Removable tower sleeve

Abstract

A tower sleeve for sliding engagement with a tower that defines a tower longitudinal axis includes a main body that defines a body longitudinal axis and a channel longitudinally extending therethrough for slidably and selectively receiving at least part of a longitudinal section of the tower therein with the body axis generally parallel to the tower axis. A closing body connectable to said main body is movable between a first limit position and a second limit position relative to the main body. The closing body at least partially closes off the channel when in the first limit position so as to secure the sleeve in sliding engagement with the tower inside the channel, and opens up the channel when in the second limit position so as to allow the sleeve to engage and disengage from the tower in a direction generally transverse relative to the body axis.

Description

FIELD OF THE INVENTION

[0002] The present invention relates to raising platforms, and more particularly to a sleeve or platform that is removable from the tower it is mounted on for displacement there along.

BACKGROUND OF THE INVENTION

[0003] Raising platforms or sleeves are well known in the construction art, as disclosed in U.S. Pat. No. 5,159,993 granted to St-Germain on Nov. 3, 1992; U.S. Pat. No. 5,746,290 granted to St-Germain et al. on May 5, 1998 or U.S. Pat. No. 6,311,800 granted to St-Germain et al. on Nov. 6, 2001. Sleeves, including either a fixed (such as a freight elevator or the like) or a releasable platform, are usually available as pre-assembled onto a lower section of tower or mast along which they are displaced. Alternatively, the sleeves need to be slidably lowered onto the lower section of the tower using a crane or the like.

[0004] Even though some pre-assembled sleeve/tower structures are relatively small, some locations are either physically impossible to reach with a pre-assembled sleeve/tower structure or simply do not allow their assembly on site, depending on the presence of surrounding equipments or on the situation due to the construction stage reached at that specific time.

[0005] Also, in case of failure of the raising mechanism or the like that is usually attached to or mounted on the sleeve, one would need to disassemble to whole tower or scaffolding structure in order to remove the sleeve from the tower for its repair or replacement, which is really time consuming and generally expensive.

[0006] Accordingly, there is a need for an improved tower sleeve or raising platform.

SUMMARY OF THE INVENTION

[0007] It is therefore a general object of the present invention to provide an improved tower sleeve.

[0008] An advantage of the present invention is that the tower sleeve obviates the above noted disadvantages.

[0009] Another advantage of the present invention is that the tower sleeve is easily removable from the tower or mountable thereon, in a direction generally transverse relative to the longitudinal axis of the tower.

[0010] A further advantage of the present invention is that the tower sleeve can be assembled onto or disassembled from the tower in a relatively small or restrained room size.

[0011] Yet another advantage of the present invention is that the tower sleeve can be easily loaded and unloaded from conventional trucks/trailers using a conventional forklift or the like.

[0012] Still another advantage of the present invention is that the tower sleeve can be remotely operated from ground, especially during the self-erecting process.

[0013] Yet a further advantage of the present invention is that the tower sleeve can be removed from the tower that needs to remain on the construction site for supporting a tower crane at the top end thereof.

[0014] According to an aspect of the present invention, there is provided a tower sleeve for sliding engagement with a tower, the tower defining a tower longitudinal axis, the tower sleeve comprises: a main body, the main body defining a body longitudinal axis, the body defining a channel longitudinally extending therethrough for slidably and selectively receiving at least part of a longitudinal section of the tower therein with the body axis generally parallel to the tower axis; a closing body connectable to the main body, the closing body being movable between a first limit position and a second limit position relative to the main body, the closing body at least partially closing off the channel when in the first limit position so as to secure the tower sleeve in sliding engagement with the tower inside the channel, and opening up the channel when in the second limit position so as to allow the tower sleeve to engage and disengage from the tower in a direction generally transverse relative to the body axis.

[0015] In one embodiment, the main body defines generally opposed first and second longitudinal body ends, the closing body being connectable to the main body adjacent at least one of the first and second body ends when in the first limit position.

[0016] In one embodiment, the channel defines generally opposed first and second longitudinal open side edges on the main body, the closing body including generally opposed first and second longitudinal components, the first and second components being connectable to the main body adjacent the first and second open side edges, respectively.

[0017] In one embodiment, the channel has a generally V-shaped cross-section.

