Furnace curtains

A plurality of cords of heat resistant material are disposed adjacent to one another in a plurality of layers. A heat resistant tape material having an adhesive formed thereon in a pair of beads is wrapped around the center portions of the cord members so as to form a pair of free hanging curtain sections effective to block gas flows in a heat treatment furnace or the like. The adhesive is also heat resistant, and the use of a tape to form this curtain assembly enables the same to be independent of mounting hardware such as clamped mounting plates. The vertical position of the curtain assembly may be adjustable so as to compensate for wear during use.

BACKGROUND OF THE INVENTION 
The present invention relates to curtain assemblies and more particularly 
to furnace curtain assemblies effective to substantially block gas flows 
in heat treating furnaces. 
In many instances, such as in connection with the heat treating of ferrous 
parts, it is necessary to establish different gaseous atmospheres in 
separate zones of a heat treating furnace, or the like. For example, in 
the neutral hardening or annealing of such parts, different gaseous 
atmospheres are established in the preheat, hot and cooling zones of a 
furnace. An example of such a furnace zoning is found in British Patent 
Application No. 81-28392 and U.S. Pat. No. 4,294,395, the latter being 
directed to a process for brazing parts in a nitrogen based atmosphere and 
which is assigned to the assignee of the present invention. Typically, 
zoning of such furnaces is achieved by the use of sliding doors which are 
raised and lowered to enable the passage of parts being treated, but which 
are cumbersome and inefficient in furnaces through which parts are 
continuously passed as, for example, on a conveyor belt or the like. As 
the sliding doors of such furnaces are frequently opened and closed, it is 
difficult to maintain zones of separate gaseous atmospheres. The use of 
gas barriers such as inert gas flows or endothermic or exothermic gas 
flows has been proposed, but such gases tend to mix with a particular 
gaseous atmosphere in zones on either side of such "barrier". 
It is also known to utilize relatively heavy but somewhat flexible 
curtains, typically at furnace entrances and exits to reduce the flow of 
ambient atmosphere into a furnace or the outward flow of furnace 
atmosphere adjacent to such inlet or outlet. One problem with the use of 
such curtains is that as the same pass over parts being translated through 
the furnace for heat treatment, etc., the curtains are deflected and 
expose considerable areas of the furnace of one zone to another zone and 
are thus relatively ineffective as gas barriers. If the weight of such 
curtains is increased to minimize such deflection, relatively light but 
large parts undergoing heat treatment, such as carburetor housings, etc., 
may be knocked over which in turn may lead to undesirable flows of brazing 
fluxes, etc. and the ineffective brazing of particular joints. 
One solution to some of the foregoing problems is the use of curtains 
formed of a plurality of cords of heat resistant material. These curtains 
are formed by clamping mounting plates above and below a plurality of 
cords laid adjacent to one another and up to several layers deep. In this 
manner, a pair of curtain sections, each formed from many such cords, hang 
freely from the edge of the mounting plates. As parts are passed through a 
heat treating furnace, etc., in which such curtain assemblies are 
disposed, individual cord members will be deflected, but as only those 
cord members which contact the parts are deflected, a relatively effective 
barrier to gas flows between zones of the furnace is established. One 
problem with such curtains is that by clamping mounting plates directly 
onto cord members, the edges of the mounting plates, as well as the bolts 
securing such plates to one another, tend to wear and cut the cord 
members. In some instances, such cut cords fall on parts being heat 
treated which requires an operator to eventually remove such cords. In 
addition, the ends of cord members wear under furnace conditions which 
also mandates replacement thereof. Heat resistant cordage such as is sold 
under the trademark "Refrasil," is expensive and replacement of the same, 
as will be described below, is relatively time consuming and/or 
inconvenient. By employing mounting plates, as mentioned above, the 
curtain assembly cannot be readily replaced or stored independently of the 
mounting hardware. Thus, in order to replace a worn curtain assembly, the 
clamps securing the mounting assembly are released which results in a mass 
of cord members, which if acceptable for reuse, must be realigned in order 
to form a rebuilt curtain assembly. Alternately, spare curtain assemblies 
must be stored attached to or secured to the mounting hardware, and as the 
same may be anywhere between 18 inches to 8 feet in length, such storage 
or inventory of mounted curtain assemblies requires considerable space and 
is frequently impractical. 
Thus, there is a clear need for furnace curtain assemblies which 
effectively block gas flows and yet are readily replaceable when worn but 
which are not excessively costly and may be easily stored when not in use. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide improved curtain 
assemblies. 
It is also an object of the present invention to provide curtain assemblies 
suitable for use in heat treating furnaces wherein curtain sections are 
independent of the mounting hardware required to support such curtain. 
It is another object of the present invention to provide improved curtain 
assemblies comprised of cord material which are suitable for use in heat 
treating furnaces. 
It is yet another object of the present invention to provide curtain 
assemblies which are effective to substantially block gas flows through 
such assemblies. 
It is still another object of the invention to provide improved curtain 
assemblies suitable for use in heat treating furnaces and which are easily 
replaceable. 
