US2071992A - Pianoforte - Google Patents

Description

Feb. 23; 1937. w 8 WHITE ET AL 2,071,992

P IANOFORTE Filed June 15, 1935 3 Sheets-Sheet 1 INVENTORS VV/L L /4M 594/0 W/Y/IE'. B REDEE/CA f L1. Ek/ELLY/V ll & F I I A ATTORNEYS 23, 1937- w. B. WHITE ET AL 2,071,992

P IANOFORTE Filed June 15, 1935 3 Sheets-Sheet, 3

M4 4 /AM den/0 M41172.

1 I I 1 I n u l I I 1 I 1 ATTORNEYS Patented Feb. 23, 1937 PIANOFORTE William Braid White. Chicago, Ill., and Frederick T. Llewellyn, Newark, N. J., asignors to United States Steel Corporation, New York, N. Y., a corporation of New Jersey Application June 15, 1935. Serial No. 26.854

19 Claims.

Our present invention relates to improvements in pianofortes and aims toprovide a structure in which the essential elements are formed of metal adapted to be integrated .in a single unit. While 5 not limited thereto, we have chosen to illustrate the invention as embodied in a so-called grand or semi-grand pianoforte. But, it is to be understood that the invention is also applicable to upright pianos, and indeed pianos of various shapes.

10 Our invention contemplates the provision of a wrought metal frame with a metal amplifying plate, a hitch pin plate, a tuning pin plate all united to form an integrated unitary structure adapted to be positioned within the wood or other 15 casing of a standard type of pianoforte.

A further feature of the invention relates to the securing of a thin sheet metal amplifier plate to a metallic frame by fused metal joints so as to inseparably secure the parts. thus avoiding the 20 known disadvantages inherent in wood sounding boards heretofore in use or in the metal sounding boards which heretofore have been otherwise secured to their supporting frames. A further feature of the invention relates to the incorpora- 25 tion in a pianoforte of an amplifying plate formed of a thin sheet of a wrought metal alloyhaving reat resistance to corrosion, a suitable material being ferrous metal alloy commonly known as stainless steel, which is low in carbon and con- 30. tains chromium and nickel. A further feature relates to the provision of a metallic bridge welded to the metallic sounding board, the bridge having a non-chattering connection with the sounding board. Further features relate to the com- 5 bination.and coordination of the several interdependent elements herein shown, described and claimed.

The various features of the invention will be fully apparent from the following detailed dis- 40 closure when read in connection with the accompanying drawings.

In the drawings- Fig. l is a plan view illustrating one embodiment of our improved pianoforte, the piano ac- 45 tion being omitted and only a few of the strings being shown in the interest of clearness; Fig. 2 is a transverse sectional view on line 2-2 of Fig. 1; Fig. 3 is a similar transverse section on line 3-3 of Fig. 1: Fig. 4 is a longitudinal section on line 4-4 of Fig. 1, a portion only of the piano action being illustrated, such action forming no part of the present invention; Fig. 5 is a horizontal section on line H of Fig. 4 illustrating the underframe bracing; Fig. 8 is an enlarged de- 55 tall view on line 0-4 of Fig. 1 illustrating details of the improved bridge; Fig. 7 is a fragmentary plan view of the bridge showing the manner in which the bridge deflects the strings from a straight line; Fig. 8 is a fragmentary section through the bridge taken on line 8-8 of Fig. 7: 5 Fig. 9 is a fragmentary side elevation of the bridge.

The essential features of any pianoforte may be divided into six principal groups, namely.

1. A set of tensioned wire strings mounted in 10 groups or so-called unisons" which exert a pressure on bridges carried on the vibrating unit or amplifier member.

2. A mechanical action including hammers and other known elements for striking the strings in response to the fingering of the usual keys.

3. A string supporting structure serving to withstand the principal stresses induced by the tension of the multiplicity of strings.

4. An amplifying system comprising a sounding board, a bridge or bridges adapted to transmit the vibrations of the strings of the soundboard and a series of reinforcing ribs usually placed on the face of the soundboard opposite that adjacent the strings.

5. A framework whose chief elements are an underframe below the soundboard, an inner rim of the soundboard and underframe, a cross beam at the front edge of the soundboard and underframe and the keybed supporting the conventional action.

6. An exterior casing whose function is chiefly to provide protection and a pleasing appearance.

The present invention contemplates radical improvements in the string supporting structure of group 3 above listed and in the amplifying system of group 4 above. It also contemplates improvements in the frame structure as in group 5 above. And an outstanding feature of distinction of the present invention resides in forming the amplifying unit, the frame, the bracing members. the hitch pin and tuning pin plates and other elements all of metal and uniting the parts by fused metal joints such as spot welding or fusion welding as will 'more fully hereinafter appear.

