Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H57/00—General details of gearing
  • F16H57/0018—Shaft assemblies for gearings
  • F16H57/0025—Shaft assemblies for gearings with gearing elements rigidly connected to a shaft, e.g. securing gears or pulleys by specially adapted splines, keys or methods
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H57/00—General details of gearing
  • F16H57/08—General details of gearing of gearings with members having orbital motion

Definitions

• the present invention relates to a device for the axial fixing of a shaft with respect to a hollow member, particularly for the axial fixing of the shaft of a sun gear with respect to a planet gear carrier in a multistage epicyclic gear system.
• Multistage epicyclic reduction units are composed of various stages serial to each other, each consisting of a planet gear carrier that supports one or more planetary gears which mesh simultaneously with a sun gear and with a ring gear with internal teeth.
• motion is transferred from one stage to the other by way of the mating of the sun gear of one stage with the planet gear carrier of the contiguous stage.
• the sun gear of each stage can be considered to consist of a male splined shaft, which engages a corresponding female splined hole provided in the planet gear carrier of the contiguous stage, and of a gear which meshes with the planetary gears of the same stage.
• the sun gear of each stage must therefore be positioned axially and locked with respect to the planet gear carrier which the corresponding splined shaft engages.
• the axial fixing of a sun gear with respect to the planet gear carrier of the contiguous stage that is coupled thereto is provided by using unilateral axial fixing devices.
• the splined shaft of the sun gear of each stage is provided with a recess in which a corresponding elastic ring is inserted which is suitable for resting against an abutment formed by the planet gear carrier of the contiguous stage, with which it is coupled, locking axially the sun gear in its direction of insertion within such planet gear carrier.
• the axial locking of the sun gear in the direction for extraction from the planet gear carrier of the contiguous stage with which it is coupled is provided by means of a shim ring or bottom, which is inserted in the hole of the planet gear carrier of the same stage of the sun gear and forms a complementary abutment on which the axial end of the sun gear that lies opposite the end inserted in the planet gear carrier of the contiguous stage rests.
• the aim of the present invention is to eliminate the drawbacks noted above of the background art, by providing a device for the axial fixing, in both directions, of a shaft with respect to a hollow member, particularly for the axial fixing of the shaft of a sun gear with respect to a planet gear carrier that makes it possible to reduce, with respect to known fixing devices, the number of elements used, consequently reducing production costs.
• an object of the present invention is to provide an axial fixing device that can be assembled easily and in a manner that is practical and can be automated easily.
• Another object of the present invention is to eliminate sliding friction between the sun gear and the corresponding shim bottom caused by the presence of any axial loads, in order to increase the efficiency of the reduction unit, reduce wear and avoid heating of the parts in contact.
• Another object of the present invention is to provide a device that is simple, relatively easy to provide in practice, safe in use, effective in operation, and of relatively low cost.
• the present device for the axial fixing of a shaft with respect to a hollow member that comprises a hole for accommodating said shaft, comprising at least one axial fixing element and at least one recess for accommodating said axial fixing element, which is formed in said shaft and is adapted to prevent the axial movements of said axial fixing element with respect to said shaft, characterized in that it comprises at least one receptacle that is formed in said hollow member and adapted to accommodate, in an axially locked manner, said axial fixing element, which can be pre-inserted in said receptacle or in said recess and can be engaged in said recess or in said receptacle, respectively, upon their substantial mutual alignment during the insertion of said shaft in said hole for the axial locking of said shaft with respect to said hollow member.
• Figure 1 is an exploded axial sectional view of a fixing device according to the invention in an epicyclic gear system
• Figure 2 is an axial sectional view of the fixing device of Figure 1 in a partially assembled configuration, with the elastic ring pre-inserted in the receptacle formed in the planet gear carrier;
• Figure 3 is an enlarged-scale view of a portion of the fixing device of Figure 2, in particular of a portion of the elastic ring that is inserted in the receptacle formed in the planet gear carrier;
• Figure 4 is an axial sectional view of the fixing device of Figure 2, with the sun gear partially inserted in the planet gear carrier;
