WO2000066328A1

WO2000066328A1 - Gearless ratchet mechanism

Info

Publication number: WO2000066328A1
Application number: PCT/CA2000/000506
Authority: WO
Inventors: Kailash C. Vasudeva; Sanjeev Bedi
Original assignee: Maxtech Manufacturing Inc.
Priority date: 1999-04-29
Filing date: 2000-05-01
Publication date: 2000-11-09
Also published as: AU4388100A

Abstract

A gearless ratchet mechanism (100) having a torque input member (110) and a torque output member (120). A plurality of substantially cylindrical rolls (180, 190) are arranged in pairs, in a first space within the housing defined by an inner surface wall (170) of the housing and outer wall surface (140) of the larger cross-section part of the torque output member. A selector (210) including a plurality of roll manipulating prongs (220), is arranged adjacent the housing (150). The distance between the inner surface wall (170) of the housing and the outer wall surface (140) of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll. The maximum distance between the outer surfaces of two rolls of a pair is minimized, so that the only forces to move a roll in and out of the pinched position, are frictional forces.

Description

GEARLESS RATCHET MECHANISM

TECHNICAL FIELD

This invention relates to a gearless ratchet mechanism for transferring a medium to high torque from a drive member to a working member along an axis of rotation, in either one selected direction of rotation or both directions of rotation, especially for use in hand tools, such as wrenches, screwdrivers, chucks or clutches, or power tools.

BACKGROUND ART

Traditionally, gearless ratchet mechanisms of the reversible friction roll type comprise a cylindrical housing having one to six rolls, rods or balls placed so that they freely spin and slide in a space defined between the housing and a shaft rotatably engaged in the housing. A selector having roll manipulating prongs is arranged to set the desired torque transfer rotation direction. The available settings are torque transfer in clockwise rotation, torque transfer in counter-clockwise rotation and torque transfer in both directions. Sloping recesses are arranged either in the housing or on the shaft, where the minimum distance between the housing and the shaft is smaller than the roll diameter and the maximum distance between the housing and the shaft is larger than the roll diameter. Depending upon the position of the selector, an individual roll may be either pinched between the housing and the shaft by friction forces or left with a gap between the roll and the housing and/or the shaft. A roll which is pinched will transfer torque between the housing and the shaft when the housing is rotated in a direction in which the slope of the recess is decreasing the space between the housing and the shaft. If the housing is rotated in the opposite direction, the roll will be released from its pinched position and the torque transfer will stop, thus allowing the housing to be rotated freely without rotating the shaft. If the selector is set in a central position where all rolls are in a pinched position, torque transfer will be possible in both rotational directions. In order for the above described arrangement to work without too much play, the rolls are biased in a direction towards the smallest gap between the housing and the shaft so that the rolls are in a pinched position. Using the selector, one or more rolls may be released from the pinched position to interrupt torque transfer in a specific direction of rotation of the housing. Normally, springs are used to bias the rolls, for example coil springs. Gearless ratchet mechanisms of the above described type are disclosed in, for example, US 1 ,136,821 (Loomis), US 1 ,265,341 (Keller), US 2,139,650 (Anderson et al.), US 2,469,572 (Pratt) and US 5,531 ,139 (Fanchang et al.). Not all of these documents describe a three-way selector, but instead have a two-way selector; torque transfer possible in either rotational direction of the housing but not both simultaneously.

Gearless ratchet mechanisms of the reversible friction roll type described above generally comprise a large number of parts which make assembly difficult and costly. Especially the biasing springs are difficult to assemble correctly with respect to the rolls, and add complexity and production cost to the mechanism.

DISCLOSURE OF INVENTION

It is an object of the invention to mitigate and/or obviate the above mentioned disadvantages to provide a gearless ratchet mechanism, which is easy and cheap to manufacture and assemble but which can transfer a high torque.

In the invention, a gearless ratchet mechanism comprises a torque input member, a torque output member including a larger cross-section part at one end of the torque output member, where the larger cross-section part of the torque output member has an outer wall surface, a housing including a through hole and an inner surface wall, the housing being fixedly attached to the torque input member, a plurality of substantially cylindrical rolls arranged in pairs, each pair comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, and a selector including a plurality of roll manipulating prongs, where the prongs divide the rolls into a plurality of working pairs inside the space within the housing.

The distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll. Each individual roll is, on one side of the roll, close to a minimum distance and is, on the other side of the roll, close to a maximum distance. When the selector prongs are engaged with either the first or the second roll of a pair, the engaged rolls are released from their pinched position.

The distance between the outer surfaces of two rolls of a pair should be kept to a minimum to ensure that the only forces necessary to move a roll in and out of the pinched position, are frictional forces. The smaller the distance is between two rolls of a pair, the smaller the play will be in the arrangement.

In one preferred embodiment of the invention, the plurality of sloping portions are arranged on the outer wall surface of the larger cross-section part of the torque output member, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

In another preferred embodiment of the invention, the plurality of sloping portions are arranged on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

In yet another preferred embodiment of the invention, the plurality of sloping portions are arranged on the outer wall surface of the larger cross-section part of the torque output member as well as on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

A preferred gearless ratchet mechanism according to the invention comprises three pairs of rolls and the selector comprises three prongs.

A further preferred gearless ratchet mechanism according to the invention comprises one pair of rolls and the selector comprises two prongs. Preferably, the gearless ratchet mechanism further comprises a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

According to still a further embodiment of the invention, a gearless ratchet mechanism preferably comprises a torque input member, a torque output member including a larger cross-section part at one end of the torque output member, the larger cross-section part of the torque output member having an outer wall surface, a housing including a through hole and an inner surface wall, the housing being fixedly attached to the torque input member, a plurality of substantially cylindrical rolls arranged in pairs, each pair comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, a selector including a plurality of roll manipulating prongs, where the prongs divide the rolls into a plurality of pairs inside the space within the housing, the selector being rotatable between three positions to transfer torque from the torque input member to the torque output member in either a clockwise direction of rotation where torque transfer is prevented in the anti-clockwise direction, an anticlockwise direction of rotation where torque transfer is prevented in the clockwise direction, or both directions where the torque transfer is provided in either direction depending upon the direction of rotation of the torque input member, wherein the distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is close to a minimum distance and, on the other side of the roll, is close to a maximum distance, and when the selector prongs are engaged with either the first or the second roll of a pair, the engaged rolls are released from their pinched position, and wherein the distance between the outer surfaces of two rolls of a pair is minimized_by providing minimized gaps between the rolls, the selector prongs, the outer surface wall and the outer surface wall, so that the only forces to move a roll in and out of the pinched position, are frictional forces. A plurality of sloping portions are preferably arranged on the outer wall surface of the larger cross-section part of the torque output member, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

