MXPA96001869A - Platform conveyor on skates, decadena gemela, supported in volad - Google Patents

Abstract

The present invention relates to a conveyor for transporting platforms on detachable runners, the conveyor comprises a transport direction or path defining a transport direction, endless driving means, and hanging means associated with the endless driving means, and defining a suspension direction and a lateral direction that is perpendicular to the plane defined by the suspension direction and by the transportation direction, each of the hanging supports has a free end comprising loading means designed to cooperate with loading means complementary on a platform on detachable skids, which supports an object to be transported, where all the hanging supports are associated with the endless driving means of a simple aerial conveyor, and where the endless drive means of the conveyor aerial comprise at least two devices of impulse n endless that are identical, parallel, and superimposed in the direction of suspension, and that are synchronized with each other, each hanging support is driven by the two identical endless drive devices and superpuest

Description

PLATFORM CONVEYOR ON SKATES, GEMELA CHAIN, SUPPORTED IN VOLADIZO FIELD OF THE INVENTION The invention relates to a platform conveyor on runners. The platform conveyors on skids are known because they comprise two overhead or aerial conveyors, without end, on either side of a transportation path that defines a transportation direction.

BACKGROUND OF THE INVENTION The function of such conveyors is to load a platform on skids that supports an object at the beginning of the transportation route, to transport the platform on skids along the transportation route, and to unload the platform on skids and the transported object, at the end of the transportation route. In addition, such conveyors are endless, with the loading means returning by way of a return path to the beginning of the transportation route to load another platform on runners. The road can pass through various workshops to transform the transported object. In particular, the transportation route may include at least one container that contains a product for the treatment of the transported object. For example, such containers may contain paint or the like, with the transported object being a vehicle body. Known carriers such as those described in German Patent DE-A-3, 024, 195 include oscillating trays, each of which is associated with two overhead or overhead conveyors. The oscillating trays carry the platforms on skids, and the objects to be transported are placed on the platforms on skids. This arrangement makes loading and unloading the platforms on skates complex, and due to the presence of the oscillating trays between the two elevated conveyors, the return track must be placed above or below the transportation track, which constitutes a space disadvantage. In addition, when the path passes through a treatment vessel, the radius of curvature of the transition where the path changes level is large.

Since the oscillating trays are free to rotate about an axis perpendicular to the direction of transportation, any sudden change in direction, due to the change in level could give rise to longitudinal oscillation of the oscillating trays, and therefore of The platform on skids and the transported object In order to limit such oscillation, the change in direction must be as gradual as possible, for example, the radius of curvature of the change in direction must be large. with this is that the transportation routes are made considerably longer.There are conveyors in which each conveyor device has its own suspended means, each of which has a free end and includes the means of loading designed to cooperate with the means of transport. complementary load, associated with the platform on skids that supports an object to be transported. When the conveyor is operated, the suspended means continuously follow a one-way transportation run over which these are associated with a platform on runners, and an empty return run over which they are returned empty at the start of the first leg transportation. Such a conveyor is described in French Patent FR-A-2 588 837. In that document, each of the elevated conveyors is a monorail conveyor, the suspended means are pendular members associated with the respective of the two monocarriers, and has free ends. in the form of hooks that serve as means to load the platform on skids. The platform on skids includes arms that serve as complementary loading means. The pendular members are returned via a return stroke from the outer side, which makes it possible to save space. Unfortunately, the conveyor as defined in French Patent FR-A-2 588 837 suffers in particular from the following drawbacks: the lateral and longitudinal degrees of freedom of the pendular members cause the platforms on runners to move or oscillate transverse or longitudinally in relation to overhead conveyors, and therefore, like the other known conveyors described above, the radii of curvature must be large for changes in direction to changes in level; Platforms are used on special skids, which have larger overall dimensions than the transported objects, due to the presence of the loading arms, thus requiring a transportation route that is wider than it could otherwise be. necessary In addition, such devices require a rectilinear transportation path due to the presence of the conveyors on either side of the mentioned road. In addition, on such a straight line transportation, only the race located between the conveyors can be used for transportation, since the return races from the outer side for the empty hanging supports, can not be used for transportation.

BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a platform conveyor on runners which in particular prevents the aforementioned drawbacks. For this purpose, the invention provides a conveyor for transporting platforms on runners, the conveyor comprises a transport path defining a conveying direction, the endless driving means, and the hanging supports associated with the endless driving means, and defining a suspension direction and a lateral direction that is perpendicular to the plane defined by the suspension direction and by the transportation direction, each of the hanging supports has a free end that comprises loading means designed to cooperate with the means of transport. complementary load, on a platform on skids that supports an object to be transported. According to the invention, all hanging supports are associated with the endless driving means of a simple elevated conveyor. According to a feature of the invention, the endless drive means comprise at least two endless drive devices which are identical, parallel, and superposed in the direction of suspension, and which are synchronized with each other, each drive being driven hanging bracket by any of two identical and superimposed endless drive devices. Each of the hanging supports is generally L-shaped, comprising a vertical column extending substantially in the direction of suspension, and a point or tooth extending substantially in the lateral direction -to the transportation route, the loading means of the hanging support comprise the loading tip or tooth, and the complementary loading means on the platform on sliding shoes comprise at least one receptacle for receiving the loading tip or tooth. Each endless drive device comprises an endless chain or the like, a plurality of chain support elements driven by the endless chain or the like, and mounted on the chain holder and the guide rail, and a plurality of absorption elements. of lateral force driven by the endless chain or the like, and mounted on a guide or lateral force absorption rail, each of the hanging supports being driven by means of at least a first and second lateral and guide force absorber elements, which belong to the respective endless drive devices. According to one characteristic of the embodiment, each of the lateral force and guide absorber elements driving a hanging support is directly secured to at least one support element. The hanging brackets are prevented from moving relative to the side and side force absorption elements either in the lateral direction as well as in the conveying direction, and these are mounted to rotate about the respective axes 5 which extend in the lateral direction in relation to the guiding and lateral force absorbing elements, with which these are associated. Advantageously, at least some of the hanging supports are suspended from the guide and lateral force absorbing elements of one of the two endless drive devices, superposed, identical, only, and at least some of the other hanging supports are suspended from the guiding and lateral force absorbing elements of the other of the two driving devices "e endless, superimposed, identical, only. In a particular embodiment, the chain support elements are trailers or trolleys that run over the guide and suspension rail, and are mounted to move in translation with the chain or _n similar, in the direction of transportation. The guide and lateral force absorber rail is a rail which is generally sectional grooved, each of the guiding and lateral force absorbing elements includes two wheels having axes of rotation perpendicular to the core of the channel section, and placed in the channel section, each of the wheels is mounted on one of the respective ends of a longitudinal beam element, the mentioned beam element includes the association means centered for the association with a hanging support, each end of the beam element being secured directly to a trailer or truck. The association means centered for the association with a hanging support comprise a spike extending in the lateral direction, and mounted substantially in the center of the beam element, the spike includes a free end, the vertical column of each hanging support extends in the general direction of suspension, being suspended from and propelled via the free end of the pin extending in the lateral direction of one of the guide and lateral force absorbing elements of one of the two endless driving devices, and merely driven via the free end of the pin extending in the lateral direction of one of the guide and lateral force absorbing elements of the other endless driving device. The platform on runners comprises two longitudinal slides interconnected by transverse pieces or crosspieces, and at least four C-shaped receptacles, each of which is placed substantially in the vicinity of a respective longitudinal end of a respective longitudinal slider, the placed receptacles in the front of the platform on runners have the openings of their C-shape facing the front of the platform on skates, the receptacles placed on the back of the platform on runners have the openings of their C-shapes facing towards the rear part of the platform on runners, a hanging support being separated from the preceding hanging support and the next hanging support by a distance substantially equal to the distance between the two receptacles on a longitudinal slide of the platform on runners. The means for loading the hanging support, and the complementary loading means on the platform on runners constitute a joint that pivots about an axis that extends in the lateral direction. The loading means of the hanging support and the complementary loading means of the platform on runners constitute a connection that offers improved security during the transportation run. A first advantage of the present invention lies in the fact that the conveyor comprises a simple elevated conveyor. In addition to saving space, this means that is possible for the transportation route includes curves in a plane perpendicular to the "direction of suspension." In this way it is possible to implement closed circuits in which the outward race and the return race are used to transport, with the empty return stroke that is as short as possible.In addition, the simple transporter is located towards one side of the transportation road and uses hanging supports in the form of L, which gives access without crowds to the The other object of the present invention lies in the fact that the suspended support is driven by the two endless drive devices, superimposed, thereby providing two points in which each of the hanging supports is associated with the raised conveyor, so that the hanging supports always remain mutually parallel, and so that the Tapes on skids oscillate longitudinally. The radii of curvature of the changes in the direction of changes in level can thus be significantly reduced, with which it becomes possible to reduce the length of the transport path.

