GB2128273A

GB2128273A - A pawl and ratchet driving assembly particularly for freewheel bicycle hubs

Info

Publication number: GB2128273A
Application number: GB08326717A
Authority: GB
Inventors: Hans Butz
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1982-10-12
Filing date: 1983-10-06
Publication date: 1984-04-26
Also published as: FR2534335A1; GB2128273B; NO833701L; GB8326717D0; JPS5989836A; DE8228602U1

Abstract

The pawls (30) pivoted in pockets in a pawl carrier ring (20) and secured by a spring ring (40). The spring ring (40) is secured against axial movement in one direction by directly engaging abutment ribs (38) of the pawl carrier ring (20) and in the other axial direction through the pawls (30) which engage an axially directed pawl engagement face (42) of a rotor member (14) receiving said pawl carrier ring (20). The pawl carrier ring (20) is made by forging, cold-pressing or sintering without substantial machining treatment. <IMAGE>

Description

SPECIFICATION A pawl and ratchet driving assembly particularly for freewheel bicycle hubs The present invention is related generally to pawl and ratchet driving assemblies and more particularly to a pawl and ratchet driving assembly for a freewheel bicycle hub.

The assembly to which the present invention relates is particularly applicable to freewheel bicycle hubs having a driver member with a plurality of sprocket wheels, a hub sleeve and the pawl and ratchet driving assembly therebetween.

The driving chain may be brought into engagement with various of said sprocket wheels in view of changing the transmission ratio.

Known pawl and ratchet driving assemblies comprise a first rotor unit and a second rotor unit having a common axis of rotation. On the first rotor unit there is mounted a pawl member. This pawl member comprises a ratchet engagement portion and a cylinder segment-shaped bearing portion. The cylinder segment-shaped bearing portion is pivotally received by a complementary cylinder segment-shaped recess of the first rotor unit. The cylinder segment-shaped bearing portion and the cylinder segment-shaped recess have a pivot axis parallel to the common axis. The second rotor unit comprises a ratchet which is at least partially co-extensive with the pawl member along the common axis.The ratchet engagement portion of the pawl member is engageable with the ratchet under the action of a circular spring ring which on the one hand biases said ratchet engagement portion towards engagement with said ratchet and on the other hand serves to axially secure the pawl member with respect to the first rotor unit. In view of this, the pawl member is provided with a slot at a location between the axial ends thereof. This slot is defined by two opposite side faces perpendicular to the common axis and by a bottom face facing the ratchet. The slot receives the circular spring ring such that the axis of said spring ring coincides with the common axis of the driving assembly. The spring ring engages the side faces of the slot and acts onto the bottom face of the slot in substantially radial direction such as to bias the ratchet engagement portion towards engagement with the ratchet.In view of securing the spring ring against axial movement with respect to the first rotor unit and to further secure also the pawl member against axial movement with respect to the first rotor unit through the spring ring, the spring ring is received by a circular slot within the first rotor unit. This circular slot within the first rotor unit is difficult to be manufactured, particularly in cases in which the pawl and the spring ring are to be provided on a radially inwardly directed circumferential face of the first rotor unit.

The present invention is directed to a pawl and ratchet driving assembly in which the manufacturing of the first rotor unit can be simplified by avoiding the annular slot which had to be made in the past by a machining treatment.

Briefly, the present invention may be described as a pawl and ratchet driving assembly, particularly for freewheel bicycle hubs comprising a first rotor unit and a second rotor unit having a common axis of rotation, said first rotor unit including at least one pawl member, said pawl member comprising a ratchet engagement portion and a cylinder segment-shaped bearing portion, said cylinder segment-shaped bearing portion being pivotally received by a cylinder segmentshaped recess of said first rotor unit, said cylinder segment-shaped bearing portion and said cylinder segment-shaped recess having a pivot axis parallel to said common axis, said second rotor unit comprising a ratchet at least partially co-extensive with said pawl member along said common axis, said ratchet engagement portion of said pawl member being engageable with said ratchet, said pawl member being provided with a slot, said slot being defined by two opposite side faces perpendicular to said common axis and by a bottom face facing said ratchet, said slot receiving a circular spring ring having an axis substantially coinciding with said common axis, said spring ring engaging said side faces and acting onto said bottom face of said slot in substantially radial direction such as to bias said ratchet engagement portion towards engagement with said ratchet, said spring ring being secured against axial movement with respect to said first rotor unit in a first axial direction only by spring ring abutment means on said first rotor unit directly engaging said spring ring and against axial movement in a second axial direction through said pawl member, said pawl member being secured against axial movement with respect to said first rotor unit in said second axial direction by a pawl member abutment face of said first rotor unit.

In a more specific aspect of the invention, the first rotor unit comprises a basic rotor member and a pawl carrier ring fixed to said rotor member.

In this specific embodiment, the cylinder segmentshaped recess may extend through the total length of the pawl carrier ring, one axial end of said cylinder segment-shaped recess being closed by an annular face of said basic rotor member, said annular face being substantially perpendicular with respect to said common axis and acting as said pawl member abutment face.

