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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to attaching plastic liners, particularly but not
only ultrahigh molecular weight polymers, to substrates. Such liners are
often used, for example, to line hoppers, railroad car and truck bodies,
and ship holds used for coal and other materials. UHMW liners are
particularly desirable because the material provides flexibility and
slipperiness with very high abrasion, impact and chemical resistance. Such
materials can outwear steel in many applications, and the slipperiness of
the material prevents the coal or other material from sticking or freezing
to the substrate.
Such liners are, however, difficult to attach securely to the substrate.
One particular problem in this regard is that the liner materials exhibit
a relatively high degree of linear thermal expansion and contraction, and
for this and other reasons glues and some other conventional arrangements
are not suitable. The expansion and contraction problem can be solved by
the known expedient of using bolts that extend through oversized holes in
the substrate to allow lateral movement, but this can make the bolt
difficult to attach.
It is also desirable and known to cap attachment bolts with plastic and
make them flush with the liner surface to provide surface continuity for
improved smoothness and wear. The closest known prior approach of this
type involves using a frusto-conical bolt head that fits in a mating
recess on the liner surface, but this is not totally satisfactory from the
standpoints of holding the bolt against rotation, particularly while a nut
is being attached, providing an adequate seal between the bolt head and
the recess, allowing field installation using conventional tools,
simplicity of manufacture, and general adaptability to various
applications.
SUMMARY OF THE INVENTION
This invention contemplates an attachment system utilizing a bolt with a
circular cylindrical cap received in a mating recess on the liner surface
and provided with a radial sealing skirt that engages the walls of the
recess to provided an effective seal. In the preferred embodiment, the
bolt shank has a squared portion that is received through and deforms a
shank opening in the liner to provide a nonrotatable engagement between
the bolt and the liner, and the shank extends through an oversized
substrate hole to receive a nut means including a plastic washer that is
against the underside of the substrate to allow lateral movement and
prevent excessive wear resulting therefrom. The system is readily
adaptable to a wide variety of applications, and the liner can easily be
attached in the field using conventional tools. The entire system is
extremely effective, while being relatively simple and inexpensive to
manufacture and use.
Other objects and advantages will appear from the description to follow.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an exploded view in perspective illustrating a preferred
embodiment of the invention;
FIG. 2 is a view in cross section showing the system of FIG. 1 in place;
and
FIG. 3 is an enlarged fragmentary view in cross section showing the sealing
skirt more clearly.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The reference numeral 1 in the drawing indicates a plastic liner in the
form of a sheet to be attached to a substrate using the system of the
invention. In the preferred embodiment, the liner 1, and the cap and
washer referred to below, are all of a suitable ultrahigh molecular weight
polymer material, but the term "plastic" is not limited to such materials
and is intended to include also all equivalent flexible materials for
which the system would by suitable. The liner 1, which can be of any
desired thickness or configuration, is attached to a substrate 2, which as
shown is a steel sheet of the type used, for example, to form the walls of
a hopper. As indicated above, the invention is usable in a wide variety of
applications with various substrates and liners; the substrate and liner
need not, for example, be completely flat sheets as shown.
The system includes a elevator bolt 3 having a circular disc-like head 4
and an attachment shank 5. In the preferred embodiment shown, the shank 5
is a conventional threaded shank that extends through the substrate 2 to
receive a nut, but other arrangements, such as a shaft received with a
friction fit by a socket in the substrate, might be used in certain cases.
The shank 5 is provided near its upper end, under the head 4, with a
squared portion 6.
A plastic cap 7 is mounted on the head 4. It is generally of a
straight-sided, circular cylindrical configuration with a vertical
dimension sufficient to make its upper surface flush with the exposed
surface of the liner 1 when placed in the recess to be described; it is a
particular advantage of the system of the invention that the cap 7 can
easily be made of any required vertical dimension for a particular
application. As seen clearly in FIG. 2, the cap 7 is recessed at its
underside to receive the head 4, the circular periphery of the cap 7
extending downwardly past the circular periphery of the head 4. At its
lower outer edge, the cap 7 is provided with a relatively thin, radially
outwardly extending, circular sealing skirt 8, and a somewhat thicker
radially inwardly extending circular mounting rim 9 that extends partially
under the head 4 to trap the bolt 3 and hold it against vertical movement,
although in the preferred embodiment shown relative rotational movement is
possible about the axis of the shank 5. The cap 7 can be attached to the
head 4 by heating it to cause expansion that allows the rim 9 to move over
the head 4.
