An apparatus for assisting in the release of a web

Abstract: An apparatus (10) is disclosed for assisting in the release of a web (W) from contact with the heated surface (S). The apparatus (10) includes a material (12) which is urged into contact with the heated surface (S) upstream relative to the contact of the web (W) to the heated surface (S). The material (12) is devoid of metallic content and the arrangement is such that when the web (W) contacts the heated surface (S) downstream relative to the material (12), thermal energy is transferred from the surface (S) to the web (W). The web (W) is released from the heated surface (S) subsequent to the transfer of the heat, such release being facilitated by the material (12) being urged against the surface (S).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an apparatus for assisting in the release of a web from contact with a heated surface. More specifically, the present invention relates to an apparatus for releasing a web from a surface such as a backing roll of a heated extended nip press or a heated surface of a dryer. INFORMATION DISCLOSURE STATEMENT In a heated extended nip press, thermal energy is supplied to the surface of a backing roll so that when a formed web travels between the heated surface of the backing roll and a cooperating press shoe, thermal energy is imparted to the web for driving therefrom as much water as possible. However, in the aforementioned heated extended nip arrangements known in the art as high temperature presses (HTP), there has been a tendency for the web to stick to the heated surface of the backing roll when the web exits the pressing section. Such sticking of the web can cause delamination of the web or at least cause picking of fibers from the surface of the web on the backing roll side thereof. In US-A-4 556 451, there is disclosed an apparatus according to the preamble of claim 1. Many compositions have been applied to the surface of the aforementioned backing rolls in an attempt to enhance the release characteristics of the backing roll and to minimize picking of fibers from the pressed web. Applicant has made the surprising discovery that by wiping the heated surface of the backing roll with a non-metallic material such as TEFLON or the like, upstream relative to the pressing section, release of the web from the heated surface subsequent to the pressing section is remarkably improved. Therefore it is a primary objective of the present invention to provide an apparatus for assisting in the release of a web such apparatus overcoming the problems associated with prior art arrangements. To achieve this, the apparatus of the invention comprises the features claimed in the characterizing part of claim 1. Other objects and advantages of the present invention will be readily apparent to those skilled in the art by consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings. SUMMARY OF THE INVENTION The present invention relates to an apparatus for assisting in the release of a web from contact with a heated surface. The apparatus includes a doctor blade, the distal end of which is fabricated by a material which is urged into contact with the heated surface upstream relative to the contact of the web with the heated surface. The material is devoid of metallic content and the arrangement is such that when the web contacts the heated surface downstream relative to the material, thermal energy is transferred from the surface to the web. Subsequent to the transfer of heat, release of the web from the heated surface is facilitated by the provision of the material being urged against the surface. Many modifications and variations of the present invention will be readily apparent to those skilled in the art by consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings. However, such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevational view of a heated extended nip press apparatus including the apparatus according to the present invention; Fig. 2 is an enlarged side elevational view of a backing roll of the heated extended nip press shown in Fig. 1 showing the material urged into contact with the heated surface of the backing roll; and Fig. 3 is a side elevational view showing an alternative embodiment of the present invention in which the apparatus includes a material urged into contact with the heated surface of a dryer cylinder. Similar reference characters refer to similar parts throughout the various figures of the drawings. DETAILED DESCRIPTION OF THE DRAWINGS Figs. 1 and 2 are side elevational views of an apparatus generally designated 10 according to the present invention for assisting in the release of a web W from contact with a heated surface S. The apparatus 10 includes a doctor blade (14), the distal end of which is fabricated by a material 12 urged into contact with the heated surface S upstream relative to the contact of the web W with the heated surface S. The material 12 is devoid of metallic content and the arrangement is such that when the web W contacts the heated surface S downstream relative to the material 12, thermal energy is transferred from the surface S to the web W. Subsequent to the transfer of heat, release of the web W from the heated surface S is facilitated by the material 12 being urged against the surface S. In a more specific embodiment of the present invention as shown in Fig. 2, the material is TEFLON. Alternatively, the material includes molybdenum disulfide. As shown in Fig. 2, the apparatus includes a doctor blade generally designated 14 having a proximal and a distal end 1 6 and 18, respectively. The distal end 18 includes the material 12 which is urged into surface contact with the heated surface S. More specifically, the apparatus 10 includes a backing plate 20 which is secured to the proximal end 16 of the doctor blade 14 for imparting rigidity to the doctor blade 14 and for permitting urging of the distal end 18 of the blade 14 against the heated surface S. As shown in Fig. 2, the apparatus 10 includes a trailing doctor blade 14 which has a distal end 18 fabricated from the material 12 so that the material 12 wipes the heated surface S prior to the surface S coming into contact with the web W. More specifically, the apparatus 10 includes a rotatable roll 22 having a peripheral surface S which is heated by for example, an induction heater 26. The roll 22 is a backing roll of a heated extended nip press generally designated 24. The heated surface has a composition which includes ARMACOR or a ceramic or CHROMEX or a combination of such materials or ARMACOR, ceramic and CHROMEX in combination with other ingredients. Fig. 3 is a side elevational view of an alternative embodiment of the present invention wherein the apparatus further includes a dryer 30 of a dryer section generally designated 32 and in which the dryer defines the heated surface SA. A blade 14A is urged against the surface SA. The distal end 18A of the blade 14A is of TEFLON or the like material. As shown in Fig. 2, the wiping doctor blade 14 further includes means 28 for selectively urging the material 12 against the heated surface S for predictably controlling the release characteristics of the heated surface S. More specifically, when the means 28 urges the material 12 against the heated surface S, the web W is readily released from the heated surface S downstream relative to the pressing thereof. However, when the means 28 withdraws the material 12 from contact with the heated surface S, the web W follows or sticks to the heated surface S. Consequently, by selectively controlling the released characteristics of the heated surface S, threading of the press section 24 is facilitated. Applicant has also discovered that when the material is urged against the side of a press felt F extending through the heated extended nip press section, and coming into surface contact with the web, release of the web from the felt is facilitated. Additionally, Applicant has observed that although the material such as TEFLON is urged against the heated surface of the backing roll or dryer cylinder, hardly any Teflon is taken up by the heated surface. The present invention greatly assists in the release of a web from contact with a heated surface of a backing roll in a press section or the heated surface of a dryer cylinder.

