US3531149A - Lift hook and method for handling prefabricated materials - Google Patents

Description

Se t.29,1970 W J.KI UEBER I 3,531,149

LIFT HOOK AND METHOD FOR HANDLING PREFABRICATED MATERIALS Filed April 29, 1969 IN VENTOR W/44/4/v AZ (/6559,

ATTORNEY United States Patent 3,531,149 LIFT HOOK AND METHOD FOR HANDLING PREFABRICATED MATERIALS William J. Klueber, Bethlehem, Pa. (588 Harvard Ave., Hillside, NJ. 07205) Filed Apr. 29, 1969, Ser. No. 820,152 Int. Cl. B66c 1/22 US. Cl. 294-89 4 Claims ABSTRACT OF THE DISCLOSURE Disclosed is an improved lift hook and method for handling prefabricated materials, particularly precast concrete slabs useful for example for floors or roofs. The hook and method of this invention involve inserting the hook from the upper side of the slab, through a tapered opening extending through the slab with the hook so constructed that it engages the slab and exerts compressive lifting forces against at least two and in many cases three separate areas of the slab. This causes the hook to bind and securely fasten to and grip the slab during lifting and does not cause undesirable tensile stresses, noting that while concrete is normally strong in compression it can be notoriously weak in tension. Release of the lifting force and simple rotation of the hook permits easy removal of the hook conveniently from the upper side of the slab without disturbing its orientation or requiring movement of the slab.

The present invention relates to an improved lift hook and method for handling prefabricated materials, and more particularly for precast, prefabricated concrete slabs useful for example for floors and roofs in constructing buildings.

Among the several objects for this invention are in cluded:

(l) the provision of a simple, low cost easy to handle hook;

(2) a hook which can be used easily with a precast concrete slab, which can be used from the upper side of the slab, which will not require moving the slab out of its stored or installed position to attach the hook for lifting or to remove the hook after the slab has been lifted and moved; which can be simply and quickly connected to the slab for lifting so that labor and expense are minimized;

(3) the provision of a hook which will easily be placed in operative lifting position with a concrete slab and which during lifting will automatically firmly grippingly engage the concrete slab and will exert primarily compressive lifting forces against the slab to take advantage of the compressive strength of the concrete and minimize the creation of tensile forces in the concrete; and

(4) the provision of a method for lifting precast concrete members which will permit flexibility of handling, storing and transportation of the precast members by not requiring special built-in attachments oftentimes required in prior handling techniques (see for example the techniques described in US. Pats. Nos. 2,772,560 and 2,794,- 336 as well as 2,886,370) which increase the cost of the slabs as well as their storing, handling and transportation.

Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, steps and sequence of steps, features of construction and manipulation, and arrangements of parts, all of which will be exemplified in the structures and methods hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of the various possible embodiments of the invention is illustrated:

FIG. 1 is a vertical section view of the hook of this invention in one embodiment thereof in operative gripping and lifting engagement with a concrete slab;

FIG. 2 is a view taken on line 22 of FIG. 1; and

FIG. 3 is a top view of the arrangement shown in FIG. 1.

Similar reference characters indicate corresponding parts throughout the several parts of the drawings.

Dimensions of certain of the parts as shown in the drawings have been modified and/ or exaggerated for purposes of clarity of illustration.

Precast concrete slabs or panels are normally stored at the factory until a number of them are ready for shipment and are needed at the construction site. These panels or slabs are very heavy, bulky and difficult to handle as well as costly in terms of time, labor, and the expensive cranes, hoists and other equipment required for this purpose. It is also very desirable from a manufacturing cost and handling cost point of view that built in handling attachments be avoided. The present invention solves these problems in a very simple, efficient and low cost way and also avoids the problem of frequent breakage or damage to the concrete which is sometimes experienced with other techniques which result in creating large tensile stresses in the concrete during lifting and handling.

Referring now to the drawings, in FIG. 1 is shown in fragmentary section a portion of a concrete slab C, which may have a plurality of reinforcing bars RB. Slab C is provided with a tapered opening referred generally at 30H, which opening extends completely through the thickness of the slab as shown and has its largest cross-sectional dimension 32 adjacent the top surface of slab C. The smallest cross-sectional dimenion 30 of the tapered opening is adjacent the bottom surface of the slab C. The tapered sidewall of the opening 30H is best seen in FIG. 1 at 34.

The lift hook according to one embodiment of this invention is shown in the drawings and generally referred at numeral 107 Hook 10 comprises an angle iron having a vertical upstanding leg or portion 12 (as shown in FIG. 1) and a horizontal leg or portion 22. Portion 12 provides an aperture 13 as means for connecting the hook 10 with a hoist through cable 15 and shackle 17 which is connected to portion 12 through pin 19 extending through aperture 13.

Hook 10 also includes another portion 18 which is spaced from and generally parallel to but extending in a direction opposite or away from leg 22. Integrally formed with leg 18 is a diagonally extending portion 16 connected adjacent or at one end thereof with leg 18 and at the other end thereof with a vertically extending (as seen in FIG. 1) portion 14. Portion 14 is secured as by welding to portion 12 to provide hook 10 which now includes three separate portions adapted to grippingly engage three separate and spaced apart portions of slab C as will be described in greater detail below.

