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
  • F15B20/00—Safety arrangements for fluid actuator systems; Applications of safety devices in fluid actuator systems; Emergency measures for fluid actuator systems
  • F15B20/001—Double valve requiring the use of both hands simultaneously
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16P—SAFETY DEVICES IN GENERAL; SAFETY DEVICES FOR PRESSES
  • F16P3/00—Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body
  • F16P3/18—Control arrangements requiring the use of both hands
  • F16P3/22—Control arrangements requiring the use of both hands for hydraulic or pneumatic control systems

Definitions

• the present invention relates to a control system which when actuated by two essentially simultaneous control signals enables a flow of compressed air to be delivered to a consumer, such as a working cylinder or like device, of the kind defined in the preamble of Claim 1.
• the control signals can be established by an operator actuating a trigger signal with each of his two hands. It is necessary to construct the control system so that the control signals must be applied within a predetermined time period of each other, for instance within an interim time period of 0.5 seconds, in order to drive the working cylinder.
• control system must be able to prevent delivery of the flow of pressurised medium to the consumer if any of the system components malfunctions, or when the respective control signals are applied with a time spacing that is greater than the chosen time interval.
• EP-A1-0 780 743 has certain weaknesses, which are manifested in exotic types of erroneous handling of the control system and malfunctioning in said system. In the worst of cases, these weaknesses can result in unintentional activation of the working cylinder or the like.
• the object of the present invention is to provide a control system which is constructed so as to reduce the risk of the occurrence of malfunctions in the system.
• a further object is to provide a control system that fulfils the requirements laid down in EN 954-1:1996, category 4.
• control arrangement/control system includes two mutually identical control units each comprising an operating device, a power valve and an accumulator.
• the working cylinder is supplied with compressed air from the mains through a conduit that includes the two power valves in series .
• the power valves are normal spring biased towards a first position in which they block the conduit.
• the power valves of respective control units can be set to their second position in which compressed air is delivered to the working cylinder.
• the air supply to the working cylinder is stopped immediately one of the operating devices is released, wherewith the working cylinder is normally caused to return to its initial state.
• Each operating device includes two driven operating valves which are moved in parallel to their actuated second position with the aid of a bridge which is actuated by a control signal, for instance by an operator depressing the bridge with one hand.
• a control signal for instance by an operator depressing the bridge with one hand.
• the outlet of said branch through the second operating valve of the second control unit forms an air throttle or constriction which defines the aforesaid chosen time interim period (e.g. an interim of 0.5 seconds) together with the accumulator volume and the pressure of the compressed air source.
• the second operating valve of the second control unit fails to close within 0.5 seconds of the actuation of the operating device of the first control unit, the volume of air in the accumulator will be insufficient to switch the power valve of the first control unit to its second position (and is then held in this second position).
• the enclosed air volume is able to hold the power valve in said switched position during the working cycle concerned. This obviates the need of other separate means to hold the power valve in its second position subsequent to said valve having switched to said position.
• each power valve may conveniently be designed so that the outlet of the through- passage of the power valve from the compressed air source to the accumulator supply conduit will cause compressed air to leak to atmosphere, for instance return the air from this conduit through an adjacent port in the power valve to atmosphere, already in response to a slight deviation in the movement of the power valve from its first position.
• This can be readily achieved in a 5/2-valve of standard design, by widening said outlet port.
• this leakage flow of compressed air taken from the net back through the power valve and out into the surroundings can be achieved by displacing the power valve through a distance of 1.5 mm when the total length of stroke of the valve is 9 mm between said two end-positions.
• the accumulator replenishing flow can be made smaller than the leakage flow that is able to switch the power valve.
• This flow limiting means may, for instance, comprise a restriction in respective accumulator charging branch conduits.
• the minus side of the working cylinder is subjected to pressure from the net through each of the power valves, which are then connected in parallel in their first positions.
• the plus side of the working cylinder is evacuated through one of the power valves, regardless of whether said valve is in its first end-position or in its second end-position.
• Compressed air is delivered to the minus side of the working cylinder from the net either via the first power valve (in its second position) and one supply conduit, or via the second power valve (in its second position) and the accumulator charging conduit connected to this latter supply conduit.
• Fig. 1 illustrates schematically a valve layout for a pneumatic two-hand control system according to the invention.
• Fig. 2 illustrates a first modification of the return of the working cylinder to its first end-position.
• Fig. 3 illustrates a second modification of the return of the working cylinder to its first end-position.
• a pneumatic two-hand control system or arrangement includes two generally identical control units 1, 1'. Since the two units 1, 1' are mutually identical, it will suffice to describe only one of these units.
• the unit 1 includes an operating device 20 that has two parallel operating valves 21, 22.
• each of these valves is provided with an associated pilot valve 11, 12 which form a pilot unit 10 and is each coupled to an operating bridge 13 so that both valves can be switched to an active state by an operator pressing down on the bridge 13 with one hand, for instance. If power amplification is unnecessary, the unit 1 can be omitted and the bridge 13 positioned so as to bridge the operating valves 21, 22.
