Apparatus for growing crystals, having a thermal casing unit

A device (200) for growing crystals, comprising

• a crucible (201, 301), which crucible (201, 301) defines an outer lateral surface (203) and moreover delimits an accommodation space (202) with an axial extension between a bottom section (204) and an opening section (205), wherein the accommodation space (202) is designed for growing the crystals,
• an enveloping unit (206), which enveloping unit (206) covers the outer lateral surface (203) at least in sections and is designed for thermally insulating the crucible (201, 301), wherein
• a holding unit (207) is provided, by means of which holding unit (207) the enveloping unit (206) is held on the crucible (201, 301) in its position relative to the crucible (201, 301),
• the holding unit (207) comprises at least one holding element (208) designed to be oblong and preferably non-rigid, having a first end section (209) and a second end section (210) spaced apart therefrom in its longitudinal extension,
• the at least one holding element (208) surrounds the enveloping unit (206) in a circumferential manner on the side facing away from the crucible (201, 301) and is arranged so as to contact the enveloping unit (206), and
• the first end section (209) and the second end section (210) are coupled to one another so as to be releasable as needed, and a holding force acting on the enveloping unit (206) in the radial direction is applied by the at least one holding element (208).