One-way pawl clutch with backlash reduction means and without biasing means

• US 8,210,331 B2
• Filed: 03/02/2007
• Issued: 07/03/2012
• Est. Priority Date: 03/06/2006
• Status: Active Grant

• Current Assignee: Hossein Estahbanati Keshtkar
• Original Assignee: Hossein Estahbanati Keshtkar
• Inventors: Keshtkar, Hossein Estahbanati
• Primary Examiner(s): Le, David D
• Assistant Examiner(s): Dodd, Ryan
• Application Number:
  US11/713,130
• Publication Number:
  US 20070205069A1
• Time in Patent Office: 1,950 Days
• Field of Search: 192/46, 192/45.1, 192/41.R
• US Class Current: 192/46
• CPC Class Codes: F16D 41/12 with hinged pawl co-operating with teeth, cogs, or the like F16D41/02, F16D41/24 take precedence

Abstract

One-way clutches primarily employ a driving ring, a driven ring, and a number of identical connectors. The driving ring and the driven ring are rotationally detached, are coaxial, and are configured to house the connectors between them. In one rotational direction, the connectors engage the driving and the driven rings, causing them to rotate in unison. In the opposite rotational direction, the connectors disengage the driving and the driven rings, causing them to freewheel. All existing one-way clutches are aided by means that bias the connectors toward engagement, introducing noise, wear, and heat while freewheeling. Additionally, existing one-way clutches that utilize relatively more efficient pawls as connectors, undergo relatively more backlash from freewheeling to engagement, introducing operational imprecision. The one-way clutch in the present invention utilizes pawls for maximum mechanical efficiency. Furthermore, this invention does not require any biasing means, and its backlash can be reduced to any desirable degree.

Claims

1. A one-way clutch mechanism comprising a driving ring, a driven ring, and a pawl ring, wherein the said three rings are coaxial and the driven ring is disposed between the driving ring and the pawl ring;

and furthermore, the mechanism comprises a generally L-shaped pawl comprising an arm, a corner, and a stem, where the free end of the pawl stem is pivoted to the pawl ring in such a way that the pawl arm is disposed between the driving ring and the driven ring;

and furthermore, the driven ring, on one surface facing the driving ring, comprises an engaging means for receiving the free end of the pawl arm;

and furthermore, the driving ring and the pawl arm are operatively coupled so as to facilitate two distinct modes of operation;

namely, the freewheeling mode and the engagement mode;

where, in the freewheeling mode, the said coupling acts in such a way that rotation of the driving ring in a first rotational direction causes the free end of the pawl arm to move toward the driving ring until the pawl arm contacts the driving ring, at which point the driving ring, the pawl, and the pawl ring rotate in unison in the same direction without affecting the driven ring;

and where, in the engagement mode, the said coupling acts in such a way that rotation of the driving ring in a second rotational direction causes the free end of the pawl arm to move away from the driving ring until the pawl arm contacts the driven ring, at which point additional rotation of the driving ring in the same direction maintains the said contact until the pawl arm is fully engaged with the engaging means on the driven ring, from which point the entire mechanism rotates in unison in the same direction;

and evidently, while in freewheeling mode, the pawl is not biased toward maintaining contact with the driven ring and hence does not ratchet against the driven ring.

2. The mechanism recited in claim 1 in which the said three rings are stacked radially, the pawl ring encircles the driven ring, and the driven ring encircles the driving ring.

3. The mechanism recited in claim 1 in which the said three rings are stacked radially, the driving ring encircles the driven ring, and the driven ring encircles the pawl ring.

4. The mechanism recited in claim 1 in which the said three rings are stacked axially such that the driven ring is disposed between the driving ring and the pawl ring.

5. The mechanism recited in claim 2 where the three coaxial rings are augmented to support each other radially and axially without altering their intended functions, and the pawl is augmented to contain an axial plane of symmetry without altering its essential geometrical and operational features;

and accordingly, the radial cross section of the driving ring assumes the shape of T, consisting therefore of a flange and a web, with the web pointing radially outward, while the radial cross section of the driven ring assumes a shape such that when the driven ring is assembled onto the driving ring, their combined radial cross section is rectangular having a hollow core in the shape of T, consisting therefore of a flange and a web, with the web pointing radially outward;

and furthermore, the radial cross section of the pawl ring is disposed at the free end of the web of the said T-shaped hollow core;

and to facilitate the assembly of the three coaxial rings, the driven ring is cut in half axially to produce a driven ring consisting of two halves that are mirror images of each other and that each half has a radial cross section in the shape of a stair with three steps, where the radially disposed edge of the third step signifies the line of symmetry of the two driven ring halves, the axially disposed edge of the third step supports the pawl ring radially, the radially disposed edge of the second step supports the pawl ring axially, the radially disposed edge of the first step supports the driving ring axially, the axially disposed edge of the first step supports the driving ring radially, and the axially disposed edge in the second step of each driven ring half is associated with the cylindrical surface of the driven ring containing the engaging means in the form of a notch, such that the two notches face each other and thus the two driven ring halves remain mirror images of each other;

and corresponding to the twin design of the driven ring, the pawl, still having an L-shaped configuration, is composed of two identical parallel arms in the shape of U that are connected at their juncture to the corner end of the stem;

and furthermore, the pawl'"'"'s arms are disposed within the flange of the said T-shaped hollow core;

so that, one arm faces the notched cylindrical surface of the first driven ring half and the other arm faces the notched cylindrical surface of the second driven ring half;

and so that, the free end of the stem extends into the web of the said T-shaped hollow core to be pivoted to the pawl ring;

and to achieve the said operative coupling, the driving ring includes on its outermost cylindrical surface a pair of keys;

one engaging key to sit behind the arms at their connection to the stem, and one disengaging key to sit in between the arms adjacent to the stem;

And evidently, in assembled configuration the three rings support each other both radially and axially while possessing a symmetric radial cross section and the pawl has a symmetric projection as viewed in any direction orthogonal to the axis of the assembled mechanism.

