Lifting device for massive precast concrete wall units

A lifting device for massive precast concrete wall units having spaced parallel front and rear wall panels and spaced apart lateral connecting arms therebetween. The device comprises a pair of pivotally connected lifting legs swingable between retracted and expanded positions. The legs have a spreader element pivotally connected therebetween intermediate their ends. At upper ends a pair of connecting links are respectively connected pivotally at lower ends with the legs and pivotally connected together at upper ends. A lift attachment is also pivotally connected at upper ends of the connecting links. At lower ends the legs have fixed or pivotal shoes with outwardly projecting toes which engage beneath the bottom surfaces of the arms of the wall units with the legs expanded. With the legs retracted the legs and shoes are freely moveable vertically between the arms of the wall units. Shoes are selectively mountable on the legs in pairs with horizontal and at least one other toe angle. A manually operable locking mechanism secures the legs in retracted position in an overcenter position and, when released, the legs assume their expanded position at the urging of gravity.

BACKGROUND OF THE INVENTION 
Modular retaining walls comprising a number of stacked precast concrete 
units now enjoy commercial acceptance. The leading commercial unit is 
disclosed in U.S. patent application Ser. No. 204,327 entitled Improved 
Precast Concrete Structural Unit and Composite Wall Structure filed Nov. 
4, 1980 by Roger L. Toffolon and William L. Brown. 
The precast modular units are massive in form and handling of the same 
raises significant problems. That is, the units must be transported, for 
example as by flat bed trailer, removed in succession from the trailer and 
carefully stacked in the construction of a retaining wall or the like. 
Efficient lifting and transporting apparatus for the individual modules or 
units has heretofore been unavailable. 
Accordingly, it is the general object of the present invention to provide a 
lifting device for massive precast concrete units having spaced parallel 
front and rear wall panels and spaced apart lateral connecting arms 
therebetween, the device being readily engageable with and disengageable 
from the units in a convenient and efficient lifting and transporting 
operation of the units. 
SUMMARY OF THE INVENTION 
In fulfillment of the foregoing object and in accordance with the present 
invention, a lifting device is provided and is particularly adapted to 
precast concrete wall units having spaced parallel front and rear wall 
panels and a pair of spaced apart lateral connecting arms therebetween. 
That is, the lifting device is designed to lift, transport, and 
efficiently deposit the units as, for example, from a flat bed trailer to 
a selected position on a retaining wall. The device enters the units 
vertically between their connecting arms in a retracted position and, on 
expansion and engagement with bottom surfaces of the arms, the lifting 
device serves to secure and balance a unit for vertical and other 
movement. The device is also capable of precise positioning of a unit atop 
a similar unit or units in a retaining wall in horizontal and in other 
attitudes of deposition. 
The lifting device comprises a pair of pivotally connected lifting legs 
swingable between retracted and expanded positions. Lower end portions of 
the legs in the retracted position have an overall horizontal dimension 
such that the legs can freely pass vertically between the arms of a 
precast concrete wall unit of the type described. In expanded position of 
the legs the lower end portions have an overall horizontal dimension such 
that they reside respectively in close proximity to the inner walls of the 
connecting arms of a precast concrete wall unit. A pair of shoes 
respectively mountable on lower end portions of the legs have opposite 
laterally outwardly projecting toe portions which are adapted respectively 
to engage bottom surfaces of the arms of a precast concrete wall unit with 
the legs of the lifting device in the expanded position. The unit is thus 
securely held and balanced for lifting and transport as desired. 
The lifting device also includes a manually operable locking mechanism 
which has lock and release positions respectively for securing the legs of 
the device in their retracted position and for freeing the legs for 
movement to their expanded position. In the preferred embodiment shown, 
the legs move to the expanded position at the urging of gravity and are 
retained in such position during lifting and transport of a concrete wall 
unit by the orientation of forces exerted thereon. 
