Apparatus for producing sewn seams

A method and apparatus for use with a sewing machine by which a liquid is injected between lapped layers of material being sewn. A supply of the liquid at atmospheric pressure is fed by gravity to a constant displacement pump, the pump being actuated by a driven part of the sewing machine so that pumping rate is proportional to sewing rate. The outlet of the pump passes through a line which divides under the control of valve means. One branch of the line leads to a tube that is disposed in a folder, the tube having a discharge end projecting from the folder and disposed just upstream of the sewing machine needle(s). A further flattening roller is disposed after the presser foot through which the needles reciprocate. The other branch of the line is a return line that leads back to the reservoir. Thus pressurized metered liquid such as sealant is injected between the layers of material and the liquid is hydrostatically pressurized by the pressure foot so that when the needle passes therethrough, the liquid is forced into the space in each needle hole surrounding the thread. A subsequent flattening or repressurizing step is provided for the seam after it has left the pressure foot. The flow of liquid is interrupted just before the end of the seam is reached, such as two inches, to prevent the discharge of an excessive amount of liquid.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method and apparatus for sewing, and more 
specifically to a method and apparatus by which a liquid is injected into 
the seam during sewing. 
2. Prior Art 
There presently is a need to seal the needle puncture holes in fabric, 
sheet plastic, and other materials after the material is sewn, by single, 
double or triple needle sewing machines. This sealing effect is 
particularly necessary on tent materials to prevent moisture penetration 
through the full-depth needle hole or through the needle hole in the top 
layer of material and then into the seam or seams between the two layers 
of material. A thread hole sealing process can also be used to act as a 
barrier for bacteria in sewn items such as hospital gowns, operating room 
gowns, and the like. Among the methods that have been tried to prevent 
leakage through the sewing needle holes are attempts such as spraying on 
exterior flexible air-drying sealing agents and applying the sealing fluid 
between seam layers before they are assembled for sewing. Also, attempts 
have been made to use sealing tapes before the material is sewn. None of 
the known methods have satisfactorily sealed the sewn area, and 
furthermore they have generated cosmetic or physical bad side effects such 
as puckering in a sewn joint, or else there has been an excessive amount 
of sealing material on the outside surfaces of the sewn material. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a method 
and apparatus by which a liquid may be applied to a seam without there 
being an excessive exterior amount of such liquid, while achieving full 
penetration of the needle holes. 
According to the invention, apparatus is applied to a known type of sewing 
machine for making improved lap seams by using a constant displacement 
pump to force a suitable liquid through the discharge end of a tube into 
the lapped material as it is about to be engaged by the presser foot and 
needle of the sewing machine, whereby the presser foot hydrostatically 
pressurizes the liquid under it and through which the needle passes. The 
flow of liquid into the lapped material is interrupted just before the end 
of the seam is reached, by means of a foot-operated control, and if 
desired, a pressure roller flattens the finished seam just as it emerges 
from the presser foot before the liquid has had time to dry. In a 
preferred embodiment, the liquid is used as a sealant and is a viscous 
suspension of latex in a water base. 
Accordingly, it is a further object of the present invention to provide 
such apparatus for modifying a sewing machine without the use of any 
external power supply. 
A still further object of the present invention is to modify a sewing 
machine for the purpose stated but in such a way that modifying apparatus 
does not interfere with the normal usage of the sewing machine. 
Another object of the present invention is to provide a method and 
apparatus that will produce a seam which is compatible with various 
fabrics or other materials as well as compatible with their uses, such as 
adequate strength and stretchability. 
Yet another object of the invention is to provide a method for producing 
such a seam which will not be toxic, which will give off no fumes, and 
wherein the liquid used will, when needed, also function as a lubricant, 
hence eliminating any need for needle cooling means as might be the case 
with sewing in vinyl fabric. 
A still further object of the present invention is to provide a method 
wherein the liquid will not adhere to the sewing machine, that will be 
slow to wet the thread, that won't leak into the machine, and that won't 
spread out much at the area of the material where the seam is located. 
Yet another object of the present invention is to provide a method and 
apparatus which, in addition to sealing, or in place thereof may enable 
the use of other liquids or additives to effect marking, mold and mildew 
prevention, a chemical reaction, dyeing, matching or contrasting coloring, 
insecticide function, and the use of heat or light activated liquids. 
Many other advantages, features and additional objects of the present 
invention will become manifest to those versed in the art upon making 
reference to the detailed description and the accompanying sheets of 
drawings in which a preferred structural embodiment incorporating the 
principles of the present invention is shown by way of illustrative 
example.

