US3652118A

US3652118A - Lifting anchor for precast concrete and like molded parts

Info

Publication number: US3652118A
Application number: US862902A
Authority: US
Inventors: Jurgen Goldberg
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-05
Filing date: 1969-10-01
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: DE1801457C3; DE1801457B2; DE1801457A1

Abstract

A lifting anchor for precast concrete and like molded parts comprises a shaft removably insertable into a hole provided in a molded part so as to extend substantially perpendicularly to an external surface of said molded part. The shaft is provided at its bottom end with at least one projection and at its top with a head for attachment thereto of a lifting means. The projection on said shaft extends in the radial direction of said shaft and is displaceable into a cross sectional enlargement in the side wall of the hole in said molded part. The cross sectional enlargement corresponds in shape to said projection and forms an undercut face in said hole. A key is likewise insertable into said hole from the end of said hole remote from said cross sectional enlargement to force said projection into said cross sectional enlargement. The key together with the shaft completely fill said hole in the region of said cross sectional enlargement.

Description

llnited States Patent Goldberg [451 Mar.28,l972

[54] LIFTING ANCHOR FOR PRECAST CONCRETE AND LIKE MOLDED PARTS [72] Inventor: Jurgen Goldberg, No. 7, Neuenburger Strasse, 78 Freiburg, Germany [22] Filed: Oct. 1, 1969 [21] Appl. No.: 862,902

Primary Examiner-Joseph Wegbreit Assistant Examiner-Bruce H. Stone, Jr. Attorney-Michael S. Striker [5 7] ABSTRACT A lifting anchor for precast concrete and like molded parts comprises a shaft removably insertable into a hole provided in a molded part so as to extend substantially perpendicularly to an external surface of said molded part. The shaft is provided at its bottom end with at least one projection and at its top with a head for attachment thereto of a lifting means The projection on said shaft extends in the radial direction of said shaft and is displaceable into a cross sectional enlargement in the side wall of the hole in said molded part. The cross sectional enlargement corresponds in shape to said projection and forms an undercut face in said hole. A key is likewise insertable into said hole from the end of said hole remote from said cross sectional enlargement to force said projection into said cross sectional enlargement. The key together with the shaft completely fill said hole in the region of said cross sectional enlargement.

12 Claims, 7 Drawing Figures PAIENTEHMARZB 1872 3,652.1 18

SHEET 1 BF 4 PAIENTEnmma 1972 3, 652.1 18

sum 3 UF 4 Fig. 4

LIFTING ANCHOR FOR PRECAST CONCRETE AND LIKE MOLDED PARTS BACKGROUND OF THE INVENTION This invention relates to a lifting anchor for precast concrete and like molded parts which comprisesa shaft insertable into a molded part substantially perpendicularly to an external surface of said molded part and provided at its bottom end with at least one radial projection and at its upper end with a head for attachment thereto of a lifting means.

Lifting anchors of this type have already been proposed, in which the retaining projection is formed by a U-shaped bend at the end of the shaft and the projecting head of the anchor consists of a screw nipple formed with an eyelet, which can be screwed onto a cooperating threaded portion at the upper end of the shaft. A metal bar may be encast in the precast concrete or like molded part transversely to the plane of the U-shaped bend which forms the retaining projection, in such a manner that the U-shaped bent end can engage said bar from underneath.

It is an objection to this known form of construction of lifting anchors that the shaft formed with the U-shaped bend at its bottom end cannot be latter removed from the precast part even after this has been incorporated in a building. Apart from the fact that only the threaded nipple of the complete lifting anchor can thus be repeatedly used and that the shaft with its U-shaped bend can merely be used once in a concrete part or the like that is to be lifted, a circumstance which must be regarded as involving unnecessary waste, it is also possible for rust marks to appear on the surface of the precast part after this has been incorporated in a building, said rust marks being caused by rusting of the anchor or its threads, unless the shaft were made of stainless steel which would likewise be extremely wasteful. Moreover, the maximum load-bearing capacity of such an anchor is substantially determined by the wall thickness of the threaded nipple in the region of its internal threads so that the nipple must have a relatively large external diameter. Consequently, after removal of the nipple, a fairly large hole remains in the precast concrete part. Another drawback is that the internal threads in the nipple as well as the threads on the shaft may wear or become fouled.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved lifting anchor of the above specified kind which can be easily attached to a concrete or like part.

