US20070267558A1

US20070267558A1 - Chock release column for use with expansible hole anchor

Info

Publication number: US20070267558A1
Application number: US11/881,309
Authority: US
Inventors: Eric Reeves
Original assignee: Sigma Ind LLC
Current assignee: SIGMA INDUSTRIES LLC; Sigma Ind LLC
Priority date: 2004-07-27
Filing date: 2007-07-26
Publication date: 2007-11-22

Abstract

A chock release column operable for use with conventional hole anchor devices is provided and generally includes a cable cylinder operable for being secured about a load cable of an expansible hole anchor, a chock clearance portion extending from the cable cylinder that it corresponds in size and shape to an end of the center chock, and an enlarged head adapted for locating outside of a hole of a structure, the enlarged head generally defining a striking surface adapted for receiving a sudden force and transferring the force through the chock release column to a center chock or at least one side chock of the expansible hole anchor, such that the at least one side chock is movable from the anchor-expanding position to the anchor-contracting position to thereby dislodge said anchor from the hole of the structure.

Description

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. patent application Ser. No. 11/069,646, filed on Mar. 1, 2005, and entitled “EXPANSIBLE HOLE ANCHOR WITH ENLARGED CHOCK-RELEASING STRIKER HEAD,” which is a continuation of and claims the benefit of priority of PCT/US04/24129, filed on Jul. 27, 2004, the content of all the aforesaid applications are relied upon and incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to safety devices and methods for fall protection, and more specifically, to safety devices including, in an exemplary embodiment, a chock release column operable for use with conventional expansible hole anchors.
2. Technical Background
In the construction industry, it is often necessary to provide fall protection for workers or objects suspended at heights. Conventionally, expansible hole anchor bolts are used to meet these needs. Contractors typically utilize the expansible hole anchors in the hopes that they provide a simple, reliable and relatively inexpensive means for connecting a cable, rope or wire to a drilled hole in a hard material, that is easy to install in and remove from the hole, and that effectively anchors to the hole while applying a minimum stress to the hole, while providing a minimum sensitivity to the angular orientation of the expansion bolt in the hole. However, substantial drawbacks and limitations exist in conventional expansible hole anchors.
A first shortcoming of conventional hole anchors is that the handle is applicable for moving the anchor from a normal expanded condition to a contracted condition for inserting and removing the anchor from the hole. In order to remove the anchor, the user is typically instructed to manually retract the handle to disengage the anchor chocks from an inside wall of the hole. In many cases, the anchor is so tightly lodged inside the hole that movement of the handle is difficult, if not impossible. This occurs often, as the operating instructions call for a tug on the load cable to set the anchor during insertion. Additional forces exerted on the anchor caused by a worker movement, or during a worker's fall cause even greater locking engagement of the anchor chocks. The instructions commonly provided for dislodging an embedded anchor are to insert a small, narrow flat screwdriver into the hole, and create an impact force on an end fitting to overcome the locking friction. In practice, this procedure is generally ineffective; often resulting in mangled or broken retraction cables, and rendering the anchor unsuitable for future use. This procedure further inconveniences the user by requiring the availability of special tools in order to access and release the anchor chocks. If all methods of removal fail, the exposed portion of the anchor is torched off, a new hole drilled, and the balance of the anchor is left in the old hole.
A further problem of conventional anchors relates to the exposure of control cables operable for moving the anchor from the expanded condition to the contracted condition. Typically, these cables will bear directly against an inside wall of the anchor hole, resulting in substantial abrasion and chaffing when the anchor is inserted into and removed from the hole. Further wear is created when the worker moves about causing the control cables to grind against the concrete lip of the hole. If left undetected, the worn cables will eventually foul the cable motion and cause the anchor to fail which may result in inoperability, serious injury, or death.
A further problem with conventional hole anchors is the number of components required for assembly and use. Existing hole anchors require a large number of parts which disadvantageously increase the complexity and cost of manufacture. In addition, conventional hole anchors disadvantageously have a striker head which may lose contact with the center chock, thus providing a defective unit.
Accordingly, it would be desirable to have an improved expansible hole anchor which overcomes the noted shortcomings of conventional devices. In one such solution, it would be desirable to provide an expansible hole anchor which reduces the manufacturing costs and the complexity of assembly. In other solutions, it would be desirable to provide an expansible hole anchor with a chock releasing column which is secured about a load cable and is operable for transmitting force to a center chock, thereby dislodging the anchor from a hole. In still other solutions, it would be desirable to provide an expansible hole anchor with a chock releasing column which decreases side load forces which may be applied to the center chock during use.

