US2987155A - Centrifugal clutches - Google Patents

Description

June 6, 1961 Filed Feb. 5, 1958 J. MAURICE ET AL CENTRIFUGAL CLUTCHES 5 Sheets-Sheet 1 June 6, 1961 .1. MAURICE E AL CENTRIFUGAL CLUTCHEIS 5\Sheets-Sheet 2 Filed Feb. 3, 1958 June 6, 1961 Filed Feb. 3, 1958 J. MAURICE ETAL CENTRIFUGAL CLUTCHES 5 Sheets-Sheet 3 June 6, 1961 J. MAURICE ET AL CENTRIFUGAL CLUTCHES 5 Sheets-Sheet 4 Filed Feb. 5, 1958 J. MAURICE ET AL June 6, 1961 CENTRIFUGAL CLUTCHES 5 Sheets-Sheet 5 Filed Feb. 3, 1958 United States Patent 0.

' 2,987,155 QENTRIFUGAL CLUTCHES Jean Maurice and Michel Rist, Paris, France, assignors to Societe Anonyme Francaise du Ferodo, Paris, France, a corporation of France Filed Feb. 3, 1958, Ser. No. 712,810 Claims priority, application France Feb. 4, 1957 3 Claims. (Cl. 192-48) The present invention relates to centrifugal clutches of the type in which the weight-head carrier is either driven at will by the driving shaft or kept stationary or braked, especially by a fixed electro-magnet, the armature of which is fixed for rotation with the weight-head carrier and is intended to make contact through friction linings with a cover or casing fixed to the driving shaft. The invention relates more particularly to such clutches in which the weight-heads co-operate with a cam mounted so as to be fixed for lateral movement and free for rotation on a transfer plate which transfers its thrust to at least one pressure plate through clutch springs, whilst a stop limits the centrifugal travel of the weight-heads. A centrifugal clutch of this type is described and shown in our United States Patent No. 2,850,131.

In the known clutches of this type, this stop is generally formed by the weight-head carrier itself, and the latter is in moulded steel and is machined so as to resist the stresses applied at the point of the stop, whilst having the required durable precision. This results in a high cost of manufacture and a troublesome inertia of the weight-heads. In addition, difliculties are encountered in regulating the relative position of the electro-magnet and of its armature, whilst the centering of the armature with respect to the weight-heads and its return towards the casing are defective. Undesirable noise is observed when the armature is attracted to the electro-magnet and/or when it is returned towards the casing. In addition, the inertia of the friction assembly of the clutch is considerable and interferes with its satisfactory operation.

One object of the invention is to simplify the manufacture of the weight-heads and to enable them to be of light construction, a special feature being that the stop which limits the centrifugal travel of the weight-heads is formed by an edge of this cam. This edge is preferably covered with an anti-noise lining and has preferably a safety surface adjacent to this lining so as to replace it when it is no longer active and without causing jamming.

The objects, particular features and advantages of the invention will further be made clear from the description which follows below of forms of embodiment chosen by way of example, reference being made to the accompanying drawings, in which:

' FIG. 1 is a view in longitudinal cross-section of a centrifugal clutch in accordance with the invention.

' FIG. 2 is a view in elevation in the direction of the arrows 11-11 of FIG. 1, of a portion of the said clutch.

FIG. 3 is a view in elevation, in the direction of the arrows III-III of FIG. 1 of a further part of the clutch. FIG. 4 is a view similar to that of FIG. 1, but relates to an alternative form of centrifugal clutch in accordance with the invention.

FIG. 5 is a view of the de-clutching electro-magnet of FIG. 4 in elevation in the direction of the arrows V-V of FIG. 4, and comprises a diagram of the electric supply of this electro-magnet.

FIGS. 6 and 7 are detail views to a slightly enlarged scale, respectively in cross-section taken along the line VI-VI and the line VII-VII of FIG. 5.

FIG. 8 is a view of the device of FIG. 7 taken along the broken line VIII-VIII of FIG. 7.

2,9871% Patented June 6, 1961 ice FIG. 9 is a view of the friction disc following the broken line IX-IX of FIG. 4.

FIG. 10 is a view to a large scale of the weight-head of FIG. 4 in its position of abutment on the cam.

