GB2173468A

GB2173468A - A walking beam mechanism

Info

Publication number: GB2173468A
Application number: GB08509521A
Authority: GB
Inventors: William James Richmond; Michael Butterworth; Hector Tidd
Original assignee: TIDD STRONGBOX Ltd
Current assignee: TIDD STRONGBOX Ltd
Priority date: 1985-04-13
Filing date: 1985-04-13
Publication date: 1986-10-15
Also published as: GB8816621D0; GB8509521D0; GB2173468B; GB2207114B; GB2207114A

Abstract

A walking beam mechanism 20, such as for conveying roll pallets 16 in a vehicle 10, has a beam 32, 34 which is lifted by the interaction of rollers 38 with cam surfaces 40. The cam surfaces 40 have a first, steep, portion 46 and a second, shallow, portion 48 so that the beam 32, 34 is first lifted rapidly to an article-engaging height and is then lifted slowly to lift the articles 16 off the support surface. Only one end of the articles 16 is lifted, and the articles are dragged or pushed along by the lifted end. Preferably the end of the articles which is not lifted has wheels 28, and guide tracks 54 are provided on the support surface for the wheels 28 to run in. Fixed support means 30 support the lifted end of the articles when set down by the beam 32, 34 ensuring that any wheels 26 on the lifted end remain clear of the support surface. This provides a braking action to prevent rolling of wheeled articles when not lifted by the beam. <IMAGE>

Description

SPECIFICATION A walking beam mechanism Field of the invention This invention relates to a walking beam mechanism for conveying articles along a path. The invention is particularly, but not exclusively, intended for use in conveying pallets, particularly roll pallets, in the interior of a vehicle adapted to transport the pallets.

The invention also relates to a vehicle equipped with a walking beam mechanism or mechanisms.

Background to the invention Walking beam mechanisms are known in a number of fields. In such mechanisms, a "walking beam" performs a regular movement cycle around a closed, generally rectangular, path. Starting from a lowered position, the beam rises generally vertically into contact with an article stationed above itself on a support, and lifts the article. Once the article is supported by the beam, the beam moves horizontally to displace the article in a horizontal direction, and at the end of the particular stroke length of the beam, the beam is lowered- and returns the article to its support, but in a horizontally displaced position. The beam then executes a return horizontal movement in a lowered position, to its original starting position whereupon the cycle is repeated.An example of such a walking beam mechanism is described in British Patent Specification 1424361.

Summary of the invention According to a first aspect of the invention, there is provided a walking beam mechanism for conveying articles along a path, the mechanism comprising a beam movable relative to a support-surface, with both horizontal and vertical components of movement, and means for moving the beam, the beam moving means including rollers running on vertical lift cams, wherein the cams have an initial steep portion which serves to lift the beam into contact with an article supported by the support surface, and a subsequent gently inclined portion which serves to raise the beam and the article so that the article is out of contact with the support surface.

Preferabiy the cams are mounted on the support surface and the rollers are mounted on the beam, but an opposite arrangement is possible.

The mechanism may be arranged so that the article is lifted only at either the leading or the trailing edge thereof, with the article being dragged (pushed or pulled) on its non-lifted edge during horizontal movement of the beam.

The article may have wheels, and may be a roll pallet.

The beam may comprise an upper and a lower beam section, with the upper section being supported on the lower section and horizontally movable relative to the lower section.

In a preferred embodiment, the lower section is provided with means for producing generally vertical movement thereof, and the upper beam section is provided with means for producing generally horizontal movement thereof.

The use of a lift cam with regions of different slope helps to raise the beam to its working position very quickly and over a short distance, and then allows the lifting work of the beam to take place over a relatively long distance. In this way the power required to do the lifting work is reduced.

According to a second aspect of the invention, there is provided a walking beam mechanism for conveying articles along a path, the mechanism comprising a beam movable relative to a support surface with both horizontal and vertical components of movement, means on the beam for engaging one of the leading and trailing edges of the article during vertical movement of the beam whilst not engaging the other of the leading and trailing edges, for lifting said one of the edges and, during horizontal beam movement, for pulling or pushing the article-along the path by said one of the edges.

The article preferably has four wheels and the beam preferably extends between a pair of wheels on the non-lifted edge. In this case a single beam can be used to lift and engage the article because the article, when lifted, will be supported at three points; ie on the beam and on its two non-lifted wheels.

If the article has two castor-type wheels, these wheels are preferably lifted whilst noncastor-type wheels are not lifted.

Guide tracks for the non-lifted wheels may be provided parallel to the walking beam.

