Abstract:
Here is disclosed a face mask provided with a rotation angle regulating means for stepwise variation of an angle of each buckle relative to associated lens frame side wall. A buckle is rotatably attached to the lens frame side wall of the face mask and the lens frame side wall and the buckle are formed with the rotation angle regulating means comprising one or more protrusions and depressions adapted to be releasably brought into mutual engagement.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to a face mask suitable to be used for diving or the like. 
   In a face mask used for diving or the like, it is well known to connect a strap to a lens frame of the face mask by means of buckles in a length-adjustable manner as disclosed in Japanese Patent Application Publication No. 2001-218869A. It is also well known to make the buckles rotatable relative to the lens frame and thereby to improve fitness of the face mask during use thereof as disclosed in Japanese Patent Application Publication No. 1997-132193A. 
   In the case of the buckle rotatable face mask as disclosed in the above-cited Publication, it is easy for the wearer to adjust the strap at a desired position relative to the lens frame but the strap may shift from this desired position as the buckles unintentionally are rotated during use of the face mask. Consequently, it may be sometimes difficult to retain the strap at the adjusted position. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to provide a face mask improved so that a position of the strap put around a wearer&#39;s head can be easily adjusted relative to the lens frame and the strap can be reliably retained at this position once it has been adjusted. 
   According to this invention, there is provided a face mask comprising a front lens, a skirt extending rearward from the front lens, a lens frame adapted to fix a front end of the skirt to a peripheral edge of the lens, a strap put around a mask wearer&#39;s head and buckles rotatably coupled to opposite side walls of the lens frame used to adjust a length of the strap along its longitudinally opposite extremities, respectively. 
   This invention further comprises an angle control means being formed on each of the side walls of the lens frame and each of the buckles associated with the side wall and adapted to be releasably brought into mutual engagement so as to retain the buckle at a predetermined rotation angle with respect to the side wall. 
   This invention includes the following embodiments. 
   The angle control means comprises a first engagement member formed on each of the side walls of the lens frame and a second engagement member formed on the buckle associated with the side wall and one of the first and second engagement members is provided in the form of a plurality of depressions and the other is provided in the form of a protrusion adapted to be releasably engaged with one of the depressions. 
   Each of the buckles comprises a first supporting member having a shaft adapted to be detachably and rotatably engaged with a bearing formed on the side wall of the lens frame, a second supporting member opposed to the first supporting member with the strap lying therebetween and having one end in a longitudinal direction of the strap pivotably supported by the first supporting member and a spring means interposed between the first and second supporting members and biasing the other end of the second supporting member to be pressed against the strap and wherein the second engagement member is formed integrally with the spring means. 
   The spring means comprises a first spring component extending in a transverse direction of the strap and pressed against the first and second supporting members, and a second spring component extending from the first spring component in the longitudinal direction of the strap and adapted to be elastically and releasably engaged with the first engagement member formed on the side wall of the lens frame. 
   At least one of the first and second engagement member is provided in form of a plurality of the engagement members arranged on one and same circular circumference defined around the shaft. 
   The lens frame or each of the buckles is provided with a stopper means serving to prevent the buckle from rotating to a position at which the buckle falls off from the lens frame during use of the face mask. 
   The face mask according to this invention has advantageous effects that the rotation angle control means provided between the lens frame and the buckles to ensure that the rotation angle of the buckles rotatably attached to the lens frame can be stepwise varied. This unique arrangement is effective not only to facilitate the strap to be adjusted to a desired position but also to eliminate an anxiety that the strap might be unintentionally shift from this desired position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of a face mask; 
       FIG. 2  is a side view of the face mask; 
       FIG. 3  is a perspective view of the face mask; 
       FIG. 4  is a partial exploded perspective view of the face mask; 
       FIG. 5  is a sectional view taken along line V—V in  FIG. 3 ; and 
       FIG. 6  is a partially scale-enlarged view of the face mask. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Details of the face mask according to this invention will be more fully understood from the description given hereunder with reference to the accompanying drawings. 
