US3580229A

US3580229A - Method and means for switching on and off the fan wheel of a regulating fan

Info

Publication number: US3580229A
Application number: US802093A
Authority: US
Inventors: Michael May
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1968-03-01
Filing date: 1969-02-25
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25
Also published as: GB1264691A; FR2003055A1; NL6903170A; SE348260B

Abstract

The cooling fan of an internal combustion engine is driven through a temperature-controlled clutch. Slipping of the clutch is held to a minimum by an auxiliary actuating mechanism which automatically moves the clutch into the fully engaged or the fully disengaged position as soon as it has been moved by a thermostat into an intermediate position. Several examples of clutch arrangements are given.

Description

United States Patent 1 1 3,580,229

[72] inventor Michael May [56] References Cited Stuttgart-B918, Germany UNITED STATES PATENTS gig- 32522 2,078,600 4/1934 Collins 192/52 2,652,816 9/1953 Dodge 123/4112 2:52:22 ill'iifa m AG 2,881,890 4/1959 Welch...... 192/82 g Schw. Main G 2,950,796 8/1960 Becker..... 192/82 [32] mm Mar "many 2,998,114 8/1961 Altmann... 192/52 [33] 3,273,68l 9/1966 Seifert 123/4112 [31] g 3,323,623 6/1967 Roper 192/58 FOREIGN PATENTS 688,243 6/1964 Canada 123/4112 Primary Examiner-Mark M. Newman Assistant Examiner-Ronald B. Cox

54 METHOD AND MEANs FOR SWITCHING ON AND AmmeY-LW and Berma" on THE FAN WHEEL 0F A REGULATING FAN 8 Chums Drawing Figs ABSTRACT: The cooling fan of an internal combustion en- [52] US. CL l23/4l.l2, gine is driven through a temperature-controlled clutch.

192/52, 192/54, 192/83 Slipping of the clutch is held to a minimum by an auxiliary ac- [51] Int. Cl F0lp 7/02, tuating mechanism which automatically moves the clutch into F 16d 7/00, F 16d 19/00 the fully engaged or the fully disengaged position as soon as it [50] Field of Search 123/41. l2; has been moved by a thermostat into an intermediate position.

192/5 2, 54, 83 Several examples of clutch arrangements are given.

Patented May 25, 1971 3,580,229

6 Sheets-Sheet 2 Inventor M 74! May $1M 444 MM Flam/7's Patented May 25, 1971 3,580,229

6 Sheets-Sheet 5 Fig. 4

Inventor: fq M4) Patented May 25, 1971 6 Sheets-Sheet 4 Fig.5

Inventor: H/aaa/ May {9 GENT;

Patented May 25, 1971 3,580,229

6 Sheets-Sheet 5 Fig. 6

Inventor fil cda M417 4) GEM/5 Patented May 25, 1911 3,580,229

6 Sheets-Sheet 6 Inventor /aae/ 7' $1M M MW METHOD AND MEANS FOR SWITCHING ON AND OFF THE FAN WHEEL OF A REGULATING FAN This invention relates to the control of the fan wheel of a regulating fan of an internal combustion engine, such as a motor vehicle engine, and particularly to a clutch control mechanism in a regulating fan.

Regulating or automatically controlled fans are known and differ from ordinary internal combustion engine fans in that their fan wheel is not constantly driven but is only switched on when the engine cooling by the normal air flow is not sufficient. This affords a number of advantages. For example, the engine reaches its operating temperature substantially more quickly. Also, there is a power saving which can amount in the case of automobiles to a few horsepower and the engine runs more smoothly. In spite of these advantages, regulating fans have not established themselves generally because they are relatively complicated and expensive to manufacture. On the other hand, known regulating fans of simple design do not operate satisfactorily and reliably. One known regulating fan is temperature controlled and comprises a drive shaft which is driven by the engine via a V-blet and adapted to be coupled to the fan wheel by a friction coupling. The temperature pickup is a wax thermostat and is exposed to the cooling air heated by the radiator. A control element of the wax thermostat acts on an expanding spring whose periphery is provided with a friction lining and adapted to bear against the coupling drum of the friction clutch. This regulating fan is admittedly of simple design; however, the friction clutch slips constantly in the critical region because the engaging and disengaging operations are effected solely by the creeping movement of the control element of the wax thermostat. The high slip has both control and operating disadvantages. Inter alia the cooling effect is impaired and the clutch lining wears rapidly.

