JPS62194104A - Gas burner and head-section assembly thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to gas burners, such as vAi! ! The present invention relates to gas burners of the type used in gas stopes or gas ranges. Although the present invention will be explained below using a gas stove for cooking as a representative example, the gas burner of the present invention can also be used for other purposes, such as various household and

[Can be used in industrial heating or heating gas stoves, etc.] The present invention particularly relates to the structure of the head portion of the gas burner, that is, the portion that generates a flame by combustion of a gas-air mixture. In the following description and claims, the head portion of the gas burner is sometimes simply referred to as the "head". [Prior Art] The head of a conventional gas burner has a saucer-shaped base and a single-piece circular plate resting on the base, and a gas chamber is formed between the plate and the base. and further includes means for supplying a pressurized gas-air mixture into the gas chamber. The upper plate has orifices or IJ nozzles (hereinafter referred to as nozzles) arranged at equal intervals in the circumferential direction on the periphery of the upper plate, and the nozzles jet out a gas-air mixture for combustion. It is for the purpose of Based on the above arrangement, a separate cone-shaped flame of ma is formed for each nozzle and occurs in an annular shape surrounding the head. [Problems to be Solved by the Invention] The conventional arrangement described above has several drawbacks. That is, when a pressurized gas-air mixture is ejected through the nozzles, the jet of gas ejected from each nozzle creates an area of reduced pressure around it, which causes surrounding air to be sucked into the mixture. As a result, a gas-air mixture containing more air than the mixture supplied to the gas chamber is supplied to the flame for combustion. This causes the gas-air mixture during combustion to contain an excessively high proportion of air, resulting in inefficient combustion and a relatively cool flame. For proper operation, the gas discharged for combustion -
The air mixture must be preheated, i.e. pre-heated, in the gas chamber by heat transmitted from the top of the gas burner.In conventional gas burners with a radial arrangement of nozzles, the nozzles are At a somewhat lower height, a stagnation pocket is created in which the hot gas-air mixture accumulates between the nozzle and the top and acts as an insulator, thereby preventing the preheating effect. As a result, direct contact between the top of the gas burner, which acts as a heating source, and the gas-air mixture flowing past is obstructed, resulting in inefficient preheating. It also contributes to inefficient combustion in prior art gas burners.A further drawback to the head configuration of conventional gas burners is that heat transfer from the flame to the vessel being heated is inefficient. This is because the annular flame formed by conventional gas burners engulfs the vessel, resulting in no direct contact or insufficient contact between the flame and the neck of the vessel. Moreover, most of the heat from the engulfing flame is wasted and lost to the surrounding atmosphere.A further disadvantage of traditional head configurations is that if the heating If the contents inside the container spill over, the spill will come into direct contact with the nozzle and clog the nozzle.To clean the clogged nozzle, clean the nozzle one by one. It is a tedious process that requires a series of manual operations, which is also one of its disadvantages.Another disadvantage is that in the conventional method, the flame inside the head of the svarna is separated from multiple separate flames. each flame is 1
The very fact that it is coming out of one nozzle is what makes this possible. That is, if one such flame is extinguished, for example by wind or air currents, it will not necessarily be rekindled. Therefore, as a result of the air flow, parts of the individual flames may be extinguished, with the distinctly undesirable phenomenon that unburned gas continues to flow out of the nozzle. The object of the present invention is to provide a completely new type of gas burner head that does not have the problems of the prior art. [Means for Solving the Problems] The gas burner of the present invention includes a cup-shaped upper member having a skirt and a top plate having a frontage portion therein, and a deep-dish-shaped lower member supporting the upper member. a gas chamber defined between the upper member and the lower member; a gas chamber disposed in the gas chamber parallel to the top plate of the upper member at a certain distance; at least one -r insert plate having an integral boss extending into an opening in the top plate of said upper member so as to define a continuous annular slot as a gas outlet nozzle with concentric bosses of other insert grates; and gas supply means for supplying a gas-air mixture into the gas chamber. The insert plate boss may be cylindrical or other suitable axisymmetric shape. According to one embodiment of the invention, the gas burner is removably suspended from the inner wall of the cup-shaped upper member;
