BUCKET CONVEYOR WITH A ROTATABLE BOOM

Abstract: Bucket conveyor (13) with a rotatable boom, which comprises a frame (18) and a plurality of pulleys (21-22-23) on which an endless catenary (17) of buckets (20) is driven, the catenary (17) consisting of at least one chain (19) bearing a plurality of buckets (20), in which bucket conveyor (13) substantially a whole lower bar (28) contained between the front lower pulley (22) and the rear lower pulley (23) is able to oscillate and is rotated about the neighbourhood of the axis (30) of rotation of the front lower pulley (22). The variant of the bucket conveyor (13) with a rotatable boom comprises in cooperation with the front lower pulley (22) a support (41) able to move substantially in the plane on which such catenary (17) of buckets (20) lies.

Description: This invention concerns an articulated bucket conveyor according to the preamble of claim 1. Such a conveyor is known from document FR-A-2,518,071 or DE-C-425 111. Bucket loaders are known which take loose material from a heap of aggregate while they are oriented by means of the effect of a resilient, constant thrust and discharge such loose material at a desired place normally in a higher position. Such loaders are mainly, but not only, employed in concrete mixing plant to produce concrete. The present applicant produced earlier an evolutive solution which consists in having made capable of oscillating a part of the horizontal or almost horizontal segment that forms an extension or tail of the carrying frame. This solution enabled a smooth and constant tensioning of the catenary of buckets to be obtained. Before such innovation, when the loader was working, the tensioning of the catenary became progressively reduced and compelled the employees involved to act once more to tension the catenary. Before such innovation there was not only a great waste of time but the catenary and frame suffered during the step of tensioning the catenary. UP to the time of much innovation the machine operator estimated the tensioning values and, when the catenary was slack, there was always the risk that it would leave its pulleys. As a result of such innovatory improvement the natural elongation of the chain is now taken up by the lowering of the tail of the bucket loader. Owing to such solution, even if the extension or tail is too high when the tensioning has been carried out, or is too low before the tensioning, no part of the machine is impaired and the machine operator can perform such maintenance work at longer intervals and more accurately. Document FR-A-2,518,071 discloses a bucket conveyor having the features disclosed in the preamble of claim 1 of the present specification. The lower bar of said conveyor is stationary during use, and may be pivoted around an axis for the purpose of coolapsing the device for transport. Said lower bar should be supported by appropriate supporting means, as wheel or a wire. Document DE-C-425.111 discloses another bucket conveyor according to the preamble of claim 1 of the present specification. Also in this case the lower bar can be supported by means of a wheel. The present invention as claimed in claim 1 arranges for the whole lower part of the frame to be made movable and able to oscillate, the chain tension being maintained solely by means of the weight of the lower bar. This invention enables bucket loaders to be constructed with a smooth and constant tensioning of the catenary even when the arm has a limited length. The invention also enables the whole machine to be constructed with a smaller quantity of materials and with less processing. It also permits considerable simplification of the operations for storage, transport, assembly and maintenance. In particular, any machine operator, whether skilled or not, can perform the assembly and maintenance work, this being a thing which was impossible beforehand. Moreover, the invention makes possible a very wide range of adjustment of the tension of the bucket catenary since the inclusion of one single lower section permits the catenary to cooperate at all times with the transmission pulleys alone without any danger of coming into contact with portions of the frame. This is achieved by a bucket conveyor of the kind mentioned above, and further comprising the features disclosed in the characterising part of claim 1. The dependent claims disclose advantageous embodiments of the present invention. Thus the invention enables the bucket loader to work on ground which is not perfectly at a right angle to the vertical centre line of the silo. According to the invention the whole lower segment of the frame, that is, the segment which connects the two lower pulleys or pairs of lower pulleys is made capable of oscillating about the axis of rotation of the front lower pulley. The invention can therefore be applied to bucket loaders with a one-chain catenary or with a two-chain catenary. A variant of the invention makes use of such oscillatable tail to provide bucket loaders with a new capability which has not been envisaged earlier. It is known that concrete mixing plants work with two or more aggregates of which one is normally positioned along one side of the bucket loader, whereas the other is normally positioned along the other side of the bucket loader. A bucket loader which loads two or more types of aggregates and is moved by a device that gives it a required thrust in the required direction, turns to the right to load sand, for instance, and to the left to load gravel. At the point, however, at which the buckets start their upward movement a deposit of aggregate begins to form and is a mixture of sand and gravel dropped during the turning movement, thus distorting the true weights of the sand and gravel. Hitherto such possibility of a mistake has been eliminated by providing a specialized bucket loader for each type of aggregate. The present invention tends to eliminate this drawback and to provide further advantages, which will become clear later in the description. According to the invention, when the required quantity of aggregate has