Abstract:
An electronic drum  30  comprises a hollow body part  10  having an opening side, a drum head stretched over the opening side of the hollow body part  10  and having a stroked surface, an elastic cushion part  40  arranged to touch with a reverse side of the stroked surface of the drum head  30,  a vibration absorber  43  that is arranged inside the body part  10  and absorbs a vibration transmitted from the body part  10,  and a sensor  41  that is arranged in the vibration absorber  43  to touch with the elastic cushion part  40  and outputs a result of detecting a stroke on the drum head  30  transmitted by the elastic cushion part  40.  The drum head  30  is made of a lamination of a plurality of elastic films and has a plurality of holes  30   h  pierced thorough all layers of the laminated films.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is based on Japanese Patent Application 2005-260996, filed on Sep. 8, 2005 and Japanese Patent Application 2005-260997, filed on Sep. 8, 2005, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   A) Field of the Invention 
   This invention relates to a percussion instrument such as an electronic drum and a drum head of the percussion instrument. 
   B) Description of the Related Art 
   For example, as inventions of an electronic percussion instrument that can obtain the same striking feel as an acoustic drum and restrain a drum beat when stroked, there are inventions disclosed in Japanese Laid-Open Patent Hei 10-20854 (hereinafter called the patent document 1) and Japanese Laid-Open Patent 2001-142459 (hereinafter called the patent document 2). The electric percussion instrument detects a stroke on a drum head and electrically outputs sound corresponding to the detected stroke, for example. 
   In the electric percussion instrument disclosed in the patent document 1, a piezoelectric device for detecting a stroke on a drum head is adhered to a supporting part positioned inside the electric percussion instrument. A conic-trapezoidal cushion part formed of elastic material such as rubber or sponge is adhered to an upper surface of this piezoelectric device, and a tip of the cushion part contacts with the drum head. Since the cushion part contacts with the drum head, the stroke on the drum head is not directly transmitted to the piezoelectric device even if the drum head is stroked with a stick, and damage of the piezoelectric device can be suppressed. 
   Moreover, the electronic percussion instrument disclosed in the patent document 1 equips with a drum head formed of a netlike part made of a lamination of a first plain-woven net and a second plain-woven net wherein a weaving direction of each net is slanted to that of the another net as. In the disclosed percussion instrument, when the drum head is stroked with a stick, air passes through openings of a mesh of the netlike parts, and a drum beat produced by striking the drum head will be small. 
   On the other hand, the electronic percussion instrument disclosed in the patent document 2 equips with a drum dead made of a punching sheet having a large number of opening holes. In the disclosed percussion instrument, when the drum is stroke with a stick, transmission of vibration of the drum head to the air is decreased by the large number of the opening holes, and the drum beat will be small. Also, since rebounding of the stick on the punching sheet is larger than that on the netlike drum head, a striking feel like a normal acoustic drum can be obtained. 
   When the instrument is shaped by imitating an acoustic drum such as the electric percussion instrument disclosed in the patent document 1, parts other than the drum head may be touched with a stick or by a performer. In the electric percussion instrument disclosed in the patent document 1, the supporting material adhered to the piezoelectric device is fixed to a body of the electric percussion instrument. Therefore, when the stick or a performer touches with a part other than the drum head, the vibration by the touch is directly picked up by the piezoelectric device adhered to the supporting part. When the vibration is transmitted to the piezoelectric device, the piezoelectric device detects the vibration, and a sound corresponding to the touch will be output without striking on the drum head. 
   Moreover, because the drum head is a nondurable part, it is necessary to also have durability in some extent. In order to improve durability of the drum head in the percussion instrument disclosed in the patent document 1, it is considered that intervals of the plain woven fibers is made to be close. However, when the intervals of the fibers are close, opening parts become narrow, and silencing ability will be degraded. In order to improve durability of the drum head in the electronic musical instrument disclosed in the patent document 2, it is considered that thickness of the punching sheet is made to be thickened. However, when the punching sheet is thickened, tension of the drum head stretched over the body (sound box) becomes high, going down of a tip of the stick to the drum head will be small. Therefore, the striking feel will be the same as that when striking a board and a good striking feel cannot be obtained. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a drum head that has both durability and silencing ability with a good striking feel. 
   It is another object of the present invention to provide an electronic drum that does not generate a sound by touching a part other than a drum head. 
   According to one aspect of the present invention, there is provided a drum head is stretched over an opening side of a hollow drum body, made of a lamination of a plurality of elastic films and having a plurality of holes pierced thorough all layers of the laminated films. 
   According to the present invention, there is provided a drum head that has both durability and silencing ability with a good striking feel. 
