The present invention relates to a masonry anchor and more particularly to a masonry anchor of the type comprising a threaded sleeve or dowel which engages onto the end of a tapered bolt or stud to be expanded as the bolt or stud is driven into the sleeve, to thereby anchor the sleeve within a hole in solid masonry.

Existing anchors of the type discussed above have conventionally comprised an expansion element in the form of a bolt which is tapered over a substantial portion of its length, with the interior of the sleeve having a matching taper- formed with a tapered thread. The sleeve is split so that when the bolt is driven into the sleeve, the sleeve progressively expands until it is anchored within the hole. The tapered thread profile within the sleeve is compatible with that of the bolt at the start of expansion. As the bolt is driven further into the sleeve, the interengaging thread forms become progressively less compatible because of the changing radii of engagement, and substantial lubrication is usually required in order to prevent seizing of the threads. Even with lubrication, the incompatibility of the threads creates large torque requirements on the bolt. In addition, when the sleeve is fully expanded within the hole, the bolt cannot be

tightened further without applying excessive torque. In many instances, in order to securely anchor a component tightly against the external surface of the masonry, the bolt may need to be tightened down beyond the point at which maximum expansion (full setting) of the sleeve has occurred and accordingly, the operator must either apply the excessive torque which will over stress the system and even then may not be sufficient to draw the component firmly down onto the masonry surface, or he must reset the anchor with the sleeve deeper into the hole.

For convenience, the end of the anchor which lies furthest within the hole will be termed herein as the "inner end", and the end of the anchor which lies adjacent the surface of the masonry will be termed herein as the "outer end". The same convention will be used when referring to the inner and outer ends of the sleeve and expansion element. ^• - ^• - - - ^■ - ^■ - ^■ - ^•

According to the present invention there is provided a masonry anchor comprising an expandable sleeve for location in a hole in masonry and an expansion element comprising an elongate shank having a substantially cylindrical thread leading to a tapered thread, the sleeve having an internal thread and being defined by a plurality of segments capable of radial displacement, the tapered thread being engageable within the sleeve to cause radial expansion of the sleeve by radial displacement of the segments, setting of the sleeve within the hole occurring when the cylindrical thread of the expansion element is substantially within the sleeve whereby the expansion element can then be further driven into the sleeve.

Further according to the present invention there is provided a masonry anchor comprising a sleeve adapted to be expanded into engagement with the circumferential surface of a hole drilled in masonry, and an expansion element insertable into the sleeve to cause such expansion, wherein the expansion element comprises a threaded shank having a substantially cylindrical thread portion followed by a tapered thread portion, the sleeve is at least partially split longitudinally and comprises an internal thread engageable with the tapered thread portion of the threaded shank such that as the expansion element is screwed into the sleeve the inner end portion of the sleeve expands radially into engagement with the circumferential surface of the hole whereby to set the sleeve within the hole, the sleeve and expansion element being so arranged that when the sleeve is set within the hole the - substantially cylindrical thread- ortion of the threaded shank is substantially within the sleeve whereby further tightening of the -expansion element can occur without further substantial radial expansion of the sleeve, and the thread in the sleeve being such that when the sleeve is expanded into its set condition the thread assumes a substantially cylindrical form compatible with that of the cylindrical thread portion of the threaded shank.

In one embodiment, the tapered thread defines the inner end portion of the threaded shank and the sleeve is initially mounted on the tapered thread and includes a mating tapered internal thread.

Preferably, the sleeve is slit by a plurality of slots extending generally axially from the inner end of the sleeve, with the slots initially being closed at the inner end and opening as the sleeve expands outwardly on setting.

The slots may be formed through the entire wall thickness of the sleeve or alternatively they may extend only partially through the wall thickness to leave a web or membrane which is ruptured or torn when the sleeve is expanded.

