US3072005A

US3072005A - Piano construction

Info

Publication number: US3072005A
Application number: US847616A
Authority: US
Inventors: John P Quitter; Merton D Corwin; William F Lakamp
Original assignee: BALDWIN PIANO CO
Current assignee: BALDWIN PIANO Co
Priority date: 1959-10-20
Filing date: 1959-10-20
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08

Description

Jan. 8, 1963 J. P. QUlTTER ETAL PIANO CONSTRUCTION 4 Sheets-Sheet 2 Filed Oct. 20, 1959 -|IILIII.N\I\II ll rallKnlllll kllllbn I I I III.

9m 0 ..z a e w m w 4. mm 0 1 WWW Y B 0 0 a n w 8, 1963 J. P. QUITTER ETAL 3,072,005

PIANO CONSTRUCTION 4 Sheets-Sheet 4 Filed 0ct. 20, 1959 it parts and the tonality of the instrument.

United States Patent 13,072,005 PIANO coNsrRUcrIoN John P. Quitter, Cincinnati, Ohio, Merton llCorwhn,

The invention pertains to the construction of pianos;

.and for the purposes of an exemplary disclosure herein,

the invention will be described in connection with a small upright piano of the type sometimse called spinet, but it will'be-evident to the skilled worker in the art that many of the teachings hereinafter made are applicable to other types of piano construction.

One of the objects of the invention is to provide improvements in the construction and assembly of pianos, which improvements establish anew and better coaction of'the parts, resultingdependable operation and improved tonality.

The piano is a relatively complex collection of parts, which hitherto have been assembled in an interdependent manner such that a deviation in one part-requires a compensating change inanother part in order to accomplish any fit. As a result, it is often remarked in the trade that no two pianos of the same manufacture are exactly alike.

Much of the craftsmanship required in conventional piano 'manufacture lies in the judgment and skill needed in producing custom 'fits between the various parts. While some of the parts can be manufactured with features of adjustment, the making of custom fits frequently results in strain and distortion, impairing the coaction of the It will be evident that the problems of servicing and replacement of :partsiare complicated by these same factors.

FItLis a basic object of this invention to provide a modified construction of :the basic elements of a piano such that many custom features are no longer required. By

.the1sameftoken, thereplacement of parts is greatly simplified. I

Another basic object of the invention is the provision of a new coaction between the aforesaid modified parts,

which not only more perfectly locates the various parts with respect to each other, facilitating their assembly and "disassembly, but also makes for complete interchangeability of aparts.

Thus, the inventionaccomplishes, and it is a basic pur- ..pose-of the invention to accomplish, a significant economy sinithe'construction,:assembly and repair of instruments of :theyclass to which this invention is addressed.

The basic 'objectswhich have been set forth above, and

themore specific objects of'the invention which will be better understood by the skilled worker in the art upon "reading the descriptions of the various parts hereinafter set forth, are accomplished by the construction. and arrangement of parts of which the aforesaid exemplary embodimentwill now be described. Reference is made to the accompanying drawings wherein:

FIG. l is an elevational view of the back frame and pin block assembly of a piano of the invention, and showing certain locating members.

ice

FIG. 2 is an enlarged sectional view taken along the section line 22 of FIG. 1.

FIG. 3 is an enlarged sectional view taken along the section line.33 of FIG. 1. 7

FIG. 4 is a sectional view taken along the sectionline 4-4 of FIG. 1.

FIG. 5 is a diagrammatic representation of the main elements of an action frame. 4

FIG. 6 is an elevational view of the backframe, pin block and sounding board, complete with bridges, of the piano of this invention.

FIG. 7 is an enlarged partial section of "the sounding board and bridge taken along the section line 7--7 of FIG. 6.

FIG. 8 is a View from the bottom showing the back frame, sounding board and plate in assembled relationship.

FIG. 9 is a perspecive view of a key frame key bed assembly hereinafter called the key bed for convenience.

