US2339752A - Piano pin block - Google Patents

Description

Patented Jan. 25, 1944 PIANO PIN' BLOCK Paull Bilhuber, Douglas Manor, N.`Y., assgnor to SteinWay-& Sons, New Y0rk,`N. Y., acorporation of'New York Application August 7, 1943, Serial No."497,770

(CLM-F188) 2 `Claims.

'i This invention relates to piano pnblocks and has for its object to provide an `improved pinblock which will cooperate with the string frame ina manner as if both string frame and'pinblock were one piece and in which the pinblock is protected against moisture and warping and loosening of tuning pins. The invention is also 'for the process of making the same.

'The invention simplifies the manufacturing of pinblock and string frame joining, and thus reduces cost.

v-Inthe making of such pinblocks, the wood of the pinblocks is removed by planing, carving and scraping or both, to bring the excess thickness of the top surface ofthe pinblock and one side thereof down to the level and shape or conformation of that part f the plate that is adjacent to the pinblock. After much trial and error on the pinblock it is nally fitted to the string frame, but at the best a true t is not obtained, and the spaces or voids between the string frame and -pinblock are subject to the entrance of moisture and air, and oxidation sets in to the injury of the proper registration or fit of the two members,

`f which also brings about the loosening of the tuningV pins. Also, the loosening of the tuning pins is due to change in moisture content of the wood of the pinblock when under or subject to atmospheric changes. Such conditions also cause string tensions and their concomitant loss of pitch in both the unisons of a tri-chord or bi-chord note, as well' ask individual notes in the piano scale or group of notes that will cause the piano to be out of tune.

The invention consists of an improvedcombined pinblock and string plate, having its adja- 1 cent surfaces fitted by an intermediate layerof material, initially plastic and then hardenedand joining the layer to the pinblock so as'to be one pitch therewith, to receive on its upper surface which is in intaglio with the lower surface of the string frame and in complete registration therewith, the said string frame, so that the pinblock and string frame form substantially one'piece though not physically joined, no voids or spaces being between the same throughout their contiguous surfaces.

The invention also contemplates the treatment of the wooden pinblock to remove moisture therefrom. The invention also contemplates coating the exposed portions with a water proofing to retain the dryness of the same.

' The invention will be further described in connection with the embodimentshown in the drawing and willfbe finally pointed out in thefclaims.

Figure 2 is a transverse section on line 2-2of VFig. 1;

. Figure 3 is a section of the improved pinblock with a filler layer without'the string plate being applied thereto;

Figure 4 is a section with the string plate applied to the ller before' pressure is applied; and

Figure 5 is a section of the improved combined pinblock and string plate,` provided with a hermetically sealed coating.

Similar characters of'reference' indicate corresponding parts throughout the various views.

Referring to the drawing, and more particularly to Figurev 1, the pinblock I0 has applied thereto the string'plate l I, which is provided with tuning pins l2, for the stringsIS. A string 'plate with pins is well knownv both in grand'and upright pianos, and such string plates on the side opposite to the side from which the pins project, rest upon a Wooden beam. i5, extending across the front of a grand piano or across the top of an upright piano. Asknown, the front of the beam l5 has glued thereto an angle piece M called case corner or bar front in grand pianos.

' of 'ply construction.

.The upper and lateral surfaces Ia and |512 of the pinblock I0, in accordance with'the invention, are slightly less in height and less in width by aboutk onek sixteenth of an inch, in respect to the pinblock heretofore used. While the reducedpin.- block is planed on its surfaces I5a and 15b, nevertheless the surfaces are not actually smooth, since under the microscope hills and depressions would appear as also molecular angularities. In consequence, when the surface i la is placed upon the surface 15a. and the surface l lb upon the surface |512; instead of being truly parallel, spaces i or voids are left therebetween, which are irregular in size and depth due to the irregularities of the'contiguous surfaces. Even when` considerable` time is spent fitting the surfaces l5a and |527 to match the surfaces Ila and Hb, spaces or voids will nevertheless remain, as there is no-accurate method known by which such spaces or voidscan Vbe detected and then removed and a perfect ht 4commercially possible is nevertheless subject to 'the objections above pointed out.

In accordance with the invention, in order to remove any and all spaces and voids, the surfaces ld and |527, are provided with a layer 20 of a filler material of about three thirty-seconds inches in depth, and this layer is trowelled to provide reasonably smooth outer surfaces, and to have the filler layer of substantially even depth.

'I'his filler is a water soluble resin paste of the urea formaldehyde or similar type with an admixture of wood flour 20% to 30% by weight, the wood flour having a sieve value of about 80 to 100. 'I'he proportion of catalyst to the formaldehyde and wood flour, is such that a hardening of the mix takes place at room temperature or at temperature higher than room temperature.

