AU2004325387A1 - Coach screw driver - Google Patents

Abstract

A coach screw driver (1) for tightening or loosening rail fastening screws (9) comprises a current generator (13), which can be driven by a combustion engine (5), and comprises a friction clutch (12), which can be electromagnetically engaged and disengaged and which can be supplied with electrical current by this current generator. In order to precisely limit torque, a potentiometer (16) is provided, which can be adjusted by an operator and which controls the current for actuating the friction clutch (12).

Description

VERIFICATION OF TRANSLATION Australian Patent Application relating to: "A screwing machine" 1, Helmut P. Wind, of Drischutzgasse 10/32, A-1 110 Vienna, Austria, am the translator of the documents attached and I state that the following is a true translation to the best of my knowledge and belief. Signature of translator: Dated 1st February 2007 [0495 - Ma] A screwing machine. The invention relates to a screwing machine for tightening or loosening rail fastening screws, including a machine frame designed to roll on a track and possessing handle bars for displacement, an internal combustion engine, and a coupling for transmitting a torque to a screw head, and also including a device for torque limitation. Screwing machines of this type, designed to roll on a track and to be moved by an operator, are known in manifold variants, particularly with regard to the coupling and the torque limiting device. The latter is particularly important since the tightening moment for the bolts should be exact and uniform for all the fastenings. According to DE 12 40 108 or DE 26 37 954, a friction clutch is known which can be loaded by spring pressure. The spring pressure is adjustable by means of a stop screw of a clutch lever. With this, however, an exact torque can not be achieved. A hydraulic screwing machine known from DE 29 43 938, while making possible a relatively precise torque limitation, is nevertheless unwieldy due to the greater weight. According to US 2 151 953, an elastic medium which changes under the effect of force is provided between a force-introducing flange and a driving flange. The torque can be read off a dial. However, this makes the precision of the effectively achieved tightening moment dependent upon the skill and the concentration of the operator. According to DD 135 510, two hydraulic pumps with different displacement capacity are employed.

In DE 76 07 578 U, several pivotable stop devices are provided which limit the path of a switch lever for selecting the torque. It is the object of the present invention to create a screwing machine of the specified type which makes it possible for an operator to control the torque precisely and in a simple manner. According to the invention, this object is achieved with a screwing machine of the kind mentioned at the beginning in that an electric generator is provided which can be driven by the internal combustion engine, and a coupling is provided in the shape of an electromagnetically switchable friction clutch which may be supplied with electrical power by said electric generator, and the device for torque limitation is designed as a control element which is adjustable by an operator and changes the current for actuating the friction clutch. By appropriate adjustment of the potentiometer relative to a dial indicating the respective torque, the required tightening moment can be set with particular precision and also with great ease by the operator. The combination of an electric generator with an electromagnetic coupling, designed to be powered by the former, also has the special advantage that both the structural expense and the increase in total mass - which is crucial for a machine to be displaced manually - is very small. Additional advantages and features of the invention become apparent from the further claims and the drawing. The invention will be described in more detail below with reference to an embodiment represented in the drawing in which Fig. 1 shows a side view of a screwing machine, and Fig. 2 shows a simplified circuit diagram. A screwing machine 1, depicted in Fig. 1, comprises a machine frame 4 which is mobile by means of rollers 2 on a rail 3 of a track 20. Said machine frame 4 is connected to an internal combustion engine 5, a transmission 6 of a drive shaft 7, and handle bars 8 for displacing the screwing machine 1. Provided for tightening or loosening a rail fastening screw 9 is a screwing head 10 designed to be set in rotation by the drive shaft 7. A device 11 for torque limitation, having the shape of an electromagnetically switchable friction clutch 12, is provided between the internal combustion engine 5 and a transmission. An electric generator 13 driven by the internal combustion engine 5 serves for supplying electric current, with the output line of the generator being connected to a rectifier 14 (Fig. 2) for transforming alternating current into direct current. The direct current is fed to an amplifier and voltage regulator 15, the output current of which - for actuation of an integrated solenoid 21 of the friction clutch 12 - is changeable by means of a control element 16 in the shape of a rotary knob 17, fastened to the handle bar 8 and designed as a potentiometer. Associated with the rotary knob 17 are a dial 18 and a pointer 19 indicating the respective maximum torque of the friction clutch 12 designed as a multiple disk clutch. The friction clutch 12 runs in a permanent oil bath in order to be able to precisely reproduce the set torque.

Claims (3)

1. A screwing machine for tightening or loosening rail fastening screws (9), including a machine frame (4) designed to roll on a track (20) and possessing handle bars (8) for displacement, an internal combustion engine (5), and a coupling for transmitting a torque to a screw head (10), and also including a device (11) for torque limitation, characterized in that an electric generator (13) is provided which can be driven by the internal combustion engine (5), and a coupling (12) is provided in the shape of an electromagnetically switchable friction clutch (12) which may be supplied with electrical power by said electric generator, and the device (11) for torque limitation is designed as a control element (16) which is adjustable by an operator and changes the current for actuating the friction clutch (12).

2. A screwing machine according to claim 1, characterized in that the electric generator (13) is designed for producing alternating current, and a rectifier (14) for transforming the alternating current into direct current able to switch the friction clutch (12) is provided as well as an amplifier and voltage regulator (15).

3. A screwing machine according to claim 1 or 2, characterized in that the friction clutch (12) is designed as a multiple disk clutch with an integrated solenoid (21).