A wrench

Abstract: A wrench comprising a housing inside which a reversible electric motor serving as a torque source and a torque transmitting mechanism connected thereto are disposed. The torque transmitting mechanism comprises a rotatable cylindrical main body 10 having, rotatably fixed thereon, a coupling element 14 with the rotation axis parallel but not co-linear with that of the main body 10. The main body 10 with one end thereof connecting to the motor spindle is engageable with a follower shaft 40 by means of the coupling element 14 to transmit torque to a socket engaging with the follower shaft 40. An arrestor 30 is provided to control the coupling element 14 so that when the rotation speed of the main body 10 exceeds a pre-specified value determined by the arrestor 30, the engagement between the main body 10 and the follower shaft 40 is enabled.

Description: This invention relates to a wrench with the features cited in the preamble of claim 1. It is well known that wheels are usually fixed on the axles by nuts and for the sake of safety, these nuts are screwed tight. This makes loosening a wheel from an axle a hard job for drivers having no powerful tools. The most powerful and useful tools for disassembling a wheel from the axle thereof is the pneumatic tools. Tools of this kind are, however, bulky in size and sometimes heavy in weight. The pneumatic tools, therefore, are suitable for garages but not for carrying in a vehicle, especially a passenger car. For a vehicle-carrying purpose wrench without applying human power, one of the best choice is an electric one using the electric system of a vehicle as the power source. US-A-4 727 780 discloses an example of such kind of electric wrenches. This design, however, has the disadvantage of less output torque. This may sometimes results in not being able to loosen wheel stud nuts. Further, the application of torque impact is controlled manually. Bad timing of applying impact also gives the result of not being able to loosen nuts. As an improvement over the above-mentioned wrench, US-A-4 920 831 discloses an electric wrench with the features cited in the preamble of claim 1. This wrench is provided with an arrestor disposed between the torque source and the nut driving shaft so as to provide an automatic control of timing of impact. This eliminates the disadvantages of the wrench according to US-A-4 727 780. The wrench according to US-A-4 920 831, however, also posseses certain disadvantages. The major drawback is that the design is complicated and thus easy to be damaged. It is therefore the object of the present invention to provide an electric wrench which is easy to carry in a vehicle and has a simple design so as to reduce manufacture cost and the possibility of worn-out and damage resulted therefrom. This object is attained by the additional features cited in the characterizing portion of claim 1. A wrench as such has a simplified structure, so that the manufacturing costs including time required to make the parts and the material costs of the parts are cut down. The overall weight is reduced which helps a user to hold and operate the wrench. The control pins correctly maintain the coupling element in the neutral position where the edges of the coupling element are not contacted. This provides a good operation of cyclically impacting the control member by the follower shaft and improves the overall effectiveness thereof. The sharpened ends of the control pins facilitate insertion thereof into the holes formed in the coupling element to maintain the coupling element in the neutral position. Advantageous features and embodiments of the invention are cited in the dependant claims. The above and other aspects of the invention, as well as other benefits, will readily be ascertained from the following detailed description of the preferred embodiment of the invention, reference being had to the accompanying drawings, in which: Fig. 1 is a partial cross-sectional view of the preferred embodiment in accordance with the present invention; Fig. 2 is a fragmental view of the torque transmitting mechanism in accordance with the preferred embodiment of the present invention; Figs. 3 and 4 are partial cross-sectional views showing the control of the coupling element by the arrestor; and Figs. 5 and 6 are cross-sectional views showing respectively the relative position of the coupling element with respect to the main body and the follower shaft when the main body engages with and disengages from the follower shaft. With reference to the drawings and in particular to Fig.1, a wrench in accordance with the invention, generally designated by reference numeral 100, comprises a housing 102, inside which a reversible motor 101 serving as a torque source and a torque transmitting mechanism 103 connected thereto are disposed. The reversible motor 101 is controlled by a switch 104 and the rotation direction thereof is determined by a steering control device 105. The power source of the wrench 100 can be any suitable external source (not shown), such as the electric system of a vehicle (not shown). since the connection of the motor to an external power source is known to those skilled in the art, no detailed description will be given herein. Referring to Fig. 2, the torque transmitting mechanism 103 comprises a hollow cylindrical main body 10 with one end closed. The closed end has a projection 12 formed thereon with a central hole 13 running therethrough in parallel with