OVERHEAD CONVEYOR

Abstract: An overhead conveyor comprises suspended trolleys (13), which are propellable along a track and which each have rollers (10) for engaging the outside of a rotatingly driven shaft (9), which is arranged adjacent to a carrying rail (2) and which by its rotation propels the trolley (13) along the track. Each trolley (13) has, in connection with its suspension, a cradle (12) with a first portion (15), on which said rollers (10) are arranged, and a second portion (16), which is spaced from the drive shaft (9) and on which the load-carrying part (14) of the trolley (13) applies a downward force (F1). The cradle (12) has, between its first and its second portion (15, 16), support rollers (11), which by coacting engagement with said carrying rail (2) produces a moment, which is generated by said downward force (F1) and which in turn gives the engaging force (F2) of the rollers (10) against the drive shaft (2).

Description: OVERHEAD CONVEYOR Field of the Invention The present invention relates to overhead conveyor systems and more specifically concerns an overhead con¬ veyor of the type stated in the preamble to claim 1. Background Art In overhead conveyors it is known to propel the load-carrying trolleys suspended from a rotatable drive shaft. A trolley included in such a system is suspended from the drive shaft by means of inclined rollers which are in rolling contact with the drive shaft. When ro¬ tating the drive shaft, the trolley is propelled along the track of the overhead conveyor. This principle is shown in e.g. PCT publication WO 88/04641 (see Fig. 2) . An alternative technique of propelling, by means of a rotatable drive shaft, trolleys in an overhead conveyor system is shown in a leaflet issued by the German company HENKE Maschinenbau GmbH & Co. KG and available, inter alia, at the Hannover fair in April 1996. In this over¬ head conveyor, called "FϋRDERSYSTEM HFS 2000", the trolleys are suspended from a superjacent track, under which a rotatable drive shaft is arranged. The suspension is such that a moment is generated around the upper suspension point of the trolley and that this moment is counteracted horizontally by a rolling contact between the drive shaft and a roller which is rotatably mounted on the trolley below and at a distance from the suspen¬ sion point. The system HFS 2000, however, suffers from certain drawbacks. Owing to the suspension arrangement, the trolley may be caused to swing around the suspension point, implying that the above-mentioned moment becomes too small or, if it comes to the worst, disappears momen¬ tarily, which may jeopardise the propulsion of the trolley. Moreover, the system is a single-side system since the trolleys can be deflected from the track in one direction only. Besides, the track must be stopped, for instance, when a trolley is to be propelled through a 180° curve or when the trolleys follow close upon each other. A further drawback is that special equipment e.g. turntables, is required m some positions where the track is to change direction, for instance in 180° curves. One more drawback is that the overall height of the system is relatively large. There is thus a need of a new overhead conveyor system which obviates these drawbacks. Summary of the Invention An object of the present invention therefore is to provide an overhead conveyor which is improved in rela¬ tion to prior art technique and which eliminates the above-mentioned drawbacks and in which the trolleys are safely suspended and have a great freedom of being de¬ flected in different directions. This and other objects, which will appear from the following description, have now been achieved by means of an overhead conveyor which is of the type described by way of introduction and which in addition has the fea¬ tures stated in the characterising clause of claim 1. Preferred embodiments of the invention are recited in the appended subclaims. According to the invention an overhead conveyor system is provided, in which the trolleys have a moment- based suspension, which ensures a contact, reliable to the propulsion of the trolley, between the engaging means and the drive shaft. Moreover, the great advantage is achieved according to the invention that the system is compact and obtains a much smaller overall height than similar prior art systems. For instance, it may be men¬ tioned that the overall height of a system according to the invention is about five times smaller than the over- all height of the known system HFS 2000 as discussed above. A further essential advantage is that the trolleys included in the inventive overhead conveyor, in the pre¬ ferred embodiment, can be deflected from the track in each direction owing to the positioning of the cradle under the drive shaft. Brief Description of the Drawings The invention will now be described in more detail with reference to the accompanying schematic drawings, which show currently preferred embodiments of the inven- tion and in which: Fig. 1 is a perspective view, seen obliquely from above and with certain parts cut away, of the suspension of a trolley included in an overhead conveyor according to a first embodiment of the invention, Fig. 2 is an elevational view of the suspension in the direction II-II in Fig. 1, Fig. 3 is a simplified view of the forces and the moment acting in Fig. 2, Fig. 4 is a view, corresponding to Fig. 2, of a second embodiment of the invention, and Fig. 5 is a view, corresponding to Fig. 4, of a third embodiment of the invention. Description of Preferred Embodiments Fig. 1 shows under the