Container with pressure relief and lid and method of manufacture therefor

[0001] The present application comprises a continuation-in-part of U.S. application Ser. No. 10/073,559, filed Feb. 11, 2002, and owned by the assignee of the present application, and further claims priority from provisional U.S. Application Serial No. 60/392,728, filed Jun. 28, 2002.

[0002] The present invention relates generally to containers, and, more particularly, to a container having a pressure relief apparatus and lid, and a method of manufacture of such a container.

[0003] Cooling containers are used to contain a variety of products and maintain such products at a reduced temperature relative to ambient temperature for a prolonged period of time. An example of a cooling container is disclosed in E. L. Smith U.S. Pat. No. 2,526,165, which describes (in connection with FIG. 6 therein) a container having an outer bowl that surrounds an inner bowl wherein the bowls are hermetically sealed to define a chamber therebetween. A suitable refrigerant liquid such as water is disposed within the chamber. A user places the container into a household freezer for a long enough period of time to freeze the refrigerant liquid. Thereafter, the user takes the container out of the freezer and may place a product, such as a perishable food item, within the container. The refrigerant liquid is capable of maintaining the food item placed in the container at a temperature below room temperature for a relatively long period of time.

[0004] Some prior art containers using a coolant or refrigerant within a cavity have included air space within the cavity to allow for expansion of the refrigerant upon freezing. Allowing for such expansion prevents such containers from rupturing. Another strategy to prevent such rupture of a cooling container is disclosed in Hilado U.S. Pat. No. 4,485,636 where the bottom of the cavity is formed by a resilient diaphragm. The diaphragm allows for expansion of the refrigerant by compressing in response to the expanding refrigerant, thereby increasing the volume of the cavity and preventing the walls of the container from breaking as a result of the expanding refrigerant.

[0005] While numerous prior art containers deal with pressure increases within a cavity due to expansion of refrigerant upon freezing, no known attempts have been made for handling pressure increases resulting from increased heat. It is possible that if a user were to place a prior art container having a substance in a sealed cavity within a microwave oven or near a radiant heat source, sufficient heat and pressure would develop within the sealed cavity to rupture the walls of the container.

[0006] In addition to the foregoing, it is desirable to have a lid that seals a container adequately over a broad temperature range. This can be difficult for containers and lids that expand or contract in response to temperature change. Some prior art containers and lids used therewith have dealt with expansion and contraction by constructing both the container and lid of a resilient material that accommodates such expansion or contraction. An example of such a container and lid is disclosed in Tupper U.S. Pat. No. 2,752,972. At least one type of container utilizes a lid wherein the lid and container have different coefficients of thermal expansion (CTE). For example, Fishman U.S. Pat. No. 4,223,800 discloses a lid and a receptacle. The lid includes a top portion made of the same material as the receptacle and a bottom portion wherein the bottom portion is made of a resilient material with a greater CTE than the receptacle. The bottom portion is integral with a resilient bead. The resiliency of the bead causes the bead to deform into sealing engagement with a wall of the receptacle when the lid is placed on the receptacle. When the receptacle and lid are placed in a refrigerator the bottom portion shrinks to a greater degree than the receptacle. However, sealing engagement of the bead and the wall of the receptacle is maintained by the matching CTE's of the top portion and the receptacle.

[0007] While numerous prior art containers incorporate lids that seal despite expansion of the container and/or lid, no known attempts have been made in the art to provide a lid that seals adequately despite expansion of a cooling container.

[0008] In accordance with one aspect of the present invention, a container comprises a sealed cavity defined by first and second walls of the container. A coolant is disposed within the cavity wherein the coolant is capable of assuming first and second phases. A portion of the first wall is joined to the second wall wherein the portion includes an off-center opening. The portion is rupturable to limit pressure in the sealed cavity. The container further comprises a container rim and a lid having an outer channel and a tab. The outer channel receives the container rim and defines a first width. The tab has a second width substantially equal to the first width. There is a first interference fit of the channel with the container rim when the coolant is in the first phase. There is a second interference fit, different than the first interference fit, when the coolant is in the second phase.

[0009] According to a further aspect of the invention, a method of manufacturing a container includes the steps of providing first and second container portions and placing a coolant in the second container portion. The first container portion is placed within the second container portion, a region of the second container portion is joined to the first container portion, and an opening is formed in the region.