It is proposed according to the invention that the engagement of the friction coupling associated with the fan wheel from an intennediate first coupling state of the friction coupling onwards and the disengagement from an intermediate second coupling state onwards take place automatically without being affected by the temperature to be controlled until complete engagement and disengagement respectively is achieved, the coupling passing rapidly through the slip range, and that the adjustment of the friction coupling necessary to reach the first and second coupling states is effected by at least one temperature pickup of the temperature-sensing device in dependence upon the temperature to be controlled.

This method is particularly distinguished by the fact that after the first or second coupling state has been reached the clutch is clearly engaged or disengaged, being in the slip range only for as long as is necessary for the rapid acceleration of the fan wheel.

The novel method has particular advantages in conjunction with regulating fans whose temperature pickups are so constructed and arranged that they can exert a coupling force directly on the friction clutch. As already mentioned, in known regulating fans the clutch can slip for long periods. Also, in these regulating fans the width of the slip range increases with increasing drive speed of the fan wheel. These disadvantages are obviated with he novel method of the invention. The temperature pickup serves only to control the friction clutch to bring it into a first or second coupling state; when this state is reached the further coupling operation proceeds automatically with rapid passage through the slip range.

It is known in regulating fans to switch the fan wheel on and off at different values of the temperature to be controlled to prevent rapid reciprocating of the control operation. This problem can also be solved simply by the method according to the invention in that the first coupling state is reached at a higher value of the temperature to be controlled than the clutch which comprises a main coupling and preferably a control coupling associated with the main coupling for controlling the latter, then first and second coupling states corresponding to transition points between the two stable coupling states of the clutch, one of which is the disengaged and the other the engaged state, and that the temperature-sensing device comprises a control device having at least one temperature pickup to sense the temperature to be controlled and bringing the bistable clutch alternately into the first and second coupling states, said device preferably being nonrotatably connected to the drive shaft of the clutch.

Further features of the invention are described hereinafter with reference to the drawings, wherein:

FIG. 1 shows a side elevation partially in section of a regulating fan according to a first embodiment of the invention,

FIG. 2 is a perspective view of a detail of FIG. 1,

FIG. 3 shows four positions of the clamping mechanism illustrated in FIGS. 1, 2 and 4 in developed views,

FIG. 4 is a plan view of a detail of FIG. 1,

FIG. 5 is a partial longitudinal section through a fan according to a further embodiment of the invention, the clutch being disengaged,

FIG. 6 shows a portion of the fan according to FIG. 7 in longitudinal section with the clutch engaged, and

FIG. 7 is an exploded perspective view of the fan according to FIGS. 7 and 8.

In the drawings corresponding parts are provided with the same reference numerals.

The regulating fan illustrated in FIG. 1 comprises a fan wheel 10, on the hub 12 of which are arranged a plurality of fan blades 11 shown partly broken away to simplify the illustrations.

The fan wheel 10 is adapted to be driven by an engine shaft (not illustrated) of a motor vehicle engine (also not shown) via a V-belt drive, of which a V-belt is indicated at 13 and the driven pulley at 14. For this purpose, the pulley 14 is fixedly arranged on a journal 15 which serves as drive shaft for the fan arrangement and which is mounted in a bearing assembly 16 fixedly connected in a manner not illustrated in detail to the engine block, said bearing assembly 16 fixedly connected in a manner not illustrated in detail to the engine block, said bearing assembly comprising a ball bearing 17 and a shaft seal 18. The journal 15 comprises a flange 19 to which by means of bolts such as 21 the pulley 14 together with one coupling or clutch member 20 of a main coupling or clutch is nonrotatably connected. Furthermore, a bushing 22 is fixedly arranged on the journal 15 and a wax thermostat 24 serving as temperature pickup and control device is screwed fixedly into the free slotted end 23 of said bushing.