6. The mechanism recited in claim 2, 3, or 4 in which the said operative coupling is achieved by interaction between a key on the driving ring surface facing the driven ring and a groove in the corner end of the pawl arm in which the said key is disposed.

7. The mechanism recited in claim 2, 3, or 4 in which the engaging means on the driven ring is in the form of a notch.

8. The mechanism recited in claim 5 wherein the pawl ring incorporates a radial cutout midway through the pivot hole in the pawl ring in order to house the free end of the pawl'"'"'s stem for pivoting.

9. The mechanism recited in claim 5 wherein the pawl ring has a T cross section, consisting therefore of a flange and a web, with the web pointing radially inward and containing the axial pivot hole;

and where the pawl employs two identical parallel stems so that the web of the T-shaped pawl ring is inserted between the stems for pivoting.

10. The mechanism recited in claim 8 or 9, wherein the driven ring halves include an equal number of a plurality of notches that are uniformly distributed in a circular pattern, in such a way that the two driven ring halves remain mirror images of each other.

11. The mechanism recited in claim 10 wherein a plurality of pawls are pivoted uniformly to the pawl ring, the driving ring includes a plurality of key pairs that are uniformly spaced and are equal in number to the number of pawls, and the number of notches on each driven ring half is a whole multiple of the number of pawls.

12. The mechanism recited in claim 11 wherein, in order to minimize backlash upon activation of the engaging mode, the driven ring includes a maximum possible number of uniformly spaced notches.

13. The mechanism recited in claim 12 wherein to minimize the backlash further, M (an integer greater than 1) set of N (an integer greater than 0) compliant variation of the rigid pawl are employed;

and where, the pawl ring includes a plurality of MN pivot holes that are uniformly distributed in a circular pattern;

and where, not only the N pawls belonging to each set are uniformly distributed around the pawl ring but also the total number of pawls MN are uniformly distributed around the pawl ring;

and correspondingly, the number of uniformly spaced key pairs on the driving ring is equal to the total number of pawls MN;

and furthermore, the number of notches on the driven ring halves is chosen such that the pawls in the same set have the same positional alignment with the notches, whereas any two pawls belonging to different sets have different positional alignment with the notches;

and consequently, the said alignment differences together with the ability of the pawls to deform facilitate an engagement mode of operation where only the pawls belonging to one set undergo engagement, the rest deform to avoid binding with the driven ring;

and furthermore, upon activation of the freewheeling mode, the engaged pawls rotate back, and the non-engaged pawls rotate and retract back to their respective freewheeling configuration.

14. The mechanism recited in claim 12 wherein to minimize the backlash further, M (an integer greater than 1) pawl assemblies are employed, where each pawl assembly consists of a pawl ring and a set of N (an integer greater than 0) uniformly spaced pawls;

and furthermore, each pawl ring includes N round pivot holes that are uniformly distributed in a circular pattern with the subtended angle of each pair of consecutive pivot holes equal to 2π

/N;

and furthermore, each pawl ring also includes a plurality N(M−

1) of sectoral slots that are situated at the same radius as that of the round pivot holes, and that divide into equal parts, 2π

/MN, the angle subtended by each two consecutive round pivot holes;

and furthermore, when the M pawl rings are overlaid, each round pivot hole in a given pawl ring aligns with M−

1 sectoral slots in the remaining pawl rings;

and furthermore, it is to the said overlaid arrangement of the pawl rings that the MN pawls are pivoted, so that an individual pawl assembly can rotate with respect to the remaining M−

1 pawl assemblies up to a limit imposed by the sectoral slots;

and furthermore, the number of notches on the driven ring halves is chosen such that the pawls in the same pawl assembly have the same positional alignment with the notches, whereas any two pawls belonging to different pawl assemblies have different positional alignment with the notches;

and consequently, the said alignment differences together with the ability of the pawl rings to have a finite rotational freedom with respect to each other facilitate an engagement mode of operation where only the pawls on one pawl ring undergo engagement, the rest slide to avoid binding with the driven ring;

and furthermore, upon activation of the freewheeling mode, the engaged pawls rotate back, and the non-engaged pawls rotate and slide back to their respective freewheeling configuration.

15. The mechanism recited in claim 13 in which the compliant pawl is constructed such that the pawl arms are connected to the pawl stem by a pin and a rotational spring;

and where, the pawl stem includes two identical cutouts facing the arms so as to provide limits of rotation between the pawl stem and the pawl arms;

and where, by virtue of an initial torque in the said rotational spring, the pawl arms are snugly fitted to the stem within the said cutouts such that in the said snugly fitted configuration the arms cannot rotate toward the stem, but can rotate away from the stem up to the limit imposed by the said cutouts on the stem.

16. The mechanism recited in claim 13 in which the compliant pawl utilizes a stem fabricated from sheet spring material;

and where, the compliant stem is rigidly joined to the arms at one end and includes a formed circular feature at the opposite end to accommodate pivoting of the pawl to the pawl ring.