   According to another aspect of the present invention, there is provided an electronic drum, comprising: a hollow body part having an opening side; a drum head stretched over the opening side of the hollow body part and having a stroked surface; an elastic cushion part arranged to touch with a reverse side of the stroked surface of the drum head; a vibration absorber that is arranged inside the body part and absorbs a vibration transmitted from the body part; and a sensor that is arranged in the vibration absorber to touch with the elastic cushion part and outputs a result of detecting a stroke on the drum head transmitted by the elastic cushion. 
   According to the present invention, there is provided an electronic drum that does not generate a sound by touching a part other than a drum head. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram showing an appearance of a percussion instrument according to embodiments of the present invention. 
       FIG. 2  is a cross sectional view of the percussion instrument according to the first embodiment of the present invention. 
       FIG. 3  is a cross sectional view of the percussion instrument according to the second embodiment of the present invention. 
       FIG. 4  is a diagram for explaining a drum head according to a modified embodiment of the present invention. 
       FIG. 5  is a cross sectional view of the percussion instrument according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A percussion instrument according to a first embodiment of the present invention will be explained with reference to the drawings.  FIG. 1  is a diagram showing an appearance of a percussion instrument according to embodiments of the present invention.  FIG. 2  is a cross sectional view of the percussion instrument according to the first embodiment of the present invention. As shown in  FIG. 1 , this percussion instrument  1  equips with a cylindrical body part (sound box)  10  and a drum head  30 . Rag cases  20  are fixed with screws at a fixed interval to a direction of circumference of the body part  10  on the peripheral surface of the cylindrical sound box  10 . As shown in  FIG. 2 , each rag nut  22  is exposing one of tips to an outside through a hole formed on the rag case  20 , and spring  23  is supporting the rag nut  22  for pushing out to outside. Each of the rag nuts  22  is shaped in a cylindrical shape, and a guard  22   a  for preventing falling out is unitedly formed on the peripheral of each rag nut  22 . Moreover, screw holes for screwing a rag bolt  24  into the rug nut  22  is pierced in the center of each rug nut  22 . 
   The periphery of the drum head  30  is supported by a head frame  31 . A fastening frame  32  formed in the periphery of the drum head  30  and the rag nuts  22  are connected by the rag bolts  24 . When the fastening frame  32  are pressured toward the head frame  31  by fastening the rag bolts  24 , tension is added on the drum head  30  so that the drum head  30  is stretched over the opening side of the body part (sound box)  10 . 
   The drum head  30  is made by laminating three layers of polyethylene terephthalate films as shown in an enlarged upper right section in  FIG. 2 , and the layers of the films are just overlapped with each other. Further, as shown in FIG.  1  and  FIG. 2 , a large number of piercing holes  30   h  with diameter of 0.5 mm to 3 mm are formed on the drum head  30 , and those opening hole ratio (an opening area/an area of whole drum head) is from 20 percent to less than 50 percent. A high processing technique is necessary to open holes with diameter of 0.5 mm or less, and it will take high cost. Therefore, the diameter of the piercing holes  30   h  according to the embodiment of the present invention is 0.5 mm or more. Moreover, when the diameter of the piercing holes  30   h  is 3 mm or more, the stick get into the piercing hole, and the drum head  30  may be broken by stroke of the stick. Therefore, the diameter of the piercing holes  30   h  according to the embodiment of the present invention is 3 mm or less. Moreover, when the opening hole ratio is 20 percent or less, air passing through the piecing holes  30   h  become less when the drum head  30  is stroked by the stick, and vibration transmitted to the air from the drum head  30  will not decrease, and loudness of a drum beat (produced sound) cannot be decreased. Therefore, according to the embodiment of the present invention, the opening hole ratio is 20 percent or more. Moreover, when the opening hole ratio is 50 percent or more, an amount (volume) of the films composing the drum head  30  decreases, and stretching strength of the drum head  30  becomes insufficient. Therefore, the opening hole ratio according to the embodiment of the present invention is less than 50 percent. 
   A shock (vibration) sensor  41  is stuck on a reverse side of a stroked surface of the drum head  30 . The shock sensor is a sensor for detecting shock (stroke or vibration) when the drum head  30  is stroked by a stick and outputs an electric signal corresponding to the detected shock. Moreover, the electric signal output from the shock sensor  41  is input to a musical tone generator (shot shown in the drawing) in the outside of the body part  10  via a signal line (not shown in the drawing). When the electric signal output from the shock sensor  41  is input to the musical tone generator, the musical tone generator outputs a drum beat (sound) based on the input electric signal. 
