Device in a quick coupling

A detachable coupling for connecting an implement, e.g. bucket, to an excavator. The coupling has two parallel link arms that are pinned to the operating arms of the excavator. A locking unit held between these arms has a slidable tension pin that engages a wedge support affixed to the implement. Two pins at either end of the locking device fit loosely into apertures in the link arms. When the tension spring is wedged against the wedge support, the pins are pressed against a surface of the aperture in the link arms to form a rigid coupling between the implement and excavator.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to a device in a quick coupling for 
detachably coupling a working implement to the operating arm of an 
excavating machine, said quick coupling comprising two parallel link arms 
supported by the operating arm, each link arm having an abutment portion 
with a support surface, and a locking means comprising a stationary wedge 
support attached to the working implement with an engagement surface 
facing the working implement and a movable tension pin displaceable by a 
power cylinder and having an engagement surface for wedging cooperation 
with the engagement surface of the wedge support, said locking means 
having support surfaces to cooperate by means of pressure with the support 
surfaces of the link arms. 
A quick coupling of the type described above has proved advantageous in 
several respects and has enjoyed wide practical use. It has the following 
advantages, for instance It has extremely low weight (about 30 kgs for a 
machine up to 14 tons) and therefore saves material, as well as being 
light to use and assamble; the construction is simple, making it quick and 
easy to mount the bucket to the excavating machine; it has no intermediate 
elevational piece which would cause building height and increased weight; 
thanks to its low weight it does not necessitate altering the bucket 
volume; it enables the force-absorbing dome of the bucket to be retained, 
thanks to the link arm construction in that the link arms may have an 
arc-shape adapted to the dome; it entails improved, even optimum 
conditions for the force transmission between bucket and operating arm and 
the link arms are not affected to any noticeable extent since the forces 
are transmitted directly to the hooks from the stick and vice versa via 
the stick shaft and sleeve, if any, abutting the hooks; thanks to its 
design and to said improved force transmission, the stipulated geometry of 
the bucket can be retained; it withstands diagonal breaking movements of 
the bucket since the link arms make the coupling resilient, because of the 
fact that the link arms have no rigid, stiffening joint between them and 
they can therefore move freely up and down at their end portions at the 
four contact points with the bucket, independently and in relation to each 
other and will thus always follow the diagonal breaking movements of the 
bucket when this is temporarily deformed and becomes distorted by lateral 
point stresses during work; it maintains a play-free joint between 
implement and operating arm at the contact points between operating-arm 
attachment means and hooks, even when the link arms follow the diagonal 
breaking movements of the bucket; it is self-adjusting with respect to any 
slight wear which may occur at the contact surfaces, and a play-free joint 
is thus always guaranteed. 
The quick coupling described above and known through patent specification 
EP 0 139 652 is designed for manual locking with the aid of a wedge-like 
tension pin which the operator forces into the desired locking position in 
the quick coupling with the aid of a suitable tool. Although the manual 
effort required is relatively little, there has been increased demand for 
the actual locking step with the tension pin to be carried out 
automatically from the driver's cab. The problem has been to achieve a 
hydraulically controlled locking device which is reliable to use, simple 
to manufacture and install, can be mounted without affecting the other 
features and functions of the quick coupling, does not increase the 
dimensions of the quick coupling, can be mounted in a protected place to 
avoid damage and dirt and which is relatively inexpensive to manufacture. 
The object of the present invention is to provide a locking device for a 
quick coupling of hydraulic or pneumatic type which can be operated from 
the driver's cab, and which solves the problem mentioned above. An 
essential advantage of the locking device according to the invention is 
also that it can be manufactured as an ancillary unit for already existing 
quick couplings, thus converting them simply from manual to hydraulic or 
pneumatic insertion of the tension pin without any structural alterations 
having to be performed on the quick coupling. 
This is obtained according to the present invention in that the locking 
means comprises a locking unit supported by the link arms, said locking 
unit having a rigid housing extending between the link arms, in which the 
tension pin is axially displaceable by the power cylinder between, in 
relation to the wedge support, an outer free position and an inner locking 
position, said housing having an opening located at a central portion 
thereof and disposed vertically in line with the wedge support of the 
working implement for friction-free receipt of the wedge support therein 
when the tension pin is in its free position, that the housing is provided 
with opposite supporting pins axially aligned to each other and arranged 
removably and with clearence freely to be received in opposite openings in 
the link arms, said supporting pins and openings being provided with said 
pressure-cooperating support surfaces, that the tension pin is of such 
sufficient length that its front end portion located at the engagement 
surface in locking position of the tension pin is positioned in a cavity 
of the housing and has a support surface for pressure-cooperation with a 
support surface in the cavity, and that one of the supporting pins is 
provided with a through-hole to receive a rear end portion of the tension 
pin in its locking position. 
BRIEF DESCRIPTION OF THE DRAWINGS 
The invention will be described further in the following, with reference to 
the accompanying drawings. 
FIG. 1 shows schematically from the side the outer end portion of the 
operating arm of an excavating machine, and top portion of a bucket 
connected to the operating arm via a quick coupling with a locking device 
according to the present invention. 
FIG. 2 shows schematically from above parts of the quick coupling with the 
locking device according to FIG. 1. 
FIG. 3 shows schematically parts of the quick coupling with the locking 
device according to FIG. 1, seen from the side. 
FIGS. 4 and 5 show the locking device according to FIGS. 1 to with a 
tension pin in locking position, seen from above and from the side, 
respectively. 
FIGS. 6 and 7 show the locking device with its tension pin in free 
position, seen from above and from the side, respectively. 
FIGS. 8 and 9 show the tension pin of the locking device, seen from the 
side and from above, respectively.

DESCRIPTION OF PREFERRED EMBODIMENT 
With reference to FIG. 1 the locking device according to the invention 
relates to a quick coupling of the type described in patent specification 
EP 0 139 652 for detachably coupling a working implement 50 to the 
operating arm 51 of an excavating machine, and which includes an 
attachment means 1 for the implement 50 and an attachment means 2 for the 
operating arm 51. The implement attachment means 1 is arranged on an 
outwardly facing surface 3 which may be the upper side of the working 
implement 50, for instance a bucket, or of a separate plate for attachment 
onto the working implement 50, or the upper side of a rotator, for 
instance, carrying the working implement. 
The implement attachment means 1 comprises a coupling device in the form of 
two hooks 52, spaced from each other and welded to said surface 3 at the 
front edge of the bucket opening 53, and open towards the upper side 3 of 
the bucket 50 to form semi-cylindrical support surfaces 54 for intimate 
cooperation with corresponding support surfaces of the operating arm 
attachment means 2. The implement attachment means 1 is provided with a 
hook-like wedge support 4 secured to the upper side 3 of the bucket 50 at 
its center line extending between said hooks 52. The wedge support 4 is 
positioned a predetermined distance from the hooks 52 and is provided with 
a functional engagement surface 5 (FIG. 3) facing down towards the upper 
side 3 of the bucket 50 to cooperate with a corresponding engagement 
surface 6 (FIG. 5) on a displaceable tension pin 7 as will be explained 
below. The wedge support 4 and tension pin 7 constitute parts of a locking 
means of the quick coupling. 
The implement attachment means 1 is also provided with two shoulder-like 
counter members 8 (FIG. 3) welded to the upper side 3, said counter 
members 8 being aligned with the hooks 52 and arranged between the wedge 
support 4 and the hooks 52, in the vicinity of the wedge support 4, i.e. 
at some considerable distance from the hooks 52. Each counter member 8 has 
a flat, functional support surface 9, located in the same plane and 
inclined inwardly towards the hooks 52 to cooperate with corresponding 
support surfaces on the operating arm attachment means 2 of the operating 
arm, as will be explained below. 
As shown in FIG. 1 the operating arm 51 of the excavating machine comprises 
a stick 55 and a hydraulic operating cylinder 56 arranged on the front 
side of the stick 55 (facing away from the excavating machine}. At its 
free end the stick 55 is provided with a horizontal pin or shaft 57 
pivotably carrying the bucket 50 and thus forming the center of 
oscillation of the bucket 50, while the hydraulic cylinder 56 either 
directly, or indirectly via links 58, is provided with a horizontally 
arranged pin or shaft 10 lying parallel to the stick shaft 57 and thus 
located in front of this and joined to the bucket 50 to give a controlled 
swinging movement of the bucket 50 about the center of the stick shaft 57. 
The stick shaft 57 and the shaft 10 form parts of an attachment means 2 of 
the operating arm 51, which also includes a link means in the form of two 
parallel link arms 11, 12 (FIGS. 1 and 2), each comprising a shaft support 
means 58 located at one end of the link arm, in the form of a sleeve or 
bushing, for instance, with a horizontal hole to receive the stick shaft 
57 and a shaft support means arranged at a predetermined distance from 
said hole in the form of a cylindrical sleeve 13 with a horizontal hole to 
receive the shaft 10. The sleeve 58 disposed at said one end has on its 
outer side a functional, concave or semi-cylindrical support surface 60 
extending transversely or axially (in relation to the stick shaft 57), 
having a predetermined radius corresponding to the radius of the 
semi-circular support surfaces 54 of the hooks 52. Maximum contact is thus 
obtained between these support surfaces 54, 60. The support surfaces 54 of 
the hooks 52 preferably encompass the largest possible sector angle, i.e. 
180.degree. The support surface 60 of the sleeve 58 cooperating with the 
hooks 52 is thus located immediately outside the stick shaft 57, as close 
to this as is permitted by the wall thickness of the sleeve 58, suitably 
about 15 mm. The support surface 60 is also located in line with and on 
both sides (similarly) of the central plane running through the centers of 
the shafts 10, 57, and on the side of the stick shaft 57 facing away from 
the link arms 11, 12. 
Each link arm 11, 12 comprises an abutment portion 14 (FIGS. 1 to 3) 
protruding freely in a backward direction from the shaft 10, i.e. in the 
backwardly extension of the link arm 11, 12, and forms an obtuse angle 
with the waist of the link arm, located between the shafts 10, 57. The 
abutment portion 14 is provided with a through-going rectangular opening 
15, the lower limit of which forms a functional, flat support surface 16, 
arranged to cooperate under pressure with a corresponding support surface 
of a supporting pin of said locking means, as will be described below. The 
two openings 15 are arranged in line with each other. 
Furthermore, each link arm 11, 12 is provided immediately below the sleeves 
13 with a counter member 17 (FIG. 3) designed with a functional, flat 
support surface 18 arranged to engage with said functional support surface 
9 of the counter member 8 of the bucket attachment means 1 to form a wedge 
effect. Said functional support surfaces 9, 18 incline towards the hooks 
52 with the same inclination. The inclination is such that an extended 
plane of the support surfaces 18 of the counter members 17 forms an acute 
angle with an extended plane of the support surfaces 16 of the abutment 
portions 14, in order to achieve the required wedge-effect when the link 
arms 11, 12 are clamped between the fixed wedge support 4 and the hooks 52 
on the bucket 50 via the counter members 17 with the aid of the 
displaceable tension pin 7 of the locking means. 
According to the present invention the locking means of the quick coupling 
comprises a separate locking unit 19 (FIGS. 2 and 4 to 7) having an 
elongate housing 20 to receive the tension pin 7, and a hydraulic cylinder 
21 to move the tension pin 7 between an outer free position and an inner 
locking position in relation to the wedge support 4. At its opposite end 
parts the housing 20 is provided with supporting pins 22, 23 inserted in 
the openings 15 of the link arms 11, 12. The lower sides of the supporting 
pins 22, 23 thus form functional support surfaces 24 for cooperation with 
the support surfaces 16 of the openings 15. The supporting pins 22, 23 are 
so dimensioned in relation to the openings 15 that they can easily be 
inserted without friction into their positions in the openings 15, 
providing a loose play joint which will allow the link arms 11, 12 to move 
freely in relation to each other when the quick coupling is subjected to 
breaking forces or other stresses, as explained in said patent 
specification EP 0 139 652. In the embodiment shown the housing 20 is 
divided into a first part 25 and a second part 26, from which said pins 
22, 23 protrude. The parts 25, 26 of the housing 20 are aligned with and 
rigidly connected to each other by a connecting element 27 extending 
substantially between the link arms 11, 12 and mounted on the side of the 
housing parts 25, 26 located nearest to the shaft 10. The hydraulic 
cylinder 21 of the locking unit 19 extends along the side of the 
connecting element 27 facing away from the housing parts 25, 26 and is 
attached to the connecting element 27 in a suitable manner, e.g. 
