Abstract:
In construction of a single valve unit for a brass musical instrument having blow-in and blow-out tubes, and multiple resonant tubes, rotation and axial displacement of a piston in a cylinder switches communication between the blow-in and blow-out tubes and the resonant tubes. Compared with prior art double valve units, the present signal valve unit simplifies valve construction, avoids the need for phase adjustment, between two valves and reduces fatigue on the operator.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a valve unit for a brass musical instrument, and more particularly relates to an improvement in a construction for effecting selective switching of communication between a plurality of resonant tubes on a brass musical instrument such as a horn and, in particular, a triple horn. 
     A triple horn is provided with three resonant tubes different in length and selective switching of communication is effected between the three tubes in order to generate sounds of three different tonal pitches. One typical conventional construction effecting such switching of communication is of a type which is provided with a pair of valves driven for operation by a single lever in order to selectively communicate blow-in and blow-out tubes to one of the three tubes. 
     Such a double type valve unit, however, is accompanied with various drawbacks. Use of two sets of valves increases the weight of the entire valve unit while requiring a large number of parts. Phase adjustment in operation between the two valves requires troublesome maintenance. In addition, driving of the two valves via a single lever poses increased fatigue on the operator. Such drawbacks are further amplified when four or more resonant tubes are arranged on the brass musical instrument. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a lightweight valve unit which is simple in construction, requires no phase adjustment in operation and significantly reduces fatigue of the operator. 
     In accordance with the present invention, a piston is inserted into a cylinder in a rotatable and axially displaceable arrangement, a blow-in tube is connected to the mouthpiece, a blow-out tube is connected to a bell flare and N sets of resonant tubes, where N is an integer, different in length are all made to communicate with the interior of the cylinder accommodating the piston. (N-1) pairs of through holes are formed radially through the piston, each pair including two like through holes so that rotation of the piston communicates the blow-in and blow-out tubes with a selected one of (N-1) sets of resonant tubes. Axial displacement of the piston causes the blow-in and blow-out tubes to communicate with the remaining one of the resonant tubes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view, partly simplified, of one embodiment of the valve unit in accordance with the present invention, 
     FIG. 2 is a perspective view of one embodiment of the piston usable for the valve unit shown in FIG. 1, 
     FIG. 3 is a section taken along a line III--III in FIG. 1, 
     FIG. 4 is a section taken along a line IV--IV in FIG. 1, 
     FIG. 5 is a side view of one end of the valve unit shown in FIG. 1, 
     FIGS. 6A and 6B are side and end views of the transmission used for the valve unit shown in FIG. 1. 
     FIGS. 7 and 8 are transverse sectional views of the valve unit when the first lever is operated for rotation of the piston, and 
     FIGS. 9 and 10 are transverse sectional views of the valve unit when the second lever is operated for axial displacement of the piston. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     One embodiment of the valve unit in accordance with the present invention is shown in FIGS. 1 to 4, in which the valve unit 20 includes a tubular cylinder 21 and a piston 22 encased in an airtight manner in the cylinder 21 in an axially rotatable and reciprocal arrangement. 
     A blow-in tube 23 communicating with a mouthpiece (not shown) of the brass musical instrument, a blow-out tube 24 communicating with the bell flare of the brass musical instrument and the first, second and third resonant tubes 25, 26 and 27, respectively of different lengths are attached to the periphery of the cylinder 21. The blow-in and blow-out tubes 23 and 24 are spaced apart in the axial direction of the cylinder 21. At junctions with the periphery of the cylinder 21, the blow-in tube 23 and ends of the tubes 25 to 27 are offset from each other by 90°. More specifically, the blow-in tube 23 and the one end of the third tube 27 are offset from each other by 180° in axial alignment, the one ends of the first and second tubes 25 and 26 are offset from each other by 180° in axial alignment, the blow-out tube 24 and another end of the third tube 27 are offset from each other by 180° in axial alignment and the other ends of the first and second tubes 25 and 26 are offset from each other by 180° in axial alignment. 
     Two pairs 28 and 29 of through holes are formed in the piston 22 in arrangements normal to the axis of the piston 22 for selective communication with the blow-in and blow-out tubes 23 and 24 and the tube 25 to 27. The first pair 28 includes a pair of bent through holes 28a and 28b which are bent at right angles on the axis of the piston 22. The bent through holes 28a and 28b are spaced apart from each other in the axial direction of the piston over a distance equal to the space between the blow-in and blow-out tubes 23 and 24 on the cylinder 21. 
     The second pair 29 includes a pair of straight through holes 29a and 29b which extend across the axis of the piston 22. The straight through holes 29a and 29b of the second pair 29 are equally spaced from one bent hole 28a of the first pair 28. The distance between the pair of straight through holes 29a and 29b is equal to that between the pair of bent through holes 28a and 28b. 
