US1977553A

US1977553A - Mechanism for driving the impeller of a supercharger for an internal combustion engine

Info

Publication number: US1977553A
Application number: US660424A
Authority: US
Inventors: Halford Frank Bernard
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-03-12
Filing date: 1933-03-11
Publication date: 1934-10-16
Anticipated expiration: 1951-10-16

Description

Oct. 16, 1934.

B. HALFORD MECHANISM FOR DRIVING THE IMPELLER OF A SUPERGHARGER FOR AN INTERNAL COMBUSTION ENGINE Filed March 11, 1933 2 SheetsrShee't 1 F F D F D I v A E 2, 1 V A F 3 V A L V A B B NIH W m V I E a l/VVf/VTOR f. B 044E040.

Oct. 16, 1934. F. B. HALFORD 1,977,553

MECHANISM FOR DRIVING THE IMPELLER OF A SUPERCHARGER FOR AN INTERNAL COMBUSTION ENGINE Filed March 11, 1935 2 SheetsShee"c 2 @l/w W HTTORNE') Patented Oct. 16, 1934 MECHANISM FOR DRIVING THE IMPELLER OF A SUPERCHARGER FOR AN INTERNAL COMBUSTION ENGINE Frank Bernard Halford, London, England Application March 11, 1933, Serial No. 660,424

In Great Britain March 12, 1932 20 Claims.

This invention relates to mechanism for driving the impeller of a supercharger for an internal combustion engine and has for its object to effect modifications in transmission mechanism of the type commonly employed for this purpose in order to obviate certain disadvantages present in this known mechanism.

A construction of this transmission mechanism as commonly employed comprises a driving shaft and a driven shaft mounted coaxially, the latter carrying the impeller. On the driving shaft is mounted a gear wheel and a pinion is similarly mounted on the driven shaft. These wheels mesh respectively with pinions and gear wheels carried on two or more lay shafts. A slipping clutch is disposed on each lay shaft, parts of the clutch being respectively connected to thev toothed wheels on that shaft. In this construction equalization of the torque through the lay- 0 shafts is effected by slip in the clutches but it is difficult to construct clutches with such similar limiting torque capacities under all conditions as will ensure the desired equalization of the torque through the lay shafts.

The improved construction comprises as in the known arrangement a driving shaft, a driven shaft which carries or is coupled to the impeller and may be coaxial with the driving shaft, and one or more pairs of lay shafts with gearing through which the drive is transmitted from the driving shaft through the lay shafts to the driven impeller device, and according to thisinvention there is included in this-gearing balancing or differential mechanism, one element of which is connected directly or through transmission gearing to the driving or driven shaft, while the other elements are connected directly or through transmission mechanism respectively to the two lay shafts so as. to ensure equalization of torque transmitted through such lay shafts.

In one arrangement according to the invention the transmission mechanism between the driving or the driven shaft and the lay shafts comprises at least one pair of twin coaxial gear wheels mounted coaxially with respect to either the driv'ng or the driven shaft, these wheels meshing respectively with toothed wheels on corresponding lay shafts, and balancing or differential mechanism through which the drive is transmitted between the twin coaxial gear wheels and the driving or driven shaft, this balancing or differential mechanism constituting such a connection between the gear wheels that its reaction on one gear wheel is dependent upon there being equal reaction on the other gear wheel so that at least some degree of relative rotationbetween the pair of gear wheels can take place and equalization -of the torque through the lay shafts is ensured.

' For example, a pair ofv twin gear wheels may be freely mounted coaxially with the, driving shaft, each of these gear wheels meshing with a pinion ;on aseparate lay shaft and also constituting one member of a differential gear; for,- example of conventional type, whose planet wheels are disposed on a carrier member constituting a driving member mounted on and driven by the. driving shaft. The drive is thus transmitted from the driving shaft to both twin wheels through the planet pinions of the differential gear while this gear permits relative rotation of the twin wheels and ensures equalization of torque in the two lay shafts.

In an alternative arrangement the main driving shaft may transmit power through gearing to a subsidiary'or intermediate driving shaft on which is mounted the driving element of diiferential or balancing gearing, the two driven elements of which are mounted to rotate freely coaxially with the subsidiary driving shaft. One of these driven elements constitutes a lay shaft and is connected by gearing to the driven shaft which is preferably coaxial with the main driving shaft, while theother element is connected by gearing, including for-example a gear wheel 35 coaxial with the main driving shaft, to a second lay shaft also connected by gearing to the driven shaft. V

In a still further arrangement similar in other respects to the above, the two driven elements of the differential mechanism may respectively be connected through gearing to two separate lay shafts through which power is transmitted to the driven shaft.

