BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a ratchet drive mechanism having features of the present invention.
FIG. 2 is a partially disassembled view of the mechanism of FIG. 1.
FIG. 3 is a further disassembled view of the mechanism of FIGS. 1-2.
FIG. 4 is a fully disassembled view of the mechanism of FIGS. 1-3.
FIGS. 5-7 are elevation, side, and top views respectively of the ratchet stop of the mechanism of FIGS. 1-4.
FIG. 8 is a sectional view taken substantially through the plane A-A shown in FIG. 1.
FIG. 9 is a perspective view from below of a first switch of the mechanism of FIG. 1.
FIG. 10 is a perspective view from below of a second switch of the mechanism of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the drawings which are provided by way of example and not limitation, there is shown a ratchet drive mechanism incorporating features of the present invention. Referring to FIGS. 1-4, a ratchet drive mechanism 20 in accordance with the present invention is exemplified, generally comprising a shaft 22, an outer switch 24, an inner switch 28, and a ratchet drum 26. A handle (not shown) may be connected with the ratchet drum 26 for manipulating and rotating the drive mechanism 20.
As exemplified in FIG. 1, the shaft 22 may include an opening 23 at the forward end, which preferably may be hexagonal in profile, and adapted to receive driver bits carrying tips of various sizes and shapes. Moving from FIG. 1 to FIG. 2, there is shown how the cylindrical outer switch 24 slides over the shaft 22, and fits rotatably over the cylindrical inner switch 28. A first C-clip 60, snapped into a groove 62 on the shaft, is configured to retain the outer switch 24 on the shaft 22. An axial spring 58 is positioned behind the outer switch to bias the outer switch forwardly. Moving from FIG. 2 to FIG. 3, there is shown how the cylindrical inner switch 28 slides over the shaft 22, and fits rotatably over the cylindrical ratchet drum 26. A second C-clip 54 snaps into a second groove 56 on the shaft to retain the inner switch on the shaft. (Accordingly, to install the inner switch 28 on the shaft, second C-clip 54 must be removed from second groove 56 as shown in FIG. 3, the inner switch must be installed, and the second C-clip snapped into second groove 56.)
Referring now to FIG. 4, there is exemplified how the shaft 22 may include gear teeth 30 circumferentially surrounding the shaft 22 and extending radially. Two pairs of pawls 32, 34 and 36, 38 are provided and are configured to fit within a complex shaped slot 40 that is machined into the ratchet drum 26. Each pawl has a side arm, 33, 35, 37, 39 (FIG. 8), whose function is explained below. As best seen in FIG. 8, each pair of pawls is configured to allow inward bias by springs 42, 44. The springs 42, 44 are preferably looped from a single strand of wire, and arranged in relation to the ratchet drum to pivot about pins or screws 50 that may be inserted or screwed into the ratchet drum when the springs are correctly positioned after the pawls are inserted. The two springs 42, 44 each have two ends, 46, 48, each end configured to bias a pawl toward the gear teeth 30 on the shaft under the correct conditions as described below.
Under a preferred method of assembly, the pawls 32, 34, 36, 38 are first installed within the slot 40 in the ratchet drum 26. The shaft 22 is then inserted within a bore 52 (FIG. 3) in the ratchet drum, until the gear teeth 30 are positioned adjacent the pawls. Thereafter, the inner switch 26 is installed over the shaft, and over the ratchet drum, as exemplified in FIG. 2. At this stage, a first C-clip may 54 be snapped onto the shaft at a groove 56 to prevent both the inner switch 28 and the ratchet drum 26 from riding up the shaft. An axial spring 58 is slid over the shaft to abut the first C-clip, after which the outer switch 24 is slid over the shaft 22 and over the inner switch 28. A second C-clip 60 is snapped onto the shaft at a groove 62 to prevent the outer switch from riding up the shaft. In this configuration, the outer switch 24 may be manually depressed against the axial spring 58 towards contact with the inner switch 28, and upon release, the spring 58 will bias the outer switch out of contact with the inner switch.
