Apparatus for tightening fasteners on axially connected rod-like members

A method and apparatus for tightening fasteners adapted to combine two bars in a linear fashion. The apparatus includes a first spanner member for engaging a first fastener and a second spanner member for engaging a second fastener. A driving apparatus is provided for rotating the second spanner member and includes a ratchet arrangement and a linear driving apparatus for driving the ratchet arrangement. The first and second spanner members are connected by a separable connection permitting easy separation or assembly. Further, the orientation of the first spanner member is adjustable therefore providing an apparatus which can be applied to and removed from the coupling assembly for two bars in spite of the random rotational orientation of the fasteners.

BACKGROUND 
This invention broadly relates to a method and an apparatus for tightening 
fasteners and more particularly to a method and apparatus for tightening 
nuts on axially connected rod-like members. 
It is a well known method to combine two bars in a linear fashion by 
providing the mating ends of the bars with threads and connecting the bars 
with at least two nuts adapted to engage the threads in a fashion so that 
one nut functions as a coupling unit while the other nuts lock the 
coupling nut against movement. When utilizing this method, some amount of 
backlash remains between the threads of the bars and the threads of the 
nuts and if the nuts are not sufficiently tightened, this residual 
backlash causes an easy loosening of the coupling or a bending at the 
coupling of the bars. The effect of backlash is of particular concern when 
two reinforcing iron bars are combined by this method and buried in 
concrete, because the action of external forces upon the concrete 
structure often times bends the reinforcing iron bars at the coupling 
causing resulting cracks in the concrete surfaces above the loosened 
coupling. 
In order to overcome the deleterious effect of backlash, studies have shown 
that minimum torque of 200 kg-m should be applied to the tightening nuts 
when coupling bars having a diameter of 32 mm. Since the conventional use 
of wrenches to tighten nuts by hand is insufficient to apply the requisite 
torque, often times, automatic tightening devices are used such as the 
hydraulic wrenches conceived by the present inventor and described in 
Japanese application No. 123999/76, No. 24277/77, and No. 36800/78. 
All of these prior art hydraulic wrenches include two axially aligned 
spanners attached to a main body, a rack device for rotatably driving one 
of the spanners having an outer surface provided with cogs, and a 
hydraulic cylinder for driving the rack back and forth. Since one spanner 
is rigidly affixed to the main body and the other spanner is driven to 
rotate with respect to the main body, when the device is attached to two 
nuts to be tightened, and the hydraulic cylinder is charged, the resulting 
torque is applied equally between the two spanners. As a consequence, the 
main body of the device rotates in order to tighten both nuts 
simultaneously. 
Some inconveniences have been noted with respect to rack-type hydraulic 
wrenches. Because the rack which is adapted to rotate the spanner is 
driven by a single stroke of the hydraulic cylinder, the length of the 
rack and the stroke of the hydraulic cylinder must be very long. As a 
result, devices of the rack-type are excessively large and heavy making it 
difficult for one operator to lift and situate the device in place. 
Further, the rack and cogs formed on the driven spanner cannot be 
disengaged from one another. Therefore, if obstructions close to the bars 
to be coupled restrict the ability of the main body to rotate, both nuts 
cannot be tightened. 
Additionally, if the main body of the hydraulic wrench encounters an 
obstacle during the tightening operation, the wrench cannot be removed 
without reversing the operation of the hydraulic cylinder thereby 
loosening the nuts to some extent. 
SUMMARY OF THE INVENTION 
It is a principle object of the present invention to provide a method and 
apparatus for tightening nuts on axially connected rod-like members 
capable of performing a tightening operation which is not disturbed by 
obstacles close to the apparatus while providing sufficient torque to 
prevent loosening of the nuts. 
Another object of the present invention relates to a method of tightening 
nuts on axially connected rod-like members utilizing an apparatus wherein 
a first spanner member to fit a nut, a second spanner to fit another nut 
and a driving arrangement for rotating the second spanner member are 
mounted on a main body such that the driving arrangement includes a linear 
driving apparatus and a ratchet device capable of rotating the second 
spanner member in only one direction. 
Another object of the present invention relates to a method of tightening 
nuts on axially connected rod-like members utilizing an apparatus which 
allows an operator to easily change the engagement angles between the 
first spanner member, the second spanner member and the main body, so that 
the main body can be returned to an initial operating position if the 
rotation of the main body is restricted by an obstacle during the 
tightening operation. 
Yet another object of the present invention relates to an apparatus for 
tightening nuts wherein ratchet cogs are formed on the outer surface of 
the second spanner member which is driven in only one rotational direction 
by a ratchet claw pivoted on a slidable carrier driven by a linear driving 
apparatus which is relatively small and compact. 
