Ratchet wrench with improved force distribution

#The present invention relates to a ratchet wrench for selectively applying torque to a fastener.

#FIG. 5 illustrates a prior art ratchet wrench 100. The prior art wrench has a wrench body 102 including a handle portion (not shown) and a head portion 106. A pawl 102 is shown in its gear driving position. In this gear driving position, the head portion 104 engages the pawl 102 so as to apply force to it during torque application is a “sidewards” direction of the pawl 102 (indicated by arrow F). That is, the force is applied mostly circumferentially with respect to the axis about which the gear 108 rotates. As a result, the force transmitted to the gear 108 by the pawl 106 tends to be focused at the teeth closest to the point of engagement. Specifically, the force is primarily focused at the outermost tooth of the pawl closest to the point of engagement. As a result, the remainder of the pawl teeth transmit considerably less force. This is an unsatisfactory load distribution.

#One aspect of the present invention provides a ratchet wrench for applying torque to a fastener. The wrench comprises a wrench body having a handle portion configured to be manually grasped and a head portion providing a pawl engaging surface; and a ratchet gear constructed and arranged to be removably engaged with the fastener such that torque applied to the gear is transmitted to the fastener to affect rotation thereof. The ratchet gear is mounted to the wrench body such that the gear and the body are rotatable relative to one another about a gear axis, the ratchet gear having a plurality of gear teeth arranged on a radially outer peripheral surface thereof in circumferential relation with respect to the gear axis. A pawl is mounted to the wrench body and having a plurality of ratcheting teeth arranged in an arc essentially complementary to the gear teeth and a load receiving surface facing generally opposite the ratcheting teeth. The ratcheting teeth include a pair of outermost teeth provided at opposing ends of the arc and inner teeth therebetween.

#FIG. 1 is an exploded view of an exemplary ratchet wrench constructed in accordance with the principles of the present invention;

#FIG. 2 is a bottom plan view showing the pawl in a gear driving position with other components of the wrench removed for clarity;

#FIG. 3 is a bottom plan schematic view showing the stress distribution between the pawl and the ratchet gear in a gray scale plot, the units being expressed in terms of pounds per square inch (PSI).

#FIG. 1 is an exploded perspective view of a ratchet wrench, generally indicated 10, constructed in accordance with the present invention. The illustrated wrench 10 is merely an exemplary embodiment of the invention and is not intended to be limiting. The wrench 10 includes a wrench body, generally indicated at 12. The wrench body 12 includes a handle portion 14 configured to be manually grasped and a head portion 16. In the illustrated embodiment, the head portion 16 is formed integrally with the handle portion 14. The head portion 16, however, may be formed separately from the handle portion 14 and movably connected thereto by a pivot pin for angular adjustment.

#The wrench 10 includes a ratchet gear 18. The ratchet gear 18 is constructed and arranged to be removably engaged with a fastener such that torque applied to the gear 18 is transmitted to the fastener to affect rotation thereof. In the illustrated embodiment, the gear 18 is provided with an axially extending lug 19 on which removable sockets are received. Alternatively, the gear 18 could be of the ring gear type with a hole formed therethrough. The hole has an internal periphery configured for suitable engagement with a polygonally-headed fastener, such as a nut or bolt. In general, the ratchet gear 18 can have any configuration for directly or indirectly engaging a fastener for torque application.

#The ratchet gear 18 is mounted to the wrench body such that the gear 18 and the wrench body 12 are rotatable relative to one another about a gear axis. In the illustrated embodiment, the gear 18 is retained in the cavities of the head portion 16 by a cover plate 20.