Plunger for hand grease guns

Claim 2

In a hand grease gun adapted to use both cartridge-packed and bulk-filled greases, said gun including a cylindrical barrel of known inside diameter extending between forward and rearward ends, an axially extending plunger guide rod, and means, including a pressure plate, coaxial with said rod for resiliently applying axial pressure therealong, the improvement which consists of a plunger assembly including a cylindrical plunger of homogeneous, flexible, elastic material for use as a sliding seal in said barrel, said plunger comprising: a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension and an axial bore to pass said guide rod, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter, greater than said known inside diameter of said barrel, near said second end of said plunger, and said plunger having a peripheral groove around said second end thereof, of radial dimension substantially equal to the radial thickness of said skirt.

Claim 3

In a hand grease gun adapted to use both cartridge-packed and bulk-filled greases, said gun including a cylindrical barrel of known inside diameter extending between forward and rearward ends and an axially extending plunger guide rod, the improvement which consists of a plunger assembly including a cylindrical plunger of homogeneous, flexible, elastic material for use as a sliding seal in said barrel, said plunger comprising: a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension and an axial bore to pass said guide rod, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter, greater than said known inside diameter of said barrel, near said second end of said plunger.

Claim 4

In a hand grease gun adapted to use both cartridge-packed and bulk-filled greases, said gun including a cylindrical barrel of known inside diameter extending between forward and rearward ends and an axially extending plunger guide rod, the improvement which consists of a plunger assembly including a cylindrical plunger of homogeneous, flexible, elastic material for use as a sliding seal in said barrel, said plunger comprising: a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension and an axial bore to pass said guide rod, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter, greater than said known inside diameter of said barrel, near said second end of said plunger.

Claim 5

The structure of claim 2 in which said skirt tapers in thickness toward said first end of said plunger substantially to a feather edge.

Claim 6

The structure of claim 2 in which said hub and said skirt coact to define an annular chamber which decreases in cross sectional area with distance from said first end of said plunger.

Claim 7

A grease gun adapted to use both cartridge-packed and bulk-filled grease comprising, in combination: a cylindrical barrel of known inside diameter extending between a forward end cap and a rearward end cap; a plunger guide rod carried in said rearward cap and extending axially in said barrel; a pressure plate slidable on said rod in said barrel; a compression spring in said barrel acting between said rearward cap and said pressure plate; and a plunger, of homogeneous, flexible, elastic material, engaged by said pressure plate and slidable on said rod in sealing engagement with said barrel, said plunger comprising, a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension and an axial bore to pass said guide rod, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter, greater than said known inside diameter of said barrel, near said second end of said plunger, and said plunger having a peripheral groove around said second end thereof, of radial dimension substantially equal to the radial thickness of said skirt.

Claim 8

A grease gun adapted to use both cartridge-packed and bulk-filled grease comprising, in combination: a cylindrical barrel of known inside diameter extending between a forward end cap and a rearward end cap; a plunger guide rod carried in said rearward cap and extending axially in said barrel; a pressure plate slidable on said rod in said barrel; a compression spring in said barrel acting between said rearward cap and said pressure plate; and a plunger, of homogeneous, flexible, elastic material, engaged by said pressure plate and slidable on said rod in sealing engagement with said barrel, said plunger comprising, a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension and an axial bore to pass said guide rod, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter, greater than said known inside diameter of said barrel, near said second end of said plunger, and said plunger having a peripheral groove around said second end thereof, of radial dimension substantially equal to the radial thickness of said skirt.

Claim 9

A cylindrical plunger of homogeneous, flexible, elastic material for use as a sliding seal in a cylindrical chamber, said plunger comprising: a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter near said second end of said plunger.

Claim 10

A cylindrical plunger of homogeneous, flexible, elastic material for use as a sliding seal in a cylindrical chamber, said plunger comprising: a peripheral hollow skirt having a predetermined axial dimension; a central hub having said predetermined axial dimension, and connected to said skirt only at one axial end thereof; and a web, of thickness less than said predetermined axial dimension, unitary with said hub at a first, forward end of said plunger and unitary with said skirt at a second, rearward end of said plunger, to comprise a generally conical partition across said plunger which is the only support for said skirt, the thickness of said skirt decreasing inwardly in both axial directions from a location of maximum outside diameter near said second end of said plunger.

Claim 11

A plunger according to claim 6 having a peripheral groove around said second end thereof, of radial dimension substantially equal to the radial thickness of said skirt.