MXPA97006027A - Centrif clutch - Google Patents

Abstract

The present invention relates to a centrifugal clutch comprising: (a) a rotating drum having a circularly cylindrical inner surface, (b) a plurality of shoes, each shoe has a front contact end and a rear contact end, a outer coupling surface extending between the contact ends for frictional contact of the inner surface of the drum; (c) means for coupling each shoe to a rotating hammer to rotate therewith when the hub rotates concentrically with the drum; d) means for allowing movement of each shoe radially inwardly and outwardly relative to the drum, and (e) a rigid shoe member of each shoe having a first locking portion projecting radially inwardly and a second locking portion which projects radially outward, circumferentially spaced from the first working portion, the first and second locking portions of one of the adjacent rigid shoe members locks the shoes preventing movement radially outward by more than a predetermined distance beyond contact with the inner surface of the drum to prevent separation of the shoes in case of axial decoupling or structural breakage of the drum during the high-speed operation of the clutch

Description

CENTRIFUGE CLUTCH BACKGROUND The present invention relates to centrifugal clutches such as those used in light vehicles, chain saws, pumps, windmills, compressors, motors, electric motors, wind driven products, and the like, to variably couple rotational power sources to loads activated. Centrifugal clutches are described in, for example, the patents of E. U.A. Nos. 2, 942, 71 1 and 3, 971, 463 of the inventor named above, said patents are incorporated herein by reference. Typically, a plurality of radially movable shoes, frictionally in contact with an inner surface of a drum that rotates concentrically with a hub to which the shoes are connected. Normally, the hub is fixed on an activation arrow or face plate that is coupled to a motor or power source, the drum being coupled to an activated load through said band, chain or direct coupled actuator. Said clutches transmit little or no torque at low speeds, and a torque is progressively increased at higher speeds in proportion to the centrifugal forces, to which the shoes are subjected. In the aforementioned patents, spring-biased elements are employed to maintain the clutches in an uncoupled condition at speeds below a predetermined threshold to allow the motor or other power source to run at idle when unloaded. Centrifugal clutches, as implemented in the prior art, are the subject of a number of problems and disadvantages. For example: 1. They are ineffective, as they fail to provide a desired torque-speed ratio to match the characteristics of the power source; 2. They have short life, since there is an excess leakage and consequent wear of the shoes, particularly when there is a large vibrational component or load of high inertia in the torque; 3. They are unstable since the springs used in them are subjected to rupture, particularly since they have fatigue induced by tension lifts in hooks at the opposite ends; 4. They are unsafe, since the shoes can run in case there is a structural breakage of the drum; and 5. They are undesirably expensive to produce. The clutch, as described in patent 711, can be assembled in a variety of ways to selectively provide, in a corresponding manner, different torque-speed ratios such as straight centrifuge with selectable coupling speeds; relatively fast drive; or relatively moderate drive. However, none of the torque-speed ratios is completely satisfactory, and there are numerous possibilities of incorrect assembly. The clutch, as described in the '463 patent, provides activation member projections, which are successively engageable with the shoes at increasing speed increases for progressively increased torque transmission. Again, neither one of the torque-speed ratios is completely satisfactory, particularly when it is desired to obtain an initial coupling to a high percentage of the full load speed of the clutch, and the clutch is successfully complex and expensive to produce . It is also known that there is direct metal-to-metal contact between the drum and the metal shoe members of the centrifugal clutches. However, the applications for such clutches are severely limited by a very low coefficient of friction, excessive wear and abrasion. Thus, there is a need for a centrifugal clutch that automatically provides a desired torque-speed profile that can moderately change from no-load to full-load on a narrow speed scale, which is safe to fault against the separation of the shoes. in the case of rotating the drum, and that is reliable, long-lasting and inexpensive to produce.

