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Title:
SHUTTLE FOR A CLIMBING PROTECTION SYSTEM
Document Type and Number:
WIPO Patent Application WO/2016/093850
Kind Code:
A1
Abstract:
A rope grab or shuttle (20) is provided for a climbing protection system (10) and includes a frame (22), a guide structure (24), a clamping member (26), a blocking member (28), and a locking member (30). The guide structure (24) is configured to receive a cable (12) and to guide the shuttle (20) along the cable (12). The clamping member (26) is mounted for movement between a free position wherein the shuttle (20) can move freely along the cable (12) and a clamping position wherein the clamping member (26) engages against the cable (12) to resist movement of the shuttle (20) relative to the cable (12). The blocking member (28) is mounted for movement between a closed position blocking removal of the cable (12) from the guide structure (24) and an open position where the blocking member (28) does not block removal of the cable (12) from the guide structure (24). The locking member (30) is mounted for movement between a locked position and an unlocked position. The clamping member (26) is also movable to an opening position from the free position. The locking member (30) in the locked position prevents movement of the clamping member (26) to the opening position. The clamping member (26) is operably engaged with the blocking member (28) to move the blocking member (28) from the closed position to the open position as the clamping member (26) is moved from the free position to the opening position.

Inventors:
EMICH FRANK (US)
Application Number:
PCT/US2014/069906
Publication Date:
June 16, 2016
Filing Date:
December 12, 2014
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HONEYWELL INT INC (US)
International Classes:
A62B1/14; A62B35/00; A62B35/04; E06C7/18
Domestic Patent References:
WO2008046446A12008-04-24
Foreign References:
US20140020983A12014-01-23
US20070119653A12007-05-31
AU2008300650B22013-05-23
US20070119653A12007-05-31
AU2008300650B22013-05-23
Attorney, Agent or Firm:
BEATUS, Carrie (Patent Services M/S AB/2B101 Columbia Road,P. O. Box 224, Morristown New Jersey, US)
Download PDF:
Claims:
CLAi S

1 . A shuttle (20) for a climbing protection system (10) wherein the shuttle (20) can be connected to a user and is guided along a cable, rope, or other elongate support member (12) as the user climbs and grips the elongate support member (12) in response to the user failing, the shuttle (20) comprising:

a frame (22);

a guide structure (24) on the frame (22) and configured to receive an elongate support member (12) and to guide the shuttle (20) along the elongate support member (12) as a user attached to the shuttle (20) climbs;

a clamping member (26) mounted on the frame (22) for movement between a free position wherein the shuttle (20) can move freely along the elongate support member (12) received in the guide structure (24) and a clamping position wherein the clamping member (26) engages against the elongate support member (12) in the guide structure (24) to resist movement of the shuttle (20) relative to the elongate support member (12), the clamping member (26) configured to move from the free position to the clamping position in response to a downward movement by the user attached to the shuttle (20);

a blocking member (28) mounted on the frame (22) for movement between a closed position blocking removal of the elongate support member (12) from the guide structure (24) and an open position where the blocking member (28) does not block removal of the elongate support member (12) from the guide structure (24); and

a locking member (30) mounted on the frame (22) for movement between a locked position and an unlocked;

wherein the damping member (26) is movable to an opening position from the free position, the locking member (30) in the locked position prevents movement of the clamping member (26) to the opening position, and the clamping member (26) is operabiy engaged with the blocking member (28) to move the blocking member (28) from the closed position to the open position as the clamping member (26) is moved from the free position to the opening position.

2. The shuttle (20) of claim 1 wherein the locking member (30) is operably engaged with the blocking member (28) to prevent movement of the blocking member (28) from the closed position to the open position with the locking member (30) in the locked position and to allow movement of the blocking member (28) from closed position to the open position with the locking member (30) in the unlocked position,

3. The shuttle (20) of any of the preceding claims wherein the clamping member (26) comprises a damping feature (48) configured to undergo permanent deformation in response to a fall of a user attached to the shuttle (20); and the frame (22) comprises two plate members (34,36) located on opposite sides of the locking, clamping and blocking members (26,28,30), with one of the two plate members (34,36) being a single piece that defines the guide structure (24).

4. The shuttle (20) of any of the preceding claims wherein the clamping member (26) is a clamping lever (41 ) mounted on the frame (22) to pivot between the free, clamping, and opening positions.

5. The shuttle (20) of any of the preceding claims wherein the damping member (26) comprises an clamping surface (44) that engages the elongate support member (12) received in the guide structure (24) with the clamping member (26) in the clamping position, and further comprises a connection feature (46) configured to receive a connector for attaching a user to the shuttle (20), the connection feature (46) being spaced from the clamping surface (44) and the clamping member (26) being pivot mounted to the frame (22) at a location between the connection feature (46) and the clamping surface (44).

6. The shuttle (20) of any of the preceding claims wherein the locking member (30) is a locking lever (70) mounted on the frame (22) to pivot between the locked and unlocked position.

7. The shuttle (20) of any of the preceding claims wherein the blocking member (28) is a blocking plate (28) mounted on the frame (22) to translate between the closed and open positions.

8. The shuttle (20) of any of the preceding claims wherein the frame (22) comprises at least one surface that engages a surface on the blocking member (28) to guide the blocking member (28) for translation between the dosed and open positions.

9. The shuttle (20) of any of the preceding claims wherein the frame (22) comprises at least one cylindrical post (40) that is received in a slot (50,52,54) formed in the blocking member (28), the slot (50,52,54) configured so that engagement of the post (40) in the slot (50,52,54) guides the blocking member (28) for translation between the closed and open positions.

10. The shuttle (20) of any of the preceding claims wherein the clamping member (26) comprises a surface that engages a surface on the blocking member (28) to move the blocking member (28) between the closed and open positions as the clamping member (26) moves between the free and opening positions.

1 1 . The shuttle (20) of any of the preceding claims wherein the locking member (30) comprises a surface that engages a surface on the blocking member (28) to prevent the blocking member (28) from moving from the closed position to the open position with the locking member (3(3) in the locked position, and to allow the blocking member (28) to move from the closed position to the open position with the locking member (30) in the unlocked position.

12. The shuttle (20) of any of the preceding claims wherein the locking member (30) comprises a surface that engages a surface on the clamping member (26) to prevent the damping member (26) from moving from the free position to the opening position with the locking member (30) in the locked position.

13. The shuttle (20) of any of the preceding claims wherein the clamping member (26) comprises a post (60) and the blocking member (28) comprises a slot (56) receiving the post (60), the slot (56) configured so that engagement of the post (60) in the slot (56) moves the blocking member (28) from the closed position to the open position as the clamping member (26) is moved from the free position to the opening position.

14. The shuttle (20) of any of the preceding claims wherein the locking member (30) comprises a post (62) and the blocking member (28) comprises a slot (58) receiving the post (62), the slot (58) configured so that engagement the post (62) in the slot prevents movement of the blocking member (28) from the closed position to the open position with the locking member (30) in the locked position and allows movement of the blocking member (28) from the closed position to the open position with the locking member (30) in the unlocked position.

15. The shuttle (20) of claim 1 wherein the clamping member (26) is a clamping lever (41 ), the locking member (30) is a locking lever (70), the blocking member (28) is a blocking plate (28), the clamping lever (41 ) and the blocking plate (28) comprise a mating slot and post combination (56,60) configured so that engagement of the post (60) in the slot (56) moves the blocking plate (28) from the closed to the open position as the clamping lever (41 ) moves from the free position to the opening position, and the locking lever (70) and the blocking plate (28) comprise another mating slot and post combination (58,62) configured so that engagement of the post (62) in the slot (58) prevents the blocking plate (28) from moving to the open position from the ciosecl position with the locking lever (70) in the locked position and allows the blocking plate (28) to move to the open position from the closed position with the locking lever (70) in unlocked position.

Description:
SHUTTLE FOR A CLIMBING PROTECTION SYSTEM

FIELD

[0001] The present disclosure relates to rope grabs or shuttles for a climbing protection system for preventing a user of a ladder, a platform or the like from falling. Such shuttles are guided along an elongate support member, typically a cable, and grip the cable if a user fails. These shuttles have a guiding mechanism for the cable and often have a rotatabiy mounted clamping lever which has a cam at a first end facing the cable and an anchor point at a second end protruding from the casing of the shuttle.

BACKGROUND

[0002] Climbing protection systems usually consist of an elongate member, for example a wire cable, and a following fail arrester guided on the cable, which is hereafter called a rope grab or shuttle. The cable can be fastened to a structure or the like by means of cable and attachments, a cable tensioner and fastening devices. A user of the climbing protection system is connected by means of a full body harness to the shuttle which follows the user. The full body harness is usually connected to a clamping lever of the shuttle which, if a user fails, ensures that the shuttle grips the cable of the climbing protection system, in order to thus prevent the free fall of the user.

[0003] A shuttle of the type described above is generally known, to which it is also possible to fasten a carabineer which connects a user's full body harness to the shuttle. In order to attach the shuttle to, or separate it from, the cable, a closing lever is released and a clamping lever, to which the carabineer is fastened, is swiveied upwards. If the user fails, a clamping jaw of the clamping lever is pressed against the cable. Furthermore, when the shuttle is used, the clamping jaw closes the gap along the guiding mechanism of the shuttle.

[0004] One example of such a shuttle was offered for sale under the product name 8.K.C. by Antec (now Sperian Fall Protection), 35-37 rue de la Bidauderie, BP334, 18103 Vierzon, France. A carabineer, which connects a user's full body harness to the shuttle, is fastened in an eye at one end of a clamping lever. The damping lever is rotatably mounted in the shuttle and is swiveled in the event of a fall by the pull exerted on it by the full body harness, with the result that the cam of the clamping lever presses against the cable guided in the guiding mechanism of the shuttle and the shuttle grips the cable. Furthermore, when the shuttle is used, the damping lever closes a gap along the guiding mechanism, which must be opened to attach the shuttle to the cable. In addition, when the shuttle is used, the gap is closed by a plastic lever which has to be folded back first before the shuttle can be removed from the cable. In order to prevent inadvertent release of the shuttle from the cable, the carabineer must be separated from the shuttle, as otherwise the clamping lever cannot be swiveled far enough to free the gap.

[0005] A problem with shuttles for a climbing protection system of the types described above is that they are not always suitable for use in a climbing protection system the cable of which is secured to a structure or the like by intermediate supports or bracket, as the shuttle cannot be moved over such intermediate supports. The shuttle must be passed manually over such intermediate supports.

[0006] US 2007/01 19653 A1 describes a climbing protection device consisting of a cable tensioned by several intermediate supports and a fall arrest device which can be moved along the cable. The fail arrest device has a U-shaped member, which encloses the cable of the climbing protection device, and a holder cam, which is rotatably mounted. In the event of a fall, the cable is clamped between the holder cam and the U-shaped member, with the result that the fall arrest device is locked in place on the cable. The fall arrest device can be removed from or attached to the cable at any time. For this purpose two mechanisms which are independent of each other must be actuated. The two mechanisms are arranged so that they cannot be actuated with one hand.

[0007] AU 2008/300650 B2 shows another example of a climbing protection device similar to the above-described devices, but having a locking or blocking plate that is spring biased to a position that reduces a gap through which the cable can be inserted and/or removed into engagement with the shuttle, and provides a user actuated button that releases this plate so that a user can move the plate to a position that opens the gap, thereby allowing a cable to be removed from engagement with the shuttle or inserted into engagement with the shuttle.

SUMMARY

[0008] In accordance with one feature of this disclosure, a shuttle for a climbing protection system is provided wherein the shuttle can be connected to a user and is guided along a cable, rope, or other elongate support member as the user climbs and grips the elongate support member in response to the user falling. The shuttle includes a frame, a guide structure, a clamping member, a blocking member, and a locking member. The guide structure is located on the frame and configured to receive an elongate support member and to guide the shuttle along the elongate support member as a user attached to the shuttle climbs. The clamping member is mounted on the frame for movement between a free position wherein the shuttle can move freely along the elongate support member received in the guide structure and a clamping position wherein the clamping member engages against the elongate support member in the guide structure to resist movement of the shuttle relative to the elongate support member. The clamping member is configured to move from the free position to the clamping position in response to a downward movement by the user attached to the shuttle. The blocking member is mounted on the frame for movement between a closed position blocking removal of the elongate support member from the guide structure and an open position where the blocking member does not block removal of the elongate support member from the guide structure. The locking member is mounted on the frame for movement between a locked position and an unlocked position. The clamping member is also movable to an opening position from the free position. The locking member in the locked position prevents movement of the damping member to the opening position. The damping member is operably engaged with the blocking member to move the blocking member from the closed position to the open position as the clamping member is moved from the free position to the opening position.

[0009] In one feature, the locking member is operably engaged with the blocking member to prevent movement of the blocking member from the closed position to the open position with the locking member in the locked position and to allow movement of the blocking member from dosed position to the open position with the locking member in the unlocked position.

[0010] As one feature, the frame includes two plate members located on opposite sides of the locking, clamping and blocking members, with one of the two plate members being a single piece that defines the guide structure.

[001 1] In one feature, the clamping member includes a damping feature configured to undergo permanent deformation in response to a fail of a user attached to the shuttle.

[0012] According to one feature, the clamping member is a clamping lever mounted on the frame to pivot between the free, clamping, and opening positions.

[0013] As one feature, the clamping member includes a clamping surface that engages the elongate support member received in the guide structure with the clamping member in the clamping position, and further includes a connection feature configured to receive a connector for attaching a user to the shuttle, the connection feature being spaced from the clamping surface and the clamping member being pivot mounted to the frame at a location between the connection feature and the clamping surface. [0014] In one feature, the locking member is a locking lever mounted on the frame to pivot between the locked and unlocked position,

[0015] According to one feature, the blocking member is a blocking plate mounted on the frame to translate between the closed and open positions.

[0016] As one feature, the frame includes at least one surface that engages a surface on the blocking member to guide the blocking member for translation between the closed and open positions.

[0017] In one feature, the frame includes at least one cylindrical post that is received in a slot formed in the blocking member. The slot is configured so that engagement of the post in the slot guides the blocking member for translation between the closed and open positions.

[0018] According to one feature, the clamping member includes a surface that engages a surface on the blocking member to move the blocking member between the closed and open positions as the clamping member moves between the free and opening positions.

[0019] As one feature, the locking member includes a surface that engages a surface on the blocking member to prevent the blocking member from moving from the closed position to the open position with the locking member in the locked position, and to allow the blocking member to move from the closed position to the open position with the locking member in the unlocked position.

[0020] In one feature, the locking member includes a surface that engages a surface on the clamping member to prevent the damping member from moving from the free position to the opening position with the locking member in the locked position.

[0021] According to one feature, the clamping member includes a post and the blocking member includes a slot receiving the post. The slot is configured so that engagement of the post in the slot moves the blocking member from the closed position to the open position as the clamping member is moved from the free position to the opening position.

[0022] As one feature, the locking member includes a post and the blocking member includes a slot receiving the post. The slot is configured so that engagement the post in the slot prevents movement of the blocking member from the closed position to the open position with the locking member in the locked position and allows movement of the blocking member from the closed position to the open position with the locking member in the unlocked position.

[0023] In one feature, the clamping member is a clamping lever, the locking member is a locking lever, the blocking member is a blocking plate, the clamping lever and the blocking plate include a mating slot and post combination configured so that engagement of the post in the slot moves the blocking plate from the closed to the open position as the clamping lever moves from the free position to the opening position, and the locking lever and the blocking plate include another mating slot and post combination configured so that engagement of the post in the slot prevents the blocking plate from moving to the open position from the closed position with the locking lever in the locked position and allows the blocking plate to move to the open position from the closed position with the locking lever in unlocked position.

[0024] It should be understood that a shuttle according to this disclosure can include any combination of the above described features.

[0025] Other features and advantages will become apparent from a review of the entire specification, including the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Fig. 1 is a isometric view of a fail protection system including a shuttle according to this disclosure; [0027] Fig, 2 is a side elevation view of the shuttle shown in Fig. 1 ;

[0028] Fig, 3 is a view similar to Fig, 2, but with a frame component of the shuttle not shown for purposes of illustration; and

[0029] Figs. 4-7 are views similar to Fig. 3, but showing various components of the shuttle in their different operating positions relative to each other.

DETAILED DESCRIPTION

[0030] With reference to Fig. 1 , a fall protection system 10 is shown and includes an elongate support member 12 in the form of a wire cable 12, a support bracket 14 for anchoring and supporting the cable 12 to a support structure, such as a wall or structural beam (not shown), and a rope grab or shuttle 20 that can be connected to a user so as to protect the user in the event of a fall. The shuttle 20 is guided along the cable 12 as the user connected to the shuttle climbs in the upward direction, such as indicated by the arrow "A" in Fig. 1 . It should be appreciated that there are many forms of elongate members 12 and support brackets 14 that are known in the art and are suitable within the scope of this disclosure for use with a shuttle 20 according to this disclosure. Accordingly, the details of the elongate member 12 and the bracket 14 are not critical to an understanding of the shuttle 20 as disclosed herein and will not be described in further detail.

[0031] As best seen in Figs. 3-7, the shuttle 20 includes a frame, shown generally at 22, a guide structure 24 on the frame, a clamping member 26 mounted on the frame 22, a blocking member 28 mounted on the frame 22, and a locking member 30 mounted on the frame 22. The guide structure 24 is configured to receive the elongate support member 12 and to guide the shuttle 20 along the elongate support member 12 as a user attached to the shuttle 20 climbs, in this regard, in the illustrated embodiment, the guide structure 24 has an elongate, semi- cylindrical channel 32 that conforms to the outer surface shape of the elongate member 12, which is cylindrical for the illustrated cable 12. [0032] The clamping member 26 is mounted to the frame 22 for movement between a free position shown in Figs. 4-6 wherein the shuttle 20 can move freely along the length of the elongate support member 12 and a clamping position shown in Figs. 2 and 3 wherein the clamping member 26 engages against the elongate support member 12 in the guide structure 24 to resist or prevent movement of the shuttle 20 relative to the elongate support member 12, thereby arresting the fall of a user. In this regard, the clamping member 26 is configured to move from the free position shown in Figs. 4-6 to the clamping position shown in Figs. 2 and 3 in response to a downward fall by a user attached to the shuttle 20.

[0033] The blocking member 28 is mounted on the frame 22 for movement between a closed position shown in Figs. 1 -3 blocking removal of the elongate support member 12 from the guide structure 24 and an open position shown in Fig. 7 where the blocking member 28 does not block removal of the elongate member 12 from the guide structure 22. In this regard, with reference to Figs. 3 and 7, there is a gap G between the blocking member 28 and the guide structure 24 that is smaller than the cross-sectional dimension, such as the diameter D, of the elongate support member 12 when the blocking member 28 is in the closed position shown in Fig. 3, but that increases to a size that is larger than the cross-sectional dimension D of the elongate support member 12 when the blocking member 20 is moved to the open position shown in Fig. 7, which allows for the elongate member 12 to be removed from the guide structure 24 and the shuttle 20. in some embodiments of the shuttle 20, the size of the gap G in the ciosed position shown in Fig. 3 is sufficient to allow movement of the shuttle 20 along the length of the elongate support member 12 past the support bracket 14. However, in some embodiments of the shuttle 20, it may be desirable for the gap G to be of a size that does not allow movement of the shuttle 20 past the support bracket 14.

[0034] The locking member 30 is mounted on the frame 22 for movement between a locked position shown in Figs. 1 -5 wherein the locking member 30 prevents movement of the blocking member 28 from the closed position to the open position, and an unlocked position shown in Figs. 6 and 7 wherein the locking member 30 does not prevent movement of the blocking member 28 from the closed position to the open position.

[0035] The clamping member 26 is mounted so that it is also moveable to an opening position shown in Fig. 7 from the free position shown in Figs. 4-6. in the locked position shown in Figs. 1 -4, the locking member 30 prevents movement of the clamping member 26 to the opening position, but when the locking member is in the unlocked position shown in Figs. 6 and 7 the locking member 30 allows movement of the clamping member 26 to the opening position. The clamping member 26 is operably engaged with the blocking member 28 to move the blocking member 28 from the closed position shown in Figs. 1 -3 to the open position shown in Fig. 7 as the clamping member 26 is moved from the free position shown in Figs. 4 and 5 to the opening position shown in Fig. 7.

[0036] Having broadly described the structure and operational features of the shuttle 20, each of the specific components 22, 24, 26, 28 and 30 of the illustrated embodiment will be described in more detail below. However, it should be understood that the illustrated embodiment and associated details describe only one of many contemplated configurations capable of meeting the structural and operational features described above.

[0037] In the illustrated embodiment, the frame 24 is composed of two plate structures 34 and 36 that are joined together with suitable fasteners 38 that pass through corresponding cylindrical posts or spacers 40 of the frame 24. The plate structure 34 is a one-piece structure and defines the guide structure 24 and its channel 32. it should be appreciated that the frame plates 34 and 36 can be formed using any suitable means and material, such as being formed metal plate or a suitable molded structural material.

[0038] As best seen in Figs. 2 and 3, the clamping member 26 of the illustrated embodiment is a clamping lever 41 and includes a cam end 42 having a clamping surface 44 that engages the elongate support member 12 and an anchor or connecting feature in the form of a circular eye 46 that is spaced from the clamping surface 44 and configured for connection to a user using any suitable means, such as, for example, a carabineer that is inserted through an opening 47 of the connection feature 48. In the illustrated embodiment, the clamping member 26 includes an optional damping feature, shown generally at 48, which allows the connection feature 46 to move relative to the remainder of the clamping member 26 and the shuttle 20 via permanent deformation of the damping feature 48. Such damping features are known and are described in more detail in WO 2008/046446 A1 . Intermediate the clamping surface 44 and the connection feature 46, the clamping member 26 is pivot mounted to the frame 22 using any suitable means, such as a cylindrical journal feature on the post 40A that passes through a bearing bore formed in the clamping member 26. This allows the clamping member 26 to pivot relative to the frame 22 between the clamping position, the free position, and the opening position. As best seen in Fig. 5, the clamping member 28 further includes a first abutment surface 49 that abuts the locking member 30 to prevent movement of the clamping member 26 from the free position to the opening position.

[0039] The blocking member 28 is provided in the form of a blocking or locking plate 28 having a plurality of guide slots 50, 52, 54, 56 and 58 formed therein, with each the guide slots 50, 52 and 54 receiving a respective one of the cylindrical posts 40. The slot 56 is engaged by a cylindrical post/stud 60 carried on the clamping member 26 for movement therewith, and the slot 58 receives a cylindrical post/stud 62, carried on the locking member 30 for movement therewith. The respective outer surfaces of the posts 40, 60 and 62 and the inner surfaces of the slots 50-58 serve to guide and move the blocking member 28 between its closed position shown in Figs. 2 and 3 and its open position shown in Fig. 7, as will be described in more detail below.

[0040] The locking member 30 is provided in the form of a locking lever 70 that is mounted to pivot between the locked position and unlocked position using any suitable pivot mount, such as a cylindrical journal feature on the post 40B of the frame 22 received within a bearing bore formed in the locking lever 70. As best seen in Fig. 5, the locking member 30 includes a surface 72 that engages with the surface 49 of the clamping member 26 to prevent movement of the clamping member 26 from the free position to the opening position when the locking member 30 is in the locked position. As best seen in Figs. 6 and 7, the surface 72 is pivoted away from contact with the surface 49 of the clamping member 26 when the locking member 30 is moved from the locked position to the unlocked position, thereby allowing the damping member 26 to be moved from the free position shown in Fig. 6 to the opening position shown in Fig. 7.

[0041] As seen in Fig. 5, the engagement of the surfaces of the posts 40, 60 and 62 with the surfaces of the slots 50-58 prevents the blocking member 28 from being moved to the open position when the locking member 30 is in the locked position and the clamping member 26 is in either the free position or the clamping position. As best seen in Fig. 6, when the locking member 30 and its post 62 are moved from the locked position to the unlocked position, the post 62 carried on the locking member 30 aligns with a horizontally extending portion of the slot 58, thereby allowing movement of the blocking member 28 from the closed position to the open position. In this regard, as best seen in Figs. 6 and 7, the engagement of the outer surface of the post 60 carried on the clamping member 26 with the inner surface of the slot 56 forces the blocking member 28 to move from the closed position shown in Figs. 2 and 3 to the open position shown in Fig. 7 as the clamping member 26 and its post 60 are moved from the free position shown in Figs. 4 and 5 to the opening position shown in Fig. 7.

[0042] It should be understood that any embodiments described herein are illustrative of the structure and operational features of the shuttle 20 and this disclosure contemplates that the shuttle 20 can be provided in other forms and configurations. By way of example, while the posts 60 and 62 have been shown as being carried on the clamping member 26 and locking member 30, respectively, and their corresponding slots 56 and 58 are shown as being formed in the blocking member 28, it is possible for the slots 58 and 58 to be provided on the clamping member 26 and locking member 30, respectively, and for the posts 60 and 62 to be carried on the blocking member 28. By way of another example, the operable connection between the blocking member 28 and the damping and locking members 26 and 30 can take other forms than posts and slots. As yet another example, while the clamping and locking members 26 and 30 have been shown as being mounted for pivoting movement between their operating positions and the blocking member 28 as being mounted for translation, other mountings and movements are possible.