WO1979000573A1 - Controlling fluid actuated piston and cylinder devices - Google Patents
Controlling fluid actuated piston and cylinder devices Download PDFInfo
- Publication number
- WO1979000573A1 WO1979000573A1 PCT/GB1979/000018 GB7900018W WO7900573A1 WO 1979000573 A1 WO1979000573 A1 WO 1979000573A1 GB 7900018 W GB7900018 W GB 7900018W WO 7900573 A1 WO7900573 A1 WO 7900573A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- piston
- cylinder
- electrical
- cylinder device
- piston rod
- Prior art date
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/20—Other details, e.g. assembly with regulating devices
- F15B15/28—Means for indicating the position, e.g. end of stroke
- F15B15/2807—Position switches, i.e. means for sensing of discrete positions only, e.g. limit switches
Definitions
- the invention relates to fluid actuated piston and cylinder devices. More particularly, but not exclusively, the invention relates to the control of compressed air actuat.ed piston and cylinder devices.
- a fluid actuable piston and cylinder device comprising a piston and piston rod which is electrically insulated from the cylinder while the piston is spaced from the ends of the cylinder, and which is electrically connected to at least a portion of the cylinder when the piston is in an end position in the cylinder, and electrical connections associated with the piston and with the said portion of the cylinder enabling an electrical voltage to be applied across the piston and cylinder.
- the cylinder is electrically connected to the associated machine frame which is maintained at a known (e.g. earth) potential while the piston is connected to a voltage source.
- a known (e.g. earth) potential for this latter purpose an electrical contact may be provided on the cylinder body, but insulated therefrom, for sliding contact with the piston rod.
- the piston may be connected to the voltage source via a flexible (preferably insulated) lead connected to the piston rod at its end remote from the piston.
- a flexible lead preferably insulated
- the nose bearing which supports the piston rod is electrically connected to the cylinder. It is necessary for the purpose of this invention that this nose bearing is insulated from the cylinder body e.g. by being mounted in a plastics bush. It will usually be necessary in addition to insulate the piston rod from the part of the machine to which it is connected and further it may be desirable to enclose the piston rod, e.g. in a flexible gaiter, to avoid unintentional earthing of the piston rod.
- Fig. 1 is a longitudinal section through a piston and cylinder device
- Fig. la is a scrap view of part of a piston and cylinder device.
- a pneumatic piston and cylinder device comprises a cylinder 1 provided with end caps 12 and 13 respectively and in which a piston 2 is slidingly mounted.
- the piston is connected to a piston rod 3 which extends outside the cylinder and which is sealed to the cylinder by means of a plastics bush 4 in the end cap 13.
- the piston 2 and rod 3 are electrically conductive but are insulated from the cylinder 1 and end caps 12 and 13 by the bush 4 and by piston seals 7.
- the cylinder 1 and end caps 12 and 13 are electrically conductive.
- a flexible wire 9 which is insulated from the cylinder and end caps is connected to the piston rod so that when the piston is in a limiting position at either end of the cylinder 1 an electrical circuit between the cylinder and the wire 9 is completed.
- the part of the piston rod protruding from the cylinder is covered by an insulating gaiter 5 to prevent unwanted earthing of the piston rod and the free end of the piston rod is connected to a machine part to be actuated by the piston and cylinder device by means of an electrically insulating coupling 6 e.g. of plastics.
- the end cap 12 of the cylinder is provided with an adjustable stroke limiting device in the form of a screw threaded bolt the bolt being electrically conductive.
- FIG. la of the drawings there is shown a modified piston and cylinder device generally similar to that described with reference to Figure 1 except that the flexible electrically conductive insulated wire 9 has been replaced by an electrical contact which makes sliding engagement with the piston rod and which comprises an electrically conductive spherical member 10 which is resiliently urged into contact with the piston rod 3 by means of a spring 11 which is preferably mounted in the end cap 13 but electrically insulated therefrom the spherical member 10 being electrically connected to an electrical pickup 9 by means of which the circuit can be completed.
- fluid actuated piston and cylinder devices may be controlled by an electrical or pneumatic programmer the steps of which are initiated by signals from the said devices which arise whenever such said devices move from one end position to the opposite end position, it being unnecessary for the programmer to 'know' which of the two end positions has been reached, but merely that a change of position has taken place.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Actuator (AREA)
Abstract
A fluid actuably piston and cylinder device arranged to act as an electrical switch so that the device can be controlled or monitored comprising a piston (2) and piston rod (3) which is electrically insulated from the cylinder (1) while the piston is spaced from the ends of the cylinder and which is electrically connected to at least a portion of the cylinder when the piston is at an end position in the cylinder, the electrical connections associated with the piston and with the said portion of the cylinder enabling an electrical voltage to be applied across the piston and cylinder.
Description
CONTROLLING FLUID ACTUATED PISTON AND CYLINDER DEVICES
TECHNICAL FIELD
The invention relates to fluid actuated piston and cylinder devices. More particularly, but not exclusively, the invention relates to the control of compressed air actuat.ed piston and cylinder devices.
