US2570102A

US2570102A - Piano resonating chamber

Info

Publication number: US2570102A
Application number: US1193A
Authority: US
Inventors: Sr Herbert O Crippen
Original assignee: PIANO CELLO TONE Co
Current assignee: PIANO CELLO TONE Co; PIANO CELLO-TONE Co
Priority date: 1948-01-08
Filing date: 1948-01-08
Publication date: 1951-10-02
Anticipated expiration: 1968-10-02

Description

3 Sheets-Sheet 1 Oct- 2, 1951 H. o. CRIPPEN, sR

PIANO RESONATING CHAMBER 'Filed Jan. 8, 1948 [n verz Zar; V/Yefbemvf 0. C72/tpe, fr. @www l H. O. CRIPPEN, SR

PIANO RESONATING CHAMBER Oct. 2, 1951 3 Sheets-Sheet 2 Filed Jan, 8. 1948 [rz ver2/Zar: Herber 0. 7x/mmm, S11

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PIANO RESONATING CHAMBER Filed Jan. 8, 1948 f77/U67@ vry: Herben? Q wp/D67@ Patented Oct. 2, 195i PIANO REsoNATING CHAMBER Herbert 0. Crippen, Sr., Chicago, Illg, alssigol to Piano Cello-Tone Company, a corporation of Illinois Application January 8, 1948, serial N96 1,19'a` 2 claims. (ol. 8f4-189) This invention relates to improvements in pianos and other instruments, and more particularly to an improvement whereby the tonal qualities of pianos and other instruments may be improved.

It is the main object of the invention to produce a piano construction which will cause the piano to give out a more mellow, fuller or other-f wise. improved tone than has heretofore been obtainable in pianos, while at the same time preserving the normal volume characteristics of such instruments.

This application is, in part, a continuation of my co-pending application, Serial. No. 752,489, filed June 4, 1947, which resulted in Patent No. 2,483,087 issued September 27, 1949.

Other objects and advantages yof the invention are to provide an improvement of the character indicated, which may be embodied in a piano or other instrument as a part of its original construction, or as an accessory added to a conventional piano; to provide an improvement of the character indicated, which may be incorporated either as an original part of the piano or as an accessory at low cost compared to the cost of a conventional piano, so that the total cost of the improved piano will not be objectionably higher than the cost of present day conventional pianos; to provide the improvement in various forms, which may be applied to various makes of conventional pianos without requiringcutting or removal of any of the conventional piano structure; and, in general, it is the object of the invention to provide an improved resonating structure for pianos and other instruments, to the end that the tones given out by the instrument have improved qualities while otherwise retaining the distinctive characteristics of the instrument.

Other objects and advantages of the invention will be understood by reference to the following specification. and accompanying drawings (3 sheets) in which there is illustrated several se-Y lected embodiments of the invention:

In the drawings,

Fig. 1` is a bottom plan of the rear portion of a grand piano, parts being broken away to more clearly illustrate certain details of one .embodiment of the invention;

Fig. 2 is a perspective showing the embodiment which is also shown in Fig. l;

Figs. 3, 4 and 5 are sections respectively on the lines 3 3, 4 4, and 5-5 of Fig. 1;

Fig. 6 is a section corresponding to Fig. 3 but illustrating a modied form of the invention;

Fig. 7 is a top plan of a grand piano in which the invention is incorporated in another form Fig. 8 is a section on the lin@ lie-8 of Fig. 7; and

Fig. 9 in part an end elevation, and in part a transverse section. 0f an upright type of maris to which one form of the invention has been applied.,

The present invention contemplates the application to a piano of conventional.construction, certain structures. which. in .cooperation with Cel"- tain. parts of the QQnYsntQrial piano Structure? form a resonatng Chamberwhsh will Serve U0 improve'the tous characteristics 0f the instrument.

The key section, hammer action, string plate, strings, and generall construction of the piano are well known and for the purpose of this applica# tion. reference 'to such parts'may be made without a preliminary detailed explanation thereof.

In the drawings, the outer frame or rim of a piano is shownat I, the inner yframe at 2, and the ribbed sound board at 3. The reinforcing ribs of the sound board areA partially indicated at 4,.

