US2841950A - Metronome - Google Patents

Description

' Filed May 16, 1955 July 8, 1958 A. MLYNARSKI 2,841,950

METRONOME 2 Sheets-Sheet 1 IN TOR VEN AZEMNDEE my AES'K/ July 8, 1958 Filed May 16, 1955 A. MLYNARSK] METRONOME 2 Sheets-Sheet 2 INVENTOR.

AZFXANDEI? MLY/VAESK/ A rrop/veyf United States Metronomes, powered by spring motors or by electric motors, are known, but while the electrically driven metronomes are much preferred, they have always been subject to the disadvantage that they are complicated, because of the necessity of maintaining an accurate beat, yet of varying that beat through a wide range, and especially the necessity of maintaining dependably a low beat, and hence have been expensive, and not fully capable of satisfying the needs of their users. It is a primary object of the present invention to devise an electrically driven metronome with which the beat may be varied dependably throughout the total range necessary, which will be so simply constructed that it can be made and sold cheaply enough that each student may provide himself with one, and so have it available during practice as well as during lesson sessions.

in a metronome the presence of a visual pendulum is essential, as much so as the presence of the baton of the conductor of an orchestra. It is, for some purposes, desirable that therebe a synchronized audible beat, yet on other occasions it is preferable that the audible beat be deemphasized or omitted altogether. It is a further object of the present invention to provide, in an inexpensive metronome of the nature indicated, both a visual pendulum and an audible beat, with provision for varying the sound level of the audible beat between zero and any desired maximum level, and, moreover, to do the latter through supplemental mechanism which may be incorporated as a part of the metronome, or which, in more simple forms, may be already available as part of a nearby radio amplifying system or the like.

it is a still further object to provide a metronome of the character indicated, which shall be simple and compact, rugged and little likely to wear out, yet enabling simple replacement of such parts as may wear or break, and one which is readily dismountable to whatever extent may be necessary, and readily adjustable as to beat.

With such objects in mind, and others as will appear more fully hereinafter, this invention comprises the novel electrically driven metronome shown in the accompanying drawings in a preferred form, and in a slightly modified form, and as will be more fully described in this specification and defined in the claims at the end thereof.

Figure l is an isometric view, partly broken away, of the operating parts of the metronome in its preferred form, and with the housing shown in dot-dash lines.

Figure 2 is a view similar to Figure l, but viewing the operating mechanism in side elevation.

Figure 3 is a top plan view of the operating mechanism, illustrating diagrammatically the associated audible beat amplifying and sounding mechanism.

Figure 4 is an isometric view, partly broken away, illustrating a modified form of the slipping clutch mechanism which is an essential part of the present invention.

In principle, the metronome of this invention comprises a synchronous electric motor connected to drive a pendulum at a rate equal to or exceeding the highest or ice most rapid beat-say, 220 beats per minute-that is ever required. The pendulums natural period can be varied by adjustment of a weight mass along it, away from or towards the rocking axis, and a tempo as low as 20 beatsv per minute is attainable. Since the motor tends to drive the pendulum at or faster than the most rapid rate, all slower rates are attained by employing what amounts to slipping clutch means between the motor and the pendulum. By such provision the rate of oscillation of the pendulum is governed by the adjusted location of its weight mass, and it rocks at its natural period consonant with each such location, and because of the slipping clutch connection does not require any change in the motors rate, regardless of change in the actual beat. Its beat is reliabie indefinitely at all tempi, from the minimum of say 20 beats per minute to the maximum of say 220 beats per minute.

It is preferred to employ a synchronous electricmotor, generally indicated at 9, as the source of power for the metronome of this invention. Such a motor is inexpensive and will operate dependably over long periods, to rotate its shaft t at a constant rotative speed, and of course requires no rewinding from time to time. Such a motor is supported in a bracket 8, preferably with means for adjusting it in a direction transverse to the axis of its driven shaft 90. Such a provision is illustrated in Figures 1 and 2, consisting, in the form shown, of the slots in the bracket 8, and clamping screws 91 passing through the slots 36 and secured in ears that project from the housing of the motor 9. The bracket 8 may be supported upon a base provided with rubber feet 82.

