GB2083586A

GB2083586A - Connector Element

Info

Publication number: GB2083586A
Application number: GB8125616A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-09-09
Filing date: 1981-08-21
Publication date: 1982-03-24
Also published as: DE3033909C2; FR2489902A1; ZA815788B; DE3033909A1; JPS5773214A; IT8168179A0

Abstract

Two members (8, 9) are fastened together by a rivet having a head (2), and a shaft formed with grooves (6) to receive a collar (11) which is swaged on by the action of a chuck (14) and deformation sleeve (13). The grooves (6) being of incrementally increasing diameter so that the shaft breaks off at the groove closest to the end of the collar (11) after the deformation of the collar (11) has been completed and under the continued traction of the chuck (14) applied to the end part (5) of the shaft. <IMAGE>

Description

SPECIFICATION Connector Element This invention relates to a connector element for connecting structural members to one another, comprising a bolt member having a head adapted to abut one side of a structural member and a shaft portion adapted to extend through the structural members, and a closure ring adapted to be deformed about the shaft portion so as to abut another side of a structural member and to fill at least one circumferential closure groove of a plurality of closure grooves formed adjacent one another along the length of the shaft portion, each closure groove with the exception of the first one outside the other side of a structural member being formed as a potential breaking point of the shaft portion, whereat the shaft portion may break off after the closure ring has been deformed to a predetermined degree by means of a setting tool consisting of a deforming sleeve for the closure ring and a traction chuck for exerting a tractive force on the shaft portion. Such an element is hereinafter referred to as of the kind described.

U.S. Patent Specification No. 4,208,943 discloses a connector element of this type, wherein all closure grooves are of the same shape and of the same radial depth. With the exception of the first closure groove, as seen from the bolt head portion, filled with the material of the deformed closure ring, each closure groove forms a potential breaking point of the shaft portion. In forming the closure grooves, the bottom of each such groove is formed as a notch area and thus a potential breaking point. The flanks of each groove extend at different angles with respect to the material flow occurring during deformation of the closure ring.Since the maximum material flow occurs adjacent the closure ring end facing away from the bolt head portion, the flanks of the closure groove at this location are subjected to forces tending to wedge them apart from one another so as to create a maximum load or tension value in the notch area. The additional tractive force of the setting tool exerted in this area is to assure that the shaft portion breaks off in the notch area of the closure groove located at the first position within the closure ring and being the first to be filled by the flowing material. In practice, however, it is extremely difficult to predetermine exactly the configuration, the actually occurring material flow conditions, and the path of the forces exerted during setting, and to coordinate these factors with one another in such a manner that the shaft portion actually breaks off at the intended notch area.On the contrary, the shaft portion does frequently not break at the intended location, but rather at another closure groove outward of the closure ring. This is because the bottom portions of all closure grooves are of the same cross-sectional area, so that they are subjected to the same tensional forces. The slightest inhomogeneity of the bolt's material or irregularities of the bottom of a closure groove inavoidably result in the actual breaking point being located at the weakened portion formed by the respective closure groove, which may be located immediately adjacent the traction chuck of the setting tool. As a result, a considerable length of the bolt shaft portion may project beyond the closure ring, with the brokenoff shaft portion end presenting the danger of injuries.The basic disadvantage of this known connector element thus resides in the uncertainty as to whether or not the shaft portion will actually break off in the intended closure groove.

It is an object of the invention to provide a connector element of the kind described which is universally usable for the connection of structural members of different thickness, and wherein the breaking point of the shaft portion is always reliably located immediately adjacent the side of the closure ring facing away from the bolt head portion, or even retracted within the closure ring, irrespective of the actual thickness of the structural connection.

According to the invention, a connector element of the kind described is characterised in that said closure grooves formed as potential breaking points are of incrementally decreasing radial depth in the direction away from said head.

With this construction, irrespective of the thickness of the structural members to be connected, the shaft portion will reliably break adjacent the closure groove located adjacent the end of the closure ring facing away from the bolt head portion and not or only partially filled with the material thereof. This is achieved by incrementally decreasing the radial depth of the closure grooves in the direction away from the bolt head portion. In this case, if towards the end of the deformation of the closure ring a number of closure grooves remain unfilled, the shaft portion will break off at the location having the smallest cross-sectional area. Due to the decreasing radial depth of the closure grooves in the direction away from the bolt head portion, the smallest crosssectional area outside of the closure ring is located in the closure groove closest to the closure ring.In the further outward located closure grooves the cross-sectional area of the shaft portion is incrementally larger. Although the closure grooves located inside the closure ring and filled with the deformed material thereof define even smaller cross-sectional areas of the shaft portion, they are not subjected to tractive fordes of the same magnitude as the smallest cross-sectional area within the first free closure groove outside the closure ring. This is because the deformation sleeve exerts a thrust force mainly on the deformed closure ring, so that the tractive force is partially taken up by the width of the beads pressed into the closure grooves, resulting in the greatest tractive force being effective between the traction chuck and the deformation sleeve at the smallest cross-sectional area of the shaft portion outside the closure ring.

From US-PS 2,955,505 it is known, as a matter of fact, to form the closure grooves of a connector element of a different kind with decreasing radial depth in the direction away from the bolt head portion. This does not suggest, however, the formation of the closure grooves as potential breaking points, since the shaft portion is not broken off and the connection is not established with the aid of tractive forces exerted on the shaft portion, but rather by supporting the shaft portion of a given length by means of a dolly engaging the head portion and by compressing the closure ring about the shaft portion.

Advantageously, the width of the annular lands formed between said closure grooves is incrementally increased or decreased in the direction away from the bolt head portion.

This relationship of the widths of the annular lands between the closure grooves meets the specific requirements of the use of the connector element. The interrelation between the depth of the closure grooves, their width, and the width of the lands results in variable distribution of the tensional forces in the shaft portion enclosed by the closure ring for various uses.

Preferably, the end of the closure ring facing away from the bolt head portion is formed with a recess coaxially aligned with the bore of the closure ring and having a larger interior diameter than the diameter of the bore, the transition from said recess to said ring bore being formed as a shoulder.

By reason of static safety it is required that the closure ring has a predetermined effective closure length under all conditions. On the other hand it is to be avoided that the broken end of the shaft portion does not present the danger of injuries if for instance the closure ring is located at the visible outer side of a structural connection. Any of these requirements are most advantageously met by the recess in the end of the closure ring.

This is because within the depth of the recess the material of the closure ring on deformation thereof is not pressed into the closure grooves formed at this location, but only onto the outer annular lands. The closure grooves within the recess thus remain free of material. Under these conditions the configuration of the connecting element ensures that the actual breaking point of the shaft portion lies within the recess, i.e. at the first closure groove not filled with the ring material. The free end of the closure ring is smooth and shields the sharp-edged breaking point, so that the danger of injuries is avoided.

It is particularly valuable in this respect if the recess is of cylindrical or slightly conical shape.

The configuration of the recess exerts a major influence on the path of the forces during setting of the connection.

It is also useful if the depth of the recess equals at least one half of the width of the closure groove forming the actual breaking point of the shaft portion. By this minimum depth of the recess it is ensured that the actual breaking point lies within the axial length of the closure ring.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein: Figures 1 to 3 show a connector element according to the invention in three phases during the formation of a connection of two structural members to one another; Figure 4 shows an enlarged view of the connector element substantially in the state shown in Figure 1; Figure 5 shows a view of a closure ring as shown in Figure 4; Figure 6 shows a closure ring substantially in the state shown in Figure 1, with a deformation sleeve in engagement therewith, and Figure 7 shows an alternative embodiment of the closure ring and a deformation sleeve in engagement therewith.

The formation of a connection by means of the connector element 1 according to the invention is clearly shown in Figures 1 to 3. The connector element 1 comprises a bolt member having a head portion 2 and a shaft portion extending therefrom. The shaft portion has a first smooth section 3 adjacent head portion 2, a second section 4 formed with circumferential closure grooves 6, and a third section 5 having a structured peripheral surface 7 for improving the gripping action of a traction chuck 14. The connector element 1 serves to rigidly connect two flat structural members 8, 9 to one another at the location of a through opening 10. This is achieved by means of a closure ring 11' surrounding shaft sections 5 and 4 and engaging the surface of structural member 9 facing away from head portion 2.

The connection of structural members 8 and 9 to one another is accomplished with the aid of a setting tool 12 which is of a generally known type and thus requires no detailed description. Setting tool 12 comprises a deformation sleeve 13 having a conically enlarged axial bore. Located within sleeve 13 is a traction chuck 14, preferably of the type having gripping claws, and a traction head 1 5 cooperating with the traction chuck 14 and provided with a spacer element 1 6 extending through deformation sleeve 13. In the phase shown in Fig. 1, deformation sleeve 1 3 is pressed against the end face of closure ring 11' facing away from head portion 2, while traction chuck 14 engages the structured surface 7 of third shaft section 5.Traction head 1 5 then exerts a tractive force towards the left in Fig. 1, resulting in a compressive force towards the right in Fig. 1 being exerted on deformation sleeve 1 3.

During the initial stage structural members 8 and 9 are forcefully pulled towards one another while the shaft portion is subjected to tensional forces. The tensional force is then increased to a point at which the deformation sleeve 1 3 starts to deform closure ring 1 1', so that the material thereof flows into the closure grooves 6 in the form of bead-shaped projections capable of transmitting forces. In the phase shown in Fig. 2, the forward end of deformation sleeve 1 3 comes close to structural member 9. Further increase of the tractive force exerted on the shaft portion causes the iatter to break off at the first closure groove 6 beyond the end surface of closure ring 11 facing away from head portion 2.

After subsequent removal of the setting tool 1 2 together with the broken-off shaft end portion, the connector element presents itself in the configuration shown in Figure 3, interconnecting structural members 8 and 9 under compressive force.

The construction of connector element 1 is more clearly shown in Figure 4. The second shaft section 4 adjacent smooth shaft section 3 is formed with the closure grooves 6. In the embodiment shown, closure grooves 6 are formed at equal spacings, although the widths of annular lands 1 8 between the grooves may vary incrementally, e.g. increase in a direction away from the head portion 2, with advantage for certain applications. The radial depths of the grooves decrease with increasing distance from the head portion 2. starting from the first closure groove 6a defining the smallest diameter d min of shaft section 4, the core diameter of shaft section 4 increases to a maximum diameter d max at each further closure groove 6b to 6h.The third shaft section 5 may have the same diameter as the annular lands 1 8 formed between adjacent closure grooves 6a to 6h. The structured surface 7 only serves to improve the grip of the traction chuck 14.

The closure ring 11 has a chamfered peripheral portion 21 at its end surface facing away from head portion 2. The conical bore 26 of the deformation sleeve 12 is shown in engagement with closure ring 11 has a chamfered peripheral edge portion 20. Closure ring 11 has an axial bore 22 the diameter dA of which is slightly greater than the shaft diameter d5 as defined by annular lands 18.

With a given length of closure ring 11 and thickness of structural members 8 and 9, the first closure groove lying outside closure ring 11 is the one'designates 6f. Since the cross-sectional area of the shaft portion within closure groove 6f is smaller than the cross-sectional area within closure groove 6h (d max), a sufficiently strong tractive force exerted by traction chuck 1 4 will result in the shaft portion breaking off at this closure groove 6f.This is because the tractive force exerted by traction chuck 14 is not directly transmitted to the head. portion 2 supported by the structural members 8 and 9, as the closure ring 11 forms an abutment for deformation sleeve 13 and the bead-shaped projections formed by the material flow in closure grooves 6a to 6e take up a proportion of these forces.

The shown bolt-closure ring combination may be employed for establishing structural connections of variable thickness. If the structural members 8 and 9 are of greater thickness, the breaking point will be located at closure groove 6h. In the case of thinner structural members 8, 9 the shaft portion may break of at any one of the closure grooves 6b to 6h. For special applications it may be advantageous to form the closure grooves of the shaft portion with increasing or decreasing width in the direction away from the head portion.

Fig. 5 shows a cross-sectional view of the closure ring 11 of Fig. 4. It is formed with an axial bore having the diameter dR, and with the chamfered edge portion 21 intended to facilitate the beginning of the deformation by deformation sleeve 13.

Fig. 6 shows a cross-sectional view of a closure ring 11', the axial bore 22 of which again has the diameter d. The chamfered edge portion 21 is replaced by an enlarged chamfer portion 21' defining a shoulder 23 at the transition to the main body of closure ring 1 1'. A particular embodiment of the deformation sleeve 13' has the rearward end of its conical bore 26' with a stop shoulder 27 adapted to seat on the end surface of the closure ring 11' at the end of the deformation step for aiding the breaking off of the shaft portion.

Fig. 7 shows a particularly advantageous embodiment of a closure ring 11" in crosssection. Again, ring 11" has an axial bore 22 the diameter dA is slightly greater than the outer diameter ds of the shaft portion of bolt 1. The end surface of closure ring 11" facing away from head portion 2 of bolt 1 is formed with a cylindrical recess 24 coaxially aligned with axial bore 22 and extending to a depth T with an inner diameter dv.

This recess 24 permits the breaking point of shaft section 4, which may be defined by any one of grooves 6b to 6h, to be located within closure ring 11" without changing the predetermined closure length of the closure ring as defined by the length of axial bore 22. In this case the shaft section 4 breaks off in such a manner that the breaking point does not project beyond the closure ring, thus avoiding any danger of injury.

The recess may also be conical. It is only important that it is connected to axial bore 22 by a shoulder 25. The interior diameter dv of recess 24 is selected such that deformation of the closure ring 11" does not result in its material being pressed into the closure grooves along the depth of the recess. This ensures that the shaft portion breaks off at the first closure groove not filled with the material of the closure ring 11".

Reference numeral 13 again designates the deformation sleeve.

The described connector element offers the particular advantage that structural connections of various thicknesses can be established by use of a single bolt size and a corresponding closure ring. It is moreover possible to employ closure rings of different lengths with bolts of one and the same size in order to obtain different gripping lengths in accordance with the requirements of any specific use. Also in this case, the actual breaking point of the shaft portion is again defined by the first free closure groove. The depth T of the recess 24 is advantageously selected so as to equal at least one half of the width b of a closure groove 6. This ensures that the breaking point lies flush with the end face of the closure ring. The cross-sectional shape of the closure grooves may be varied in the known manner for adapting the connector element to various uses.

In a particularly useful embodiment, the grooves are of a U-shaped, rounded cross-sectional configuration facilitating the flow of the material thereinto. Since the width b of the closure grooves contributes to determining the loadcarrying capacity of the bead-shaped projections of the material formed therein, it is advantageous to select a greater width b in the case of closure rings of a softer material than in the case of harde closure rings.

Claims

1. A connector element for connecting structural members to one another, comprising a bolt member having a head adapted to abut one side of a structural member and a shaft portion adapted to extend through said structural members, and a closure ring adapted to be deformed about said shaft portion so as to abut another side of a structural member and to fill at least one circumferential closure groove of a plurality of closure grooves formed adjacent one another along the length of said shaft portion, each said closure groove with the exception of the first one outside said other side of a structural member being formed as a potential breaking point of said shaft portion, whereat said shaft portion may break off after said closure ring has been deformed to a predetermined degree by means of a setting tool consisting of a deforming sleeve for said closure ring aid a traction chuck for exerting a tractive force on said shaft portion, characterized in that said closure grooves (6b to 6h) formed as potential beaking points are of incrementally decreasing radial depth in the direction away from said head (2).

2. A connector element according to claim 1, characterized in that the width of the annular land (18) formed between said closure grooves (6) is incrementally increased or decreased in the direction away from the bolt head portion.

3. A connector element according to claim 1 and/or 2, characterized in that the end of the closure ring (11") facing away from the bolt head portion (2) is formed with a recess (24) coaxially aligned with the bore (22) of the closure ring and having a larger interior diameter (dv) than the diameter (dR) of said bore, the transition from said recess to said ring bore (22) being formed as a shoulder (25).

4. A connector element according to claim 3, characterized in that said recess (24) is of cylindrical er slightly conical shape.

5. A connector element according to claim 3 and/or 4, characterized in that the depth (T) of said recess (24) equals at least one half of the width (b) of the closure groove (6) forming the actual breaking point of the shaft portion.

6. A connector element substantially as described with reference to the accompanying drawings.