Abstract:
The motor-operated valve for regulating a gas flow is the lift type with a modulating valve cut-off member ( 11 ), coupled to a valve spindle ( 10,10   a ) sliding linearly along a central gas flow conduit ( 5 ). A flame safety valve is open initially due to the pressure of the spindle ( 10   a ) and in case of the movement of the spindle being locked because of the change in the direction of rotation of the motor, safety cut-off means ( 5   a   , 21-24, 21′-22 ′) drawn by the spindle ( 10 ) are interposed between the valve inlet conduit ( 6 ) and the outlet conduits ( 7,8,20 ) to prevent gas escaping, while the modulating cut-off member ( 21,21 ′) is still not actuated.

Description:
The present invention relates to the regulation of the supply of fuel gas to a domestic heating appliance by means of a control valve driven by an electric motor, modulating the flow in response to the variations in temperature, the valve being of lift valve type, with an electromagnetic safety valve. 
   PRIOR ART 
   EP-0875720-A2 and equivalent U.S. Pat. No. 5,979,484 disclose a gas flow regulating valve actuated by a rotary motor in both directions, for supplying a heating appliance. The valve is adapted to supply one flow to a appliance main burner by way of a valve outlet conduit and a pilot flow to a appliance pilot burner by way of a valve pilot outlet conduit. Motor actuation is controlled by an ambient temperature sensor, moving the valve spindle linearly for the gradual opening of the main flow outlet conduit valve hole. The valve in the afore-mentioned publication further comprises a valve member coupled to the spindle, which, being actuated by a motor, moves in both directions by way of an axial flow conduit to control the flow of gas through the valve elements, and a safety valve magnetic unit pushed by the free end of the valve spindle. 
   DISCLOSURE OF THE INVENTION 
   The object of the invention is a valve for regulating the flow of gas to a domestic environment heating appliance, of the lift type actuated by a motor and with a central flow conduit in the valve body, which comprises a flame safety valve at the valve inlet and safety means for closing the central conduit to prevent gas escaping from the valve. 
   The valve spindle is moved linearly by the motor in both directions by changing the direction of rotation, in the first direction to actuate the flame safety valve for its resetting, and in the second opposing direction to regulate gas flow by means of a modulating valve. The safety valve is held open by a thermocouple heated by a pilot flame in the heater appliance. In the event of motor rotation getting locked, once the safety valve has opened, the valve spindle would continue exerting pressure on the flame safety valve and stopping it from closing if the pilot flame goes out. The control valve according to the invention has safety cut-off means to prevent the flow of gas to any of the valve outlet conduits, even though the electromagnetic flame safety valve is open, until the valve spindle has moved forward away from it. The valve spindle is a one-piece stem with its forward movement controlled by a step motor, a single valve cut-off member permits the supply of a pilot flow and a main flow modulated between a minimum and a maximum flow, and said means for the safety cut-off of the flow conduit between the gas inlet and outlet are coupled to the valve spindle and are of simple construction. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of an initial embodiment of a gas regulating valve with the “closed” position with the flame safety valve in the inlet actuated. 
       FIG. 2  is a sectional view of the embodiment of the valve of  FIG. 1  in the “open” condition for the passage of maximum flow. 
       FIG. 3  is a sectional view of a second embodiment of a gas regulating valve in the “closed” position, with the flame safety valve in the inlet actuated. 
       FIG. 4  is a sectional view of the regulating valve of  FIG. 3 , in the “open” position for the passage of “maximum flow”. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In reference to  FIGS. 1-4 , a first embodiment 1 ( FIGS. 1-2 ) and a second embodiment ( FIGS. 3-4 ) of a regulating valve according to the invention are described here, adapted for the supply of a pilot flow  2  to a pilot burner and of a main flow  3  to a main burner of a heating appliance, controlled by an ambient temperature sensor, not represented in the drawings. 
   Both regulating valve embodiments 1, 1′ comprise a valve body  4  with an axial flow conduit  5  traversing the body  4 , an inlet conduit  6  from an external gas source, an outlet conduit  7  for a pilot flow  2  and an outlet conduit  8  for a main flow  3 , all oriented transversely to the flow conduit  5 , and a valve spindle  10 . A step motor  9  is located on the body  4  and actuates the valve spindle  10 , and a magnetic safety assembly  14  is housed in the opposite end of the body  4  forming a flame safety valve  14 , 15 . The motor  9  moves the valve spindle  10  linearly for the gradual opening of a modulating valve  11 , 12  which regulates the passage of the main gas flow  3  to the outlet conduit  8  from a regulating chamber  18 . The main flow  3  is supplied in two states: a “minimum” flow  3  dependent on the adjustment of the bypass screw  19  and a modulated flow  3 , dependent on the travel  13  effected by the modulating valve cut-off member  11 . 