BACKGROUND ART
It is known to control such devices pneumatically by means of control valves. mounted at each end of the cylinder. Such an arrangement doubles or trebles the number of fluid lines associated with the device and an automatic machine employing several such devices therefore requires a large and unwealdy number of such lines.
More importantly devising the circuitry necessary for correct sequential control of the various operations of the piston and cylinder devices of the automatic machine, using fluid actuated switches operating in "cascade", involves many hours of skilled labour. This problem is particularly acute where "one-off" automatic machines are involved since for each different machine a unique circuit will need to be devised.
This problem can be mitigated by controlling all of the piston and cylinder devices of the machine by means of any one of a number of known multi-channel, electrical or pneumatic programmers. Such an arrangement requires however the use of piston and cylinder devices provided with means for sensing when the piston is in an end position in the cylinder. It is known to provide piston and
cylinder devices with micro-switches or micro-valves for this purpose but such devices are too expensive for many applications.
DISCLOSURE OF INVENTION We have now discovered that it is possible to make a fluid actuated piston and cylinder device operate as an electrical switch without the necessity of separate microswitches.
According to the invention there is provided a fluid actuable piston and cylinder device comprising a piston and piston rod which is electrically insulated from the cylinder while the piston is spaced from the ends of the cylinder, and which is electrically connected to at least a portion of the cylinder when the piston is in an end position in the cylinder, and electrical connections associated with the piston and with the said portion of the cylinder enabling an electrical voltage to be applied across the piston and cylinder.
Preferably the cylinder is electrically connected to the associated machine frame which is maintained at a known (e.g. earth) potential while the piston is connected to a voltage source. For this latter purpose an electrical contact may be provided on the cylinder body, but insulated therefrom, for sliding contact with the piston rod. Alternatively the piston may be connected to the voltage source via a flexible (preferably insulated) lead connected to the piston rod at its end remote from the piston. Such arrangements will of course require the piston and rod to be electrically interconnected, but this is usually the case in practice. One convenient way of electrically insulating the piston and rod from the cylinder is by employing conventional plastics seals.
However, in most cylinder devices the nose bearing which supports the piston rod is electrically connected to the cylinder. It is necessary for the purpose of this
invention that this nose bearing is insulated from the cylinder body e.g. by being mounted in a plastics bush. It will usually be necessary in addition to insulate the piston rod from the part of the machine to which it is connected and further it may be desirable to enclose the piston rod, e.g. in a flexible gaiter, to avoid unintentional earthing of the piston rod.
BRIEF DESCRIPTION OF DRAWINGS
Typical embodiments of piston and cylinder device are illustrated by way of example in the accompanying drawings in which:-
Fig. 1 is a longitudinal section through a piston and cylinder device, and
Fig. la is a scrap view of part of a piston and cylinder device.
BEST MODE OF CARRYING OUT THE INVENTION
In Figure 1 of the drawings a pneumatic piston and cylinder device comprises a cylinder 1 provided with end caps 12 and 13 respectively and in which a piston 2 is slidingly mounted. The piston is connected to a piston rod 3 which extends outside the cylinder and which is sealed to the cylinder by means of a plastics bush 4 in the end cap 13. The piston 2 and rod 3 are electrically conductive but are insulated from the cylinder 1 and end caps 12 and 13 by the bush 4 and by piston seals 7. The cylinder 1 and end caps 12 and 13 are electrically conductive. A flexible wire 9 which is insulated from the cylinder and end caps is connected to the piston rod so that when the piston is in a limiting position at either end of the cylinder 1 an electrical circuit between the cylinder and the wire 9 is completed. The part of the piston rod protruding from the cylinder is covered by an insulating gaiter 5 to prevent unwanted earthing of the piston rod and the free end of the piston rod is connected to a machine part to be actuated by the piston and cylinder
device by means of an electrically insulating coupling 6 e.g. of plastics. The end cap 12 of the cylinder is provided with an adjustable stroke limiting device in the form of a screw threaded bolt the bolt being electrically conductive.
In Figure la of the drawings there is shown a modified piston and cylinder device generally similar to that described with reference to Figure 1 except that the flexible electrically conductive insulated wire 9 has been replaced by an electrical contact which makes sliding engagement with the piston rod and which comprises an electrically conductive spherical member 10 which is resiliently urged into contact with the piston rod 3 by means of a spring 11 which is preferably mounted in the end cap 13 but electrically insulated therefrom the spherical member 10 being electrically connected to an electrical pickup 9 by means of which the circuit can be completed.
Where it is desired to sense separately when the piston is at one or other end of the cylinder this can be achieved by insulating one end of the cylinder from the other, e.g. by providing a plastics seal between the body of the cylinder and one end cap thereof, both parts of the cylinder having electrical connection to the control circui t. It may be advantageous in this case to maintain the piston at earth potential and to apply the voltage to the cylinder and end cap.