In the form of embodiment shown in FIGS. 1 to 3, which concerns an application (without any implied limitation) of the invention to automobile vehicles, there can be seen in FIG. 1 at 10 the driving shaft and at 11 the driven shaft of the centrifugal clutch in accordance with the invention. The gripping plates of the clutch are constituted, one by the fly-wheel 12 which is fixed to the shaft 10 and which carries the starter crown-wheel 14,. and the other 13, which is mounted fast for rotation but free for lateral movement with respect to the fly-wheel 12.

The plates 12 and 13 are intended to grip a frictiondisc 15 which is mounted fast for rotation and sliding on the driven shaft 11. The disc 15 carries a ratchet-wheel 16 (see FIGS. 1 and 3) the teeth 17 of which co-operate with pawls 18 carried by the fiy-wheel 12. Each pawl 18 is pivotally mounted on a shaft 19 so as to move away from the teeth 17 of the wheel 16 when it is subjected to the action of centrifugal force due to rotation of the driving shaft. A blade return-spring 20 is provided on each pawl 18 in order to engage it in the teeth 17 when the centrifugal force is insufficient to move it away, and especially when the driving shaft is stopped.

With each tooth 17 of the wheel 16 is associated a mask 21 of bent steel sheet, which has the shape of a saddle and which is pivotally mounted at 22 on the wheel 16 so as to be raised above the tooth and to prevent the engagement of the pawl with the tooth when this mask 21 is subjected to the action of centrifugal force due to the rotation of the driven shaft. A helicoidal return-spring 23 is provided on each mask 21 in order to withdraw it beneath the tooth 17 when the centrifugal force is insufiicient to lift it, that is to say when the driven shaft is stopped or rotates slowly, for example at a speed less than 180 rpm. The mask 21 is preferably provided with lateral extensions 24 beyond the summit 25 of the saddle so as to increase its sensitivity to the action of centrifugal force.

It will be noted that the device 21 is light and simple to mount, and that the helicoidal spring 23 ensures precise operation.

When the engine is running, the pawls 18 are freed from the teeth 17 and are inactive. When the engine is not running, the pawls 18 engage in the teeth 17, which enables the engine to be driven by the vehicle and also allows the vehicle to be locked in position during parking, by the effect of the engine compression. However, when the vehicle is running at an appreciable speed and a the engine stops unexpectedly, the masks 21 prevent the pawls from coming into engagement with the teeth 17.

' A torque-limiting device 26 may be interposed between the wheel 16 and the shaft 11. It is preferably arranged so as to limit the torque transmitted in reverse and thus to prevent skidding of the driving Wheels of the vehicle. The limiter device 26 is preferably of the type described later in detail in connection with FIG. 9.

The centrifugal mechanism of the clutch (see FIG. 1) is housed in a cover or casing 27 fixed to the fly-wheel 12. This fixation preferably consists of screws screwed into the fiy-wheel 12 and clamping the casing 27 against an elastic block 81 inset in the fiy-Wheel 12, which is provided with a safety shoulder 82. This arrangement enables noise to be eliminated or reduced at the moment when the electro-magnet 58 attracts or releases the armature 57, which will be described in detail later. The centrifugal mechanism of the clutch controls the clamping of the plate 13 against the friction-disc 15 which itself has just been gripped by forcing against the plate 12.

3 When the centrifugal mechanism does not act on the plate 13, the latter frees the disc 15 due to the action of release springs (not shown) which act between the plates 12 and 13. It has been found that when the .de-clutching play of the plate 13 is considerable, shocks and noise are produced when re-engaging the clutch. In order to remedy this defect, the return movement of the plate 13 is made controllable, in accordance with the invention, by means of stops 28 interposed between the plate 13 and a member fixed to the plate 12, such as the periphery of the casing 27. The stops 28 are uniformly distributed in circular symmetry and are for example three in number. Each stop 28 consists of a screw, the body of which is screwed into a threaded hole in the plate 13, and the head 29 of which extends between the plate 13 and the casing 27, whilst at the other extremity a lock-nut 30 is screwed oh the screw 28. The varying extent to which the screws 29 are screwed into the plate 13 enables the limit of the return travel of the plate 13 to be regulated at will. A regulation of this kind can be carried out once and for all at the time of assembly without there being any subsequent need to modify it in order to take account of wear in the linings of the disc 15, the limited travel of the plate 13 remaining usually always fairly small so as to ensure silent operation.