COMPENDIUM OF THE INVENTION The present invention satisfies this need to provide a centrifugal clutch having a combination of interlock of compression deflection springs and springs, and a spring deflected wedge that moderately shifts between low gain and high gain orientations within a narrow speed range. . In one aspect of the invention, the clutch includes a rotating drum having a cylindrical internal surface; a plurality of shoes, each shoe having an external engagement surface for contacting friction with the inner surface of the drum; means for coupling each shoe to a rotating hammer to rotate with it when the hub rotates concentrically with the drum; means for allowing movement of each shoe radially inwardly and outwardly relative to the drum; and a rigid shoe member of each shoe having a first locking portion projecting radially inwardly and a second locking portion projecting radially outwardly, circumferentially spaced apart from the first locking portion, the first and second locking portions of the adjacent shoes locking the shoes to move radially outward by more than one predetermined distance beyond contact with the inner surface of the drum to avoid separation of the shoes in the case of uncoupling axia or structural breakage of the drum.

The means for coupling may include a plurality of fasteners formed on the hub, each fastener engaging one of the corresponding ones of the shoes. Preferably, the means for allowing include a radially oriented notch formed on each clutch shoe for engaging the corresponding latch. Each shoe may have opposite drum contact ends, the notch being located approximately midway between the contact ends. The clutch may include a plurality of compression springs, at least one of the compression springs being positioned for compression between the first and second locking portions of the adjacent shoes to deflect the shoes in a radially inward direction, from the inner surface of the drum, the combination of the springs and the locking portions locking the shoes of the movement radially outward for more than the predetermined distance beyond contact with the inner surface of the drum. The inner surface may have a diameter of approximately 15.24 cm, the compression springs being selected to avoid frictional contact at speeds of the hub below about 1800 RPM. The clutch may be capable of transmitting the torque increasing at a speed of at least 2.07 kg-m per hundred RPM above 1800 RPM. The speed can be at least about 2.76 kg-m per thousand RPM. Preferably, the clutch further includes a guide on each shoe for circumferentially coupling an adjacent shoe, thereby radially stabilizing the shoes relative to the drum. Each guide can be formed through a pair of separate guiding surfaces that look parallel extending from the nearest of the locking portions of the respective shoe, a torque portion of each shoe extending from the other of the locking portions in coupling with the guide surfaces of the adjacent shoe. The guide surfaces of each shoe may extend from the first locking portion, the torque portion extending from the second locking portion. In another aspect of the invention, the clutch includes: the plurality of shoes; the means for attaching each shoe to the rotatable mallet; means for allowing the movement of each shoe radially inwardly and outwardly relative to the drum; the rigid shoe member; and a plurality of compression springs, at least one of the compression springs being positioned for compression between the first and second locking portions of the adjacent shoes to deflect the shoes in a radially inward direction from the inner surface of the drum, the combination of the springs and the locking portions locking the movement shoes radially outward for more than a predetermined distance beyond contact with the inner surface of the drum to prevent separation of the shoes in the case of axial decoupling or structural breakages of the drum. In a further aspect of the invention, the clutch includes the rotating drum; a hammer rotatably mounted with the drum and having a plurality of fasteners extending outwardly, a surface being formed on each of the fasteners; the plurality of shoes; the rigid shoe member; a plurality of wedge members being interposed between the activation surface of a shoe member and the corresponding ramp surface of the hub; and wedge deflecting means for deflecting the wedge members radially inward relative to the shoe members, the combination of the wedge members and the wedge deflecting means providing a first low gain coupling mode, wherein each member The shoe moves circumferentially relative to the hub since the corresponding wedge member moves radially relative to the shoe member; and a second high gain coupling mode, wherein each wedge member is radially fixed relative to the corresponding shoe.

DRAWINGS These and other features, aspects and advantages of the present invention will be better understood by reference to the following description, appended claims and drawings to nexuses, wherein: Figure 1 is a sectional end view of a centrifugal emulsion according to the present invention; Figure 2 is a sectional side view of the clutch of Figure 1; Figure 3 is a graph showing a torque-speed profile of the clutch of Figure 1; Figure 4 is a sectional end view showing an alternative configuration of the clutch of Figure 1 operating and coupled in the low gain mode; Figure 5 is a detailed end view showing the clutch of Figure 4 engaged in a medium gain mode; Figure 6 is a detailed end view showing the clutch of Figure 4 engaged in a high gain mode; Figure 7 is a vector diagram of the clutch of Figure 4 in the low gain mode; Figure 8 is a vector diagram of the clutch of Figure 4 in the high gain mode; and Figure 9 is a graph showing a torque-speed profile of the clutch of Figure 4.