detachably as shown in FIG. 2, by means of a lateral extension of the end 
plate 28 of the hydraulic cylinder 21, said end plate 28 being provided 
with a pin 29 for friction-free insertion into a corresponding hole in the 
end of the connecting element 27, which is thus shortened to leave space 
for the end plate 28. Furthermore, the connecting element 27 is also 
provided with a longitudinal slot 30 (FIGS. 5 and 7), through which a side 
pin 31 of the tension pin 7 extends to connect the tension pin 7 to the 
piston-rod 32 of the hydraulic cylinder 21. The slot 30 is somewhat longer 
than the length of the first housing part 25. The housing 20 is provided 
with an opening 33, freely accessible at least from below and in front, 
said opening being formed as a gap in that the housing parts 25, 26 being 
spaced from each other. The opening 33 is located in the vertical center 
plane of the quick coupling and is slightly wider than the width of the 
wedge support 4, allowing the wedge support to be received in the opening 
33 without inconvenience when the bucket and operating arm is coupled 
together via the quick coupling. 
The second housing part 26 is provided with a cavity 34 (FIGS. 2 and 5) of 
sufficient height and axial extension (with respect to the housing 20) to 
permit requisite axial displacement of the tension pin 7 in the second 
housing part 26 when actuated by the hydraulic cylinder 21. The first 
housing part 25 is also provided with a cavity 35 which is, however, 
through-going and has a cross-sectional area slightly larger than that of 
the tension pin 7 allowing the tension pin 7 to move to and fro therein 
without obstruction when influenced by the hydraulic cylinder 21. The 
supporting pin 22 pertaining to the first housing part 25 is provided with 
a through-hole 36 forming an extension of the cavity 35 in the housing 
part 25, so that the rear end portion 45 of the tension pin 7 can be moved 
freely through the supporting pin 22 in a direction out from the link arm 
11 when actuated by the hydraulic cylinder 21. 
The tension pin 7, shown in more detail in FIGS. 8 and 9 is elongate with 
rectangular cross-section increasing from the foremost end 37 to form a 
wedge portion 38 having on its upper 
side a functional, flat engagement surface 6. The wedge portion 38 is of 
predetermined length, its length being greater than the width of the wedge 
support opening 33, so that when the tension pin 7 is inserted in locking 
position, a sufficient length of its front end portion 40 will be located 
in the cavity 34 of the second housing part 26. However, this end portion 
40 must at the same time be sufficiently short when the tension pin 7 is 
fully withdrawn to its free position, for the front end 37 to be located 
in the cavity 35 of the first housing part 25, free from the wedge support 
4, thus allowing the bucket to be disconnected from the quick coupling. 
The engagement surface 6 of the wedge portion 38 has the same inclination 
as the engagement surface 5 of the wedge support 4 so that the desired 
wedge-effect is obtained. The lower side of the tension pin 7 has 
functional front and rear support surfaces 41. 42 for cooperation under 
pressure with corresponding inner support surfaces 43, 44 (FIG. 5) on the 
second housing part 26 and the supporting pin 22 of the first housing part 
25. The intermediate surface 39, located in the first housing part 25 seen 
in the locking position of the tension pin 7, is thus free from pressure 
cooperation with this housing part 25. The length of the tension pin 7 is 
sufficient so that a rear end section 45 is obtained having an axial 
extension substantially equivalent to the thickness of the link arm 11. 
The tension pin 7 itself thus compensates for the weakening effect 
resulting from the shape of the supporting pin 22 with at least one 
relatively thin bottom wall so that the supporting pin 22 is reinforced by 
the inner tension pin 7 when inserted and maintained in its locking 
position by the hydraulic cylinder 21. Furthermore, the wedging force F 
(FIG. 5) existing in locking position is distributed between a larger 
partial force F.sub.2 exerted on the front end section 40, and a smaller 
partial force F.sub.1 exerted on the supporting pin 22. This advantageous 
distribution is thus obtained by the end section 40 being located closer 
than the rear end section 45 to the wedge position where the wedge-force F 
is exerted. 
