DE102020003624B4 - Conveyor device for conveying components - Google Patents

Abstract

Conveying device for conveying components, with two conveyor tracks (3, 17) arranged in a vertical plane one above the other and at a distance from one another and inclined at opposite angles (α, β) in a straight line to one another, on which pallet trucks (2) can be conveyed primarily by gravitational force, with a upper conveyor track (3) which has a loading station (4) in which the pallet carriages (2) are loaded with components to be conveyed, the conveyor track (17) arranged under the upper conveyor track (3) receiving the unloaded pallet carriages (2) from a lifting device (13) that can be unloaded manually or by a robot, and these empty pallet trucks (2) can also be conveyed back to the loading station (4) predominantly by gravitational force, with the empty pallet trucks (2) being transported at the loading station (4) by a motor-driven, for example, by means a flexible traction means - rope or chain - drivable lift device (18) between the conveying levels of the conveyor tracks (3, 17) hub are movable, wherein the tensile force of the flexible traction means (28) can be limited to a safety amount by an optionally adjustable tensile force limiting device and the weight of the pallet truck (2) and the proportional liftable weight of the lifting device (18) and preferably that to be arranged on the pallet truck (2). components is completely or almost completely balanced by a gravimetric mass balancing device (27), the traction force limiting device being arranged on the side of the flexible traction means (28) opposite the activator and the traction force limiting device having one or more gear wheels which are connected to the flexible traction means designed as a link chain (28) mesh, adjustable friction clutches interacting non-positively with the gearwheels and limiting the tensile force transmitted to the lifting carriage (26) by the flexible traction means (28) to a predetermined value.

Description

The invention relates to a conveying device for conveying components.

Conveying devices are previously known in an incalculable number of constructions for different areas of application. In body construction in the automotive industry, such conveying devices for conveying components are used in many ways. Most conveying devices have motorized, usually electric, drives and have either conveyor belts made of elastic material or rollers for conveying components, which are arranged with low friction in roller bearings in order to convey components, for example pallet trucks with components, thereon.

From the DE 20 2007 016 549 U1 a conveyor device for components is already known, the component holders having a component guide for positioning and guiding one or more components. The conveyor tracks are designed as separately arranged feed and return tracks for the component holders, the feed and return tracks having oppositely directed slopes and the component holders being transported by gravity. A conveyor track can have a storage area at the end of the conveyor. The feeders are arranged on racks.

From the DE 20 2013 101 531 U1 a pneumatic lifting device for lifting a component carrier on a feed device is already known, wherein the lifting device has a lifting element for driving a component holder and wherein the lifting force of the lifting element is limited and the component carrier holder is moved between an insertion position and a feed position by applying an additional manual force.

the WO 2014/001333 A3 shows a feed device and a feed method for components, the feed device having a mobile component carrier and a downwardly inclined guide track and rolling bodies on the guide track and/or on the one or more component carriers for the rolling component carrier transport. The feeding device also has a braking device which is assigned to a rolling body and brakes it.

Also from the WO 2014/006014 A1 a feed device for components is already known, which has mutually inclined guideways.

A similar feeder shows the EP 3 170 772 A1 with conveyor tracks inclined in opposite directions, on which pallet trucks can be conveyed by gravitational force. Also the EP 2 653 410 A1 relates to such a feed device with mutually inclined conveyor tracks on which component receptacles can be conveyed by gravitational force.

Such a feeder relates to WO 2009/068241 A1 .

the DE 20 2012 102 447 U1 describes a feed device for components, the feed device having a downwardly inclined guide track, a mobile component carrier detachably connected to the guide track and interacting sliding and guiding means, in particular rolling bodies and rails, on the guide track and on the component carrier, the feed device having a loading point, where a component carrier is connected to the guideway by a worker and, if necessary, loaded with one or more components. At the loading point, the feed device has a transfer device that can be operated manually and actuated by hand against a restoring element for the positioned transfer of a component carrier to the guide track.