According to this invention, the manufacturing of the assembly is simplified not only in view of avoiding the provision of a circumferential slot within the rotor unit but also in view of simplifying the application of the spring ring.

A further advantage of this specific embodiment of the invention is that the pawl carrier ring has only a small axial dimension which exceeds the axial dimension of the pawl only a bit, if at all.

The pawl carrier ring can be manufactured by cold-pressing, forging or preferably sintering methods and machining operations can be reduced to a minimum or even completely avoided.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings: Figure 1 is a sectional view taken through the pawl and ratchet driving assembly along the common axis thereof; Figure 2 is a section according to Figure 1 in which the pawl member and the second rotor unit have been eliminated in view of a better illustration of the engagement of the spring ring and the annular rib means; Figure 3 is an axial view of the pawl carrier ring separate from the driving assembly and seen from the left in Figure 1; Figure 4 is a sectional view taken through the pawl carrier ring of Figure 3 along the common axis of the assembly and through one of the cylinder segment-shaped recesses; Figure 5 is an enlarged sectional view corresponding to the frame 5 of Figure 3 and showing the engagement of the pawl member and the ratchet, the basic rotor member of Figure 1 being eliminated; and Figure 6 is an end view of a pawl member as seen from the left in Figure 5.

In Figure 1, a hub shaft is designated 10. On this hub shaft there is fixed a bearing member 12.

A hub sleeve 14 made of a light metal alloy is rotatably mounted on the bearing member 1 2 through a ball bearing 16. The hub sleeve 14 is provided with an annular bearing cup 18 made of steel and being pressed into the hub sleeve 14. A pawl carrier ring 20 is received by the hub sleeve 14. This pawl carrier ring 20 is in more detail shown in Figures 3 and 4. The pawl carrier ring 20 is knurled on its radially outer circumferential face, as indicated at 22 in Figure 4. This knurled circumferential outer face 22 is in torque transmitting engagement with the radially inner circumferential face of an axially directed flange 24 of the hub sleeve 14. As indicated in Figures 3 and 4, the pawl carrier ring 20 is provided with pockets 26 in its radially inner circumferential face.These pockets 26 comprise, as indicated in Figure 3, cylinder segment-shaped recesses 28.

Pawl members 30 are, as indicated in Figures 1 and 5, received by the pockets 26. The pawl members 30 comprise a ratchet engagement portion 32 and a cylinder segment-shaped bearing portion 34 pivotally received by the cylinder segment-shaped recess 28. The pawl member is in more detail shown in Figure 6. The pawl member 30 is provided with a slot 36 having two side faces 36a, 36b and a bottom face 36c.

The pawl carrier ring 20 is further provided on its radially inner circumferential face with circumferentially extending ribs 38.

The pawl members 30 are axially and radially fixed within the recesses 28 by a circular spring ring 40, as indicated in Figures 1,2 and 5. This spring ring 40 is received by the slot 36 of the pawl members 30 such as to engage the side faces 36a, 36b and the bottom 36c. The spring ring 40 is further engaged on its right-hand side, as shown in Figure 2, by the circumferentially extending ribs 38 so that the spring ring 40 is secured against axial movement towards the right, as seen in Figure 2. On the other hand, the pawl members 30 engage by their left-hand axial end face, as seen in Figure 1, a pawl member abutment face 42 of the hub sleeve 14.So, the pawl members 30 are secured against movement to the left, as seen in Figure 1, by the pawl member abutment face 42 and against movement to the right in Figure 1 by the spring ring 40 which is on the other hand secured against movement to the right in Figure 1 by the ribs 38.

The spring ring 40 is further secured against rotation with respect to the hub sleeve 14 by an end portion 40a bent in axial direction and engaging a notch 44 defined by subsequent ribs 38.

As can be seen from Figure 1, also a driver member 46 is mounted on the bearing member 12 by a ball bearing 48. The driver member may be provided with a plurality of chain sprockets and may further be mounted on the hub shaft 10 by a further ball bearing not shown. The driver member 46 is provided with a ratchet 50, as more particularly shown in Figure 5. The pawl member 50 is biased towards engagement with the ratchet 50 by the spring ring 40 which engages the bottom 36c of the slot 36 near the left-hand end thereof, as seen in Figure 5, so as to create a clockwise torque onto the pawl member 30 which brings the ratchet engagement portion 32 in engagement with the ratchet 50.

It is to be noted that the pawl carrier ring 20 can be manufactured easily by cold-pressing, forging or preferably sintering without any machining operation. This is particularly due to the lack of a circumferential slot at the radially inner circumferential face of the pawl carrier ring 20. In assembling, the pawl members 30 and the spring ring 40 can be mounted after the pawl carrier ring 20 has been inserted into the hub sleeve 14. It is, however, also possible to pre-assemble the pawl carrier ring 20 with the pawl members and the spring ring 40 before pressing the pawl carrier ring 20 into the hub sleeve 14. This latter way of assembling is preferred.

