Slab lifter

This invention relates to a simple tool which can be used by two people manually to lift and position slabs of various thicknesses. A slab lifter according to the invention comprises two bars adapted to rotate with respect of each other about a mutually perpendicular axis, each bar having at one end a slab-gripping portion bent at an obtuse angle A of 100 to 140 degrees towards the position of the slab-gripping portion of the other bar so that it can be inserted between adjacent slabs and together with the other slab-gripping portion can grip opposite edges of a slab to distance L apart, the distance from the axis of rotation to the slab-gripping portion of the bar being approximately equal to 0.5 L/sine (A+a) where a is an angle of zero to 5 degrees representing "toe-in" of the slab-gripping portion when gripping the slab, and the rest of the bar on the other side of the axis of rotation being of such length and shape that it can project laterally at least as far as the vertical plane of the opposite edge of a gripped slab so as to provide a handle.

This invention relates to a simple tool which can be used by two people 
manually to lift and position slabs of various thicknesses. 
A slab lifter according to the invention comprises two bars adapted to 
rotate with respect of each other about a mutually perpendicular axis, 
each bar having at one end a slab-gripping portion bent at an obtuse angle 
A of 100 degrees to 140 degrees towards the position of the slab gripping 
portion of the other bar so that it can be inserted between adjacent slabs 
and together with the other slab-gripping portion can grip opposite edges 
of a slab of distance L apart, the distance from the axis of rotation to 
the slab-gripping portion of the bar being approximately equal to 0.5 
L/sine (A+a) where a is an angle of zero to 5 degrees representing 
"toe-in" of the slab-gripping portion when gripping the slab, and the rest 
of the bar on the other side of the axis of rotation being of such length 
and shape that it can project laterally at least as far as the vertical 
plane of the opposite edge of a gripped slab so as to provide a handle. 
The obtuse angle A is preferably 115 to 125 degrees. 
The slab-gripping portions may be parallel (and generally vertical) when 
gripping the slab or they may converge slightly with a "toe-in" angle a on 
each of up to 5 degrees. 
The angle (A+a) is related to the angle B between the lower parts of the 
bars at the axis of rotation in an ideal gripping position by the formula: 
EQU B=360 degrees-2(A+a). 
Thus, assuming a is zero, when the obtuse angle A is 120 degrees B is also 
120 degrees and this is about the optimum. Gripping is possible, however, 
with values of B between 70 and 155 degrees. 
Conveniently, each bar of the slab lifter is flat in the plane of rotation 
and the slab-gripping portion is formed at one end by a right-angle twist, 
the part beyond the twist being bent at the requisite obtuse angle A. 
The distance from the axis of rotation to the slab-gripping portion of the 
bars in the slab lifter can preferably be varied to suit different 
gripping distances L, thus enabling the slab lifter to be used with 
various sizes of slab. For example, the bars may be bolted together in 
various positions to take 12 inch (0.30 meters), 18 inches (0.46 m), 24 
inches (0.61 m) and 36 inches (0.91 m) slabs while also accommodating many 
in-between sizes. 
Alternatively each bar may be composed of releasably secured elements 
relatively movable longitudinally for adjustment in length. In this way 
the distance between the axis of rotation to the slab-gripping portion can 
be altered without changing the place of the axis of rotation. Similarly 
the length of the other part of the bar (i.e. the distance from the axis 
of rotation to the handle) may be varied independently of the distance 
from the axis of rotation to the slab-gripping portion. This is 
conveniently achieved by constructing the bars from a hollow piece which 
slides over a solid piece, with means to fix the relative positions of the 
pieces in any desired position. For example, a hollow handle section may 
be fitted over a solid main bar containing several locations for the axis 
of rotation and formed into a slab-gripping portion at the lower end. 
Alternatively the main bar including the handle may be hollow with a 
single site for the axis of rotation, and the slab-gripping portion may be 
formed on a solid element which fits into the lower part of the main bar. 
The bars may conveniently be straight, but when they are gripping at an 
angle B of less than 110 degrees the position of the axis of rotation can 
be too high unless the handles are curved outwardly or set parallel to the 
upper surface of the slab. Such shaped handles are required, for example, 
to lift a 24 inch (0.61 m) slab at values of B below 80 degrees 
(preferably below 90 degrees) and to lift a 36 inch (0.91 m) slab at 
values of B below 110 degrees; in the later case values of B below 95 
degrees are impracticable. 
