Abstract:
The proposed solution to problems associated with pad leveling and effective tone hole closure, employs a pad with a beveled backer that is relatively rigid, and an adjoining contact layer that seals a corresponding tone hole when a musical instrument key is actuated. In one embodiment, the backer features a sloping side wall, and optionally a side wall portion having a curved contour. Leveling of the pad is accomplished by placing the backer partially within a pad cup, adjusting the pad orientation while maintaining sliding contact between the backer and the pad cup, and fixing the pad within the pad cup. The backer is preferably shaped to provide support to all portions of the contact layer. Another embodiment features a step-bevel backer that is sized to fit a pad cup, and preferably supports all portions of an adjoining contact layer whose diameter exceeds that of the pad cup.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of the filing date of U.S. provisional application No. 60/564,812, filed on Apr. 22, 2004, Inventor Edward O. Kraus. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates generally to musical instruments, and more particularly to a musical instrument pad suitable for use in musical instruments.  
         [0004]     2. Description of the Related Art  
         [0005]     A pad is used for closing a tone hole on a woodwind musical instrument, including but not limited to a piccolo, flute, clarinet, saxophone, oboe, or bassoon. A pad contains a sealing surface, which is placed in contact with a corresponding tone hole when it is desired to close the tone hole. A pad is typically circularly symmetric about an axis normal to the sealing surface of the pad.  
         [0006]     A pad is typically attached to a pad cup (a pad cup is also called “key cup” herein) of a musical instrument. The pad cup is typically situated at one end of a key mechanism. The key mechanism (“key” herein) may be actuated by a player of a musical instrument, and functions to open and close one or more tone holes located within the length of the musical instrument, which results in a change of pitch of the note being produced. The pad&#39;s position is usually fixed within the pad cup through the use of a pad adhesive, or by mechanical means involving any combination of screws, snaps, nuts, washers, and press-fit rings (also called grommets). When an adhesive is used to fix the pad in the pad cup, the process of positioning the pad, by heating the adhesive and adjusting the pad position relative to the pad cup, is known as “floating” the pad.  
         [0007]     An effective pad has the following characteristics: a) it opens and closes a corresponding tone hole, typically as a result of light finger pressure or spring tension placed on the key; b) it produces as little noise as possible when contacting the tone hole; c) when in closed position, it makes a reliable and repeatable air-tight seal between the pad&#39;s sealing surface and the corresponding tone hole, preventing air (whose pressure is slightly higher than ambient air pressure) in the interior of the instrument (“bore” herein) from escaping through the tone hole.  
         [0008]     When closing a tone hole, the position of the sealing surface of a pad relative to the tone hole is critical. In practice, any one or a combination of the following mechanical characteristics inherent in woodwind instrument key design may cause problems in sealing: 
        the pad cup moves in an arcuate motion about a center pivot point of the key, which is mounted on a small screw or small hinge rod;     the key is a complicated assembly of many parts brazed together that may have assembly tolerance positional errors, or may be in a bent or damaged condition. Positional errors may include translational error in three axes, and rotational error around two axes. (Because a pad is typically circular and symmetric about a centerline normal to the pad sealing surface, rotation about the vertical axis of a tone hole during installation does not affect pad effectiveness). Typically a pad is tolerant of some translational position error with respect to the tone hole, so long as the sealing surface of the pad remains level with the tone hole. By manipulating the pad orientation (known herein as “leveling”), through e.g., tipping of the pad within the pad cup, small errors may be corrected. When the pad has been positioned properly within its pad cup, it is said to be “leveled” with respect to the tone hole that it closes.        
 
         [0011]     For a pad to function properly, the pad must contact a tone hole with a light and uniform compression around a circle formed by the intersection of the top of the tone hole (“tone hole edge” herein) and a plane defined by an outer surface of the pad (known as “the sealing surface”), such that every portion of the tone hole edge is in contact with the pad. In order to produce an air-tight seal when a key is in the closed position, it is crucial that the sealing surface of the pad be at the proper height, and in the same plane as the tone hole edge. Adjusting a pad to effectively seal a tone hole is typically more difficult to achieve if the diameter of the pad cup is very nearly the same as the diameter of the tone hole (rather than the pad diameter being larger than the diameter of the tone hole) because there is a smaller tolerance for positional error.  