From the DE 20 2017 102 428 U1 a transfer device for a feed device with differently inclined guideways and a mobile component carrier for a component that can be connected to the guideways is already known, the transfer device having a manually operable lifting device with an upright lifting axis and with a track section that can be connected in alignment with the guideways. The lifting device has a base with a height-adjustable, frame-like lifting beam with a pivoting device, the lifting beam being aligned transversely or at an angle to the lifting axis and the track section being pivotably mounted on the lifting beam by means of the pivoting device. The conveyor tracks are also arranged at an angle to one another.

the DE 20 2012 102 405 U1 describes a feed device with mutually inclined conveyor tracks for components, the feed device having a mobile, brakeable building carrier and a downwardly inclined guide track and rolling bodies. The feeding device has a braking device which is assigned to a rolling body and brakes it.

From the DE 10 2006 018 718 A1 a loading device for highly automated production lines is already known, in particular in the automotive industry, in which a conveyor feeds parts, in particular semi-finished parts, from a storage unit via a conveyor line to a remote processing unit of the production line. The conveyor line includes an elongated guide element, the parts on said guide element is threaded on and the parts are provided with at least one bore for this purpose.

From the JP H09-136715 A a conveyor device for conveying components with conveyor tracks inclined in opposite directions is already known and one that is to be loaded manually, with the loading station being height-adjustable via a block and tackle.

the JP 2014-201426 A also shows a conveyor device with oppositely inclined conveyor tracks and a height-adjustable loading station, which is arranged at the end of the two conveyor tracks.

From the WO 2018/197384 A1 is a transfer device previously known with oppositely inclined conveyor tracks on which movable pallets for loading goods are arranged via rollers. The device has a manually operable lifting device with an upright lifting axis and with a track section that can be connected in alignment with the conveyor tracks, the lifting device having a base with a height-adjustable, frame-like lifting support with a pivoting device, and the lifting support is aligned transversely or at an angle to the lifting axis and the Track section is pivotally mounted on the lifting beam by means of the pivoting device.

From the JP 2015-40132 A a conveyor device with conveyor tracks running inclined to one another is already known, with lifting devices being provided at both ends, which have traction means guided via rollers in order to load or unload the conveyor tracks arranged at different heights from one another.

From the DE 21 2010 000 076 U1 a conveyor device defined as a picking device with conveyor tracks inclined in the same direction is already known, which is used to pick articles from goods containers in picking containers provided on a conveyor device, which is integrated in a storage rack, with a container providing device for feeding a goods container to a picking location, with a picking location for providing a goods container at a first end of the container staging device and with a container manipulation device at a second end of the container staging device opposite the picking location. The container manipulation device is formed by a conveyor device, which can be driven reversibly by an external drive means, for the supply and removal of a goods container.

task

The invention is based on the object of creating a conveyor device for conveying pallet trucks with components, in particular for use in body construction in the automotive industry, in which the risk of injury for a worker when loading pallet trucks is minimized and the drive power of a lifting device for lifting pallet trucks is reduced between stacked guideways.

This object is achieved according to the invention by a conveyor device for conveying components, in particular in body construction in the automotive industry, with two conveyor tracks which are arranged one above the other in a vertical plane and are spaced apart from one another and are inclined in a straight line towards one another at opposite angles, on which pallet trucks can be conveyed primarily by gravitational force, with an upper conveyor track, which has a loading station in which the pallet trolleys are loaded with components to be conveyed, with the conveyor track arranged under the upper conveyor track taking over the unloading pallet trolleys from a lifting device that can be unloaded manually or by a robot and these empty pallet trolleys also being lifted up mainly by gravitational force the loading station can be conveyed back, the empty pallet wagons being driven by a motor at the loading station, for example by means of a flexible traction means - cable or chain - between the conveying level NEN of the conveyor tracks are liftable, the tensile force of the flexible traction means can be limited to a safety amount by an optionally adjustable tensile force limiting device and the weight of the pallet truck and the proportionate liftable weight of the lifting device and preferably the components to be arranged on the pallet truck are completely or almost completely by a gravimetric mass balancing device is balanced, with the traction force limiting device being arranged on the side of the flexible traction means opposite the activator and in that the traction force limiting device has one or more gears which mesh with the flexible traction means designed as a link chain, with adjustable friction clutches interacting in a non-positive manner with the gears, which the on the Limit the traction force transmitted by the flexible traction means to a predetermined value for the lift truck.

