GB2079511A - Sound generator - Google Patents

Abstract

A sound generator or audible warning device for incorporation in the pressurised water supply of a coal cutter, includes a water driven turbine the output shaft of which has a member having a ridge extending transversely of the axis of rotation fixed thereto and a diaphragm having a centrally mounted member including at least one groove also arranged transversely of the axis of the turbine shaft, whereby rotation of the turbine produces oscillations of the diaphragm resulting in sound production.

Description

SPECIFICATION Hydraulic sound generator The present invention concerns an hydraulic sound generator. The invention is intended for use especially but not exclusively on coal cutting machines for use in coal mines.

In such machines sprays of water are used to damp down dust generated by the coal cutter, the water having been used also for cooling purposes in the machine.

The water supply to the spray jets includes a pressure sensitive valve and the valve is so interconnected with the controls of the machine that it does not permit the cutter to start until a predetermined time has elapsed after a predetermined pressure has been built up at the pressure sensing means. This ensures that the flow of water is adequate for the purposes it has to fulfil.

For protection and safety the electrical circuitry of the machine is virtually inaccessible and consequently it is a difficult engineering operation to tap the supply of electricity to power an accessory. Furthermore there are many electrically powered audible warning deviceslpresently employed on mining apparatus and as a result it is often difficult to obtain a distinctive electrically generated warning sound.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to the present invention there is provided a sound generator including a fluid motor having a rotatable output shaft, a diaphragm and connection means between the shaft and the diaphragm to cause the diaphragm to vibrate on rotation of the shaft.

Preferably the connection means includes a first member mounted for rotation with the shaft and having a ridge extending transversely of the axis of rotation and a second member mounted at the centre of the diaphragm, facing said first member and having at least one radially extending groove therein whereby entry of the ridge into the groove causes a movement of the diaphragm. There may be several grooves formed in the second member.

Preferably the sides of said ridge and said groove(s) are inclined and the transverse dimensions of the ridge are less than the corresponding transverse dimensions of the groove(s).

A sound amplifying and directing horn may be provided on the generator on the side of the diaphragm remote from the fluid motor.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a sectional elevation of an hydraulic sound generator; and Figure 2 is an end elevation thereof.

An hydraulic sound generator comprises a fluid motor 10 the construction of which is standard and as a result it will not be described in detail in this specification. The motor converts the pressure energy of a fluid passing therethrough into rotation of its output shaft 1 2 and rigidly attached to the output shaft 12, for example by grub screws 14 whose ends engage in a keyway 1 6 formed in the shaft, is a sleeve 1 8 which carries at its outer end a first member 20 of a connecting device.

A first member is made from hardened steel and is provided on its outer transverse face with a ridge 22, the side faces 24 of which are inclined with respect to the top face which lies on a plane transverse to the axis of rotation.

The framework 24 which supports the motor and mounting means 26 for the sound generator supports also the annular region at the edge of a circular diaphragm 28 which carries a second member 30 of the said connecting device. The second member is also manufactured from hardened steel and has a series of grooves formed in its transverse face facing the first member. The grooves are arranged at equal angles relative to each other and each has a base lying in a plane transverse to the axis of rotation of the shaft and sides inclined relative thereto, the angle of inclination being equal to the angle of inclination of the side faces of the ridge 22 of the said one member of the connecting device. The transverse dimensions of the groove are greater than the corresponding dimensions of the ridge 22 so that when the ridge is accommodated in a groove it never completely occupies it.

A sound amplifying and directing horn 32 is mounted on the framework 24 on the side of the diaphragm 28 remote from the fluid motor 10.

In operation, when fluid is supplied to the fluid motor 10 the shaft 1 2 is caused to rotate thus causing the ridge 22 to rotate. On rotation the ridge is accommodated in sequence in the grooves formed in the member 30 and as it moves from groove to groove it causes a displacement of the centre of the diaphragm along the axis of rotation. The speed of the shaft 1 2 is such that the diaphragm generates a particular audible signal which is directed and amplified by the horn 32.

The sound generator is particularly useful in coal cutting machines of the type described in the introduction to this specification as it can readily be interposed in the fluid supply line to the spray jets downstream of the pressure sensitive device. As a result it operates at least as soon as the predetermined pressure is achieved and, as described above, there then follows a predetermined delay before the machine operates. Thus it is guaranteed that the warning sound will be made before the coal cutter starts. Furthermore if insufficient pressure is generated in the supply pipe to the spray jets the warning device may not sound but the pressure sensing device in such circumstances will not permit the operation of the cutter.

Various modifications can be made without departing from the scope of the invention. For example the connection means between the motor shaft and the diaphragm may take any suitable form which conveniently translates the rotational movement of the shaft into an oscillation of the diaphragm. Thus the end of the shaft may include an off-centre peg cooperable with a suitable formation on the diaphragm, for example a saw tooth formation.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to whether or not particular emphasis has been placed thereon.

Claims (7)

1. A sound generator including a fluid motor having a rotatable output shaft, a diaphragm and connection means between the shaft and the diaphragm to cause the diaphragm to vibrate on rotation of the shaft.

2. A sound generator as claimed in claim 1, in which the connection means includes a first member mounted for rotation with the shaft and having at least one ridge extending transversely of the axis of rotation and a second member mounted at the centre of the diaphragm, facing said first member and having at least one radially extending groove therein whereby entry of the ridge into the groove causes a movement of the diaphragm.

3. A sound generator as claimed in claim 1 or claim 2, in which the sides of said ridge or ridges and said groove or grooves are inclined.

4. A sound generator as claimed in any one of claims 1 to 3, in which the transverse dimension of the ridge or ridges is less than the corresponding transverse dimension of the groove or grooves.

5. A sound generator as claimed in any one of claims 1 to 3 including a sound amplifying and directing horn. on the side of the diaphragm remote from the fluid motor.

6. A sound generator substantially as hereinbefore described with reference to the accompanying drawings.

7. A coal cutter including a water supply, means for pressurising said supply, pressure sensing means and a timing device, said pressure sensing means being adapted to actuate the timing device which is arranged to prevent the operation of the cutter until a predetermined delay has elapsed after said sensing means detects a predetermined pressure and a sound generator as claimed in any one of the preceding claims arranged upstream of said pressure sensing means.