US 3436992 A
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Description (OCR text may contain errors)
April 8, 1969 J. A. OVER ET AL 3,436,992
REVERSIBLE RATCHET WRENCH WITH FLOATING PAWLS Filed March 10, 1967 INVENTOR5 U.S. Cl. 81-631 4 Claims ABSTRACT OF THE DISCLOSURE A reversible ratchet wrench has a pair of floating pawls selectively engageable with ratchet teeth on a rotatable member. The pawls are designed to be loaded in compression only, thereby permitting their manufacture economically by powder metallurgy techniques.
Background of the invention This invention relates generally to hand tools and more particularly to improvements in reversible ratchet wrenches for applying torque to nuts, bolts or the like.
Ratchet wrench structures of great variety have been devised in the past. General objects of these have been to produce features which are highly favored in the indrustry, especially the characteristics of simplicity, compactness, and light weight. In brief, wrench structures comparable to that with which the present invention is concerned, comprise an operating handle, a rotary driven member, and a ratchet mechanism including a pawl by which torque is transmitted from the handle to the driven member. A single, double-acting pawl which shifts bodily between two alternate positions or which rocks about a central pivot, has characterized many of the earlier constructions. The shapes and arrangements of the various pawls are such that bending or shear stresses are produced in the pawl when a load is applied through the handle. This imposes certain limitations upon the fabrication of the pawls which, heretofore, have not been objectionable. An example of this type of wrench is found in Patent 893,097 issued to I. M. Reams; and the present wrench is considered to be an improvement over the design of that patent.
Hand tool manufacturing in general and especially the manufacture of ratchet wrenches is highly competitive. As a consequence, an improvement which reduces the cost of manufacture creates a definite competitive advantage in the marketplace, an advantage which can be very substantial although the change in construction is seemingly small.
One of the particularly costly items of manufacture of a ratchet wrench is the pawl. In the past, it has been the practice to machine the pawl from a solid piece of metal. Because of the precision and accuracy with which the pawl must be made to assure reliable and proper operation of the ratchet mechanism, machining of the pawl has been resorted to; but the machine operations have inevitably been reflected in a relatively high cost of the final product.
A ratchet pawl fabricated by the techniques of powder metallurgy can be shaped economically with the desired degree of precision; but such a pawl creates new design problems because the body so produced is one which is relatively weak in tension or in shear. Thus, the structure produced by this technique is not suitable for existing designs of pawls having high bending or shear stresses. The powder metallurgy pawl is satisfactory only when it States Patent 3,436,992 Patented Apr. 8, 1969 is subjected substantially to compression forces which it has a high capacity to resist; but its weakness in shear would result in loss of the pawl teeth at normal values of applied torque for this type of tool.
Accordingly, it becomes a general object of the present invention to provide an improved design of the pawl mechanism in a reversible ratchet wrench which permits the use of powder metallurgy to fabricate a pawl for this purpose at much less cost than by machining a block of steel.
More particularly, it is an object of the invention to produce a new design of a reversible ratchet wrench in which the pawl mechanism is placed substantially only in compression when it is loaded to transmit force from the operating handle or body to the ratchet and the driving member, thus making available to the pawl manufacturer, the manufacturing economies of powder metallurgy techniques.
A further object of the invention is to provide a wrench having the above characteristics, but which is also characterized by a minimum number of major parts, simplicity of construction, and reliability in operation so that there is no sacrifice in other desirable characteristics of the wrench as a result of the cost economies effected through the novel manufacturing procedure for producing the pawl.
Summary of the invention The above and other objects and advantages of the present invention are achieved in a wrench constructed according to the present invention that has a body including a head with a recess therein and a handle, and a rotatable member journaled to turn within the recess and having a plurality of ratchet teeth around its periphery. A driving shank is connected to the rotatable member to be turned thereby and is adapted to receive a socket or other tool. A pair of floating pawls are located in the recess, each pawl having teeth engageable with the ratchet teeth on the rotatable member to drive the latter member in response to rotation of the head when torque is applied to the head by the handle.
