Apparatus and method for applying heat-sensitive adhesive tape to a web moving at high speed

Apparatus for applying pieces of heat-sensitive adhesive tape, such as frontal diaper tape, of the type having a layer of heat sensitive adhesive material that is generally tacky at an elevated temperature substantially greater than room temperature but substantially not tacky at room temperature to a web moving at high speed, such as a web of water-resistant material designed for use as the outer layer of disposable diapers, the pieces of tape being applied in spaced relationship along the web, the apparatus comprising:

• a tape feed wheel for feeding the tape to the apparatus from a supply of generally continuous tape, the tape fed wheel being adapted to rotate at a feed velocity appropriate for feeding a sufficient quantity of tape to the apparatus for application to the web;
• preheating means for heating the tape-feed wheel to heat the tape to a tape-feed temperature at which the heat-resensitive adhesive layer is tacky or substantially softened;
• a tape-applying wheel in rolling engagement with the web for applying tape fed to it from the tape feed wheel to the web, the tape-applying wheel including a generally circumferential surface having sufficiently low friction for sliding engagement with the tape such that the tape is substantially undistorted and untorn by the sliding engagement, the tape-applying wheel being adapted to rotate at a tape-applying velocity greater than the feed velocity and with a circumferential surface velocity substantially equal to the speed of the web;
• vacuum means for providing suction through the circumferential surface of the tape-applying wheel to hold the tape thereon;
• the vacuum means including walls in the tape-applying wheel forming a plurality of spaced vacuum passageways generally adjacent the surface of the wheel extending longitudinally of the wheel from one end of the wheel, each vacuum passageway having a plurality of spaced openings communicating with the cylindrical surface of the tape-applying wheel;
• a stationary vacuum manifold in sealing-sliding engagement with the one end of the tape-applying wheel for applying vacuum to the vacuum passageways that are adjacent the tape to hold the tape on the tape-applying wheel, the vacuum manifold being generally crescent shaped with an arc substantially about the axis of rotation of the tape-applying wheel;
• heating means for heating the circumferential surface of the tape-applying wheel to heat the tape to the elevated temperature at which the heat-sensitive adhesive is generally tacky and for maintaining the tape at the elevated temperature unit it is applied to the web;
• cutting means for cutting successive end portions of the tape in sliding engagement with the tape-applying wheel into pieces to be applied to the web, the cutting means being actuated in response to the rotary position of the tape-applying wheel;
• and
• buffing means adjacent a surface of the web opposite the tape-applying wheel for pressing the web and the piece of tape to be applied to the web together between the buffing means and tape-applying wheel so that the piece of tape adheres to the web;
• the vacuum means being adapted to hold tape fed to the tape-applying wheel in sliding engagement with the circumferential surface of the tape-applying wheel with the tape moving at the tape-feed velocity until it is cut, and the tape-applying wheel being adapted to accelerate each successive piece of tape cut from a successive end portion of the tape from the tape-feed velocity to the tape-applying velocity substantially equal to the velocity of the web so that the tape and web are moving at substantially equal velocity when the tape is applied to the web;
• the tape-applying wheel including a strike plate extending longitudinally along the circumferential surface of the tape-applying wheel and having an outer surface against which the cutting means cuts the tape, the vacuum means having vacuum ducts in the strike plate extending longitudinally of the tape-applying wheel from the one end of the wheel for providing suction through the outer surface of the strike plate for holding a piece of tape-cut from a successive end portion of the tape on the strike plate, the vacuum manifold, vacuum passageways and vacuum ducts being arranged such that suction is applied only to portions of the circumferential surface of the tape-applying wheel and outer surface of the strike plate that are engaging the tape or a piece of tape cut from a successive end portion of the tape;
• the tape-applying wheel further including an insulating plate mounted on the wheel adjacent the one end of the wheel and an end plate mounted on the wheel adjacent the insulating plate and sandwiching the insulating plate between it and the wheel, the end plate being in sealing-sliding engagement with the vacuum manifold, and the insulating and end plates having vacuum passageways and ducts registering with the corresponding vacuum passageways and ducts of the tape-applying wheel.

A method of applying pieces of heat-sensitive adhesive tape, such as frontal diaper tape, of the type having a layer of heat sensitive adhesive material that is generally tacky at an elevated temperature substantially greater than room temperature but substantially not tacky at room temperature to a web moving at high speed, such as a web of water-resistant material designed for use as the outer layer of disposable diapers, the pieces being applied in spaced relationship along the web, the method comprising the following steps:

• maintaining a peripheral surface of a tape-applying wheel in rolling engagement with the web and rotating the tape-applying wheel at a tape-applying velocity where the velocity of the peripheral surface of the tape-applying wheel is substantially equal to the speed of the web;
• feeding the tape along a tape-feed wheel to the tape-applying wheel from a supply of generally continuous tape at a tape-feed velocity lower than the tape-applying velocity and appropriate for feeding a sufficient quantity of tape for application to the web;
• preheating the tape along the tape-feed wheel to a tape-feed temperature at which the heat-sensitive adhesive layer is tacky or substantially softened;
• providing suction through a portion of the peripheral surface of the tape-applying wheel to hold the tape thereon;
• heating the peripheral surface of the tape-applying wheel to heat the tape substantially to the elevated temperature at which the heat-sensitive adhesive is generally tacky and for maintaining the tape substantially at the elevated temperature until it is applied to the web;
• cutting successive end portions of the tape against the tape-applying wheel into pieces to be applied to the web in response to the rotary position of the tape-applying wheel;
• maintaining the portion of the tape to be cut in generally low-friction sliding engagement with the peripheral surface of the tape-applying wheel such that the tape is substantially undistorted and untorn by the sliding engagement and with the tape moving at the tape-feed velocity until it is cut;
• accelerating each successive piece of tape cut from the successive end portions of the tape from the tape-feed velocity to the tape-applying velocity substantially equal to the velocity of the web so that the tape and web are moving at substantially equal velocity when the tape is applied to the web;
• and
• pressing the web and the piece of tape to be applied to the web together between a buffing means and the tape-applying wheel so that the piece of tape adheres to the web.