Preferably, the sleeve is produced by a method comprising the steps of producing a cylindrical thread form compatible with that of the cylindrical thread portion of the threaded shank and deforming the body of the sleeve to produce from the cylindrical thread form a tapered form capable of threaded engagement with the tapered thread at the end portion of the threaded shank. It is advantageous for the sleeve to be produced by a cold forming operation with the slots formed only partially through the wall thickness to leave a web or membrane as discussed above. The web or membrane remains at the inner surface of the sleeve and facilitates threading by tapping the inner surface.

In another embodiment, the threaded shank has a further substantially cylindrical thread beyond the tapered thread and of a smaller diameter than the main cylindrical thread, the sleeve initially being mounted on this smaller cylindrical thread and expanding as the tapered thread moves into the sleeve.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a side view of an anchor in accordance with a first embodiment of the invention;

Figure 2 is a side view of a bolt of the anchor shown in Figure 1;

Figure 3 is a side view of a sleeve of the anchor shown in Figure 1;

Figure 4 shows the sleeve as viewed from its inner end;

Figure 5 shows a body from which the sleeve of Figures 3 and 4 is produced;

Figur 5a shows to an enlarged scale, interengaging substantially cylindrical thread forms of the sleeve and.bolt.

Figures 6 and 7 are views equivalent to Figures 3 and 5 of a modified form of sleeve;

Figures 8 and 9 are views equivalent to Figures 3 and 5 of another modified form of sleeve;

Figure 10 is a side view, partially in section, of yet another modified form of sleeve;

Figure 11 shows the sleeve of Figure 10 after expansion on the bolt;

Figure 12 shows a sheet metal blank for forming the sleeve of Figure 11;

Figure 13 is a side view of a bolt of an anchor in accordance with a second embodiment of the invention;

Figure 14 shows the end of the bolt of Figure 13 with an expansion sleeve mounted thereon;

Figure 15 is a plan view of a blank for forming the sleeve of Figure 14; and

Figure 16 shows the blank of Figure 15 after partial shaping.

As shown in Figures 1 to 5 of the accompanying drawings,- a. masonry anchor in accordance with a preferred embodiment- with the present invention comprises a bolt 2, having a threaded shank which is tapered at its inner end portion 2a. The portion 2b of the thread outwardly of the tapered end portion 2a is substantially cylindrical. The thread of the portion 2b may be exactly cylindrical or there may be a very slight taper in the direction of the tapered end portion 2a. The taper angle of the tapered end portion 2a will be dependant on the diameter of the bolt. For small bolts, a taper angle of up to 24° can be used, and for large bolts, the taper may need to be as low as 3°. This is necessary, in order to achieve maximum mechanical advantage on the one hand, whilst ensuring that the operator can

"feel" that the bolt is sufficiently tight. If the cylindrical portion 2b has a slight taper, the angle will only be a small fraction of the taper angle of the portion 2a; for example for a medium sized bolt where the end portion 2a is tapered to an angle of 12°, the cylindrical portion 2b can have a slight taper of up to 2°. The thread tip diameter of the substantially cylindrical thread portion 2b is somewhat less than the diameter of the unthreaded portion 2c of the bolt shank for reasons which will be discussed later.

The bolt 2 is used with a sleeve 4 (Figures 1, 3 and 4) which is formed from a tubular body 6 (Figure 5) having a wall thickness which progressively increases from its outer to its inner end. The body 6 has a cylindrical inner surface 8 and the increasing wall thickness provides a frustoconical outer surface 10 with the larger diameter being at the inner end of the body 6. -The body 6 has a series of angularly-spaced slots 12 (as shown, four, slots) which extend longitudinally from its inner end to a position adjacent the outer end. The cylindrical inner surface 8 of the body 6 is formed with a cylindrical thread which is fully compatible with that of the thread on the cylindrical portion 2b of the bolt. The sleeve 4 is produced from the tubular body 6 by radially compressing the body 6 at its inner end. This deformation is accommodated by closure of the inner end portions of the slots 12 as is shown in Figures 3 and 4. The deformation has the effect of transforming the outer frustoconical surface 10 into a cylindrical outer surface on the sleeve 4 and transforming the threaded

inner cylindrical surface 8 into a conical surface, the angle of which corresponds to the angle of the tapered end portion 2a of the bolt. The thread within the sleeve, thus becomes a tapered thread. The overall length of the sleeve 4 is approximately equal to the length of the tapered end portion 2a of the bolt and the outer diameter of the sleeve 4 in its radially compressed state is approximately equal to the diameter of the unthreaded shank portion 2c of ^tne bolt. This latter relationship means that the diameter of the shank portion 2c can be substantially the same as the diameter of the hole in the masonry whereby the shank diameter can be a maximum for a given hole size which provides improved torque-carrying characteristics for the bolt.

In order to set the anchor, the tapered end portion 2a of the bolt is initially screwed into the tapered thread in the sleeve 4 which -has been formed during manufacture b xadially compressing the outer end of the body 6 as discussed above. As the tapered sleeve thread was originally formed as a cylindrical thread there will initially be a degree of thread mismatch between the tapered thread in the sleeve and the tapered thread on the bolt. However, this mismatch occurs at a point where the torque requirements are a minimum and the mismatch progressively reduces as the torque requirements increase, as will be described. In contrast, in the existing anchors discussed earlier, the thread compatibility is a maximum at minimum torque requirements and the threads increasingly mismatch as the torque requirements increase. With the sleeve 4 screwed onto the tapered end portion 2a of the bolt,

the sleeve and bolt are inserted into the hole with the sleeve frictionally engaging the wall of the hole. Screwing of the bolt down into the sleeve causes the tapered portion 2a to move down through the sleeve and thereby expand the sleeve radially at its inner end by opening the slots 12 at that end. As the tapered portion 2a starts to move through the sleeve in order to expand the sleeve radially at its inner end, the cylindrical thread portion 2b of the bolt starts to move into the outer end of the sleeve. At the designated maximum expansion of the sleeve which provides the desired degree of setting of the sleeve within the hole, the tapered end portion 2a of the bolt has moved beyond the sleeve, and the sleeve is wholly engaged with the cylindrical thread portion 2b of the bolt.

It will be appreciated as the sleeve expands radially outwardly at its inner end, its threaded inner surface will tend to ^" return in shape towards its original cylindrical shape and at the point of maximum expansion when the tapered thread portion 2a is beyond the sleeve, the interior surface of the sleeve will have returned to its original cylindrical shape where there is complete thread compatibility between the original cylindrical thread formed in the sleeve and the cylindrical thread on the bolt and such compatibility exists at the maximum torque requirement corresponding to maximum expansion. The use of the interengaging thread forms which are substantially cylindrical at the point of maximum expansion means that when the sleeve has been fully set within the hole, the bolt can still be screwed further down into the sleeve without further

increasing the torque requirements. Accordingly, even although the sleeve has been fully set, the bolt may be screwed down further into the sleeve in order to draw the component firmly against the surface of the masonry without the use of additional and excessive torque requirements. The compatibility of the interengaging threads at setting of the sleeve also means that the torque requirements on the bolt for a required setting force are significantly less than with the existing anchors and minimal lubrication is required. The use of a bolt shank diameter which is a maximum for a given size of hole means that the shear carrying characteristics of the bolt are also a maximum. The reduced torque requirements and the maximum shear load characteristics obviate the need for special heat treatments to be applied to the bolt for strengthening purposes.

With conventional v-thread forms- there tends to be a wedging action between the opposed flanks of the male thread portion and the corresponding flanks of the female portion. In the thread mechanism of the anchor under consideration there are very substantial radial forces between the interengaging threads due to the expansion effect which forces the sleeve radially outwards into contact with the wall of the hole. If the threads on the bolt and sleeve were conventional v-threads, the radial forces would tend to cause wedging to occur between the interengaging threads which would give rise to large torque requirements on the bolt. In order to avoid this effect, as shown in Figure 5a the interengaging threads are preferably so related that an axial gap

exists between the trailing flank 20 of the male bolt thread and the adjacent flank 22 of the corresponding female thread section in the sleeve 4. In addition, the root surface area 24 of the female thread section of the bolt and the corresponding tip area 26 of the male thread section of the sleeve thread are made relatively large and in contact so that a significant component of the radial load is carried by these surfaces. In this manner the high radial loads necessary to effect expansion and setting of the sleeve in the hole does not result in high friction between the interengaging threads and hence high torque requirements on tightening. It will be appreciated that this effect can be achieved by thread forms of other than the specific shape shown. For example these effects can be achieved by thread forms which are sinuous rather than rectilinear, and again the arrangement would be such that at the trailing edge there is a space between the opposing flanks and there is also a substantial root/tip contact area to carry the high radial loading.

As explained above, the thread in the sleeve is initially formed as a cylindrical thread which is deformed into a tapered thread by radially compressing the inner end of the sleeve. Apart from the substantial advantages in operation which arise from this as previously discussed, manufacture of the sleeve is also facilitated. The thread, being a cylindrical thread, can be formed by means of conventional thread forming techniques with the cylindrical thread being converted into a tapered thread by a simple radial compression of the sleeve and this technique is significantly simpler than the

techniques necessary for forming tapered threads as occurs in the existing anchors.

There is shown in Figure 6 a modified form of sleeve, designated 28. The tubular body 30

(Figure 7) from which the sleeve 28 is formed is of stepped outer profile comprising a cylindrical surface 32 of larger diameter at its inner end with the main body portion 34 being of cylindrical form of smaller diameter. The body is formed with an internal cylindrical thread and slots 36 equivalent to the slots 12 of the sleeve of Figures 4 and 5. To produce the sleeve 28, the body 30 is radially compressed at its inner end portion such that the surface 32 remains cylindrical after compression with the remainder of the body portion 34 tapering towards that end in order to provide the tapered thread within the sleeve. The cylindrical surface 32 of the sleeve after compression is of substantially the same diameter as the outer end of the sleeve. When the sleeve is set into the hole there is initially a large cylindrical contact area (provided by the surface 32) available at the inner end of the sleeve for contact with the wall of the hole during initial expansion of the sleeve and this area carries the whole of the radial holding.

The sleeve 38 shown in Figure 8 is formed from a tubular body 40 (Figure 9) having an internal cylindrical thread and slots 41 extending from its inner end. The inner end portion 42 of the body is cylindrical with the main body portion 44 having a progressive taper. When the body 40 is radially compressed at its inner end to form the tapered

thread, the main body portion 44 of the sleeve becomes cylindrical with the inner end portion 42 being of frustoconical form. Upon subsequent expansion on setting of the sleeve in the hole, the inner end portion 42 returns to a substantially cylindrical form which provides a large surface area to carry most of the radial loading, with the then frustoconical main body portion 44 carrying the remainder of the radial loading.

The sleeve 48 shown in Figures 10 and 11 can be formed from a flat metal blank 50 (Figure 12) on which a cylindrical thread 52 is produced by a rolling or coining process. The blank 50 is then pressed into the form of a generally conical slotted sleeve with end portions 53 of the blank being bent to lie externally of the sleeve to provide an increased thickness at its inner end portion so as to permit the necessary, setting ef_fect on expansion. The sleeve is expanded* at its inner end portion.ljy the bolt in substantially the same way as discussed in relation to the first embodiment.

It is not essential for the bolt to be a headed bolt and may alternatively be threaded along its entire length, thus forming a stud.

In the embodiment shown in Figures 13 to 15, the bolt comprises an additional cylindrical portion 2d at the end of the tapered portion 2a and of reduced diameter relative to the main cylindrical thread portion 2b. In this embodiment, the sleeve 60 comprises two (or more) segments 62 of part-cylindrical form and which are separated by

longitudinal slots 64 extending the length of the sleeve so that each segment 62 can be displaced as a whole from a smaller to a larger diameter by opening of the slots 64 throughout their length. Although the segments are essentially separate segments, they are held in assembled relation by bridging portions 66 extending forwardly of the segments. The bridging portions 66 are of a structure such that they permit the segments 62 to displace each relative to the other as a whole by opening of the slots 64. The sleeve 60 is formed with a cylindrical thread which mates with the cylindrical thread portion 2d at the end of the bolt and the sleeve 60 is mounted on the bolt by engagement with that thread portion. The thickness of the sleeve 60 is such that when the sleeve is mounted on the cylindrical thread portion 2d the outer surface 68 of the sleeve lies at a diameter equivalent to the diameter of the masonry hole. It will be noted that in this embodiment the unexpanded sleeve is mounted on a cylindrical thread on the bolt rather than on a tapered thread and accordingly, the sleeve does not require-a thread which is initially tapered.

When the anchor is inserted into the hole and the bolt is rotated, the tapered thread portion 2a moves into the sleeve 60 to cause expansion of the sleeve. As the tapered portion enters the sleeve 60, the segments 62 will tilt relative to each other by opening of the slots 64 so that the thread within the sleeve becomes a tapered thread compatible to a degree with that of the tapered bolt thread. As the larger cylindrical thread portion 2b moves into the sleeve 60, the segments 62 displace into parallel

relationship so that the thread of the sleeve transforms back into a cylindrical thread, but at a larger diameter commensurate with that of the larger diameter cylindrical thread of the bolt. Although the thread diameter of the main cylindrical portion 2b of the bolt is larger than that of the smaller diameter end portion 2d, the thread is at the same pitch and the cylindrical thread of the sleeve will cooperate satisfactorily with both the smaller and larger diameter cylindrical threads of the bolt.

This form of sleeve in which the segments of the sleeve are essentially separate segments, can be fabricated from a thinner material than the sleeve of the preceding embodiments in which the outer end of the sleeve is of continuous form in order to connect the sleeve segments. The reduced thickness of the sleeve in this embodiment means that the required expansion of the sleeve can be achieved with a larger diameter main cylindrical thread of_ the _bolt whereby this portion of the bolt is of an increased strength. Although when the sleeve has expanded onto the main cylindrical portion 2b of the bolt, there will be a slight mismatch between the expanded sleeve and the bolt, as the thread pitch of the cylindrical thread on the bolt is the same as that of the cylindrical thread on the sleeve, there will still be substantial compatibility between the interengaging threads. When the sleeve is in its unexpanded state on the smaller diameter thread portion 2d, the sleeve is not exactly cylindrical, but rather, is slightly out of round in order to prevent rotation of the sleeve within the hole as the bolt starts to be screwed into the sleeve. Alternatively, the sleeve can be formed with

anti-rotation lugs which engage the surrounding surface of the hole.

The sleeve is preferably formed from a sheet metal blank 70 as shown in Figure 15 having end portions 72 which can be deformed as shown in Figure 16 to form the two semi-cylindrical segments 62, the end portions 72 being interconnected by the bridging portions 66 and having a thread form as shown at 74. The partially deformed blank of Figure 16 is then folded so that the semi-cylindrical segments 62 lie side by side to define the cylindrical sleeve, such folding being accommodated by bending of the bridging portions 66. The bridging portions include axially spaced notches 76 whereby the bridging portions preferentially bend in the area of the notches to assume the shape shown in Figure 14.

The anchors described herein ^" provide a relatively high contact area between ^" the sleeve and the masonry which provides a rigid setting which can be displaced -only upon application of-a very substantial load. Despite this effect, the bolt can still be tightened further after setting to such an extent as is necessary to draw the component into tight engagement with the outer surface of masonry.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention.