There are, however, other types of speed changers in use including traction drive speed changers. These depend on friction between rolling elements to transmit torque from the input member to the output member.

The rolling elements are held together with a prescribed normal force to generate the required friction force based on the power to be transmitted by the device. However, these devices are not self-actuating. Further, these devices often require a separate clutch to allow the output to be disengaged from the input.

It is therefore a principal object of this invention to provide a traction drive speed changer which is self-actuating.

It is a further object of this invention to provide a traction drive speed reducer that does not require a clutch.

A further object of this invention is to provide a self-actuating traction drive speed changer wherein the normal force on the roller members is only present when needed to permit the rolling elements to be operationally disengaged.

A still further object of this invention is to provide a self-actuating traction drive speed changer which can be easily engaged and disengaged in response to changing speed requirements.

These and other objects will be apparent to those skilled in the art.

SUMMARY OF THE INVENTION A self-actuating traction drive speed changer has a movable force input element having a planar drive surface, and a movable force output element having a planar drive surface which is connectable to an output load. One or more movable roller elements has a planar drive surface operatively connected for movement to the input element, and are in frictional engagement with the planar drive surface of the output element so that movement of the input element will cause the planar drive surface of the roller element to engage and frictionally move the output element.

A modified form of the invention mounts the input and output elements on one each of a pair of spaced support elements. An elongated link having a center and opposite ends is pivotally secured at its center to one of the support elements. One each of first and second roller elements are secured to the ends of the link with each roller element having a planar drive surface. The planar drive surface of the first roller element is in friction driving engagement with the planar surface of the input element. Rotation of the input element will rotate the first roller to pivot the link so that the planar drive surface of the second roller will engage the planar drive surface of the output element to rotate the output element.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational view of the speed changer of this invention; Figure 2 is an elevational view similar to that of Figure 1 with a support plate shown thereon; Figure 3 is an elevational view similar to that of Figure 1 but shows the roller elements in a state of physical separation or disengagement with the output element; Figure 4 is an elevational view similar to that of Figure 1 but shows the use of additional roller elements suitable for use in a transmission environment; Figure 5 is a perspective view of this invention in a planetary system; Figure 6 is a sectional view taken on line 6-6 of Figure 5; Figure 7 is a schematic view of a pair of rollers reflecting the normal and tangential forces exerted thereon; Figure 8 is a free body diagram of roller 4 of

Fig. 7; Figure 9 is an elevational view of an alternative form of the invention utilizing a linear output; Figure 9A is a view similar to that of Figure 9 but shows an alternative way to obtain linear output; Figure 10 is an elevational view of a further alternative embodiment of the invention showing the use of a single roller element; and Figure 11 is a view similar to that of Figure 10 wherein the input element is located externally of the output element.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to Figure 1, the speed changer 10 has a horizontal base mounting plate A to which is rigidly mounted a vertical back mounting or support element B. A bearing 12 having a center axis C supports force input shaft D. A roller E is cylindrical in shape and is rigidly mounted on shaft D.

Roller E has cylindrically shaped planar drive surface 13. The term"planar drive surface"as used herein designates a relatively smooth"non-tooth" surface, such as the exterior surface of a geometric cylinder or cone. Inner roller F and outer roller G (also denominated as"3"and"4", respectively) are rotatably mounted on the inner and outer ends 14 and 16, respectively, of links H. (Cylinders or conical shapes can be used.) Links H are pivotally mounted at their center 18 on center pins I. Pins I are mounted in radially extending slots 19 on a middle supporting plate Al (Fig. 2) which in turn is secured any convenient way (not shown) to base A. In Figure 1, the pins I are mounted on plate B, for plate Al is removed. Inner and outer rolls F and G are rotatably mounted by pins 20 and 22, respectively, to the respective ends 14 and 16 of links H. (In both Figs. 1 and 2.) Slots J on the outer ends of link H receive the pins 22 of outer rollers G.

Slots J (Figure 1) allow the inner and outer rollers F and G to press against one another, generating sufficient torque to transmit through the unit. Each of the inner and outer rolls F and G have a planar drive surfaces 13. The links H and inner and outer rollers F and G are free to rotate about pins I, with the center axes of pins I being the axes of rotation of the links.

In Figure 2, the slots 19 are elongated to allow the links H and the inner and outer rollers F and G to seek a configuration with the inner roller F pressed firmly against the input roller E, and the output roller G pressed firmly against the inner surface of output roller K. The inner surface 24 of output roller K is a planar drive surface.