It is to be noted that the ribs 8 are within the axial extent of the pawls 30 and that the axial extent of the pawl carrier ring 20 is substantially equal to the axial extent of the pawls 30 so that the total axial extent of the assembly comprising the pawl carrier ring 20 and the pawl members 30 is a minimum one.

The manufacturing expenses are low in view of the fact that the pawl carrier ring 20 need not have any machining treatment.

Generally spoken, the hub sleeve 14 and the pawl carrier ring 20 may be regarded as a first rotor unit, whereas the driver member 46 may be regarded as a second rotor unit.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

The reference numerals are only for a better understanding of the claims and are by no means of restrictive character.

Claims

1. A pawl and ratchet driving assembly, particularly for freewheel bicycle hubs comprising a first rotor unit (14, 20) and a second rotor unit (46) having a common axis of rotation, said first rotor unit (14, 20) including at least one pawl member (30), said pawl member (30) comprising a ratchet engagement portion (32) and a cylinder segment-shaped bearing portion (34), said cylinder segment-shaped bearing portion (34) being pivotally received by a cylinder segmentshaped recess (28) of said first rotor unit (14, 20), said cylinder segment-shaped bearing portion (34) and said cylinder segment-shaped recess (28) having a pivot axis substantially parallel to said common axis, said second rotor unit (46) comprising a ratchet (50) at least partially co-extensive with said pawl member (30) along said common axis, said ratchet engagement portion (32) of said pawl member (30) being engageable with said ratchet (50), said pawl member (30) being provided with a slot (36), said slot (36) being defined by two opposite side faces (36a, 36b) perpendicular to said common axis and by a bottom face (36c) facing said ratchet (50), said slot (36) receiving a circular spring ring (40) having an axis substantially coinciding with said common axis, said spring ring (40) engaging said side faces (36a, 36b) and acting onto said bottom face (36c) of said slot (36) in substantially radial direction such as to bias said ratchet engagement portion (32) towards engagement with said ratchet (50), said spring ring (40) being secured against axial movement with respect to said first rotor unit (14, 20) in a first axial direction only by spring ring abutment means (38) on said first rotor unit (14, 20) directly engaging said spring ring (40) and against axial movement in a second axial direction through said pawl member (30), said pawl member (30) being secured against axial movement with respect to said first rotor unit (14, 20) in said second axial direction by a pawl member abutment face (42) of said first rotor unit (14,20).

2. A pawl and ratchet driving assembly as set forth in claim 1, said first rotor unit (14, 20) comprising two pawl members (30) spaced in circumferential direction about said common axis by an angle of about 1 80O.

3. A pawl and ratchet driving assembly as set forth in claim 1, said spring ring (40) being secured against rotation with respect to said first rotor unit (14,20).

4. A pawl and ratchet driving assembly as set forth in claim 1, said first rotor unit (14, 20) comprising a basic rotor member (14) and a pawl carrier ring (20) fixed to said basic rotor member (14).

5. A pawl and ratchet driving assembly as set forth in claim 4, said cylinder segment-shaped recess (28) extending through the total length of said pawl carrier ring (20), one axial end of said cylinder segment-shaped recess (28) being closed by an annular face (42) of said basic rotor member (14), said annular face (42) being substantially perpendicular with respect to said common axis and acting as said pawl member abutment face (42).

6. A pawl and ratchet driving assembly as set forth in claim 1, said spring ring abutment means (38) being defined by annular rib means (38) integral with said pawl carrier ring (20), said annular rib means (38) being interrupted by said cylinder segment-shaped recess (28).

7. A pawl and ratchet driving assembly as set forth in claim 6, said spring ring (40) being an open spring ring and having an end portion (40a) engaging a notch (44) of said rib means (38).

8. A pawl and ratchet driving assembly as set forth in claim 1, said ratchet (50) being provided on a radially outer face of said second rotor unit (46), said cylinder segment-shaped recess (28) being provided in a radially inner face of said first rotor unit (14, 20), and said rib means (38) projecting radially inwardly from said radially inner face.

9. A pawl and ratchet driving assembly as set forth in claim 1, said pawl carrier ring (20) being secured to said rotor member (14) for common rotation therewith by a knurled radially directed surface (22) of said paw carrier ring (20) engaging a complementary surface of said rotor member (14).

10. A pawl and ratchet driving assembly as set forth in claim 1, said pawl carrier ring (20) being formed by one of a cold-pressing method, forging method or sintering method.

11. A pawl and ratchet driving assembly as set forth in claim 10, said pawl carrier ring (20) being formed without machining treatment.

12. A pawl and ratchet driving assembly as set forth in claim 1, said first rotor unit (14, 20) comprising a hub sleeve (14), and said second rotor unit (46) comprising a driver member (46) of a freewheel bicycle hub.

13. A pawl and ratchet driving assembly substantially as herein described herein with reference to Figures 1 to 6 of the accompanying drawings.