In either of the above arrangements, in place of a differential gear of conventional type the balancing mechanism may comprise a rotatable member, hereinafter referred to as a driving member, carrying radial bearing members on each of which is freely mounted a two-armed 10- ver one arm of which is connected to one driven element arranged to rotate coaxiallywith the driving member, while the other arm engages the other .driven element also arranged coaxially with the driving member, stituting in effect differential mechanism butv being such, by reason of the connection of the twoarmed levers respectively to the two driven elements, that only limited relative rotation between the two driven members can take place. no

the arrangement conshafts.

mitting power to the differential or balancing mechanism or between the driven shaft and the impeller for the purpose of limiting the torque which can be transmitted through the mechanism and preventing excessive stresses, for example when the driving shaft accelerates or decelerates rapidly. Again, where differential mechanism of conventional type is employed permitting free relative rotation to any required extent between the three elements of the differential mechanism, one or more slipping clutch devices, for example of the friction or hydraulic type, may be arranged so that the slip therein results in relative rotation between the parts of the differential mechanism.

The invention may be carried into practice in various ways but a number of constructions according to the present invention are illustrated somewhat diagrammatically by way of example in the accompanying drawings, in which Figure 1 is a side elevation partly in section of one construction employing a direct drive without the interposition of friction or other slipping clutches between the driving and driven Figure 2 is a similar view to Figure 1 of an alternative construction incorporating clutches of the slipping friction type.

Figure 3 is a similar view to Figure 1 showing an alternative construction employing a "hydraulic transmission device of the reaction type through which the drive is transmitted from one of the lay shafts to-the driven shaft.

Figure 4 is a similar view to Figure '1 of a still further arrangement employing a slipping clutch between the driving shaft and a driving member.

Figure 5 is a similar view to Figure 1 of a still further arrangement employing a hydraulic transmission device of the reaction type between the driven shaft and the impeller of the supercharger, and

Figure 6 shows a still further arrangement employing a friction clutch in the transmissionfl mechanism.

In the construction shown in Figure ,1 the apparatuscomprises adriving shaft A mounted in fixed-bearings A and arranged coaxially. with a driven shaft B mounted in fixed bearings B and carrying an impeller B. Mounted to rotate freely coaxially with the driving shaft are twin gear wheels C, C The gear wheel C meshes with agear wheel D on a lay shaft D mounted in fixed bearings D and carrying a gear wheel. D which V meshes with a gear wheel B on the driven shaft B while the gear wheel C meshes with a gear wheel E on a lay shaft E mounted in fixed bearings E and carrying a gear wheel E meshing with the gear wheel B on the driven shaft B, the axes of the two lay shafts D and E lying on diametrically opposite sides of the com-- mon axis of the driving and driven shafts A and B and thegear wheels D and E being of the same diameter as are also the gear wheels D 'G It, will beseen that; with this arrangement 'tially-the: same as that shown in Figure-2..-

and E Mounted on the driving shaft A is a driving member F in the form of a carrier having supported therein two radial shafts F on each of which is rotatably mounted a coupling member F having two arms the ends of which are provided with spherical or like bearing members F engaging corresponding sockets in the two gear wheels C and C "It will thus be seen that power is transmitted from the driving shaft A through the carrier F and themembers F to the two gear wheels 1' C and (.7 so as to cause these to rotate substantially in unison whereby power is transmitted through the two lay shafts D and E to the driven shaft B. At the same time by reason of the ability of the members F to rock about their pivot pins F? slight relative rotational movement. can take place between the two gear wheels C and C so that the two gear wheels C and C and the members F, F F maybe re-. garded as constituting differential mechanism permitting only. limitedrelative movement between the partsthereof which, however, is suflicient to ensure that substantially the same torque shallbe transmitted respectively through the two lay shafts D and E so that this torque and the forces applied to the driven shaft by the gearwheels D andli; aresubstantially balanced.

