Cam Operated Clamp Housing for Injection Molding Heaters

The present invention relates to a clamp for an injection molding heater that simply and easily provides clamping force to clamp a heater onto a cylindrical nozzle for heating the nozzle.

Nozzle heaters for injection molds are helically wound around the nozzles. The nozzles are recessed into cavities, and access for tightening the heaters onto the nozzle is restricted. The ability to adjust the heater clamping force from the open end of the recess is desired, and one form of accomplishing this is shown in U.S. Pat. No. 4,859,176. The clamp in U.S. Pat. No. 4,859,176 is a multi part device and thus can be difficult to assemble.

The present invention relates to a very simple clamp for a heater used with injection nozzles, or other cylindrical objects or heaters, which utilizes a formed, generally cylindrical housing which has a slit or slot along a longitudinal line. A pair of journals are formed on one side of the slit for rotatably mounting a cam pin, while the other side of the slit has a loop that fits over a cam portion in the center of the pin. The pin has a recessed socket hex end for use with a key or wrench that is accessible in axial direction of the heater. The assembly is relatively easy to make, and once in place the cam pin can be rotated for increasing or decreasing the clamping force. Friction on the cam parts will hold the cam locked in place.

The outer housing is very easily formed, and can be stamped out of a single piece of metal. The cam pin journals and cam follower loop are formed integrally with the housing. A heater can be placed inside the housing and then slipped over the nozzle from its accessible end. Thereafter the cam pin can be operated to tightly clamp the heater housing onto the helically wound heater, which tightens the heater against the nozzle for efficient conduction of heat to the nozzle.

FIG. 1 is a side elevational view of a heater clamp housing made according to the present invention shown in place on an injection nozzle, with parts in section and parts broken away;

FIG. 2 is a side elevational view of the clamp housing;

FIG. 3 is an end elevational view of the clamp housing as taken on line 3--3 in FIG. 1;

FIG. 4 is a side elevational view from an opposite side of FIG. 2;

FIG. 5 is a top plan view of the heater clamp housing;

FIG. 6 is a sectional view taken as on line 6--6;

FIG. 7 is a side view of a cam used with the clamp of the present invention; and

FIG. 8 is a flat layout of the housing before forming it into its clamp shape.

A heater clamp indicated generally at 10 includes a clamp housing 11 which surrounds a heater element 12. The heater element 12 is a helically wound heater pad which surrounds barrel or nozzle 13 that is part of a molding assembly indicated generally at 15. The heater is positioned in a recess 15A. The clamp housing 11 is a formed housing preferably made from a stainless steel sheet, and is of size in relation to the outside diameter of the heater so that when it is in its cylindrical shape there is a slit 16 that extends longitudinally with respect to the central axis of the helically wound heater 12. The heater 12 has leads or extensions 17 and 18 extending from the opposite ends thereof. As can be seen the lead 17 is formed to extend toward the open end of recess 15A and is shaped to clear a clamp cam operator indicated generally at 20 which is provided in the central portions of the housing 11 and is designed so that it will permit clamping the interior surface of housing 11 tightly against the helically wound heater 13 by providing a force tending to reduce the width of the slit 16 and thus reduce the diameter of housing 11.

The housing 11 itself is formed from a flat sheet, as seen in FIG. 8, and is formed (as shown) with an integral U shaped member 25 at one edge thereof, and an integral T shaped member 26 at the other edge. The U shaped member 25 has a pair of straps 27,27 which are spaced apart, and a connecting end member 28 that joins the straps 27. The T shaped member has a central cam follower web 30, and a T end 31 at the outer end thereof.

When the housing 11 is formed, the main portion is formed into a cylindrical shape while leaving the slit 16 between the edges of the sheet. The U shaped portion 25 is rolled or formed in an opposite direction from the cylindrical forming, so that the end member 28 is doubled back onto the adjacent edge portion of the housing, with the straps 27 being formed into cylindrical journals. The end member 28 is formed down against the outer surface of the cylindrical housing 11 and is tack welded in place, as perhaps best shown in FIGS. 2,3 and 4.

The T shaped member 26 is also formed back in an opposite direction from the cylindrical forming of the main portion of the housing 11 and the center cam follower web 30 is formed to be of size specifically to tighten onto a cam portion of a pin 40 that is used for adjusting the clamping action of housing 11. The T end 31 is then tack welded down onto the outer surface of the housing as shown in FIGS. 3, 4 and 5, respectively.

The cam follower web 30 formed from the member 26 fits in between the straps 27, and the bores formed in the web 30 and straps 27 overlap. The straps 27 form journals for rotatably mounting cam pin 40. The cam pin 40 has hub ends 41,41 that are of size to fit into the journals formed by the straps 27 and rotate therein. The cam loop formed by web 30 fits over a cam center portion 42 of the pin 40. The cam portion 42 is between the hubs 41. The cam portion 42 is formed by making a recess in the pin center portions between the hubs 41.

As can be seen in FIG. 5 in particular, the center cam web 30 fits around the cam portion upper surface 42A. As the cam pin 40 is rotated, the tightening or clamping effect is achieved by distance changes between the central axis of hubs 41 on the pin ends in the journals formed by straps 27 and the central axis of cam portion 42. The cam action tends to increase or decrease the width of slot 16 and thus the diameter of housing 11 to either loosen or tighten the housing with respect to the heater coil.

The clamp can be assembled onto the heater before the heater is slid into position in the recess 15A of the injection molding assembly, so that the clamp is easily used. The end socket indicated at 44 of the cam pin 40 is accessible easily from the open end of the blind hole or recess 15A that is shown in FIG. 1, so that a key such as that shown at 45 can be inserted and removed easily and the clamping adjustment can take place without having to operate in the blind hole.

The housing 11 is quite easily made and low cost, and fulfills the needed functions using few parts for clamping heaters for retaining them in heat conducting relationships to an injection molding nozzle.

The housing material can be made sufficiently thin to permit clamping and to insure that the cam web 30 forms of bends over the pin cam section 42, but yet strong enough to carry the necessary tightening loads for adjustment.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.