[0010] A further alternative aspect of the present invention comprehends a method of manufacturing a container including the steps of providing a coolant within the container wherein the coolant is capable of assuming first and second phases and providing a lid that forms first and second seals with the container. A nominal interference for the first seal is selected and is effective when the container is exposed to a particular condition. The second seal ensures sealing of the lid with the container when the container is exposed to a condition other than the particular condition.

[0011] According to another aspect of the present invention, a container comprises a container body including a hollow cavity and a rim. A coolant is disposed within the hollow cavity wherein the coolant is capable of assuming first and second phases. A lid has a peripheral member wherein the peripheral member forms first and second seals with the rim and wherein the seals have different interference fits with the rim when the container is exposed to different temperatures.

[0012] According to a further aspect of the invention a lid for a container includes a peripheral member defining an outer channel. The peripheral member has a peripheral wall that carries a bead. The bead contacts a rim of the container. A tab extends from the peripheral wall and interrupts contact of the bead with the rim. The outer channel has a first width, and the tab has a second width substantially equal to the first width.

[0013] In accordance with a still further aspect of the invention, a lid for a container, includes an outer channel of a first width and a tab extending outwardly from the channel. The tab has a second width substantially equal to the first width.

[0014] In accordance with yet another aspect of the invention, a lid for a container comprises an outer channel defined by a peripheral wall that carries a bead. The bead contacts a rim of the container. A tab extends outwardly from the peripheral wall and interrupts contact of the bead with the rim.

[0015] Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.

[0016] FIG. 1 is an isometric view of a container according to the present invention looking down from above;

[0017] FIG. 2 is a bottom view of the container of FIG. 1;

[0018] FIG. 3 is an isometric view of a lid for use with the container of FIG. 1 looking down from above;

[0019] FIG. 4A is a sectional view taken generally along the lines 4A-4A of FIG. 2;

[0020] FIG. 4B is a sectional view similar to FIG. 4A illustrating rupture of a first connection region;

[0021] FIG. 5 is a front elevational view of a container which does not include a second connection region;

[0022] FIG. 6A is a sectional view similar to FIG. 4A of a second embodiment of a container illustrating a tear-away weld as the pressure relief apparatus;

[0023] FIG. 6B is a sectional view similar to FIG. 4A illustrating rupture of the tear-away weld of the container of FIG. 6A;

[0024] FIG. 7 is an enlarged sectional view similar to FIG. 4A of a third embodiment of a container illustrating a thinned wall portion as the pressure relief apparatus;

[0025] FIG. 8 is a sectional view similar to FIG. 4A of a fourth embodiment of a container illustrating a valve as the pressure relief apparatus;

[0026] FIG. 9 is an enlarged full sectional view of a fifth embodiment illustrating an opening as the pressure relief apparatus;

[0027] FIG. 10 is an isometric view of a sixth embodiment of a container illustrating a different shape of container looking down from above;

[0028] FIG. 11 is a bottom view of a seventh embodiment of a container;

[0029] FIG. 12 is an enlarged sectional view taken along lines 12-12 of FIG. 11;

[0030] FIG. 13 is a fragmentary bottom view of the abutted section of the container of FIG. 11;

[0031] FIG. 14 is a sectional view taken along lines 14-14 of FIG. 13;

[0032] FIG. 15 is a view of the abutted section illustrating rupture of the weld;

[0033] FIG. 16 is an isometric view of a lid disposed on the container of FIG. 11 looking down from above;

[0034] FIG. 17A is an exploded sectional view taken generally along lines 17A-17A of FIG. 16;

[0035] FIG. 17B is an exploded fragmentary sectional view of a portion of the container and lid of FIG. 17A further illustrating dimensions thereof;

[0036] FIG. 18 is an enlarged fragmentary sectional view taken generally along lines 18-18 of FIG. 16;

[0037] FIG. 19 is an enlarged fragmentary sectional view taken generally along lines 19-19 of FIG. 16; and

[0038] FIG. 20 is an enlarged fragmentary isometric bottom view of the bottom of the lid.

