Variable speed power transmission for small vehicles and the like

#The invention relates to power transmission devices, and more particularly to a transmission device capable of infinitely changing ratios and reversing rotation without disengaging and shifting gears.

#Power transmission devices including a rotatable carrier member supporting a counter shaft for providing two different output shaft speeds are well known in the transmission art. See, for example, U.S. Pat. No. 602,253. The counter shaft on the carrier member usually includes a gear enmeshed with a gear on the input shaft and another gear enmeshed with a gear on the output shaft. Means are provided for engaging the carrier member for direct rotation with the input shaft, thereby driving the output shaft along with the carrier and the input shaft, or for restraining the carrier member against rotation, thereby driving the output shaft at a different speed from the input shaft. When the carrier member is neither driven or restrained, a non-driving or neutral mode is established. While such transmissions are useful for providing two output speeds, such as in an overdrive for a vehicle, they are limited to such uses and cannot provide variable speeds, reverse speeds or change ratios as does the present invention described below.

#The present invention provides a variable speed forward and reversing transmission for use as a transmission-clutch for a garden tractor, lawn mower or other small service vehicle. In the preferred embodiment of the invention, the apparatus includes infinitely variable forward and reverse speeds, a principal forward speed, and a neutral.

#FIG. 1 is a sectional plan view, in part schematic, of a power transmission according to the invention, illustrating in solid outline the setting of the shift device thereof for primary speed (1:1 gear ratio) "forward" mode of operation;

#FIG. 2 is a fragmentary sectional view of the shift device of FIG. 1 in another setting for "forward" variable gear ratio mode of operation;

#FIG. 3 is a fragmentary sectional view like FIG. 2 showing still another setting of the shift device for "reverse" mode of operation; and

#In the drawings, FIG. 1 may be considered a plan view of the power transmission apparatus according to the invention. The apparatus includes a primary transmission device 10 and a secondary transmission device 11 each rotatably mounted on structural members of a vehicle in which the transmission apparatus is incorporated. The primary transmission 10 is rotatably mounted in a bearing 12 journaled in vehicle member 13 and bearing 14 journaled in member 15. Rotatable on and with respect to a pump shaft 16 is a housing 17 of the primary transmission which supports an internal housing shaft 18 (also referred to as counter shaft 18) parallel to the pump shaft 16. Counter shaft 18 is rotatable in housing 17 and is driven and is driveably connected with gear 19 keyed thereon in mesh with gear 20 keyed on pump shaft 16. Preferably, gears 19 and 20 are of different diameter, the gear 20 on the pump shaft being the larger, which provides the most efficient means of control by the pump. An output shaft 21 is rotatable independently of the bearing 14 on the opposite axial side of housing 17 and is coaxial with the pump shaft 16. A sprocket 22 is keyed on the inner end of shaft 21 for rotation together. A similar sprocket 23 is keyed on counter shaft 18 and is driven by the latter. The sprockets 22 and 23 are connected for rotation together by endless chain 24. Preferably, one of the internal connections comprises enmeshed gears (such as 19, 20), and the other comprises chain-connected sprockets (such as 22, 23), so that the direction of rotation of the output shaft 21 is that of the housing 17 when the counter shaft 18 rotates, forming the forward speed of the transmission apparatus. The relative sizes of the gears 19, 20 and of the sprockets 31, 32 are chosen according to the desired gear ratio of the transmission. As stated the larger gear 20 is selected for the pump shaft 16. As an example, the gears in the primary transmission may provide a ratio of 1:5, but a higher or lower ratio could be used. Preferrably, the gear ratio is different than 1:1. A counterweight 25 may be included on the housing to counter balance countershaft 18, gears 19, sprocket 23 and chain 24.

#The housing 17 of primary transmission device 10 is rotatably driven through a power shaft 26 rotatably supported in a part of the vehicle member 13 and connected to a power source, such as the engine of the vehicle (not shown). An input rotary drive means for the housing 17 is provided by the drive gear 27 running the endless drive chain 28 reeved about the annular gear 29 fastened securely on the perimeter of housing 17.

#A variable resistance means is connected with shaft 16 for restraining rotation of the shaft and gear 20 thereon. The variable resistance in the illustrated embodiment herein comprises an hydraulic pump 30 to be driven by pump shaft 16. When pump shaft 16 is rotated, the pump 30 circulates a fluid through a closed circuit conduit which includes line 31 in which is positioned an adjustable flow regulating valve 32. For preventing or substantially preventing rotation of the gear 20, the valve 32 may be completely closed. This causes the driven housing 17 to run gear 19 on gear 20 and rotate counter shaft 18. Shaft 18 drives output shaft 21 through the sprockets 23, 22 and chain 24. Assuming clockwise rotation of the housing 17, this causes the output shaft 21 to be driven clockwise; and assuming the secondary transmission device (to be presently described) is in the "forward" mode of operation, completely closing valve 32 in the pump circuit produces the maximum variable gear ratio (1:5 in the stated example) of the primary transmission device 10. On the other hand, by fully opening the valve 32 to reduce the resistance load of pump 30 to its minimum, neutral mode is obtained. Therefore, through the manipulation of the single control (valve 32), the rotation of the output shaft 21 can be controlled very precisely without varying the speed of the engine. An almost infinite combination of gear ratios designed into the transmission are available; in the example above given, any gear ratio between 1:1 and 1:5 can be obtained.