Said wax thermostat may be of any suitable conventional construction and comprises a casing 25 whose cylindrical inner chamber 26 contains wax 27 having a high thermal expansion coefiicient. Mounted for axial displacement in a bearing bore 28 in the end face 29 of the casing 25 is a ram 30 serving as control element.

Spaced in front of the wax thermostat 24 is a radiator not further illustrated for cooling the coolant of the motor vehicle engine. The cooling air flowing through this radiator impinges in the direction of the arrow A on the wax thermostat. When the temperature of this air exceeds a predetermined limit, in a manner described in detail herein after the fan wheel 10 is switched in by a bistable clutch. As soon as the cooling air drops below a predetermined lower temperature the fan wheel 10 is switched off again by disengagement of the clutch.

Secured to the hub 12 of the fan wheel 10 is a coupling member 31 whose lining 34 cooperates with the coupling member 20 as a main coupling or axial disc clutch. Secured to the front end face 32 of the coupling member 31 is a lining 33 which forms with the rear end face 60 of a clamping a member 39 a further axial disc clutch which is a control coupling via which the main coupling connected in series therewith may be actuated. The two coupling linings comprise substantially different different mean diameters. This construction of the coupling member 31 and provision of a control coupling and a main coupling is intended more especially to obtain a smooth jerk-free acceleration of the fan wheel on engaging. For this purpose, the coefficients of friction of -the

linings

33, 34 may advantageously be different, the coupling disc 34 preferably having the greater coefficient. The coupling member 31 is mounted for rotation and axial displacement on the bushing 22 by means of a bearing bushing 36 of sintered metal advantageously secured to the inner wall 35 of the coupling member 31. In the disengaged state of the friction coupling said member 31 is in the illustrated axial location in which it is not in contact with the coupling and clamping members 20, 39 continuously driven by the journal 15.

The friction coupling also comprises a clamping mechanism 37 which is a rotary friction locking mechanism and is illustrated in detail in FIGS. 2 to 4. Said clamping mechanism comprises two clamping members coaxial with the journal 15, namely a first clamping member 38 and a second clamping member 39, which are relatively rotatable and axially displaceable. The clamping member 39 forms at the same time a coupling member of the control coupling. This clamping mechanism is illustrated in detail in FIGS. 2 and 4. The first clamping member 38 is pressed in the direction of the arrow B towards the wax thermostat 24 by means of a spring 40 bearing on the free end face of the journal 15, the rear end face of the casing 25 of said wax thermostat forming a stop for the axial end position of said clamping member. Said first clamping member 38 further comprises a central cylindrical inner recess 41 in which is arranged a spring 42 which bears on the one hand on the first clamping member 38 and on the other hand on the end face of the ram 30. Said spring 42 is so rigid that on normal axial movement of the ram 30 it cannot be further compressed. Its purpose is rather that of an overload protection when in the engaged state of the friction coupling the ram 30 tends to move further to the left due to increasing temperature of the wax 27. Consequently, in the normal case the spring 42 represents a rigid connection between the ram 30 and the firs clamping member 38, a spring ring 43 being fitted in the upper edge of the recess 41 to engage behind the collar 44 of the ram 30 and to effect that when the ram 30 moves in the direction of the arrow C the first clamping member 38 is constrained to move therewith.

The first clamping member comprises two radial diametrically opposite pins 45 and 46 which project with slight clearance through

longitudinal slots

47 and 48 in the bushing 22. Secured to the

pins

45 and 46 are

springs

50 and 51 which cooperate with the cylindrical outer wall 52 of the second clamping member 39 and form a freewheel clutch for the fan wheel. This clutch ensures that in the engaged state of the friction coupling the fan wheel is prevented from running faster than its drive speed. This achieves a smooth running of the fan on rapid speed fluctuations of the engine.

The second clamping member is biased in the axial direction by means of a pressure spring 54 bearing against a ring 53 let into the wall of the bushing 22 and is thereby constantly pressed against the

pins

45, 46 of the first clamping member. Disposed on the radial end wall 55 of the second clamping member 39 are two diametrically opposite clamping cams 56, 57 (FIGS. 24) whose ramp-shaped guide surfaces 58, 59 inclined at an angle a (FIG. 3) to the wall 55 form inclined planes and cooperate with the

pins

45, 46 to produce the pressure necessary from the first coupling state onwards. The height of these

cams

56, 57 determines the position of the second coupling state at which the friction coupling is automatically disengaged.

