U.S. patent number 3,593,528 [Application Number 04/885,252] was granted by the patent office on 1971-07-20 for safety trenching box.
Invention is credited to John R. Pavese.
United States Patent |
3,593,528 |
Pavese |
July 20, 1971 |
SAFETY TRENCHING BOX
Abstract
A safety trenching box is provided having a pair of
earth-retaining wall members which are tapered at one end thereof
to form a pair of vertical cutting edges. The vertical cutting
edges permit the box to be dragged through trench excavations
having little or no clearance between the sides of the box and the
sides of the trench, since the edges shear off projecting portions
of the trench walls. The bottom edge of each wall member is also
tapered to form a pair of horizontal cutting edges on the box and
push plates are provided on the top edge of each wall member to
permit the trenching box to be driven downwardly into the trench by
externally applied forces. The outer surface of each of the wall
members in contact with the sides of the trench is cambered to
provide the box with increased structural strength under laterally
applied load conditions. Horizontally disposed beams employed in
the construction of each wall member are provided with inclined
cover plate to form skid paths for earth and stone accidentally
dropped into the trenching box, thereby preventing any dangerous
accumulation of such materials on such beams and adding to the
structural strength of the box. If desired, legs may be mounted on
the bottom tapered edges of the wall members to facilitate the
stacking of a number of such boxes for use in deep trench
excavations or for storage purposes.
Inventors: |
Pavese; John R. (Rivervale,
NJ) |
Family
ID: |
25386492 |
Appl.
No.: |
04/885,252 |
Filed: |
December 15, 1969 |
Current U.S.
Class: |
405/282 |
Current CPC
Class: |
E02D
17/08 (20130101); E21D 9/06 (20130101) |
Current International
Class: |
E02D
17/06 (20060101); E21D 9/06 (20060101); E02D
17/08 (20060101); E21d 007/00 () |
Field of
Search: |
;61/41,41A,72.1,46,72.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Taylor; Dennis L.
Claims
What I claim is:
1. A safety trenching box adapted to be disposed in an excavated
trench or the like to prevent the sides of the trench from
collapsing comprising
a pair of earth-retaining wall members, each of said wall members
having a rigid frame formed by horizontally disposed top and bottom
beam members and a plurality of vertical column members
interconnecting said beam members, a sheet member mounted on and
covering said frame to provide a smooth outer surface for the wall
member in contact with the side of the trench, said sheet member
having one edge thereof extending beyond the edge of said frame at
one end of the wall member and the bottom edge thereof extending
below the bottom beam member along the entire length of the wall
member, first cover plate means connected between said one extended
edge of the sheet member and the inner surface of the column member
adjacent thereto to form a vertically extending cutting edge at
said one end of the wall member, second cover plate means connected
between said bottom extended edge of the sheet member and the inner
surface of the bottom beam member to form a horizontally disposed
cutting edge along the bottom of the wall member, and third cover
plate means disposed between each of said column members, said
third cover plate means connecting the inner surface of the sheet
member and the upper surface of the bottom beam member along the
length thereof to provide an inclined skid path on each wall member
for earth and stone falling into the box; and
a pair of spreader members removably connected between the column
members at the ends of the frames of said wall members for
separating and laterally supporting said wall members against the
lateral force exerted by the sides of the trench.
2. A safety trenching box as claimed in claim 1, wherein
push plates are mounted on the top beam member of each of said wall
members in vertical alignment with the column members thereof,
and
at least two legs are mounted on the second cover plate means of
each wall member in vertical alignment with said push plates, so
that said push plates are adapted to function as load-bearing
surfaces for the application of vertically applied forces to permit
the box to be driven downwardly into the trench and also function
as load bearing surfaces for the legs of another box when two or
more boxes are employed in a stacked arrangement.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to safety devices for use in the
construction industry and more particularly to a safety trenching
box which is especially suited for use in trench excavations and
the like having a close-working clearance between the sides of the
box and the sides of the trench.
