CA1143598A

CA1143598A - Expansion dowel assembly

Info

Publication number: CA1143598A
Application number: CA000309303A
Authority: CA
Inventors: Erwin Schiefer
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 1977-09-05
Filing date: 1978-08-14
Publication date: 1983-03-29
Also published as: NO783015L; AU3927878A; SE425928B; FI64981B; FI64981C; CH632320A5; ES238036Y; GB2003572B; DK387378A; MX144869A; DE2739929A1; AU527398B2; IT1098169B; FR2437522A1; YU193278A; NO144937C; IT7826836A0; SE7808901L; FR2437522B1; BE869543A

Abstract

ABSTRACT OF THE DISCLOSURE
In an anchor assembly, an axially elongated dowel is provided with an inclined slot near its front end, that is, the end which extends first into a bore-hole. The slot is inclined away from the dowel axis in the direction toward the front end. An anchor member is held in form-locking engagement within the slot and during displacement relative to the dowel, it rides on an inclined support surface toward the front end of the dowel. The anchor member is a trapezoidally shaped plate having a pair of sides extending transversely of the axis of the dowel with one side longer than the other. The longer side is located further from the front end of the dowel and its opposite ends project outwardly from the slot. A tool can be connected to the rear end of the dowel for displacing the dowel relative to the anchor member. The tool includes a guide bar having stops attached to its opposite ends and a solid annular body axially displaceably mounted on the bar for movement between the stops.

Description

35~8 The present invention is directed to an anchor assembly consisting of a dowel body and an anchor member which can be displaced relative to the dowel body into an anchoring position. More particularly, the invention concerns a dowel body arranged to receive axially extending forces at its rear end and having a supporting surface for the anchor member adjacent its front end. The supporting surface is inclined relative to the longitudinal axis of the dowel body and diverges away from the axis toward the front end of the dowel. The anchor member is a small trapezoidal plate with a pair of sides extending trans-versely of the axis and the longer side is located more remGtely from the front end of the dowel. The opposite ends of the longer side project outwardly from the circum-ferential surface of the dowel when the assembly is initially inserted into a borehole, that is, before the anchoring action takes place.
When dowels are used in large quantities, for example, for suspended ceilings and the like, it is important to produce such dowels economically and to ensure that they do not exceed a certain price level.
For safety reasons in the event of a fire, plastic dowels cannot be used, instead only metal dowcls can be employed. ~urthermore, the dowels must have a sufficient anchoring characteristic and must bc able to withstand dynamic alterna-ting loads.
One known anchor dowel of this general type consists of a dowel body threaded at its rear end for the application of force and having a recess adjacent to and tapering toward the front end. An anchor member - 1 - ... ~

1~3~8 is positioned in the recess and the front end is the end first inserted into a receiving material. In this known dowel, the anchor member is wedge-shaped and has a detent projecting beyond the circumferential surface of the dowel body. A spring washer holds the anchor member on the dowel body before the dowel is inserted into a receiving bore.
In view of its relatively complicated shape, the anchor member involves a complicated production operation making its use economically questionable.
The separate holding member for the anchor member also ;; contributes to this problem. ~ncther problem is that the detent of the anchor member which projects beyond the surface of the dowel body, often effects only an insufficient contact with the surface of the receiving bore so that not only is the prespreading operation ,:, insufficient but the final anchoring is of questionable effectiveness. It is not possible to enlarge the detent beyond a certain siæe, since its enlarged size would make it signi~icantly more difficult to drive the dowel into a receiving bore.
In another known anchor tlowel of thc samc general type, for reasons oE cconomy thc anchor member is formed as a small trapezoidal plate. In place of a separate holding member for the anchor member, the anchor member has been held in the dowel body by magnetic force. Such a holding action has proved to be disadvan-tageous, since the slightest amount of dirt in the vicinity of the anchor member reduces the holding force to the extent that the anchor member may fall out of the dowel body before

- 2 -3S~38 ,'.
, ` it is inserted into a receiving bore. In addition, the magnetization of the various parts involved is cumbersome and, as a result, uneconomical.
Therefore, a primary object of the present invention is to provide an anchor dowel assembly which . assures not only effective use without any problems, but also economical production and sufficient anchoring values.
In accordance with the present invention, the anchor dowel assembly includes an anchor member held in a self-locking manner within a slot in the dowel body, the slot being inclined to the longitudinal axis of the dowel and being open toward and adjacent the front end of the dowel body. The supportiny surface in the slot along which the anchor member slides during the anchoring operation is located closer to the axis of the dowel adjacent the front end of the dowel. When the dowel assembly is inserted into a borehole, the diameter of the borehol~ is adjusted to -the climension of the dowel ~0 body so that the anchor member colltacts the surfaces of the borehole. The contactiny action i'3 especially efective in the trailing port:ion oE the anchor member which project5 laterally from thc circumferential surface of the dowel body. In view oE the small sizcd trapezoidal shapéd plate employed as the anchor member, the anchor member tapers inwardly in the direction toward the front end of the dowel body so that the projecting rearward portions have a saw-tooth shape. Due to the saw-tooth shape, the dowel assembly can be inserted into a borehole without encountering any significant resistance. However, 5~8 the projecting portion of the anchor member ensures that it will afford a holding action as the dowel is inserted.
When an axial force is applied to the dowel pulling it j out of the borehole, the projecting portions of the anchor member become tightly engaged into the wall surface of the borehole. As a result, the anchor member remains in a fixed position relative to the surface of the borehole, since the slot is open toward the front end of the dowel and the dowel can move relative to the anchor member.
When such relative movement occurs, the projecting portions of the anchor member in contact with the surface of the borehole increase because of the inclination of the slot with respect to the axis of the dowel. As the withdrawing force is increased, the anchor member becomes more tightly secured into the surface of the borehole and provides a fixed stop for the dowel body. Moreover, the inclined slot in the dowel body has the effect that by increasing the application of force in withdrawing the dowel Erom the borehole, the anchoring action within the borehole is similarly increased and an cffective Eorm-lockincJ connection between the two parts oE the asembly is ensurecl.
In accordance with the inverltion, thc inc~ined slot has the advantage tha-t it can be cconomically formed, for example, in a sawing or cutting operation, without involving any time consuming operations or the n~ed Eor cumbersome tools. The width of the slot between its opposing surfaces is preferably somewhat less than the thickness of the anchor plate so that an effective self-locking action is attained and an additional holding action becomes unnecessary. Since the slot is open laterally 35~8 from its rear end toward tne front end of the dowel, the anchor member can move relative to the dowel for providing an optimum anchoring characteristic.
In expansion dowels of this type it is often difficult to effect the anchoring action, since there are no surfaces on the dowel against which hammer blows can be directed, accordingly, another feature of the present invention is the provision of a suitable anchoring tool.
The tool includes a guide bar having stops at its opposite ends with a solid annular body reciprocally movable along the bar between its stops. Further, at least one of the stops can be attached to the rear end of the dowel body for applying axial force in moving the dowel body relative to the anchor member.
After the spreading tool is connected to the rear end of the dowel, the solid body is displaced along the bar against the stop more remote from the end of the dowel. The impacting action of thc reciprocating body against the stop is transmitted to the dowel in the form of an axially directed pulling -Eorcc. The extent to which the anchoring of the dowel a~sembly is attained can be controlled by varying the numer of blows providcd by the solid body.
In a majority of such dowels the rearward erld of the dowel is threaded so that thc anchoring tool can be connected to it by a corresponding thread. sy providing threads of different diameters in each of the s-tops on the opposite ends of the anchor member, the same tool can be utilized in dowels of different sizes. Depending on the dowels to he anchored, the threads formed in the stops ~ ~3~38 can be either male or female. Changeover from one type or size of thread to another can be effected in a simple manner by appropriately designed adapters.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments o the invention.
IN THE DRAWINGS
Figure 1 is a side view of an anchor dowel assembly embodying the present invention;
Figure 2 is another side view o the dowel assembly of Figure 1 taken in the direction of the arrow II shown in Figure 1, and, Figure 3 is a side view, partly in section, of a setting o~ tool embodying another feature of the present invention.
In ~igures 1 and 2 an anchor dowel a~;sembly, embodying the present invention, consists of an ~xially elongated dowel body 1 and an anchor mcmber in the form of a small plate. As vlewed in thc drawing, the upper end of the dowel body 1. is its front end, that 1~, the end first inserted into a borehole and the lower end is its rear end. The rear end of the dowel body 1 has an axially extending thread 3 so that axially directed forces can be transmitted to the dowel. Adjacent its front end, the dowel body 1 has a slot 4 open toward the front end ,r . 'y ~

of the dowel and the slot is inclined relative to the longitudinal axis of the dowel. As can be seen in Figure 1, the slot 4 diverges away from the dowel axis as it approaches the front end of the element. Anchor member 2 in the form of a small trapezoidally shaped plate is held in engagement within the slot 4, that is, the spacing between the opposite sur~aces of the slot is slightly less than the thickness of the plate so that the plate is securely held in -the slot. The trape-zoidally shaped plate has a pair of sides extending transversely of the dowel axis with the longer side 2a abutting against the closed end of the slot. The opposite ends 2b oE the longer side 2a project outwardly beyond the circumferential periphery of the dowel. As can be seen in Figure 2, the dimension of the plate along its longer side 2a is greater than the diameter of the dowel body 1. Accordingly, when the dowel assembly is inserted into a borehole, and hefore any anchoring action takes place, the ends 2b of the Longer side 2a extend outwardly Erom the dowel body so that they encJacJe the surface of the borehole. Sincc the sides 2c extending from the opposite ends 2b of the lorlc3er side tal)er inwardly toward one another, thc ends 2b provide a saw-tooth shape to the rearward end of the plate. Whcn the cdowel is anchored by effecting a relative movement between -the dowel body 1 and the anchor member 2, the plate 2 slides along the supporting surface la within the slot and its lateral ,~ edges 2c extending between the transversely extending ;
edges progressively extencl outwardly from the circum-ferential surface of the dowel providing a progressively 5~38 tighter wedging action by contact with the surface of the borehole by means of which the dowel is anchored in the borehole.
: In Figure 3 a tool is shown for effecting the relative movement between the dowel body 1 and the anchor member 2. The tool consists of an annular solid body 5 reciprocally movable along an axially extending guide bar 6 between stops 7, 8 each located at an opposite end of the guide bar. Each of the stops 7, 8 has a connection means, such as threads 9, 10. These threads 9, 10 are arranged to engage one end of the dowel for transmitting axially extending forces to the dowel. In each of the ` stops 7, 8 a different size and type of thread 9, 10 is provided so that a single tool can be used for different dowel assemblies.
After the setting tool is attached to the dowel body 1 by threading one of the stops 7, 8 onto the thread

3 on the rear end of the dowel body, the solid annular body 5 is driven against the stop spaced from the rear end of the dowel so that an axially directed pulling action is applied to the dowel and a movement relative to the anchor member is developed for effecting the anchoring action.
The saw-tooth shape of the ends 2b of the longer edge 2a, while permitting the movement of the dowel body 1 and plate 2 into a borehole, causes the plate to be gripped in the borehole surface with the result tha-t the pulling . action withdraws the dowel relative to the plate. The extent of the anchoring action can be controlled by the ` number and intensity of the blows effected by the solid ¦ 30 body 5 striking against the stop spaced outwardly on the ~35~8 setting tool from the rear end of the dowel. As mentioned previously, because of the inclined supporting surface la, as the dowel 1 is withdrawn from a borehole, the plate 2 riding on the supporting surface 1 is displaeed laterally so that an increasing length of plate 2 and the lateral edges 2c begin to engage the surface of the borehole increasing the anchoring effect.
After the application of a suitable number of blows by the member 5, the stop 7 or 8 can be disconnected from threads 3 of the dowel, and some other fixture may then be attached by means of a threaded nut (not shown) usually, as such a nut is tightened up, it will increase the anehoring effeet of member 2 by applying further pull out forees to the dowel, although such i-urther forees are not in fact essential to obtain effective anehoring in most eases.
~laving deserihed what is believed to be the best mode by wh.ich the :invention may be performed, it will be seen that the invention may be part:icularly defined as follows:
Anehor assembly eompxising an axia.lly elorlcJ-Ited dowel and an anehor member movable yenerally loncJitu(iinally , relative to said dowel from a startincJ position i.nto an anehored position, said dowel havincJ a Eirst cnd to be inserted f.irst into a borehole and an opposite second enci, means on the seeond end of said dowel ior applying axially aetir.g forees to said dowel, a supporting surface for suppor-ting said anehor member and located in and adjacent the first end :; of said dowel, said supporting surface being inclined to the:
~; 30 axis of said dowel and diverging from the axis in the direction ,~., . _ g _ ':
' ~ `
.

3~8 toward the first end of said dowel, said supporting surface having a rear end extending transversely of the axis of said dowel and a front end spaced in the axial direction of said dowel from the rear end toward the first end of said dowel and the front end of said supporting surface being located adjacent to the peripheral surface of said dowel, said anchor member comprising a trapezoidally shaped plate having a pair of first sides extending transversely of the axis of said dowel and a pair of second sides extending between said first sides, said first sides consisting of a longer side and a shorter side and in the starting position of said anchor member on said supporting surface said longer side is located adjacent said rear end of said supporting surface and the opposite ends of said longer side project outwardly from the circum-ferential periphery of said dowel, wherein the improvement comprises that said dowel has a slot formed therein with said slot having a pair of oppositely spaced surfaces holding said plate therebetween, one of said surfaces being said supporting ~urface so that said 510t iS inclined in the same manner as ~aid support.ing surface, said slot extending generally longitudinally relative to said dowel and at the end oE said slot closer to the second end of ~aid dowel said supporting surface is located closcr to the axis of said dowel than the opposite surface oE said s~.ot.
While specific embodiments of the invention have been shown and described in detail to illustrate the applica-tion of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

., . - 10 -:

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Anchor assembly comprising an axially elongated dowel and an anchor member movable generally longitudinally relative to said dowel from a starting position into an anchored position, said dowel having a first end to be inserted first into a borehole and an opposite second end, means on the second end of said dowel for applying axially acting forces to said dowel, a supporting surface for supporting said anchor member and located in and adjacent the first end of said dowel, said supporting surface being inclined to the axis of said dowel and diverging from the axis in the direction toward the first end of said dowel, said supporting surface having a rear end extending trans-versely of the axis of said dowel and a front end spaced in the axial direction of said dowel from the rear end toward the first end of said dowel and the front end of said supporting surface being located adjacent to the peripheral surface of said dowel, said anchor member comprising a trapezoidally shaped plate having a pair of first sides extending transversely of the axis of said dowel and a pair of second sides extending between said first sides, said first sides consisting of a longer side and a shorter side and in the starting position of said anchor member on said supporting surface said longer side is located adjacent said rear end of said supporting surface and the opposite ends of said longer side project outwardly from the circumferential periphery of said dowel, wherein the improvement comprises that said dowel has a slot formed therein with said slot having a pair of oppositely spaced surfaces holding said plate there-between, one of said surfaces being said supporting surface so that said slot is inclined in the same manner as said supporting surface, said slot extending generally longitudinally relative to said dowel, and at the end of said slot closer to the second end of said dowel said supporting surface being located closer to the axis of said dowel than the opposite surface of said slot.

2. Anchor assembly as set forth in Claim 1, wherein said slot is closed at the rear end of said supporting surface by said dowel and the remaining edge surfaces of said slot are open through the circum-ferential surface of said dowel and the second sides of said plate with the longer first side thereof adjacent with the closed rear end of said slot extend laterally outwardly through the open edge surfaces of said slot.

3. Anchor assembly, as set forth in Claim 1, wherein said plate has a thickness slightly greater than the spacing between said supporting surface and the oppositely spaced surface of said slot so that said plate is held in said slot in form locking engagement and being releaseable therefrom by the application of pull out forces on said dowel.