         [0012]     If the key is in alignment with the tone hole, then it is typically easy to install and level a pad. In practice however, perfect alignment of key and tone hole is rarely the case, and labor necessary to achieve perfect pad alignment may be costly.  
         [0013]     To cope with some alignment problems, several practices known in the art have developed. Adjustment of the pad&#39;s position may be accomplished by one or more of the following methods: selecting a thicker or thinner pad; floating the pad on a molten bed of pad adhesive (typically a hot melt glue) which is cooled to solidification after the part is in position; bending the key to change its position with respect to the tone hole; or adjusting the position of the pad through the use of thin paper shims placed between the back of the pad and the inside of the key cup. If heat sensitive pad adhesive is used for pad installation, once the pad is initially placed in the pad cup, a combination of light pressure and gentle warming can be used to adjust the pad so that the sealing surface of the pad conforms to the tone hole. A properly installed pad will have a small circular impression (pad seat) that is typically between 0.010 and 0.020 inches deep within the sealing surface of the pad. To create a pad seat, either a cushion layer or an outer sealing layer of the pad is slightly deformed. Seating is accomplished when every portion of the tone hole edge is in contact with the pad, and there is uniform contact pressure around the entire circumference of the pad seat.  
         [0014]     It is crucial that pads be adjusted to be level, i.e., parallel to the plane of the corresponding tone hole edge prior to seating. A pad that is not leveled before seating will result in an unequal depth of impression, i.e., unequal compression around the circumference of the pad seat. Unequal compression of the pad materials does not remain stable over time. Due to elastic memory of the materials, regions of greater compression will tend to regain their original thickness, causing gaps between the pad seat and the edge of the tone hole over time, and consequent air leaks.  
         [0015]     Prior art includes a non-beveled pad, a cross-section of which is shown in  FIG. 1 , and which may be assembled from straight-sided, die cut sheet materials (cork, silicone rubber, paper, cardboard, various polymer foams, and various pressure-sensitive adhesives) or from die cut laminated sheets of various combinations of sheet materials. A typical prior art non-beveled pad  10  as shown in  FIG. 1  has a backer  120  (a backer is also called a backing layer herein) which is typically made of paper or cardboard, a cushion layer  140 , a sealing layer  160 , and a straight side wall  180  perpendicular to a plane defined by sealing surface  190 . Typically, all layers, i.e., backer, cushion layer and sealing layer, are cut to a same diameter  122 .  
         [0016]     Problems with prior art non-beveled pads, such as that depicted in  FIG. 1 , may include difficulty controlling the final firmness of the pads, poor sealing characteristics of some materials, and heat sensitivity of some foam materials. Each of these problems may contribute to failure of the pad to seal properly after installation. Heat sensitivity (e.g., low melting temperature, propensity to deform upon heating) polymer foams is particularly problematic, often resulting in pad failure when a hot melt adhesive is used for installation.  
         [0017]      FIG. 2  shows a cross-sectional view of a pad cup  210  and corresponding tone hole  220  prior to pad installation. A non-beveled pad is relatively easy to construct, but difficult to install correctly into a pad cup. Several problems can arise from the choice of a non-beveled pad. First, a non-beveled pad must fit entirely within pad cup inside diameter  230 , and therefore the pad&#39;s diameter cannot exceed key cup inside diameter  230 . Problems can arise if tone hole diameter  240  is approximately the same as pad cup inside diameter  230 , because a non-beveled pad, e.g. pad  10  will typically meet tone hole edge  250  at the pad&#39;s outermost edge. As is known by those skilled in the art, a pad seat situated on the extreme outer edge of a pad makes a poor seal when attempting to close a tone hole. Second, as seen in  FIG. 3 , if a non-beveled pad  10  closely fits inside pad cup  210 , pad side wall  180  tends to self-align with pad cup inside edge  340 , which prevents making small adjustments, both in translation and rotation, of pad  10 . Thus for a non-beveled pad, it is difficult to correct a misalignment of pad cup  210  with tone hole edge  250 . Misalignment causes pad sealing surface  190  to be non-parallel to a plane defined by tone hole edge  250 , resulting in air leakage when closing the tone hole  220  with pad  10 .  