As the input shaft D and roller E rotate counterclockwise, the links H and rollers F and G rotate clockwise and the pins I move radially outwardly in their respective slots 19. Because of the inclined orientation angle of the intermediate roller assemblies (links H and rollers F and G), the clockwise torque generated on the output roll K by the output load produces the necessary normal forces to press the rolling members against one another.

This in turn creates sufficient friction between rolling elements to prevent slip.

Furthermore, the angle of inclination is designed for the expected coefficients of friction to ensure that slip will not occur no matter what the output load.

Hence, the traction effect is automatically achieved at just the right level to transmit the instantaneous torque required for the unit.

Figure 3 shows the assembly of Figure 1 in an"overrun"mode when the speed of rotation of output roller K has risen to a given level, and the speed of rotation of input shaft D has been reduced from its initial speed. In that situation, the output rollers"disengage"the surface 24 and no longer convey rotational power to K. The term"disengage"herein refers to withdrawing rotational power, and not necessarily withdrawing physical contact. In either situation, the output element K continues to rotate ("coast") at its given speed even though the speed of input element D is decreased or eliminated.

The geometry of the device is designed so that, given a specific coefficient of friction between the various contacting surfaces, the appropriate normal force will be induced, which will allow the required tractive force to be generated. Thus, the device will not slip, no matter how much load is applied to the output member. Parts will fracture before slippage occurs.

DESCRIPTION OF FIRST ALTERNATIVE EMBODIMENT OF THE INVENTION Figure 4 shows an embodiment of the invention that is used for a transmission with two different speed ratios. Along a vertical line are two intermediate roller assemblies with outer rollers labeled A, and along a horizontal line are two other intermediate roller assemblies with outer rollers labeled B.

The A set of rollers is shown engaged while the B set of rollers is disengaged. The general idea is that the diameters of the A set of rollers are designed to be different than the B set of rollers. This produces different speed ratios for the two sets of rollers. Thus, the device is shifted from one speed to another by disengaging by any convenient means (not shown) the A set of rollers and engaging the B set of rollers. More than two sets of rollers can be included in the device, allowing for more than two speed ratios.

It should be noted that for this configuration, the output member rotates in the same direction as the input member. It should also be noted that for the configuration shown in Figures 1-4, the input member must rotate counterclockwise to drive the output member through the intermediate roller assemblies. If the input member rotates clockwise, the output member will not rotate because the intermediate roller assemblies are inclined to self actuate for counterclockwise rotation.

If the input member rotates counterclockwise driving the output member counterclockwise, and the output member speeds up in a counterclockwise direction, it will simply overrun the input and coast along at the higher speed.

DESCRIPTION OF THE SECOND ALTERNATIVE EMBODIMENT OF THE INVENTION Figures 5 and 6 show a modification of the structure of Figure 1. Input roller 2 engages inner roller 3 which drives outer roller 4 which engages inner surface 24 of output roller 5. Links H support rollers 3 and 4 by pins 20 and 22, respectively. Links H are pivotally mounted by pins I to bracket 26 which

has three radially extending arms 28. Bracket 26 is rotatably mounted on input shaft C1. Drive bracket 30 with three radially extending arms 32 is rigidly secured to input shaft D. Arms 32 terminate in slots 34 which slidably and pivotally engage pins J on links H. Input shaft D drives bracket 30 which drives links H supported on the arms 28 of bracket 26. The rollers 4 and 3 function as rollers F and G in Figure 1.

The"sun gear"2 can be held in a stationary position with the receiving structure to rotate therearound.

Figure 7 shows one set of dimensioned intermediate rollers 3 and 4.

Relationships were developed to calculate the angles. and α2 in terms of radii of the various members. In conjunction with friction coefficients, these angles are critical to ensure the speed changer's self-actuating characteristic.

The distances along horizontal and vertical directions were considered to obtain: By squaring and adding these two equations to eliminate I P 11, and 72 and solve for : Similarly, ß and Q were eliminated to solve for (a, +a2) ;

By rearranging the same scalar equations so that when squared and added, and #. were eliminated.

This provides a solution for a, : Where R is: R = {(r2 + r3)2 + r32 + 2r3(r2 + r3)cos#}1/2 Thus, 0, dz and a2 are calculated once the values are set for the radii of all the members.

Summation of forces and torques in Figures 7 and 8 produces two scalar equations for the normal forces, F3 and F4: where F = F3 = F4

To prevent slip between the input member E and the inner roller F (3) as well as between the outer roller G (4) and the output member K (i.e., Figure 1): <BR> <BR> <BR> <BR> <BR> <BR> # f # µ3F3<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> ! where jj. g is the coefficient of friction between the input member E and the inner roller F and p4 is the coefficient of friction between the outer roller G and the output member K.