Yet another object of the present invention relates to an apparatus 
including a disengagement device capable of disengaging the ratchet claw 
from the ratchet cog formed on the outer surface of the second spanner 
member. 
Yet another object of the present invention relates to a tightening 
apparatus wherein the first spanner member includes a rotation adjustment 
arrangement which allows easy application and removal of the apparatus 
from a work site without the need to alter the rotational orientation of 
the nuts as well as providing an arrangement for easily returning the main 
body to the initial operating position. 
Yet another object of the present invention relates to a tightening device 
wherein the first and second spanner members may be separated from one 
another as well as the linear driving apparatus to provide easy handling 
of the apparatus. 
In accordance with principles of the present invention, a method for 
tightening nuts on axially connected rod-like members is carried out by an 
apparatus wherein a first spanner member to fit a nut, a second spanner 
member to fit another nut, and a driving arrangement to rotate the second 
spanner member are mounted to a main body. The driving arrangement is 
adapted to rotate the second spanner member in only one rotational 
direction relative to the main body and includes a device for 
disconnecting the driving arrangement from the second spanner member. A 
rotation adjustment device connects the first spanner member to the main 
body and provides an arrangement for returning the main body of the 
apparatus to an original operating position when the driving arrangement 
is disconnected from the second spanner member. 
The method of tightening nuts on axially connected rod-like members 
comprises the steps of applying the apparatus to the nuts to be tightened, 
driving the linear driving apparatus to turn the second spanner member 
relative to the main body, returning the linear driving apparatus to an 
original position, and repeating the driving and returning operations to 
tighten the nuts. Further, the method may include the additional step of 
returning the apparatus to an original operating position in the midst of 
the tightening operation and beginning the repetition of the driving and 
returning operations.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 2, a tightening device 1 is illustrated wherein a first 
spanner member 6, a second spanner member 9 and a linear driving apparatus 
14 are attached to a main body 2. The main body comprises a first body 
portion 3 and a second body portion 4 which are detachably connected to 
one another by a separable connection arrangement 63 which prevents the 
relative rotation of the body portions with respect to one another. 
As seen in FIGS. 1, 2, and 4, the first body portion 3 includes a housing 
having an upper plate 16, a lower plate 17, two side plates 18, 19 and a 
rear plate 20. U-shaped notches 34,35 are formed in the upper and lower 
plates 16,17 respectively. 
Rotatably attached to the front of the housing of the body portion 3 by a 
rotation adjustment device 7 is the spanner member 6 having a worm gear 26 
formed upon its outer surface which is adapted to engage a worm 24 mounted 
in the housing by bearings 22,23 fixed to the side plates 18,19 by bolts 
or other suitable fasteners 21. On the top and bottom of the spanner 
member 6 are guide arcs 27,27 which are held in place by arc plates 29,29 
affixed to the inner surface of plates 16,17 by bolts or other suitable 
fasteners 28. When an operator rotates a knob 25 which operatively engages 
worm 24; the spanner member 6 is driven to rotate in the arc plate 29,29 
around an imaginary center axis formed by the arc plates 29,29. 
As seen in FIGS. 1, 2, 6 and 7 the spanner member 6 includes a spanner 
portion 5 adapted to engage a nut to be tightened. At the upper half of 
the spanner portion 5 is a narrow U-shaped notch 30 and the lower half of 
the spanner member 5 includes a polygonal surface 31 adapted to fit around 
a nut (in the embodiment, the nuts are assumed to be hexagonal). At the 
front of the polygonal surface 31 are two bent plates 32,32 which are 
fixed to the first spanner member 6 by bolts or other suitable fasteners 
33. 
The U-shaped notch 30 and the U-shaped notches 34 and 35 formed in the 
upper and the lower plates 16,17 have a diameter sufficient to prevent 
interference with the rod-like members to be combined when the tightening 
apparatus 1 is attached to a work site. 
Additionally, the first body portion 3 has a fitting device 37 formed on 
the bottom surface of the lower plate 17 comprising two fitting members 
36,36 situated on both sides of the bottom. The fitting device 37 engages 
a separable connection arrangement 63 which connects the first body 
portion 3 and the second body portion 4. 
As can be best seen in FIGS. 2 and 4, the second body portion 4 has a 
housing formed by a front plate 40, a side plate 41, and rear plates 
42,43. 
Referring to FIG. 3, a carrier 10 is arranged in the housing to be slidable 
along the longitudinal axis of the second body portion 4. The carrier 10 
includes an upper board 44, a lower board 45, and two side boards 46,47. 
