Patent Description:
A flow rate measurement device configured to measure a flow rate of purge gas in a purge device configured to supply the purge gas to a container is known. For example, Patent Literature <NUM> discloses a technique for measuring the flow rate of purge gas, which additionally uses a flow rate measurement device (FOUP for measurement) having the same shape as that of a container (FOUP for storage).

In the technology described above, the flow rate measurement device is manufactured by, for example, preparing a container used for a purge device, cutting and processing the container, and installing a flow-rate measurer and other equipment on the container. Thus, measuring the flow rate of purge gas involves a problem in that much time and labor are required. <CIT> discloses a sealable transportable container for use with processing equipment having a port plate and port door sealably mating to the port plate. The container includes a box having an interior space for containing articles and a conduit for communicating between the interior space and the environment external of the box.

In view of this, it is an object of an aspect of the present invention to provide a flow rate measurement device that can easily measure the flow rate of purge gas in a purge device.

A flow rate measurement device according to an aspect of the present invention is a flow rate measurement device configured to measure a flow rate of purge gas in a purge device configured to supply the purge gas to a container including a bottom lid configured to be attached to and detached from a container body. The flow rate measurement device includes: a base on which a flow-rate measurer is mounted; an engaged part provided in the base and configured to be engaged with the bottom lid; and a flow passage through which the purge gas injected from an injection port of the bottom lid is circulated to the flow-rate measurer when the engaged part is engaged with the bottom lid.

With this flow rate measurement device, when the engaged part is engaged with the bottom lid, the flow rate of purge gas in the purge device can be measured by effectively utilizing an existing function of the injection port, for example, of the bottom lid. Thus, the flow rate of purge gas in the purge device can be easily measured.

In the flow rate measurement device according to an aspect of the present invention, the bottom lid may include a latch and be attached to the container body with the latch, and the engaged part may be engaged with the latch. In this case, the engaged part can be engaged with the bottom lid by effectively utilizing the latch of the bottom lid.

In the flow rate measurement device according to an aspect of the present invention, the base may include a frame having a frame shape corresponding to an outer shape of the bottom lid and configured to be stacked on the bottom lid so as to surround an edge of the bottom lid, and the engaged part may be a hole or a groove, formed in the frame, into which the latch is inserted. In this case, the configuration in which the engaged part is engaged with the bottom lid by effectively utilizing the latch can be concretely implemented.

In the flow rate measurement device according to an aspect of the present invention, the frame may have a stepped surface configured to be brought into contact with an upper surface of the bottom lid to restrict upward movement of the bottom lid. In this case, the bottom lid can be prevented from moving upward away from the frame, and thus the engaged part can be easily engaged with the bottom lid.

In the flow rate measurement device according to an aspect of the present invention, the flow passage may include an inlet pad configured to be brought into intimate contact with a rim of the injection port on the upper surface of the bottom lid when the engaged part is engaged with the bottom lid. In this case, leakage of purge gas can be prevented, and the flow rate of the purge gas can be reliably measured.

In the flow rate measurement device according to an aspect of the present invention, the inlet pad may include a first layer provided on a side closer to the injection port and made of elastic material and a second layer stacked on the first layer and made of gel material. In this case, leakage of purge gas can be further prevented.

In the flow rate measurement device according to an aspect of the present invention, the base may have a pressing surface disposed opposite to the bottom lid and configured to press the inlet pad, which is in intimate contact with the rim of the injection port, against the bottom lid when the engaged part is engaged with the bottom lid. In this case, leakage of purge gas can be further prevented.

In the flow rate measurement device according to an aspect of the present invention, in the base, at least one of a positioning hole into which a positioning projection provided on the bottom lid is inserted and a positioning projection configured to be inserted into a positioning hole provided in the bottom lid may be formed. In this case, the bottom lid can be positioned with respect to the base.

According to an aspect of the present invention, the flow rate measurement device that can easily measure the flow rate of purge gas in the purge device can be provided.

An embodiment will now be described with reference to the drawings. In the description of the drawings, like elements are designated by like reference signs, and duplicate description is omitted. The scale in the drawings does not necessarily coincide with the size of a described object.

A flow rate measurement device according to the embodiment measures the flow rate of purge gas in a purge device. The purge device is a device configured to purge the inside of a storage container with purge gas, and is disposed in a purge stocker, for example. First, the purge device and the purge stocker will be described.

