Drum tensioning apparatus
BACKGROUND OF THE INVENTION 
     1. Field of The Invention 
     The present invention is directed to the field of musical instruments. More particularly, it relates to an apparatus for instantaneously varying the tension on a drum head to change the pitch of the instrument while it is being played. 
     2. Description of Related Art 
     The pitch of a percussion type musical instrument, such as a drum, is dependent upon the tension in the head covering the instrument. The pitch of the tone produced by striking the instrument is raised by increasing the tension in the head. Similarly, by decreasing the tension in the head, the pitch of the tone is lowered. 
     A drum head may be manually tensioned before a performance to produce a desired tone. An apparatus for manually tensioning a drum head is disclosed in U.S. Pat. No. 2,061,244. This apparatus requires that the musician manually turn a crank to change the pitch of the drum. When manual tensioning is employed it is very difficult or impossible to vary the tone of the instrument during a performance and several drums, each tuned to a different pitch, may be required to perform a given composition. An electronic device for automatically tuning a drum to a selected pitch is disclosed in U.S. Pat. No. 4,023,462. This device eliminates the need for the musician to manually adjust the tension in the drum head, but it is not entirely suitable for varying the pitch of the drum repeatedly during a performance. 
     It is therefore desirable for a musician to have the capability of instantaneously changing the pitch of a drum during a performance. In addition to providing a range of tones from a single instrument, such a capability may reduce the number of drums required for the performance. 
     At least one technique by which drum head tension may be varied during a performance is known in the prior art. This technique, disclosed in U.S. Pat. No. 3,590,680, involves pressurizing the drum with compressed air or gas and selectively varying the gas pressure, thereby varying the pitch of the drum. This method of drum pitch control requires that the drum itself be made essentially gas tight. Many types of drums, however, are made of gas-permeable materials and/or are designed with open-ended barrels to achieve specific sound qualities. The gas pressure method of pitch control is thus inapplicable to most drums. 
     Because it is often desirable to vary the pitch of drums during a musical performance, there is a need for a drum head tension control system which is adaptable to all drum types. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus capable of instantaneously changing the tension on a drum head during a musical performance to vary the pitch and quality of the drum sound. The invention utilizes a rigid ring, concentric with, and installed within, the drum barrel, to apply pressure on the drum head. The drum head tensioning ring is supported by a frame connected to an actuation mechanism for moving the ring against the drum head. The ring actuation mechanism is driven by means of a power supply mechanism capable of instantaneous directional reversal. The musician can thus control the pitch of one or more drums from a central control apparatus by causing the power supply mechanism to drive the ring actuation mechanism in the appropriate direction, either applying or releasing tension on the drum head. The control apparatus is capable of being programmed to alter drum pitch in increments and at variable speeds. 
     The apparatus according to the present invention is thus able to provide an effective means of raising or lowering the pitch of one or more drums instantaneously during a musical performance. 
     Further, the apparatus according to the present invention is able to alter drum pitch by one or more preselected increments and at variable speeds. 
     Still further, the apparatus according to the present invention is suitable for installation in all types of drums, including open barrel designs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully understood when the following detailed description of the preferred embodiment is considered with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a drum tensioning apparatus of the present invention, configured to control the tension of the heads of several drums simultaneously; 
     FIG. 2 is a perspective view of a drum head tensioning ring and its supporting frame and actuation mechanism; 
     FIG. 3 is a sectional elevation view taken along line 3--3 of FIG. 1 of the transmission for controlling the tension of the heads of several drums simultaneously; and 
     FIG. 4 is a sectional elevation view taken along line 4--4 of FIG. 2 of the drum had tensioning ring actuator. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, the drum tensioning apparatus of the present invention includes an electric motor 10, an electric cable 12, a power shaft 14, a transmission 16, output shafts 18a, 18b, and 18c, a control actuator 20, control pedals 22, and drum head tensioning assemblies generally indicated by the reference numerals 30a, 30b, and 30c. 
     The drum tensioning apparatus is actuated by means of an electric motor 10, which is powered by electric current supplied through electric cables 12. Electric motor 10 is capable of causing instantaneous reversal of the direction of rotation of power shaft 14. Power shaft 14 is capable of rotation in either a clockwise or a counter-clockwise direction and at any speed up to the maximum speed of electric motor 10. The direction, speed, and extent of rotation of power shaft 14 are controlled by a musician operating control actuator 20 by means of input signals produced by control pedals 22. Alternative embodiments of the present invention may employ other means of interface with control actuator 20. These alternative means may include knee-operated control pedals or hand-operated control panels. Other means of actuating electric motor 10 include the use of proximity switches 21 or photoelectric switches 23. Proximity switches 21 include dual source heads 24 which produce magnetic fields. When the musician places a portion of his body near either source head 24 the magnetic field is disturbed and the source head 24 senses this disturbance. The source head 24 translates this disturbance into a signal to actuate electric motor 10. 
