JPH0440158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pneumatic tool for tightening threaded connections. In particular, the present invention includes a housing, a first motor for obtaining an initial degree of tightening on the threaded connection, a second motor for obtaining a desired final degree of tightening on the threaded connection, and a power source for the motor. The present invention relates to a threaded connection tightening tool of the type comprising a power transmission system for transmitting power to an output spindle connectable to the connection.

BACKGROUND OF THE INVENTION A tool of this type is described in US Pat. No. 3,529,513.

A problem with conventional power tools of this type is high air consumption. Both motors of the two-motor nut-driving tools available today are supplied with compressed air simultaneously during the entire tightening process. This means that the second motor, which always operates in a lower gear than the first motor, runs unloaded during the initial stages of installation in order to achieve the final tightening of the threaded connection. Such idling of the second motor wastes a considerable amount of compressed air and, in addition to undesirably high energy costs, it is difficult to use a more common single motor of the impact or stall type, such as an impact wrench or nut driver. Switching from the tool to this fast-acting tool may result in very expensive measures having to be taken to enlarge the compressor unit and air distribution network.

In addition to the high level of air consumption that today's two-motor tools experience, it would be extremely difficult to adapt these tools to portable tool details. First, the required air supply and exhaust conduits are not flexible or lightweight enough to allow satisfactory handling of the tool, and second, the air passages inside the tool housing, including the throttle valve, are ,
The dimensions and weight of the tool housing shall be such as to permit it to be used as a portable tool.

SUMMARY OF THE INVENTION The main object of the present invention is to provide an air-operated two-motor screw connection tightening device that effectively reduces compressed air consumption. According to the invention 50%
It is possible to achieve reductions in air consumption up to.

Another object of the present invention is to control the supply of working air to a low high speed torque motor, which is arranged to act at a constant difference between the back pressure from the high speed low torque motor and the actual air source pressure. An object of the present invention is to provide a pneumatically operated two-motor nut turning tool equipped with a compressed air supply valve.

(Means for Solving the Problems) To this end, the air-operated tool of the present invention includes a first motor 11 for achieving an initial proportion of pressing force on the threaded connection, and a first motor 11 for achieving a desired final proportion of the force on the threaded connection. a second motor 12 for obtaining pressing force;
a power transmission system 18,1 for transmitting the power of said first motor 11 and said second motor 12 to an output spindle 17, which can be connected to a screw connection;
a first motor 11;
The air inlet 31 of the second motor 12 and the air inlet 32 of the second motor 12 are connected to an air supply valve 33, 133, and the supply valve has the air inlet 32 connected to the air inlet 32 of the second motor 32 from a position that closes the air inlet 32 of the second motor 12. a valve that can be automatically moved to a position where it opens, and which moves the air inlet 32 to a position where it opens and connects it to the compressed air source only when the back pressure from the first motor 11 exceeds the pressure of the air source to a certain extent; Elements 39, 13
9 is provided, and the air supply valves 33, 13
3 is airtightly guided in the cylinder holes 38, 138, and the first motor 11 is guided in the valve opening direction.
The valve element 3 is arranged to be pressurized by the compressed air source pressure in the direction of closure of the valve due to the back pressure from
9,139, the valve element 39,139 comprising:
having one or more openings 41, 141;
It is characterized in that air with a certain pressure drop passes through the openings 41, 141 from the compressed air source to the air inlet of the first motor 11.

Further objects and advantages will be apparent from the following description and claims.

Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The power tool shown in the figures is an air-operated nut driver comprising a housing 10 in which a first motor 11 and a second motor 12 are held. Both motors are of the air sliding vane type, which is the type of motor commonly used in this type of tool. The motors are of equal size and rotate in opposite directions, as shown in FIG.

The illustrated tool is a portable tool and the housing 10 is formed with a pistol-shaped handle 13 through which the tool's main air supply passage 14 extends. A throttle valve 15 mounted on the pistol grip 13 is actuated by a trigger 16 to control the flow of compressed air through the air supply passage 14.

The motors 11 and 12 are connected to an output spindle 1 with square ends via a connecting gear 18 and a reduction gear 19.
7 (see FIG. 1). The reduction gear comprises two conventional planetary gears, which are not shown in detail.