To place the hook 10 into operative position for lifting slab C it is only necessary to insert hook 10 into opening 30H by inserting leg 18 through the opening and then rotating the hook 10 in the direction of arrow R1 as shown in FIG. 1 so that leg 18 compressively grippingly engages the bottom side CU of the slab C and diagonally extending portion 16 compressively grippingly engages tapered side 34. When the hook 10 is rotated in the direction of R1 (see FIG. 1) leg 22 will also bear against and grippingly, compressively engage the top surface CT of slab C. When a lifting force P is applied to cable 15 as shown hook 10 will tend to further rotate in the direction R1 and automatically cause the hook 10 to increase its compressive gripping force against slab C. It is significant to note that the forces exerted by the hook through the lifting force according to this invention are predominantly compressive rather than undesirable tensile forces.

It will of course be understood that a given slab C may have several (for example 4) openings 30H formed therein during fabrication for the reception of book 10 therein which in turn would be connected by cables to a suitable hoist mechanism (not shown). After the slab has been lifted and moved to a desired location (if it is to be stored or transported) or has been installed and it is desired to remove the hook 10 this can be done very simply and from the top surface. When the lifting force is removed from the shackle and hook 10 the hook 10 is rotated in the direction R2 shown in FIG. 1 so that diagonal member 16 is moved out of contact with surface 34 and leg 18 moves out of engagement with surface CU and leg 18 (and hook 10) is withdrawn from opening H and disengaged from slab C.

Thereafter the opening 30H may easily be filled with cement or grouting when the slab has been installed in the desired final location. The tapered shape of opening 30H also conveniently facilitates filling of the opening from the more accessible top surface all of which further adds to the reduction of effort and cost of handling and installation of the slab.

Typical examples of sizes to illustrate further the invention are: 5 inches in width for legs 12 and 22 with each leg 4 inches long and /2 inch thick; portions 14, 16, and 18 being about 3 inches wide, /2 inch thick and with leg 18 being about 5 inches long. In this example slab C would be 3 inches thick with tapered opening 30H about 3 /2 inches wide with the length of dimension 32 being 1 /2 inches and that of dimension 30 being inch.

In practice slabs are lifted through use of pairs of hooks which may have a common cable or single individual cables connected with a hoist whereby the lifting force (such as P) is applied at an angle to the vertical so that the pull on leg 12 is not axial but is in a direction so as to cause rotation of hook 10 in the direction of R1 as shown in FIG. 1. This rotation as earlier explained causes compressive gripping engagement with the slab.

In accordance with this invention it is possible to lift and handle relatively large fiat and relatively thin slabs (which are weak in tension) without damaging the slab and without taking any special precautions or unusual (and expensive) preparations. For example with a series of four lifting hooks 10 according to this invention, slabs as large as 8 feet wide, feet long and only 3 inches thick and having a total weight of 32 pounds per square foot have been successfully lifted and handled without damaging the slab and in a quick and efficient manner. The hooks used for lifting the slabs described were made of high stressed stainless steel.

It will thus be seen that I have disclosed a hook which when in use and lifting pressure is applied through the lifting cable will rotate and bind against the slab in compressive automatic gripping engagement, and which can conveniently be inserted or withdrawn from the top of the lslab Without damaging the slab and with a minimum of abor.

It will be understood that the hook of this invention is capable of being fabricated in one integral unit as well as the preferred configuration shown and that it is also capable of use with other prefabricated members as well as concrete slabs.

As many changes could be made in the above con structions and method without departing from the scope of the invention, 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, and it is also intended that the appended claims shall cover all such equivalent variations as come within the true spirit and scope of the invention.

I claim:

1. In a method of lifting and handling a prefabricated concrete member, said member having formed therein a tapered opening extending therethrough with the largest cross-section of said opening adjacent the upper side of said member; the steps of inserting a lift hook into said tapered opening from said upper side, rotating said hook within said member and opening to place portions of said hook into engagement respectively with the tapered portion of said opening and opposite sides of said concrete member adjacent said opening, exerting a lifting force on said hook to lift and move said member to a desired location, releasing said lifting force and rotating said hook within said tapered opening in a direction opposite to said first named direction to disengage said hook from contact with said member and withdraw said hook from said member through the upper side thereof.

2. A lift hook for a prefabricated member having a tapered opening therethrough with the largest cross-sectional dimension of said opening being adjacent the top side of said mmeber, said hook being adapted to be inserted into said opening and grippingly engage at least two out of three spaced locations on said member, said locations comprising respectively the tapered side of said opening and opposite top and bottom sides of said member adjacent said opening; said hook including an upstanding portion having means thereon for connecting said hook with a lifting hoist, said hook also having first and second portions substantially parallel, spaced from each other and extendnig in opposite directions, said hook further including a diagonally extending portion connected adjacent the ends thereof with and between said first and second portions, when said hook is grippingly engaged with said member and a lifting force is applied, said first, second, and diagonal members being adapted to respectively grippingly engage said top and bottom sides of said member and tapered side of said opening.

3. The arrangement as set forth in claim 2 and wherein said member comprises a prefabricated concrete slab useful for floor and roof construction.

4. The arrangement as set forth in claim 2 and wherein said hook includes an angle iron which provides said upstanding and first portions and said diagonal portion is welded adjacent one end thereof to said upstanding portion and is integrally formed at the other end thereof with said second portion.

References Cited UNITED STATES PATENTS 1,373,438 4/1921 McDowell 29489 FOREIGN PATENTS 1,126,412 9/1968 Great Britain.

EVON C. BLUNK, Primary Examiner A. N. GOODMAN, Assistant Examiner US. Cl. X.R. 294-92

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