[0018] In one embodiment, the channel has a generally U-shaped cross-section.

[0019] Typically, the tower has a generally square-shaped cross-section, the channel having a generally square-shaped cross-section for slidably and selectively receiving at least part of a longitudinal section of the tower therein.

[0020] In one embodiment, the closing body pivotally connects to the main body about a pivot axis generally parallel to the body axis, the closing body being pivotable between the first and second limit positions.

[0021] Typically, the closing body defines first and second body segments, the first body segment pivotally connecting to the main body between the first and second limit positions, the second body segment being for sliding engagement with the tower when the closing body is in the first limit position.

[0022] Typically, the second body segment includes at least one low friction surface member mounted on the first body segment for sliding engagement with the tower when the closing body is in the first limit position.

[0023] Alternatively, the second body segment includes a roller assembly mounted on the first body segment for rolling engagement with the tower when the closing body is in the first limit position.

[0024] Typically, the roller assembly includes a shaft and at least one roller, the shaft having generally opposed first and second longitudinal shaft ends, the first shaft end connecting to the main body, the shaft second end rotatably supporting the at least one roller for rolling engagement with the tower when the closing body is in the first limit position.

[0025] Alternatively, the second body segment includes at least one roller rotatably mounted on the first body segment for rolling engagement with the tower when the closing body is in the first limit position. The first body segment is a shaft, the shaft having generally opposed first and second longitudinal shaft ends, the first shaft end releasably connecting to the main body, the second shaft end rotatably supporting the at least one roller.

[0026] In one embodiment, the closing body includes at least two components, each of the at least two components being connectable to the main body independently from each other, each of the at least two components being movable between the first and second limit positions, each of the at least two components at least partially closing off a respective section of the channel when in the first limit position.

[0027] In one embodiment, the tower further includes first and second tower engaging bodies mounted on the main and closing bodies respectively for sliding engagement with the tower, the first tower engaging body extending inwardly from the main body into the channel, the second tower engaging body extending inwardly from the closing body into the channel when the closing body is in the first limit position.

[0028] Typically, each of the first and second tower engaging bodies includes either a roller assembly for rolling engagement with the tower or a low friction surface member for sliding engagement with the tower.

[0029] In one embodiment, the main body includes at least one actuator assembly for selectively securing and displacing the tower sleeve along the tower when the closing body is in the first limit position.

[0030] Typically, the at least one actuator assembly includes a piston ram mounted generally longitudinally on the main body and a piston head support, the piston ram defining generally opposed first and second longitudinal ram ends, the first ram end pivotally mounting on the main body, the second ram end pivotally mounting on the piston head support, the piston head support slidably securing to the main body.

[0031] Typically, the main body includes a head support guiding rail mounted thereon, the head support guiding rail slidably supporting the piston head support therein. The head support guiding rail includes a low friction surface member mounted thereon for sliding engagement with the piston head support.

[0032] In one embodiment, the closing body includes a securing member, the securing member releasably connecting to the main body for securing the closing body in the first limit position.

[0033] According to an aspect of the present invention, there is provided a tower sleeve for sliding engagement with a tower, the tower defining a tower axis and a tower longitudinal sidewall generally parallel to the tower axis, the tower sleeve comprises: a sleeve longitudinal sidewall for selectively covering at least a longitudinal section of the tower sidewall, the sleeve sidewall including a first longitudinal wall section and a second longitudinal wall section, the first and second longitudinal wall sections being generally transversely adjacent to one another, the second wall section movably connecting to the first wall section; the second wail section being movable between a first limit position and a second limit position, the second wall section being configured and sized so as to secure the tower sleeve in sliding engagement with the tower when in the first limit position, and so as to allow the tower sleeve to engage and disengage from the tower in a direction generally transverse relative to the tower axis when in the second limit position.

[0034] Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further aspects and advantages of the present invention will become better understood with reference to the description in association with the following Figures, in which like reference characters indicate like elements throughout, wherein:

[0036] FIG. 1 is a top perspective view of an embodiment of a tower sleeve in accordance with the present invention, showing the tower sleeve with a U-shaped channel mounted on a tower with a square-shaped cross-section;

[0037] FIG. 2 is a front perspective view of the embodiment of FIG. 1, showing the closing panels in the open limit position;

[0038] FIG. 3 is a side perspective view of the embodiment of FIG. 1, showing the closing panels in the closed limit position;

[0039] FIG. 4 is a top view of the embodiment of FIG. 1, showing the closing panels in the closed limit position with the tower located into the sleeve channel;

[0040] FIG. 5 is an exploded top view similar to FIG. 4, showing the closing panels in the open limit position with the tower moved away from the sleeve channel;

[0041] FIG. 6 is an enlarged partially broken section view taken along line 6 of FIG. 4, showing the tower sleeve mounted on a tower using low friction surface plates;

[0042] FIG. 7 is a schematic view similar to FIG. 6 of another embodiment of a tower sleeve in accordance with the present invention, showing a tower sleeve with a V-shaped channel and roller assemblies for slidably supporting a tower with a triangle-shaped cross-section; and

[0043] FIG. 8 is an enlarged partially broken section view taken along line 8-8 of FIG. 3, showing the sliding engagement between the piston head support and the tower sleeve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] With reference to the annexed drawings the preferred embodiments of the present invention will be herein described for indicative purpose and by no means as of limitation.

[0045] Referring to FIGS. 1 and 2, there is shown an embodiment of a tower sleeve 10 in accordance with the present invention for sliding engagement with a conventional tower 12, or mast used in scaffoldings or the like, that defines a tower longitudinal axis 14. The tower sleeve 10, guided for up-and-down movement along the tower 12 (see arrow A of FIG. 1), is conventionally used to releasably and securely support a platform (not shown) or the like on an interface plate structure 16, as shown in U.S. Pat. No. 5,159,993 granted to St-Germain on Nov. 3, 1992; U.S. Pat. No. 5,746,290 granted to St-Germain et al. on May 5, 1998 or U.S. Pat. No. 6,311,800 granted to St-Germain et al. on Nov. 6, 2001. One skilled in the art would understand that the tower sleeve 10 could be an integral part of a platform that moves up and down along the tower 12 without departing from the scope of the present invention.

[0046] The sleeve 12 includes a main body 18 and a closing body 20 connectable thereto. The main body 18 defines a body longitudinal axis 22 and includes a channel 24 longitudinally extending therethrough for slidably and selectively receiving a longitudinal section of the tower 12 therein, with the sleeve axis 22 generally parallel to the tower axis 14. The sleeve 10 typically forms a sleeve longitudinal sidewall 11 that selectively covers a longitudinal section of the tower 12. The sleeve sidewall 11 includes first and second longitudinal wall sections thereof formed by the main body 18 and the closing body 20 respectively.

[0047] The closing body 20, or second wall section, is movable between a first closed limit position and a second open limit position relative to the main body 18, or first wall section. The closing body 20 at least partially closes off the channel 24 when in the first closed limit position so as to secure the sleeve 10 in sliding engagement with the tower 12 inside the channel 24, as shown in FIGS. 13, and 4, and opens up the channel 24 when in the second open limit position, as shown in FIGS. 2 and 5, so as to allow the sleeve 10 to engage and disengage from the tower 12 in a direction generally transverse relative to the sleeve axis 22, as indicated by arrow B in FIG. 5.

[0048] Typically, the channel 24, and the sleeve sidewall 11, have a generally U-shaped cross-section. As shown in FIGS. 4 and 5, the tower has a generally square-shaped cross-section and the channel 24 also has a generally square-shaped cross-section for slidably and selectively receiving a longitudinal section of the tower 12 therein.

[0049] The main body 18 defines generally opposed first and second longitudinal body ends 26, 28, and the closing body 20 is connectable to the main body 18 adjacent at least one of the first and second body ends 26, 28 when in the open position.

[0050] The channel 24 defines two generally opposed longitudinal open side edges 30 on the main body 18 extending between the first and second body ends 26, 28.

[0051] The closing body 20 includes two generally opposed components 32, preferably longitudinal, that are independently and releasably connectable to the main body 18 adjacent a respective one of the open side edges 30. Preferably, the closing body 20 defines a slit 33 extending there along. The slit 33 allows for the sleeve 10 to clear some wall anchors (not shown) retaining the tower 12 along a building structure (not shown) during its up-and-down movement along the tower 12, as illustrated in U.S. Pat. Nos. 5,159,993 and 5,259,479 granted to St-Germain on Nov. 3, 1992 and Nov. 9, 1993, respectively. Typically, each longitudinal component 32 is pivotally connected to the main body 18 about a pivot axis 34 generally parallel to the sleeve axis 22 so as to form door panels 36 pivotable between the open and closed limit positions using conventional hinges 38 or the like, as indicated by arrow C of FIGS. 2 and 5, in a similar fashion than well known double doors or French doors. In order to releasably secure the panels 36 to the main body 18 when in the closed limit position, a securing member, typically bolts 40 or the like fasteners are located along the panels 36. Also, some locking mechanism (not shown) could be used for latching the panels 36 in their open limit position. Although not shown in the Figures, the closing body 20 could eventually be a single panel closing off the entire channel opening and securing to both open side edges 30 when in the closed limit position without departing from the scope of the present invention.

[0052] In order to ensure a proper sliding engagement between the sleeve 10 and the tower 12 during the up-and-down displacement of the sleeve 10 along the tower 12, the sleeve 10 includes first and second tower engaging bodies 42, 44 mounted on the main and closing bodies 18, 20 respectively. The first tower engaging body 42 extends generally inwardly from the main body 18 into the channel 24, and the second tower engaging body 44 extends generally inwardly from the closing body 20 into the channel 24 when the closing body 20 is in the closed limit position.

[0053] As shown in FIGS. 1 to 6, each first and second tower engaging bodies 42, 44 includes at least one low friction surface member 46, including conventional guiding bushings mode out of plastic-type materials such as Teflon T™ or the like, for the sliding, and abutting, engagement with the tower 12, preferably at the corners thereof.

[0054] Referring more specifically to FIGS. 4 to 6, the closing body 20, or each panel 36 thereof, defines first and second panel segments 48, 50 connected to each other. Alternatively, the first and second panel segments 48, 50 are integral with each other. The first panel segment 48 pivotally connects to the main body 18 between the closed and open limit positions while the second panel segment 50 is for sliding engagement with the tower 12 when the panel 36 is in the closed limit position.

[0055] Typically, the second panel segment 50 includes at least one low friction surface member 46 of the second tower engaging body 44 secured to the first panel segment 48 for sliding, and abutting, engagement with the tower 12 when the panel 36 is in the closed limit position.

[0056] Now referring more specifically to FIG. 7, there is shown another embodiment of a tower sleeve 10′ in accordance with the present invention for sliding engagement with a conventional tower 12′ having a generally triangle-shaped cross-section. Accordingly, the channel 24′, and the sleeve sidewall 11′, have a generally V-shaped cross-section for slidably and selectively receiving a longitudinal section of the tower 12′ therein.

[0057] In this embodiment 10′, the first second tower engaging bodies 42, 44 are roller assemblies 52 rotatably mounted on the main and closing bodies 18′, 20′, respectively, for rolling, and abutting, engagement with the tower 12′ when the closing body 20′ is in the closed limit position; which is sufficient for relatively low load capacity rated sleeve 10 with platform.

[0058] Accordingly, the first body segment 48′ of each closing body component 32 is a roller assembly 52. The roller assembly 52 has a shaft 54 defining generally opposed first and second longitudinal shaft ends 56, 58. The first shaft end 56 releasably connects to the main body 18′ and the second shaft end rotatably supports, typically using conventional roller bearings (not shown) or the like, at least one roller 60 thereon, the latter being in rolling engagement with the tower 12′ when the component 32 is in the closed limit position. The roller 60 forms the second body segment 50′.

[0059] Obviously, although the second tower engaging body 44 includes roller assemblies 52, the first tower engaging body 42 could remain with low friction surface member 46, or vice and versa, without departing from the scope of the present invention.

[0060] Referring back to FIGS. 1 to 3, the main body 18 of sleeve 10 includes at least one, typically two generally opposed actuator assemblies 62 for selectively securing and actuating displacement the sleeve 10 along the tower 12 when the closing body 20 is in the closed limit position. Each actuator assembly 62 includes a piston ram 64, preferably a double-acting hydraulic ram, mounted generally longitudinally on the main body 18 and a piston head support 66. The piston ram 64 defines generally opposed first and second longitudinal ram ends 68, 70. The first ram end 68, or cylinder, pivotally mounts on the main body 18, preferably at the second body end 28 and the second ram end 70, or piston rod, pivotally mounts on the piston head support 66, the latter slidably securing to the main body 18.

[0061] The main body 18 includes a head support guiding rail 72 mounted thereon to slidably support the piston head support 66 therein. The head support guiding rail 72 includes a low friction surface member 74, including conventional guiding bushings mode out of plastic-type materials such as Teflon TM or the like, mounted thereon for sliding engagement with the piston head support 66, as shown in FIG. 8.

[0062] Each second ram end 70 is provided with a hook 76 pivotally mounted thereon. The hooks 76 successively engage, and disengage, generally horizontally oriented rungs 78 of the tower 12. The rungs 78 are substantially equally spaced apart along the tower 12. Each hook 76 pivots between a hooking position in which the hook 76 engages a rung 78 of the tower 12 and an unhooking position in which the hook 76 cannot engage the rungs 78. A hook biasing means (not shown) biases the hook 76 in its hooking position. In the upward movement of the sleeve 10, the top end surface of the hook 76 abuts the next higher rung 78 and forces the hook 76 to momentarily pivot in the unhooking position while passing at the rung level. In the downward movement of the sleeve 10, a conventional operator-activated unhooking means (not shown) for maintaining the hook 76 in the unhooking position is activated by an operator (not shown) to allow the hook 76 to clear the rungs 78 while passing at the rung level, as explained in further details in U.S. Pat. No. 5,746,290 granted to St-Germain et al. on May 5, 1998. Obviously, different types of actuator mechanism could be used without departing from the scope of the present invention.

[0063] At least one well known conventional safety/emergency braking system 80 is mounted on the main body 18 to prevent any accidental downward movement of the sleeve 10 along the tower 12; such typical safety/emergency braking system 80 are illustrated in U.S. Pat. No. 5,159,993 granted to St-Germain on Nov. 3, 1992; U.S. Pat. No. 5,746,290 granted to St-Germain et al. on May 5, 1998 or U.S. Pat. No. 6,311,800 granted to St-Germain et al. on Nov. 6, 2001.

[0064] Preferably, the sleeve 22 carries its own power system unit 82 to activate the hydraulic rams 64.

[0065] Although the embodiments shown and described hereinabove have their channel 24 substantially entirely receiving a section of the tower 12 therein with the closing body 20 being substantially a door or the like to close off the channel 24, one skilled in the art would understand that the channel 24 could receive only a portion (such as a first half) of such a section of the tower with the closing body 20 covering the remaining portion of the tower section (the other half) without departing from the scope of the present invention.

[0066] Although the present tower sleeve has been described with a certain degree of particularity it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope and spirit of the invention as hereinafter claimed.

Claims

1. A tower sleeve for sliding engagement with a tower, said tower defining a tower longitudinal axis, said tower sleeve comprising: a main body, said main body defining a body longitudinal axis, said body defining a channel longitudinally extending therethrough for slidably and selectively receiving at least part of a longitudinal section of the tower therein with said body axis generally parallel to the tower axis; a closing body connectable to said main body, said closing body being movable between a first limit position and a second limit position relative to said main body, said closing body at least partially closing off said channel when in said first limit position so as to secure said tower sleeve in sliding engagement with the tower inside said channel, and opening up said channel when in said second limit position so as to allow said tower sleeve to engage and disengage from the tower in a direction generally transverse relative to said body axis.

2. The sleeve of claim 1, wherein said main body defines generally opposed first and second longitudinal body ends, said closing body being connectable to said main body adjacent at least one of said first and second body ends when in said first limit position.

3. The sleeve of claim 1, wherein said closing body pivotally connects to said main body about a pivot axis generally parallel to said body axis, said closing body being pivotable between said first and second limit positions.

4. The sleeve of claim 1, wherein said channel defines generally opposed first and second longitudinal open side edges on said main body, said closing body including generally opposed first and second longitudinal components, said first and second components being connectable to said main body adjacent said first and second open side edges, respectively.

5. The sleeve of claim 1, wherein said channel has a generally V-shaped cross-section.

6. The sleeve of claim 1, wherein said channel has a generally U-shaped cross-section.

7. The sleeve of claim 6, wherein the tower has a generally square-shaped cross-section, said channel having a generally square-shaped cross-section for slidably and selectively receiving at least part of a longitudinal section of the tower therein.

8. The sleeve of claim 3, wherein said closing body defines first and second body segments, said first body segment pivotally connecting to said main body between said first and second limit positions, said second body segment being for sliding engagement with the tower when said closing body is in said first limit position.

9. The sleeve of claim 8, wherein said second body segment includes at least one low friction surface member mounted on said first body segment for sliding engagement with the tower when said closing body is in said first limit position.

10. The sleeve of claim 8, wherein said second body segment includes a roller assembly mounted on said first body segment for rolling engagement with the tower when said closing body is in said first limit position.

11. The sleeve of claim 10, wherein said roller assembly includes a shaft and at least one roller, said shaft having generally opposed first and second longitudinal shaft ends, said first shaft end connecting to said main body, said shaft second end rotatably supporting said at least one roller for rolling engagement with the tower when said closing body is in said first limit position.

12. The sleeve of claim 1, wherein said closing body defines first and second body segments, said first body segment releasably connecting to said main body, said second body segment being for sliding engagement with the tower when said closing body is in said first limit position.

13. The sleeve of claim 12, wherein said second body segment includes at least one roller rotatably mounted on said first body segment for rolling engagement with the tower when said closing body is in said first limit position.

14. The sleeve of claim 13, wherein said first body segment is a shaft, said shaft having generally opposed first and second longitudinal shaft ends, said first shaft end releasably connecting to said main body, said second shaft end rotatably supporting said at least one roller.

15. The sleeve of claim 12, wherein said second body segment includes at least one low friction surface member mounted on said first body segment for sliding engagement with the tower when said closing body is in said first limit position.

16. The sleeve of claim 1, wherein said closing body includes at least two components, each of said at least two components being connectable to said main body independently from each other, each of said at least two components being movable between said first and second limit positions, each of said at least two components at least partially closing off a respective section of said channel when in said first limit position.

17. The sleeve of claim 1, further including first and second tower engaging bodies mounted on said main and closing bodies respectively for sliding engagement with the tower, said first tower engaging body extending inwardly from said main body into said channel, said second tower engaging body extending inwardly from said closing body into said channel when said closing body is in said first limit position.

18. The sleeve of claim 17, wherein each of said first and second tower engaging bodies includes a roller assembly for rolling engagement with the tower.

19. The sleeve of claim 17, wherein each of said first and second tower engaging bodies includes a low friction surface member for sliding engagement with the tower.

20. The sleeve of claim 1, wherein said main body includes at least one actuator assembly for selectively securing and displacing said tower sleeve along the tower when said closing body is in said first limit position.

21. The sleeve of claim 20, wherein said at least one actuator assembly includes a piston ram mounted generally longitudinally on said main body and a piston head support, said piston ram defining generally opposed first and second longitudinal ram ends, said first ram end pivotally mounting on said main body, said second ram end pivotally mounting on said piston head support, said piston head support slidably securing to said main body.

22. The sleeve of claim 21, wherein said main body includes a head support guiding rail mounted thereon, said head support guiding rail slidably supporting said piston head support therein.

23. The sleeve of claim 22, wherein said head support guiding rail includes a low friction surface member mounted thereon for sliding engagement with said piston head support.

24. The sleeve of claim 1, wherein said closing body includes a securing member, said securing member releasably connecting to said main body for securing said closing body in said first limit position.

25. A tower sleeve for sliding engagement with a tower, said tower defining a tower axis and a tower longitudinal sidewall generally parallel to the tower axis, said tower sleeve comprising: a sleeve longitudinal sidewall for selectively covering at least a longitudinal section of the tower sidewall, said sleeve sidewall including a first longitudinal wall section and a second longitudinal wall section, said first and second longitudinal wall sections being generally transversely adjacent to one another, said second wall section movably connecting to said first wall section; said second wall section being movable between a first limit position and a second limit position, said second wall section being configured and sized so as to secure said tower sleeve in sliding engagement with the tower when in said first limit position, and so as to allow said tower sleeve to engage and disengage from the tower in a direction generally transverse relative to the tower axis when in said second limit position.