Abstract: A method of forming a coating on an electron emitting cathode, in which (1) a black coating is formed on the inner surface of a cathode sleeve constituting the electron emitting cathode, (2) the cathode sleeve is filled with a suspension as a coating material, and (3) a porous absorbent member is brought into contact with or near an opening portion of the cathode sleeve at the same time or after the cathode sleeve is filled with the suspension, thereby causing the porous absorbent member to absorb an unnecessary portion of the suspension. Thereafter, the cathode sleeve to which the coating material is adhered is heat-treated. As a result, a black coating having a uniform thickness is formed, on the inner surface of the cathode sleeve, as a sintered layer obtained by mixing tungsten having an average particle diameter in a range of 0.5 .mu.m (inclusive) to 2 .mu.m (inclusive) with alumina having an average particle diameter in a range of 0.1 .mu.m (inclusive) to 1 .mu.

Abstract: A hammer drill includes a spindle supported by a housing and movable in an axial direction relative to the housing within a predetermined range, a motor for rotating the spindle, a rotary cam member fixedly mounted on the spindle, a clutch cam member which supports a weight member is axially movably mounted on the spindle, and a biasing member for normally biasing the clutch cam member and weight member toward the rotary cam member in the axial direction of the spindle. A first cam and a second cam are provided on the rotary cam member and the clutch cam member, respectively, facing each other in the axial direction of the spindle. The first cam and the second cam cause the clutch cam and weight member to repeatedly move toward and away from the rotary cam member as the spindle is rotated causing the spindle to vibrate in the axial direction. The ratio: ##EQU1## determines the intensity of vibrations transmitted to the hands of an operator.

Abstract: A black coating having a uniform thickness is formed, on the inner surface of the cathode sleeve, as a sintered layer obtained by mixing tungsten having an average particle diameter in a range of 0.5 .mu.m (inclusive) to 2 .mu.m (inclusive) with alumina having an average particle diameter in a range of 0.1 .mu.m (inclusive) to 1 .mu.m (exclusive) at a weight ratio of the tungsten to the alumina in a range of (90:10) to (65:35).

Abstract: A mechanism for returning a hammer of an electrically-operated tacker from the tack-driving position to the starting position, in two stages, includes first and second hammer-returning elements and a rotating element for returning the hammer to the starting position.

Abstract: An elecrically-operated tacker includes means for driving a tack which is urged toward a muzzle section by a spring, an operating means for moving the driving means back to a starting position, a switch having a push button, a trigger means having a pair of first and second depressing elements, a control member for maintaining the first depressing element in an operative position, a safety means for normally maintaining the control member in a safety position, first and second engaging elements provided on the operating means, third, fourth and fifth engaging elements on the driving means, and a release means. Initially the driving means is located in a starting position immediately before a first extreme position. When the trigger is depressed, the push button is depressed by the first depressing element to move the driving means for a slight distance to the first extreme position so that the driving means springs to the second extreme position by the action of the spring to drive a tack.