A PLANETARY GEAR CONSTRUCTION

Abstract: In planetary gears for example the sun wheel may adjust itself freely within certain limits with respect to the planet wheels so that it seeks such a place for itself in which the load is divided evenly among the planet wheels. However a result of this arrangement is the tendency of the gearing to vibrate especially when the load on the gearing is small. The invention presents a planetary gear construction in which the shaft (7; 12) leading to the gearing or both the shafts leading to and away from (20; 21) the gearing are fastened to the gearing's frame (17) with bearings with the aid of an elastic part (10; 15; 22, 23). The said elastic part is a circular rubber bushing or such that is placed in connection with that bearing (19; 14; 24, 25) that is closest to the planetary gear and which represses the said tendency to vibrate but which at the same time allows the centralizing of the sun wheel or such. The invention can be applied to both planetary gears that are equipped with a ring wheel (3; 18) or to so-called incomplete planetary gears that do not have a ring wheel.

Description: A planetary gear construction The object of this invention is a planetary gear construction that consists of a sun wheel, planet wheels with carrier, and a ring wheel, the gear construction being such that at least one of the transmission shafts leading to the gearing is supported on the planetary gear region in such a way that it is able to adjust itself in such a manner that the said shaft allows the wheel or gearing that it is carrying to move freely within certain limits as a result of the centralizing power created by the gearing. The purpose of this invention is to improve planetary gear bearing especially in such transmission constructions in which a certain part of the gearing can move freely with respect to the other parts. It is already well known that in certain applications it is advantageous for the durability of the planetary gear to allow for example the sun wheel to move freely with respect to the planet wheels at which time it seeks such a place for itself among the planet wheels so that the load is divided equally amongst: the wheels. If the shaft is at this point heavy and its free length quite large, the shaft and at the same time the whole gearing may however tend to vibrate especially if the load on the gearing is small- The said tendency to vibrate results from the face that since there is a lack of centralizing power due to torsion, the sun wheel tends to fal-1 a small distance in between the planet wheels, a distance that is large enough however to start the apparatus vibrating. An analogous phenomenon occurs of course in any case where a part of the gearing is freely supported. The purpose of this invention is to eliminate the aforementioned drawback. To achieve the aforementioned aim and others that will be clarified later the main feature of the invention is that the shaft: or shafts in question are fastened with bearings to the frame of the gearing at the planetary gear or in its near vicinity ' with the aid of an O H elastic part. The elasticity of the said part is chosen so that it is rigid enough to prevent the radial movement caused by gravity or such of the said shaft and of the wheel it is carrying with respect to the other wheels when the torque transmitted by the gearing is small, but the elasticity is chosen so that it gives way enough to allow the centralizing of said wheel with respect to the other wheels when the torque transmitted by the gearing is large. Thus as a result of this invention a construction is obtained that performs well with both a partial and a full load. In the following text the invention is described in detail by referring to the attached drawing whose schematic figures illustrate some examples of the invention's applications. Figure 1 illustrates a planetary gear in accordance with the in¬ vention in which the sun wheel's shaft can adjust itself elastically with respect to the rest of the gearing. In figure 2 the planet wheels' carrier is connected to the frame with the aid of an elastic bearing. In the construction in figure 3 both the ring wheel and the sun wheel are elastically fastened with bearings to the stationary planet wheels' carrier. Figure 1 shows a conventional planetary gear which consists of a sun wheel 1, planet wheels 2, and ring wheel 3. The ring wheel 3 is connected to the frame 4 of the gearing and power is transmitted from the sun wheel 1 to the planet wheels' 2 carrier 5 or vice versa. The planet wheels' 2 carrier is firmly connected to its shaft 6 which is fastened with bearings in a normal manner to the frame 4. That end of the sun wheel's 1 shaft 7 that is away from the gearing is fastened directly to the frame with the aid of for example a con- ventional needle roller bearing 8 but at the end that is near the gearing the bearing is elastic in accordance with this invention by fastening the ball-bearing 9 to the frame with the aid of a rubber _OM?I circular bushing 10. The rigidity of the said rubber bushing 10 is chosen so that it allows the sun wheel 1 to adjust itself with respect to the planet wheels 2 in such a way that its load is equally divided among all of the wheels when the torque transmitted by the gearing is large. This is advantegous because in this manner an even and gear-saving per¬ formance is achieved even when the tolerances given by the manu¬ facturer for the gearing are not particularly strict or if the gearing is otherwise not quite symmetrical as is always to some extent the case in practice. On the other hand the rubber bushing 10 is rigid enough to prevent the sun wheel 1 from falling in between the planet wheels 2 where the shaft's 7 own weight tends to press the shaft 7 within the limits set by the clearance of the toothing on the wheels. The manner described above can be used to prevent the tendency of the shaft 7 to vibrate when the torque transmitted by the gearing and at the same time the centralizing power that the sun wheel 1 creates is small. In the construction in accordance with the invention that is illustrated in figure 2, the shaft 12 of the planet wheels' carrier 11 is elastically fastened to the frame 13 with the aid of a bearing 14 and a circular rubber bushing 15. In all other respects the construction performs in the same manner as the planetary gear in the previous example. In the construction illustrated in figure 3 the planet w eels' 16 carrier 17 is stationary and the shafts 20,21 of both the ring wheel 18 and the sun wheel 19 are fastened elastically with bearings to the frame with the aid of rubber bushings 22 and 23 which are placed in connection with those bearings 24,25 of the shafts 20 and 21 that are closest to the planetary gear. In the above text the invention is described in application to such planetary gears that have a ring wheel 3,18. It must however be emphasized that the invention can as well be used on so-called in— complete planetary gears that have no ring wheels but instead the sun wheel on the input shaft turns the input wheels which are located on side shafts which also carry the output wheels. The output wheels turn a wheel that corresponds to the sun wheel and which is connected to the end of the output shaft. In this kind of an in¬ complete planetary gear the invention's arrangement can be used in connection with the sun wheel's input shaft and/or in connection with the said output shaft. The invention is of course not restricted to the examples whose realizations are illustrated above, on the contrary it can be applied to many different kinds of planetary gears and to their different combinations any time that a self-centralizing construction is desired without the harmful tendency of the rotating part to vibrate within the limits set by the toothed surface. Here follow the patent claims which describe the bounds of the in¬ vention's idea around which the different details of the invention may vary. tϋϊ "