Alternatively, a plurality of sloping portions are arranged on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

Preferably, the gearless ratchet mechanism further comprises a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

A further embodiment of a gearless ratchet mechanism according to the invention comprises a torque input member, a torque output member including a larger cross- section part at one end of the torque output member, the larger cross-section part of the torque output member having an outer wall surface, a housing including a through hole and an inner surface wall, the housing being fixedly attached to the torque input member, a pair of substantially cylindrical rolls comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, a selector including a pair of roll manipulating prongs, where the prongs flank the rolls inside the space within the housing, the selector being rotatable between three positions to transfer torque from the torque input member to the torque output member in either a clockwise direction of rotation where torque transfer is prevented in the anti- clockwise direction, an anti-clockwise direction of rotation where torque transfer is prevented in the clockwise direction, or both directions where the torque transfer is provided in either direction depending upon the direction of rotation of the torque input member, wherein the distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is close to a minimum distance and, on the other side of the roll, is close to a maximum distance, and when the selector prongs are engaged with either the first or the second roll of the pair of rolls, the engaged roll is released from its pinched position, and wherein the maximum distance between the outer surfaces of the pair of rolls is minimized by providing minimized gaps between the rolls, the selector prongs, the outer surface wall and the outer surface wall, so that the only forces to move a roll in and out of the pinched position, are frictional forces.

The gearless ratchet mechanism further advantageously comprises a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

According to yet a further embodiment of the invention, a box-end wrench has a head end and a handle end, the head end having a tool mount, for attaching tools or engaging nuts, and a substantially cylindrical housing portion, the housing portion having a ratchet mechanism comprising a torque output member having a circular outer surface, which is provided with a plurality of splines, the torque output member being rotatably arranged in the housing and further has a cutout chamber, which accommodates a pair of rolls held apart and biased in one direction of rotation by a biasing prong, the rolls being squeezed between an inner surface of the housing and a curved portion of the cutout chamber, to provide torque transfer in the direction of rotation of the wrench handle, the housing further comprising a backup ratchet sound generating mechanism having a spring biased ratchet arm engageable with a splined portion of the torque output member.

In the box-end wrench, the substantially cylindrical housing portion further preferably has a first chamber, a second chamber and a generally circular cutout arranged between the first chamber and the second chamber, the circular cutout having a ratchet arm cutout arranged adjacent the handle end, a ratchet arm being insertably arranged in the ratchet arm cutout, and biased towards the circular cutout by a ratchet arm biasing means, the biasing means being held in a biasing means extension of the ratchet arm cutout, the ratchet arm being pivotably held in a ratchet arm extension of the ratchet arm cutout, so that the ratchet arm is pivotable in a direction towards the circular cutout, and against the biasing force of the biasing means in a direction towards the biasing means, the torque output member being rotatably arranged in the circular cutout, and the ratchet arm being biased towards the plurality of splines, the ratchet arm having a hooked end, which is arranged on the end of the ratchet arm which is pivoted by the biasing means, whilst the opposite end of the ratchet arm is held by the ratchet arm extension, the hooked end of the ratchet arm having an outer end surface which is substantially perpendicular to the longitudinal direction of the ratchet arm, and an inner surface which is rounded, so that when the ratchet arm makes contact with the torque output member and the plurality of splines, the hooked end of the ratchet arm will allow rotation of the torque output member only in the direction where the plurality of splines make contact with the substantially perpendicular surface of the hooked end of the ratchet arm, and when the wrench is rotated in the other direction, the rounded surface of the hooked end will allow the ratchet arm to slip over the plurality of splines, producing a ratchet sound.

The gearless ratchet mechanism according to the invention thus does not comprise any biasing means, such as springs or spacers, for biasing the rolls towards their pinched position.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be more clearly understood, the preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:

Fig. 1A is a perspective exploded elevational side view of a gearless ratchet mechanism according to a first embodiment of the invention,

Fig. 1B is a perspective and partially sectioned elevational side view of the first embodiment of the invention,

Fig. 1 C is a perspective elevational side view of the first embodiment of the invention, showing the device in an assembled state,

Fig. 2 is a sectional view from above of a ratchet mechanism according to the first embodiment of the invention, showing the selector positioned such that torque transfer is possible in both directions of rotation,

Fig. 3A is a sectional view from above corresponding to Fig. 2, showing the selector positioned such that torque transfer is possible only in the counter clockwise direction, and the handle is being rotated in the counter-clockwise direction,

Fig. 3B is a sectional view from above corresponding to Fig. 3A, but the handle is being rotated in the clockwise direction,

Fig. 4A is a sectional view from above corresponding to Fig. 2, showing the selector positioned such that torque transfer is possible only in the clockwise direction, and the handle is being rotated in the clockwise direction,

Fig. 4B is a sectional view from above corresponding to Fig. 4A, but the handle is being rotated in the counter-clockwise direction,

Fig. 5 is a sectional view from above of a ratchet mechanism according to a second embodiment of the invention, showing the selector positioned such that torque transfer is possible in both directions of rotation,

Fig. 6A is a sectional view from above corresponding to Fig. 5, showing the selector positioned such that torque transfer is possible only in the counter-clockwise direction, and the handle is being rotated in the counter-clockwise direction,

Fig. 6B is a sectional view from above corresponding to Fig. 6A, but the handle is being rotated in the clockwise direction,

Fig. 7A is a sectional view from above corresponding to Fig. 5, showing the selector positioned such that torque transfer is possible only in the clockwise direction, and the handle is being rotated in the counter-clockwise direction,

Fig. 7B is a sectional view from above corresponding to Fig. 7A, but the handle is being rotated in the clockwise direction,

Fig. 8 is a sectional view from above of a ratchet mechanism according to a third embodiment of the invention, showing the selector positioned such that torque transfer is possible in both directions of rotation,

Fig. 9A is a sectional view from above corresponding to Fig. 8, showing the selector positioned such that torque transfer is possible only in the counter clockwise direction, and the handle is being rotated in the counter-clockwise direction,