DESCRIPTION The present invention is directed to a centrifugal clutch that is particularly safe, reliable, and effective to move moderately from no load to full load within a narrow speed scale. Referring to Figures 1 - 3 of the drawings, a centrifugal clutch 10 includes a drum 12 having a circularly cylindrical internal surface 14, the drum 12 being rotatably mounted through a pair of ball bearings 16 to an activation arrow 18, the arrow 18 being rotatably mounted concentrically with the drum 12 through conventional means (not shown). A hub 20 having fasteners 22 radially projecting, is fixedly mounted to the arrow 18, the fasteners 22 engaging the corresponding centrifugal shoes 24 moving radially therewith. Each shoe includes a rigid shoe member 26 and a liner 28 for frictional engagement of the drum 12, whereby the transmission capacity of the clutch torque 10 increases with the speed of the arrow 18. The liner 28 extends circumferentially on the shoe member 26 between a front end 30A and a rear end 30B of the liner 28, the ends 30A and 30B being generically referred to as liner ends 30. It will be understood that the shoe member 26 can be adapted for direct contact with the drum 12, the liner 28 being omitted. In reality, the clutch 10 of the present invention can have a full metal configuration in many applications that have been excluded in the prior art. Each of the shoe members 26 is formed with a radially oriented activation notch 32 which is engaged by the corresponding latch 22 of the hub 20. In the illustrative configuration of the clutch 10 as shown, the activation notch 32 is located circumferentially. and l slightly closer to the front end 30A than the rear end 30B of the liner 28 to produce a smooth firing response of the shoes 24. The centrifugal force produced by the frictional engagement is proportional to the square of the rotational speed. It will be understood that locating the activation notch 32 in the middle between the ends 30A and 30B provides a neutral response. Conversely, locating the activation notch 32 closer to the rear end 30B provides a torque profile (of higher gain) characteristic of the rapidly progressive torque of the clutch 10 as described in the US patent. . No. 2, 942, 71 1 mentioned above. According to the present invention, each shoe member 26 has a first engaging portion 34 projecting inward, circumferentially spaced apart, and a second working portion 36 projecting outwards. The locking portions 34 and 36 of the adjacent shoes 24 are interlocked to prevent separation of the shoes 24 by more than a predetermined amount beyond the coupling with the drum 12. Thus, in the case of fracture of the drum 12, or of an axial movement thereof away from the shoes 24, the shoes 24 are advantageously retained in the end-to-end engagement around the arrow 18, instead of being thrown outwards. This is a significant advantage, since the hub 20 is likely to be rotated at significantly higher speeds than those obtained by the drum 12, in the event of breakage of the drum 12. In the bracket 10 shown in the drawings, a plurality Laterally separated from compression springs, designated as the shoe springs 38, is interposed between the first and second locking portions 34 and 36 of the adjacent shoes 24 to divert the shoes 24 inwardly away from the drum 12. The interlock for the coupling longitudinal of the shoes 24, in case the drum fails, is achieved in combination with the springs 38, the springs 38 being helical compression springs. It will be understood that compression springs, such as springs 38, in addition to being less bulky, are inherently stronger in compression than tension springs of equivalent active load capacity, and are less subject to breakage by fatigue. In addition, the structural breakage of the springs 38 does not result in complete loss of support, since the locking portions 34 and 36 provide longitudinal engagement of the shoes 24 even in the absence of the springs 38. Furthermore, the springs 38 are confined between the locking portions 34 and 36 as described below, producing at least some separation between them, even if the springs 30 are fractured. As shown in Figure 2, a pair of disk-shaped retainer members 40 are rigidly clamped on opposite sides of the hub 20 through a plurality of rivet fasteners 42, the shoes 24 being slidably confined between the clamps. retaining members 40. The retainer members 40 also serve to confine the springs 38, between the first and second locking portions 34 and 36 of the shoe members, in the event of fracture of the springs 38. Otherwise, each spring 38 it is located at opposite ends thereof through locating