Dispensing – With discharge assistant – Motor operated
Reexamination Certificate
2002-12-12
2004-02-10
Hirsch, Paul J. (Department: 3754)
Dispensing
With discharge assistant
Motor operated
C418S175000
Reexamination Certificate
active
06688498
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to liquid supply and dispensing assemblies, and more particularly to a new and improved liquid supply assembly, such as, for example, at least one liquid supply assembly for supplying hot melt adhesive or other thermoplastic materials toward a liquid dispensing assembly, wherein the at least one liquid supply assembly preferably comprises a plurality of gear pump assemblies which are separate and independent with respect to each other such that any one gear pump assembly can be readily removed from the operatively associated drive gear manifold, wherein further, if any one gear pump assembly should seize or become frozen, it will not itself experience any further damage or adversely affect any of the other gear pump assemblies, and wherein still further, the rotary gear members of each one of the plurality of independent gear pump assemblies are fixedly mounted upon rotary shafts which are disposed in an entirely enclosed arrangement within each one of the gear pump assemblies such that external dynamic shaft seals, which can have a tendency to fail and thereby lead to leakage of the materials being supplied, are effectively eliminated.
BACKGROUND OF THE INVENTION
In connection with liquid dispensing applicator assemblies, and more particularly, in connection with liquid dispensing applicator assemblies which are being used to dispense hot melt adhesives or other thermoplastic materials, a typical applicator assembly conventionally comprises a supply source of the adhesive or thermoplastic material, means for precisely or accurately metering the adhesive or thermoplastic material through the applicator, and means for pumping the adhesive or thermoplastic material to the metering means of the applicator. In connection with particular applications or procedures, it is usually necessary to accurately or precisely meter the liquids being dispensed so as to ensure that a specific or predetermined volume of the liquid is in fact dispensed within a specific or predetermined period of time. For example, in connection with the dispensing of hot melt adhesive materials, it is often necessary to provide a plurality of individual pumps for providing predetermined volumes of the adhesive material, which may in fact comprise similar or different volume amounts or quantities, to discrete, separate, or respective applicator outlets. The individual pumps conventionally comprise rotary gear pumps which are operatively connected to a drive motor through means of a common rotary drive shaft, and dynamic seals, that is, stationary seals which are operatively disposed around or operatively associated with the rotary drive shaft, are provided for effectively preventing any external or outward leakage of the hot melt adhesive material from the applicator assembly at the interfaces defined between the rotary drive shaft and the rotatably driven gears of the rotary gear pumps. An example of such a conventional or PRIOR ART rotary gear pump hot melt adhesive applicator or dispensing assembly is disclosed, for example, within U.S. Pat. No. 6,422,428 which issued to Allen et al. on Jul. 23, 2002.
More particularly, as disclosed within
FIG. 1
, which corresponds substantially to
FIG. 3
of the aforenoted patent, one of a plurality of gear pump assemblies, as utilized within a hot melt adhesive applicator assembly, is disclosed at
20
, and it is seen that each gear pump assembly
20
comprises a conventional sandwiched construction comprising three plates
220
,
222
,
224
encompassing or enclosing a pair of gears
230
,
232
. Gear
230
comprises an idler gear, whereas gear
232
comprises a driven gear operatively mounted upon a rotary drive shaft
234
. The rotary drive shaft
234
has a hexagonal cross-sectional configuration so as to define the drive connection with the driven gear
232
, and it is noted that the drive shaft
234
extends through each gear pump assembly
220
. A pair of seals
240
, only one of which is shown in
FIG. 1
, are provided within suitable apertures defined within the end plates
220
,
224
so as to annularly surround the rotary drive shaft
234
and thereby prevent any leakage of the hot melt adhesive material out from the gear pump assembly
20
. A threaded port
244
is provided for receiving a temperature sensor for ensuring that each gear pump
20
has been heated to a predetermined temperature level prior to operation, and a rupture disk assembly
242
is provided for pressure relief under over-pressure conditions. A bore
248
is provided for receiving a pressure transducer which can read output liquid pressure, and when the pressure transducer is not being utilized, a plug assembly
250
is adapted to be disposed within the bore
248
.
While a gear pump assembly
20
such as that disclosed within the aforenoted patent is operatively viable, the gear pump assembly
20
of the aforenoted type nevertheless exhibits several operative drawbacks and disadvantages. Firstly, for example, it is noted that in view of the fact that the seals
240
of the gear pump assembly
20
are located upon external surface portions of the end plates
220
,
224
of the gear pump assembly
20
, should the seals
240
experience failure, external leakage of the hot melt adhesive material poses obvious maintenance problems, not to mention the likelihood of the leaking hot melt adhesive material causing fouling of other operative components of the gear pump assembly
20
. In addition, it has been noted in the aforenoted patent that the rotary drive shaft
234
extends through each one of the gear pump assemblies
20
. Accordingly, if, for example, one of the gear pump assemblies
20
should experience failure or exhibit leakage, and therefore needs to be removed for repair or replacement, the particular gear pump assembly
20
cannot in fact simply be removed from the overall applicator assembly. To the contrary, the rotary drive shaft
234
must firstly be removed so as to subsequently permit the particular gear pump assembly
20
to be removed and separated from the other gear pump assemblies
20
in order to repair or replace the failed or leaking gear pump assembly
20
. Upon completion of the repair or replacement of the failed or leaking gear pump assembly
20
, the repaired gear pump assembly
20
, or the new gear pump assembly
20
, can effectively be re-inserted into the bank or array of gear pump assemblies
20
whereupon, still further, the rotary drive shaft
234
can be re-installed in connection with the plurality of rotary gear pump assemblies
20
so as to again be operatively engaged with each one of the plurality of rotary gear pump assemblies
20
. Still yet further, if one of the gear pump assemblies
20
should experience failure and effectively become frozen, the failed and frozen gear pump assembly
20
will effectively prevent rotation of the rotary drive shaft
234
whereby the failed or frozen gear pump assembly
20
can experience or undergo further damage, and in turn, cause operative freezing or failure of the other gear pump assemblies
20
which are rotatably engaged with and driven by means of the common rotary drive shaft
234
.
Accordingly, a need exists in the art for a new and improved gear pump assembly for use in connection with a liquid dispensing assembly wherein the liquid dispensing assembly comprises at least one gear pump assembly, and preferably a plurality of gear pump assemblies which are mounted upon the liquid dispensing assembly such that all of the gear pump assemblies are independent with respect to each other, wherein the plurality of gear pump assemblies are operatively driven by means of a common rotary drive shaft in such a manner that no external dynamic seals are required, that any particular one of the gear pump assemblies can be readily removed from the array or bank of gear pump assemblies independently of the other gear pump assemblies, and subsequently be re-inserted into the array or bank of gear pump assemblies, or replaced by means of a new gear pump assembly, and
Cartagena Melvin A
Hirsch Paul J.
Illinois Tool Works Inc.
Schwartz & Weinrieb
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