As illustrated in <FIG> and <FIG>, a purge stocker <NUM> purges the inside of a storage container <NUM> with purge gas, and also functions as a repository configured to store a plurality of the storage containers <NUM>. Each storage container <NUM> is a container such as an SMIF pod or a reticle pod in which an object to be stored such as a semiconductor wafer or a glass substrate is stored. As the purge gas, for example, nitrogen gas or air is used. The purge stocker <NUM> is provided in a clean room, for example. The purge stocker <NUM> mainly includes a partition <NUM>, racks <NUM>, a crane <NUM>, an overhead hoist transfer (OHT) port <NUM>, and a manual port <NUM>.

The partition <NUM> is a plate covering the purge stocker <NUM>. Inside the partition <NUM>, a storage area for storing the storage containers <NUM> are formed. The racks <NUM> are sections in which storage containers <NUM> are stored, and are provided in one or a plurality of rows (herein, two rows) in the storage area. Each rack <NUM> extends in a certain direction x, and two adjacent racks <NUM>, <NUM> are disposed parallel to each other so as to be opposed in a direction y. In each rack <NUM>, a plurality of purge shelves 7A on which the respective storage containers <NUM> are placed to be stored are formed along the certain direction x and the vertical direction z. The purge shelves 7A are disposed so as to be aligned in plurality along the vertical direction z, and are also disposed so as to be aligned in plurality along the certain direction x.

The crane <NUM> is a conveying device configured to bring a storage container <NUM> onto and out from a purge shelf 7A, and also move a storage container <NUM> between a purge shelf 7A and each of the OHT port <NUM> and the manual port <NUM>. The crane <NUM> is disposed in an area sandwiched between the opposed racks <NUM>, <NUM>. The crane <NUM> moves on a traveling rail (not illustrated) installed on a floor along the certain direction x in which the racks <NUM> extend. The crane <NUM> includes a guide rail 9A extending in the vertical direction z and a platform 9B configured to be movable up and down along the guide rail 9A. Conveyance of the storage containers <NUM> by the crane <NUM> is controlled by a crane controller <NUM>. The crane controller <NUM> is an electronic control unit including a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM), for example.

The storage containers <NUM> are brought into and out from the purge stocker <NUM> through the OHT port <NUM> and the manual port <NUM>. The OHT port <NUM> is a section where a storage container <NUM> is transferred between an overhead traveling vehicle (OHT) <NUM>, which travels on a traveling rail <NUM> installed on a ceiling, and the purge stocker <NUM>. The OHT port <NUM> includes a conveyor 21A configured to convey a storage container <NUM>. The manual port <NUM> is a section where a storage container <NUM> is transferred between an operator and the purge stocker <NUM>. The manual port <NUM> includes a conveyor 23A configured to convey a storage container <NUM>.

The storage containers <NUM> will be specifically described. Each storage container <NUM> includes a container body <NUM> and a bottom lid <NUM>. In the storage container <NUM>, the bottom lid <NUM> is attached to and detached from the bottom side of the container body <NUM>. The container body <NUM> has a rectangular box shape. The bottom lid <NUM> has a rectangular plate shape. In the storage container <NUM>, a sealed space <NUM> is formed by the container body <NUM> and the bottom lid <NUM>. In the sealed space <NUM>, a plurality of semiconductor wafers (not illustrated) are stored.

As illustrated in <FIG>, <FIG>, and <FIG>, in both left and right rear end portions of the bottom lid <NUM>, injection ports 52A are provided. In both left and right front end portions of the bottom lid <NUM>, discharge ports 52B are provided. Each injection port 52A is configured to be connectable to a nozzle, which is not illustrated, provided at a distal end of a supply pipe <NUM> of the purge device <NUM>. Each discharge port 52B is configured to be connectable to a nozzle, which is not illustrated, provided at a distal end of a discharge pipe <NUM> of the purge device <NUM>. In the injection port 52A and the discharge port 52B, check valves are provided. The "front" and the "rear" correspond to the near side and the far side of each purge shelf 7A, respectively, and the "left" and the "right" correspond to one side and the other side of a horizontal direction orthogonal to the front-and-rear direction, respectively.