   When a performer strikes the drum head  30  having the above-described structure with a stick, the air compressed in the percussion instrument  1  by the stroke comes out from the plurality of piercing holes  30   h  formed on the drum head  30  to the outside of the percussion instrument  1 . When the air compressed in the percussion instrument  1 , air compressing ratio near the upper and bottom surfaces of the drum head  30  dramatically falls, and transmission of the vibration of the drum head  30  to the air decreases. Therefore, the loudness of the drum beat is lower comparing to a case without a piercing hole. 
   Moreover, in order to obtain the drum head  30  with the opening hole ratio of 20 percent or more, thickness of the drum head should br thickened for sufficient stretching strength. However, if the drum head  30  is thickened, rigidity of the drum head also becomes high, and it will cause a striking feel to be bad. However, in the embodiment of the present invention, the drum head is composed by laminating the plurality of the films, and each film is not adhered with others. Therefore, a gap (shifting) is generated between films when stroked and deforming amount is larger than a thick single layer. Therefore, even though the drum head is thickened in order to obtain stretching strength, a striking feel will not be bad. 
   Next, a percussion instrument according to the second embodiment of the present invention will be explained with reference to the drawings. Moreover, in the below-described second embodiment explained, the same parts as in the structure of the first embodiment are added with the same numerals, and the explanations for those parts will be omitted. 
   As shown in  FIG. 3 , a percussion instrument  1 A according to the second embodiment of the present invention is different from the first embodiment present invention in a structure for detecting shock (vibration) generated by a stroke of a stick. As shown in  FIG. 3 , the percussion instrument  1 A is consisted of a cushion part  40 , a shock (vibration) sensor  41 , a pedestal part  42 , shock (vibration) absorbers  43 - 1  to  43 - 3  and adjusting screws  44 - 1  to  44 - 3 . The pedestal part  42  is equipped with the shock sensor  41  in a concave part  42   a  and supported by the shock absorbers  43 - 1  to  43 - 3 , and is pressed to a direction of the drum head  30  by the shock absorbers  43 - 1  to  43 - 3 . 
   The sphere-shaped or sphere like shaped cushion part  40  that transmits shock (vibration) generated on the drum head  30  is, for example, made of polyurethane and placed between the drum head  30  and the shock sensor  41 . Because the cushion part  40  is shaped in a sphere like shape, when the shock given by a stroke with a stick is small, a contacting area of the cushion part  40  and the drum head  30  will be small, and the shock given to the shock sensor  41  will be also small. On the other hand, when the shock given by a stroke with a stick is large, a contacting area of the cushion part  40  and the drum head  30  will be large, and the shock given to the shock sensor  41  will be also large. Shock can be precisely detected corresponding to a magnitude of shock given by a stroke. Even if shock given by a stroke with a stick is large, a contacting area of the cushion part  40  and the drum head  30  becomes large; therefore, vibration of the drum head  30  is absorbed by the cushion part  40  to improve a silencing effect. 
   The shock sensor  41  is a sensor for detecting shock (vibration) transmitted via the cushion part  40  and outputs an electric signal corresponding to the detected shock. 
   The shock absorbers  43 - 1  to  43 - 3  are equipped with springs and dampers (both are not shown in the drawing) inside the shock absorbers along a direction of axis. One tips of the shock absorbers  43 - 1  to  43 - 3  are stuck to the pedestal part  42 , and another tips are stuck to the adjusting screws (wing screws)  44 - 1  to  44 - 3  piercing a bottom surface of the body part  10 . Moreover, an electric signal output from the shock sensor  41  is input to a musical tone generator (not shown in the drawing) that is outside of the body part  10  via a signal line (not shown in the drawing). When the electric signal output from the shock sensor  41  is input to the musical tone generator, the musical tone generator outputs a drum beat based on the input electric signal. 
   The adjusting screws  44 - 1  to  44 - 3  are screws for adjusting positions of the pedestal part  42 . When the adjusting screws  44 - 1  to  44 - 3  are screwed, a distance between the bottom of the body part  10  and the shock absorbers  43 - 1  to  43 - 3  changes, and the shock absorbers  43 - 1  to  43 - 3  change their positions. Corresponding to the movement of the shock absorbers  43 - 1  to  43 - 3 , the position of the pedestal part  42  changes its position, and pressure that the shock sensor  41  positioned on the pedestal part  42  pushes the cushion part  40  will change. That is, by screwing the adjusting screws  44 - 1  to  44 - 3 , the pressure that the shock sensor  41  pushes the cushion part  40  is adjusted so that the contacting area of the cushion part  40  and the drum head  30  will be adjusted. When the contacting area is changed, the shock transmitted to the shock sensor  41  will change even though the drum head  30  is stroked with the same power. That is, sensitivity to detect shock is adjusted by screwing the adjusting screws  44 - 1  to  44 - 3 . 