A further advantage of the present invention resides in the fact that the hanging supports are prevented from moving in the lateral direction, whereby the platform on the runners is prevented from oscillating laterally. This feature makes it possible to use hanging L-shaped supports by capturing the lateral forces generated by the cantilevered position of the platforms on runners in the hanging supports.

DESCRIPTION OF THE DRAWINGS Other advantages and features of the present invention will appear from the following description given with reference to the accompanying drawings, in which: Figure 1 is a cross sectional, fragmentary, diagrammatic view of a conveyor of the invention; Figure 2 is a diagrammatic view seen in the direction of transportation, showing an endless drive device that is part of a conveyor of the invention; Figure 3 is a diagrammatic view seen in the lateral direction, showing an endless drive device that is part of a carrier of the invention; Figure 4 is a diagrammatic view seen in the direction of transportation, showing how a hanging support is associated with the endless drive devices; Figure 5 is a diagrammatic view of a level change in a conveyor of the invention; Y Figure 6 is a diagrammatic view showing a step of loading the platform on runners, a curved stage, and a step of unloading the platform on runners on a conveyor of the invention.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a conveyor for transporting platforms 1 on runners. The conveyor comprises a simple two overhead conveyor, positioned along a transportation path 3, which defines a conveying direction 4. The overhead conveyor 2 comprises the endless drive means 5 and the hangers 6 associated with means endless drive 5. the hangers 6 define a direction suspension 7 (substantially vertical) which corresponds to the direction in which the hangers hang under normal operating conditions, and a lateral (substantially horizontal) direction 8 which is perpendicular to the plane defined by the suspension direction 7 and the transportation direction 4. Each hanging support 6 has a free end 9 comprising the loading means 10 designed to cooperate with the complementary loading means 11 on the platforms 1 on runners, that support the objects to be transported 12. The endless drive means 5 of each conveyor e The output 2 comprises at least two endless drive devices 15a, 15b, which are identical, parallel, and superimposed in the direction of suspension 7. The endless drive devices 15a, 15b are synchronized with one another. Each of the hanging supports 6 is substantially L-shaped, comprising a column 25 that extends substantially in the suspension direction 7, and associated with both. endless drive devices 15a, 15b, identical and superimposed, and a tooth or discharge tip 25 extending substantially in the lateral direction 8 towards the transportation path 3. The biasing means 10 on the hanger 6 comprise tooth or tip 26, and supplementary means of load 11 on the platform skid, comprising at least one receptacle 11 for receiving the tooth or tip load 26. in order to prevent oscillate longitudinally hangers, each hanger 6 on the elevated conveyor 2 is driven by the two synchronized devices 15a, 15b, identical and superimposed. Thus, each hanger 6 is driven at two points which are mutually synchronized drive and superimposed, thus remaining mutually parallel in the direction of suspension 7, and this prevents hangers they oscillate longitudinally. Each endless drive device 15a, 15b includes an endless chain 16 or the like, a plurality of chain support elements 17 driven by the chain 16 and mounted on a rail 18 to guide and support the chain 16. <• In order to counteract the influence created by the weight of the platform 1 on skids resting against the tooth or loading tip 26 of each of the hanging supports 6, each endless driving device 15a, 15b includes a plurality of lateral force absorption elements 19, driven by the endless chain 16 or the like, and mounted on a guide and lateral force absorption rail 20, the hanging supports being associated each with the endless driving devices 15a and 15b respectively , via at least the first and second guide and lateral force absorption elements 19. The hanging supports 6 are prevented from moving relative to the guide and lateral force absorption elements 19 in the lateral direction 8 and in the conveying direction 4, and these are mounted to rotate about respective axes extending in the lateral direction 8 relative to the guide and lateral force absorption elements 19. Advantageously, and in order to relieve the load on the chain 16, each of the guide and lateral force absorption elements 19 driving a hanging support 6 is directly secured to at least one support element 17. * In one embodiment of the invention, shown in the figures, the chain support elements 17 are trucks or trailers 17 running on the guide rail and suspension rail, and these move in translation with the chain 16 or the like, in the transport direction 4. The guide and lateral force absorption rail 20 is a rail generally sectional grooved, positioned so that a core of the channel section is perpendicular to the direction of suspension 7. Each absorption element 19 of guide and lateral force includes two wheels 21 having axes of rotation perpendicular to the web of the grooved section, and placed in the grooved section, each of said wheels 21 is mounted in a respective end 24 of a longitudinal beam element 22. The beam element 22 includes the association means 23, centered, for association with a hanging support 6, and each end 24 of the beam element 22 is directly secured to a respective trailer or truck 17.