It should be noted that the return travel of the plate 13 can be stopped before the stops 28 come into efiective action, by the effect of an elimination of the successive plays between the parts which are located behind the plate 13. These parts comprise a transfer plate 31, a cam 32, weight-heads 33, a weight-head carrier 34, which are described in detail later, and finally the casing 27.

This will take place when the weight-heads come into contact with the cam, if the sum of these successive plays is small, but the stops 28 ensure in any case that the return travel of the plate 13 does not exceed the limit fixed by the setting of the said stops 28, and considered as preventing any undesirable shock or noise in the vicinity of the plate 13, even if the said sum of plays were greater than the limit.

Actually, when this sum of plays is large, which implies the active intervention of the steps 28, this intervention increases the approach travel of the weight-heads 33 towards the cam 32. Tests have shown that the contact of the weight-heads with the cam takes place without shock and can practically not be felt, doubtless because of the inclination of the surface of the cam at the point where the play between the cam and the weight-heads is eliminated. Y

The transfer-plate 31, which is located immediately behind the plate 13, is slidably mounted on this plate by tenons 35 and mortices 36. The distance between the plates 31 and 13 is limited by small plates 37 and screws 38. The clutch springs 39 are applied against the plate 13 through the intermediary of heat-insulating washers 40 intended, when the plate 13 becomes hot, to prevent the transmission of its heat to the springs 39 thus tending to alter their calculated properties. The springs 39 are housed in sockets 41 which are supported against the transfer-plate 31.

The cam 32 is mounted free for rotation on the transfer-plate 31 by means of a ball-bearing 42 and co-operates with rollers 43 of the weight-heads 33 which are pivotally mounted at 44 on the weight-head carrier 34. The rollers 43 are mounted on needle-bearings 45 on the weight-heads 33 and have a continuous rolling surface which is free from holes. The pivotal shafts 44 of the weight-heads on the weight-head carrier 34 are also provided with needle-bearings 46. The weight-head carrier 34 is itself mounted for free rotation on the casing 27 by means of a ball-bearing 51.

Means provided for protecting the bearings 42 and 51 and the needle-bearings 45 and 46 against dust consist of a ring 70 of felt or other suitable elastic material, and/or which is an absorbent for the lubricant, fixed to Mme r the casing 27 by a sheet steel ring 71 screwed on to this casing at 72. Against the ring 70 is applied a bell 73 which is fixed at 74 to the transfer-plate 31 and having flexibility so as to be able to slide on the ring 70 while retaining therewith a fluid-tight relation during the course of the axial movements of the plate 31.

In addition, in order to keep the bearings 42 and 51 well lubricated, lubricant casings 77 are provided and are made fluid-tight by joints of plastic material, at least at the time of assembly, having a base of rubber or of polymerisable glue or jointing paste. These joints are applied not only at the points at which the leakage of lubricant is liable to occur as a result of centrifugal force, such as 75, but also at points at which this leakage may take place due to a siphon elfect due to the indirect action of centrifugal force, such as 76.

The oscillation travel of the weight-heads 33 on the weight-head carrier 34 is limited towards the axis by an anti-noise washer 47 fixed to the weight-head carrier 34 and intended to receive the rollers 43 in abutment. This travel is limited towards the exterior by an edge 48 rigidly fixed to the cam, internally lined by an antinoise washer 49 and intended to receive in abutment the bearing surfaces 50 of the weight-heads.

The provision of a stop for the weight-heads towards the exterior on the cam at 48 and 49, rather than on the weight-head carrier 34, enables the latter to be freed from large stresses,'so that it no longer needs to be made of moulded steel but can be of light material or alloy. The inertia of the weight-head carrier is thus reduced with advantage, which ensures a more rapid response of the weight-head carrier when it is required either to be run-up to high speed or to be braked. In addition, the weight-head carrier 34 may then be made by casting in its semi-final form. It does not require to be subjected to costly milling operations, whilst the machining of the weight-heads 33 is itself simplified and is reduced only to the bearing surfaces 50 which are turned in the displaced position of the weight-heads.