Further features of the inner switch 28 and outer switch include the following structure. On a surface of the inner switch 28 there are a plurality of preferably radial teeth 64 (FIGS. 2-4) which are configured to mate with teeth 66 (FIG. 9) on an opposing surface of the outer switch 24. When the outer switch 24 is manually depressed against the spring 58, the opposing teeth sets 64, 66 are configured to engage with each other, and to disengage when the depressing force is released. The inner switch 28 includes, affixed to a surface, posts 68 which preferably extend axially downwardly to be positioned adjacent the pawls 32, 34, 36, 38 when the mechanism is assembled (FIG. 8).
In order to stabilize the angular rotational position of the inner switch 28 in relation to the ratchet drum 26, a radial groove 70 is machined into the ratchet drum 26 for positioning a helical spring 72 within. A steel ball 74 is inserted in the groove at the end of the spring so that the spring biases the ball radially outwardly. The inner switch 28 is shaped to include three depressions, 76, 78, 80, each positioned at the level of the groove 70, and configured to receive a portion of the ball 72. When the inner switch is rotated, the outwardly biased ball may come to rest in one of the depressions, and, in combination with the spring 72, biases the inner switch 28 against further rotation in relation to the ratchet drum 26. This bias against rotation may be overcome by the user, to select stable positions for the inner switch 28 corresponding to the positions of the three depressions 76, 78, 80.
In use, and with reference to FIG. 8, the ratchet drive mechanism of the present invention may be operated as follows. The user, wishing to change the direction of the ratchet drive from clockwise to counterclockwise, manually depresses the outer switch 24, from a first forwardly position of equilibrium, against the bias of the spring 58 to a second rearwardly position where it engages the teeth 64, 66 interface on the inner switch 28 and outer switch 24. The outer switch is rotated to the right as indicated by the direction arrows B in FIG. 8, thereby rotating the inner switch by the same amount to the right. The posts 68 of the inner switch engage the side arms (in this case 39, 35) of two pawls (in this case 36, 34) in the pawl pairs, thus biasing those pawls away from engagement with the teeth 30 on the shaft 22. Each pawl that is biased away from the teeth biases the spring end (in this case 48) with which it is in contact, thereby biasing the opposite spring end 46 toward the teeth 30. The spring end 46 in turn biases the remaining pawl (32, 38) in each pawl pair toward the teeth. A corner of the latter pawls 32, 38 is thus inserted between the teeth to prevent the shaft from rotating in a counterclockwise direction in relation to the ratchet drum 26. At this point, the biased ball 74 is configured to snap into one of the depressions 76, 78, 80, to hold the ratchet drum 26, and hence the pawls, in a fixed and stable angular relationship with the shaft 22. This will allow any rotational force applied by the user to the ratchet drum via a handle (not shown) to be transmitted to the shaft for rotating a driver tip or the like. It also has the result that when the user rotates the mechanism in the direction opposite to the driving direction, the teeth, because of their shape, do not lock on the pawls 32, 38, but bias them out of the way against the bias of spring ends 46, causing the familiar clicking sound of a ratchet drive mechanism.
It will be further appreciated that, by depressing the outer switch 24 rearwardly into contact with the inner switch, and turning the outer switch leftwards will have the same result as above, only in a reverse direction, causing the alternate pawls 34, 36 to engage with the teeth 30 while pawls 32, 38 disengage (not shown), and providing a clockwise driving direction for the shaft. A final possibility is for the user to rotate the switches 24, 28 to set the pawls in an intermediate position (not shown) in which all the pawls engage the teeth to provide both a clockwise and anti-clockwise driving direction.
Once the pawls are moved to the desired position in the ratchet drum as above, the user releases hold of the outer switch 24. The axial spring 58 urges the outer switch 24 axially forwardly along the shaft, thereby disengaging the sets of teeth 64, 66 between the two switches 28, 24 respectively from each other.
It will now be appreciated that, when the outer switch 24 is its forwardly position as set by the axial spring, any unintentional impact to the outer switch 24 will cause the outer switch to rotate freely about the inner switch, without resetting the position of the pawls to reverse the drive direction of the ratchet drive mechanism, or engage the mechanism to drive in both directions. This feature provides the advantage that the user will not frequently find the drive direction being accidentally switched by inadvertent bumps or knocks to the switching mechanism, a characteristic common in prior art devices and highly annoying when the user is working in an awkward or confined space that prevents him from easily resetting the switch.
The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
Patent Application
20080092695