Supported in a cross bar 83 of the bracket 8, and in the end of a spring arm 84 which is supported from the bracket 8, is a rock shaft it), upon which is fixed a pendulum arm 1. It is preferred that the mounting of the rock shaft be such that by springing the arm 84 the rock shaft and the pendulum arm, as a unit, may be removed if there should be need for its removal. The pendulum arm is provided, as is usual, with a principal mass 11 located below the rock shaft upon the lower end of the pendulum arm, and with a secondary weight mass 12 which is adjustably mounted to slide lengthwise of the upper end of the pendulum arm. Desirably the principal weight mass 11 is also adjustable lengthwise of the arm, as by means of making the weight mass of two parts clamped together by a clamping screw 13 passing through and joining the two halves of the weight mass 11, and passing also through a longitudinal slot 14 in the pendulum arm 1 (see Figures 1 and 2). The upper end of the pendulum arm is graduated with tempo indications, and the adjustable secondary weight mass 12 is provided with an index cooperating with the scale on the pendulum arm 1.

The rock shaft 10 is provided also with two collars 16 which are part of an escapement device. The escapement device, however, may be of any suitable nature, although that illustrated is a preferred form. The escapement device shown includes also a toothed wheel 2, which is fixed upon a jackshaft 20 supported in the bracket 8 in a position close to but disposed transversely of the rock shaft 10. The parts are so located that the teeth 21 on the toothed wheel 2 will engage the collars 16, and rotation of the wheel 2 will be restrained until the collars 16 reach a given rotative position, whereupon the toothed wheel 2 will be permitted to advance by the distance between two teeth, and the rotation of the wheel 2 will again be halted until the position of the pendulum arm and the collars 16 at the next beat is such as to permit a further advance of the toothed wheel by the distance of one tooth. The escapement device will also have cam surfaces which give an added impetus to the pendulum, at each release. Since all this is common in escapement devices no further detailed description is deemed necessary. It may be remarked that it has been found quite feasible to manufacture the rock shaft and the collars 16 integrally of molded nylon, as a result of which it is not necessary to oil the escapement device, and it will continue to function properly over long periods of time.

It is an essential part of the present invention that there is provided, intermediate the driving shaft 90 and the jack-shaft 20, or whatever other escapement device may be employed, a slipping clutch device. Such a slipping clutch device is to be distinguished from a frictional drive which may incidentally permit slippage if the load is unduly heavy, but which is not normally intended to slipwhile driving, or one which can be shifted to vary the rate of rotation of a driven element. The slipping clutch of the present invention, on the contrary, is intended to slip during most of the driving period. It functions to drive only at such time as the escapement device is operating to permit advance, and at all other times it holds the escapement device in readiness to function, but slips and does not actually effect any advance in the escapement device, notwithstanding that the driving shaft is continually advancing at a constant rate.

Any suitable slipping clutch device which will function as indicated may be employed, and two types of such devices have been shown herein. In the form shown in Figures l to 3, which is the preferred form because of its simplicity and cheapness, and the ease with which the part that will fail from time to time can be replaced, the driving shaft 90 is employed as a driving pulley, or may have such a pulley mounted upon it, and a driven pulley '22, preferably somewhat larger than the shaft 90 or its driving pulley, is mounted upon the jack-shaft 20. Between these two is stretched an elastic rubber belt 3. An ordinary elastic band will serve quite well for such a driving belt. It can be adequately stretched by adjusting the position of the motor 9 by means of the slot 80, or any other suitable belt-tensioning means may be employed. Obviously any like elastic belt may be used, but the one mentioned has the advantages of cheapness, simplicity, and ready availability. The belt 3 being stretched to the proper extent, and the driving shaft 0 and the driven pulley 22 being both of metal and smooth, the shaft 90 will tend to drive the elastic belt 3, but this, extending also round the'pulley 22 of larger diameter, will not advance, but will yield and stretch in one run and tend to form a loop in its other run. The added tensioning of the belt 3 in the one 11111 will serve, as soon as the escapement device 16 operates to release a tooth 21, to effect immediate advance of the toothed wheel 2, but by the time the wheel 2 has advanced by the distance between two teeth, the collars 16 have rocked into a position to stop the rotation of the wheel 2 again, and again the belt 3 builds up extra tension, which is not released until the next release of the escapement device, as the pendulum swings back again.

In lieu of the slipping clutch arrangement justdescribed that shown in Figure 4 may be employed. Here a glass disk 30 and a connected toothed disk or gear wheel 31 are loose upon the motor shaft 90a. Spring fingers 33, fast upon the shaft, press, with regulatable pressure, upon the glass disk 30. By this means or in any equivalent manner the shaft 0a may continue to rotate-at its constant speed, and the fingers 33 will rotate with it, tending to rotate the disks 3% and 31, but the latter will rotate only when permitted to do so by the escapement device. The toothed disk 31 is in mesh with a pinion 23 which is secured upon the jack-shaft 2G. The friction between driving and driven members, in any form of the slipping clutch device, is sufficient to effect advance without delay when the driven element is released, yet is insuificient to produce heat or wear to an undesirable degree.

