This disclosure relates to pin blocks (also called “wrestplanks” in the piano industry) for receiving tuning pins in pianos and like musical instruments.
A pin block or wrestplank is a laminated plank that sits under the iron plate at the front of the piano, where it defines a plurality of holes for receiving steel tuning pins. An end of each piano string is wrapped about the end of a corresponding tuning pin. The tuning pins are rotated in the pin block holes to tighten each piano string up to concert pitch. The pin blocks must hold the tuning pin tightly enough against loosening to allow the piano to stay in tune.
Multi-laminate wood planks used for less expensive pin blocks often have layers of glue of excessive thickness or excessive quantity of layers, which may lead to tuning instability. Many pin blocks or wrestplanks include layers of wood. Constant turning of the tuning pin can rapidly wear down the wood and enlarge the tuning pin hole, which eventually reduces the ability of the pin block to hold the tuning pin against loosening.
Different manufacturers vary the number of laminations (i.e. layers) forming the pin block. For example, a Steinway piano typically contains a pin block with six or seven thick laminations, e.g. often about ⅛ inch to about 5/16 inch in thickness, of maple, beech, and/or bubinga hardwoods, with the direction of grain in each layer disposed at an angle of approximately 45° to the direction of grain in opposing surfaces of adjacent layers. Other piano manufacturers provide pin blocks with seven or more laminations, in which the direction of grain in each layer is disposed substantially perpendicular to the direction of grain in opposing surfaces of adjacent layers.
In one aspect, a wrestplank, for use in a stringed instrument, includes first and second outer working plies, and at least seven median working plies stacked in between the first and second outer working plies. Each working ply defines a direction of grain. The working plies collectively define a tuning pin hole configured to securely receive a tuning pin. The tuning pin is substantially surrounded by and in engagement with end wood of the working plies. The directions of grain of the outer working plies are oriented substantially parallel with respect to a longitudinal axis defined by the wrestplank. The directions of grain of two of the median working plies are oriented at an angle of between about 60° and about 75°, preferably about 60°, with respect to the longitudinal axis. The directions of grain of two of the median working plies are oriented substantially perpendicular to the longitudinal axis. Furthermore, the directions of grain of two of the working plies are oriented at an angle of between about 105° and about 120°, preferably about 120°, with respect to the longitudinal axis. In some implementations, the directions of grain of at least one of the median working plies are oriented substantially parallel to the longitudinal axis. The median working plies may be stacked in a symmetric order with respect to the orientation of their directions of grain.
In another aspect, a wrestplank, for use in a stringed instrument, includes first and second outer working plies, and nine median working plies stacked in between the first and second outer working plies, each working ply defining a direction of grain. The working plies collectively define a tuning pin hole configured to securely receive a tuning pin. The tuning pin is substantially surrounded by and in engagement with end wood of the working plies. The directions of grain of the outer working plies are oriented substantially parallel with respect to a longitudinal axis defined by the wrestplank. The directions of grain of the first and ninth median working plies are oriented substantially perpendicular to the longitudinal axis, and the directions of grain of the second, fifth, and eighth median working plies are oriented substantially parallel to the longitudinal axis. The directions of grain of the third and seventh median working plies are oriented at an angle of between about 60° and about 75°, preferably about 60°, with respect to the longitudinal axis, and the directions of grain of the fourth and sixth median working plies are oriented at an angle of between about 105° and about 120°, preferably about 120°, with respect to the longitudinal axis.
Implementations of the disclosure may include one or more of the following features. In some implementations, each working ply is adhered to an adjacent working ply. Each working ply comprises rotary cut wood, in some examples. However, other appropriate cuts of wood may be used as well, such as quarter-sawn wood or flat sawn wood. For example, the median working plies oriented at an angle with respect to the longitudinal axis may comprise quarter sawn wood or flat sawn wood. Each working ply is made of a suitable hardwood, such as maple, beech, or bubinga hardwoods. In some examples, the median working plies oriented at an angle with respect to the longitudinal axis have a thickness greater than the other working plies. In other examples, each working ply has a substantially equal thickness. However, in some examples, the outer working plies each have a thickness different from the median working plies. Preferably, at least the median working plies each have a thickness of at least 3 mm.