[0039] Referring now to FIG. 1, a container 36 defines an interior space 37 for placement of products therein. Referring also to FIG. 4A, the container 36 includes a first container portion 39 and a second container portion 42. The container portions 39 and 42 are constructed of polypropylene but other suitable materials may be employed. The first container portion 39 includes a first rim 45. The second container portion 42 includes a second rim 48 wherein the second rim 48 is joined to the first rim 45, thereby defining a sealed cavity 51 between the container portions 39 and 42. The rims 45 and 48 may be joined by any suitable means including ultrasonic welding, spin welding, hot plate welding or by use of an adhesive, but the portions 39 and 42 are preferably joined by vibration welding. Alternatively, the portions 39 and 42 could be joined in a mechanical fashion (not shown), such as by press fitting or interfitting, such that the portions 39 and 42 are substantially sealed to define the cavity 51. A coolant (not shown) is placed within the sealed cavity 51. The first container portion 39 includes a first base portion 54, and the second container portion 42 includes a second base portion 57. A pressure relief apparatus 58 comprises a joined section 60 (seen also in FIG. 2) that joins the first base portion 54 to the second base portion 57 at first and second connection regions 63 and 66.

[0040] Any suitable coolant may be disposed within the cavity 51, but preferably the coolant is a cross-linked gel having a generally solid structure such that if the gel were heated the gel matrix tends to remain intact allowing only water vapor to escape from the gel matrix. In operation, the container 36 is first placed in a freezer for a long enough time to freeze the gel. Thereafter, a user may take the container 36 out of the freezer and place products within the interior space 37. The frozen gel should maintain food or other perishable items placed within the interior space 37 of the container 36 within a temperature range between about 10 C. to about 15.5 C. for about four to about six hours in a room temperature environment. In an above room temperature environment, the time and temperature ranges are affected somewhat depending on the ambient temperature. A preferred formulation of the gel comprises a mixture of about 98.2% water and a solid polymer blend of about 1.8% to about 2.1% solids. The solids include about 80-85% sodium carboxymethylcellulose, roughly 10-16% sodium benzoate and about 4-6% cross-linkers. The solid polymer blend is available from Progressive Polymer Application of Sheridan, Wyo. and is sold under the trade name UNIGEL. A small amount of paraben (an anti-microbial preservative) is added to the gel as an additional component of the preferred gel formulation. Of course, other suitable gel formulations may be employed. It should be noted that the container 36 is not limited to use with only perishable food products. Rather, many other products may be kept cool by placement within the container 36. For example, human organs intended for transplant surgery may be placed temporarily therein. Alternatively, a cosmetic product, beverage or chemical compound may be placed in the container 36.

[0041] FIG. 3 illustrates a lid 67 that may be used to seal contents placed within the container 36 in an airtight manner. The lid 67 includes a grasping tab 68 to facilitate removal of the lid 67.

[0042] Assembly of the container 36 includes the following steps. The components of the gel are mixed together at room temperature. While still in a liquid state, the gel is poured into the second container portion 42. The first container portion 39 is placed within the second container portion 42, thereby displacing the gel upwardly along the walls of the portions 39 and 42 defining the cavity 51. Within several hours, the gel cures such that it assumes a generally solid structure. Thereafter or before curing of the gel, the joined section 60 is vibration welded to join the base portions 54 and 57. Simultaneously, the rims 45 and 48 are also joined together by vibration welding to seal the cavity 51. However, the respective steps of welding the portions 54 and 57 and of welding the rims 45 and 48 could be performed sequentially.

[0043] Referring to FIGS. 4A and 4B, the first connection region 63 includes a projection portion 69 integral with the first container portion 39. The projection portion 69 is vibration welded within an opening 72 of the second container portion 42. The opening 72 is preferably about inch in diameter. The first connection region 63 is rupturable upon exposure to elevated pressure within the sealed cavity 51. The elevated pressure may result from heating the gel and/or container 36 such as by placement in a microwave oven. Heat developed within the sealed cavity 51 elevates pressure within the sealed cavity 51 forcing the walls of the first and second container portions 39 and 42 to push away from one another. When sufficient elevated pressure is reached, the walls of the first and second container portions 39 and 42 push away from one another with sufficient force to cause separation (rupture) of the first connection region 63. During separation, the base portion 54 carries the projection portion 69 upwardly away from the base portion 57, thereby removing the projection portion 69 out of the opening 72 and exposing the cavity 51 to the opening 72 as illustrated in FIG. 4B. Exposure of the opening 72 allows steam from the heated gel (or other heated coolant in vapor and/or solid form) to escape from the cavity 51. This prevents the walls of the container 36 from rupturing.