In a preferred embodiment of the invention, each pawl when in driving engagement with the ratchet bears at its opposite side against a curved section of the recess wall, such curved section preferably being a circular arc and the pawl face in contact with the wall being similarly curved to produce a maximum area of mutual contact. The faces of the teeth on the pawl and on the rotatable member transmitting forces to the pawl each lie in a plane substantially normal to a radius from the center of curvature of the curved section of the recess and passing through a tooth face, whereby the forces transmitted to the pawl are limited to forces which produce compressive stresses in the pawl.
Two individual and separate pawls are located in the recess and a spring is carried by and between the two pawls urging them apart. A reversing means moves a selected pawl in and out of driving engagement with the ratchet while the spring urges the other pawl into driving engagement with the ratchet.
Description 0 the drawings How the above objects and advantages of the present invention, as well as others not specifically mentioned, are attained will be more readily understood with reference to the following description and annexed drawing in which:
FIG. 1 is a perspective view of a portion of a wrench constructed according to the present invention, showing the head and a portion of the handle.
FIG. 2 is a longitudinal median section through the head and ratchet mechanism on line 22 of FIG. 1.
FIG. 3 is an enlarged fragmentary section showing the two floating pawls and a portion of the ratchet taken on line 33 of FIG. 2, the pawls being in a position for counterclockwise rotation as viewed in FIG. 3.
FIG. 4 is a view similar to FIG. 3 with. the pawls shifted to the alternate or reverse position for clockwise rotation as viewed in FIG. 4.
FIG. 5 is a fragmentary section on line 5-5 of FIG. 2, at the same scale as FIG. 3, showing the pivoted level mechanism for reversing the pawls.
FIG. 6 is an enlarged fragmentary section on line 6-6 of FIG. 2 showing the spring-loaded ball detent on the reversing lever.
FIG. 7 is a diagram at a further enlarged scale showing one pawl in driving relation to the ratchet and illustrating the tooth configuration on the pawl and ratchet.
Description of a preferred embodiment The ratchet wrench illustrated in FIG. 1 comprises a head 10 which is integral with a driving handle 11. Only a portion of the handle 11 is illustrated, the handle extending away from the head for a convenient distance and having a grip at the end remote from head 10, as is well known in the art.
As may be seen in FIG. 2, particularly, head 10 has an internal recess 12 which opens to one face of the head; and in this recess is journaled the rotatable member 14. Member 14 has a short hub 15 which projects from the inner side thereof and tits within a bearing depression at the base of recess 12. The other side of rotatable member 14 carries a square driving shank 16 which is adapted to receive a socket or other tool for turning a nut, a bolt, or the like, as is well known in the art.
Rotatable member 14 is provided around its periphery with a plurality of ratchet teeth 18, shown in greater detail in FIGS. 3 and 7. Teeth 18 extend axially of rotatable member 14 and are equally spaced around the periphery of the member. As will become apparent, these teeth are the ratchet teeth which mesh with the teeth of similar size and shape on the pawls, as later described.
The member 14 is held in place in recess 12 by a cover plate 20 having an opening therein adapted to receive the cylindrical portion 21 rotatable member 14 which is of lesser diameter than the portion with ratchet teeth 18. Cover plate 20 is held in place by spring retainer 22 which snaps into an undercut groove in the wall of recess 12 located outwardly of cover plate 20.
In order to transmit torque from body 10 to rotatable member 14 to turn shank 16, suitable pawl means are provided. The pawl means comprises a pair of independent and separate floating pawls 24 and 25 which are substantial duplicates of each other, except that they are reversed so that they constitute in effect, right hand and left hand members which are alternately engageable with the ratchet teeth, as shown in FIGS. 3 and 4.
