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Description  |
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This invention relates to a novel packing, especially a rod packing having
an additive material to improve the surface gliding and heat resistance
characteristics of the packing, and the process and apparatus for its
production.
Sometimes different requirements are made of material which comprises the
frictional surface of a packing, and the material of the other cross
section of the packing. The surface exposed to movement preferably has
particularly favorable frictional characteristics which are heat resistant
and have great mechanical strength while the remaining packing material is
under less stress in this respect but has heat conducting characteristics.
However, because of the mechanical strength, one will endeavor to anchor
the threads constituting the surface of the packing, in the depth of the
cross section of the packing on the basis of the braiding technique
selected, which will be realized to a variable degree in the case of the
various methods of braiding used for packings, for example plait braiding,
concentric or diagonal braiding. It has been known to braid into the base
material a small quantity of a particularly valuable additive, for
example, graphite or Teflon edging in order to improve the gliding and
heat conducting characteristics of a packing. The consolidation with the
braiding takes place in such a way that a few bone bobbins are equipped
with an additive. In the finished braiding the additive follows the
braiding paths determined by the braiding system selected. For example,
based on a diagonal braiding it passes through the entire packing cross
section. Since the valuable characteristics of the additive material are
required only or overwhelmingly on the surface exposed to friction, the
equipping of individual bone bobbins with the additive material results in
a consumption of the additive material, which is in an unfavorable
relationship to the frequency of the appearance of the additive material
on the surface exposed to friction.
It had been known to cover only the packing surface exposed to friction
with a thin strip of the more valuable material. However, it has been
found to be difficult to achieve a sufficiently homogenous connection of
the cover strip or layer and the packing.
Therefore the invention is based on the object of improving a braided
packing, which in the main consists of a base material and to a small
extent of threads of another material, through the fact that the threads
of the other material are concentrated in a certain area of the surface
and are connected in a secure manner with the base material.
The solution according to the present invention consists in that the
threads of the other material are threaded into the braiding of the base
material in the surface area of the packing. For example, the additional
threads can be braided into, looped around, overcast, crocheted around, or
sewn into the basic material. This results in the desired anchoring of the
additive material in the depth of the cross section of the packing,
whereby it nevertheless will be exclusively in or adjacent to the surface
that is to be finished.
In selecting the basic material, its running characteristics just play a
subordinate role so that the main emphasis can be placed on its heat
conductivity, absorptive capacity, hardness and also on its price.
Particularly, wear resistant, easily sliding, heat resistant and
mechanically high quality threads can be used as additive material.
Preferably, the threads of the additive material are braided into the base
material. That can be accomplished particularly by guiding the bone
bobbins of the additive material around the bone bobbins of the base
material, whenever the latter pass through the braiding area assigned to
the surface that is to be finished. In other words, different bobbin paths
are fixed for the bone bobbins of the base material and for the bone
bobbins of the other material. While the braider has the customary paths
for the bone bobbins of the base material, which result for example in a
plait, a diagonal or concentric braiding, special bobbin paths may be
provided for the bone bobbins equipped with the other material which
merely pass through the surface area to be finished with this material. It
would be possible to use paths for this purpose which are completely
separate with regard to type from those of the bobbin paths of the base
material. However, it is preferable that the bobbin paths of the other
material likewise follow the circumferential lines of the impellers,
provided for the standard bobbin paths on the side of the surface to be
finished, which as a result of their switch arrangement extend only across
the surface cross section that is to be finished.
For this purpose bobbin paths, running in parallel to the other bobbin
paths can be provided in the area to be finished for the bone bobbins of
the additive material. However, it would be possible even in this area to
use the same bobbin paths, i.e., guide grooves for the feet of the
bobbins, for all bone bobbins and to provide differences only in case of
those switches where the bone bobbins of one or the other kind follow
different directions. For example, these switches may be under forced
control or in connection with a variable development of the bobbin feet,
they can have different guide surfaces for the guidance of the one type of
bone bobbins in one direction and of the other bone bobbins in the other
direction.
The invention will be explained in the following paragraphs in more detail
and with reference to the accompanying drawings wherein:
FIG. 1 shows the cross section of a diagonal braiding finished according to
the invention;
FIG. 2 shows the operating and schematic diagram of a machine suitable for
braiding according to the invention;
FIG. 3 illustrates the arrangement of the guide grooves in case of a
machine according to FIG. 2; and
FIGS. 4 and 5 are a top view and a sectional view of the piece of a switch
to be used in the case of the machine according to FIG. 3.
As seen in the drawings, the solid lines in FIG. 1 indicate the braids of
the base material following the standard course of a four-ribbed diagonal
braiding. The additional braiding of other material is shown in the
drawings as dash-dot lines. The base material constitutes a fixed skeleton
of threads, threads reaching the area of one surface are encircled by
additional threads. Accordingly, it will be assured on the one hand that
the additional threads are safely connected with the base braiding, and on
the other hand they will participate to the greatest possible extent in
the formation of the pertinent surface, which represents the running
surface of the packing. The basic braiding consists of customary material,
for example, asbestos threads. The additional threads may consist, for
example, of polytetra fluoroethylene or graphite fibers. They may be
either strips or monofil threads. Thus, a packing will be created, which,
owing to the choice of the base material, is distinguished by having a
high degree of elasticity and good heat conductivity, which, owing to the
additive material, has excellent erosion and corrosion resistance and is
considerably cheaper compared to the packings which are presently on the
market. The additionally woven-in braid can have a round, angular or flat
shape. To improve the heat flow it can have a metallic or mineral core, or
it can be developed in some other way such that it will meet the
requirmements occurring in the area of the running surface of the packing
in the best way, whereby even an expensive construction need not be
feared, because the braid constitutes only a small part of the total
volume of the packing.
The use of the braiding according to the present invention can be used in
connection with concentric braiding because of a relatively high
hose-skeleton. At the same time, the additional braiding is limited to the
circumferential area assigned to the running surface of the packing.
As compared to known packings, wherein additional working material is woven
through the entire cross section of the packing, about 30 to 50% of the
high priced working or raw material will be saved.
The expansion in volume of the rod packing according to the present
invention is considerably less in case of use of Teflon threads or
Teflon-impregnated fiber substances as additional braiding threads, than
in case of a packing, consisting exclusively or overwhelmingly of Teflon
threads. Moreover, the framework of the packing advancing to the area of
the gliding surface contributes to the emission of heat from here. It has
been known that fiber substances from organic base material or mineral
base materials have a poor heat conducting capacity. In order to make the
braiding skeleton useable at higher temperatures and in order to improve
the heat conductivity, metal threads or metal powders can be inserted into
the braiding thread by drilling or impregnation. This metallically
enriched thread results in a considerably increased useful life and in
better heat emission from the gliding surface of the packing. In that
case, even under high temperature loads, where graphite threads would
otherwise have to be used, Teflon saturated fiber substances can still be
used as additional threads, since the temperature load will be smaller
because of the improved heat flow from the gliding surface.
The diagram of the bobbin paths shown in FIG. 2 corresponds to the course
of the braids shown in FIG. 1. It can be seen that the machine, even if it
is equipped only with diagonal bone bobbins, will deliver a customary
quadruple diagonal braiding. The diagonal bobbins leave a group of four
control openings free on the wheels A, B, C, and D, which as shown in FIG.
2 are equipped with additional bone bobbins. If one follows the path of
these bone bobbins, then one will find that the thread of the additional
bobbin 5.1 crosses with the diagonal bone bobbin 1.1 and thus is
interlaced. If one continues to observe the path of the additional bobbin
5.1, then one will find a crossing of the paths with bone bobbin 2.3, and
after that with the bone bobbin 4.5 in the area of the wheel D. On the
return trip an encirclement with the thread of bobbin 3.4 results.
Analogous results happen to the remaining additional bobbins.
The machine arrangement shown permits a maximum of four additional bone
bobbins. It is obvious that these machines can also be operated with a
smaller number of additional bobbins. Whenever a larger number of
additional bobbins are desired then this can be made possible by providing
a larger number of driver openings at wheels A to D.
If no forcibly controlled switches are to be provided at the places of
transition between the two wheels at which the diagonal bobbins and the
additional bobbins are to follow in different paths, it would entail
considerable expenditure, then different guide grooves can be arranged in
the base plate for the bone bobbins of one and of the other kind, as shown
in FIG. 3. Assuming that in the range of the wheels, wheels E to H as
indicated, which are circled exclusively by diagonal bobbins, there is
always only one guide groove provided in a known manner, which also
continues tangentially in the area of the wheels A to D. Beyond that,
however, another pair of additional guide grooves are indicated in the
area of the wheels A to D, which grooves are intended for the additional
bobbins. While the feet of the diagonal bobbins are equipped with the
customary guide pegs running in the middle grooves, the feet of the
additional bobbins do not have a peg at this place, but instead they have
a pair of pegs laterally thereof, which cooperate with the outside guide
grooves. Thus, different paths can be made available for the various bone
bobbins.
In FIG. 3 as illustrated by circles W in the contact area of adjacent
wheels, the switch elements are exchangeable in a known manner and are to
be located at these places. The switch elements between wheels encircled
exclusively by diagonal bobbins have a conventional structure. The switch
elements between the wheels which are encircled by both diagonal bobbins
and the additional bobbins always have the customary guide grooves for the
diagonal bobbins and parallel thereto on both sides a groove for the
additional bobbins. The switch elements between one wheel which is
encircled by additional bobbins and other wheel which is encircled
exclusively by diagonal bobbins, has the shape shown in FIG. 4 at a larger
scale. These switch elements W resemble by contour or outline 8, the
remaining switch elements. They also agree with them insofar as they have
two grooves 9 and 10, crossing in the middle for guiding the diagonal
bobbins, which are to be conducted by the switch element from one wheel to
the adjacent one. However, they also have a pair of grooves 11, which run
concentrically to that wheel which is to be encircled by the additional
bobbins. Assuming that the switch element shown in FIG. 4 is the one which
is located between the wheels A and E according to FIG. 3, then the groove
9 constitutes the guide for the bone bobbins of the series 1, the groove
10 constitutes the guide for the bobbins of the series 2 and grooves 11
guide the additional bobbins of the series 5. While the diagonal bobbins
are transferred by the grooves 9 and 10 from the wheel E to wheel A, the
additional bobbins are held by the grooves 11 in the area of wheel A.
FIG. 5 shows a cut through a switch element according to FIG. 4 along the
line of intersection indicated in FIG. 4.
The switch elements W between the wheels, which are encircled both by
diagonal as well as by additional bobbins only differ from the switch
element illustrated in FIG. 4 by having two pairs of grooves 11, one pair
of which runs diagonally and parallel to groove 9, and the other pair runs
parallel to groove 10, in such a way that the additional bobbins are
transferred from the area of one wheel to that of another wheel.
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