• Figure 5 is an enlarged-scale view of a portion of the axial fixing device of Figure 4, in particular of the elastic ring inserted in the receptacle formed in the planet gear carrier during the insertion of the sun gear in said planet gear carrier;
• Figure 6 is an axial sectional view of the axial fixing device of Figure 2 in the assembly configuration
• Figure 7 is an enlarged-scale view of a portion of the fixing device of
• Figure 8 is a front elevation view of the axial fixing device of Figure 6;
• Figure 9 is an axial sectional view of the fixing device of Figure 1 in a partially assembled configuration, with the elastic ring pre-inserted in the recess formed in the sun gear shaft;
• Figure 10 is an axial sectional view of the fixing device of Figure 9, with the sun gear partially inserted in the planet gear carrier;
• Figure 1 1 is an axial sectional view of the fixing device of Figure 9 in the assembly configuration. Ways of carrying out the Invention
• the reference numeral 1 generally designates a device for the axial fixing of a shaft 2 with respect to a hollow member 3, said hollow member comprising a hole 4 for accommodating the shaft 2.
• the device 1 comprises at least one axial fixing element 6 and at least one recess 7 for accommodating the fixing element 6, which is formed on the shaft 2.
• the recess 7 forms an abutment 7a and a complementary abutment
• the device 1 comprises a receptacle 5 that is formed in the hollow member 3, at the hole 4, and is adapted to accommodate the fixing element 6 in a manner that is locked axially.
• the receptacle 5 forms an abutment 5a and a complementary abutment 5b, which are adapted to prevent the axial movements of the fixing element 6 with respect to the hollow member 3.
• the axial fixing element 6 can be pre-inserted in the receptacle 5 or in the recess 7 and is adapted to engage respectively the recess 7 or the receptacle 5 upon their mutual substantial alignment during the insertion of the shaft 2 in the hole 4 for the axial locking of the shaft 2 with respect to the hollow member 3.
• the fixing element 6 is locked axially, in one direction by the abutments 5a and 7a and in the opposite direction by the complementary abutments 5b and 7b, both with respect to the shaft 2 and with respect to the hollow member 3.
• the shaft 2 is therefore locked axially and bilaterally with respect to the hollow member 3 by way of the interposition of the fixing element 6.
• the shaft 2 can be inserted in the hollow member 3 by making an axial end portion 2a thereof pass through the hole 4 starting from an axial end 3 a of said hollow member.
• the axial fixing element 6 consists of an elastic ring, for example having a rectangular cross-section, which can expand and be compressed in a radial direction and has, in inactive conditions, an inside diameter that is smaller than the diameter of the shaft 2 and an outside diameter that is larger than the diameter of the hole 4.
• the elastic ring 6 is therefore adapted to enter by snap action, by way of an elastic reaction, the receptacle 5 or the recess 7, which have a substantially circular shape.
• At least one of the shaft 2 and the hollow member 3 is beveled, at the axial end portion 2a and at the region of the axial end 3 a that suiTounds the hole 4, respectively, so as to facilitate, during the step for insertion of the shaft 2 in the hollow member 3, the expansion or constriction of the elastic ring 6 that is pre-inserted in the receptacle 5 or in the recess 7, respectively.
• Figures 1 to 1 1 are views of a preferred but not exclusive application of the fixing device 1 related to a multistage epicyclic reduction unit.
• Epicyclic reduction units generally comprise, as is known to the person skilled in the art, a structure for the containment of the various stages of such reduction unit and one or more rolling bearings, which are interposed between the containment structure and the input and output shafts of the reduction unit; neither the containment structure nor the input and output shafts are shown in the figures.
• the shaft 2 consists of the shaft of a sun gear 20 of a stage of the multistage epicyclic reduction unit and the hollow member 3 consists of the planet gear carrier of the upstream stage of such epicyclic reduction unit.
• the sun gear 20 is composed of the male splined shaft 2, which engages the female splined hole 4 formed in the planet gear carrier 3 of the contiguous stage, and of a gear 21, which is adapted to mesh with the planetary gears of the respective stage, which are not shown in the figures.
• the planet gear carrier 3 supports one or more planetary gears 30, which are locked axially with respect to such planet gear carrier by means of respective elastic rings 31.
• the multistage epicyclic reduction unit consists of a plurality of stages adapted to transmit the motion to each other by means of the meshing of the shaft 2 of the sun gear 20 of one stage with the planet gear carrier 3 of the contiguous stage.
