Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02242888 1998-07-14
2391 1\980402P1
-1-
Chain ConveYor
The invention refers to a chain conveyor according to the preamble of claim 1.
The chain conveyors discussed herein are used in general in storage shelves of
rack storage facilities where they serve as a conveying means for the goods to be stored.
The conveying means is usually looped over two deflections to form an endless conveying
means, whereby there is provided, as the real conveying means, a conveyor chain pro-
vided with rollers. In order to save costs and weight, however, not the entire circulating
conveying means is constituted as chain, but only about half of it, while the other half is
constituted by a strap.
As a support for the goods to be stored, in most cases pallets are used. Upon
storing the goods, the latter ones are laid onto the conveyor chain and, mostly by means
of a fork lift truck, pushed into the storage rack. If the need arises, the goods are pulled
out again by this fork lift truck.
The document WO 94/00370 entitled "Pallet-Support Rail and Slide-in Pallet-Stor-age Unit with Pallet-Support Rails and Pallet-Conveyor Track" discloses a chain conveyor
of the generic concept discussed herein. This conveyor is provided with a roller chain, the
supporting rollers thereof being connected to each other on both sides by means of a pair
of lateral link plates, whereby each second link of the chain is designed as supporting
strap member. The lateral link plates project downwards to such an extent that they can
laterally guide the upper run of the roller chain along the rail, whereby, for this purpose,
the rail is smaller in its width than the mutual distance of the two link plates of a pair. In its
lower portion, the rail made of aluminum comprises a return channel in which the lower
run of the roller chain is received, guided and supported.
The problems in connection with the chain conveyor discussed above consist in
that the lateral link plates of the roller chain have to take both tractive forces as well as
guiding forces. Thus, the lateral link plates cannot be made continuously of a material
CA 02242888 1998-07-14
2391 1~980402P1
- 2 --
which has good self-lubricating properties, like PTFE, but they have to be manufactured,
at least partially, of a high-strength material, for example steel. This design results in the
disadvantage that the frictional values between roller chain and guiding rail are relatively
high. This is also particularly true for the lower chain run received in the return channel
because here additionally the intrinsic weight of the roller chain has to be supported by
the lateral link plates. Due to the high frictional values arising between roller chain and
supporting rail, the constructional length of a chain conveyor with such a design is limited.
Moreover, it has shown that the frictional resistance is additionally increased by the trac-
tive load of the lateral link plates simultaneously designed as guiding means.
Further problems in connection with a chain conveyor as discussed herein before
consist in the fact that the chains used hereby can take only tractive forces. As soon as
thrust forces act on the chain, what is always the case upon loading of goods, the danger
exists that the chain folds by the mutual rotation of particular chain links that are subjected
to thrust forces.
Particularly that chain portion which is situated between the pallet to be pushed in
and the goods already stored is subjected to thrust forces to a high extent. The pallet to
be pushed in exerts a tractive force onto the chain portion situated behind that pallet and
guided around the front deflection. Since such deflections have a very small diameter due
to the limited available space, they have a bad efficiency and are nut suited for high trac-
tive forces. The tractive force in the chain deflected around the deflection is transmitted
via the elastic strap to the rear deflection which further decreases the efficiency, whereby
it is to be considered that the mass of the stored goods can amount up to 20 tons.
It is understood that a folding of the chain is most undesirable under the explained
circumstances because the total length of the chain is suddenly changed by this folding;
in an extreme case, this can result in a rupture of the strap and in a damage of the deflec-
tions. Moreover, by a folding of the chain, a distance between the goods, that possibly
has to be observed for the protection of the stored goods, can be changed. Also, it can
CA 02242888 1998-07-14
2391 1\980402P1
- 3 -
happen that particularly light weight goods are raised and rotated out of the horizontal
position upon a folding of the chain.
A folding cannot be avoided when conventional chains are used because the total
length of the chains and the circulating conveying means, respectively, can vary to a large
extent due to for instance temperature changes and expansion of the strap.
Thus, it is the object of the invention to improve a chain conveyor of the kind re-
ferred to in the preamble of claim 1 such that the chain can also take and transmit thrust
forces.
This object is met by the characteristics listed in the characterizing portion of claim
1.
By providing chain links which have stop elements that limit a mutual rotation of
adjacent chain links exceeding a certain angle of rotation in such a way that the roller
chain can transmit thrust forces, the danger that particular portions of the chain are folded
together is kept off and the disadvantages connected thereto are avoided.
