GB2236828A

GB2236828A - Power transmission apparatus

Info

Publication number: GB2236828A
Application number: GB9021197A
Authority: GB
Inventors: Frederick Herbert Tilley
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-12
Filing date: 1990-09-28
Publication date: 1991-04-17
Anticipated expiration: 2010-09-28
Also published as: GB2236828B; GB9021197D0

Abstract

A pair of drive units are coupled together to form a power transmission apparatus, each unit having a housing 10 in which is rotatably mounted a rotor 18 keyed to a shaft 13. The rotor has grooves 19 formed on its periphery, and a helical channel 20 is formed internally within the housing. An endless column of rigid balls 21 extends round the channel 20, along tubes 23 connected to the two ends of the channel, and around the corresponding channel of the other drive unit, the balls in the channels engaging the grooves of the respective rotor 18. Rotation of one shaft 13 forces the column of balls to circulate, thus turning the rotor of the other drive unit. <IMAGE>

Description

POWER TRANSMISSION APPARATUS This invention relates to power transmission apparatus arranged to transfer power from a drive unit to a driven unit, and also to a drive (or driven) unit for use in such lower trarsmission apparatus.

In machinery of all kinds, it is frequently necessary to transfer power from one part of a machine to another. In a case where the machine has one rotating shaft which is to rotate another shaft at some distance from the one shaft, there have been designed innumerable power transmission devices to achieve this end. If the two shafts are parallel, belting running 2round pulleys fixed to the shafts may be employed though if non-slip power transfer is required, an endless chain running around sprockets, or a gear train may be employed. If the shafts are not parallel, then special measures have to be taken to accommodate the relative angle of the shafts; if gears are employed for this purpose, they may nend specially to be cut, leading to very high costs.As a consequence, hydraulics are often employed for power transfer, especially the shafts are non-parallel, despite all of the attendant problems relating to sealing, providing a liquid reservoir, valve mechanisms and so on. An alternative solution may lie in the use of an electric generator coupled by wires to an electric motor, but either of these indirect solutions will give rise to much higher costs, and the added complexity will reduce reliability.

It is principal object of the present invention to provide power transmission apparatus having a drive unit adapted to transfer power to a driven unit, which apparatus is wholly mechanical in its construction but which does not impose any limitation on the relative disposition of the input shaft of the drive unit and the output shaft of the driven unit.

Accordingly, one aspect of this invention provides power transmission apparatus comprising a drive unit having an input shaft and a driven unit having an output shaft, each of which units comprises a housing defining a bore in which is rotatably mounted a rotor carried on the shaft of the unit and which rotor flays a plurality of grooves each extending parallel to the rotor axis, a channel formed in the bore of the housing and having an inlet port and an outlet port at the two ends respectively of the channel, the respective crosssect ions of the channel and each groove being such that a ball may lie partially within the channel and partially within a groove, the apparatus further comprising ducts interconnecting the respective inlet and outlet ports of one unit with the outlet and inlet ports of the other unit, and a plurality of rigid balls extending in an endless column around the channels in the two units and along the ducts, whereby rotation of the shaft of the drive unit causes the transfer of power to the output shaft of the driven unit.

It will be appreciated that the power transmission apparatus of this invention employs an endless column of balls guided around the rotors of the drive unit and the driven unit, the columns extending along the ducts between the two units whereby rotation of one rotor causes a corresponding rotation of the other rotor.

However, since the ducts need not be linear, the shafts of the two drive units may lie at any angle with respect to each other, without affecting the power transfer, in any way. Moreover, the column of balls is whclly contained within the ducts or within the housings of the two units, and so there are no exposed moving parts, except for the input and output shafts.

Also, because the apparatus is relatively simple, it may be made robust and so reliable in operation.

If the channel formed in each housing lies in a radial plane, balls may contact the rotor over at best 270 of arc, in order to allow balls to be fed into the channel through the inlet port and removed from that channel out of the outlet port. It is therefore greatly preferred for each channel to be helically formed and to extend around the associated rotor for at o least 360 of arc, each groove in the rotor having an axial extent at least as great as the axial spacing between the inlet and outlet ports. In a typical power transmission apparatus of this invention, the channel o may extend for 7200 of arc, whereby a relatively large number of balls in the column thereof may be in contact with the rotor, so greatly increasing the power which may be transmitted from the drive unit to the driven =znit.

In the case of a helical channel, the pitch of the helix should be as small as possible to minimise losses and to minimise the axial length of the rotor.

