Abstract: An electrical sleeve heater for an element having a generally cylindrical outer surface. The heater has a generally helical coil centered on an axis and having a pair of opposite coil ends, a pair of generally coaxial, axially aligned, and similar tubes each fixed to a respective one of the coil ends and surrounding the coil so that relative rotation of the coil can radially increase or decrease an inside diameter of the coil. The tubes having axially adjacent inner ends and outer ends, and means for releasably fixing together the coil inner ends.

Abstract: A sleeve heater has an electrical and generally cylindrical heater coil centered on an axis and shaped to fit over a part to be heated, a radially compressible and generally cylindrical inner sleeve snugly coaxially surrounding the heater coil, and a radially generally inextensible and generally cylindrical outer sleeve fitted coaxially over the inner sleeve. The outer sleeve has an inner surface bearing tightly radially inward on the inner sleeve and radially compressing the inner sleeve and the coil inward. The inner sleeve is formed with two or more axially extending and axially oppositely open slots that are angularly equispaced, with alternate slots open axially in opposite directions.

Abstract: A mounting sleeve fits around a nozzle extending along an axis and a heating coil wrapped around the nozzle and having an outer surface generally centered on the axis. The a mounting sleeve has a sleeve-shaped bimetal body having inner and outer layers and a pair of angularly juxtaposed edges. The body is shaped and dimensioned to fit around the coil with the inner layer engaging the coil outer surface. The inner layer has a smaller coefficient of thermal expansion than the outer layer so that when heated the body contracts radially inward. Interengaging formations at the edges generally prevent radial outward expansion of the body when interengaged.

Abstract: A sleeve heater has an electrical and generally cylindrical heater coil centered on an axis and shaped to fit over a part to be heated, a radially compressible and generally cylindrical inner sleeve snugly coaxially surrounding the heater coil, and a radially generally inextensible and generally cylindrical outer sleeve fitted coaxially over the inner sleeve. The outer sleeve has an inner surface bearing tightly radially inward on the inner sleeve and radially compressing the inner sleeve and the coil inward. The inner sleeve is formed with two or more axially extending and axially oppositely open slots that are angularly equispaced, with alternate slots open axially in opposite directions.

Abstract: A mounting sleeve fits around a nozzle extending along an axis and a heating coil wrapped around the nozzle and having an outer surface generally centered on the axis. The a mounting sleeve has a sleeve-shaped bimetal body having inner and outer layers and a pair of angularly juxtaposed edges. The body is shaped and dimensioned to fit around the coil with the inner layer engaging the coil outer surface. The inner layer has a smaller coefficient of thermal expansion than the outer layer so that when heated the body contracts radially inward. Interengaging formations at the edge generally prevent radial outward expansion of the body when interengaged.

Abstract: A method of making a heater element has the steps of inserting into a smooth tubular casing a heating wire, filling a space between the wire and the casing with a compressible insulating mass, and closing ends of the space to confine the mass in the casing. Then the casing is radially inwardly compressed to form therein a successive of radially outwardly open annular grooves extending circumferentially fully around the casing and thereby radially compressing the insulating mass. The casing is formed with a succession of such grooves, which can be of V-shape and which are each endless so that the casing is corrugated. Alternately the grooves are interconnected helically. Either way in accordance with the invention the grooves form axially relatively long and radially relatively thick outer rings and axially relatively short and radially relatively thin inner rings.

Abstract: An electrical sleeve heater has an inner tube centered on an axis and formed with an axially extending and radially inwardly open cutout open at an axial end of the tube, an electrical heater coil wound around the tube, an outer tube engaged around the heater coil and tube, and an axially elongated thermal sensor probe having a sleeve and a pair of wires extending axially in the sleeve fitted in the cutout. The inner tube has substantially cylindrical inner and outer surfaces and the thermal sensor probe has a radial thickness smaller than a radial distance between the inner and outer surfaces.

Abstract: A sleeve heater is made by first cutting in one face of a flat metal plate a continuous groove and then fitting to the groove a heater wire with at least one end of the wire projecting past an edge of the plate. The plate is then plastically deformed with the wire to a tubular shape centered on an axis with the one face directed radially inward. The installation on a body to be heated is completed by fitting the deformed plate over the body to be heated and tightening the plate on the body to grip it snugly. The plate is formed of a heat-conducting metal, for instance brass, copper, or aluminum. The face of the plate from which the wire projects is directed radially inward so the wire directly engages the body. The tightener, which can be a band that circumferentially surrounds the sleeve or fittings provided at edges of the sleeve, bridges edges of the plate.

Abstract: An electrical sleeve heater has a tubular outer wall and a heating coil inside the outer wall. An outer sleeve inside the heating coil formed with an axially throughgoing slot having angularly confronting edges is made of a material having a high coefficient of thermal expansion. An inner sleeve inside the outer sleeve is formed with an axially throughgoing slot and with outwardly projecting lips engaged through the outer-sleeve slot bearing angularly on the outer-sleeve slot edges. It is made of a material having a low coefficient of thermal expansion so that when the sleeves are heated the outer-sleeve edges press the inner-sleeve lips together and thereby decrease the radial inner diameter of the inner sleeve.

Abstract: An electrical heater for heating an object having a generally cylindrical outer surface has a helicoidal coil having a plurality of turns centered on an axis and inner and outer ends and adapted to fit around the object in contact with the outer surface thereof. A source of electricity is connected to the inner end for supplying electricity thereto and thereby heating the coil. An anchor fixed on one of the turns adjacent the outer end is connected to an element extending to the anchor for drawing the outer end and anchor together and thereby reducing an inside diameter of at least an outer turn of the coil and tightening the outer turn around the object around which the coil is fitted.

Abstract: A die-casting apparatus has a pair of mold parts together defining a mold cavity and a feed sleeve set in one of the parts and defining a passage having a short inner portion opening into and flared toward the cavity, a long outer portion of uniform cross-sectional shape and having an outer end, and a restriction between the portions. Molten metal is fed to the outer end and through the passage to the cavity. A heater surrounds the sleeve at the outer portion for heating the sleeve substantially only at the outer portion and insulation surrounds the heater. The sleeve and any metal therein are cooled at a location in the sleeve downstream of the passage outer portion, normally at the restriction.

Abstract: A heater used on a body having a substantially cylindrical outer surface has a heatable generally cylindrical sleeve fittable over the body and having one end formed with a screwthread and a ring threadable into the screwthread locks the sleeve on the body. More particularly the ring is also formed with a screwthread complementary to the body screwthread and both screwthreads are tapered. This ring is split along its full length so that when the ring is screwed into the body it is compressed radially of a central axis of the body.