DE3001731A1 - SPEED-DEPENDENT ENGINE SWITCH-OFF DEVICE FOR A COMPRESSED AIR TOOL - Google Patents

Description

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Jan. 17, 1980 D- Hg / K

Cooper Industries, Inc. Houston, Texas / USA

"Speed-dependent motor cut-off device for a compressed air-operated tool"

The invention relates to a speed-dependent engine shutdown _{device for a compressed air-operated nut screwing device p} in which the exhaust air flow from the engine is interrupted at a predetermined minimum speed of the device engine when the engine approaches stalling.

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In the case of the control devices for tools operated by air pressure, in particular nut tightening devices, screwdrivers or the like, A number of inventions have been made which utilize a speed dependent valve for shutting off engine intake flow concern when the engine speed is approaching stall. U.S. Patents 3,904,305; 4,004,859 and 4 120 604 describe compressed air-operated tools that have speed-dependent valve mechanisms for shutting off the flow of compressed air to the engine input when the engine is approaching stalling from a relatively high working speed. The US-PS 3,785,442, 3,791,458 and 3,850,553 describe speed-dependent devices, which a pressure medium signal at generate a predetermined minimum speed of the tool motor in order to cause a servo-controlled valve to switch the flow on Interrupt compressed air.

The devices described in the first three patents have a common disadvantage which is that although the speed-dependent devices are effective be to direct the influx of compressed air to the engine inlet To interrupt, these facilities all have a so-called bypass valve for applying compressed air to start the engine need so that the corresponding centrifugal force dependent mechanism can open an engine intake port, which when removed the engine speed is closed again.

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The last three patent specifications also describe a complicated mechanism, the speed-dependent valve devices makes necessary that a pressure medium signal to operate separate compressed air shut-off valves.

The aim of the invention is to provide a pressure medium shut-off device which is dependent on the speed for a tool operated by compressed air, such as a pneumatic nut unscrewing device or the like, which causes the exhaust air flow from the tool motor to be switched off depending on the decrease in motor speed.

As a result, the cut-off device according to the invention can be used to control the maximum torque that exerted by the tool on a screwed fastener will. The engine shutdown device according to the invention also serves to indicate that the engine speed has reached a predetermined one Minimum has decreased and is approaching the stalling conditions. In addition, the engine shutdown device designed according to the invention to minimize the torque reaction acting on the operator of the tool, when the tool motor approaches stalling at high torque.

The speed-dependent engine exhaust air flow shut-off valve is special advantageous because a disc or plate-like valve

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Closing member is arranged in the engine exhaust air flow path and is operated almost directly by a speed-dependent centrifugal weight mechanism. Furthermore, the engine exhaust shutoff device does not require a bypass valve to apply DrudsLuft _T to start the engine, as has been the case with known mechanisms.

For this reason, the speed-dependent engine shutdown device according to the invention is compact, technically simple, not Complicated and cheaper than previously known speed-dependent motor cut-off devices for compressed air-operated tools.

In the drawing is an embodiment of an inventive, speed-dependent engine shut-off device shown. In this drawing show:

Fig. 1 is a side view of a portable air pressure operated Tool comprising a speed-dependent engine shutdown device according to the invention;

FIG. 2 shows a longitudinal section through the speed-dependent engine shut-off device in the one shown in FIG. 1 Tool and

FIG. 3 shows a section along the line 3-3 in FIG. 2.

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The speed-dependent engine shut-off device according to the invention is suitable for use in a portable compressed air-operated tool, which is designated as a whole by 10 and represents a nut unscrewing device. The tool 10 comprises a housing part 12 _S in which a conventional rotary vane expansion chamber motor 14 is arranged. Drive medium, for example compressed air, is fed to the tool via a flexible line 16 which is connected to the handle 18 of the tool. A manually operable shut-off valve 20, which is shown schematically in FIG. 1, is used to control the supply of compressed air via a duct 22 to the motor. The valve 20 is shown schematically in Figure 1 for clarity; however, it is arranged in the housing of the tool and can be operated by an actuating lever 24. The tool also includes a housing portion 26 surrounding a drive shaft 28 which is connected to a nut driver (nut) 30 for screwing on a nut or other threaded fastener in a known manner.