The upper surface of the beam is preferably provided with a channel section for engaging a bar on the underside of the article, so that when the beam has lifted one edge of the article, the article can either be pulled or pushed depending on the direction of movement of the beam.

According to a third aspect of the invention, there is provided a method of conveying wheeled articles along a path using a walking beam mechanism, wherein a vertical movement of the beam causes either the leading or the trailing edge of the article to be engaged and lifted, while the other of the leading and trailing edges is supported by the article's own wheels, and wherein horizontal movement of the beam when raised causes the article to be pulled or pushed along the path with part of the weight of the article being supported by, and running on, the article's own wheels.

According to a fourth aspect of the inven tion, there is provided a vehicle having a loading deck for wheeled containers and at least one walking beam mechanism as set forth above provided on the loading deck.

In a preferred embodiment, there are two vertically-spaced loading decks, and each deck has more than one, preferably three, parallel walking beam mechanisms.

In order to hold the containers stationary after they have been lowered by the walking beam, fixed support structures may be provided at spaced positions alongside the walking beam, so that when the lifted edge of a container is lowered, it is lowered onto the fixed support structures with the lifted wheels still out of contact with the deck of the vehicle.

The beam preferably comprises upper and lower beam sections, and means associated with the lower beam section produces up and down movement of the beam and means associated with the upper beam section produces horizontal movement of the upper beam section relative to the lower section. Independent pneumatically operated double-acting rams can be associated with each beam section to initiate the respective movement.

Where there are upper and lower beam sections, rollers may be provided between the sections, suitably journalled in the top of the lower section, to allow relative horizontal movement between the sections.

Limit switches-may be associated with the mechanism to control the sequencing of the various pneumatic cylinders.

A vehicle according to the invention may be provided with a tail lift to raise articles to the level of the walking beam mechanism, and to allow the articles to be picked up by the walking beam mechanism.

Brief description of the drawings The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a vehicle according to the invention showing the positions of roll pallets and the position of a walking beam mechanism; Figure 2 is a rear view of the vehicle of Fig.

1; Figure 3 is an enlarged detail of the area shown in the balloon A from Fig. 2; Figures 4a, 4b, 4c and 4d are schematic views illustrating various stages in the operation of a walking beam mechanism in accordance with the invention; Figure 5 is a detail of one end of the walking beam mechanism; Figure 6 is a section through the beam mechanism of Fig. 5 on the line VI--VI; Figure 7 is a section through the part of the mechanism shown in Fig. 6, on the line VI 1-VIl; Figure 8 is a section through the mechanism shown in Fig. 5 on the line VIII-VIII; and Figure 9 shows a detail of part of the- beam mechanism.

Description of preferred embodiments Fig. 1 shows an articulated trailer 10 which has conventional running gear. Inside the trailer there is a space 12 which will be taken up by a refrigeration unit. There is a horizontal platform 14 which divides the interior of the trailer into two decks. Pallets 16 (only some of which are shown) are carried on both upper and lower decks. It will be seen that the pallets are roll pallets (which are in themselves well known) and that the front pallet wheels are on castors and the rear pallet wheels are not on castors.

A conventional tail lift 18 is provided at the rear of the trailer and can lift pallets to the level of the lower deck or the level of the upper deck, as desired.

Along the fioor of the upper deck and along the floor of the lower deck are provided walking beam mechanisms 20 which are used to convey pallets into and out of the interior of the vehicle. These mechanisms will be described in more detail with reference to the other drawing figures.

Fig. 2 shows the view at the rear ofthe trailer of Fig. 1, and it will be seen that in addition to the platform. 14, vertical bulkheads 22 are provided to divide the interior space of the trailer into six parallel tracks for receiving pallets 16. In Fig. 2, a pallet 16 is shown in the central upper track, but no pallets are shown in the other tracks. The platform 14 and the vertical walls 22 are preferably all of heat insulating material, so that the trailer can be used to transport refrigerated goods, particularly foodstuffs.

Fig. 3 shows more detail of the walking beam mechanism which is used to move the roll pallets backwards and forwards along the respective tracks in the trailer. The pallet 16 has a base 24 with a pair of front wheels (on castors) 26 and a pair of rear wheels 28. The front edge of the pallet base 24 is supported on two supports 30 so that the front castor wheels 26 are out of contact with the deck of the trailer. The supports 30 are clearly.visible in Fig. 1, at spaced positions along the length of each track. The supports 30 are arranged to hold the front pallet wheels just out of contact with the deck as a means of securing the pallet in position within the container. No other braking devices are then needed.

A single walking beam mechanism 20 extends down the centre of each of the tracks in the trailer. Each mechanism is designed to lift the front edge of a pallete base- and then transport it a horizontal distance corresponding to the distance between two of the supports 30, and then to lower it onto the next one of the supports.

