Patent Grant
7247976
1. Field of the Invention
The present invention relates to a piezoelectric vibrator used in an acoustic transducing electronic appliance (such as an enclosure vibration type flat speaker or receiver) or in a vibration transducing electronic appliance such as a vibrator. More particularly, the invention relates to a piezoelectric vibrator having improvements in shock resistance, mountability, and reliability.
2. Description of the Related Art
Piezoelectric vibrators utilizing piezoelectric elements are widely employed as simple electro-acoustic transducers and actuators. Especially, in recent years, they are often used in the field of mobile phones, personal digital assistants, and so on. A conventional piezoelectric vibrator (e.g., Japanese Patent Laid-open No. 2000-224696-, especially
In another actuator, plural piezoelectric vibrating plates having different resonant frequencies are used to produce a distribution mode. For example, International Publication WO 01/54450, especially
Lead wires 222 and 228 are connected to the electrodes of the piezoelectric vibrating plates 206 and 212 and the vibrating plates 208, 214 by a conductive paste or by solder 218, 220, 224, 226, for example. An electrical signal is applied via the lead wires 222 and 228, so that the piezoelectric vibrating plates 206 and 212 vibrate. The vibration is transmitted to the pillar 204. The vibration is further transmitted via the pillar 204 to the acoustic panel 202 to which the piezoelectric vibrating body 201 is fixed. Consequently, the acoustic panel 202 vibrates, producing sound. However, the conventional device described so far has the following problems.
(1) When an impact load is applied to the piezoelectric vibrating body, an excessive stress is applied to the piezoelectric vibrating plates. This may destroy the piezoelectric elements made of a fragile material, or they may come off the pillar or the vibrating plates may bend. In this way, structural damage occurs. In addition, a pyroelectric effect produces an electromotive force. Concomitantly with this, there arises the danger that the circuit is affected. Furthermore, where plural piezoelectric vibrating plates are used, contact between any piezoelectric vibrating plate and its enclosure leads to destruction of the piezoelectric elements. Further, collision between the piezoelectric vibrating plates destroys the piezoelectric elements.
(2) Where plural piezoelectric vibrating plates are used, mounting methods including an electrical connection method such as soldering using cotton threads, bonding of the piezoeletric vibrating plates to the pillar, and mounting of the pillar and electrical connector terminals are complicated. This deteriorates the productivity and increases the cost of production.
In view of the foregoing, in an embodiment, an object of the present invention is to provide a piezoelectric vibrator having excellent shock resistance. Another object is to provide improved mountability and reliability of piezoelectric vibrating plates.
To achieve at least one of the above objects, in an embodiment, the present invention provides a piezoelectric vibrator having at least one piezoelectric vibrating plate made of a piezoelectric element on which electrodes are formed, the vibrating plate being supported to an enclosure so as to be vibratable. This piezoelectric vibrator is characterizable in that it has support means mounted around the center of the piezoelectric vibrating plate and amplitude limitation means mounted between the piezoelectric vibrating plate and one of the main surfaces of the enclosure. The support means may support the piezoelectric vibrating plate nearly or substantially parallel to this main surface. The thickness of the amplitude limitation means may be less than a distance between the piezoelectric vibrating plate and the main surface to effectively prevent contact between the piezoelectric vibrating plate and the main surface. In a preferred embodiment, the at least one piezoelectric vibrating plate is plural in number. These vibrating plates may be supported by the support means so as to be nearly or substantially parallel to each other. The amplitude limitation means may be mounted between the plural piezoelectric vibrating plates to prevent contact between the piezoelectric vibrating plates. Preferably, Young's modulus of the amplitude limitation means may be less than 2 GPa.
The foregoing and other objects, features, and advantages of the invention will become apparent from the following detailed description and accompanying drawings.
According to various embodiments of the present invention, one or more of the following advantages (including each advantage described within each section) can be obtained.
(1) When the amplitude limitation means are mounted between one main surface of the enclosure and each piezoelectric vibrating plate and between the plural piezoelectric vibrating plates, large amplitudes are suppressed. Stress applied to the piezoelectric elements can be mitigated. Damage can be prevented. Furthermore, the shock resistance can be improved because damage due to collision between the plural piezoelectric vibrating plates and due to collision between each piezoelectric vibrating plate and the enclosure can be prevented.