In order to optimise the power transfer characteristics, it is also preferred that the total number of balls in contact with the rotor, and so the length of the channel in the housing, in the drive unit is equal to the total number of balls in contact with the rotor in the driven unit, or if there is more than one driven unit, in each of the units. In the sase of one dive unit and one driven nit, rotors of different diameters may be employed in order to achieve a nonunity velocity ratio between the input shaft of the drive unit and the output shaft of the driven unit, the angular extent of the respective channels being adjusted in order to achieve the same number of ball/rotor contacts (i.e. the same total channel lengths) in the two units.

Though it would be possible for grooves and channels of various cross-sectional shapes to be employed, it is preferred for each groove to have a part-circular cross-sectional shape of slightly less o than 180 of arc, and for each channel to have a corresponding part-circular cross-sectional shape. It is also preferred for the bore in the housing closely to fit against tha respective rotor.

Each duct may comprise a smooth-bore rigid tube the internal diameter of which is slightly greater than the diameter of the balls, whereby the balls may be smoothly transferred along the ducts, with the contacts between one ball and its two next adjacent balls taking place along a diameter of said one ball. Any bend in the ducts must be formed in such a way that the internal shape and diameter are accurately maintained throughout the bend. In some applications, it may be possible to use flexible ducts.

Advantageously, the bore in each housing together with the dcts interconnecting the housings form a closed systom whereby the free spaces in that system may substantially be filled with oil or other lubricating fluid, to assist the smooth transfer of the balls from one unit to the other, and also to assist the transfer of power from the driven column of balls to the driven rotor.

The housing of the driven unit may be configured to accommodate two or more coaxial rotors which may be selectively coupled to the output shaft of the driven unit, the housing having a like number of channels as separate rotors, and the channels for the various respective rotors being connected in series whereby the column of balls is circulated round all of the rotors in succession. Since only one of the rotors may be connected to the output shaft at any one time, the number of rotor/ball contacts for each rotor is preferably equal to the number of such contacts associated with the drive unit rotor, in order to optimise power transfer from the drive unit to the driven rotor for the time being connected to the output shaft. By arranging to have two rotors with different diameters, a two-speed transmission unit may be provided.Conversely, by arranging the channels associated with the two rotors of the driven unit so as to have helical forms but handed in the opposite sense, a reversing driven unit may be provided. Of course, when the channels are oppositely handed in this way, the rotors may also have different diameters so providing a reversing unit which operates at different speeds, depending upon the sense of output rotation.

As an alternative to handing the helical form of the channels in the opposite sense, the channels may have similar helices but the direction of circulation of the balls along those channels may be in opposite senses, so as still to permit the furnishing of a reversing unit.

According to a further aspect of the present invention there is provided a drive or driven unit for use in power transmission apparatus which unit comprises a housing defining a bore and rotatably supporting shaft, a rotor mounted on the shaft for rotation within the bore, the rotor having a plurality of grooves each extending parallel to the rotor axis, a channel formed in the bore of the housing and h-ving an inlet port and an outlet port at the two ends respectively of the channel, the respective crosssect ions of the channel and each groove being such that a ball may lie partially within the channel and partially withi.n a groove, whereby a plurality of rigid balls may be fed into the inlet port, pass along the channel and leae out of the outlet port, the rotor being turned as the transfer of balls from the inlet port to the outlet port takes place.

By way of example only, certain specific embodiments cf apparatus of this invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is a vertical sectional view through a drive unit constructed and arranged in accordance with the invention; Figure 2 is a partial transverse sectional view through the drive unit of Figure 1; Figure 3 is a vertical sectional view through a twospeed reversing driven unit constructed and arranged in accordance with the invention; Figure 4 is a sectional view taken on line A-A marked on Figure 3; Figure 5 is a sectional view taken on line B-B marked on Figure 3; and Figures 6A to 6D show diagrammatically four of the many possible power transmission configurations for apparatus of this invention.

Referring initially to Figures 1 and 2, there is shown a drive unit of a power transmission apparatus of this invention. The drive unit comprises a housing 10 having a closed end plate 11 and a further end plate 12 through which an input shaft 13 extends, the shaft being carried by a roller bearing 14 provided in end plate 12 and a ball bearing (not shown) mounted in end plate 11. The end plates 11 and 12 are heid in pace by means of bolts 15, threaded into the housing, 0-ring seals 16 (only one of which is shown) being provided between the end plates and the housing to form a fluidtight seals. A further oil seal 17 is provided around the shaft 13, within the housing 12.