   Following the mode of operation of the regulating valve  1 , 1 ′, the valve spindle  10  is moved linearly by the motor  9  in both directions of the flow conduit  5 . At the start of the regulating valve  1 , 1 ′ operation , the spindle  10  moves in the opposite direction to the motor  9  and one end  10   a  of the valve spindle pushes the magnetic assembly  14  overcoming the resistance of its return spring (FIG.  1  and FIG.  3 ). Thus, the safety valve  14 ,  15  is open and the gas enters the axial conduit  5 . In the direction “e” ( FIG. 1 ) of forward movement of the spindle  10  towards the motor  9 , the cut-off member  11  gradually lifts off its seat  12 , overcoming the resistance of a return spring  17 . The cut-off member  11  is held in successive operating positions along the regulating chamber  18  formed downstream in series with the flow conduit  5 . In the cut-off member  11  regulating position shown in FIG.  2  and in  FIG. 4 , the outlet conduit  8  supplies a “maximum” flow. 
   When initially the modulating valve  11 , 12  is still closed by the pressure of the return spring  17 , a pilot flow  2  is supplied by the outlet conduit  7 , and a “minimum” main flow  3  is supplied via a communicating hole  20  fitted with said “bypass” screw  19 , which forms a bridge to the regulating chamber  18 , setting the gas access from the safety valve seat  15  to the main outlet conduit  8  in direct communication. The pilot outlet conduit  7  and said communicating hole  20  start transverse from the central conduit  5  each of them extending in a direction towards a side of the valve body  4  opposite to the other. 
   When the direction of motor  9  rotation changes, the spindle  10  retracts in direction “e” at the termination of a period of heating of the thermocouple which supplies the magnetic assembly  14 , whereby the safety valve  14 , 15  may close in the event of the pilot flame going out. When the motor  9  has to change direction of rotation for the retraction of the spindle  10 , motor failure may occur and the consequent locking of spindle  10  forward movement. In this case it is necessary to prevent gas escaping. The two regulating valve embodiments 1,1′ are provided with cut-off means  21 - 24 ,  21 ′- 22 ′ respectively, housed in an intermediate portion of the flow conduit  5 , between the pilot outlet conduit  7  and the direct communication hole  20  with the main outlet conduit  8 . 
   In reference to  FIGS. 1-2 , in an initial regulating valve embodiment 1 the flow conduit  5  cut-off means  21 - 24  comprise a lift valve  21 , 22  with a flat disc-shaped cut-off member  21  resting on a seat  22  coaxial with the spindle  10 , and located upstream of the modulating valve cut-off member  11 . The cut-off member  21  is drawn by a washer  23  attached to the spindle  10 , overcoming the force of a return spring  24 . 
   The safety cut-off member  21  is raised by the forward movement “e” of the spindle  10  up to two relative positions (not represented in the drawings) prior to that of modulating valve  11 , 12  opening. In a prior position of the spindle  10  the tip  10   a  of the spindle is separated from the magnetic assembly  14 , but the flow of gas to the outlet conduits  7  and  20  remains closed. In a subsequent intermediate position of the spindle  10 , the safety cut-off member  21  is separated from its seat  22  so as to supply pilot flow  2  and said “minimum” flow via the direct outlet conduit  20 , but the regulating cut-off member  11  still remains closed on its seat  12  owing to the fact that the compression coefficient “k” of the modulating valve spring is higher than that of the spring  24  of the safety cut-off valve  21 , 22 . As the forward movement of the spindle  10  continues, the modulating valve cut-off member  11  also effects a travel  13 , so that now the main flow  3  is also supplied via the outlet conduit  8 . In the embodiment represented in  FIG. 2  the cut-off member  11  of the modulating valve  13  has completed a maximum travel  13 , drawn by the safety cut-off member  21 , so as to supply a “maximum flow”. 
   In reference to  FIGS. 3-4 , in a second embodiment of the regulating valve, the flow conduit  5  sealing means  5   a ,  21 ′, 22 ′ comprise a flat disc  21 ′ attached to spindle  10  encircled by a sealing O-ring  22 , which slides snugly in an intermediate portion  5   a  of the axial flow conduit  5 , adjacent downstream to the safety valve  14 , 15 . In this embodiment 1′ represented in  FIGS. 3-4 , the flow conduit  5  downstream of the regulating chamber  18  is made up of two portions  5   a , 5   b  of conduit, both of smaller diameter than the chamber. The pilot flow outlet conduit  7  and the direct outlet conduit  20  leave transversely from the portion  5   b  of conduit adjacent to the chamber. The sealing disc  21 ′, 22 ′ slides in the portion  5   a  of conduit located upstream, and it is of smaller diameter than the portion  5   b  of conduit adjacent to the regulating chamber  18 . In this way, in its forward movement “e”, once the safety valve has opened  14 ,  15 , the spindle  10  will effect a prior movement during which the safety sealing disc  21 ′, 22 ′ slides along the portion  5   a  of conduit to seal it and prevent gas escaping (FIG.  3 ), and in this way it is ensured that the spindle  10  is not locked when the motor  9  changes its direction of rotation. When the disc  21 ′, 22 ′ is positioned in the portion  5   b  of larger diameter conduit, the passage is open to the pilot outlet conduit  7  and to the “minimum flow” communication hole  20 . In the position of spindle  10  represented in  FIG. 4  the sealing disc  21 ′, 22 ′ is exerting pressure on the modulating valve cut-off member  11  and raising it from its seat  12 , thereby supplying a maximum flow  3  along the outlet conduit  8 .