GB1582857A - Resilient coupling - Google Patents

Description

(54) RESILIENT COUPLING (71) We, ANSCHÜTZ & CO., GMBH, a German Body Corporate, of 32-36 Mec klenburger Strasse, 2300 KIEL 14, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a resilient coupling of the kind specified in the preamble to claim 1, "the preamble" being that part of claim 1which precedes the words "characterized in that" Such resilient couplings are for example used to couple a gyro-rotor to its drive shaft for common rotation in such a way that the rotor can tilt in all directions. In this case an intermediate body is connected to the drive shaft by two resilient joints which are aligned on a first transverse pivot axis and to the gyro-rotor by two resilient joints which are aligned on a second transverse pivot axis, with the first transverse pivot axis, the second transverse pivot axis and the main axis of the coupling intersecting each other at right angles. The intermediate body which forms the gyrorotor (or is rigidly attached to the latter), and a body which is rigidly attached to the drive shaft as well as leaf spring- which constitute the resilient joints which connect these bodies are obtained from a single blank of material by means of channels and slots formed in that blank. In a known resilient universal coupling of this kind (U.S. patent specification 3,575,475) the channels are of circular cross-section. Each of the four resilient joints of the coupling is thus produced by their piercing of four bores in the blank. There are two groups of four bores each in that coupling. The axes of each group of four bores are parallel to one of the transverse pivot axes and pass through the corners of a square and each bore is connected to others by milling slots in the blank. In this way there are produced the afore-mentioned leaf springs, their surfaces being formed partly by portions of the walls of the bores and partly by the walls of milled slots. The two leaf springs which constitute a r-esilient joint cross each other.

The centre of each leaf spring thus coincides with the centre of the square. This is the point at which the leaf spring have their maximum thickness and the main axis of a resilient joint passes also through this point.

The leaf springs have their thinnest portions on either side of this axis. They extend from these portions with an arcuate contour into the bodies connected by the resilient joints.

the diameter of the four bores of each resilient joint is determined by the length of the leaf springs. The greater the diameter of the bores, the larger and heavier must the intermediate body be made. Since the leaf springs can be flexed to any substantial extent only at their thinnest portions, they are relatively stiff. This drawback is compensated by the advantage that the leaf springs are in their longitudinal direction highly resistant to compression, tractice and buckling forces and have a great resistance to shearing forces in the transverse direction.

Resilient universal couplings are also known in which the bodies which are tilt able relative to one another are connected by similarly arranged leaf springs which are of constant. width and thickness over their entire length. Such leaf springs can be more easily flexed than leaf springs of comparable dimensions which have been described in the foregoing, but they are less resistant to compression, traction and buckling in the longitudinal direction and less shearresistant in the transverse direction.

The object of the invention is to provide a resilient coupling in which the configuration of the leaf springs combines the advantages set-out above of the leaf springs produced by forming interconnected bores with the advantages of the leaf springs which are of the same width and thickness over their whole length. This has the result that the length of the leaf springs, the dimensions of the channels formed by the bores and the dimensions of the bodies connected by the leaf springs can be considerably reduced.

When applying the invention to a driven gyro-rotor, this means that for crossed leaf springs of a given length, the intermediate body can be reduced in size and thus the mass of the rotor be increased, with the lood capacity of the coupling remaining. the same. The achieving of this object results in a considerable advance, for the following reasons: 1. The reduction in the mass of the intermediate body facilitates balancing.

2. The channels of the known coupling have a pumping effect which, because of the gas turbulence and gas friction, can cause upsetting moments. The latter are considerably reduced if the channels formed by the bores are of reduced cross-section.

3. The ratio between the rotating masses can be more precisely controlled if less material has to be removed on forming the channels. Dynamic adjustment is simplified.

4. If the cross-section of the channels is reduced, then the bodies through which they pass will have increased stability and it will thus be possible to achieve iso-elasticity in the joint formed by the crossed leaf springs simply by dimensioning them suitably.

5. The overall size of the coupling can be reduced.

The object of the invention is achieved by providing a reslient coupling for the pivotal connection of two bodies said coupling comprising pairs of leaf springs, the leaf springs crossing each other and merging at their ends with said bodies via concave surfaces having relatively small radii of curvature, said leaf springs being formed in one piece with said bodies by providing in a blank of material four parallel elongated cavities of non-circular cross-section, each of said cavities being closer to two of the three other cavities than to the third cavity, said cavities extending through said bodies, the end portions of each leaf spring which merge with a body via said concave surfaces being spaced from the other end portions by sections whose length is considerable as compared to their thickness characterised in that said sections have concave surfaces whose radii of curvature exceed the maximum transverse dimension of the cavities.