AS SHOWN ON THE DRAWINGS 
The apparatus for producing sewn seams in lapped layers of material is 
shown in FIG. 1 as including a modified conventional sewing machine, 
generally indicated by the numeral 10. The machine 10 may have 1, 2 or 
more needles 11, a 2-needle machine being illustrated. The needles are 
reciprocated through openings in a presser foot 12, best shown in FIG. 3. 
A bobbin 13 provides thread to one needle and a bobbin 14 provides thread 
to the other needle. The sewing machine 10 has a conventional 
foot-operated speed control or pedal 15 and a conventional knee-operated 
device 16 for raising and lowering the presser foot 12. Although the 
layers of material to be sewn together may be lapped in several ways, or 
by hand, one way of arranging the materials is to feed their edges 
simultaneously through a folder 17. The folder 17 is a modified 
conventional folder which has a base 18 which may be adjustably secured to 
the top of the sewing machine as shown in FIG. 3. The base 18 extends 
upwardly along one edge as shown in FIG. 7 to provide a support surface 19 
which, in this view, extends to the left and follows a generally S-shaped 
configuration merging into a generally C-shaped configuration that 
terminates along an edge 20. One layer of material 21 can be pushed in 
laterally until its leading edge 22 is disposed within the lower curve of 
the S-shape. A further support surface 23 extends from the left to the 
right in generally concentric relation with the lower curve of the S-shape 
to enable it to guide a second sheet of material 24 around the outside of 
the lower curve of the S-shape and into the upper curve of the S-shape. 
The operator can than feed the material to the presser foot 12 which, in 
FIG. 7, is in a direction away from the viewer. The guide surfaces 
converge as shown in FIG. 6 to enable such guidance. 
As shown in FIG. 4, the apparatus includes a pump 25 of the constant 
displacement or metering type to which liquid is fed from a reservoir 26, 
the outlet of the pump 25 leading to a fluid line 27 to which there is 
connected a tube 28. A return line 29 is connected to the fluid line 27 
for conducting liquid back to the inlet of the pump 25 through the 
reservoir 26. Valve means generally indicated by the numeral 30 comprise a 
foot-operated valve which includes a foot-operated pedal control 31. If 
desired, a pressure roller 32 is secured to the sewing machine and is 
disposed to roll on and flatten the newly-formed seam as it emerges from 
beneath the rear side of the presser foot 12. 
The valve means 30 are illustrated in FIG. 5. The liquid from the pump 25 
is brought through the fluid line 27, and at a connection between the 
return line 29 and the fluid line 27, the liquid can flow in one or 
another path. To that end, the return line 29 has a first collapsible 
portion 33 and the fluid line 27 has a second collapsible portion 34 
disposed downstream from the connection with the return line 29. A lever 
35 is pivoted at 36, there being a bias spring 37 which normally urges one 
end of the lever 35 upwardly so as to compress and close the second 
collapsible portion 34, thus leaving the return line 29 open at the first 
collapsible portion 33. The foot-operated control 31 includes a Bowden 
wire assembly 38 which has a fixed sheath 39 and a movable wire 40 
connected through an overtravel spring 41 to the pivoted lever 35. The 
spring 41 is sufficiently stiff to transmit a force to the wire 40 
emanating from the bias spring 37, and yet it will yield in response to 
excess downward travel of the wire 40 after the first collapsible portion 
33 has been closed. 
The constant delivery or metering pump 25 is mounted on the sewing machine 
head just beneath the reservoir 26 as shown in FIG. 1. With this 
arrangement, the reservoir 26 is not pressurized and can conduct liquid by 
gravity to the inlet of the pump 25. The pump 25 is actuated by a driven 
part of the sewing machine 10. One structure for driving the pump is to 
utilize a cam on the upper sewing machine drive shaft for directly 
activating the pump. Other sources of power take-off from the sewing 
machine may be employed. For example, a drive wheel could be used to 
frictionally engage the internal main drive belt at the upper section of 
the sewing machine. Also, the pump may be driven by the external V-belt 
machine drive. The pump could include an integral cam activator or could 
be directly driven. If desired, a gear or other speed reducer can be used 
to slow down the pump reciprocating speed without affecting its metering 
ability. The details of a particularly advantageous pump for this purpose 
are disclosed and claimed in my application for U.S. patent on a "Pump", 
filed Apr. 12, 1979, Ser. No. 029,395 which is incorporated herein by 
reference. With such an arrangement, the volumetric pumping rate will be 
proportional to the speed at which the sewing machine is being operated, 
or in otherwords, will be in proportion to the sewing rate. 