As far as the visual operation of the metronome is concerned itwill be readily apparent that the rocking of the pendulum arm 1 at a tempo that is governed by the positions of the masses 11 and 12 in the length of the arm will effect regular functioning of the escapement device as the toothed wheel 2 of the latter is driven through the slipping clutch device from the synchronous motor 9. This rocking of the pendulum arm will continue without change of tempo so long as the weight masses remain in their given position and so long as the motor fi is energized. The motor circuit is controlled by an on-off switch 98.

It is sometimes desirable to produce an audible beat in addition to the visual beat of the pendulum am. To this end I provide an inexpensive phonograph needle cartridge 40, which I mount upon a bracket 88 in such manner that the needle 4 is pressed against the bracket 8 or some equivalent part of the mechanism. In this manner the needle 4 and the cartridge 40 are sensitive to the sound of the escapements release. The signal thus initiated may be transmitted through the wire circuit 41 to an amplifier 42, and thence to a radio or phonograph speaker 43, which may be built in as part of the metronome or which may be, and in many cases might more conveniently be, a radio speaker already available to the student. Indeed, the amplifier 42 may be also part of his radio. By regulating the amplifier 42 by any convenient -means (not shown) the loudness of the signals given by the speaker 43 may be regulated at will.

It will be observed that the metronome is extremely simple, and made of inexpensive and readily available components. If the rubber belt 3 should wear out or break accidentally, an ordinary rubber band, available at any stationery store, may be used to replace it, and any necessary adjustment in its tension can be effected at the adjusting screws 91. If for any reason it is necessary to remove the shaft 10 this can be done by merely springing outwardly the flexible arm 84. The beat of the pendulum arm may be initially adjusted by adjusting the principal mass 11 in the slot 14, and thereafter change in tempo is readily accomplished by sliding the secondary weight mass 12 lengthwise of the arm to the proper position. The swinging of the pendulum arm may be interrupted at any time without the possibility of damage to the mechanism, for while the pendulum arm is held stationary the slipping clutch device continues to function as before, permitting the shaft 90 to continue to rotate at its constant speed, but without affecting the jack shaft 20.

When the swinging of the pendulum arm is to be resumed it is only necessary to start its oscillation, whereupon the slipping clutch drive and the escapement mechanism resume functioning as before. By making the rock shaft 10 and the escapement collars 16 of nylon, as indicated above, there is no need to oil the device, and synchronous motors of a type which will operate indefinitely without oiling are readily available.

The whole of the operating mechanism, with the exception of the pendulum arm, may be housed within an attractive casing, indicated at 7 in dot-dash lines.

I claim as my invention:

1. A metronome for reliably and indefinitely maintaining a constant beat over the entire range of tempi, comprising a pendulum arm; a rock shaft to which said pendulum arm is secured for conjoint rocking back and forth; means to vary the periodicity of the pendulum arm; a jack-shaft disposed transversely of and adjacent said rock shaft; an escapement device including a toothed wheel upon the jack-shaft and cooperating collars on the rock shaft to enable advance of the jack-shaft by the distance between adjacent teeth of the wheel at each swing of the pendulum arm; a constant-speed electric motor; and drive means including a slipping clutch, interposed between said motor and said jack-shaft.

2. A metronome for reliably maintaining a constant beat indefinitely over the entire range of tempi, comprising, in combination with a constant speed electric motor; a rock shaft and a visible pendulum mounted thereon; driving means, including an escapement device, interconnecting said motor and said rock shaft to oscillate the latter and its pendulum, in the absence of slippage in said driving means, at a maximum rate in excess of a practical tempo; a slipping clutch means incorporated in said driving means intermediate the motor and said escapement device; and means to vary the inherent periodicity of the pendlum, to lower the rate of oscillation of the rock shaft to and to maintain it at any of a plurality of desired rates each less than such maximum rate; and in all such cases said slipping clutch means serving to compensate for the difference in rate between the motor and the rock shaft and pendulum.

3. A metronome as in claim 2, wherein the slipping clutch comprises a driving shaft and a parallel driven shaft; and an elastic belt stretched between said shafts.

6 4. A metronome as in claim 2, wherein the slipping clutch comprises a driving shaft having a driving eelment fast thereto and a driven disk nose thereupon; and means to urge said element and said disk into frictional engagement.

References Cited in the file of this patent UNITED STATES PATENTS

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