The mode of operation of this regulating fan is as follows. As long as the temperature to be controlled of the cooling air impinging on the wax thermostat 24 does not exceed a predetermined upper limit, the fan is in the disengaged state illustrated in FIG. 1 so that the fan wheel 10 is not driven by the journal constantly driven by the vehicle engine.

The pressure of the spring 54 holds the rotary clamping mechanism 37 in a disengaged position, as is illustrated in FIG.

2 or 4, in which it exerts no clamping pressure and thus produces no axial coupling pressure. Such a position is also indicated in FIG. 3 in the developed view a. FIG. 3 shows four relative positions of the end wall 55 of the second clamping member 39 and of the

pins

45, 46 of the first clamping member. As mentioned, the position illustrated in the development a of the rotary clamping mechanism is its normal position in the disengaged state. The pins then lie on the

base sections

62, 63 with their lower surface, which is slightly curved a.

When the temperature to be controlled exceeds a value at which an additional cooling by the fan wheel is necessary to avoid overheating of the internal combustion engine, the ram 30 moves as a result of the increased temperature in the direction of the arrow D to the left and displaces the clamping mechanism 37 as a whole axially in the same direction, thus changing the coupling state of the friction coupling. Since the first clamping member 38 of the clamping mechanism 37 is nonrotatably connected to the rotating journal 15 and drives the second clamping member 39, a drive torque is exerted on the coupling member 31 as soon as the coupling face 60 of the coupling member 31 as soon as the coupling face 60 of the second clamping member 39 is pressed by the pressure of the ram 30 of the wax thermostat against the lining 33 of the coupling member 31 (first coupling state). Following this first coupling state the fan wheel It) begins to rotate and the torque transmitted for this purpose by the friction coupling pivots the second clamping member 39 of the clamping mechanism relatively to the clamping member 38 into a position in which the

pins

45, 46 run onto the inclined guide surfaces 58, 59 of the

cams

56, 57. The

pins

45, 46 tend to displace the second clamping member 39 axially in the direction of the arrow E (FIG. 3), thus increasing the coupling pressure exerted by the second clamping member. The inclination (angle a) of the guide surfaces 58, 59 is such that following the first coupling state brought about by the wax thermostat the clamping pressure until the main coupling is fully engaged without slip, i.e. until the coupling lining 34 bears against the opposing face 64 of the coupling member 20 with a pressure sufficient to ensure the slip-free entraining of the fan wheel 10. As is the disengaged state, this engaged state is a stable coupling state because the coupling pressure exerted by the clamping mechanism cannot cease spontaneously. The clamping mechanism is then in the position shown in FIG. 3b. The cooling action of the fan wheel thereafter reduces the coolant temperature and thus the temperature of the air acting on the wax thermostat 24. As a result the ram 30 of the wax thermostat creeps back in the direction of the arrow C, the

pins

45, 46 thus moving correspondingly slowly in the direction of the arrow F upwardly on the guide surfaces 58, 59 of the cams; as this happens, the full coupling pressure is maintained. As soon as the temperature of the cooling air has dropped to a value at which the bottom surfaces of the

pins

45, 46 reach the upper edges 66, 67 (FIG. 4) of the cams (second coupling state), they slide over the

cams

56, 57 as indicated in FIG. 30. The pressure of the spring 54 thereby causes the second clamping member to niove in the direction of the arrow G, thus moving the clamping mechanism into its position shown in FIG. 2; the coupling is disengaged again, passing rapidly through the slip range. The first and second clamping members pass through the intermediate position illustrated in FIG. 3d, again into a position as shown in FIG. 3a. Since the additional cooling effect of the fan wheel 10 is now removed, the temperature of the cooling air impinging on the wax thermostat can rise again depending on the driving conditions and the engine output of the vehicle and the same control process may be repeated. This two-point control does not end until an additional cooling by the fan is no longer necessary.