It is yet another object of the present invention to provide curtain 
assemblies which may be adjustably positioned in heat treating furnaces. 
Other objects of the present invention will become apparent from the 
following description of exemplary embodiments thereof which follows and 
the novel features will be particularly pointed out in conjunction with 
the claims appended hereto. 
SUMMARY 
In accordance with the invention, a curtain assembly comprised of a 
plurality of heat resistant cord members or cordage is provided and 
includes elongated tape means for encircling the cordage about a position 
approximately centrally located along the length of the cord members to 
form a pair of free hanging curtain sections. Heat resistant adhesive 
material is applied to the cordage members and to the tape in such a 
manner as to secure the cordage and tape member so that the curtain 
assembly may be easily handled and stored independently of the mounting 
hardware such as clamping or mounting plates. Alternately, the tape member 
encircling the cordage may be sewn so as to secure the cordage to the tape 
member. 
Preferaby, the curtain assemblies are formed by winding cordage on a frame 
or other suitable device, typically to a depth of two or more layers. The 
elongated tape means are affixed about the wound cordage in locations 
spaced from one another from the frame after which the cordage is cut to 
form curtain assemblies of the desired curtain length. The width of the 
curtain assemblies will correspond essentially to the width of the frame 
member and typically, for use in heat treating furnaces, widths of 18 
inches to 8 feet may be employed. 
The curtain assemblies so formed may be releasably secured to mounting 
hardware such as a pair of mounting or clamping plates disposed above and 
below tape members along the length thereof. Bolts or other suitable means 
are utilized to releasably secure the clamping members to the tape means 
which facilitate the retention of cord members cut by the bolts, etc. 
Thus, even though certain cord members may be cut by bolts, etc., the cord 
members will still be adhesively secured to the tape means, and the 
resulting curtain assembly will not be deficient in cordage when mounted 
in a heat treating furnace. In order to enable the proper adjustment of 
curtain assemblies in accordance with the invention, means are provided to 
dispose the same in any of a plurality of vertical locations in the 
furnace. This enables the curtain of a particular length to be lowered 
from the roof of a furnace when relatively flat parts are passed 
therethrough for heat treatment. Also, upon wearing of the free ends of 
the curtain assembly, the same may be lowered to enable gas flows under or 
through the curtain assembly to be substantially blocked and thus 
facilitate the preservation of different gaseous atmospheres in furnace 
zones defined by the curtain assembly.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to FIG. 1 of the drawing, illustrated therein is an exemplary 
embodiment of curtain assembly 10 according to the invention which is 
essentially comprised of cord members 12, beads of adhesive material 13, 
and tape member 14. Cord members 12 are preferably comprised of a silicone 
based heat resistant material such as is available commercially under the 
trademark "Refrasil." Cord members 12 may be set out on elongated tape 
member 14 adjacent to one another with a total width defined by cord 
members 12 defining the width of curtain assembly 10. The length of cord 
members 12 will define the height of the curtain which will equal 
approximately one-half the length of cord members 12 less the width of the 
elongate tape member 14. Preferably, each curtain assembly 10 will be 
comprised of a plurality of layers of cord members 12 and two to five 
layers will be suitable. In order to retain cord members 12 to one another 
and to elongate tape member 14, an adhesive material 13 is preferably 
deposited in a bead-like fashion which is depicted in FIG. 1. Adhesive 
material 13 is applied, again preferably in two beads, on each layer of 
cord members 12 prior to curing as will be subsequently described. 
Elongate tape member 14 is preferably longer than the width of curtain 
assembly 10 to enable the ends of member 14 to be folded over onto the 
upper layer of cord members 12 and into contact with the beads of adhesive 
material 13 thereon. As illustrated in FIG. 2, an additional piece of tape 
member 15, the length of which will substantially equal the distance 
between the ends of tape member 14, when folded over cord members 12, is 
affixed to beads of adhesive material 13 and the top layer of cord members 
12. Alternately, tape members 14 and 15 may be sewn together with heat 
resistant thread to secure cord members 12 to tape members 14 and 15. The 
elongate tape member 14 of curtain assembly 10 is shown in FIG. 2 and may 
be clamped and heated to cure adhesive material 13 to effectively bond 
cord members 12 to one another and to elongate tape member 14. Curtain 
assembly 10 then will be formed and will be comprised of two free hanging 
curtain sections extending outwardly and downwardly from elongate tape 
members 14 and 15. It will be appreciated that by utilizing such tape 
members to retain cord members 12, the resulting curtain assembly 10 may 
be handled and stored independently of the mounting hardware, exemplary 
embodiments of which are illustrated in FIGS. 3 and 4 and which will be 
subsequently described. In addition, curtain assembly 10 may be easily 
handled as cord members 12 are secured to one another and to tape members 
14 and 15 as mentioned above so that the problems of attempting to handle 
and store many individual lengths of cord material are simply averted by 
the present invention. 
