GB2068284A

GB2068284A - A pneumatic screwing tool provided with a device holding a screw by air suction

Info

Publication number: GB2068284A
Application number: GB8041536A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-01-31
Filing date: 1980-12-31
Publication date: 1981-08-12
Also published as: SE8100427L; DE3003390C2; DE3003390A1; SE455582B; JPH0244672B2; GB2068284B; JPS56119380A

Abstract

A pneumatic screwing tool holds a screw through suction air in a passage (16) generated by means of an ejector effect. Exhaust air from the screw motor is separated from the low pressure passage (16) on the suction side. An ejector nozzle is opened by a manual valve (34) so that suppply air (8) passes through a mixed air passage (21) and the nozzle to provide the suction. Upon exhaust air pressure build-up, an optimal non-return valve may block-off the passage (16) from the nozzle. <IMAGE>

Description

SPECIFICATION A pneumatic screwing tool provided with a device for feeding and holding a screw by air suction State of the art The invention originates from a pneumatic screwing tool according to the preamble to the main claim. Such a pneumatic screwing tool is already known from U.S. specification 2 570 1 64. In that specification, the exhaust air both from the suction air flow and from the screw motor are blown out laterally of the screwing tool through the same openings. In so doing, the outlet openings from the ducts for the suction air flow and the exhaust air from the screw motor are located directly opposite each other so that both air flows are directed against each other. The predominance of the exhaust air flow from the screw motor causes a dynamic pressure when the screwing operation is started. Screws which are sucked in are allowed to fall.Moreover, the operation of a pneumatic screwing tool constructed in that manner is very noisy and annoying for the operator due to the existence of draught.

Advantages of the invention As opposed to this, the pneumatic screwing tool comprising the characterising features of the main claim has the advantage that, by separating the exhaust air from the screw motor from the exhaust air of the suction air flow, sucked in screws are prevented from faliing.

Advantageous further developments and improvements of the pneumatic screwing tool set forth in the main claim are made possible by the measures set forth in the sub-claims.

The insertion of a non-return valve in the low pressure duct which permits the combining of the exhaust air both from the screw motor and from the suction air guide at a common exhaust air outlet, is of special advantage.

Finally, it is also of special advantage that by moving the exhaust air openings both for the screw motor and for the suction air guide to the rear end of the housing portion, a low noise and draught-free discharge of both air flows is possible which can be further improved by the favourable inclusion of noise dampers or a central exhaust system.

Drawing Three embodiments of the subject matter of the invention are illustrated in the drawing and are described in detail in the following specification. Figure 1 shows a longitudinal section through a pneumatic screwing tool in accordance with the invention, Figure 2 is a partial section through the rear housing portion of the pneumatic screwing tool according to Fig. 1, with a modified control valve for the suction air and Figure 3 is a partial section like Fig. 2 with an additionai variant of the control valve for the suction air and a special discharge air connection for the inlet blower.

Description of the embodiments In the embodiment according to Fig. 1, a housing 1 of the pneumatic screwing tool accommodates a screw motor 2 and in its rear housing portion 3 a valve 4, an ejector nozzle 5, a non-return valve 6 and a shut-off valve 7.

A supply air connection 8 and an exhaust air connection 9 are also fixed in the rear housing portion 3. The outlet opening from the ejector nozzle 5 leads into a communicating duct 10 to the exhaust air connection 9. If necessary, the exhaust air connection 9 is formed by a noise damper 11. A coupling housing 1 2 connects the housing 1 to a locating and holding sleeve 1 3. Moreover, the coupling housing 1 2 is sealed with respect to the housing 1 by a sealing disc 14 which has an opening 1 5 through which a low pressure duct 1 6 in the housing 1 is connected to the interior of the coupling housing 1 2. The coupling housing 1 2 accommodates a driver 1 7 which in its turn forms a receiving device 1 8 for a screwdriver blade 1 9. In this instance, the driver 1 7 can be driven by the screw motor 2 in a manner not illustrated in detail.

The valve 4 has a housing with a nozzle opening 20 for the air supply to to the screw motor 2, a mixed air opening 21 and a bore 22. The air inlet connection 8 is screwed into the bore 22. Before that, a ball 23 and a compression spring 24 are inserted in the bore 22. The compression spring 24, which serves as an abutment for the air supply connection 8, forces the ball 23 into the conical mouth of the bore 22 which issues into the nozzle opening 20. The mixed air opening 21 is not sealed by the ball 23. It leads to an air duct 25 in the adjacent ejector nozzle 5 which in its turn issues into a nozzle opening 26. This nozzle opening 26 leads to a nozzle bore 27 to which a nozzle bore 28 is also connected.The nozzle bore 28 leads into the low pressure duct 1 6 through the interior of the non-return valve 6 which accommodates a ball 29. A rod 30 which is guided in a bore 31 in the housing 1 projects into the nozzle opening 20 of the valve 4. One end of the rod 30 contacts the ball 23. The purpose of this rod 30 is to sense a longitudinal movement of the screwdriver blade 1 9 on the insertion of the screw in the bore associated therewith and thus raise the ball 23 from its conical seat in order to release the air supply opening for the screw motor 2. A screw 32 with a sealing plate serves as a shut-off valve 7 which can close the nozzle bore 27.

