Abstract:
A ventilated insole including a pad ( 10 ) having a bladder ( 20 ), an air entry ( 30 ), an air exit ( 40 ), an entry conduit ( 50 ) interconnecting the air entry ( 30 ) and the bladder ( 20 ), an exit conduit ( 60 ) interconnecting the bladder ( 20 ) and the air exit ( 40 ), and two one-way valves ( 70 ) wherein one one-way valve ( 70 ) is at a joining portion of the bladder ( 20 ) and the entry conduit ( 50 ) and the other one-way valve ( 70 ) is at a joining portion of the bladder ( 20 ) and the exit conduit ( 60 ). Each of the entry conduit ( 50 ) and the exit conduit ( 60 ) has a triangular section so as to increase resistance, thereby facilitating air flow in the entry conduit ( 50 ) and the exit conduit ( 60 ) and planarizing the pad ( 10 ). The insole can be disposed in one of a variety of shoes and brings a degree of comfort to wearer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to shoe soles and more particularly to a planarized ventilated insole including a plurality of conduits each having a triangular section so that fresh air can be introduced into the insole during walking for comforting and drying the footbed of a wearer. 
         [0003]    2. Description of Related Art 
         [0004]    Sole of a shoe is provided for wear resistant and cushioning purposes during walking. Further, comfort, shock absorbing capability and ventilation are a shoe sole are needed to consider in the devising stage. 
         [0005]    Ventilation of most typical ventilated insoles is achieved by cooperating with other layers of a sole or being integrally formed therewith. For example, Taiwan Utility model No. 180,846 entitled “Removable ventilated insole” discloses an internal bladder, a one-way entry valve, and a one-way exit valve. The entry and exit valves are removably provided at one side of the bladder for communicating air with the exterior of a shoe. The bladder and adjacent valves are removably disposed in a cavity at a front portion of the sole. Taiwan Utility model No. M312,209 entitled “Unitary ventilated insole” discloses a projection on a heel, the projection including a hollow cylinder having a central stem as support and a plurality of entry and exit troughs on a periphery communicating with the hollow cylinder. However, a wearer cannot replace the ventilated insole when it is worn due to its unitary characteristics. Further, it is useless when it is removed. This can adversely decrease the applicability of the ventilated insole and thus decrease consumer&#39;s selections. 
         [0006]    For allowing consumers to replace a worn ventilated insole by themselves, a number of removable ventilated insoles have been devised. For example, Taiwan Publication No. 200624048, entitled “ventilated insole” discloses a main layer, a spacer layer, a first and a second one-way valve, and a bladder. The bladder communicates with the aperture. The first one-way valve is between the main layer and the spacer layer for introducing external air into the bladder. The second one-way valve is between the main layer and the spacer layer for exiting smell air from the aperture to the atmosphere. However, it is disadvantageous because the bladder is too large to sufficiently suck air or purge air. As a result, air in the bladder is still rather than being expelled or refreshed by external air. The ventilation effect is very poor. 
         [0007]    Among prior art literature, a number of patents regarding ventilated insole which allow users to replace the worn insole and have conduits for purging air are disclosed. For example, Taiwan Utility Model No. 515,243, entitled “removable ventilated insole” discloses a pad, a bladder, at least one entry conduit, a first one-way valve in the entry conduit, at least one exit conduit, and a second one-way valve in the exit conduit. The bladder is in the heel of the pad and is comprised of internal elastic members of springs. Entry and exit are provided on the bladder and connected to the entry and exit conduits respectively. The footbed intermittently presses bladder during walking so as to introduce fresh air into the bladder through the entry conduit and exit smell air from the bladder to the atmosphere through the exit conduit. However, a number of drawbacks have been found in the removable ventilated insole having entry and exit conduits as detailed below. 
         [0008]    1. The entry and exit conduits are liable to block because if they are made of flexible material. 
         [0009]    2. A wearer may have a feeling of pain because something hard touches his/her footbed during walking if the entry and exit conduits are made of hard material. 
         [0010]    3. The exposed bladder is liable to wear and thus an uneven surface is formed on the outsole. To the worse, the wearer may slip during walking due to decreased friction. 
         [0011]    4. The single conduit arrangement can purge air to the front of the footbed, thereby limiting air flow in a single path between two specific toes. 
         [0012]    5. The exposed bladder can be blocked by foreign objects if it is worn. Further, the wearer may have a feeling of uncomfortable when the footbed touches the curved one-way valve. 