The association means 23 for the association with a hanging support 6, comprise a tang 27 extending in the lateral direction 8, and mounted substantially in the center of the beam element 22, the tang having a free end 28. The column 25 of each hanging support 6, which extends in the general direction of suspension 7, is associated with and propelled via the free end 28 of the spigot 27 extending laterally of a guide and lateral force absorption element 19 of each endless drive device 15a, 15b. Advantageously, in order to distribute the load on the two endless driving devices 15a, 15b, certain hanging supports 6 are suspended from one of the two endless driving devices 15a, 15b only, and are merely driven by the other driving device without end 15b, 15a. For example, the column is supported by means of the free end 28 of a tang 27 of a guide and lateral force absorption element 19, of one of the endless driving devices 15a, 15b, and is associated with the free end 28 of a pin 27 of a guide and lateral force absorption element 19 of the other endless driving device 15b, 15a, by means of an oblong slot having its main axis extending in the direction of suspension, and through which the spigot 27 passes without the column carrying it on it. In the embodiment of the invention, shown in the figures, the platform 1 on runners comprises two longitudinal runners 30 interconnected by transverse pieces or crossheads, and at least four C-shaped receptacles 11 positioned substantially in the vicinity of the longitudinal ends of the runners. longitudinal slides 30, the receptacles 11 are placed in front of the platform 1 on runners, the openings of their C-shaped faces facing the front of the platform 1 on runners, and the receptacles placed on the rear part of the platform 1 on skids, having the openings of its C-shaped faces facing the rear of the platform 1 on runners, a hanging support 6 of the raised conveyor 2 which is separated from the preceding hanging support 6 and the following hanging support 6 by a distance substantially equal to the distance between the two receptacles 11, on a longitudinal slide 30 of the platform 1 on skates. The teeth or charging tips 26 of the hanging supports 6 are long enough to cooperate with the two front receptacles, or with the two rear receptacles. In the loaded position, the diagonal or loading tip 26 of each hanger 6 and the respective loading receptacles 11 of the platform 1 on runners constitute a connection that pivots about an axis extending in the lateral direction 8. In addition, the teeth or loading tips 26 of the hanging supports 6, and the loading receptacles 11 of the platform 1 on runners, constitute connections that offer improved safety. The teeth or loading tips 26 may pivot about the columns 25 to keep the loading teeth 26 mutually parallel and in alignment with the receptacles on the platform 1 on runners, while the latter is being transported around a curve. In this way, the transportation route 3 can include changes in the transportation direction 4, which correspond to the curves lying in a plane perpendicular to the direction of suspension 7. In the embodiment shown in the figures, the loading tooth 26 , front, can move in pivot with backward direction, and the rear loading tooth, 26, can move in pivot with forward direction. Each of the receptacles includes a limit 40 such that, when the platform 1 on runners goes to a curve, the front loading tooth 26 comes into contact with the boundaries 40 of the front receptacles 11, and is constrained to pivot with backward direction, and the rear loading tooth 26 comes into contact with the boundaries of the rear receptacles 11, and is constrained to pivot in a forward direction, thus the front and rear loading teeth retain an excellent position to support the platform 1 on skates, transported. The conveyor operates as follows. A front hanging bracket 6 goes from the return stroke 14 to the transportation stroke 13, being pivotably displaced. The platforms 1 on skids to be loaded, are taken at the beginning of the transportation path 3 by a lower roller or chain type handling device (not shown). The displacement of the platform 1 on runners is synchronized with the forward speed of the hanging supports 6, so that the front receptacles 11 are coupled around the tip or loading tooth 26 of the hanging support 6, once the hanging support The front one is on the transport race 13. The platform 1 on runners is then moved on the handling device at »the forward speed of the hanging supports 6. A hanging support 6 then goes from the return stroke 14 towards the travel stroke. transport 13, being pivotably displaced and engaged in the rear receptacles 11. This results from the fact that the spacing between the two hanging supports 6 on the elevated conveyor 2 corresponds to the spacing between the receptacles 11, front and rear, on the platform about roller skates. The platform 1 on skids is then supported on the front and on the back, so that it can be removed from the lower handling device. Upon finding a change in level, the hanging supports 6 remain vertical and mutually parallel, and the platform 1 on runners gradually adopts the inclination of the change in level through the receptacles 11, pivoting around the loading teeth 26 of the hanging supports 6. When finding a level change with downward direction, the front receptacles 11 limit against the load tooth 26 of the front hanging support 6, thereby preserving the inclination towards the front of the platform 1 on runners. Upon finding a level change with an upward direction, the rear receptacles 11 limit against the loading tooth 26 of the front hanging bracket 6, whereby the platform 1 is pulled on skids which slopes in a backward direction. Upon finding a curve, the teeth or charging points 26, front and rear, pivot to keep mutually parallel and in alignment with the receptacles of the platform 1 on runners, along the entire length of the curve. These are prevented from pivoting when they come into contact with the limits 40 in the receptacles 11. At the end of the transportation path, a lower handling device supports the platform 1 on runners, again, reaching the front hanging support 6 at the end of the transportation path 3, being pivotably moved around the end wheels of the endless driving devices 15a, 15b, and is released from the front receptacles 11 on the platform 1 on runners. The platform 1 on runners is then withdrawn in a downward direction from the transportation path 3, either at a speed that is greater than the speed of the hanging supports 6, or pushed by the rear hanging support 6 until the rear hanging support It is pivotally displaced. The hanging supports 6 then travel empty along the return run 14 to the start of the transportation path 3, after which they take on board another platform 1 on runners, as described above. Since the conveyor includes only an elevated conveyor located along the transportation path 3, since the hanging supports 6 can accommodate the curves, and since the platforms 1 on runners are cantilevered outwards, the transportation route can take many configurations. Such a conveyor can accommodate changes in level and curves. In particular, such a conveyor offers twice the working length of a conveyor having two elevated conveyors, making it possible to transform the return stroke for empty hangers to a transportation race 13, with the return stroke 14 which is then made as short as possible. An auxiliary elevated conveyor located facing a portion of the conveyor, and equipped with hanging L-shaped supports for the application of a voltage or voltage to the transported object in electrophoresis steps, can be provided. The auxiliary conveyor does not support the platform on runners. Naturally, the invention is not limited to the modality described and shown, but rather numerous variants accessible to a person skilled in the art can be made, without going beyond the invention. In particular, without going beyond the scope of the invention, any means can be replaced by equivalent means.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (15)

1. A conveyor for transporting platforms on runners, the conveyor comprises a transport path defining a conveying direction, the endless driving means, and the hanging supports associated with the endless driving means, and defining a direction of suspension and a lateral direction that is perpendicular to the plane defined by the suspension direction and by the transportation direction, each of the hanging supports has a free end comprising the loading means designed to cooperate with the complementary loading means on a platform above skates, which supports an object to be transported; the conveyor is characterized in that all the hanging supports are associated with the endless driving means of a simple overhead or overhead conveyor.

2. A conveyor according to claim 1, characterized in that each of the hanging supports is generally L-shaped, comprising a vertical column extending substantially in the direction of suspension, and a charging tip or tooth extending substantially in the lateral direction towards the transport path, the loading means of the hanging support comprise the tooth or loading tip, and the complementary loading means on the platform on runners, comprising at least one receptacle for receiving the loading tooth.

3. A conveyor according to claim 1 or 2, characterized in that, when a hanging support is associated with a platform on runners, the means for loading the hanging support, and the complementary loading means on the platform on runners, constitute a connection that The pivot moves revolves around an axis that extends in the lateral direction.

4. A conveyor according to any of claims 1 to 3, characterized in that, when a hanging support is associated with a platform on runners, the means for loading the hanging support and the complementary loading means of the platform on runners, constitute a connection that offers improved security.