Two people each holding one of the handles can lift a slab by dropping the 
slab-gripping portions centrally over opposite edges of the slab and then 
raising the handles to grip the slab and lift it safely from its position. 
The length and shape of the handle part allows them to stand clear of the 
slab edges and also have a mechanical advantage promoting effective 
gripping. Using the slab lifter they can carry the slab and lower it into 
position, placing it against other slabs with a small acceptable joint, 
without unduly bending their backs or risking their fingers. 
It may also be possible for one person alone to use the slab lifter, 
particularly on slabs which are not too large and heavy, by holding both 
handles. 
If a slab already in position is on too high a bed or has dropped, over the 
years, the slab-gripping portions of the slab lifter are pushed into the 
joints along opposite edges so that the slab can then be raised and 
removed. The slab lifter can also be used to replace that slab. 
The slab lifter may be used for lifting many kinds of objects. For example, 
it may be used to grip lengths of pipe for laying land drains end to end 
in trenches up to 1 meter in depth. It may be used to lift and position 
various types of curb stones and for moving objects such as concrete 
bicycle stands. A slab lifter having suitably narrow slab-gripping 
portions, preferably turned in slightly at the bottom edge to provide 
short grabs, may also be used for raising manhole covers and for removing 
certain types of drain covers. By attaching ropes to the handles and also 
one rope to the axis of rotation, the slab lifter may be dropped down 
wells or pits to retrieve objects. Other uses include raising duck boards 
and pit boards and raising many kinds of objects when submerged in up to 1 
meter of water. The slab lifter may also be used for removing objects from 
fires. 
The slab-gripping portions may each be longer than the thickness of the 
slab to be lifted and may end in a short grab for the slab e.g. of about 
1/4 inch (6 mm). The grabs must be sufficiently small to fit within the 
joints between adjacent slabs. For many purposes, however, the 
slab-gripping portions may be without a terminal grab in which case it 
need not be as long as the thickness of the slab. The bottom edge may be 
serrated to grip other objects as well as slabs. 
The slab-gripping portion is preferably flat to bear on the edge of the 
slab or consists of at least two spaced-apart prongs or tines to bear on 
the edges of the object to be lifted. Various fork-shaped configurations 
are possible. 
The slab lifting portion may be 11/2 inches to 18 inches (35 to 460 mm) and 
preferably 2 to 6 inches (50 to 155 mm) across. It is preferably 11/2 to 3 
inches (35 to 75 mm), desirably about 2 inches (50-60 mm) from top to 
bottom. It may be formed integrally with a stabilizer to bear horizontally 
on the upper surface of the slab adjoining the edge or a length in from 
the edge of 1/2 inch to 6 inches (10 to 155 mm), preferably 11/2 to 3 
inches (35-80 mm). Alternatively such a stabilizer as a seperate element 
may be fitted to one or both bars immediately above and transverse to the 
slab-gripping portion. The fitting may be adjustable to allow adjustments 
of the position of the stabilizer up the bar. Such a stabilizer may be 
useful when lifting uneven natural stone or broken concrete blocks when 
the balance is distorted. However, the slab lifter will perform most tasks 
without this attachment. 
Different types of slab lifting portions are readily interchangeable when 
this forms part of an element seperate from but releasably secured to the 
rest of the bar. The same is true for the handle element when this is 
seperate. 
Means may be fitted to the slab lifter to interact with both bars near to 
the axis of rotation so as to maintain them releasably in a slab-gripping 
position. Such means may comprise, for example, a resilient block of 
elastomeric material mounted laterally between the bars or a 
counterbalanced pawl mounted on the upper part of one bar interacting with 
a ratchet on the lower part of the other bar.

In the slab lifter shown by way of example in FIGS. 1 and 2, two flat bars 
M and N each have a right-angle twist C, D beyond which the bar is bent at 
an obtuse angle of 120 degrees at Y, Z to provide vertical slab-gripping 
portions each terminating in a short grab B, A. The other end of the bar 
is a handle E, F. The length of each bar from the twist C, D to the handle 
E, F is 1.12 meters (44 inches). The bars are loosely held together at Q 
by a 6.4 mm (1/4 inch) bolt, wit spring friction washer and nut, or a pin 
with spring holding clip complete with washer or spring friction washer 
passing through holes in the bars to serve as an axis of rotation and 
dividing each bar into a handle portion EQ, FQ and a gripping portion BYQ, 
AZQ. The holes in the bar at Q represent an adjustment to grip a slab S 
having a length between opposite edges of 0.61 meters (24 inches). The 
distance from Q to the beginning of the slab-gripping portion of each bar 
at C, D is approximately equal to 1/2 L/sine A where L is 0.61 meters and 
A is 120 degrees (as shown in FIG. 1, this distance is actually 0.37 
meters (141/2 inches) and therefore slightly greater than the distance of 
0.352 meters (13.86 inches) prescribed by the mathematical formula). 
