Patent ID: 8162184

Claim:
A lubricating gun comprising a barrel for holding either lubricant in bulk or a tubular cartridge containing lubricant, a follower packing unit in the barrel, a follower rod for moving the follower packing unit in the barrel along a longitudinal axis of the barrel, said follower packing unit comprising an elastomeric seal comprising a hollow annular body of elastomeric material having a front wall, an annular side wall and a rear wall defining a cavity in the body, a first opening in the front wall allowing entry of lubricant into the cavity under pressure, a second generally cylindrical opening in the rear wall aligned with the first opening such that the follower rod extends through both openings, said rear wall being configured at the second opening for sealing engagement with the follower rod, and at least one annular projection on the rear wall projecting into said second generally cylindrical opening, said annular projection having a diameter smaller than said generally cylindrical opening to provide a concentrated sealing force against the follower rod, a rigid back structural support for rigidly supporting the rear wall of the elastomeric seal, a rigid front structural support for rigidly supporting the front wall of the elastomeric seal, said front and back structural supports having openings therein aligned with the first and second openings in the elastomeric seal for receiving the follower rod, and one or more fasteners for fastening the elastomeric seal, the front structural support and the back structural support to one another in a manner preventing separation such that the elastomeric seal and front and back structural supports form a unitary follower structure movable as a unit in the barrel, the annular side wall of the elastomeric seal being resiliently deformable under said pressure in a radial direction for sealing against an interior surface of the barrel or the tubular cartridge, wherein said rear wall is deformable under said pressure to increase a radial sealing force of the rear wall against the follower rod at said second opening, wherein the back structural support comprises a elongate member, and wherein the opening in the back structural support comprises a bore in the elongate member having a cylindrical portion that receives said follower rod and is sized such that the elongate member seals against the follower rod.