Dispensing – With discharge assistant – Container with follower
Reexamination Certificate
2000-04-17
2002-01-01
Kaufman, Joseph A. (Department: 3754)
Dispensing
With discharge assistant
Container with follower
C222S504000, C222S146500
Reexamination Certificate
active
06334554
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hot melt adhesive dispensing systems, and more particularly to a new and improved snuffback valve for dispensing hot melt adhesive whereby quick shutoff of the adhesive supply is able to be achieved at the end of a dispensing operation and during closure of the valve such that undesirable stringing of the adhesive does not occur.
BACKGROUND OF THE INVENTION
In connection with the dispensing of highly-viscous materials, such as, for example, hot melt adhesives, it is imperative that the dispensing system comprise what is known in the art as a snuffback valve by means of which shut off of the dispensed adhesive is readily achieved upon closure of the valve whereby stringing of the adhesive does not occur. One type of known PRIOR ART snuffback valve is disclosed in
FIG. 1
wherein the snuffback valve is generally indicated by the reference character
10
. The snuffback valve
10
is adapted to be fixedly mounted upon a valve stem, note shown, which, in turn, is adapted to be fixedly connected, for example, to a piston drive, also not shown, by means of which the snuffback valve is moved linearly with respect to its valve seat member, not shown, so as to attain its relative opened and closed positions with respect to the valve seat.
More particularly, the PRIOR ART snuffback valve
10
comprises a substantially cylindrical structure having an axis
11
, and is seen to comprise a first bore
12
and a second counterbored portion
13
with a shoulder
14
defined therebetween. The valve stem, not shown, extends through the counterbored portion
13
and the valve end of the stem is seated upon the shoulder portion
14
. A bolt type fastener, not shown, extends through bore
12
and threadedly engages the valve end of the valve stem, not shown, so as to fixedly mount the valve stem within the valve
10
. The valve
10
further comprises a cylindrical throat portion
15
which has an external peripheral cylindrical surface portion
16
wherein the external surface portion
16
is adapted to be disposed internally within the valve seat member, not shown, when the snuffback valve
10
is moved to its closed position so as to cooperate with the valve seat member in terminating flow of the adhesive. An annular tolerance, gap, or space, of, for example, 0.010 inches, is defined between the external cylindrical surface portion
16
of the snuffback valve
10
and the internal peripheral cylindrical surface portion of the valve seat member, not shown, so as to readily permit linear movement of the snuffback valve
10
with respect to its valve seat member, not shown, during opening and closing cycles of the valve, as well as to define or determine the snuffback action of the valve
10
. Downstream of the throat portion
15
, the snuffback valve
10
comprises an external frusto-conical surface portion
18
which is adapted to be mated with a complimentarily shaped frusto-conical surface portion of the valve seat member, not shown, when the snuffback valve
10
is disposed at its closed position and is therefore seated upon the valve seat member.
Still further, the snuffback valve
10
comprises a second cylindrical portion
20
having an external peripheral cylindrical surface portion
22
which is disposed downstream of the frusto-conical portion
18
as considered in the dispensing direction of the hot melt adhesive. The external diametrical extent of the second peripheral cylindrical surface portion
20
is substantially greater than that of the throat portion
15
such that the external peripheral cylindrical surface portion
22
of the second cylindrical portion
20
cooperates with an internal peripheral cylindrical surface portion of a valve seat adapter or dispensing block, not shown, so as to define a discharge path for the adhesive to be dispensed. It is lastly noted that the front or down-stream face
24
of the snuffback valve
10
is disposed perpendicular to the axis
11
of the snuffback valve
10
, and that the diametrical extent of the front or downstream face
24
of the snuffback valve
10
is such as to extend radially outwardly with respect to the axis
11
and has an external diametrical extent which is substantially equivalent to that of the second cylindrical portion
20
.
While the aforenoted PRIOR ART type of snuffback, valve
10
has performed substantially satisfactorily, the structure of the aforenoted PRIOR ART snuffback valve
10
has in fact presented several operational problems or drawbacks. For example, it is firstly noted that the throat portion
15
of the PRIOR ART snuffback valve
10
has a substantially elongated axial length dimension. In addition, the external diametrical extent of the throat portion
15
is such that, as has been noted hereinbefore, a relatively large clearance of, for example, 0.010 inches, is defined between the external peripheral cylindrical surface portion
16
of the snuffback valve
10
and the internal peripheral cylindrical surface portion of the valve seat member, not shown. Consequently, while the snuffback valve
10
is of course able to achieve its closed position with respect to the valve seat, not shown, when the snuffback valve
10
is appropriately energized by its associated drive mechanism or system, not shown, such that dispensing of the adhesive by the valve
10
is terminated, the stroke of the snuffback valve
10
is considerably long, thereby rendering the speed of the valve relatively slow. This operative feature, which also results in more extensive wear of the seal members and therefore a shortening of the seal life, along with the relatively large tolerance or clearance space defined between the external peripheral cylindrical surface portion
16
of the throat portion and the internal peripheral cylindrical surface portion of the valve seat member, delays the onset or achievement of the snuffback operation of the valve thereby permitting stringing of the adhesive to nevertheless occur.
In addition, due to the provision or structure of the front or downstream surface or face
24
of the snuffback valve
10
as being disposed perpendicular to the axis
11
of the valve
10
, and in addition, in view of the fact that such surface or face
24
extends radially outwardly so as to have substantially the same external diametrical extent as that of the second cylindrical portion
20
, the snuffback valve
10
causes a phenomenon, known as bursting, to occur when a new adhesive dispensing cycle is commenced. Bursting is the sudden expulsion, discharge, or dispensing, upon the commencement of a new adhesive dispensing operation or cycle, of a predetermined amount or glob of adhesive which residually remains disposed between the downstream end or front face of the snuffback valve and the exit orifice, not shown, of the adhesive dispensing mechanism when a previous dispensing operation or cycle is terminated. The front face or surface
24
of the snuffback valve
10
therefore acts, in effect, as a type of plow forcing the glob or residual adhesive to be suddenly dispensed as a result of the linear movement of the valve
10
attendant the opening of the valve
10
and the unseating of the throat portion
15
of the valve
10
with respect to the valve seat member upon commencement of a subsequent dispensing cycle or operation.
A need therefore exists in the art for a new and improved snuffback valve wherein the structure of the valve is such that when dispensing of, for example, highly viscous materials, such as, for example, hot-melt adhesives, is to be achieved, the various operational drawbacks and disadvantages characteristic of such dispensing systems, such as, for example, stringing and bursting, do not occur, and in addition, the valve is characterized by means of a relatively short movement stroke with a relatively quick operational response time.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new and improved snuffback valve for use in connection with the dispensing of highly viscous materials, su
Bauer Mark D.
Bolyard, Jr. Edward W.
Illinois Tool Works Inc.
Kaufman Joseph A.
Schwartz & Weinrieb
LandOfFree
Snuffback valve for hot melt adhesive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Snuffback valve for hot melt adhesive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Snuffback valve for hot melt adhesive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2832740