Rotatable spray head, multi-material spraying apparatus using thereof, and method for spraying multiple materials

A multi-material spraying apparatus, comprising

• a rotatable spray head, comprising an outer shell and an inner shaft tube, wherein the outer shell defines a receiving cavity, an ejecting outlet and at least two radial inlets, wherein the receiving cavity communicates with the ejecting outlet, the radial inlets communicate with the receiving cavity, wherein the inner shaft tube is coaxially received in the receiving cavity, the inner shaft tube defines a central channel and a lateral through hole, wherein one of two openings of the central channel communicates with the ejecting outlet of the outer shell, and the other opening of the central channel is a gas inlet, wherein the lateral through hole is defined on the inner shaft tube and communicates with the central channel, wherein the inner shaft tube is rotatable relative to the outer shell, and the lateral through hole selectively communicates with one of the radial inlets;
• at least two material holders, wherein a material supplying pipe is extended from each of the material holders to communicate with the corresponding radial inlet of the outer shell;
• and
• a gas supplying device, comprising a gas supplying pipe communicating with the gas inlet of the inner shaft tube, wherein an electromagnetic valve is coupled to the gas supplying pipe to control the motive gas supply to the gas inlet.

A method for spraying multiple materials, comprising:

• supplying a motive gas to a central channel of an inner shaft tube, wherein the inner shaft tube defines a lateral through hole in communication with the central channel;
• pressurizing a first material holder to enable a first material therein to be delivered to a first radial inlet of an outer shell through a first material feed pipe, wherein the outer shell defines a receiving cavity to receive the inner shaft tube, the first radial inlet communicates with the lateral through hole of the inner shaft tube, the first material is delivered through the lateral through hole and the central channel, and the first material is ejected from an ejecting outlet of the outer shell;
• and
• stopping pressurization of the first material holder and establishing communication between the first material holder and the ambient atmosphere and continuously supplying the motive gas to the central channel for urging the first material through the lateral through hole, the first radial inlet, and the first material feed pipe in sequence for recycling the first material back to the first material holder.