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CPC Definition - Subclass F01B

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Last Updated Version: 2025.01
F01B
MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES (of rotary-piston or oscillating-piston type F01C; of non-positive-displacement type F01D; internal-combustion engines F02B; combustion-product engine plants F02G; machines or engines, other than of positive-displacement type, for liquids F03B; positive-displacement engines driven by liquids F03C; wind motors F03D; positive-displacement machines for liquids F04B; rotary-piston, or oscillating-piston, positive-displacement machines for liquids F04C)
Definition statement

This place covers:

Machines or engines, in general or of positive-displacement type.

References
Limiting references

This place does not cover:

Rotary-piston or oscillating-piston machines or engines

F01C

Non-positive-displacement machines or engines, e.g. steam turbines

F01D

Internal-combustion engines

F02B

Combustion-product engine plants

F02G

Machines or engines, other than of positive-displacement type, for liquids

F03B

Positive-displacement engines driven by liquids

F03C

Wind motors

F03D

Positive-displacement machines for liquids

F04B

Rotary-piston, or oscillating-piston, positive-displacement machines for liquids

F04C

Informative references

Attention is drawn to the following places, which may be of interest for search:

Steam engine plants

F01K

Cyclically operating valves for machines or engines

F01L

Lubricating of machines or engines in general

F01M

Pumps for liquids or elastic fluids

F04

Crankshafts, crossheads or connecting-rods

F16C

Flywheels

F16F

Gearings for interconverting rotary motion and reciprocating motion in general

F16H

Pistons, piston rods or cylinders, for engines in general

F16J

Glossary of terms

In this place, the following terms or expressions are used with the meaning indicated:

engine

a device for continuously converting fluid energy into mechanical power, thus, this term includes, for example, steam piston engines or steam turbines, per se, or internal-combustion piston engines, but it excludes single-stroke devices.

machine

a device which could equally be an engine and a pump, and not a device which is restricted to an engine or one which is restricted to a pump.

pump

a device for continuously raising, forcing, compressing, or exhausting fluid by mechanical or other means. Thus, this term includes fans or blowers.

positive displacement

the way the energy of a working fluid is transformed into mechanical energy, in which variations of volume created by the working fluid in a working chamber produce equivalent displacements of the mechanical member transmitting the energy, the dynamic effect of the fluid being of minor importance, and vice versa.

non-positive displacement

the way the energy of a working fluid is transformed into mechanical energy, by transformation of the energy of the working fluid into kinetic energy, and vice versa.

oscillating-piston machine

a positive-displacement machine in which a fluid-engaging work-transmitting member oscillates. This definition applies also to engines and pumps.

rotary-piston machine

a positive-displacement machine in which a fluid-engaging work-transmitting member rotates about a fixed axis or about an axis moving along a circular or similar orbit. This definition applies also to engines and pumps.

rotary piston

the work-transmitting member of a rotary-piston machine and may be of any suitable form, e.g., like a toothed gear.

free piston

a piston of which the length of stroke is not defined by any member driven thereby.

cylinders

positive-displacement working chambers in general. Thus, this term is not restricted to cylinders of circular cross-section.

main shaft

the shaft which converts reciprocating piston motion into rotary motion or vice versa.

plant

an engine together with such additional apparatus as is necessary to run the engine. For example, a steam engine plant includes a steam engine and means for generating the steam.

working fluid

the driven fluid in a pump or the driving fluid in an engine. The working fluid can be in a compressible, gaseous state, called elastic fluid, e.g. steam; in a liquid state; or in a state where there is coexistence of an elastic fluid and liquid phase.

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)
References
Limiting references

This place does not cover:

Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft

F01B 3/00

Reciprocating-piston machines or engines with cylinder axes arranged substantially tangentially to a circle centred on main shaft axis

F01B 5/00

{the connection of the pistons with an element being at the outer ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 1/0603

media0.jpg

{the connection of the pistons with an actuating or actuated element being at the inner ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 1/062

media1.jpg

{Disconnecting the pistons from the actuating or actuated cam}
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Disengagement of connections between pistons and main shafts

F01B 31/24

with more than one main shaft, e.g. coupled to common output shaft
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Combinations of two or more machines or engines

F01B 21/00

Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis
Special rules of classification