FIG. 10 is an elevational view showing the sounding board and plate in assembly, with a partial showing of the strings.

FIG. 11 is an enlarged partial sectional view showing the connection of a string to a hitch pin on the plate.

FIG. 12 is an enlarged general longitudinal section showing the relationship of the action to the plate and keys of an instrument of this invention.

FIG. 13 is an enlarged partial sectional view showing another mode of attaching an abstract to a key.

FIG. 14 is a partial sectional view showing one means for retaining the abstracts after they have been detached from the keys.

FIG. 15 is a partial perspective view showing a means for supporting the rail which carries the kick-off means for the jacks.

FIG. 16 is an elevational view of a portion of an eX- emplary action showing the coaction of the parts thereof.

It will be understood by the skilled worker in the art that piano cases may take various forms for styling and appearance, which do not constitute a limitation on the invention. In general, however, upright piano cases comprise a main frame member called the back and comprising a heavy wooden frame of interspaced upright posts connected top and bottom by horizontally disposed wooden members.

In the invention, side elements of the piano case are attached to the back. The back supports a pin block, a

sounding board, and a cast metal string plate. In conventional previous constructions, the action was supported in the pianos generally on rails extending between the side frame elements and sometimes so-called action brackets were adjustably attached to the plate. The keyboard and key bed in conventional painos were generally independently supported by-means of the side frame elements; but the action had to be adjusted with respect to the keyboard and key bed, and for other purposes.

In the piano of this invention the parts are standardized, are interchangeable, and are also self-locating, all as will hereinafter be explained. The back frame element carries means for the positive location of side frame elements. It carries a pin block in a fixed location. It is provided with a rim for the attachment of a pre-assembled sounding board; and it is further provided with means for the accurate location of the sounding board. The sounding board has means for the accurate location of standardized bridge elements.

The structure thus far described has means for the accurate location of the string plate. The action is assembled to a rigid frame; while the string plate carries means for the accurate location of the action frame so that no adjustment is required in assembling the action to the plate. Other features of the invention will be made clear in the ensuing description in which the several parts are taken up generally in the order of their assembly.

The construction of the back frame is indicated in FIGS. 1-4. The back frame comprises

uprights

10, 11, 12, 13, and 14 in the embodiment shown. T he outer uprights and 14 may be provided with

holes

15 and 16 extending part way through from the rear side in order to assist in machining the outer edges of the back frame to a corrected relationship to the other elements. The various parts of the frame are made of wood and are glued together or fastened by resinous cements as will be understood in the art. Uprights It to 14 may be made in one piece, or of two, three or more longitudinal pieces glued together. A pin block 19 is glued to the upper ends of the inner or forward faces of the uprights. The accurately located pin block will be provided with accurately located

dowels

17 and 18 for positioning the string plate as hereinafter described.

As shown in FIG. 2 the pin block usually consists of a back portion 20 and a front portion 21, the latter being made up of a plurality of veneer-like laminations. The pin block is made up separately and is glued to the uprights and fillers hereinafter described forming an integral part of the back frame. As indicated, the pin block will normally be wider in the treble portion of the piano by reason of the larger'number of tuning pins located thereat.

Fillers

22, 23, 24 and 25 are located between the uprights at the upper edge of the frame and give support to the pin block, while

additional fillers

26, 27, 28 and 29 are located between the uprights in such positions as to support the lower edge of the pin block. There is usually a finishing board 30, wider than the widest portion of the pin block, and extending across the back frame at its upper portion.

At the lower edge of the back frame there are

filler elements

31, 32, 33 and 34 between the uprights, and if desired there may be a lower rail 35. At the rear side of the back frame there will usually be a finishing board 36 at the bottom, mortised into the uprights as shown.

The back frame may, if desired, carry handles 37 and 38 to assist in moving the piano. The outer uprights 1t) and 14 will carry

dowels

39, 40, 41 and 42 for the precise location of the side elements (not shown) of the piano case.