The lifting device also includes a lift attachment which is connected with 
the legs at upper end portions for releasably securing a vertically 
moveable power hoist to the lifting device. Any suitable hoist means may 
be employed with the lifting device of the present invention. 
In its preferred form and as illustrated in the drawings, the lifting 
device includes a spreader element pivotally connected with the legs 
intermediate their ends. At upper end portions the legs have a pair of 
operatively associated connecting links, each pivotally attached to its 
leg and extending to a common pivotal connection with the lift attachment. 
The aforementioned manually operable locking mechanism is disposed between 
the lifting legs above the spreader element and below their connection 
with the connecting links. An overcenter operation of the mechanism is 
provided for convenient manual manipulation securing the legs in their 
retracted position. On release of the locking mechanism, the legs freely 
swing to their expanded position as described. 
Provision is made for the deposition of the wall units in a horizontal 
attitude and at other angles of inclination by employing a plurality of 
pairs of shoes selectively mountable in pairs at lower end portions of the 
lifting legs. That is, shoes are provided for holding wall units in a 
horizontal attitude and when desired, a pair of horizontal shoes may be 
removed from the lifting legs and replaced with a similar pair of shoes 
having toes at angles which depart from the horizontal. The toes may have 
a slight angle of inclination as required to construct an inclined 
retaining wall of the type known in the trade as a "batter" or "battered" 
wall. The inclined toes on the shoes lift and transport the wall units at 
a slight angle of inclination, front wall to rear wall, and the units are 
so stacked in the construction of the retaining wall. Obviously, pairs of 
shoes having toes with various angles of inclination may be provided for 
selective use on the legs of the lifting device. Similarly, the length of 
the shoe elements may vary in accordance with the size or vertical 
dimension of precast concrete wall units to be handled thereby.

PREFERRED EMBODIMENTS 
Referring particularly to FIGS. 1 and 2, a precast concrete wall unit 
indicated generally at 10 has front and rear wall panels 12,14. The wall 
panels 12,14 are spaced apart and in parallel relationship and have 
integral connecting arms 16,16. The connecting arms 16,16 are spaced apart 
laterally and in parallel relationship and include a mortise-tenon 18,20 
for the interconnection of vertically stacked wall units. That is, a 
portion of a subadjacent wall unit 10a in FIG. 1 has its tenon 20a entered 
in the mortise 18 at a lower surface of the connecting arm 16 shown 
therein. 
Precast wall units such as 10,10a may of course be stacked in various 
configurations to form composite wall structure such as retaining walls 
and reference may be had to the aforementioned patent application for 
further description and illustration of the modular wall units and 
composite walls. As mentioned above, the wall units may be removed, as for 
example from a flat bed trailer, transported to an adjacent wall site and 
successively stacked in a precisely vertical or "battered" attitude. 
A lifting device constructed in accordance with the present invention and 
indicated generally at 22 in FIGS. 3 and 4 includes a pair of similar 
pivotally connected lifting legs 24,26. As illustrated, the lifting legs 
24,26 are indirectly pivotally connected by means of a pair of connecting 
links 28,30 but other pivotal connections are contemplated, as for 
example, a direct pivotal connection between the legs. 
The connecting links 28,30 have pivotal connections respectively with pivot 
pins 32,34 at lower end portions and a common pivotal connection at upper 
end portions with a pivot pin 36. The pivot pin 36, as best illustrated in 
FIGS. 6 and 7, connects the links 28 and 30 together and also pivotally 
connects a lift attachment 38. The lift attachment 38 takes the form of a 
generally U-shaped member in an inverted position and with its depending 
legs pivotally engaged with the pin 36, FIGS. 6, 7. A wide variety of 
power hoist means can thus be readily attached to the lifting device as 
for example a hook member 40 in FIG. 4 which may depend from a 
construction crane. With a crane disposed adjacent a flat bed trailer and 
a retaining wall site, wall units may be readily lifted from the trailer 
and deposited in their desired position in a base or succeeding course of 
units in order to construct a composite wall structure. 
As illustrated in FIG. 3 and in their retracted position, the lifting legs 
24,26 depend generally vertically from the pivot pins 32,34. They are held 
in such position by a spreader element 42 and a locking mechanism 
comprising the links 44,46. The spreader element 42 is pivotally connected 
at a left hand end portion at 48 with the left hand lifting leg 24 and at 
a right hand end portion at 50 with the right hand lifting leg 26. 
The locking mechanism comprising the links 44,46 is adapted for manual 
operation and for lock and release positions respectively for securing the 
legs 24,26 in their retracted position and for freeing the legs for 
movement to their expanded position, FIG. 4. Link 44 has a pivotal 
connection at 52 with the left hand leg 24 and a pivotal connection at 54 
with the link 46. At its right hand end the link 46 has a pivotal 
connection 56 with the right hand lifting leg 26. A bifurcated handle 58 
is rigidly connected with the link 46 as by welding and extends 
rightwardly in FIGS. 3-4 for manual operation of the locking mechanism. 
Two generally U-shaped members 60,62 depend from the handle 58, FIGS. 6-7 
for ease and convenience of manual manipulation. 
With the locking mechanism positioned as shown in FIG. 3 a small horizontal 
stop member 64 at an inner end of the link 46 engages the link 44 to limit 
the central upward swinging movement of both links 44,46 in an overcenter 
position as illustrated. Thus, the links 44,46 serve as a second spreader 
element at an upper portion of the lifting legs 24,26 and retain the legs 
in the retracted position shown in FIG. 3. 
When the handle 58 is swung upwardly as illustrated in FIG. 4 whereby to 
pivot the link 46 downwardly the link 44 is similarly swung downwardly to 
allow the legs 24,26 to swing inwardly at upper end portions and outwardly 
at lower end portions to the FIG. 4 position. The legs swing at the urging 
of gravity once the links 44,46 pass the horizontal in their downward 
swinging movement. That is, the weight and geometrical configuration of 
the legs and the various links is such as to cause the legs to assume the 
FIG. 4 position with the links 28,30 extending upwardly therefrom and 
forming a continuation or an apex of a generally V-shaped configuration. 
It will be noted that the leg 24 and the link 28 reside substantially in 
linear relationship as do the leg 26 and the link 30. Thus, any upwardly 
exerted force on the lift attachment 38 is exerted linearly through the 
links and legs to the lowermost portions of the legs. 
Preferably, an abutment means is provided for limiting the movement of the 
legs 24,26 toward their expanded position and for establishing the 
V-shaped configuration of FIG. 4. As best illustrated in FIG. 4, a pair of 
stop members 65,65 are provided respectively on the legs 24,26 and when 
the legs 24,26 assume the desired V-shaped configuration the stop members 
65,65 engage the spreader member 42 whereby to limit swinging movement of 
the legs. Similarly, the small horizontal member 64 on the link 46 may 
engage the leg 26. With the lifting device in the FIG. 4 position, and 
prior to engagement and lifting of a wall unit, the stops 65,65 serve to 
prevent free or unintended movement about the pivot pins 32,34 as might 
cause one leg to depart slightly from the desired V-configuration. That 
is, the lowermost portion of one leg might be slightly higher than the 
other and there may be a tendency for free individual swinging movement of 
the legs about their pivot pins making engagement of the lifting device 
with the wall unit difficult. Once the lifting device is engaged with the 
wall unit as shown in FIG. 4 and an upward force is exerted at the lift 
attachment 38, the legs and their connecting links will remain in linear 
relationship due to the linear forces exerted thereon and the stops 65,65 
may be unnecessary in this phase of operation. 
The engagement of the lifting device with the wall units for lifting and 
transporting the units is provided for by a pair of shoes 66,68 mounted 
respectively at lower end portions of the legs 24,26. As best shown in 
FIGS. 3 and 4, the shoes 66,68 have oppositely laterally outwardly 
projecting toe portions 70,72 which engage bottom surfaces 74,76 of the 
arms 16,16 of a wall unit in FIG. 4. More specifically, the toes 70,72 
engage bottom surfaces 74,76 of the mortises formed at the bottom of the 
walls 16,16 as in FIG. 1. With the toes 70,72 in engagement with the 
surfaces 74,76, the wall unit is balanced and supported for lifting and 
transport by the lifting device of the present invention. If, for example, 
the wall unit is to be removed from a flat bed trailer and stacked in the 
construction of a retaining wall, the lifting device is lowered vertically 
in the direction of the arrow 78 in FIG. 3 between arms 16,16 of a wall 
unit. The lifting device is of course in its retracted position during 
free vertical movement between the arms 16,16 and when the locking 
mechanism is moved to the FIG. 4 position, the lifting device may be 
engaged with the wall unit as shown in FIG. 4. Lifting of the wall unit 
may then be effected in the direction of the arrow 80 in FIG. 4 and the 
unit may be positioned as desired in the stacking and construction of the 
retaining wall. Re-engagement of the locking mechanism moving the same to 
the FIG. 3 position allows the lifting device to be withdrawn upwardly 
from between the arms 16,16 of the wall unit and a next succeeding wall 
unit may then be engaged on the trailer for transport to the wall. 
The shoes 66,68 in FIGS. 3 and 4 have tubular upper portions which are 
telescopically received by lower end portions of the lifting legs 24,26 
and which may be removably secured in position by means of suitable bolts 
82,82. Thus, it will be apparent that shoes can be provided in pairs for 
selective mounting on the legs 24,26 of the lifting device. The shoes 
66,68 shown in FIGS. 3,4,6 and 7 have horizontal toes or toe plates 70,72 
and thus serve to balance a wall unit in a horizontal position or attitude 
when the lifting device is engaged with the unit. 
Similarly, a shoe such as illustrated in FIG. 5 at 84 may be provided with 
a toe 86 which is inclined slightly from the horizontal. When a pair of 
such shoes are mounted on the legs 24,26 they provide for a corresponding 
inclination of a wall unit supported by the lifting device. That is, a 
wall unit such as the unit 10 shown in FIGS. 1 and 2 may be inclined 
slightly downwardly from front to rear and the wall may be so constructed. 
Such a wall, known in the trade as a "batter" or "battered" wall as 
mentioned, is stacked at a slight angle of inclination from the horizontal 
whereby to provide a wall that is inclined slightly from the vertical. The 
angle may only be a few degrees but it is nevertheless important to 
deposit the wall units efficiently atop one another at the desired angle 
of inclination. Accordingly, a horizontal toe such as the toes 70,72 may 
create a cumbersome situation in attempting to deposit a wall unit 
supported horizontally atop a wall unit which is slightly inclined from 
the horizontal. On the other hand, with inclined toes such as the toe 86, 
the operation can be carried out with a high degree of efficiency. 
A lifting device 22a shown in FIGS. 8 and 9 forms a second embodiment of 
the present invention and may be substantially identical with the lifting 
device described above except for the shoes 66a and 68a. That is, the 
lifting device 22a includes lifting legs 24a,26a supported by connecting 
links 28a and 30a, a locking mechanism 44a, 46a having a handle 58a and a 
spreader 42a disposed beneath the locking mechanism and between the 
lifting legs. The device may be attached to a power hoist or the like for 
lifting and transport of precast concrete wall units such as 10a by means 
of a lift attachment 38a. The precast concrete wall unit 10a is shown 
broken away for clarity but may be regarded as identical with the wall 
unit 10 above. 
The shoes 66a and 68a are similar to the shoes described above but are 
provided with a pivotal connection with their respective lifting legs 24a 
and 26a. Thus, pivot pins 88 and 90 interconnect the lifting legs and the 
shoes and the shoes are freely swingable about the pivot pins relative to 
the lifting legs. In FIG. 8, the shoe 66a includes an extension element 92 
fixedly connected to the shoe and having a toe plate 70a fixedly connected 
at its lower end portion. Similarly, an extension 94 is fixed to the shoe 
68a and carries a toe plate 72a at its lower end portion. The toe plates 
70a,72a engage bottom surfaces 74a and 76a respectively at mortises 
18a,18a in connecting arms 16a,16a of the wall unit 10a. 
The pivotal connection of the shoes 66a and 68a provides for an important 
improvement in the operation of the lifting device. With the fixed shoes 
and toe plates of the lifting device of FIGS. 1-7, a precast unit 
supported thereby may be tilted relative to the toe plates as it is 
deposited on a retaining wall. That is, with either a vertical or a 
battered wall, and more particularly with the latter, the power hoist 
associated with the lifting device may lower the device and a precast unit 
held thereby so that the lower surfaces of the unit are not precisely in 
horizontal or inclined registry with a subadjacent wall unit. For example, 
a front wall of a descending wall unit may engage the front wall of a 
subadjacent unit slightly before the engagement between the rear walls of 
the unit occurs. This may result in a slight tilting of the descending 
unit such that surfaces 74,76 may be displaced slightly relative to the 
toe plates 70,72. Further, this may result in line rather than plane 
contact between the toe plates and the surfaces 74,76 and may even result 
in damage to the surfaces 74,76 and rupture of adjacent concrete areas. 
The foregoing functional or operational difficulties are completely 
overcome with the pivotally attached shoes 66a,68a of FIG. 8. In the event 
of a slight misalignment of a descending wall unit such as 10a and a 
subadjacent wall unit in a retaining wall, the unit 10a may for example 
make initial contact with the subadjacent unit at its front wall. The 
shoes 66a,68a thereupon pivot slightly allowing the toe plates 70a,72a to 
remain in firm planar contact at all times with the surfaces 74a,76a. 
Thus, the wall unit is deposited gently atop the subadjacent unit and 
damage to the surfaces 74,76 is avoided with potential rupture of adjacent 
areas positively prevented. 
The shoes 68b in FIG. 9 is substantially identical with the shoe 68a of 
FIG. 8 except for the provision of toe plate 72b immediately at the lower 
surface thereof. That is, the extension 94 is eliminated in FIG. 9 with 
the shoe 68b adapted for pivotal movement relative to leg 26a through the 
provision of pivot pin 98. As will be apparent, the shoe 68b is employed 
with wall units having a somewhat lesser vertical dimension than the wall 
unit 10a. Similarly, a plurality of extensions 92,94 may be provided in 
pairs for wall units of varying height. The extensions 92,94 are adapted 
for selective connection with the shoes 66a,68a and each such extension 
carries a toe plate 70a,72a. In all cases the necessary pivotal or slight 
swinging movement of the shoes and extensions is provided for by the 
pivotal connection between the shoes and their respective lifting legs. 
In view of the foregoing, it will be apparent that it is within the scope 
of the present invention to provide a plurality of pairs of shoes 
selectively mountable on the legs of a lifting device of the invention. 
The shoes are of course mounted in pairs and may have horizontal toes, 
toes at a slight angle of inclination, or, other variations in shoe and 
toe design such as pivotal shoes may be accommodated. Further, shoes of 
varying length may be desirable for handling wall units of varying 
vertical dimension. 
It will be apparent that a novel lifting device has been provided in 
accordance with the present invention. The device is particularly adapted 
for efficient use with precast concrete wall units of the type described 
and provides for a rapid and efficient operation in the lifting and 
transporting of the wall units. The device is yet simple in concept and 
construction and exhibits a high degree of durability an dependability in 
use.