[0044] It should be noted that the joined section 60 could alternatively join side portions 73a and 73b (FIG. 4A) of the respective first and second container portions 39 and 42 together. However, the joined section 60 preferably joins the base portions 54 and 57. The opening 72 could also be disposed in the first container portion 39. However, the opening is preferably disposed in the second container portion 42 to prevent contamination of product placed within the interior space 37 of the container 36 by the heated gel. The second connection region 66 joins the first and second container portions 39 and 42 together more securely than the first connection region 63 such that when an elevated pressure is reached within the cavity 51, the first connection region 63 ruptures exposing the opening 72 while the second connection region 66 remains intact. The connection region 66 thus prevents possible inversion of the container portion 39, for example as illustrated in FIG. 5. In this regard, once the first connection region 63 ruptures, the cavity 51 is no longer sealed and it is not possible for sufficient pressure to develop within the unsealed cavity to cause rupture of the second connection region 66.

[0045] As described above, the first connection region 63 ruptures in response to elevated pressure to limit pressure in the sealed cavity 51. However, the region 63 could be replaced with a region that alternatively limits elevated pressure by rupturing in response to a different parameter, such as an elevated temperature. By way of example only, a region could be employed that melts below the boiling point of the coolant within the cavity 51. Melting of the region exposes the cavity 51 to the ambient surroundings so that pressure in the cavity 51 is limited. For example, the projection portion 69 might be constructed of a material having such a relatively low melting point that the portion 69 melts in response to such temperature, thereby exposing the opening 72 to the cavity 51. Alternatively, the portion 69 might consist of a material that splinters or cracks in response to such temperature, thereby exposing the opening 72. In such a container, the second connection region 66 would not melt or otherwise rupture in response to the elevated temperature, and as in other embodiments described herein, would prevent possible inversion illustrated in FIG. 5.

[0046] FIGS. 6A and 6B illustrate a second embodiment wherein elements common to the various embodiments are given like reference numerals. The first connection region 63 is replaced by a tear-away weld 78 connecting the base portions 54 and 57 adjacent the connection region 66. Upon exposure to an elevated pressure, the base portion 54 separates from the base portion 57 such that the portion 54 tears away a part of the portion 57 welded thereto (at the weld 78) to create an opening 84 (seen in FIG. 6B). The newly created opening 84 exposes the cavity 51, thereby preventing undesirable pressure build-up therein. As discussed above, the assembly of the container 36 includes the step of first filling the container portion 42 with gel while the gel is still in a pourable, liquid state. In the first embodiment illustrated in FIGS. 4A and 4B, pouring the liquid gel into the container portion 42 might result in some spilling or leakage of the gel through the opening 72 in the second container portion 42. The embodiment illustrated in FIGS. 6A and 6B overcomes this problem by employing the tear-away weld 78 that does not require a pre-existing opening (like the opening 72) in the container portion 42. It should be noted that the weld 78 could alternatively create several smaller openings or perforations (not shown) in the base portion 57 rather than the single opening 84.

[0047] FIG. 7 illustrates a third embodiment wherein the joined section 60 is replaced by a thinned wall portion 87 preferably disposed in the base portion 57 of the second container portion 42. Exposure to an elevated pressure in the cavity 51 causes the portion 87 to rupture. A connection region (not shown) identical to the connection region 66 could be disposed near the portion 87 in this or any of the following embodiments discussed hereinafter.

[0048] FIG. 8 illustrates a fourth embodiment wherein the joined section 60 is replaced by a valve 90 that opens in response to an elevated pressure in the cavity 51 to limit pressure in the cavity 51.

[0049] FIG. 9 illustrates a fifth embodiment wherein the joined section 60 is replaced by a small opening 93 disposed in one of the container portions 39 or 42 (but preferably in the base portion 57 of the container portion 42) which prevents pressure rise beyond a certain level. A resilient plug (not shown) made of rubber or other suitable material could be disposed within the opening 93 to prevent contaminants from entering the cavity 51. Such a plug would eject from the opening in response to an elevated pressure in the cavity 51.