5. A conveyor according to any of claims 2 to 4, characterized in that the platform on runners comprises two longitudinal runners interconnected by crossarms, and at least four receptacles in the form of C, each of which is placed substantially in the vicinity of a respective longitudinal end of a respective longitudinal slider, the receptacles are placed in front of the platform on runners, having the openings of their C-shapes facing towards the front of the platform on runners, the receptacles are placed in the rear part of the platform on runners, having the openings of their C-shapes facing towards the rear of the platform on runners, a hanging support is separated from the preceding hanging support and the following hanging support, by a distance substantially equal to the distance between two receptacles on a longitudinal slide of silver skid-on form, the front receptacles are associated with the tooth or loading tip of a front hanging bracket, and the rear receptacles are associated with the tip or load tooth of a rear hanging bracket. -

6. A conveyor according to any of claims 1 to 5, characterized in that the endless driving means of the raised conveyor comprise at least two endless driving devices which are identical, parallel, and superimposed in the suspension direction, and which they are synchronized with each other, each hanging support being driven by the two identical and superimposed endless drive devices.

7. A conveyor according to claim 6, characterized in that each endless driving device comprises an endless chain or the like, a plurality of chain supporting elements driven by the endless chain or the like, and mounted on a chain support and a guide rail, and a plurality of side force absorbing elements driven by the endless chain or the like, and mounted on a guide and lateral force absorption rail, each of the hanging supports being driven via at least the first and second guide and lateral force absorption elements, which belong to the respective endless drive devices.

8. A conveyor according to claim 7, characterized in that each of the guide and lateral force absorption elements driving a hanging support is directly secured to at least one chain support element.

9. A conveyor according to claim 7 or 8, characterized in that the hanging supports are prevented from moving relative to the guide and lateral force absorption elements, either in the lateral direction as well as in the direction of transportation, and these they are mounted to rotate about respective axes extending in the lateral direction relative to the guide and lateral force absorption elements.

10. A conveyor according to any of claims 7 to 9, characterized in that at least some of the hanging supports are suspended solely from the guide and lateral force absorption elements of one of the two, superimposed, identical, endless drive devices. , and at least some of the other supports are suspended solely from the guide and lateral force absorption elements of the other of the two, superimposed, identical, endless drive devices. - -

11. A conveyor according to any of claims 7 to 10, characterized in that the chain support elements SOJI trucks or trailers that run on the guide and suspension rail, and these are mounted to move in translation with the chain or the like, in the direction of transportation, and because the guide and lateral force absorption rail is a rail that is • generally grooved in section, each of the guide and side force absorption elements includes two wheels that have perpendicular rotation axes to the web of the grooved section, and placed in the channel section, with each of the wheels being mounted on a respective one of the ends of a longitudinal beam element, the beam member includes the centered association means for association with a suspension bracket, each end of the beam element is secured directly to a truck or trailer.

12. A conveyor according to claim 10 or 11, characterized in that the centered association means, for the association with a hanging support, comprise a spigot extending in the lateral direction and mounted substantially in the center of the beam element, the spike includes a free end, the vertical column of each hanging support extends in the general direction of suspension, being suspended from and propelled via the free end of the shank extending in the lateral direction of one of the absorption elements of guide and lateral force of one of the two endless driving devices, and merely driven via the free end of the pin, which extends in the lateral direction of one of the guide and lateral force absorption elements of the other driving device endless.

13. A conveyor according to any of claims 1 to 12, characterized in that the transport route includes at least one change in the direction of transportation, which corresponds to a curve that falls in a plane perpendicular to the direction of suspension.

14. A conveyor according to claim 13, characterized in that the teeth or loading tips are mounted to pivot around the vertical columns, to keep the loading tips mutually parallel and in alignment with the receptacles on the platform on runners, while is being transported around a curve

15. A conveyor according to claim 14, characterized in that the front loading tip or tooth can pivot or rotate in the rearward direction, and the rear loading tip or tooth can pivot s rotate forwardly, each receptacle includes a limit so that when the platform on runners goes to a curve, the front loading tip or tooth comes into contact with the boundaries of the front receptacles and pivots in a backward direction, and the tooth or rear loading tip comes into contact with the boundaries of the moving forward receptacles in forward pivot, the front and rear loading teeth or tips are thus retained in an excellent position to support the platform on runners, transported.