In a hand-operated label printing machine, including a hand lever and a printing head attached to the hand lever; a printing pressure buffer mechanism or a constant pressure printing mechanism which comprises: in a first embodiment, a spring-actuated engaging member formed in the hand lever and a cooperating checking shoulder which is formed in the main body of the machine; an inclined groove leads to the shoulder; the shoulder is brought into disengageable engagement with the spring- actuated engaging member for moderating the printing pressure; and when the spring-actuated engaging member rides over the checking shoulder, the printing head is actuated; in a second embodiment, a pressure receiving engaging member is carried on the hand lever, through a lost motion connection; a pressure contact member and a guide member are both carried on the main body of the machine and are spaced apart; the pressure receiving engaging member is integrally provided with a pressure receiving piece having a cam surface at the tip end thereof and with a guide piece, spaced from the pressure receiving piece and having an engaging portion at the tip end thereof; when the hand lever is actuated, the cam surface of the pressure receiving engaging member rides across the pressure contact member and the printing is performed at a predetermined pressure; at the same time, the engaging portion of the guide piece is brought into resilient engagement with the guide member to moderate the shock in the printing stroke.
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