The weight-head carrier 34 is provided with a hollow central boss 52 which extends towards the rear inside the bearing 51 and round the shaft 11. A flange 53 which extends behind the casing 27, is positively fixed by screws 54 to the extremity of the boss 52, whilst a number of flexible radial blades 55 (see FIGS. 1 and 2) extend between the flange 53 and the casing 27, and are gripped between the members 52 and 53 by the screws 54. At their outer extremities, the blades 55 are fixed by rivets 56 to a magnetic armature 57 which they thus maintain correctly centered and rigidly fixed for rotation, whilst by virtue of their flexibility they permit axial movements of the said armature.

The rear face of the armature 57 co-operates with a fixed immobilising electro-magnet 58, the circuit of which is closed during the operations of gear-changing and is open when these operations are not taking place. In more detail the circuit feeding the coil of the electromagnet 58 comprises the battery of the vehicle, the ignition contact 116 and a switch 117 which is incorporated in the gear-changing lever 118. The switch 117 is controlled by the lever 118 so as to be closed during the course of gear-changing operations to energize the electromagnet 58 and to be open except during these operations to deenergize the said electromagnet. A capacitor 119 and a resistor 120 having a very ;high resistance are provided in parallel with the switch 117 to protect the contacts without excessive consumption. As shown in FIG. 1 it is understood that the circuit is completed by grounding of one terminal of the battery 115 and of one terminal of the switch 117. The capacitor 119 and the resistor 120 are also grounded as shown. The front face of the armature 57 is lined with arcuate elements 59 of friction material which alternate with the blades 55. The elements 59 are intendedto be in frictional engagement with the casing 27 and have a section of stepped or tiered form (see FIGS. 1 and 2) so that only their portion 60 which is the closest to the axis and to the springs 62 is permitted to come into contact, whilst the other portion 61 is not in contact.

The supporting surfaces of the linings 59 on the armature 57 is large since, in addition to the active portion 60, it comprises the portion 61. This permits of a very strong adhesion of the linings 59 on the armature 57 and results in complete suppression of noise and vibration. In addition, the reduced radial width of the active portion 60 permits a satisfactory application against the casing 27, even if the armature or the casing are not strictly fiat or become deformed during the course of operation. The application pressure is increased, which on the one hand prevents any polishing action likely to reduce the coefiicient of friction of certain linings, and on the other hand, it accelerates running-in.

Helicoidal application springs 62 distributed in circular symmetry and arranged in the vicinity of the active parts 60 of the elements 59, act between the flange 53 and the armature 57 so as to ensure the application of the elements 59 against the casing 27 when the electromagnet 58 is de-excited, the blades 55 taking no substantial part in this applying action and serving only to keep the armature 57 centered during the course of its movements, and to form a coupling fast for rotation between the armature and the weight-head carrier.

The coefficient of elasticity of the helicoidal springs 62 may be chosen to be small since these springs, which are distant from the axis are numerous, twelve in the example shown, and by their helicoidal nature have a strength which varies only slightly with variations in elongation, due to wear of the linings 59. For the same reason, it is possible to dispense with the provision of accurate movable adjustment wedges. The force of application being distributed very uniformly in the immediate vicinity of the zone of application 60, a large transmitted torque is obtained for the same effort. This torque is subject only to negligible variations during working. The pre-stress of the set of springs may be made moderate by reason of the fidelity of the characteristics of the springs 62, which enables the restoring force of the electromagnet 58 to be limited.

In the alternative form of embodiment shown in FIGS. 4 to 10, the arrangement is'similar to that which has just been described with reference to FIGS. 1 to 3, and the same reference numbers have been used in FIGS. 4 to and in FIGS. 1 to 3 to indicate similar parts.

