Abrading device

A surface treating apparatus comprising a housing containing a supply of abrasive material having an outlet at the bottom thereof, a source of vacuum connected to the housing and applying a negative pressure to the upper surface layer of said abrasive material, a gun for directing abrasive material in the direction of a surface area to be abraded and having a passageway therethrough, a shroud surrounding the passageway of said gun and bearing against said surface area, a first conduit connecting the inside of said shroud with the inside of said housing above said abrasive material, a source of positive pressure air connected to one end of said gun passageway, a second conduit having a first end portion connected to said outlet and a second end portion connected to said gun passageway downstream of the connection of said source of positive pressure to said gun, abrasive material from the housing occupying said first end portion under the influence of gravity when the apparatus is inoperative, an aperture formed in said first end portion of the second conduit adjacent the abrasive material therein and said housing outlet, the aperture permitting ambient atmospheric pressure to communicate with said second conduit downstream to the gun and upstream through said first end portion to the housing only through said outlet, whereby positive pressure air flowing through said gun passageway across the end of said second conduit creates a negative pressure in said second conduit, the negative pressure in said second conduit causing ambient air to flow in through said aperture toward the gun and to draw abrasive material from said first end portion and from said housing through said outlet and to propel said abrasive material to the gun passageway so that positive pressure in said passageway propels the abrasive material onto the surface area, the negative pressure in said housing above said material causing the return of the abrasive material through the first conduit from the shroud and into the housing above said supply of abrasive material.

A surface treating apparatus comprising a housing containing a supply of abrasive material and having an outlet at the bottom thereof, a gun for directing abrasive material in the direction of a surface area to be abraded and having a passageway defined therethrough, a source of positive pressure air connected to one end of said gun passageway, a conduit having a first end portion connected to said outlet and a second end portion connected to said gun passageway downstream of the connection of said source of positive pressure to said gun, abrasive material from the housing occupying said first end portion under the influence of gravity when the apparatus is inoperative, aperture means formed in said first end portion of the conduit adjacent the abrasive material therein and the housing outlet, said aperture means permitting ambient atmospheric pressure to communicate with said conduit downstream to the gun and upstream through said first end portion to the housing only through said outlet, whereby positive pressure air flowing through said gun passageway across the end of said conduit creates a negative pressure in said conduit, the negative pressure in said conduit causing ambient air to flow in through said aperture means toward the gun and to draw abrasive material from said first end portion and from said housing through said outlet and to propel said abrasive material to the gun passageway so that positive pressure in said passageway propels the abrasive material onto the surface area.

A surface treating apparatus comprising a housing containing a supply of abrasive material having an outlet at the bottom thereof, a source of vacuum connected to the housing and applying a negative pressure to the upper surface layer of said abrasive material, a gun for directing abrasive material in the direction of a surface area to be abraded and having a passageway therethrough, a shroud surrounding the passageway of said gun and bearing against said surface area, a first conduit connecting the inside of said shroud with the inside of said housing above said abrasive material, a source of positive pressure air connected to one end of said gun passageway, a second conduit having a first end portion connected to said outlet and a second end portion connected to said gun passageway downstream of the connection of said source of positive pressure to said gun, abrasive material from the housing occupying said first end portion under the influence of gravity when the apparatus is inoperative, aperture means formed in said first end portion of the second conduit adjacent the abraisive material therein and said housing outlet, the aperture means permitting ambient atmospheric pressure to communicate with said second conduit downstream to the gun and upstream through said first end portion to the housing only through said outlet, whereby positive pressure air flowing through said gun passageway across the end of said second conduit creates a negative pressure in said second conduit, the negative pressure in said second conduit causing ambient air to flow in through said aperture means toward the gun and to draw abrasive material from said first end portion and from said housing through said outlet and to propel said abrasive material to the gun passageway so that positive pressure in said passageway propels the abrasive material onto the surface area, the negative pressure in said housing above said material causing the return of the abrasive material through the first conduit from the shroud and into the housing above said supply of abrasive material.