protrusions 44 which are formed on the shoe members 26. As shown further in Figure 2, the shoes 24 have a width W that is approximately 6.35 cm, in the configuration illustratively presented of the clutch 10, the springs 38 being laterally separated into groups of four between each adjacent pair of shoes 24. The locking portions 34 and 36 each solidly the entire length W is extended substantially to improve the prevention of shoe separation in the case of high speed structural breakage of the drum 12. The springs 38 of the shoe are selected to provide a desired threshold speed of engagement S0, the clutch 10 being substantially decoupled below the speed So as shown in Figure 3. In an illustrative and preferred configuration of the clutch 10, the inner surface 14 of the drum 10 has a diameter D of approximately 15.24 cm, each of the three lugs 24 having a weight of approximately 1,135 kg. With the springs 38 selected to provide a force of approximately 83.99 kg between one of the adjacent shoes, the speed S0 is approximately 1 800 RPM. The torque capacity is increased with the centrifugal component of the frictional coupling increasing proportionally to the square of the rotational speed of the hub 20, as discussed above. In this way, the transmission of the torque through the clutch 10 is limited to TN = K (N2-18002), wherein N varies upwards from 1800 RPM and K is proportional to the weight of the shoes 24 and the coefficient of friction between the shoes 24 and the drum 12. When the liners 28 are formed of a representative composition such as RF-38, which is available from Sean Pac of Milwaukee, Wl, the drum 12 being formed of mild steel on the inner surface 14, the clutch 10 is capable of transmitting approximately 1 1 .04 kg-m at 2200 RPM, being suitable for use with a diesel engine determined at 40 horsepower at 3000 RPM, for example, 40 horsepower being equivalent to 9.66 kg-m at 3000 RPM. The torque transmitted by the clutch 10 is initially increased to a gain or speed of approximately 2484 kg-m per 100 RPM as further shown in Figure 3. In this configuration of the clutch 10, the shoes 24 are locked against clearance. beyond a diameter predetermined by the locking portions 34 and 36 of the shoe members 26, at speeds in excess of 3000 RPM, and preferably at least 4000 RPM. Referring further to Figures 4-7, an alternative configuration of the clutch, designated 10 ', has the hub 20 formed with inclined counterparts of the detents, designated 22'. A wedge member 46 is interposed within the activation groove 32 between each shoe member 26 and the corresponding sear 22 ', the wedge member 46 being deviated inwardly to the hub 20 through at least one wedge spring 48 to produce a variable gain torque characteristic of clutch 10 '. More particularly, the wedge member 46 has an inclined wedge surface 50 in contact with the sear 22 ', the wedge surface 50 being inclined at an angle? from a back surface 52 of the activation groove 32, the rear surface 52 being laterally offset from a radial bisector 54 of the groove 32 by a distance C. As shown in Figure 4, the sear 22 'simultaneously contacts itself. with the wedge surface 50 and the rear surface 52 of the activation groove 32, when the wedge member 46 is advanced fully inward relative to the hub 20 through the wedge spring 48, a normal direction of rotation of the hub 20 relative to the drum 12 being conformed to the clock hands as indicated by the curved arrow. As further shown in Figure 4, the shoes 24 can move outwardly to contact the drum 12, while the wedge members 46 are advanced fully inward relative to the hub 20, the wedge member 46 sliding. to contact a front surface 56 of the activation groove 32, the surfaces 52 and 56 of the groove 32 being parallel. This condition of the clutch 10 ', referred to herein as a threshold gain mode, is obtained at the speed S0 and continues until the speed increases at a first intermediate speed Si, at which the wedge member 46 begins to moving outwardly relative to the hub 20 in response to the centrifugal force on the wedge member 46 in combination with a radial torque component that can be applied to the wedge member through the sear 22 'in response to the load of clutch torque 10 '. In the threshold gain mode, the shoes 24 are driven out only by the centrifugal force acting on the shoes 24, the shoe springs 38, and the wedge springs 48, plus the compressive load of the wedge springs 48. , to the extent that these forces overcome the inward deflection of the shoe springs 38. As shown in Figure 5, from a first intermediate speed Si to a second intermediate speed S2, the clutch 10 'operates a first mode