US2205593A - Tympano - Google Patents

Description

Patented June 25, 194!) UNITED STATES TYMIPANO Le Roy J. Jeffries, Elkhart, Ind., assignor to C. G. Conn Ltd., Elkhart, Ind., a corporation of Indiana Application March 6, 1939, Serial No. 260,119

5 Claims.

This invention relates to improvements in machine tympano and has for its object the provision of foot-operated means for tuning a tympano which means will remain in any of an infinite number of positions to which it may be adjusted.

Another object is the provision of such a tuning means having a treadle so that the drummer may, for example, operate the mechanism with his toe to increase the pitch of the tympano and with his heel to decrease the pitch. Such a treadle-operating device enables the drummer to rest a portion of his weight upon the foot used in tuning and consequently makes the operation more comfortable.

Other objects and desirable particular constructions will become apparent upon reading the detailed description of one illustrative embodiment of my invention shown in the accompanying drawing in which:

The figure is a vertical axial section of a machine tympano constructed in accordance with my invention.

Referring to the figure the tympano may comprise a base l0 having a plurality of feet I2 to provide adequate support upon the floor. A vertical column M of tubular form extends upwardly from the base and is clamped therein by a clamp l6. At the upper end of the column is secured, by means of a clamp l8, a bowl seat 20 in which the bowl or kettle 22 rests. The kettle may be provided at its lowermost portion with a reinforcement 24 riveted thereto and which acts to position the bowl in the seat 20. The usual head 26 is stretched across the open end of the bowl and is tucked around a flesh hoop 28 which surrounds but is spaced from the outer surface of the bowl. The flesh hoop is engaged by a flanged pressure ring 38 which carries a plurality of brackets 32 (in the illustrated case six in number) An equal number of brackets 34 are secured to the outer surface of the bowl a short distance below the edge thereof and have pivoted therein bell cranks 36 which carry pivots 38 at the ends of one of their arms. The brackets 34 are provided with abutments 40 which engage the pivots 38 in their uppermost positions. A plurality of tuning pins 42 project downwardly through openings in the brackets 32 and are threaded into openings in the pivots 38. The tuning pins are provided at their upper ends with handles 44 and engage the brackets 32 by means of semispherical washers 46.

The other arms of the bell cranks 36 are provided at their ends with pivots 48 in which are secured the ends of a plurality of pull rods 50 which project into the bowl 22 through openings 52. The rods 58 project radially inwardly and downwardly to the center of the bowl 22 and have their inner ends secured to a. crown member 54 by means of suitable length adjusting mechanism 56 which need not be described in detail. The crown member 54 is connected to a primary vertical pull rod 58 extending downwardly through an opening 59 in the bottom of the bowl. I prefer to provide the pull rod 58 in two portions joined by suitable means such as a knurled nut 60 positioned in the bowl support 28 and accessible through hand holes 62 so that the bowl may be conveniently'removed from the seat 20. The nut 60 is preferably freely rotatable upon the lower portion of the rod 58 and secured thereto by means of a shoulder 64.

The lower end of the rod 58 is threaded into a tubular member 66 at the lower end of which are pivoted at 68 a pair of parallel links 10. The links 78 are in turn pivoted at their lower ends at 12 to one pair of ends of a generally horizontal pair of parallel levers 14 having their other ends pivoted in the base I0 at 16. Intermediate the ends of the levers I4 are pivoted at 11 one pair of ends of a pair of parallel links 18 extending upwardly at a small angle with the vertical and having their other ends pivoted at 88 to another pair of parallel links 82 inclined in the opposite direction to the vertical and pivoted at 84 to the base I0. The pairs of parallel links 18 and 82 form a toggle mechanism and pivoted on the pivot at the joint or knee 80 is a shoe 86 engaged by a cam 88 mounted upon a treadle 90 which is pivoted at 92 near the end of one of the feet I2. I prefer to provide abutments 94 on the treadle engageable with a portion Of the base III to limit its rocking movement. A coiled spring 19 may be tensioned between the pivots 84 and H to hold the various parts in proper relationship when the two parts of the primary pull rod 58 are separated by unscrewing the nut 60.

The links and levers are preferably arranged symmetrically in pairs to avoid side thrusts and twisting with a consequent improvement in rigidity and elimination of lost motion.

The cam 88 is preferably an arc of a circle having its center at C so that the dot and dash line 96 represents the normal to the point of contact of the shoe 86 and the cam 88. The center C of the cam arc must be so positioned with relation to the treadle pivot 92 that, if the line 98 is laid out with the angle A between it and the line 96 equal to the are ten of the coefficient of friction between the shoe 86 and the cam 88, the line 98 will fall beyond the pivot 92 of the treadle. This makes the cam 88 irreversible (i. e. force exerted on the shoe 86 will not move the cam). The cam 88 is actually a portion of an eccentric and consequently the cam and the shoe 86 form what is defined in the science of mechanism as a lower pair. More particularly they form an imperfect or pressure closed lower pair in that one does not completely surround the other and thus prevent independent relative movements. A lower pair is characterized by having surface contact and in having the relative motion between the parts limited to translation, rotation, or a combination of the two. Common examples of these pairs are the screw and nut, a wedge and members engaged thereby, a rectilinear slide and guide, journal and bearing etc. I consider it essential or at least highly desirable to use such a pair in the present invention because the surface contact with its result ing low unit pressure enables my novel device to operate for long periods of time with little wear and without other lubrication than a thin coat of good grease applied at the time of assembly. lfhis results in the exact and definite transmission of the movements necessary in a device of this character.

