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EP 1 085 950 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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07.05.2003 Bulletin 2003/19 |
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Date of filing: 26.05.1999 |
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International Patent Classification (IPC)7: B21D 1/12 |
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International application number: |
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PCT/SE9900/891 |
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International publication number: |
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WO 9906/4179 (16.12.1999 Gazette 1999/50) |
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A DEVICE FOR CLAMPING A VEHICLE TO A BENCH ATTACHMENT
VORRICHTUNG ZUM VERBINDEN EINES FAHRZEUGS MIT EINER RICHTBANK
DISPOSITIF DE FIXATION D'UN VEHICULE A UN MARBRE
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Designated Contracting States: |
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DE ES FR GB IT |
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Priority: |
09.06.1998 SE 9802038
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Date of publication of application: |
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28.03.2001 Bulletin 2001/13 |
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Proprietor: CAR-O-LINER AB |
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736 21 Kungsör (SE) |
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Inventor: |
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- HENBLAD, Peter
S-632 27 Eskilstuna (SE)
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Representative: Axelsson, Rolf et al |
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Kransell & Wennborg AB
Box 27834 115 93 Stockholm 115 93 Stockholm (SE) |
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References cited: :
WO-A1-89/11352 WO-A1-96/01158
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WO-A1-89/11353 DE-A1- 3 149 215
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- DATABASE WPI Week 8434, Derwent Publications Ltd., London, GB; AN 1984-211511/34 &
SU 1 061 881 A (CAR ENGINE RES INST) 23 December 1983
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The present invention relates to an arrangement for use when clamping a vehicle to
a straightening or aligning bench, wherein the arrangement includes a support arm
whose one leg is provided with means for mounting the arm in a mounting groove that
extends along the sides of the bench, while the other leg of said arm is intended
to carry clamping means for clamping the chassis of a vehicle onto the arm.
[0002] Support arms of this kind that are intended to be clamped firmly in mounting grooves
on chassis straightening benches have been long known in the art. One leg of the mounting
arms is provided with a fixed mounting jaw which is inserted into the groove on the
bench and secured in a desired position with the aid of bolt-equipped clamping jaws.
The mounting grooves have a generally C-shaped profile and the mounting jaw is designed
to enable it to be clamped firmly against the flanges extending along the upper and
lower edges of the groove with the aid of said clamping jaws.
[0003] This means that the mounting jaw must either be inserted from one end or the other
of the mounting groove or, alternatively, at least one flange, normally the flange
extending along the upper edge of the groove, must be provided with recesses at one
or more positions in order to enable that part or parts of the jaw which shall run
inwardly of the flange to be inserted into the groove. This prevents the support arm
from being locked firmly in precisely these positions if so required. Furthermore,
the procedure of inserting the jaws into the ends of the grooves or at said recessed
positions and then moving the jaws to desired working positions is relatively complicated.
[0004] A primary object of the present invention is to provide an arrangement which will
enable a support arm to be mounted directly in the position desired along a mounting
groove, without needing the use of a tool to this end. One should be able to lock
the arm securely in this position with the aid of bolts that can be accessed from
one side.
[0005] This is achieved in accordance with the invention with the aid of two mounting jaws
which are moveable in relation to one another and which enable a support arm to be
snapped firmly into a mounting groove.
[0006] The particular characteristic features of an arrangement of the kind defined in the
first paragraph are that said means for mounting one leg of the support arm in the
mounting groove of the bench includes two mounting jaws, that a first of these jaws
is fixed to the arm and adapted to grip behind a flange along one edge of the groove,
that the other jaw is moveable relative to the first jaw and can be displaced towards
said jaw while overcoming a spring force and is adapted to grip behind a flange along
the other edge of the groove, and that the arm can be fitted into the groove by swinging
the arm upwards with the lower jaw resting in the lower part of said groove.
[0007] An arrangement of this kind will thus enable a support arm to be readily fitted into
the mounting groove, by placing the arm in the groove and swinging the arm up around
the lower support point until the upper jaw grips behind the upper flange of the groove.
This can be effected in one single movement, without the use of a tool or like means.
[0008] The moveable jaw is guided conveniently in a groove in a part of the fixed jaw located
behind said moveable jaw.
[0009] The jaws can therewith be held apart with the aid of springs disposed therebetween.
