Modular toy system with arc toy building element

A modular toy system comprising toy building elements, the toy building elements comprising:

• complementary coupling elements in the form of one or more knobs formed on a top surface of at least some of the toy building elements or one or more knob receiving openings formed in a bottom surface of at least some of the toy building elements, the coupling elements on the toy building elements arranged to cooperate in a regular two-dimensional pattern on the toy building elements spaced apart by a first modular distance,
• a length and width which are both an integer of the first modular distance,
• a height between the bottom surface and the top surface, which is an integer of a second modular distance, the second modular distance being ⅖ of the first modular distance,
• an arc toy building element, the arc toy building element having:
• at least one knob receiving opening formed in a bottom surface or at least one knob formed in a top surface configured for coupling to complimentary coupling elements of another toy building element in a first direction;
• an arc surface formed as a convex surface on the arc toy building element and extending over a second length in a direction parallel to the top surface or to the bottom surface of the arc toy building element, the second length is an integer multiple of the first modular distance, the arc surface having:
• an axis of curvature which is perpendicular to the first direction,
• a second height in a direction transverse to the bottom surface or to the top surface of the arc toy building element, the second height is an integer multiple of the second modular distance, the second height being 5, 7, 10, 12, 15, 17 or 20-times the second modular distance, and
• a second length of two to eight modular distances,
• such that when a ratio between the integer multiple of the second modular distance of the second height and the integer multiple of the first modular distance of the second length is 5/2, the arc surface is a continuously curved surface from the top surface to the bottom surface of the toy arc building element, and
• when the ratio is different from 5/2, but within an interval of 5/2 minus 10%, the arc surface comprises a vertical planar surface portion and a continuously curved surface portion extending between the vertical planar surface portion and the top surface or the bottom surface), the vertical planar surface portion having a third length, which is equal to the second modular distance.

An arc toy building element for coupling with other toy building elements, the toy building elements arranged to cooperate in a regular two-dimensional pattern spaced apart by a first modular distance, the toy building elements having a length and width which are both an integer of the first modular distance and a height which is an integer of a second modular distance, the second modular distance being ⅖ of the first modular distance, the arc toy building element comprising:

• at least one knob receiving opening formed in a bottom surface or at least one knob formed in a top surface configured for coupling to complimentary coupling elements of another toy building element in a first direction;
• an arc surface formed as a convex surface on the arc toy building element and extending over a second length in a direction parallel to the top surface or to the bottom surface of the arc toy building element, the second length is an integer multiple of the first modular distance, the arc surface having:
• an axis of curvature which is perpendicular to the first direction,
• a second height in a direction transverse to the bottom surface or to the top surface of the arc toy building element, the second height is an integer multiple of the second modular distance, the second height being 5, 7, 10, 12, 15, 17 or 20-times the second modular distance, and
• a second length of two to eight modular distances,
• such that when a ratio between the integer multiple of the second modular distance of the second height and the integer multiple of the first modular distance of the second length is 5/2, the arc surface is a continuously curved surface from the top surface to the bottom surface of the toy arc building element, and
• when the ratio is different from 5/2, but within an interval of 5/2 minus 10%, the arc surface comprises a vertical planar surface portion and a continuously curved surface portion extending between the vertical planar surface portion and the top surface or the bottom surface, the vertical planar surface portion having a third length, which is equal to the second modular distance.