Fig. 9B is a sectional view from above corresponding to Fig. 9A, but the handle is being rotated in the clockwise direction,

Fig. 10A is a sectional view from above corresponding to Fig. 8, showing the selector positioned such that torque transfer is possible only in the clockwise direction, and the handle is being rotated in the counter-clockwise direction,

Fig. 10B is a sectional view from above corresponding to Fig. 10A, but the handle is being rotated in the clockwise direction,

Fig. 11A is a perspective exploded elevational side view of a gearless ratchet mechanism according to an alternative embodiment of the invention, showing the reverse arrangement of the mechanism compared to the first embodiment,

Fig. 11B is a perspective and partially sectioned elevational side view of an embodiment corresponding to Fig. 11 A, but showing the mechanism in an assembled state,

Fig. 12A is an exploded partially sectioned side view of a further embodiment of the invention, showing a mechanism having dual ratchet arrangements,

Fig. 12B is a partially sectioned side view of a further embodiment of the invention, showing a mechanism having dual ratchet arrangements,

Fig. 12C is a partially sectioned side view of the ratchet mechanism of the embodiment of Fig. 12B,

Fig. 13A is a partially sectioned side view of a torque output member of the embodiment of Fig. 12A,

Fig. 13B is a top view of the torque output member of Fig. 12A,

Fig. 13C is a bottom view of the torque output member of Fig. 12A,

Fig. 14A is a sectioned side view of a selector of the embodiment of Fig. 12A,

Fig. 14B is a side view of a selector of the embodiment of Fig. 12A,

Fig. 14C is a top view of a selector of the embodiment of Fig. 12A,

Fig. 14D is a bottom view of a selector of the embodiment of Fig. 12A,

Fig. 15A is a side view of a torque input member of the embodiment of Fig. 12A,

Fig. 15B is a partially sectioned side view of a torque input member of the embodiment of Fig. 12A, seen along line B-B of Fig. 15A, Fig. 15C is a top view of the torque input member of Fig. 12A,

Fig. 15D is a sectioned view of the torque input member of Fig. 12A, seen along line C- C of Fig. 15A,

Fig. 16A is a side view of a rocker arm of the embodiment of Fig. 12A,

Fig. 16B is a bottom view of the rocker arm of the embodiment of Fig. 12A,

Fig. 16C is an end view of the rocker arm of the embodiment of Fig. 12A,

Fig. 17A is a sectioned side view of a housing of the embodiment of Fig. 12A,

Fig. 17B is a partial top view of the housing of the embodiment of Fig. 12A,

Fig. 17C is a bottom view of a housing of the embodiment of Fig. 12A,

Fig. 18A is an elevational side view of a rocker spring of the embodiment of Fig. 12A,

Fig. 18B is a side view of the rocker spring of Fig. 12A,

Fig. 19A is a sectioned view of the ratchet mechanism of the embodiment of Fig. 12A, seen along line A-A of Fig. 12C, showing the selector positioned such that torque transfer is possible in both directions of rotation,

Fig. 19B is a detail view of the rocker mechanism of Fig. 19A,

Fig. 20A is a sectioned view of the ratchet mechanism of the embodiment of Fig. 12A, seen along line A-A of Fig. 12C, showing the selector positioned such that torque transfer is possible only in a clockwise direction of rotation, Fig. 20B is a detail view of the rocker mechanism of Fig. 20A,

Fig. 21A is a sectioned view of the ratchet mechanism of the embodiment of Fig. 12A, seen along line A-A of Fig. 12C, showing the selector positioned such that torque transfer is possible only in a counter-clockwise direction of rotation,

Fig. 21 B is a detail view of the rocker mechanism of Fig. 21 A,

Fig. 22A is a partial top view of a further embodiment of the invention, showing a box- end wrench having a ratchet mechanism similar to the one described in Figs. 12A to 21 B, but here the rocker arm is not tiltable between two positions, necessitating the wrench being flipped over for change of ratchet direction,

Fig. 22B is a top view of the wrench of Fig. 22A, showing the mechanism cover removed,

Fig. 22C is a partially sectioned side view of the wrench of Fig. 22A,

Fig. 22D is a partially sectioned side view of the wrench of Fig. 22A, showing the wrench head empty, without ratchet mechanism,

Fig. 23 is a partially sectioned side view of a ratchet housing of Fig. 22A, and

Fig. 24 is a top view of the ratchet mechanism of Fig. 22A.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to Figs. 1A and 1 B, a gearless ratchet mechanism 100 according to the present invention comprises a torque input member 110 and a torque output member 120 including a larger cross-section part 130 at one end of the torque output member. The torque input member is preferably connected to a handle 10 and the torque output member may be a screwdriver blade or a tool shaft with exchangeable bits, for example. The larger cross-section part of the torque output member has a first outer wall surface 140. The ratchet mechanism further comprises a housing 150 and an inner wall surface 170. The housing is fixedly attached to the torque input member 110. Further, a plurality of substantially cylindrical rolls are arranged in pairs, each pair comprising a first roll 180 and a second roll 190, in a first space 200 within the housing. The first space within the housing is defined by the inner wall surface 170 of the housing and the outer wall surface 140 of the larger cross-section part of the torque output member.

A selector 210, including a plurality of roll manipulating prongs 220, is arranged adjacent the housing 150 with the prongs protruding into the first space 200 within the housing. The prongs physically divide the rolls into a plurality of pairs inside the space within the housing. The torque output member 120 freely passes through a through hole 160 of the selector so that the larger cross-section part 130 of the torque output member remains inside the selector. The distance between the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is adjacent a minimum distance and, on the other side of the roll, is adjacent a maximum distance. Thus, a plurality of sloping portions 230, are formed.

When the selector prongs 220 are engaged with either the first 180 or the second 190 roll of a pair so that the rolls are displaced, the engaged rolls are released from their pinched position. To ensure that only frictional forces are required, to move a roll in and out of the pinched position, the two rolls of a pair will have to be relatively close to each other, even when both rolls are in the pinched position. The maximum distance between the outer surfaces of two rolls of a pair will, according to the invention, be kept to a minimum to ensure that the only forces necessary to move a roll in and out of the pinched position are frictional forces. The two rolls of a pair can be in contact when the mechanism is in a released position, i.e. one roll of a pair is in its non-pinched position, and the housing 150 is rotated in the direction of increasing distance between the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross- section part of the torque output member of the pinched roll. All of the rolls 180, 190 preferably have substantially the same diameter and may have bevelled edges or convex end surfaces to reduce the risk of the edges of the rolls cutting into the material of the housing 150 or the selector 210 when the edges of the rolls slide on the housing and the selector, respectively. The mechanism is shown in the fully assembled state in Fig. 1C.