     Photoelectric switches 23 include multiple light sources 25 and a reflector 26. When the musician places a portion of his body between a light source 25 and reflector 26, the photoelectric switch 23 senses the interruption in the reflected light beam and produces a signal to actuate electric motor 10. Control actuator 20 is capable of being programmed to alter drum pitch continuously or in variable increments and at variable speeds. Power shaft 14 provides input power to transmission 16. 
     As illustrated in FIG. 3, transmission 16, incorporates multiple spur gears 17a, 17b, and 17c arranged about a central spur gear 19 and distributes the input power to multiple output shafts 18a, 18b, and 18c. Output shafts 18a, 18b, and 18c are comprised of flexible cables capable of transmitting torque. Each of output shafts 18a, 18b, and 18c is connected to drum head tensioning assemblies, 30a, 30b, and 30c, installed in drums, generally indicated by the reference numerals 40a, 40b, and 40c. 
     Drums 40a, 40b, and 40c consist generally of a barrel, 42a, 42b, and 42c, and a head, 44a, 44b, and 44c. Depending upon the direction of rotation of output shafts, 18a, 18b, and 18c, drum head tensioning assemblies, 30a, 30b, and 30c, act simultaneously to either increase or decrease the tension on drum heads, 44a, 44b, and 44c. Each of control pedals 22 controls a single function of the drum tensioning apparatus, serving either to increase or decrease tension on drum heads, 44a, 44b, and 44c. Depending upon which of control pedals 22 is depressed, and the extent to which it is depressed, the tone of drums, 40a, 40b, and 40c, is raised or lowered. The process by which drum head tensioning assemblies, 30a, 30b, and 30c, act to vary the tension on drum heads, 44a, 44b, and 44c, will be more fully discussed below in conjunction with FIG. 2. 
     Alternative embodiments of the present invention may incorporate other suitable means, including pressurized fluid, for actuating drum head tensioning assemblies, 30a, 30b, and 30c. 
     Referring now to FIG. 2, the drum head tensioning assembly, generally indicated by the reference numeral 30, includes a tensioning ring 32, a tensioning ring frame 34, a tensioning ring drive shaft 36, a tensioning ring actuator 38, and a tensioning ring actuator support 39. Tensioning ring actuator 38 can be any convenient device such as a gear nut or screw jack. One drum head tensioning assembly is deployed per drum. The drum head tensioning assembly is entirely contained within the barrel of the drum. For clarity, only drum 40a is described below. Tensioning ring actuator support 39a attaches to barrel, 42a, of drum, 40a, and supports drum head tensioning assembly, 30a, within drum, 40a. Tensioning ring 32a, slightly smaller in diameter than barrel 42a, abuts against the inside of drum head, 44a, and is held in position by tensioning ring frame 34a. Tensioning ring frame 34a is supported at its center by tensioning ring drive shaft 36a. The tensioning ring drive shaft 36a is movable along its axis and is actuated by tensioning ring actuator 38a. Tensioning ring actuator 38a is more fully illustrated in FIG. 4. Tensioning ring actuator 38a acts to convert the rotary motion of output shaft 18a to linear motion of tensioning ring drive shaft 36a. Tensioning ring actuator 38a is comprised of a housing 50a, a right angle gear reducer, including worm 51a and worm gear 52a, connected to a screw jack attached to tensioning ring drive shaft 36a. Worm 51a is fitted to the end of output shaft 18a and rotates with output shaft 18a. Worm 51a meshes with worm gear 52a. Worm gear 52a is confined to rotate only within bearing block 53a. Tensioning ring drive shaft 36a passes through worm gear 52a and forms the axis of rotation of worm gear 52a. The bore of worm gear 52a is threaded to mesh with the threads 54a on tensioning ring drive shaft 36a. Thus rotation of output shaft 18a causes tensioning ring drive shaft 36a to displace linearly. Alternative embodiments of the present invention which utilize a pressurized fluid to actuate tensioning ring 32a incorporate a piston-cylinder or rotary activator tensioning ring actuator to convert fluid pressure to linear motion of tensioning ring drive shaft 36a. 
     When tensioning ring drive shaft 36a is moved toward drum head 44a, tensioning ring 32a exerts pressure on drum head 44a, raising the pitch of drum 40a. Conversely, when tensioning ring actuator 38a moves tensioning ring drive shaft 36a in the direction away from drum head 44a, the pressure which tensioning ring 32a exerts on drum head 44a is reduced, thereby lowering the pitch of drum 40a. 
     Although the invention has been described with reference to its preferred embodiment, those of ordinary skill in the art may, upon reading this disclosure, appreciate changes and modifications which do not depart from the scope and spirit of the invention as described above or claimed hereafter.