Ratchet Wrench

The present invention relates to a ratchet wrench or spanner of the kind which comprises a handle having mounted on one end thereof a ratchet head which accommodates a rotatable mechanism. The direction of rotation of the mechanism can be adjusted by means of a ratchet device, and the other end of the handle is provided with a grip surface for facilitating manual operation of the ratchet wrench.

Ratchet wrenches of the aforesaid kind are known generally. The ratchet device used with the most common type of ratchet wrench available today is located in the immediate vicinity of the rotatable mechanism. Naturally, it is highly impracticable for the fitter in having the ratchet device positioned away from the handle gripping surface, since this would either force the fitter to release his grip on the handle in order to reset the ratchet device when wishing to rotate or turn the wrench in an opposite direction, or to reset the ratchet device with his other hand (which is often used to support or to grip the work in progress in some other way).

In recent times, ratchet wrenches have been introduced with which a ratchet-device operating element is provided on the wrench handle, more or less in the vicinity of the handle gripping surface. In this case, the operating element has the form of a button which can be moved in the direction of the handle axis. This button is intended to be operated with the thumb of the hand used to grip the handle gripping surface, and although having solved the problem of needing to lift a hand in order to reset the ratchet device, the button device is still not an optimal manoeuvering device when seen from an ergonomical aspect. In order to satisfy any such requirement, it is necessary to reconstruct the whole of the ratchet wrench in a qualified fashion.

Penetrative studies as to how ratchet wrenches are manoeuvered in different situations have established that the wrench handle, and particularly its gripping surface, shall preferably have a generally round cross-section. In order to achieve optimum ergonometry, the means used to reset the rotational direction of the rotatable mechanism of the ratchet wrench shall have a form which is well adapted to the gripping surface and which is located in the immediate vicinity of said gripping surface.

This is achieved with the inventive ratchet wrench, in that a rotatable device is provided on the wrench handle, and connected to the operating element used to reset the ratchet device.

According to one preferred embodiment of the inventive ratchet wrench, the rotatable device has the form of a sleeve situated in the immediate vicinity of or within the gripping surface of the handle, and the manoeuvering element is arranged to move along the handle, in its longitudinal direction. A recess is preferably provided in the handle to accommodate the manoeuvering element, which includes a ratchet spring. One end of the ratchet spring engages the ratchet device at the head of the handle and the opposite end of the spring has the form of a hairpin-shaped element which is connected to the sleeve.

The sleeve can be advantageously rotated about the longitudinal axis of the handle, between two end positions. Rotation of the sleeve activates the hairpin-like element of the ratchet spring, said element being mounted for movement over a shoulder provided on the bottom of a chamber which forms part of the recess formed in the handle. The hairpin-like element thus has a bistable function, in that the element has two rest positions, one on each respective side of the aforesaid shoulder. When the hairpin-like element passes from one rest position to the other, the ratchet spring is rotated so that a crank-like part of the element which engages the ratchet device functions to reset said device.

The ratchet device of the inventive ratchet wrench has per se a configuration which enables the inventive ratchet wrench to be given an optimal ergonometrical design. In the case of the preferred embodiment of the inventive ratchet wrench, the ratchet device is accommodated in a ratchet chamber provided in the handle head. The ratchet chamber is open towards a wheel chamber in which a ratchet wheel is journalled, together with the rotatable mechanism. Rotation of the ratchet wheel is always latched by means of the ratchet device in one direction relative to the handle while permitting rotation of said wheel in the opposite direction. The ratchet device can be adjusted between two ratchet positions, corresponding to the bistable positions of the hairpin-like element of the ratchet spring.

In the case of the preferred embodiment of the inventive ratchet wrench, the ratchet wheel has a toothed peripheral surface in which the ratchet device engages. The ratchet device conveniently has a kidney-shaped body whose surface is intended to engage with the ratchet wheel and the radius of curvature of which corresponds to the radius of the ratchet wheel, whereas the opposite surface of the body has a smaller radius of curvature and is intended to coact with two mutually opposite walls of the ratchet chamber. The radius of curvature of said opposing walls of the ratchet chamber coincide with the convex radius of curvature of the ratchet device. The convex radius of curvature of the ratchet device merges with an inwardly angled straight line at both ends.