SUMMARY OF THE INVENTION

The present invention is designed to overcome the deficiencies and shortcomings of the devices described above. The present invention is designed to reduce the manufacturing costs and the complexity of assembly. In all exemplary embodiments, the present invention relates to an improved expansible hole anchor with a chock releasing column which is advantageously secured about a load cable of the hole anchor and is operable for transmitting force to a center chock of the hole anchor, thereby dislodging the anchor from a hole. In all exemplary embodiments, the present invention advantageously provides an improved hole anchor which decreases side load forces which may be applied to the center chock during use through the use of an improved chock release column. The present invention is easily installed and removed from a hole formed with a solid structure. In one application, the present invention discloses a chock release column for use with a conventional hole anchor that is inserted into a hole drilled in a concrete wall at a construction site. A safety harness, lifeline, and other fall protection gear is secured to the worker and to the anchor to arrest the worker in the event of a fall. In another application, the present invention is directed to a chock release column for use with a conventional hole anchor that is applicable for use in securing equipment, such as scaffolding, to a concrete structure, or as a lift connection point for items with a suitable hole, such as preformed concrete or boulders, or for use in recreational rock climbing.
According to an exemplary embodiment, a chock release column is provided for use with a conventional, expansible anchor that is adapted for insertion into a hole formed with a structure provided. The hole anchor generally includes a load cable, a center chock attached to an end of said load cable, at least one, but preferably two, side chocks adjacent to said center chock and adapted for movement between an anchor-contracting position and an anchor-expanding position, whereby in said anchor-contracting position, said anchor is readily inserted into and removed from the hole of the structure, and in said anchor-expanding position, said anchor is locked inside the hole of the structure, and a chock release column secured about the load cable. In exemplary embodiments, the chock release column generally includes an enlarged head adapted for locating outside of the hole, said enlarged head defining a striking surface adapted for receiving a sudden force and transferring the force through said chock-release column to said center chock or at least one side chock, such that said at least one side chock is movable from the anchor-expanding position to the anchor-contracting position to thereby dislodge said anchor from the hole of the structure.
In exemplary embodiments, the chock release column is secured about a load cable such that it abuts the center chock. In other exemplary embodiments, the chock release column is secured about the load cable such that it is spaced from the center chock. In such embodiments, force applied to the chock release column may be transmitted through the load cable to the center chock, thereby dislodging the same from a hole. The chock release column may be secured to the load cable by a fastener. In other embodiments, the chock release column may be swaged to the load cable. In exemplary embodiments, the chock release column may be held in position by a positioning block.
In exemplary embodiments, the chock release column includes a chock clearance portion, a cable cylinder or shaft, and an enlarged head. The chock clearance portion is configured such that it corresponds in size and shape to an end of the center chock. This configuration permits the side chock to translate along the center chock from an anchor expanding potion to an anchor contracting position. At least one, but preferably two, cable guides are provided about the shaft.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present exemplary embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the detailed description, serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which:
FIG. 1 is a side view of a chock release column constructed in accordance with one exemplary embodiment of the present invention, wherein the chock release column is secured to a load cable of a conventional expansible hole anchor such that a space exists between the chock release column and the center chock;
FIG. 2 is perspective view of the hole anchor of FIG. 1;
FIG. 3 is a perspective view of the hole anchor of FIG. 1, wherein the center chock is provided with a cylindrical wedge type configuration and the side chocks are provided with a corresponding shape which allows for sliding movement;
FIG. 4 is side view of a chock release column constructed in accordance with another exemplary embodiment of the present invention, wherein the chock release column is secured to the load cable of a conventional expansible hole anchor such that is abuts the center chock; and