The connecting gear comprises at its front end a central shaft 20 on which teeth 21 are formed for engaging the reduction gear 19 . The centerline 20 is provided with a spur gear 22 at its rear end, which meshes with a small spur gear 23 driven directly by the first motor 11 . A small-diameter spur gear 24 , directly driven by the second motor 12 , meshes with an internal gear 25 of the connecting sleeve 26 . The connecting sleeve is rotatably supported on the central shaft 20 by axially spaced roller bearings 27,28. A one-way clutch 30 is installed between these roller bearings 27 and 28.
is arranged to allow free rotation of the central shaft 20 in the threaded joint tightening direction with respect to the connecting sleeve 26. Clutch 30 is a one-way clutch of conventional design and therefore will not be described in detail.

In the illustrated connecting gear 18, the spur gear 23
Spur gear 22 drive-coupled to counter-reduction motor 11
The reduction ratio is 2:1, while the spur gear 24 to the second
The reduction ratio of the internal gear 25 drivingly connected to the motor 12 is approximately 7.5:1. Thus, the deceleration of the second motor 12 is approximately that of the first motor 11.
It is 3.75 times. This connecting gear 18 combines a compact design with a fairly high reduction ratio for the second motor 12.

The two motors 11 and 12 are provided with air inlets 31 and 32, respectively, through which the motors are supplied with compressed air from a supply valve 33. For this purpose, the supply valve 33 has an air inlet port 37 communicating with the main air supply passage 14 of the housing 10.
is provided.

The air supply valve 33 comprises a cylinder bore 38 and a valve element 39 slidingly guided therein. The valve element 39 is cup-shaped and has a valve opening 40 in its peripheral wall and a number of air communication openings 41 extending through its bottom or end wall.
The end wall of the valve element 39 is also provided with a central opening 42 through which a rod 43 extends. Rod 43 and valve element 3
9 are axially connected by a lock ring 44.

The rod 43 has one end on the left side in FIG.
Tubular section 4 coaxially mounted within cylinder bore 38
Accepted to guide within 5. Tubular part 4
The bottom end of 5 communicates with the atmosphere via passageway 46.
Like the gap seal between valve element 39 and cylinder bore 38, rod 43 and tubular portion 45 prevent compressed air supplied through air inlet port 37 from escaping to the atmosphere through passageway 46. Work together to prevent.

The rod 43 extends directly through the valve element 39 and is provided at its right hand end with a vibration damping device 48, which includes a brake piston 49, an O-ring 50,
and a support ring 51. These three elements are prevented from axial movement by two locking rings 52. The brake piston 49 fits within the cylinder bore 38 with a circumferential gap, but is attached to the rod 43 with an annular gap that is larger than the circumferential gap at the outer periphery.

This means that air is passed through the gap by the brake piston 49 and that the brake piston 49 can move freely relative to the rod 43 within very narrow axial travel limits.

The valve element 39, the rod 43 and the brake device 48 are
The end of the rod 43 can be displaced as a unit in the cylinder bore 38 between its final end positions, said positions being the end of the rod 43 striking the bottom wall of the tubular part 45 and the right-hand wall 53 of the cylinder bore 38, respectively. It is determined accordingly. A weak coil spring 55 is arranged to force the entire unit to the right in the figure, thus ensuring that the valve element 39 is always in its right-hand end position when the tool is started.

In addition to the air inlet port 37 , the cylinder hole 38 has a first service port 56 communicating with the air inlet 31 of the first motor 11 and a second service port 56 communicating with the inlet 32 of the second motor 12 . A service port 57 is provided. As shown in FIGS. 2 and 3, air inlet port 37 and first service port 56 are located within cylinder bore 38 such that they are in no way blocked by valve element 39. As shown in FIGS. The second service port 57 is connected to the valve element 3
When 9 occupies its right-hand position, it is occluded by the valve element, but when the valve element 39 is displaced to the left-hand position, the valve opening 40 is unobstructed.

The operating sequence of the apparatus shown in FIGS. 2 and 3 is as follows.

Before the valve 33 is supplied with compressed air, as well as during the initial steps of the threaded connection tightening process, the valve element 39 occupies its right-hand position as shown in FIG. When compressed air is not supplied to the valve 33, the biasing load of the spring 55 ensures that the valve element 39 assumes its right-hand or closed position.

The tool is started by pressing trigger 16 to open throttle valve 15. Compressed air is then supplied to the tool via passage 14.

During the initial steps of operation, compressed air is supplied to inlet port 3.
7 into the valve 33 and the opening 41 of the valve element 39
, and also connects the first service port 56 and the first
It reaches the first motor 11 via the air inlet 31 of the motor.

The first motor 11 rotates the central shaft 20 via spur gears 23 and 22, and the first motor 1
The power generated by 1 is transmitted to the outlet spindle 17 via a reduction gear 19. During the shutdown procedure, the resistance to rotation generated in the tightened screw connection is low, which means that the rotational speed of the first motor 11 as well as the air flow through the supply valve 33 is high.

