Freeze Plug

Other objectives and advantages of the invention will be more apparent from the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a perspective view of a cup-shaped freeze plug in accord with the principles of this invention;

FIG. 2 is a cross-sectional view illustrating an intermediate assembly step of the freeze plug with an engine block's hole; and

FIG. 3 is a view similar to FIG. 2 illustrating the final sealing position of the freeze plug with the engine block's bore.

The freeze plug 10 in accord with the principles of this invention is a cup-shaped type freeze plug that is circular in cross-section as shown in FIG. 1. The freeze plug 10 is adapted for use in a circular cross-sectional coolant hole 11 in an engine block 12. The coolant hole 11 has a nominal diameter 13.

The cup-shaped freeze plug 10 basically includes a base section 15 having an outside diameter 16 less than the nominal diameter 13. The base diameter 16 is sized to permit the plug 10 to be hand-fitted into the coolant hole 11 at an intermediate non-sealing position as shown in FIG. 2. In other words, the outside diameter 16 of the plug's base section 15 is sized so that no tools are required to fit the freeze plug into the engine block's coolant hole at that position shown in FIG. 2.

The freeze plug 10 also includes a rim section 20 formed integral with the base section 15. The rim section has an outside diameter 21 greater than the nominal diameter 13. The rim diameter 21 is sized to allow the plug 10 to be force fitted into the coolant hole 11 at a final coolant sealing position as shown in FIG. 3. It is necessary that hand or power tools be used to translate the freeze plug 10 from the FIG. 2 intermediate non-sealing position into the FIG. 3 final coolant sealing position. For example, a punch 25 and hammer (not shown) can be used, the punch being sized to fit inside the cup-shaped freeze plug 10 against its floor 26, and the hammer being used to drive the plug 10 into place, all as shown in FIG. 3.

It is preferred that the freeze plug's base diameter 16 be between about 0.2% and about 0.8% less than the engine block coolant hole's nominal diameter 13. This will ensure that the freeze plug 10 can be easily hand-fitted into the engine block's coolant hole from exterior thereof until the FIG. 2 intermediate position is achieved. It is also preferred that the freeze plug's rim diameter 21 be between about 0.7% and about 0.9% greater than the engine block coolant hole's nominal diameter. It has been found that this rim diameter 21 allows a goods friction fit seal to be achieved between the freeze plug 10 and the engine block 12 when the freeze plug is in the sealing position shown in FIG. 3. It is further preferred that the freeze plug's base section 15 have a depth 30 of between about 50% and about 70% of the overall depth 31 of the freeze plug 10. And it has been found that the freeze plug's rim section 20 is preferably of a depth 32 of between about 30% and about 50% of the overall depth 31 of the freeze plug 10. The depth 30-32 relationships of the freeze plug's base section 15 and rim section 20, in combination with the diameter 16, 21 relationships between the freeze plug's base section and rim section vis-a-vis the hole's nominal diameter 13, have unexpectedly been found to provide a freeze plug 10 which can be easily hand-fitted in an intermediate assembly position within an engine block's coolant hole 11, see FIG. 2, while providing a complete friction-fitted seal for the hole after the freeze plug is driven into final sealing position, see FIG. 3. This very simple freeze plug 10 structure solves a long outstanding problem in that it practically ensures that the freeze plug will be put in straight in the block's hole 11, and that the friction fit outside side wall surface 27 of the plug's rim section 20 will not be unduly nicked or gouged as it is put in.

A freeze plug 10 in accord with the principles of this invention, when it is metal freeze plug, is manufactured by a series of steps. First, a blanking step is used in which a flat plug blank (not shown) is stamped out of a metal sheet. When the engine block's coolant hole 11 is circular in cross-section as in the embodiment illustrated in this application, the flat plug blank is formed simply by stamping out a flat round metal piece. Second, the metal blank stamped out is then formed into the cup-shaped configuration of the freeze plug illustrated in FIG. 1. This forming step requires use of a male mandrel and a female die, the male mandrel being relieved at its tip to allow undersizing of the freeze plug's base section 15. Specifically, the male mandrel cooperates with a female die through which the flat plug blank is drawn. As the plug blank is drawn through the female die by the male mandrel, the blank is sized to establish the freeze plug's major diameter rim section 20 by virtue of the female die, and is sized to establish the minor diameter base section 16 due to the relief configuration on the mandrel's tip.