Heretofore, it has been the usual practice to construct pianofortes chiefly of wood largely because of the availability of the same and the ease in its workability.

This general trend has been largely responsible for the belief that wood as a material possesses the inherent properties which tend to produce purity of tone. There are certain inherent shortcomings in wood, notably when used as a sound ing board, which our invention aims to overcome.

There have been attempts to construct certain parts of pianofortes such as the string supporting structure of metal because of the inability of wood to withstand the high tension of modern steel wire strings without resorting to the use of timbers of such size that they would not be portable. But even in the most modern constructions heretofore used, of which we are aware, the string supporting structure and the amplifying system have been formed of separate elements connected by movable fastening means, such as lag-screws and the like. Such prior construction cannot act as an integral acoustic unit, as can the improved structure of our invention. In our improved structure, the fact that all of the elements are integrally united will result in a more rigidly secured amplifying plate than that which would be possible in prior constructions heretofore available and it is our belief that such an integral unit will produce tones possessing greater purity and more desirable musical properties than would be the case where the elements are separable.

Heretofore, it has generally been the practice to crown the sounding board in the form of an arch or dome. As a consequence of such crowning, the prevailing stresses caused by the down ward pressure of the strings on the bridges were compression stresses. Such stresses extend to the edges of the soundboard where the amplification is at a minimum. It is known that such compressive stresses always engender other collateral stresses which tend to buckle the elements. In the soundboards heretofore used, in order to resist such stresses the same have to be of considerable thickness, which in the case of wood construction approximated of an inch. This produces a comparatively stiff and inflexible vibrator. Also the presence of collateral stresses sets up a complex condition of equilibrium in the soundboard whose adverse effect on its resonance is particularly noticeable near its edges and at the treble end where it tends to still further reduce the amplification.

The conventional wooden sounding boards of the prior art are further objectionable due to their known tendency to crack or to be otherwise adversely affected as a result of atmospheric changes. 7

Our invention is predicated in part upon the realization that the acoustic response of our amplifier, especially near its edges, can be greatly improved and made more uniform by providing means for supporting and maintaining it under tension somewhat like the tympanum of a drum.

Instead of the usual soundboard, we employ a relatively thin sheet of low carbon stainless steel, which is a ferrous alloy of relatively low carbon and containing approximate y 18% chromium and 8% nickel. This amplifying plate is preferably secured by fused metal joints to a marginal frame, the plate or sheet being substantially perfectly flat when applied. Such plate when pressed down by the strings acting through the bridges will deflect or dish the amplifier approximately of an inch, thus putting it under tension. The pull on the plate is resisted by the welded connections to the marginal frame member hereinafter described in detail. Such a tensioned amplifying plate is more advantageous than the sound boards used under compression as the tensile stresses are direct in their nature and do not engender other collateral stresses.

Hence, in our improved sounding board the conditions of equilibrium are simple and cause no adverse effect on the acoustic response to the amplifying system.

One feature of our invention rests on the belief that the vibratory response of the pianoforte amplifying element depends largely on the uniformity of material used and the homogeneity of its connections and that a thin amplifying clement, because of its greater flexibility is more effective than a thick one. We, therefore, preferably select for the amplifying system materials which are manufactured under conditions that insure a high degree of uniformity and which can be homogeneously united and whose physical properties give them so high a degree of strength that they can be embodied in elements of minimum thickness and weight.

For the amplifier plate, we prefer to use stainless steel of the composition above mentioned. When this material is used, uniformity is assured due to the fact that such steel is usually made in an electric furnace under accurately controllable conditions. And the homogeneity of connections which assures integrating the coacting elements into a unitary structure is preferably secured by resistance shot welds, spot welds or scam welding processes, in which no extraneous metal is introduced. The high physical property of stainless steel of the alloy referred to has been demonstrated. Its tensile strength in the annealed condition contemplated under our invention ranges from eighty thousand to ninety-five thousand pounds per square inch, or approximately 50% greater than the strength of ordinary grades.