In the application of the invention to provide a resilient coupling for a gyroscope, the invention also cosists in that a body rigidly attached to the rotor of the gyro-scope is connected by a first pair of co-axial resilient joints and a body rigidly attached to the drive shaft is connected by a second pair of co-axial resilient joints to an intermediate body, the longitudinal axes of said two pairs forming the transverse axes of said coupling, said transverse axes being at right angles to each other, said three body being produced from one single blank by removing material from said blank, characterised in that each resilient joint is formed in accordance with claim 1.

In the case of a resilient coupling for a pivoting connection between two bodies which consists of only a single leaf spring which merges at its ends into the bodies via concave curved surfaces and which is formed together with the bodies out of a single piece of material by providing therein two parallel bores passing through the piece from one side-face to the opposite side-face and by supplementing the'bores with slots, the proposal has already been made to replace the bores by non-circular channels (German Offenlegungsschrift. 25 25 530, p.39, 1.17 - 26). In this proposal nothing is said about the configuration of the noncircular channels.

It is proposed in the case of the lastmentioned coupling that the channels be formed by spark erosion.

-This procedure may also be adopted in the case of the coupling of the invention. In this the case, the erosion electrode used is preferably a wire which passes through the entire length of the channel. The use of a wire as an erosion electrode is not novel in itself.

In the known resilient- -universal coupling mentioned above (U.S. patent specification 3,575,475) one of the spring leaves of each of the resilient joints is perpendicular to the plane of the transverse pivot axes, while the other spring leaf of that joint is situated in this plane. When applying the invention to a resilient universal coupling for a gyro, the individual resilient joints may be arranged in the same manner. However, favourable symmetry characteristics can be obtained if the individual springs form the same angle with the plane defined by the two transverse pivot axes. It is also possible for the angle at which the longitudinal planes of the leaf springs of a joint intersect to be other than 90". This may be desirable in order to achieve iso-elasticity to oppose shear forces.

A number of embodiments of the invention will now be explained in detail by way of example with reference to the drawings in which: Figure 1 shows, looking in the directionof arrows 1 in Figure 2, two co-axially arranged annular bodies which are connected by a resilient coupling according to the invention in such a way as to be able to pivot, with the longitudinal axis of pivot coinciding with the common axis of the two annular bodies, Figure 2 is a section on line 2 - 2 of Figure 1, Figure 3 shows a resilient universal coupling for driving a gyro-rotor, the coupling being seen partly in the direction of arrows III of Figure 4 and partly in section on line 3 - 3 of Figure 4, Figure 4 shows the coupling of Figure 3, looking in the direction of arrows 4, Figure 5 is a developed view, partly broken away, of the circumferential surface of the coupling shown in Figures 3 and 4, Figure 6 is a view, corresponding to the central part of Figure 5, of the circumference of a resilient universal coupling which differs from that shown in Figures 3 to 5 in respect of the angular position of its leaf springs, Figure 7 is a view corresponding to Figure 6 of a resilient universal coupling having leaf springs of a different outline, Figure 8 shows a resilient universal coupling in which the angle of intersection of the longitudinal axial leaf spring planes is other than 90".

Figure 9 is a view corresponding to Figure 3 of a three-part annular resilient universal coupling and of the tools for the removal of material by spark erosions, the view being taken looking in the direction of the arrows 9 of Figure 10, Figure 10 is a side-view of the resilient universal coupling and tools shown in Figure 9, partly in section on line 10 - 10 of Figure 9, and Figure 11 is a section on lines 11 - 11 of Figures 9 and 10.

The resilient coupling shown in Figures 1 and 2 is used to connect to each other two co-axial annular bodies 20 and 22 of the same outside diameter, which are axially spaced a short distance from one another by a gap 24 and which are so connected together by separate superposed leaf springs 26, 28, whose longitudinal axial planes intersect so that the bodies 20 and 22 are able to pivot with respect to each other relative to their common axis 30. The annular bodies have co-axial cylindrical circumferential outer faces 32, 34, outer flat end-faces 36, 38 which extend perpendicularly to the axis 30, and inner circumferential faces which consist of an approximately 200e long arc 40 of larger radius, an approxi mately 1600 long arc 42 of smaller radius, and shoulders 44 which connect the ends of Bone of the arcs to those of the other. Thus, the radial thickness of each ring, measured at arc 40, is smaller than that measured at arc 42. The thicker portion of each annulus has a thin, part-cylindrical projection 46 which extends into the interior of the other annulus to the outer end-face 36 or 38 thereof. The two leaf springs 26 and 28, each extend in the direction of diameters of the bodies 20, 22, the lower spring 26 extending from the inner face 43 whose outline is determined by the arc 42 to the projection 46 from the upper annulus 20, below the centre plane 48 of the space between the two annuli which is created by the gap 24. The upper leaf spring 28 extends above the plane 48 from the inner face 45 of annulus 20 to the projection 46 of annulus 22 which is located opposite. The crosssectional parts of the springs which are shown hatched in Figure 2, are situated in surfaces extending diagonally through the midpoint of the leaf springs.