Figs. 4 illustrate the operating mechanism of the walking beam mechanism. These figures are only schematic and are shown for the purposes of explaining the operation of the mechanism.

The beam itself consists of an upper beam section 32 and a lower beam section 34. Rollers 36 positioned between the sections 32 and 34 allow the two sections to slide relative to one another. The lower beam section is provided with rollers 38 which cooperate with lift cams 40 fixed-to the deck 42. A pneumatic lift cylinder 44 is mounted between the deck 42 and the lower beam section 34. As the cylinder 44 is extended from the position shown in Fig. 4a to the position shown in Fig.

4b, the rollers 38 run on the lift cams 40 and lift the beam 32, 34. The lift cams have an initially steep portion 46 and a subsequent gently inclined portion 48. During the intial stages of actuation of the cylinder 44, the rollers 38 ride on the steep portion 46 and produce rapid initial lift of the beam. This rapid initial lift lifts the beam into contact with the pallet to be lifted. Once the beam and the pallet are in contact, the rollers 38 begin to roll on the more gently inclined portions 48 and it is over this portion that lift of. the pallet takes place.

In the situation shown in Fig. 4a, a pallet would be supported on a support 30. In the position shown in Fig. 4b, the pallet would now be supported in a lug 50 welded to the top face of the upper beam section 32. However, at this stage no horizontal displacement has taken place.

Next, a transverse cylinder 52 is extended whilst the lift cylinder 44 remains extended, and this causes the upper beam section 32 to move relative to the lower section 34. The pallet is thus moved in a horizontal direction.

Because only one edge of the pallet is being lifted by the beam, the pallet is actually wheeled along with its rear wheels 28 running in guide tracks 54 on the platform 14 (see Fig. 3).

Once the traverse cylinder 52 has been extended, the lug 50 will line up with the next fixed support 30 (not shown in Figs. 4). The lift cylinder 44 is then retracted so that the pallet can be lowered onto the next support 30, so that the beam takes up the position shown in Fig. 4d. To return to the start position shown in Fig. 4a, the traverse cylinder 52 is then retracted to slide the upper beam section 32 back over the lower beam section 34.

The stroke of the traverse cylinder 52 will be equal to the spacing between the fixed supports 30 which will also be equal to the spacing between the lugs 50 secured to the top of the upper beam section 32. For the sake of clarity, these details have not all been shown in Figs. 4.

The operational sequence just described will move pallets from left to right in Fig. 4. To move pallets in the opposite direction, from right to left, the traverse cylinder 52 must be extended before the beam is raised by the lift cylinder 44, and then retracted once the pallet has been lifted by the beam.

Fig. 5 illustrates the sequence of events when a pallet 24 is picked up the walking beam mechanism from the tail lift 18 and moved into the vehicle (from right to left in Fig. 5). In Fig. 5, a pallet 24 is shown over the lift platform 18. In the start position, the upper beam section 32 takes up the position B where a lug 50 fixed at the extreme end of the upper beam section is beneath a cross member at the front of the pallet base 24.

The lift cylinder 44 is then actuated to cause the rollers 38 to run up the lift cams 40 so that the beam is lifted, lifting the front wheels 26 of the pallet off the lift platform 18. The traverse cylinder is then actuated to move the upper beam section 32 to the left, to the position shown in full lines in Fig. 5. This distance, which is equal to the stroke length of the traverse cylinder 52, and to the spacing between the fixed supports 30 is also equal to the overall length of a standard pallet 24.

It can be seen from Fig. 6 that the upper and lower beam sections 32 are both of a generally inverted U shape. The lugs 50 which are welded to the top of the upper beam section 32 are of a conventional channel configuration and are designed so that a front cross bar on a standard pallet will be easily received in the channel 50 and can be then either pulled or pushed when the upper beam section is moved horizontally, in the raised position. The height of the vertical limbs of the lug 50 should be such that, when the beam is in the lowered position, horizontal movement of the upper beam section will not interfere with the pallet.

The rollers 36 which separate the upper and lower beam sections 32 and 34 run on journals in the lower beam section, as can be seen from Figs. 6 and 9. In addition, longitudinal guide strips 54 are mounted between the upper and lower beam sections to assist in smooth relative movement between these components.

Fig. 7 shows the beam in a raised position and illustrates how, in the raised position, the base of the channel lugs 50 lies just above the top of the support 30, so that horizontal movement of a pallet is possible without being obstructed by the supports. It can also be seen from this figure that the lift cam 40 ends in a shoulder 56 which prevents overrun on the lift stroke.