[0010] It is preferred that the lower jaw is fixed to the arm and that the upper jaw is
pressed downwards against the spring force as a result of coaction with a downwardly
projecting flange along the upper edge of the groove when the arm is swung upwards,
so that the upper jaw is able to grip behind said flange. The upper jaw is suitably
provided with a bevelled surface that coacts with the flange projecting down from
the upper edge of the groove, when the arm is swung upwards.
[0011] One mounting jaw is suitably provided with two rearwardly projecting bolts with one
clamping jaw disposed on each bolt, said clamping jaws functioning to firmly clamp
the lower and upper mounting jaws inserted into the mounting groove against the flanges
extending along the upper and lower edges of said groove, with the aid of bolts.
[0012] The clamping jaws will preferably include outwardly projecting spacer flanges which
project in between the mounting jaws when said jaws are clamped firmly in the mounting
groove, so as to prevent said jaws moving towards each other when subjected to load.
[0013] Further features of the invention will be apparent from the accompanying Claims.
[0014] The invention will now be described in more detail with reference to an exemplifying
embodiment thereof and also with reference to the accompanying drawings.
[0015] Fig. 1 is a perspective view of an earlier known straightening bench with support
arms fitted in mounting grooves.
[0016] Fig. 2 illustrates component parts of an inventive arrangement for mounting and fixing
a support arm to a straightening bench.
[0017] Fig. 3 shows the arrangement mounted on the support arm.
[0018] Fig. 4 shows the arrangement while fitting the support arm to a straightening bench.
[0019] Fig. 5 shows the arrangement of Fig. 4 with the arrangement mounted in position.
[0020] Fig. 1 shows a known straightening bench 1 for use in straightening a vehicle. The
bench is comprised of beams 2 which include generally C-shaped mounting grooves 3
along their outer surfaces. The groove therefore has a downwardly projecting flange
4 along its upper edge and an upwardly projecting flange 5 along its lower edge. Angled
support arms 6 and support wheels 7 are mounted in these grooves. The upper legs of
the support arms support clamping devices 8, so-called cramps, which are intended
to be clamped firmly about a flange which projects out downwardly from the saddle
beam sill of a vehicle chassis, so as to clamp the chassis firmly to the support arms
6.
[0021] The support arms 6 are fitted into the grooves 3 with the aid of a fixed, lower mounting
jaw 9 provided on respective arms and adapted for insertion into the groove behind
the flanges 4 and 5 and to be clamped against said flanges with the aid of clamping
jaws 28 provided with bolts 10. The fixed mounting jaws 9 can be inserted into the
grooves from the ends thereof or at a position midway of the beam 2, where parts 11
of the upper flange 4 have been removed to permit insertion of the part of respective
mounting jaws 9 that grip behind said flange.
[0022] This means that in the case of the known straightening bench the task of positioning
the support arms in desired working positions is relatively complicated, since the
support arms must first be threaded into the groove and then moved therealong to a
desired position. This part of the work that is entailed when fitting an arm to a
known bench is eliminated by the present invention, since when practising the invention
the support arm can be mounted directly in its desired position.
[0023] Fig. 2 shows component parts of an inventive arrangement. A fixed mounting jaw 12
is fitted to the lower part of the angled support arm 6. The mounting jaw 12 includes
a groove 13 which is intended to receive the flange 5 that extends along the lower
edge of the mounting groove 3 on a straightening bench according to Fig. 1. Extending
upwardly from the jaw 12 is a part that includes an inner groove 14 in which a moveable,
upper mounting jaw 15 is guided. The mounting jaw 15 includes a groove 16 for receiving
the flange 4 that extends along the upper edge of the groove 3. Arranged between the
jaws 12 and 15 is a spring 17 which in a normal position holds the jaw 15 pressed
against an upper stop member 18 mounted to the support leg 6. The jaw 15 includes
laterally projecting flanges 19 which are guided in the inner grooves 14 in the jaw
12.