(2) When the space between one main surface of the enclosure and each piezoelectric vibrating plate and the space between the plural piezoelectric vibrating plates are filled with acceleration suppression means, vibration is transmitted via the acceleration suppression means. Therefore, displacement having a sharp rising edge can be suppressed. Generation of load inducing destruction of the piezoelectric elements can be suppressed.
(3) When both ends of each piezoelectric vibrating plate are fixed with pillars and supported so as to be nearly or substantially parallel to the main surface of the enclosure, the generated displacement can be suppressed as compared with a cantilevered structure in which the piezoelectric vibrating plate is supported only around its center. Hence, destruction of the piezoelectric elements can be prevented.
(4) When the piezoelectric vibrating plates fitted with positioning means are incorporated in the enclosure having the pillars therein, positioning can be performed with greater ease. The plural piezoelectric vibrating plates can be supported by members fitted with connector terminals. In consequence, mounting including electrical connection can be facilitated. Furthermore, the case structure permits easy handling. It is not necessary to take account of the effects on the surroundings of the mounted parts. Also, the piezoelectric vibrating plates do not come off the pillar. In addition, when acceleration suppression means is sealed in the enclosure, rapid deformation acceleration of the piezoelectric vibrating plates can be suppressed. The shock resistance can be improved. At the same time, electromotive force due to deformation can also be reduced.
(5) The piezoelectric vibrating plates provided with the positioning means may be incorporated in the enclosure incorporating the pillar. The plural piezoelectric vibrating plates may be supported by the members fitted with the connector terminals. Slopes for suppressing the restriction to the piezoelectric vibrating plates are provided. Therefore, bending of the vibrating plates and cracks in the piezoelectric bodies can be prevented. The shock resistance can be improved.
In all of the foregoing embodiments, any element used in an embodiment can interchangeably be used in another embodiment, and any combination of elements can be applied in the embodiments, unless it is not feasible.
For purposes of summarizing the invention and the advantages achieved over the related art, certain objects and advantages of the invention have been described above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.
These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention.
As explained above, the present invention can be accomplished in various ways including, but not limited to, the foregoing embodiments. The present invention will be explained in detail with reference to the drawings, but the present invention should not be limited thereto.
The best mode for carrying out the present invention is hereinafter described in detail based on its some embodiments. These embodiments are preferred embodiments and do not intend to restrict the present invention, and elements described in each embodiment can interchangeably be used in another embodiment unless application is not feasible.
Embodiment 1 of the present invention is first described with reference to
As shown in the figures, a piezoelectric vibrator 10 of the present embodiment has substantially rectangular piezoelectric vibrating plates 16 and 24. Nearly central portions of the plates 16 and 24 are mounted to one main surface of the enclosure or case 12 of a mobile phone or the like by pillars 14A and 14B so as to be substantially parallel to the enclosure 12. The piezoelectric vibrating plates 16, 24 and pillars 14A, 14B are stacked in the following order enclosure 12, pillar 14A, piezoelectric vibrating plate 24, pillar 14B, and piezoelectric vibrating plate 16. They are fastened with adhesive or the like. This lamination may be held from above with a machine screw or with a screw. The pillars 14A and 14B are made of an iron-based alloy such as stainless steel, a copper-based alloy such as brass, or a hard resin such as polycarbonate. The material is not limited to these examples. Rather, various well-known materials can be used.
The piezoelectric vibrating plate 16 is a bimorph structure fabricated by bonding piezoelectric elements (piezoelectric ceramics) 20 and 22 on the front and rear surfaces of a substantially rectangular vibrating plate 18. The piezoelectric elements 20 and 22 are substantially identical in dimensions with the vibrating plate 18 and polarized in the direction of thickness. Each of the piezoelectric elements 20 and 22 consists of a piezoelectric body having driving electrode layers (not shown) formed on its front and rear surfaces. The other piezoelectric vibrating plate 24 is similar in structure and has piezoelectric elements 28 and 30 bonded to the front and rear surfaces of the vibrating plate 26, thus forming a bimorph structure. Also, with respect to the piezoelectric elements 28 and 30, electrode layers (not shown) are formed on the front and rear surfaces of each element. For example, 42 alloy, brass, or the like is used as the vibrating plates 18 and 26. For instance, PZT (lead zirconate titanate) or the like is used as the piezoelectric bodies of the piezoelectric elements 20 and 22. Silver, platinum, or palladium, for example, is used as the electrode layers.