The upper or exposed surface of the liner 1 is provided with a circular
cylindrical, straight sided recess 10 that extends downwardly only
partially through the liner 1, and a smaller circular shank opening 11
that continues through the liner 1. As seen most clearly in FIG. 2, the
cap 7 is peripherally smaller than the recess 10, or in other words, the
diameter or periphery of the recess 10 is somewhat larger than the major
diameter or pheriphery of the cap 7. The cap 7 is received in the recess
10 with its upper or exposed surface flush with the exposed surface of the
liner 1. The skirt 8 is peripherally larger than the recess 10, or in
other words its outer diameter or periphery is larger than that of the
recess 10, and when the cap 7 is inserted in the recess 10 the skirt 8 is
rolled up against the walls of the recess 10, as seen most clearly in FIG.
3, to provide a very effective seal in either direction. The specific
dimensions of the parts will depend on a number of factors, including the
specific plastic material being used. The thickness or vertical dimension
of the skirt 8 in its initial state should be such as to allow uniform
rolling up, given the flexibility and other characteristics of the
specific plastic material. It has been found that the diameter of the
recess 10 should be greater than the major diameter of the cap 7 plus
twice the thickness of the skirt 8 to prevent difficult installation and
shearing of the skirt 8. The diameter of the recess 10 should, however, be
less than the outer diameter of the skirt 8 to provide an adequate seal.
In the preferred embodiment shown, the diameter of the recess 10 is
approximately equal to the major diameter of the cap 7 plus one-fourth of
the difference between the major diameter of the cap 7 and the outer
diameter of the skirt 8, although this may be varied depending on the
thickness of the skirt 8. These and other dimensions, such as the
thickness of the rim 9 and the depth of the recess 10 can all be readily
determined for any particular application by those skilled in the art.
The shank opening 11 in the linear 1 is large enough to accommodate the
shank 5, but is effectively smaller than the squared portion 6. When the
bolt 3 is in place, the squared portion 6 is received in the opening 11,
and deforms it into a non-circular configuration, thus providing a
nonrotatable engagement between the bolt 3 and liner 1. This is
particularly advantageous when attaching the nut means described below.
The shank 5 extends through a substrate shank opening 12. The opening 12 is
substantially oversized or larger than the shank 5, which allows relative
lateral movement of the bolt 3 and liner 1 with respect to the substrate 2
to accommodate linear expansion and contraction of the liner 1. On the
opposite or bottom side of the substrate 2 is a nut assembly or means
comprising a plastic washer 13 that is directly against the underside of
the substrate 2, a steel washer 14 against the washer 13, and a
conventional elastic or other lock nut 15 engaged with the threaded shank
5 and against the washer 14. The plastic washer 13 is preferred because of
the contemplated relative laterial movement. It minimizes or eliminates
abrasion wear on the steel washer resulting from such movement, and also
prevents corrosion or freezing to the substrate which would hamper such
movement.
Using the system of the invention, liner installation can easily be
accomplished in the field using conventional tools. The liner will
obviously be selected or cut for the particular substrate. Suitable
attachment points will then be selected, and it is a particular advantage
of the invention that pre-forming attachment points is not needed and they
can readily be field-located where desired for the particular application.
Once these preliminaries have been accomplished, the liner 1 will first be
drilled at the selected location or locations to form, in each case, the
recess 10 and shank opening 11; a simple conventional counterbore tool can
be used for this purpose. The liner 1 can then be used as a template to
locate the substrate shank opening 12, whereupon the liner is removed and
the hole 12 drilled using a conventional drill. The bolt 3, with the cap 7
in place, is then inserted through the aligned openings and the nut means
attached to complete the installation.
While the preferred embodiment of the invention shown and described
provides all of the indicated advantages, it will be obvious that various
modifications might be made without departure from the spirit of the
invention. By way of additional example over those already mentioned, the
cap and recess need not be circular. The invention is not, therefore,
intended to be limited by the showing or description herein, or in any
other manner, except insofar as may specifically be required.
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