of gain, wherein the sear 22 'is no longer in contact with the front surface 56 of the activation groove 32, and the wedge member 46 is displaced partially outwardly within the activation groove 32. In the first gain mode, the shoes 24 are urged outwardly through the centrifugal force and the load of the wedge springs 48, as in the threshold mode described above, with the difference that the load of the wedge springs 48 increases as the wedge member 46 moves outwardly within the activation groove 32. As used in FIG. present, the threshold gain mode and the first gain mode are collectively referred to as a low gain mode. As shown in Figure 6, at speeds exceeding the second speed S2, the wedge member 46 is fully retracted outwardly into the activation slot 32, the clutch 10 'operating in a second mode or high gain, in where the shoes 24 are urged outwardly through the centrifugal force on the shoes 24, the shoe springs 38, the wedge springs 48 and, in addition, the wedge members 46, plus the radial component of the torque reaction torsion against the wedge member 46 by the sear 22 ', and deflected by the inward deflection by the shoe springs 38. It will be understood that the centrifugal force on the wedge members 46 at the second speed S2 (at the start of the high torque) is equal to that of the compressive load of the wedge springs 48. Thus, there is a moderate transition between the low gain and high gain modes in the clutch 10 ', in accordance with the present invention. on The clutch 10 'of Figures 4-6, having a diameter D = 15.24 cm (0.25') and W = 2.85 cm (0.094 '), is configured as described herein for use with a 40 BH P diesel engine. . The factors that will be considered to evaluate the capacity of centrifugal clutches include the diameter of the drum, the weight and the radius of rotation of the shoes, the spring forces applied to the shoes, the radius and the contact angle with the activators that activate the shoes, and the coefficient of friction. In a type of clutch activation (as opposed to a straight centrifugal clutch), the radial component of the force between each fastener and the respective shoe is vectorially added to the centrifugal force of the shoe, the combined forces coupling the torque of the fasteners to the shoes. Thus, the torque capacity of the engine or other source of clutch activation is an additional factor that must be considered. An example of such a source of 40 BHP, known as "Isusa", has a rather flat torque curve, providing 9.93 kg-m at 1400 RPM, 10.19 kg-m at 2400 RPM and 9.97 kg-m at 3000 RPM . In the following analysis, the available torque is taken as the average of the above, TE = 10.03 kg-m. Referring to Figures 7 and 8, the following clutch analysis 10 'is based on the formulas that have been developed and successfully used to evaluate the torque capacity of a clutch as described in the '71 patent, discussed previously, assembled for the moderate start operation, and the same clutch assembled for high activation. The formulas were confirmed in dynamometer tests performed in an independent laboratory, at an accuracy of approximately 1.5%. For the moderate start configuration, which corresponds to the low gain mode of the clutch 10 ', as shown in Figures 4 and 7, the torque capacity, TCL, is found from: TCL = n [FGs-Fs -F ??] μDd where FGS is the centrifugal force on the shoe 24, 0.0003408 WSRGSN ', N being the speed in RPM, Ws the weight of the shoe in kilograms, and RGs the turning radius of the shoe 24. In the configuration of the clutch 10'. , shown in Figure 4, the shoe member 26 has an area of 29.74 cm2 (a volume of 84.98cm3) and a turning radius of 0.0573 meters. By using a concreted nickel-aluminum alloy, having a density of 6.8012 g / cm3, the weight of the shoe member 26 is 0.578 kg. The liner 26 weighs 0.0308 kg, moving in the radius of rotation of the shoe 24 outwards approximately 0.0018288 meters from that of the shoe member 26 only, so that Ws = 0.6097 kg and RGS = 0.04632 meters. Figure 7 shows the shoe 34 rotated slightly from the orientation of Figure 4, so that RGS extends vertically from the center of the hub 20. Also, FSR is the radial component of the forces on the shoe member 26 from the shoe springs 38 and wedge springs 48, FSR = FGS to N = So- In addition, FY1 is a radial component, directed parallel to RGS, of the force between wedge member 46 and shoe member 46, designated FTE , by which the motor torque, TE, is coupled to the shoe 24, the force FTE being directed to an angle? from 20 ° to the X direction. Thus, the motor is transmitting the torque TE, FYI = TF (without?) = 72.7 x .342 n L, (3) (.193) 19,522 kg More generally, F? 