and has one insert plate with a port for passing gas. In another embodiment of the invention, the gas burner has a central post and an insert plate removably arranged around the central post, the insert plate being attached to the cup-shaped upper part. The insert plate is of a smaller size than the upper member, thereby leaving a gap between the peripheral edge of the insert plate and the upper member, so that there is no distance from the gas supply means inside the gas chamber. It constitutes a tortuous passageway for the gas-air mixture. In yet another embodiment of the invention, at 13, the gas burner includes a central post and at least two concentric insert plates including an innermost insert plate removably disposed about the central post. The insert plates are all smaller in size than the cup-shaped upper member, and the peripheral edges of all the insert plates are inserted into the gas chamber with a gap left between them and the upper member. It constitutes a tortuous passage for the gas-air mixture arriving from the gas supply means, and every insert plate after the second from the inside connects the boss of the inner sylate by a certain distance. (A) has an annular boss that surrounds each other, so that annular nozzles are formed between two adjacent insert plates, so that a plurality of concentric annular nozzles are formed; Said 2
Spacer means are provided for maintaining the independent insert plates spaced apart from each other so that each of the insert plates numbered L and onwards rests on the insert plate one innermost thereof. The plurality of concentric portal nozzles in the above embodiment are:
Large size 63, useful when heating containers in large cooking vessels for public use such as hotels, military camps, hospitals, etc., and in various industrial applications. . In another embodiment of the invention, the gas burner has one insert plate, or two or more concentrically arranged insert plates, the innermost of which is arranged around the central post of the gas burner. It is installed in J3, and the insert plate is
It hangs from the center post. In another variation of the embodiment of the invention, the gas burner is arranged such that one or more of the insert plates, one or more inner ones, extend a cylindrical passage between the center post of the gas burner. Support means are provided around the center post to support the insert plate on the F member. In said last variant, the cylindrical channel acts as an additional innermost nozzle. In some of the above-described embodiments, the central post, optionally with an insert plate mounted thereon, is cylindrical and electrically conductive for generating a spark on the outer surface of the top plate of the upper member. The ignition device may be housed therein. In such embodiments, the insert plate is suspended from a central post and has a central aperture formed in the insert plate that is aligned with the cylindrical central post. In a preferred embodiment of the present invention, the gas supply means for supplying a gas-air mixture into the gas chamber includes a cylindrical intake chamber coaxial with the gas chamber; - vibrating means for creating a tangential flow of the air mixture; If desired, the heat transfer surface of the insert plate may be provided with protrusions or recesses, such as radial ribs or grooves, on its L side to improve heat dissipation. The annular nozzle or nozzles in J3 of the gas burner of the invention may have various shapes, such as polygonal, elliptical, or circular. The invention provides a gas stove having at least one gas burner of the type described above. Furthermore, the present invention relates to a head assembly for a gas burner of the type mentioned in I)a, comprising: a cup-shaped upper member having a skirt and a tongue plate having a frontage therein; between a boss that is disposed below the top plate in parallel with the top plate at a certain distance and is integrally formed within the frontage of the top plate, and 1) the opening portion described in (b); or a head assembly with an insert plate having an integral boss inserted to leave a continuous annular slot between the boss and a concentric boss of another insert plate. In one embodiment of the gas burner head assembly of the present invention, the head assembly of the gas burner includes: 1. : configured and provided with one insert plate with a boat for passing gas. Furthermore, a gas burner head assembly according to another embodiment of the present invention includes a 1111 il insert plate 1 provided around the central post of the gas burner, the size of the insert plate being equal to the size of the cup-shaped upper member. has been smaller than. In another embodiment of the head assembly of the present invention, the tubular upper member J has at least 62 concentric insert plates of smaller size, with the innermost insert plate having at least 62 concentric insert plates of smaller size. A dove plate is configured to be provided around the central post of the gas burner, and 2? V
The r-th and subsequent insert plates have a boss surrounding the boss of the insert plate one innermost with a certain distance to form an annular nozzle between the boss of the insert plate one innermost. , each of the second and subsequent insert plates rests on the insert plate one position inside thereof with a space therebetween. In one variation of the embodiment, the insert plate may be suspended from the central post. In another variation, an insert plate may be arranged around the center post to leave a cylindrical passage between the center post and the center post. In such an embodiment, the head plate is configured as a cylindrical post having a space for accommodating an electrical ignition device, and the inner plate is in line with the cylindrical post in the assembled state. Preferably, it has an array of central holes. [Operation and Effects of the Invention] In the head of the gas burner of the present invention, the insert plate acts as a heat exchanger Mk for preheating the gas-air mixture. That is, in the head of the gas burner of the present invention, unlike those of the prior art, the jet of gas-air mixture occurs at the top of the gas burner, no pocket of gas-air mixture is formed, and the gas-air mixture flows inside the gas chamber. The mixture flowing therethrough comes into contact directly with the insert plate and the top of the cup-shaped upper member without any intervening material. During the direct contact between such a gas-air mixture and the surface of the heat supply, smooth heat transfer takes place by conduction, so that the gas-air mixture flowing inside the gas chamber is
