JP2020016423A - Seal device of sintering machine - Google Patents

Abstract

To provide a seal device of a sintering machine capable of suppressing leaked air even in a case where phenomena to be various causes of leaked air occur.SOLUTION: A seal device of a sintering machine comprises: a pair of wear bars 13 arranged at positions in contact with the lower surfaces of a pair of seal bars 4 attached to the lower surface of a pallet truck 10; a pair of wear bar supports 12 respectively supporting the pair of wear bars 13 below the pallet truck 10; and a seal sheet 14 attached to the wear bar support 12 and contacting a horizontal surface 2a on the lower surface of the pallet truck 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sealing technique for a sintering machine having a plurality of pallet trucks arranged adjacent to each other on an endless track.

  The sintering machine has a plurality of pallet trucks arranged on an endless track. The pallets are adjacent to each other and form a continuous conveyor. Raw materials for sintering are loaded and transported on a plurality of continuous pallets. During transportation, fuel such as coke breeze in the loaded raw material is ignited. After ignition, the fuel in the raw material burns, so that the iron ore in the raw material is heated and partially melted to form sintered ore. A group of wind boxes for generating a negative pressure is arranged below the plurality of pallets on which the raw materials are loaded. The group of wind boxes is composed of a plurality of wind boxes arranged continuously in the transport direction. The group of wind boxes is connected to an induced exhaust fan. The combustion exhaust gas of the raw material loaded on the pallet is sucked into the wind box. Therefore, air is always supplied to the raw material from above.

  In order to maintain the negative pressure of the wind box, the space connected to the wind box below the pallet truck must be sealed. Therefore, in the conventional sintering machine, in a state where a pair of seal bars provided on the lower surface of the pallet truck are brought into contact with a pair of wear bars extending in the transport direction along the side walls of the wind box group, The pallet truck is transported. Thereby, the space between the pair of seal bars, that is, the space in the wind box is shielded from the atmosphere. Note that the wearer may be referred to as a slide bed.

  However, a gap is generated around the seal bar due to various factors, and air leakage occurs. Leakage is the wind that does not pass through the loaded raw material layer, but passes between the pallet trucks, between the pallet trucks and the wind box, or through the gap between the side plate of the pallet truck and the raw material layer to reach the wind box. is there. Leakage does not contribute to the firing reaction described above. If there is a large amount of air leakage, the power of the induced exhaust fan is increased, and the productivity is significantly reduced. For this reason, many proposals have been made regarding the air leakage reduction technology.

  For example, in Japanese Utility Model Laid-Open No. 61-55700 (Patent Document 1), a magnetic plate is fixed to a slide bed or a side surface of a bed, and a free non-fixed end of the magnetic plate is brought into close contact with a slide seal plate, that is, a seal bar by magnetic force. There is disclosed a configuration for causing this to occur.

Japanese Utility Model Publication No. 61-55700

  The inventors investigated the cause of the leak. As a result, the following causes were found. As in Patent Document 1, a configuration is considered in which a holding cover that opens downward is attached to a depression on the lower surface of a pallet truck, and a seal bar is held in the holding cover in a vertically movable state. In this configuration, the seal bar moves up and down while sliding on the holding cover. In the case of this configuration, a gap is generated between the seal bar and the holding cover. Also, a gap is formed between the depression of the pallet truck housing the holding cover and the holding cover. In addition, when the wear bar is deformed due to undulation, inclination, or the like, or when dust is caught between the seal bar and the wear bar, contact between the seal bar and the wear bar becomes incomplete. As a result, a gap may be formed between the seal bar and the wear bar, and a sufficient pressure cutoff may not be achieved. This can occur in a sintering machine of either a gravity type or a movable seal bar structure in which a seal bar is pressed against a wear bar by a spring. A seal bar is provided for each pallet truck. For this reason, the seal mechanism is configured such that the seal bar is divided from the continuous wear bar. As a result, between the pallet trucks, a gap is also formed between adjacent seal bars.