FIG. 5 is a perspective view of the hole anchor of FIG. 4.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numbers refer to like elements throughout the various drawings. Further, as used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The present invention overcomes the shortcomings of conventional hole anchors by securing a chock release column of a hole anchor device about a load cable such that it abuts a center chock or is operable for transmitting force through the load cable to the center chock when dislodging the same from a hole is desired. This method of securing the chock release column and the center chock together reduces the overall cost and the number of components required for manufacture. Further, the present invention prevents the chock release column from defectively losing contact with the center chock and provides space for an ergonomic pivot handle to be used, while shortening the overall length of the unit. Still further, the chock release column of the present invention advantageously enters into the inside of the hole during use, thus decreasing side loads which may be placed upon the center chock.
In exemplary embodiments of the present invention, an expansible hole anchor is provided which generally includes a load cable having a center chock connected to one end and a loop at the opposite end, at least one side chock abutting the outer surfaces of the center chock such that they may translate between an expanded position and a retracted position, a handle interconnected to the at least one side chock by at least one chock cable, a retractor spring to bias the at least one side chock in the extended position, and a chock release column having an enlarged head and being interposed between the handle and the center chock. In exemplary embodiments, the chock release column is secured to load cable such that it abuts the center chock. In other exemplary embodiments, the chock release column is secured or swaged to the load cable such that it is spaced apart from the center chock. In such embodiments, the chock release column is operable for transmitting force applied thereto through the load cable to the center chock, thereby dislodging the same from a hole.
In exemplary embodiments, the expansible hole anchor is generally operated by pulling back the handle which retracts the at least one side chock, reducing the outside diameter over the combination of the center chock and the at least one side chock. The anchor is then inserted into a hole (in rock, concrete, etc.) and the handle is released. Spring pressure causes the at least one side chock to translate along the center chock and expand to the hole diameter. When tension is placed upon the load cable, it pulls the center chock outward. The at least one side chock tends to remain stationary because of friction between the hole and their outer surfaces. This, in turn, results in the center chock being driven between the at least one side chock, expanding laterally and increasing the outward gripping pressure. The greater the external load placed upon the anchor, the higher the gripping pressure.
To release the anchor, the handle is again retracted. This, in turn, retracts the at least one side chock to a diameter smaller than the hole. If the handle is stuck in position, an enlarged head of the chock release column, exposed outside the hole, may be pushed by hand or struck with a hammer or other tool to dislodge the center chock and allow the at least one side chock to retract. The striking of the enlarged head transmits force through the load cable to, at least, the center chock or, in the alternative, transmits force directly to, at least, the center chock.
Referring now specifically to the drawings, a conventional, expansible hole anchor constructed in accordance with an exemplary embodiment of the present invention is illustrated in FIG. 1, and shown generally at reference numeral 10. The hole anchor 10 is adapted for insertion into a hole (not shown) formed with a solid structure, such as a concrete wall, and is applicable for use with safety harnesses, lifelines, and other fall protection devices (not shown) worn by a worker to arrest the worker in the event of a fall. In exemplary embodiments, the anchor 10 comprises a load cable 12 looped at one end 14 for attaching a safety device, and a center chock 16 located at an opposite end. It will be understood by those skilled in the art that the load cable 12 may be comprised of a steel wire. Further, it will be understood by those skilled in the art that any suitable material may be used. Still further, it will be understood by those skilled in the art that the load cable 12 may be a rod or rod like structure as opposed to a flexible cable type structure. At least one side chock 18 is provided along the center chock 16 and cooperates, as described below, to constrict and expand the anchor 10 relative to the hole of the structure. In the exemplary embodiments described herein two side chock are shown 18, 20 for purposes of illustration only.