properly preheated. Furthermore, the flame produced by the head of the gas burner of the invention is excluded from the periphery of the head and is therefore located directly below the bottom of the container to be heated. Therefore, the gas-air mixture ejected from the annular nozzle does not draw in any excess air, and therefore the burning gas-
The composition of the air mixture is essentially the same as that ejected from the nozzle. Combustion is therefore optimized by suitably adjusting the composition of the gas-air mixture discharged into the gas chamber. The fact that in the gas burner of the invention the flame is located only directly beneath the vessel being heated further ensures optimization of heat transfer to the vessel and minimization of heat lost to the surrounding atmosphere. Unlike the flame of a conventional gas burner, which has individual minutes associated with one nozzle each, the flame produced by the gas burner of the present invention is continuous. Such flames are therefore not extinguished even by relatively strong air currents. If the contents of the heated container boil over, the spill generally does not reach the annular nozzle of the gas burner of the present invention. Therefore, even such skewered rato continues to burn. The gas burner head of the present invention is extremely easy to clean because the annular nozzle is formed by an assembly of a cup-shaped upper member and an insert plate;
This can be easily done by simply separating the component parts. This is a significant advantage over conventional gas burners, which have separate orifices or nozzles at the periphery of the F-plate, which are extremely difficult to clean. [Example] Next, examples of the gas burner of the present invention will be described with reference to the drawings, but the present invention is not limited to these examples. FIG. 1 is a perspective view showing an embodiment of the gas burner of the present invention;
Figure 2 is a plan view of the head of Subarna, which is shown in Figure 1;
The figure is a sectional view taken along the line (11)-(1) in Figure 2, Figure 4 is an exploded perspective view of the head assembly of the gas burner shown in Figure 1, and Figure 5 is a book with an insert plate of 1111;l. Show other embodiments of the gas burner of the invention? FIG. 6 shows another embodiment of the gas burner of the present invention having a plurality of insert plates. 1 A longitudinal sectional view and FIG. It is a longitudinal cross-sectional view showing still another example. The gas burner (1) of the present invention shown in FIG.
a head assembly (2) consisting of a cylindrical lower member (3) carrying a venturi-type cylindrical member (4) vertically concentrically integrated with said lower member (3); and a control valve (6), and the cylindrical member (4) is provided with an opening (5) for air intake (
is being pulled. Upper member (sword and lower member (3)
The space defined between the two is a gas chamber. The head assembly (2), also known as the burner head, is
It is shown in more detail in Figures 2-4. As shown, the cylindrical cup-shaped upper member (7) constituting the head assembly (2) has a top plate (8) with a concentric opening (9). The cup-shaped upper member ('7) further has a skirt (K)) on its outer periphery, from which a circular insert plate 011 is suspended. The insert plate a11 has an integrally formed central boss (12+) which is inserted into the frontage (9) of the upper member (7) with the central boss (12) and the opening ( An annular slot (hereinafter referred to as an annular nozzle) serving as a gas ejection nozzle is formed between the insert plate 01) and the inner peripheral edge of the insert plate 01). It has a plurality of ports 01) that constitute gas passages through which gas passes. An annular concave groove is provided on the surface of the insert plate (Ill) so that each part of the concave FUH connects two adjacent boats 04. In order to suspend the insert plate (Ill) from the inside of the skirt (G) of the upper member (7), the outer peripheral edge of the insert plate (Ill and the skirt (K)) have complementary circumferential grooves, The annular spring a0 has the shape of a split O-ring and is designed to hold the insert plate 01) in a fixed position. It is designed to. However, by slightly pushing the integrated central boss OZ, the insert plate (Old) is made to come off the upper member (7), and the insert plate (Old) first inserts the annular spring mouth into the insert plate (01). By fitting it onto the outer peripheral edge of the inserter 1 and then positioning the inserter 1-plate 01), it can be easily inserted into the original position. The head assembly (2) can thus be easily assembled and disassembled. The lower periphery of the skirt is designed to fit closely in a substantially air-tight manner onto the upper periphery of the dish-shaped lower member (3), so that the two parts A chamber is formed in between. In use, a pressurized gas-air mixture is supplied into the gas chamber from a venturi-type tubular member (4), passes through the boatman, and passes through the upper member (7).
