Premixing apparatus

Abstract

A premixing apparatus has: a fan; an air tube; and a gas tube inside the air tube; provided that a direction toward an air flow upstream side inside the air tube is defined as an X+ direction, an air adjusting valve facing an air inlet port positioned at an end, in the X+ direction, of the air tube; a gas adjusting valve facing a gas outlet port positioned at one end of the gas tube; and a common actuator driving the air adjusting valve and the gas adjusting valve. At an end, in the X direction, of the gas tube, is disposed a valve seat having formed therein the gas outlet port, and a gas adjusting valve inside the gas tube. A valve stem penetrates through an end wall, in the X+ direction, of the gas tube. The gas adjusting valve is driven by the actuator through the valve stem.

Claims

1. A premixing apparatus for mixing air with fuel gas, thereby supplying a burner with air-fuel mixture, the premixing apparatus comprising: a fan for supplying air; an air tube which is disposed on an upstream side or on a downstream side of the fan so that air flows therethrough, wherein a longitudinal direction of the air tube is defined as an X-axis direction; in the X-axis direction, the direction looking toward an upstream side of air flow is defined as an X-axis plus direction; and the direction looking toward a downstream side of the air flow is defined as an X-axis minus direction; a gas tube which is connected to a downstream end of a gas supply passage for supplying the fuel gas and which is disposed inside the air tube; an air adjusting valve lying opposite to an air inlet port which is positioned at an end part, in the X-axis plus direction, of the air tube, in a manner to be linearly movable back and forth in the X-axis direction to thereby vary an opening degree of the air inlet port; a gas adjusting valve lying opposite to a gas outlet port which is positioned at a first end part, in the X-axis minus direction, of the gas tube, in a manner to be linearly movable back and forth in the X-axis direction to thereby vary an opening degree of the gas outlet port; and a common actuator which drives in the X-axis direction both the air adjusting valve and the gas adjusting valve wherein the gas tube has an end wall part at a second end part thereof, opposite from the first end part in the X-axis plus direction, wherein at the first end part, in the X-axis minus direction, of the gas tube, there is disposed a valve seat for the gas adjusting valve, the valve seat having formed therein the gas outlet port, the gas adjusting valve being disposed inside the gas tube, and wherein a valve stem is disposed so as to be extended from the gas adjusting valve to penetrate through the end wall part, in the X-axis plus direction toward the actuator, such that the gas adjusting valve is driven via the valve stem by the actuator in the X-axis direction.

2. The premixing apparatus according to claim 1, the common actuator connects with direct contact both to the air adjusting valve and the gas adjusting valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view to show a premixing apparatus according to an embodiment of this invention.

(2) FIG. 2 is a sectional side view of the premixing apparatus according to the embodiment of this invention.

(3) FIG. 3 is a sectional view taken along the line III-III in FIG. 2.

MODES FOR CARRYING OUT THE INVENTION

(4) With reference to FIG. 1, reference numeral 1 denotes a premixing apparatus according to an embodiment of this invention, in which fuel gas is mixed with air to supply a burner (not illustrated) with air-fuel mixture. This premixing apparatus 1 is provided, as shown in FIGS. 2 and 3, with a fan 2 which supplies air, and an air tube 3 which is disposed on an upstream side of the fan 2 and through which the air passes. By the way, the fan 2 is constituted by a centrifugal type of fan in which an impeller 25 to be driven for rotation by a motor 24 is housed in a fan casing 23 which has a suction port 21 and an outlet port 22.

(5) Suppose: that a longitudinal direction of the air tube 3 is defined as an X-axis direction; that, in the X-axis direction, the direction looking toward an upstream side of air flow is defined as an X-axis plus direction; and that the direction looking toward a downstream side of the air flow is defined as an X-axis minus direction. Then the premixing apparatus 1 is provided with a gas tube 5: which is connected to a downstream end of a gas supply passage 4 which supplies the fuel gas; which is disposed inside the air tube 3; and which is of a bottomed shape with an end part thereof in the X-axis plus direction being closed. Further, there is disposed an air supply case 6 which encloses the air tube 3 with a clearance therebetween. It is thus so arranged that the air flows from an air supply duct 61 disposed at one end of, and in communication with, the air supply case 6 to the air tube 3 through the internal space of the air supply case 6.