The housing 10 defines a cylindrical bore, and a rotor 18 keyed to the input shaft 13 fits closely within that bore, for rotation with respect to the housing 10 on rotation of the shaft 13. Provided around the periphery of the rotor 18 is a plurality of part-circular grooves 19, each extending parallel to the rotor axis and each of slightly less than 180 arcuate extent. Within the bore in the housing 10, there is formed a helical channel 20 also of partcircular form, of substantially the same radius as the grooves 19 in the rotor 18. Each groove 19 and channel 20 are arranged so that a substantially spherical shape is defined therebetween, whereby balls 21 may be disposed end-to-end in the channel 20, with each ball engaged in a respective groove 19 in the rotor.

The two ends of the helical groove 20 communicate with ports 22 formed through the housing 10, tubes 23 boing connected to those ports 22 by means of respective gland seal assembiies 24, each tube 23 having an internal diameter very slightly greater than the diameter of each ball 21, whereby the balls may run freely along that tube. At least one of the seal assemblies 24 is adjustable through one ball diameter, to permit an adjustment of the overall length of the path followed by balls in the system. This allows the accommodation of an exact multiple of ball diameters, whereby clearance between the balls may be maintained to a minimum.

Two drive units as have been described above may be connected together by means of the tubes 23 with a continuous, endless column of balls extending around the two rotors of the two drive units respectively and along the two tubes 23. Rotation of the input shaft 13 of one drive unit will thus drive the column of balls through the tubes 23 and around the rotor of the other unit whereby the rotor of the other unit will be driven so turning its output shaft; in this way power will be transferred frozen the input shaft of one drive unit to the output shaft of the other drive unit. To assist the free running of the column of balls, the closed system may be at least partially be filled with oil or other lubricating fluid.

Turning now to Figures 3 to 5, there is shown a driven unit which may be used in place of a second drive unit corresponding to that of Figures 1 and 2.

This driven unit comprises a housing 30 having a first section 31 defining a first bore and having an associated end plate 32, and a second section 33 defining a bore of a larger diameter than that of the first section 31, the second section 33 having an associated end plate 34. The two sections 31 and 33 are linked together co-axially by means of an adapter plate 35 with oil seals 36 being provided as appropriate. O-ring seals are disposed between the end plates 32 and 34 and the associated sections 31 and 33.

A clutch shaft 60 is carried in ball bearings 36 and 37, provided respectively in end plates 32 and 34, with oil seals 38 and 39 being arranged to prevent oil leakage from the bearings. Rotatably mounted on plain bearings 40 and 41 are two rotors 42 and 43, rotor 42 fitting closely within the bore defined by first section 31, and rotor 43 within the bore defined by the second section 33. Each rotor has a plurality of grooves 44 formed therein, in the same manner as has been described above in connection with the drive unit of Figures 1 and 2; similarly, each housing section surrounding the respective rotor has a helical channel 45 or 46 formed therein. These grooves, channels and the associated ports 47 and 48 will not be described again here.

The helical forms of the channels in the first and second sections 31 and 33 are both right-handed, but the outlet port 47 from the first section 31 is coupled by a transfer tube 49 to the further port 48 of section 33, the outlet port from that second section being nearer the outlet port from the first section. In this way, a continuous column of balls extends around the two rotors 42 and 43, but the directions of movement of the balls are in the opposite senses with respect to the associated rotors.

Two ball clutches 51 and 52 are provided selectively to allow either rotor 42 or rotor 43 to be coupled to the clutch shaft 60. Each ball clutch comprises three balls 53 mounted in equi-spaced radial openings 54 in the clutch shaft 60, the hub 55 of the associated rotor having three recesses 56 in which the balls 53 may be accommodated, each recess having a ramp surface 57 to allow a ball in the recess to be driven back into its opening 54 in the clutch shaft 60.

A clutch operating rod 58 is slidably mounted coaxially within the hollow clutch shaft .50, the operating rod 58 having a central portion 59 of a reduced diameter, and two enlarged sections 61 and 61A, connected to the central portion 59 by conical surfaces 62. The length of the central section 59 is such that the balls 53 of both clutches 51 and 52 may lie thereon simultaneously, immediately adjacent the conical surfaces 62. When the clutch operating rod 58 is in this position, neutral is selected and no drive will be transmitted to the clutch shaft 60, upon rogation of the rotors.Movement of the clutch operating rod in either direction from this central position will engage the balls 53 of one of the two clutches 51 and 52 with the respective rotor 42 or 43, whereby drive is thereafter imparted from that rotor (in Figure 3, rotor 42) to the clutch shaft 60.

An output shaft 63 is connected to the clutch shaft 60 by means of spring pin 64 whereby driving of the column of balls through the driven unit (for example by means of a drive unit as illustrated in Figures 1 and 2) will cause the output shaft 63 to rotate, in a sense and at a speed dictated by the engagement of either clutch 51 or clutch 52.