The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
The present disclosure provides a multilayer wrestplank 100, also known as a pin block, which is capable of securely holding against loosening a series of tuning pins 150 subjected to the stresses of corresponding tensioned strings in a stringed instrument. In the case of a piano, each tuning pin 150 is attached to a string which is under between about 150 to about 250 pounds of tension, while the complete set of strings is under anywhere from about 30,000 to about 40,000 pounds of tension.
Referring to
The multilayer wrestplank 100 provides a retaining action upon the tuning pin 150 that is relatively less dependent upon the moisture content of the surrounding air, and remains dimensionally relatively more stable under all conditions, e.g. as compared to a single layer wrestplank. The wrestplank 100, with its multi-oriented median working plies 300, substantially eliminates the so-called “slip-stick” phenomenon in retaining action upon the tuning pin 150 to provide a relatively more nearly uniform retaining action in all radial directions. The uniform retaining action allows the tuning pin 150 to be easily, exactly and firmly set in a desired position of rotation, while maintaining the qualities of easy, yet solid, tuning throughout long periods of use.
The wrestplank 100 is configured so that the direction of grain of at least one layer or working ply 210, 220, 300 is substantially parallel to the direction of maximum stress upon its associated tuning pin 150. The direction of grain orientations of the median working plies 300 provide a relatively greater percentage of end grain bearing string loads on the tuning pin 150 in a plane of maximum stress on the tuning pin 150. As demonstrated in the examples described below, the median working plies 300 may be stacked in different order or arrangements.
FIGS. 1 and 3-5 illustrate implementations of the wrestplank 100 having seven median working plies 300, nine working plies 210, 220, 300 total.
Other permutations of layer orders are possible as well, such as symmetrical and asymmetrical orders or arrangements. For example, the order of the median working plies 300, from bottom to top, stacked between the first and second outer working plies 210, 220 may be one of the 60°-median working plies 3060 in first position (immediately above the second outer working ply), one of the 90°-median working plies 3090 in second position, one of the 120°-median working plies 3120 in third position, one of the 0°-median working plies 3000 in fourth position, one of the 60°-median working plies 3060 in fifth position, one of the 90°-median working plies 3090 in sixth position, and one of the 120°-median working plies 3120 in seventh position (immediately below the first outer working ply).
Each working ply 210, 220, 300 is adhered or laminated to an adjacent working ply 210, 220, 300. A urea-formaldehyde adhesive resin is preferably used. Adhesive is applied to the top surface of the second outer working ply 220. Adhesive is applied to both the top and bottom surfaces of the median working plies 300, which are then stacked on top of the second outer working ply 220. Adhesive is applied to the bottom surface of the first outer working ply 210, which is then stacked on top of the median working plies 300. The stack or book of working plies 210, 220, 300 is pressed for a period of time (e.g. until the adhesive is set) and then cured in a conditioning room, which provides a controlled environment (e.g. controlled temperature and humidity). The resulting wrestplank 100 is cut into a desired shape and assembled into a piano.
Referring again
Deformation of the tuning pin hole 110 is greatly reduced when the direction of grain is parallel with the direction of stresses to which the tuning pins 150 are subjected by the associated strings 50 (see e.g.
Between the horizontal piano 10A and the upright piano 10B, the maximum string load angle A, B, C, D, W, X, Y, Z is about 25°, which when applied to the tuning pin 150 results in the wrestplank 100 bearing the string load in the tuning pin hole 110 at angles of about 115° and about 65° with respect to the longitudinal axis 105. The orientations of the median working plies 300 provide end grain bearing the string loads on the tuning pin 150 substantially at angles of about 120° and about 60° with respect to the longitudinal axis 105. As a result, the wrestplank configuration described herein provides a greater percentage of end grain bearing the string loads on the tuning pin 150 than currently known wrestplanks. The resulting tuning feel of the wrestplank 100 is enhanced.