INDUSTRIAL APPLICABILITY
By means of the invention, fluid actuated piston and cylinder devices may be controlled by an electrical or pneumatic programmer the steps of which are initiated by signals from the said devices which arise whenever such said devices move from one end position to the opposite end position, it being unnecessary for the programmer to 'know' which of the two end positions has been reached,
but merely that a change of position has taken place.
The movement of the piston from one end of the cylinder to the other breaks a circuit and then re-makes it. It is this break and remake of a switch (i.e. the piston/cylinder) that can be used directly or indirectly to operate a stepping relay.
Claims
1. A fluid actuable piston and cylinder device comprising a piston and piston rod which is electrically insulated from the cylinder while the piston is spaced from the ends of the cylinder, and which is electrically connected to at least a portion of the cylinder when the piston is in an end position in the cylinder, and electrical connections associated with the piston and with the said portion of the cylinder enabling an electrical voltage to be applied across the piston and cylinder.
2. A fluid actuable piston and cylinder device according to claim 1, comprising an electrical contact on the cylinder body, but electrically insulated therefrom, for sliding contact with the piston rod.
3. A fluid actuable piston and cylinder device according to claim 1, wherein the piston is connected to the voltage source via a flexible lead connected to the piston rod at its end remote from the piston.
4. A fluid actuable piston and cylinder device according to any preceding claim, wherein one end of the cylinder is electrically insulated from the other, both parts of the cylinder having electrical connections.
5. A fluid actuable piston and cylinder device according to any preceding claim, wherein one end of the cylinder carries an electrically conductive adjustable stop member arranged to contact the piston to limit movement thereof in one direction.
6. A fluid actuable piston and cylinder device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB3904/78 | 1978-01-31 | ||
GB390478 | 1978-01-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1979000573A1 true WO1979000573A1 (en) | 1979-08-23 |
Family
ID=9767066
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1979/000018 WO1979000573A1 (en) | 1978-01-31 | 1979-01-31 | Controlling fluid actuated piston and cylinder devices |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0010096A1 (en) |
WO (1) | WO1979000573A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4412465A (en) * | 1981-12-07 | 1983-11-01 | Lamb Technicon Corp. | Tool compensator |
US4934906A (en) * | 1988-01-29 | 1990-06-19 | Williams James F | High pressure diaphragm pump |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE801790C (en) * | 1948-11-09 | 1951-01-22 | Casp Arn Winkhaus Fa | Device for teaching the length of tenons on workpieces |
FR1053810A (en) * | 1950-01-10 | 1954-02-05 | Bendix Aviat Corp | Improvements to electro-mechanical devices for controlling the stroke of the piston of a cylinder actuated by pressurized fluid |
US3096497A (en) * | 1961-03-06 | 1963-07-02 | Ling Temco Vought Inc | Combination hydraulic actuator and potentiometer |
FR1410863A (en) * | 1964-10-09 | 1965-09-10 | Maxam Power Ltd | Sheep improvements and similar devices |
DE2245627A1 (en) * | 1972-09-16 | 1974-03-21 | Bosch Gmbh Robert | WORK CYLINDERS, IN PARTICULAR FOR ELECTROCHEMICAL MACHINING MACHINERY |
DE2515019A1 (en) * | 1974-04-10 | 1975-10-23 | Fuji Plastic Co | CONTROL DEVICE |
-
1979
- 1979-01-31 WO PCT/GB1979/000018 patent/WO1979000573A1/en unknown
- 1979-07-30 EP EP19790900140 patent/EP0010096A1/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE801790C (en) * | 1948-11-09 | 1951-01-22 | Casp Arn Winkhaus Fa | Device for teaching the length of tenons on workpieces |
FR1053810A (en) * | 1950-01-10 | 1954-02-05 | Bendix Aviat Corp | Improvements to electro-mechanical devices for controlling the stroke of the piston of a cylinder actuated by pressurized fluid |
US3096497A (en) * | 1961-03-06 | 1963-07-02 | Ling Temco Vought Inc | Combination hydraulic actuator and potentiometer |
FR1410863A (en) * | 1964-10-09 | 1965-09-10 | Maxam Power Ltd | Sheep improvements and similar devices |
DE2245627A1 (en) * | 1972-09-16 | 1974-03-21 | Bosch Gmbh Robert | WORK CYLINDERS, IN PARTICULAR FOR ELECTROCHEMICAL MACHINING MACHINERY |
DE2515019A1 (en) * | 1974-04-10 | 1975-10-23 | Fuji Plastic Co | CONTROL DEVICE |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4412465A (en) * | 1981-12-07 | 1983-11-01 | Lamb Technicon Corp. | Tool compensator |
US4934906A (en) * | 1988-01-29 | 1990-06-19 | Williams James F | High pressure diaphragm pump |
Also Published As
Publication number | Publication date |
---|---|
EP0010096A1 (en) | 1980-04-30 |
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Designated state(s): FR |