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Title:
GEARED SPEED REDUCER
Document Type and Number:
WIPO Patent Application WO/2018/109637
Kind Code:
A1
Abstract:
Speed reducer comprising a housing box within which a first reduction stage is located, the first reduction stage including a primary motion input shaft having an end protruding from the housing box, a torque limiter connected to the primary motion input shaft at its protruding end and located externally to the housing box, a motion output shaft connected to the first reduction stage downstream of the torque limiter, a secondary synchronisation shaft (212) driven from connected between the first reduction stage downstream of the torque limiter and the motion output shaft, upstream thereof, so that, even after the intervention of the torque limiter (400), synchrony is maintained between the motion output shaft (207) and the auxiliary synchronisation shaft.

Inventors:
CASAROTTO, Giorgio (Via Coatelle, 426/B, Badia Polesine, 45021, IT)
Application Number:
IB2017/057790
Publication Date:
June 21, 2018
Filing Date:
December 11, 2017
Export Citation:
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Assignee:
CASAROTTO, Giorgio (Via Coatelle, 426/B, Badia Polesine, 45021, IT)
International Classes:
F16H35/10
Foreign References:
US20060126430A12006-06-15
DE10322642A12004-12-16
US20120267210A12012-10-25
Attorney, Agent or Firm:
CANTALUPPI, Stefano et al. (Cantaluppi & Partners S.r.l, Piazzetta Cappellato Pedrocchi 18, Padova, 35122, IT)
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Claims:
CLAIMS

1. Speed Reducer (200; 300, 400) comprising :

• at least one first reduction stage (21) comprising a primary motion input shaft (208);

• one motion output shaft (207) connected to said first reduction stage (21);

• one torque limiter (400) connected to said primary shaft (208);

• one housing box within which said first reduction stage is located;

• wherein said primary shaft comprises one end protruding from said housing box and said torque limiter is connected to said protruding end and located externally to said housing box;

characterized in that it comprises a secondary synchronisation driven shaft (212) from the first reduction stage downstream of the torque limiter so that, even after the intervention of the torque limiter (400), synchrony is maintained between the output shaft (207) and the auxiliary synchronisation shaft.

2. Speed Reducer according to claim 1, wherein the primary shaft (208) transmits its rotation to a hollow bevel pinion of the first reduction stage, coaxial to it, by means of said torque limiter, said hollow bevel pinion being coaxial to said primary shaft.

3. Speed reducer according to claim 1, wherein said primary shaft transmits its rotation to a hollow cylindrical pinion of the first reduction (302) by means of said torque limiter, said hollow cylindrical pinion being coaxial to said primary shaft.

4. Speed reducer according to one of the preceding claims, in which the pinion of the first reduction (202 -302) is hollow and is, simultaneously, the driven shaft of the limiter (400) containing, coaxially in its interior, the drive shaft mutually connected in rotation through motion transmission of said limiter elements (401-402-403)

5. Speed reducer according to the preceding claims, wherein said limiter comprises a conduct element (402),

6. Speed reducer according to claim 5, when dependent on 2, wherein said driven element of the limiter (402) is at the same time the bevel pinion conductor (202) of the first reduction stage (21) of the reducer (200)

7. Speed reducer according to claim 5, when dependent on 3, wherein the driven element of the limiter (402) is simultaneously the cylindrical pinion conductor (302) of the first reduction stage (31) of the reducer (300).

8. Speed reducer according to one of the preceding claims, in which the limiter is placed externally in an opposite area to the motor (23 -33) with respect to said housing case.

9. Speed reducer according to one of the preceding claims, comprising a second reduction stage.

10. Speed reducer according to one of the preceding claims wherein said auxiliary shaft defines a secondary motion output perpendicular to said primary shaft.

Description:
GEARED SPEED REDUCER

DESCRIPTION

The present invention relates to a geared speed reducer, comprising at least one reduction stage and provided with a system for limiting the transmitted torque wherein said limiter is functionally integrated with the reducer being kinematically interposed between the motion input and the subsequent reduction stages and positioned in an area opposite to the motor externally to the body of the gear reducer.