Illustrative example of subject matter classified in F01B 3/00

media2.jpg

{having stationary cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0002

media3.jpg

{having two or more sets of cylinders or pistons}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0005

media4.jpg

{having self-acting distribution members, e.g. actuated by working fluid}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0008

media5.jpg

{Cylindrical distribution members}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0011

media6.jpg

{Conical distribution members}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0014

media7.jpg

{having rotary cylinder block}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0032

media8.jpg

{inclined to main shaft axis}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0038

media9.jpg

{Arrangements for pressing the cylinder barrel against the valve plate, e.g. fluid pressure}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0041

media10.jpg

{Particularities in the contacting area between cylinder barrel and valve plate}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0047

media11.jpg

{Bearing arrangements}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/005

media12.jpg

{Cylinder barrel}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0052

media13.jpg

{Conical valve means}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0061

media14.jpgmedia15.png

{Swash plate}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/007

media16.jpg

{Connection between cylinder barrel and inclined swash plate}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/0076

media17.jpg

{having pistons with rotary and reciprocating motion, i.e. spinning pistons}
Definition statement

This place covers:

Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis, wherein the pistons rotate (spin) about their longitudinal axis as they reciprocate.

Illustrative example of subject matter classified in this place:

media72.jpg

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Piston motion being transmitted by curved surfaces

F01B 3/04

with wobble-plate
Special rules of classification

Illustrative example of subject matter classified in F01B 3/02

media19.jpg

the piston motion being transmitted by curved surfaces
Definition statement

This place covers:

Piston motion being transmitted by curved surfaces, e.g. by cams or grooves.

Illustrative example of subject matter classified in this place:

media73.png

{by two or more curved surfaces, e.g. for two or more pistons in one cylinder}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/045

media21.jpg

by multi-turn helical surfaces and automatic reversal
Special rules of classification

Illustrative example of subject matter classified in F01B 3/06

media22.jpg

the helices being arranged on the pistons
Special rules of classification

Illustrative example of subject matter classified in F01B 3/08

media23.jpg

Control of working-fluid admission or discharge peculiar thereto
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Cyclically operating valves for machines or engines in general

F01L

{for machines with rotary cylinder block}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/103

media24.jpg

{by turning the valve plate}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/104

media25.jpg

{by changing the inclination of the swash plate}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/106

media26.jpg

{by turning the swash plate (with fixed inclination)}
Special rules of classification

Illustrative example of subject matter classified in F01B 3/108

media27.jpg

{by changing the inclination of the axis of the cylinder barrel relative to the swash plate}
Definition statement

This place covers:

Illustrative example of subject matter classified in this place:

media74.png

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Control of working-fluid admission or discharge by changing inclination of the swash plate

F01B 3/106

Reciprocating-piston machines or engines with cylinder axes arranged substantially tangentially to a circle centred on main shaft axis
Special rules of classification

Illustrative example of subject matter classified in F01B 5/00

media29.jpg

{the connection of the pistons with an actuated or actuating element being at the outer ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 5/003

media30.jpg

{the connection of the pistons with an actuated or actuating element being at the inner ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 5/006

media31.jpg

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)
References
Limiting references

This place does not cover:

Coaxial cylinders in opposite arrangement relative to main shaft

F01B 1/08

Special rules of classification

Illustrative example of subject matter classified in F01B 7/00

media32.jpg

with oppositely reciprocating pistons
Special rules of classification

Illustrative example of subject matter classified in F01B 7/02

media33.png

using only connecting-rods for conversion of reciprocatory into rotary motion or vice versa
Special rules of classification

Illustrative example of subject matter classified in F01B 7/06

media34.jpg

with side rods
Special rules of classification

Illustrative example of subject matter classified in F01B 7/08

media35.png

having piston-rod of one piston passed through other piston
Special rules of classification

Illustrative example of subject matter classified in F01B 7/10

media36.png

using rockers and connecting-rods
Special rules of classification

Illustrative example of subject matter classified in F01B 7/12

media37.png

acting on different main shafts
Special rules of classification

Illustrative example of subject matter classified in F01B 7/14

media38.jpg

with pistons synchronously moving in tandem arrangement
Special rules of classification

Illustrative example of subject matter classified in F01B 7/16

media39.jpg

with differential piston (F01B 7/20 takes precedence)
References
Limiting references

This place does not cover:

With two or more pistons reciprocating one within another

F01B 7/20

Special rules of classification

Illustrative example of subject matter classified in F01B 7/18

media40.jpg

with two or more pistons reciprocating one within another, e.g. one piston forming cylinder of the other
Special rules of classification

Illustrative example of subject matter classified in F01B 7/20

media41.jpg

Reciprocating-piston machines or engines characterised by connections between pistons and main shafts, not specific to groups F01B 1/00 - F01B 7/00
Definition statement

This place covers:

Reciprocating-piston machines or engines characterised by connections between pistons and main shafts and not specific to groups F01B 1/00 - F01B 7/00, e.g. when no recognisable crank shaft is present or the main shaft is a cam shaft.