Because the crank part of the ratchet spring is rotatably journalled directly in the ratchet body, the ratchet body can be immediately snapped to another setting by commensurate rotation of the gripping surface sleeve .

An exemplifying embodiment of the inventive ratchet wrench will now be described in more detail with reference to the accompanying drawings, in which

FIG. 1 is a top view of the basic body structure of the preferred embodiment of an inventive ratchet wrench, this basic body structure forming the handle and head of the ratchet wrench;

FIG. 2 is a longitudinal section view of the basic body structure taken on the line II--II in FIG. 1;

FIG. 3 is a sectional view corresponding to the view of FIG. 2, taken through parts of the assembled inventive ratchet wrench;

FIGS. 4A and 4B are cross-sectional views of the inventive ratchet wrench, seen in the direction A--A in FIG. 3, and showing respective settings of the ratchet spring of said wrench;

FIG. 5 is a longitudinal section view corresponding to the longitudinal section view of FIG. 3, taken through the sleeve which functions to activate the ratchet spring;

FIG. 6 illustrates the sleeve of the FIG. 5 embodiment, seen in the direction A--A in FIG. 3;

FIG. 7 is a top view of the rotatable mechanism and its ratchet wheel accommodated in the wrench head; and

FIGS. 8A and 8B show the head end of the wrench, with the covering plate removed in order to show the ratchet device in its inoperative position and in its operative driving position respectively.

The ratchet wrench according to the preferred embodiment of the present invention is constructed around a base body structure, illustrated in FIGS. 1 and 2. The basic body structure has the form of a handle 2 which is terminated at one end with a head 12. Extending along the handle 2 is a recess 6 which merges with a crank chamber 15 in the vicinity of the head 12 and with an operating chamber 7 at the opposite, hand-grip end of the handle. The recess 6 forms journalling means for an operating element which, in the preferred embodiment, has the form of a ratchet spring 1 which is movable between two distinct rest or terminal positions. These rest positions are defined by a shoulder 8 located on the bottom surface of the operating chamber 7, as described in more detail here below with reference to FIGS. 3 and 4. The crank chamber 15 located adjacent the head 12 of the wrench connects with a wheel chamber 16 whose main axle is generally perpendicular to the longitudinal axis or main of the handle 2 and which forms a through-passing hole that extends from the upper surface of the head 12 and out through its bottom surface. The wheel chamber 16 is intended to form journalling means for a rotatable ratchet wheel 14, as described below in more detail with reference to FIGS. 7 and 8.

Illustrated to the left of FIG. 3 is the transition part of the shaft 2 to the wrench head (not shown) while illustrated to the right of FIG. 3 is the hand grip-end of the handle 2. As shown in the Figure, the ratchet spring 1 is journalled in the recess 6 beneath a cover plate 5 which extends from the wheel chamber 16 (FIGS. 1 and 2) and closes the crank chamber 15 and the recess 6 and terminates at the operation chamber 7. The cover plate 5 rests against the planar surfaces 9, 10 located around the recess 6 (FIG. 1), said plate being preferably secured to said surfaces with the aid of screws or some other appropriate fastener (not shown).

The handgrip-end of the handle 2 carries an ergonomically configured gripping sleeve 4 which is provided with a well-shaped gripping surface suited to the hand of the person using the wrench. The gripping sleeve 4 extends axially in the longitudinal direction of the handle 2 along the whole of the operation chamber 7 and continues a short distance in over the recess 6. The end of the gripping sleeve 4 located adjacent the recess 6 carries a partially rotatable resetting sleeve 3. The resetting sleeve 3 can thus be rotated around the longitudinal axis of the handle 2, between two end positions which are determined by mutually coacting stop means (not shown) mounted on the resetting sleeve-attachment means and in the gripping sleeve 4. These two end positions correspond to the two distinct rest positions of the ratchet spring 1.