) top plate (8) and insert plate 011
It passes through the annular space between the At this time, since there is an annular concave groove, the gas inside the space is uniformly distributed and is ejected in a uniform flow through the annular nozzle 0. The combustion gas heats the central boss 021, and by heat conduction, the entire insert plate (Ill) is also heated. Due to the direct contact between the gas-air mixture in the gas chamber and the insert plate 01, the annular Nozzle 03
Direct heat transfer takes place resulting in a suitable preheating of the gases which are ejected for combustion through them. The container being heated in use is provided with at least the same extent as the top plate (8), so that the annular nozzle is exposed from the lower end of the container. As is generally known, appliances heated by gas stoves rest on support members such as grilles, rims, etc. which hold the container at a slight distance from the head of the gas burner. As can be easily understood from this, during operation of the gas burner of the present invention, the two surfaces, namely the top surface of the head and the bottom surface of the container, are exposed to the burning flame from around the annular nozzle. This has the effect of not creating a large airflow. Therefore, the composition of the gas mixture ejected through the 11-shaped nozzle C does not change appreciably. This greatly contributes to the effective utilization of gas. In the above description, d3 is a cup-shaped upper member ('71
Although described as a snake with a flat top plate (8), the one-tub plate may have other shapes, such as an upwardly bulging shape, if desired. As will be readily understood, in the gas burner of the present invention, the flame is permanently confined below the bottom of the vessel being heated, so that heat loss is minimized and the effectiveness of the heat produced by the flame is It is significantly superior to conventional gas burners. As a result of all the above advantages, it can be seen that the time required to boil the contents of the container with the gas burner of the invention is reduced by 20-30% compared to a conventional gas burner of the same caloric capacity. It is clear from this that significant gas savings are achieved using the gas burner of the invention. Also, from the above explanation, even if the contents of the heated container boil over, the boiled over contents will be transferred to the annular nozzle 0.
Even under such difficult circumstances,
In general, it can be seen that the flame always burns at 1F and the number of flames increases. The gas burner according to the embodiment of the invention shown in FIG. 5 has a conical cup-shaped upper member opening. The upper member (171 has a top plate with a central opening 09 and a sloped skirt),
It rests on the edge of the circular deep dish-shaped F member. Further, the lower member (211 is provided at the peripheral edge of the complementary cylindrical member (hereinafter referred to as the complementary member) n,
The complementary part Ut2Z has a stepped part formed at its upper end Q4, and has a central n-shaped post for setting the insert plate 4 with its integral boss. As shown, the insert plate is smaller than the cup-shaped upper member (I7), so that an annular gap is left between them. The upper and integral bosses each have a central hole, the central holes being aligned with each other to accommodate an electric ignition device (not shown). ). The upper member 07) and the lower member 2v define a gas chamber (33) between them. As in the gas burner embodiment shown in Figures 1-4, the annular nozzle has an integral boss base. and upper member (17)
is formed between the top plate Oa and the top plate Oa. The cylindrical prosthesis has an axisymmetric inlet chamber (30) extending vertically downward, the inlet chamber (30) recessed into the gas chamber (33);
and is formed between the outer wall of prosthetic member (1) and the n-shaped post. Although the intake rotary member (30) is cylindrical here,
Other shapes may also be used, such as non-axisymmetric shapes. A gas supply member is arranged tangentially so as to communicate with the inlet chamber (30), the cylindrical part (31) on the outside of the prosthesis n of the gas supply member being in communication with the gas inlet chamber (30). It is connected to a supply pipe (32). The gas supply pipe (32) has an air intake (not shown) and the assembly of the tube (31) and supply pipe (32) allows the flow of the precomposed gas-air mixture to be tangentially It is designed to emit in the direction. The entire assembled svarna is placed as shown, for example on a stove plate (34). During operation, the gas-air mixture flowing out from the venturi set of gas supply pipes (32) is the intake chamber (30
) is ejected radially to create a vortex within. The swirling gas-air mixture enters the intake chamber (30
) to the gas chamber (33), and within the gas chamber (33), the gap between the lower surface of the insert plate 4 and the deep dish-shaped lower member, the outer peripheral edge of the insert plate 4, and the Proceed along the winding path consisting of the gap between 1-■ and the gap between the top surface of the insert plate and the top surface of the top plate □□□,
Finally, it is ejected from the annular nozzle. As explained with reference to Figs. 1 to 4, the burning flame heats the integrated boss (■) and the insert plate (4), as in the case of the svarna embodiment, and as a result +
The gas flowing along the tortuous path in contact with the insert plate, such as Wi'r+, is preheated. The embodiment of the gas burner of the present invention shown in FIG. 6 has the same basic configuration as the one shown in FIG. 5, but is provided with a plurality of insert plates. The same parts in this embodiment are given the same reference numerals. This thing has bosses (36) and (38), respectively, as shown in the figure.
