CLAIMS
1 Desiccant cartridge (100) for an air processing unit (1000), the desiccant car-
tridge (100) having:
a housing (102) defining an inner volume (104) for a desiccant material (106) and having an opening (108) defined by a housing rim (110) at a proximal end (102a) of the housing (102), the housing (102) being fixedly connected to a crimp ring (114) at the housing rim (110), wherein the crimp ring (114) is fixed to a plate-like base ring (10) that extends in a radial direction (R) and comprises a central opening (116) for allowing a flow of air (F) into and out of the inner volume (104), the base ring (10) being an integral base ring (10) and comprising:
- a ring inner end section (11) including a flange rim (12) defining the central opening (116), and a flat ring inner section (13) adjacent to the flange rim (12);
- a ring outer end section (14) including an abutting rim (15) for abutting an inner side (112) of the housing (102) proximate the housing rim (110), and a flat ring outer section (16) adjacent to the abutting rim (15); and
- a middle section (17) that is arranged between the flat ring inner section (11) and the flat ring outer section (14) for connecting the flat ring inner section (11) to the flat ring outer section (14);
wherein at least one of an inner connecting transition section (18) connecting the flat ring inner section (11) to the middle section (17) and an outer connecting transition sec¬tion (19) connecting the flat ring outer section (14) to the middle section (17) comprises a formed region (18a, 19a) of the base ring (10);
characterized in that the formed region (18a, 19a) has a hardness value (HV) lower than that of the ring inner end section (11) and lower than that of the ring outer end section (14).
2. The desiccant cartridge (100) of claim 1, wherein the inner connecting transi-
tion section (18) and the outer connecting transition section (19) comprise an inner formed region (18a) and an outer formed region (19a) respectively, and wherein both the inner formed region (18a) and the outer formed region (19a) have a hardness value (HV) that is lower than that of the ring inner end section (11) and lower than that of the ring outer end section (14)

3. The desiccant cartridge (100) of claim 1 or 2, wherein the formed region (18a, 19a) provides less burst resistance in a burst test where a pressure is increased in the desiccant cartridge (100) until a structural failure of the desiccant cartridge (100) occurs.
4. The desiccant cartridge (100) of any of the preceding claims, wherein the hardness (HV) at a particular section (11, 13,14,16,17,18,19) depends on an aver-age size of material grains in said section.
5. The desiccant cartridge (100) claim 3, wherein the base ring (10) is a cold-formed grain-coarsened base ring (10), wherein the cold-formed grain-coarsened base ring is produced by cold forming resulting in an initial average size (S1) of the material grains (G) and wherein the average size (S1) of the grains (Gf) at the formed region (18a, 19a) is increased until afinal average size (S2) by performing a grain coarsening process on the cold formed base ring (100), in particular by annealing the cold formed base ring (100).
6. The desiccant cartridge (100) of any of the preceding claims, wherein the base ring (10) comprises a ferritic material.
7. A plate-like base ring (10) for use in a desiccant cartridge (100) according to
any of the preceding claims, the base ring (10) comprising:
- a ring inner end section (11) including a flange rim (12) defining the central opening (116), and a flat ring inner section (13) adjacent to the flange rim (12);
- a ring outer end section (14) including an abutting rim (15) for abutting an inner side (112) of a housing (102) of a desiccant cartridge (100) proximate a housing rim
(110), and a flat ring outer section (16) adjacent to the abutting rim (15); and
- a middle section (17) that is arranged between the flat ring inner section (11)
and the flat ring outer section (14) for connecting the flat ring inner section (11) to the
flat ring outer section (14);
wherein at least one of an inner connecting transition section (18) connecting the flat ring inner section (11) to the middle section (17) and an outer connecting transition sec¬tion (19) connecting the flat ring outer section (14) to the middle section (17) comprises a formed region (18a, 19a) of the base ring (10);

characterized in that the formed region (18a, 19a) has a hardness value (HV) lower than that of the ring inner end section (11) and lower than that of the ring outer end section (14).
8. Air processing unit (1000) comprising a desiccant cartridge (100) in accord¬ance with any of the claims 1 to 6, a valve section (200) arranged and configured to control a flow of compressed air (F) into and out of the inner volume (104) of the desic¬cant cartridge (100) and a gasket (202) arranged between the valve section (200) and the desiccant cartridge (100), and wherein the formed region (18a, 19a) of the base ring (10) is proximate the gasket (202).
9. Method (500) of manufacturing a plate-like base ring (10) for a desiccant car¬tridge (100) for an air processing unit (1000), the method (500) comprising:

- cold forming (502) an annular plate into a cold formed base ring having an ring inner end section (11) including a flange rim (12) defining a central opening (116), and a flat ring inner section (13) adjacent to the flange rim (12), an ring outer end section (14) including an abutting rim (15) for abutting an inner side (112) of a housing (102) proxi¬mate a housing rim (110), and aflat ring outer section (16) adjacent to the abutting rim (15), and a middle section (17) that is arranged between the flat ring inner section (11) and the flat ring outer section (14) for connecting the flat ring inner section (11) to the flat ring outer section (14), wherein at least one of an inner connecting transition section (18) connecting the flat ring inner section (11) to the middle section (17) and an outer connecting transition section (19) connecting the flat ring outer section (14) to the mid¬dle section (17) comprises a formed region (18a, 19a) of the base ring (10); and
- performing a grain coarsening process (504) on the cold formed base ring, in particular annealing the cold formed base ring, to selectively increase an average grain size (Gf) at the formed region (18a, 19a).