Dispensing – With discharge assistant – Container with follower
Reexamination Certificate
1999-09-30
2001-01-23
Shaver, Kevin (Department: 3754)
Dispensing
With discharge assistant
Container with follower
C074S141500, C074S169000
Reexamination Certificate
active
06176398
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to dispensing devices and, more particularly, to improved drive mechanisms for hand-held caulk guns that include an effective trigger grip power device (“ETG”) for maintaining effective thrust operation in a dispensing device for high viscosity fluids, such as a caulking gun.
BACKGROUND OF THE INVENTION
Conventional economy brand caulking guns are generally manual trigger-operated devices incorporating a unidirectional gripping assembly which urges a piston rod forward to eject the compound from a cartridge. As shown in
FIG. 1
(prior art), a common gripping assembly includes a piston rod
4
passing through a gripping plate
6
that, in turn, is controlled by the operation of a trigger
8
to grip and move the piston rod
4
in a forward direction for dispensing the caulking composition. The trigger
8
cants the gripping plate
6
clockwise when the trigger is actuated until it grips the piston rod
4
, thereafter urging the piston rod
4
forward. Upon release of the trigger
8
, the gripping plate
6
is returned to a neutral upright position to allow retraction of the piston rod
4
. However, the piston rod
4
also passes through a release plate
10
that prevents undesired retraction of the piston rod
4
. The release plate
10
is commonly located at the rear of the gun and remains disengaged from the piston rod
4
during dispensation. However, when the trigger
8
is released, the release plate
10
rides the piston rod
4
rearwardly and becomes increasingly canted relative to the piston rod
4
until it engages the piston rod to thereby prevent inadvertent retraction. The user must depress the release plate
10
to free the piston rod
4
for full retraction.
Over time the alternating clockwise and counterclockwise torques imposed on the steel thrust components of the above-described mechanism tend to create wear and tear tolerances. Specifically, the hole through the gripping plate
6
and the release plate
10
become enlarged. These wear tolerances combine with the inherent manufacturing tolerances to the point that they effect the operation of the gripping plate and release plate. The effects includes excessive trigger slack and “piston rod lock”. With regard to
FIG. 1
, piston rod lock occurs when the hole in the gripping plate becomes so large that the gripping plate tends to return past its normally-neutral upright position (ø
1
) to an oppositely-canted position (ø
2
) Because of the undesired cant of angle (ø
2
), the rod
4
again grips the piston rod
4
, and the rod
4
cannot be pulled back even if the release plate
10
is released.
There have been previous attempts at implementing wear compensating devices to prevent the above-described problem. For instance, U.S. Pat. No. 5,370,282 to Sedlmeier shows an advancing mechanism (
6
) with two pivoting clamping levers (
12
,
13
) mounted on the piston rod (
7
). Clamping lever (
12
) is for forward advancement while lever (
13
) prevents retreat. Two springs (
14
,
15
) are required, each in contact with a corresponding clamping lever (
12
,
13
). In addition, an unlocking lever (
17
) operates via a transmission element
18
to substantially simultaneously unlock both of the clamping levers (
12
,
13
) to free the piston rod (
7
). The clamping lever
13
rests in a pendular manner in a recess of the frame
5
. When the piston rod
7
moves forward, the clamping lever
13
pivots forward along with rod
7
to a perpendicular position (clockwise about the top). When the rod
7
is released, the clamping lever
13
pivots backward (counterclockwise about the top) until it inclines enough to bite the rod
7
, thereby locking it in position. When the cartridge is spent, the unlocking lever (
17
) operates through the transmission element
18
to kick clamping lever
13
forward to release the rod. Thus, the use of the transmission element
18
to unlock both of the clamping levers (
12
,
13
) somewhat resolves the problem of a worn gripping plate that returns past its normally-neutral upright position to improperly regrip the piston rod. However, the '282 transmission element
18
is a small tube that rides the piston rod. It is only capable of pushing against the immediate periphery of the hole in the clamping lever
13
. This gives the transmission element
18
very poor leverage against the rod, and as wear becomes worse the transmission element
18
loses its ability to return the clamping lever
13
to a vertical position. The problem of piston rod lock reoccurs. Moreover, the thrust mechanism is complex inasmuch as it requires two separate pivoting clamping levers (one for moving the piston rod forward and one for locking the piston rod in the forward position), two springs each contacting one of the clamping levers, plus a release lever, and the transmission element. The additional parts and labor greatly increases manufacturing costs and assembly time.
Similarly, U.S. Pat. No. 5,823,403 to Schneider shows a drive mechanism that provides a double-lever action to bias the gripping plate into a neutral position in a controlled manner to permit the piston rod to be retracted. A gripping (or recoil) plate
52
is normally biased by spring
50
into a canted position to prevent rearward movement of the piston rod
26
. However, when the piston rod
26
moves forwardly the recoil plate
52
pivots forward along with rod
26
to a perpendicular position (counter-clockwise about the bottom) and rod
26
becomes free to slide through the recoil plate
52
. The recoil plate
52
is situated rearwardly of the frame and this necessitates a backplate
40
. The '403 patent appears to be functionally similar to the above-described '282 patent except that the release lever
17
of the '282 gun kicks both levers
12
and
13
out via sleeve
18
, while the '403 lever
62
only kicks out the recoil plate
52
. Otherwise, both mechanisms requires three separate pivoting levers (one for moving the piston rod forward, one for locking the piston rod in the forward position, and a release plate). Moreover, both require two springs each contacting one of the clamping levers, plus a transmission element. The sleeve
18
only pushes against the immediate periphery of the hole (giving it very poor leverage against the rod), and this provides a temporary solution at best to the wear problem because sleeve
18
eventually loses its ability to prevent piston rod lock.
It would be advantageous to provide a more reliable solution to piston rod lock and other wear-and-tear problems to ensure proper advancing and releasing operation in an economical two-lever drive assembly.
SUMMARY OF THE INVENTION
In accordance with the above, it is an object of the present invention to provide simpler, less costly, and more efficient drive assemblies with simple economical gripping plate canting device that compensates for piston rod lock and other problems caused by wear and tolerances to ensure proper advancing and releasing operation.
In accordance with the present invention, there are disclosed various embodiments of an effective trigger grip power device (“ETG”) for conventional manual caulking guns. The drive assemblies are shown in the context of an open frame (which may be a single piece of molded plastic) having a downwardly extending handle. A piston rod is slidably supported in the frame for dispensing caulking composition, and a trigger is pivoted to the frame and retractable against the handle. The effective trigger grip device is positioned behind the gripping member and generally has a pushing member at one end for bearing against the gripping member to urge it into a vertical position, and a base section that is slidably channeled through the frame and extending rearwardly to said release lever for actuation thereby. In operation, depression of the release lever drives the effective trigger grip device to urge the gripping member into a substantially vertical position to eliminate trigger lock.
Two alternative configurations of the effective trigge
Bonderer David A
Law offices of Royal W. Craig
Shaver Kevin
LandOfFree
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