, (40), and (42) are provided. Four insert plates (35), (31), (39), and (41) are provided. ), (40), (42
) are sleeve-shaped and each surround the boss of the insert plate below it. As shown in the figure, an annular throat l~ is left between the adjacent insert plates 1~ and between the outer boss (42) and the edge of the opening Og, each concentric with the other. Four annular nozzles (43), (44), (45), and (46) are formed. In order to maintain the vertical and radial spacing between adjacent insert plates, spacer elements indicated by symbols (47), (48), etc. are provided between the insert plates. In the embodiment shown in FIG.
3), each of which is of essentially the same design as the tortuous passage described with reference to FIG. Four annular flame nozzles (43), (44),
(45) and (46). The embodiment of the gas burner of the present invention shown in FIG.
The configuration is basically the same as that shown in the figure. However, in this case, insert 1 to plate are arranged so as to leave a cylindrical passage around the center post, and support means for supporting the insert plate is provided on the lower member. In this embodiment, the same parts as those not shown in Fig. 5 are given the same reference numerals.As shown in the figure, the tub-shaped member is a venturi tube (
There is a socket (50) on the right for pulling the discharge end of the machine (not shown). A passageway (not shown) leads from the socut (50) to the injection head (51). The injection head (51) injects a tangential flow of the gas-air mixture discharged from the venturi tube into the intake chamber (30). The center boss ■ of insert plate 4 has a cylindrical opening (52
), and the cylindrical opening (52) has a diameter somewhat larger than the diameter of the central post so as to leave a cylindrical passageway (53) around the central post. The insert plate rests on the lower member (2D) via a few integral spacers or bosses (54). The bosses (54) direct the tortuous flow of the gas-air mixture in the gas chamber. An annular groove (55) is provided on the upper surface of the insert plate 4 to improve heat dissipation. As shown in FIGS. 5 and 6. The central bore of the central boss 1- is a space for accommodating an electrical igniter. In addition to contributing to the normal operation of the head of the electric igniter, in addition, upon ignition, the gas-air mixture passing through it is immediately ignited by the spark produced by the electric igniter, and the flame spreads rapidly. The annular nozzle ignites the gas-air mixture from the annular nozzle. The annular groove (55) increases the dissipation of heat from the insert plate 4, improves the efficiency of the gas burner head, and This prevents overheating.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the gas burner of the present invention;
Figure 2 is a plan view of the head of the gas burner shown in Figure 1;
The figures are a sectional view taken along the button-CIll line of FIG. 2, FIG. 4 is an exploded perspective view of the head assembly of the gas burner not shown in FIG. 1, and FIG. A vertical sectional view showing another embodiment of the gas burner, FIG. 6 is a longitudinal sectional view showing another example of the gas burner of the present invention having a plurality of insert plates 1, and FIG. 7 shows a longitudinal sectional view showing another example of the gas burner having one insert plate. It is a longitudinal cross-sectional view showing still another embodiment of the gas burner of the present invention. (Main symbols in the drawing) (1): Gas burner (2) double head assembly (3), (2v = lower member (4) , (221 = cylindrical member (7), On =, E section member (8), dark nidotsubu plate □□□, ■Niscart 01), ゐ, (35), (37), (39), (41 ): Insert plate (121,
■, (36), (38), (40), (42): Boss Dl, (43), (44), (45), (46): Annular nozzle (32): Gas supply vibrator (33) : Gas chamber annular nozzle +t'' Fig, 1

Claims (1)

[Claims] 1. A gas burner having a head assembly, comprising: a cup-shaped upper member having a skirt and a top plate having an opening therein; and a saucer-shaped lower member supporting the upper member. a gas chamber defined between the upper member and the lower member; and a gas chamber disposed within the gas chamber parallel to and at a distance from the top plate of the upper member, and having the opening or other insert plate. at least one insert plate having an integral boss extending into an opening in the top plate of said upper member to define a continuous annular slot as a gas outlet nozzle with a concentric boss of said gas chamber; - a gas burner consisting of gas supply means for supplying an air mixture; 2. The gas burner according to claim 1, wherein both the cup-shaped upper member and the deep-dish lower member are circular. 3. 1 which is removably suspended from the inner wall of the cup-shaped upper member and has a port for passing gas.