Claims: An apparatus (10) for assisting in the release of a web (W) from contact with a moving surface (S) said apparatus comprising: a rotatable roll (22), the moving surface (S) being a peripheral surface of said roll (22), a trailing doctor blade (14) urged into contact with the moving surface (S) upstream relative to the contact of the web (W) with the moving surface (S), said trailing doctor blade (14) having a proximal end (16) and a distal end (18), characterized in that said moving surface (S) is a heated surface (S), the arrangement being such that when the web (W) contacts the heated surface (S) downstream relative to said trailing doctor blade (14), thermal energy is transferred from the heated surface (S) to the web (W),and in that said distal end (18) of the doctor blade (14) is fabricated from a material (12) being devoid of metallic content so that said material (12) wipes the heated surface (S), wherein release of the web (W) from the heated surface (S) subsequent to the transfer of heat being facilitated by said material (12) being urged against the heated surface (S). An apparatus as set forth in claim 1, characterized in that said material (12) is TEFLON. An apparatus as set forth in claim 1, characterized in that said material (12) includes molybdenum disulfide. An apparatus as set forth in claim 1, characterized in further including a backing plate (20) which is secured to said proximal end (16) of said blade (14) for imparting rigidity to said blade (14) and for permitting urging of said distal end (18) of said blade (14) against the heated surface (S). An apparatus as set forth in claim 1, characterized in that said roll (22) is a backing roll (22) of a heated extended nip press. An apparatus as set forth in claim 5, characterized in that the heated surface (S) is of a composition which includes ARMACOR. An apparatus as set forth in claim 5, characterized in that said surface (S) has a composition which includes a ceramic. An apparatus as set forth in claim 5, characterized in that said surface (S) has a composition which includes CHROMEX. An apparatus as set forth in claim 5, characterized in that said surface (S) has a composition which includes ARMACOR and CHROMEX. An apparatus as set forth in claim 1, characterized in further including a dryer (30) of a dryer section, said dryer (30) defining the heated surface (SA). An apparatus as set forth in claim 1, further including means (28) for selectively urging said material (12) against the heated surface (S) thereby predictably controlling the release characteristics of the heated surface (S).

Inventors: CROUSE JERE WILMOT, CROUSE, JERE WILMOT
Applicants: BELOIT TECHNOLOGIES INC, BELOIT TECHNOLOGIES, INC.
Application year: 1999
Main classification: D21G3
IPC codes: D21G3