CA2129181A1

CA2129181A1 - Apparatus for supporting a human forearm during a work operation, such as a keuboard operation

Info

Publication number: CA2129181A1
Application number: CA002129181A
Authority: CA
Inventors: Rainer Schmidt
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-07-31
Filing date: 1994-07-29
Publication date: 1995-02-01
Also published as: DE9311467U1; US5402972A; EP0639431A1

Abstract

APPARATUS FOR SUPPORTING A HUMAN FOREARM DURING
A WORK OPERATION, SUCH AS A KEYBOARD OPERATION

ABSTRACT OF DISCLOSURE
Apparatus for supporting at least one forearm for the operation of keyboards, assembly operations, etc. At least one lever can be fastened to a tabletop or work surface and is connected, by means of at least one locking joint with a pivoting support, to hold a support plate. The joint has two endpieces which can be clamped together, between which there are several plates secured non-rotatably in alternation on different arms of the joint. The support and the lever have at least one pivot located in the joint axis to hold the plates. Every second plate is secured non-rotatably on the pivot. The pivot, together with all the plates, projects into a recess of one endpiece, and the other plates are secured in the recess against rotation.

Description

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APPARATUS FOR SUPPORTING A HUMAN FOREARM DURING
A WORK OPERATION, SUCH AS A KEY~OARD OPERATION

BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to a device for the support of at least one forearm, i.e. at least one human forearm, for the operation of keyboards, assembly operations etc., having at least one clamp which can be fastened to a tabletop or work surface and which is connected by at least one locking joint, possibly even a hinge, link or articulation, to a pivoting holder which holds a support plake, whereby the joint has two endpiece3 which can be alamped to one another, between which there are several plates secured in a non-rotating fashion alternately to different articulated arms, or brackets.

2. Backqround Information: .
Generally known are devices which are used to support forearms for the operation o keyboards, assembly operations etc.
These known devices tend to include a support plate, which is generally cushioned or padded, and which i5 fastened to a tabletop or work surface. It is thereby desirable that it be possible to position the support plate at different heights and at different inclinations as a function of the size of the object and the working position of the forearm. To be able to change the height and the inclination of the suE)port plate, the support plate must be connected by means o~ at least one locking double joint to a clamp which can be fastened to the tabletop or work surface. In the unclamped state, the support plate can now be NHL:iks/be 1 KOB-01 CA 01/~OB001 2 1 2 ~

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:~ ';' ' placed at a suitable height and inclination, and can then be secured by a clamping action.
OBJECT OF THE INVENTION
The object of the invention is therefore to configure a -~
device for the support of at least one forearm for the operation of keyboards, assembly operations, etc., so that pro~lem~
encountered with known fastening arrangements to fasten the plates to the fastening clamp and to the support plate can be eliminated, and so that the plates and their operation essentially will not be adversely affected by dust and dirt. An additional object of the invention is to provide improved visual appearance.
The invention teaches that the above objects can be achieved by means of a device in which the support and the clamp have at least one pivot located in the joint axis to hold the plates, every second plate is secured non-rotationally to the pivot, the pivot together with all the plates project into a recess of one endpiece, and the other plates are secured against rotation iIl ~-the recess.
As a result of this configuration, a special fastening o the plates corresponding to the fastening clamp and to the support plate is essentially not necessary, so that the assembly process for the manufacture of such a device can be simplified.
Plates which act as a lever with a double joint can be eliminated. The plates will thus essentially be located in a -~
closed recess, so that their clamping function is essentially not adversely affected by dust and dirt. As a result of the ~ -~ -NHL:iks/be 2 KOB-01 C~ 01/XOB001 .

2i29181 N~L-KOB-01 CA

concealed location of the plates, the device can have a significantly improved appearance.
In summary, one aspect of the invention resides broadly in apparatus for supporting a first object, such as a human forearm, with respect to a second object, the apparatus comprising: at least one lever; means for fastening the at least one lever to the second object; support means for supporting the first object, the support means being pivotally connected to the at least one lever; joint means for permitting pivotal movement of the at least one lever and the support means with respect to one another; the joint means comprising at least one endpiece connected to the at lea~t one lever; the ~oint means havlng means for pivotally connecting the at least one endpiece and the support means with one another; means for locking the joint means to hold the at least one endpiece and the support means in a substantially fixed position with respect to one another; the ~ ~ -joint means comprising: a plurality of plates; a lug supporting at least some of the plurality of plates; a recess disposed in : :
one of the first and second endpieces; the lug and the plurality of plates being disposed to project into the recess; a first set of the plurality of plates being secured on the lug so as to be non-rotatable with respect to the lug; a second set of the plurality of plates being secured within the recess so as to be :~
non-rotatable with respect to the recess; and the first set of plates and the second set of plates being disposed in alternation with respect to one another.
BRIEF DESCRIPTION OF ~HE DRAWINGS
The invention is explained in greater detail below with :

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reference to an embodiment illustrated in the accompanying drawing , wherein:
Figure 1 shows an elevational view of a device as claimed by the invention, Figure 2 shows an enlarged cross section through a joint of the device illustrated in Figure 1, Figure 3 shows a side view of the device fastened to a tabletop or work surface, Figùre 4 shows a clamping device which is designed as a cam, Figure 5 shows another clamping device which also acts as a cam, Figure 6 schematically illustrates a human engaged in a work operation with a device according to the present invention, j Figures 7a and 7b illustrate different positions of a device according to the present invention, Figure 8 is suhstantially the same view as Figure 2, but more detailed, Figures 9 and 10 are schematic, side elevational views of different embodiments of a pivot and plates; and Figures 11 and 12 are schematic, side elevational views of different embodiments of a recess and plates.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The device illustrated in Figure 1 of the accompanying ~-~
drawings can preferably be used to support at least one forearm i during the operation of a keyboard, or during assembly operations~ etc., on a tabletop or work surface. The device thereby preferably includes two lever~ 1, which can each have a T-shaped cross section, for example, and which, in the vicinity NHL:iks/be 4 KOB-01 CA 01/KOB001 .. - , ~ .~ , 212 .31~1 NHL-KOB-01 CA

of their webs 2, are each preferably designed as a clamp 22 (see Figure 3). Pre~erably, clamps 22 are each fastened to a tabletop or work surface 24 ~see Figure 3) by clamping, e.g. by means of screws 23. The screws 23 are preferably inserted in rotational fashion in an extension 25, and on their upper or exposed end preferably support a plate 26 provided with a knurled area, by means of which the screw 23 can be turned; thus, the device can be clamped firmly to the tabletop or work surface (Figure 3~.
The legs 3 of the lever 1 are preferably connected by means of a double joint 4, in hinged fashion, with legs 5, respectively, of a plate-like support 6. Legs 5 are preerably provided with holes 7a for fas~ening a support plake 27. The ~upport plate 27 i3 preferably in contact with, or support3, the forearm, and is preerably cushioned or upholstered, whereby a flexible layer of rubber or a similar material can be provided in the support plate.
In the illustrated example, as shown in Figure 2, on the leg 5 of a support 6, each leg 3, 5 preferably has on each side a pivot 7, which in this embodiment preferably has a square cross section. Located on each pivot 7 there are preferably ~everal `
plates 8, whereby, for purposes of illustration in Figure 2, these plates are shown only on the left pivot 7. The right pivot 7 shown in the drawing can also be equipped with plates 8 in a ;~
similar manner.
In accordance with at least one preferred embodiment of the present invention, each pivot 7 may alternatively be considered to be a "pin", "journal", or "lug".

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All the plates 8 preferably have a central opening which makes it possible to insert the plates on the pivot 7. But this opening is preferably different in the plates 8. Particularly, in accordance with a preferred embodiment of the present invention, every second plate 8a preferably has an opening which coincides essentially exactly with the cross section of the pivot 7, so that these plates 8a are essentially secured non-rotationally on the pivot 7. The other plates 8b preferably have an opening which is the same as, or ~lightly larger than, the width across the corners, possibly diameter, of the pivot 7.
That means that the plates 8b can rotate on, essentially w:L~h respect to, the pivot 7.
Thus, in accordance with a preferred embodiment of the present invention, plates 8 are preferably constituted by a first set of plates 8a and a second set of plates 8b, which plates 8a and 8b preferably alternate with one another along the longitudinal direction of pivot 7. Preferably, plates 8a each have an opening which is of a size such that, when pivot 7 is introduced therethrough, each plate 8a will essentially be secured non-rotationally with respect to pivot 7. Accordingly, ~ ~
such non-rotational securing may be accomplished, for example, by - :
a force-locking relationship between each plate 8a and the pivot 7. Conversely, plates 8b each preferably have an opening which - .
is of a sufficient size such that, when pivot 7 is introduced therethrough, each plate 8b will essentially be rotatable with respect to pivot 7.
In the illustrated embodiment, the plates 8a preferably have ~:
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a circular outer contour. But, in accordance with a pxeferred embodiment of the present invention, the plateq 8b can preferably have a contour which i~ different from that of the plate_ 8a.
The outer contour of the plates 8b can be qquare, for example, and the corners of the square outside contour can preferably be rounded. The length of a 3ide of this square is preferably approximately equal to the diameter of the plates 8a. The plates ; 8b can also conceivably have an area, i.e. a general base or outline, which is embodied by a semicircle and a rectangle.
Thuq, in accordance with a preferred embodiment o~ the present invention, the plates 8b can conceivably have an outer contour, quch aq a generally square aontour, which i~ different from that of plates 8a. For example, plates 8b could conceivably even have an outer contour which is semicircle in one half of the -i plate, and qenerally rectili~near/rectangular in the other half. ~ -I The pivot 7 equipped with the plates 8 now essentially projects into a graduated recess ~ of an endpiece 10. The smaller cross section of the recess 9 can thereby preferably be slightly }axger than the width across the corners, possibly diameter, o the pivot 7, so that the pivot 7 can be rotatable within the recess 9. The larger cross section of the recess 9 preferably essentially exactly equals the area of the plates 8b, so that the latter are preferably secured non-rotationally in the rece~s 9.
Thus, in accordance with a preferred embodiment of the present invention, plates 8b each preferably have an outer contour which is of a size such that, when plates Rb are NHL:iks/be 7 KOB-01 CA 01/KOB001 . . .

2129~81 introduced into rece~s 9, each plate 8b will essentially be secured non-rotationally with respect to recess 9. Accordingly, such non-rotational securing may be accomplished, for example, by a force locking relationship between each plate 8b and the recess 9. Conversely, plates 8a each preferably have an outer contour which is of a size such that, whe~ plates 8a are introduced into recess 9, each plate 8a will essentially be rotatable with respect to recess 9.
The pivot 7, or portion of pivot 7, in Figure 2 which is not loaded with plates, prefexably projects into a recess 11 in a spacer 12, which spacer 12is preerably loca~od between the n~ighbo.ring leg9 3 and 5 o~ the lever 1 and the support 6. The cross section o the reces~ 11 in the spacer 12 i8 preferably essentially exactly equal to the larger cross section of the ~:~
graduated reces~ 9 in the endpiece 10.
To form the device, all the pivots 7 are pre~erably loaded ~ .
in alternation with the different plates 8a, 8b, and are ~ ~:
preferably inserted in the corresponding recesses 9, 11. All the plates 8a are preferably secured non-rotationally on the pivots 7, while all the plates 8b are preferably held non-rotationally in the recesses 9, 11. In what may be designated the "unclamped"
state, the lever 1 and the support 6 are preferably turned or pivoted freely within the limits of their specified pivoting range. By means of a clamping element 13, e.g. designed as a screw, the two endpieces 10 can now essentially be clamped together. Consequently, all the plates 8 are preferably thence clamped together, and the position of the support 6 with the NHL:iks/be 8 KOB-01 CA 01/KOB001 ,: " ~

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support plate 27 can thus preferably be secured in an essentially precisely defined position in relation to the levers 1 fastened to the tabletop or work surface 24.
If necessary, the clamping element 13 designed as a screw can preferably be divided and can be embodied by a pin provided with a thread, and a sleeve which can be pushed partly over the pin. The revolving joint between the sleeve and the pin can preferably be accomplished by means of a pivot which is stuck through, whereby the pin can have a slot which runs in the axial direction to hold the pivot. It i9 thereby possible to limit the opening motion of the endpieces 10 and ~hu~ ~o essentially guarantee that the plates 8 essentially cannot escape rom the corresponding recesses 9, 11.
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In the embodiment illustrated in Figure 4, the clamping element 13 is not designed as a screw. In Figure 4, the clamping element 13 is guided in a sleeve 28 which is supported with its one end on the endpiece 10 to the right in the figure, while the other end supports a clamping plate, possibly backplate, 29, through which the clamping element 13 projects. In this area, the clamping element 13 can be designed with a fork-like configuration, and can have a hole 30 for a pivot 31. A tension lever 32 is also mounted on the pivot 31 and has a clamping surface 33 which preferably acts as a cam and can be pivoted around the pivot 31. During this pivoting motion, the clamping element 13 is pre~erably displaced axially, and thus the plates 8a, 8b are clamped together.
The clamping capabilities illustrated in Figures 1 and 3 are NHL:iks/be 9 KOB-01 CA 01/K0~001 2129181 N~L-KOB-01 CA

normally only g0nerally suitable for use by right-handed people.
For left-handed people, the clamping element 13 should p~eferably be located on the left side of the device, which would, under certain circumstances, tend to imply that two di.fferent devices may be necessary. ~ut in this case, Figure 5 illustrates a solution which can be correctly operated hy left-handed people and by right-handed people. The clamping element 13 is preferably divided into a left-hand part 13a and a right-hand part 13b, both of which are preferably guided on a plate 14.

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Each part 13a, 13b preferably has a fork-shaped end with a pivot -15 and preferably holds a common disc 17 which can rotate around an axis 16~ The disa 17 is preferably provided with two grooves 18 whiah can prefe~ably act as cams, in~o which ~he pivo~s 15 are preferably inserted. When the disc 17 is rotated by means of a lever 19 in the direction in~icated by the arrow 20, the two parts 13a, 13b of the clamping element 13 are preferably displaced in the direction indicated by the two arrows, thereby~
executing the clamping movement.
In a modification of the embodiment explained above, the plates 8 can have a diferent shape or area. In such a case, however, it should essentially always preferably be guaranteed ' that the plates 8a are non-rotationally secured on the pivot 1 ` and the plates 8b are non-rotationally secured in the recess 9,11. If the clamping with one packet of plates 8 on each leg 3, 5 is sufficient, the leg 3, 5 can have a pivot 7 only on one -~ side, and the corresponding recess 9 or 11 - generally the recess ~`~ 11 - can be eliminated. The levers 1 which are used to fasten `'. ~ --~HL:iks/be 10 KOB-01 CA 01/KOB001 ~
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the device to a tabletop or work surface can be designed in a different manner, and consequently can also be ~astened to the tabletop or work surface in another manner.
Figure 6 schematically illustrates, in accordance with a preferred embodiment of the present invention, a human forearm 100 positioned on support plate 27, a wrist 101 and a keyboard or workpiece 102, as well as other components. ~ ~ ~
Figures 7a and 7b schematically illustrate, in accordance ~- -with a preferred embodiment of the present invention, that, gene-rally, the angle and/or height of the support plate 27 can be adjusted as a function of the position of the forearm for each individual user or activity.
Flgure 8 more partlcularly illu~trates ~he graduated recess 9 as discussed hereinabove. Particularly, recess 9, in accord-ance with a preferred embodiment of the present invention, can s preferably be constituted by a recess section 9a of smaller diame-ter and/or cross-sectional area and an adjacent recess section 9b of greater diameter and/or cross-sectional area. As discussed hereinabove, in accordance with a preferred embodiment of the present invention, pivot 7 can preferably be configured so as to be rotatable within smaller recess section 9a.
; Figure 9 illustrates that, in accordance with a preferred embodiment of the present invention, pivot 7 can preferably have a generally square cross-sectional shape, which would preferably ~;
translate into a generally similar square cross-sectional shape of the hole of each plate 8a.
Figure 10 illustrates that, in accordance with another pre- -ferred embodiment of the present invention, pivot 7 can prefer~
NHL:i~sibe 11 KOB-01 CA 01/KOB001 , ably have a generally hexagonal cross-sectional shape, which would preferably translate into a generally similar hexagonal cross-sectional shape of the hole of each plate 8a.
Figure 11 illustrates that, in accordance with a preferred embodiment of the present invention, recess 9 can preferably have ~-a generally square internal cross-sectional shape, with rounded corners 104, for accommodating plates 8b.
Figure 12 illustrates that, in accordance with another preferred embodiment of the present invention, recess 9 can preferably have a generally oval internal cross-sectional shape for accommodating plates 8b.
One feature o the invention reside~ broadly in the device for supporting at least one orearm or the operation o keyboards, assem~ly operations etc., consisting of at least one lever which can be fastened ko a tabletop or work surface and which is connected by means of at lea~t one locking joint with a pivoting support to hold a support plate, whereby the joint has two endpieces which can be clamped together, between which there are several plates secured non-rotationally in alternation on different arms of the joint, characterized by the fact that the support 6 and the lever 1 have at least one pivot 7 located in the joint axis to hold the plates 8, that every second plate 8a is secured non-rotationally on the pivot 7, that the pivot 7, together with all of the plates 8, projects into a recess 9 of one endpiece 10, and that the other plates 8b are secured in the recess 9 against rotation.
Another feature of the invention resides broadly in the ' ~
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, ~ ' de~ice, cha~acterized by the fact that the support 6 and the clamp 1 have a pivot i on both sides.
Yet another feature of the invention resides broadly in the device, characterized by the fact that the pivot 7 has a polygon-al cross section and the plates 8a secured non-rotationally on the pivot 7 have an opening with the same cross section.
Still another feature of the invention resides broadly in the device, characterized by the fact that the pivot 7 has a square or hexagonal cross section.
Yet still another feature of the invention resides hroadly in the device, characterized by the fact that the recess 9, 11 has a polygonal or oval cross section, and the plates 8b secu~ed non-rotationally in it have the ~ame a~ea.
Still yet another ~eature o ~he invention reside~ broadly in the device, characterized by the fact that the corners of the recess 9, 11 and of the plates 8b are rounded. ~ -Another feature of the invention resides broadly in the -~
device, characterized by the fact that a spacer 12 is located between the two endpieces 10.

Still another feature of the invention resides broadly in . . ' ' the device, characterized by the fact that the spacer 12 also has a recess 11, at least on one end surface.
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Still yet another feature o~ the invention resides broadly in the device, characterized by the fact that the plates 8 can be ~ ., . .. - .. ..
clamped together by means of a screw or a cam, to the endpieces 10 and, if necessary, to the spacer 12. ~ --.::
~ Examples of keyboard arrangements, which may be utilized in ~ ~

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accordance with the embodiments o the present invention, may be found in the ollowing U.S. Patents: No. 4,890,561, which issued to Hampshire et al. on Jan. 2, 1990; No. 5,11R,172, which issued to Ugalde on June 2, 1992; and No. 5,294,087, which issued to Drabczyk et al. on March 15, 1994.
Examples o arrangement3 for assembly operations, which may be utilized in accordance with the embodiment~ o e the present invention, may be found in the following U~S. Patents: No.
5,082,038, which issued to Teel on Jan. 21, 1992; and No.
5,251,501, which issued to Katahira on Oct. 12, 1993.
The invention as described hereinabove in the context of the preexred embodiments i~ not to be taken ag limited to all o the pxovided details thereo, since modiication~ and variations ~hereo may be made without depar~ing rom the spirit and ~cope o the invention. , . ',., NHL:iks/be 14 KOB-01 C~ 01/KOB001 ~ . : :, . . : . . ~, - ::: . - . . - . -

Claims

1. Apparatus for supporting a first object, such as a human forearm, with respect to a second object, said apparatus comprising:
at least one lever;
means for fastening said at least one lever to the second object;
support means for supporting the first object, said support means being pivotally connected to said at least one lever;
joint means for permitting pivotal movement of said at least one lever and said support means with respect to one another;
said joint means comprising at least one endpiece connected to said at least one lever;
said joint means having means for pivotally connecting said at least one endpiece and said support means with one another;
means for locking said joint means to hold said at least one endpiece and said support means in a substantially fixed position with respect to one another;
said joint means comprising:
a plurality of plates;
a lug supporting at least some of said plurality of plates;
a recess disposed in one of said first and second endpieces;
said lug and said plurality of plates being disposed to project into said recess;

a first set of said plurality of plates being secured on said lug so as to be non-rotatable with respect to said lug;
a second set of said plurality of plates being secured within said recess so as to be non-rotatable with respect to said recess; and said first set of plates and said second set of plates being disposed in alternation with respect to one another.

2. The apparatus according to Claim 1, wherein said joint means comprises additional lug means, said additional lug means having means for pivotally connecting said at least one endpiece and said at least one lever with one another.

3. The apparatus according to Claim 2, wherein:
each of said plurality of plates has an opening disposed therethrough;
said lug is disposed through said openings of said plurality of plates;
said lug has a polygonal cross-sectional shape; and said opening in each of said first set of plates is polygonal and is substantially the same size and substantially the same shape as the polygonal cross-sectional shape of said lug.

4. The apparatus according to Claim 3, wherein said lug has one of:
a generally square cross-sectional shape; and a generally hexagonal cross-sectional shape.

5. The apparatus according to Claim 4, wherein:
said recess has a cross-sectional shape;

each of said second set of said plates has an outer cross-sectional shape; and said outer cross-sectional shape of each of said second set of plates has a is substantially the same size and substantially the same shape as the polygonal cross-sectional shape of said recess.

6. The apparatus according to Claim 5, wherein:
the cross-sectional shape of said recess and the outer cross-sectional shape of each of said second set of plates are one of:
oval; and polygonal with rounded corners.

7. The apparatus according to Claim 6, further comprising a spacer disposed between said first endpiece and said second endpiece.

8. The apparatus according to Claim 7, wherein:
said spacer has an additional recess disposed therein;
said additional recess of said spacer has substantially the same cross-sectional shape of said recess of said one of said first and second endpieces; and said lug additionally projects into said additional recess.

9. The apparatus according to Claim 8, wherein:
said means for locking said joint means comprises means for clamping said plurality of plates with respect to at least one of:
said one of said first and second endpieces; and said spacer; and said clamping means comprises one of:
screw means; and cam means.

10. The apparatus according to Claim 1, wherein:
each of said plurality of plates has an opening disposed therethrough;
said lug is disposed through said openings of said plurality of plates;
said lug has a polygonal cross-sectional shape; and said opening in each of said first set of plates is polygonal and is substantially the same size and substantially the same shape as the polygonal cross-sectional shape of said lug.

11. The apparatus according to Claim 10, wherein said lug has one of:
a generally square cross-sectional shape; and a generally hexagonal cross-sectional shape.

12. The apparatus according to Claim 11, wherein:
said recess has a cross-sectional shape;
each of said second set of said plates has an outer cross-sectional shape; and said outer cross-sectional shape of each of said second set of plates has a is substantially the same size and substantially the same shape as the polygonal cross-sectional shape of said recess.

13. The apparatus according to Claim 12, wherein:
the cross-sectional shape of said recess and the outer cross-sectional shape of each of said second set of plates are one of:
oval; and polygonal with rounded corners.

14. The apparatus according to Claim 13, further comprising a spacer disposed between said first endpiece and said second endpiece.

15. The apparatus according to Claim 14, wherein:
said spacer has an additional recess disposed therein;
said additional recess of said spacer has substantially the same cross-sectional shape of said recess of said one of said first and second endpieces; and said lug additionally projects into said additional recess.

16. The apparatus according to Claim 15, wherein:
said means for locking said joint means comprises means for clamping said plurality of plates with respect to at least one of:
said one of said first and second endpieces; and said spacer; and said clamping means comprises one of:
screw means; and cam means.

17. The apparatus according to Claim 10, wherein:
said recess has a cross-sectional shape;
each of said second set of said plates has an outer cross-sectional shape; and said outer cross-sectional shape of each of said second set of plates has a is substantially the same size and substantially the same shape as the polygonal cross-sectional shape of said recess.

18. The apparatus according to claim 17, wherein:
the cross-sectional shape of said recess and the outer cross-sectional shape of each of said second set of plates are one of:
oval; and polygonal with rounded corners.

19. The apparatus according to Claim 18, further comprising a spacer disposed between said first endpiece and said second endpiece.

20. The apparatus according to Claim 19, wherein:
said spacer has an additional recess disposed wherein;
said additional recess of said spacer has substantially the same cross-sectional shape of said recess of said one of said first and second endpieces;
said lug additionally projects into said additional recess;
said means for locking said joint means comprises means for clamping said plurality of plates with respect to at least one of:
said one of said first and second endpieces; and said spacer; and said clamping means comprises one of:
screw means; and cam means.