The ram 30 of the wax thermostat forms an abutment which absorbs the coupling pressure. To keep the necessary coupling pressure as small as possible the mean diameter D of the lining 34 is made as large as possible and preferably substantially larger than the effective diameter d of the clamping mechanism i.e. the diameter of the end wall 55 of the second clamping member 39. To ensure slip-free driving of the fan blade the angle a (FIG. 3) of the guide surfaces 58. 59 of the earns 56, 57 must not exceed a predetermined maximum value. If the friction between the

pins

45, 46 and the guide surfaces 58, 59 is negligible, tan a }LD/Cl is approximately true, where p. is the coefficient of friction between the lining 34 and coupling face 64 and d, D the said diameters.

Furthermore, it can be seen that engaging of the friction clutch takes place at a higher temperature of the cooling air than disengaging, since at the instant of the first coupling state the ram 30 is displaced further to the left than at the instant of the second coupling state in which the

pins

45, 46 slide over the

edges

58, 59 of the

cams

56, 57. This is desirable to prevent too rapid repeated reversal of the engaging and disengaging operations. The magnitude of the temperature difference of engaging and disengaging depends on the height h of the cam (FIG. 3). In the illustrated embodiment this is so chosen that said temperature difference is approximately 5 C.

The friction coupling illustrated is also more especially distinguished by the fact that although on engaging the fan wheel accelerates and passes rapidly through the slip range of the coupling to nonslip drive, this acceleration is smooth and jerk-free. The smooth start is further improved by dividing the friction clutch into control and main couplings. Although this division of the friction coupling is particularly advantageous, it may nevertheless be dispensed with in many cases.

The regulating fan illustrated in FIGS. 7 to 9 comprises a bistable clutch which includes a main coupling 110 which is a band clutch, a control coupling 111 which is an axial disc clutch and a clamping mechanism 112 similar to the clamping mechanism according to FIGS. 1 to 4. The clamping mechanism has two positions which determine the first and second coupling states.

113 denotes a V-belt pulley which is fixedly mounted on a rotatably mounted journal 114 and driven by means of the V- blet (not shown) by the vehicle engine. Also fixedly mounted on the journal 114 is a hollow shaft 115 whose end 116 is slotted. Fitted in the free slotted end is a wax thermostat 119 on which acts the cooling air heated by the radiator (not shown) of the vehicle engine, said thermostat being held in place by a locking washer 117. This wax thermostat comprises an axially displaceable ram 121 which passes through the thermostat casing 120 and which can move in the axial direction in dependence upon the temperature of the wax thermostat. The higher the temperature, the more the ram projects from the casing. Guided for axial displacement in the slots 122 of the end 116 are two axial diagonally opposed arms 124 of a U- shaped first clamping diagonally opposed arms 124 of a U- shaped first clamping member 123 whose center web 125 is pressed constantly against the free end face of the ram 121 by means of a conical spring 126 bearing on the end face of the journal 114, so that the clamping member participates in the axial movements of the ram. As is particularly apparent from FIG. 9, the two axial arms 124 are bent outwardly to form lugs 129 which cooperate in turn with a cam plate 130 of a second clamping member 131 of the clamping mechanism, the latter member comprising two lugs 133 bent out of the plane of the disc and having obliquely inclined cam faces 132 whose function will be described hereinafter.

The disc-shaped second clamping member 131 is pressed by a pressure spring 127 against the lugs 129 of the first clamping member. The pressure spring 127 bears on a retaining ring 134 which is inserted into the hollow shaft 115 and which secures the inner ring 135 of a bearing 136 mounted on the hollow shaft. Also fixedly mounted on the hollow shaft 115 is a cup-shaped main coupling member 137 which carries a cylindrical lining 139. The

components

113, 115, 117, 119, 123, 126, 134, 135 and 137 are nonrotatably connected to the journal 114. The second clamping member 131 with the pressure spring 127 also constantly participates in the rotation but can turn relative to the first clamping member 123 and is also axially displaceable with respect thereto.