By combining these inequalities with both of the above equations, the minimum requirements for the coefficients of friction to avoid slip are Similarly, to ensure that slip does not occur between inner and outer rollers F and G : where µ34 is the coefficient of friction between the inner and outer rollers 3 and 4.

DESCRIPTION OF A THIRD ALTERNATIVE EMBODIMENT OF THE INVENTION It should be understood that the input and output can be linear in nature and not just rotational. Further, this invention can use various combinations of linear input or output with rotational input or output. Two types of the linear concepts are shown in Figures 9 and 9a.

In Figure 9, a stationary linear member 1 is located opposite and in spaced relation to movable linear member 7. Both members have planar drive surfaces 13. Member 7 has an outer surface 13A in engagement with rolls 36 mounted on stationary brackets 38. An inclined arm 2 located in a plane parallel to the plane occupied by members 1 and 7 pivotally supports compound concentric rolls 3,4 and 5,6 by pins 40. Rolls 3 and 4 are of unitary construction as are rolls 5 and 6. All the rolls 3,4,5 and 6 have planar drive surfaces 13. Roll 3 engages linear member 1; roll 4 engages roll 5; and roll 6 engages linear member 7. As shown in Figure 9, an input force F applied to the outer end of arm 2 will result in a linear output force P in member 7 through rolls 3-6. Thus, if F moves upward a distance d, and if roll 3 moves without slipping on linear member 1, roll 3 will rotate along with roll 4 in a counterclockwise direction.

Since there is no slip, points on the periphery of roll 3 that contact 1 at the initial and final times are separated by an arc length equal to d. Hence, the member compound roller consisting of rolls 3 and 4 rotates <BR> <BR> <BR> <BR> <BR> <BR> d<BR> 034 =- r3 Then, if rolls 4 and 5 roll without slippage relative to one another, the compound roller consisting of rolls 5 and 6 rotates clockwise <BR> <BR> 0 r40<BR> <BR> <BR> <BR> <BR> <BR> /#56 = r5#324

Roll 6 then rolls without slip relative to linear member 7 for a distance s given by s = r6056 When the first two above equations are substituted into the foregoing equation, the value of s is r4r6 <BR> <BR> S = d<BR> r3r5 Finally, the distance member 7 moves relative to member 1 is If the product r4r6 < r3r5 then member 7 will move upwardly for a distance less than arm 2. If, however, the product r4r6 > r3r5 then member 7 moves down while member 2 moves upwardly. If the two products are equal, then member 7 remains stationary while member 2 moves upwardly.

The work input and work output are reflected in: Fd = Py (8) When equation (5) is substituted into (8), F has a value of: The arrangement shown in Figure 9a is similar to that of Figure 9 except arm 2 of Fig. 9 is substituted by roller 2 in Fig. 9a which is rotatably mounted on a fixed bracket 2a, and rolls 3,4 and 5 and 6 are rotatable at fixed bracket 2c.

DESCRIPTION OF FOURTH ALTERNATIVE EMBODIMENT OF THE INVENTION In Fig. 10, input roll 2 rotates about fixed axis 2a within the circumference of output roll 5 which rotates about offset fixed axis 5a. An arm 3 has its inner end pivoted at 2a, and its outer end rotatably supports roll 4 within elongated radial notch 3a. Rolls 2,4 and 5 have planar drive surfaces 13. Roll 4 engages the surface 13 of roll 2. The arm 3 is moved from the position of the dotted lines in Figure 10 to the position of the solid lines by some means not shown. This causes roll 4 to engage rollers 2 and 5 by moving into the converging space 42, whereupon output roll 5 will rotate in a clockwise direction.

The arrangement in Figure 11 is similar to that of Figure 10 except that the axes of rotation 2a and 5a of rolls 2 and 5 are separated further so that roll

2 is not located within the periphery of roll 5. Rather, the rolls 2 and 5 are not overlapping, and roll 4 engages the outer planar drive surface 13a rather than the inner surface 13 as was the case in Fig. 10.

The geometry of the device is designed so that, given a specific coefficient of friction between the various contacting surfaces, the appropriate normal force will be induced, which will allow the required tractive force to be generated. Thus, the device will not slip, no matter how much load is applied to the output member. Parts will fracture before slippage occurs. Also, the device can be configured to operate in one direction only, and it will"overrun" in the opposite direction. Or, if one or more intermediate roller pairs are oriented in the opposing direction, the device can be operated in both directions.

From the foregoing, it is seen that this invention in its several embodiments will accomplish at least all of its stated objectives.