Another object of the invention is the provision of an improved lifting anchor in the case of which the major part of the material or metal of which it is made can be repeatedly used and in which, after the removal from the concrete of these parts of the anchor that can be reused, there is no risk of rust marks being formed and/or of threads being damaged or fouled.

Moreover, yet another object of the invention is that the opening where the anchor had been attached to the precast part should be as small as possibleand capable of being closed without being obviously noticeable.

To attain these objects the lifting anchor proposed by the present invention consists substantially of a shaft provided with at least one radial projection for engaging a cross sectional enlargement in a hole, extending into the precast or like molded part substantially perpendicularly to one of its surfaces, said enlargement forming an undercut recess having a wider cross section than that of said shaft and being formed in at least one side of said hole, and of a key which is removably insertable into said hole on the side remote from said enlargement in such a manner that said key together with said shaft completely fill the cross section of the hole at least in the region of said cross sectional enlargement.

The additional use of a key as an essential part of the proposed lifting anchor permits the shaft of the anchor in practice to be repeatedly used many times. To the extent a special reinforcement inside the concrete part for cooperation with the bottom end of the shaft is dispensed with, the risk of the formation of rust marks is excluded because after the removal of the shaft and of the associated key from the hole no metal parts which might give rise to the formation of rust remain inside the hole. Even if a metal reinforcement plate with a central opening is provided in the concrete or like molded part at the level of the junction between the enlarged and normal cross sections of the hole, as is proposed in a particular embodiment of the present invention, the risk of rust marks being formed is in practice very remote because the reinforcing plate is embedded well down inside the interior of the concrete or like molded part where it is protected from penetrating moisture. Moreover, if desired it would not be unacceptably expensive to make the reinforcement plate of stainless steel.

BRIEF DESCRIPTION OF THE DRAWINGS Several embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 is a first embodiment of a lifting anchor according to the invention after having been loosely inserted into a precast concrete or molded part, prior to its affixation thereto, part of the shaft of the anchor being shown in section;

FIG. 2 is the lifting anchor according to FIG. I after having been affixed to and secured in the molded part;

F IG. 3 is a section taken on the line Ill-III of FIG. 2;

FIG. 4 is a section taken on the line lV-IV of FIG. 2;

FIG. 5 is a representation similar to that shown in FIG. 1 of another embodiment of a lifting anchor according to the invention after having been connected to a molded part;

FIG. 6 is a representation similar to that shown in FIG. 5 of an embodiment of a casting core for the production in a precast concrete or molded part of a hole suitable for the reception of a lifting anchor according to the invention, and

FIG. 7 is a section taken on the line VIIVII of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 a precast concrete part 1, for instance in the form of a slab, is provided with a recessed hole 4 extending substantially perpendicularly into the concrete part from one of its surfaces 2 and formed at its inner end with a cross sectional enlargement 3 with undercut faces. A shaft 7 of a lifting anchor resembling a split pin comprising two

halves

5 and 6 and at its upper end forming a loop 40 is provided at the bottom end of each

half

5 and 6 with a radial projection 8 and 9. The cross section of the shaft 7 at its bottom end formed with these projections 8 and 9 is so chosen in relation to the cross section of the upper part of the recessed hole 4 that this bottom end is insertable into said recessed hole. The radial projections 8 and 9 of the

halves

5 and 6 of the split shaft 7 can be splayed apart into contact with the undercut walls of the enlargement 3 in the recessed hole 4 by driving a loose key 10 (FIG. 2) between the halves of the split shaft 7. As will be understood from FIG. 3 the key 10 is of rectangular cross section and its upper end is provided with means for reextracting the same. In the embodiment illustrated in FIGS. 1 to 4 these means have the form of an eye 11 formed integral with the key 10 and projecting laterally from the lifting anchor or possibly located at right angles to its position shown in FIG. 2. In the illustrated embodiment the cross sections of the two

halves

5 and 6 of the split shaft 7 combine to form a circle when the two halves of the shaft are held closely together, whereas when splayed apart by the rectangular section key 10 the overall cross section is substantially oval, as will be seen by reference to FIG. 3. The side faces of the key 10 may be slightly convexly arched.