In the, alternative construetion illustrated in v Figure .2 the generalarrangement; issimilar to that shown in Figure l and comprises a driying shaft A mounted; infixed bearings-A and arranged coaxially with a driven shaft l3 mounted in fixed bearings. B and carrying animpeller B. The driving shaft A has mounted to rotate freely coaxiallytherewith-two gear wheels G, G The ,gear wheel G meshes with a gear wheel H on a lay shaft H while. the gear wheel G meshes with a gearwheel J on a lay shaft J The lay shaft H..-has freely mounted thereon a gear wheel H which is connected to: the lay shaft through a friction clutchnevice Hit the driving member-H ,-of which is secured tothe lay shaft while the driven member is constituted by a sleeve H rigidly connected to thegear wheel. Similarlythe lay shaft J has freely mounted thereon a gear wheel Ji-whichis ,con-

nected to. the lay shaft by a-- friction clutch device J The gear wheelsf l and-Ji-both mesh with a gear wheel=B -.on the driven, shaft-1B Formed on the adjacent inner faces of-the; two gear wheels G and G are teeth constitutin bevel wheelswhich mesh-with bevel; wheels K 1 freely mountedbnradial shafts K supported by a carrierK? rigidly connected to. the driving shaft A, this mechanism constituting, a difleren:

tial gear whereby power can be transmitted from the driving-shaft A;to the two,- gear wheels G,

torqu'eis transmittedfrom the driving shaft A equally to the twolay shafts H Jl through the difierential gear irrespective of differences in slip which may take place in'the two clutches 'J- and H Moreover these clutches act to prevent exce'ssivetorque being transmitted through the mechanism as-awhol'e'. i

In the arrangement shown-'in-"Figure '3' the construction and "arrangement of the driving shaft A and driven shaft B, thetwm gear wheels G, G andthe diiferential mechanism-is substanthis construction, however, the lay shaft J has a; gear wheel 11* rigidly mounted thereon and meshingwith thegear wheel IB=,."wher,eas the? lay shaft H haslmountedthereon one part H of a hydraulic transmission device of the reaction typ the other part H" of which is rigidly connected to a gear wheel H meshing with the gear wheel B In this construction it will be seen that power is transmitted from the driving shaft A through the differential mechanism K, K K to the two gear wheels G, G and thence to the two lay shafts H J so that substantially the same torque is transmitted to each lay shaft. Relative rotation between the two parts of the hydraulic transmission device H", H can, however, take place by reason of relative rotation which can take place between the two gear wheels G, G Thus during acceleration of the driving shaft the rotational speed of the shaft H1 may exceed considerably that of the shaft J Moreover when the driving shaft is accelerated rapidly so that slip tends to take place in the hydraulic clutch device the, differential mechanism acts as multiplying gearing to increase the speed of the member H and due to this effect the hydraulic clutch can be of smaller size than would'be the case if the speed of its driving member was always proportional to the speed of the driving shaftj In the arrangement shown in Figure 4 the apparatus comprises a driving shaft A mounted in bearings A and a coaxial driven shaft B mounted in fixed bearings B and carrying an impeller 3*, the shaft B carrying a gear wheel B which meshes with gear wheels L and M respectively on lay shafts L and M mounted in fixed bearings L and M and carrying also gear wheels L and M Power is transmitted to the gear wheels L and M by twin gear wheels N, N mounted to rotate freely coaxially with the driving shaft A and having bevel wheels formed on their adjacent faces and meshing with cooperating bevel wheels N rotatably mounted on radial pivot pins N supported by a carrier N which is rigidly connected to a sleeve 0. It will thus be seen that power can 'be transmitted from the sleeve 0 through the differential mechanism N N N equally to the twin gear wheels N, N and thence through the two lay shafts U, M to the driven shaft B. Power is transmitted from the driving shaft A to the sleeve 0 through a slipping clutch device P of the friction type, the driving member P of which is rigidly connected to the driving shaft while the sleeve 0 constitutes the drivenv member. With this arrangement it will be seen that the friction clutch device P limits the torque which can be transmitted through the mechanism as a whole.

In the construction shown in Figure 5 the arrangement is generally similar to that shown in Figure 4 except that instead of the member N being mounted on a sleeve Oand connected to the driving shaft by a friction clutch device, the carrier N is directly mounted on the driving shaft A while, instead of the driven shaft B being directly connected to the impeller, the gear wheel 13 which meshes with the two gear wheels L and M is rigidly connected to one part Q of v a hydraulic transmission device of the reaction type, the other part Q of which' is rigidly con-' differential mechanism ensures equalization of torque in the two lay shafts.