A voltage is applied to each of the upper and lower electrodes of the piezoelectric element 20 and across the upper and lower electrodes of the piezoelectric element 22 to induce a polarization in each of the piezoelectric bodies of the piezoelectric elements 20 and 22. The piezoelectric elements 20 and 22 polarized in this way are bonded to the vibrating plate 18 using a conductive adhesive, for example. Consequently, the piezoelectric vibrating plate 16 is obtained. In the present embodiment, the lower electrode of the piezoelectric element 20, upper electrode of the piezoelectric element 22, and vibrating plate 18 are at a common potential and grounded if necessary.
Furthermore, in the present embodiment, spacers 34A and 34B are mounted on both end portions 24A and 24B of the piezoelectric vibrating plate 24. Other spacers 32A and 32B are mounted on the main surface of the enclosure 12 and in positions opposite to the spacers 34A and 34B. These spacers 32A, 32B, 34A, and 34B act to forcibly suppress the amplitude to prevent the piezoelectric vibrating plates 16 and 24 from exhibiting large amplitudes exceeding a designed range. The spacers are made of a soft material having a Young's modulus of less than 2 GPa. Any material may be used as the material of the spacers 32A, 32B, 34A, 34B as long as the Young's modulus is satisfied. For example, a bulk material such as polyethylene, polypropylene, nylon, or synthetic rubber or a material whose rigidity has been substantially deteriorated by foaming a hard resin such as polystyrene, or melanin resin, can be used.
The operation of the present embodiment is next described. The piezoelectric vibrating plates 16 and 24 of the aforementioned bimorph structure act as general piezoelectric bimorphs and vibrate. That is, in the piezoelectric vibrating plate 16, because of the direction of polarization of the polarizing bodies of the piezoelectric elements 20 and 22 and because of the relation of the outer electrode voltage to the vibrating plate 18 acting as a central electrode, if one piezoelectric element elongates in the longitudinal direction, the other piezoelectric element shrinks in the longitudinal direction. Consequently, the vibrating plate is flexed and displaced in the up-and-down direction in the figure. Similar principle applies to the piezoelectric vibrating plate 24. The piezoelectric vibrating plates 16 and 24 are set to different lengths such that the gain of the whole vibrator shows a flat frequency characteristic.
In this case, in the present embodiment, spacers 32A and 32B are mounted between the main surface of the enclosure 12 and piezoelectric vibrating plate 24. Also, spacers 34A and 34B are mounted between the piezoelectric vibrating plates 16 and 24. Therefore, excessive amplitudes can be suppressed by presetting the sizes and installation positions of the spacers 32A, 32B, 34A, and 34B to prevent the piezoelectric vibrating plates 16 and 24 from showing amplitudes exceeding designed ranges.
As described so far, according to the present embodiment, the spacers made of a soft material having a Young's modulus of less than 2 GPa are mounted between the enclosure 12 and piezoelectric vibrating plate 24 and between the piezoelectric vibrating plates 24 and 26. Therefore, excessive amplitudes can be suppressed without varying the resonant frequencies of the piezoelectric vibrating plates 16 and 24 so much. Stress applied to the piezoelectric elements 20, 22, 28, and 30 is mitigated. Their destruction is prevented. Furthermore, damage due to contact between the piezoelectric vibrating plate 24 and enclosure 12 or between the piezoelectric vibrating plates 16 and 24 can be prevented. The shock resistance is improved. In consequence, the reliability is improved.
Embodiment 2 of the present invention is next described with reference to
As shown in
According to the present embodiment, vibration of the piezoelectric vibrating plates 16 and 24 is transmitted to the enclosure 12 via the resilient material 42 that has a quite small modulus of elasticity and a large volume modulus of elasticity. Therefore, vibration in a relatively low frequency range such as the audible range is attenuated only a little. With respect to a displacement having a sharp and large rising edge such as an impact displacement, the acceleration of the displacement can be suppressed. The same advantages as those of the above-described embodiment can be obtained. The spaces may be totally filled with the resilient material 42 or the spaces may be partially filled with it. Where the spaces are partially filled, the assembly workability improves. Furthermore, where the spaces are totally filled, the acceleration-suppressing effect can be obtained stably without being affected by the posture of the piezoelectric vibrator.
Embodiment 3 of the present invention is next described with reference to
As shown in
The pillars 52 and 54 may be made of a homogeneous material (e.g., a material with high rigidity having a Young's modulus of more than 100 GPa) such that vibrations of the piezoelectric vibrating plates 16 and 24 are transmitted from both pillars equally. Alternatively, one pillar (e.g., 52) may be made of a material having a rigidity that is more than 10 times as high as that of the other pillar (e.g., 54). Vibrations of the piezoelectric vibrating plates 16 and 24 may be transmitted from the pillar having the higher rigidity (52 in this case). In this case, a metal having a Young's modulus (e.g., iron-based material such as stainless) of more than 100 GPa can be used as the pillar material having the higher rigidity. A resinous material having a Young's modulus (e.g., PET or nylon) of less than 10 GPa can be used as the material having the lower rigidity. According to the present embodiment, both ends of the piezoelectric vibrating plates 16 and 24 are supported by the pillars 52 and 54 and so even in a case where an impact load is applied, the produced displacement can be suppressed compared with the cantilevered type as in the background art. Accordingly, destruction of the piezoelectric elements can be prevented. Also, undesired large displacements can be suppressed without varying the resonant frequencies so much.
The above-described Embodiments 1 to 3 are next described by quoting specific examples. Specific Examples 1-4 and Comparative Examples 1-3 were fabricated as described below. Comparative tests were performed according to a method described below.
The structure was the same as that of Embodiment 1. Nylon having a Young's modulus of 1.2 GPa was used as the spacers. Stainless was used as the pillars.
This was similar in structure with the piezoelectric vibrator 60 shown in
This was similar in structure with Embodiment 1. Hard nylon having a Young's modulus of 3 GPa was used as the spacers. Stainless was used as the pillars.
This was similar in structure with Embodiment 2. A silicone gel having a Young's modulus of 60 MPa and a Poisson's ratio of 0.47 was used as the resilient material. Stainless was used as the pillars.
This was similar in structure with Embodiment 2. A resilient rubber having a Young's modulus of 400 MPa and a Poisson's ratio of 0.4 was used as the resilient material (filling material). Stainless steel was used as the pillars.
This was similar in structure with Embodiment 3. Stainless steel having a Young's modulus of 200 GPa was used as both pillars.
This was similar in structure with Embodiment 3. A stainless steel having a Young's modulus of 200 GPa was used as one pillar, while a hard nylon having a Young's modulus of 3 GPa was used as the other pillar.
In the manufacture of the above-described Specific Examples and Comparative Examples, each piezoelectric vibrating plate had a length of 40 mm and a width of 7 mm. The thickness of each metallic vibrating portion was 0.04 mm. The thickness of each piezoelectric element was 0.1 mm. Two of such elements were used to construct a bimorph structure. The distance between the piezoelectric vibrating plates 16 and 24 and the distance between the vibrating plate 24 and the main surface of the enclosure 12 were set to 1 mm.
Piezoelectric vibrators of Comparative Examples 1-3 and Specific Examples 1-4 fabricated in this way were mounted to an ABS resin enclosure 12 having dimensions of 50 mm×50 mm and a thickness of 1.5 mm. An AC voltage of 3 V rms was applied. The frequency characteristics of the produced sound were measured. At this time, the distance from the enclosure 12 to a microphone for measurement was set to 10 cm. To check the shock resistance, a shock load of 3000 G was applied using an impact testing machine. After the test, the piezoelectric elements were observed to check whether there were cracks. The results of the test are shown in the following Table 1.
Comparison of the results shown in Table 1 reveals that in Comparative Example 1 having no countermeasures against impact, application of an impact load produced cracks. Specific Examples 1-4 having a countermeasure against impact are similar with Comparative Example 1 in resonant frequency and sound pressure. However, generation of cracks was not observed. It can be recognized from these results that the means of this embodiment, i.e., insertion of the spacers, filling with the resilient material, and support of each piezoelectric vibrating plate at both ends, are effective in improving the impact resistance.