The forward side of the back frame is provided with a means for the mounting of the sounding board. The sounding board will be mounted at its edges and spaced from the uprights of the back frame by an amount suificient to clear the ribs which lie on the rear face of the sounding board. The mounting means for the sounding board on the back frame consist of upper and

lower elements

43 and 44 and

side elements

45 and 46. These are made of the required thickness for the purpose hereinabove set forth; but since the sounding board is preferably bowed to make it more responsive to the vibrations of the strings, the elements 4346 are made with curved outer surfaces. Thus the

side elements

45 and 46 may be an inch in thickness at their ends but 1% inches at their central portions, while the

longitudinally extending members

43 and 44 may be an inch in thickness at their ends and 1% inches in thickness at their centers.

The sounding board, which will be described in greater detail hereinafter, will be provided with a pair of holes at its edges which fit over

dowels

47 and 43 on the side elements of the back frame. The holes and dowels are accurately located so that sounding boards separately reduced to exact specifications can be accurately fitted to the back frames constructed as hereinabove described. It will be understood that edge portions of the sounding board will be glued or cemented respectively to the

members

43, 44, 45 and 46 and will be clamped thereagainst during the setting of the cement. The configuration of the

frame members

43, 44, 45 and 46 will produce a bowing of the sounding board.

FIG. 6 shows the sounding board glued to the rim strips on the back frame. The sounding board 49, as is understood in this art, is made of thin wood and bears upon its rear surface a series of stiffening ribs 50 which are feathered or reduced at their ends as indicated at 51-. On its forward face the sounding board carries two

bridge structures

52 and 53. In the practice of the invention the bridge structures are preferably pre-formed and preassembled to the sounding board. The sounding board is provided with holes 54, 55, 56 and 57 accurately located thereon, while the upper bridge structure 52 is provided similarly with accurately located holes, while the lower bridge 53 has holes 58 and 59. In assembling the bridges to the sounding board, pins may be thrust through these several holes so as to locate the bridges while they are being glued in place. Afterwards the pins may be removed, if desired, and replaced by screws. The bridges are made to accurate specifications. In the practice of this invention, since the bridges and their locations are standardized, it is possible to drill the holes in the bridges for the string-engaging pins 60 and 60a (FIG. 7), by means of gang drills. The greater length of the upper bridge, as is usual, is rib-like in form and is cemented to the sounding board. The lower end of the upper bridge and the lower bridge itself have a cantilever construction providing for some resilient deflection as is also well known in the art. The cantilever construction is illustrated in FIG. 7 and will not need further description.

Holes to accept the tuning pins may be drilled in the pin block individually or by means of gang drills in suitable boring machines. This is, however, best done after the plate has been mounted as hereinafter described, the holes being drilled through the pre-cast holes in-the portion of the plate covering the pin block. However, the accurate location of dowels, holes to receive the dowels, and holes in elements to be fitted over the dowels as described above and hereinafter is best accomplished by means of boring machines, templates and the like in accordance with sound manufacturing practice.

It is an advantage of the structure thus far described that the pin block is generally configured to provide at a given point only the area which will be required for the tuning pins so that a substantial diminution in the overall size of the pin block has been found possible in the piano of this invention. Space may thus be provided for a generally larger sounding board if desirable for improving the tonal quality of the instrument, especially in the bass.

FIGS. 8 and 10 show the string plate assembled to the combination of the back frame, pin block and sounding board which has been described. The plate is preferably a cast iron structure which is capable of taking various forms depending on the type of instrument being produced. It is a precision cast structure made to close tolerances, but generally comprising an upper portion 61 and a lower portion 62 which are interconnected by the usual raised rib structures 63, 64 and 65 and by an end structure 66. As is usual in such structures, one set of strings 67 crosses a portion of the other set 68 at an angle. The strings engage hitch pins on the lower portions of the plate. Certain upper portions of the plate as indicated at 69 are perforated as shown for the passage of the tuning pins, the lower threaded portions of which engage in the pin block; and the upper portion of the plate in general is slightly recessed for the accommodation of the pin block. There is an opening in the lower portionv of the frame so that the strings of the group 68 may en;

gage .the lower 'bridge'53' as will be evident from FIG.