         [0018]     Prior art also includes a traditional beveled pad  40 , as shown in  FIG. 4 , made with multiple layers including: backer  420  containing one or more disks (typically made of cardboard) for stiffening; cushion layer  440  containing one or more disks typically made of wool felt, for cushioning an impact due to contact with a tone hole, and for reduction of noise; and membrane  460  typically made of bladder or leather, wrapped around the assembly and glued to backer  420 , which membrane forms sealing surface  480  to make an air-tight seal with a tone hole. Traditional beveled pad  40  has its backer  420  cut to a smaller diameter  418  than diameter  422  of cushioning layer  440  that it supports. A beveled pad  40  having backer vertical side wall  424  and cushion layer side wall  448  is commonly called a “step-bevel” pad  
         [0019]     Beveled pad  40  has two distinct advantages over non-beveled pad  20 . First, as seen in  FIG. 5  for pad  40  (membrane  460  has been omitted for clarity), cushion layer  440  has a diameter  422  that is larger than pad cup inner edge diameter  230 , allowing cushion layer  440  to overhang pad cup inner edge  534 , enabling better coverage of tone hole  220 . Second, backer  420  has a backer diameter  418  that is smaller than pad cup inner edge diameter  230 , resulting in some clearance between pad  40  and pad cup  210 . The clearance allows for adjustment (e.g., via tipping) of pad  40  relative to tone hole  220 , and may be accomplished by “floating” pad  40  on a bed of pad adhesive  550  that liquefies upon heating.  
         [0020]     If a traditional step-beveled pad as depicted in  FIG. 4  and  FIG. 5 , is sized to overhang pad cup  210 , several drawbacks exist. The first drawback, as can be seen with reference to  FIG. 2  and  FIG. 5 , is that thickness  546  of cushion layer  440  must precisely match projection distance  242  between plane  234  and plane  246 . If cushion layer  440  is too thick or too thin, pad  40  will contact tone hole  220  unevenly, causing unequal compression of cushion layer  440 , with eventual consequent air leaks. The second drawback, as seen in  FIG. 4 , is that cushion layer outer edge portion  442  is not supported by backer  420  because there is no direct contact with backer  420 . Hence when the pad  40  contacts a tone hole  220 , cushion layer outer edge portion  442  has the potential to flex when pressure is applied to pad  40  to close the tone hole  220 , which flexing can result in a poor seal. Additionally, step-beveled pad  40  as shown in  FIG. 5 , relies upon contact with pad cup bottom edge  536  to support cushion layer outer edge portion  442 . As will be recognized by one skilled in the art, any error in installation can result in cushion layer outer edge portion  442  unsupported by pad cup bottom edge  536 , resulting in a higher likelihood of air leakage when tone hole  220  is closed by pad  40 .  
       SUMMARY OF THE INVENTION  
       [0021]     To overcome the problems of prior art musical instrument pads, a new type of musical instrument pad has been developed, employing a backer having a contoured side wall. The new pad is easier than prior art designs to install and position relative to a corresponding tone hole, and more reliable in providing an air-tight seal to the tone hole.  
         [0022]     The new pad can be made from any combination of pad materials such as cardboard, wool, felt, leather, bladder, various polymer foams, solid plastic, plastic film, wood products, and metal. In one embodiment of the invention, a pad can be made in a completely unitized fashion, whereby the backing, cushion layer, and sealing layer are securely bonded to each other by any combination of adhesive or laminating methods. In another embodiment of the invention, a pad can be constructed by assembling a backer and a cushion layer, and wrapping the assembly in one or more layers of an air-tight membrane, which is then glued in place. The membrane can be made of bladder, leather, or a polymer film.  
         [0023]     A key feature of one embodiment of the invention is a backer having a sloping (also called “tapered” or “contoured” herein) side wall, a portion of which may have a curved contour (also called “rounded contour”, or alternatively “radiused” or alternatively “radiused contour” herein).  
         [0024]     According to an embodiment of the invention, wherein the pad contains a backer and a contact layer (the contact layer containing a sealing layer, and in addition, optionally a cushion layer), the backer is preferably sized so that the diameter of the backer inner surface is substantially the same as the diameter of the contact layer, providing support from the backer to the outermost edge of the contact layer. This design permits the advantageous use of a larger diameter pad than is possible with a non-beveled pad, and also enables easy leveling of the pad. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  illustrates a prior art non-beveled pad.  
         [0026]      FIG. 2  illustrates the geometry of a typical pad cup and its corresponding tone hole.  
         [0027]      FIG. 3  illustrates a pad cup and tone hole with a typical prior art non-beveled pad installed in the pad cup.  