         [0013]    6. The elastic members of springs inside the bladder may hurt the foot during walking after aging. In view of above problems including being no provision of planarized ventilated insole and unsuccessful commercialization experienced by the prior art, the inventor thus devises a novel ventilated insole by eliminating the prior problems. The ventilated insole of the invention is thin, simple, easy to manufacture, durable, comfort during walking, and appropriate for mass production. 
       SUMMARY OF THE INVENTION 
       [0014]    It is therefore one object of the invention to provide a planarized ventilated insole for carrying out forced ventilation through the shoe during walking. Further, the insole can be disposed in one of a variety of shoes and brings a degree of comfort and dryness to the foot of a wearer. 
         [0015]    In a first aspect of the invention, there is provided a planarized ventilated insole comprising a pad comprising an upper member and a lower member secured to the upper member; a bladder disposed in the pad; an air entry disposed in the pad; an air exit disposed in the pad; an entry conduit disposed in the pad for interconnecting the air entry and the bladder; at least one exit conduit disposed in the pad for interconnecting the bladder and the air exit; and two one-way valves wherein one one-way valve is disposed at a joining portion of the bladder and the entry conduit and the other one-way valve is disposed at a joining portion of the bladder and the at least one exit conduit; wherein the lower member covers both the entry conduit and the at least one exit conduit from below; wherein the upper member comprises an upper opening with an upward arched upper half of the bladder fastened therein; wherein the lower member comprises a lower opening with a downward arched lower half of the bladder fastened therein; and wherein each of the entry conduit and the at least one exit conduit has a triangular section so as to increase resistance to external force, thereby facilitating air flow in the entry conduit and the at least one exit conduit and planarizing the pad. 
         [0016]    Preferably, thickness of the pad externally of the bladder is in the range of about 2 cm to 5 cm. 
         [0017]    Preferably, further comprises a plurality of equally spaced ribs radially extending from a center of the bladder to a periphery thereof wherein each of the ribs has a longitudinal section of half circle having an area gradually increased from a first end at the center of the bladder to a second end at the periphery of the bladder. 
         [0018]    Preferably, further comprises a lengthwise arched ridge disposed in the entry conduit and a lengthwise arched ridge disposed in the exit conduit respectively. 
         [0019]    Preferably, the air exit comprises a transverse exit groove under the pad and connecting to the exit conduit, and a plurality of exit apertures in the exit groove through the upper member, and wherein the air entry is concave on a rear end of the pad. 
         [0020]    Preferably, each of the exit apertures comprises an arched top. 
         [0021]    Preferably, the bladder comprises two channels at an edge, each channel having one of the one-way valves disposed therein and including a well; wherein each of the one-way valves comprises a divider plate including a through hole, and a flap including a hinge secured to the divider plate; and wherein the flap is vertical to close the through hole when no force is exerted on the bladder. 
         [0022]    Preferably, the bladder comprises two tunnels each having an oval longitudinal section for disposing one of the one-way valves therein; wherein each of the one-way valves comprises an outer sleeve including a lengthwise slit on an outer surface and having a first end open to the bladder and a second end formed with a through hole, an inner sleeve of an oval longitudinal section, the inner sleeve including a lengthwise ridge on an outer surface, the ridge being inserted into the slit for assembling the outer and inner sleeves, and a flap pivotably secured to a first end of the inner sleeve, the flap being vertical to close the through hole when no force is exerted on the bladder. 
         [0023]    In a second aspect of the invention, there is provided a planarized ventilated insole comprising a pad; an air entry disposed in the pad; and an air exit disposed in the pad; wherein the pad comprises an upper member, an upward arched upper element integrally formed with the upper member, a lower member secured to the upper member, and a downward arched lower element integrally formed with the lower member wherein the upper and lower elements are attached together to form a bladder. 
         [0024]    Preferably, further comprises a plurality of spaced ribs radially extending from a center of the upper element to a periphery thereof, each of the ribs being of a longitudinal section of half circle and having an area gradually increased from a first end at the center of the upper element to a second other end at the periphery thereof; and a plurality of spaced ribs radially extending from a center of the lower element to a periphery thereof, each of the ribs being of a longitudinal section of half circle and having an area gradually increased from a first end at the center of the lower element to a second other end at the periphery thereof. 
