Drum

Claim 1

An adjustable musical drum comprising: a. a cylindrical casing having a vertical longitudinal axis; b. a drum head comprising: a circular skin and a hoop attached to the periphery of the skin and adapted to fit relatively closely over the casing with the skin stretched over an upper end of the casing; c. a rim adapted to engage the hoop for drawing the hoop over the casing to tension the skin on the said end of the casing; d. adjustable means coupled to the casing and operable to draw the rim axially of the casing and towards the other end of the casing to apply a predetermined tension to the skin; e. a tensioning mechanism operable to move the adjustable means axially thereby varying the tension in the skin between the predetermined tension and a higher tension; f. a foot pedal assembly for coupling to the tensioning mechanism and to the mounting means for moving the tensioning mechanism to change the tension in the skin continuously between the said predetermined and higher tensions; g. the adjustable means comprising: a plurality of axial bolts each of which has a head end engaged against the rim and a threaded end; and a plurality of sliders coupled to the casing for reciprocal axial movement, each slider having an axially extending opening for threadably receiving a corresponding threaded end of a bolt, the sliders being coupled to the tensioning mechanism so that the bolts can be tightened to draw the rim towards the sliders to apply the predetermined tension to the skin; and h. the tensioning mechanism comprising: i. a lower pivot block adapted to reciprocate along said axis in response to pedal assembly movements ii. an axial push rod reciprocally coupled to the casing and having an upper end attached to the lower pivot block and a lower end coupled to the foot pedal assembly for transmitting movement from the foot pedal assembly to the lower pivot block; iii. a plurality of lower arms extending radially of the lower pivot block and pivotally connected at their respective outer ends to the casing; iv. means connecting the inner ends of the lower arms to the lower pivot block so that the arms are free to rotate about their outer ends in response to axial movements of the lower pivot block; v. an upper pivot block adapted to reciprocate along said axis; vi. a plurality of intermediate arms extending radially outwards and downwardly from the upper pivot block, each of the intermediate arms having an inner and connected to the upper pivot block and an outer end pivotally connected to a corresponding lower arm intermediate the ends of the lower arm so that movement of the lower pivot block in one axial direction is transmitted by the lower and intermediate arms to the upper pivot block to move the upper pivot block in the same direction; vii. a plurality of upper arms extending radially from the upper pivot block and having outer ends projeCting through the casing; viii. fulcrum means coupling the upper arms to the casing adjacent outer ends of the upper arms for pivotal movement of the upper arms such that a relative large movement of the inner ends of the upper arms results in a relatively small movement of the outer ends; and ix. means coupling respective inner and outer ends of the upper arms to the upper pivot block and to the sliders whereby axial reciprocal movement of the upper pivot block in response to movement at the foot pedal assembly pivots the upper arms in the fulcrum means resulting in axial movement of the sliders in the opposite direction to the direction in which the upper and lower pivot blocks move.