Claims: Claims 1. A planetary gear construction that consists of a sun wheel (1;19), planet wheels (2;16) with carrier (5;11;17), and a ring wheel (3;18) or a planetary gear construction that consists of a so-called in¬ complete planetary gear that does not have a ring wheel, the gear construction being such that at least one of the transmission shafts (7;12;20;21) leading to the gearing is supported on the planetary gear region in such a way that it is able to adjust itself in such a manner that the said shaft allows the wheel or gearing that it is carrying to move freely within certain limits as a result of the centralizing power created by the gearing, the planetary gear having such a construction, characterized in that the shaft (7;12) or shafts (20;21) in question are fastened to the gearing's frame (4;17) with bearings at the planetary gear or in its near vicinity with the aid of an elastic part (10;15;22,23) . 2. A construction according to patent claim 1, characterized in that the said elastic part is an elastic part (10;15;22,23) that is placed in connection with that bearing (9;14;24,25) of said shaft (7;12;20,21) that is closest to the planetary gear. 3. A construction according to patent claim 1 or 2, characterized in that the said elastic part is a circular rubber bushing or such that is arranged around the outer race of the bearing (9;14) or bearings (24,25) in question and the outer surface of the bushing leans against the parts of the planetary gear construction's frame or such that are at the area in question. _QMPI ""

Inventors: MAEKITALO SEPPO
Applicants: VALMET OY
Application year: 1981
Main classification: F16H1
IPC codes: F16H1, F16H57