The tube 28 receives liquid from the fluid line 27 and is supported by the 
sewing machine. The tube 28 is curved to accommodate any particular type 
of lap seam that is to be sewn, and to accommodate any particular folder 
17 that may be used. As shown in FIG. 6, the tube 28 enters the folder 17 
and then is curved about so as not to interfere with any of the movements 
of the fabric or other material therein, the tube 28 terminating at a 
discharge end 42 which is adjacent to the presser foot 12 and which 
projects from the folder 17. FIG. 7 shows the curvature of the tube 28 
from a different perspective, illustrating that it lies beneath the upper 
sheet of material 21, beginning from a point located quite a distance away 
from the curving guide surfaces so as not to be located in a position to 
interfere with the operator's work. The tube 28 then follows through an 
opening at 43 in the S-shaped guide wall, and then it passes between the 
lower guide surface 23 and the lower end of the S-shape against which it 
engages and is secured. Such a disposition places the tube 28 in that 
region above the other sheet 24. 
As soon as the sewing machine 10 is started, the pump 25 also starts and as 
soon as the operator wants liquid to be present in the seam, the operator 
actuates the foot-operated control 31 to open the line 27 to the tube 28 
where liquid discharges from the discharge end 42, just as the lapped 
portions of the material are about to enter beneath the presser foot 12 to 
be sewn by the needles 10. In this embodiment, with two needles the 
discharge end 42 is disposed midway between the prospective lines of 
sewing. If there were three needles, a further liquid discharge end 42 
would be provided between the other adjacent pair of prospective seams. 
While the sewing is going on, the material continues to pass freely both 
over and below the tube 28. 
With viscous liquid present between the layers, the force from the presser 
foot 12 creates a hydrostatic pressure in the area being sewn, and each 
needle 11 pierces the thin layer of pressurized sealant, shown in enlarged 
form at 44 in FIG. 2, whereupon liquid is hydrostatically forced in to 
fill the needle hole around the thread as shown at 45. Where the material 
constitutes waterproof fabric or other material such as nylon, 
urethane-coated nylon, vinyl fabric or the like, the liquid should be a 
sealant, for example, a viscous latex suspension carried in a water base, 
the viscosity being approximately that of a soft ice cream or syrup. 
Because of the speed at which the seam is made, there is little 
opportunity for the viscous liquid to wet the thread but the subsequent 
roller 32 appears to force the liquid into the thread and into the 
portions of the thread that bridge the needle holes. The roller 32 also 
flattens the seam and fills any voids that exist in the space occupied by 
the sealant shown at 44 in FIG. 2. Thus, where the sealant is an adhesive, 
the layers of material are also adhesively bonded along the lapped 
stitched seam. 
In one test, nylon fabric was sewn as shown in FIG. 2 but omitting the 
sealant 44. The stitched seam leaked at various points along its length 
beginning just above zero psi and going up to 5 psi. With the seam made as 
shown in FIG. 2, and as described, the pressure leakage rating had a 
consistent value between 15 and 25 psi, the material itself having a 
fabric burst test rating of about 50 psi. Larger needle holes are filled 
with a greater quantity of sealant automatically as the flow resistance 
into a large hole is less than the flow resistance for a small hole. A 
very small quantity of sealant liquid is used and thus the cost per linear 
foot has been as low as 0.1 cent. 
Certain materials will tend to heat the needles, such as vinyl fabric. 
Using the method and apparatus of the present invention, such heating has 
been reduced. It is believed that the liquid lubricates the needle, thus 
minimizing temperature rise and avoiding any need for needle cooling 
means. 
Other configurations and locations for the discharge end 42 as well as 
other liquids to be injected enhance the usefulness of the present 
invention. 
If it be desired to have a second seal 44 within the lapped portion of the 
sheet of material 21, then, as understood from FIG. 7, a second tube 28 
may be added so that its discharge end is directly above the one 
illustrated, and secured to the S-shaped guide 19 within the lower curve 
of the S, and thus just above and adjacent to the edge 22 of the sheet 21. 