.10; and the bridge 52 lies above the lower part of the plate so asto be engaged by the strings of the ;group'67, all as is well known in the piano art.

The plate has an upper edge which coincides substanlatter, the rear surface of the edge portions of the plate is formed with pads or lugs most clearly shown at 70 in PEG. 8. With the precision-casting of the plate his not vnecessaryto grind or machine the rear surfaces thereof,

which saves considerable expense. The lugs 70 will ordinarily be accurate enough to permit the direct attachment of the plate to the back frame through the sounding board. The lugs will be cast to varying heights depending upon the crown of the strip 43--46 to which the sounding board is glued; and the rear surface of the plate may be correspondingly bowed if desired. The

lugs do not require special finishing; and fitting operations of cut-and-try character, as have been usual 'in the past,

are completely eliminated. The cast string plates may be classified, if variations are found to occur, by means of suitable gauges and, to the extent that variations are found to occur, simple wood or metallic shims may be providedfor use under one or a plurality of the lugs. During the gauging operation the string plates may be color-coded at places where shims are required, and the shimsithernselves may be colored to facilitate assembly withoutxmeasuring.

Since the plates are made by precision casting and are accuratelyv located with respect tothe pre-formed assembly of back frame and sounding board in the ways hereinabove described, it is not necessary to select particular plates for assembly with particular frames.

The plate having been located by means of the dowels v1'? and 18 may be fastened inplace 'by screws71 which pass through the sounding board frame, or Pass into the pin block, or pass into and engage other members associated with the back frame. There may be substantial variations in the placement of these .screws, the purpose being to hold the plate securely; but it may be kept in mind that when the plate is accurately fittedto and located upon thecombinationsof back frame, pin block and sounding board, fewer screws will generally be required to hold it in position since screws will be made to engage stress carrying members. FIG. 8 shows screws .71'passing through the plate intermediate pairs of spacing lugs 70. .In fitting theframe tothecombination aforesaid, it is not necessary to' warp or distort the-frame. Consequently the positions of the strings of the groups 67 and 6% will be standardized. This makes possible the .pre-

assembling

of'standardized bridges

52 and 53 to the'sounding board 49; Adjustments are not required to obtain the scorrect down bearing of thestrings on thebridges. The

strings 67 or 68 will engage hitch pins 73 atthe' lower .portionscif the frame and will pass over ridges 74 thereon as'shown in FIGURE'II.

The upper'ends of the'strings, :as will be understood, engage tuning pins 72.which"passv through holes .in-ithe string frame and engage inthe pin block. In certain sections at least of the piano the strings may pass over ribs 75on their way to tuning pins, and pressure devices 76 in the form of channel-shaped sheet metal members conveniently engage over the strings and are held to the plate byiscrews 77.

The plate has another novel characteristic in that it is provided with pre-formed means for locating a pre -assembled action. It is of'cou'rse old to mount piano actions to brackets, one end of which at least will be attached to a piano plate. In a common construction, the upper ends of action brackets are so attached, while the lower ends thereof have adjustable connections with a rail extending at a suitable height horizontally across the piano case. In other instances attempts have been made to attach both ends of action brackets to a string frame; but it has always been necessary to adjust the action to the frame and the strings thereof, which again requires cut-and-try methods. As distinguished from such structures the actions in the pianos of this invention are mounted to rigid frames. The string plates. are provided with means for the positive and standardized location of these frames, together with means whereby the frames may be attached to the plates. While adjustment of the individual operating instrumentalities of an action is always required, the actions of this invention do not require over an adjustment either to the string plates or to the strings thereon.