The bottom lid <NUM> is provided with a latch mechanism <NUM>, for example. The latch mechanism <NUM> includes latches 58A and a cam 58B. In the latch mechanism <NUM>, when a key (not illustrated) is inserted into insertion holes 58C formed in a bottom surface 53a of the bottom lid <NUM> and this key is turned, the latches 58A are moved in and out (brought in and out) by the cam 58B. The latches 58A are provided on the front side and the rear side of the bottom lid <NUM>. The latches 58A provided on the front side can protrude forward from the front surface of the bottom lid <NUM>, and the latches 58A provided on the rear side can protrude backward from the rear surface of the bottom lid <NUM>.

The latches 58A are fitted into fitting grooves 51A provided in the container body <NUM>. By this fitting, the bottom lid <NUM> is fixed to the container body <NUM>. In other words, the bottom lid <NUM> is attached to the container body <NUM> with the latches 58A. On two front corners of the four corners of the bottom lid <NUM>, positioning projections <NUM> are formed upright. The positioning projections <NUM> are protrusions for positioning the bottom lid <NUM> with respect to the container body <NUM>.

The purge device <NUM> will be specifically described. As illustrated in <FIG>, the purge device <NUM> is a device configured to supply purge gas to the storage container <NUM> placed on the purge shelf 7A, and includes supply pipes <NUM>, a mass flow controller (MFC) <NUM>, a purge gas source <NUM>, discharge pipes <NUM>, a flowmeter <NUM>, and a purge controller <NUM>.

The supply pipes <NUM> are pipes for supplying purge gas, and are connected to the injection ports 52A of the bottom lid <NUM>. The MFC <NUM> is an instrument configured to measure the mass flow rate of purge gas flowing through the supply pipes <NUM> to control the flow rate. The purge gas source <NUM> is a tank configured to store purge gas. The discharge pipes <NUM> are pipes for discharging purge gas, and are connected to the discharge ports 52B of the bottom lid <NUM>. The flowmeter <NUM> is an instrument configured to measure the flow rate of purge gas flowing through the discharge pipes <NUM>. The purge controller <NUM> controls various purging processes in the purge device <NUM>. The purge controller <NUM> is an electronic control unit including a CPU, a ROM, and a RAM, for example.

The following describes the flow rate measurement device according to the embodiment.

As illustrated in <FIG> and <FIG>, a flow rate measurement device <NUM> is a device detachably attached to the bottom lid <NUM> and configured to measure the flow rate of purge gas in the purge device <NUM> by using the bottom lid <NUM>. The flow rate measurement device <NUM> includes a frame <NUM> on which two flow-rate measurers <NUM> are mounted, long holes <NUM> provided in the frame <NUM>, and flow passages <NUM> connected to the flow-rate measurers <NUM>. Hereinafter, the terms "upper" and "lower" correspond to the upper and lower directions in a state of being attached to the bottom lid <NUM>.

As illustrated in <FIG>, <FIG>, and <FIG>, the frame <NUM> is a member having a frame shape corresponding to the outer shape of the bottom lid <NUM>. Herein, the frame <NUM> has a rectangular frame shape. The frame <NUM> is formed of thermoplastic resin (such as polyacetal (POM)), for example. The frame <NUM> includes as its framework members a front ledge 110F, a rear ledge 110B, and side ledges <NUM>, 110R. The front ledge 110F and the rear ledge 110B are members extending along the left-and-right direction. The side ledges <NUM>, 110R are members extending along the front-and-rear direction. The side ledge <NUM> is continuous with the left ends of the front ledge 110F and the rear ledge 110B, and the side ledge 110R is continuous with the right ends of the front ledge 110F and the rear ledge 110B. The frame <NUM> constitutes the base.

The frame <NUM> is stacked on the bottom lid <NUM> so as to surround edges of the bottom lid <NUM>. The frame <NUM> is stacked on the bottom lid <NUM> such that the bottom lid <NUM> is placed within its framework. When viewed from above, the outer shape of the frame <NUM> includes the outer shape of the bottom lid <NUM>. The frame <NUM> has a stepped surface <NUM> at an inner peripheral portion of its lower surface 110a. The stepped surface <NUM> is a planar surface that extends inward with a step interposed therebetween above the lower surface 110a and is parallel to the lower surface 110a. The stepped surface <NUM> is brought into contact with the upper surface of the bottom lid <NUM> to restrict the upward movement of the bottom lid <NUM>.