2. Description of the Prior Art
Safety trenching boxes or so-called "safety drag boxes" are
commonly employed in the construction industry during earth
excavation work to prevent the walls of the excavation from
collapsing and filling the excavated area. The problem presented by
the collapse of the walls of an excavation is particularly acute in
trench excavations of the type commonly made during the
installation or repair of water and sewer pipes, for example, where
a somewhat deep but narrow trench is dug to conform to the layout
of the pipe system. When a back hoe or similar piece of mechanical
digging equipment is employed, the walls or sides of the trench are
usually substantially vertical and are sharply defined, thereby
increasing the possibility that the sides of the trench may
collapse to cause death or injury to workmen working at the bottom
of the trench.
The known types of safety trenching boxes generally includes a pair
of vertically disposed wall members which act to keep or retain the
earth of the trench walls in position. The wall members are
separated and laterally supported by at least two spreader members
which are fabricated in varying widths to permit the trenching box
to be used in trenches of various widths. The spreader members are
bolted to the wall members of the box to create a trenching box of
the proper width for a particular job. As the trench is dug, the
box is repositioned for each section under construction by either
dragging it through the trench or lifting it out and reinserting it
at the next location. It is usually desirable to drag the box
through the trench rather than lift the box in and out of the
trench for repositioning, since the latter method requires expert
handling of the lifting equipment and is time consuming as well.
With presently known safety drag boxes, however, the dragging
operation becomes difficult when the side walls of the trench
narrow down to a point where they exert a substantial frictional
drag on the walls of the box. Minor projections and outcroppings on
the trench walls may even make further movement impossible and the
box must usually be removed from the excavation for repositioning.
A somewhat similar problem may arise when the safety trenching box
is being lowered into position in a trench having a width too small
to accommodate the box. In this situation, the box may become
jammed after being lowered a distance into the trench and
considerable time and effort may be required to remove it.
Safety hazards may also exist with trenching boxes employing an
open beam construction. In this type of construction, each of the
wall members of the box is formed by a sheet metal member, usually
steel, which is supported by a vertically disposed frame. The frame
itself is formed by upper and lower horizontal beam members which
are connected by vertically disposed columns to provide the needed
structural strength. When loose earth or stones are accidentally
dropped into the trenching box they may become lodged on the upper
surface of the horizontally disposed beam members and may
accumulate to a point where a slight movement of the box will send
a heavy mass of such material crashing down on workers employed
within the box.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a safety trenching box
which is especially adapted for use in excavations, such as
trenches and the like, wherein close working conditions are
encountered.
It is a further object of this invention to provide a safety
trenching box which is readily repositioned in the trench being
excavated by being dragged through the trench or by being lowered
or driven vertically into the trench with a minimum of effort.
It is a still further object of this invention to provide a safety
trenching box which is so constructed as to prevent a dangerous
buildup or accumulation of earth and stones on the sides of the box
under adverse working conditions.
It is another object of the invention to provide a safety trenching
box which is so constructed as to facilitate the stacking of a
plurality of boxes for use in deep trench excavations or for
storage of the boxes.
It is an additional object of this invention to provide a safety
trenching box of exceptionally strong construction which is capable
of easily withstanding the large lateral forces exerted on the
walls of the box by the sides of deep trench excavations.
Briefly, the safety trenching box of the invention comprises a pair
of earth-retaining wall members each of which is tapered at one end
thereof to form a pair of vertically disposed cutting edges on the
box, and a pair of spreader members which are connected between the
wall members for separating and laterally supporting the wall
members against the lateral force exerted by the sides of a trench
or other excavation. When the trenching box of the invention is
dragged through a trench, the pair of vertically disposed cutting
edges function as side cutters to widen the trench by shearing off
earth and stone projecting from the sides of the trench. The bottom
edge of each of the wall members is also tapered to form a pair of
horizontally disposed cutting edges on the bottom of the box and
push plates are provided on the top edge of each of the wall
members to provide load bearing surfaces for the application of
externally applied forces, to thereby permit the trenching box to
be driven downwardly into a trench by the application of external
forces to the push plates, so that the horizontal cutting edges
also function as side cutters to widen the trench. The invention
also contemplates the addition of legs to the tapered portion of
the bottom edge of each of the wall members, so that the box is
adapted to be placed on top of another box in a stacked
arrangement, to thereby permit multiple stacked boxes to be
employed in trenches having a depth greater than the height of a
single box and to facilitate storage of the boxes.