In exemplary embodiments and as best shown in FIGS. 1-2 and 4-5, the center chock 16 has a generally conically-shaped body. However, in other exemplary embodiments, the center chock may be provided with a cylindrical wedge type configuration 21 (FIG. 3). The side chocks 18 and 20 reside adjacent the center chock 16, and have complementary profiles designed to provide maximum uniform gripping action when set inside the structure hole. In exemplary embodiments, the outside surface of each side chock 18 and 20 is preferably curved to conform to an inside wall of the structure hole, while the inside surface is convexly curved for sliding along an outside surface of the center chock 16. In other exemplary embodiments, the inside surface of the side chocks 18 and 20 may be provided with substantially planar surfaces that correspond and cooperate with the cylindrical wedge type configuration 21 of the center chock 16, if the center chock 16 is provided with the wedge configuration 21.
The side chocks 18 and 20, are attached to respective steel-wire, polymer, or composite chock cables 28 and 30. The chock cables 28, 30 extend rearward to a spring-loaded handle 32. The handle 32 is carried on the load cable 12, and is adapted for being manually retracted by the user to move the side chocks 18, 20 from a normal anchor-expanding position to an anchor-contracting position. In the anchor-contracting position, the side chocks 18, 20 are more closely spaced apart on opposite sides of the center chock 16 such that the anchor 10 is readily inserted into and removed from the hole of the structure. The rear portion of the center chock 16 has a relatively small diameter, thereby allowing substantial contraction of the anchor 10. Preferably, the smallest section of the center chock 16 has a profile dimension just greater than the diameter of the load cable 12. In the anchor-expanding position, the side chocks 18, 20 are urged forward along diverging outer surfaces of the center chock 16. In use, the anchor 10 does not fully expand inside the hole, but instead forces the side chocks 18, 20 into sufficient frictional engagement with the inside wall of the structure hole to prevent inadvertent dislodging of the anchor 10. After inserting the anchor 10 into the hole, the side chocks 18, 20 are set by one controlled pull on the cable loop 14.
Referring again to FIG. 1, a chock-release column 38 is carried on the load cable 12 adjacent the center chock 16, and comprises an integral cable cylinder 40, enlarged-diameter head 42 and a tapered, narrowed, stepped down, necked, or chock clearance portion 46. In other exemplary embodiments, the chock release column 38 may comprise the cable cylinder 40, the enlarged head 42 and the chock clearance portion 46 as separate components, as opposed to integral ones. The chock release column 38 may be secured or swaged to the load cable 12. Preferably, the chock clearance portion 46 of the chock release column 38 is sized and shaped to correspond to the size and shape (e.g., the diameter) of the center chock end 17 nearest the column 38. By providing the chock clearance portion 46 with a corresponding size and shape of the center chock end 17, the side chocks 18, 20 may fully operate to an anchor expanding or anchor contracting position. In other exemplary embodiments (not shown), the chock release column 38 is comprised of a cable cylinder 40 which corresponds directly to the size and shape of the center chock end 17 and an enlarged head 42. In such embodiments, the cable cylinder 40 extends to the center chock end 17 or to a spaced portion 22 located between the center chock 16 and the chock release column 38.
In exemplary embodiments wherein the chock release column 38 is directly swaged or fastened to the load cable 12 and spaced apart from the center chock 16, a positioning block or spacer 50 is provided between the enlarged head 42 and the handle 32 such that the handle 32 remains correctly spaced from the column 38. In other exemplary embodiments, the handle 32 may be provided with an extended portion (not shown) which extends outwardly from the handle 32 to the enlarged head 42. In still other exemplary embodiments wherein the chock release column 38 is not directly swaged or fastened to the load cable 12 and abuts the center chock 16, a positioning block or spacer 50 is provided for holding the chock release column 38 in place. In turn, a ferrule stop 55 which is swaged about the load cable 12 is provided to maintain the spacer 50 in position.
In use, the enlarged head 42 locates outside of the structure hole, and defines a flat annular striking or bearing surface 44 designed to receive a force applied using the thumbs or any rigid object, such as a snap hook. In exemplary embodiments, the chock release column 38 abuts the center chock 16 such that the force is transferred directly through the chock-release column 38 to the center chock 16 to dislodge the side chocks 18, 20 from friction-locking engagement inside the hole. In other exemplary embodiments, the chock release column 38 is spaced apart from the center chock 16 such that the force is transmitted from the chock release column 38 through the spaced portion 22 of the load cable 12 to the center chock 16 to dislodge the side chocks 18, 20. Once dislodged, the side chocks 18, 20 are easily retracted by the handle 32; moving from the anchor-expanding position to the anchor-contracting position to remove the anchor 10 from the structure hole.
