Ratchet wrench with dual pawl members

A ratchet wrench includes a ring-shaped head having a threaded inner periphery and an operation member is rotatably retained in the head. The operation member has a ridge member extending from one end thereof and two pawl members are respectively retained on two sides of the ridge member. Each pawl member has a first side with teeth defined therein and a second side of each pawl member includes two inclined surfaces on two end of the second side and a straight surface is connected between the two inclined surfaces. The teeth of each pawl member are engageable with the threaded inner periphery of the head. One of the two inclined surfaces and the straight surface of each pawl member is engaged with respective one of the two parallel surfaces of the ridge member. An operation disk is mounted to the head and two torsion springs are respectively connected between the two pawl members and the operation disk.

FIELD OF THE INVENTION
 The present invention relates to a ratchet wrench having two pawl members
 separated by an operation member in the head of the wrench and each pawl
 member is connected with a spring. Each pawl member has two inclined
 surfaces which alternatively contacts the operation member when the pawl
 member is engaged with the threaded inner periphery of the head.
 BACKGROUND OF THE INVENTION
 A conventional ratchet wrench known to applicant was disclosed in U.S. Pat.
 No. 4,762,033 to Chow; Kirk K., with the title of "Ratchet Wrench With
 Manual Disassembly Capability". Chow's wrench employs a single pawl member
 to engage with a threaded inner periphery of the head of the wrench so as
 to output an torque when rotating the shank of the wrench. However, the
 single pawl member obviously can provide only limited numbers of teeth of
 the pawl member to match with the threaded inner periphery of the head so
 that the wrench cannot generate a large torque.
 Some ratchet wrenches improve the inherent shortcoming and were disclosed
 in U.S. Pat. No. 3,372,612 to M. T. Rozmus, with the title of "Pawl Type
 Ratchet Wrench", U.S. Pat. No. 4,137,801 to Imperio; Charles D., with the
 title of "Combined Ratchet And Torsion Wrench", U.S. Pat. No. 5,537,899 to
 Thomas J. Diedrich, with the title of "Dual-Pawl Ratcheting Mechanism With
 Provision For Preventing pawl Jamming", and U.S. Pat. No. 5,782,147 to
 Peter Constantine Chaconas et. Al., with the title of "Ratchet Wrench
 Having Two-Pawl Action".
 Although there are two pawl members engaged with the threaded inner
 periphery of the head, when rotating the wrench, each pawl member is
 pushed by the operation member in the head by only a point. This could
 break the corner end of the pawl members when a large torque is applied.
 The present invention intends to provide a ratchet tool that provides a
 sufficient contact surface to each pawl member when the other end of each
 pawl member is engaged with the threaded inner periphery of the head.
 SUMMARY OF THE INVENTION
 In accordance with one aspect of the present invention, there is provided a
 ratchet wrench and comprising a ring-shaped head with a threaded inner
 periphery and an operation member is rotatably retained in the head. The
 operation member has a disk portion, an engaging shaft extending from one
 side of the disk portion and a ridge member extending from the other side
 of the disk portion. A flange extends from the ridge member so as to
 define two recesses radially between the disk portion and the flange. The
 two recesses are separated by the ridge member and two pawl members are
 respectively received in the two recesses. Each pawl member has a first
 side with teeth defined therein, a second side of each pawl member
 comprising two inclined surfaces on two end of the second side and a
 straight surface connected between the two inclined surfaces. The teeth of
 each pawl member are engageable with the threaded inner periphery of the
 head and one of the two inclined surfaces and the straight surface of each
 pawl member is engaged with respective one of the two parallel surfaces of
 the ridge member. An operation disk is mounted to the head and two torsion
 springs are respectively connected between the two pawl members and the
 operation disk.
 The object of the present invention is to provide a ratchet wrench that
 employs two pawl members and each pawl member has two inclined surfaces
 connected by a straight surface. One of the two inclined surfaces and the
 straight surface of each pawl member is engaged with respective one of two
 parallel surfaces of the ridge member so as to provide a sufficient
 support when applying a large torque.