The tool 10 further comprises a housing part 32 which lies between the housing parts 12 and 26 and with these through Threaded collar 34 and 36 is screwed. As can be seen from FIG is, the housing part 32 has inner chambers 38 and 40 which are in compressed air communication with one another to a To form duct for the flow of exhaust air from the engine 40. The exhaust air

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from the engine 14 is via the engine exhaust port 42 in the Motor end plate 44 supplied to chamber 38. The exhaust air flows from the chamber 40 through the hollow interior of the housing part 26 and flows out of the tool via air slots shown in FIG. 1 46 off.

The fig. 2 it can also be seen that the motor 14 comprises a rotor 48 which has an output part 50 which is connected with an intermediate drive shaft 52 is drivingly coupled. The intermediate drive shaft 52 is rotatably supported in the housing part 32 and includes a portion that the sun gear 54 of a planetary gear forms. The planetary gear includes a planetary gear carrier 56 which is connected to the drive shaft 28 stands. The speed-dependent engine shutdown device according to the invention comprises an element 58 which is on the intermediate drive shaft 52 is non-rotatably arranged. The element 58 has a number of approximately radially extending grooves 60 which are formed in this, as FIG. 3 shows. The grooves 60 are formed so that they have sloping bottom surfaces 62 and one displaceable centrifugal weight or one ball 64 each which can be moved radially outward from the intermediate drive shaft 52 along the groove as a function of the centrifugal force are. The speed-dependent nut shut-off device also has an axially movable member and a valve closing member to interrupt the flow of exhaust air from chamber 38 to chamber 40. The locking member 66 is through a hub

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part 68 of the motor end plate 44 and supported by the intermediate drive shaft 52 so as to be axially displaceable. The closure member 66 is slidable to lie against a seat 70 formed by the surface of a transverse wall facing the interior the Chamber 38 is executed. The closure member 66 is by a coil spring 72 which is arranged between a flange 74 on the closing element and the motor end plate 44, biased towards seat 70.

The closure member has a recess 76 which is open towards one end and in which the element 58 partially is arranged. In the recess 76 an annular plate 78 is also arranged and rests on the balls when they are are in their radially innermost position in the grooves 60. A circular spring washer 80 is between the Ring plate 78 and the bottom of the recess 76 arranged. The stiffness or the spring force of the spring washer 80 is greater than the spring force of the coil spring 72 and (Se spring washer 80 exerts a tension force against the spring 72 the end. As a result, the spring washer © 80 keeps the striker 66 a short distance from the seat 70, such as Fig. 2 shows when the pressure of the compressed air in the chambers 38 and 40 is approximately the same. When compressed air is supplied to the motor 14 To start this, the exhaust air can flow through the Chambers 38 and 40 flow to allow the engine to start. Once the engine 14 has started, the intermediate drive shaft

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52 quickly put in circulation, the balls 64 in the grooves 60 are driven radially outward and thanks to the inclined Bottom surfaces 62 push the balls, the ring plate 78 and the locking member 66 to the right in Fig. 2 to the dimension of the Channel formed between the closure member and the seat 70 to enlarge. Because of this, the exhaust air flow is not hindered when the engine 14 is operating at a speed that is greater than the idle speed or greater than about 10 # s "one free speed or its unloaded speed.

During normal operation of the tool for screwing and tightening a threaded fastener, when the motor 14 is stationary and the valve 20 is closed, the closing member 66 is in its position illustrated in FIG. Before the valve 20 is moved to the position in which pressurized air flows through the duct 22 to the motor 14, the initial flow of the drive medium, which is made possible through the narrow opening between the closing member 66 and the seat 70, is sufficient to keep the motor so to accelerate that the balls 64 move the locking member to its fully open position. The closing member 66 will remain in an almost completely open position, the spring 72 being compressed until the speed of the motor 14 and the intermediate drive shaft 52 decreases to approximately the free or unloaded speed. This reduced speed normally corresponds to the desired maximum torque that the motor applies to the load to be tightened.

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The force of the spring 72 will push the balls 64 radially inward in the grooves 60 _and overcome the reduced centrifugal force acting on the balls y, and the locking member will become the seat 70 move there. If the flow between the closing element 66 and the seat is more reduced ₉ by the movement of the closing element, the pressure of the exhaust air in the chamber 38 increases compared to the pressure in the chamber 40 and a pressure force acting on the flange 74 causes the closing element to be applied quickly the seat overcoming the spring force of the spring washer 80. If the exhaust air flow is completely interrupted, the engine 14 will stop and the fluid pressure differential across the engine will quickly decrease to reduce the engine output torque, regardless of whether that
Valve 20 remains open or is closed »

When the valve 20 by the operator of the tool is released, the pressure of the compressed air in the motor 14 as well as in the chamber 38 is increased by the leakage flow and the venting is reduced via the valve 20 which is in its closed position. Is the compressed air pressure in the chamber 38 sufficient lowered, the spring washer 80 is the closing member 66 from the seat 70 back to that shown in FIG Move position and the cut-off device is ready for another working cycle of the tool 10.

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Claims (9)

Jan. 17, 1980 D-Hg / K Cooper Industries, Inc, Houston, Texas, USA claims 1. ) Air pressure operated tool for tightening threaded fasteners with a housing, an air pressure operated motor in the housing, an exhaust air duct in the housing to divert the exhaust air from the motor to the outside, a valve closing element which, from an open position, allows exhaust air to flow through the exhaust air duct , and a closed position is moveable in the flow of exhaust air is interrupted by the exhaust duct _s is to cause a stopping of the motor, characterized by means (58, 64, 72, 78, 80) at decreasing engine speed moving causes the closing member (66) in the closed position. 2 ♦ Tool according to claim 1, characterized in that that the device responsive to the decreasing engine speed comprises an element (58) which is in driving connection with and driven by the engine is, and flyweights (64), which are connected to the element (58) 030035/0627 cooperate and when starting the engine, the valve member (66) into its fully open position allowing the exhaust air to flow out via the exhaust air duct. 3. Tool according to claim 2, characterized by a spring (72) through which the closing member (66) when the centrifugal force decreases due to the engine speed falling below a predetermined value on the flyweights (64) is moved toward the closed position. 4. Tool according to claim 3, characterized by a second the closing member (66) into one partially opened position allowing an initial flow of exhaust air from the engine when it is started Spring (80). 5. Tool according to claim 4 with a drive medium shut-off valve, which is connected to a supply channel leading to the engine, characterized that the shut-off valve (20) in its closed position prevents the drive medium from flowing out from the motor and the exhaust air duct (38) located between this and the closing element (66). 030035/0627 _ 6. Tool according to claim 4, characterized in that that the element (58) which is in drive connection with the motor is essentially several comprises radially extending grooves (60) each having an inclined bottom surface (62), and that the flyweights are formed by balls (64), one of which is arranged in each groove (60) and depending on the Centrifugal force pushing the closing member (66) into its fully open position, movable radially outward is. 7. Tool according to claim 6, characterized in that the speed-dependent device comprises an annular plate (78) which is connected between the closing member (66) and the balls (64) and rests against them, and that the second spring is formed by a spring washer (80) which rests against the ring plate (78) and the closing element (66) and is connected between them. 8. Tool according to claim 3, characterized in that that the housing forms a first and a second at least part of the exhaust duct Chamber (38 and 40) and a in the first chamber (38) a valve seat (70) forming transverse wall, wherein the Closing member (66) to interrupt the flow of exhaust air 030035/0627 _ ₄ _ 001731 the first to the second chamber on the valve seat (70) can be applied. 9. Tool according to claim 8, characterized in that that the valve member (66) comprises a pressure application surface (74) on which the rising Air pressure in the first chamber (38) to support the first spring (72) to the closing member (66) on the Pushing the seat (70) acts as the closure member (66) moves towards its closed position. 030035/0627