         [0025]    By utilizing the invention, the following advantages can be obtained: 
         [0026]    1. No conducts are required to mount in the insole. Thickness of the pad externally of the bladder is planarized to be in the range of about 2 cm to 5 cm. A wearer may not have a feeling of pain because something hard touches his/her footbed during walking. Wearer can feel a degree of comfort during walking. 
         [0027]    2. With the triangular sections of the entry conduit interconnecting the air entry and the bladder and the exit conduit interconnecting the bladder and the air exit rather than the typical circular section, pointed tops of the exit conduit and the entry conduit have are not liable to become flat or block when pressure is built thereon during walking. Further, the pad can be made thinner with decreased thickness. As a result, a wearer may feel a degree of comfort when wearing shoes incorporating the ventilated insoles during walking. 
         [0028]    3. A plurality of equally spaced ribs radially extend from a center of the bladder to a periphery thereof wherein each of the ribs has a longitudinal section of half circle having an area gradually increased from a first end at the center of the bladder to a second end at the periphery of the bladder. As a result, the bladder is capable of quickly returning to its original shape after releasing pressure exerted thereon. 
         [0029]    4. The one-way valves are easy to manufacture, install, and replace and are durable. 
         [0030]    5. The one-way valves having an oval longitudinal section can decrease height (i.e., thickness) of the bladder to a minimum. In addition to correct positioning, it is an error-proof design to prevent an erroneous installation from occurring. 
         [0031]    6. The one-way valves are disposed in the bladder and thus a wearer may not have a feeling of pain due to projections contacting his/her footbed during walking. Further, locations of air entry and air exit are not interfered. For example, the air entry can be disposed in a rear end of the pad. This eliminates the need of mounting a valve in an opening on an outer surface of outsole as experienced by the typical ventilated insole. 
         [0032]    7. The air exit is provided under the pad corresponding to the toes at the front of the footbed. Thus, the exit apertures correspond to the gaps between the toes and each exit aperture has an arched top. As a result, the exit apertures are not liable to be flattened or blocked by applying force thereon. 
         [0033]    The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a perspective view of a ventilated insole according to a first preferred embodiment of the invention; 
           [0035]      FIG. 1A  is another perspective of the ventilated insole of  FIG. 1 ; 
           [0036]      FIG. 2  is an exploded view of the ventilated insole of  FIG. 1 ; 
           [0037]      FIG. 2X  a detailed view of a circle X of  FIG. 2  and  FIG. 2Y  a detailed view of a circle Y of  FIG. 2  respectively; 
           [0038]      FIG. 3  is a longitudinal sectional view of the air exit of  FIG. 1 ; 
           [0039]      FIG. 4  is a perspective view of the bladder of  FIG. 1 ; 
           [0040]      FIGS. 4A ,  4 B and  4 C are broken away perspective views showing steps of mounting the one-way valve in the bladder; 
           [0041]      FIG. 5  is a fragmentary perspective view of a ventilated insole according to a second preferred embodiment of the invention; 
           [0042]      FIG. 5A  is a detailed view of a circle of  FIG. 5 ; 
           [0043]      FIG. 6  is a longitudinal sectional view of  FIG. 5 ; 
           [0044]      FIG. 7  is a fragmentary view of  FIG. 6  showing air being introduced into the bladder with the bladder being expanded; 
           [0045]      FIG. 7A  is a detailed view of a circle of  FIG. 7 ; 
           [0046]      FIG. 8  is a view similar to  FIG. 7  showing air being expelled out of the bladder with the bladder being contracted after a result of pressing by the footbed; 
           [0047]      FIG. 8A  is a detailed view of a circle of  FIG. 8 ; 
           [0048]      FIG. 9  is an exploded view of the bladder of  FIG. 5 ; 
           [0049]      FIGS. 9A ,  9 B and  9 C are views showing the construction of the one-way valve of  FIG. 5A ; 
           [0050]      FIG. 10  is an exploded view of a ventilated insole according to a third preferred embodiment of the invention; 
           [0051]      FIG. 10A  is a detailed view of the left circle of  FIG. 10  showing entry conduit and 
           [0052]      FIG. 10B  is a detailed view of the right circle of  FIG. 10  showing exit conduit respectively; 
           [0053]      FIG. 11  is a fragmentary view of the heel portion of the ventilated insole of  FIG. 10  but viewing from the bottom; 