     FIGS. 1 and 2  are front and side views, respectively, of a face mask for diving according to this invention. The face mask  1  is bilaterally symmetrical as viewed in  FIG. 1  and comprises a front lens  2 , a skirt  3 , a lens frame  4  adapted to fix a front end of the skirt  3  to a peripheral edge of the lens  2 , a strap  6  put around a mask wearer&#39;s head and buckles  7  adapted to connect longitudinally opposite extremities  6 A of the strap  6  to opposite side walls  4 A of the lens frame  4 , respectively so that a length of the strap  6  can be adjusted. The buckles  7  are partially covered with side covers  8  detachably mounted on the lens frame  4 . To wear this face mask  1 , the strap  6  is put around the wearer&#39;s head with a rear end of the skirt  3  placed against the wearer&#39;s face. Referring to  FIG. 2 , a position of the strap  6  extending rearward along a horizontal line H which is orthogonal to the lens  2  can be adjusted by clockwise or counterclockwise rotating the buckles  7  as indicated by imaginary lines and thereby varying an angle of the buckles  7  relative to the lens frame  4 . 
     FIGS. 3 and 4  show the face mask  1  in a perspective view and a partially exploded perspective view, respectively. The frame  4  of the mask  1  is formed with two pairs of through-holes  5  on the respective side walls  4 A and the through-hole  5  are spaced apart from each other in a vertical direction. By means of these through-holes  5 , the side covers  8  can be detachably coupled to the frame  4 .  FIG. 3  illustrates one of the covers  8  as has been detached from the frame  4  and this cover  8  is not illustrated in  FIG. 4  merely for the purpose of simplification. The strap  6  is made of flexible elastic material such as rubber or plastic elastomer and defined by a longitudinal direction corresponding to a circumferential direction of the wearer&#39;s head, a transverse direction corresponding to the vertical direction as viewed in  FIGS. 3 and 4  and a thickness direction orthogonal to these two directions. Each of the longitudinally opposite extremities  6 A is formed on its one side with a plurality of first engagement teeth  12  spaced apart from one another in the longitudinal direction of the strap  6  and each of these teeth  12  fully extends in the transverse direction of the strap  6 . Each of the buckles  7  comprises a first supporting member  21 , a second supporting member  22  and a spring member  23  interposed between these first and second supporting members  21 ,  22 . The spring member  23  is fixed to the first supporting member  21  by means of a screw  52 . The second supporting member  22  has pivot pins  29  extending in the transverse direction of the strap  6  and adapted to be brought into bearings  49  of the first supporting member  21  in a direction of an arrow M. The pivot pin  29  is received in the bearing  49  of the first supporting member  21  so that the second supporting member  22  can pivot in both directions of the arrows A and B. The strap  6  extending forward are folded back by the respective buckles  7  so that the longitudinally opposite extremities  6 A is directed to rearward of the mask  1  and put though respective belt loops  43 . 
   Referring now to  FIG. 4 , each of the frame side walls  4 A is formed with a through-hole  26  and a plurality of depressions  54  arranged on one and same circular circumference defined around the through-hole  26 . The through-hole  26  is formed with a pair of guide grooves  46  for stoppers  27  radially opposed to each other. The first supporting member  21  making a part of each buckle  7  comprises a planar plate  47  extending parallel to the associated side wall  4 A of the frame  4 , a wall section  38  formed on a front end of the plate  47  and a pair of side wall sections  48 A,  48 B formed integrally with the plate  47  and extending rearward parallel to each other. The bearings  49  formed in the side wall sections  48 A,  48 B have circular arc-shaped concave surfaces. A surface of the plate  47  opposed to the frame side wall  4 A is formed with a cylindrical shaft  24  from which a pair of stoppers  27  extend radially outwardly. The shaft  24  is inserted into the through-hole  26  of the frame side wall  4 A serving as a bearing in a direction of an arrow R so that the stoppers  27  go through the guiding grooves  46 , respectively. Then the first supporting member  21  is rotated clockwise, i.e., in a direction of an arrow S so that the stoppers  27  may be placed against the frame side wall  4 A from the inside of the mask  1 . In this manner, the first supporting member  21  is rotatably coupled to the frame side wall  4 A (See  FIG. 5 ). In the vicinity of the rear end of the first supporting member  21 , the associated extremity  6 A of the strap  6  turns round along a periphery of a pin  28  extending in the transverse direction of the strap  6 . 
