Two part grommet with hard plastic locking prongs
A grommet for sealing a cable to a panel opening includes a hard plastic part formed with curved locking prongs projecting at an angle from the perimeter of a main piece is molded to a soft elastomeric second part having a boot portion to receive the cable and a perimeter flange. The prongs lock to the panel upon being fully inserted into the panel opening.
1. A grommet for use with a cable and for sealing a hole formed in a panel comprising:
a first part, the first part including a main piece defining an opening;
a series of resiliently deflectable prongs separated from each other to define spaces between the prongs, the series of prongs projecting from the main piece to define a relief on a back face of the main piece between the prongs and the main piece; the prongs including an outer contact surface having a profile curved to increase the angle of the contact force as the prongs are advanced into the hole to decrease The vector force on the prongs, the prongs of a shape and material to provide audible indication that the grommet has been seated;
a second part formed of an elastomeric material the second part formed of a material softer than a material of the first part, the second part attached to the first part and extending into the spaces between the prongs to bond each prong to an adjacent prong, the elastomeric material extending into the relief between the prongs and the main piece, the second part including a boot portion disposed within the opening of the first part, the boot portion for sealingly engaging the cable, and a flange portion for sealing against the panel, the boot portion extending in a direction opposite of a contact with the panel; and
clearance scallops formed on a front face of the main piece for accommodating angular movement of the boot portion from an angled cable extending through the boot portion of the second part wherein the boot portion remains sealed to the cable.
2. The grommet of claim 1 wherein the outer contact surface is curved along a radius.
3. The grommet of claim 2 wherein an angle of a normal reaction force vector relative to a plane of the hole changes along the radius.
4. The grommet of claim 2 wherein the radius is selected such that the angle of the normal reaction force vector relative to the plane of the hole at an initial contact of the prong with the edge of the hole exceeds sixty degrees.
5. The grommet of claim 4 wherein the prong is sized relative to the second part to provide a gap sufficient to be inserted through a thickness of the panel wherein the prongs lock against a side of the panel when the grommet is seated in the hole.
6. The grommet of claim 1 wherein the grommet includes an elongated generally rounded shape defining two sides and two ends, and wherein two prongs are located on each side, and one prong is located on each end.
7. The grommet of claim 1 wherein the first part is formed of glass filled polypropylene and the second part is formed of a soft thermoplastic elastomer.