Three guide pins 48,48,48 and two plates 38,39 form a longitudinal passage 
to guide the carrier 10 as it is slidably driven by the linear driving 
apparatus 14. 
A ratchet claw 11 is pivotably connected by pivot 49 to both plates 44,45 
of the carrier 10. A resilient member or spring 13 is also included having 
one end attached by pin 50 to the carrier 10 and its other end attached to 
the ratchet claw 11 by a pin 51. The resilient member 13 biases the 
ratchet claw 11 so as to apply a rotational force to drive the ratchet 
claw in a counter-clockwise direction as seen in FIG. 3. A stop bolt 52 is 
attached to the side board 47 to restrict the ratchet claw 11 from 
rotation in the clockwise direction. A return spring 55 is provided to 
return the carrier 10 to an original operating position after it has been 
driven by the linear driving apparatus 14 and the return spring 55 is 
situated between a spring holder 56 on the carrier 10 and a spring box 57 
located on the side plate 41 of the housing. 
With reference to FIG. 5, the upper plate 38 is provided with a slit 53 
which extends in a longitudinal direction. At the top of the carrier 10 is 
a knob bolt 54 having a head which projects through the slit 53 to provide 
a convenient fine adjustment arrangement. 
Ratchet cogs 12 are cut out on the outer surface of the second spanner 
member 9 adapted to engage the pivotably mounted ratchet claw 11 of 
carrier 10. The spanner member 9, having a spanner portion 8, is rotatably 
mounted in the housing 1 by two guide arcs 58,58 held by arc plates 60,60 
attached to the upper and lower plates, 38,39 respectively by bolts or 
other suitable fasteners 59. This arrangement allows the second spanner 
member 9 to rotate around an imaginary center axis determined by the arc 
plates 60,60 such that the rotational axes of both spanner members 6,9 are 
axially aligned. 
U-shaped notches are formed in the upper and lower plates 38,39 
respectively, each having a diameter greater than the U-shaped notch 30 of 
the first spanner portion 5 so that the second spanner member 9 can engage 
or disengage a nut by movement in a direction perpendicular to the axis of 
rotation of the nut. 
Formed on the upper plate 38 behind the second spanner member 9 is a main 
column 61 provided to cooperate with the separable connection arrangement 
63. A top plank 66 is adapted for insertion between the two fitting 
members 36 of the fitting device 37 provided on the first main body 3 and 
a shaft portion 65 provide for insertion into the main column 61. The 
separable connection arrangement 63 joins the first body portion 3 to the 
second body portion 4 when the shaft portion 65 is inserted into the main 
column 61 and a fastening pin 67 is inserted through aligned pin holes 
62,62 and 64,64 provided in the shaft portion 65 and the main column 61 
respectively. This arrangement prevents the rotation of the first body 
portion 3 relative to the second body portion 4. 
Referring to FIG. 3, FIG. 4 and FIG. 7, a receptacle casing 70 is affixed 
to the side of the second body portion 4 and includes an opening 68 
providing access to an inner cavity 69. The linear driving apparatus 14 
includes an insertion portion 67 having a neck 75 and cross-shaped 
protuberances 74 which cooperate with the opening 68. The driving 
apparatus 14 can be detachably connected to the second body portion 4 by 
inserting the insertion portion 76 into the cavity 69 through the opening 
68 and rotating the driving apparatus 14 approximately 45.degree. around 
its longitudinal axis. Since the linear driving apparatus is separable 
from the main body, the overall weight of the tightening apparatus 1 can 
be reduced making it convenient to convey the apparatus from a work shop 
to a building site. 
In this particular embodiment, the driving apparatus 14 comprises a 
mono-drive hydraulic cylinder 71 having a piston rod 72 which is pushed 
forward by compressed oil injected through a coupling 73 from an external 
pump (not shown) and returned to an original position by a return spring 
(not shown) situated inside the casing. It is understood by those skilled 
in the art that instead of a mono-drive hydraulic cylinder, a doubledrive 
hydraulic cylinder is suitable as well as an electric motor or a fluid 
motor, and a reduction gear device driven by the motor. 
Referring to FIG. 3 a disengagement device 15 is provided to disengage the 
ratchet claw 11 from the ratchet cog 12. The disengagement device 15 
includes a pin 80 which is rotatably supported by the upper plate 38 and 
the lower plate 39; an arm 81 affixed to the middle of the pin 80; and a 
lever 82 is attached to the top of the pin 80. When the operator rotates 
the lever 82 in a clockwise direction, with reference to FIG. 3, the 
ratchet claw 11 is rotated clockwise and slips out of engagement with the 
cog 12. 
In order to facilitate easy handling of the device, a vertical holder 78 is 
erected on the receptacle casing of the second body portion 4 which 
cooperates with a side holder 79 projecting from the side of the main 
column 61. 