The bridges used in our pianoforte are also preferably formed of such stainless steel. This Referring to the drawings, l0 represents our marginal frame member as a whole. This includes substantially parallel side portions l2 and M, which are integral with the reversely bent rear portion l6. These portions of the frame conform substantially in outline to the plan of the casing of the usual type of grand or semi-grand piano. Extending transversely, there is a member IS, the ends of which are welded to the side portions l2 and Id of the marginal frame. The marginal frame, as illustrated in the drawings is provided with an upper substantially horizontal flange 20 and a lower flange 22, these flanges being connected by an upright web portion. Although a channel-shape is illustrated, it will be understood that other flanged shapes may be employed.

For properly stiffening the marginal frame so as to adequately resist the stresses set up by the multiplicity of strings of the piano, we provide underframe bracing members such as indicated at 24, these being arranged in truss-like forma-- tion and extending from the transverse member 3 to the rear portion l6 of the marginal frame, these members being united by means of gusset :-cated at-28 which registers approximately with plates preferably welded to the transverse member and to the marginal frame as shown.

The amplifying plate of our improved unit is indicated at 26. It comprises a thin sheet of approximately 22 gauge of the alloy known generally as stainless steel, which is a ferrous alloy of the composition hereinabove referred to. This plate conforms, generally in outline to the contour of the marginal frame, the forward edge however terminating in a straight line, as indithe forward edge of the transversely extending indicated at 30. and is similarly secured by spot member ii. The amplifying plate is secured at a multiplicity of spaced intervals to the upper flange of the marginal frame by spot welds,

welds 32 to the transverse member l8.

A metallic hitch pin plate 34 is also secured to the amplifying plate and the upper substantially horizontal flange 20 of the frame by said spot ,welds 30. At the front of the pianoforte, there is a transversely extending tuning pin plate 36 whose rear edge is welded to a transversely extending bar 38. The plate 36 carries suitable tuning pins 40 and the plate 24 carries hitch pins 42. The strings 44 extend from the tuning pins around the hitch pins and exert a downward pressure on the amplifier plate through the bridge, indicated as a whole at 48. This bridge, as best illustrated in Figs. 6 to 9 inclusive, is of special form and is secured to the amplifier plate in a manner to prevent chattering. As will be apparent from Fig. 6, the bridge is substantially X- shape in cross section. It is formed of two substantially angular portions 42 and Ill which are initially separately formed parts, but welded at their apenes, as indicated at 52. The lower legs of the bridge members are provided with foot flanges M which are secured by spot welds 56 to the amplifier plate 2.

As illustrated, we preferably provide either a seam of welded metal or a soldered seam which extends continuously along the edges II and 60, so as to form a continuous metal seal throughout the length of the bridge and thus prevent chattering,-which might be apt to occur, if one of the members were permitted to vibrate relatively to the other.

The upper edges of the portions II and 50 of the bridge have oppositely inclined notches 62 and 84 formed therein, as indicated in Figs. 8 and 9. These notches provide portions which overhang the strings and serve to prevent upward motion thereof especially during the tuning process. The notch 62 and N are offset relativelyto one another so that when a given string is positioned therein it will be deflected somewhat from the straight line between its hitch pin and tuning pin. I

, lathe unitary pianoforte structure herein illustrated'and described, it is manifest that the elements are united or integrated with the marginal .frameby welded joints. Thus a homogeneous bond is efiected by the fusion and union of the metals of the various parts. This is particularly important in a musical instrument employing metal parts, as it prevents the setting up of independent vibration between the parts which in other types of joints might cause chattering or other objectionable sounds.

In the string supporting structure disclosed, the arrangement is suchas to withstand and resolve the principal stresses caused by the direct tension of the strings, although it also serves to resist rigidly the indirect tension in the amplifier plate in somewhat the same manner as the barrel of a drum resists the tension of its tympanum. While the various elements and their individual functions have in some cases been separately described, it is to be noted that our amplifying system and our string supporting instrunentalities are all so coordinated as to form a single acoustic unit, the bond between the various elements being effected by the welded connections disclosed. In the described string supporting structure, the method and means of resolving the principal forces caused by the pull of the strings is entirely novel. Our arrangement differs from the conventional cast iron plate construction heretofore used among other things in the elimination of any intermediate bars or struts in the plane of the strings extending from the tuning plate to the hitch plate. The elimination in our construction of these bars leaves a large unimpeded area for the placement of the strings and an unimpeded soundboard area for substantially the full width of the pianoforte, thereby permitting a more uniform or orderly arrangement of the strings and the parts of the piano action. This uniformity effects important manufacturing economies, as it greatly simplifies the arrangement of the parts in the action and it contributes materially to greater uniformity in tone gradation between adjacent unisons. The unimpeded area of the amplifier plate also enhanccs and makes its amplification more uniform.