In the conveyor device according to the invention, only a small driving force is required to move the lifting device for the pallet truck between the conveyor tracks arranged one above the other, since the weight of the lifting device of the lifting device, which is to be arranged on it, is absorbed by the lower conveyor track taking empty pallet truck is practically compensated by the gravimetric mass balancing device. Therefore, only an extremely small driving force is required for the manual or motor drive of the lift device. The tensile force of the flexible traction device (rope or chain) can be adjusted to such a force that a worker in the area of the charging station cannot be injured. For example, the pulling force can be set to a remaining weight of 5 kilograms, which can be overcome by the manual strength of the person working in the area of the loading station without great exertion. The traction force limiting device designed as a friction clutch then simply slips through so that no injuries can occur. The tensile force limiting device can be produced with simple, robust components and can be continuously adjusted to the desired tensile force of the flexible traction means—cable or chain.

Further inventive developments are described in patent claims 2 to 11.

Patent claim 2 describes a conveyor device in which the lifting device is assigned a lifting carriage, which is connected to a flexible traction device, for example, at the end section of which weights are freely suspended on one or both sides of the lifting carriage, which form the gravimetric mass balancing device. Such a construction ensures with simple means that the weight of the lifting carriage of the lifting device can be practically compensated so that, in combination with the tensile force limiting device, the worker working at the loading station cannot be injured. The gravimetric mass balancing device forming the weights can be produced with simple, maintenance-free means.

Claim 3 describes a conveying device in which the flexible traction means can be driven by a motor to move in a lifting manner by an activator working in opposite directions. According to patent claim 4, this motor drive is formed by a pneumatic activator to be acted upon on both sides. Since compressed air is available everywhere, especially in body construction in the automotive industry, such pneumatic activators can be used particularly inexpensively.

If necessary, the motor drive for the flexible traction means can also be an electric motor, as described in claim 5, which can be reversed in a suitable manner in order to drive the lifting carriage of the lifting device in opposite lifting directions.

It is particularly advantageous if, according to patent claim 6, the motor drive for the flexible traction means is a pneumatic activator without a piston rod. Such an activator takes up relatively little space and can be assigned to the loading station in the longitudinal direction at low cost.

Patent claim 7 describes a conveying device in which the friction clutch has brake shoes which are loaded by compression springs and act in a non-positive manner on opposite side faces of the associated gear wheel.

Another advantageous embodiment is described in patent claim 8, which is characterized in that the adjustable tensile force that can be transmitted to the lifting carriage of the lift device by the flexible traction means can be reduced to a low lifting mass of 1 to 15 kilograms, preferably 2 to 8 kilograms, in particular 3 to 5 kilograms, is limited.

The conveying device shown in patent claim 9 is characterized in that the lifting device has two or more vertical tubes arranged parallel to one another and at a distance from one another, between which the rodless activator designed as a pneumatic cylinder is arranged on one side of the loading station and rollers are assigned to vertical tubes, via which the traction means in question is arranged, at the end of which the mass balancing device is arranged in the form of exchangeable weights. Such a conveying device can be set up and dismantled without any problems at suitable points in the halls of the automotive industry.

According to patent claim 10, the conveyor device is characterized in that the pallet trucks have rollers on their underside with which they roll smoothly on the rails of the conveyor tracks. The pallet trucks with the components can be easily moved by gravity.

Claim 11 describes a further advantageous embodiment, which is characterized in that the conveyor tracks are arranged on the floor by means of frames which are formed from tubes which are polygonal in cross-section.

• 1 Eine Fördervorrichtung in schematischer Seitenansicht beim Beladen einer Palette durch einen Werker;
• 2 den Entladebereich des aus 1 ersichtlichen Förderers, wobei sich die Palette mit der Last noch in Entladestellung befindet;
• 3 den aus 2 ersichtlichen Endbereich des aus 1 ersichtlichen Förderers, wobei die entladende Palette auf die untere Förderebene der aus 1 ersichtlichen Fördervorrichtung abgesenkt wurde;
• 4 die aus 1 ersichtliche Fördervorrichtung beim Rücktransport von Palettenwagen zur Beladestation;
• 5 eine Einzelheit aus der Beladestation, im größeren Maßstab, mit Massenausgleichsvorrichtung und kolbenstangenlosem Aktivator;
• 6 die aus 5 ersichtliche Einzelheit in konstruktiver Darstellung, im größeren Maßstab;
• 7 eine Einzelheit aus der Beladestation;
• 8 eine Zugkraftbegrenzungsvorrichtung der Beladestation, abgebrochen dargestellt, in perspektivischer Darstellung;
• 9 eine Einzelheit aus 8, teils im Schnitt;
• 10 einen Palettenwagen in Unteransicht, in perspektivischer Darstellung;
• 11 eine Stoppeinrichtung oder Bremsvorrichtung, in perspektivischer Darstellung, und
• 12 die aus 11 ersichtliche Stoppeinrichtung oder Bremsvorrichtung in Anordnung an Führungsschienen der Fördervorrichtung, ebenfalls perspektivisch und abgebrochen dargestellt.