In Comparative Example 2, the Young's modulus of the spacers was more than 2 GPa, unlike in Specific Example 1. In Comparative Example 2, the sound quality did not vary but the vibrating plates collided against the spacers, producing cracks. Similarly, in Comparative Example 3 where the Young's modulus of the filler was more than 100 MPa and the Poisson's ratio was less than 0.45 unlike in Specific Example 2, the displacement-suppressing effect was too strong that production of cracks due to excessive displacements did not take place. However, even under normal operating conditions, the displacement was suppressed. The first-order resonant frequency was as high as 800 Hz. The sound pressure decreased to 60 dB. It can be seen from the results given so far that it is important that the Young's modulus of the spacers, the Young's modulus of the filling resilient material, and the Poisson's ratio be within their respective appropriate ranges given in the Specific Examples above.
Embodiment 4 of the present invention is next described with reference to
Firstly, the case 71 is so designed that it can be split into a lower case 72 and an upper case 78 as mentioned previously. The pillar 74 in contact with the piezoelectric vibrating plate 84 is previously incorporated around the center of the bottom surface 72A of the lower case 72. The pillar 74 is shaped like a triangular pole of substantially triangular cross section that is sharpened toward the piezoelectric vibrating plate 84 not to hinder the vibration of the piezoelectric vibrating plate 84. In the illustrated embodiment, the cross section is substantially triangular. The cross-sectional shape may be trapezoidal or semicircular if it does not hinder the vibration of the piezoelectric vibrating plate 84. A receiver portion 76 for receiving protruding portions 86A and 91 mounted to the piezoelectric vibrating plate 84 is formed at the upper end of a substantially central portion of the side surface 72B of the lower case 72. The upper case 78 is constructed similarly. The pillar 80 is mounted on the upper surface 78A. A receiver portion 82 for receiving protruding portions 94A and 99 mounted to the piezoelectric vibrating plate 92 is formed at the lower end of a substantially central portion of the side surface 78B.
The case 71 is molded from a metal-based material such as stainless steel or a resinous material such as PET or ABS. In the illustrated embodiment, the piezoelectric vibrating plates 84 and 92 are sandwiched from above and below. They may also be sandwiched from left and right. A cover may be placed on one of the top and bottom sides or on one of the left and right sides.
Then, as shown in
The fringes of the piezoelectric vibrating plate 84 are sandwiched between the insulating film 89 and conductive tape 90 from up and down. The film and tape are mounted such that their overlapping portions extend outwardly. The extending protruding portion 91 is anchored to the receiver portion 76 of the lower case 72 and forms pullout portions of the upper electrode layer 88A of the piezoelectric element 88 and lower electrode layer 87C of the piezoelectric element 87. If the piezoelectric vibrating plate 84 of the construction described so far is lowered from above the lower case 72 in such a way that the protruding portions 86A and 91 are fitted over the receiver portion 76, the piezoelectric vibrating plate 84 can be fastened substantially parallel at a preset height position within the lower case 71.
Similarly, with respect to the other piezoelectric vibrating plate 92, as shown in
The support rod 100 positioned between the piezoelectric vibrating plates 84 and 92 is next described. The support rod 100 is a rodlike body of substantially rectangular cross section. Connector terminals 104A and 104B for making electrical connection with the electrode layers of the piezoelectric vibrating plates 84 and 92 are mounted on both ends of the body 102. The connector terminals 104A and 104B are fabricated by applying a conductive adhesive such as silver or copper, for example. Furthermore, electrical connection between the piezoelectric vibrating plates 84 and 92 can be made by using a spring of phosphor bronze plated with gold or otherwise processed instead of the support rod 100 and by bringing the spring into contact. That is, if the piezoelectric vibrating plate 84, support rod 100, and piezoelectric vibrating plate 92 are superimposed, the protruding portions 86A and 94A of the piezoelectric vibrating plates 84 and 92 make electrical connection with the connector terminal 104A of the support rod 100. The other protruding portions 91 and 99 are connected with the connector terminal 104B. Thus, the electrodes of the piezoelectric elements 86 and 92 on both surfaces can be electrically conducted.
As shown in
In this way, according to the present embodiment, one or more of the following advantages (including each advantage described within each section) are obtained.
(1) Since the piezoelectric vibrating plates 84 and 92 having the protruding portions 86A, 91, 94A, and 99 acting also as positioning and electrode pullout portions are entered in the case 71 incorporating the pillars 74 and 80, the mounting is facilitated. Positioning of the piezoelectric vibrating plates 84 and 92 can be easily performed. In addition, the mounting is facilitated from a viewpoint of electrical connection, because the piezoelectric vibrating plates 84 and 92 are supported by the support rod 100 provided with the connector terminals 104A and 104B.