Fig. 8 shows, in cross-section, the raised and lowered positions of the beam and illustrates how, in the lowered position, the channel lug 50 lies entirely below the base of the recesses in the tops of the supports 30 and how, in the raised position, the lug lies wholly above the supports 30.

Use of the beam mechanism described in a vehicle for transporting pallets can lead to a great increase in efficiency of the pallet handling. Together with a list identifying the contents of individual pallets, the mechanism can be used for quickly loading or unloading identified pallets. The various controls needed can be brought to a central control panel which can be operated by one person to bring pallets from any one of the tracks to an unloading position.

Claims

1. A walking beam mechanism for conveying articles along a path, the mechanism comprising a beam movable relative to a support surface, with both horizontal and vertical components of movement, and means for moving the beam, the beam moving means including rollers running on vertical lift cams, wherein the cams have an initial steep portion which serves to lift the beam to a first height and a subsequent gently inclined portion which serves to raise the beam from the first height to a second height so that the article is out of contact with the support surface.

2. A walking beam mechanism according to claim 1 in which the cams are mounted on the support surface and the rollers are mounted on the beam.

3. A walking beam mechanism according to claim 1 and 2 in which the beam comprises an upper and a lower beam section, - with the upper section being supported on the lower section and horizontally movable relative to the lower section.

4. A walking beam mechanism according to claim 3 in which the lower section is provided with means for producing generally vertical movement thereof, and the upper beam section is provided with means for producing generally horizontal movement thereof.

5. A walking beam mechanism according to claim 4 in which respective independent pneumatically operated double-acting rams are associated with each said beam section to initiate the respective said movement.

6. A walking beam mechanism according to claim 5 in which limit switches are associated with the mechanism to control the sequencing of the said pneumatic cylinders.

7. A walking beam mechanism according to any one of claims 3 to 6 in which rollers are provided between the sections, journalled in the top of the- lower section, to allow relative horizontal movement between the sections.

8. A walking beam mechanism according to any one of the preceding claims in which the cams have an end stop to limit the travel of the rollers.

9. An article handling system comprising a plurality of articles and a walking beam mechanism for conveying the articles along a path on a support surface, the mechanism comprising a beam movable relative to the support surface with both horizontal and vertical components of movement, means on the beam for engaging one of the leading and trailing edges of the article during vertical movement of the beam whilst not engaging the other of the leading and trailing edges, for lifting said one of the edges and, during horizontal beam movement, for pulling or pushing the article along the path by said one of the edges.

10. An article handling system according to claim 9 in which the said articles have four wheels and the beam preferably extends between a pair of wheels on the non-lifted edge during movement of an article along the path.

11. An article handling system according to claim 10 in which the articles have two castor-type wheels which are lifted by the beam and two non-castor-type wheels which are not lifted.

12. An article handling system according to claim 10 or claim 11 in which guide tracks for the non-lifted wheels are provided parallel to the walking beam.

13. An article handling system according to any one of claims 9 to 13 in which fixed support structures are provided at spaced positions alongside the walking beam, so that when the lifted edge of a container is lowered, it is lowered onto the fixed support structures with the lifted wheels still out of contact with the supporting surface so as to hold the containers stationary after they have been lowered.

14. An article handling system according to any one of claims 9 to 13 in which the upper surface of the beam is provided with a channel section for engaging a bar on the underside of the article when the beam lifts one edge of the article, so that when the article has been lifted it can either be pulled or pushed, depending on the direction of movement of the beam, via the said engagement.

15. An article handling system according to any one of claims 9 to 14 in which the said walking beam mechanism is in accordance with any one of claims 1 to 8.

16. A method of conveying wheeled articles along a path using a walking beam mechanism, wherein a vertical movement of the beam causes either the leading or the trailing edge of the article to be engaged and lifted, while the other of the leading and trailing edges is supported by the article's own wheels, and wherein horizontal movement of the beam when raised causes the article to be pulled or pushed along the path with part of the weight of the article being supported by, and running on, the article's own wheels.

17. A vehicle having a loading deck for wheeled containers and at least one walking beam mechanism according to any one of claims 1 to 8 or on article handling system according to any one of claims 9 to 15 provided on the loading deck.

18. A vehicle according to claim 17 in which there are two vertically-spaced loading decks, and each deck has more than one parallel walking beam mechanism.

19. A vehicle according to claim 18 which has a tail lift to raise articles to the level of the walking beam mechanism, and to allow the articles to be picked up by the walking beam mechanism.

20. A walking beam mechanism substantially as herein described with reference to the accompanying drawings.

21. An article handling system substantially as herein described with reference to the accompanying drawings.