an axis of the cylinder 10. the hole 13 is engageable with a spindle 106 (Fig. 1) of the motor 101. The main body 10 has a radial notch 11 into which a coupling element 14 of the complemental shape is inserted and is rotatably fixed thereon with a pivotal pin 15. The pivotal pin 15 is parallel but not co-axial with the axis of the main body 10 so as to provide the coupling element 14 with a relative rotational movement with respect to the main body 10. The coupling element 14 has thickened lateral edges 16 which slightly project into the interior of the main body 10. This is best seen in Fig.5. to facilitate the rotation of the coupling element 14 about the pivotal pin 15, an annular projection 17 around the pivotal pin 15 is provided on each axial end of the coupling element 14. The annular projections 17 are best seen in Figs. 3 and 4. To control the rotation of the coupling element 14 about the pivotal pin 15, a plurality of spring-biased control pins 18 are provided. Each of the control pins 18 has an enlarged end 19 and a sharpened end 20. The control pins 18 are slidable disposed in holes 21 formed on the closed end of the main body 10 and biased away from the coupling element 14 and finally inserted into holes 23 formed on the coupling element 14. The insertion of the control pins 18 into holes 23 prevents the coupling element 14 from being rotated about the pivotal pin 15. An arrestor 30 is provided on the projection 12 of the main body 10 and is fixed thereon by a ring retainer 31. The arrestor 30 comprises a pair of spring-biased weight blocks 32 which, under the circumstances of fast rotation, move outwards due to the action of centrifugal forces and will pull a disk 33 which is slidable along the projection 12 and abuts against the control pins 18 away from the main body 10 to allow the control pins 18 leaving the holes 23 under the action of spring forces. This enables the rotation of the coupling element 14 about the pivotal pin 15. When the arrestor 30 does not rotate fast, the weight blocks 31 withdraw back and the disk 33 moves towards the main body 10. This pushes the control pins 18 into the holes 23 and forces the coupling element 14 back to its non-rotated position. The follower shaft 40 has an expanded end 41 disposed inside the main body 10 and a shaped end 42 to engage a socket (not shown). Formed around the expanded end 41 are a pair of spaced teeth 43 which are inclined toward each other and engageable with the lateral edges 16 of the coupling element 14. These teeth 43, when engaging with one of the lateral edges 16 of the coupling element 14 transmit angular momentum from the main body 10 to the follower shaft 40 and then to the socket (not shown). With an axis co-axial with the cylindrical main body 10, the follower shaft 40 rotates with the main body 10 when the teeth 43 engage the coupling element 14. As a common sense to those skilled in the art, bearings are necessary and are disposed at any suitable locations. The operation of the invention will be described with the reference to Figs. 3 to 6. At first, when the motor 101 is just switched on, the main body 10, as well as the arrestor 30, start to accelerate. At the moment, the weight blocks 32, due to the lack of centrifugal forces, remains at "withdrawn" positions and the disk 33 abuts and forces the control pins 18 into the holes 23, as shown in Fig. 3. The coupling element 14 is not rotatable about the pivotal pin 15 and remains at the non-rotated position under this situation. When the main body 10 gains speed, the weight blocks 32 gradually move outwards due to the increasing centrifugal forces. This results in the withdrawal of the control pins 18, as shown in Fig. 4. The coupling element 14 is rotatable about the pivotal pin 15 at the moment. To facilitate the engagement of the coupling element 14 with the teeth 43 of the follower shaft 40, a spring-biased ball 24 is disposed in a hole 25 formed adjacent to each of the lateral edges 16 of the coupling element 14. The balls 24 may be fixed inside the holes 25 by any suitable means, such as screws 26. the balls 24 are allowed to partially protrude out of the inside surface of the coupling element 14. This is best seen in Figs. 5 and 6. With the partial protrusion, the balls 24 are contactable with the teeth 43 each time a tooth 43 passes the balls 24. When the coupling element 14 is allowed to rotate about the pivotal pin 15 ( as the situation shown in Fig. 4), the coupling element 14 will be rotated about the pivotal pin 15 by the contact of one of the balls 24 with one of the teeth 43. The contact makes the opposing lateral edge 16 move into the space between the teeth 43 and later abut one of the teeth 43 (Fig. 6). Since this happens rapidly, an impact will be generated and transmitted to the socket (not shown) by way of the follower shaft 40. This impact will then be applied to a nut (not shown) to be loosened and the resistance of the nut results in the slow-down of the follower shaft 40 together with the main body 10. Because of the decrease of centrifugal forces, the slow-down of the main body 10 move the disk 33 towards the main body 10 and force the control pins 18 entering the holes 23 to rotate the coupling element 14 back to the non-rotated position. The coupling element 14 disengages from the teeth 43 and the main body 10 accelerates again to be ready to apply an impact to the nut (not shown) again. This procedure repeats cyclically until the nut is loosened.