         [0028]      FIG. 4  illustrates a prior art step-bevel pad containing a backer, a cushion layer, and a sealing membrane.  
         [0029]      FIG. 5  illustrates a pad cup and tone hole with a traditional step-bevel pad installed in the pad cup.  
         [0030]      FIG. 6A -D illustrates, according to various embodiments of the invention, a pad with a backer having a sloping side wall, and a contact layer that contains both a cushion layer and a sealing layer.  
         [0031]      FIG. 7  illustrates a pad with a backer having a sloping side wall, and a contact layer containing one cushion/sealing layer, according to another embodiment of the invention.  
         [0032]      FIG. 8  illustrates a pad with backer having a sloping side wall, and a contact layer containing a cushion layer and a sealing membrane, according to another embodiment of the invention.  
         [0033]      FIG. 9A ,B illustrates a pad cup and tone hole with a beveled pad installed, the beveled pad featuring a backer having a sloping side wall, according to an embodiment of the invention.  
         [0034]      FIG. 10  illustrates a beveled aperture pad, with a center hole through the pad for venting and/or attachment purposes, according to an embodiment of the invention.  
         [0035]      FIG. 11A ,B illustrates a closed-hole pad cup with a beveled aperture pad installed, according to an embodiment of the invention.  
         [0036]      FIG. 12  illustrates an open-hole aperture pad cup with a beveled aperture pad installed, according to an embodiment of the invention.  
         [0037]      FIG. 13  illustrates another aperture pad cup with a beveled aperture pad installed, according to an embodiment of the invention.  
         [0038]      FIG. 14  illustrates another embodiment of the invention having a step-bevel backer, with a contact layer that contains a cushion layer and sealing layer.  
         [0039]      FIG. 15  illustrates another embodiment of the invention with a step-bevel backer and a contact layer containing a single cushion/sealing layer.  
         [0040]      FIG. 16  illustrates another embodiment of the invention with step-bevel backer, and a contact layer containing a cushion layer and a sealing membrane.  
         [0041]      FIG. 17  illustrates a pad containing a backer having a sloped side wall that has a radiused portion, according to an embodiment of the invention.  
         [0042]      FIG. 18  illustrates a pad containing a backer having a sloped side wall, according to another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]     For each of the figures described and illustrated herein, a cross-sectional view, at the respective midpoint of each of the objects being illustrated, is presented.  FIG. 6A  shows a beveled pad  60  according to an embodiment of the invention, with a backer [ 620  (also called “rigid backer” herein) containing a sloping side wall  612 , and a contact layer  650  that contains cushion layer  640  and sealing layer  660 . (A contact layer herein refers to the set of all layers residing between a backer inner surface and a sealing surface that will be contact with a tone hole plus the sealing surface itself. For instance, in  FIG. 6A , cushion layer  640  and sealing layer  660  taken together, are referred to as contact layer  650 .) Backer  620  is typically made from a material that is relatively rigid in comparison with material used to make cushion layer  640  or sealing layer  660 . Backer inner surface  618  is preferably substantially planar, thereby providing substantially uniform support to all portions of cushion layer  640 . Also, cushion layer  640  includes a corresponding substantially planar cushion layer surface  642  in contact with backer inner surface  618 , enabling cushion layer  640  to receive uniform support from backer  620 . (For each embodiment of the invention presented herein, a preferred embodiment includes both a planar backer inner surface and a corresponding planar contact layer surface with which the backer is in contact.)  
         [0044]     For all embodiments of the invention described herein, a backer, e.g., backer  620 , is preferably made of a sufficiently rigid material so that it provides adequate support to an adjoining contact layer, e.g., contact layer  650 . Materials of suitable rigidity include materials with a tensile modulus of elasticity greater than or equal to approximately 20,000 PSI, and preferably at least 300,000 PSI. Materials such as cork, composition cork, and rubber cork, and other materials with tensile modulus typically in the range 200-1500 PSI, do not have sufficient rigidity to be usable in constructing a backer according to embodiments of the invention. Materials suitable for making a backer may include plastics such as LDPE and other such materials, having a modulus of elasticity in the range of approximately 25,000 PSI. Examples of preferred materials include, but are not limited to hard woods, most soft woods (e.g., pine, alder), cardboard, fiberboard, metals, plastics such as rigid (type 1) polyvinyl chloride (PVC), ceramics, glass, and various composite materials.  