• Figures 2 to 7 are views of the assembly solution of the sun gear 20 in the planet gear carrier 3 of the contiguous stage with the elastic ring 6 pre- inserted in the receptacle 5.
• the receptacle 5 is formed at the axial end 3 a of the hollow member 3.
• the planet gear carrier 3 has at least one protruding region 8, which is formed at its axial end 3a, in which the receptacle 5 is formed.
• the planet gear carrier 3 has at least two, preferably three, protruding regions 8 which are shaped like circular sectors and lie around the mouth of the hole 4.
• the protruding regions 8 are mutually separated by respective gaps 9 for the insertion of means for extracting the shaft 2 from the planet gear carrier 3, which are not shown in the figures and can for example be of the type of pliers, which are adapted to widen the elastic ring 6 at its notch, so as to remove it from the recess 7.
• the protruding region 8 is substantially annular, lies around the mouth of the hole 4 and is provided with a gap 9 for the insertion of means for extracting the shaft 2 from the planet gear carrier.
• Figures 9 to 1 1 are instead views of the assembly solution of the sun gear 20 in the planet gear carrier 3 of the contiguous stage, with the elastic ring 6 pre-inserted in the recess 7.
• the elastic ring 6 is pre-inserted in the recess 7, such recess is formed proximate to the axial end portion 2a and the receptacle 5 is formed proximate to the axial end 3b of the planet gear carrier 3 that lies opposite the axial end 3 a.
• the portion of the lateral surface of the shaft 2 that is interposed between the recess 7 and the axial end portion 2a is smooth, i.e., not splined, in order to facilitate pre-insertion of the elastic ring 6 in the recess 7.
• the portion of the shaft 2 that is not splined is in any case reduced with respect to the splined portion, in order to ensure nonetheless correct engagement with the splined hole 4 and therefore correct transfer of the rotary motion to the planet gear carrier 3.
• This operation is performed by exploiting the radial elasticity characteristics of the elastic ring 6, which is compressed or expanded in a radial direction, in order to pre-insert it in the receptacle 5 or in the recess 7, respectively.
• the elastic ring 6 Depending on whether the elastic ring 6 has been pre-inserted in the receptacle 5 or in the recess 7, during the insertion of the shaft 2, it expands radially within the receptacle 5 or is compressed radially within the recess 7, respectively, as shown in Figure 5, so as to not hinder the insertion of the shaft 2 in the hollow member 3.
• the elastic ring 6 When, during the insertion of the shaft 2 within the hole 4, the recess 7 is substantially aligned with the receptacle 5, the elastic ring 6 enters by snap action, by way of an elastic reaction, the recess 7 or the receptacle 5 depending on where it was pre-inserted.
• the elastic ring 6 is now inserted simultaneously in the receptacle 5 and in the recess 7 and is therefore locked axially with respect to them in one direction by the abutments 5a and 7a and in the opposite direction by the complementary abutments 5b and 7b, thus providing bilaterally the axial locking of the shaft 2 with respect to the hollow member 3.
• extraction means such as for example pliers.
• shaft 2 and/or the hollow member 3 are, during use, rotating members, as in the case of an epicyclic reduction unit, it is necessary to stop their motion before performing the operations for removing the elastic ring 6 from the receptacle 5 or from the recess 7.
• the extraction means are inserted, depending on whether the elastic ring is pre-inserted in the receptacle 5 or in the recess 7, in the gaps 9 that separate the various protruding regions 8 or between the lateral surface of the shaft 2 and the surface of the hole 4 on the side of the axial end 3b.
• the ends of the pliers are engaged with the ends of the notch of the elastic ring 6, so as to expand it or compress it radially, removing it from the recess 7 or from the receptacle 5. If the elastic ring 6 is pre-inserted in the receptacle 5 and its notch is not located at one of the gaps 9, it is necessary to turn such elastic ring with respect to the receptacle 5 and the recess 7 so that its notch can be accessed from the outside.
• the device according to the invention makes it possible to discharge any axial forces that act on one stage of the reduction unit onto the containment structure of the reduction unit itself, by means of the transfer of said axial forces between the contiguous stages and between said stages and the rolling bearings that separate them from the containment structure.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Cable Accessories (AREA)
• Suspension Of Electric Lines Or Cables (AREA)
• Clamps And Clips (AREA)
• General Details Of Gearings (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (2)

Cited By (2)

Citations (5)

• 2008
  • 2008-09-02 IT IT000224A patent/ITMO20080224A1/it unknown
• 2009
  • 2009-08-28 WO PCT/EP2009/061148 patent/WO2010026109A1/en active Application Filing

Patent Citations (5)

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