Compressed air passes through the opening 41 of the valve element 39 and is released into the cylinder bore 38, thereby creating a pressure drop. This means that the pressure on the right side of the valve element 39 is lower than the pressure on its opposite side, ie the pressure of the compressed air source to which the tool is connected. However, the difference between the two loads acting on the valve element 39 in opposite directions is such that a portion of the left cross-sectional area of the valve element 39, i.e. the surface portion represented by the cross-section of the rod 43, is exposed to the exhaust passage 46. Since only the tip is exposed to atmospheric pressure, this pressure difference is not as large as it appears. Rod 43 is exposed to the same pressure as the valve element at its opposite end. The control piston 49 has no practical influence on the pressure acting on its right hand side.

The dimensions of both sides of the valve element 39 as well as the dimensions of the opening 41 are such that when the screw connection resistance increases and the rotational speed of the first motor 11 decreases to a certain range, the back pressure from the first motor 11 becomes apparent. Selected to provide an increase. With a predetermined degree of tightening on the threaded connection, the back pressure from the first motor 11 is large enough to move the valve element 39 to the left and occupy its open position, thereby forcing the valve opening 40 into the second 2 service port 57
(See Figure 3). first motor 1
The supply valve 33 thus supplies compressed air to the second motor 12 without interrupting the air supply to the motor 1 .

The second motor 12 is energized to carry out the final tightening procedure together with the first motor 11. The output torque of the second motor 12 is transmitted to the connecting sleeve 26 via a spur gear 24 and an internal gear 25 . The gear ratio of this internal gear to spur gear set is greater than that of this spur gear set to the spur gear set connected to the first motor 11 . This means that the connecting sleeve 26 is rotated more slowly and at a higher torque level than the central shaft 20 would originally be. However, due to the increased resistance of the threaded connection being tightened, the first motor 11 is slowed down to a lower speed level that the second motor 12 can catch up, and the one-way clutch 30 causes the second The power of motor 12 is transmitted to central shaft 20 and added to the power still generated by first motor 11 .

Once the desired final degree of tightening is achieved at the threaded connection, either as a result of total backpressure from both motors being substantially equal to the preset air source pressure, or as a result of the closing of the backpressure responsive isolation valve. The resulting stall causes motors 11 and 12 to stop rotating. The isolation valve is not shown but is of conventional design and is located upstream of the supply valve 33.

The damping device 48 is used to prevent the valve element 39 from vibrating and to achieve accurate actuation of the supply valve 33. For this purpose, the brake piston 49 is arranged so as to prevent air flow to a certain extent from or into the right hand and part of the cylinder bore 38 . However, damping of the valve element 39 during movement to the left, ie towards the open position, is preferably less effective than during movement in the opposite direction. Braking piston 49
A second air passage through the brake piston 49 is established by an annular gap between the brake piston 49 and the rod 43. However, this passage is only opened when the valve element 39, the rod 43 and the brake piston 49 are moved to the left. Moving to the right, brake piston 49 is brought into sealing contact with O-ring 50 to close the second air passage and provide more effective braking action.

A modified embodiment of the air supply valve is shown at 133 in FIG. The purpose and main operating sequence are almost the same as the valves described above. A feature of the valve according to FIG. 4 is a differently designed rod 143, which is provided with a coaxial exhaust passage 146 and passes at its right-hand end through an opening 180 in the cylinder end wall 153. Thus, on the one hand, the tubular section 145 and the rod 14
Communication is achieved between the chamber formed by 3 and the atmosphere on the other hand. A head 181 is formed at the left hand end of the rod 143. This head 18
1 is hermetically guided in the tubular part 145 and, because of the exhaust passage 146, the head is exposed to atmospheric pressure at its left end. Head 181 also defines an annular shoulder 182 that is exposed to air source pressure.

The operation of the supply valve according to the embodiment shown in FIG. 4 is very similar to that of the valves shown in FIGS. 2 and 3. This is because valve element 139 is connected to the air source pressure and the first
This means that a balance is maintained between the back pressure from the motor and the back pressure from the motor. In the previous embodiment, the valve element 39
The large difference between the pressure-related forces acting in two opposite directions on the rod 4, which is communicated with the atmosphere,
3, while the right hand side is exposed to the back of the first motor.

In the valve shown in FIG. 4, the right end face of rod 143 is actuated solely by atmospheric pressure. Instead, the pressure of the compressed air source acts on annular shoulder 182 to move rod 143 to the left.