general designation 1 an overhead conveyor according to a first embodiment of the invention. The conveyor 1 comprises a supporting means, generally designated 2, in the form of a sectional ele¬ ment of substantially U-shaped cross-section, both U legs 3, 4 being directed downwards and the U web 5 being arranged horizontally. The U web 5 has, in a manner known per se, means 6 for suspending the carrying sectional element 2 from the roof (not shown) . The one U leg 3 is longer than the other U leg 4 and has at its lower longitudinal edge a downwardly directed portion 8 of forked or U-shaped cross-section, which will be described in more detail below. Inside the carrying sectional element 2 between the U legs 3, 4, a drive shaft 9 is arranged, which is here shown in the form of a tube and which is rotatably mounted by means of mounting elements (not shown) arranged inside the carrying sectional element 2. A cradle 12 provided with rollers 10 and support rollers 11 and belonging to a trolley generally designated 13 is arranged under the drive shaft 9. As the drive shaft 9 is rotated in the direction of arrow A, the cradle 12 and, thus, the trolley 13 are propelled in the direction of arrow B by the two inclined, freely rotatable rollers 10 being in rolling and fπctional contact with the circumferential surface of the drive shaft 9. During this propulsion, the four inclined, freely rotatable support rollers 11 are in rolling contact with the two opposite, arched upper sides 8a, 8b of the lower forked edge portion 8 of the U leg 3, said edge portion being parallel with the drive shaft 9. The axes of rotation 19 for two opposite support rollers 11 intersect in a point above said edge portion 8 where rolling contact takes place. The angle of intersection is advantageously about 45°. Fig. 2 illustrates in more detail the design of the cradle 12 and the rolling contact of the rollers 10 with the rotatable drive shaft 9 as well as the rolling con- tact of the support rollers 11 with the lower edge por¬ tion 8 of the carrying sectional element 2. During opera¬ tion, a schematically illustrated load carrier 14 belong¬ ing to the trolley 13 applies a downward force which is indicated by an arrow FI . Owing to this downward force FI, the support rollers 11, together with the forked por¬ tion 8 of the U leg 3, will form abutment means which generate a moment M, which in turn gives the essentially upwardly directed engaging force of the rollers 10 against the drive shaft 9. This engaging force is mdi- cated by an arrow F2 in Fig. 2. The play of forces between the forces FI and F2 which generate the moment M around a point P is shown schematically in Fig. 3. As indicated by a double arrow C in Fig. 2, the load carrier 14 is displaceably attached to the cradle 12 such that the distance between the point of attachment and the drive shaft 9 is adjustable with a view to producing dif- ferent moments M acting on the same. The overhead conveyor 1 according to the first em¬ bodiment of the invention thus comprises a number of sus¬ pended trolleys 13 which are propellable along a track and of which only one is shown in the drawings and which each have a means in the form of the rollers 10 for engaging the outside of the rotatable drive shaft 9, which by its rotation propels the trolley 13 along the track via said engagement. The cradle 12 belonging to the trolley 13 and arranged in connection with the suspension of the trolley 13 has a first portion 15, on which the engaging rollers 10 are arranged, and a second portion 16, which is spaced from the drive shaft 9 and on which the load carrier 14 of the trolley 13 applies the downward force FI . An abutment means in the form of the support rollers 11, which are in coacting engagement with the carrying sectional element 2 at the lower edge portion 8 thereof, is arranged between said first and second portions 15 and 16 of the cradle 12. As a result, the moment M is generated, which ensures the engaging force F2 of the engaging rollers 10 against the drive shaft 9. The arrangement is such as to accomplish a very reliable suspension of the trolley 13, conditioned by the moment M. The advantageous generation of moment, which results in a reliable suspension of the trolley 13, is advantage- ously achieved by the suspension point, in contrast to the system HFS 2000 mentioned by way of introduction, being arranged under the drive shaft 9 and being lat¬ erally offset thereto. This results in the engaging rollers 10 having their engaging positions on the under- side of the drive shaft 9. This confers the advantage that the conveyor 1 will be very compact and that its overall height can be kept considerably smaller than in prior art systems, as discussed by way of introduction. The moment-based suspension illustrated in Fig. 2 confers one more important advantage compared with e.g. the system HFS 2000. By the entire suspension means, thus the cradle 12 and its associated rollers and support rollers 10, 11, being positioned under both the drive shaft 9 and the lower free edge of the U leg 4, the trolley 13 can be deflected from the track in both directions. In practice, this is achieved by a branch track, which preferably has a roller profile corre¬ sponding to the forked portion 8, being swung into a broken-off portion of the carrying sectional element 2, the freely rotatable support rollers 11 rolling onto said branch track (not shown) . This makes the inventive over¬ head conveyor 1 very flexible. Moreover, the composition of the entire system will be flexible, since curves and the like can easily be provided by means of various bends and designs of the carrying sectional element. In curves and other changes of direction of the track, the rollers 10 can be disengaged from the drive shaft 9 and the trolley 13 can be propelled only by the rolling contact of the support rollers 11 with, for instance, a curved carrying sectional element or the like (not shown) . The number of engaging rollers 10 and support rol¬ lers 11 is not decisive of the invention as long as an appropriate engagement with the drive shaft 9 is obtained and the required abutment for generation of moment is obtained between the support rollers 11 and the carrying sectional element 2. However, it has been found advan¬ tageous to provide the cradle 12 with two pairs of in¬ clined, freely rotatable support rollers 11 which are each in rolling engagement with the two inclined surfaces 8a and 8b of the carrying sectional element 2 on the longitudinal lower edge portion 8. The two rolling sur¬ faces 8a and 8b on both sides of the U leg 3 preferably have a rounded or arched shape in order to facilitate the deflection of the trolleys 13. Furthermore, it has been found that the engaging means preferably comprises two inclined, freely rotatable rollers 10, which in their driving position are m rolling and frictional contact with the circumferential surface of the drive shaft 9. According to the first embodiment, each roller 10 is permanently inclined by its axis of rotation 18 making an angle with the axis of rotation 17 of the drive shaft 9. In a variant (not shown) , the rollers 10 are adjustably inclined between two end positions, in which the axis of rotation of the rollers 10 makes a maximum angle of de¬ flection with the axis of rotation 17 of the drive shaft 9. In an intermediate position, the axis of rotation 18 of the rollers 10 is parallel to the axis of rotation 17 of the drive shaft 9. When the rollers 10 are in the one end position, the trolley 13 is propelled in one direc¬ tion along the track, and in the other end position, the trolley 13 is propelled in the other direction. In the intermediate position, the rollers 10 have no inclination and then the trolley 13 stands still even if the drive shaft 9 as well as, of course, the rollers 10 rotate. The second and the third embodiment of the invention will be described below, parts already described m re¬ spect of the first embodiment having the same reference numerals. Fig. 4 shows the second embodiment, in which the supporting means 2 is differently designed and the cradle 12 has a slightly modified suspension. The supporting means 2 comprises an elongate rail 20, which, via a schematically shown connection 21, is connected to one leg 3 of the supporting means 2. The previously inclined support rollers 11 in the first embodiment are replaced by opposite support rollers 11a, lib, which are in rol¬ ling contact with the rail 20. The rolling surfaces of the support rollers 11a, lib are so adapted to the corre¬ sponding, arched upper and lower rolling surfaces of the rail 20 as to obtain a reliable rolling contact and ab¬ sorption of moment. The third embodiment, which is based on the second, is shown m Fig. 5. The supporting rail 20a connected with the leg 3 has been given a modified design, and the lower support rollers lib are replaced by a moment- absorbing sliding contact. The supporting rail 20a has in fact a downwardly directed, fixed flange 22, which is in sliding contact with a fixed projection 23 on the cradle 12. This embodiment results in a very reliable absorption of moment. A common feature of the described three embodiments is that the cradle 12 between its first and its second portion 15, 16 has an abutment means, which by rolling or sliding contact with some part of the supporting means 2 generates a moment which ensures the rolling contact between the rollers 10 and the drive shaft 9, which in turn ensures the propulsion of the trolley 13. It should also be pointed out that the play of forces F1-F2 and the moment generated therefrom are similar in the three em¬ bodiments. The invention is generally applicable also to other techniques of propelling trolleys in an overhead conveyor system. The rotatable drive shaft may for instance have an external, helical groove (not shown) , with which the engaging means of the cradle is engaged. The engaging means then preferably has the form of a freely rotatable roller, which runs in the helical groove of the drive shaft. However, it will be appreciated that the engaging means may be of a different design, e.g. a fixed follower in the form of a pin extending into the groove. The advantages of the invention in the form of im¬ proved suspension and reliable generation of moment are achieved also m the embodiments just mentioned. Finally, it may be emphasised that the invention is in no way restricted to the embodiments described above, and several modifications are feasible within the scope of the inventive idea as expressed in the appended claims. For example, it may be mentioned that the drive shaft need not necessarily be arranged in the supporting means, which may have a different cross-sectional shape, and that other arrangements are possible with a view to achieving the intended engagement with the drive shaft and abutting effect against the supporting means. That part of the supporting means with which the support rollers are in rolling contact, may have a different design as long as the intended rolling is achieved. Regarding the abutting effect, use can alternatively be made of different slide bearings or meshing.