The purpose of the limiter is to protect the entire transmission from functional or accidental overloads, mainly but not exclusively, in machines in which two or more speed reducers drive as many shafts of the machine synchronised mechanically with each other by means of the kinematic mechanisms of the respective reducers and external connecting members. In such cases, the limiter has to intervene maintaining mandatorily the synchrony even during and after the intervention of the limiter itself inasmuch as, in this type of machines, the loss of shaft synchrony leads to malfunctions or breakdowns.

In the reference sector, various ways of constructing said transmissions are known, but they do not simultaneously and satisfactorily solve the various technical and economic aspects required by the sectors of application. In general, in the "gear reducer" version, it is usual to prevent transmission breakdowns, due to overloads, dimensioning the parts affected by torque with high safety factors, or, alternatively, inserting torque limiters externally, between motor and transmission; both solutions, in the known ways, entail considerable dimensions and cost increases. An example of a reducer according to the prior art is disclosed in DE 103 22 642. The speed reducers described therein are used to set in rotation the mixing members of a mixing carriage for feeding cattle. While these reducers are provided with torque limiters, they do have the drawback of not maintaining synchrony between the mixing members in case of intervention of the torque limiters.

This observation also applies for US 2006/0126430.

US 2012/0267210 describes a speed reducer for wind turbines. In this case, too, the problem of the synchronisation between two or more transmissions has not been addressed.

The problems which the present invention intends to overcome can be summarised in the following main points able in their entirety to optimise the required characteristics, mainly but not exclusively, for the gear reducers installed on machines with synchronised shafts.

1) Limitation of the torque transmissible from the motor to the driven shaft and/or of the torque circulating between the reducers connected in synchrony.

2) Maintenance of the synchrony of the machine shafts even in the presence of intervention by the torque limiter.

3) Containment of the dimensions adapted to meet the constraints imposed by the interaxis distance of the machine shafts and by the other parts of the machines adjacent to the transmissions.

4) Optimisation of the arrangement of the elements constituting the limiter with the purpose of allowing easy access thereto for calibration of maintenance purposes. 5) Possibility of obtaining from a single configuration of the reducer a plurality of ways of managing torque, such as:

- interruption of the transmission with mandatory restoration intervention.

- limitation of the torque without interruption in the operation.

- dampening of the vibrations due to load non-uniformity.

- combination of multiple functions.

In the preferred embodiment of the invention, some elements of the limiter are placed outside the box of the reducer in a position that allows easy access for adjustments or maintenance operations, not constituting, furthermore, an encumbrance in areas that, as is highlighted below, are critical in some types of machines for which the invention is particularly intended such as, for example, mixers and chippers with two synchronised shafts. In this way, those parts of the limiter that can generate heating or malfunctions if placed inside the reducer are located outside the reducer. Furthermore, the limiter is variously configurable according to the best mode required by the machine.

It is also still possible to make a basic version, without limiter but with the same configuration of the reducer, contributing to rationalise production overall, in order to reduce costs.

In a preferred embodiment the speed reducer comprises:

• a housing box within which a first reduction stage is a first reduction stage is located;

• the first reduction stage comprising a primary motion input shaft having one end protruding from said housing box;

• a torque limiter connected to said primary motion input shaft at said protruding end and connected externally to said housing box;

• a motion output shaft connected to said first reduction stage downstream of the torque limiter;

• a secondary synchronisation shaft (212) connected between the first reduction stage downstream of the torque limiter and the motion output shaft, upstream thereof, in such a way that, also as a result of the intervention of the torque limiter (400), synchrony is maintained between the motion output shaft (207) and the auxiliary synchronisation shaft.

The features and the advantages of the invention shall become more readily apparent from the diagrams and from the detailed description that follows of some preferred embodiments thereof, illustrated, by way of non-limiting indication, with reference to the accompanying drawings in which :

- figures 1A and IB schematically show, respectively, the plan and front view of a mixer with synchronised shafts.

- figures 2A and 2B show respectively a front and a lateral detailed view, according to the section X-X', of a first preferred embodiment of the invention.

