (7, 13; 7a, 13a) of the first and second toothed wheels. 3. A gear drive according to claim 2, w h e r e i n the housing shaft coincides with one (7) of the toothed wheel shafts. 4. A gear drive according to claim 2, w h e r e i n the housing shaft (17) is arranged in line with and spaced from the first and second toothed wheel shafts (7a, 13a) . 5. A gear drive according to claims 1 - 4, c o m ¬ p r i s i n g at least three gear steps. 6. A gear drive according to claims 1 - 5, w h e r e ¬ i n at least one gear train comprises two gear-wheels in engagement with each other. 7. A gear drive according to claims 1 - 6, w h e r e - i n the gear train for at least one gear step comprises two gear-wheels (8, 11; 8a, 11a; 10, 12; 10a, 12a) with different diameters arranged one above the other with coinciding pivot shafts and secured together to prevent rotation in relation to each other, one of said gear wheels when in engagement position being in driving engagement with one of the stationary toothed wheels, while the other gear-wheel in engagement position is in driving connec- tion with the other stationary toothed wheel. 8. A gear drive according to claim 7, w h e r e i n one of the gear-wheels (8, 8a; 12, 12a) with coinciding pivot shafts overlaps or, seen in axial direction, is overlapped by a gear wheel in an adjacent gear train and/ or one of the stationary toothed wheels. 9. A gear drive according to claim 7 and 8, w h e r e - i n the gear-wheels (8, 11; 8a, 11a; 10, 12; 10a, 12a) with coinciding pivot shafts are executed in one piece in the form of a double toothed wheel. 10. A gear drive according to claims 1 - 9, c o m ¬ p r i s i n g a locking mechanism by means of which the housing (6, 6a) can be locked in its various engagement positions.

Inventors: NEUMAN KARL ERIK, NEUMAN, KARL, ERIK
Applicants: NEOS KARLSSON NEUMAN TAMM, NEOS PRODUCTS HB, KARLSSON, NEUMAN, TAMM
Application year: 1986
Main classification: F16H3
IPC codes: F16H1, F16H3