In the alternative form of FIGS. 4 to 10, there can be seen at 85 the fixed casing in which the centrifugal clutch is housed. There is again seen at 12 and 13 the gripping plates of the friction-disc 15. As in the previous case, the disc 15 carries a ratchet-wheel 16, which is in this casein the form of a bell of stamped steel sheet, and the ratchet teeth 17 of which are small cut-out plates which are fixed in position. The teeth 17 co-operate with the pawls 18 pivotally mounted at 19 on the fly-wheel 11. With each tooth 17 is associated the mask 21, pivoted at 22. The torque-limiter 26 is interposed between the disc 15 and the shaft 11 and comprises (see FIGS. 4 and 9) a wedging member 86 which is fixed to the disc 15 and to the wheel 16, and which co-operates with shoes 87. The latter rub against a drum 88 which is rigidly fixed to the hub 89 of the disc engaged by flutings on the shaft 11, springs 90 being interposed between the member 86 and the shoes 87. The member 86 and the shoes 87 are of cast-iron and respectively comprise large hollowed portions 91 and 92, so that the inertia of the assembly of the disc 15 with the wheel 16 and the limiter 26 is reduced.

There is again shown at 31 the transfer-plate and at 39 the clutch springs which are strongly pre-stressed. The pressure plate 13 has a safety bearing surface 93 from which the transfer-plate 31 is separated at its periphery by a very small radial clearance in order to limit the relative displacements which might occur after prolonged wear. The heat-insulating washer 40, interposed between the spring 39 and the plate 13 is in this case provided with a stamped undulating shape for the circulation of air.

There is again shown at 32 the cam which co-operates with the rollers 43 of the weight-heads 33, pivoted at 44 on the weight-head carrier 34. Each weight-head 33 is in abutment in its position of rest against the buffer 47 of flexible material of the weight-head carrier and in the maximum centrifuged position is in abutment against the anti-noise washer 49 of elastic material which is fixed, preferably by sticking, to the edge 48 of the cam 32. There is seen more particularly in FIG. 10 at 50 the bearing surface of the weight-head 33 which is intended to be applied against the washer 49. The washer 49 is in this case embedded in the edge 48, which has an adjacent face 94 slightly below the level of the washer 49 when the latter is new. By means of this arrangement, if the washer 49 does not function any more for any particular reason, the bearing surface 50 of the weight-head would find in the last resort a support which remains suitable, against the face 94, the latter constituting in this way a safety abutment such that any jamming of the weightheads is prevented.

The weight-head carrier 34 (see FIG. 4) is preferably of light alloy and is carried through the intermediary of the bearing 51 by the casing 27 which is in this case of stamped steel sheet and has a double edge 95 in order to receive and house the outer track of the bearing 51.

The face of the armature 57 which is turned towards the casing 27 is lined with elements 59 of friction material, which alternate with the blades 55. The linings 59 have preferably a base of cork or are of the usual friction material, and are carried through the medium of an elastic under-layer 96 of cork or rubber in order to prevent noise. For the same purpose, a stack of steel sheets could be provided on the casing at the point where the linings 59 are in rubbing contact.

The opposite face of the armature 57 co-operates with a fixed immobilising electro-magnet, of which the yoke is shown at 97 and the coil at 58. The yoke 97 (see FIGS. 4 to 8) is provided in this case with three outer lugs 99 each comprising a threaded hole 100 parallel to the axis of the clutch, and a dished portion 101 directed towards the fixed casing 85. In the dished portion 101 is housed a pastille 102 of hard material.

A screw 103 having a cylindrical neck 104 and a hexagon head 105, passes freely through a hole 106 in the fixed casing 85 and is screwed into each threaded hole 100 in the yoke 97, while a screw 107 having a long hexagon head 108 is screwed into a member 109 rigidly fixed to the casing 85, and is intended to abut against the pastille 102. A clip 110 intended to prevent accidental slackening of the screws is engaged round the collar 104 and grips the head 108. Washers 111 are ar ranged round the collar 104 between the clip 110 and the casing 85. The two heads and 108, the clip and the washers 111 are located on the outer side of the casing 85.

This arrangement enables the position of the electromagnet 97 to be defined with convenience and precision with respect to the armature 57 both at the time of assembly and after a period of service when the linings 57 will be worn, in order to maintain the air-gap existing between the yoke 97 and the armature 57 at a precise and suitable value.

In order to carry out this adjustment, the three screws 103 are first of all screwed sufiiciently to bring the yoke 97 into contact with the armature 57 which gives a faithful and precise reference point. Then each screw 103 is unscrewed by an amount previously determined, for example one or a number of turns or fractions of turns, which moves the yoke 97 away from the armature while keeping it parallel to the conjugate face of this armature.