As may be seen most clearly from the illustration of the pawl 24 in FIG. 7, each of the pawls is generally a triangular member. Along one face, are transversely extending teeth 26 which mesh with, and are complimentary in shape, to ratchet teeth 18. Another face 27 of the pawl which may be termed as that opposite teeth 26 is arcuate or curved to match the curvature of the wall 12a of recess 12 at this point.
Although recess 12 may have other shapes if desired, it is generally circular in cross section and is slightly greater in diameter than the maximum diameter of rotatable member 14 at ratchet teeth 18, except that at a position on the axis of the handle, recess 12 is provided with a bay 12b having an arcuate concave wall 12a as shown most clearly in FIG. 3. The wall of this bay is preferably a circular are having its center of curvature at 28 which is spaced from the center of curvature of the main portion of recess 12, such main portion being coaxial with the axis of rotation of rotatable member 14. The curvature given to the side 27 of each pawl opposite teeth 26 4 is the same curvature as that of wall 12a so that the pawl fully engages the wall at all positions Within its range of movement and also can slide smoothly over wall 12a.
Both pawls 24 and 25 are mounted in the bay of the main recess 12 formed by the ,arcuate wall 12a, the two pawls together occupying something less than the available space in the bay. The opposed faces of the two pawls are provided with shallow bores in which the two ends of a helical coil spring 30 are inserted. The spring is normally under a slight compression, thus urging the pawls apart.
Since it is desired that only one selected pawl mesh with ratchet teeth 18 at any given time, pawl reversing means are provided which not only reverse the direction of ratchet action, but also disengage a selected pawl from the ratchet teeth. The reversing means comprises lever 32 which, as shown in FIG. 5, is mounted centrally of the lever to pivot about an axis established by a pin 33. The two arms 32a of the lever slide over the bottom wall of recess 12 and each arm engages a short pin 35 at the underside of pawl 24 or 25. Pin 33 which pivotally mounts the lever extends outwardly through body 10 to a connection with an external thumb operating lever 36 by which the operator may rock lever 32 between two alternate extreme positions. The one position of lever 32 is shown in full lines in FIG. 5 while the other position is shown in dotted lines in FIG. 4.
As will be more readily apparent from later description, it is desirable that the pawl reversing arm 32 be yieldingly held in each of the two extreme positions. For this purpose, there is provided in pivot pin 33 a spring-loaded ball detent 38 which can enter either one of two recesses 39 in the wall of the bore constituting the journal for pin 33 or, when spring 40 yields allowing ball 38 to move inwardly, the ball can ride over the ridge intervening between the two recesses 39. Thus, detent 38 yields to pressure by the operator on lever 36 to shift reversing levers 32 from one position to the other; but when seated in a depression 39, the detent holds arm 32 in a selected position at the extreme end of its range of movement.
As lever 32 approaches each extreme position, one arm of lever 32 engages a pin 35 on a pawl and moves the pawl out of driving engagement with ratchet teeth 18. More explicitly, when the lever 32 is in the dotted line position shown in FIG. 4, it engages the pin on pawl 24 and holds the pawl in a position radially outwardly from ratchet teeth 18. Now if the lever is shifted to the position of FIGS. 3 and 5 by manipulation of lever 36, the other arm of lever 32 moves into engagement with the pin on pawl 25. Movement of the lever moves the pawl radially away from ratchet teeth 18 and at the same time slides the pawl bodily circumferentially along the surface of arcuate wall 12a to disengage pawl 25 from teeth 18. The force exerted by spring 30 on the other pawl 24, since the pawl 24 is now released by lever 32, is sufficient to move pawl 24 into driving engagement with ratchet teeth 18, as illustrated in FIG. 3.
The ratcheting action of the wrench is thus reversed by the operator by such clockwise movement of lever 36 to the dotted line position of FIG. 5, swinging pivot 33 through the angle 41. Reverse angular movement of pin 33 shifts lever 32 back to the dotted line position in FIG. 4 in which the lever is in contact with the pin on pawl 24, such movement of the lever disengaging pawl 24 from engagement with ratchet teeth 18.