On the other hand, the components carried by the outer ring 140 of the ball bearing do not rotate with the journal 114 in the disengaged state of the main and control coupling. These are the drum 141 fixedly arranged on the outer ring 140, the control coupling member 142 bearing on the surface of the drum via a washer 143 and a cup spring 144, an annular spring 145 disposed at the underside of the control coupling member, a coupling band 147 secured to the inside of the outer casing 146 of the drum 141, the other end of which band is engaged in the free end 149 of the annular spring bent in the axial direction, and a fan wheel 151 shown in dot-dash line and secured to the outer flange of the drum 141 by means of bolts which are not shown. These components are coupled to the journal 114 only in the engaged state of the main and control couplings (FIG. 8). The control coupling 111 consists of the second clamping member 131, the control coupling member 142, on the upper part of which is fixedly mounted an annular coupling lining 152, and of the annular spring 145 secured to the control coupling member at 153. The band clutch consists of the drum 141, the band 147 and the main coupling member 137.

The bentup lugs 154 of the drum engage with their inwardly bent free ends over the coupling bear 142 and in the disengaged state of the control coupling (FIG. 7) the assembly consisting of the washer 143, the cup spring 144 and the control coupling member 142 is mounted with slight axial clearance between the bent ends of the lugs 154 and the upper end face of the drum 141, so that said assembly can turn with respect to the drum. The control coupling member 142 comprises on its outer surface three radial projections 155 which project radially beyond the lugs 154 and thus enable an angular movement of about 100 of the control coupling member 142 with respect to the drum 141. The annular spring145 ensures that in the disengaged state the lugs 154 bear in the position shown in dot-dash line at 156 in FIG. 9 against the projections 155. In this position the coupling band 147 is relaxed and in the position shown in FIG. 7. The annular spring, whose end 149 can move resiliently in the direction of the double arrow C (FIG. 9) ensures a smooth engaging of the band coupling. In the engaged state the lugs 154 bear against the other sides of the projections 155, thus limiting the resilient bending of the annular spring 145 and therefore the control force exerted thereby on the coupling band 147. This ensures a smooth engagement of the band coupling.

FIG. 8 is an exploded view of the most important components of the bistable clutch illustrated in FIGS. 7 and 8; the journal and all components not essential for the understanding of the invention, such as locking washers, bolts and the like, have been omitted for clarity.

The mode of operation of this bistable clutch is as follows:

In FIG. 7 the bistable clutch is in its disengaged state. The ram 121 of the wax thermostat 119 projects slightly beyond the casing 120 so that the first clamping member 123 assumed the position illustrated. The second clamping member 131 is pressed by means of the spring 127 against the lugs 129, only one of which can be seen. In the disengaged state the lugs 129 can bear only on the deepest portion of the cam disc 130 and not on the inclined cam faces 132 and thus exert no clamping pressure. The control coupling member is in its highest position. The control coupling (axial clutch) and the band clutch are disengaged.

When the temperature of the wax thermostat 119 increases, the ram 121 moves correspondingly to the right, causing the first and

second clamping members

123, 131 to be moved to the right of the same extent. Following this movement the bottom of the second clamping member 131 comes into contact with the coupling lining 152, this corresponding to the first coupling state. Since the second clamping member then rotates with the journal, it engages the control coupling member 142, thus being braked and rotating relatively to the lugs 129 of the first clamping member until said lugs run onto the cam faces 132 and thus increase the axial pressure on the second clamping member, the latter being pressed against the lining 152 of the coupling member 142 (FIG. 8). The second clamping member is pressed downwardly by the camming engagement of the lugs 129 with the inclined cam faces 132. 133 against the action of the cup spring 144 until stopped by a shoulder of the hollow shaft 115 which determines the maximum application pressure of the coupling faces of the control coupling 111 in conjunction with the cup spring 144, resulting inter alia in a smoother engagement. The control coupling member 142 is pivoted relatively to the drum 141 in the direction of the arrow A (FIG. 9). The annular spring 145 which is engaged in the lug 157 of the coupling band 147 by means of its bent end 149 participates in this angular movement and thus resiliently tensions the band 147 so that said band is pressed against the associated coupling lining 139. The coupling band engages the lining 139 over an arc of about 320. A slip-free connection is then established very rapidly between the band 147 preferably consisting of metal and the friction lining 139. With the control coupling engaged the coupling band is constantly tensioned by means of the clamping mechanism and the annular spring 145 since the drum 141 tends to lag with respect to the driven coupling member 142 due to the braking torque exerted on said drum by the fan wheel connected thereto. The driven coupling lining 139 tends to engrain the band and amplifies the tension of the latter, thus resulting in a considerable increase in the surface pressure of the band. The torque D exerted on the end 157 of the band by the annular spring produces a frictional torque D, of the band coupling of D,=D (e el where ,a is the coefficient of friction and D the angle of contact. In this manner it is possible with a low coupling pressure of the control coupling and a low tension of the annular spring to couple the drum 141 and the associated fan wheel without slippage to the coupling lining 139 and thus to the shaft journal. From the first coupling state onwards the engagement takes place automatically and is not influenced by the wax thermostat. The engaged state of the band clutch is maintained as long as the lugs 129 press against'the inclined surfaces of the cams 133.