According to a first preferred embodiment of a gearless ratchet mechanism 100 of the invention, shown in Figs. 1A to 4B, the plurality of sloping portions 230 are arranged on the first outer wall surface 140 of the larger cross-section part of the torque output member, to provide the varying distance between the inner wall surface 170 of the housing and the outer wall surface of the larger cross-section part of the torque output member.

The three possible positions for the selector 210 are shown in Figs. 2 to 4B. In Fig. 2, the selector is turned to its intermediate position where the prongs 220 are not engaged with any of the rolls 180, 190. In this position of the selector, both rolls of a pair are free to move into and out of their respective pinched position. If the housing 150 is rotated in the clockwise direction, the second roll 190 of the pair is moved in a direction towards a narrowing distance between the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member. Thus, the second roll will be in its pinched position, and torque will be transferred from the housing to the torque output member. If the housing 150 is rotated in the counterclockwise direction, the first roll 180 of the pair is moved in a direction towards a narrowing distance between the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member. Thus, the first roll will be in its pinched position, and torque will be transferred from the housing to the torque output member. In this way, torque is transferred in both directions of rotation of the housing 150. The smaller the distance is between two rolls of a pair, the smaller the play will be in the arrangement.

In Figs. 3A and 3B, the selector 210 is turned to its extreme position following an counter-clockwise rotation of the selector. In this position, the prongs 220 engage with the second roll 190 of a pair to displace the second roll from its pinched position. The second roll is thus prevented from being moved to its pinched position. If the housing 150 is rotated in the clockwise direction, as shown in Fig. 3A, no torque transfer will take place since the second roll is prevented from moving to its pinched position and the first roll 180 is moved out of its pinched position, towards the second roll, by frictional forces. There will be a gap between the second roll and either or both of the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member, which prevents any torque transfer by frictional forces. Likewise, there will be a gap between the first roll and either or both of the inner wall surface of the housing and the first outer wall surface of the larger cross-section part of the torque output member, also preventing any torque transfer by frictional forces.

If the housing 150 is rotated in the counter-clockwise direction, as is shown in Fig. 3B, the first roll 180 will be moved into its pinched position by frictional forces, and torque transfer will be possible from the housing to the torque output member 120 via the first roll. The second roll 190 will be moved towards the first roll by frictional forces, there will thus be a gap between the second roll and either or both of the inner wall surface of the housing and the outer wall surface of the larger cross-section part of the torque output member. Any torque transfer by frictional forces via the second roll is prevented, all torque transfer is taking place via the first roll.

In Figs. 4A and 4B, the selector 210 is turned to its extreme position following a clockwise rotation of the selector. In this position, the prongs 220 engage with the first roll 180 of a pair to displace the first roll from its pinched position. The first roll is thus prevented from being moved to its pinched position. If the housing 150 is rotated in the counter-clockwise direction, as is shown in Fig. 4A, no torque transfer will take place since the first roll is prevented from moving to its pinched position and the second roll 190 is moved out of its pinched position, towards the first roll, by frictional forces. There will be a gap between the first roll and either or both of the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member, which prevents any torque transfer by frictional forces. Likewise, there will be a gap between the second roll and either or both of the inner wall surface of the housing and the first outer wall surface of the larger cross-section part of the torque output member, also preventing any torque transfer by frictional forces.

If the housing 150 is rotated in the clockwise direction, as shown in Fig. 4B, the second roll 190 will be moved into its pinched position by frictional forces, and torque transfer will be possible from the housing to the torque output member 120 via the second roll. The first roll 180 will be moved towards the second roll by frictional forces, there will thus be a gap between the first roll and either or both of the inner wall surface 170 of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member. Any torque transfer by frictional forces via the first roll is prevented, all torque transfer is taking place via the second roll.

According to a second preferred embodiment of a gearless ratchet mechanism 100 of the invention, shown in Figs. 5 to 7B, the plurality of sloping portions 230 are arranged on the inner wall surface 170 of the housing, to provide the varying distance between the inner wall surface of the housing and the first outer wall surface 140 of the larger cross-section part of the torque output member. The three possible positions for the selector 210 are shown in Figs. 5 to 7B. Fig. 5 shows the selector 210 in an analogous position as that shown in Fig. 2. The only difference compared to Fig. 2 is that the sloping portions 230 defining the roll pinching areas are arranged on the housing 150 as described above. Fig. 6A is, in this context, analogous to Fig. 3A, Fig. 6B is analogous to Fig. 3B, Fig. 7A is analogous to Fig. 4A and Fig. 7B is analogous to Fig. 4B.

The gearless ratchet mechanism 100 of the invention, as shown in Figs. 1 to 7B, preferably comprises three pairs of rolls 180, 190 and the selector 210 comprises three prongs 220. Three pairs of rolls will provide the required friction forces between the housing 150 and the larger cross-section part 130 of the torque output member to transfer a higher torque.

According to a third preferred embodiment of a gearless ratchet mechanism 100 of the invention, shown in Figs. 8 to 10B, the mechanism comprises one pair of rolls 180, 190 and the selector 210 comprises two prongs 220. The larger cross-section part 130 of the torque output member comprises an enlarged section 130', arranged opposite the one pair of rolls. The gap between the inner wall surface 170 of the housing and a second outer wall surface 135 of the enlarged section of the larger cross-section part of the torque output member is relatively small, to allow contact between the inner wall surface and the second outer wall surface, when one or both of the one pair of rolls 180, 190 is in the pinched position. The torque output member (not shown) is arranged to be able to move slightly, in the radial direction, in the through hole (not shown) of the selector 210. The larger cross-section part 130 of the torque output member is thus free to move slightly, within the first space 200 of the housing 150. This embodiment is simpler in construction and still cheaper to produce, compared to the first and second embodiments, but will also transmit a high torque from the handle to the torque output member. The three possible positions for the selector 210 are shown in Figs. 8 to 10B. Fig.8 shows the selector 210 in an analogous position as that shown in Fig.2. The only difference compared to Fig. 2 is that only one pair of rolls 180, 190 is used. Fig. 9A is, in this context, analogous to Fig. 3A, Fig. 9B is analogous to Fig. 3B, Fig. 10A is analogous to Fig. 4A and Fig. 10B is analogous to Fig. 4B.

The gearless ratchet mechanism 100 according to the invention, thus does not comprise any biasing means, such as springs or spacers, for biasing the rolls 180, 190 towards their pinched position. Small gaps and tolerances between the rolls 180, 190, the selector prongs 220, the outer surface wall 140 of the larger cross-section part of the torque output member and the inner surface wall 170 of the housing are necessary to minimize the play in the mechanism according to the invention. The mechanism lends itself perfectly to medium- to high-torque applications, such as larger hand tools, such as wrenches, screwdrivers, chucks or clutches, or power tools.

The selector 210 preferably cooperates with a click-stop mechanism, which enables the selector to be positioned in its three distinct positions. In Figs. 2 to 4B, one embodiment of the click-stop mechanism is shown, comprising a protrusion 300 arranged on the outside of the housing 150 and a first recess 310, a second recess 320 and a third recess 330 all three arranged on the inside of the selector. The protrusion is of a size and shape which corresponds to the size and shape of the first, second and third recesses, respectively.

When the selector 210 is rotated counter-clockwise, the protrusion 300 engages the first recess 310 so that the selector is held in a position where torque transfer from the handle (not shown) to the torque output member (not shown) is possible only when the handle is rotated in the clockwise direction.

When the selector 210 is rotated clockwise, the protrusion 300 engages the third recess 330 so that the selector is held in a position where torque transfer from the handle (not shown) to the torque output member (not shown) is possible only when the handle is rotated in the counter-clockwise direction.

When the selector 210 is rotated to a middle position, the protrusion 300 engages the second recess 320 so that the selector is held in a position where torque transfer from the handle (not shown) to the torque output member (not shown) is possible both when the handle is rotated in the clockwise direction as when it is rotated in the counter- clockwise direction.

The person skilled in the art would realize that the protrusion may be arranged on the inside of the selector and the recesses may be arranged on the outside of the housing.

In Figs. 11A and 11B, a gearless ratchet mechanism according to an alternative embodiment of the invention is shown. The housing 150 is arranged on the torque output member 120 and the larger cross-section part 130 is arranged on the torque input member 110, otherwise the mechanism is identical to the mechanism shown in Figs. 1A and 1B. The reference numerals correspond to the features shown in Figs. 1A and 1B. An outer sleeve 300 is shown, which is arranged to fit tightly over the selector, to facilitate turning the selector. This feature may, of course, be incorporated in other embodiments of the invention also.

A further variation of the earlier described embodiment is shown in Figs. 12A to 21 B. The gearless ratchet mechanism 100' according to this embodiment comprises a torque input member 110' and a torque output member 120' including a larger cross-section part 130' at one end of the torque output member. The torque input member is preferably connected to a handle (not shown) and the torque output member may be a screwdriver blade or a tool shaft with exchangeable bits, for example. The larger cross- section part of the torque output member has a first outer wall surface 140". The ratchet mechanism further comprises a housing 150' and an inner wall surface 170". The housing is fixedly attached to the torque input member 110'. Further, a plurality of substantially cylindrical rolls are arranged in pairs, each pair comprising a first roll 180' and a second roll 190', in a first space 200' within the housing. The first space within the housing is defined by the inner wall surface 170' of the housing and the outer wall surface 140' of the larger cross-section part of the torque output member.

A selector 210", including a plurality of roll manipulating prongs 220', is arranged adjacent the housing 150', with the prongs protruding into the first space 200' within the housing. The prongs physically divide the rolls into a plurality of pairs inside the space within the housing. The torque output member 120' freely passes through a through hole 160' of the selector so that the larger cross-section part 130' of the torque output member remains inside the selector. The distance between the inner wall surface 170' of the housing and the first outer wall surface 140' of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is adjacent a minimum distance and, on the other side of the roll, is adjacent a maximum distance. Thus, a plurality of sloping portions 230', are formed.

When the selector prongs 220' are engaged with either the first 180' or the second 190' roll of a pair so that the rolls are displaced, the engaged rolls are released from their pinched position. To ensure that only frictional forces are required, to move a roll in and out of the pinched position, the two rolls of a pair will have to be relatively close to each other, even when both rolls are in the pinched position. The maximum distance between the outer surfaces of two rolls of a pair will, according to the invention, be kept to a minimum to ensure that the only forces necessary to move a roll in and out of the pinched position are frictional forces. The two rolls of a pair can be in contact when the mechanism is in a released position, i.e. one roll of a pair is in its non-pinched position, and the housing 150' is rotated in the direction of increasing distance between the inner wall surface 170' of the housing and the first outer wall surface 140' of the larger cross- section part of the torque output member of the pinched roll. All of the rolls 180', 190' preferably have substantially the same diameter and may have bevelled edges or convex end surfaces to reduce the risk of the edges of the rolls cutting into the material of the housing 150' or the selector 210" when the edges of the rolls slide on the housing and the selector, respectively. The mechanism is shown in the fully assembled state in Figs. 12B and 12C.

The plurality of sloping portions 230' are preferably arranged on the first outer wall surface 140' of the larger cross-section part of the torque output member, to provide the varying distance between the inner wall surface 170' of the housing and the outer wall surface of the larger cross-section part of the torque output member.

Further, the torque output member 120' has a splined portion 400, having axially extending splines, is arranged on the end of the torque output member which has the larger cross-section part 130'. The housing 150' comprises a cutout 112 arranged adjacent the splined portion 400, when the housing is assembled over the torque output member 120'. The housing cutout 112 preferably has a first pivot point enlargement 113 and a second pivot point enlargement 114, to accommodate a rocker arm 450. The rocker arm is substantially oblong and curved, having a first end 451 and a second end 452. The rocker arm 450 further has a first hook 455, arranged at the first end, and a second hook 456, arranged at the second end. The pointed portion of each hook faces away from the rocker arm, and in the same direction as the rocker arm is curved, see Fig 16A. Arranged substantially at the middle of the rocker arm, and protruding perpendicularly to the longitudinal direction of the rocker arm, are a first rocker pivot extension 460 and a second rocker pivot extension 461. The first rocker pivot extension and the second rocker pivot extension are cooperating and held by the first pivot point enlargement 113 and the second pivot point enlargement 114, respectively, of the housing cutout 112, to enable the rocking arm, when mounted in the housing cutout, to tilt between two end positions and make contact with the splined portion 400 with either the first hook 455 or the second hook 456, depending upon which end position is reached. If the rocker arm 450 is in an intermediate position, no contact is made with the splined portion.