         [0045]     For all embodiments according to the invention described herein, a material used to make a backer, e.g., backer  620 , is also preferably relatively unaffected by short-term heating though contact with molten adhesive. Materials that are relatively unaffected by short-term heating through contact with molten adhesive and hence are suitable for making a backer include, but are not limited to: hard woods, most soft woods (e.g., pine, alder), cardboard, fiberboard, metals, plastics such as rigid (type 1) polyvinyl chloride (PVC), ceramics, glass, and various composite materials.  
         [0046]     Beveled pad  60  can be made in a completely unitized fashion, whereby backer  620 , cushion layer  640 , and sealing layer  660  are securely bonded to each other by any combination of adhesive and/or laminating methods known by those skilled in the art. A preferred feature of this embodiment is a radiused portion  614  of the sloping side wall  612 . Radiused (also “curved contour” herein) portion  614  begins at backer outside surface  610  and has a continuously curved contour to side wall portion  616 . Side wall portion  616  has an approximately straight line i.e., linear, contour. Alternatively, for an embodiment of the invention shown in  FIG. 6B , backer  622  has sloping side wall  625 , which has an approximately straight line contour, and no curved contour portion.  FIG. 6C  illustrates an embodiment of the invention wherein side wall  630  has a curved contour, i.e., is radiused along the full extent of the side wall.  FIG. 6D  shows an embodiment of the invention in which backer  626  has a backer outer surface  628  that is contoured throughout its extent. In each of the embodiments 6 A-D, support is provided by the respective backer to all portions of the corresponding cushion layer  640  (i.e., to the outer extent of the corresponding cushion layer) that, in turn, supports sealing layer  660 .  
         [0047]      FIG. 7  shows another embodiment of the invention, containing a backer  720  with a sloping side wall  712 , and a single cushion/sealing layer  760  (which, for this embodiment, is the same as the pad contact layer). Side wall  712  contains a curved contour portion  714 , in similar fashion to  FIG. 6 . Backer inner surface  718  is preferably planar, which serves to provide support to all portions of contact layer  760 . Also, backer inner surface diameter  730  is preferably equal to cushion/sealing layer diameter  770 , which serves to provide support to all portions of cushion/sealing layer  760 . Other side wall profiles, in similar fashion to FIGS.  6  B-D, may be employed according to this embodiment, i.e. having a contact layer containing a single cushion/sealing layer.  
         [0048]      FIG. 8  shows another embodiment  80  according to the invention, which is constructed by assembling backer  820  and cushion layer  840 , wrapping backer  820  and cushion layer  840  in one or more air-tight membrane layers  860 , and gluing membrane edges  870  to backer outer surface  810 . Membrane layer  860  acts as a sealing layer when in contact with a tone hole (not shown). Membrane layer  860  may be made of materials including but not limited to bladder, leather, or various polymer films. Backer inner surface  850  is preferably planar, providing support to all portions of cushion layer  840 . Cushion layer inner surface  842  is preferably planar, thereby receiving support from all portions of backer  820 . Backer inner surface diameter  880  is typically substantially equal to cushion layer diameter  890 , which serves to provide support for all portions of cushion layer  840 . Backer  820  features a sloping side wall  812  that includes a curved contour portion  814  and a linear sloping portion  816 , promoting ease of leveling of pad  80  within a pad cup (not shown).  
         [0049]      FIG. 9A  illustrates pad  60  of  FIG. 6A  installed in a pad cup  210 , according to an embodiment of the invention. At installation, side wall  616  contacts pad cup bottom inside edge  936 . This contact provides several advantages: 1) pad  60  cannot sink too deeply into molten pad adhesive  948  within pad cup  210 , which would result in pad  60  being too far from tone hole  220  for proper leveling to occur; 2) contact between pad cup bottom inside edge  936 , and side wall  616  serves to center pad  60  relative to the pad cup  210 . Pad  60  is therefore constrained in translational movement, and the only remaining possible motion of the pad is rotational, i.e., tipping; 3) small errors in overall thickness of the pad can be compensated for by tipping the pad, enabling a positive seal to be established when sealing surface  680  contacts tone hole  220 . With this embodiment, if pad cup  210  is slightly out of parallel with tone hole edge  250  when pad  60  is initially brought into contact with tone hole  220  through activation of a key mechanism (not shown), orientation of sealing surface  680  can be adjusted through tipping of pad  60  within pad cup  210  while adhesive  948  is heated to a molten state. Adhesive  948  is then allowed to cool and solidify, thus fixing pad  60  relative to pad cup  210 . This adjustment of pad orientation through tipping can compensate for a small misalignment of pad cup  210  relative to tone hole  220 .  