The end of the ratchet spring 1 which projects into the crank chamber 15 has the form of a crank 11 which is intended to coact with a ratchet device 13, or pawl means as described in more detail herebelow with reference to FIGS. 7 and 8. That part of the spring 1 which projects into the operating chamber 7 has a hairpin-like fold from which two legs 21, 22 extend. The one leg 21 is guided generally along the bottom of the chamber 7 up to the shoulder means 8 provided on said chamber bottom, where said one leg 21 merges with the other leg 22, which extends back through the chamber 7 above the first leg 21 and coacts with the resetting sleeve 3. The leg 21 and the crank 11 may have a mutually coinciding rotational axis, whereas that part which mutually connects these parts of the ratchet spring 1 is journalled excentrically in the recess 6. The rotational axes of the crank 11 and the leg 21 are preferably located at different distances from the main rotational axis of the spring 1.

FIGS. 5 and 6 are separate views of the resetting sleeve 3. As will be seen from both FIGS. 3 and 6, the resetting sleeve 3 has the shape of a truncated cone which coincides with the terminating shape of the gripping sleeve 4 and its junction with the handle 2. Mounted on the inner surface of the resetting sleeve 3 is an attachment device 23 in which the outer end 24 of the second leg 22 of the spring 1 engages. The attachment device 23 thus has an attachment 25 for the end 24 of the spring leg 22, as shown in FIG. 5. The attachment device 23 is arranged to extend in an opening 26 in the gripping sleeve 24. Similar to the outer surface of the gripping sleeve 4, the outer surface of the resetting sleeve 3 is provided with a grip-friendly embossment pattern. As shown in FIG. 6, an appropriate surface patterning of the resetting sleeve 3 has the form of crests and troughs 28 which extend in the longitudinal direction of the sleeve.

FIG. 4 illustrates the operation chamber 7 as seen from the end marked with the directional arrows A--A in FIG. 3. In this respect, FIGS. 4A and 4B illustrate respectively two possible end positions of the ratchet spring 1 in the spaces 30, 31 on either side of the should means 8. As will be seen from FIG. 4, the gripping sleeve 4 is attached to the handle 2 and the recess 6 is covered by the plate 5. As indicated by the arrows B1 and B2, the resetting sleeve 3 and its attachment device 23 for attachment of the second ratchet-spring leg 22 is rotatable, wherein rotation of the sleeve results in the leg 21 snapping over the shoulder 8 and adopting a respective end position in the spaces 30 and 31. These end positions correspond to the extent to which the resetting sleeve 3 is able to rotate.

As described below with reference to FIG. 8, FIG. 4A illustrates the end position of the spring 1 when the ratchet wrench is released for return idling movement to the right (in the direction of the arrow P1 in FIG. 8A) during which idling movement the mechanism 19 (FIGS. 7 and 8) is movable relative to the handle. FIG. 4B illustrates the end position of the ratchet spring 1 when the wrench is released for corresponding return movement in the opposite direction (to the left).

FIG. 7 is a separate view of the mechanism 19 mounted rotatably in the wheel chamber 16 of the wrench head 12 illustrated in FIGS. 1 and 2. The mechanism 19 comprises a ratchet wheel 14 which carries a tool holder or boss 40, for example in the form of a square peg onto which a suitable so-called box socket can be fitted for nut-tightening and nut-loosening purposes. The tool holder 40 is preferably connected fixably to the ratchet wheel 14 and rotates together therewith. The peripheral side surface 17 of the ratchet wheel 14 is provided with a ring of teeth 18 which preferably cover the whole of the surface 17. The number of teeth in the ring 18 should be sufficient to provide a satisfactory pitch for engagement of a ratchet device 13 or pawl means (FIG. 8) upon completion of an idling return movement. The number of teeth, however, should not be excessively large, in view of the fact that it must be possible to obtain a depth of tooth engagement or mesh sufficient to obtain the torque to be transmitted to the mechanism 19 when the wrench is rotated in its driving direction with the ratchet device 13 in its operative ratchet position (FIG. 8B). In the case of a ratchet wrench having a ratchet wheel 14 with a diameter of 30 mm, it has been found that a tooth number of between 60 and 80 is acceptable. An optimum function is achieved with 72 teeth.

