GB2138099A - Toothed coupling - Google Patents

Abstract

In toothed couplings with a compensation capability, the relative movement of those parts of the coupling which are in mutual toothed engagement does not allow the transmitted power to be increased, as would be desirable. The invention provides a toothed coupling for the transmission of high torques at high rotational speeds, in which a considerable increase in the transmitted power is made possible by the grinding of flanks of the external and internal crowned teeth of the parts during manufacture.

Description

SPECIFICATION Toothed coupling The present invention relates to toothed couplings for transmitting high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts.

In prior art couplings of this type, the relative movement of those parts of the coupling which are in mutual toothed engagement does not allow the transmitted torques and rotational speeds to be increased, as would be desirable. In this respect, it has not been possible previously to increase the rotational speeds beyond about 30,000 min1 for a simultaneous output of about 70,000 kW.

Even the most careful lubrication and cooling do not permit any further increase.

In many branches of mechanical engineering, however, it is desirable to be able to increase the transmitted torque for simultaneously increased rotational speeds. The object of the present invention, therefore, is to provide a coupling of the type described initially, which permits the desired increase in the transmitted torques and rotational speeds.

In order to attain this object, the invention provides a toothed coupling of the aforesaid type, in which the flanks of the external and internal teeth are ground. During manufacture of the coupling, the teeth are ground after the hardening process. The step of using wholly ground teeth, which is unusual in coupling manufacture, allows a considerable and surprising increase in the values of the transmitted torque and rotational speed.

In a preferred and advantageous embodiment of the invention, a camber ratio R e=, rO where R is the camber radius and r0 the pitchcircle radius, of between approximately 25 and 40 is chosen.

The immediate advantages of the present invention over couplings of the prior art are a reduction in the reaction forces which have to be absorbed by the bearings of the associated machinery, a considerable improvement in the ratio of the area of contact between the teeth to the total area of the teeth, and quieter running even under partial loads. Overall, with the coupling of the invention, the power throughput is increased considerably for low weight. Thus, for example, torques ranging from 1,400 Nm at 40,000 min-' to 250,000 Nm at up to 9,000 mien~' can be transmitted. Having regard to the grinding step characterising the invention, this considerable increase is both surprising and unpredictable.

1. A toothed coupling for the transmission of high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts of the coupling, in which the flanks of the external and internal teeth are ground.

2. A toothed coupling as claimed in Claim 1, in which the chamber ratio e, defined as the ratio of the camber radius R to the pitchcircle radius r0 of the external teeth, is between 25 and 40.

3. A toothed coupling substantially as described herein.

4. A method for manufacturing a toothed coupling for the transmission of high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts of the coupling, in which the method includes the step of grinding the flanks of the external and internal teeth after hardening.

5. A method for manufacturing a toothed coupling, substantially as described herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Toothed coupling The present invention relates to toothed couplings for transmitting high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts. In prior art couplings of this type, the relative movement of those parts of the coupling which are in mutual toothed engagement does not allow the transmitted torques and rotational speeds to be increased, as would be desirable. In this respect, it has not been possible previously to increase the rotational speeds beyond about 30,000 min1 for a simultaneous output of about 70,000 kW. Even the most careful lubrication and cooling do not permit any further increase. In many branches of mechanical engineering, however, it is desirable to be able to increase the transmitted torque for simultaneously increased rotational speeds. The object of the present invention, therefore, is to provide a coupling of the type described initially, which permits the desired increase in the transmitted torques and rotational speeds. In order to attain this object, the invention provides a toothed coupling of the aforesaid type, in which the flanks of the external and internal teeth are ground. During manufacture of the coupling, the teeth are ground after the hardening process. The step of using wholly ground teeth, which is unusual in coupling manufacture, allows a considerable and surprising increase in the values of the transmitted torque and rotational speed. In a preferred and advantageous embodiment of the invention, a camber ratio R e=, rO where R is the camber radius and r0 the pitchcircle radius, of between approximately 25 and 40 is chosen. The immediate advantages of the present invention over couplings of the prior art are a reduction in the reaction forces which have to be absorbed by the bearings of the associated machinery, a considerable improvement in the ratio of the area of contact between the teeth to the total area of the teeth, and quieter running even under partial loads. Overall, with the coupling of the invention, the power throughput is increased considerably for low weight. Thus, for example, torques ranging from 1,400 Nm at 40,000 min-' to 250,000 Nm at up to 9,000 mien~' can be transmitted. Having regard to the grinding step characterising the invention, this considerable increase is both surprising and unpredictable. CLAIMS

1. A toothed coupling for the transmission of high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts of the coupling, in which the flanks of the external and internal teeth are ground.

2. A toothed coupling as claimed in Claim 1, in which the chamber ratio e, defined as the ratio of the camber radius R to the pitchcircle radius r0 of the external teeth, is between 25 and 40.

3. A toothed coupling substantially as described herein.

4. A method for manufacturing a toothed coupling for the transmission of high torques at high rotational speeds, of the type comprising respective parts with external and internal crowned teeth for allowing radial and angular relative movement between the parts of the coupling, in which the method includes the step of grinding the flanks of the external and internal teeth after hardening.

5. A method for manufacturing a toothed coupling, substantially as described herein.