         [0050]     As shown in  FIG. 9A , backer  620  allows for construction of a pad with a sealing surface  680  of sealing surface diameter  615  that is larger than would be possible using a non-beveled pad, because backer  620  projects partially into distance  942  between pad cup inside bottom edge  936  and tone hole edge  250 . Unlike prior art step-beveled pads, backer  620 , with backer inner surface  618  extending to diameter  615  of contact layer  650 , supports the entirety of contact layer  650 . Backer  620 , preferably constructed of a rigid material, completely supports cushion layer  640  (which in turn supports sealing layer  660 ), regardless of angular orientation of pad  60  relative to pad cup  210 . This support allows for installation of a larger diameter pad than a non-beveled pad, without incurring stability problems of an unsupported cushion layer typically experienced when employing a traditional step-beveled pad. Backer  620  with curved contour  614  and sloping side wall  616 , further promotes ease of tipping to achieve leveling of pad  60  relative to plane  946 , which plane is defined by tone hole edge  250 . Backer inner surface  618  is preferably planar, thereby providing substantially uniform support to all portions of the contact layer  650 . In similar fashion, contact layer inner surface  642  is preferably planar, enabling substantially uniform support to be received by all portions of contact layer  650  from backer  620 . (For each of the subsequent embodiments of the invention presented, backer inner surface and contact layer inner surface are both preferably planar.)  
         [0051]      FIG. 9B  illustrates that the beveled pad  60  may be tipped to compensate for a misaligned pad cup  210  relative to its corresponding tone hole  220 . Pad cup  210  is misaligned with respect to tone hole edge  250 , situated at an angle  960  with respect to a plane  970  defined by tone hole edge  250 . Pad  60  is adjusted by tipping, in order to render sealing surface  680  level with respect to a plane  970 , enabling sealing surface  680  to make an air-tight seal with tone hole edge  250 . The process of leveling pad  60  is typically accomplished by melting adhesive  948  by heating pad cup  210 , and then adjusting the orientation of pad  60  by sliding pad  60  while maintaining contact with pad cup pad cup bottom inside edge  936 , thus changing pad orientation with respect to tone hole  220 .  
         [0052]     Backer  620  is preferably made of a sufficiently rigid material so as to enable adjustment, by sliding pad  60  while maintaining firm contact, throughout the adjustment, with pad cup bottom inside edge  936 , which edge is circular. The backer  620  should be of sufficient rigidity so that, during adjustment, backer  620  will slide on pad cup bottom inside edge  936  in a smooth fashion with low force required to change orientation.  
         [0053]     Various techniques, e.g. use of a leak light, or use of thin feeler gauges, enable a person skilled in the art to determine if pad  60  is level with respect to tone hole  220 . When adhesive  948  is permitted to cool and solidify, pad  60  is rendered invariant in position with respect to pad cup  210 , thereby fixing the pad orientation. To achieve leveling of pad  60 , adhesive  948  may need to be heated, an adjustment of pad orientation made, adhesive  948  cooled, pad  60  tested for air leakage, and these steps repeated until no leakage is detected.  
         [0054]     Alternatively, according to an embodiment of the invention, a pad of a smaller diameter may be installed, fitting entirely within a pad cup inside diameter. One skilled in the art may choose to use a smaller diameter pad for various acoustical and/or air venting reasons, so long as the diameter of the respective tone hole is small enough to permit use of a smaller diameter pad. A pad according to an embodiment of the invention, even when fitting entirely within the cup, has advantages as follows: 1) the sloping side wall (and optionally curved contour portion) of the beveled backer provides more clearance with the inside of the pad cup, facilitating ease of leveling; 2) due to the rigidity of the material used to construct the backer, a pad according to an embodiment of the invention is highly dimensionally stable, and 3) the backer, when constructed from preferred materials, is more resistant to heat from pad adhesives than are prior art synthetic pads. Beveled pads with a sloping side wall, employing a sealing layer made from a traditional material such as, bladder, leather, or various plastic films, can also fit entirely inside a pad cup.  