In the construction shown in Figure 6 the apparatus comprises a main driving shaft R having rigidly mounted thereon a gear wheel R which meshes with a gear wheel S on a subsidiary driving shaft S mounted in fixed bearings S. Mounted on the subsidiary driving shaft S is differential mechanism comprising a driving element formed integral with or rigidly connected to the shaft S and having radial bearing members S carrying bevel wheels 3*, and two driven elements in the form of bevel wheels T and U meshing with the bevel wheels 8*. The gear wheel T is rigidly connected to a gear wheel T! which meshes with a gear wheel V on the driven shaft V carrying the impeller V of a supercharger. The gear wheel' U is rigidly connected to a gear wheel U which meshes with a gear wheel W freely mounted coaxiallywith the maindriving shaft R and in turn meshing with a gear wheel X on a lay shaft X --The lay shaft X is connected through a friction clutch device X to a gear wheel X also meshing with the gear wheel V on the driven shaft V The arrangement is such that the transmission ratio as between the gear wheel U and the gear wheel X is a 1:1 ratio, the two gear wheels '2? and T being of the same diameter.

In thisconstruction it will be seen that the drive is transmitted from the main driving shaft R to the subsidiary driving shaft S 'and thence a balanced driveis transmitted through the differential mechanism respectively on the one hand direct to the gear wheel T and on the constituted by the gear'wheels T and T and their connecting sleeve and the lay shaft X to the driven shaft B.

In an alternative construction otherwise generally similar to that shown in Figure 6, the gear wheel T instead of meshing directly with the gear wheel on the driven shaft, may be of the same diameter as the gear wheel U and may mesh with a gear wheel on a second lay shaft which in turn carries a gear wheel meshing with the gear wheel on the driven shaft at a point diametrically opposite to the gear wheel X What I claim as my invention and desire to secure by Letters Patent is:-

1. Mechanism for driving the impeller of a. supercharger for an internal combustion engine, including in combination a main driving shaft, a driven shaft, an impeller coupled to the driven shaft, an intermediate driving shaft arranged with its axis parallel to that of the mainldriving shaft, gearing connecting the intermediate driving shaft to the main driving shaft, differential balancing mechanism arranged coaxially with the intermediate driving shaft and comprising a driving member connected to the intermediate driving shaft and two driven members freely rotatable about the axis of the in--' termediate driving shaft, a gear wheel rigidly connected to one of such driven elements, a gear wheel on the driven shaft with which such driven element gear wheel meshes, a lay shaft, a gear wheel on said lay shaft meshing with the gear wheel on the driven shaft, and gearing connecting the other driven element of the differential mechanism to the lay shaft, the arrangement being such that transmission ratio of 1:1 exists as between the lay shaft and its associateddriven element. I

2. Mechanism for driving/the impeller of asupercharger for an internal combustion engine including in combination a driving shaft, a driven shaft, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and to the driven shaft, the gearing between the lay shafts and one of such driving and driven shafts including mechanical differential mechanism ensuring equalization of torque through the lay shafts, and a slipping clutch device included in the mechanism to prevent transmission of excessive torque therethrough.

3. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination a driving shaft, a driven shaft, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and to the driven shaft, the gearing between the lay shaft and one of such driving and driven shafts including mechanical differential mechanism one element of which is connected to said one of such driving and driven shafts while the other two elements act respectively on the two lay shafts, and a slipping clutch device between the driven shaft and the impeller to prevent excessive torque transmission therethrough. I

4. Mechanismfor driving the impeller of a supercharger for an internal combustion engine including in combination a driving shaft, a driven shaft, an impeller connected to the driven shaft, at least two lay shafts, gearing, connecting each lay shaft to the driving and to the driven shaft, the gearing between the lay shaft and one of such driving and driven shafts including mechanical differential mechanism, of

. a type in which the extent of relative rotation necting each lay shaft to the driving and to the driven shaft; the gearing between the lay shafts and one of such driving and drivenshafts including mechanical differential mechanism one element of which is connected to said one of such driving and driven shafts while the other two elements act respectively on the two lay shafts, and a slipping clutch of the hydraulic reaction type between the driven shaft and the impeller to prevent excessive torque transmission therethrough.

6. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with a gear wheel on one of such coaxial shafts, gearing between the second coaxial shaft and the 'lay shafts comprising mechanical differential mechanism one element of which is rigidly connected to the said,

second coaxial shaft while the other two elements are each freely mounted coaxially with the said second coaxial shaft and are connected by gearing respectively to the two lay shafts,

and a slipping clutch device incorporated in the transmission mechanism 'to limit the torque which can be transmitted therethrough.

'l. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with a gear wheel on one of such coaxial shafts, gearing between the second coaxial shaft and the lay shafts comprising mechanical diiferential mechanism one element of which is rigidly connected to the said second coaxial' shaft while the other two elements are each freely mounted coaxially with the said second coaxial shaft and are'connected by gearing respectively to the two lay shafts, and a-slipping clutch device of the hydraulic reaction type for transmitting power between driving and driven parts of one of the lay shafts.

8. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination a main driving shaft, a driven shaft coaxial therewith, an impeller carried by the driven shaft, an intermediate driving shaft arranged parallel to the main driving shaft, gearing connecting the main driving shaft to the intermediate driving shaft, mechanical differential transmission mechanism arranged coaxially with the intermediate driving-shaft and comprising a driving element connected to the intermediate driving shaft, and two driven elements arranged coaxially with this intermediate driving shaft, a gear wheel on the driven shaft, driving gear wheels meshing with. diametrically opposite parts of the gear wheel on the driven shaft, means for transmitting -power from one driven element of the differential mechanism to one of such driving gear wheels and from the other driven element of the differential mechanism to the other driving gear wheel, the arrangement being such that the transmission ratio as between each of the driven elements of the differential mechanism and its associated driving gearwheel is the same, and a slipping clutch device for transmitting power between one driven element of the differential mechanism to its associated driving gear wheel.

9. Mechanism for driving the impeller of a supercharger for an internal combustion engine, including in combination a main driving shaft, a driven shaft coaxial therewith, an impeller coupled to the driven shaft, an intermediate driving shaft arranged with its axis parallel to that of the main driving shaft, gearing connecting theintermediate driving shaft to the main driving shaft, mechanical differential mechanism arranged coaxially with the intermediate driving shaft and comprisingadriving member connected to the intermediate driving shaft and two driven elements freely rotatable about the axis of the intermediate driving shaft, a gear wheel rigidly connected to one of such driven elements, a gear wheel on the driven shaft with which suchvdriven element j gear wheel meshes, a lay shaft, a gear wheel on said lay shaft meshing with the gear wheel on the driven shaft, gearing connecting the other driven element of the differential mechanism to the lay shaft, and a slipping clutch device for transmitting power between the lay shaft and the gear wheel which to the gear wheel through which gine including in combination a main driving shaft, a driven shaft coaxial therewith, an impeller carried by the driven shaft, an intermediate driving shaft arranged parallel to the main driving shaft, gearing connecting the main driving shaft to the intermediate driving shaft, mechanical differential mechanism arranged coaxially with the intermediate driving shaft and comprising a driving element connected to the intermediate driving shaft and two driven elements arranged coaxially with this intermediate driving shaft, a gear wheel on the driven shaft, gear wheels meshing with diametrically opposite parts of the gear wheel on the driven shaft, means for transmitting power from onedriven element of the differential mechanism to one of such gear wheels and from the other drivenelement of the differential mechanism to the other gear wheel, and a slipping clutch device coupling the lay shaft to the gear wheel through which power is transmitted to the driven shaft.

11. Mechanism for driving the impeller of a supercharger for an internal combustion engine, including in combination a main driving shaft, a driven shaft coaxial therewith, an impeller coupled to the driven shaft, an intermediate driving shaft arranged with its axis parallel to that of the main driving shaftjgearing connecting the intermediate driving shaft to the main driving shaft, mechanical differential mechanism arranged coaxially with the intermediate driving shaft and comprising a driving member connected to the intermediate driving shaft and two driven elements freely rotatable about the axis of .the intermediate driving shaft, a. gear wheel rigidly connected to one of such driven elements, a gear wheel on the driven shaft with which such driven element gear wheel meshes, a lay shaft, a gear wheel on said lay shaft meshing with the gear wheel on the driven shaft, gearing connecting the other driven element of the differential mechanism to vthe lay shaft, and a slipping clutch device coupling the lay shaft power is transmitted to the driven shaft.

12. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination a driving shaft, 2. driven shaft, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and driven shafts and comprising mechanical differentialmechanism having three elements two of which are operatively connected respectively to the two lay shafts while the third element is operatively connected to one of the other shafts, and a slipping clutch device included in the mechanism to prevent the transmission of excessive torque therethrough.

13. Mechanism for driving the impeller of a supercharger for an internal combustion engine, including in combination a driving shaft, 8. driven shaft, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and driven shafts, mechanical differential mechanism comprising three elements two of which are operatively connected respectively to the .two lay shafts while the third element is operatively connected tothe driving shaft, and a-slipping clutch device ine eluded-in the mechanism to prevent the transmission of excessive torque therethrough.

, '14. Mechanism-for driving the impeller of a supercharger for an internal combustion engine including in combination a driving shaft, a driven shaft coaxial therewith, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and driven shafts, the gearing between the lay shafts and one of such driving and driven shafts including mechanical, differential mechanism ensuring equalization of torque through the lay shafts, and a'slipping clutch device included in one of said lay shafts to prevent the transmission of excessive torque therethrough.

15. Mechanism for driving the impeller of a supercharger for an internal combustion engine including in combination a driving shaft, a driven shaft coaxial therewith, an impeller connected to the driven shaft, at least two lay shafts, gearing connecting each lay shaft to the driving and driven shafts, the gearing between the lay shafts and one of such driving and driven shafts including mechanical differential mechanism ensuring equalization of torque through the lay shafts, and a slipping clutch device of the hydraulic reaction type included in the mechanism to prevent the transmission of excessive torque therethrough.

16. Mechanism for driving the impeller of a supercharger for an internal combustion engine from and at a higher speed than a driving shaft, including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with diametrically opposite points of a gear wheel on the driven shaft, gearing between the driving shaft and the lay shafts comprising mechanical differential mechanism ensuring equalization of torque through the lay shafts, and a slipping clutch device included in the mechanism to prevent the transmission of excessive torque therethrough.

17. Mechanism for driving the impeller of a supercharger for an internal combustion engine from and at a higher speed than a driving shaft, including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with diametrically opposite points of a gear wheel on the driven shaft, gearing between the driving shaft and the lay shafts comprising mechanical differential nected to the said driving shaft while the other two elements are each freely mounted coaxially with the said driving shaft and are connected by gearing respectively to the two lay shafts, and a slipping clutch device incorporated in the mechanism to prevent the transmission of excessive torque therethrough.

18. Mechanism for driving the impeller of a supercharger for an internal combustion engine from and at a higher speed than a driving shaft, including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with diametrically opposite points of a gear wheel on the driven shaft, gearing between the driving shaft and the lay shafts comprising mechanical differential mechanism of a type in which the relative rotation between the element is not limited, one

driving shaft and are connected by gearing respectively to thetwc lay shafts, and a slipping clutch device included in at least one of the lay shafts to prevent the transmission of excessive torque therethrough.

19. Mechanism for driving the impeller of a supercharger for an internal combustion engine from and at a higher speed than a driving shaft, including in combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with diametrically opposite points of a gear wheel on the driven shaft, gearing between the driving shaft and the lay shafts comprising mechanical differential mechanism of a type in which the relative rotation between the elements is not limited, one element of which is rigidly connected to the said driving shaft while the other two elements are each freely mounted coaxially with the said driving shaft and are connected by gearing respectively to the two lay shafts, and a slipping clutch device of the hydraulic reaction type included in one of the lay shafts to prevent the transmission of excessive torque therethrough.

20. Mechanism for driving the impeller of a supercharger for an internal combustion engine from and at a higher speed than a driving shaft,

including in. combination coaxial driving and driven shafts, an impeller connected to the driven shaft, at least two lay shafts, gear wheels on the lay shafts meshing with diametrically opposite, points of a gear wheel on the driven shaft, gearing between the driving shaft and the lay shafts comprising mechanical differential mechanism of a type in which the relative rotation between the elements is not limited, one element of which is' rigidly connected to the said driving shaft while the other two elements are each freely mounted coaxially with the said driving shaft and are connected by gearing respectively to the two lay shafts, and a slipping clutchdevice between the impeller and the driven shaft to prevent the transmission of excessive torque therethrough.

, FRANK BERNARD HALFORD.