US20070032350A1

US20070032350A1 - Gymnastic machine

Info

Publication number: US20070032350A1
Application number: US11/497,682
Authority: US
Inventors: Nerio Alessandri; Alessandro Monaco
Original assignee: Individual
Current assignee: Technogym SpA
Priority date: 2005-08-03
Filing date: 2006-08-01
Publication date: 2007-02-08
Also published as: EP1749553A2; CN1907519A; ITRA20050030A1

Abstract

Gymnastic machine including an epicycloidal mechanism (2) for connecting an application member (3) of a driving device to resistive means (36); the mechanism (2) being provided with a satellite member (4) connected to the application member (3) by means of a first crank (5) having a pin (6); with a planetary member (7); with a second crank (8) which rotationally connects a movable rotation centre (9) on the satellite member (4) to a fixed centre (10) on the planetary member (7); and with transmission devices (11, 12, 13) for transmitting a relative motion between the satellite member (4) and the planetary member (7); the planetary member (7) being supported in freely rotatable manner around an axis (14) passing through the fixed centre (10); actuating members (15) being provided for imparting to planetary member (7) an angular movement (α) around the fixed centre (10) which corresponds to a relative angular variation (β) of the first and second cranks (5, 8), and a corresponding variation of the orientation of the path (21, 22) of the pin (6) of the satellite member (4).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a gymnastic machine. In particular, the present invention relates to a gymnastic machine which includes an epicycloidal mechanism. In more detail, the present invention refers to a gymnastic machine which includes an epicycloidal mechanism capable of connecting together a device capable of producing a resistive load to an organ for the application of a driving load.
2. Description of the Prior Art
A mechanism is known from document U.S. Pat. No. 6,334,836, in the name of the present Applicant, of general use which, if applied to a machine for gymnastic exercise, may be usefully employed for connecting a member for applying a muscular driving load, generated by the user of the machine, to resistive means opposing the applied muscular load. The mechanism essentially includes:
a satellite member (an externally-toothed wheel) rigidly carrying a first crank, radial, having a head which rotationally connects the application member applying the load to a pin on the satellite member;
a planetary fixed member (an internally toothed wheel);
a second crank which rotationally connects a rotation centre on the satellite member with a fixed centre on the planetary member; and
transmission means, for the coordinated transmission of a relative motion between the satellite member and the planetary member.
The rotation of the first crank produces, simultaneously and in synchronized manner:
the rotational movement of the satellite member around its own centre of rotation;
the revolving movement of the satellite member around the fixed centre of the planetary member; and
the movement of the pin applying the driving load to the satellite member which occurs along a generally elliptical path, concentric with the fixed centre of the planetary member.
In general, the elliptical path described by the application pin for applying the load can be determined completely from the position of the axes of the ellipse. A first axis of the ellipse, in fact, lies permanently on the straight line identified by the alignment condition of three points: that is, by the alignment condition of the fixed centre of the planetary member, with the movable centre of the satellite member, and with the pin of the satellite member in proximity to which the driving load is applied to the self-same satellite member.
The second axis of the ellipse is obviously perpendicular to the first axis, and passes through the fixed centre of the planetary member.
According to the relative phasing of the various members, it is possible to obtain paths for the application pin for applying the muscular load, however oriented in the plane in which the mechanism lies.
For example, if the mechanism is configured in such a way that the condition of alignment of the three above-mentioned points is reached along a horizontal straight line, then the major axis of the ellipse will be exactly on the vertical. Vice versa, if the condition of alignment of such points is along a vertical straight line, then the major axis of the ellipse will be on the horizontal. The condition of alignment along any oblique line whatsoever allows the major axis of the ellipse to be aligned perpendicularly to this oblique line.
The shape of the elliptical path is determined by the distance separating the centre of rotation of the satellite member and the position of the pin applying the load to the self-same satellite member. In fact, if the pin applying the load coincides exactly with the centre of rotation of the satellite member, the elliptical path of the pin decays into a circle. Vice versa, the greater the distance between the centre of rotation of the application pin, the more marked is the difference in length between the axes of the ellipse. With suitable choices for the dimensions of the mechanism, it is even possible to determine elliptical paths so flattened as to be practically assimilable to straight lines traveled in reciprocal motion by the pin applying the load. In such a device, the adjustment of the paths of the pin applying the load is obtained by varying precisely the characteristic distance mentioned above by assigning to the first crank a conformation capable of allowing the pin applying the load to be positioned at the desired distance from the movable centre of the satellite member.
This entails several disadvantages. In the first place, in fact, it is necessary to have a first crank with a rather considerable longitudinal extension.
In fact the crank should possess an extension such as to allow the positioning of the pin within a more or less broad range of positions corresponding to all those possible for the various users, or at least related to the statistically most common among the various types of users who access the gymnastic machine. But a sizeable longitudinal dimension of the first crank implies a consequent proportional geometrical conditioning of the overall dimensional configuration of the machine using the mechanism.
Another disadvantage, furthermore, is represented by the fact that adjustment of the mechanism through variation of the distance of the application pin applying the load, from the centre of the satellite member is an operation feasible only with the machine stationary.