Preferred embodiments of the invention are described in the dependent claims 2 to
10.
A further object of the invention consists in to provide a chain conveyor that is de-
signed with means for laterally guiding the roller chain, which are simply arranged and
can be manufactured at low costs, whereby the guide means shall present very low fric-
tional resistances between roller chain and support rail.
This object is met by the characteristics listed in the characterizing portion of claim
11.
In the following, the invention will be further explained, with the help of drawings. In
these drawings,
Figs. 1 to 3 show an individual chain link for a roller chain in three different views;
Figs. 4 to 6 show a guiding element for the roller chain in three different views;
Figs. 7 to 9 show a catch member for the roller chain in three different views;
CA 02242888 1998-07-14
2391 11980iO2P1
Fig. 10 shows a cross section through a support rail as well as through the roller
chain;
Fig. 11 shows a top view of a portion of a roller chain equipped with chain links ac-
cording to Figs. 1 to 3;
Fig. 12 shows a portion of the roller chain according to Fig. 11 in a side view.The Figs. 1 to 3 show a chain link 1 for a roller chain in a side elevation, a front
elevation and a top elevation. The chain link 1 is designed essentially U-shaped and
comprises a base portion 10 as well as two legs 11, 12. The base portion situated be-
tween the two legs 11, 12 constitutes the top cover of the chain link 1. Both legs 11, 12 of
the chain link 1 are provided with bores 13 which serve for receiving in each case a shaft
for interconnecting the chain links 1 and for bearing and supporting a support roller.
The base portion 10 of the chain link 1 is provided with two recesses 16 arranged
along one of the legs 11 and having a width b2 that is greater than the wall thickness of a
leg 11, 12. By providing these recesses 16, the assembling of several uniformly designed
chain links 1 to a chain is favored inasmuch as one leg 11, 12 of a preceding or subse-
quent chain link 1, in each case rotated by 180~ around the height axis, engages such a
recess 16.
Moreover, the base portion 10 is provided with a slot 15 running crosswise to its
longitudinal axis. This slot serves for receiving a catch member made of an elastic mate-
rial, as will be further explained herein below with the help of Figs 7 to 9
The basic shape of such a chain link 1 is manufactured preferably by punching,
while the U-shaped design is created by a subsequent bending of the punched out part.
The two end portions 17, 18 of the base portion 10 of a chain link 1 are preferably
of oblique shape. On the other hand, the two end portions of the base portion can be pro-
vided with a stepping, as outlined by the broken lines L.
The one leg 12 is provided with two projections 14 towering above the top side of
the base portion 10, whereby, due to manufacturing reasons, in each case the leg 12 ad-
CA 02242888 1998-07-14
2391 1~02P1
jacent to the shorter portion 1 7a, 1 8a of the base portion 10 comprises such projections
14.
In the Figs. 4 to 6, a guiding element 2 for the roller chain is shown in three differ-
ent views. This guiding element 2 essentially consists of a guiding plate 21 as well as of a
clamping part 24. Integrally formed at the inner side of the guiding plate 21, there is pro-
vided a strip member 23. The lower portion 26 of the guiding plate 21 serves for laterally
guiding the roller chain, while the guiding plate comprises a rest surface provided at its
top side and is designed to support the lower chain run of a circulating chain. The mode of
operation of this guiding plate 21 will be further explained herein below with the help of
Fig. 10.
The Figs. 7 to 9 show the catch member 19 in a side elevation, a front elevationand a top elevation. The catch member 19, preferably manufactured of rubber, serves as
a rest for goods to be supported by the chain links. For fixing it in the slot machined into
the base portion of the chain link, the catch member 19 comprises a holding portion 15
(should read "20") which is correspondingly designed to the that slot. For fixing, the hold-
ing portion 15 (should read"20") is slid through the slot and, thereafter, the catch member
is rotated by 90~. The catch member 19 preferably slightly towers above the projections of
the chain link such that light goods do not rest on the projections, but on the catch mem-
ber. However, by the elastic design of the catch member 19, it is ensured that heavy
goods compress the catch member and, thereby rest against the projections, whereby a
safe, non-positive connection between chain link and goods to be stored - pallet - is en-
sured.
Fig. 10 shows a cross section through a support rail 5 as well as a roller chain 8.
