Spring-loaded hammer

Claim 1

A spring-loaded hammer or percussive drill with a mechanical vibratory system comprising one or more vibratory masses (1) and several component springs including a main spring and a buffer spring (12a-c and 15) for cushioning the vibratory masses against fixed bearing members (13) mounted within the hammer casing, and with means (6 and 7) whereby the vibratory masses can be caused to vibrate, as well as means of transmission (14) whereby, at every vibration of those masses, part of the energy of vibration is transferred in impact form to a percussive tool bit (16) in such a way that the times of application of the spring action produced by the component springs, of the oscillatory displacement of the center of gravity of the vibratory masses, and of the force vector of the impact transmitted to the bit at every vibration, lie in the produced longitudinal center line of the bit, while that side of the vibratory masses which faces away from said means of transmission bears against said main spring (12a-c), said buffer spring (15) being provided on that side of the vibratory masses which faces towards the said means of transmission; characterized in that said main spring, at particular points (I and II) along its length, has different spring characteristics from those which apply elsewhere along its length, said main spring being divided at such particular points.