Abstract: A backstop for an automatic ball server has a frame, a net and a curtain. The frame is adapted to be mounted on a table for table tennis. The net is mounted on the frame and is mounted around the automatic ball server. An opening facing the table is defined in the net. The curtain is attached to the net to close the opening in the net, has a gap defined in the curtain through which the automatic ball server can serve balls and is comprised of multiple strips. Each strip has a proximal end attached to the net and a free distal end to allow the ball pass through the curtain and into the net when the ball strikes the curtain. Accordingly, a ball striking the net is slowed down, and the ball can be kept from sticking in the net or rebounding onto the table.

Abstract: A jam free device for a table tennis serving machine includes a body provided with a through hole adapted to be defined to correspond to and coincide with the entrance of the table tennis serving machine, and a stirring extension movably extending into the through hole. Therefore, ping pong balls falling into the entrance of the table tennis serving machine are stirred by the stirring extension and will not jam the entrance.

Abstract: A service machine mountable on a court for table tennis comprises a service machine body, wherein a micro-controller is used to control a ball-positioning mechanism built in the service machine body and a ball-projecting mechanism coupled with the ball-positioning mechanism. The ball-positioning mechanism further comprises an elevation control motor and a sway control motor, while the ball-projecting mechanism comprises a ball-conveying device and a ball-projecting device. A ball-collecting tray is arranged to collect plural balls, which will be delivered via a conveyer from the service machine body to the ball-projecting device sequentially through the ball-positioning mechanism and a spin. control motor for projection. The micro-controller can be set by a user or provided with a preset program to enable the service machine to shoot spun balls one after another at various angles or directions in continuous or intermittent mode automatically or manually.