The body formed by the annuli 20 and 22 and the leaf springs 26 and 28 which connect them consists of one single piece. It is produced in the following way: a cylindrical blank having an axis 30 and end-faces 36 and 38 is provided, by machining or by removing material in some other manner, with four parallel channels which extend through the body from an end-face 36 to the opposite end-face 38 and whose longitudinal axes A (Figure 1) Are parallel to the axis 30 and pass through the corners of a square. It follows from this that each of the channels is closer to two of the other three channels than to the third one.

In the case of the embodiment shown in Figures 1 and 2, the four channels have all of the same cross-section. Its outline consists of- an outer arc whose centre of curvature coincdes with axis 30 and of two approximately radial arcs which define concavecurved lateral surfaces of the leaf springs 26 and 28. These three arcs thus form a curved-sided triangle the corners of the triangle are radiussed.

The cylindrical body having the two endfaces 36 and 38 is then provided with a deep groove extending around it in a circle the groove being bordered by the inner endfaces of the two annuli 20 and 22, which end-faces are spaced apart by the gap 24.

An arcuate groove 50 which extends axially as far as the gap 24 and which communicates therewith is then milled into the end-face 36, the groove 50 being parallel to the arc 42. The groove 50 extends peripherally from one of the shoulders 44 to the other shoulder 44. A corresponding arcuate groove 52 is milled into end-face 38 and likewise opens into the gas 24. Then, a channel 54 of rectangular cross-section is formed perpendicularly to axis 30 by removing material, from the cylindrical body, in such a way that the longitudinal axis 56 of the channel 54 cuts the axis 30 in plane 48.

Now, starting from the end-face 38, the leaf springs 28 are produced by removing material by milling, cutting or in some other way as far as the inner end-face of the annulus 20. In a similar manner and starting from the end-face 36, the leaf-springs 28 are .produced by removing material as far as the inner end-face of annulus 22. Consequently, all that is left inside the annulus 22 is the leaf spring 26, while all that is left inside the annulus 20 is the leaf spring 28. The two leaf springs are separated from one another by the channel 54. They cross each other at right angles.

Finally, the two projections 46 have to be separated from the respective annuli into which they project, as this is not fully accomplished by the arcuate grooves 50, 52.

For complete separation, internal grooves 58 parallel to the axis 30 are milled into the annuli 20 and 22 and because of the outline of these grooves, the shoulders 44 are obtained in two opposite channels.

The only remaining connection between the two annuli 20 and 22 are then the two leaf springs 26 and 28.

An essential feature of the resilient cou pling of the invention according to the embodiment of Figures 1 and 2 is that the concave curved faces of the leaf springs 26 and 28 which faces are defined by the channels (the spring being at their thinnest on either side of the pivot axis 30 at approximately 60 in Figure 1) have a radius of curvature R which exceeds the maximum transverse dimension of a channel. In the case of the embodiment shown in Figure 1 the radius of curvature R of the concave curved surface of the leaf spring 26 is approximately twice the length of the sides of the curved-sided triangle which repre sents the cross-sectional outline of a chan nel. Were the channels of circular outline in cross-section, as is the case in the known resilient universal coupling (U.S. patent specification 3,575,475), R would be only half the diameter of the channel.

The result of the radius of curvature R being large is that the thickness of the leaf springs, beginning from the point 60 where it is at its smallest, increases in an outward direction first slowly and then very rapidly.

With springs of a given stiffness, this results in very great strength in a moderate height for the entire coupling and in optimum stressing conditions for the material of the springs.

It is best for the radius of curvature R and the width and minimum thickness of the two leaf springs, to be selected in such a way that their capacity to accept radial thrusts i9 equal to their capacity to accept buckling loads. This results in the leaf springs having the maximum load-bearing capacity.

If a relative tilting moment whose vector has a first component which coincides with the axis 30 and a second component extend ing transversely thereto acts on the two annuli 20 and 22, then the leaf springs flex under the influence of the'first component and permit the two annuli 20 and 22 to tilt resiliently relative to each other and to the axis 30, whereas the leaf springs offer a very stiff resistance to the second component.

When the channels are of the outline shown in Figure 1, the resilient coupling is consid erably more supple and yielding then a coupling of the same size whose channels were of circular outline in cross-section.

Figures 3, 4 and 5 show a resilient uniersal coupling which may for example be used for driving a gyro-rotor. The coupling consists of a hollow cylindrical structure having two parallel end-faces 70 and 72, which is divided into three bodies by slots and passages which are located in the circum ferential surface of the structure. A first body 74 has the end-face 70. Another body 76 has the end-face 72 and between the two .bodies 74 and 76 is situated a third body 78.

The body 78 constitutes an intermediate body which is connected to body 74 in such a way as to pivot about a first transverse axis 84 and to body 72 in such a way as to pivot about a second transverse axis 82. Both transverse axes extend in the direction of a diameter of the cylindrical structure, and the axis 80 of that structure passes through the point of intersection of the axes 82 and 84. Axis 80 is perpendicular to the axis 82 and axis 84.

Two resilient joints whose leaf springs are formed in the way described with reference to Figures 1 and 2 are aligned with the axis 82 and form a first universal joint, the leaf springs being grouped in pairs. Two other resilient joints of the same design are aligned with axis 84 and form a second universal joint.

The three bodies 74, 76 and 78 are connected together solely by the four pairs of leaf springs (the fourth pair being not shown in Figure 5 as it is in the broken-away part). Everywhere else the three bodies separated from one another by the slots mentioned above. These slots comprise arcuate slots 86 and 88 which extend parallel to end-faces 70 and 72, straight slots 90 and 92 which extend parallel to axis 80 and to the transverse axes 84 and 82 respectively, and further arcuate slots 94 which extend parallel to end-faces 70 and 72. The slots open into two groups of four channels which are parallel to the transverse axes 82 or 84 and which define and outline of the pairs of leaf springs.

In the same way as the two leaf springs 26 and 28 are separated in the middle by a passage 54 which extend in the diametric direction in the case of the resilient joint in Figures 1 and 2, the leaf springs shown in Figures 3 to 5 are separated by means of four bores 96 which extend parallel to axis 80 and which intersect the transverse axes 82 and 84.

The structure shown in Figure 3 to 5 differs from the prior -art -(U.S. patent specification 3,575,475) essentially by the outline of the channels which define the leaf springs. Whereas in the case of the prior art the channels are of circular cross-section, they are in the present instance of the form described with reference to Figures 1 and 2. A further similarity to the prior art coupling is that some of the leaf springs are situated in the plane containing the trans verse axes 82, 84 whilst others are perpendi cular to that plane.

It is of considerable advantage if indi vidual leaf springs form the same angle, e.g.

an angle of 45 , with the plane 98 (Figure 4) which contains the two transverse'axes 82 and 84. An embodiment of this arrangement is shown in Figure 6, which corresponds to the central portion of Figure 5.

When the invention is applied to the drive of a gyro-rotor, the intermediate body 78 is connected to the body 76, which is rigidly connected to the drive shaft, by two aligned leaf spring joints, and to the body 74, which is rigidly mounted on the gyro-rotor by the other two aligned leaf spring joints and is therefore coupled to the rotor for common rotation with it, but in such a way as to be able to tilt in all directions relative to it.

The advantage of the embodiment shown in Figure 6 in comparison with that shown in Figures 3 to 5 is that favourable symmetry characteristics are achieved. A further embodiment is shown in Figure -7, which, like Figure 6, shows part of a developed view of the hollow cylindrical structure. The embodiment in Figure 7 differs from that in Figures 3 to 5 only as regards the configuration of the leaf springs in that the four channels by which each pair of leaf springs is defined are of different cross-sectional outline, the'latter consisting of a straight or substantially straight outer side 100 and two curved sides 102 and 104.

Furthermore, the thinnest point 106 of each sp?ing-limb is approximately the same dis tance away from the central crossing-point 108 as it is from the point 110 at which the leaf spring merges with the body connected to it. The thinnest point is thus much farther away from the centre of the leaf springs than is the case in the embodiment shown in Figures 3 to 5.