The support rail 5 comprises, at its top side, a track surface 6 projecting upwards that is
laterally limited by two guide faces. At the bottom side, the support rail 5 is provided with a
hollow chamber H having an open bottom in which are provided two auxiliary rails 7 on
CA 02242888 1998-07-14
2391 1U3~iO402P1
which the guiding plates 21 of the guiding elements 2 rest with their rest surfaces 25 and
on which the lower run 8b of the chain is vertically supported.
The roller chain 8 is constituted by a plurality of chain links 1 designed according to
Figs.1 to 3 and by supporting rollers 3, whereby in each case two chain links are inter-
connected by a shaft 28 in an articulated manner. The shafts 28 simultaneously serve for
bearing the supporting rollers 3. Into the particular shaft 28, a guiding element 2 is in-
serted which towers below the chain link 1 at one side. At the other side, the clamping
part 24 of the guiding element 2 engages the leg 12a whereby both the shaft 28 as well as
the guiding element 2 can be fixed in the position shown here. Additionally, for securing
the guiding element 2, a safety pin 29 can be provided, as illustrated, which is anchored
in a self-locking manner. In order to form a chain of uniform chain links 1, these are ar-
ranged alternately rotated by 180~ around their height axis, whereby the one chain links is
offset with regard to the other chain link, as seen in longitudinal direction of the roller
chain, by an amount corresponding to the wall thickness of a leg of a chain link. Besides
the chain links 1, also the guiding elements 2 are arranged alternately rotated by 180~;
this means, in other words, the guiding elements 2 are inserted into the particular shaft 28
alternately once from the left side and once from the right side, such that the roller chain 8
is guided on both sides of the track surface 6. The strip member 23 of the guiding element
2 extends along the bottom side of the particular leg of a chain link and prevents the
guiding element 2 from being rotated, whereby the height of the strip member 23 approxi-
mately corresponds to the wall thickness of a leg of a chain link. It is to add that the roller
chain 8 constitutes only approximately 60% of the circulating conveying means, while the
remaining 40% consist of a strap that is fixed to the two end of the chain.
Fig. 11 shows a top view of a portion of a roller chain that is provided with uniform
chain links 1 according to Figs.1 to 3 as well as with guiding elements 2 according to
Figs. 4 to 6. It can be seen from this illustration that the chain links 1 a, 1 b,1 c, 1 d are ar-
ranged alternately rotated around the height axis by 180~ and that the one chain link is
CA 02242888 1998-07-14
2391 ~\980402P1
offset with regard to the other chain link 1 a, 1 b, 1 c 1 d, as seen in the longitudinal direction
of the roller chain 8, by an amount of the wall thickness of the leg of a chain link 1 a, 1 b,
1 c, 1 d, such that in each case the one leg 11, 12 of a chain link engages the recess 16
(Fig. 3) in the base portion of the adjacent chain link. This design allows that the chain
links 1a, 1b, 1c, 1d, also can take up and transmit lateral forces.
Moreover, it is evident that the mean length L of the base portion 10 at least ap-
proximately corresponds to the distance A of the axes of two adjacent supporting rollers 3.
The base portion 10 preferably is shorter than the distance of the axes of two adjacent
supporting rollers by approximately 0.5 to 3 mm, such that, the chain being in its stretched
state, also a gap b in the order of 0.5 to 3 mm is created between the front faces of adja-
cent base portions 1 Ob, 1 Oc of adjacent chain links 1 b, 1 c. This design has the effect that
the mutual rotational movement of adjacent chain links, exceeding a certain angle of rota-
tion, is limited due to the fact that the front faces of adjacent base portions abut against
each other upon mutual turning back the chain links. In this connection, it is important that
the front faces of adjacent base portions of adjacent chain links are designed correspond-
ingly. A roller link designed in such a way, thus, can transmit thrust forces, without the
danger that the chain folds together at certain portions.
Fig. 12 shows the portion of the roller chain according to Fig. 11 in a side view. In
this illustration, the alternatingly arranged guiding elements 2 can be seen that tower be-
low the chain links.
A chain conveyor designed in such a way is of very simple construction and can be
manufactured at low costs, because both the chain links as well as the guiding elements
are of uniform design. By the provision of stop members limiting the mutual rotating
movement of adjacent chain links exceeding a predetermined angle in the above ex-
plained manner, the roller chain can also transmit thrust forces.