SUMMARY OF THE INVENTION

An object of the present invention is to obviate the disadvantages described above through a mechanism of the type mentioned above, of limited dimensions, in which the adjustment of the path of the application pin applying the load is performable during use.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a gymnastic machine including at least one mechanism for connecting an application member for applying a driving load to resistive means opposing said load. The mechanism is provided with a satellite member connected to the load application member by means of a first crank having a pin on the satellite member with a planetary member, with a second crank which rotationally connects a movable rotation centre on the satellite member to a fixed centre on the planetary member and with transmission means for the coordinated transmission of a relative motion between the satellite member and the planetary member. In the mechanism, the rotation of first crank determines, in synchronized manner, the rotational movement of satellite member around its own centre of rotation, the revolving movement of satellite member around the fixed centre of planetary member, and the movement of pin on satellite member along a generally elliptical path concentric with the fixed centre of planetary member. In the machine, the planetary member of mechanism is supported in freely rotatable manner around an axis passing through the fixed centre, actuating means provides for imparting to planetary member an angular rotation around the fixed centre, to which correlatively corresponds a relative angular variation of the first and second cranks, and a corresponding variation in the orientation of the path of the pin on the satellite member.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the gymnastic machine according to the present invention will appear more clearly from the following description, explained by reference to the attached drawings which illustrate at least one non-limiting example of embodiment, in which identical or corresponding parts of the said device are identified by the same reference number, barring instructions to the contrary.
In the drawings:
FIG. 1 is a schematic perspective view of a gymnastic machine for gymnastic exercise according to the present invention in a determinate operating position;
FIG. 2 is a schematic perspective view of a gymnastic machine for gymnastic exercise according to the present invention in a determinate operating position;
FIG. 3 a is a schematic perspective view, on an enlarged scale and with parts removed for clarity, of a rear portion of FIG. 1 in a determinate operating position;
FIG. 3 b is a schematic perspective view, on an enlarged scale and with parts removed for clarity, of a front portion of FIG. 1 in a determinate operating position
FIG. 4 is a view in lateral elevation, with parts removed for clarity, of FIG. 3 a;
FIG. 5 is a view in lateral elevation, with parts removed for clarity, and on a reduced scale, of FIG. 4 in a determinate operating position;
FIG. 6 is a view in lateral elevation, with parts removed for clarity, of FIG. 5 in a different operating position;
FIG. 7 is a view in lateral elevation, with parts removed for clarity, of FIG. 5 in a different operating position;
FIG. 8 is a schematic view in lateral elevation of the machine in FIG. 1, with parts removed for clarity, in a determinate operating position corresponding to FIG. 5;
FIG. 9 is a schematic view in lateral elevation of the machine in FIG. 1, with parts removed for clarity, in a determinate operating position corresponding to FIG. 7; and
FIG. 10 is a schematic view in lateral elevation of the machine in FIG. 1, with parts removed for clarity, in a determinate operating position corresponding to FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the attached drawings, in FIGS. 1 and 2, reference numeral 1 globally identifies a machine for gymnastic exercise which includes a frame 20 supporting a pair of epicycloidal mechanisms adjacent to each other and located symmetrically with respect to a vertical longitudinal median plane of machine 1, not illustrated in the attached drawings for convenience. The two mechanisms 2 are therefore capable of being activated in two respective parallel planes, vertical and longitudinal, of machine 1.
Each mechanism 2 includes a member 3 for applying a driving load to a reaction device 36, better visible in FIG. 3 a. The driving load is generated by the muscular action of a user of machine 1 and, by means of footboard 35 is transmitted to each application member 3 of the two mechanisms 2. The reaction device 36 can be created ad hoc but can also reproduce a constructive structure already tested and described in a number of patent applications by the applicant, among them application No. RA2004A000044, filed on 16 Sep. 2004, without this being interpretable as a limitation of the executive modality of reaction device 36 itself. In any event, according to FIG. 3 a, reaction device 36 includes an electromagnetic brake 37 which is supported by frame 20 at the rear and in a central position between mechanisms 2 and is provided with a disc 38 of a flywheel 39 coaxial with disc 38 itself, susceptible of being subjected to braking through an electromagnetic unit 40 of known type. In FIGS. 3 a and 4 it can be observed that each mechanism 2 is provided with a satellite member 4, which is actuated in particular by a wheel provided with an externally toothed sprocket 12, and is connected to member 3 for applying the load by means of the interposition of a first crank 5.
