Abstract: In a water-hammer preventing unit for a check valve according to the present invention, a retainer pipe having openings at two edges thereof is provided inside a short pipe to form a circular space with the short pipe, and openings are formed on this retainer pipe. Further an elastic tube is provided on an external peripheral surface of the retainer pipe and covers the openings, and a communication path is formed between the short pipe and the valve body holder, and the communication path communicates the circular space to the flow path in the upstream side of the valve body and, when a fluid flows in the reverse direction, a portion of the fluid is accommodated from the opening into the circular space by expanding the elastic tube toward the circular space, and also flows a portion of the fluid in the said circular space to the flow path in the upstream side from the valve body.

Abstract: An image forming apparatus including a development unit rotatably supported by a body of the apparatus and including a plurality of developing subunits and a plurality of replaceable developer containers each storing a developer to be replenished to a particular one of the developing subunits. Also included is a stepping motor configured to cause the developing unit to rotate in order to bring any one of the developing subunits to a developing position, a preventing mechanism configured to prevent the developing unit from rotating at a time of replacement of any one of the developer containers due to an unexpected change in a voltage or a current driving the stepping motor, and a locking portion included in either one of the developing unit and the body and an engaging portion included in the other of the developing unit and the body, in which the locking portion and the engaging portion selectively engaging with each other for preventing the developing unit from rotating.

Abstract: In an image forming apparatus using dry toner, a toner replenishing device includes cleaning means for cleaning the sensing surface of remaining toner sensing means. The cleaning means is driven by the same drive source as agitating means for agitating the toner. To clean the sensing surface, the cleaning means is driven in a particular manner different from a manner for usual toner replenishment. While the cleaning means cleans the sensing surface, the output signal of the remaining toner sensing means is detected. The device achieves highly accurate toner concentration control and toner end detection at the same time.

Abstract: Image forming equipment having an image carrier and a developer carrier located face-to-face and forming an AC-superposed DC electric field between them to develop a latent image electrostatically formed on the image carrier. Sensors responsive to image forming conditions are provided and protected from noise ascribable to an AC component included in the electric field in the event when the sensors operate.

Abstract: An image forming apparatus having a developing device of the type using a two-component type developer and developing an electrostatic latent image by a bias electric field having an alternating electric field. A predetermined reference latent image is electrostatically formed on an image carrier by a reference latent image forming device and then developed by the developing device to become a reference toner image. An irregularity detecting circuit determines the degree of difference between the density of the edge and the density of the central portion of the reference toner image. A bias electric field control circuit controls the bias electric field in matching relation to the output of the irregularity detecting circuit, thereby preventing the image quality from being degraded by a change in the resistance of the carrier.

Abstract: A method and apparatus for demounting a metal plate spot welded to a metal member. In accordance with the method, a hollow electrode rod is placed in opposition to the periphery of a spot weld between the metal plate and the metal member, an electric arc is formed between the electrode rod and the metal plate, the periphery of the spot weld is melted with arc heat, and the resultant molten metal is drawn up through the hollow portion of the electrode rod. The method may be performed with an apparatus having a hollow internal rod which includes an electrode rod retaining portion at a forward tip end thereof. A rod retaining mechanism retains the internal rod for free longitudinal movement in opposite forward and rearward directions, elastically urged in the forward direction. A sliding block is movable in the forward and rearward directions, urged forward by an elastic member. Structure is provided to prevent movement of the sliding block forward of a predetermined forward position.