Each bar has a series of other holes for coupling the bars together, 
representing adjustments to grip 0.30 meters, 0.46 meters and 0.91 meters 
(12 inch, 18 inch and 36 inch) slabs respectively instead of the 0.61 
meters (24 inches) slab catered for by coupling at Q. Even when the bars 
are coupled through the holes for the 0.91 meter slab (i.e. the holes 
shown between Q and E and between Q and F, the distance from these holes 
to the slab-gripping portion of each bar at Y and Z is only 0.53 meters 
(203/4 inches) which is less than the distance from the holes to the 
handles E and F of 0.65 meters (253/4 inches). 
The slab-gripping portion of each bar beyond Y and Z is 63.5 mm (21/2 
inches) long and terminates in a 3.2 mm (1/8th inch) grab at B and A 
respectively. 
FIG. 1 shows an adjustable stabilizer fitted to one bar between the twist C 
and the beginning of Y of the slab-gripping portion. The stabilizer, the 
fitting of which is shown in more detail in FIG. 2, consists of an 0.18 
meter (71/4 inches) long piece of 32 mm (11/4 inch) channel iron with the 
top side angled at I to fit the angle of the bar between C and Y and with 
the bottom side J horizontal to bear on the top of the slab. The top side 
has a centrally positioned slot 6.4 mm (1/4 inch) wide extending in the 
direction of the bar for a length of 25 mm (1 inch). A 6.4 mm (1/4 inch) 
bolt with a butterfly nut H passes through the slot and through the hole 
(not shown) in the bar between C and Y so as to fasten the stabilizer to 
the bar and allow adjustment of its position up the bar by the length of 
the slot. 
The handles E and F, instead of being raised directly by a person on each, 
may be lifted by ropes passing through holes in the bars near the ends as 
shown in FIG. 1. A third rope may be passed through a central washer hole 
K linked to the bolt at Q to drop the slab lifter down a pit or well for 
retrieving an object which can then be lifted using the ropes through the 
handles. 
In a slab lifter of alternative construction not shown in the drawings, the 
slab-gripping portion is 51 mm (2 inches) long and about the same 
thickness of the slab S, and has no terminal grabs. In all other respects 
this slab lifter is the same as the slab lifter shown in FIGS. 1 and 2. 
Whether a stabilizer is fitted is a matter of choice and the slab lifter 
in its simplest construction has neither a stabilizer nor means for 
attaching one. 
In the slab lifter shown by way of example in FIGS. 3 to 6, each bar is 
composed of two releasably secured elements relatively moveable 
longitudinally for adjustment of length. The main elements 10, 11 of each 
bar are of hollow steel of rectangular cross-section having a wall 
thickness of approximately 1/16th inch (1.6 mm) minimum 291/2 inches (0.75 
m) long and are permanently pivoted together at a point 23 inches (0.58 m) 
from the handle end by means of a rivet 13 passing through the pressed out 
section of the nearest wall of each hollow section and dressed down below 
the main inner face leaving the interior of the hollow section 
unobstructed. The slab-gripping portions 14 and 15 of the bars are borne 
on the ends of solid or hollow section steel elements 16 and 17 which fit 
inside the hollow sections 10, 11 respectively. If solid, these elements 
can be an 1/4 to 1 inch (6 to 25 mm) in thickness and 3/4 inch to 21/2 
inches (19 to 63 mm) in width. 
As shown in more detail in FIG. 5, the elements of the bars are secured 
together in the desired relative position by fixed spring pins 18 and 19 
each mounted on an passing through a hole in the outer hollow section 10, 
11 into a hole 20 which is one of a series in predetermined desired 
locations in the inner element 16, 17. These elements 16, 17 incorporating 
the slab-gripping portions 14, 15 slide up inside the outer hollow element 
10, 11 to the required position to take 36 inch, 24 inch, 18 inch or 12 
inch slabs and are secured in the correct position by the spring pins 18, 
19. 