In a former construction, in which it was attempted to eliminate the intermediate bars in the string supporting plate by the substitution of lateral rim members, these members were necessarily inordinately thick and heavy. Their excess thickness was undesirable because it necessitated either a decrease in the width of the action, and thus a more limited scale of strings, or else an increase in the total width of the pianoforte thereby making it more cumbersome and less attractive in appearance.

Our string supporting structure as a whole differs from any prior construction of which we are aware in that we utilize, we believe for the first time in the history of the art elements with parts arranged so as to form a truss to withstand and transmit the forces in question to the reaction points at the two ends of a tuning pin plate. Heretofore, the underframe of the pianoforte has consisted of several heavy radiating wooden members technically known as "posts", whose chief function was to stiffen the inner rim and the exterior case of the pianoforte. Such posts did not and could not resolve the pull of the strings to any measurable extent because of their radial arrangement and because the conventional forms of cast metal hitch plate to which the strings were attached was connected to such posts only indirectly through intermediate lag screws bearing on the inner wooden rim which in turn engaged the posts.

In contradistinction, in our construction, however, because of the fact that our metallic elements are all united and integrated by the fused metal joints described, ti entire stress is transmitted from our wrought metal hitch pin plate 34 to the wrought metal marginal frame member (comprising portions l0, l2, I i, and I6) which form the cord of a truss, which includes the members 24 and the transverse member ID. The poi"- tions i0 and ll of the marginal frame member located in front of the transverse member II in effect constitute extension members which carry the stresses forward to the ends of the wrought metal tuning pin plate 36, thereby resolving them. The proportion of these extension members is novel and important. Manifestly, they must be very strong since the total pull of the strings in a pianoforte ranges from approximately fifteen to twenty tons depending on the type of construction in question. And each of the extension members must withstand approximately one-half of this stress. It is desirable that their depth should approximate that of the parts which they unite. Since in our improved structure the parts to be united are respectively the portion of the marginal frame, which is beneath the amplifier plate, and the tuning pin plate which is above the plane of the amplifier plate, we can and preferably do make our extension members unusually deep extending at least to the plane coinciding with the center of gravity of the member 24. And this great depth compensates for the comparatively narrow width to which we desire to and do restrict them. Thus, we provide extension members of adequate strength without encroaching on the internal width needed for a full range of action and without increasing the external width of the pianoforte.

In the construction of our string supporting unit, it is preferable to use a metal capable of being welded. It is also preferable to use metal which can be formed into the desired shape by pressing operations. Wrought or rolled metal is, therefore, preferred, as distinguished from cast metal which is not capable of being wrought or pressed to the desired shape.

While we prefer to use stainless steel for the amplifier plate and the bridges, for the string supporting structure, it is not necessary to use a metal quite as homogeneous and expensive. For this string supporting structure such as the hitch pin and tuning pin plates, marginal frame and stiffening elements, strength and rigidity rather than vibratory characteristics are the chief requirements. Hence, any strong and rigid metal capable of being wrought by pressing and integrated with other parts by welding may be used. In our preliminary investigations and experiments, we have used an alloy steel containing substantially .01% to .60% carbon, .3% to less than 2% chromium, .15% to 3% copper, 25% to 3% silicon, .07% to .75% phosphorus, .02% to .50% manganese and not over .10% sulphur, the balance being substantially all iron. Steel of this analysis is a comparatively inexpensive alloy steel having a high tensile strength and being characterized by a high resistance to corrosion. This enables us to keep down the overall weight of the structure. However, a weaker, but cheaper metal could be used provided it was made proportionately heavier to withstand the stresses imposed.

In the integral structure described, the arrangement of the parts is such that a fairly simple analysis of the stresses in the string supporting structure can be made. We believe we are the first in this art to provide-an arrangement in which the size of the members for any type of pianoforte can be rationally and readily determined by computation. Heretor'ore, with the old complicated non-unitary structures, employing hetrogeneous materials, the stresses were largely indeterminate and the proper size of members for each different type of construction frequently had to be ascertained by the tedious and expensive process of trial, error and experimentation.

Various modifications may be made by those skilled in the art without departing from the invention as defined in the appended claims.

What we claim is:

1. A pianoforte including a string supporting structure of ferrous metal and a ferrous metallic amplifier plate integrally united thereto.

2. A pianoforte including a ferrous metallic string supporting structure and a ferrous metallic amplifier plate integrated therewith by welded Joints.