[0050] FIG. 10 illustrates a sixth embodiment of a square container 96 that incorporates pressure relief apparatus, but which differs from the container 36 in shape. A lid (not shown) of suitable dimension could be placed on the container to seal products placed within the interior space 37. It should be evident from the container 96 of FIG. 10 that many variations of geometric shape and dimension are possible for a container incorporating any of the pressure relief apparatuses illustrated in FIGS. 4A and 4B and FIGS. 6-9.

[0051] FIGS. 11 through 20 illustrate another embodiment of a container 100 according to the present invention wherein many of the features of the embodiment are similar in structure and function to the embodiments described above. As before, elements common to the various embodiments are given like reference numerals.

[0052] The joined section 60 is replaced by an abutted section 103 having a first base portion 104 and a second base portion 105 (FIG. 12). The abutted section 103 includes a welded portion 106 that joins the base portions 104 and 105 together. Unlike previous embodiments, the base portions 104 and 105 are joined only at the welded portion 106 between margins 106a and 106b (shown as dashed lines in FIG. 14), while the remainder of the base portions 104 and 105 are simply in abutment. As seen in FIGS. 14 and 15, the welded portion 106 is disposed off-center of the abutted section 103. Upon exposure to an elevated pressure, the base portions 104 and 105 separate from one another such that the opening 109 is exposed to the ambient surroundings, thereby limiting pressure within the cavity 51.

[0053] It is believed that placing the welded portion 106 off-center on the abutted section 103 effectively facilitates rupture or peeling apart of the welded portion 106 more so than if the welded portion 106 were centered. For example, separation forces exerted at distal points 112 have longer moment arms L than separation forces developed at more proximal points 113. It is believed that these longer moment arms L are responsible for the more effective rupture of the welded portion 106 in response to elevated pressure within the cavity 51. Also, it is believed that placing the opening 109 closer to a point of peeling (i.e., the margin 106b) rather than the center of the welded portion 106 more effectively facilitates rupture.

[0054] A cross-linked gel is disposed in the cavity 51, similar to that used in the previous embodiments but having a somewhat different formulation. The paraben is replaced by about 0.1% by weight DOWICIDE A (an antimicrobial preservative sold by the Dow Chemical Company). Also, about 0.1% by weight propionic acid is added. Adding the DOWICIDE A tends to decrease the solid strength of the gel and also makes the gel somewhat alkaline. Adding the propionic acid counters these effects, increasing the solid strength of the gel sufficiently to ensure that the resulting gel is not pourable or flowable and reducing the pH to substantially neutral.

[0055] Assembly of the embodiment of FIGS. 11-20 is similar to the assembly described above and includes the following steps. The components of the gel are mixed together at room temperature. Prior to curing of the gel, while the gel is still in a substantially liquid state, the gel is poured into the second container portion 42. The first container portion 39 is placed within the second container portion 42, thereby displacing the gel upwardly along the walls of the portions 39 and 42 defining the cavity 51. Either before or after curing of the gel, the welded portion 106 is formed in the abutted section 103 by vibration welding. Shortly thereafter, the base portion 105 is drilled or cut between the margins 106a and 106b to form the opening 109 within the welded portion 106. Simultaneously, the rims 45 and 48 are also joined together by vibration welding to seal the cavity 51. Within several hours, the gel cures such that it assumes a generally solid structure.

[0056] If desired, the steps of forming the welded portion 106 and of welding the rims 45 and 48 could be performed sequentially, with either step being undertaken before the other. Also, the step of forming the opening 109 could be performed before or after either of the foregoing steps.

[0057] Referring to FIG. 16, the lid 67 is replaced by a lid 116 having a tab 117 and an inverted U-shaped peripheral member 118 defining a channel 119 (FIGS. 16-20) that receives a container rim 122 when the lid 116 is disposed on the container 100. Referring to FIG. 18, the peripheral member 118 includes first and second beads 125 and 128 wherein the first bead 125 is disposed in interfering relationship with a moisture retention ridge 131. The ridge 131 is disposed on an inner wall 133 of the container rim 122 adjacent the interior space 37 and the first bead 125 contacts the inner wall 133 below the moisture retention ridge 131 about the entire periphery of the container 100. The second bead 128 contacts an exterior or outer wall 136 in a discontinuous fashion, as noted in greater detail hereinafter. If desired, the ridge 131 could be placed on the outer wall 136 of the rim 122.