In the drawing, the invention is illustrated - partly schematically - using an exemplary embodiment. Show it:

• 1 A conveyor device in a schematic side view when loading a pallet by a worker;
• 2 the unloading area of the 1 shown conveyor, with the pallet with the load still in the unloading position;
• 3 the off 2 visible end of the 1 visible conveyor, with the unloading pallet on the lower conveyor level of the out 1 apparent conveyor has been lowered;
• 4 from 1 Conveyor device that can be seen when transporting pallet trucks back to the loading station;
• 5 a detail from the loading station, on a larger scale, with mass balance device and rodless activator;
• 6 from 5 visible detail in constructive representation, on a larger scale;
• 7 a detail from the loading station;
• 8th a tensile force limiting device of the loading station, shown broken off, in a perspective view;
• 9 a detail 8th , partly in cut;
• 10 a pallet truck in bottom view, in perspective;
• 11 a stopping device or braking device, in perspective view, and
• 12 from 11 Apparent stopping device or braking device arranged on guide rails of the conveyor device, also shown in perspective and broken off.

In 1 For example, a worker 1 loads a pallet truck 2, which is provided with rollers 1a on its underside, with a component, not shown in detail, designed as piece goods, which is to be transported in the X direction.

The loaded pallet truck 2 is pushed onto the conveyor track 3, which is inclined at an acute angle α, by the worker 1 and then moves in direction X with its rollers 1a mounted in roller bearings be provided or rollers, which are mounted in roller bearings and move the pallet truck 2 from the loading station 4 to the unloading station 5. In this case, the roles 1a are omitted. If necessary, one or more of the rollers or rollers arranged parallel and at a distance from one another can also be motor-driven. The movement of the pallet truck 2 is supported in the X direction by the gravitational force corresponding to the angle of inclination by the downhill force G sin α, where α and β correspond to the respective angle of inclination of the conveyor tracks 3, 17 and G the total weight of the pallet truck 2.

The loaded pallet wagons 2 move to the unloading station 5 and can accumulate one behind the other and thus require a kind of buffer for the further pallet wagons 2 ( 1 and 2 ).

A stopping device can be provided at the end of the conveyor track 3, which will be discussed further below. Over the length of the conveyor track 3, several such 11 apparent stopping devices 6 may be provided. The pallet truck 2 carries a type of fin 7 on its underside. The stopping device 6 has a pair of opposing brake shoes 8, 9 through which the fin 7 of a pallet truck 2 can slide. The brake shoes 8, 9 are loaded by springs in the closed position, ie against the outer surfaces 10 of the fin 7. The brake shoes 8, 9 can be moved by a wedge 11 in the open position. The wedge 11 is pushed between the brake shoes 9 by a controllable pneumatic cylinder 12 . If a pallet truck 2 is braked, the fin 7 is held in place by the brake shoes 8, 9 in a non-positive manner with the associated pallet truck 2. If the brake shoes 8, 9 are moved into the open position by the wedge 11, the pallet truck 2 is released and can move on the conveyor track 3 in the X direction.

As already mentioned, such stopping and braking devices as they are made of 11 as can be seen, can be provided at various points on the conveyor track 3 and can also serve as a speed reducer in order to prevent the pallet trolleys 2 from hitting each other hard and also enable gentle transport and also prevent the goods to be transported from falling off the pallet trolleys 2.

At the end of the conveyor track 3 is the unloading station 5, which has a lifting device 13, which essentially consists of a piston rod 14 and a cylinder 15, which is to be acted upon alternately on both sides with a hydraulic fluid and has a plate shape 16 connected to the piston rod 14, on which the pallet truck 2 runs up at the end of the conveyor track 3 and as a result the corresponding vertical lifting movement of the piston rod 14 can be lowered in direction T to the level of the lower conveyor track 17 and can then be pushed in direction V onto this. In principle, the conveyor track 17 can be equipped like the conveyor track 3 .