Apart from these differences, the operating principle is the same in the two embodiments of the valve. The valve element 139 of the valve shown in FIG.
pressed towards its right side or closed position by the This means that the valve element 139 assumes its closed position before the tool is moved in any way. However, when the initial stages of the tightening process are initiated, the force resulting from the pressure drop across opening 141 will dominate the biasing force generated by spring 155. In this closed position, the second service port 157 in the cylinder bore 138 is blocked by the valve element 139, thus preventing starting air from reaching the second motor 12. When the torque resistance from the tightened threaded connection increases to a certain level, back pressure from the first motor 11 moves the valve element 139 to its open position. In this position, valve element 139
The valve opening 140 of the second service port 157
, and compressed air is supplied to the second motor 12. At both positions of valve element 139, air inlet port 137 as well as first service port 156
is open.

The vibration damping device 148 of this embodiment is designed and operates similarly to the devices of the previously described embodiments.

An advantage of both embodiments is their independence from a certain air source pressure. In other words, this valve also operates correctly even when, for some reason, the pressure of the supplied air deviates from the standard pressure, which is usually 6 bar. A pressure drop of 2-3 bar is not unusual at such a tool connection point. However, the air supply valve mentioned above is balanced between the supply pressure and the back pressure from the first motor, which means that the pressure level itself is important. It should be noted that the biasing springs 55, 155 are too weak to affect valve actuation.

Referring again to FIG. 1, the tool reduction gear 19
is seen enclosed within a casing 90 which is rotatably supported in the tool housing 10 by ball bearings 91. The ball bearing includes a housing 10 and a reduction gear casing 90.
A swivel joint is formed between the A torque reaction bar 92 is rigidly attached to the forward end of the casing 90 and is in contact with stationary objects such as protrusions on any of the parts that are secured together by threaded connections that are tightened. be made to do. The reason is that the torque reaction is too large to be manually balanced by the tool operator.

The purpose of the swivel joint is to allow quick and satisfactory adjustment of the recoil rod, providing a tight fit for the recoil rod without compromising the possibility of the operator holding the pistol grip in a satisfactory position. It's about finding a safe point of support.

In conventional single motor tool applications, a simple free rotating swivel joint is sufficient because the reaction torque transmitted from the motor alone to the tool housing is low enough to be harmless to the operator. However, in the two-motor tool shown in FIG. 1, the torque reaction transmitted to the tool housing 10 is substantially greater. The reason is,
The coupling device 18 itself provides a reduction/torque increase ratio, which is transmitted to the housing 10 and further to the operator, in particular by the additional reduction gear formed by the spur gear 24 and the internal gear 25 of the second motor 12. torque is amplified.

In order to protect the operator from the reaction torque generated in the housing 10, the casing 90 is provided with a circumferential row of notches 93, which are hemispherical and uniformly distributed around the rear end of the casing 90. (See Figures 1 and 6).
There is a vertical hole 95 between the casing 90 and the handle 94 of the trigger 16, into which two steel balls 96, 9 are inserted.
7 is possible. Hole 95 is notch 93
The upper ball 96 is located in the same vertical plane as
to one of the notches 93.

A locking sleeve 99 is slidably guided in the trigger handle 94, and a spring 100 is arranged to bias the locking sleeve 99 in the direction of the trigger 16.

The locking sleeve 99 is provided with a circumferential groove 98 which is dimensioned and arranged to partially receive the lower ball 97 when the trigger 16 assumes its rest position. This position is shown in FIG. The dimensions of the balls 96, 97 are matched to the distance between the trigger handle 94 and the casing 90;
Thus, when the trigger 16 is pulled to start the tool, the groove 98 is moved out of its alignment with the hole 95 so that the upper ball 96 engages and locks in one of the notches 93 in the casing 90. Ru.
In other words, the casing 90 is always fixed with respect to the tool housing 10 when the tool is started. This means that the entire recoil force generated on the tool is balanced by the recoil rod 92.

When the trigger 16 assumes its rest position as shown in FIG. 1, the lower ball 97 enters the groove 98;
Also, the upper ball 96 is removed from the notch 93,
Allowing rotation of casing 90 relative to housing 10. In yet another condition, the holes 95 are arranged such that any of the notches 93 receive the upper ball 96.
If not properly aligned, the trigger 16 cannot be moved. This means that the tool cannot be operated unless the housing 10 is fixed with respect to the reduction gear casing 90 and the reaction bar 92.