   The second supporting member  22  making a part of the buckle  7  comprises the pivot pins  29  extending in a vertical direction as viewed in  FIG. 4 , a first arm section  31  extending from the pivot pins  29  rearward of the mask  1  and a second arm section  32  extending forward from the respective pivot pins  29 . The pivot pins  29  may be brought into engagement with the respective bearings  49  in the direction of the arrow M so as to be supported by the first supporting member  21  (See  FIG. 3 ), so the second supporting member  22  can be rotated around the pivot pins  29  selectively in one of the directions of the arrows A and B with the wearer&#39;s finger applied to a rear end  31 A of the first arm section  31 . A rear side wall  37  of the spring member  23  is pressed against forward end  33  of the second arm section  32  (See  FIG. 3 ). 
   The spring member  23  comprises a first spring component  23 A having a U-shaped cross-section and fully extending in the transverse direction of the strap  6  and a second spring component  23 B extending in a direction orthogonal to the first spring component  23 A, i.e., in the longitudinal direction of the strap  6 . The first spring component  23 A is inserted in a direction of an arrow Q between the wall section  38  of the first supporting member  21  and the forward end  33  of the second supporting member  22 . The first spring component  23 A has front and rear walls  36 ,  37  extending side by side and these walls  36 ,  37  are pressed against the wall section  38  of the first supporting member  21  and the forward end  33  of the second supporting member  22  and thereby elastically compressed in such a manner that a width of the U-shape defined by these front and rear walls  36 ,  37  is correspondingly reduced. In this compressed state, the spring member  23  biases the second supporting member  22  to be rotated in the direction of the arrow A. The second spring component  23 B is formed, in the vicinity of its rear end, with a protrusion  53  extending toward the frame side wall  4 A and adapted to be detachably engaged with one of the depression  54  arranged on the frame side wall  4 A (See  FIG. 5 ). The spring member  23  is fixed to the first supporting member  21  by rotating a screw  52  into a threaded hole  50  via a through-hole  51  of the second spring component  23 B. Thereupon, the second spring component  23 B is received in a forwardly opened square U-shaped cutout  22 A of the second supporting member  22 . 
     FIG. 5  is a sectional view taken along a line V—V in  FIG. 3 , in which a part of the strap  6  is illustrated from the side. In the illustrated state of the buckle  7 , the shaft  24  of the first supporting member  21  has been inserted into the through-hole  26  of the frame side wall  4 A while the stoppers  27  are placed against the peripheral edge of the through-hole  26  from the inside of the mask  1  (from below as viewed in  FIG. 5 ). The spring member  23  is fixed to the first supporting member  21  by the screw  52  and the first spring component  23 A thereof indicated by an imaginary line is interposed between the wall section  38  defining the forward end of the first supporting member  21  and the forward end  33  of the second supporting member  22 . As for the first spring component  23 A, small protrusions  41  extending forward from the first spring component  23 A come in engagement with holes  42  formed in the wall section  38  of the first supporting member  21  to retain the spring member  23  between the first and second supporting members  21 ,  22 . As for the second spring component  23 B, the protrusion  53  extending downward from a rear end of the component  23 B as viewed in  FIG. 5  comes in engagement with one of the depressions  54  formed on the frame side wall  4 A. The protrusion  53  may be elastically deformed so as to shift upward, i.e., in a direction of an arrow T and disengaged from the depression  54  as the buckle  7  is rotated around the shaft  24 . The second supporting member  22  has a second stopper tooth  35  formed on the inner side of its first arm section  31 . In the illustrated state, this second stopper tooth  35  is pressed against one of the first stopper teeth  12  formed on the strap  6  from the front under a biasing force to the direction of the arrow A which is exerted by the first spring component  23 A so as to prevent the extremity  6 A of the strap  6  from moving in a direction of an arrow P. With such a function of the second supporting member  22 , it is not likely that the strap  6  may be unintentionally slackened. Pulling the extremity  6 A of the strap  6  so that the strap  6  may move in the direction opposite to the direction of the arrow P causes a slant face  12 A of the first stopper tooth  12  to push the first arm section  31  upward in the direction of the arrow B (See  FIG. 3 ) so that the strap  6  can move so as to be tightened around the wearer&#39;s head. 