[0058] Referring to FIG. 19, the channel 119 of the lid 116 has a first width W1 that is approximately equal to a width W2 of the tab 117 (i.e., within about 0.02 inches). The tab 117 may be pulled upwardly by a user to remove the lid 116 from the container. The tab 117 is preferably substantially trapezoidal in shape and includes first through third raised stiffening ribs 141a-141c (FIG. 16). As seen in FIGS. 19 and 20, the bead 128 extends about only a portion of the periphery of the lid 116 so that the tab 117 and portions adjacent thereto interrupt the contact of the second bead 128 with the outer wall 136. The peripheral member 118 further includes a peripheral stiffening lip or flange 142 that further increases the rigidity of the tab 117 and the lid 116 as a whole. By incorporating the relatively short dimension W2 and the stiffening ribs 141, the tab 117 is sufficiently rigid and resistive to bending that it serves as an effective lever arm for removal of the lid 116.

[0059] FIGS. 17A and 17B show a dimension A measured at diametrically opposite points of the second bead 128, a dimension B measured at diametrically opposite points of the first bead 125, a dimension C measured at diametrically opposite points of the inner wall 133, and a dimension D measured at diametrically opposite points of the outer wall 136. Referring also to FIG. 18, a first seal 144 is defined by the first bead 125 and the wall 133. The first seal 144 may be described as a B-C interference fit, dimension B being greater than dimension C, such that the material of the peripheral member 118 flexes when the lid 116 is placed on the container 100 so that the lid 116 is retained on the container 100.

[0060] The water component of the gel is capable of assuming first and second phases. For example, the water is in the liquid phase at room temperature and the solid phase when frozen. When the water freezes, the gel expands within the cavity 51 causing the wall 133 to move toward the interior space 37 somewhat, thereby reducing dimension C and creating an increased B-C interference fit. For this reason, a nominal B-C interference is selected that is sufficiently small (or loose) at room temperature so that the B-C interference does not become overly tight when dimension C is reduced. At the same time, it would be desirable to select a nominal B-C interference that is sufficiently large to provide adequate sealing at room temperature.

[0061] However, while it is possible to select a nominal B-C interference capable of satisfying the above conditions simultaneously, there is typically some deviation below nominal due to manufacturing variations (e.g., due to tolerances) such that the first seal 144 (i.e., the B-C interference) is too loose and does not provide adequate sealing at room temperature for certain combinations of containers and lids. An A-D interference (or second seal 146 seen in FIG. 18) is provided that ensures adequate sealing in instances when the actual B-C interference is below nominal. This is because the magnitude of the actual A-D interference tends to deviate above nominal (the nominal A-D interference being 0) when the actual B-C interference deviates below nominal. (Dimension A tends to decrease with dimension B when dimension B decreases below nominal.) In this regard, the A-D interference tends to compensate for inadequate sealing of the B-C interference in instances where the combination of lid and container has an actual B-C interference below the nominal value thereof. In addition, dimension D tends to increase when dimension C increases above nominal; this also tends to provide a greater actual A-D interference when the actual B-C interference is below nominal.

[0062] By way of example, and not as a limitation, the foregoing values have the nominal dimensions noted below at room temperature (all dimensions are in inches):

	Reference	Nominal
	Letter	Dimension
	A	8.474
	B	7.975
	C	7.952
	D	8.474
	W1	0.310
	W2	0.328

[0063] As noted above, when the water component of the gel freezes, dimension C is reduced. For example, in a container having the above dimensions, dimension C is reduced from 7.952 inches to about 7.942 inches (i.e., about 0.010 inches), thereby increasing the B-C interference.

[0064] The container and lid of the present invention provide improved sealing and lid removal characteristics. Improved protection against sudden rupture of the container in the event of placement of the container in a microwave oven is also provided.

[0065] If desired, the round container and lid of FIGS. 11-20 may instead have the substantially square configuration of FIG. 10 or any other configuration.

[0066] Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as exemplary of the claimed invention and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.