Generally, referring to FIGS. 6 and 7, a conventional water spray gun comprises a main body (50) and a spray head (60), and the main body (50) further has a handle (51) and a barrel portion (52). A water outlet unit (53) is formed at a front end of the barrel portion (52) while a valve rod (54) is located at an interior space thereof. Also, the valve rod (54) further has a sealing pad (541), and a rear end of the valve rod (54) protruding from the main body (50) is connected to a pressing unit (55) which is pivotally engaged with the handle (51). The pressing unit (55) is configured to control on/off operation of water flow by driving the valve rod (55) to shift inside the barrel portion (52). A spring (56) is borne against between the valve rod (54) and a lateral end of the barrel portion (52), and an interior space of the water outlet unit (53) has a water channel (531) which comprises an opening at a rear end thereof. A front end of the water channel (531) has two water outlet holes (532) which laterally penetrate the water outlet unit (53) and are located at corresponding positions, and the spray head (60) is connected to a front end of the water outlet unit (53) by screws. Also, a stepped rod (533) is formed at a front end of the water outlet unit (53), and a front end of the spray head (60) has a tapered spout (61). As a result, a user can turn the spray head (60) to adjust a separated distance between the stepped rod (533) and the spout (61) to change patterns of spraying water such as solid stream (as shown in FIG. 6), full cone (as shown in FIG. 7), and etc.
However, the conventional water spray gun has following disadvantages: (i) since the spray head is usually made of metal such as copper ingot by turning processing, the manufacturing process is complicate and the cost is higher; and (ii) before spraying out from the tapered spout (61), water needs to flow from the opening of the water channel (531) through the water channel (531), the water outlet unit (53) and the water outlet holes (533) into the spray head (60), which has multiple transitions and reduces the momentum of flow and the spraying range of water flow, resulting in wasting time and water in large-scale water spraying. Therefore, there remains a need for a new and improved design for a water spray gun to overcome the problems presented above.