 These and further objects, features and advantages of the present invention
 will become more obvious from the following description when taken in
 connection with the accompanying drawings which show, for purposes of
 illustration only, several embodiments in accordance with the present
 invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIGS. 1 to 5, the ratchet wrench in accordance with the
 present invention comprises a ring-shaped head 10 with a shank 100
 extending from the head 10. The head 10 has a threaded inner periphery 101
 defined in an inside of the head 10 and the threaded inner periphery 101
 in the head 10 has an even number of teeth. An operation member 20 is
 rotatably retained in the head 10 by a C-shaped clip 201 and has a disk
 portion 200, an engaging shaft 21 extending from one side of the disk
 portion 200 and a ridge member 22 extending from the other side of the
 disk portion 200. A circular flange 23 extends from the ridge member 22 so
 as to define two recesses 24 radially between the disk portion 200 and the
 flange 23. The two recesses 24 are separated by the ridge member 22 which
 has two parallel surfaces on two sides thereof.
 Two pawl members 30 are respectively received in the two recesses 24 by two
 respective torsion springs 50. Each pawl member 30 has a first side with
 teeth 31 defined therein and a second side of each pawl member 30
 comprises two inclined surfaces 301 on two end of the second side with a
 straight surface 302 connected between the two inclined surfaces 301. The
 teeth 31 of each pawl member 30 are to be engageable with the threaded
 inner periphery 101 of the head 10. An operation disk 40 is mounted to the
 head 10 and has two notches 41 defined in a bottom thereof and two rods 60
 are respectively received in the two notches 41. Each torsion spring 50
 has a first end connected to one of the two rods 60, a second end of each
 torsion spring 50 extends through a hole defined through the flange 23 and
 connected to the pawl member 30 corresponding thereto. The first end and
 the second end of each torsion spring 50 are separated by the ridge member
 22 of the operation member 20. When the straight surface 302 of each pawl
 member 30 is engaged with the two respective parallel surfaces of the
 ridge member 22 as shown in FIG. 4, the two pawl members 30 are not
 engaged with the threaded inner periphery 101 of the head 10. The purpose
 of equipping two pawl members 30 ill the head 10 is to reduce the "lost
 motion" when rotating the ratchet wrench. That is to say, when rotating
 the ratchet wrench, the maximum of the lost motion will be only a half
 tooth of the threaded inner periphery 101 because either one of the two
 pawl members 30 is surely engaged with the threaded inner periphery 101
 whichever direction the ratchet wrench is rotated.
 A passage 25 is defined through the operation member 20 and the engaging
 shaft 21 has a hole 210 defined radially therein. The hole 210
 communicates with the passage 25 and a ball 211 is movably received in the
 hole 210 so as to secure a socket or the like onto the engaging shaft 21.
 A push rod 70 movably extends through a sink hole 41 in the operation disk
 40 and is received in the passage 25 of the operation member 20, wherein a
 concavity 71 is defined radially in the push rod 70. A spring 72 is
 mounted to a top of the push rod 70 and a bolt 73 extends through a hat
 member 74 and threadedly engaged with the top of the push rod 70. The
 spring 72 is biased between the hat member 74 and the convergent periphery
 of the sink hole 41 so that when the push rod 70 is pushed, the concavity
 71 is in alignment with the hole 210, the socket can be removed from the
 engaging shaft 21 by a known manner.
 As shown in FIG. 6, when in use, the operation disk 40 if rotated to let
 the two pawl members 30 engage with the threaded inner periphery 101 of
 the head 10. When rotating the shank clockwise, two respective inclined
 surfaces 301 of the two respective pawl members 30 are engaged with the
 parallel surfaces of the ridge member 22 so that the pawl members 30 are
 firmly engaged with the threaded inner periphery 101, and rotated with the
 head 10 to output a large torque.
 As shown in FIG. 7, when rotating counter clockwise, the threaded inner
 periphery 101 of the head 10 will push the pawl members 30 to skip off the
 teeth in the threaded inner periphery 101 so that the head 10 is rotated
 while the operation member 20 is remained still.
 The pawl members 30 are engaged with the two parallel surfaces of the ridge
 member 22 with sufficient area so that a large torque can be applied to
 the pawl members 30. Each pawl member 30 may be composed of two or more
 than two overlapped smaller pawl members and each of the smaller pawl
 members are arranged to let the teeth thereof be alternate so as to
 eliminate empty motion of the engagement of the teeth of the smaller pawl
 members and the threaded inner periphery of the head.
 FIG. 8 shows that the number of the teeth of the threaded inner periphery
 101 of the head 10 can also be made to be an odd number.
 While we have shown and described various embodiments in accordance with
 the present invention, it should be clear to those skilled in the art that
 further embodiments may be made without departing from the scope and
 spirit of the present invention.