How from the 1 and 4 can be seen, the conveyor track 3 is inclined at an acute angle α in a straight line in the direction X, while the conveyor track 17 is inclined at the acute angle β in a straight line in the direction V, ie in the direction of the loading station 4 . The acute angles α and β can be the same, but they can also be different.

The so-called downhill force supports the movement of the pallet truck 2 both in the X direction and in the V direction, since the downhill force is formed by the product of the weight of the respective pallet truck 2 and the sine of the angle of inclination α or β. As a result, if necessary, a special motor drive for the pallet truck 2 can be dispensed with both for the drive in the X direction and for the drive in the V direction.

In any case, there is a uniform, jerk-free movement of the pallet truck 2 both in the X direction and in the V direction according to the angles of inclination α or β.

Pallet trucks 2 can also be stacked one behind the other on the lower conveyor track 17 as on the upper conveyor track 3 . As in the upper conveyor track 3 , stopping devices 6 or braking devices, as have been described in connection with the upper conveyor track 3 , can likewise be arranged in the lower conveyor track 17 .

The pallet trolleys 2 moving in direction V on the lower conveyor track 17 reach the loading station 4, where they can be raised or lowered by a lifting device 18, which can also be moved vertically up and down, to the height loading area for the worker 1 by means of a pneumatic cylinder 19 without a piston rod. A chain hoist 20 is used for this purpose, which in the present case consists of a link chain and toothed wheels 21 and 22 which are arranged on a frame-like frame 23 . The frame-like frame 23 is assigned spaced, parallel and spaced-apart tubes, which extend in the lifting direction AB and have a cross-section running transversely to their longitudinal axis. They are polygonal and have numerous through-holes. The through holes can also be omitted.

Arranged between the vertical tubes 24, 25 is a lifting carriage 26 which can be moved in directions A and B via the chain hoist 20 by acting on the pneumatic cylinder 19 in opposite directions.

The empty pallet wagons 2 are in turn moved into the loading area for the worker 1 so that he can load the respective pallets with goods.

A mass balancing device 27 is assigned to both sides of the chain hoist 20 and thus the lifting carriage 26 , which consists of weights which are each connected to the lifting carriage 26 and thus indirectly also to the chain hoist 20 via a flexible traction mechanism 28 . The respective flexible traction mechanism 28 is guided over rollers 29 and 39 and connected to the lifting carriage 26 . The lift truck 26 is positively guided in the vertical direction A and B on opposite guides 31 . The mass balancing device 27 balances the weight of the lift truck 26 and possibly also a partial weight of the chain hoist 20 and the load on the lift truck 26, i.e. pallet truck 2, and if necessary the load, completely or almost completely, so that for the drive of the loaded lift truck 26 only a small driving force by the pneumatic cylinder 19 is required in direction A. In addition, the worker 1 is largely protected against unintentional movement of the lift truck 26 during loading, since this is practically completely or almost completely weightless for the worker 1 after loading. In contrast to the embodiment shown, it may be sufficient to provide a mass balancing device 27 on only one side, just as it is usually sufficient to provide only one rodless pneumatic cylinder 19 for driving the lifting truck 26 and the pallet truck 2 with load to be arranged on it.

A traction force limiting device 32 which interacts with the chain hoist 20 is assigned to the lift truck 26 . As a result, the tensile force can be limited to a value that is not harmful to the worker 1, for example to 5 kilograms, so that no injuries can occur.

The conveyor tracks 3 and 17 are arranged on frames 33, 34 which, in the illustrated embodiment, consist of tubes with a polygonal cross-section, in this case octagonal, which each consist of opposing, preferably in pairs, coaxially arranged through bores that extend over the longitudinal axis of the respective frames 33 , 34 are arranged at equal distances from one another. As a result, any device parts can be arranged intermittently on the conveyor tracks 3 and 17 by means of screws or the like. Several tubes can be arranged, which form a frame-like framework in order to store the conveyor tracks 3 and 17 at a height distance from the floor 35 .