The working plies 210, 220, 300 are made of a suitable wood, preferably a carefully selected, rotary cut hard maple, mahogany-bubinga hard wood, or an equivalent, suitable hardwood. Rotary cut veneers are generally obtained by placing a log in a lathe and rotating the log along its longitudinal axis against a stationary knife. As the log revolves, the cutting knife moves slowly toward the center (varying by thickness of the veneer being cut, for instance), and a continuous sheet of veneer is peeled from the log. However, other appropriate cuts of wood may be used as well, such as quarter-sawn wood. Quarter sawn veneers are generally obtained by cutting a log longitudinally into wedges or four substantially equal “quarters” and then slicing the quarters as nearly to the radius of the log as possible into veneers of a desired thickness.
Each working ply 210, 220, 300 may have an equal thickness of about ⅛ inch, preferably 3.35 mm. Preferably, at least the median working plies each have a thickness of at least 3 mm. Equal thicknesses of the working plies 210, 220, 300 also contribute to a distribution of stresses on the wrestplank 100, and the tendency to warp or otherwise deform is less pronounced. This results in a more balanced and thus more stable wrestplank 100. In some examples, the outer working plies 210, 220 are veneers having a thickness relatively less than the median working plies 300. In order to provide relatively more end grain bearing the string loads on the tuning pin 150, in some implementations, the 120°-median working plies 3120, 60°-median working plies 3060, and optionally the 90°-median working plies 3090 have a thickness (or thicknesses) greater than the remaining working plies 210, 220, 300, and preferably a thickness of about 6 mm. These median working plies 3060, 3090, 3120 may also be made of flat sawn or quarter sawn wood, while the remaining working plies 210, 220, 300 are made of rotary cut wood.
As mentioned earlier, wood remains hygroscopic, even when seasoned. Accordingly, wood tends to give up moisture to dry air or absorb moisture from moist air to either shrink when drying or to expand when becoming more wet. Shrinkage of the wood will cause side grain exposed to the tuning pin 150 to shrink away from the tuning pin 150 and reduce the overall area of the bearing surface for the tuning pin 150. Swelling will cause side grain exposed to the tuning pin 150 to bind unduly on the tuning pin 150 and, eventually, through compression set, reduce the bearing area or tightness still further when the wood again dries and shrinks. The tuning pin hole 110 tends to become oval. The quality of the wrestplank 100, therefore, is important to the life of the piano, and a properly designed wrestplank, made with selected, well seasoned woods, may last the life of the piano if it is kept in the right climatic conditions. Since the dimensional variations of the wood are negligible along the grain but are considerable across the grain, a multi-ply construction with alternating grain directions remains comparatively stable because the adhesive bond between the working plies 210, 220, 300 will tend to prevent or at least reduce the dimensional changes in the wrestplank 100 by locking the expanding working plies 210, 220, 300; to the non-expanding working plies 210, 220, 300. It is preferred to arrange the plies 210, 220, 300 symmetrically and to use outer working plies 210, 220 of equal thicknesses and median working plies 300 or equal or greater thickness than the outer working plies 210, 220. The working plies 210, 220, 300 may be of the same kind of wood and grain figure in order to equalize the stresses and to thus balance the wrestplank 100, which will accordingly remain stable.
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.
This U.S. patent application is a continuation of, and claims priority under 35 U.S.C. § 120 from, U.S. patent application Ser. No. 12/015,783, filed on Jan. 17, 2008. The disclosure of this prior application is considered part of the disclosure of this application and is incorporated herein by reference in its entirety.
Number | Date | Country | |
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Parent | 12015783 | Jan 2008 | US |
Child | 12397387 | US |