  The inventors have studied a seal configuration to cope with the various causes as described above. For example, as in Japanese Utility Model Application Laid-Open No. 55700/1986, a configuration in which one end of the seal member is in contact with the side surface of the wear bar and the other end is in contact with the side surface of the seal bar was studied. In this case, when the pallet truck meanders more than the specified range and the position in the width direction changes, a gap is likely to be formed due to a shortage of the length of the sealing member and a deviation of the contact position. In addition, when the position of the pallet truck in the vertical direction is lower than the specified value, the contact position of the seal member is shifted or the length of the seal member is excessively wrinkled, so that a gap is easily generated. Further, with this configuration, it is difficult to cope with a gap between the seal bar and the holding cover and a gap between the holding cover and the pallet truck.

  Therefore, an object of the present invention is to provide a sealing device for a sintering machine that can suppress the air leak between the wind box and the pallet truck even when various phenomena causing the air leak occur.

  A sealing device for a sintering machine according to one embodiment of the present invention includes a pair of wearers, a pair of wearer supports, and a seal sheet. The pair of wear bars are arranged at positions in contact with the lower surfaces of the pair of seal bars attached to the pallet truck. The pair of seal bars are vertically movably mounted on the lower surface of a pallet truck loaded with a raw material for sintering and conveyed on an endless track. The pair of wearers are formed to extend in the transport direction. The pair of wearer supports respectively support the pair of wearers below the pallet truck. The pair of wearer supports are integrated with side walls that define both widthwise sides of a group of wind boxes provided below the pallet truck. The seal sheet is attached to the wear bar support, and is in contact with a horizontal surface of the lower surface of the pallet truck outside the seal bar in the width direction.

  According to the present disclosure, it is possible to provide a sealing device for a sintering machine that can suppress the air leak between the wind box and the pallet truck even when various phenomena causing the air leak occur.

FIG. 1 is a diagram of the pallet truck according to the present embodiment as viewed from a transport direction. FIG. 2 is an enlarged view of a portion including the wearer of FIG. FIG. 3 is a side view of two adjacent pallet trucks.

  A sealing device of a sintering machine according to an embodiment of the present invention includes a pair of wearers, a pair of wearer supports, and a seal sheet. The pair of wear bars are arranged at positions in contact with the lower surfaces of the pair of seal bars attached to the pallet truck. The pair of seal bars are vertically movably mounted on the lower surface of a pallet truck loaded with a raw material for sintering and conveyed on an endless track. The pair of wearers are formed to extend in the transport direction. The pair of wearer supports respectively support the pair of wearers below the pallet truck. The pair of wearer supports are integrated with side walls that define both sides in the width direction of a group of wind boxes provided below the pallet truck. The seal sheet is attached to the wear bar support, and is in contact with a horizontal surface of the lower surface of the pallet truck outside the seal bar in the width direction.

  In the above configuration, the seal sheet extends upward from the wearer support integrated with the side wall of the wind box, and reaches a horizontal surface on the lower surface of the pallet truck outside the seal bar, that is, closer to the atmosphere. That is, the lower portion of the seal sheet is supported by the wearer support, and the upper end of the seal sheet is in contact with the horizontal surface of the lower surface of the pallet truck. Thereby, for example, when the position of the width direction of the pallet truck is displaced, the seal sheet can move in the width direction with respect to the pallet truck while being in contact with the horizontal surface of the lower surface of the pallet truck. Therefore, sealing performance for closing the gap between the wind box and the pallet truck is maintained. Further, even when the vertical position of the pallet truck is lowered, the sealing performance can be maintained by sliding the seal sheet on the horizontal surface on the lower surface of the pallet truck. Therefore, a decrease in sealing performance due to displacement of the pallet cart with respect to the wear bar can be suppressed. Further, in the above configuration, the seal sheet seals between the wind box and the pallet truck at a position outside the seal bar in the width direction, that is, at a position closer to the atmosphere. Thereby, the space around the seal bar is shielded from the atmosphere from outside the seal bar. For example, a space such as between the seal bar and the holding cover or between the holding cover and the pallet truck can be shielded from the atmosphere outside the space regardless of the change in the size of the space. Therefore, it is possible to suppress the air leakage caused by the gap generated between the seal bar and the pallet truck. As described above, according to the above configuration, even when various phenomena causing a leak occur, the leak can be suppressed. In addition, the above-mentioned structure can obtain the above-mentioned effects regardless of whether it is used for a sintering machine having any structure of a gravity type seal bar or a movable seal bar which presses the seal bar against the wear bar by a spring.