         [0055]     By controlling backer thickness, the angle of taper (i.e., slope of side wall) of the backer, and the thickness of the cushion layer, pads according to embodiments of the invention can be made to fit virtually any pad cup and tone hole combination. According to another embodiment (not shown), variations can include provisions for integral or attached resonators, either by incorporating a resonating surface into the backer or by attaching a resonator to the pad with adhesive, rivets, screws, or other means. Resonators, their purpose, use, and installation are well known to those of ordinary skill in the art, and their details will not be described in this application further.  
         [0056]      FIG. 10  shows an embodiment of the invention suitable for a key having either a center mounting spud, or a hole in the center of the key for air venting. In this center aperture beveled pad  1000 , constant slope taper  1012  and radiused contour  1014  are seen on the outside portion of the pad, and additional clearance for mounting is provided by a chamfer  1052  on backer  1020 , extending from backer outer face  1010  to aperture  1050 .  
         [0057]     Beveled center aperture pad  1000  may be installed in a pad cup by situating sloping side wall portion  1012  so as to rest on an inside bottom edge of a pad cup (such as inside bottom edge  936  shown in  FIG. 9A ). Alternatively, a center aperture pad  1000  may be installed completely within a pad cup.  FIGS. 11A, 12 ,  13  within this document depict an aperture pad situated completely within a pad cup; however, placement wholly within a pad cup, or partially within a pad cup and with sealing layer extending beyond the outside diameter of a pad cup (as shown in  FIG. 11B ), may be employed.  
         [0058]      FIG. 11A  shows a beveled center aperture pad  1000  installed into a pad cup  1132  by use of pad screw  1164  and pad washer  1166 . The type of key system depicted is called Plateau or Closed Hole Cup. Alternative attachment hardware, such as plastic snaps (not shown), may be used, and are well known to those skilled in the art. For this type of pad cup  1132 , a central raised section with internal threads, called a “pad cup spud”  1162 , is provided. Pad cup spud  1162  is typically soldered to pad cup  1132 , and provides a mechanical attachment point for pad screw  1164  and pad washer  1166 . Beveled central aperture pad  1000  provides a central aperture  1138  for mechanical attachment to pad cup  1132 . Adjustment of pad height and tipping is typically accomplished by placing one or more pad shims  1160  between backer  1020  and pad cup  1132 . Clearance between pad  1000  and pad cup  1132  is provided by sloping side wall portion  1012  and radiused contour  1014 , facilitating tipping of pad  1000  within pad cup  1132  to achieve leveling with respect to a corresponding tone hole (not shown).  
         [0059]      FIG. 11B  shows a beveled center aperture pad  1000  installed into a pad cup  1134 . Here the beveled center aperture pad  1000  is oversized, i.e., it has a contact layer diameter  1140  that exceeds key cup inner diameter  1142 . Beveled center aperture pad  1000  is supported by contact with pad cup inside edge  1138 , providing stability and preventing pad  1000  from tilting when contacting and closing a corresponding tone hole. Adhesive  1145  is optional, providing additional support, and further stabilizing the position of beveled center aperture pad  1000 . If adhesive  1145  is present, leveling is accomplished by heating adhesive  1145  to a molten state, orienting pad  1000 , and then allowing adhesive  1145  to cool and solidify.  
         [0060]      FIG. 12  shows pad cup  1232  containing a beveled central aperture pad  1000  featuring sloping side wall  1012  and optionally, a curved contour portion  1014 , according to an embodiment of the invention. Central aperture  1254  in pad cup  1232  allows for air venting through the center of pad cup  1232 . This type of pad cup design is called a French (or Open Hole) Cup, typically seen in flutes. Typically one or more pad shims  1260  is employed for height and tipping adjustment of beveled central aperture pad  1000 . Fastening is accomplished through use of a grommet  1268 . Grommet  1268  is installed into pad cup  1232  by a gentle press-fit. Grommet  1268 , in turn, holds pad  1000  in place by friction fit. Clearance between pad  1000  and pad cup  1232  is provided by sloping side wall portion  1012  and optional radiused contour  1014 , facilitating tipping of pad  1000  within pad cup  1232  to achieve leveling with respect to a corresponding tone hole (not shown).  