From FIGS. 3 and 4 it will be understood that the radial projections 8 and 9 extend from the shaft 7, as indicated by the two-headed arrow Pf, in the direction in which the shaft can be expanded, their contours merging substantially tangentially into the shaft contour. In a direction normal to the direction of shaft expansion the projections 8 and 9 do not project beyond the maximum dimensions of the shaft 7 and the key 10. This facilitates the insertion of the lifting anchor into and its extraction from the recessed hole 4, since the required grip in the concrete part 1 is established merely by expansion of the anchor shaft 7 in one plane.

The upper transitions between the radial projections 8 and 9 and the shaft 7 proper are formed by inclined faces 12 and 13, preferably set at an angle of 1-r/4 radians to the shaft axis. The insertion of the shaft 7 into the recessed hole 4 is facilitated by the provision of similar inclined faces 14 and 15 on the radial projections 8 and 9 at the bottom end of the split shaft. At the level of the transition between the enlargement 3 and the normal cross section of the remainder of the recessed hole 4 a reinforcement plate 16, preferably consisting of metal or plastics, is encast in the concrete part 1 and has a central opening 17 which concentrically surrounds the axis of the hole 4 and defines an inclined face between the sides of the enlargement 3 in the hole and the normal cross section of the rest of the hole. In the region surrounding the opening 17 the reinforcing plate 16 is bent downwards, forming a coned portion 18, so that the inside circumference of the opening 17 in the reinforcing plate 16 is normal to the surface of the coned portion 18. The reinforcing plate 16 distributes the load transmitted through the shaft 7 to the concrete part 1 more evenly around the hole and thus provides increased safety against the risk of the lifting anchor breaking away after having been locked in position by the key 10 as shown in FIG. 2. Altematively, the reinforcing plate 16 may have an opening formed with a countersink on one side with which the two inclined faces 12 and 13 on the radial projections 8 and 9 cooperate.

For lifting the concrete part 1 the split shaft 7 is inserted into the hole 4, as indicated in FIG. 1, until the radial projections 8 and 9 enter the enlargement 3 at the bottom of the hole 4. The key 10 is then driven in between the

halves

5 and 6 of the split shaft 7 far enough to ensure that the two

halves

5 and 6 together with the key completely fill the cross section of the hole 4 in and at least directly above the enlargement 3. Preferably the key 10 should be driven to the bottom end face of the two radial projections 8 and 9. A rope or the like can then be threaded through the loop 40 and the concrete part 1 can be lifted by means of the lifting anchor. It will be understood that several lifting anchors of the described kind could be provided on a single concrete part if the latter has been provided with the necessary holes 4 having cross sectional enlargements 3 at their inner bottom ends. Moreover, it is not essential for the bottom of the hole 4 to be level with the undersides of the radial projections 8 and 9. In fact, the hole may traverse the concrete part 1 from top to bottom completely, particularly if the parts are slabs of limited thickness. Moreover, the cross sectional enlargement of the hole may be formed by the underside of the slab itself, should the length of the shaft 7 to its radial projections exceed the thickness of the slab, and a bottom plate may then be provided on the underside of the slab for distributing the load.

The lifting anchor is removed by first extracting the key 10, by means of its eye 11, closing the two

halves

5 and 6 of the shaft, possibly by taking advantage of the natural resilience of the shaft 7, until the two halves make contact as in FIG. 1, if necessary with the employment of a pinching tool, and by then pulling the shaft 7 out of the hole 4.

The reinforcement plate 16 is located well down in the interior of the concrete part 1 where it is protected from moisture and driving rain, so that even if this plate consists of ordinary carbon steel it is unlikely to rust or to create rust marks on the face 2 of the concrete part. However, if desired, the reinforcing plate 16 and/or also the shaft 7 itself and its loop 40 could be made of stainless steel with the consequent advantage that the shaft 7 could be used over and over again.