           [0054]      FIG. 11A  is an enlarged broken away view of the air entry of  FIG. 11 ; 
           [0055]      FIG. 12  is a side elevation of a shoe showing the ventilated insole of  FIG. 10  disposed therein; 
           [0056]      FIG. 13  is a top view of the ventilated insole of  FIG. 10  schematically showing the footbed thereon; 
           [0057]      FIG. 14  is a longitudinal sectional view of the air entry and adjacent components of  FIG. 11 ; 
           [0058]      FIG. 14A  is a view similar to  FIG. 14  showing a depressing thereof during walking; 
           [0059]      FIG. 15  is an exploded view of a ventilated insole according to a fourth preferred embodiment of the invention; 
           [0060]      FIG. 15A  is a fragmentary view of the left part of  FIG. 15  and  FIG. 15B  is a fragmentary view of the right part of  FIG. 15  respectively; and 
           [0061]      FIG. 16  is a longitudinal sectional view of the assembled ventilated insole of  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0062]    Referring to  FIGS. 1 to 4C , a ventilated insole in accordance with a first preferred embodiment of the invention is shown in which  FIG. 1  is a perspective view of a ventilated insole according to the first preferred embodiment of the invention,  FIG. 1A  is another perspective of the ventilated insole of  FIG. 1  and  FIG. 2  is an exploded view of the ventilated insole of  FIG. 1 . The ventilated insole comprises a pad  10 , a bladder  20  in the pad  10  proximate a heel portion, an air entry  30  on a rear end of the pad  10 , an air exit  40  in the pad  10  proximate a toe portion, an entry conduit  50  interconnecting the bladder  20  and the air entry  30 , and at least one exit conduit  60  (one being shown) interconnecting the bladder  20  and the air exit  40 . 
         [0063]    The pad  10  comprises an upper member  11  and a lower member  12  secured to the upper member  11 . Each of the entry conduit  50  and the exit conduit  60  has a triangular section (see  FIGS. 2X and 2Y ) and is disposed on the bottom of the upper member  11 . The lower member  12  is adapted to cover the entry conduit  50  and the exit conduit  60  from below. With the triangular sections of the entry conduit  50  and the exit conduit  60 , the entry conduit  50  and the exit conduit  60  have pointed tops which are not liable to become flat or block when pressure is built thereon during walking. Further, the pad  10  can be made thinner with decreased thickness. As a result, a wearer may feel a degree of comfort when wearing shoes incorporating the ventilated insoles during walking (see  FIG. 10 ). 
         [0064]    Thickness of the pad  10  externally of the bladder  20  is in the range of about 2 cm to 5 cm. 
         [0065]    The upper member  11  comprises an upper opening  111  with an upward arched upper half of the bladder  20  fitted therein, and a plurality of projections  112  on a top, the projections  112  being for massaging the footbed. The upper member  11  further comprises a plurality of protrusions  113  on a bottom, the protrusions  113  being for pressing acupuncture points on the footbed (see  FIG. 1A ). The lower member  12  comprises a lower opening  121  with a downward arched lower half of the bladder  20  fitted therein. The air entry  30  is on a rear end of the pad  10 . 
         [0066]    Refer to  FIG. 3  in conjunction with  FIG. 2  in which  FIG. 3  is a longitudinal sectional view of the air exit  40  of the first preferred embodiment of the invention. The air exit  40  comprises a transverse exit groove  41  connecting to the exit conduit  60  and being under the pad  10 , a plurality of exit apertures  42  in the exit groove  41  through the upper member  11 , each exit aperture  42  having an arched top  43 , and a plurality of half cylindrical pegs  44  on the edge of the exit groove  41 , the half cylindrical pegs  44  being projecting into the exit groove  41  for increasing the structural strength of the exit groove  41 . The exit conduit  60  is connected to the exit apertures  42 . 
         [0067]    Refer to  FIG. 4  and  FIGS. 4A to 4C  in conjunction with  FIG. 2  according to the first preferred embodiment of the invention in which  FIG. 4  is a perspective view of the bladder  20  of  FIG. 1 , and  FIGS. 4A ,  4 B and  4 C are broken away perspective views showing steps of mounting the one-way valve  70  in the bladder  20 . The bladder  20  is shaped as a flying soccer. One one-way valve  70  is on an edge of the bladder  20  communicating with the entry conduit  50 , and the other one-way valve  70  is on the edge of the bladder  20  opposite to the first one-way valve  70  and communicating with the exit conduit  60 . 