• An accumulator 30 is arranged to coact with the operating device 20 so as to be emptied via the one operating valve 21 when said valve is switched, wherewith the accumulator is emptied of air through the conduit 81 and its branch 82 and therewith cause the power valve 40 to be displaced to its second position.
• the power valve 40 is biased to its first end-position by means of a spring 41.
• the plus side of a working cylinder 50 is connected to a compressed air source
• conduit 90 that includes the two power valves 40
• each of the power valves 40, 40' will function to supply compressed air from the net to the minus side of the cylinder 50, wherewith the plus side of the cylinders is evacuated to atmosphere via one, 40, of the power valves .
• the conduit branch 83 extends to the surroundings through the second operating valve 22' of the control unit 1', although this passageway through the valve 22' (in its first position) has relatively small cross- sectional dimensions and has a throttling function such that the accumulator 30 is able to hold the power valve 40 switched in its second position over at least said selected time period.
• the conduit 83 is closed immediately the operating device 20' is switched to its second position, thereby keeping the volume of air in the accumulator enclosed therein and enabling the power valve 40 to be kept in its second position.
• the accumulator 30' is emptied to the power valve 40' therewith switching said valve.
• the power valves 40, 40' are comprised of conventional 5/2-valves that have been modified with respect to the port 4 , which has been widened to provide a leakage facility from the port 4 to the port 1 and thus to atmosphere already when the valve 40, 40' has been displaced through only a slight distance from its first position.
• the accumulators 30, 30' are each emptied via their respective operating devices 20, 20' in their first position through the conduit 73, 72 and via the malfunctioning/leaking power valve 40' and its associated conduit branch 71'.
• a "puff" of compressed air through the branch conduit 71 would be able to float up through the supply conduit 72 to the accumulators, although the valves 75, 75' in the conduit sections 73 will ensure that the accumulators 30, 30' cannot be charged.
• the accumulators are therefore evacuated relatively quickly through the conduit 71'.
• the power valves and the operating valves of the illustrated embodiment may be conventional 5/2-path valves, which enables the two-hand control system or arrangement to be constructed with standard components.
• the pilot control arrangement 10 is of conventional design and is provided to enable an operator to effect switching of the two operating valves 21, 22 by exerting a small force on the bridge 13, as will be understood by those skilled in this art.
• operating valves 21, 22 may be physically built together with the pilot valves 11, 12 or rather together with parts of a larger valve unit, if so desired.
• the working cylinder 50 may include conventional flow regulating valves and safety valves, as shown in the drawing.
• the port 1 of one power valve 40' connects with an outlet conduit 94 which opens into atmosphere
• the conduit 90 to the plus side of the working cylinder 50 passes between the ports 2 and 1 of the power valve 40 when said power valve is in its first position, wherewith a conduit 92 connects from the port 1 of the valve 40 to the outlet conduit 94 between the port 1 and the valve 40' and the outlet of the conduit 94.
• the conduit 90 leading to the plus side of the cylinder 50 is also evacuated through the valve 40 when said valve is in its second position, and from there through a conduit 93 and to atmosphere through the valve 40' with said valve in its first position, and then out through a conduit 94.
• compressed air is delivered to the minus side of the cylinder 50, i.e. the conduit 91, through each of the valves 40, 40' with said valves in their first position.
• the cylinder 50 it is necessary for the cylinder 50 to return or having had returned to its withdrawn position before the accumulator 30, 30' can be filled.
• the inventive control system is a duplicate or duplicated two-channel pneumatic control system for controlling the flow of fluid from a fluid pressure source to a consumer, such as a working cylinder or the like. If the air leaking from the valves is greater than the volume of air that can pass through the constriction 73, 73', the pressure in the accumulator will decrease so as to prevent the power valve from being switched in a later manoeuvre. Thus, in order for the accumulators to be filled with sufficient energy to switch or reset the power valve, it is necessary for all valves to be in their first position and that no substantial leakage occurs.
• Figs. 2 and 3 illustrate alternative means for restoring the working cylinder 50 to its first deactivated position.
• Fig. 1 shows the minus chamber of the cylinder 50 coupled with a conduit 51 to the conduit 71 for evacuation through the valve 40 in its second position.
• the minus chamber of the cylinder 50 is no longer connected to any part of the pneumatic two-hand control arrangement, but stands open to the surroundings, wherewith the piston of the cylinder 50 is biased towards the deactivated end-position of the cylinder by a mechanical compression spring.
• Fig. 3 shows a pneumatic variant of the return spring shown in Fig. 2.
• the minus chamber of the cylinder 50 is coupled to the net 60 via a conduit 95 which includes a valve 96 that closes the conduit 95 when the pressure in the minus chamber equals the net pressure.
• An accumulator VI6 is coupled to the conduit 95 to enable the piston of the working cylinder 50 to be returned quickly, by discharging the contents of the accumulator.
• the accumulator V16 includes an overpressure valve V17 which relieves the pressure when the working cylinder 50 is manoeuvred to its activated second end-position.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Fluid-Pressure Circuits (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)

Applications Claiming Priority (3)

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• 1999
  • 1999-05-07 SE SE9901670A patent/SE9901670L/ not_active IP Right Cessation
  • 1999-12-16 WO PCT/SE1999/002387 patent/WO2000068610A1/en not_active Ceased
  • 1999-12-16 EP EP99964887A patent/EP1177400A1/de not_active Withdrawn
  • 1999-12-16 AU AU30918/00A patent/AU3091800A/en not_active Abandoned

Non-Patent Citations (1)

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