Whereas in the case of the embodiments so far described the longitudinal axial planes of the leaf springs intersect at right angles, it is also possible for the outline of the channels to be such that the angle of intersection is other than 90". An example of this is shown in Figure 8. In this Figure, the outline of the two channels on the right and left hand sides of Figure 8 is different from that of the channels which are shown at its fop and bottom. In this case the thinnest point of the limbs is again much nearer to the central crossrpoint of the leaf springs than to the points at which the leaf springs merge with the bodies they connect.

The resilient universal coupling which is described with reference to Figures 3 to 5 thus has four pairs of leaf springs whose longitudinal axial planes intersect, each pair being defined by four parallel channels which pass right through the annular structure from its inner circumferential face to its outer circumferential face. These channels correspond. to those whose cross-sectional centres, marked A in Figure 1, are Ibcated at the corners of a square.

The recently developed spark erosion technique for' shaping and contouring metal bodies offers various possibilities for producing the channels. The erosion may for example be performed by using a tensioned wire which is passed through a bore in the annular body parallel to a transverse axis and which is moved along a path which corresponds to the desired outline of the channels. This wire then cuts cores out of the hollow cylindrical structure and the cores are then extracted whereby the channels in the structure are produced.

Because two pairs of superposed leaf springs are provided on each of the two transverse axes 82 and 84 (Figure 3), with each pair defined by a group of four channels, the four channels making up one group of channels are exactly aligned with the four channels making up the other group. Thus, if the erosion wire is made longer than the outside diameter of the hollow cylindrical structure formed by the bodies 74, 76 and 78, the wire can be drawn through the whole structure parallel to a transverse axis. If, in the erosion process, the wire is then guided to follow the triangular outline of a channel, it cuts out two cores which are aligned with one another. If for exaple the wire extends parallel to transverse axis 82, then one of the cores is situated to the right and the other to the left of transverse axis 84. The channels which are obtained after the sores have been extracted and hence also the leaf springs left after the extraction are exactly aligned with one another. This considerably simplifies manufacture and has other advantages mentioned hereinafter.

Spark erosion also provides the possibility of using electrodes as illustrated in Figure 9 to 11 to produce the resilient universal coupling shown in Figures 3 to 5. In.this case, an outer electrode 112 and an inner electrode 114 are used to produce each pair of crossed leaf springs The outer electrode consists of a conductive bar which has two parallel prismatic spigots 116 and 118 of equal close to its end. Their length corresponds to the depth of a leaf spring plus the distance between the crossed leaf springs.

The adjacent side-faces of the spigots 116 and 118 extend transversely to the bar 112.

The cross-sectional outline of the two spigots 116 and 118 can be seen from Figure 11.

This outline is such that the cross-sectional outline of the space 120 between the two spigots is the same as that of a leaf spring.

The inner electrode 114 has two spigots 120 and 122, whose adjacent sides extend para- llel to the inner electrode. In all other respects the two spigots 120 and 122 correspond to the spigots 116 and 118 as regards their cross-sectional configuration and length.

To carry out the erosion operation, the two electrodes 112 and 114 are mould into the positions shown in Figures 9 and 10. The electrode 114 is thus introduced into the interior of the annular structure parallel to the axis of the latter. When this is done the spigots 120 and 122 are lined up relative to the transverse plane in which the transverse axes 82 and 84 are to be situated. On the outside of the annular structure, electrode 112 is moved into a position parallel to electrode 114 and in which the spigots 116 and 118 allow the plane containing the transverse axes to pass between them. The two electrodes 112 and 114 are then advanced in radial directions as indicated by the arrows. This operation takes place in a bath contaning an electrolyte, the tools thus closing a circuit. Spigots 116 and 118 then penetrate into the workpiece from the outside and spigots 120 and 122 from the inside and as they do so they form between them superposed leaf springs whose longitudinal axial planes intersect and which are separated from one another by bores 96, as has been explained before with reference to Figure 3 (channel 54). Once the two bars 112 and 114 have been withdrawn radially in directions opposite to the arrows in Figures 9 and 10, to the starting position shown there, the pair of leaf springs is finished.

The cylindrical structure is then rotated about its axis 80 relative to the bars 112 and 114 through 90" and the next pair of superposed leaf springs is then produced.

After all its four pairs of superposed leaf springs have been formed the, coupling is completed.

In the case of the embodiment of Figure 7, the position of the spigots 116 to 122 is altered accordingly.

The method of manufacture described ensures that the planes of the leaf springs are exactly aligned with respect to the transverse axis about which the resilient joints formed by the leaf springs can tilt.