The strings oi a grand piano are in eiect divided into `two units, there being a treble section and a bass section, the strings of the treblesection resting intermediate their ends on a bridge, in?- dicatel at 5, and the `strings of the bass section similarly bearing on a bass bridge 6. These bridges are represented Ain dotted lines in Fig. 1 merely for ,the purpose of illustrating the preferred location of certainelements ofthe struc,- ture which isadded to the piano in accordance with the present invention.

At the back or rear of the piano, the usual leg 'l depends from a plate 8 on a horizontal bottom element' of the frame structure.

As shown in Figs; 3 and 5, vthe peripheral rear and side portions of the sound board rest on the inner frame members? to which the sound board is securely attached andas shown in Figs. 2 and 4, the forward pc'irtionofthe sound board extends forwardly over a transverse frame member l0, and restszon another transverseframe element I l.

The space surroundedby the transverse member I0 and the side and rear portions of the frame members l and 2 and the rear frame element 9, is employed according to my invention to provide a resonatingl chamber under the sound board of the piano. One embodiment of such a resonat-` ing chamber whichmay be added to a conventional piano as-an accessory or, if desired, built in as a part of the original construction, consists.

of a bottom IZ, front and rear walls I3 and I4, respectively. .and opposite side walls ,l5 and I6, rsF spectivelmthese walls extending upwardly from the margins of the ylocittolrl `Il t0 form a Chamber, The chamber ,is shaped to correspond to the spass within the

piano members

2, 9 and Il] and the depth or height of the front, rear and side elements I3, E4, I and I6 is preferably such that the entire depth of the chamber will be received Within the depth of the piano space below the sound board 3 so as to be not visible below the frame I of the piano.

The bottom I2 of the chamber is preferably concavely arched on its upper side so that the concave side of the bottom II faces the concave lower side of the sounding board 3, it being understood that piano sounding boards are always more or less arched upwardly as a matter of standard practice.

In my patent, No. 1,530,984, I have shown an arrangement in which a resonating chamber is added to a piano by fastening the chamber to a central portion of the sound board, the reinforcing ribs being cut away to avoid interference with the added chamber. According to th'e present invention, the sound board with its reinforcing ribs need not be altered and the resonating chamber structure is attached to the bottom of peripheral portions of the sound board where normal vibration of the sound board will not be significantly affected.

rl'he bottom and the walls of the resonating chamber are made quite thin, for example, in the neighborhood of one-quarter of an inch or less. This thickness may vary but it is preferably so small that it does not provide sunicient surface for gluing the chamber to the sound board. To provide a sumcient top edge width for gluing purposes, a molding strip I'I is glued or otherwise secured to the outside of the upper margins of the front, rear and side walls of the chamber. This strip may be of any desired width to provide, in cooperation with the upper edges of said Walls, the desired area for bonding purposes.

The front, rear and side wall portions of the chamber are preferably set in place and glued to the sound board before the bottom I2 is attached to the said walls. This permits inspection and better application. The walls have their upper edges notched to straddle the ribs Ii as indicated at I8, the fit of the walls around said ribs being preferably a tight fit so as to avoid leaks between the walls and the sound board. All of the interengaging areas of the chamber walls and the sound board are to be tightly butted together and glued so that there can be no rattle between these parts. Instead of actually notching the walls of the chamber to t around the ribs, the upper edges of said walls may be made straight and the spaces between said ribs may be filled with suitable filler strips so as to present a continuous flat surface against which a continuous fiat edge may be butted and fastened.

The bottom I2 is next glued to the bottom edges of the walls and to facilitate secure attachment, a molding or strip I9 is employed. If desired, nails or screws may be employed to hold the glued parts together while the glue sets. However, other temporary supporting means may be employed.

The bottom I2 of the chamber structure is preferably carved from a fairly thick board to provide the desired concave shape without bending the material. This bottom member, as well as the side members of the chamber, may be made of spruce pine wood (which is commonly used for piano sounding boards) or of other wood, such as, for example, hard maple which has satisfactory grain characteristics to facilitate the 1 required planing and shaping, and to provide the 4 desired resonating characteristics when the chamber is applied to the piano.