Each of the wall members of the safety trenching box of the
invention may comprise a rigid frame formed by top and bottom beam
members and a plurality of column members interconnecting the beam
members. A sheet member is mounted on the frame to cover it and to
provide a relatively smooth outer surface for the wall member in
contact with the sides of the trench. Cover plate means are
disposed between each of the column members and are arranged to
connect the inner surface of the sheet member with the upper
surface of the bottom beam member along the length of the bottom
beam member, to provide an inclined skid path for earth and stone
falling into the trenching box. The outer surface of each of the
wall members adjacent the side of the trench is preferably cambered
to provide a convex curvature therefor in the horizontal pane of
the box, to thereby increase the lateral load-carrying capacity of
the box.
The nature of the invention and other objects and additional
advantages thereof will be more readily understood by those skilled
in the art after consideration of the following detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a safety trenching box constructed
in accordance with the teachings of the present invention;
FIG. 2 is an elevational view of one of the wall members of the
safety trenching box shown in FIG. 1 of the drawings with the
spreader members and the other wall member removed;
FIG. 3 is a fragmentary perspective view of the front portion of
the wall member shown in FIG. 2 of the drawings with the front
cover plate and the inclined cover plates partially broken away to
reveal details of construction;
FIG. 4 is a full sectional view taken along the line 4-4 of FIG. 2
of the drawings; and
FIG. 5 is an elevational view of the front ends of a pair of safety
trenching boxes constructed in accordance with the teachings of the
invention showing the boxes in a stacked arrangement and indicating
in dotted outline the addition of legs to the upper trenching box
to facilitate the stacking of the boxes.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Referring now to FIG. 1 of the drawings, there is shown a safety
trenching box constructed in accordance with the teachings of the
present invention comprising a first wall member 10, a second wall
member 11, a front spreader member 12, and a rear spreader member
13. As seen in FIGS. 2, 3 and 4 of the drawings, the wall member 10
has a substantially rectangular, rigid frame 14 which is formed by
a top beam member 15, a bottom beam member 16, and column members
17, 18, 19 and 20. The top beam member 15 is horizontally disposed
and may conveniently comprise a structural steel channel. The
bottom beam member 16 is also horizontally disposed and may
conveniently comprise a structural steel I beam. The vertically
disposed columns 17, 18, 19 and 20 are preferably structural steel
I beams or wide flange sections. All of the columns and beam
members forming the frame 14 may be welded together to form a rigid
assembly of great structural strength.
A sheet member 21, which may be fabricated from steel sheet, is
arranged to cover the frame 14 and is preferably secured thereto by
means such as welding, to provide a smooth outer surface for the
wall member 10. The provision of a smooth outer surface for each of
the wall members is desirable to reduce the frictional drag on the
trenching box when the box is being dragged through or lowered into
a trench having little or no clearance between the sides of the box
and the sides of the trench. In order to increase the lateral
load-carrying capacity of the box, i.e., the ability of the box to
withstand forces exerted by the sides of the trench, the sheet
member 21 is cambered outwardly to produce a convex outer surface
for each of the wall members in contact with the sides of the
trench when viewed in the horizontal plane of the box. The
cambering of the outer surface of the sheet member 21 may
conveniently be accomplished by bending or curving the top beam
member 15 in the horizontal plane and similarly bending the bottom
beam member 16, so that the entire frame 14 is cambered in the
desired manner. The sheet member 21 may then be welded to the beam
and column members forming the frame to thereby produce the convex
outer surface for the wall member. Although the degree of camber is
not critical and is too small to be adequately shown in the
drawings herein, it may be mentioned that a satisfactory camber for
a wall member having a length of 20 feet would produce a "bowing
out" of approximately one inch measured at the midpoint of the wall
member between the ends thereof.