The string frame is formed with a pair of

integral lugs

78 and 79. These lugs are of a proper height to space from the strings the lower rail of an action frame ashereinafter described; and the lugs are provided with dowels 8t and 31 on which the said rail may rest or which may be received in holes in said rail, all for the purpose of establishing the vertical height of the action frame accurately with respect to the plate. Threaded holes 82 and 83 are provided for attaching the said lower rail to the plate; and other threaded holes 84 are provided at a higher position on the plate for the attachment of the upper ends of the action brackets. The latter holes may be provided with surrounding bosses to establish the correct spacing of the action bracket ends from the plate.

Reference is now made to FIG. 5 wherein there is shown in a semi-diagrammatic representation an action frame comprising

action brackets

85, 86, 87 and 88 of metal, and upper, intermediate and lower rails, marked respectively 89, 90 and 91 to which the action brackets are attached. The action brackets are most conveniently andinexpensively made'of sheet metal of suitable strength, formed in dies to a channel shaped'cross section which provides great rigidity, and having aside elevational shape which will most readily be appreciated from FIGS. 12 and 14. To rigidity and brace the frame against side sway, one or more metal links 92 maybe employed interconnecting one or more of the action brackets and the lower rail 91.

As shown in FIG. 12 each action bracket is preferably formed with a lower vertically extending portion 88a to which the lower rail '91 is attached, an intermediate portion 88b which extends generally slantwise toward the plate and to which the intermediate and

upper rails

90 and 91 are attached, a rearwardly extending portion 88c,1and an attachment portion 88d substantially paralleling the plate. It is this portion which may be attached directly to the plate 3tiby a screw 93 passing through a boss 84a surrounding one of the tapped holes in the plate.

The brackets may be attached to the rails by means of wood screws or .in any othersuitable way.

It will be clear that when the action frame is attached' to the plate as described, the frame will be very rigid, will be accurately located both vertically and horizontally with respect to the plate, and will be accurately spaced from the plate and the strings carried thereby. Also it will be free of any connection with the side members of the piano case. FIG. 12. shows the lower rail91 of the action frame resting upon the dowel or locating pin 81 on the boss 79 of the string frame. Since it is frequent in initial actionassembly to work on an action disconnected from the string plate of the instrument, the lower rail of the action frame may be provided with feet 94 as shown at the lower part of FIG. 12.

In the exemplary structure of this invention, the action proper is wholly supported by the action frame.

The precise nature of the action may be varied; but an action of suitable character for use with the frame mounting described above will now be outlined. The rail 90 is a relatively heavy wooden member to which wippens 95 are pivoted by the usual pivoting devices 96 mounted on the rail. The wippens will be connected respectively to the keys of the instrument by means hereinafter set forth. Upwardly extending members 97 on the wippens are used for the pivoting of jacks 98 having kick-oil? shoulders 99, and controlled by springs 100. If desired in the structure there may be a small rail 101 extending across the structure beneath the wippens 95 and serving to prevent too great a downward, counter-clockwise movement of the wippens, should the abstracts hereinabove described be disconnected from the keys.

At the upper edge of the rail 90 there are pivoting members 102 to which hammer blocks 103 are mounted, these hammer blocks carrying the usual rods 104 and hammers 105 of suitable configuration for striking the strings which in FIG. 12 have been given the index numeral 67.

In the embodiment specifically disclosed herein, the type of action shown is called a drop action. This means that the wippens are located below the keys and are connected therewith by upwardly extending abstracts or motion transmitting means. A drop action is normally used in small or spinet type pianos. However, the skilled worker in the art will understand that the principles of the invention are equally applicable to taller pianos of the upright class not requiring drop actions, but in which the wippens may be located directly above the playing keys so as to be actuated thereby through the medium of capstan screws or like adjusting means.

The wippens, in the exemplary embodiment, are moved by abstracts 106 which, in the preferred form, are wirelike members, the upper ends of which have engagement with the keys as hereinafter explained and the lower ends of which are bent at a right angle and again at an angle in an L-shaped configuration. The L-shaped ends of the wippens may be engaged in the conventional felt-lined, keyhole-shaped slots 107 in the ends of the wippens 95.

