Electric heating – Heating devices – With heating unit structure
Reexamination Certificate
1999-11-03
2001-04-10
Paik, Sang (Department: 3742)
Electric heating
Heating devices
With heating unit structure
C239S135000
Reexamination Certificate
active
06215109
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hot melt adhesive application systems, and more particularly to a new and improved system or arrangement, and a method, for heating incoming air used to fiberize or determine the control pattern of the adhesive conveyed to the adhesive spray modules and dispensed therefrom.
BACKGROUND OF THE INVENTION
In connection with the spraying, dispensing, or discharge of hot melt adhesive materials, air is routed to the spray modules in order to control the particular patterns of the adhesives being dispensed. More specifically, such air is preheated so as to maintain the adhesive in its heated state such that the hot melt adhesive can properly achieve its adhesive functions. If cooled or ambient air was employed, the hot melt adhesive would experience an inappropriate amount of cooling whereby the utility of the adhesive would be lost. It has also been found to be imperative that the preheated air provided to the plurality of adhesive spray modules be uniform in temperature, density, and flow rate parameters in order to ensure uniformity of the resulting adhesive spray patterns from the adhesive spray modules. Currently, two basic air preheater design systems or arrangements are conventionally in use, however, each one of such systems or arrangements exhibits inherent operational drawbacks or disadvantages.
For example, as disclosed within
FIG. 1
, a first conventionally known and utilized system is illustrated, is generally indicated by the reference character
10
, and is seen to comprise a conduit
12
for introducing incoming air into a heater block
14
within which a plurality of heaters
16
,
16
are serially disposed. Each one of the heaters
16
may take the form of a conventional spiral tube heater which is illustrated in FIG.
5
. As seen in
FIG. 5
, each one of the heaters
16
comprises an outer housing
18
within which is disposed a hollow aluminum tubular member
20
. Tubular member
20
is open at a first left end portion
22
thereof, while the second op-posite right end portion thereof is closed by means of an end face or wall
24
integral with the tubular member
20
. The open end portion
22
of the tubular member
20
is provided with an external flanged portion
26
within which a O-ring type seal member
28
is disposed, and the outer peripheral surface of the tubular member
20
is provided with a helical thread or finned structure
30
which extends substantially the entire axial length of the tubular member
20
from within the vicinity of the flanged portion
26
to within the vicinity of the end face or wall
24
. An air inlet port
32
is defined within a first sidewall portion of the housing
18
at an axial position adjacent to the flanged portion
26
so as to introduce relatively cool air CAI into the housing
18
, and an air outlet port
34
is similarly defined within a second sidewall portion of the housing
18
at an axial position adjacent to the end wall or face
24
so as to permit heated air HAO to exit. It is of course to be appreciated that the helical thread or finned structure
30
cooperates with the interior peripheral surface of the housing
18
so as to in effect define a helical path or conduit along which the air is conducted from the air inlet port
32
to the air outlet port
34
. The helical path or conduit provides increased residence time for the air within the heater housing
18
whereby the air is sufficiently heated. In order to provide the heat input for the air, a cartridge type heater, not shown, is axially inserted into the open end
22
of the tubular member
20
and disposed within a heater cartridge cavity
36
defined within the tubular member
20
.
Returning then to the system
10
disclosed within
FIG. 1
, the heater block
14
also has disposed therein a temperature sensor
38
which senses the temperature of the heater block
14
and controls the energization of the heaters
16
,
16
accordingly. The heated air HAO, after exiting from the heater block
14
is conducted or distributed toward the adhesive dispensing modules
40
by means of a common conduit
42
and a plurality of branch conduits
44
,
46
,
48
,
50
. As may readily be appreciated, however, this structural system poses several operative drawbacks or disadvantages. Firstly, it is noted that due to the different distances, for example, of the conduits
44
and
50
from the common conduit
42
, relative to the distances of the conduits
46
and
48
from the common conduit
42
, non-uniform distribution of the heated air to the various conduits can occur. Secondly, due to the fact that the temperature sensor
38
is in effect embedded within the heater block
14
and is not disposed within the heated air stream, only poor or unreliable temperature control of the air stream is achieved.
With reference now being made to
FIG. 2
, a second conventionally known and utilized system is illustrated and is generally indicated by the reference character
110
. The system
110
is seen to comprise an inlet conduit
112
for introducing relatively cold ambient air into a heated block
114
. In particular, the incoming relatively cold ambient air stream
112
is initially divided or distributed into separate air streams which are conducted through branch conduits
144
,
146
,
148
,
150
. The air streams or conduits
144
,
146
,
148
,
150
respectively pass through the heated block
114
such that the separate air streams are heated within the heated block
114
. The heated air streams are then conducted by means of the conduits
144
,
146
,
148
,
150
to the adhesive dispensing modules
140
.
While the system of
FIG. 2
appears to have resolved the problem of dividing the heated air stream into multiple heated branched air streams and the resulting non-uniform distribution characteristics of the same, non-uniform temperature levels or gradients can nevertheless exist within the conduits
144
,
146
,
148
,
150
of the heated block
114
which can of course result in the creation of non-uniform temperature levels within, and heating of, the air streams. In addition to non-uniform fluidic transmission characteristics that may be inherent within the air stream passages defined by the conduits
144
,
146
,
148
,
150
, one of the major factors contributing to the creation of such non-uniform temperature levels within the individual air streams and conduits
144
,
146
,
148
,
150
is the embedded disposition of the single temperature sensor
138
within the heated block
114
whereby it is not possible to accurately control the temperature level within each one of the air streams passing through the conduits
144
,
146
,
148
,
150
.
A need therefore exists in the art for a new and improved system, and a method of operating the same, wherein the air streams supplied to the dispensing modules can be heated to a desired temperature level, wherein the temperature levels of the air streams supplied to the dispensing modules can be rendered uniform, wherein the temperature levels of the air streams supplied to the dispensing modules can be properly and accurately controlled, and wherein the air stream flow rates provided to the dispensing modules can effectively be rendered uniform.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus or systems for dispensing hot melt adhesives.
Another object of the present invention is to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus for dispensing hot melt adhesive wherein the various drawbacks and operative disadvantages of the known PRIOR ART systems, as discussed hereinbefore, are effectively overcome.
An additional object of the present invention is to provide a new and improved air preheater system,
Breh Donald J.
Croll Marc W.
Illinois Tool Works Inc.
O'Brien John P.
Paik Sang
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