         [0068]    The bladder  20  comprises a channel  21  communicating with inside of the bladder  20  and the external thereof with each one-way valve  70  disposed therein, and a U-shape well  22  vertically disposed in the channel  21 . Each one-way valve  70  comprises a divider plate  71  and a flap  72  having a hinge  73  secured to the divider plate  71 . 
         [0069]    The divider plate  71  has a central through hole  711 . Both sides and bottom of the divider plate  71  is sealingly fastened in the well  22  so that fresh air can only communicate from the entry conduit  50  to the bladder  20  through the through hole  711  of one one-way valve  70  and foul air can only communicate from the bladder  20  to the exit conduit  60  through the through hole  711  of the other one-way valve  70 . The divider plate  71  and the flap  72  of each one-way valve  70  are formed integrally from the same material with the hinge  73  of the same material made thinner. 
         [0070]    The flap  72  is vertical to close one mouth of the through hole  711  due to gravity when the bladder  20  is not pressed. That is, fresh air can only communicate through the through hole  711  and the flap  72  of one one-way valve  70  to inside of the bladder  20  by pivotably pushing the flap  72  upward. In other words, air inside the bladder  20  is not allowed to exit by passing through the flap  72  and the through hole  711  of one one-way valve  70 . The divider plate  71  is shaped as trapezoid so as to prevent it from being incorrectly disposed in the complementarily shaped well  22  during installation. 
         [0071]    Further, a plurality of equally spaced ribs  23  radially extend from a center of the bladder  20  to a periphery thereof. The rib  23  has a longitudinal section of half circle having an area gradually increased from one end at the center of the bladder  20  to the other end at the periphery of the bladder  20 . Thus, in response to being flexibly depressed, the bladder  20  can be quickly returned to its original shape after the depressing force is released. 
         [0072]    The flap  72  of the other one-way valve  70  is at one end of the exit conduit  60 . Thus, air in the bladder  20  can only communicate through the through hole  711  and the flap  72  of the other one-way valve  70  to enter the exit conduit  60 . In other words, foul air in the bladder  20  can only communicate through the through hole  711  and the flap  72  of the other one-way valve  70  to enter the exit conduit  60  for exiting during walking. 
         [0073]    The flap  72  of one one-way valve  70  is provided between the divider plate  71  and inside of the bladder  20  so that air is only allowed to enter the bladder  20  by pivotably upward pushing the flap  72 . A partial vacuum is created in the bladder  20  when a person wearing the shoe incorporating the ventilated insole lifts his/her foot. Thus, fresh air is introduced into the bladder  20  via the air entry  30 , the entry conduit  50  and one one-way valve  70  and next foul air is purged out of the bladder  20  by leaving the other one-way valve  70 , the exit conduit  60  and the air exit  40  in response to the footbed of the wearer pressing the bladder  20 . 
         [0074]    Referring to  FIGS. 5 to 9C , a ventilated insole in accordance with a second preferred embodiment of the invention is shown. The characteristics of the second preferred embodiment are substantially the same as that of the first preferred embodiment except the following: The bladder  20  comprises two tunnels  24  each having an oval longitudinal section for disposing either one-way valve  70  therein. Either one-way valve  70  comprises an outer sleeve  74  having one end open to the bladder  20  and the other end formed with a through hole  75 , a lengthwise slit  741  on an outer surface of the outer sleeve  74 , an inner sleeve  76  having an oval longitudinal section, a lengthwise ridge  761  on an outer surface of the inner sleeve  76 , the ridge  761  being adapted to insert into the slit  741  for assembling the outer and inner sleeves  74 ,  76  in an error-proof manner. For facilitating manufacturing and quality control, a flap  77  is pivotably secured to the other end of the inner sleeve  76 . The flap  77  is vertical to close the through hole  75 . One end of the inner sleeve  76  is open to the bladder  20 . 
         [0075]    Air introduction and air exit operations of the second preferred embodiment are the same as that of the first preferred embodiment. Air in the bladder  20  is only allowed to leave through the flap  77  of the other one-way valve  70  connected to the exit conduit  60  (see  FIGS. 8 and 8A ). In short, air in the bladder  20  is expelled out to the atmosphere via the other one-way valve  70  and the exit conduit  60  in response to pressing the bladder  20  by the footbed of a wearer during walking. Fresh air is introduced into the bladder  20  via the entry conduit  50  and the flap  77  of one one-way valve  70  connected to the entry conduit  50  (see  FIGS. 7 and 7A ). A partial vacuum is created in the flexibly expanding bladder  20  when a person wearing the shoe incorporating the ventilated insole lifts his/her foot. Thus, fresh air is introduced into the bladder  20  via the entry conduit  50  and one one-way valve  70  and next foul air is out of the bladder  20  by leaving the other one-way valve  70 , the exit conduit  60  and the air exit  40  in response to the footbed of the wearer pressing the bladder  20 . 