It will be understood by the worker in the art that when the wippens are moved in a clockwise direction by the abstracts, the jack members 98, engaging felt-lined surfaces 108 of the hammer blocks will drive the hammers toward the strings. Just before the hammers hit the strings, however, the jacks will be disengaged from the hammer blocks by a kick-out mechanism. The hammers will continue to travel under their own momentum until they hit the strings 67, but they will then be free to return instantly to inoperative position.

One form of kick-out mechanism is shown in FIGS. 12 and where a small rail 109 is mounted by means of threaded fittings 110 in the spaced position from the rail 90 and is provided with holes 111. The ordinary adjustable kick-out means comprising a threaded member 112 carrying at its lower end a felt-lined abutment 113 is employed, engaged in the several holes 111. The abutment members 113 engage the jack shoulders 99 upon continued upward movement of the wippens, as will be readily understood.

The hammer blocks 103 are provided with control means comprising the felt-covered extensions 114 and felt covered means 115 mounted to the wippens by rods or Wires 116. These control means act to prevent or minimize hammer rebound when a key remains in the depressed position. As shown in FIG. 16 a flexible bridle 117 may be engaged between the hammer block 103 and bridle wire 118 also mounted on the wippen.

The upper rail 91a may also carry a spring 119 which engages the hammer block and assists in returning the hammer to the inoperative position. In the exemplary embodiment the hammers come to rest in the inactive position on a felt pad 120 mounted on a movable rail 121. This rail is pivoted by arms 122 to bracket members 123 attached to the action brackets. Rail 121 rests on sound deadening pads 124 on these brackets. A pedal-controlled means (not shown) may be caused to move the rail 121 on its pivots to a position closer to the strings 67, thus decreasing the force of the hammer blows against the strings for a given force of key actuation, and producing a soft pedal effect.

The intermediate rail may also be caused to carry pivoting means 125 for dampers. These dampers may comprise a body 126 pivoted as shown and connected by a damper wire 127 to heads 128 carrying felt elements 129 engaging individual strings 67. A novel feature of this invention is the prebending of the end of the damper wire 1.27 to the correct position to cause the damper wire to enter the damper head 128 in a direction perpendicular to the particular string or string group 67 being damped. This feature improves the seating alignment of the damper on the string or string group and greatly reduces the manufacturing time for damper regulation. The damper body may be controlled by a spring 130 engaging the pivoting means 125 as shown. The wippen 95 is indicated as carrying a conventional spoon 131 which, when the wippen is actuated, will move the damper body so as to disengage the sound deadening material 129 from its string.

A pedal actuated means for removing the dampers from all or a substantial portion of the strings is a necessary provision in a piano. It may take various forms. In the particular illustrated embodiment a rod member 132, which is moved by a bell crank 133 (which may be attached to a pedal by means of a link 134) co-acts with a wedge-shaped configuration 135 on the damper body to move all or a series of dampers in unison. The rod 132 may be controlled by a spring 136, and the rod 132 may operate against a felt sound deadening pad 137. There are various ways in which the abstracts 106 may be detachably connected to the ends of playing

keys

138 and 139. One of these ways is shown in FIG. 12 where a member 140 having a threaded shank On one end and a fork on the other is screwed into the end of the key. The fork engages a grommet 141 of rubber or similar material. The upper end of the abstract is threaded, passes through the grommet and may be provided with a lock nut 142. Another way of accomplishing a similar result is illustrated in FIG. 13 where the end of the key 138 may be slotted to receive the end of the abstract as at 143. There will be an engagement means 144 perforated to receive the end of the abstract 106 and lock nuts 145 are provided for adjustability, together with a felt washer 146 or the like for sound deadening purposes. The abstracts may be flattened as at 147 for known purposes.