The traction force limiting devices 32 each have a carriage 36 on which in pairs Gears 37 are arranged, each of which is associated with adjustable friction brakes 39 . Each of the brakes has two brake shoes 40, 41 which can be pressed on opposite side surfaces of the associated gear wheels 37 and which are guided and mounted in opposite brake cylinders 42, 43 so as to be longitudinally displaceable. Each of the brake shoes 40, 41 is pressed against the respective side surface by a prestressed compression spring 44, with 9 only the two side surfaces 45, 46 have been provided with reference symbols. The prestressing of the compression springs 44 can be adjustable, so that the frictional force with which the brake shoes 40, 41 are pressed in direction P against the side surfaces 45, 46 can also be adjusted.

The features described in the patent claims and in the description and evident from the drawing can be essential for the realization of the invention both individually and in any combination.

Claims (11)

Conveying device for conveying components, with two conveyor tracks (3, 17) arranged in a vertical plane one above the other and at a distance from one another and inclined at opposite angles (α, β) in a straight line to one another, on which pallet trucks (2) can be conveyed primarily by gravitational force, with a upper conveyor track (3) which has a loading station (4) in which the pallet carriages (2) are loaded with components to be conveyed, the conveyor track (17) arranged under the upper conveyor track (3) receiving the unloaded pallet carriages (2) from a lifting device (13) that can be unloaded manually or by a robot, and these empty pallet trucks (2) can also be conveyed back to the loading station (4) predominantly by gravitational force, with the empty pallet trucks (2) being transported at the loading station (4) by a motor-driven, for example, by means a flexible traction means - rope or chain - drivable lift device (18) between the conveying levels of the conveyor tracks (3, 17) hub are movable, wherein the tensile force of the flexible traction means (28) can be limited to a safety amount by an optionally adjustable tensile force limiting device and the weight of the pallet truck (2) and the proportionate liftable weight of the lifting device (18) and preferably that to be arranged on the pallet truck (2). components is completely or almost completely balanced by a gravimetric mass balancing device (27), the traction force limiting device being arranged on the side of the flexible traction means (28) opposite the activator and the traction force limiting device having one or more gear wheels which are connected to the flexible traction means designed as a link chain (28) mesh, with adjustable friction clutches interacting non-positively with the gearwheels, which limit the tensile force transmitted to the lifting carriage (26) by the flexible traction means (28) to a predetermined value. conveyor device claim 1 , characterized in that the lifting device (18) is assigned a lifting carriage (26) which is connected, for example, to a flexible traction mechanism (28) at the end section of which weights are arranged in a freely suspended manner on one or both sides of the lifting carriage (26). , which form the gravimetric mass balancing device (27). conveyor device claim 1 or 2 , characterized in that the flexible traction means (28) can be driven by a motor in a lifting manner by an activator working in opposite directions. conveyor device claim 1 or one of the preceding claims, characterized in that the motor drive for the flexible traction means (28) is a pneumatic activator to be acted upon alternately on both sides. conveyor device claim 1 or one of the claims 2 or 3 , characterized in that the motor drive for the flexible traction means (28) is an electric motor. conveyor device claim 1 or one of the claims 2 until 4 , characterized in that the motor drive for the flexible traction means (28) is a rodless pneumatic activator. conveyor device claim 1 or one of the preceding claims, characterized in that the friction clutch has brake shoes which are loaded by compression springs and act in a non-positive manner on opposite side faces of the associated gear wheel. conveyor device claim 1 or one of the preceding claims, characterized in that the adjustable tensile force that can be transmitted to the lifting carriage (26) of the lifting device (18) by the flexible traction means (28) is limited to a low lifting mass of 1 to 15 kilograms. conveyor device claim 1 or one of the preceding claims, characterized in that the lifting device (18) has two or more vertical tubes (24, 25) arranged at a distance and parallel to one another, between which on one side of the loading station (4) the rodless activator designed as a pneumatic cylinder (1) is arranged and rollers (29, 30) are assigned to vertical tubes (24, 25), over which the relevant traction means (28) is arranged, at the end of which the mass balancing device (27) is arranged in the form of interchangeable weights. conveyor device claim 1 or one of the preceding claims, characterized in that the pallet carriages (2) have rollers (1a) on their underside, with which they roll smoothly on rails of the conveyor tracks (3, 17). conveyor device claim 1 or one of the preceding claims, characterized in that the conveyor tracks (3, 17) are arranged on the floor by frames (33, 34) which are formed from tubes which are polygonal in cross-section.

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