The first crank 5 is connected rotationally to a rotation centre 9 on satellite member 4 and to a pin 6 on satellite member 4 itself. The pin 6 is suitably offset with respect to the rotation centre 9, and is capable of transmitting to first crank 5 the driving load from application member 3.
The mechanism 2 also includes a planetary member 7 and a second crank 8. The planetary member 7 is activated by a wheel having an externally toothed sprocket 13, which is supported by a fixed structure 25 on machine 1.
The second crank 8 rotationally connects the movable centre of rotation 9 on satellite member 4 with a fixed centre 10 on planetary member 7. The toothed sprockets 12 and 13, belonging respectively to satellite member 4 and planetary member 7, are kinetically connected to each other by means of a toothed belt 11 or an equivalent chain which runs round both of them and which, by meshing with them, contributes to constituting transmission devices 11, 12, 13 provided for allowing the coordinated transmission of a relative motion between satellite member 4 and planetary member 7.
The operation of mechanism 2 can be summarized by observing the following. The application of the muscular load to the relative application members 3 brings about the oscillation in the vertical plane of members 3 and the setting into rotation of the first crank 5 around the rotation centre 9 of satellite member 4; but such a rotation implies the simultaneous and synchronized motorization in a chain of the whole mechanism 2 which manifests itself not only in the contemporaneous rotation of satellite member 4 around its own centre of revolution 9, but also in a simultaneous revolution of satellite member 4 around fixed centre 10 of planetary member 7. While this is occurring, by reason of the composition of the movements, the pin 6 of satellite member 4 comes to move along a path 21 or 22, better visible in FIG. 4, on the basis of mechanism 2 which is to be considered as a reference, and therefore in relation to right-hand footboard 35 or left-hand footboard 36. This path 21/22 is generally elliptical and concentric with the fixed centre 10 of planetary member 7.
Since footboards 35 constitute extended bodies, which are rigidly connected to respective application members 3 for applying the load, simultaneously and parallel to the elliptical movement of the corresponding pin 6 on satellite member 4, there occurs a parallel elliptical movement described by each material point on footboards 35. It will be noted that what has been said and what follows are independent of the mode in which members 3 are supported by frame 20 at the opposite end to epicycloidal mechanisms 2. The decision to represent the connection between members 3 and frame 20 by means of a lever 27, visible only in FIGS. 1 and 2, hinged to the frame 20, must be interpreted without therefore deducing limitations for the constructional modalities of machine 1 itself. Besides, it is clear that members 3 are movable antisymmetrically with respect to a longitudinal midline plane of machine 1 itself, and therefore in phase opposition, through the fact of being movable by the lower limbs of the user and allowing the equilibrium of these limbs to be maintained. It should be noted that each lever 27 includes at least one grip area, which for simplicity is identified by a handle 44, in which the configuration of the paths of significant points of such handle 44 is variable in order to reproduce corresponding adjustments of reach for the user who grips it.
The movement of the material points of footboards 35 can be visualized with reference to characteristic points on the footboards, in particular the front and rear ends of each footboard 35 which, in use, correspond respectively to a path of the toe and heel respectively of the user's foot. The paths of the front and rear ends of each footboard 35 being indicated by 28 and 29, by comparative observation of FIGS. 8, 9 and 10 it is possible to note that such paths change their characteristic shape and their relative position depending on the orientation of elliptical path 21 described by the corresponding satellite member 4. In fact, more particularly, returning to FIGS. 3 b and 4, it will be noted that machine 1 provides for each planetary member 7 of mechanism 2 to be supported by fixed structure 25 with the possibility of rotating around an axis 14 passing through the fixed centre 10, upon activation of suitable actuating device, generically indicated by 15.