In operation, the kettle is placed upon the seat 2211 with the reinforcement E i centered therein and the two portions of the primary pull rod 53 are joined by rota the knurled nut Gil. Next the drum is tuned to the lowest desired pitch by rotating the handles M to draw down the pres-- sure ring Eli and :ficsh hoop Ziiand tension til head over the rim of the kettle 22. It will be noted that the abutments ltl on the brackets hold the pivots at a predetermined uppermost position so that once this preliminary tuning is accomplished, it remains undisturbed when the kettle is removed from the seat. The pull rods 56 and the primary pull rod must all be adjusted once to suitable lengths so that when the pivots 38 are against he abutments 'lii and the treadle iii: is in its uppermost position, there is a slight tension throughout the system sunlcient to take upall lost motion.

Thereafter, when the drummer desires to raise the pitch of the drum he depresses his toe on the treadle The cam iii! iorces the shoe ti toward the right and causes the toggle lit-fill to straighten so that the distance between the pivots 8d and ET increased. The straightening of the toggle swings the lever is? clockwise and draws the link i the tubular member the primary pull rod and the crown member downwardly. The downward motion of the crown member draws the pull rods iiil radially inwardly and swings the bell cranks 36 to move the pivots 38 away from the abutments Aid and draw the tuning pins the pressure ring til and the flesh hoop 28 downwardly to further tension the head 26 over the rim oi the kettle 22.

It is well understood that the increased tensicn oi": the head increases the pitch of the drum.

When the treadle has been moved far enough to give the desired elevation in pitch, the drummer may remove his foot and it will stay in the position at which leaves it, due to the irreversible character of the cam 88 previously described.

Now, assuming that the pitch has been. raised, and that the drummer desires to lower it, it only necessary for him to depress the heel portion of the treadle. All the motions previously described take place in reversed directions with a consequent decrease in the tension of the head and lowering in the pitch of the drum.

While only one illustrative embodimentof my invention has been described in detail, it is not my intention that the scope be limited to that embodiment, or otherwise than by the terms of the appended claims.

I claim:

1. In a tympano, a base, a kettle, a head, means for Varying the tension of the head including a primary pull rod, a shoe operatively connected to the primary pull rod, pedal means mounted on the base, an elongated cam member moved by said pedal means and having self locking wedging surface engaging the shoe and moved lengthwise across the shoe when the pedal means is operated to vary the pull on the primary pull rod, said self-locking wedging surface being so constructed that its wedging angle is less than the angle whose tangent is equal'to the coefficient of friction between the shoe and said wedging surface, said pedal means being constructed with a heel portion and a toe portion and being operable in opposite directions by pressure of either the heel or the toe.

2. In tympano, a base, a kettle, a head, means for varying the tension of the head including a primary pull rod, a lever pivoted to the base and to the primary pull rod, a toggle pivoted at one end to the lever and at the other end to the base, a shoe at the knee of the toggle, self-docking wedging means engaging the shoe and operative to straighten the toggle, and means operable at the will of the drummer to lift the selif-locking wedging means, said sell-locking wedging means being so constructed and arranged that its wedging angle is than the angle whose tangent is equal to the eoefilcient of friction between the self-locking wedging means and the shoe.

3. In a tympano, a base, a kettle, a head, means for varying the tension of the head including a primary pull rod, a lever pivoted to the base and to the primary pull rod, a toggle pivoted at one end to the lever and at the other end to the base, a shoe at the knee of the toggle, self-locking Wedging means engaging the shoe and operative to straighten the toggle, and pedal means mounted on the base and operable to shift the selflocking wedging means, said self-locking wedging means being so constructed and arranged that its wedging angle is less than the angle Whose tangent is equal to the coeffieient oi friction between the self-locking wedging means and the shoe.

l. In a tympano, a base having a plurality of supporting feet, a kettle, head, means for varythe tension of the head including a central tuning member, a lever pivoted to the base and to the central tuning member, a toggle pivoted at one end to the lever and at the other end to the base, a shoe at the knee of the toggle, pedal means pivoted at the outer end of one of the feet, and self-locking wedging means formed on the inner end oi the pedal means and engageable with the shoe.

5, In a tympano, a base having a plurality of supporting feet, a kettle, a head, means for varying the tension of the head including a central tuning member, an operator--cont-rolled treadle, and means for connecting the treadle to the tuning member comprising members forming a toggle which is operated by the treadle and which is straightened to increase the tension on the tuning member, and means having a seli-locking wedging action acting on said toggle to hold it in any position to which it is shifted by the treadle.

LE RQY J. JEFFRIES.

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