As may best be seen in FIG. 3 of the drawings, one edge 23 of the
sheet member 21 is arranged to extend a distance beyond the front
column member 17 which forms the front end of the frame 14. A front
cover plate member 22 is then welded to the extended edge 23 of the
sheet member and to the inner flange or surface of the front column
member 17. If desired, the top and bottom beam members may be
tapered at the ends thereof adjacent the front cover plate 22 to
completely enclose the front end of the wall member, and one or
more triangular gusset plates 24 may be inserted between the front
column 17, the sheet member 21 and the cover plate 22 to provide
increased structural strength for the assembly. The foregoing
arrangement provides a vertically disposed cutting edge along the
extended edge 23 of the sheet member 21. Since the cutting edge
lies within the outer surface of the sheet member 21, it functions
as a side cutter to shear off projecting portions of the sides of
the trench when the trenching box is dragged or pushed through the
trench.
As seen in FIG. 3 of the drawings, the bottom edge 26 of sheet
member 21 is arranged to extend below the bottom surface of the
bottom beam member 16, so that a bottom cover plate 25 may be
mounted between the bottom edge 26 of the sheet member and the
inner flange or surface of the beam member 16, to thereby form a
horizontally disposed cutting edge along the entire length of the
wall member 10. Again, the cover plate 25 may be secured to the
flange of beam 16 and to the bottom edge of sheet member 21 by
means such as welding and a plurality of gussets 27 may be inserted
between beam 16, sheet member 21 and cover plate 25 at spaced
intervals along the entire length of the bottom of the wall member
to provide additional structural strength. If the abutting ends of
the front cover plate 22 and the bottom cover plate 25 are tapered
as shown along the line 28, and welded together, the front end and
bottom of the wall member 10 are effectively enclosed to provide
smooth surfaces adjacent the vertical and horizontal cutting edges
of the box. In practice, the front cover plate 22 and bottom cover
plate 25 may be fabricated from steel plate.
The invention also contemplates the use of push plates or pads, 29,
30, 31 and 32 which are respectively mounted in vertical alignment
with columns 17, 18, 19 and 20 on the top surface of the beam
member 15. The push plates may all be rectangular in shape, with
the exception of push plate 29 which is tapered to fit the tapered
cutting edge at the front end of the wall member 10. Push plates
29, 30, 31 and 32 may conveniently comprise steel plate and are
preferably welded to the top surface of beam 15, so that each push
plate functions as a load-bearing surface disposed above a column
member. This arrangement permits the safety trenching box of the
invention to be driven down into a trench or other excavation by
external forces applied to the push plates, since the horizontally
disposed cutting edge 26 on the bottom of each wall member
functions as a side cutter to shear off projections from the side
of the trench. The external forces, which may be supplied from
construction equipment available at the site, such as a backhoe for
example, are applied to the load-bearing surfaces provided by the
push plates and are transmitted directly through column members 17,
18, 19 and 20 to the bottom cutting edge of the wall members. When
the trench is of adequate width to receive the box or when the
sides of the trench have only small projections to impede movement
of the box, the box may, of course, be lowered into position
without any externally applied forces.
In order to prevent falling earth and stone from accumulating on
bottom beam member 16, top cover plates 33, 34 and 35 are disposed
between adjacent column members and are connected by mean such as
welding to the inner surface of sheet member 21 and the flange or
upper surface of the bottom beam member. As seen in FIGS. 2, 3, and
4 of the drawings, the top cover plate 33 is disposed at an acute
angle with respect to the inner surface of sheet member 21 and is
connected to the flange portion of the beam member 16, so that the
cover plate forms inclined skid path means between the columns 17
and 18 which serve to prevent earth, stones and other material from
accumulating on top of the beam 16. Top cover plate 34 is similarly
arranged between columns 18 and 19 and top cover plate 35 performs
the same function between columns 19 and 20. Accordingly, any
stones or other matter falling into the box will be guided to the
bottom of the trench without building-up or accumulating on the
beam 16. When earth or stone is permitted to accumulate on the
sides of the trenching box, a slight movement of the box could
cause the accumulated material to fall on workmen employed in the
box and could produce serious injury or death. In deep excavations,
where a number of trenching boxes are stacked on top of each other,
the problem becomes even more serious, since the accumulated earth
and stone will have a longer distance to fall before hitting the
bottom of the excavation. With the safety trenching box of the
invention, however, any matter falling into the box will be guided
immediately to the bottom of the trench even though a number of
boxes are employed in a stacked arrangement for work in very deep
trenches.