     FIG. 6  is a view showing a part of  FIG. 2  in an enlarged scale. In  FIG. 6 , solid lines indicate the buckle  7  to which the strap  6  extending rearward along the horizontal line H is connected, on the other hand, imaginary lines indicate the buckle  7  rotated in a counterclockwise so that the strap  6  may extend obliquely upward and the protrusion  53  of the second spring component  23 B may be engaged with the uppermost depression  54 A of the depressions  54  circumferentially arranged on the frame side wall  4 A (See  FIG. 4 ). If the face mask wearer counterclockwise rotates the buckle  7  indicated by the slid lines, the second spring component  23 B is elastically deformed so that the protrusion  53  may come off the depression  54 . The buckle  7  can be rotated until the protrusion  53  is engaged with next depression  54 . The buckle  7  is retained at this position unless an added force is exerted upon the buckle  7 . The protrusion  53  is engaged with the uppermost depression  54 A as seen in  FIG. 4  when the added force is exerted upon the buckle  7  to rotate counterclockwise. Thereby the strap  6  is brought to its position indicated by the imaginary lines in  FIG. 6 . The buckle  7  can be rotated clockwise also. In this way, it is possible for the face mask  1  according to this invention to regulate an angle of the strap  6  relative to the horizontal line H by engaging the protrusion  53  formed on the second spring component  23 B of the buckle  7  with the desired one of the depressions arranged on the frame side wall  4 A. 
   During use of the face mask  1 , even if the protrusion  53  moves beyond the uppermost depression  54 A as the buckle  7  is counterclockwise rotated, further rotation is stopped as the side wall section  48 A of the first supporting member  21  comes up against a side wall section  8 A of the cover  8  (See  FIGS. 3 and 6 ) attached to the associated frame side wall  4 A. On the other hand, clockwise rotation of the buckle  7  is stopped as the side wall section  48 B of the first supporting member  21  comes up against a side wall section  8 B of the cover. So long as the buckle  7  rotates between these side wall sections  8 A,  8 B, there is no anxiety that the stoppers  27  of the buckle  7  might coincide with the guide grooves  46  and the buckle  7  might fall off from the frame side wall  4 A. While the first engagement member is in form of the protrusion  53  extending from the second spring component  23 B and the second engagement member is in form of the depressions  54  formed on the frame side wall  4 A in the illustrated embodiment, these first and second engagement members may be implemented in the other appropriate forms so far as these engagement members can be releasably engaged one with another. It is also possible without departing from the scope of this invention to replace the protrusion  53  by a depression and vice versa. The angle included between each pair of the adjacent depressions  54  arranged on one and same circular circumference as well as the total number of these depressions  54  is not limited to those in the illustrated embodiment. Preferably, three to nine depressions  54  are formed on the frame side wall  4 A with the angle of 10° to 20° included between each pair of the adjacent depressions  54 . It is also possible without departing from the scope of this invention to form the second spring component  23 B with a plurality of protrusions  53  arranged on one and same circular circumference. 
   For implementation of this invention, the first and second supporting members  21 ,  22  in the buckle  7  may be formed by rigid plastic material and the spring member  23  may be formed by various types of material such as rigid plastic material, plastic elastomer, rubber or metal. While the first and second spring components  23 A,  23 B are formed integrally with each other in the illustrated embodiment, these two components may be separately formed using materials different from each other. The face mask  1  of this invention can be used not only for diving but also for skiing or motorbike riding.