The abstracts thus are capable of being dissociated from the keys while remaining in association with the respective wippens; and it is desirable therefore to provide a means which will retain the abstracts when the dissociation is made. In FIGURES 12 and 14 arms 148 are pivoted to the brackets 123, the ends of the arms being interconnected by rail means 149 lying beyond the abstracts. These rails do not interfere with the normal functioning of the abstracts, but when the abstracts have been disconnected from the keys they may be swung to retain the abstracts in close proximity to the other elements of the action.

A preferable construction is that illustrated in FIGURE 13 where the index numeral 150 indicates a somewhat different type of bracket. This bracket has a rear flange for attachment to the action bracket 88; and it has a lower flange or flanges to which an outer rail 151 may be attached. This rail lies far enough forwardly of the normal positions of the abstracts 106 so as not to interfere with their functions as motion transmitting devices. However, when the abstracts are disconnected from the keys the rail 151 will prevent them from falling forwardly away from the action assembly.

The lower flange of the bracket 150 may also be used .9 as part of the support'for the rail 109 which supports the kick-off devices. It will be understood that there will be a bracket 150 on each of

theaction brackets

85, 86, 87 and 88. Intermediate portions of the rail109 may, if desired, be supported by fittings 110 as hereinabove described. 7

'In FIGURE 12 there is also illustrated a novel key bed assembly. The key bed proper is shown in FIGURE 9 as comprising

transverse elements

152, 153, 154 and 155, and

longitudinal rail elements

156, 157 and 158. These elements form a frame of unusual rigidity. The front rail 156

bears aligning pins

159 and 160 for the outer ends of the

keys

138 and 139. The center rail 157 carries the usual pivot pins 161 for the keys, there being a sound deadening element 162 beneath each key. The rear rail 158 carries a sound deadening rest 163 for the rear ends of the keys when in unactuated position. The use of the described key frame eliminates the concurrent use of a key base and a key bed as in prior constructions. The open underside of the frame may be closed by a thin member 164 made of wood, Masonite or other board-like material to minimize the infiltration of dust.

The key frame which has been described may rest on brackets 165 attached to the end frame members of the piano case. The key bed is preferably located with respect to the brackets 165 on the end frame members of the piano keys by means of dowels, one of which is shown at 169. As will be understood, the dowels will be ac curately located either with respect to the end frame brackets 165, or the end members 152 or 155 of the key bed. Additional rigidity may be added by a front case rail 166 and a rear case rail 167 extending across between the side members. The toe strip 168 at the front of the key assembly may simply be held in place by spring clips and may be made removable to facilitate replacement or adjustment of the keys or the elements with which they operate.

Modifications may be made in the structure herein described without departing from the spirit of the invention. The invention having been described in an exemplary embodiment, what is claimed as new and desired to be secured by Letters Patent is:

1. In a piano construction a back frame, a pin block attached to said back frame, edge supporting means for a sounding board also attached to said back frame, said edge supporting means carrying accurately located dowel means for the location of a sounding board thereon, and a sounding board having accurately located holes for coacting with said dowel means.

2. The structure claimed in claim 1 wherein said supporting means for said sounding board is configured to provide a predetermined bowing of said sounding board when the edges thereof are attached to said edge supporting means. I

3. The structure claimed in claim 2 wherein said sounding board prior to assembly to said back frame carries ribs on its rear surface, on its front surface accurately located pins for the positioning of bridge means thereon, said bridge means being pre-assembled to said sounding board.

4. The structure claimed in claim 3 including accurately located dowel means on the combination of back frame and pin block for the location of a string plate, and a standardized string plate having holes therein for coacting with said dowel means to position said plate with respect to said back frame and to support said plate prior to its attachment to said back frame.

5. The structure claimed in claim 4 wherein said plate has on its rear surface accurately formed lugs to space the body of said plate from said sounding board and to determine the down-bearing of strings attached to said plate on the said bridge elements.

6. The structure claimed in claim wherein said plate carries on its surface opposite said lugs, additional lugs for the location of an action frame having a rail, and in 1 0 which certain of said lugs have projecting pin means on which said rail can rest whereby to predetermine the position of said action frame with respect to said plate.