1 = .591T, where T is the actual torque that is transmitted by the clutch 10 '. Also, the coefficient of friction μ has been experimentally determined as discussed above to be 0.34. A) Yes, TCL = 0.255 [7.0029 X 10"5 (N -14002) -0.591 Tc] = 1.551 X 10'5N2- 30.409 In the high activation configuration, which corresponds to the high gain mode of the clutch 10 'as shown in Figures 6 and 8, the centrifugal force in the block 46 is added to that of the shoe, so that the torque capacity torsion, Tcw, is of, TCH = [FGs + FGw-FsR-F? 2] μRD wherein FGW is the centrifugal force of the wedge member 46, 0.0003408 W RowN2, Ww the weight of the wedge member 46 in kilograms, and RGW the radius of rotation of the member 46. In the configuration of the clutch 10 ', shown in the Figure 4, the wedge member 46 has an area of 1.98 cm2 (a volume of 8 799 cm3) and a rrnrry nirn R -., .. rltn n DflQI mptrn? On completion of the shoe member 26, the weight of the wedge member 46 is 0.0599 kg, approximately 0.0635 kg, including a pair of shoe springs 38. Figure 38 shows the shoe 24 rotated slightly from the orientation of Figure 7, so that the coordinate axes are aligned with the radius of gyration of the combination of the shoe 24 and the wedge member 46. Also, Fsw is the radial component of the forces on the member of wedge 46 from the wedge springs 38, FSw = FGW to N = S2. In addition, FY2 is a radical component, directed in the Y direction, of the force FN between the projection 44 and the wedge member 46. The force FN is normal to the wedge surface 50 at the angle? 53 ° from a force FTE, by which the torque of the motor Te is coupled to the wedge member 46, the force FN being positively inclined at an angle? of 48 ° from the X direction. Thus, Y2 - Tcsin? nL2cos? Tcsin48 (3 (0.156) cos53 ° = 2.639TC Thus, TCH = 0.255 [7.0029 X 10'5 (N2-14002) + 8.7272 X 10-6N2 + 2.639Tc] = 2.0083 X 10"SN ~ 35 + 0.673TC Tc = 6.140 X 10" SN2 = 107.0 Figure 9 shows TCL and TCH plotted for engine speeds starting at 1400 RPM, the vertically fade line oriented at 1800 RPM indicating the transition from low gain mode to high gain mode. Another vertically oriented fade line is located at 2000 RPM to show that the speed S2 can be adjusted through proper selection of the wedge spring 48. It will be understood that an increase in force from the wedge spring 48 produces a slight upward displacement in the TCL graph that is not plotted in Figure 9, other factors being equal. As also shown in Figure 4, the first locking portion 34 of each shoe member 26 is formed near a rear end 58 of the respective liner 28, the second locking portion being separated beyond a front end 60 of the liner 28. In this manner, the trailing end 58 extends circumferentially at a greater distance from the activating groove 32 than does the leading end 60 to stabilize the pads 24. As shown more in Figure 4, a preferred configuration of the clutch 10 ' It has a pair of adjacent shoes 24 in narrow sliding coupling to improve the dynamic stability of the combination, avoiding vibration, and reducing wear. More particularly, each shoe member 26 has a guide tab 62 extending from the first locking portion approximately in line with the associated shoe spring 38, the guide tab 62 slidably engaging the opposing side surfaces 66 of a guide groove 64 that it is formed in the adjacent shoe member 26. Preferably, the opposite sides of the tongue 62 and the surfaces 66 of the groove 64 are parallel, having a clear of only about 0.0127 cm. The engagement of the tongues 62 with the respective notches 64 thus located adjacent the rear ends 58 and the forward ends 60 of the adjacent shoes 24 in a coincident radial separation from the drum, further stabilizing the dynamic behavior of the shoes 24, as well as ensuring even wear of the liners 28 facing the rear and front ends 58 and 60 of the adjacent shoes 24. Preferably, each of the guide tabs 62 and the grooves 64 extend solidly and substantially all of the width W of the shoes. shoes 24 to further improve dynamic stability by preventing relative twisting between shoes 24, and to resist excessive wear. An additional advantage of the sliding coupling between the shoe members 26 is that the shoes 24 are restrained in a substantially circular relationship, wherein the space between one of the adjacent shoe members is closely matched. Consequently, an uneven hold or "vibration" is prevented through the liners 28 which are held closely concentric with the hub 20. In contrast, the existing centrifugal brackets of the prior art are subjected to excess vibration, where the drum is reasonably flexed towards an eccentric relationship with the