Actuating device 15 enable planetary member 7, starting from a certain initial reference position, to be imparted with an angular range of travel for positional adjustment, indicated by angle α around fixed centre 10, which is correlated in the geometry of mechanism 1 with a corresponding relative angular position β, between the axes of the first and second cranks 5 and 8. In other words, once an initial configuration has been fixed for mechanism 1, for every value assigned to the adjustment angle α, there is a differing inclination of ellipse 21 designating the path of pin 6 on the satellite member. In parallel to this variation, the angle of inclination β also varies. This is shown in FIGS. 5, 6 and 7, which represent in particular: the first, FIG. 5, a configuration in which angles α and β have the maximum respective size, corresponding to the maximum obliquity of elliptical path 21; the second, FIG. 6, a configuration of minimum size for such angles in which elliptical path 21 is substantially horizontal; the third, FIG. 7, a configuration of intermediate size, in which angles α and β have intermediate sizes with respect to those relating to the preceding configurations.
In other words, since pin 6 of the satellite member and the movable centre of rotation 9 of the satellite member 4 have an invariable mutual distance, the possibility of imparting an angular travel to planetary member 7 translates into the possibility of adjusting the mechanism 2 differently and much more advantageously than is the case with known gymnastic machines.
In practice, if FIG. 8 for example is observed, it may be noted that: when pin 6 on satellite member 4 describes the elliptical path in which the major axis has the greatest obliquity, in other words a position nearest to the vertical, paths 28 and 29 of the front and rear ends of footboards 35 have a characteristic configuration relatively little flattened in the direction of the minor axis of the ellipse; a maximum inclination with respect to the horizontal and a certain degree of overlap in the relative parallelism of such paths which obviously belong to the two parallel mechanisms 2 which are fitted to machine 1.
When the obliquity of elliptical path 21 diminishes, in other words when elliptical path 21 tends to approach most nearly to the horizontal, as is visible in FIG. 9, the paths 28 and 29 tend to lengthen in line with their major axes, to shorten in line with their minor axes, to overlap more in their relative parallelism, and finally to assume less obliquity with respect to the horizontal. When, finally, the elliptical path 21 is substantially horizontal, as is visible in FIG. 10, paths 28 and 29 appear once more less squashed by comparison with the preceding configuration, less overlapping in their relative parallelism, and substantially horizontal.
From simple dimensional comparison of comparable paths, and from the different degree of overlap of dissimilar paths for the characteristic points of footboards 35, it can clearly be deduced that in the transition of mechanism 2 from one configuration of machine 1 to the other, a variation is created in the length of the user's pace, in other words the adjustment carried out on mechanism 2 enables various types of stride to be reproduced on machine 1, and constrains users to adapt their movement to the various configurations of machine 1.
As regards the actuating device, from FIGS. 3 a and 4 it may be noted that such device can be made for example in such a way as to provide a simple adjustment lever 16 which carries a first end 17 rigidly connected to planetary member 7 and a second end 18 which is suitable for receiving a command to vary the angular position around axis 14 of planetary member 7.
It is obvious that this can be achieved according to a plurality of different methods of actuation. For example it is possible to see to it that the actuating device 15 include: a guide 23, such as a sliding slot formed in the structure 25 of the machine; and a slider 24 connected to lever 16 and coupled to guide 23 with freedom of relative movement, to adjust the position of fixing of end 18 of lever 16.
By activating the sliding of slider 24 in guide 23, it is therefore possible to move slider 24 in guide 23 and then lock it in the desired adjustment position, and vice versa to unlock it and move it each time it is desired to effect an adjustment different from the existing one.
Obviously, the adjustment of slider 24 in guide 23 can be effected for a series of relative coupling positions, prearranged and selectable at the user's choice, in a discrete series of positions of adjustment.
Alternatively it is possible for slider 24 and guide 23 to be able to assume relative coupling positions variable at the discretion of the user in a continuous series of adjustment positions.
The adjustment may also be facilitated by the use of an activating organ 26 which imparts materially to the slider 24 the force necessary to result in its sliding inside guide 23 and to then retain slider 24 in a condition of immobility in guide 23 in the desired position. The user is in this way limited simply to operating the activating organ 26 depending on the adjustment of stride desired.