7. The structure claimed in -claim 6 in combination with an action frame, said frame comprising a plurality of vertically extending action brackets, said action brackets being interconnected by a plurality of substantially horizontally-extending rails, one of said rails being a rail adapted to rest on said pins.

8. The structure claimed in claim 6 in combination with an "action frame, said frame comprising a plurality of vertically extending action brackets, said action brackets being interconnected by a plurality of substantially horizontally extending rails, one of said rails being a rail adapted to rest on said pins and at least one diagonally extending brace interconnecting a rail with an action bracket at a position on said action bracket remote from said rail to prevent racking of said frame.

9. The structure claimed in claim 8 including action elements assembled to said frame.

10. The structure claimed in claim 8 including action elements assembled to said frame and including wippens, dampers and hammer blocks pivoted to one of said rails.

11. The structure claimed in claim 8 including action elements assembled to said frame and including wippens, dampers and hammer blocks pivoted to one of said rails, abstracts connected to said wippens for transmitting motion thereto from playing keys, supplementary bracket means attached to said action bracket, and means on said supplementary bracket means for maintaining said abstracts in a position close to said action assembly when said abstracts are disconnected from said keys.

12. In combination a precision'cast string plate, and action means comprising a frame having substantially vertically extending action brackets interconnected by a plurality of substantially horizontally disposed rails, one of said rails lying at the bottom of said action brackets, said string plate having bosses formed thereon at upper and lower positions and having threaded openings therein, the bosses in said upper position adapted for the direct connection thereto of the upper ends of said action brackets. and bosses in the lower position being provided with projecting pin means upon which said lower rail may rest for the pre-positioning of said action frame with respect to said string plate.

13. The structure claimed in claim 12 includin action elements assembled to said frame, said action elements including wippens, dampers and hammer blocks pivoted to an intermediate one of said rails.

14. The structure claimed in claim 13 wherein said dampers include damper wires the outer ends of which are pre-bent to a position perpendicular to the direction of a string to be damped, and wherein said dampers also include heads mounted on the pre-bent portions of said Wires so as to be adjustable for contact with said strings.

15. The structure claimed in claim 13 including crossbracing means for preventing racking of said frame.

16. The structure claimed in claim 15 including supplementary brackets attached to said action brackets, abstracts for connecting said wippens and playing keys, and means on said supplementary brackets for maintaining said abstracts in proximity to said action elements when said abstracts are disconnected from said keys.

17. The structure claimed in claim 16 wherein said action elements include jacks and wherein said supplementary brackets support a substantially horizontally extending rail carrying kick-off means for said jacks.

18. In a piano structure a combination in the order named of a back frame, a pin block, a sounding board including back ribs and bridges, a string plate, an action frame, and an action associated with said frame, each of said elements supporting the next recited element, each of said elements being made to close tolerances and standardized, and each of said back frame, pin block, sounding board and plate elements in the order named carrying accurately positioned dowel-like elements for the exact location of the next succeeding element prior to the attachment of the said succeeding element to the preceding element.

19. The structure claimed in claim 18 wherein the said back frame carries accurately positioned dowel elements for the exact location of said frame elements, side frame elements of a piano case located thereby and attached to said back frame, and a key bed means comprising longitudinal and lateral members in rigid union extending across, between and supported-by said side frame members, and accurately positioned dowel elements for exact location of said key frame-key bed assembly.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. IN A PIANO CONSTRUCTION A BACK FRAME, A PIN BLOCK ATTACHED TO SAID BACK FRAME, EDGE SUPPORTING MEANS FOR A SOUNDING BOARD ALSO ATTACHED TO SAID BACK FRAME, SAID EDGE SUPPORTING MEANS CARRYING ACCURATELY LOCATED DOWEL MEANS FOR THE LOCATION OF A SOUNDING BOARD THEREON, AND