While one seal 44 is normally sufficient, the second seal may be provided 
to have some different property. If a three-needle machine is utilized, 
then a second tube 28 may be disposed in parallel to the one illustrated 
and also secured to the lower side of the S-shape in slightly spaced 
relation so that the space between the two tubes would be aligned with the 
center needle. This arrangement is also advantageous for a single or 
double needle machine where a second liquid is desired in the lap of the 
seam. Further, a second tube 28 may be provided concentric with the 
illustrated tube 28 to enable blending of two liquids as they discharge 
from the discharge ends of the tubes. Normally, the discharge end 42 is 
round in cross section, but the same may be flattened slightly to minimize 
the thickness thereof between the laps of material. One advantage to the 
location of the seal 44 as shown in FIG. 2 is that the edge of it is 
visible to the operator which is of importance in regulating the flow rate 
of the liquid in the first instance. 
Although a viscous sealant is an especially useful liquid, other liquids 
may be employed to be able to provide other properties or functions. For 
instance, a liquid with an adhesive property applied to the thread can 
prevent unraveling of a seam made on a bobbinless sewing machine. This is 
the kind of seam that ordinarily if you pull on one end of the thread, the 
entire seam unravels. With an adhesive, in such seam, unraveling is 
prevented. Further, a liquid may be used to provide marking or 
identification if there is a contrasting color. Also, an additive to a 
liquid or a liquid may be provided for preventing mold or mildew. A liquid 
may be selected in order to provide a desired chemical reaction such as 
dye coloring. A liquid may be selected to provide matching or contrasting 
color. The method and apparatus may be used to inject a heat or light 
activated liquid into the seam for subsequent treatment. A liquid or an 
additive may be utilized to provide an insecticide property. With all 
these potential uses, it is clear that the method and apparatus can be 
utilized to provide a specialized sewn seam. 
No matter what the type of seam desired is, assuming that a folder is used, 
each tube 28 is wound around the surfaces and surface edges of the folder 
in a serpentine fashion to have the discharge end at or just beyond the 
end of the folder, with the tube so disposed that it will not interfere 
with movement of the fabric through the folder. 
The sealant or other liquid is also applied to other parts of the thread 
illustrated in FIG. 2 that extend beyond the seal 44. During bobbin type 
of sewing, the thread is picked up from the tip of the needle after the 
needle has fully penetrated the seam, and an excess loop is passed 
physically around the bobbin which floats in a mechanical chamber of the 
sewing machine. After looping around the bobbin and the bobbin thread, the 
excess needle thread is drawn back up through the needle eye until tight, 
which is the process for making a stitch. This long section of thread is 
thus pulled through the hole in the fabric and the liquid two times for 
each stitch. To prevent build up of liquid on the needle, the liquid 
should be relatively thick and may even be thixotropic so that the high 
speed moving thread will not be wetted at first. But when the stitch has 
been made, the hydrostatic pressure is adequate to shear thin the fluid 
enough to fill the needle holes, the seam lap, and slowly wet the 
stationary thread in the holes and the short thread sections spanning the 
needle holes. 
As there normally is a film of oil on all parts of the sewing machine, and 
as a water-based liquid is used, the sealant or other liquid will not 
adhere to these parts, even after the liquid has dried. Any excess liquid 
that inadvertently gets on the outer surface of the sewing machine will 
not run and spread to other parts of the machine and it will not leak into 
the crevices of the machine. Also, any excess thick fluid does not spread 
on the surface of the sewn fabric, but remains in the localized area of 
the seam where it quickly dries without much cause of contamination to 
other sections of the sewn article. 
Generally speaking, the smallest possible fluid lines, return lines or 
tubes should be used to minimize the volume of liquid contained therein. 
As there is a tendency for liquids to have air or vapor voids, there is a 
tendency for the liquid to be compressively resilient, and this tendency 
is minimized by minimizing the liquid volume under pressure. 
Where the liquid contains a latex suspension, it is preferable that 
surfaces contacted by such liquid be of stainless steel or plastic as 
these materials minimize the possibility of latex conglomeration. In use, 
no contamination of the needles or breakage of the thread occurs. If there 
is an excess amount of sealant on the needle, it is believed that the last 
layer of fabric being penetrated would serve as a wiper for any such 
excess. 
A cap or plug (not shown) may be provided on the discharge end 42 of the 
tube 28 when the device is not in use. 
When the device is to be placed into use, the air in the lines needs to be 
bled out by the liquid. However, if any air or vapor pocket should form in 
the line and pass through the tube 28, the result will be harmless because 
the presser foot 22 and the roller 32 squeegees the liquid to fill any 
such void. If any air or vapor pocket passes into the return line 29, then 
when it reaches the reservoir 26, it becomes vented to atmospheric 
pressure. 
Although various minor modifications might be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent warranted hereon, all such embodiments as reasonably and 
properly come within the scope of my contributions to the art.