Claims: A wrench (100) comprising a housing (102) inside which a reversible motor (101) serving as a torque source controlled by switching means (104) and a torque transmitting mechanism (103) connected to a spindle (106) of said motor (101) to transmit torque to a socket engaging therewith, said torque transmitting mechanism (103) comprising: a hollow cylindrical main body (10) comprising an interior with one end closed, said closed end having a projection (12) formed thereon in parallel with an axis of said main body (10), a hole (13), co-axial with said axis of the main body (10), formed on said projection (12) to receive said spindle (106) therein, said main body (10) further comprising a radial notch (11) into which a coupling element (14) complemental shape is inserted and rotatable fixed thereon with a pivotal pin (15) which is parallel but not co-axial with said axis so that said coupling element (14) is rotatable with respect to the main body (10) about said pivotal pin (15) to have a first lateral edge (16) of said coupling element (14) rotate into the interior of said main body (10); a plurality of control pins (18), each of said control pins (18) being disposed in a hole (21) formed on the closed end of the main body (10); an arrestor (30) fixed on said projection (12) by fastening means (31), said arrestor (30) comprising a pair of weight blocks (32) and a disk (33) slidable along said projection (12), said disk (33) being moved towards said closed end of the main body (10) when said main body (10) does not rotate, under the action of centrifugal forces resulted from a high speed rotation of said main body (10) together with said arrestor (30), said weight blocks (32) moving outwards and pulling said disk (33) away from said closed end of the main body (10); and a follower shaft (40) having a shaped end (42) to engage with said socket and an expanded end (41) with a pair of teeth (43), a first one and a second one, formed therearound, said expanded end (41) of the follower shaft (40) being disposed inside the interior of said main body (10) so that when said coupling element (14) rotates about said pivotal pin (15) to have said first lateral edge (16) enter said interior, said first lateral edge (16) contact and engage with said first tooth (43) so as to transmit angular momentum resulted from torque provided by said motor (101) to said follower shaft (40) and to said socket; when said first lateral edge (16) hits said first tooth (43), the rotation speed of said main body (10) being suddenly and sharply decelerated and then said first lateral edge (16) being fixed non-rotatable about said pivotal pin (15) and disengaging from said first tooth (43) to allow said main body (10) to accelerate again, characterized in that, each of said control pins (18) being spring biased and having an expanded end (19) and a sharpened end (20), said sharpened end (20) being slidable into associated holes (23) formed on said coupling element (14) to prevent said control pins (18) are pushed against the biasing springs (22) thereof; said control pins (18) interact with said disk (33) and are pushed into said holes (23) formed on the coupling element (14) by said disk (33) when said main body does not rotate so that the coupling element (14) can not rotate with respect to said pivotal pin (15) and said control pins (18) leave said holes (23) formed on said coupling element (14) under the action of said biasing springs (22) when said main body rotates at a high speed so that said coupling element is rotatable with respect to said pivotal pin (15). A wrench (100) as claimed in claim 1, characterized in that, said coupling element (14) further comprising a first spring-biased ball (24) disposed close to a second lateral edge (16) of said coupling element (14) which is opposite to said first lateral edge (16), said first ball (24) partially protruding into the interior of said main body (10) so that when said first ball (24) passes said second tooth (43), said first lateral edge (16) is rotated down into a space between said teeth (43) and abuts said first tooth (43). A wrench (100) as claimed in claim 2, characterized in that, said coupling element (14) further comprising a second spring-biased ball (24) disposed close to said first lateral edge (16) with said second ball (24) partially protruding into the interior of said main body (10) so that when said second ball (24) passes said first tooth (43), said second lateral edge (16) is rotated down into said space between said teeth (43) and abuts said second tooth (43). A wrench (43) as claimed in claim 1, wherein said fastening means (31) is a ring retainer.

Inventors: HUANG DORA HSIAO-LING, HUANG, DORA HSIAO-LING
Applicants: HUANG DORA HSIAO LING, HUANG, DORA HSIAO-LING
Application year: 1990
Main classification: B25B21
IPC codes: B25B21, B21B21