Figures 6A to 6D show four possible configurations for power transfer apparatus of this invention, using drive units as illustrated in Figures 1 and 2, or optionally as shown in Figures 3 to 5. Figure 6A shows a simple direct-drive arrangement with a non-unity velocity ratio as between the input shaft of drive unit 70 and the output shaft of driven unit 71. Figure 6B shows an off set reverse drive., with a unity velocity ratio, whereas Figure 6C shows a direct drive between drive unit 73 and driven unit 74 and a less than unity velocity ratio therebetween, as well as a reverse drive unit 75 with a greater than unity velocity ratio.

Figure 6D shows a direct drive but with the input and output shafts at 900 to each other.

Claims

1. Power transmission apparatus comprising a drive unit having an input shaft and a driven unit having an output shaft, each of which units comprises a housing defining a bore in which is rotatably mounted a rotor carried on the shaft of the unit and which rotor has a plurality of grooves each extending parallel to the rotor axis, a channel formed in the bore of the housing and hiving an inlet port and an outlet port at the two ends respectively of the channel, the respective crosssect ions of the channel and each groove being such that a ball may lie partially within the channel and partially within a groove, the apparatus further comprising ducts interconnecting the respective inlet and outlet ports of one unit with the outlet and inlet ports of the either unit, and a plurality of rigid balls extending in an endless column around the chaniiels in the two units and along the ducts. whereby rotation of the shaft of the drive unit causes the transfer of Dower to the output shaft of the driven unit.

2. Power transmission apparatus according to Claim 1, wherein each channel is helically formed, each groove in the rotcr having an axial extent at least as great as the axial spacing between the inlet and outlet ports.

3. Power transmission apparatus according to Claim 2, wherein each channel extends around the associated rotor for at least 360 of arc.

4. Power transmission apparatus according to any of the preceding Claims, wherein the total number of balls in contact with the rotor in the drive unit is substantially equal to the total number of balls in contact with the rotor in the driven unit.

5. Power transmission apparatus according to any of Claims 1 to 3, wherein there is more than one driven unit, the balls being circulated sequentially through each driven unit, in turn.

6. Power transmission apparatus according to Claim 5, wherein the total number of balls in contact with the rotor of the drive unit is substantially equal to the total number of balls in contact with the rotors of all of the drive units.

7. Power transmission apparatus according to any of the preceding Claims, wherein the rotors of the drive and drive units have different diameters.

8. Power transmission apparatus according to any of the preceding Claims, wherein each rotor groove has part-circular cross-sectional shape of slightly less than 180 of arc.

9. Power transmission apparatus according to any of the preceding Claims, wherein each channel has a partcircular cross-sectional shape less than 180 of arc.

10. Power transmission apparatus according to any of the preceding Claims, wherein the bore in each housing closely fits against its respective rotor.

11. Power transmission apparatus according to any of the preceding Claims, wherein the bore in each housing together with the ducts interconnecting the housings form a closed system, whereby the free spaces in that system may substantially be filled with oil or other lubricating fluid.

12. Power transmission apparatus according to any o the preceding Claims, wherein the housing of the driven unit is configured to accommodate two or more coaxial rotors which may selectively be coupled to the output shaft of the driven unit, the housing having a like number of channels as separate rotors, and the channels for the various respective rotors being connected in series whereby the column of balls is circulated round all of the rotors in succession.

13. Power transmission apparatus according to any of th preceding Claims, wherein the rotors of the driven unit have different diameters.

14. Power transmission apparatus according to Claim 12 or Claim 13, wherein the channels associated with two rotors of the driven unit have helical forms handed in the opposite sense.

15. Power transmission apparatus according to Claim 12 or Claim 13, wherein the channels associated with two rotors of the driven unit hive helical forms handed in the same sense and the balls are circulated through those channels in the opposite directions.

16. Power transmission apparatus as claimed in Claim 1 and substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.

17. A drive or driven unit for use in power transmission apparatus, which unit comprises a housing defining a bore and rotatably supporting shaft, a rotor mounted on the shaft for rotation within the bore, the rotor having a plurality of grooves each extending parallel to the rotor axis, a channel formed in the bore of the housing and having an inlet port and an outlet port at the two ends respectively of the channel, the respective cross-sections of the channel and each groove being such that a ball may lie partially within the channel and partially within a groove, whereby a plurality of rigid balls may be fed into the inlet port, pass along the channel and leave out of the outlet port, the rotor being turned as the transfer of balls from the inlet port to the outlet port takes place.

18. A drive or driven unit according to Claim 17 and substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, or in Figures 3, 4, and 5 of the accompanying drawings.