In the embodiment illustrated in FIG. 5 the shaft of the lifting anchor comprises two halves 5a and 6a which are axially juxtaposed and held together by an elastic band 19, and which at their bottom ends are formed with radial projections 8a and 9a, the upper ends of each half being bent over to form an eyelet 40a and 40b respectively for attachment thereto of hoisting tackle for lifting a concrete part la as well as for pulling the two halves 5a and 60 out of the concrete. A key 10a is provided similar to that shown in FIG. 2, excepting that for handling the same its upper end is formed with a crosspiece 11a.

Contrary to FIGS. 1 and 2 the drawing shows no reinforcement plate at the level of the junction between the normal cross section of the hole and its enlargement 3a. Moreover, the enlargement 3a continues through the entire remaining thickness of the concrete part 1a. The shape of the radial projections 8a and 9a and of their

inclined faces

12a and 13a corresponds to that in the previous embodiment shown in FIGS. 1 to 4. However, the strength of the anchorage may also be improved by the provision of a reinforcement plate.

The lifting anchor according to FIG. 5 is fitted and secured in substantially the same way as the embodiment according to FIGS. 1 to 4. When the lifting anchor is to be removed the key is extracted by means of its crosspiece 11a. The shaft halves 5a and 6a are automatically pulled together into mutual contact by the elastic band 19 and the two halves 5a and 6a of the shaft can then be easily lifted out of the hole.

For the purpose of creating a hole in a precast concrete part for the reception of a lifting anchor of the kind hereinabove described, the shaft halves 5 and 6 or 5a and 6a and their radial projections 8 and 9 or 8a and 9a in association with the key 10 or 100 shown in FIGS. 1 to 4 and FIG. 5 respectively may be used as a core, the lifting shaft being fitted so that it projects through a hole in one wall of the shuttering or mold when the concrete is being poured and later removed when the concrete has set. Care must merely be taken to ensure that the concrete will not stick to the surface of the shaft halves 5 and 6 or 5a and 6a and to the key 10. This can easily be done by covering these surfaces with shuttering grease or the like.

However, with advantage a special core may be used for forming the holes during pouring. An embodiment of such a core is shown in FIGS. 6 and 7 and comprises two

shaft halves

21 and 22 that are pulled together by an elastic band 20 and a key 23 which can be forced between the two halves, the upper end faces 24 and 25 of the shaft halves and of the key being adapted to be secured flush against the inside face of a mold or shuttering 26 used for precasting a concrete part lb. The two

shaft halves

21 and 22 of the core are provided with extracting means in the form of a

rectangular recess

27 and 28 in each of the faces of the shaft halves 21 and 22 that make contact with the key 23 or with each other. Since the upper end face of the key 23 bears flush against the inside face of the mold or shuttering 26 a screw 29 can be screwed into the end of the key 23 for pulling the key out when the mold or shuttering 26 is removed. For forming the enlargements the core is provided with appropriate projections 8b and 9b with inclined faces 12b, 13b, The shape of these projections likewise corresponds to the shape of the projections described with reference to FIGS. 1 to 4.

It may be mentioned that several radial projections could be provided along the length of a shaft, each projection extending in the direction in which the shaft is expanded. In such an arrangement the radial projections may be shorter, or such an anchor may be used for lifting concrete parts of major weight.

The advantage afforded by the presence of the inclined faces on the radial projections of the anchor shaft is that after removal of the key the anchor will automatically detach itself when an extracting force is applied. This incidentally increases the safety of the device, since it will not lift at all unless properly fixed.

All the features and structural details shown in the drawings and described in the specification are intended to form part of the subject matter of the present invention, both severally and in any combination.