  The seal sheet may be formed so as to extend in the transport direction so as to contact a horizontal surface of a lower surface of a plurality of adjacent pallet trucks. Thereby, the seal sheet is continuously arranged over the plurality of pallet trucks. Therefore, for example, the gap between the seal bars of two adjacent pallet trucks can be closed with the seal sheet.

  In this specification, in the pallet truck, the direction in which the raw material for sintering is loaded is up, and the opposite direction is down. The transport direction is the traveling direction of the pallet truck when the pallet truck loaded with the raw material is transported on the track. The width direction is a direction orthogonal to the transport direction and the vertical direction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated.

(Embodiment 1)
The sintering machine in the present embodiment includes a plurality of pallet trucks arranged adjacent to each other on an endless track. FIG. 1 is a diagram of the pallet truck according to the present embodiment as viewed from a transport direction. The x-axis of the rectangular coordinate system shown in FIG. 1 is the width direction of the pallet truck, the y-axis is the transport direction of the pallet truck, and the z-axis is the vertical direction of the pallet truck. The pallet truck 10 includes a pallet frame 2, a pair of side plates 1 disposed at both ends in the width direction of the pallet frame 2, and a plurality of great bars 8 disposed on the pallet frame 2 between the pair of side plates 1. . The plurality of great bars 8 constitute a grate. The pair of side plates 1 is attached to the upper surface of the pallet frame 2. The pair of side plates 1 extend upward from the pallet frame 2. A pair of wheels 7 is rotatably attached to both ends of the pallet frame 2 in the width direction. The axles 7a of the pair of wheels 7 extend in the width direction. Raw materials for sintering are loaded on a grate. That is, a raw material for sintering is stored in a space surrounded by the grate of the plurality of great bars 8 and the pair of side plates 1.

  The wheels 7 roll on rails 11 extending in the transport direction. A pair of wear bars 13 extending in the transport direction and a pair of wear bar supports 12 (wear bar support portions) that respectively support the pair of wear bars 13 are arranged inside the rail 11 in the width direction. The wearer 13 and the wearer support 12 are arranged below the pallet truck 10. On the lower surface of the pallet frame 2, two concave portions 2b extending in the transport direction are formed. The two concave portions 2b are separated from each other in the width direction. A pair of seal bars 4 extending in the transport direction are inserted into each of the two concave portions 2b. Each of the pair of seal bars 4 is attached to the pallet frame 2 so as to be vertically movable. When the pallet truck 10 loads and conveys the raw material, the seal bar 4 moves relative to the wear bar 13 in the conveyance direction with the lower surface of the seal bar 4 in contact with the upper surface of the wear bar 13. That is, the seal bar 4 slides with respect to the wear bar 13.

  A plurality of wind boxes 21 are arranged below the pallet cart 10. The plurality of wind boxes 21 are arranged in the transport direction, that is, in the y direction. The space between the pair of seal bars 4, the pair of wear bars 13, and the pair of wear bar supports 12 below the great bar 8 of the pallet cart is connected to the space in the wind box 21. The gas in the wind box 21 is sucked by an induced air blower (not shown). The space in the wind box 21 is connected to an induced exhaust fan through a duct. A negative pressure is generated in the wind box 21. That is, the space surrounded by the great bar 8, the pair of seal bars 4, the pair of wear bars 13, and the pair of wear bars 12 has a negative pressure. Thereby, the gas in the raw material is sucked into the wind box 21 through the grate of the great bar 8, and the air above the raw material is taken into the raw material.

  The wind box 21 has a side wall 21a. The side walls 21a define both sides in the width direction of the wind box 21. That is, the side wall 21a defines the edge, that is, both ends, of the wind box 21 in the width direction. The side wall 21a extends in the transport direction.