When the fan wheel has been started up the increased air flow cools the radiator and the temperature of the cooling air impinging on the wax thermostat 119 also falls steadily, causing the ram 121 to move to the left. The first clamping member 123 also moves to the left accordingly, i.e. the lugs 129 move upwardly on the cam faces 132. As this happens, the position illustrated in FIG. 8 of the second clamping member 131 is maintained unchanged. When the lugs 129 reach the upper edges of the inclined planes 132, thus leaving the latter, the second coupling state is reached and from this point onwards the disengaging proceeds automatically. At this instant the second clamping member 131 is pressed to the left by the pressure spring 127 until the lugs 129 lie on the deepest portion of the cam disc 130, i.e. no longer on the inclined cam faces. The clamping mechanism is thus released and the control coupling disengaged, cf. FIG. 7, so that torque is no longer exerted by the second clamping member on the control coupling member and the annular spring can no longer tension the coupling band, the band clutch thus rapidly disengaging automatically.

1 claim:

1. In a fan arrangement for cooling an engine, the arrangement including a rotatable fan wheel,

a drive member adapted to be rotated by said engine,

a clutch operatively interposed between said drive member and said wheel for drivingly connecting said member to said wheel, and temperature responsive clutch-operating means including a movable actuating member,

a body of temperature sensitive material in thermal contact with ambient air and connected to said actuating member for moving the same in response to a change in the temperature of said air, and

motion-transmitting means connecting said actuating member to said clutch for engaging and disengaging the clutch in response to movement of the actuating member, the motion-transmitting means including two clamping members mounted for relative angular movement about an axis movement, a first one of said clamping members being connected to said actuating member for movement thereby in the direction of said axis, and to said drive member for rotation thereby about said axis,

coupling means for connecting the second coupling member to said wheel in response to an axial movement of said second clamping member from a first to a second position and for thereby displacing the two clamping members angularly relative to each other when the rotary speeds of said fan wheel and of said drive member differ from a predetermined relationship, and

cam means interposed between said clamping members for further axially moving said second clamping member from said second position toward a third axial position away from said first position, and for thereby engaging said clutch in response to said angular displacing,

the improvement which comprises:

a. said cam means including a cam member on one of said clamping members having a first face sloping obliquely in a circumferential direction and axially toward the other clamping member and a second cam face offset from said first face in said circumferential direction and leading away from said other clamping member;

b. the cam means further including cam follower means on said other clamping member for engagement with said cam member; and

c. yieldably resilient means holding said cam follower means in consecutive abutting engagement with said first and second faces during angular movement of said clamping members relative to each other in one direction, whereby said clamping members are moved apart and thereafter moved toward each other during said angular movement in said one direction.

2. In an arrangement as set forth in claim 1, said axis being the axis of rotation ofsaid drive member.

3. In an arrangement as set forth in claim 2, securing means securing said first clamping member against rotation relative to said drive member while permitting axial movement of said clamping member.

4. In an arrangement as set forth in claim 3, means securing said first clamping member to said actuating member for joint movement in the direction of said axis.

5. In an arrangement as set forth in claim 4, said second clamping member being rotatably and axially movably mounted on said drive member.

6. In an arrangement as set forth in claim 5, said cam means including an additional cam member on said one clamping member and substantially indentical with said first-mentioned cam member, said cam members being angularly distributed about said axis, said cam follower means including two cam follower members on said other clamping member distributed about said axis for simultaneous engagement with said first faces of said axis for simultaneous engagement with said first faces of said cam members during said angular movement of the clamping members in said one direction, and for simultaneous engagement with said second faces.