The frame <NUM> has overhangs <NUM> that are provided on the respective inner portions of the two rear corners so as to overhang inward. The overhangs <NUM> have a plate shape. The overhangs <NUM> are disposed opposite to the bottom lid <NUM> and located above the injection ports 52A when the frame <NUM> is stacked on the bottom lid <NUM>. The upper surfaces of the overhangs <NUM> are continuous with an upper surface 110b of the frame <NUM>. The lower surfaces of the overhangs <NUM> are planar surfaces that extend inward with steps interposed therebetween above the stepped surface <NUM> and are parallel to the lower surface 110a. The lower surfaces of the overhangs <NUM> constitutes pressing surfaces 112a configured to press inlet pads <NUM> against the bottom lid <NUM> as described later.

The frame <NUM> has positioning holes <NUM> into which the positioning projections <NUM> provided on the bottom lid <NUM> are inserted. The positioning holes <NUM> are formed in the two front corners of the four corners of the frame <NUM>. The positioning holes <NUM> are through holes passing through vertically and each having a cross section corresponding to the shape of the positioning projections <NUM>.

On the upper surface 110b of the frame <NUM>, a plate member <NUM> is stacked and fixed. The plate member <NUM> supports various instruments mounted on the frame <NUM>. The plate member <NUM> is formed of a material (such as metal) having a stiffness higher than that of the frame <NUM>. The plate member <NUM> is disposed to extend over the rear ledge 110B and the side ledges <NUM>, 110R. On the plate member <NUM>, two mass flowmeters <NUM>, a battery <NUM>, a converter <NUM>, and a data logger <NUM> are fixed.

Each mass flowmeter <NUM> is an instrument configured to measure the flow rate of purge gas. The mass flowmeter <NUM> is not limited to a particular one, and various flowmeters may be used. The battery <NUM> is a storage battery configured to store electric power to be supplied to the mass flowmeters <NUM> and the data logger <NUM>. The battery <NUM> is not limited to a particular one, and various batteries may be used. The converter <NUM> transforms the electric power from the battery <NUM> to supply the transformed electric power to the mass flowmeter <NUM> and the data logger <NUM>. The converter <NUM> is a DC-DC converter, for example. The converter <NUM> is not limited to a particular one, and various converters may be used. The data logger <NUM> is a recorder configured to record results of measurements taken by the mass flowmeter <NUM>. The data logger <NUM> is not limited to a particular one, and various data loggers may be used.

The long holes <NUM> are engaged parts formed in the frame <NUM> and configured to be engaged with the latches 58A (see <FIG>) inserted thereinto. In other words, the latches 58A are fitted into the long holes <NUM> when the frame <NUM> is stacked on the bottom lid <NUM>. The long holes <NUM> are formed in the front ledge 110F and the rear ledge 110B of the frame <NUM>. Each long hole <NUM> is a hole, the longitudinal direction of which corresponds to the left-and-right direction, penetrating in the front-and-rear direction. The long holes <NUM> have a vertical width corresponding to the vertical width of the latches 58A. When the frame <NUM> is stacked on the bottom lid <NUM>, the long holes <NUM> are disposed opposite in the front-and-rear direction to the latches 58A not protruding from the bottom lid <NUM>. The long holes <NUM> are provided, the number of which is the same as or more than that of the latches 58A.

The flow passages <NUM> allow purge gas injected from the injection ports 52A of the bottom lid <NUM> to circulate therethrough to the flow-rate measurers <NUM> in a state in which the frame <NUM> is stacked on the bottom lid <NUM> and the long holes <NUM> are engaged with the latches 58A of the bottom lid <NUM> (hereinafter, also simply referred to as the "engaged state of the frame <NUM>"). Each flow passage <NUM> includes a vent hole <NUM>, a tube <NUM>, and the corresponding inlet pad <NUM>.

The vent hole <NUM> is a through hole formed in the corresponding overhang <NUM>. The vent hole <NUM> communicates with the corresponding injection port 52A of the bottom lid <NUM> in the engaged state of the frame <NUM>. One end of the tube <NUM> is connected to the corresponding flow-rate measurer <NUM>. The other end of the tube <NUM> is connected to the upper end of the vent hole <NUM>.