  The wearer support 12 is integrated with the side wall 21a of the wind box. In the example shown in FIG. 1, the pair of wearer supports 12 are respectively fixed to the pair of side walls 21 a of the wind box 21. The pair of wearer supports 12 are in contact with the outer surfaces of the pair of side walls 21 a of the wind box 21, that is, the surfaces on the atmosphere side without any gap. Thereby, the wearer support 12 is integrated with the side wall 21 a of the wind box 21 to form shielding plates on both sides in the width direction of the space in the wind box 21. Thus, the form in which the side wall 21a of the wind box 21 and the wearer support 12 are integrated does not necessarily mean that the side wall 21a and the wearer support 12 are integrally formed of the same material. Further, another member may be provided between the side wall 21 a of the wind box 21 and the wearer support 12. In the example shown in FIG. 1, the wearer support 12 supports the wearer 13 at a position slightly above the upper end of the side wall 21a of the wind box.

  FIG. 2 is an enlarged view of the vicinity of the wearer 13 in FIG. A seal sheet 14 is attached to the wearer support 12. The seal sheet 14 is a plate-shaped member. The seal sheet 14 is attached to the outside of the wearer support 12, that is, to the side surface on the atmosphere side. The seal sheet 14 extends upward from the wearer support 12 and reaches the horizontal surface 2 a on the lower surface of the pallet truck 10. The upper end of the seal sheet 14 contacts the horizontal surface 2a on the lower surface of the pallet truck 10. The seal sheet 14 is provided entirely between the wearer support 12 and the horizontal surface 2 a on the lower surface of the pallet truck 10. The seal sheet 14 is a sheet whose transport direction is the longitudinal direction. The contact portion between the seal sheet 14 and the horizontal surface 2a on the lower surface of the pallet truck 10 extends continuously in the transport direction. The portion where the seal sheet 14 is attached to the wearer support 12 also extends continuously in the transport direction. The seal sheet 14 closes the space between the pallet truck 10 and the wearer support 12 outside the seal bar 4, that is, on the atmosphere side.

  The seal sheet 14 blocks the wind (arrow F2) from flowing into the wind box even if the contact between the seal bar and the wear bar is incomplete, for example. FIG. 2 shows an example in which the dust D1 bites between the seal bar 4 and the wear bar 13 which are originally in contact with each other. In this case, a slight gap is generated between the seal bar 4 and the wear bar 13 around the bite. Also in such a case, the leakage (arrow F3) passing through the gap is prevented by the seal sheet 14. In addition to the biting of dust, for example, when the wear bar 13 is deformed due to undulation, inclination, or the like, a slight gap may occur between the seal bar 4 and the wear bar 13. In this case, too, the seal sheet 14 prevents the air from leaking through the gap.

  The seal sheet 14 slides on the horizontal surface 2 a on the lower surface of the pallet truck 10. That is, the pallet truck 10 moves in the transport direction with the seal sheet 14 in contact with the horizontal surface 2a on the lower surface of the pallet truck 10. It is preferable that the horizontal surface of the lower surface of the pallet truck 10, that is, the sliding surface with the seal sheet 14, be finished smoothly by machining. Thereby, the sealing property of the seal sheet 14 can be improved. For example, the horizontal surface of the lower surface of the pallet truck 10 may have a surface roughness of Ra 6.3a or more, preferably Ra 25a. It is desirable that the contact surface of the pallet truck 10 with the seal sheet 14 be as smooth as possible.

  The seal sheet 14 preferably has flexibility. Further, the seal sheet 14 preferably has heat resistance. For example, the seal sheet 14 can be formed of heat-resistant rubber.

  The wearer support 12 has a base plate 12a on which the wearer 13 is placed. As a specific example, the wearer support 12 is formed by integrally forming a base plate 12a, a support portion 12b extending in a vertical direction for supporting the base plate 12a, and a bottom portion 12c for supporting a lower portion of the support portion 12b. is there. The base plate 12a extends outward from the upper end of the support portion 12b in the width direction. The bottom part 12c extends outward from the lower end of the support part 12b in the width direction. The support portion 12b contacts the side wall 21a of the wind box 21 without a gap.

  The seal sheet 14 is attached to a side surface of the base plate 12a of the wearer support 12. As a specific example, the seal sheet 14 is fixed to the attachment 15 attached to the base plate 12 a by the fastening member 16. The attachment 15 has a horizontal portion in contact with the upper surface of the base plate 12a, and a vertical portion extending from an end of the horizontal portion along the side surface of the base plate 12a. The surface of the seal sheet 14 contacts the vertical portion. The fastening member 16 penetrates the seal sheet 14 and the vertical portion of the fixture 15. As a result, the surface of the seal sheet 14 is fixed to the wearer support 12 in a direction in which the normal line coincides with the width direction. Desirably, the seal sheet 14 also contacts the side surface of the wear bar 13.