The three possible positions for the selector 210' are shown in Figs. 19Ato 21 B. In Figs. 19A/19B, the selector is turned to its intermediate position where the prongs 220' are not engaged with any of the rolls 180', 190'. In this position of the selector, both rolls of a pair are free to move into and out of their respective pinched position. If the housing 150" is rotated in the clockwise direction, the second roll 190' of the pair is moved in a direction towards a narrowing distance between the inner wall surface 170' of the housing and the first outer wall surface 140' of the larger cross-section part of the torque output member. Thus, the second roll will be in its pinched position, and torque will be transferred from the housing to the torque output member. If the housing 150' is rotated in the counter-clockwise direction, the first roll 180' of the pair is moved in a direction towards a narrowing distance between the inner wall surface 170' of the housing and the first outer wall surface 140" of the larger cross-section part of the torque output member. Thus, the first roll will be in its pinched position, and torque will be transferred from the housing to the torque output member. In this way, torque is transferred in both directions of rotation of the housing 150'. The smaller the distance is between two rolls of a pair, the smaller the play will be in the arrangement.

In Figs. 21A and 21 B, the selector 210' is turned to its extreme position following an counter-clockwise rotation of the selector. In this position, the prongs 220' engage with the second roll 190' of a pair to displace the second roll from its pinched position. The second roll is thus prevented from being moved to its pinched position. If the housing 150^* is rotated in the clockwise direction, as shown in Fig. 21 A, no torque transfer will take place since the second roll is prevented from moving to its pinched position and the first roll 180' is moved out of its pinched position, towards the second roll, by frictional forces. There will be a gap between the second roll and either or both of the inner wall surface 170* of the housing and the first outer wall surface 140' of the larger cross- section part of the torque output member, which prevents any torque transfer by frictional forces. Likewise, there will be a gap between the first roll and either or both of the inner wall surface of the housing and the first outer wall surface of the larger cross- section part of the torque output member, also preventing any torque transfer by frictional forces.

If the housing 150' is rotated in the counter-clockwise direction, as is shown in Fig. 21 B, the first roll 180' will be moved into its pinched position by frictional forces, and torque transfer will be possible from the housing to the torque output member 120^* via the first roll. The second roll 190' will be moved towards the first roll by frictional forces, there will thus be a gap between the second roll and either or both of the inner wall surface of the housing and the outer wall surface of the larger cross-section part of the torque output member. Any torque transfer by frictional forces via the second roll is prevented, all torque transfer is taking place via the first roll.

In Figs. 20A and 20B, the selector 210' is turned to its extreme position following a clockwise rotation of the selector. In this position, the prongs 220' engage with the first roll 180' of a pair to displace the first roll from its pinched position. The first roll is thus prevented from being moved to its pinched position. If the housing 150' is rotated in the counter-clockwise direction, as is shown in Fig. 20A, no torque transfer will take place since the first roll is prevented from moving to its pinched position and the second roll 190' is moved out of its pinched position, towards the first roll, by frictional forces. There will be a gap between the first roll and either or both of the inner wall surface 170' of the housing and the first outer wall surface 140' of the larger cross-section part of the torque output member, which prevents any torque transfer by frictional forces. Likewise, there will be a gap between the second roll and either or both of the inner wall surface of the housing and the first outer wall surface of the larger cross-section part of the torque output member, also preventing any torque transfer by frictional forces.

If the housing 150' is rotated in the clockwise direction, as shown in Fig.20B, the second roll 190' will be moved into its pinched position by frictional forces, and torque transfer will be possible from the housing to the torque output member 120" via the second roll. The first roll 180' will be moved towards the second roll by frictional forces, there will thus be a gap between the first roll and either or both of the inner wall surface 170' of the housing and the first outer wall surface 140" of the larger cross-section part of the torque output member. Any torque transfer by frictional forces via the first roll is prevented, all torque transfer is taking place via the second roll.

An end cap 500 is arranged to be mounted over the housing 150'. The end cap thus has an inner shape substantially corresponding to the external shape of the housing. The end cap further has a first spring recess 501 , a second spring recess 502, a first spring activating protrusion 503 and a second spring activating protrusion 504. A rocker spring 510 is arranged to selectively press the rocker arm 450 towards either of its end positions or hold the rocker arm in the intermediate position. The elongate rocker spring has a middle portion 511 , a first hooked end 512 and a second hooked end 513. Since the end cap 500 is attached to the housing 150', the end cap is moved relative the selector 210', when the selector is manipulated to set the torque transfer direction (as described in conjunction with the previous embodiment). The rocker spring is located between the rocker arm 450 and the inside wall of the end cap, so that the first hooked end 512 is engageable with a first spring detent 453, arranged on the first end 451 of the rocker arm and the second hooked end 513 is engageable with a second spring detent 454, arranged on the second end 452 of the rocker arm. Both the first spring detent and the second spring detent face away from the direction in which the rocker arm 450 is curved. Thus, when the selector is held in a position for torque transfer in either direction, the rocker spring is pressed by the first spring activating protrusion 503 on one side of the middle portion 511 and the second spring activating protrusion 504 on the other side, keeping the rocker spring in a position where it presses equally on the two ends of the rocker arm. The rocker arm is held in a position where it is not making contact with the splined portion 400, as is shown in Figs. 19A and 19B. When the selector is held in a position for torque transfer in the clockwise direction (as shown in Figs.20A and 20B), the first spring activating protrusion 503 is rotated to the right in the Figs., applying pressure to the second hooked end 513 of the rocker spring 450. At the same time, the second spring activating protrusion 504 will be rotated so that it does not contact the rocker spring. Since there is pressure applied only to the second hooked end of the rocker spring, the rocker spring will press the rocker arm 450 so that the second end 452 of the rocker arm will contact the splined portion 400. The second hooked end has a hook shape which is rounded on the outer side and substantially straight on the inner side, enabling the second hooked end to securely grip the splined portion 400 when the splined portion is rotated (together with the torque output member 120") in an clockwise direction. When the splined portion 400 is rotated in the anti-clockwise direction, the second hooked end 513 will slip on the splined portion because the rounded outer side of the second hook end cannot grip the splined portion. Thus, the torque transfer via the first rolls 180' and the second rolls 190' of the torque transfer mechanism (see description above) is augmented by the ratcheting action of the rocker arm 450, providing a reassuring clicking sound, when the mechanism is rotated in the direction opposite the direction of torque transfer. Similarly, when the selector is held in a position for torque transfer in the anti-clockwise direction (as shown in Figs. 21 A and 21 B), the second spring activating protrusion 504 is rotated to the left in the Figs., applying pressure to the first hooked end 512 of the rocker spring 450. At the same time, the first spring activating protrusion 503 will be rotated so that it does not contact the rocker spring. Since there is pressure applied only to the first hooked end of the rocker spring, the rocker spring will press the rocker arm 450 so that the first end 451 of the rocker arm will contact the splined portion 400. The first hooked end has a hook shape which is rounded on the outer side and substantially straight on the inner side, enabling the second hooked end to securely grip the splined portion 400 when the splined portion is rotated (together with the torque output member 120') in an anti-clockwise direction. When the splined portion 400 is rotated in the clockwise direction, the first hooked end 512 will slip on the splined portion because the rounded outer side of the first hook end cannot grip the splined portion.

