Patent Publication Number: US-6216562-B1

Title: Wrench

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a wrench, which comprises a hollow casing having multiple ends, a plurality of coupling shafts respectively mounted in the ends of the casing to hold a respective tool accessory for synchronous rotation, and a transmission mechanism coupled between the coupling shafts for enabling the coupling shafts to be synchronously rotated. 
     Various wrenches have been dislcosed, and have appeared on the market. FIG. 1 shows a wrench, which comprises a hollow two-way casing, two coupling shafts respectively mounted in the two ends of the casing for holding a respective tool accessory. The coupling shafts each have an inner end meshed together by means of a respective bevel gear for synchronous rotation. This structure of wrench is still not satisfactory in function. Because lubricating grease can not be applied to the bevel gears, the teeth of the bevel gears wear quickly with use. When the teeth of the bevel gears start to wear, driving power can not be positively transmitted from one coupling shaft to the other. 
     The present invention provides a wrench, which eliminates the aforesaid drawbacks. According to one aspect of the present invention, the wrench comprises a hollow three-way (or two-way) casing, a plurality of coupling shafts respectively mounted in the ends of the casing for holding a respective tool accessory, and a transmission mechanism coupled between the coupling shafts for enabling the coupling shafts to be rotated synchronously. The transmission mechanism comprises a plurality of transmission members respectively coupled to the coupling shafts inside the casing and meshed with one another, and a plurality of compression springs respectively mounted in the coupling shafts to force the transmission members into engagement with one another. The transmission members each have a rectangular shank at one end inserted into a rectangular coupling hole on the respective coupling shaft and supported on the corresponding compression spring, and a bevel gear at an opposite end meshed with the bevel gear at the trasmission member in an adjacent coupling shaft. According to another aspect of the present invention, lubricating grease is applied to the bevel gears of the transmission members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a wrench according to the prior art. 
     FIG. 2 is an elevational view of a wrench according to a first embodiment of the present invention. 
     FIG. 3 is an exploded view of a wrench according to a second embodiment of the present invention. 
     FIG. 4 is a sectional assembly view of the wrench shown in FIG.  3 . 
     FIG. 5 is a sectional view of the wrench shown in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. from  2  through  5 , a wrench is shown comprised of a hollow casing  1 , and a plurality of coupling shafts  2  and  2 ′ respectively mounted in the casing  1 . According to the embodiment shown in FIG. 2, the casing  1  is a hollow angle bar, and the number of the coupling shafts  2  and  2 ′. According to the embodiment shown in FIGS. 3 and 4, the casing  1  is a hollow T-bar, and the number of the coupling shafts  2  and  2 ′. The coupling shafts  2  and  2 ′ are respectively mounted in the ends of the casing  1 , and secured in place by a respective C-shaped clamp  4  for holding a socket  3  or spanner  5 . The coupling shafts  2  and  2 ′ each comprise a rectangular coupling hole  21  axially extended at one end inside the casing  1 , which receives a compression spring  6  and a transmission member  7  or  7 ′. The transmission member  7  or  7 ′ comprises a rectangular shank  72  inserted into the rectangular coupling hole  21  on the corresponding coupling shafts  2  or  2 ′, and a bevel gear  71  formed integral with one end of the rectangular shank  72  and disposed outside the corresponding coupling shaft  2  or  2 ′ within the casing  1 . When assembled, the bevel gear  71  or the transmission member  7  or  7 ′ at one coupling shafts  2  or  2 ′ is meshed with the bevel gear  71  of the transmission member  7  or  7 ′ at another coupling shafts  2  or  2 ′. Because the transmission members  7  and  7 ′ are supported on the respective compression springs  6 , the transmission members  7  and  7 ′ are respectively forced outwards from the respective coupling shafts  2  and  2 ′, keeping the bevel gears  71  of the transmission members  7  and  7 ′ in positive engagement with one another. Further, the casing  1  comprises at least one lubricating hole  11  through which lubricating grease is applied to the bevel gears  71  of the transmission members  7  and  7 ′. 
     In the embodiment shown in FIGS. 2 and 5, each coupling shafts  2  or  2 ′ comprises a screw hole  211  axially extended from the inner end of the respective rectangular coupling hole  21 , and screw rods  8  are used inserted of the aforesaid compression springs  6 . The screw rods  8  each have one end threaded into the screw hole  211  in the respective coupling shaft  2  or  2 ′, and an opposite end suspended in the rectangular coupling hole  21  in the respective coupling shaft  2  or  2 ′ and stopped against the rectangular shank  72  of the corresponding transmission member  7  or  7 ′. By means of adjusting the screw rods  8  in the respective screw holes  211 , the bevel gears  71  of the transmission members  7  and  7 ′ are maintained in positive engagement with each other.