| 1/00 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) |
| 1/01 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with one single cylinder |
| 1/02 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with cylinders all in one line |
| 1/04 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with cylinders in V-arrangement |
| 1/06 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with cylinders in star or fan arrangement |
| 1/08 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with cylinders arranged oppositely relative to main shaft and of "flat" type |
| 1/10 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) with more than one main shaft, e.g. coupled to common output shaft (combinations of two or more machines or engines F01B 21/00) |
| 1/12 | Reciprocating-piston machines or engines characterised by number or relative disposition of cylinders or by being built-up from separate cylinder-crankcase elements (F01B 3/00, F01B 5/00 take precedence) Separate cylinder-crankcase elements coupled together to form a unit |
| 3/00 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis |
| 3/02 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis with wobble-plate |
| 3/04 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis the piston motion being transmitted by curved surfaces |
| 3/06 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis the piston motion being transmitted by curved surfaces by multi-turn helical surfaces and automatic reversal |
| 3/08 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis the piston motion being transmitted by curved surfaces by multi-turn helical surfaces and automatic reversal the helices being arranged on the pistons |
| 3/10 | Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis Control of working-fluid admission or discharge peculiar thereto (suitable for more general application F01L) |
| 5/00 | Reciprocating-piston machines or engines with cylinder axes arranged substantially tangentially to a circle centred on main shaft axis |
| 7/00 | Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B 1/08) |
| 7/02 | Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B 1/08) with oppositely reciprocating pistons |
| 7/04 | Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B 1/08) with oppositely reciprocating pistons acting on same main shaft |
| 7/06 | Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B 1/08) with oppositely reciprocating pistons acting on same main shaft using only connecting-rods for conversion of reciprocatory into rotary motion or vice versa |
| 7/08 | Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B 1/08) with oppositely reciprocating pistons acting on same main shaft using only connecting-rods for conversion of reciprocatory into rotary motion or vice versa with side rods |