been reached and brought from the heap to the pre-selected place or unit, an elevation means lifts the front pulley of the almost horizontal segment momentarily. This lifting action enables the catenary to disengage itself from the heap of aggregate which forms at the position where the buckets start ascending. Such lifting action can be made to coincide with a halt of the catenary or with a momentary backward movement thereof. Such combination of a temporary lifting of the central pulley together with a halt or momentary backward movement of the catenary has the effect that the dosage of materials is not distorted but is very accurate. Moreover, the action according to the invention makes it possible to obtain the same effect as that produced hitherto by two orientable bucket loaders acting on separate heaps of aggregate. Let us now see an example of the invention, which is non-restrictive, with the help of the attached figures, in which:- Fig.1 gives a side view of a traditional application of a bucket loader; Fig.2 shows the example of Fig.1 from above; Fig.3 shows an application of the invention; Fig.4 shows a detail of a part of the embodiment of Fig.3; Fig.5 shows a variant of the invention; Fig.6 shows the embodiment of Fig.5 during the loading step; Fig.7 shows a resistance tooth or catch; Fig.8 shows the embodiment of Fig.5 during the lifting step; Fig.9 shows the embodiment of Fig.5 during the lowering step. Reference is made in the figures to a loader with a two-chain catenary, but the invention can also be transferred directly to a loader with a catenary consisting of one chain. Figs.1 and 2 show a concrete mixing plant 10 consisting of a silo 11, concrete mixer 12, dosing unit 42 and bucket loader 13. The bucket loader 13 comprises a frame 18 with an axis of orientation 27 and a catenary 17 of buckets 20. The plant 10 is installed on ground 14 over which a substantially horizontal segment 117 of the catenary 17 runs. As work proceeds, a frontal deposit 45 of aggregate builds up at the front part of the loader 13; such deposit 45 consists of the aggregate which falls from the buckets 20 because it is in excess or because of the swinging of the buckets 20, and which falls onto a chute 44 and is transferred thereby to a position where it is not contacted. As we said earlier, the bucket loader 13 can be oriented about the axis 27 by means of a substantially constant thrust provided by means which are known and are therefore not shown here. Such orientation takes place towards the right or left according to the arrows 29. If the loader 13 turns to one side, it withdraws aggregate from a heap 16, whereas if it turns to the other side, it takes aggregate from a heap 116. Such type of loader 13 and its method of working have been studied and embodied by the present applicant and are well known in the art. According to the invention the whole lower part of the frame 18, namely the lower bar 28, is pivoted on the same axis 30 as a front lower pulley 22 or in the neighbourhood of such axis 30 in the preferred embodiment shown in Fig.3. To assemble the bucket loader, the person employed for this purpose has only to insert a pin which acts as an axle 30, and the whole frame 18-28 is assembled. The catenary of buckets 17 is fitted next, so that it is positioned on a plurality of pulleys 21-22-23, of which the pulley 21 is normally powered and is driven by a motor 31. To tension the chain requires no particular care on the part of the machine operator, who only has to act on a threaded tensioner coupling 25 and then to clamp it with a clamp means 26. By means of this operation the lower bar 28 is raised slightly and thereafter gradually takes up its normal position during a long working period as a result of the natural elongation of the chain 19. Within this range of variation the whole catenary 17 remains at a constant tension owing to the force of the weight of the lower bar 28 acting on the rear lower pulley 23. Weights to govern the tensioning can be provided on the lower bar 28 or in cooperation therewith. According to the invention the tensioner coupling 25 can be located near the pulley 23 or at any position along the lower bar 28 and can be a two-threaded coupling or be a jack or be operated by a cam or be of another type. The above description shows clearly how easy it is to produce, store, transport, assemble or adjust the bucket conveyor. Moreover, the maintenance problems are considerably reduc ed, the precision of construction of the various elements forming the lower part of the frame having been made less evident. Let us now see how a specific case is shown as an example in Fig.5. The solution of the variant shown in Fig.5 provides a mechanical embodiment of the invention actuated by the direction of feed of the catenary. We have preferred to show this embodiment since it is the most complex one, but the engagement or disengagement action can be caused also by a jack, winch or any other unit suitable for obtaining the action of temporary lifting of the front pulley. In the operations of weighing by precision dosage, the presence of the frontal deposit 45 creates shortcomings and uncertainty regarding the accuracy of dosage of the components. As we said earlier, this invention tends to overcome such shortcomings and to broaden the field of application of bucket loaders. Let us suppose that the loader is applied to the heap of aggregate 16 and that a weighing unit 42 shows that the required weight of such aggregate has been reached. The electrical inverter of the motor 31 which drives the catenary 17 is then tripped and makes the catenary move in the reversed direction 138 (Fig.8). When the chain 19 is reversed, a catch or resistance tooth 132 with a prong 133 anchors itself to the chain 19 by swinging on the axis 143. The catch 132 is anchored so as to be able to swing on an oscillatable support or fork 41, which supports the pulley or pulleys 22. Owing to the action of the catch 132, which swings in the direction 139 together with the chain 19, the oscillatable fork 41 moves in the direction 40 (Fig.8), being pivoted at 35. Such movement of the oscillatable fork 41 brings the front lower pulley 22 upwards (Figs.5 and 8) in relation to its working position. Through such upward movement the buckets 20 are taken out of the area of contact with the deposit 45, which has formed at the position where such buckets 20 start their upward travel. Such lifting action is made possible by the articulated structure comprising the oscillatable fork 41 and lower bar 128, which is anchored so as to be able to swing on such oscillatable fork 41. In fact, the catenary 17 running on the pulleys 21-22-23 is deformed by the action of the fork 41 on the lower bar 128 (Fig.5) and assumes a triangular form without losing its tension. The tensioning is obtained by acting on the tensioner coupling 25, which presses against a fork 24 that bears the pulley 23, and by clamping at the required tension by means of the clamp 26. The oscillatable fork 41 is anchored so as to be able to oscillate at 35 on the frame 18. A mechanical safety end-of-run stop 37 is provided advantageously so as to avoid damage in the event of abrupt action. When the pulley 22 has reached its required raised position, the catch 132 is disengaged from the chain 19 and permits the catenary 17 of buckets to move backwards to perform any suitable requirements. The loader 13 is now detached from the heap 16 and is brought near the heap 116; the movement of the catenary of buckets 17 is then inverted once more and thus is in the direction of loading 38 of such catenary 17. This movement brings into action a catch 32, which clamps the chain 19 and brings the pulley 22 from 122 to the loading position (Figs.9 and 6). As in the case of Fig.8, owing to the position of the pivot 43 the catch 32, which has moved according to 39, becomes disengaged after a short length of travel of the chain 19, which thus becomes free to run once again. In the meantime the pulley 22 has reached bottom dead centre in its loading position. The movement of the pulley 22 to its higher position 122 with a resulting lifting of the bucket catenary 17 (Fig.5) from 117 to 217 and the return of the catenary 17 to its working position are actuated, in the example shown, by inversion of the motion (from 38 to 138 and then back to 38 again) of the catenary 17 bearing the buckets 20 and by means of the action of the catches 32-132. However, as we said earlier, the movement of the pulley 22 can be actuated also by jacks, turnbuckle couplings, winches or springs caused to act on the fork 41 or on the support of such pulley 22 or on the lower bar 128. The variant of the invention provides not only the advantages detailed above but also the same quality of dosage as can be obtained with several loaders of aggregate each of which is specially produced to handle only one type of aggregate.

Claims: Bucket conveyor (13) with a boom rotatable in a horizontal plane, the boom comprising a generally vertical frontal frame element (18) with a driving pulley (21) at its upper end and a lower bar (28-128) having a first end and a second end, the first end being fixed and pivoted at the lower end of the frame element (18), the lower bar (28-128) being able to pivot in a vertical plane, the rotatable boom comprising also a front lower pulley (22) positioned in the neighbourhood of the first end of the lower bar (28-128), a rear lower pulley (23) positioned in the neighbourhood of the second end of the lower bar (28-128), and endless catenary of buckets (17) comprising a plurality of buckets (20) carried on at least one chain (19) and means (25) for the tensioning of the catenary (17) by modifying the distance between the lower pulleys (22, 23) thereby determining a tensioned and generally horizontal travel for the catenary (17), the buckets (20) being transported along this horizontal travel in a loading position, from the rear lower pulley (23) to the front lower pulley (22) above the surface on which the bucket conveyor (13) operates, the bucket conveyor being characterized in that the lower bar (28, 128) is supported at its second end by the chain (19) running over the rear pulley (23) and in that the angular position of the lower bar (28, 128) in the vertical plane is determined solely by the tensioning of the catenary (17). Bucket conveyor (13) as claimed in Claim 1, in which the means for tensioning said catenary (17) consist of a threaded coupling (25). Bucket conveyor (13) as claimed in Claim 1, in which the means for tensioning said catenary (17) consist of auxiliary weights which are applied as required. Bucket conveyor (13) as claimed in any preceding Claim, in which the shaft (30) of the pulley (22) is removable to dismantle the lower bar (28). Bucket conveyor (13) as claimed in any preceding Claim, in which said lower bar (128) is anchored so as to oscillate on a support (41) able to move substantially in the plane on which said catenary (17) of buckets (20) lies. Bucket conveyor (13) as claimed in claim 5, in which there are means to move the support (41) in an oscillatory manner. Bucket conveyor (13) as claimed in Claim 6, in which said means to move said movable support (41) cooperate with said lower bar (128). Bucket conveyor (13) as claimed in Claim 7, in which the means to move the support (41) in an oscillatory manner are jacks. Bucket conveyor (13) as claimed in Claim 7, in which the means to move the support (41) in an oscillatory manner are winches. Bucket conveyor (13) as claimed in Claim 7, in which the means to move the support (41) in an oscillatory manner are screw shackles. Bucket conveyor (13) as claimed in Claim 7, in which said means to move said support (41) comprise catches (32-132) cooperating with said at least one chain (19) and actuated (39-139) by the direction of movement (38-138) of the catenary (17) of buckets (20) Bucket conveyor (13) as claimed in Claim 11, in which said catches (32-132) are positioned at the two sides of said front lower pulley (22).

Inventors: ZACCARON, LUIGI
Applicants: ZACCARON, LUIGI
Application year: 1984
Main classification: B28C7
IPC codes: B28C7