  The upper end (the part including the upper end) of the seal sheet 14 contacts the horizontal surface 2a on the lower surface of the pallet truck. In the example shown in FIG. 2, the upper surface of the seal sheet 14 is bent outward in the width direction, and the surface of the seal sheet 14 is in contact with the horizontal surface 2 a on the lower surface of the pallet truck. That is, the seal sheet 14 extends upward from the wearer support 12 and bends outward in the width direction on the way. The bent portion, that is, the portion of the seal sheet 14 between the curved portion and the upper end contacts the horizontal surface 2a on the lower surface of the pallet truck. Thus, it is desirable that the upper end of the seal sheet 14 is in contact with the horizontal surface 2a on the lower surface of the pallet truck with a certain width in the width direction. That is, it is desirable that the upper end of the seal sheet 14 and the horizontal surface 2a make surface contact.

  In the cross section of the surface perpendicular to the transport direction, the natural length B1 from the upper surface to the tip of the wear bar 13 of the seal sheet 14 is the vertical direction between the upper surface of the wear bar 13 and the horizontal surface 2a of the lower surface of the pallet truck. (B1> B). For example, in the example shown in FIG. 2, the seal sheet 14 is arranged such that the natural length of the seal sheet 14 from the fastening member 16 to the upper end is longer than the distance between the fastening member 16 and the horizontal surface 2a on the lower surface of the pallet truck. It is attached to the wearer support 12. Thereby, the seal sheet 14 contacts the horizontal surface 2a on the lower surface of the pallet truck in a bent state. The upper end of the seal sheet 14 is pressed against the horizontal surface 2a on the lower surface of the pallet truck.

  It is desirable that the seal sheet 14 be attached to the wearer support 12 in a state where the seal sheet 14 is bent outward in the width direction, that is, toward the atmosphere. As a result, the upper end of the seal sheet 14 comes into contact with the lower surface of the pallet truck with the upper end of the seal sheet 14 facing outward. Since the upper end of the seal sheet 14 faces outward in the width direction, the upper end of the seal sheet 14 is further pressed against the lower surface of the pallet truck due to the atmospheric pressure. Thereby, the sealing function of the seal sheet 14 can be strengthened, and the space in the wind box 21 can be shut off from the outside air.

  It is preferable that the width (that is, the length in the width direction) W of the horizontal surface 2a on the lower surface of the pallet truck is larger than the displacement amount of the pallet truck in the width direction. More preferably, the width W is at least twice the amount of displacement of the pallet truck in the width direction. For example, the width W is a gap between the collar 7b of the other wheel 7 and the head of the rail 11 in a state where one of the wheels 7 is in contact with the head of the rail 11 (length in the width direction). ) A can be twice or more than A (W ≧ 2A). Thus, even when the position of the pallet truck in the width direction is displaced due to the meandering of the pallet truck, the sealing function of the seal sheet 14 can be maintained.

  The width of the wear bar 13 (the length in the width direction of the pallet truck) is larger than the width of the seal bar 4. It is preferable that the difference between the width of the wear bar 13 and the width of the seal bar 4 is larger than the amount of displacement of the pallet truck in the width direction. For example, the difference between the width of the wear bar 13 and the width of the seal bar 4 can be equal to or larger than the gap A between the wheel collar 7b and the rail 11 head.

  In the example shown in FIG. 2, projecting portions 2 c projecting downward are provided at both ends in the width direction of the pallet frame 2. The horizontal surface of the lower surface of the pallet truck with which the seal sheet 14 is in contact is located between the widthwise outer end of the recess 2b and the widthwise inner end of the protrusion 2c.

  In the example shown in FIG. 2, the holding cover 5 whose lower part is opened is attached to the concave part 2b. The seal bar 4 is vertically movably held in the holding cover 5. A spring is also provided between the seal bar 4 and the holding cover 5 as an elastic body 6. The seal bar 4 is pressed against the wear bar 13 by the elastic body 6. In addition, the mounting configuration of the seal bar 4 is not limited to this example.

