EXPANSION BOLT

Abstract: An expansion bolt for mounting a rail to a wall, especially a wall having limited thickness, such as a plaster wall. The expansion bolt comprises an anchor (16) having an outer screw portion (20) formed for receiving a screw (17) an intermediate slit portion (21) forming anchor legs (26), and an inner sleeve portion (22). The anchor (16) extends along the screw so that the sleeve portion (22) of the anchor is located adjacent the head of the screw. A sleeve (19) is concentric with the anchor (16) and is located between the head of the screw and the anchor (16) and is formed for co-operating with the sleeve portion (22) of the anchor (16). The sleeve (19) comprises a collar (27) located adjacent the head of the screw. In mounting, the sleeve is inserted in a through hole in the rail and the wall until the collar (27) abuts the outer edge of the hole and the sleeve extends partially through the hole or almost completely through the hole, while the slit portion (21) and the screw portion (20) of the anchor extend on the inner side of the wall. Then the screw is tightened until the anchor legs have expanded behind the wall.

Description: EXPANSION BOLT Field of the invention The present invention relates to an expansion bolt for mounting a rail on a wall of limited thickness. More specifically, the invention relates to an expansion bolt for mounting a rail on a wall comprising a plasterboard or the like, the bolt expanding on the inner side of the wall without this having to be accessible. Prior art When mounting a rail on a plaster wall normally a bolt of the expansion type is used, such as a MOLLY bolt, which is inserted into a hole in the wall and expanded with a tool for this purpose. The MOLLY bolt comprises a portion expanding behind the wall. However, such a MOLLY bolt suffers from a plurality of disadvantages, such as for instance that the bolt is relatively weak and that the screw of the MOLLY bolt easily is subjected to such shearing forces that it is not dimensioned to resist. Furthermore, it is impossible to remove a MOLLY bolt completely on the subsequent disassembly, since the part of the MOLLY bolt being in and behind the plasterboard is not removable. If this detail is puttied up a quite big swelling remains on the wall. Summary of the invention The object of the present invention is to provide a bolt especially suitable for use in connection with the mounting of a rail on a plaster wall. Thus, according to the invention, an expansion bolt is provided for mounting a rail, a board or the like on a wall of limited thickness, such as a plaster wall. The expansion bolt comprises an anchor having an outer screw portion formed for receiving a screw, an intermediate slit portion forming anchor legs, and an inner sleeve portion. The anchor extends along the screw so that the sleeve portion of the anchor is located adjacent the head of the screw. According to the invention the expansion bolt has a sleeve concentric with the anchor and located between the head of the screw and the anchor and formed for co-operation with the sleeve portion of the anchor. The sleeve comprises a collar located adjacent the head of the screw. When mounting the expansion bolt it is inserted in a through hole in a wall or the like until the collar abuts the outer edge of the wall and the sleeve partially extends through the hole or almost completely through the hole while the slit portion and the screw portion of the anchor extend on the inner side of the wall, whereupon the screw is tightened until the anchor legs have expanded behind the wall. Suitably, the sleeve and the sleeve portion of the anchor of the expansion bolt comprise co-acting engagement means, which prevents a relative rotation between the sleeve and the anchor. Furthermore, the-_sleeve comprises engagement means arranged to engage the edge of the hole in order to prevent the sleeve and thereby the anchor from rotating relative the hole. Furthermore, the slit portion of the anchor is provided with slits having circular indentations at their ends and semi-circular indentations approximately at their centres. The indentations form bending notches on tightening and expanding the bolt, whereby anchor legs are formed between the slits having a shape that provide a large abutment surface against the inner side of the wall and provide strong support legs preventing deformation thereof. According to a preferred embodiment the sleeve is an inner sleeve located concentrically in the sleeve portion of the anchor or the sleeve is an outer sleeve located concentrically exterior of the sleeve portion of the anchor. The outer sleeve may be provided with an outer coating of latex or silicon or a similar material, which coating covers the interior surface of the collar for sealing the hole in the wall. At the remote end from the head of the screw this coating may form an annular rib expanding against the inner edges of the hole on expanding the screw in order to secure the sleeve as well as the anchor against rotation. In the case of the inner sleeve it is suitable that the anchor comprises a shallow annular recess at the interface between the sleeve portion and the slit portion, in which recess a rubber ring is located and on expanding the anchor is pressed against the inner edges of the hole to prevent rotation of the anchor in the hole. The recess may be provided with a plurality of circumferentially spaced axial slits, the sleeve being provided with means engaging the slits to press the rubber ring against the edge of the hole when tightening the bolt. The rubber ring may be formed integral with a rubber sleeve enclosing the sleeve portion of the anchor. Brief description of the drawings The advantages and features of the invention will become apparent from the subsequent detailed description of the invention with reference to the accompanying drawings. Fig. 1 is a view in perspective partially in cross section showing the mounting of a horizontal rail to a plaster wall. Fig. 2 is a cross-sectional view showing the mounting of a supporting rail for hospital equipment in accordance with the prior art. Fig. 3 is a cross-sectional view showing the disadvantages with this prior art mounting. Fig. 4 is a cross-sectional view showing the mounting of the same rail as in Figs. 2 and 3 with an expansion bolt in accordance with the present invention. Fig. 5 is an exploded view in perspective of an expansion bolt in accordance with the present invention. Fig. 6 is an exploded view in perspective of an alternative embodiment of the expansion bolt in accordance with the present invention. Fig. 7 is a view in perspective, partially in cross section, of a rail in accordance with Fig. 1 being mounted with an expansion bolt in accordance with Figs. 5 or 6. Fig. 8 is a cross-sectional view taken according to the same cross section as in Fig. 7 and shows a first variant of the expansion bolt. Fig. 9 is a cross-sectional view similar to Fig. 8 and shows a second variant of the expansion bolt. Fig. 10 is a cross-sectional view, through a securing rail in accordance with Fig. 1 mounted with an expansion bolt in -accordance with Figs. 5 or 6. Fig. 11 is a view in perspective showing a vertical rail mounted with the expansion bolt in accordance with the invention. Fig. 12 is an exploded view of the upper expansion bolt of Fig. 11. Fig. 13 is an exploded view of the lower expansion bolt of Fig. 11. Fig. 14 is a cross-sectional view through a variant of the expansion bolt in accordance with Figs. 5 or 6. Fig. 15 is an exploded view in perspective of a further variant of the expansion bolt. Fig. 16 is a view in perspective of the expansion bolt in accordance with Fig. 15 in the assembled condition. Detailed description of preferred embodiments In Fig. 1 a rail 1 is shown, which is intended for mounting on a wall in a hospital for carrying various equipment ' of a more or less permanent kind. The rail is shown in Fig. 1 mounted to a plaster wall of the type often found in hospitals. However, it is understood that the invention is not limited to be used on a plaster wall. Neither is the invention limited to applications in hospitals. The rail 1 shown in Fig. 1 comprises a surface 2 abutting the wall and an engagement portion 3 projecting from the wall and designed for carrying the intended equipment. A cellular plastic tape 4 with adhesive on both sides is located in a groove 5 for initially securing the rail during the mounting thereof. With reference to Figs. 2 and 3 the rail 14 is shown mounted in accordance with the prior art. The prior art rail 14 is constituted of a rectangular profile mounted with a usual MOLLY bolt 15 via a spacing sleeve. The proper and intended mounting function may be seen from Fig. 2. The screw of the MOLLY bolt is intended to pull the rail with sufficient force against the wall, so that it is fixed due to the friction against the wall. However, the screw has a diameter substantially less than the diameter of the sleeve of the MOLLY bolt, which makes the screw radially movable in the sleeve. When it has been in use for a time the situation demonstrated in Fig. 3 easily occurs, wherein the screw is significantly bent. The strain is on the screw, which furthermore is movable in the sleeve of the MOLLY bolt. It is understood that the screw is sheared in a way it is not intended for and therefore will not resist the potential loads but breaks easily. In addition to this, the profile slides down the wall, which is not aesthetically attractive. In Fig. 4 the corresponding mounting is shown with an expansion bolt in accordance with the present invention described more in detail below. In accordance with the present invention an expansion bolt is provided, which is especially designed for securing a rail -to a plaster wall. The expansion bolt is shown in an exploded view in Fig. 5 and comprises an anchor 16, a screw 17 with a washer 18 as well as a sleeve 19. The anchor 16 is of a structure that looks like a MOLLY bolt and comprises a top screw portion 20, an intermediate slit portion 21 and a bottom sleeve portion 22. The screw portion 20 is provided with an internal thread fitting the external thread of the screw 17. In the intermediate slit portion 21 between the slits » anchor legs 26 are formed with a special design. The slits 23 are provided with generally circular indentations 24 at their upper and lower ends, respectively, and approximately at their centre there are semi-circular indentations 25. This indentations together form bending notches enabling the anchor legs 26 between the slits to bend in a predetermined way when the expansion bolt is tightened, as may be seen more in detail in Fig. 10. By designing the slits 23 and hence the anchor legs 26 in this way the advantage is obtained that the anchor legs abut with a larger surface against the plasterboard than in the case of completely straight slits. In this way a stronger mounting is obtained and at the same time the force required for initially expanding the bolt will not be unnecessarily great. Furthermore, a higher safety against demolition when overloading, is obtained. The sleeve 19 is dimensioned so that it fits the sleeve portion 22 of the anchor 16. At the outer end of the sleeve 19 it is provided with a collar 27 comprising two barbs 28 intended for engaging the paper surface of the plasterboard for preventing rotation of the bolts on the tightening thereof. Furthermore, the sleeve 19 comprises one or more slits 29 at the inner end thereof, which co-operate with inwardly projecting ribs 30 formed in the sleeve portion 22 of the anchor 16. In this way the barbs 28 of the sleeve 19 also prevents the anchor 16 from rotating in an undesired way during the tightening. The expansion bolt is mounted in a hole in a plaster wall simply by sliding the bolt into the hole, as is shown in Fig. 7, until the collar 27 abuts the rail. In the case shown in Fig. 7 the sleeve 19 is of such a length that it extends through the hole in the rail and substantially through the plaster wall. After that the anchor legs 26 are bent by tightening the screw 18 or by using a special tool for extracting the screw. Then the anchor legs are bent in accordance with the bending notches formed by the indentations 24 and 25 and form a pyramide-like form, as is shown in Fig. 10. The barbs 28 fit in grooves in the rail (Fig. 8), so that the sleeve 19 and thereby also the anchor 16 are prevented from rotating when the screw 17 is tightened. In Fig. 6 a second embodiment of the expansion bolt in - accordance with the invention is shown. This expansion bolt comprises an anchor 16', a sleeve 19' and a screw 17', exactly like the embodiment according to Fig. 5, but the sleeve 19' is designed to be located outside the sleeve portion 22' . In this connection the sleeve portion 22' is instead provided with a projecting rib 30', while the outside sleeve 19' has a longitudinal slit 29' fitting around the rib 30' . Furthermore, the hole 31' in the sleeve portion 22' is dimensioned for receiving the screw 17' with adequate fitting. As may be seen in Figs. 7 and 9 the sleeve 19 (or the sleeve portion 22') passes through the rail as well as the wall, whereby potential loads will be carried by the sleeve 19 (or the sleeve portion 22'). Furthermore, the hole 31 in the sleeve 19 is dimensioned so that the screw 17 is relatively snugly received in the sleeve to avoid a too large clearance in the radial direction. Hereby a bolt joint is obtained, which can carry very heavy loads with a very good contact between the plaster wall and the rail without disrupting the plaster wall. The function of the screw is now only to clamp the anchor. By constructing the expansion bolt with a separate loose sleeve the advantage is obtained that the bolt is completely removable from the wall by extracting the sleeve and pushing the remaining part of the bolt into the space behind the plaster wall. Then the hole may be puttied up and completely masked. In Fig. 8 it is shown that the collar 27 and the barbs of the sleeve co-operate with longitudinal grooves 32 in the rail. Alternatively, the collar may of cource be of rectangular 33 or any other suitable shape, so that is co-operates with and is secured against rotation by the rail, as is shown in Fig. 9. In Fig. 10 the rail in accordance with Fig. 1 is shown mounted with an expansion bolt in accordance with Figs. 5 or 6. As is shown, the expansion bolt comprises the cellular plastic tape 4 with adhesive on both sides, so that this assists in holding the rail to the wall if it is subjected to high and rapid torques. In Fig. 10 it is further shown how the rail carries a vice 34, which in turn carries the equipment to be suspended on the rail. In Fig. 11 it is shown how the expansion bolt in accordance with the present invention may be used to mount a vertical rail 36 of the U-profile type on the wall or any other type of rail as well as an ordinary wooden board. A complementary shaped fastener 35 is arranged to engage the U-profile rail 36. The fastener 35 has a through hole 38 and two small holes 37 located on both sides thereof. The collar 27 of the sleeve 19 is provided with two small pins 28'', which engage said holes 37 to prevent rotation. The mounting may be seen in Fig. 12. The collar 27 is located between the U-profile rail 36 and the fastener 35. Alternatively, the collar 27 may also be located outside the fastener 35, the two small pins 28'' being directed inwardly. In Fig. 13 an alternative with rectangular collar 33 is shown. The sleeve 19 may provided with an external rubber or silicon coating 38 provided with an annular rib 39, as is shown in Fig. 14. The rubber coating 38 may be formed by immersing the sleeve in a latex bath, whereby the rib 39 is formed relatively automatically. The rubber coating 38 may also be manufactured separately and threaded onto the sleeve. When mounting the expansion bolt the rib 39 will be pressed against the inner edge of the plasterboard, as is shown in Fig. 14. Thereby, the extension bolt is prevented from rotating and the barbs 28 may possibly be omitted. The rubber coating 30 also covers the inside of the collar 27 so that the hole in the plasterboard is sealed if the collar directly abuts the plasterboard. Naturally, a rubber coating may be used also in the case of an internal sleeve, as is shown in Figs. 15 and 16. In this case, the slit portion 22 is provided with a recess 40, in which a rubber ring ring 41 is arranged. The rubber ring has a profile looking like an inverted D and fills the recess 40 without preventing the insertion of the expansion bolt in the hole. The sleeve 19 is provided with sleeve pins 42 engaging slits 43 formed in the recess. In Fig. 16 it is shown how the sleeve pins 42 press the rubber ring outwardly, so that it engages the inner edge of the hole, and thereby prevents rotation and seals the hole. In Fig. 15 it is also shown that the collar of the sleeve 19 may be provided with a cellular plastic tape with adhesive on both sides substituting the securing means. It is also possible to provide the part of the anchor legs abutting the inner side of the wall with a rubber coating, which on one hand prevents a possible sliding of this part of the legs over the plaster wall and on the other hand protects the paper layer of the plaster wall from being torn. The hole, that is drilled, may, but not necessarily, be a through hole, such as in plasterboards. Various types of fasteners may be used depending on the type of the wall. Furthermore, the rail may be of various types, such as any of the rails shown in Figs. 1, 2 or 11, or it may be an ordinary wooden board etc. However, the greatest advantages are obtained when mounting a rail (taken in the widest sense of the word) on a plaster wall with the expansion bolt in accordance with the invention. Naturally, the invention is not limited to the embodiments described above but may be modified in many ways within the scope of the invention such as defined by the claims below.

Claims: C L A I M S 1. An expansion bolt for mounting a rail, a board or the like on a wall having limited thickness, such as a plaster wall, comprising an anchor (16) having an outer screw portion (20) designed for receiving a screw (17), an intermediate slit portion (21) forming anchor legs (26) and an inner sleeve portion (22), the anchor (16) extending along the screw so that the sleeve portion (22) of the anchor is located adjacent the head of the screw, c h a r a c t e r i z e d by a sleeve (19) concentric with the anchor (16) and located between the head of the screw and the anchor (16) and formed to co-operate with the sleeve portion (22) of the anchor (16), which sleeve (19) comprises a collar (27) located adjacent the head of the screw, the bolt in mounting being arranged to be inserted in a through hole in a wall or the like until the collar (27) abuts the outer edge of the hole and the sleeve extends partially through the hole or almost completely through the hole, while the slit portion (21) and the screw portion (20) of the anchor project on the inner .side of the wall, whereupon the screw is tightened until the anchor legs have expanded behind the wall. 2. An expansion bolt according to claim 1, c h a r a c t e r - i z e d in that the sleeve and the sleeve portion (22) of the anchor (16) comprise engagement means (29, 30) co-operating with each other and preventing a relative rotation between the sleeve and the anchor and in that the sleeve (19) possibly comprises engagement means (28) arranged to engage the outer edge of the hole in order to prevent the sleeve and thereby the anchor from rotating relative the hole. 3. An expansion bolt according to claim 1 och 2, c h a r a c¬ t e r i z e d in that the slit portion (21) of the anchor is provided with slits (23) having circular indentations (24) at their ends and semi-circular indentations (25) approximately at their centres, which indentations form bending notches on tightening and expanding the bolt, whereby anchor legs (26) are formed between the slits with a shape that provides a large abutment surface against the inner side of the wall and provides strong support legs preventing deformation thereof. 4. An expansion bolt according to any one of the preceding claims, c h a r a c t e r i z e d in that the sleeve (19) is an inner sleeve located concentrically within the sleeve portion (22) of the anchor (16). 5. An expansion bolt according to any one of claims 1 - 3, c h a r a c t e r i z e d in that the sleeve (19') is an outer sleeve located concentrically outside the sleeve portion (22') of the anchor (16' ). 6. An expansion bolt according to claim 5, c h a r a c t e r ¬ i z e d in that the outer sleeve (19') is provided with an external coating (38) of latex or silicon or similar material, which coating covers the inner surface of the collar for sealing the hole in the wall, and that the coating (38) possibly forms an annular rib (39) at the remote end of the screw from the head, which rib during the expanding of the screw is expanding against the inner edges of the hole in order to secure the sleeve as well as the anchor against rotation. 7. -An expansion bolt according to claim 4, c h a r a c t e r - i z e d in that the anchor at the interface between the sleeve portion (22) and the slit portion (21) comprises a shallow annular recess in which a rubber ring is located and during the expansion of the anchor is pressed against the inner edges of the hole in order to prevent the anchor from rotating in the hole, and that the recess possibly is provided with a plurality of peripherally spaced axial slits, the sleeve (19) being provided with means engaging the slits to press the rubber ring against the edge of the hole when the bolt is tightened and that the rubber ring possibly is formed integral with a rubber sleeve enclosing the sleeve portion of the anchor. 8. An expansion bolt according to any one of the preceding claims for mounting a rail, a board or the like to a wall having limited thickness by means of at least one hole passing through the rail and the wall, c h a r a c t e r i z e d in that the sleeve (19) and the sleeve portion (22) of the anchor together pass through the hole in the rail as well as the hole in the wall to carry the shearing torque that results when the rail and the bolt are loaded, the engagement means (28) possibly engaging a longitudinal groove (32) in the rail. 9. An expansion bolt according to any one of the preceding claims, c h a r a c t e r i z e d in that a fastener (35) having a form complementary to the rail (36) is arranged to enclose the rail, the bolt passing through holes in the fastener (35) as well as the rail (36) and the wall, and that the fastener (35) possibly comprises holes (37) for engagement with engagement means (28'') on the sleeve (19).

Inventors: NILSSON AGNE
Applicants: MTD MEDICAL DEV & TECH LTD, NILSSON AGNE
Application year: 1985
Main classification: E04B1
IPC codes: F16B13