If screws are to be sucked in and held by negative pressure, then the shut-off valve 7 is opened (Fig. 1). The air supplied through the air supply connection 8 is forced through the mixed air opening 21 and the air duct 25 provided with the adjacent nozzle opening 26 and flows out through the nozzle opening 27 into the communication duct 10. In so doing, the air through the nozzle bore 28 is entrained therewith so that a suction air flow exists in the low pressure duct 16, in the coupling housing 1 2 and in the locating and holding sleeve 1 3. If a screw is sucked in, then it is forced into the hole provided for screwing up by means of the screwdriver blade 1 9. This pressure exceeds the force of the compression spring 24 and opens the nozzle opening 10 for the air supply for driving the screw motor 2.When the exhaust air from the screw motor 2 flows away, an excess pressure exists in the communication duct 10 which acts through the nozzle bores 27 and 28 on the ball 29 in the non-return valve 6. This ball 29 closes the opening to the low pressure duct 1 6. As soon as the screwing operation has ended and the screwing tool is removed from the screw, the compression spring 24 closes the nozzle opening 20 once again with the aid of the ball 23. Air immediately flows through the mixed air opening 21 up to the communication duct 10 and the suction operation can begin afresh.

In the embodiment according to Fig. 2, only the shut-off valve 7 is replaced by another valve construction. This comprises a rod 33 which carries a sealing cone 34 at its inner end and a push button 35 at its outer end. The rod 33 is guided in a bore 36 in a closure cover 37 which closes the rear end of the housing 1. A compression spring 38 inserted between the pushbutton 35 and the closure cover 37 always seeks to retain the sealing cone 34 on its seat in the air duct 25.

In this embodiment, the pushbutton 35 must be pushed towards the closure cover 37 in order to start the suction air flow. Thereafter, the method of operation is as described with respect to the embodiment according to Fig. 1.

In the embodiment according to Fig. 3, a shut-off valve similar to that of Fig. 2 is so arranged that its push rod 39 provided with the actuating knob 40 projects laterally out of the housing 1. The inner end of the push rod 39 carries a ball 41 which is forced by a compression spring 42 onto a conical seat in the air duct 25 of the injector nozzle 5. In this arrangement, a non-return valve 6 is dispensed with and an exhaust air chamber 43 is connected directly to a separate noise damper 44 which delivers the exhaust air into the surrounding area of the pneumatic screwing tool and to the rear of the latter. In this instance, the noise damper 11 only accepts exhaust air from the screw motor 2.

As in the embodiment according to Fig. 2, the suction air flow is controlled by depressing the push rod 39 through the actuating knob 40. The remaining method of operation is likewise the same as that according to Fig. 1.

Claims

1. A pneumatic screwing tool provided with a device for feeding and holding the screws through suction air generated by means of an ejector effect, comprising a locating and holding sleeve surrounding the screwdriver blade and a mixed air opening branched on the supply side which connects the chamber receiving the air supply to an ejector nozzle from which a low pressure duct extends up to the locating and holding sleeve, characterised in that, the exhaust air from the screw motor is separate from the low pressure duct.

2. A pneumatic screwing tool according to claim 1 characterised in that the suction air and the air flow which it generates derived from the air supply is transmitted through the communication duct to the motor exhaust air connection and a non-return valve is arranged in the low pressure duct which allows the suction air flow to pass unhindered but shuts off the prevailing counter air flow from the outlet when the screw motor is running.

3. A pneumatic screwing tool according to claim 1 characterised in that a separate exhaust air connection is provided for the suction air flow in the rear housing portion or in a closure cover for the said rear housing portion.

4. A pneumatic screwing tool according to one of claims 1 to 3 characterised in that it includes a manually actuable valve for shutting off the air flow derived from the air supply for the screw motor and with it the suction air flow.

5. A pneumatic screwing tool according to claim 4 characterised in that the valve is formed as a screw valve.

6. A pneumatic screwing tool according to claim 4 characterised in that the valve is retained in the closed position under the action of a spring and is connected to a push rod which carries a handle for opening the valve.

7. A pneumatic screwing tool according to one of claims 1 to 6 characterised in that a screwing tool housing including the screw motor, the ejector nozzle and the valve controlling the air supply for the screw motor is connected through a coupling housing to the locating and holding sleeve.

8. A pneumatic screwing tool according to claim 7 characterised in that the screwing tool housing forms a low pressure duct for the suction air, whilst the coupling housing and the locating and holding sleeve together serve as a suction air guide.

9. A pneumatic screwing tool according to one of claims 7 and 8 characterised in that a sealing disc is inserted between the screwing tool housing and the coupling housing the disc having an opening for connecting the low pressure duct in the screwing tool housing to the interior of the coupling housing.

10. A pneumatic screwing tool according to one of claims 1 to 9 characterised in that a noise damper is mounted on the exhaust air connection or connections.

11. A pneumatic screwing tool according to one of claims 1 to 10 characterised in that the exhaust air connection or connections can be connected to a central exhaust system.

1 2. A pneumatic screwing tool substantially as herein described with reference to Figs. 1, Figs. 1 and 2 or Figs. 1 and 3 of the accompanying drawings.