The inlet pad <NUM> is brought into intimate contact with the rim of the injection port 52A on the upper surface of the bottom lid <NUM> in the engaged state of the frame <NUM> (see <FIG>). The inlet pad <NUM> is a ring-shaped member. As illustrated in <FIG>, the inlet pad <NUM> is provided on the lower surface of the overhang <NUM> so as to surround the vent hole <NUM> when viewed from below. The inlet pad <NUM> includes: a first layer 133x provided on a side closer to the injection port 52A (lower side) and made of elastic material; and a second layer 133y provided on a side closer to the overhang <NUM> (upper side) and made of gel material. The first layer 133x and the second layer 133y are stacked on one another. The first layer 133x is formed of polyurethane rubber, for example. The second layer 133y is formed of a gel material containing silicone as a main raw material and having high flexibility.

When the flow rate measurement device <NUM> configured as described above is attached to the bottom lid <NUM>, for example, an operator positions the flow rate measurement device <NUM> above the bottom lid <NUM> as illustrated in <FIG>. At this time, the front-and-rear orientation of the flow rate measurement device <NUM> is aligned such that the positioning holes <NUM> are positioned above the positioning projections <NUM>. The latches 58A are set in a state of not protruding from the bottom lid <NUM>.

Subsequently, the operator stacks the frame <NUM> on the bottom lid <NUM> such that it surrounds the edges of the bottom lid <NUM> as illustrated in <FIG>, and connects the vent holes <NUM> to the injection ports 52A with the inlet pads <NUM> interposed therebetween. At this time, the positioning projections <NUM> are inserted into the positioning holes <NUM>. The inlet pads <NUM> are brought into intimate contact with the rims of the injection ports 52A, and the inlet pads <NUM> are pressed against the bottom lid <NUM> by the pressing surfaces 112a of the overhangs <NUM>, whereby the inlet pads <NUM> are deformed so as to be compressed vertically.

Subsequently, the operator inserts the key into the insertion holes 58C (see <FIG>) of the bottom lid <NUM> and turns the key, thereby causing the cam 58B to protrude the latches 58A from the bottom lid <NUM> as illustrated in <FIG>. By this operation, the latches 58A are inserted and fitted into the long holes <NUM>. Consequently, the frame <NUM> is engaged with the bottom lid <NUM>, whereby attachment of the flow rate measurement device <NUM> to the bottom lid <NUM> is completed.

In the same manner as for each storage container <NUM>, the flow rate measurement device <NUM> attached to the bottom lid <NUM> is brought in and out from the purge shelves 7A in a predetermined order by the crane <NUM>, and when placed on each purge shelf 7A, purge gas is supplied thereto by the purge device <NUM>. The flow rate measurement device <NUM> attached to the bottom lid <NUM> measures the flow rate of the purge gas with the mass flowmeters <NUM>, and records the measurement results in the data logger <NUM>.

When the flow rate measurement device <NUM> is then removed from the bottom lid <NUM>, the operator inserts the key into the insertion holes 58C of the bottom lid <NUM> and turns the key, thereby causing the cam 58B to retract the latches 58A into the bottom lid <NUM> and withdrawing the latches 58A from the long holes <NUM> to release the engagement. The operator then lifts the flow rate measurement device <NUM> upward and pulls out the positioning projections <NUM> from the positioning holes <NUM> to complete the removal.

With the flow rate measurement device <NUM> described above, when the long holes <NUM> are engaged with the bottom lid <NUM> and the flow rate measurement device <NUM> is attached to the bottom lid <NUM>, the flow rate of purge gas in the purge device <NUM> can be measured by effectively utilizing an existing function of the injection ports 52A, for example, of the bottom lid <NUM>. Thus, the flow rate of purge gas in the purge device <NUM> can be easily measured. The flow rate measurement device <NUM> can also be attached to another bottom lid different from the bottom lid <NUM>, and thus versatility can be increased.

In the flow rate measurement device <NUM>, the long holes <NUM> are engaged with the latches 58A configured to attach the bottom lid <NUM> to the container body <NUM>. In this case, the long holes <NUM> can be engaged with the bottom lid <NUM> by effectively utilizing the latches 58A of the bottom lid <NUM>. The flow rate measurement device <NUM> can be easily attached to the bottom lid <NUM>.