A gas burner according to claim 1 or 2, having two insert plates. 4 having a central post and an insert plate removably provided around the central post, the insert plate having a smaller size than the cup-shaped upper member; Claim 1 or 2, wherein the peripheral edge leaves a gap with the upper member to form a tortuous passage for the gas-air mixture reaching the interior of the gas chamber from the gas supply means. Gas burner as described in section. 5. It has a central post and at least two concentric insert plates including the innermost insert plate removably provided around the central post, and each of the insert plates is connected to the cup-shaped insert plate. is smaller in size than the upper member of the insert plate, and the peripheral edges of all insert plates are curved for the gas-air mixture reaching from said gas supply means into the gas chamber, leaving a gap between said upper member and said upper member. The second and subsequent insert plates from the inside each have an annular boss that surrounds the boss of the insert plate one innermost by a certain distance, so that the insert plates are adjacent to each other. By configuring annular nozzles between two insert plates, a plurality of concentric annular nozzles are formed, and each of the second and subsequent insert plates rests on the insert plate one innermost. and spacer means for maintaining the independent insert plates spaced apart from each other.
Gas burner according to item 1 or 2. 6. The gas burner according to claim 4 or 5, wherein the central post is cylindrical and an electric ignition device is provided within the central post. 7. The gas burner according to claim 4 or 5, wherein the insert plate provided around the central post is suspended from the central post. 8. The insert plate is provided around the center post so as to leave a cylindrical passage between it and the center post, and support means are provided for supporting the insert plate on the lower member. A gas burner according to claim 4 or 5. 9 The gas supply means for supplying the gas-air mixture into the gas chamber includes a cylindrical intake chamber coaxial with the gas chamber and a connecting flow of the gas-air mixture into the intake chamber. Claims 1, 2 and 3 comprising pipe means for producing
Gas burner according to item 4, 5 or 6. 10 A head assembly for a gas burner comprising: a cup-shaped upper member having a skirt and a top plate with an opening therein; and inserted into the opening of said top plate to leave a continuous annular slot between an integral boss and said opening, or between an integral boss and a concentric boss of another insert plate. A gas burner head assembly comprising at least one insert plate having an integral boss. 11. The head assembly of claim 10, further comprising an insert plate configured to be suspended from an inner wall of the cup-shaped upper member and having a port for passing gas therethrough. 12 1 installed around the central post of the gas burner
11. The head assembly of claim 10, further comprising: insert plates having a size smaller than the size of the cup-shaped upper member. 13 having at least two concentric insert plates of a smaller size than the cup-shaped upper member, the innermost insert plate being configured to be disposed around the central post of the gas burner;
The second and subsequent insert plates have a boss surrounding the boss of the insert plate one innermost with a certain distance to form an annular nozzle between the second and subsequent insert plates. 11. The head assembly according to claim 10, wherein each of the second and subsequent insert plates rests on the insert plate one innermost thereof at a distance. 14. Claim 1, wherein the insert plate is configured to be suspended from the central post.
The head assembly according to item 2 or 13. 15. The head assembly of claim 12, wherein said insert plate is provided around said center post leaving a cylindrical passage therebetween.