Claims: CLAIMS 1. An overhead conveyor comprising suspended trolleys (13), which are propellable along a track and which each have a means (10) for engaging the outside of a rotatingly driven shaft (9), which is arranged adjacent to a support¬ ing means (2) and which by its rotation propels the trolley (13) along the track via said engagement, c h a r a c t e r i s e d in that each trolley (13) , in connection with its suspension, has a cradle (12), which comprises a first portion (15) , on which said engaging means (10) is arranged, and a second portion (16) , which is spaced from the drive shaft (9) and on which the load- carrying part (14) of the trolley (13) applies a downward force (FI), the cradle (12) having between its first and its second portion (15, 16) an abutment means (11; 11a, lib; 22, 23), which by coacting engagement with said supporting means (2) produces a moment (M) , which is generated by said downward force (FI) and which in turn gives said engaging means (10) its engaging force (F2) against the drive shaft (9) . 2. An overhead conveyor as claimed in claim 1, wherein the cradle (12) is located under the drive shaft (9) laterally offset in relation thereto, said engaging means (10) having its position of engagement on the underside of the drive shaft (9) . 3. An overhead conveyor as claimed in claim 1 or 2, wherein said abutment means comprises at least one freely rotatable support roller (11; 11a, lib) , which is in rolling engagement with a longitudinal portion (8; 20) of said supporting means (2), said portion extending in parallel with the drive shaft (9) . 4. An overhead conveyor as claimed in claim 3, wherein the abutment means comprises at least two pairs of support rollers (11; 11a, lib) , which each are in rolling engagement with arched rolling surfaces of said longitudinal portion (8; 20) of the supporting means (2) . 5. An overhead conveyor as claimed in claim 4, wherein the support rollers (11) included in a pair of support rollers are inclined and have axes of rotation (19) which intersect m a point above said rolling sur¬ faces (8a, 8b) . 6. An overhead conveyor as claimed in claim 4, wherein said longitudinal portion of the supporting means (2) consists of a rail (20) with opposite rolling sur¬ faces, with which opposite pairs of support rollers (11a, lib) are in rolling engagement. 7. An overhead conveyor as claimed in claim 1 or 2, wherein said abutment means comprises a fixed part (23) of the cradle (12), which is in sliding contact with a fixed part (22) of the supporting means (2) . 8. An overhead conveyor as claimed in any one of the preceding claims, wherein the engaging means comprises at least one freely rotatable roller (10), which m its driving position is in rolling and fπctional contact with the circumferential surface of the drive shaft (9) . 9. An overhead conveyor as claimed m claim 8, wherein the roller (10) in its driving position is perma¬ nently inclined by its axis of rotation (18) making an angle with the axis of rotation (17) of the drive shaft (9) . 10. An overhead conveyor as claimed in claim 8, wherein the roller (10) has an adjustable inclination between two end positions, in which the axis of rotation (18) of the roller (10) makes a maximum angle of deflec¬ tion with the axis of rotation (17) of the drive shaft (9), and an intermediate position, in which the axis of rotation (18) of the roller (10) is parallel to the axis of rotation (17) of the drive shaft (9) . 11. An overhead conveyor as claimed in any one of claims 1-7, wherein the drive shaft has an external, helical groove, with which the engaging means of the cradle is engaged. 12. An overhead conveyor as claimed in claim 11, wherein said engaging means has the form of a freely rotatable roller, which runs in the helical groove of the drive shaft. 13. An overhead conveyor as claimed in any one of the preceding claims, wherein the load-carrying part (14) of the trolley (13) is displaceably attached to the second portion (16) of the cradle (12) such that the distance between the point of attachment and the drive shaft (9) is adjustable with a view to producing different moments acting on the same.

Inventors: PERSSON ANDERS, SOELUND JOERGEN, PERSSON, ANDERS, SOELUND, JOERGEN
Applicants: OCS OVERHEAD CONVEYOR SYSTEM A, PERSSON ANDERS, SOELUND JOERGEN, OCS OVERHEAD CONVEYOR SYSTEM AB, PERSSON, ANDERS, SOELUND, JOERGEN
Application year: 1997
Main classification: B65G35
IPC codes: B65G35