In exemplary embodiments, the preferable maximum diameter of the striking head 42 is greater than the maximum distance between the side chocks 18 and 20 in the anchor-expanding condition. As such, upon insertion of the anchor 10 into the hole, the enlarged striking head 42 is pushed directly against the mouth of the hole, thereby locating the anchor chocks 16, 18 and 20 inside the hole in a position of maximum effectiveness and safety, while maintaining ready access to the exposed striking surface 44.
According to one embodiment, the enlarged head 42 of the chock-release column 38 has three openings for receiving the load cable 12 and chock cables 28, 30, respectively. Preferably, the center opening has a radiused edge to minimize wear on the load cable 12 when pulled vertically. A reduced diameter, integral neck 48 extends forward of the enlarged head 42 has interior passages or longitudinal exterior grooves to designed receive the chock cables 28, 30.
A retractor spring 54 is carried on the load cable 12 rearward of the handle 32. The retractor spring 54 is compressed between the handle 32 and cable loop 14, and operates to normally urge the handle 32 and chock cables 28, 30 forward thereby biasing the side chocks 18 and 20 in the anchor-expanding position. The retractor spring 54 is preferably pre-loaded in the anchor-expanding position at greater than 20% of its maximum compression force. Preferably, the cable loop 14 is secured by a duplex ferrule 56 and reinforced with a metal thimble (not shown). In still other exemplary embodiments, one or more retractor springs may be placed around at least one of the chock cables between the side chocks and the chock release column, or extending into recesses within the chock release column.
In some exemplary embodiments, the chock release column 38 may be secured to the load cable 12 such that the chock release column 38 cannot translate or slide along the load cable 12. In other exemplary embodiments, the chock release column 38 may be secured to the center chock 16 by a fastener 80. It will be understood by those skilled in the art that the fastener 80 may be any suitable fastening device for securing the chock release column 38 to the center chock 16 including, but not limited to rivets, screws, nails, rods, ties, etc. The fastener 80 may extend through a bore located in the cable cylinder 40 and may extend at least partially into the load cable 12. Advantageously, this manner of attachment permits the chock release column 38 to pivot about the center chock 16, but not translate or slide. In other exemplary embodiments, a pivot relief angle may be provided at the left edge of the chock release column 38. Further, this manner of attachment permits the use of a unit having a smaller overall length when compared to conventional hole anchors.
As illustrated in FIGS. 1, 2, 4, and 5 shows a center chock 16 having an outer surface including convex portions along with side chocks 18 and 20 having complementary concave inner surfaces. Preferably, the surfaces 16, 18 and 20 are each rotationally symmetric about the longitudinal axis, and more preferably still, the surfaces of the center and side chocks are complementarily shaped. An example of complementarily shaped center and outer chocks is shown in the FIGS. 1, 2, 4 and 5. Here, the center chock 16 is shaped as a frustum so that the surface is convex and the side chock surfaces 18 and 20 are concave and substantially conform to the frustum. The reverse geometry may also be employed for this example, wherein the surfaces 18 and 20 are convex and shaped as portions of frustums, and the center chock surface 16 is concave and substantially conforms to these portions. Moreover, the surfaces 16, 18 and 20 may include only portions that are complementarily frustoconical where desired. Further still, as detailed above the center chock 16 may have a cylindrical wedge type configuration 21 (FIG. 3).
The complementarily shapes provide a preferred means for ensuring intimate conformance between the respective ramping surfaces of the center and side chocks over a range of relative linear movement therebetween, wherein the force exerted between the chocks is distributed over a maximum surface area. This increases reliability by decreasing stress and wear, as well as increases hole-engaging strength by permitting the aforementioned force to be maximized.
The embodiments described above provide advantages over conventional expansible hole anchors and associated methods of manufacture. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Furthermore, the foregoing description of the preferred embodiment of the invention and best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation—the invention being defined by the claims.