The top cover plates 33, 34 and 35 also function to increase the
structural strength of the wall member 10 and are preferably
fabricated from steel plate. If desired, a plurality of gusset
plates 36 may be disposed between the top cover plates and the
inside of sheet member 21 at spaced intervals along the bottom beam
member 16 to further increase the structural strength of the entire
assembly. Additional cover plates 37, 38 and 39 may be employed
between the bottom surface or flange of top beam member 15 and the
inner surface of the sheet member 21, as shown in FIGS. 2 and 4 of
the drawings, to further increase the structural strength and
stability of the unit. Since the lateral thrust exerted by the
sides of the trench is applied to the outer surface of the sheet
member 21 and is then transmitted to the frame 14, a plurality of
vertically disposed stiffeners 40 are provided along the entire
length of the box on the inner surface of sheet member 21 between
the cover plates 37, 38 and 39 and the cover plates 33, 34 and 35,
to prevent buckling of the sheet member 21 and to thereby increase
the structural strength of the unit. In practice, the stiffeners 40
may comprise steel angles which are welded to the inner surface of
the sheet member 21. Finally, lift eyes 41 may be welded to the
four inside corners of the wall member 10 formed by the beams 15
and 16 and the columns 17 and 20, to provide convenient means for
lifting and moving the box. The four lift eyes may be fabricated of
steel plate.
The wall member 11 is constructed in the same manner as wall member
10 and will not be described further herein, except to note that in
the arrangement of its component parts it constitutes a "mirror"
image of wall member 10, so that the vertical cutting edges are
both disposed at one end of the trenching box and the horizontal
cutting edges are both disposed on the bottom of the box. The
spreader members 12 and 13 which separate and laterally support
wall members 10 and 11 are usually made in several standard widths
or sizes and are bolted to the wall members to permit the trenching
box to be adjusted to handle trenches of different widths. As seen
in FIG. 1 of the drawings, the front spreader member 12 may
comprise a substantially rectangular frame or assembly 42 which is
formed by horizontal beam members 43 and 44 and vertical column
members 45. The beam members 43 and 44 and column members 45 may be
fabricated from structural steel and welded together to form a
rigid assembly. The frame 42 is preferably welded to a sheet steel
member 46 to enclose the end of the trenching box and to impart
structural rigidity to the assembly. The ends of frames 42 are
welded to a pair of end columns 47 which are connected to the end
columns 17 of the wall members 10 and 11 by suitable connecting
means.
When the connecting means comprise nuts and bolts, the front cover
plate 22 of each wall member is formed with a plurality of
apertures 48 adjacent bolt holes 49 in the front column member 17,
to permit access to those nuts or bolts located within the closed
end of each wall member formed by the column 17, cover plate 22 and
sheet member 21. In practice, the apertures 48 may be formed by
castellating the edge of cover plate 22 which abuts the flange of
column member 17. The apertures 48 may be omitted, of course, if
the holes 49 are tapped to avoid the need for nuts, or if the nuts
are welded to the interior surface of the flange portion of column
17. It is usually preferable, however, to employ separate nuts and
bolts, since a bolt may shear in a tapped hole or the thread on a
nut may become stripped at the construction site, thereby
presenting a difficult and time-consuming repair job. The front
spreader member 12, as thus far described, is of sufficiently
rugged construction to permit the trenching box to be dragged
through a trench by the bucket of a back hoe gripping the spreader
member or to permit the box to be hammered into position in a
trench by blows applied to the spreader member itself. When this
type of operation is contemplated, however, the bolts employed in
connecting the spreader member to the wall members should have a
suitably high shear strength. For reasons which will be described
hereinafter, the front spreader member 12 may be made so that its
bottom width is slightly greater than its top width, thereby
imparting a gradual taper to the box over the height of the
box.