Illustrative example of subject matter classified in this place:

media75.png

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Connections disengageable during idling

F01B 31/24

with crankshaft
Special rules of classification

Illustrative example of subject matter classified in F01B 9/02

e.g. non-conventional crankshafts:

media43.jpg

{of Bourke-type or Scotch yoke}
Special rules of classification

Illustrative example of subject matter classified in F01B 9/023

media44.jpg

with rotary main shaft other than crankshaft
Special rules of classification

Illustrative example of subject matter classified in F01B 9/04

media45.jpg

{the connections comprising gear transmissions}
Special rules of classification

Illustrative example of subject matter classified in F01B 9/042

media46.jpg

{with rack and pinion}
Special rules of classification

Illustrative example of subject matter classified in F01B 9/047

media47.jpg

the piston motion being transmitted by curved surfaces
Special rules of classification

Illustrative example of subject matter classified in F01B 9/06

media48.jpg

with ratchet and pawl
Special rules of classification

Illustrative example of subject matter classified in F01B 9/08

media49.jpg

{in which the movement in the two directions is obtained by one double acting piston motor}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/001

media50.jpg

{one side of the double acting piston motor being always under the influence of the fluid under pressure}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/002

media51.jpg

{the fluid under pressure being continuously delivered to one motor chamber and reacting the other chamber through a valve located in the piston, to bring the piston back in its start-position}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/003

media52.png

FR2508568 A1

{in which the movement in the two directions is obtained by two single acting piston motors, each acting in one direction}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/004

media53.jpg

{one single acting piston motor being always under the influence of the fluid under pressure}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/006

media54.png

"...the steam supplied through the inlet 13 and the passage 12 enters the port 18, and acting upon the 1 upper face of the element 4 of the double piston (4,5), causes the latter to move downwards against the opposing action of the steam continuously supplied to the space 11...

{in which the movement in only one direction is obtained by a single acting piston motor, e.g. with actuation in the other direction by spring means}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/007

media55.jpg

{with actuation in the other direction by gravity}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/008

media56.jpg

{in which the movement in two directions is obtained by two or more double acting piston motors}
Special rules of classification

Illustrative example of subject matter classified in F01B 11/009

media57.jpg

Equalising or cushioning devices
Special rules of classification

Illustrative example of subject matter classified in F01B 11/02

media58.jpg

Engines combined with reciprocatory driven devices, e.g. hammers
Definition statement

This place covers:

Illustrative example of subject matter classified in this place:

media76.png

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Engines combined with pumps

F01B 23/08

for generating vibration only
Special rules of classification

Illustrative example of subject matter classified in F01B 11/06

media60.png

with direct fluid transmission link
Definition statement

This place covers:

Illustrative example of subject matter classified in this place:

media77.png

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Equalising or cushioning devices

F01B 11/02

Reciprocating-piston machines or engines with rotating cylinders in order to obtain the reciprocating-piston motion
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Machines or engines of flexible-wall type

F01B 19/00

with one cylinder only
Special rules of classification

Illustrative example of subject matter classified in F01B 13/02

media62.jpg

with more than one cylinder
Definition statement

This place covers:

Illustrative example of subject matter classified in this place:

media85.png

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis having rotary cylinder block

F01B 3/0032

{with cylinder axes arranged substantially tangentially to a circle centred on main shaft axis}
Special rules of classification

Illustrative example of subject matter classified in F01B 13/045

media64.jpg

{the connection of the pistons with the actuated or actuating element being at the outer ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 13/061

media65.jpg

{the connection of the pistons with an actuated or actuating element being at the inner ends of the cylinders}
Special rules of classification

Illustrative example of subject matter classified in F01B 13/068

media66.jpg

Reciprocating-piston machines or engines with movable cylinders other than provided for in group F01B 13/00
Definition statement

This place covers:

Reciprocating-piston machines or engines with movable cylinders other than provided for in group F01B 13/00, e.g. reciprocating-piston machines or engines having reciprocating cylinders or pivoting and oscillating cylinders.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Slide-valve gear or valve arrangements, with cylindrical, sleeve or part-annularly-shaped valves, surrounding working cylinder or piston

F01L 5/06

Reciprocating-piston machines or engines characterised by use of uniflow principle
Definition statement

This place covers:

Reciprocating-piston machines or engines characterised by use of uniflow principle:

E.g. compressed gas engines where the working fluid enter a working cylinder, expands and then exits the cylinder.