  For example, a configuration may be used in which the seal bar 4 is pressed against the wear bar 13 by its own weight without using an elastic body. The sealing device using the seal sheet 14 of the present embodiment can be applied to both a configuration using an elastic body (for example, a spring-type seal bar) and a configuration not using an elastic body (for example, a gravity-type seal bar). Can be.

  The seal sheet 14 seals between the seal bar 4 and the wear bar 13. Further, the seal sheet 14 seals between the seal bar 4 and the holding cover 5 and between the holding cover 5 and the concave portion 2b of the pallet truck 10.

  FIG. 3 is a side view of two adjacent pallet trucks viewed from the width direction. In FIG. 3, the position of the seal sheet 14 is indicated by a broken line. The seal sheet 14 is formed to extend in the transport direction over a plurality of adjacent pallet trucks 10A and 10B. One seal sheet 14 is in contact with the lower horizontal surface of the plurality of pallet trucks 10A and 10B. The length of the seal sheet 14 in the transport direction is preferably longer than the length of the two adjacent pallet trucks in the transport direction. Thereby, the gap between the seal bars 4 of the continuous pallet truck can be covered with the seal sheet 14. Although FIG. 3 shows two pallet trucks, one seal sheet 14 may be formed to extend in the transport direction over two or more pallet trucks. For example, the length of one seal sheet 14 in the transport direction can be 10 m or more.

  According to the seal structure using the seal sheet 14 in the present embodiment, even when various phenomena causing a leak occur, the leak can be suppressed. For example, when a gap is generated between the seal bar 4 and the holding cover 5, the seal sheet 14 suppresses air leakage. Even when a gap is formed between the concave portion 2b of the pallet truck 10 and the holding cover 5, air leakage is suppressed by the seal sheet 14. Further, even when the wear bar 13 is deformed due to undulation, inclination, or the like, the contact surface between the seal bar 4 and the wear bar 13 becomes small, and the pressure cutoff becomes insufficient, the air leakage is suppressed by the seal sheet 14. Further, even when dust particles are caught between the seal bar 4 and the wear bar 13, the air leakage is suppressed by the seal sheet 14. Furthermore, even when the position of the pallet truck 10 in the vertical direction is lowered due to the wear of the wheels 7 and the rails 11, the contact state between the seal sheet 14 and the pallet truck 10 is not substantially changed, and a good contact state can be maintained. Therefore, the sealing property of the seal sheet 14 is maintained. Further, even when the pallet truck meanders and the position of the pallet truck in the width direction is displaced, the contact between the seal sheet 14 and the horizontal surface 2a on the lower surface of the pallet truck 10 is maintained. Therefore, the sealing property is maintained.

  The seal device of the present embodiment includes the wearer 13 and the seal sheet 14 and has double air sealing means. According to the present embodiment, a large air leak does not occur when the various phenomena described above occur. For this reason, the sintering machine can be operated under a stable unit of air flow to continue production.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the seal sheet 14 is disposed outside the seal bar 4 in the width direction, that is, on the atmosphere side. However, the present invention is not limited to this, and the seal sheet 14 may be disposed inside the seal bar 4 in the width direction.

  As mentioned above, although one Embodiment of this invention was described, the above-mentioned embodiment is only an illustration for implementing this invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

1: Side plate 2: Pallet frame 3: Seal member 4: Seal bar 10: Pallet truck 12: Wear bar support 13: Wear bar 14: Seal sheet

Claims (2)

A sealing device for a sintering machine,
It is arranged at a position in contact with the lower surface of a pair of seal bars movably mounted in the vertical direction on the lower surface of a pallet truck on which the raw material for sintering is loaded and transported on the endless track, and is formed to extend in the transport direction. A pair of wearers,
Below the pallet truck, a pair of wearer supports respectively supporting the pair of wear bars, which are integrated with side walls defining both sides in the width direction of a group of wind boxes provided below the pallet truck. Wearer support,
A seal sheet attached to the wearer support and in contact with a horizontal surface of a lower surface of the pallet truck outside of the seal bar in a width direction.   The sealing device for a sintering machine according to claim 1, wherein the seal sheet is formed to extend in the transport direction so as to contact a horizontal surface of a lower surface of a plurality of pallet trucks adjacent to each other.

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