- figure 3 shows a front view of a second alternative embodiment of the invention.

- figures 4 and 5 show as many examples of types of torque limiters that can be combined with the invention.

In the following context, the terms "upstream" and "downstream" refer to the flow of the motion in the kinematic chain of the reducer, i .e. consideration is given to the fact that the motion enters from the primary motion input shaft and exits from the motion output shaft. With initial reference to figures 1A and I B, the diagram of a mixer with two synchronised shafts, indicated in its entirety with the numeral 100, is shown. This diagram is illustrated solely to better understand the needs and the objectives indicated above according to the following description. The mixer 100 consists of a tank 101 to contain the material to be mixed, of two shafts 102a and 102b, supported in rotation by supports 103. On said shafts are mounted various blades 104 positioned so as to mutually intersect. At one end of the shafts are mounted to gear reducers 105a and 105b, both provided with a secondary motion output 106a and 106b, in turn connected in rotation by means of a joint 107. This kinematic scheme of the transmissions is able to maintain the shafts 102a and 102b in synchronised rotation, necessary to prevent contact between the blades 104. In figure lb, some dimensions are also pointed out: A, B, C, D which are significant; the dimension B determines the minimum possible interaxis distance A between the shafts 102a and 102b, the dimension C determines the height of the motor D above the shafts of the machine 102a and 102b.

With reference to figures 2A and 2B, the reference numeral 200 indicates in its entirety in a schematic manner, shown in a front view 2A and detailed lateral view 2B, a speed reducer according to the present invention which forms a transmission between a motor 23 and a motion output shaft 207. The motion flows in the reducer from the motor 23 to the motion output shaft 207.

The reducer 200 comprises a housing box 201 within which are contained : an orthogonal first reduction stage 21, also indicated hereafter as bevel gear, consisting of a motion input bevel pinion 202, holed coaxially; of the respective bearings 204, of a bevel gear wheel 203,

a second reduction stage with parallel axes 22, also indicated hereafter as cylindrical gear, comprising a cylindrical pinion 205 and the related gear wheel 206 coupled in rotation to the motion output shaft 207; a primary motion input shaft 208 and a joint 209 for connection to the motor 23, for example of the electrical type.

Meshing with the gear wheel 203 is shown a second bevel pinion 211 supported by an auxiliary shaft 212 by means of the bearings 213.

Additionally, an inner bearing 214 and an oil seal 215 are interposed between the primary shaft 208 and the bevel pinion 202. To the transmission 200 is combined a torque limiter 400, consisting, in a first embodiment thereof, of a driving flange 401, of a driven flange 402 and of one or more shear pins 403.

In normal operation, the transmission behaves in a traditional manner, transmitting the rotation from the motor 23 to the output shaft 207 through the kinematic chain consisting, in cascade, of the joint 209, of the shaft 208, of the bevel gear 21 and of the cylindrical gear 22. The torque limiter 400 is the rotation connection element between the input shaft 208 and the pinion of the first reduction 202, the flange 401 being fastened in rotation to the shaft 208 by means of coupling 216 and the flange 402 being fastened in rotation to the bevel pinion of the first reduction 202 by means of coupling 116. The two flanges 401 and 402 are made integral by means of the shear pin 403. If the maximum torque prescribed for the transmission is exceeded, the shear pin 403 shears, interrupting the connection between the flanges 401 and 402 and, consequently also between the motion input shaft 208 and the pinion of the first reduction 202. For this purpose, the shear pin 403 comprises, in one embodiment, a reduced section segment, which is dimensioned so as to be sheared when the torque to be transmitted exceeds the predefined limit.