Before hardening of the mix and shortly after the filler layer has been smoothed, the string plate is applied and pressed thereupon. It is allowed to remain a shorttime to permanentize the impressions of the lower surfaces f the string frame upon the plastic filler layer, when' the string frame is removed. Thus, the'string frame acts as a male die to duplicate its configuration upon the plastic filler layer'throughout both the surfaces of the filler layer and the surfaces of the string frame. Such pressing of the string frame upon the filler layer removes all possibility of voids and spaces between the pinblock. Removal of the string frame from the pinblock leaves the exact reverse contour of the plate surface in the nature of an intaglio or seal impression. The excess material is squeezed out t0 the front, sides and bottom, and to prevent this excess from entering the tuning pin openings of the plate, a thin cloth is placed between the surface I la and the top of the filler layer, these holes having been drilled into the plate beforehand.

To hasten the drying and curing of the ller layer which at room temperature would take place in about three to ve hours, depending on the amount of catalyst used as a hardener, use is made of an electrostatic field of high frequency current to heat the filler and the pinblock.

The layer coated pinblock is placed between two copper sheet electrodes and the moisture is driven out of the layer, and the resin is cured and converted and hardened in accordance with a greatly accelerated rate. At the same time drying and dispersing of the moisture in the pinblock is intended to be carried out. Instead thereof, stray-field electrostatic heating with a grid type electrode brought near the surface to be cured may be used. A temperature rise of 100 F. above room temperature is suiiicient to permanently set the layer in or 20 minutes at frequencies of 2 to 4 megacycles in a voltage range of 3000 to 5000. Under such treatment, the filler layer fully hardens and retains the exact impression left by the surfaces of the string frame and results in a permanence of it, a waterproofing layer and a considerable reduction of the curing time.

When cured a layer or film of this material is waterproof and effectively seals the pores of the wood against penetration of moisture under changing climatic conditions. Due to the registration of pinblock and string plate, moisture is excluded therebetween. The remaining surfaces not covered by the filler layer are then covered with a resin finish or moisture resistant coating of Ian oil varnish type preventing moisture gain or loss and inhibiting warping, checking and distortion of the wood and preserving thereby the grip or friction between wood and .tuning pins that are subsequently inserted in the holes of batch of ureaV the pinblock drilled to receive them. The retention of friction is a desirable feature to assist in the tuning of the piano and by this means such friction is prolonged for years beyond the point where the pins in the standard construction often become loose, necessitating their removal and the substitution of oversize pins to restore the friction, or replacement of the entire pinblock because of checking, splitting or warpage.

The advantages of the invention consist in having a waterproof protective layer that becomes an integral part of the pinblock; in having a layer to provide the pinblock with a surface the exact counterpart of the string f'rame adjacent to it, thereby securing an eiiicient t; reduction in loss of pitch of the strings through warpage, distortion or buckling due to improper or partial t; saving of time in the tting operation; reduction in the time of curing such iilm by use of heating by electrostatic field of high frequency; retention of the friction between wood and tuning pins under climatic changes and the ravages of time for prolonged periods due to changes in moisture contents through atmospheric changes and securing the pinblock against moisture entrance.

The filler layer is of such a material that when acted upon as described it will bond to the Wooden pinblock and register perfectly with the string frame throughout the entire surface, making the three parts as one tted unit. At the same time, it is important that the treatment of the wood is such that it is free from moisture and that it is exteriorly covered against moisture, so that the wooden pinblock and metal string frame with the layer therebetween become substantially one moisture proof entity, having at the same time all the advantages of vibration translation due to their intimate chemical and physical bonding.

While pinblocks as heretofore supplied to be manipulated are substantially free from moisture when originally supplied, by the time the fitting operation by trial and error is completed in the normal procedure described, a certain degree of moisture is absorbed from the air in the shop. It is essential, in accordance with this invention, to expel such added moisture, and the subsequent heating by electrostatic means expels this moisture.

The improved process consists in applying to the upper surface of the pinblock a layer of resin paste in plastic state, impressing the lower surface of the string frame upon said layer, subjecting the impressed layer to the action of an electrostatic current to harden the same and congeal the impressions, subjecting the pinblock to the action of an electrostatic current to remove the moisture from the body of the pinblock, and enclosing the pinblock by an envelope of water repellant material to prevent the entrance of moisture in the pinblock.

I have described several forms of my invention, but obviously various changes may be made in the details disclosed without departing from the spirit of the invention as set out in the following claims,

What I claim is:

l. An improved combined pinblock and string frame, a string frame having its under surface provided with an irregular surface of projections and depressions, a pinblock having its upper surface provided with a layer bonded thereto and having the exposed surface of the layer provided with impressions in complete registration with the contiguous under surface of the string frame, without voids or spaces between said contiguous surfaces, said layer being hard and free from moisture, the pinblock with its layer being detachably joined to the string frame.

2. An improved combined pinblock and string frame, a string frame having its under surface provided with an irregular surface of projections and depressions, a pinblock having its upper surface provided with a layer bonded thereto and having the exposed surface of the layer provided 10 with impressions in complete registration with the contiguous under surface of the string frame, Without voids or spaces between said contiguous surfaces, said pinblock being covered throughout all of its exposed surfaces including the layer bonded thereto with a moisture repelling coating, the pinblock itself and its layer being free of moisture, the pinblock With its layer being detachably joined to the string frame.

PAUL H. BILHUBER.

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