         [0076]    Referring to  FIGS. 10 to 14A , a ventilated insole in accordance with a third preferred embodiment of the invention is shown in which  FIG. 10  is an exploded view of a ventilated insole according to the third preferred embodiment of the invention, and 
         [0077]      FIG. 11  is a fragmentary view of the heel portion of the ventilated insole of  FIG. 10  but viewing from the bottom. In  FIG. 10 , the pad  10  is exploded in a sequence opposite to that of  FIG. 2  in which the lower member  12  is correspondingly disposed on top of the upper member  11 . 
         [0078]    In the third preferred embodiment, as shown in  FIGS. 10A and 10B , for facilitating air flow a lengthwise arched ridge  51  is provided in the entry conduit  50  and a lengthwise arched ridge  61  is provided in the exit conduit  60  respectively. The provision of the ridges  51 ,  61  thus can increase flexibility of the entry conduit  50  and the exit conduit  60 . In detail, force exerted from tops of the entry conduit  50  and the exit conduit  60  can be withstood by the ridges  51 ,  61  so as to ensure a smooth air flow through the entry conduit  50  and the exit conduit  60  even when the entry conduit  50  and the exit conduit  60  are compressed to their minimums (see  FIG. 14 ). 
         [0079]    As shown in  FIGS. 11 and 11A , on an upper portion of the air entry  30 , the upper member  11  comprises a thin piece  31  including a plurality of small apertures  311  for flowing air so that foreign objects are prevented from entering the triangular concave end of the entry conduit  50  to block same. It is desired that the foreign objects are prevented from entering the rear opening of the entry conduit  50  without interfering with air introduction. 
         [0080]    Refer to  FIGS. 12 and 13  in which  FIG. 12  is a side elevation of a shoe  100  showing the ventilated insole of  FIG. 10  disposed therein, and  FIG. 13  is a top view of the ventilated insole of  FIG. 10  schematically showing the footbed thereon. Preferably, for enabling a user to install the ventilated insole of the invention in the shoe  100 , the bladder  20  is provided at position at the heel  200 , the air entry  30  is provided on a rear end of the pad  10  corresponding to a rear end  201  of the heel  200 , and the air exit  40  is provided under the pad  10  corresponding to the toes  203  at the front of the footbed  202 . Thus, the exit apertures  42  correspond to the gaps  204  between the toes  203 . As a result, a maximum air introduction and expelling effect can be brought about to sufficiently dry the footbed and bring a degree of comfort thereto. 
         [0081]    Referring to  FIGS. 15 to 16 , a ventilated insole in accordance with a fourth preferred embodiment of the invention is shown in which  FIG. 15  is an exploded view of a ventilated insole according to the fourth preferred embodiment of the invention,  FIG. 15A  is a fragmentary view of the left part of  FIG. 15 , and  FIG. 15B  is a fragmentary view of the right part of  FIG. 15  respectively. In the fourth preferred embodiment, the pad  10 A comprises an upper member  11 A, an upward arched upper element  111 A integrally formed with the upper member  11 A, a lower member  12 A secured to the upper member  11 A, and a downward arched lower element  121 A integrally formed with the lower member  12 A. The upper and lower elements  111 A and  121 A are attached together to form a bladder (see  FIG. 16 ). This can simplify the assembly and the manufacturing processes. 
         [0082]    A plurality of equally spaced ribs  13 A are radially extend from a center of the arched upper element  111 A to a periphery thereof. The rib  13 A has a longitudinal section of half circle having an area gradually increased from one end at the center of the arched upper element  111 A to the other end at the periphery of the arched upper element  111 A. A plurality of equally spaced ribs  14 A radially extend from a center of the arched lower element  121 A to a periphery thereof. The rib  14 A has a longitudinal section of half circle having an area gradually increased from one end at the center of the arched lower element  121 A to the other end at the periphery of the arched lower element  121 A. Thus, in response to being flexibly depressed, the arched upper and lower members  111 A and  121 A can be quickly returned to its original shape after the depressing force is released. This effect is the same as that described in the first preferred embodiment. 
         [0083]    While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.