hub, in the case of momentary increased frictional engagement between a shoe and the drum, the variation in friction coupling between the shoes and the drum is exacerbated by a shoe moving farther of the hub, while the other shoes are displaced closer to the hub, with a correspondingly increased centrifugal load of one of the shoes and a reduced centrifugal load of the other shoes. The clutch 10 'of the present invention thus provides a particularly advantageous combination of soft start and high gain which provides a high capacity in a relatively small package. Automatic scrolling between low and high gain modes is bidirectional. Thus, the clutch 10 'also provides protection against excessive overloading of the power source, since the low gain mode enters almost immediately by the occurrence of a blockage of a pump, for example, and although the clutch 10' can finally Overheating, the more expensive pump and motor are protected by the clutch 10 'from damage that might otherwise occur. Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. For example, liners 28 may be omitted as discussed above. Also, the angle? it can be selected for more or less activation of the clutch 10 '. The diameter D can be selected according to the application on a wide scale, such as from 2.8575 cm to more than 1.82 meters. Operating speeds may vary from less than 500 RPM to over 10,000 RPM. Therefore, the spirit and scope of the appended claims should not ssarily be limited to the description of the preferred versions contained herein.

Claims (10)

1. CLAIMS 1 .- A centrifugal clutch comprising: (a) a rotating drum having a circularly cylindrical internal surface; (b) a plurality of shoes, each shoe having a front contact end and a rear contact end, an external coupling surface extending between the contact ends for frictional contact of the inner surface of the drum; (c) means for coupling each shoe to a rotating hammer to rotate therewith when the hub rotates concentrically with the drum; (d) means for allowing movement of each shoe radially inwardly and outwardly relative to the drum; and (e) a rigid shoe member of each shoe having a first locking portion projecting radially inwardly and a second locking portion projecting radially outward, circumferentially spaced apart from the first locking portion, the first and second locking portions of one of the members of adjacent rigid shoes locking the shoes of the movement radially outward for more than a predetermined distance beyond contact with the inner surface of the drum to prevent separation of the shoes in the case of axial decoupling or structural breakage of the drum during operation high clutch speed.
2. 2. The clutch according to claim 1, wherein the means for coupling comprise a plurality of fasteners formed on the hub, each fastener coupling one of the corresponding shoes.
3. 3. The clutch according to claim 2, wherein the means for permitting comprise a radially oriented notch formed on each shoe for coupling the corresponding latch.
4. 4. The clutch according to claim 3, wherein each shoe has opposed drum contact ends, the notch being located approximately midway between the contact ends.
5. 5. A centrifugal clutch comprising: (a) a rotating drum having a circularly cylindrical internal surface; (b) a rotatably mounted hub concentric with the drum and having a plurality of outwardly facing fasteners, a fastener surface being formed on each of the fasteners; (c) a plurality of shoes, each shoe having an external engagement surface for frictionally contacting the inner surface of the drum; (d) a rigid shoe member of each shoe having an activation surface extending inwardly for engagement with one of the corresponding latches for rotation therewith, the activation surface allowing movement of each shoe radially inwardly and outwardly in relation to the drum; (e) a plurality of wedge members, each wedge member being interposed between the activation surface of a shoe member and a corresponding detent surface of the hub; and (f) means of wedge deflectors for deflecting the wedge members radially inward relative to the shoe members, the combination of wedge members and wedge deflection means providing: (i) a first gain coupling mode low, wherein each shoe member moves circumferentially relative to the hub as the corresponding wedge member moves radially relative to the shoe member, while engaging the clutch torque between the hub and the hub member. shoe and (ii) a second high gain mode, wherein each wedge member is radially fixed relative to the corresponding shoe, the wedge member continuing to engage the clutch torque between the hub and the shoe member.