(6) The premixing apparatus 1 is further provided with: an air adjusting valve 7 lying opposite to an air inlet port 31 which is positioned at an end part, in the X-axis plus direction, of the air tube 3, in a manner to be movable back and forth in the X-axis direction to thereby vary an opening degree of the air inlet port 31; a gas adjusting valve 8 lying opposite to a gas outlet port 51 which is positioned at an end part, in the X-axis minus direction, of the gas tube 5, in a manner to be movable back and forth in the X-axis direction to thereby vary the opening degree of the gas outlet port 51; and a common actuator 9 which drives in the X-axis direction both the air adjusting valve 7 and the gas adjusting valve 8.

(7) In this embodiment, by providing the gas tube 5, at the end part in the X-axis minus direction, with a valve seat 52 for the gas adjusting valve 8, and by forming the gas outlet port 51 in this valve seat 52, the gas outlet port 51 is positioned at the end part, in the X-axis minus direction, of the gas tube 5 and also the gas adjusting valve 8 is disposed inside the gas tube 5. There is further disposed a valve stem 81 which extends from the gas adjusting valve 8 through an end wall part 53, in the X-axis plus direction, of the gas tube 5 to the actuator 9 side.

(8) The actuator 9 is constituted by a motor 91, and a feed screw mechanism 92 on an output side. The feed screw mechanism 92 is constituted by: a nut 92a which is driven for rotation by a motor 91; a rod 92b which has a male-thread part to be brought into screwed engagement with the nut 92a; and a guide sleeve 92c which supports the rod 92b inserted therethrough in a manner to be movable in the X-axis direction while preventing the rod 92b from rotating. As a result of operation of the motor 91, the rod 92b moves back and forth in the X-axis direction. By fixing the air adjusting valve 7 to an end part, in the X-axis minus direction, of the rod 92b, the air adjusting valve 7 is arranged to move back and forth integrally with the rod 92b. In addition, there is disposed a spring 82 which pushes the gas adjusting valve 8 in the X-axis plus direction and, by means of the pushing force of this spring 82, the valve stem 81 is brought into contact with an end surface, in the X-axis minus direction, of the rod 92b so that the gas adjusting valve 8 can be moved back and forth in the X-axis direction integrally with the rod 92b.

(9) Here, in a region in which the number of fan revolution according to the required combustion amount exceeds a lower-limit number of revolution at which the proportional characteristics of the amount of air blowing can be maintained, the number of fan revolution is controlled to supply the amounts of air and fuel gas corresponding to the required combustion amount. On the other hand, in a region in which the required combustion amount falls below the predetermined value corresponding to the lower-limit value of the number of fan revolution, in a state in which the number of fan revolution is maintained at the lower-limit number of revolution, the opening degrees of the air inlet port 31 and of the gas outlet port 51 are adjusted by the air adjusting valve 7 and the gas adjusting valve 8, respectively. In this manner, the air and the fuel gas according to the required combustion amount below the predetermined value are supplied.

(10) Then, in this embodiment, since the gas outlet port 51 is positioned at the end part, in the X-axis minus direction, of the gas tube 5, the effect of the dynamic pressure of the air that flows in from the air inlet port 31 positioned at the end part, in the X-axis plus direction, of the air tube 3, will not be extended to the gas outlet port 51. The pressure that acts on the gas outlet port 51 will therefore become equal to the suction negative pressure corresponding to the number of fan revolution. Accordingly, in a region in which the required combustion amount exceeds the above-mentioned predetermined value, by controlling the number of fan revolution according to the required combustion amount, the air and the fuel gas according to the required combustion amount can surely be supplied to the burner.

(11) Further, since the air adjusting valve 7 and the gas adjusting valve 8 are separate entities in this embodiment, at the time of converting the kind of gases to be used, it is sufficient to replace only the gas adjusting valve 8. The workability at the time of converting the kind of gases will thus be improved and, also, the number of replacement parts may economically be reduced.

(12) Descriptions have so far been made of embodiments of this invention with reference to the drawings. However, this invention shall not be limited to the above. For example, in place of the zero governor 41, a proportional valve may be interposed in the gas supply passage 4. In this case, it is also possible to dispose the air tube 3 on the downstream side of the fan 2. Further, in the above-mentioned embodiment, the actuator 9 is constituted by the motor 91 and the feed screw mechanism 92, but other actuators such as of electromagnetic solenoid type and the like may be used.

(13) TABLE-US-00001 Explanation of Reference Characters 1 premixing apparatus 2 fan 21 suction port 3 air tube 31 air inlet port 4 gas supply passage 5 gas tube 51 gas outlet port 52 valve seat 53 end wall part 7 air adjusting valve 8 gas adjusting valve 9 actuator