AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: SWIMMING GOGGLES The following statement is a full description of this invention, including the best method of performing it known to :- us SPECIFICATION SWIMMING GOGGLES BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION [0001] The present invention relates to a pair of swimming goggles, and particularly to swimming goggles having buckles for adjusting wearing length of a head strap thereof directly when the swimming goggles are worn. 2. RELATED ART [0002] Swimming goggles are worn with a head strap thereof being fastened to a user's head. The head strap is usually adjustable to be tight or loose to the user's head thereby making the user comfortable. Referring to Fig. 1, conventional swimming goggles 7 include a head strap 70 and two buckles 71 at opposite sides thereof. Each buckle 71 defines two slots 710, 711 therein. Each of opposite free ends 701, 702 of the head strap 70 extends through the two slots 710, 711 of each buckle 71 in turn and then is wound at the buckle 71 thereby connecting the head strap 70 to the buckles 71. The connection between the head strap 70 and the buckles 71 is adjustable through one or both of the free ends 701, 702 of the head strap 70 sliding along the slots 710, 711 of the buckles 71. Thus, the head strap 70 is adjustable to fasten the swinuning goggles 7 to the user. [0003] However, the swimming goggles 7 must be taken off before the adjustment of the head strap 70. Then the swimming goggles 7 are worn again after the adjustment of the head strap 70. It is hard to fit the swimming goggles 7 to the user though once of the adjustment. In fact, it often need several times of adjustment to fittingly wear the swimming goggles 7. So, the user has to wear and take off the swimming goggles 7 1 several times. Even so, the user may still feel uncomfortable to wear the swimming goggles 7. It is inconvenient to adjust the swimming goggles 7. SUMMARY OF THE INVENTION [0004] Accordingly, an object of the present invention is to provide a pair of swimming goggles which is ready to adjust wearing length of a head strap thereof for being fit to a user, and which does not need to be taken off during the adjustment. [0005] To achieve the above-mentioned object, a pair of swimming goggles in accordance with the present invention includes left and right goggle frames, a connection bridge connected between the left and right goggle frames, a pair of buckles respectively attached to the left and right goggle frames opposite the connection bridge, and a head strap adjustably fastened to the buckles. Each goggle frame has outer and inner surfaces. A receiving hole is defined between the outer and inner surfaces of each goggle frame and receives a lens therein. Each buckle includes a base and a cover attached to the base. A chamber is cooperatively defined in the base and the cover and receives a shaft and a fastener therein. An entrance is defined between the base and the shaft. An exit is defined between the shaft and the cover. The fastener is adjacent to the shaft and includes a handle and an engagement protrusion. Each of free ends of the head strap extends into the entrance of the buckle, extends out of the exit of the buckle and abuts against the shaft. Each free end of the head strap selectively engages with the engagement protrusion of the buckle thereby fixing the head strap to the buckle. The handle is rotatable to disengage the engagement protrusion from the head strap whereby wearing length of the head strap is adjustable through moving the free ends of the head strap relative to the shaft. 2 [0006] Other objects, advantages and novel features of the present invention will be drawn from the following detailed embodiment of the present invention with attached drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS [0007] Fig. 1 is a perspective view 'of conventional swimming goggles; [0008] Fig. 2 is an exploded view of a pair of swimming goggles of the present invention; [0009] Fig. 3 is an assembled view of Fig. 2; [0010] Fig. 4 is a cross-sectional view of half of the swimming goggles; [0011] Fig. 5 is similar to Fig. 4 but showing a fastener disengaging from a head strap; [0012] Fig. 6 is a front elevational view of Fig. 3 without the head strap; [0013] Fig. 7 is a cross-sectional view taken along line 7-7 in Fig. 6; and [0014] Fig. 8 is similar to Fig. 7 but having the head strap. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0015] Referring to Figs. 2 , 3 and 6, a pair of swimming goggles 1 of the present invention includes a left goggle frame 2, a right goggle frame 3, a connection bridge 4, a head strap 5, and a pair of adjustable buckles 6. Each of the left and right goggle frames 2, 3 has an outer surface 20, 30 and an inner surface 21, 31. A pair of receiving holes 28, 38 are defined between the outer surfaces 20, 30 and the inner surfaces 21, 31 and receive lenses 9 therein, respectively. A pair of protection pads 8 are integrally formed at the inner surfaces 21, 31 of the left and right goggle frames 2, 3 3 for comfortable contact with a user's face. The connection bridge 4 is connected between the left and right goggle frame 2, 3. The left and right goggle frames 2, 3 are similarly configured. For easy illustration, only the left goggle frame 2 is exploded, as shown in Fig. 2. A mounting hole 22 is defined at a side portion of the left goggle frame 2 opposite the connection bridge 4. [0016] Each buckle 6 includes a base 60, a fastener 67 and a cover 61. The base 60 includes an upper wall 601 substantially perpendicularly extending from an upper portion thereof, and a lower wall 602 substantially perpendicularly extending from a lower portion thereof. A pair of shaft holes 603 and axial holes 604 are defined in the upper and lower walls 601, 602, respectively. A shaft 64 is rotatably assembled between the upper and lower wall 601, 602 with end portions thereof received in the shaft holes 603. A pair of recesses 605 is defined in the upper and lower walls 601, 602. A post 606 extends from the base 60 for engagingly extending into the mounting hole 22 of the left goggle frame 2 thereby fixing the buckle 6 to the left goggle frame 2. [0017] The fastener 67 includes an axial portion 671, a handle 672 extending from the axial portion 671 and an engagement protrusion 673 extending from the axial portion 671 opposite the handle 672. The fastener 67 is rotatably assembled between the upper and lower walls 601, 602 with end portions of the axial portion 671 received in the axial holes 604. The handle 672 is generally arc-shaped. The engagement protrusion 673 is generally barb-shaped. The axial portion 671 is parallel and adjacent to the shaft 64. [0018] The cover 61 includes a pair of fixing protrusions 611 for snappingly engaging with the recesses 605 of the base 60 thereby fixing the cover 61 to the base 60. A chamber 63 is cooperatively defined in the base 60 and the cover 61 for receiving the shaft 64 and the fastener 67 therein. Also referring to Fig. 7, an entrance 65 is defined between the shaft 64 and 4 the base 60 for extension of a free end 51 of the head strap 5. An exit 66 is defined between the shaft 64 and the cover 61 for extension of the free end 51 of the head strap 5. The arc-shaped handle 672 is depressable each of the free ends 50, 51 of the head strap 5 to close a user's head. A number of engagement slots 52 are defined in each free end 50, 51 of the head strap 5 for selectively engaging with the engagement protrusion 673 of the fastener 67 thereby fixing the head strap 5 to the buckle 6. [0019] Referring to Figs. 2 and 7, in assembly of the buckle 6, the shaft 64 and the fastener 67 are rotatably coupled to the shaft holes 603 and the axial holes 604 of the base 60. The post 606 is received in the mounting hole 22 of the left goggle frame 2. The cover 61 is attached to the base 60 with the fixing protrusions 611 thereof engaging with the recesses 605 of the base 60. Thus, the buckle 6 is assembled to the left goggle frame 2. Likewise, the other buckle 6 is assembled to the right goggle frame 3. [0020] Also referring to Fig. 8, the free ends 50, 51 of the head strap 5 respectively extend into the entrances 65 of the buckles 6, extend out from the exits 66 of the buckles 6 and abut against the shafts 64. One of the engagement slots 52 of each free end 50, 51 of the head strap 5 engages with the engagement portion 673 of the fastener 67. Thus, the head strap 5 is assembled to the buckles 6. [0021] Figs. 4 and 5 show adjustment operation of wearing length of the head strap 5. Referring to Fig. 4, the handle 672 of the fastener 67 is depressed to be received in the chamber 63 and presses the free end 50 of the head strap 5 to close a user's head. The engagement protrusion 673 of the fastener 67 receivingly engages with one of the engagement slots 52 of the head strap 5. Thus, the head strap 5 is securely fixed to the buckle 6. Referring to Fig. 5, the handle 672 of the fastener 67 is pushed to rotate the axial portion 671 of the fastener 67. The engagement protrusion 673 of the fastener 67 disengages from the engagement slot 52 of the head strap 5. The free end 50 is movable relative to the shaft 64, thereby adjusting the 5 wearing length of the head strap 5 to meet size requirement of a user. [00221 Also referring to Fig. 8, the handle 672 is pushed outward to move the free ends 50, 51 of the head strap 5 relative to the shaft 64. When the head strap 5 is fit to a user, the handle 672 is depressed inward to fix the head strap 5 to the buckles 67. Thus, the swimming goggles 1 can be directly adjusted to meet size requirement of a user, when worn by the user. Furthermore, the swimming goggles 1 can be fittingly worn though once of adjustment. Therefore, it is convenient to use the swimming goggles 1 of the present invention. [0023] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. 6