The screw 107 is then screwed-up to the abutment at 102, which locks the yoke 97 in the desired position.

I It will be noted from FIG. 4 that thepole face of the yoke 97 is provided on each side of the coil .58 with two annular beads of material with a base of cork, these heads 121 projecting slightly. This arrangement is intended to prevent noise, both by the elastic action of the beads 121 and by the dash-pot effect which they produce. In order to avoid any excessive suction of air between the beads, there can preferably be provided in the beads 121 several narrow passages through which the air is forced wih a throttling effect. It is to be noted that the dashpot effect could be produced by projections formed in the armature 57. In the same way, an elastic action only could be provided and obtained by a single bead 121 with a base of cork, in particular the outer bead, instead of two.

One of the lugs 99 (see FIGS. 5 and 6) is provided with insulating supports carrying two electric terminals 112 and 113 which are respectively coupled to the two ends of the coil 58 by conductors 114 passing behind the yoke 97, that is to say without causing any discontinuity in the pole faces of either the yoke 97 or in the beads 121. The terminal 112 is supplied by the battery 115 of the vehicle through the intermediary of the ignition contact 116, while the terminal 113 is grounded through the medium of the switch 117. So in FIGURE 1, the switch 117 is controlled by the gear-changing lever 118 so as to be closed during the course of gear-changing operations and to be open except during these operations. The capacitor 119 and the resistor 120 may-be also provided in parallel with the switch 117.

What we claim is:

1. In a centrifugal clutch of the kind comprising: a driving shaft and a driven shaft; a friction drive unit, including a fly-wheel fast with said driving shaft, a pressure-plate fast for rotation with said driving shaft but axially movable with respect thereof and a friction disc fast for rotation with said driven shaft and axially slidable thereon, said friction disc being located between said fly wheel and said pressure-plate and being provided with friction linings for being gripped between said flywheel and said pressure-plate when the clutch is engaged; a dished casing fixed to said fly-wheel; and a centrifugal unit housed in said casing, said centrifugal unit including a transfer-plate axially slidable on said pressure-plate and fast for rotation therewith, a plurality of axially-mounted clutch springs between said transfer plate and saidpressure plate, an annular cam mounted freely rotatable and fast for axial movement on said transfer-plate, and a weight-head carrier mounted freely rotatable on said casing and carrying pivoted weight-heads cooperating with said cam, said weight-heads being pivoted on said carrier so that they'are pushed axially against said cam by centrifugal force, the axial thrust of said weight-heads on said cam being transferred through said transfer-plate and said clutch springs to said pressure-plate, the combination with said cam and weight-heads of an abutment member extending towards the weight-heads and encircling them to be abutted by them, the said abutment being constituted by a peripheral axially-projecting annular member forming part of the said cam.

2. A clutch as claimed in claim 1, in which the internal face of said abutment with which the weight-heads make contact is provided with an inset lining ring of rubber like material.

3. A clutch as claimed in claim 2, in which the said ring projects only slightly from the inner surface of said annular abutment, the said inner surface acting as a stop for the said weight-heads when the lining ring becomes worn.

References Cited in the file of this patent UNITED STATES PATENTS 1,810,360 Loeffler June 16, 1931 2,107,075 Lyman Feb. 1, 1938 2,278,547 Herrington Apr. 7, 1942 2,280,736 Winther Apr. 21, 1942 2,301,600 Wilson Nov. 10, 1942 2,400,625 Bloomfield May 21, 1946 2,462,457 Berndtson Feb. 22, 1949 2,559,765 Gravina et a1. July 10, 1951 2,635,722 Wemp Apr. 21, 1953 2,729,310 Le Tourneau Jan. 3, 1956 2,774,452 Wisman Dec. 18, 1956 FOREIGN PATENTS 151,478 Great Britain Sept. 30, 1920 829,954 France May 2, 1938 568,409 Great Britain Apr. 4, 1945 1,066,576 France Ian. 20, 1954 1,086,389 France Aug. 11, 1954 1,133,704 France Nov. 19, 1956 1,134,189 France Nov. 26, 1956

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