A further embodiment of the invention is shown in Figs. 22A to 24. A box-end wrench 600 having a head end 605 and a handle end 650 is shown. The head end has a tool mount 610, preferably a hex opening for attaching tools (not shown) or engaging nuts (not shown). The head end further has a substantially cylindrical housing portion 606, which encloses the ratcheting mechanism. The housing has a first chamber 615, a second chamber 616 and a generally circular cutout 617 arranged there between. The circular cutout has a ratchet arm cutout 645, preferably arranged adjacent the handle end 650. A ratchet arm 630 is insertably arranged in the ratchet arm cutout, and biased towards the circular cutout 617 by a ratchet arm biasing means 635, such as a screw spring or similar means. The biasing means is preferably held in a biasing means extension 640 of the ratchet arm cutout 645. The ratchet arm is pivotably held in a ratchet arm extension 646 of the ratchet arm cutout 645, so that the ratchet arm is pivotable in a direction towards the circular cutout 617, and against the biasing force of the biasing means 635 in a direction towards the biasing means. The ratcheting mechanism comprises a torque output member 620 having a circular outer surface, which is provided with a plurality of splines 621. The torque output member is rotatably arranged in the circular cutout 617, and the ratchet arm 630 is biased towards the plurality of splines 621. The ratchet arm has a hooked end 631 , which is arranged on the end of the ratchet arm which is pivoted by the biasing means, whilst the opposite end of the ratchet arm is held by the ratchet arm extension 646. The hooked end 631 of the ratchet arm has an outer end surface which is substantially perpendicular to the longitudinal direction of the ratchet arm, and an inner surface which is rounded. When the ratchet arm makes contact with the torque output member 620 and the plurality of splines 621 , the hooked end of the ratchet arm will allow rotation of the torque output member (torque transfer from the wrench handle to the torque output member) only in the direction where the plurality of splines make contact with the substantially perpendicular surface of the hooked end of the ratchet arm. If the wrench is rotated in the other direction, the rounded surface of the hooked end will allow the ratchet arm to slip over the plurality of splines, producing a ratchet sound. To allow rotation of the torque output member in any desired direction, the wrench can be flipped over 180 degrees and the tool or nut attached on the desired side of the wrench head.

To further augment the torque transfer (to allow higher torque), the torque transfer member 620 has a cutout chamber 660, which accommodates a pair of rolls 665 held apart and biased in one direction of rotation by a biasing prong 670. The rolls are thus squeezed between the inner surface of the first chamber 615 and a curved portion 675 of the cutout chamber 660, to provide torque transfer in the direction of rotation of the wrench handle, similarly to what has been described earlier concerning the torque transfer using pairs of rolls. However, the configuration of rolls and housing surfaces etc. used in this embodiment only allows torque transfer in one direction of rotation.

It will be appreciated that the above description relates to the preferred embodiment by way of example only. Many variations on the invention will be obvious to those knowledgeable in the field, and such obvious variations are within the scope of the invention as described and claimed, whether or not expressly described.

For example, the plurality of sloping portions may be arranged on the first outer surface wall of the larger cross-section part of the torque output member as well as on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the first outer wall surface of the larger cross-section part of the torque output member. An alternative embodiment of the click-stop mechanism for the selector is a traditional biased ball, held in either the selector or the housing, which clicks into recesses arranged either in the housing or the selector. Thus, the ball cooperates with a plurality of recesses to engage the selector in its distinct positions.

The torque output member has been shown as having the large cross-section part 130, and the housing 150 has been shown attached to a handle. The person skilled in the art would realize that the arrangement may be reversed, without hampering the function of the device, so that the large cross-section part would be arranged on the handle and the housing would be arranged on the torque output member, as is shown in Figs. 11 to 12.

INDUSTRIAL APPLICABILITY

The invention provides a simplified gearless ratchet mechanism for use with power tools or hand tools, which has a backup ratchet mechanism for providing, on one hand, a sound feedback for when the mechanism is used in its non-torque transfer direction of rotation, and on the other hand, an additional torque transfer mechanism for use in case of failure or slippage of the roll type torque transfer mechanism.

Claims

CLAIMS:

1. A gearless ratchet mechanism comprising a torque input member, a torque output member including a larger cross-section part at one end of said torque output member, the larger cross-section part of the torque output member having an outer wall surface, a housing including a through hole and an inner surface wall, said housing being fixedly attached to the torque input member, a plurality of substantially cylindrical rolls arranged in pairs, each pair comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, a selector including a plurality of roll manipulating prongs, where the prongs divide the rolls into a plurality of pairs inside the space within the housing, wherein the distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is close to a minimum distance and, on the other side of the roll, is close to a maximum distance, and when the selector prongs are engaged with either the first or the second roll of a pair, the engaged rolls are released from their pinched position, and wherein the maximum distance between the outer surfaces of two rolls of a pair is minimized, so that the only forces to move a roll in and out of the pinched position, are frictional forces.