[0024] The reference numeral 20 identifies a threaded stud bolt which is intended to be
screwed into the fixed jaw 12 on one side of the arm 6 and locked in said jaw. A corresponding
stud bolt is provided on the other side of the arm 6. Arranged on respective stud
bolts is a spring 21 which coacts with an associated clamping jaw 22. The jaws 22
can be moved towards the mountings jaws 12 and 15 on respective sides of the arm 6,
so as to clamp the mounting flanges 4 and 5 on the bench 1 between the clamping jaws
22 and the jaws 12 and 15 subsequent to having inserted said jaws into the groove
3. The jaws 22 are moved with the aid of an associated sleeve 23 having a nut head
24 and an internal thread which coacts with the thread on the stud bolt 20.
[0025] The reference numeral 25 identifies a generally U-shaped actuator which has a leg
projecting down on each side of the support leg 6 and which is fitted on respective
stud bolts 20. The actuator 25 is intended to be pressed obliquely downwards with
the operator's foot, so as to release the mounting jaws from the groove 3, as will
be explained in more detail below.
[0026] Fig. 3 shows the support arm 6 with an associated mounting arrangement firmly fitted
thereto.
[0027] Fig. 4 shows how the support arm 6 is fitted in the mounting groove 3 on the beam
2 of a vehicle straightening bench. The lower jaw 12 is inserted into the groove 3
so that the inner part of the jaw grips behind the flange 5. The arm 6 is then swung
upwards in the direction of the arrow A, wherewith the upper mounting jaw 15 is pressed
down against the lower jaw 12 and then snaps in behind the upper flange 4 of the groove
3; see Fig. 5. The jaw 15 is provided with a bevelled surface 26 so as to facilitate
insertion of the jaw into the groove 3, said surface coacting with the flange 4 during
insertion of the jaw.
[0028] When the jaws 12 and 15 are in position in the groove 1, the support arm 6 is clamped
firmly in this position with the aid of the clamping jaws 22, which are pressed against
the outer surfaces of the groove flanges 4 and 5 with the aid of associated sleeves
23. As before mentioned, a clamping jaw 22 is provided on each side of the support
arm 6.
[0029] Thus, when using an inventive arrangement, the support arms 6 can be fitted directly
in desired positions along the bench, without needing to be subsequently moved, which
greatly facilitates mounting of the support arms and shortens the time taken in this
respect. The support arms can also be fitted even if holders of the bench support
wheels or other means are inserted in the mounting groove.
[0030] The clamping jaws 22 are provided with an outwardly projecting flange 27 which when
clamping the jaws project in between the mounting jaws 12 and 15 and therewith prevent
said jaws from tilting in the groove while moving slightly towards each other when
subjected to load.
[0031] The lower mounting jaw 12 and/or the clamping jaws 22 are constructed so that a mounting
arm 6 can be suspended provisionally in a desired position without snapping fully
into the groove 3, as illustrated in Fig. 4. This facilitates the work involved in
clamping a vehicle chassis, since the support arms can first be fitted provisionally
to the straightening bench and then swung up and finally fitted in the groove 3 in
another working step.
[0032] The same applies when dismantling a support arm 6 from the position shown in Fig.
5. In this regard, the clamping jaws 22 are first loosened and the U-shaped member
25 is then pressed obliquely downwards with the operator's foot, therewith pressing
down the upper jaw 15 and releasing it from the groove 3. The arm 6 will then fall
under its own weight to the position shown in Fig. 4, and can then be easily lifted
away.
[0033] Although the invention has been described above with reference to the exemplifying
embodiment shown in the drawings, it will be understood that this embodiment can be
modified in several respects within the scope of the following Claims. For instance,
the lower jaw may be moveable towards the upper jaw while overcoming a spring force,
instead of the upper jaw being moveable towards the lower jaw. The precise design
of both the mounting jaws and the clamping jaws may be varied as desired, provided
that the required function is maintained. This also applies to the design of the actuator
25 and/or its attachment in the arrangement. The actuator may thus be connected directly
to the moveable jaw. The devices by means of which pressure is exerted on the clamping
jaws may, of course, be chosen as desired.