FIGS. 8A and 8B show the same view of the wrench head 12 as that shown in FIG. 1, but with the ratchet wheel 14 and ratchet device 13 mounted in the wheel chamber 16 and the ratchet chamber 26 respectively. Thus, the ratchet wheel 14 is journalled in the wheel chamber 16, which connects with the crank chamber 15 via the ratchet chamber 26. The crank-part 11 of the ratchet spring 1 projecting out in the crank chamber 15 is rotatably mounted and axially displaceable in the ratchet device 13. The ratchet device 13 can be adjusted between two end positions by means of the ratchet spring 1, by rotating or twisting the resetting sleeve 3 in the aforedescribed manner, such as to bring the ratchet spring 1 into one of the positions illustrated in FIGS. 4A and 4B. FIGS. 8A and 8B show one of these two end positions, namely the position which corresponds to the spring position shown in FIG. 4A. This enables the wrench to be moved freely in a return direction indicated by the arrow P1, during which the handle 2 moves freely in relation to the mechanism 19 and its ratchet wheel 14, as illustrated in FIG. 8A. When the handle 2 is moved in the opposite direction, the ratchet wheel 14 is locked so as to accompany the rotational movement in the direction of the arrow P2 shown in FIG. 8B, during which the mechanism 19 carries out a rotational movement such as to tighten a nut or bolt, for instance.

The ratchet device 13 has a form which generally coincides with the form of the ratchet chamber 26, although its width will be smaller than the space between the ratchet wheel.sup.14 /and the mutually opposing walls 33, 34 of the ratchet chamber. By causing the ratchet device 13 to adopt a laterally displaced position with the aid of the spring crank 11, the ratchet device will function as a wedge between the ratchet wheel 14 and the wall (33 in FIG. 8) against which it is displaced by the crank 11 when the fitter rotates the wrench in this direction, as illustrated in FIG. 8B. This wedging action locks the handle to the ratchet wheel 14, thereby forcing the mechanism 19 to accompany rotation in this direction. When the handle 2 is turned in the opposite direction, the direction shown by the arrow P1 in FIG. 8A, the ratchet device 13 is released from its wedging action with the ratchet wheel 14 and moves against the two walls 33, 34 of the ratchet chamber 26, as shown in FIG. 8A.

When the spring crank 11 is adjusted to its end position opposite to that shown in FIG. 8, there is, of course, obtained an opposite function in the two directions of handle.sup.2 /rotation. In this case, the wedging action between the ratchet device 13, the ratchet wheel 14 and the walls 34 of the ratchet chamber 26 is achieved when the handle 2 is rotated or turned in the direction of the arrow P1, resulting in force transmission to the mechanism 19. When the handle 2 is turned in the opposite direction, the handle moves freely without moving the mechanism 19.

In order to obtain an improved wedging function with subsequent improvement of force transference to the ratchet wheel 14, the ratchet device 13 preferably comprises a generally kidney-shaped body which is movably arranged in the ratchet chamber 26. The concave side of the kidney-shaped body 13 facing towards the ratchet wheel 14 is provided with a toothed ring 27 which corresponds to the teeth 18 of the ratchet wheel 14. The concave surface of the body 13 has a radius of curvature which corresponds to the radius of the ratchet wheel 14. The sides of the body 13 facing towards the handle 2 have a radius of curvature which coincides with the convex radius of curvature of the body 13, which towards both ends of the body 13 merges with a respective inwardly angled straight line.

As will be evident from the aforegoing, it is not necessary to provide the ratchet wheel 14 and the ratchet body 13 with teeth, even though this is to be preferred. Furthermore, the ratchet wrench can be modified in other respects without departing from the inventive concept. For example, the ratchet body 13 and the ratchet chamber 26 can be given other configurations than that illustrated, without excluding the desired wedging effect. Another example of possible modification is that the resetting sleeve 3 can be caused to move axially instead of rotationally as in the aforedescribed case. In the case of an axially movable sleeve 3, the sleeve would cause the ratchet spring 1 to snap over from one to the other of the positionally defined spaces 30 and 31, through the medium of a Z-shaped slot in the sleeve attachment device 23. Other modifications are conceivable within the scope of the inventive concept, and consequently the invention cannot be considered restricted to the aforedescribed and illustrated embodiment, but all alternative solutions and modifications are embraced by the scope of the following claims.