3. A pianoforte including a metallic string supporting structure and a metallic amplifier plate of a ferrous alloy containing chromium and nickel integrally united thereto.

4. A pianoforte including a metallic string supporting structure and a metallic amplifier comprising a sheet of stainless steel welded thereto.

5. A pianoforte including a string supporting structure of wrought metal, an amplifier plate of non-corrodible ferrous metal welded thereto, a bridge of non-corrodible ferrous metal welded to the amplifier plate, and strings secured to mem bers carried by said structure and acting through said bridge to subject the amplifying plate to tension.

6. A pianoforte comprising a ferrous metal marginal frame including side portions joined by a bent rear portion and a transverse member secured at its ends to said side portions, a ferrous metal amplifier plate, a ferrous metal hitch pin plate, a metal tuning pin plate, all of said parts being secured in a manner to form an integrated unitary structure.

7. A pianoforte comprising a metal frame including side portions Joined by a bent rear portion and a transverse member secured at its ends to said side portions, a metal amplifier plate welded to the latter and side and rear portions of the frame, a metal hitch pin plate welded to said frame and amplifier plate, and a tuning pin plate welded to the frame.

8. A pianoforte comprising a wrought sheet metal marginal frame, a wrought metal amplifier plate,-metal hitch pin and tuning pin plates, all of said parts being integrated into a unitary structure by fused metal joints, a bridge on said amplifier plate, and strings tensioned thereover and secured to members carried respectively by said hitch pin plate and said tuning pin plate.

9. A pianoforte comprising a wrought metal flanged frame and a metal amplifier plate integrated therewith by a homogeneous union of the metals of said parts.

10. A pianoforte comprising a flanged metal frame comprising side members joined at the rear by an integral bent portion, a transverse member secured at its ends to said side members, a metal amplifier plate secured to the flange of said frame and said transverse member by a union of the metal of said parts, strings, string securing means and a bridge between the strings and the amplifying plate whereby the latter is subjected to tension.

11. A pianoforte comprising a wrought metal marginal frame, an amplifier plate of a ferrous alloy known as stainless steel which is a low carbon steel containing approximately 18% chromium and 8% nickel, said amplifier plate being spot welded to said frame.

12. A pianoforte comprising :2 wm t meta;

frame having an amplifier plate of non-corrodi- 7 ble metal alloy integrated therewith by a welded union of the metals of said parts.

14. A pianoforte comprising a wrought metal frame having an amplifier plate of non-corrodible metal alloy integrated therewith by a welded union of the metals of said parts, strings. string securing means upported from said frame 15. A pianoi'orte mm-ting a wrought metal frame having an amplifier plate of nsn-oorrodible ferrous metal alloy integrated therewith by a welded union of the mm of said parts. strings, string securing means from said frame and a metal bridge of like non-corrodible alloy coacting with said strings and being welded to said plifier plate.

16. A pianoforte including a metallic frame, asheetmetalamplinerplatelecundtheretda metal bridge of substantMIly X-ahape in cross section and whose upper legs are fumed with string positioning notches and whose lower legs have flanges which are secured by a non-chattering Joint to said amplifier plate.

17. A pianoforte including a sheet metal ampliflerplate andametal bridgeapair of angularly bent members welded to one another at their apexes thus forming a substantially x-shaped bridle. said members having base iiangesweldedatintervalstotheampliflerplate. metal seam uniting the free ilangetotha wliiierpiate and a continuum edge of each base so as to prevent chattering whenthe parts are vibrated.

18. A pianoforte comprising a frame of wrought metal having respective side and rear portionaacrcssmemberandatuningpin plate eaehseeuredatitsrespectiveendstotheside portions of the frame. a sheet metal amplifier plate welded to said frame and said cross member, a hitch pin plate welded to the amplifier plate and to said frame, and underframing braces beneath the amplifier plate and secured to and extending from said cross member to the rear portion of said frame.

19. A pianoforte comprising a frame of wrought metal having substantially parallel side portions Joined by a rear curved portion conforming substantially in plan to the outline of the casing of a grand piano, a metallic cross member secured at its ends to the side portions of a tuning pin plate spaced forwardlv cross member and secured to the side portions of said frame, a sheet metal amplifier plate welded at its forward end to said cross member and welded at its side and rear edges to said frame member, a hitch pin plate above the ampliiier plate and welded adJacent its outer edges thereto and trussed. braces below the amplifier plate secured at their forward ends to said cross membez-andattheirmarwardendstotherear portion of said frame.

WILLIAM BRAID WHITE. WC! '1. mm

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