1. An arrangement for use in clamping a vehicle to a straightening bench (1) and including
a support arm (6) whose one leg is provided with means for fitting the arm in a mounting
groove (3) that extends along the sides of the bench, and whose other leg is intended
to carry clamping means (8) for clamping a vehicle chassis to the arm, characterised in that said means for fitting one leg of the support arm (6) in the mounting groove of said
bench includes two mounting jaws (12, 15); in that a first (12) of said jaws is fixed to the arm (6) and intended to grip behind a flange
(5) along one edge of the groove (3); in that the second jaw (15) is moveable relative to the first jaw and displaceable towards
said jaw whilst overcoming a spring force (17) and is adapted so that it can grip
behind a flange (4) along the other edge of the groove (3); and in that the arm can be fitted into the groove by swinging the arm upwards (A) with the lower
jaw (12) resting in the lower part of the mounting groove (3).
2. An arrangement according to Claim 1, characterised in that the moveable mounting jaw (15) is guided in a groove (14) in a part of said fixed
jaw (12) located behind said moveable jaw.
3. An arrangement according to Claim 1 or 2, characterised in that the lower jaw (12) is fixed to the arm (6); and in that the upper jaw (15) is pressed downwards against said spring force (17) as a result
of coaction with a downwardly projecting flange (4) along the upper edge of the groove
(3) as the arm (6) is swung upwards, so that the upper jaw (15) is able to grip behind
said flange (4).
4. An arrangement according to Claim 3, characterised in that the upper mounting jaw (15) has a bevelled surface (26) which coacts with the flange
(4) projecting down from the upper edge of the mounting groove (3) as the arm (6)
is swung upwards.
5. An arrangement according to any one of Claims 1-4, characterised in that one mounting jaw (15) is provided with two rearwardly projecting bolts (20); in that a clamping jaw (22) is disposed on each bolt; and in that the clamping jaws are able to clamp the lower and upper mounting jaws (12, 15) inserted
in the mounting groove (3) against the flanges (4, 5) extending along the upper and
lower edges of the groove (3) with the aid of said bolts.
6. An arrangement according to Claim 5, characterised in that the clamping jaws (22) are provided with an outwardly projecting spacer flange (27)
which projects in between the mounting jaws (12, 15) when said jaws are clamped in
the mounting groove (3), therewith preventing said jaws moving towards each other
when subjected to load.
7. An arrangement according to Claim 5 or 6, characterised in that the jaws (12, 15; 22) are constructed so that the arrangement will remain hanging
on the lower flange (5) of the mounting groove (3) when the bolts (20) have been loosened
and the upper mounting jaw (15) no longer engages said groove.
8. An arrangement according to any one of Claims 5-7, characterised by a release device (25) mounted on the bolts (20), said release device when activated
in an obliquely downwards direction urges the mounting jaws (12, 15) towards each
other so as to release the upper jaw (15) from engagement in the mounting groove (3).
9. An arrangement according to any one of Claims 5-8, characterised in that the release device (25) has the form of a U-shaped member that surrounds the lower
leg of the support arm (6).
10. An arrangement according to any one of Claims 5-9, characterised by a spring (21) which endeavours to hold respective clamping jaws (22) spaced from
the mounting jaws (12, 15), so as to facilitate insertion thereof into the mounting
groove (3).
1. Anordnung zur Verwendung beim Klemmen eines Fahrzeuges auf einer Richtbank (1) und
einen Tragarm (6) enthaltend, dessen eines Bein mit Einrichtungen versehen ist zum
Einpassen des Arms in eine Montageaussparung (3), die sich entlang der Seiten der
Bank erstreckt, und wessen anderes Bein dazu gedacht ist, Klemmeinrichtungen (8) zum
Klemmen eines Fahrzeugchassis an den Arm zu tragen, dadurch gekennzeichnet, dass die Einrichtung zum Einpassen eines Beins des Tragarms (6) in die Montageaussparung
der Bank (2) Montagebacken (12, 15) enthält; dass eine erste (12) der Backen an dem
Arm (6) angebracht ist und dazu gedacht ist, hinter einen Flansch (5) entlang einer
Kante der Aussparung (3) zu greifen, dass die zweite Backe (15) relativ zu der ersten
Backe bewegbar ist und verschiebbar in Richtung der Backe, während sie eine Federkraft
(17) überwindet und angepasst ist, so dass sie hinter einen Flansch (4) entlang der
anderen Kante der Aussparung (3) greifen kann; und dass der Arm in die Aussparung
eingepasst werden kann durch nach oben (A) Schwingen des Arms mit der unteren Backe
(12), die in dem unteren Teil der Montageaussparung (3) aufliegt.
2. Anordnung gemäß Anspruch 1, dadurch gekennzeichnet, dass die bewegbare Montagebacke (15) in einer Aussparung (14) in einem Teil der fixierten
Backe (12) geführt wird, die hinter der bewegbaren Backe positioniert ist.
3. Anordnung gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass die untere Backe (12) an dem Arm (6) angebracht ist; und dass die obere Backe (15)
nach unten gedrückt wird gegen die Federkraft (17) als Ergebnis der Zusammenwirkung
mit einem nach unten hervorstehenden Flansch (4) entlang der oberen Kante der Aussparung
(3), während der Arm (6) nach oben geschwungen wird, so dass die obere Backe (15)
in der Lage ist, hinter den Flansch (4) zu greifen.
4. Anordnung gemäß Anspruch 3, dadurch gekennzeichnet, dass die obere Montagebacke (15) eine abgeschrägte Oberfläche (26) aufweist, welche mit
dem Flansch (4) zusammenwirkt, der nach unten von der oberen Kante der Montageaussparung
(3) hervorsteht, während der Arm (6) nach oben geschwungen wird.
5. Anordnung gemäß irgendeinem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass eine Montagebacke (15) mit zwei nach hinten hervorstehenden Bolzen (20) versehen
ist; dass eine Klemmbacke (22) auf jedem Bolzen angeordnet ist; und dass die Klemmebacken
in der Lage sind, die untere und obere Montagebacke (12, 15) zu klemmen, die in die
Montageaussparung (3) eingeführt sind, gegen die Flansche (4, 5), die sich entlang
der oberen und unteren Kanten der Aussparung (3) erstrecken mit Hilfe der Bolzen.
6. Anordnung gemäß Anspruch 5, dadurch gekennzeichnet, dass die Klemmbacke (22) mit einem nach außen hervorstehenden Abstandshalterflansch (27)
versehen ist, welcher zwischen den Montagebacken (12, 15) hervorsteht, wenn die Backen
in der Montageaussparung (3) geklemmt sind, dadurch verhindernd, dass die Backen in
Richtung zueinander bewegt werden, wenn sie einer Belastung unterliegen.
7. Anordnung gemäß Anspruch 5 oder 6, dadurch gekennzeichnet, dass die Backen (12, 15; 22) so konstruiert sind, dass die Anordnung auf dem oberen Flansch
(5) der Montageaussparung (3) hängend verbleiben werden, wenn die Bolzen (20) gelockert
worden sind und die obere Montagebacke (15) nicht länger die Aussparung in Eingriff
nimmt.
8. Anordnung gemäß irgendeinem der Ansprüche 5 bis 7, gekennzeichnet durch eine Lösevorrichtung (25), die auf den Bolzen (20) montiert ist, wobei die Lösevorrichtung,
wenn sie in einer schräg nach unten gerichteten Richtung aktiviert wird, die Montagebacken
(12, 15) in Richtung zueinander zwingt, um so die obere Backe (15) aus dem Eingriff
in der Montageaussparung (3) zu lösen.
9. Anordnung gemäß irgendeinem der Ansprüche 5 bis 8, dadurch gekennzeichnet, dass die Lösevorrichtung (25) die Form eines U-förmigen Elements aufweist, das das untere
Bein des Tragearms (6) umgibt.
10. Anordnung gemäß irgendeinem der Ansprüche 5 bis 9, gekennzeichnet durch eine Feder (21), welche bemüht ist, die jeweiligen Klemmbacken (22) beabstandet von
den Montagebacken (12, 15) zu halten, um so ein Einsetzen davon in die Montageaussparung
(3) zu erleichtern.