As is clear from FIG. 6, one end of a tension spring 48 is secured to the 
lower side of the hydraulic cylinder 21, its other end being secured to 
the outer end of the piston rod 32. This tension spring 48, which has been 
omitted in the other figures for the sake of simplicity, endeavours to 
retain the piston rod 32 in the hydraulic cylinder 21, and thus the 
tension pin 7 in locking position. The tension spring 48 thus constitutes 
a safety device in the event of the hydraulic pressure failing in the 
cylinder if the hoses to the hydraulic cylinder become damaged, for 
instance. Besides this safety device, the safety system also includes a 
pilot-controlled non-return valve which forms a hydraulic lock in the 
hydraulic circuit which ensures that the necessary pressure is always 
maintained in the hydraulic cylinder when the tension pin 7 assumes 
locking position. Moreover, double control means, independent of each 
other, are provided in the driver's cab for connection of the hydraulic 
cylinder 21. 
In the embodiment shown the double-acting hydraulic cylinder 21 is disposed 
so that its greatest force is utilized to move the tension pin 7 out of 
its locking position. This is advantageous in view of the wedge forces 
which must be momentarily overcome then. Since the hydraulic rod 32 takes 
up part of the pressure surface on the piston only a small force is 
obtained when the tension pin 7 is moved to locking position. However, 
this has proved sufficient to achieve the desired wedge-effect. 
The bucket 50 is coupled extremely quickly and easily to the operating arm 
51 of the excavating machine by means of the quick coupling described. The 
first step is to adjust the operating arm 51 so that the stick shaft 57 is 
brought into direct engagement with the hooks 52 of the bucket 50, after 
which the counter member 8 of the bucket 50 and the counter member 17 of 
the link arms 11, 12, by connection of the hydraulic cylinder of the 
operating arm 51, are brought into alignment with each other at said 
support surfaces 9. In this starting position the wedge support 4 of the 
bucket 50 is located in the opening 33 between the two housing parts 25, 
26 of the locking unit 19 and the upper edge 46 at the front end 37 of the 
tension pin 7 is located in a sufficiently low level in relation to the 
engagement surface 5 of the wedge support 4 for the tension pin 7 to be 
moved in under the lip 47 of the wedge support 4 by connection of the 
hydraulic cylinder 21. The engagement surfaces 5 and 6 thus achieve a 
permanent wedge-action and a play-free joint is obtained. The wedge-force 
thus produced is transmitted to the slidingly cooperating counter members 
8, 17 so that the support surfaces 18 of the link-arm counter-members 17 
slide down along the support surfaces 9 of the counter member 8 of the 
bucket attachment means. This sliding movement builds up a permanent 
wedge-force which results in increased permanent abutment of the shaft 
sleeves 59 against the hooks 52 so that a permanent joint is obtained, 
entirely play-free, this abutment force against the hooks 52 deriving from 
said wedge-forces transmitted via the counter members 8, 17. 
The play-free joint thus obtained will be subject to very little wear. Such 
a little wear as does occur will not in any case give rise to any 
clearance since it is automatically and immediately compensated by the 
inherent wedge-force so that the joint remains play-free and a wedge-force 
is always maintained since the hydraulic cylinder 21 constantly exerts 
pressure on the tension pin 7. In other words, the joint is 
self-adjusting. 
The openings 15 in the link arms 11, 12 are provided in an existing quick 
coupling on the market to receive a through-going tension pin which is 
inserted manually with the aid of a tool to produce a wedge-action with 
the wedge support 4. The supporting pin 22, 23 of the locking unit 19 are 
designed to fit into these openings 15: This enables both new and old 
quick couplings of the described link-arm type to be equipped with a 
hydraulic or pneumatic locking unit 19 according to the present invention. 
In the latter case the unit may be considered an ancillary unit for quick 
couplings existing on the market enabling them to be easily converted to 
automatic locking control from the driver's cab, either hydraulically or 
pneumatically.