In the above embodiment, following the intervention of the torque limiter 400, there is no interruption of the transmission of motion between the output shaft 207 and the auxiliary shaft of the secondary output 212 intended to take-off the motion towards the other transmissions combined in synchrony as is typically required in machines with synchronised shafts, shown, for example, in figure 1A and I B. Figure 2B shows the lateral view according to the section X - X' of the bevel gear 21 to highlight that preferably the gear wheel 203 is mounted in overhang on the extension of the pinion 205 of the second reduction 22 supported, in turn, by bearings 218. This arrangement allows the free passage of the shaft 208. In normal operation, the shaft 208 is maintained in coaxial position by the inner bearing 214 in a static manner, inasmuch as there is no relative motion with respect to the pinion 202; the oil seal 215 also provides fluid tightness statically; only on the occasion of the intervention of the limiter 400 is there relative rotation between 208 and 202. Stressed herein is the particularity of the invention in which the limiter 400 is opposite the motor 23, in an area external to the box 201 to achieve some of the objectives listed above, not constituting an encumbrance between motor 23 and box of the reducer 201 and simultaneously making the active parts of the limiter 400 perfectly accessible; in addition, with its operation it does not entail any problems to the transmission as could be experienced if instead they were located inside the box. Obviously, the pins 403 can also be so dimensioned that they do not intervene in overloads, thereby obtaining a transmission without torque limitation.

Figure 3 shows a second version of the invention in which the reducer, indicated in its entirety with the numeral 300, consists of a box 301 containing a first reduction stage with cylindrical gears 31 consisting of a holed pinion 302 that meshes with the related gear wheel 303 coupled in rotation to the hub 304 and respectively supported by bearings 305 and 306. A second stage with orthogonal gears 32 consists of a bevel pinion 307a, supported in rotation by the hub 304 and by the related bevel gear wheel 308, in turn connected in rotation to the output shaft 309. Additionally, a second bevel pinion 307b constitutes, together with the shaft 310 and the related bearings 311, a secondary motion synchronisation output. The motor 33 is connected to the primary shaft 313 through the joint 312; a bearing 314 drives the shaft 313 and the oil seal 315 contains the oil of the reducer. Externally to the reducer is mounted a torque limiter 400, exactly identical to the one shown in figure 2A. The operation of the transmission is similar to the preceding example, inasmuch as the intervention of the limiter does not interrupt the transmission of motion between the output shaft 309 and that of the secondary motion take-off 310. Therefore, in this second embodiment, too, the invention achieves the objectives.

Figure 4 shows, by way of example, a functionally alternative torque limiter based on the prior art of friction clutches. The limiter is indicated in its entirety with the numeral 500 and it is conceived to be used interchangeably on the same reducers described previously. The limiter 500 consists of at least a driving disk 501, a driven toroidal box 502, a pressure disk 503, a spring, for example of the conical spring washer type 505 and at least two friction gaskets 506. During normal operation the disk 501 is set in rotation by the driving shaft 208 through the coupling 216; the friction generated by the pressure of the spring 505 between the surfaces in mutual contact determines a transmissible torque proportional to the force exerted by the spring and to the friction coefficient of the affected surfaces driving in rotation the box 502 which in turn drives in rotation the pinion of the first reduction 202 through the coupling 217. If the set torque is exceeded, there is sliding between the surfaces in mutual contact, but the kinematic mechanism remains subjected to the torque defined by the calibration of the system until the normal operation torque is restored or the motor stops. This torque limitation mode does not interrupt the transmission definitively but it protects it until the motor protection systems intervene to stop it. This transmission, too, maintains synchrony between the transmissions, like the preceding examples.

In figure 5, the numeral 600 indicates in its entirety a further example of torque limiter based on the prior art of the elastic damping of transitory load peaks and of the vibrations induced by load irregularity. The driving flange 601 is set in rotation by the input shaft 208 through the coupling 216; the driven flange 604 is made integral with the flange 601 through the elastic element 603 fastened to both through the counter-flanges 604. The driven flange 602 is integral with the pinion of the first reduction 202 through the coupling 217. During operation, the elastic element 603 absorbs, within its own elastic deformation limits, the irregularities of the transmitted torque, thereby allowing the reduction of the service factor to be applied to the gear reducer. This joint system does not interrupt the transmission of torque. This version of damper joint, too, can be interchangeable with the ones illustrated above and it can be mounted on the same version of reducer having the interfaced elements common to the other versions of limiters.