     Shafts 32 and 33 extend axially outwards from both longitudinal ends of the piston 22. The shaft 32 is operationally coupled to the first lever 35 via a later described transmission so that it will be rotated over a prescribed angle when the first lever 35 is operated. The shaft 33 is circumferentially and concentrically provided with a circular stopper 36 so that when shaft 33 is axially moved by the second lever 37, as shown by the arrows in FIG. 5, stopper 36 will abut against the end of cylinder 21. 
     The transmission between the first lever 35 and the shaft 32 on the piston 22 is shown in FIGS. 6A and 6B. The transmission 40 includes a ring cap 41, a rotary base 42 and a C-shaped stopper 43. The cap 41 is coupled to the end of the cylinder 21 on the side of the shaft 32 while covering the shaft 32 and providing at its radial periphery a circumferential slot 44 extending in the direction of rotation of the rotary base 42. The rotary base 42 is provided with a connector pin 45 projecting radially outwards and a long projection 46 extending axially. This projection 46 is received within a long axial groove 47 formed in the periphery of the shaft 32 so that the shaft 32 is displaceable in the axial direction relative to rotary base 42, but they are locked together against relative rotation, i.e., shaft 32 and rotary base 42 rotate together. This rotary base 42 is inserted into an axial hole of the ring cap 41 and its connector pin 45 is received in the circumferential slot 44 in the ring cap 41. The stopper 43 is fixed by screws to the end of cylinder 21 on the side of the shaft 32 and its cutout faces the circumferential slot 44 in the ring cap 41. Rotation of the rotary base 42 is limited by abutment of its connector pin 45 against open ends 48 and 49 of the stopper 43 defining the above-described cutout. The first lever 35 in FIG. 1 is coupled in one body to a link 35a which is pivoted to the lower end of lever 50. The apex between the lever 35 and the link 35a is pivoted to a fixed pin 36. The top end of the lever 50 is pivoted to the connector pin 45 of the rotary base 42. 
     As the first lever 35 is moved as shown with an arrow in FIG. 6A from position A (shown in phantom) to position B, the lever 50 is rotated upwards and the rotary base 42 rotates clockwise as viewed from end 32 of piston 22, or counterclockwise as viewed from end 33 of the piston. This rotation of the rotary base 42 causes corresponding rotation of the shaft 32 and the piston 22 over 90°. 
     With such a construction of the valve unit 20 in FIG. 1, switching is carried out as follows. 
     In the normal state in which the first and second levers 35 and 37 are out of operation, the blow-in tube 23 communicates with one end of the first tube 25 via the bent through hole 28a in the piston 22 as shown in FIG. 3 and the blow-out tube 24 communicates with the other end of the first tube 25 via the bent through hole 28b in the piston 22 as shown in FIG. 4. 
     When the first lever 35 is operated, corresponding operation of the transmission 40 in FIG. 6A rotates the piston 22 counterclockwise over 90° as viewed from end 33 (FIG. 1) of piston 22. Then, the blow-in tube 23 communicates with one end of the second tube 26 via the bent through hole 28a and the blow-out tube 24 communicates with the other end of the second tube 26 via the bent through hole 28b. Thus, the communication is switched from the first to the second tube. This state is shown in FIGS. 7 and 8. 
     FIG. 5 shows an arrangement for moving piston 22 rightwards in FIG. 1. When the radial orientation of through holes 28a and 28b is as shown in FIGS. 3 and 4, movement of the second lever 37 in the direction shown by the arrows in FIG. 5 causes movement of the piston 22 rightwards in FIG. 1 until the stopper shown in FIGS. 1, 2, and 5 abuts against the corresponding end of the cylinder 21. Then, the bent through holes 28a and 28b are placed out of the position communicatable with the blow-in and blow-out tubes 23 and 24 and the communication is now taken over by the straight through holes 29a and 29b. More specifically, as shown in FIGS. 9 and 10, the blow-in tube 23 communicates with one end of the third tube 27 via the straight through hole 29a and the blow-out tube 24 communicates with the other end of the third tube 27 via the straight through hole 29b. 
     Since the valve unit of the present invention includes one set of piston and cylinder only, it has a very simple construction with a reduced number of parts. Greatly reduced power is required for operation of such a single type valve unit posing less fatigue on the operator. Further, use of the single type valve unit beneficially removes the need for inter-valve phase adjustment. 
     In the case of the illustrated embodiment, selective switching of communication is effected between three resonant tubes 25 to 27 different in length. But, with simple modifications obvious to one skilled in the art, the present invention is beneficially applicable to selective switching of communication between four or more resonant tubes. For example, when the valve unit is to be used for switching of communication between four resonant tubes, switching of communication between three resonant tubes may be effected by rotation of the piston and switching of communication to the other one may be effected by axial displacement of the piston 22. 
     Although the present invention has been described in connection with a plurality of preferred embodiments thereof, many other variations and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.