Coplanar reverted gear train loop

Details Coplanar reverted gear train loop Coplanar reverted gear train loop

2002-04-05

2003-12-30

Lorence, Richard M. (Department: 3681)

Planetary gear transmission systems or components

Planet periphery surrounds axis of interacting gear

Means to change speed ratio between input and output

C192S048910, C192S066210

Reexamination Certificate

active

06669594

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a variable ratio gear box. In particular, the present invention relates to a variable ratio gear box employing a coplanar reverted gear train loop and a clutch assembly for changing the gear ratio of the gear box.
BACKGROUND OF THE INVENTION
Conventional variable ratio gear boxes typically include an input shaft, an output shaft, a pinion gear coupled to each shaft, and a cage assembly disposed around the input and output shafts. The cage assembly comprises at least one pair of cluster gears coupled to the pinion gears and mounted on a shaft adjacent to and parallel to the input and output shafts. A clutch assembly selectively couples the cage assembly to the gear box housing to provide a first gear ratio, or to the input or output shaft to provide a second gear ratio. The conventional variable ratio gear box may include a series of cascaded cage assemblies for providing a plurality of gear ratios.
The conventional variable ratio gear box has been widely used in manual incrementally-variable transmissions. However, the manufacture and assembly of such transmissions has been troublesome due, in part, to the difficulty of aligning the teeth of each gear element of the cluster gears to each other. Further, radial alignment errors of the cluster gear elements or their mounting shaft can cause uneven load sharing. Additionally, the cluster gears and pinions are generally manufactured with helical teeth to increase the contact ratio between the cluster gears and opinions. However, the use of helical teeth produces point contact between congruent teeth flanks, thereby subjecting teeth bearing surfaces to high contact stresses.
Attempts have been made to overcome the deficiencies of the conventional variable ratio gear box. For example, Roeder (U.S. Pat. No. 2,005,167) teaches an incrementally-variable transmission comprising coaxial input and output shafts, and a coplanar reverted gear train loop coupled to the input and output shaft through a rotating clutch. The coplanar reverted gear train loop comprises a toothed section disposed around the input shaft, a first ring gear disposed around the toothed section, a second ring gear disposed around the first ring gear, and an eccentric mounting ring for maintaining the first ring gear eccentric to the toothed section. The second ring gear is coupled to the output shaft and is coaxial to the toothed section. The rotating clutch is coupled between the input shaft and the mounting ring. When the clutch engages the mounting ring, the mounting ring rotates with the input shaft, thereby providing a first gear ratio of unity. When the clutch is disengaged from the mounting ring, a pair of toothed rings secured to the transmission housing hold the mounting ring against rotation, thereby providing a second gear ratio. Since the transmission does not require multiple gears to be mounted on a common shaft, the design reduces the alignment problems associated with the conventional variable-ratio gear box.
Gear changes are effected by providing the inner end of the input shaft with a series of axially extending teeth for slidably engaging with a similarly toothed hub carried on the input shaft. The hub is coupled to ratchet-toothed cylinder which engages a similarly-toothed cylinder coupled to the driving means. The rotating clutch is provided with actuation arms which engage a cam formed on the input shaft. With little or no load applied to the output shaft, the clutch engages the mounting ring to thereby produce the first gear ratio. However, when the load on the transmission increases, the ratchet teeth force the input shaft to be axially displaced. As a result, the cam applies pressure to the actuation arm, thereby disengaging the clutch from the mounting ring and producing the second gear ratio.
The transmission taught by Roeder includes a series of cascaded coplanar reverted gear train clutch assemblies for providing a plurality of gear ratios. However, as gear changes are affected by axial displacement of the respective input shafts, the transmission is only capable of producing gear ratios in which either all of the coplanar gear loops rotate with their respective input shaft, or one of the coplanar gear loops rotates with its respective input shaft and the mounting rings of all the preceding coplanar gear loops are held against rotation. Therefore, the total number of gear ratios available is limited. Furthermore, manufacturing and assembly costs are unnecessarily increased since the transmission requires both a rotating clutch, and toothed rings secured to the transmission housing. Accordingly, there remains a need for a variable ratio gear box which reduces the alignment problems associated with the prior art without limiting the number of gear ratios available and without unnecessarily increasing manufacturing and assembly costs.
Attempts have also been made to produce gear elements having an increased contact ratio between congruent teeth flanks. For example, Rennerfelt (U.S. Pat. No. 5,030,184) teaches an eccentric gear comprising a fixed spur gear having internal teeth, an eccentric cam secured to the input shaft of the eccentric gear, and an eccentric gear wheel rotatably coupled to the eccentric cam and having teeth engaging the internal teeth of the fixed spur gear. The teeth of the eccentric gear wheel and the teeth of the fixed spur gear are corrected by profile shifting to prevent collisions between the teeth and by stubbing to prevent collisions between the lands. The patentee states that the described profile shifting and stubbing increases the number of teeth in mesh. However, the patentee also acknowledges that, in theory, only one tooth in each loading direction will simultaneously be in mesh and that, in practice, one can achieve a greater number of teeth in mesh only by relying on the resilient nature of the teeth. However, such a practice can only increase the stress on each tooth. Accordingly, there remains a need for gear box having gears manufactured with teeth shaped to increase the contact ratio between congruent teeth flanks so as to reduce contact stress on the teeth bearing surfaces.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a variable ratio gear box having reduced sensitivity to gear alignment and having a greater number of available gear ratios in comparison with prior art gear boxes. It is also an object of the present invention to provide a variable ratio gear box having gears manufactured with teeth shaped to have an increased contact ratio between congruent teeth flanks.
In accordance with these objects, in a first embodiment of the invention there is provided a variable-ratio gear assembly comprising torque input means, torque output means, at least two intercoupled independently-variable coplanar reverted gear train loops coupled to the torque input means and the torque output means, and a clutch for varying a velocity ratio of the coplanar reverted gear train loops. Each coplanar reverted gear train loop comprises a torque input member, a torque output member and a reactive member. The clutch is coupled to the coplanar reverted gear train loops for independently switching at least two of the members from coupling to one of a rotational reference, the torque input means and the torque output means to coupling to another of the rotational reference, the torque input means and the torque output means.
In a second embodiment of the invention, there is provided a variable-ratio gear assembly comprising a coplanar reverted gear train loop including a primary torque input member, a primary torque output member, a primary torque reactive member, and an auxiliary torque member; and a clutch for varying a velocity ratio of the gear loop. The auxiliary torque member is one of a secondary torque input member, a secondary torque output member and a secondary reactive member. The clutch is coupled to the gear loop for switching the primary reactive member between coupling to one of a rotational reference, the primary torque inp

Affiliated with

Also associated with

Rating

Coplanar reverted gear train loop does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Coplanar reverted gear train loop, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coplanar reverted gear train loop will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3138303