With reference to FIGS. 8-11, a preferred method is illustrated for 
combining two bars. It is understood that at least two nuts are necessary 
to combine two bars A and B having threads A' and B' respectively; however 
in this embodiment, three nuts C, D, and E are utilized. 
Initially, a lock nut C is screwed on the standing bar A (FIG. 8) then a 
long coupling nut D is threaded on the remaining exposed thread portion A' 
until the coupling nut D abuts the lock nut C (FIG. 9). Thereafter, the 
second bar B, which has lock nut E affixed thereon, is coupled to the nut 
D until the respective ends of the bars A and B contact one another (FIG. 
10). The two lock nuts C and D are then turned by hand after which the 
tightening apparatus 1 is attached to the coupling site (FIG. 11). 
In order to attach the tightening apparatus 1 to the work site, the 
fastening pin 67 is removed so that the first body portion 3 is separated 
from the second body portion 4. The operator can then easily lift the 
first body portion 3 above the top of the upper bar B so that the first 
spanner member 6 surrounds the bar B. The first main body 3 is then moved 
in a downward direction along the bar B until the U-shaped notch 30 
engages the nut E. Since the U-shaped notch 30 is narrower than the nut E, 
the first body member 3 hangs upon the upper nut E. The operator can turn 
the knob 25 of the rotation adjustment device 7 to adjust the first body 
portion 3 to coincide with the arrangement of the lower nut C. Thereafter, 
the operator lifts up the second body portion 4 holding the vertical 
holder 78 and the side holder 79 and inserts the top plank 66 of the 
separable connection arrangement 63 into the fitting device 37 of the 
first body portion 3 so that the second spanner member engages the lower 
nut C (FIG. 11). This coupling operation is necessary when the hexagonal 
surfaces of the nuts C and E are not parallel. If the hexagonal surface of 
the nuts C and E are parallel, then the operator can fit the fully 
assembled apparatus including both body portions 3 and 4 directly onto the 
two nuts C and E simultaneously. 
Once the tightening apparatus 1 is attached to the work site, the operator 
charges the hydraulic cylinder 71 with compressed fluid provided by the 
fluid pressure pump (not shown). This drives the piston rod 72 so as to 
slide carrier 10 such that the ratchet claw 11 engages the ratchet cog 12 
on the second spanner member 9 which rotates nut C. 
Because the first body portion 3 and the second body portion 4 are coupled 
against rotation with respect to one another, the torque is applied to 
both spanner members 6,9 equally and if the friction of the nut C and E 
are the same, both nuts are rotated simultaneously in opposite direction. 
If one tightening operation is not sufficient, the operator exhausts fluid 
from the hydraulic cylinder 71 and the ratchet claw 11 pivotably mounted 
on carrier 10 returns to an initial position so as to engage a second cog 
12 on the second spanner member 9. The operator again charges the cylinder 
71 with compressed fluid to drive the carrier 10 so that the ratchet claw 
11 rotates the second spanner member 9 with respect to the main body 2. 
This operation may be repeated as many times as there are cogs 12 on the 
spanner member 9. In this particular embodiment, the spanner member 9 is 
provided with four cogs although it is understood that the spanner member 
9 could be provided with more ratchet cogs. 
To remove the tightening apparatus 1 from the nuts C and E, the operator 
removes the fastening pin 67 to separate the first and the second body 
portions 3 and 4 from one another. The operator then turns the lever 82 to 
disengage the ratchet claw 11 from the cogs 12 and rotates the second body 
portion 4 until the spanner member 9 returns to the original operating 
position so that the second body portion 4 can be removed from the nut C. 
The first body portion 3 can then be lifted above the upper bar B and 
removed from the work site. 
The above noted method of operation is suitable when the work site is not 
situated close to obstacles, such as the bars depicted in FIG. 1 by 
imaginary lines, which restrict the ability of the main body 2 to rotate 
during the tightening operation. In this instance, the tightening 
operation is repeated until the apparatus 1 collides with a bar which 
makes further rotation impossible thereby preventing tightening of the 
nuts. In this case, the operator disengages the ratchet claw 11 from the 
cog 12 by pulling the lever 82 of the disengagement device 15 with his 
right hand, and utilizing his left hand, rotates the knob 25 of the 
rotation adjustment device 7 to return the apparatus 1 to the original 
operating position. The tightening operation is then repeated until the 
nuts are tight. 
While the invention has been particularly shown and described with 
reference to preferred embodiments thereof, it is understood by those 
skilled in the art that various changes in form and detail may be made 
therein without departing from the spirit and scope of the invention as 
described by the appended claims.