(2) The case structure permits easy handling. It is not necessary to take account of the effects on the surroundings of the mounted parts by the exposure of the piezoelectric vibrating plates 84 and 92. Furthermore, the sealed structure of the case 71 prevents the piezoelectric vibrating plates 84 and 92 from coming off the pillars 74 and 80. This further facilitates mounting. Also, a cost reduction can be expected.
(3) Since the viscous liquid 108 is sealed in the case 71, if excessive stress is applied to the piezoelectric vibrating plates 84 and 92, quick deformation acceleration of the piezoelectric vibrating plates 84 and 92 is suppressed. This prevents bending of the vibrating plates and cracks in the piezoelectric bodies. The shock resistance can be improved. At the same time, electromotive force due to deformation can be reduced. Additionally, improvement of the shock resistance permits the vibrator to be adopted in a mobile appliance that requires durability.
Embodiment 5 of the present invention is next described with reference to
As shown in
In this way, according to the present embodiment, local excessive deformation of the piezoelectric vibrating plates 84 and 92 are suppressed because the slopes 122A-126A and 122B-126B are formed. The same advantages are obtained as those of the Embodiment 4. In addition, the shock resistance can be improved further by fabricating the slopes 122A-126A and 122B-126B from a resinous material such as PET or ABS or from a resilient material such as foamed rubber.
Embodiment 6 of the present invention is next described with reference to
The present invention is not limited to the above embodiments. Various changes can be made within a scope not deviating from the gist of the present invention. For example, the following are also included.
(1) The materials, shapes, and dimensions shown in the above embodiments merely give examples. The design can be modified so as to produce similar operation. The structure of each piezoelectric vibrating plate may be either the unimorph or bimorph structure. Furthermore, the piezoelectric element itself may be a laminate structure in which piezoelectric layers and electrode layers are alternately stacked. The number of the stacked layers, the connection pattern of the internal electrodes, the pullout structure, and so on may be appropriately modified according to the need. Moreover, in the above aspect, two piezoelectric vibrating plates are used. More piezoelectric vibrating plates may be used. A structure including only one piezoelectric vibrating plate may be adopted. The number may be appropriately increased or reduced according to the circumstances. Additionally, the above embodiments may be combined. For example, the inside of the case of Embodiment 5 or Embodiment 6 is filled with the viscous liquid shown in Embodiment 4.
(2) The shape of the spacers shown in the above Embodiment 1 gives an example. The shape may be appropriately modified to produce similar advantages. For example, the slope shape shown in Embodiments 5 and 6 is adopted. Furthermore, in the above Embodiment 1, the spacers are mounted on the main surface of the enclosure 12 and on the piezoelectric vibrating plate 24. Their positions may be appropriately changed to produce similar advantages. For example, in a piezoelectric vibrator 140 shown in
Furthermore, as in a piezoelectric vibrator 160 shown in
(3) Preferred examples of application of the present invention include speakers of various electronic appliances such as mobile phone, personal digital assistant (PDA), voice recorder, and personal computer. Besides, the invention may be applied to various applications including actuators.
According to the present invention, the shock resistance of the piezoelectric vibrating plate is improved in some embodiments so that the invention can preferably be applied to an appliance or device to which an impact is applied when dropped such as a mobile phone.
It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-279478 | Jul 2003 | JP | national |
This is a divisional of U.S. patent application Ser. No. 10/897,588, filed Jul. 23, 2004, which claims foreign priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2003-279478, filed Jul. 24, 2003, and the disclosure of which is herein incorporated by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4045695 | Itagaki et al. | Aug 1977 | A |
| 4430529 | Nakagawa et al. | Feb 1984 | A |
| 4453044 | Murphy | Jun 1984 | A |
| 6865277 | Bank et al. | Mar 2005 | B2 |
| 20030053642 | Bank et al. | Mar 2003 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 574 297 | Sep 2005 | EP |
| 2000-134682 | May 2000 | JP |
| 2000-224696 | Aug 2000 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20070013270 A1 | Jan 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10897588 | Jul 2004 | US |
| Child | 11533245 | US |