2. A gearless ratchet mechanism according to claim 1 , wherein a plurality of sloping portions are arranged on the outer wall surface of the larger cross-section part of the torque output member, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross- section part of the torque output member.

3. A gearless ratchet mechanism according to claim 1 , wherein a plurality of sloping portions are arranged on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outerwall surface of the larger cross-section part of the torque output member.

4. A gearless ratchet mechanism according to claim 1 , wherein a plurality of sloping portions are arranged on the outerwall surface of the larger cross-section part of the torque output member as well as on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

5. A gearless ratchet mechanism according to claim 1 , comprising three pairs of rolls and where the selector comprises three prongs.

6. A gearless ratchet mechanism according to claim 1 , comprising one pair of rolls and where the selector comprises two prongs.

7. A gearless ratchet mechanism according to claim 1 , which does not comprise any biasing means, such as springs, for biasing the rolls towards their pinched position.

8. A gearless ratchet mechanism according to claim 1 , further comprising a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

9. A gearless ratchet mechanism comprising a torque input member, a torque output member including a larger cross-section part at one end of the torque output member, said larger cross-section part of the torque output member having an outer wall surface, a housing including a through hole and an inner surface wall, said housing being fixedly attached to the torque input member, a plurality of substantially cylindrical rolls arranged in pairs, each pair comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, a selector including a plurality of roll manipulating prongs, where the prongs divide the rolls into a plurality of pairs inside the space within the housing, said selector being rotatable between three positions to transfer torque from said torque input member to said torque output member in either a clockwise direction of rotation where torque transfer is prevented in the anti-clockwise direction, an anti-clockwise direction of rotation where torque transfer is prevented in the clockwise direction, or both directions where the torque transfer is provided in either direction depending upon the direction of rotation of said torque input member, wherein the distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is close to a minimum distance and, on the other side of the roll, is close to a maximum distance, and when the selector prongs are engaged with either the first or the second roll of a pair, the engaged rolls are released from their pinched position, and wherein the distance between the outer surfaces of two rolls of a pair is minimized by providing minimized gaps between said rolls, said selector prongs, said outer surface wall and said outer surface wall, so that the only forces to move a roll in and out of the pinched position, are frictional forces.

10. A gearless ratchet mechanism according to claim 9, wherein a plurality of sloping portions are arranged on the outerwall surface of the larger cross-section part of the torque output member, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross- section part of the torque output member.

11. A gearless ratchet mechanism according to claim 9, wherein a plurality of sloping portions are arranged on the inner surface wall of the housing, to provide the varying distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member.

12. A gearless ratchet mechanism according to claim 9, further comprising a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

13. A gearless ratchet mechanism comprising a torque input member, a torque output member including a larger cross-section part at one end of the torque output member, said larger cross-section part of the torque output member having an outer wall surface, a housing including a through hole and an inner surface wall, said housing being fixedly attached to the torque input member, a pair of substantially cylindrical rolls comprising a first roll and a second roll in a first space within the housing defined by the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member, a selector including a pair of roll manipulating prongs, where the prongs flank the rolls inside the space within the housing, said selector being rotatable between three positions to transfer torque from said torque input member to said torque output member in either a clockwise direction of rotation where torque transfer is prevented in the anticlockwise direction, an anti-clockwise direction of rotation where torque transfer is prevented in the clockwise direction, or both directions where the torque transfer is provided in either direction depending upon the direction of rotation of said torque input member, wherein the distance between the inner surface wall of the housing and the outer wall surface of the larger cross-section part of the torque output member varies from a minimum value, which is smaller than the diameter of an individual roll, to a maximum value, which is larger than the diameter of an individual roll, so that each individual roll, on one side of the roll, is close to a minimum distance and, on the other side of the roll, is close to a maximum distance, and when the selector prongs are engaged with either the first or the second roll of said pair of rolls, the engaged roll is released from its pinched position, and wherein the maximum distance between the outer surfaces of said pair of rolls is minimized by providing minimized gaps between said rolls, said selector prongs, said outer surface wall and said outer surface wall, so that the only forces to move a roll in and out of the pinched position, are frictional forces.

14. A gearless ratchet mechanism according to claim 13, further comprising a backup ratchet sound generating mechanism having a spring biased rocker arm engageable with a splined portion of the torque output member.

15. A box-end wrench having a head end and a handle end, the head end having a tool mount, for attaching tools or engaging nuts, and a substantially cylindrical housing portion, the housing portion having a ratchet mechanism comprising a torque output member having a circular outer surface, which is provided with a plurality of splines, the torque output member being rotatably arranged in the housing and further has a cutout chamber, which accommodates a pair of rolls held apart and biased in one direction of rotation by a biasing prong, the rolls being squeezed between an inner surface of the housing and a curved portion of the cutout chamber, to provide torque transfer in the direction of rotation of the wrench handle, the housing further comprising a backup ratchet sound generating mechanism having a spring biased ratchet arm engageable with a splined portion of the torque output member.

16. A box-end wrench according to claim 15, the substantially cylindrical housing portion further having a first chamber, a second chamber and a generally circular cutout arranged between the first chamber and the second chamber, the circular cutout having a ratchet arm cutout arranged adjacent the handle end, a ratchet arm being insertably arranged in the ratchet arm cutout, and biased towards the circular cutout by a ratchet arm biasing means, the biasing means being held in a biasing means extension of the ratchet arm cutout, the ratchet arm being pivotably held in a ratchet arm extension of the ratchet arm cutout, so that the ratchet arm is pivotable in a direction towards the circular cutout, and against the biasing force of the biasing means in a direction towards the biasing means, the torque output member being rotatably arranged in the circular cutout, and the ratchet arm being biased towards the plurality of splines, the ratchet arm having a hooked end, which is arranged on the end of the ratchet arm which is pivoted by the biasing means, whilst the opposite end of the ratchet arm is held by the ratchet arm extension, the hooked end of the ratchet arm having an outer end surface which is substantially perpendicular to the longitudinal direction of the ratchet arm, and an inner surface which is rounded, so that when the ratchet arm makes contact with the torque output member and the plurality of splines, the hooked end of the ratchet arm will allow rotation of the torque output member only in the direction where the plurality of splines make contact with the substantially perpendicular surface of the hooked end of the ratchet arm, and when the wrench is rotated in the other direction, the rounded surface of the hooked end will allow the ratchet arm to slip over the plurality of splines, producing a ratchet sound.