Claims

1. An expansible anchor adapted for inserting into a hole formed with a structure, said anchor comprising:

a load cable;

a center chock attached to an end of said load cable;

at least one side chock adjacent to said center chock and adapted for movement between an anchor-contracting position and an anchor-expanding position;

a chock release column having a cable cylinder portion and an enlarged head adapted for locating outside of the hole, said enlarged head defining a striking surface adapted for receiving a sudden force and transferring the force through said chock-release column to said center chock, such that said at least one side chock is movable from the anchor-expanding position to the anchor-contracting position to thereby dislodge said anchor from a hole of a structure; and

a handle carried by said load cable and adapted for moving said at least one side chock from the anchor-expanding position to the anchor-contracting position.

2. The expansible hole anchor of claim 1, wherein the chock release column further comprises a chock clearance portion.

3. The expansible hole anchor of claim 1, wherein the chock release column is swaged about the load cable.

4. The expansible hole anchor of claim 3, wherein the chock release column abuts the center chock.

5. The expansible hole anchor of claim 3, wherein the chock release column is spaced apart from the center chock.

6. The expansible hole anchor of claim 1, wherein the chock release column is secured to the load cable by a fastener.

7. The expansible hole anchor of claim 6, wherein the chock release column abuts the center chock.

8. The expansible hole anchor of claim 6, wherein the chock release column is spaced apart from the center chock.

9. The expansible hole anchor of claim 2, wherein the chock clearance portion is corresponding in size to and end of the center chock which is nearest the chock release column.

10. A chock release column operable for use with an expansible hole anchor, comprising:

a cable cylinder portion; and

an enlarged head adapted for locating outside of a hole, said enlarged head defining a striking surface adapted for receiving a sudden force and transferring the force through said chock-release column to a center chock of the expansible hole anchor, such that at least one side chock of the expansible hole anchor is movable from the anchor-expanding position to the anchor-contracting position to thereby dislodge said anchor from the hole.

11. The chock release column of claim 10, wherein the chock release column further comprises a chock clearance portion.

12. The chock release column of claim 10, wherein the chock release column is swaged about a load cable of the expansible hole anchor.

13. The chock release column of claim 12, wherein the chock release column abuts the center chock.

14. The chock release column of claim 12, wherein the chock release column is spaced apart from the center chock.

15. The chock release column of claim 10, wherein the cable cylinder is corresponding in size to and end of the center chock which is nearest the chock release column.

16. The chock release column of claim 11, wherein the chock clearance portion is corresponding in size to and end of the center chock which is nearest the chock release column.

17. The chock release column of claim 11, wherein the cable cylinder, the enlarged head and the chock clearance portion are integral in construction.

18. The chock release column of claim 11, wherein the cable cylinder, the enlarged head and the chock clearance portion are separate components joined together.

19. A chock release column supported on a load cable of an expansible hole anchor, the chock release column comprising:

a cable cylinder portion; and

an enlarged head defining a striking surface; and

a chock clearance portion, said chock clearance portion corresponding in size to and end of a center chock of the expansible hole anchor which is nearest the chock release column.

20. The chock release column of claim 19, wherein said striking surface of the enlarged head is adapted for receiving a sudden force and transferring the force through the chock-release column to the center chock, such that the expansible hole anchor is movable from the anchor-expanding position to the anchor-contracting position.