System, method, and apparatus for controlling circulation of fluid to, and evacuation of the fluid from, an external fluid circuit for heat transfer. A single control valve selectively stops the circulation of fluid from a supply passageway to an external fluid circuit and diverts fluid to a bypass passageway which creates a suction force at a venturi valve region therein. The venturi valve region includes a fluid jacket that encases at least a portion of the venturi valve region. A suction passageway couples the suction force of bypass passageway to either return passageway or supply passageway, for evacuating fluid from external fluid circuit. No more than a single suction passageway is required to be coupled to either supply passageway and/or return passageway. A return check valve disposed in return passageway prevents backflow of fluid through return passageway.

A welding electrode includes an electrode holder and an electrode cap removably attached to the holder and having a central longitudinal axis. The cap includes a body having an end, and a welding surface that is substantially smooth and free from any grooves defined therein, and has a first diameter of from about 7 to 10 mm, a first radius of curvature, and a second radius of curvature that is different from the first radius. The cap includes a skirt portion extending away from the body and configured to bear against the holder. The skirt portion has a first face that is substantially parallel to the axis and spaced apart from the surface. The body has a second face interconnecting the first face and the surface, and the body tapers from the first face to the surface. A method of forming a resistance spot weld joint is also disclosed.

A welding cap cooling water control system has a cooling water conduit with a cooling water inflow leading in direction of the welding cap and a cooling water return flow leading away from the welding cap, in which a flow sensor and a control valve are seated. On the side of the inflow or the return flow the cooling water flow is controlled by a flow control valve which also serves for emergency shut-off in the case of pressure loss.

A resistance welding electrode includes a shaft-shaped holder and an electrode part in the form of an electrode cap or a pin electrode which are non-positively connected via tapered surfaces. Furthermore, cooling bores are also present. In such a resistance welding electrode the tapered cone angle is in a region of about 1 degree to 3 degrees and the holder and the electrode part are connected such that the holder and the electrode part are further in axial contact with each other via a radial surface contact, and the edge of the electrode part facing the holder is restrained in an associated reception recess on the holder side by means of reduction.

A guide pin made of a heat-resistant hard material and a sliding member made of an insulating synthetic resin material are integrated. An inserted portion and an extended portion are provided in the sliding member. The thickness of the extended portion is set to be thinner than the thickness of the inserted portion. An air passage is formed in the extended portion thereby forming a thin-wall deformable portion. The surface of the thin-wall deformable portion is configured to bulge toward the air passage side when the extended portion is thermally expanded.

An electrode tip for resistance spot welding includes a main body with tip and base portions. The tip portion has a bottomed and substantially cylindrical shape. The base portion has a substantially cylindrical shape and merges into the tip portion. The main body is made of a copper alloy such as chromium copper. The tip portion has a bottom part and a barrel part. The bottom part has a pressure-contact surface that is not recessed with respect to a workpiece to be pressed. The barrel part has a substantially cylindrical shape and merges into the bottom part. The electrode tip may have an inner diameter ratio (inner diameter of the barrel part to an outer diameter of the base portion) of 0.4 to 0.6, and may also have a bottom thickness ratio (thickness of the bottom part to the outer diameter of the base portion) of 0.15 to 0.5.