media67.jpg

Glossary of terms

In this place, the following terms or expressions are used with the meaning indicated:

In patent document the word "uniflow" is often used with the meaning "open circuit where gas enters cylinder, expands, and is then released"

Engines
Definition statement

This place covers:

Compressed gas engines.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Arrangement or mounting of steam or gaseous-pressure propulsion units of the piston type in vehicles

B60K 3/02

Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, prime movers comprising combustion engines and a chargeable fluidic accumulator for storing fluid energy

B60K 6/12

{with fluid heating}
Special rules of classification

Illustrative example of subject matter classified in F01B 17/022

media68.jpg

{using separators}
Definition statement

This place covers:

Separators for separating liquid or oil from compressed gas for gas engines.

Steam engines
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Toys

A63H

Steam engine plants

F01K

Positive-displacement machines or engines of flexible-wall type
Definition statement

This place covers:

Positive-displacement machines or engines of flexible-wall type. E.g. where the piston is made of a diaphragm or bellows.

media69.jpg

with plate-like flexible members
Special rules of classification

Illustrative example of subject matter classified in F01B 19/02

media70.jpg

with tubular flexible members
Special rules of classification

Illustrative example of subject matter classified in F01B 19/04

media71.jpg

Combinations of two or more machines or engines (F01B 23/00 takes precedence)
Definition statement

This place covers:

Combinations of two or more machines or engines, e.g. a combined internal combustion engine and steam engine.

References
Limiting references

This place does not cover:

Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby

F01B 23/00

Informative references

Attention is drawn to the following places, which may be of interest for search:

Combinations of two or more positive-displacement pumps in pumping installations or systems specially adapted for elastic fluids

F04B 41/06

Combinations of two or more machines or pumps, each being of rotary-piston or oscillating-piston type; Pumping installations

F04C 11/00

Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids

F04C 23/00

Combinations of two or more non-positive-displacement pumps in pumping installations or systems

F04D 13/12

Combinations of two or more non-positive-displacement pumps in pumping installations or systems specially adapted for elastic fluids

F04D 25/16

Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution

F16H 39/00

Rotary fluid gearing of the hydrokinetic type

F16H 41/00

Other fluid gearing, e.g. with oscillating input or output

F16H 43/00

Combinations of fluid gearings for conveying rotary motion with couplings or clutches

F16H 45/00

Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Reciprocating-piston machines or engines without rotary main shaft, e.g. of free-piston type

F01B 11/00

Rotary fluid gearing using pumps and motors of the volumetric type, i.e. passing a predetermined volume of fluid per revolution

F16H 39/00

Rotary fluid gearing of the hydrokinetic type

F16H 41/00

Other fluid gearing, e.g. with oscillating input or output

F16H 43/00

Combinations of fluid gearings for conveying rotary motion with couplings or clutches

F16H 45/00

Regulating, controlling or safety means (controlling combustion engines F02D)
References
Limiting references

This place does not cover:

Controlling combustion engines

F02D

Informative references

Attention is drawn to the following places, which may be of interest for search:

Regulating or controlling in general

G05

Regulating or controlling by varying working-fluid admission or exhaust, e.g. by varying pressure or quantity
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Distributing or expansion valve gear

F01L

Arrangements or adaptations of working-fluid admission or discharge valves
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Valves in general

F16K

Starting of machines or engines (starting combustion engines F02N)
References
Limiting references

This place does not cover:

Starting combustion engines

F02N

Means for moving crank off dead-centre
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Turning-gear in general

F16H

Engines
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Refrigeration machines

F25B

Component parts, details or accessories not provided for in, or of interest apart from, other groups
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Machine or engine casings, other than those peculiar to steam engines

F16M

Means for equalising torque in reciprocating-piston machines or engines
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion

F16F 15/00

Cooling of steam engines; Heating; Heat insulation
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Cooling of fluid machines or engines in general

F01P

Heat insulation in general

F16L 59/00

Lubricating arrangements of steam engines
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Lubricating arrangements of fluid machines or engines in general

F01M

Arrangements of measuring or indicating devices
References
References out of a residual place

Examples of places in relation to which this place is residual:

Warning devices

F01B 25/26

Informative references

Attention is drawn to the following places, which may be of interest for search:

Measuring instruments or the like per se

G01

Silencers specially adapted for steam engines
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Arrangements of exhaust pipes or tubes on steam engines

F01B 31/30

Gas-flow silencers or exhaust silencers for machines or engines in general

F01N

Safety means against water hammer or against the penetration of water
References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Steam traps

F16T