The use of such an activating organ, besides being easier and not requiring any physical effort on the part of the user, has the further advantage of the adjustment being able to be performed even with machine 1 in motion, which enables machine 1 to be configured each time depending on the personal and/or anatomical characteristics of the user, and also can assist the user in effective exercise conditions and/or in varying the configuration of the machine in accordance with the execution of particular work programs. In the example described above, reference was made to the description of one of two mechanisms fitted to machine 1, which appear visible in their entirety in FIGS. 1 and 2. It is perfectly evident that, with the exception of the phase displacement of mechanisms 2 and the antisymmetry of positioning of footboards 35 with respect to the longitudinal mid-line plane of the gymnastic machine in these figures, what has been said for one of the two mechanisms 2 is perfectly repeatable also for the other.
In the example being described, the transmission devices include, as was said, a pair of toothed sprockets 12 and 13, belonging respectively to the satellite member 4 and the planetary member 7, which are inscribed in, and in mesh with, a flexible organ consisting of a belt 11 running in a loop around sprockets 12 and 13. It is however perfectly evident that in completely equivalent manner, when satellite member 4 is made in the form of a toothed disc and planetary member 7 is activated by an internally toothed ring-gear, in mesh with disc-type satellite member 4, the of transmission devices can also be activated by direct engagement of the externally toothed sprocket 12 of the satellite member 4 with internally-toothed ring-gear 13 of planetary member 7.
It should furthermore be noted that making satellite member 4 and planetary member 7 with radii which are in ratio with each other according to the numbers 1 and 2, in other words in the transmission ratio 1:2, or 0.5, confers the additional advantage of having a wide range of adjustment of the stride, since it is evident that if an angular travel of a determinate amplitude a is applied to planetary member 7, the corresponding angular travel β correlatively undergone by first crank 5 and by second crank 8, has an amplitude exactly double that imparted. The machine according to the invention fully achieves the objects stated earlier and presents the further advantages of adjustment device which being connected to stationary members are simpler and less expensive to execute. Equally simple and inexpensive is the fabrication of the relative cranks which both have fixed and invariable lengths.
It is further evident that the first crank 5 being of invariable length, this crank 5 does not impose on the general structure of machine 1 any kind of geometrical conditioning which is not strictly relevant to the typical and proper functions of machine 1; which machine 1, what is more, does not come to suffer any type of conditioning as regards its own overall dimensions. In the description of an example of the invention, reference has been made to a machine 1 fitted with footboards 35. This must be understood as being solely by way of example and without the effect of limiting the invention, as it is perfectly evident that what has been said for one such machine can be extended in equivalent manner to other types of machine. For example, supposing footboards 35 were replaced by components to be gripped manually, on a machine designed for the gymnastic exercise of the upper limbs of the person, epicycloidal mechanism 2 described above could be used to equal advantage to provide adjustment for the reach of the user.
Finally, it is clear that modifications and variations may be made to the gymnastic machine here described and illustrated without for this reason departing from the protective scope of the present invention.
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. Gymnastic machine comprising at least one mechanism (2) for connecting an application member (3) for applying a driving load to resistive means (36) opposing said load, said mechanism (2) being provided with a satellite member (4) connected to the load application member (3) by means of a first crank (5) having a pin (6) on the satellite member (4); with a planetary member (7); with a second crank (8) which rotationally connects a movable rotation centre (9) on the satellite member to a fixed centre (10) on the planetary member (7); and with transmission means (11, 12, 13) for the coordinated transmission of a relative motion between the satellite member (4) and the planetary member (7); in said mechanism (2), the rotation of first crank (5) determining, in synchronized manner: the rotational movement of satellite member (4) around its own centre of rotation (9); the revolving movement of satellite member (4) around the fixed centre (10) of planetary member (7); and the movement of pin (6) on satellite member (4) along a generally elliptical path concentric with the fixed centre (10) of planetary member (7); said machine (1) being characterized by the fact that said planetary member (7) of mechanism (2) is supported in freely rotatable manner around an axis (14) passing through said fixed centre (10); actuating means (15) being provided for imparting to planetary member (7) an angular rotation (α) around said fixed centre (10), to which correlatively corresponds a relative angular variation (β) of said first and second cranks (5, 8), and a corresponding variation in the orientation of the path (21, 22) of said pin (6) on the satellite member.