At either end of the travel of lever 32, one pawl is floating and is free to move along the wall 12a under only the force applied by spring 30 and accordingly, this free pawl is now urged by spring 30 into driving engagement with ratchet teeth 18. With pawl 25 in driving engagement, driving torque that is clockwise when viewed as in FIG. 4 is transmitted from body 10 through the pawl to rotatable member 14 to turn shank 16 in a clockwise direction. Driving torque in the opposite direction is applied to member 14 by the driving engagement of pawl 24, as shown in FIG. 3. In either position, the pawl in driving engagement is moved along wall 12a and out of driving engagement against spring 30 by torque from handle in the reverse direction to the driving torque. This condition permits the ratchet action of the wrench for either direction of drive.
When either pawl is in torque-transmitting position, it is wedged in between recess wall 12a and the ratchet teeth with its own teeth 26 in engagement with the ratchet teeth. Referring to FIG. 7, the pawl 24 is in position to transmit counterclockwise torque to rotatable member 14. The driving force from the handle is transmitted through the pawl to member 14 at the pawl tooth faces 26a. The force is transmitted perpendicularly to the tooth faces. Since these faces are designed to be normal to a radius from center 28 passing centrally through the faces, it follows that the force transmitted at any face 26a to the rotatable member is along a radius passing through center 28 and is accordingly in a direction perpendicular to wall 12a at the point of intersection of a radius with that wall. This is true, since center 28 is the center curvature of wall 12a. The teeth 18 being uniformly spaced around the periphery of the rotatable member, the direction of force transmitted at each tooth face, changes uniformly around the periphery of the rotatable member.
The pawl teeth are preferably designed to have their faces at 90 to each other, as indicated in FIG. 7, and the included angle between the faces of teeth 18 is less than 90 by an amount which is determined by the number of teeth around the periphery of the rotatable member. All teeth being symmetrical, the same relationships of the teeth and the forces transmitted is maintained for both pawls 24 and 25. From the foregoing de scription it will be apparent that various changes may be made in the detailed construction and relationship of the parts without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the foregoing description is considered as being illustrative above, rather than limitative upon, the invention as defined by the appended claims.
1. A reversible ratchet wrench, comprising:
a body having a head with a recess therein and a handle, said recess having at one side a bay with a concave sidewall;
a rotatable member journalled in the recess and having a plurality of ratchet teeth around its periphery;
a driving shank connected to the rotatable member to turn therewith;
a pair of floating pawls in said bay, each pawl having on one side a smooth arcuate face complementary to and slidably engaging the concave sidewall of the bay and on an opposite side a plurality of teeth engageable with the ratchet teeth on the rotatable member to wedge the pawl in one end of the bay and drive the rotatable member in response to rotation of the head when torque is applied thereto by the handle;
reversing means moveable to hold a selected pawl out of said driving engagement;
and spring means carried by and between the two pawls urging the two pawls apart and urging the other pawl into said driving engagement with the rotatable member.
2. A reversible ratchet wrench according to claim 1 in which the reversing means includes a pivotally mounted lever movable to engage and hold a selected pawl away from an end of the bay and spring loaded detent means yieldingly holding the lever in either of two extreme positions.
3. A reversible ratchet wrench according to claim 1 in which the curved section of the bay wall and the pawl faces engageable therewith are circular arcs.
4. A reversible ratchet wrench according to claim 1 in which the mutually engaging faces of the teeth on the pawls and on the rotatable member transmitting stress to the pawl each lie in a plane substantially normal to a radius from the center of curvature of the curved section of the recess wall and passing through a tooth face.
References Cited UNITED STATES PATENTS 1,827,202 10/1931 Klein 81-61 2,542,323 2/1951 Gearhart 81-63.1 X 3,044,591 7/1962 Kilness 8l-63.2 X 3,149,707 9/1964 McInnis 81-62 X 3,356,117 12/1967 Wagner 81-177 MYRON C. KRUSE, Primary Examiner.