7. A fan arrangement for cooling an engine by means of a stream of air comprising, in combination:

a drive member having an axis;

b. means for rotating said member about said axis when said engine operates;

c. a fan wheel;

d. a clutch having a driven portion secured to said drive member for joint rotation and a driving portion secured to aid wheel for joint rotation with the wheel about said axis;

e. actuating means including an actuating member and temperature responsive means in thermal contact with said air operatively connected to said actuating member for axially moving the same in response to a change in the temperature of said air; f. clamping means for engaging and disengaging said clutch,

said clamping means including 1. a first clamping member secured to said drive member for joint rotation and secured to said actuating member for joint axial movement,

2. a second clamping member axially interposed between said first clamping member and said driving portion, said second clamping member being axially movable and rotatable about said axis,

3. cooperating cam means on said clamping members responsive to relative angular displacement of the same in a predetermined circumferential direction for axially moving said second clamping member toward said driving portion and responsive to further relative angular displacement of said clamping members in said predetermined direction for releasing said second clamping member,

4. yieldably resilient means biasing said second clamping member axially toward contact with said first clamping member, and

5. coupling means on said second clamping member and said driving portion engageable by axial movement of said second clamping member for impeding relative rotation of said second clamping member and of said driving portion; and

g. motion-transmitting means responsive to the axial movement of said clamping member toward said driving portion for engaging said members of said clutch for joint rotation.

8. An arrangement as set forth in claim 7, wherein said actuating means are mounted on said drive member for rotation therewith.

Claims

1. In a fan arrangement for cooling an engine, the arrangement including a rotatable fan wheel, a drive member adapted to be rotated by said engine, a clutch operatively interposed between said drive member and said wheel for drivingly connecting said member to said wheel, and temperature responsive clutch-operating means including a movable actuating member, a body of temperature sensitive material in thermal contact with ambient air and connected to said actuating member for moving the same in response to a change in the temperature of said air, and motion-transmitting means connecting said actuating member to said clutch for engaging and disengaging the clutch in response to movement of the actuating member, the motiontransmitting means including two clamping members mounted for relative angular movement about an axis movement, a first one of said clamping members being connected to said actuating member for movement thereby in the direction of said axis, and to said drive member for rotation thereby about said axis, coupling means for connecting the second coupling member to said wheel in response to an axial movement of said second clamping member from a first to a second position and for thereby displacing the two clamping members angularly relative to each other when the rotary speeds of said fan wheel and of said drive member differ from a predetermined relationship, and cam means interposed between said clamping members for further axially moving said second clamping member from said second position toward a third axial position away from said first position, and for thereby engaging said clutch in response to said angular displacing, the improvement which comprises: a. said cam means including a cam member on one of said clamping members having a first face sloping obliquely in a circumferential direction and axially toward the other clamping member and a second cam face offset from said first face in said circumferential direction and leading away from said other clamping member; b. the cam means further including cam follower means on said other clamping member for engagement with said cam member; and c. yieldably resilient means holding said cam follower means in consecutive abutting engagement with said first and second faces during angular movement of said clamping members relative to each other in one direction, whereby said clamping members are moved apart and thereafter moved toward each other during said angular movement in said one direction.

2. In an arrangement as set forth in claim 1, said axis being the axis of rotation of said drive member.

5. coupling means on said second clamping member and said driving portion engageable by axial movement of said second clamping member for impeding relative rotation of said second clamping member and of said driving portion; and g. motion-transmitting means responsive to the axial movement of said clamping member toward said driving portion for engaging said members of said clutch for joint rotation.

7. A fan arrangement for cooling an engine by means of a stream of air comprising, in combination: a drive member having an axis; b. means for rotating said member about said axis when said engine operates; c. a fan wheel; d. a clutch having a driven portion secured to said drive member for joint rotation and a driving portion secured to aid wheel for joint rotation with the wheel about said axis; e. actuating means including an actuating member and temperature responsive means in thermal contact with said air operatively connected to said actuating member for axially moving the same in response to a change in the temperature of said air; f. clamping means for engaging and disengaging said clutch, said clamping means including