In FIGS. 7 to 10 the outer hollow element 11 and the inner elements 16 and 
17 incorporating various slab-gripping portions 14, 15 are generally 
similar to the corresponding parts shown in FIGS. 4 and 5 except that the 
elements are secured together by a pin (not shown) passing through holes 
22 or 24 in the outer element and 26 or 28 in the inner element. The 
slab-gripping portions shown in FIGS. 7 and 8 incorporate a stabilizer 30 
to bear on the horizontal surface of the slab. The slab-gripping blades or 
forks of the two arms of the slab lifter may be parallel (vertical) in the 
gripping position or they can "toe in" at the bottom by 2 or 5 degrees out 
of upright. 
In the slab lifter shown by way of example in FIG. 11 the main parts 16, 17 
of the bars have series of holes 32, 34 and 36 for coupling the bars 
together as described for the slab lifter of FIG. 1. The main parts 16, 17 
of the bars incorporate slab-gripping portions 14, 15 in a fashion 
analogous to that shown in FIGS. 7 and 8. The handle elements 10, 11 of 
the bars are formed of steel hollow section similar to that used for the 
main parts 10, 11 of the bars in FIGS. 3 and 4 and they are releasably 
secured to the main parts 16, 17 by spring clips 18, 19 operating in 
predetermined series of holes in the inner elements as described with 
reference to FIG. 5. 
This enables the distance from the axis of rotation (e.g. 36 in FIG. 11) to 
the handle 38, 39 to be varied independently of the distance from the axis 
of rotation (e.g. 36) to the slab-gripping portion (14, 15). The handle 
can thus be made to stick out past the end of any size slab by a 
convenient amount for lifting; a good position is approximately 4 inches 
(0.1 m) beyond the vertical plane of the edge of the slab. 
The slab-gripping portion of the bars as shown in any of the FIGS. 1, 3 and 
4, 7, and 11 may be the same or different on the two bars and each may 
have any of the configurations described above or shown in FIGS. 1 and 2 
and any of FIGS. 7 to 10. 
FIGS. 12 and 13 illustrate by way of example the provision of means capable 
of interacting with both bars 6, 7 near to the axis of rotation 8 so as to 
maintain them releasably in a slab-gripping position. In FIG. 12 a block 
40 of firm elastomeric material is mounted on a plate 41 which is secured 
to the slab lifter at the axis of rotation 8. When the bars 6, 7 are 
gripping a slab the block 40 is compressed sufficiently to maintain them 
in that position. To engage or release the slab, the ends of the bars are 
momentarily moved to compress the block 40 further. The plate 41 retains 
the block 40 in position when the slab lifter is not in use. It has one 
metal stop which fits under the upper bar (7 in FIG. 12). The resilient 
understop may alternatively be formed by spring steel instead of 
elastomeric material as in block 40. 
In FIG. 13 a counterbalanced pawl 42 is rotatably mounted on the upper bar 
7 and interacts with a ratchet 43 on the edge of the lower bar 6. The pawl 
is formed with a handle to facilitate release from the ratchet and with a 
stop of either side so that it cannot turn further than its workable arc. 
The tooth of the pawl automatically selects the correct serration of the 
ratchet when a slab is gripped and the handles of the slab lifter are 
raised. It then remains in position gripped to the slab if the operators 
remove their hands from the handles. Where the slab lifter has a series of 
holes in the bars to choose from as the axis of rotation, as shown for 
example in FIGS. 1 and 11, a corresponding series of holes is required in 
one of the bars for mounting the pawl (these holes conveniently being of a 
smaller size for ease of identification) and corresponding lengths of the 
other bar must accordingly be serrated to form the requisite ratchet. 
FIG. 14 is a diagram showing how an outwardly curved handle 5 or a 
horizonally set handle 4 may be provided on a slab lifter for lifting a 36 
inch slab at an angle B between the bars 6, 7 of 104 degrees at the axis 
of rotation 8. 
FIG. 15 shows a preferred form of slab lifter, generally efficient to use 
and relatively cheap to produce, which comprises two straight solid flat 
bars as described with reference to FIG. 1 but each with an angled lower 
end on to which is welded a short 0.1 meter (4 inch) piece of 50 
mm.times.50 mm (2 inch.times.2 inch) of angle iron. 
Alternatively a simple slab lifter with pivot holes as seen in FIG. 1, can 
be made up with two hollow section bars (M N), the grab element can be 
formed by inserting any type of the grab elements (similar to those shown 
in FIGS. 7, 8, 9 and 10) but with shorter insert bars which slide inside 
the hollow sections and are fixed securely.