1. Agencement destiné à être utilisé pour serrer un véhicule sur un marbre à dresser
(1) et comprenant un bras de support (6) dont un pied est muni de moyens permettant
d'emboîter le bras dans une gorge de fixation (3) qui s'étend le long des côtés du
marbre, et dont l'autre pied est prévu pour supporter des moyens de serrage (8) destinés
à serrer un châssis de véhicule sur le bras, caractérisé en ce que lesdits moyens permettant d'emboîter un pied du bras de support (6) dans la gorge
de fixation dudit marbre comprend deux mâchoires de fixation (12, 15) ; en ce qu'une première (12) desdites mâchoires de fixation est fixée au bras (6) et est prévue
pour se prendre derrière une bride (5) le long d'un bord de la gorge (3) ; en ce que la deuxième mâchoire de fixation (15) est mobile par rapport à la première mâchoire
de fixation, qu'elle peut se déplacer vers ladite première mâchoire de fixation tout
en s'opposant à une force de rappel d'un ressort (17) et qu'elle est prévue pour se
prendre derrière une bride (4) le long de l'autre bord de la gorge (3) ; et en ce que le bras peut s'emboîter dans la gorge lorsqu'on fait basculer le bras vers le haut
(A), la mâchoire de fixation inférieure (12) reposant sur la partie inférieure de
la gorge de fixation (3).
2. Agencement selon la revendication 1, caractérisée en ce que la mâchoire de fixation mobile (15) est guidée dans une gorge (14) d'une partie de
ladite mâchoire de fixation fixe (12) qui est située derrière ladite mâchoire de fixation
mobile.
3. Agencement selon la revendication 1 ou 2, caractérisée en ce que la mâchoire de fixation inférieure (12) est fixée au bras (6) ; et en ce que la mâchoire de fixation supérieure (15) s'appuie vers le bas en s'opposant à ladite
force de rappel du ressort (17), ce qui résulte de son action conjointe avec une bride
(4) faisant saillie vers le bas le long du bord supérieur de la gorge (3) lorsqu'on
fait basculer le bras (6) vers le haut, de façon à ce que la mâchoire de fixation
supérieure (15) puisse se prendre derrière ladite bride (4).
4. Agencement selon la revendication 3, caractérisée en ce que la mâchoire de fixation supérieure (15) possède une surface biseautée (26) qui coopère
avec la bride (4) faisant saillie vers le bas depuis le bord supérieur de la gorge
de fixation (3) lorsqu'on fait basculer le bras (6) vers le haut.
5. Agencement selon l'une quelconque des revendications 1 à 4, caractérisé en ce qu'une mâchoire de fixation (15) est munie de deux boulons faisant saillie vers l'arrière
(20) ; et en ce qu'une mâchoire de serrage (22) est disposée sur chaque boulon ; et en ce que les mâchoires de serrage peuvent serrer les mâchoires de fixation inférieure et supérieure
(12, 15) qui sont insérées dans la gorge de fixation (3) contre les brides (4, 5)
qui s'étendent le long des bords supérieur et inférieur de la gorge (3) à l'aide desdits
boulons.
6. Agencement selon la revendication 5, caractérisé en ce que les mâchoires de serrage (22) sont munies d'une bride d'écartement (27) faisant saille
extérieurement entre les mâchoires de fixation (12, 15) lorsqu'on serre lesdites mâchoires
de serrage dans la gorge de fixation (3), en empêchant lesdites mâchoires de fixation
de se déplacer l'une vers l'autre lorsqu'elles sont soumises à une charge.
7. Agencement selon la revendication 5 ou 6, caractérisé en ce que les mâchoires (12, 15 ; 22) sont construites de façon à ce que l'agencement reste
en repos sur la bride inférieure (5) de la gorge de fixation (3) lorsque les boulons
(20) sont desserrés et que la mâchoire de fixation supérieure (15) n'est plus engagée
dans ladite gorge de fixation.
8. Agencement selon l'une quelconque des revendications 5 à 7, caractérisé en ce qu'un dispositif de déblocage (25) est monté sur les boulons (20), ledit dispositif de
déblocage appuyant les mâchoires de fixation (12, 15) l'une vers l'autre lorsqu'il
est actionné dans une direction inclinée vers le bas de façon à débloquer la mâchoire
supérieure (15) et à la libérer de son engagement dans la mâchoire de fixation (3).
9. Agencement selon l'une quelconque des revendications 5 à 8, caractérisé en ce que le dispositif de déblocage (25) a la forme d'un élément en U qui entoure le pied
inférieur du bras de support (6).
10. Agencement selon l'une quelconque des revendications 5 à 9, caractérisé en ce qu'un ressort (21) s'efforce de maintenir les mâchoires de serrage (22) respectivement
écartées des mâchoires de fixation (12, 15), de façon à faciliter leur insertion dans
la gorge de fixation (3).