What is claimed is:

1. A lifting anchor arrangement for precast concrete and like molded parts, wherein each of said molded parts is formed with a hole extending thereinto substantially nonnal to an external surface thereof and having an enlarged end portion spaced from said surface of a cross section wider than the remainder of said hole and extending to opposite sides of the latter, said arrangement comprising a reinforcing plate embedded in said molded part between said end portion and the remainder of said hole and being formed with an opening coaxial with said hole, said opening tapering from said enlarged end portion toward the remainder of said hole and being in part defined by a pair of oppositely inclined surface portions; and anchor means insertable into said hole and said opening in said reinforcing plate and removable in its totality therefrom and comprising shaft means comprising two parts each provided at one end thereof with a lateral projection facing away from the projection on the other part, said two parts being movable between an inserting position abutting with faces thereof opposite said projection against each other and an anchoring position in which said faces are spaced transversely from each other and in which said projections engage with inclined faces thereof said inclined surface portions of said opening in said reinforcing plate, and means insertable between said faces of said parts after said shaft means have been inserted in said hole with said ends thereof extending through said opening for moving said parts from said inserting to said anchoring position.

2. A lifting anchor arrangement as defined in claim 1, wherein said two parts of said shaft means are constituted by symmetrical halves of said shaft means.

3. A lifting anchor arrangement as defined in claim 1, wherein said two parts of said shaft means are integrally connected at the other end thereof to form a loop for attachment of lifting means.

4. A lifting anchor arrangement as defined in claim 1, wherein each of said two parts is provided at the other end thereof with means for attachment of lifting means thereto, and including elastic means connecting said parts in the region of said other ends thereof and tending to maintain said parts in said inserting position.

5. A lifting anchor arrangement as defined in claim 4, wherein said elastic means comprises a band of elastomeric material tightly surrounding said two parts in the region of said other end.

6. A lifting anchor arrangement as defined in claim 1, wherein said two parts in said inserting position have together a substantially circular cross section.

7. A lifting anchor arrangement as defined in claim 6, wherein said means for moving said parts from said inserting to said anchoring position comprises a member of substantially rectangular cross section and forming when inserted between said two parts together with the latter a substantially oval cross section.

8. A lifting anchor arrangement as defined in claim 1, wherein said lateral projections on said two parts are provided at the ends thereof distant from said inclined faces with oppositely inclined faces for facilitating insertion of said projections into said hole and through said opening in said reinforcing plate.

9. A lifting anchor arrangement as defined in claim 1, wherein said opening in said reinforcing plate has a maximum cross section substantially equal to that of said enlarged portion of said hole and a minimum cross section substantially equal to that of the remainder of said hole.

10. A lifting anchor arrangement as defined in claim 9, wherein said reinforcing plate has a central portion bent conically away from said external surface of said molded part, said opening being formed in said bent portion and said surface portions of said opening extending substantially normal to said bent portion of said plate.

11. A lifting anchor arrangement as defined in claim 10, wherein said surface portions of said opening and said inclined faces on said projections include equal angles with each other.

12. A lifting anchor arrangement as defined in claim 11, wherein said angles are sub tan tially 42.

Claims

1. A lifting anchor arrangement for precast concrete and like molded parts, wherein each of said molded parts is formed with a hole extending thereinto substantially normal to an external surface thereof and having an enlarged end portion spaced from said surface of a cross section wider than the remainder of said hole and extending to opposite sides of the latter, said arrangement comprising a reinforcing plate embedded in said molded part between said end portion and the remainder of said hole and being formed with an opening coaxial with said hole, said opening tapering from said enlarged end portion toward the remainder of said hole and being in part defined by a pair of oppositely inclined surface portions; and anchor means insertable into said hole and said opening in said reinforcing plate and removable in its totality therefrom and comprising shaft means comprising two parts each provided at one end thereof with a lateral projection facing away from the projection on the other part, said two parts being movable between an inserting position abutting with faces thereof opposite said projection against each other and an anchoring position in which said faces are spaced transversely from each other and in which said projections engage with inclined faces thereof said inclined surface portions of said opening in said reinforcing plate, and means insertable between said faces of said parts After said shaft means have been inserted in said hole with said ends thereof extending through said opening for moving said parts from said inserting to said anchoring position.

12. A lifting anchor arrangement as defined in claim 11, wherein said angles are substantially 45* .