Advancing material of indeterminate length – With adherence or attraction of material to advancing means – By pneumatic pressure
Reexamination Certificate
2000-08-30
2002-12-03
Mansen, Michael R. (Department: 3654)
Advancing material of indeterminate length
With adherence or attraction of material to advancing means
By pneumatic pressure
C271S276000
Reexamination Certificate
active
06488194
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to vacuum assisted rolls, and more particularly to a vacuum timing device that compensates for the delay in vacuum propagation along the length of the roll.
BACKGROUND OF THE INVENTION
It is well known to utilize vacuum means to transfer webs from roll to roll or from a roll to another device such as a set of guide rods. The vacuum is selectively applied through apertures at selected circumferential locations on the rotating roll in order to hold a web of material to the roll for a desired time or along a desired path. As used herein and in the appended claims, the term “web” means any material (including without limitation paper, metal, plastic, rubber or synthetic material, fabric, etc.) which can be or is found in sheet form (including without limitation tissue, paper toweling, napkins, foils, wrapping paper, food wrap, woven and non-woven cloth or textiles, etc.). The term “web” does not indicate or imply any particular shape, size, length, width, or thickness of the material.
FIG. 1
illustrates a typical prior art vacuum roll system
10
for use in operations requiring web transfer. The prior art vacuum roll system
10
includes a roll
14
having an axis of rotation
18
and a surface
22
. The surface
22
has a plurality of apertures
26
therein which are spaced longitudinally along the length of the roll
14
forming a straight row
30
. Typically, there are a plurality of straight rows
30
(e.g., four rows spaced at ninety-degree angles), around the surface
22
. Each row
30
is in fluid communication with a vacuum line
34
. Normally, the vacuum line
34
is a bore that extends longitudinally along the length of the roll
14
just beneath the surface
22
. The apertures
26
are typically drilled through to the vacuum line
34
, thus providing the fluid communication between the apertures
26
and the line
34
. The line
34
has an vacuum inlet
38
in at least one end of the roll
14
, the purpose of which will be described below.
In prior art devices, a rotary vacuum valve
42
is usually coaxially coupled to the roll
14
at one end and is fixed against rotation. The valve
42
is connected to a vacuum source (not shown) at a valve inlet
50
. The valve
42
also includes an arcuate groove
54
in the end adjacent the roll
14
. The arcuate groove
54
is in fluid communication with the valve inlet
50
. The arcuate groove
54
is spaced radially from the axis of rotation
18
such that it can be in fluid communication with the line
34
. In operation, the vacuum source creates a vacuum that enters the valve
42
at the valve inlet
50
. As the roll
14
rotates to angular position A, the vacuum inlet
38
of the line
34
is adjacent the arcuate groove
54
. The vacuum therefore enters the vacuum inlet
38
and propagates longitudinally along the length of the line
34
. As the vacuum propagates, the apertures
26
experience the vacuum which is then applied to the web, holding the web to the surface
22
of the roll
14
. As the roll
14
rotates to angular position B, the fluid communication between the vacuum inlet
38
and the arcuate groove
54
is blocked, thereby cutting off the vacuum supply to the line
34
and apertures
26
. The line
34
is often vented in a conventional manner to remove the vacuum inside the line
34
quickly. By changing the length of arcuate groove
54
, the timing of vacuum application and removal can be modified to suit a specific application. The description of the prior art vacuum valve
42
is only presented by way of illustration. Other types of vacuum valves (not shown) are also commonly used in prior art vacuum roll systems
10
.
Surface speeds of the roll
14
typically vary depending upon application, but can reach 600 feet per minute or higher. Vacuum propagates through each line
34
at the speed of sound. Therefore, for long rolls
14
rotating at such high speeds, it is common to encounter angular delay in the propagation of the vacuum along the lines
34
. For example, when roll
14
reaches angular position A, and the vacuum is introduced into the vacuum inlet
38
, it is common in longer rolls
14
for the vacuum to reach the apertures
26
closest to the vacuum inlet
38
almost instantaneously while reaching the apertures
26
located farthest from the vacuum inlet
38
at a measurably later time. Often, the vacuum will not reach the apertures
26
located farthest from the vacuum inlet
38
until the roll has rotated to an angular position A+&Dgr;A. When this angular delay occurs, the portion of the web (not shown) closest to the vacuum inlet
38
will experience the vacuum before the portion of the web farthest from the vacuum inlet
38
. This can cause binding, inadequate web retention, or misalignment of the web, resulting in flawed product, jams, misfeeds, wrinkling and/or even line shut-down.
Angular delay will also be experienced when vacuum is removed from the lines
34
. For example, when roll
14
reaches angular position B, and the communication between the vacuum inlet
38
and the arcuate groove
54
is blocked, it is common in longer rolls
14
for the vacuum to remain in the apertures
26
located farthest from the inlet opening longer than the vacuum remains in the apertures
26
located nearest to the vacuum inlet
38
. Thus, the vacuum will not be removed from the apertures
26
located farthest from the vacuum inlet
38
until the roll has rotated to an angular position B+&Dgr;B. When this occurs, the portion of the web closest to the vacuum inlet
38
will be released from the surface
22
earlier than the portion of the web farthest from the vacuum inlet
38
. Again, this can cause the above-mentioned problems.
FIG. 2
shows an exaggerated profile of the angular delay just described. The profile illustrates the angular location of the apertures at the actual point of vacuum removal.
Attempts to alleviate the problem of angular delay have led to the use of two rotary vacuum valves
42
, one on each end of roll
14
. Each valve
42
has its own valve inlet
50
and arcuate groove
54
. Each arcuate groove
54
communicates with an adjacent vacuum inlet
38
at either end of the line
34
. This configuration has reduced angular delay problems associated with long rolls
14
in that the vacuum need only propagate half the length of the roll
14
. However, the high rotational speed demanded in many applications still results in angular delay near the center of the roll
14
. Furthermore, the use of two vacuum valves
42
adds more parts to the vacuum roll assembly
10
which increases the cost, complexity and maintenance required of the system.
In light of the problems and limitations of the prior art described above, a need exists for a vacuum timing device that can account and compensate for angular delay of vacuum in a rotating vacuum roll, can perform such compensation at a variety of roll rotational speeds, presents a simple and inexpensive solution to the angular delay problems described above and permits the use of a vacuum roll at high speeds without the angular delay experienced in prior art vacuum rolls. Each preferred embodiment of the present invention achieves one or more of these results.
SUMMARY OF THE INVENTION
The invention provides a vacuum timing device for applying a vacuum on a roll. The vacuum timing device includes a roll with an axis of rotation, a surface, and a surface longitudinal axis that is oriented in a direction substantially parallel to the axis of rotation. The device also includes at least one vacuum inlet communicating with at least one vacuum line running along at least a portion of the length of the roll. The device also includes a plurality of apertures defined in a surface of the roll and in fluid communication with the vacuum line. In order to alleviate angular delay of vacuum propagation, the plurality of apertures is arranged in a line that is skewed with respect to the surface longitudinal axis. Preferably, the plurality of apertures is arranged in a line that is skewed away from th
C.G. Bretting Manufacturing Company, Inc.
Mansen Michael R.
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