In the flow rate measurement device <NUM>, the frame <NUM> has a frame shape corresponding to the outer shape of the bottom lid <NUM> and is stacked on the bottom lid <NUM> so as to surround the edges of the bottom lid <NUM>. In the frame <NUM>, the long holes <NUM> into which the latches 58A are inserted are formed. In this case, the configuration in which the long holes <NUM> are engaged with the bottom lid <NUM> by effectively utilizing the latches can be concretely implemented.

In the flow rate measurement device <NUM>, the frame <NUM> has the stepped surface <NUM> configured to be brought into contact with the upper surface of the bottom lid <NUM> to restrict the upward movement of the bottom lid <NUM>. In this case, the bottom lid <NUM> can be prevented from moving upward away from the frame <NUM>, and thus the long holes <NUM> can be easily engaged with the bottom lid <NUM>.

In the flow rate measurement device <NUM>, the flow passages <NUM> include the inlet pads <NUM> configured to be brought into intimate contact with the rims of the injection ports 52A on the upper surface of the bottom lid <NUM> when the long holes <NUM> are engaged with the bottom lid <NUM>. In this case, airtightness between each injection port 52A and the corresponding vent hole <NUM> can be ensured to prevent leakage of purge gas from between the injection port 52A and the vent hole <NUM>, and thus the flow rate of purge gas can be reliably measured.

In the flow rate measurement device <NUM>, each inlet pad <NUM> includes the first layer 133x made of elastic material and the second layer 133y made of gel material. In this case, leakage of purge gas from between the injection port 52A and the vent hole <NUM> can be further prevented, and thus the flow rate of purge gas can be more reliably measured.

In the flow rate measurement device <NUM>, the frame <NUM> has the pressing surfaces 112a configured to press the inlet pads <NUM> against the bottom lid <NUM> when the long holes <NUM> are engaged with the bottom lid <NUM>. In this case, leakage of purge gas from between the injection port 52A and the vent hole <NUM> can be further prevented, and thus the flow rate of purge gas can be more reliably measured.

In the flow rate measurement device <NUM>, in the frame <NUM>, the positioning holes <NUM> into which the positioning projections <NUM> provided on the bottom lid <NUM> are inserted are formed. In this case, the bottom lid <NUM> can be positioned with respect to the frame <NUM>.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. In the above embodiment, various modifications can be made within the scope of the invention as claimed.

In the above embodiment, the positioning projections <NUM> are provided on the bottom lid <NUM>, and the positioning holes <NUM> are formed in the frame <NUM> into which they are inserted. However, instead of or in addition to these, positioning holes may be provided in the bottom lid <NUM>, and positioning projections configured to be inserted thereinto may be formed on the frame <NUM>.

In the above embodiment, the long holes <NUM> are formed as engaged parts. However, the engaged parts are not limited to the long holes <NUM>. The engaged parts may be holes having other shapes such as round holes, may be grooves, or may be protrusions. In short, the engaged parts only need to have a configuration in which the engaged parts can be engaged with the bottom lid <NUM>. In the above embodiment, the engaged parts are engaged with the latches 58A of the bottom lid <NUM>, but may be engaged with engaging parts other than the latches 58A.

In the above embodiment, the frame <NUM> is included as the base. However, the base may have another configuration other than the frame <NUM>. The shape of the frame <NUM> is not limited to a rectangular frame shape, and may be of various frame shapes. In the above embodiment, each inlet pad <NUM> does not have to include a plurality of layers, and may be formed of a single material.

Claim 1:
A flow rate measurement device (<NUM>) configured to measure a flow rate of purge gas in a purge device (<NUM>) configured to supply the purge gas to a container (<NUM>) including a bottom lid (<NUM>) configured to be attached to and detached from a container body (<NUM>), the flow rate measurement device (<NUM>) comprising:
a base (<NUM>) on which a flow-rate measurer (<NUM>) is mounted;
an engaged part (<NUM>) provided in the base (<NUM>) and configured to be engaged with the bottom lid (<NUM>); and
a flow passage (<NUM>) through which the purge gas injected from an injection port (52A) of the bottom lid (<NUM>) is circulated to the flow-rate measurer (<NUM>) when the engaged part (<NUM>) is engaged with the bottom lid (<NUM>).