   When a performer strikes the drum head  30  of this structure with a stick, only shock transmitted from the drum head  30  via the cushion part  40  will be transmitted to the shock sensor  41 . Because the pedestal part  42  equipped with the shock sensor  41  is supported by the shock absorbers  43 - 1  to  43 - 3  and does not directly contact with the body part  10 . Moreover, since the vibration generated by touching with the body part  10  by the performer and the vibration generated by touching the stick with a part other than the drum head  30  are absorbed by the shock absorbers  43 - 1  to  43 - 3 , the signal output from the shock sensor  41  represents only the stroke given to the drum head  30  by the stick, and influence of the vibration from outside will be less. 
   Although the present invention has been explained along with the preferred embodiments, the invention is not limited only to the above embodiments. It is apparent that various modifications, improvements, combinations, and the like can be made by those skilled in the art. For example, the above-described embodiments may be modified as below and may be executed. 
   In the above-described embodiments, the material of the drum head  30  is polyethylene terephthalate; however, it is not limited to that. For example, it may be polyimide, polyethylene naphthalate and other material. Moreover, the films may be laminated with more than three layers for the drum head  30 , or it may be two layers other than three layers. Moreover, thickness of the laminating films may be changed corresponding to the material of the films. The thickness of the films composing the drum head  30  may be changed by every laminating layer. In the above-described embodiments, the diameter of the piercing hole  30   h  formed on the drum head  30  is 0.5 mm to 3 mm; however, it may be 3 mm or more when the film material composing the drum head is strong enough. Moreover, each layer of the drum head may be adhered to others by using a weak adhesive. 
   Further, as shown in  FIG. 4 , a donut-shaped (ring-shaped) film  45  may be adhered to the reverse side of the surface of the drum head  30  according to the above-described embodiments, and piercing holes piercing this film and the drum head  30  may be opened. Moreover, the donut-shaped film that is adhered to the drum head  30  may be formed of a lamination of a plurality of films other than the single layer. Moreover, density (the number of the piercing holes per unit area) of the piercing holes in the center part of the drum head may be sparse, and density of the piercing holes in an outer rim (periphery) of the drum head  30  may be dense. According to these structures, a high-level vibration mode having many vibration loops in the outer rim of the drum head  30  decreases, and the vibration around the drum head  30  is suppressed so as to increase silencing ability in high frequencies. Moreover, the diameter of the piercing holes  30   h  in the center part of the drum head and the diameter of the piercing holes  30   h  in the outer rim part (periphery) of the drum head  30  may be different. 
   In the above-described second embodiment, the shape of the cushion part  40  is a sphere or a mostly sphere; however, it is not limited to that. For example, as shown in  FIG. 5 , bottoms of two cushion parts of circular cones (or cushion parts shaped in a polygonal pyramid such as a triangular pyramid and a rectangular pyramid) may be stuck for using them as the cushion part  40 . In this case, the cushion parts are placed between the drum head  30  and the shock sensor  41  in order to a one top of the stuck circular cone (polygonal pyramid) contacts with the drum head  30  and another top of the circular cone (polygonal pyramid) contacts with the shock sensor  41 . Moreover, in the above-described second embodiment, the cushion part  40  is placed between the drum head  30  and the shock sensor  41 ; however, the cushion part  40  may be adhered to the drum head  30 , and the cushion part  40  may be pushed with the shock sensor  41  to place the cushion part  40  between the drum head  30  and the shock sensor  41 . 
   In the above-described second embodiment, the shock absorbers  43 - 1  to  43 - 3  are equipped with the springs and dampers inside the absorbers; however, the structure not to transmit vibration and shock from the body part  10  to the shock sensor  41  is not limited to that. For example, only the spring may be used for absorbing vibration and shock from the body part  10 , and an elastic material other than a spring may be used for absorbing the vibration and the shock. The number of the shock absorbers is not limited to three but may be four or more. The shock absorbers may be equipped in any numbers anywhere unless the shock absorbers can be stably supported by the pedestal part. 
   Although in the embodiments of the present invention, the drum head is made of laminating the plurality of the films, the drum head may be a single film. Moreover, the piercing holes  30   h  may not be formed on the drum head  30 . 
   Moreover, the structure for detecting stroke on the drum head is not limited to the above-described structure. Further, vibration of the drum head  30  may be detected by the vibration sensor, and the beat sound may be output from the musical tone generator based on the detected vibration.