(Effects of the Invention) Since the air-operated power tool according to the present invention has the configuration as described above in detail, it has a remarkable effect of reducing the consumption of compressed air as shown in the following example.

The two-motor nut-driven motors currently manufactured and sold by Applicant provide approximately 80% more compression in normal use with an average threaded connection when the air supply valve of the present invention is removed. Consumes air. However, the air supply passages in the nutdriver housing are adapted to a reduced air flow rate and will not pass such large amounts of air at normal supply pressures. Note that the above numbers are for the case where the two motors are equal.

If the air supply valve according to the invention were installed in a nut driver having an air supply passage adapted to a higher flow rate, the reduction in compressed air flow rate would be even more noticeable. The reason such a large airflow reduction is obtained is that the vane motor has a large amount of airflow at high idle rotation during the main part of each tightening process, namely the deceleration (stop) phase.

[Brief explanation of drawings]

FIG. 1 shows a partially cutaway side view of a portable power wrench having features of the present invention. Second
The figure schematically shows a power tool according to the invention, with the air supply valve shown in its closed position. FIG. 3 shows a cross-sectional view of a portion of the air supply valve in the open position.
FIG. 4 shows a longitudinal sectional view of the air supply valve of a modified embodiment. FIG. 5 shows a cross-sectional view taken along the - line in FIG. 6 shows a side view of a portion of the tool of FIG. 1; FIG. DESCRIPTION OF SYMBOLS 10... Housing, 11... First motor, 1
2...Second motor, 13...Pistol-shaped grip,
17... Output spindle, 18, 19... Power transmission system, 31, 32... Air inlet, 33, 133... Air supply valve.

Claims (1)

[Claims] 1. A first motor 11 for achieving an initial proportion of pressing force on the threaded connection, and a second motor 12 for obtaining a desired final proportion of pressing force on the threaded connection. , a power transmission system 18, 19 for transmitting the power of the first motor 11 and the second motor 12 to an output spindle 17, which can be connected to a screw connection.
0, wherein the first
The air inlet 31 of the second motor 11 and the air inlet 32 of the second motor 12 are connected to the air supply valves 33, 133.
connected to the supply valve, the supply valve is capable of automatically displacing from a position of closing the air inlet 32 of the second motor 32 to a position of opening the air inlet 32, and has a back pressure from the first motor 11. A valve element 39, 139 is provided which is displaced into a position to open the air inlet 32 and connects it to the compressed air source only when the pressure of the air source exceeds the pressure of the air source to a certain extent, and the air supply valve 33, 133 hole 38,1
a valve element 39 guided air-tight within 38 and arranged so as to be pressurized by back pressure from said first motor 11 in the valve opening direction and by compressed air source pressure in the valve closing direction; 139, said valve element 39, 139 having one or more openings 4
1,141, characterized in that through said openings 41,141 air with a certain pressure drop is flowed from a source of compressed air to the air inlet of said first motor 11. 2 the air supply valve 33, 133 is connected to the valve element 39, 139;
Balance pistons 43, 14 with surfaces that are continuously acted upon by atmospheric pressure in the closing direction of 139
3. A power tool according to claim 1 comprising: 3. 3. The power tool of claim 2, wherein the balance piston 143 includes an auxiliary surface 182 that is pressurized in the direction of opening of the valve element 139 by air source pressure. 4 the balance piston is connected to the valve element 39, 139;
and a rod 43,1 coaxial with the valve element and fixed to the valve element.
43. A power tool according to claim 2 or 3 formed by 43. 5 The cylinder holes 38, 138 have an air inlet port 37, 137 connected to a compressed air source, a first service port 56, 156 communicating with the first motor 11, and a first service port 56, 156 connected to the second motor 11. a second service port 57 in communication with 12;
157 are provided, the air inlet port 37,
5. A power tool according to any one of claims 1 to 4, wherein the first service port 56, 156 is in no way blocked by the valve element 39, 139. 6 The valve element 39, 139 is located in the cylinder hole 38,
Claims 1 to 5, characterized in that a check valve 50 is provided, which is connected to a brake piston 49 movably guided in 138 and for reducing the braking action in the opening direction of said valve element 39, 139. The power tool according to any one of the items above. 7 The rod 43, 143 is connected to the valve element 39,
139 and supporting said brake piston 49 on the low pressure side of the valve element.
Power tools listed in section. 8. The housing includes a pistol-shaped grip 13;
8. Any one of claims 1 to 7, wherein said grip constitutes a portable tool comprising a compressed air supply passage 14 for communication with a source of compressed air and a manually actuated throttle valve 15. Power tools listed in section.