Referring now to FIG. 3, illustrated therein is a roof portion 34 of heat 
treating furnace 11, to which is mounted curtain assembly 10. A pair of 
mounting plates 20 and 22 are preferably disposed above and below curtain 
assembly 10, respectively, and are secured to one another by means of 
bolts 24. A plurality of such bolts may be utilized along the length of 
mounting plates 20 and 22 which length is substantially coextensive with 
the width of curtain assembly 10. It will be appreciated that stresses 
generated by bolts 24 and plates 20 and 22, as the same pass through and 
retain curtain assembly 10, are absorbed by elongate tape members 14 and 
15 (FIG. 2) which results in less stress imposed upon cord members 12. 
Similarly, as a consequence of adhesively securing cord members 12 to tape 
members 14 and 15, as described above, the tendency of bolts 24 and the 
edges of mounting plates 20 and 22 to cut individual cord members 12 is 
significantly reduced. This in turn results in less selvage of cord 
members falling onto parts undergoing heat treatment and thus does not 
impair full heat treating of such parts while enabling curtain assembly 10 
to last longer in service. 
Mounting plates 20 may be affixed by weldments 31 and 32 or other suitable 
means to support member 30, which may take the form of a plate disposed 
vertically through an appropriately formed slot in roof 34 of furnace 11. 
Support member 30 is provided with a plurality of apertures defined 
therein as illustrated by apertures 40, 42 and 44. Brackets 36 and 38 may 
be rigidly affixed along the bottom surfaces thereof to the top of roof 
portion 34 or other suitable surface above furnace 11, and such brackets 
are spaced from one another by a distance substantially equal to the 
thickness of support member 30. A bolt 46 and nut 48 may be utilized to 
releasably secure support member 30 to brackets 36 and 38. It will be 
understood that depending upon the aperture 40, 42, 44, etc. utilized to 
receive bolt 46, the height of curtain assembly 10 in furnace 11 will be 
adjusted accordingly. Preferably, the fit of member 30 between bracket 
members 36 and 38 is substantially gas tight so that any leakage above 
curtain assembly 10 is minimized. By enabling the vertical position of 
curtain assembly 10 to be adjusted as mentioned above, further use may be 
made of this assembly as the ends of cord members 12 wear away from 
repeated contact with parts undergoing heat treatment. 
Referring now to FIG. 4, illustrated therein in a further exemplary 
embodiment of the present invention wherein a curtain assembly 10 is 
mounted in a channel 50 welded to top 51 of a box 49 disposed adjacent to 
the entrance and/or exit of furnace 11 (not shown). Typically, channel 50 
is generally inverted and U-shaped and is provided with a bolt 52 
extending downwardly therethrough. Clamping plates 55 and 56 are supported 
on head 53 of bolt 52 as the latter will extend through plates 55 and 56. 
A nut 57 is provided with bolt 52 on top of channel 50 so that by 
adjusting the position of nut 57 on bolt 52, the height of clamping plates 
55 and 56 and hence the height of curtain assembly 10 may be adjusted. 
Thus, as the ends of cord member 12 wear upon use in heat treating furnace 
11 (FIG. 3), curtain assembly 10 may be lowered to enable the effective 
life thereof to be increased. In practice, curtain assembly 10 will occupy 
substantially the full width of channel 50 and thereby provide a gas seal. 
That is, curtain assembly 10 should not be lowered to enable the 
unobstructed passage of gas thereabove from one side of channel 50 to the 
other. 
It will be understood that as the length of channel 50 and mounting plates 
55 and 56 is substantially coextensive with the width of curtain assembly 
10, two or more sets comprised of bolts 52 and nuts 57 may be required to 
adequately support curtain assembly 10. However, replacement of a worn 
curtain assembly 10 may be easily achieved by releasing nut 57 and 
removing assembly 10 from mounting plates 55 and 56. In addition, several 
channels 50, each with an accompanying curtain assembly 10, may be 
provided with box 49 to assure that box 49 substantially precludes gas 
flows therethrough; i.e. blocks the flow of gaseous atmosphere from 
furnace 11 (FIG. 3) outwardly of box 49 and inhibits the inward flow of 
ambient atmosphere into furnace 11. In addition, an inert gas such as 
nitrogen may be introduced into box 49 to inert the same and assist 
curtain assembly 10 in blocking the inward flow of ambient atmosphere as 
mentioned above. 
In summary, curtain assemblies according to the present invention 
constitute an improvement over prior art curtain devices in that curtain 
sections may be handled and stored independently of the mounting hardware 
required therefor. This desirable result is achieved by wrapping 
heat-resistant cord material with a tape-like member and adhesively 
securing these materials together which in turn significantly reduces the 
tendency of individual cord members to loosen between clamping plates. In 
addition, by disposing clamping plates in contact with the elongate tape 
member, the tendency of bolts extending through the curtain assembly to 
cut individual cord members is also substantially reduced. Furthermore, by 
mounting the curtain assembly such that the same is vertically adjustable 
in a furnace, etc., the curtain assembly may be lowered as ends of the 
cord material wear. The foregoing attributes of the present invention all 
cooperate to extend the effective life of such cord members which are 
usually relatively expensive. 
The foregoing and other various changes in form and details may be made 
without departing from the spirit and scope of the present invention. 
Consequently, it is intended that the appended claims be interpreted as 
including all such changes and modifications.