2. Machine according to claim 1, characterized by the fact that said pin (6) on the satellite member and said movable centre of rotation (9) have an invariable mutual distance.

3. Machine according to claim 1, characterized by the fact that actuating means (15) include an adjustment lever (16), pivoting on the fixed structure (25) of machine (1), which carries a first end (17) rigidly connected to said planetary member (7) and a second end (18) which is capable of receiving a command for altering the angular position, around said axis (14) of planetary member (7).

4. Machine according to claim 3, characterized by the fact that said actuating means (15) include a sliding guide (23) and a slider (24) coupled together with freedom of relative movement between at least two successive positions in which slider (24) and guide (23) can be locked together and unlocked; said guide (23) and said slider (24) connecting said lever (16) indifferently to the fixed structure (25) of machine (1).

5. Machine according to claim 4, characterised by the fact that said slider (24) and said guide (23) have relative coupling positions variable, at the discretion of the user, in a discrete series of adjustment positions.

6. Machine according to claim 4, characterised by the fact that said slider (24) and said guide (23) have relative coupling positions variable, at the discretion of the user, in a continuous series of adjustment positions.

7. Machine according to claim 1, characterised by the fact that said actuating means (15) include an activating organ (26) capable of imparting a relative movement between said slider (24) and said guide (23) at the command of the user.

8. Machine according to claim 7, characterized by the fact that said command can be executed with machine (1) in motion.

9. Machine according to claim 1, characterized by the fact that said one or both mechanisms (2) is applied to two said application members (3) for applying the load, movable on parallel planes to each other, in such a way as to render configuration of paths (28, 29, 30, 31) of significant points on said application members (3) for applying the load, variable at the discretion of the user.

10. Machine according to claim 9, characterized by the fact that said application members (3) are movable antisymmetrically with respect to a longitudinal midline plane of machine 1.

11. Machine according to claim 10, characterized by the fact that said application members (3) for applying the load include footboards (35) in which the configuration of the paths (28, 29, 30, 31) of said significant points is variable to reproduce corresponding adjustments of stride for the user who treads the footboard (35).

12. Machine according to claim 10, characterized by the fact that each said application member (3) for applying the load includes at least one handle (44) in which the configuration of the paths of significant points of each said handle (44) is variable for reproducing corresponding adjustments for the reach of the user who grasps the corresponding said handle (44).

13. Machine according to claim 1, characterized by the fact that the means of transmission include a pair of toothed sprockets (12, 13), belonging respectively to the satellite member (4) and to the planetary member (7), which are inscribed in, and in mesh with, a flexible organ running in a loop around said sprockets (12,13).

14. Machine according to claim 1, characterized by the fact that the transmission means are actuated by direct meshing of an externally-toothed sprocket (12) on the satellite member (4) with an internally-toothed ring gear, on the planetary member (7), inside which the satellite member (4) is located.

15. Machine according to claim 1, characterized by the fact that the satellite member (4) and the planetary member (7) have radii which stand to each other substantially in the approximate ratio 0.5.