6. 6. The clutch according to claim 5, further comprising first and second integrally formed locking portions, spaced near the opposite ends of each shoe member., which engage the respective locking portions of the corresponding shoe members by securing the shoes against the separation of the shoes in the case of axial decoupling or structural breakage of the drum during high speed operation of the clutch.
7. 7. The clutch according to claim 1 or 6, wherein it further comprises a plurality of compression springs, at least one of the compression springs being positioned for compression between the first and second locking portions of one of the shoes. adjacent to divert the shoes in a radially inward direction from the inner surface of the drum, the combination of the springs and the locking portions locking the shoes of the movement radially outward by more than the predetermined distance beyond contact with the inner surface of the drum. drum.
8. 8. The clutch according to claim 7, wherein the internal surface has a diameter of about 15.24 cm, and the compression springs are selected to avoid frictional contact at speeds the mace below about 1800 RPM.
9. 9. The clutch according to claim 8, wherein the clutch is capable of transmitting the torque that increases at a speed of at least about 2.07 kg-m per hundred RPM above 1800 RPM.
10. 10. The clutch according to claim 9, wherein the speed is at least about 2.76 kg-m per hundreds of RPM. 1 .- The clutch according to claim 1 or 6, wherein it further comprises a guide rigidly placed on each shoe member to circumferentially couple an adjacent shoe member, thereby radially stabilizing the shoes relative to the drum. 12. The clutch according to claim 1, wherein each guide is formed by a pair of parallel guiding surfaces that look parallel, integrally extending from one of the circumferentially close contact ends of the respective shoe, a portion of torque of each shoe rigidly extending from the other of the circumferentially close contact tips into engagement with the guide surfaces of the adjacent shoe. 13. The clutch according to claim 12, wherein the guide surfaces of each shoe extend from the circumferentially close front contact end, the torque portion extending from the circumferentially close rear contact end. 14. The clutch according to claim 12, wherein the guide surfaces are formed with a gap of no more than about 0.0127 cm, on the respective tongue portions. 15. The clutch according to claim 1, wherein the shoe members each or not have a total width, and the guides have a locating contact with the adjacent shoes substantially and completely over the entire width to improve the stability dynamics of the shoes in relation to the drum. 16. The clutch according to claim 1, wherein the internal surface has a diameter of approximately 15. 24 cm, and the locking of the shoes through the locking portions of the shoe members is effective at rotational speeds of at least 3000 RPM. 17. The clutch according to claim 1, wherein the shoe members each have a width, and the locking portions of the shoe members each extending solidly over the entire width. SUMMARY A centrifugal clutch (10) includes a rotating drum (12) having a circularly cylindrical internal surface (14); a plurality of shoes (24), each shoe having an external engaging surface (28) for frictional contact of the inner surface of the drum, each shoe being coupled to a rotating hub (20) to rotate therewith as the hub rotates concentrically with the drum, the movement of each shoe is allowed radially inwardly and outwardly relative to the drum; a rigid shoe member (26) of each shoe having a first locking portion projecting radially inwardly (34) and a second locking portion projecting outwardly (36) circumferentially spaced apart from the first locking portion; and a plurality of compression springs (48), at least one of the springs being positioned for compression between the first and second locking portions of one of the adjacent shoes to deflect the shoes in a radially inward direction from the inner surface of drum, the combination of the springs and the locking portions locking the shoes moving radially outward for more than a predetermined distance beyond contact with the inner surface of the drum to avoid separation of the shoes in the case of axial decoupling or structural breakage of the drum. A movable wedge member (46) can be interposed between a sear (22) of the hub and a corresponding notch (22) of each shoe member to provide low and high gain modes. The dynamic stabilization can be improved through narrow fitting circumferential guides (66) that couple the adjacent shoes.