This prevents opposite groups of four channels being skewed or maladjusted and hence any undesirable stiffening of the joints.

WHAT WE CLAIM IS: 1. A resilient coupling for the pivotal connection of two bodies, said. coupling comprising pairs of leaf springs, the . leaf springs of a pair crossing' each other' and merging at their ends with' said bodies via concave surfaces having relatively small radii of curvature, said leaf springs being formed in one piece with said bodies by providing in a blank of material four parallel elongated cavities of non-circular cross section, each of said cavities being closer to two of the three other cavities than tod the third cavity, said cavities extending through said bodies, the end portions ofeach leaf sp

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. distance between the crossed leaf springs. The adjacent side-faces of the spigots 116 and 118 extend transversely to the bar 112. The cross-sectional outline of the two spigots 116 and 118 can be seen from Figure 11. This outline is such that the cross-sectional outline of the space 120 between the two spigots is the same as that of a leaf spring. The inner electrode 114 has two spigots 120 and 122, whose adjacent sides extend para- llel to the inner electrode. In all other respects the two spigots 120 and 122 correspond to the spigots 116 and 118 as regards their cross-sectional configuration and length. To carry out the erosion operation, the two electrodes 112 and 114 are mould into the positions shown in Figures 9 and 10. The electrode 114 is thus introduced into the interior of the annular structure parallel to the axis of the latter. When this is done the spigots 120 and 122 are lined up relative to the transverse plane in which the transverse axes 82 and 84 are to be situated. On the outside of the annular structure, electrode 112 is moved into a position parallel to electrode 114 and in which the spigots 116 and 118 allow the plane containing the transverse axes to pass between them. The two electrodes 112 and 114 are then advanced in radial directions as indicated by the arrows. This operation takes place in a bath contaning an electrolyte, the tools thus closing a circuit. Spigots 116 and 118 then penetrate into the workpiece from the outside and spigots 120 and 122 from the inside and as they do so they form between them superposed leaf springs whose longitudinal axial planes intersect and which are separated from one another by bores 96, as has been explained before with reference to Figure 3 (channel 54). Once the two bars 112 and 114 have been withdrawn radially in directions opposite to the arrows in Figures 9 and 10, to the starting position shown there, the pair of leaf springs is finished. The cylindrical structure is then rotated about its axis 80 relative to the bars 112 and 114 through 90" and the next pair of superposed leaf springs is then produced. After all its four pairs of superposed leaf springs have been formed the, coupling is completed. In the case of the embodiment of Figure 7, the position of the spigots 116 to 122 is altered accordingly. The method of manufacture described ensures that the planes of the leaf springs are exactly aligned with respect to the transverse axis about which the resilient joints formed by the leaf springs can tilt. This prevents opposite groups of four channels being skewed or maladjusted and hence any undesirable stiffening of the joints. WHAT WE CLAIM IS:

1. A resilient coupling for the pivotal connection of two bodies, said. coupling comprising pairs of leaf springs, the . leaf springs of a pair crossing' each other' and merging at their ends with' said bodies via concave surfaces having relatively small radii of curvature, said leaf springs being formed in one piece with said bodies by providing in a blank of material four parallel elongated cavities of non-circular cross section, each of said cavities being closer to two of the three other cavities than tod the third cavity, said cavities extending through said bodies, the end portions ofeach leaf spring which merge with a body via said concave surfaces being spaced from the other end portions by sections whose length is considerable as compared to their thick ness characterised in that said sections have concave surfaces whose radii of curvature exceed the maximum transverse dimension of the cavities.

2. A resilient universal coupling for a gyro-scope in which a body rigidly attached to the rotor of the gyro-scope is connected by a first pair of co-axial resilient joints and a body rigidly attached to the drive shaft is connected by a second pair of co-axial resilient joints to an intermediate body, the longitudinal axes of said two said pairs forming the transverse axes of said coupling, said transverse axes being at right' angles to each other, said three bodies being pro duced from one single blank by removing material from said blank, characterised in that each resilient joint is formed in accord ance with claim 1.

3. A resilient universal coupling accord ing to claim 2, characterised in that, in order to achieve favourable symmetry characteris tics, the individual springs form, equal angles with the plane formed by the two transverse axes of the coupling.

4. A resilient universal coupling accord ing to claim 2 or 3, characterised in that the angle of intersection of the leaf springs is other than 90" in order to obtain iso ,elasticity against shear forces.

5. A resilient coupling, substantially as described herein with reference to the accompanying drawings.