         [0061]      FIG. 13  shows another pad cup  1300  employing a beveled aperture pad  1000  with sloping side wall  1012  and optionally, a radiused contour  1014 , according to an embodiment of the invention. Here pad cup  1300  has a central aperture  1354 . Pad installation is typically accomplished through the use of pad adhesive  1348 . The beveled pad  1000  as shown in  FIGS. 11A, 11B ,  12 , and  13  may be made in unitized fashion, whereby backing, cushion, and sealing layers are securely bonded to each other by any combination of adhesive and laminating methods. Alternatively, beveled pad  1000  can be made by positioning a rigid backer with a sloping side wall (and optionally, a radiused contour side wall portion), against a cushion layer, wrapping backer and cushion layer with a sealing membrane such as bladder, leather, or a plastic film, and attaching the sealing membrane to the backer outer surface, i.e., the surface of the backer closest to the pad cup when the pad is installed.  
         [0062]     Occasionally there are pad cup and tone hole combinations for which the sloping side wall beveled pad as depicted in  FIG. 6A -D, cannot be made large enough in diameter to properly seal the hole, e.g., where the diameter of the tone hole is very large relative to the corresponding pad cup, In this case, a step-bevel pad, according to another embodiment of the invention, is needed to seal the corresponding tone hole.  
         [0063]      FIG. 14  shows a step-bevel pad  1400  according to an embodiment of the invention. Backer  1420  is not die cut with straight sides of a single diameter, but instead has a step profile. Backer outer face  1410  has a backer outer face diameter  1412 , which is smaller than backer inner face diameter  1425 . Side wall portion  1418 , shown in  FIG. 14  to be vertical, is optionally vertical or tapered. Backer step  1422  extends backer  1420  to the full extent of cushion layer  1440 . Backer inner face  1424  matches cushion layer diameter  1438  of cushion layer  1440 . When step-bevel pad  1400  is installed in a pad cup, backer step  1422  typically projects beyond the outer edge of the pad cup (not shown).  
         [0064]     Backer  1420  provides rigid support to all portions of cushion layer  1440 . Cushion layer  1440 , in turn supports sealing layer  1460 . The support from backer step  1422  to contact layer  1470  promotes flatness, and hence effectiveness, of pad  1400  over time.  
         [0065]      FIG. 15  illustrates step-bevel pad  1500  according to another embodiment of the invention, where contact layer  1560  is a single layer, serving as both a cushion layer and a sealing layer. In similar fashion to pad  1400  of  FIG. 14 , backer step  1522 , which is a portion of backer  1520 , provides rigid support for contact layer  1560 , enhancing flatness of the pad, thus promoting, over time, an air-tight seal with a corresponding tone hole.  
         [0066]      FIG. 16  shows a step-bevel pad  1600  according to yet another embodiment of the invention, which includes a step-bevel backer  1620 , with backer inner surface  1650  having backer inner face diameter  1652  that is larger than backer outer surface diameter  1632 . Backer inner face  1650  is situated adjacent to a cushion layer  1640 . Backer  1620  and cushion layer  1640  are wrapped within a sealing membrane  1660  made from, e.g., bladder, leather, or a plastic film. Sealing membrane  1660  is typically attached to backer  1620  at backer outer face  1630 . In similar fashion to the embodiments depicted in  FIGS. 14 and 15 , backer step  1662  provides rigid support to all portions of cushion layer  1640 , which in turn provides extended radial support to sealing membrane  1660 , helping to ensure over time, an air-tight seal with a corresponding tone hole (not shown).  
         [0067]      FIG. 17  shows a beveled pad  1700  according to another embodiment of the invention. Backer  1720  contains a sloping side wall  1712 , of which portion  1714  has a curved contour, i.e., radiused, and portion  1716  has a constant slope, i.e. straight line profile. In this embodiment, backer inner face diameter  1742  is smaller than contact layer diameter  1752  of contact layer  1750 . In similar fashion to FIGS.  9 A,B, sloping side wall  1712  enhances ease of leveling of pad  1700  relative to a corresponding tone hole edge (not shown).  
         [0068]      FIG. 18  shows a beveled pad  1800  according to another embodiment of the invention. Backer  1820  includes sloping side wall  1812 , which has a straight line profile. Backer inner face diameter  1842  is smaller than contact layer diameter  1852  of contact layer  1850 . Sloping side wall  1812  enhances ease of leveling of pad  1800  relative to a corresponding tone hole edge (not shown).  
         [0069]     Although the invention has been described above with reference to specific embodiments, persons skilled in the art will understand that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The foregoing description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.