Mud pulser

A mud pulser, comprising:

• an inlet assembly adapted to receive a mud stream;
• a main-valve assembly that comprises a main valve, a main-valve shaft, and a main-valve conduit,
• wherein the main valve comprises a main-valve plugging member, a main valve seat adapted to receive the main-valve plugging member, and a main-valve chamber housing the main-valve plugging member,
• wherein the main-valve plugging member is affixed to the main-valve shaft, and
• wherein the main-valve conduit is arranged in the main-valve shaft and connected to the inlet assembly;
• a servo-valve assembly that comprises a servo-valve, a servo-valve shaft, and a servo-valve conduit,
• wherein the servo-valve comprises a servo-valve plugging member and a servo-valve chamber housing the servo-valve plugging member and having a first orifice and a second orifice,
• wherein the servo-valve shaft is connected to the servo-valve plugging member and configured to be driven to perform a reciprocating linear movement that causes the servo-valve plugging member to alternately block the first orifice and the second orifice one at a time, and
• wherein the servo-valve conduit is connected to the servo-valve chamber and the main-valve assembly;
• a motor assembly that comprises a motor connected to the servo-valve shaft and driving the servo-valve shaft to perform the reciprocating movement;
• and
• a collar that houses the inlet assembly, the main-valve assembly, the servo-valve assembly and the motor assembly, and forms a mud channel that receives a mud flow therein about the main-valve assembly, the servo-valve assembly and the motor assembly.