The sound board 3 is provided with one or more sound openings, such as represented at 20, these openings being located between ribs 4 so as to avoid cutting of said ribs. One or more tone posts 2l, of spruce pine or other Suitable wood, and of such length as to fit snugly between the chamber bottom I2 and the sound board 3, are inserted into place after the chamber structure is applied and mounted. These tone posts are inserted through the openings 20 which are so located that the posts may be positioned in the desired relation to the treble and

bass bridges

5 and 6. tone posts are located in approximate vertical alignment with the end portions of the treble bridge 5, and two others somewhat forwardly of the bridge. One of the latter two posts is preferably vertically aligned with an overlying portion of the middle C string of the piano. Suitable tools for positioning the tone posts through the sound openings are well known in the musical instrument art and similar tools may be employed positioning the tone posts in the desired piano structure.

The location and number of tone posts and sound holes may be varied and may be different on different makes and models of pianos, depending on the characteristics of the particular instrument. Also, the shape of these posts and holes, especially the holes, may be varied to secure the desired appearance effect as well as tone effect.

Another tone post 2Ia is placed between the sound board and chamber bottom slightly in advance of the bass bridge 6 and about midway of its length. A sound hole 20a is also provided in the sound board in front of the bass bridge. This sound hole 20a may be of the same form as the other holes 20 but it is preferably somewhat larger to more effectively handle the bass tones of the instrument. Additional posts and holes may, of course, be associated with the bass section of the instrument if desired and the location of the hole 20a and post 2Ia may also be varied from that shown.

The

sound openings

20 and 20a may be provided in the bottom I2 of the chamber instead of in the sound board, but where the resonating chamber is built into the piano as original equipment during construction of the piano, I prefer to have the openings in the sound board. Where the resonating chamber is to be applied as an accessory, it is more convenient to form the openings in the resonator bottom because the presence of the strings makes it a rather difficult matter to Cut these openings in the sound board.

The tone posts may have their ends coated with glue or other adhesive, or they may be provided with suitable impaling pins of slight depth to anchor the ends of the pins in the position in which they are set. I prefer not to cut into the sounding board of the piano or into the bottom panel of the chamber structure wherefor the use of glue is preferred over the use of impaling pins. However, it is not necessary to employ glue, it being entirely practicable to depend upon the tight fit of the posts between the sound board and bottom wall to hold the posts in place.

A modification of the invention is shown in Fig. 6 wherein a panel 22 of suitable material is cut to fit within the space surrounded by the

piano frame members

2, 9, and I0, and is secured by means of moldings or strips such as repre-A As represented in Fig. 1, two of theV sented at 23 to the insideof the said surroundingr frame portions. The panel 22 may be a plain, nat panel or it may be of arched construction corresponding to the bottom I2 of the above described chamber construction. Sound openings may be provided in either the panel 22 or inthe overlying piano sound board, one such hole being represented atV 24 in the panel 22, and tone posts 25 are, of course, to be inserted between the panel 22 and the sound board in the manner above explained in connection with the chamber structure.

1 The mounting strips may be first glued or otherwise secured to the piano. frame elements and the panel then'secured by gluing or other fastenings to either the top or the bottom of the strips. The mounting strip may also be initially secured to the top or bottom of the margin of the panel and the entire assembly then secured to the piano. This latter arrangement would, of course, require more accurate fitting of the panel into the piano. This simplified arrangement is advantageous especially in respect of cost considerations. It corresponds substantially to the construction shown in my said U. S. Patent No. 2,483,087.

Still another modification contemplates the positioning of a panel 26 (Figs. 7 and 8) within the confines of the portions of the side frame structure I and a front transverse member 21 which extend upwardly above the sound board 3. The panel 26 would thus be located above the strings of the piano so as to substantially cover and conceal `the same. Tone posts 28 should be inserted through sound holes of suitable form, such as represented at 29, which are provided in the panel 26. While it is preferred that the tone posts 28 be located in the areas of maximum vibration of the strings and sound board, it may be impracticable to so locate them in this form of the invention. However, the tone posts (and sound holes) may easily be located just outside of the string-occupied area and at any location where the strings do not prevent the positioning of the tone posts between the resonator panel and the sound board. In some instances the tone posts may pass through weight reducing holes such as indicated at 30 which are found in the metal frame parts of most pianos, one of which parts is h-ere represented lat 3l.

The panel 26 may be mounted by means of a series of mounting blocks 32 spaced around the periphery of the panel excepting the front edge thereof which is spaced rearwardly from the frame member 2'I and provided with a reinforcing rib 33. The resonating chamber formed by the panel 26, the sound board 3 and the frame portion I, has its front end open and the spacing of the front end of the panel 26 from the frame member 2'I maintains free access to the tuning pins 34 which, together with the strings, are more or less diagrammatically represented in Fig. 7. In Figs. 7 and 8, the panel 26 is shown as a flat panel but it may be arched upwardly more or less in parallelism with the normal arch of the sound board. If the panel is arched, it should have its margins set somewhat lower down in the piano so that the higher central portion of the crowned or arched panel will not project a'bove the level of the upper edges of the frame so as to not interfere with the closingr of the lid of the piano.

In the arrangement shown in Figs. 1 to 5, inclusive, the resonating chamber is suspended in its entirety from the sound board, and from a peripheral portion of the sound board where the sound board is kmounted on the frame structure ofi the piano. The chamber does not,` at any point, touch the inside of the piano frame, the sides of the chamber being spaced from the piano frame a. distance sufiicient to accommodatek the mounting strip or molding II. Hence, there is no dampening of the vibrations set up in any part of the resonating chamber, and the entire chamber may freely vibrate in accordance with the vibrations transmitted to it through the tone posts, the chamber walls, and through the air.

While the resonating chamber constructions above described embody woodconstructions, it is possible to `make them of plywood, metal, or of one or more of the thermoplastic or thermosetting plastics such as Bakelite, Formica, etc. The metals and plastics may. of course, be cast to the required shape either to produce a chamber structure as shown in Figs. 1 to 5, inclusive, or to provide the bottom or top closing panels as shown in Figs. 6 to 8, inclusive. The desired arches, curves, and sound openings may easily and inexpensively be embodied in such cast structures with corresponding reductions in production costs.

In the foregoing description, the invention ls illustrated as applied to a grand or horizontal piano. The improvement may also be applied to vertical or upright pianos as represented in Fig. 9. In the upright piano the sounding board appears at 34 and a resonating chamber, embodying a back panel 35 and side walls 36, is secured to the sound board adjacent the periphery of the latter as explained above in connection with Figs. 1 to 5, inclusive. In this instance, the resonator chamber panel 35 is shown provided with a sound opening 36, it being understood, of course, that the opening may be in a location other than that shown and that additional openings may be provided if desired. Also, the sound opening or openings may be in the sound board instead of in the back panel. Again. one or more tone posts 31 are positioned between the sound board and resonating chamber main panel 35.

Various changes in the details of the described structure may be made without departing from the spirit of the invention.

I claim:

1. A piano of the grand type, having a horizontally disposed sound board and tensioned strings associated with said sound board on the upper face thereof, a frame extending around the periphery of said sound board and laterally upwardly from said upper face thereof, and a panel in overlying, upwardly spaced relation to said sound board and strings and peripherally secured to and supported by said frame, said panel cooperating with said sound board and frame to form a chamber, and said panel having a smooth, uni-planar inside face area and there being provided an opening to the interior of said chamber whereby the latter is adapted to function as a resonating chamber to improve the tone quality and volume of the piano.

2. A piano of the grand type comprising a horizontally disposed frame having front, side, and rear portions, a horizontally disposed sound board secured to said frame, tensioned strings overlying said sound board, tuning pins within said frame adjacent the front portion thereof for adjusting the tension of said strings, said frame extending upwardly beyond said strings, and a panel in overlying, upwardly spaced relation to said sound board and strings and having --perpheal side and rear portions secured to upper edge portions of said upwardly extending side and rear frame portions, said panel cooperating with said sound board and said side and rear frame portions to form a chamber, and said panel having a smooth, uniplanar inside face area and the front edge portion of said panel being spaced rearwardly from said front frame portion so as to leave said tuning pins exposed for access and so as to provide an opening to said chamber, whereby the latter is adapted to function as a vresonating chamber to improve the tone quality and volume of the piano.

HERBERT O. CRLPPEN, SR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Number Name Date Caddick Feb. 12, 1884 OShaughnessy Dec. 17, 1918 Weiser Oct. 30, 1928 Muckey Dec. 11, 1928 Vasey Apr. 15, 1930 Crippen, Sr. Sept. 27, 1949 FOREIGN PATENTS Country Date Great Britain Dec. 2'2, 1897 Great Britain July 9, 1898 Germany May 8, 1882