The rear spreader member 13 may be fabricated in exactly the same
manner as the front spreader member 12 and will not be described
further herein. It may be noted, however, that the front spreader
member is customarily made somewhat wider than the rear spreader
member, to provide a gradual taper for the trenching box over its
entire length. This arrangement permits the box to be dragged
through a trench or other excavation with a minimum of frictional
drag. Under these conditions, it is believed apparent that the
vertical cutting edges 23 formed at the front end of the box will
serve as side cutters to widen the trench to the required width as
the box is dragged or pushed through the trench. If the trench is
widened sufficiently to permit passage of the front end of the box,
the tapered configuration of the box will insure that the rest of
the box will pass through without binding.
Referring now to FIG. 5 of the drawings, it is seen that two or
more of the safety trenching boxes of the invention may be employed
in a stacked arrangement. When the boxes are stacked vertically, it
is possible to utilize a number of such boxes to create a safe
enclosure for trenches and other excavations wherein the depth of
the trench or excavation is substantially greater than the height
of a single trenching box. As seen in FIG. 5, the safety trenching
box described in FIGS. 1 through 4 of the drawings is placed on top
of an identical safety trenching box 100 which has a wall member
101 and a wall member 102. By suitably proportioning the front and
rear spreader members as previously described, the trenching box
may be given a vertical taper so that the distance between the
bottom cutting edges is greater than the distance between the tops
of the wall members. When this is done, the bottom cutting edges of
one box will "straddle" the top of the box underneath it, as
illustrated to provide lateral stability for the stacked boxes. The
vertical taper also functions to prevent binding when the box is
lowered into a trench having a small clearance between the walls of
the box and the sides of the trench.
When two boxes are stacked as shown in FIG. 5, it is seen that the
tapered bottom of each of the wall members 10 and 11 formed by the
cover plate 25 of the upper box provides only a line contact with
the corresponding surface of the wall members 101 and 102 of the
lower box 100. Accordingly, the weight of the top box and any force
applied to the top box is transmitted to the bottom box over the
very small surface area provided by the line contact. Furthermore,
since the bottom of wall members 10 and 11 is tapered, any vertical
force applied to the upper box will be split into vertical and
horizontal components at the line contact of each wall member with
the wall member of the box below, thereby decreasing the force
applied to the cutting edges 103 on the bottom box. Although the
boxes may be stacked in this manner by securing the respective lift
eyes 41 of the boxes together by chains or cables (not shown), the
invention also provides that support legs 52 (shown in dotted
outline) may be mounted on the bottom cover plate 25 of each of the
wall members to provide flat, load-bearing surfaces of larger area
between the two boxes. The legs 52, which may comprise truncated
steel I beams, are preferably welded to the bottom cover plates 25
in vertical alignment with the columns 17, 18, 19 and 20 of each
wall member, so that they bear directly on the push plates mounted
on top of the wall members 101 and 102 of the lower trenching box
100. By virtue of this arrangement, if the stacked trenching boxes
are hammered or driven downwardly into a trench by the application
of forces to the push plates 29, 30, 31, and 32 of the top box, the
vertical forces so applied will be transmitted through the columns
17, 18, 19 and 20 and the legs 52 of the upper box directly to the
corresponding push plates and column members of the lower box 100,
to thereby provide maximum driving force at the bottom cutting
edges 103 of the bottom box.
It is believed apparent that many changes could be made in the
construction and described uses of the foregoing safety trenching
box and many seemingly different embodiments of the invention could
be constructed without departing from the scope thereof. For
example, it is believed obvious that the particular structural
configuration employed for the frame portion of each of the wall
members of the trenching box could be varied in design and still
provide the required structural rigidity and strength. Accordingly,
it is intended that all matter contained in the above description
or shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *