EP0460500B1 - Hand shrink apparatus - Google Patents

Abstract

The invention relates to a hand-held shrinking apparatus which comprises an injector-type burner with a combustible gas nozzle (4) arranged in a mixing nozzle which tapers in the direction of flow and sucks combustion air in through its end having the larger cross-section, and a combustion chamber. To improve the performance of a hand-held shrinking apparatus and make it easier to handle, a number of mixing nozzles (6, 7, 8) are to be arranged one behind the other in the direction of flow, the outlet orifice of the mixing nozzle arranged upstream in each case projecting into the intake end of the mixing nozzle arranged downstream in each case. <IMAGE>

Description

The invention relates to a hand-held shrinking device with an injector burner, which has an outlet nozzle designed as a flat nozzle and a fuel gas nozzle which is arranged in a mixing nozzle which tapers in the direction of flow and which draws combustion air through its larger cross-section, and with a combustion chamber.

Hand shrinking devices are known in various designs. They are used to shrink shrink films that surround a stack of goods or the like. Via a fuel gas supply, which is connected to a handle containing control devices, valves and the like, fuel gas is fed to the hand shrinking device and is mixed with combustion air in the mixing chamber. The mixture is burned in a combustion chamber and from there it passes through an outlet nozzle into the open or into the area of the shrink film to be shrunk. In a known hand shrinking device of the type described at the beginning (DE-A-28 22 192), the injector burner has only a single mixing nozzle. In order to achieve a sufficient mixing of fuel gas and combustion air, the mixing nozzle must be relatively long. The hand shrinking device must also be correspondingly large, so that its handiness is unsatisfactory. Furthermore, the performance of a hand shrinking device is limited due to this construction.

The object of the invention is to improve the performance and handiness of a hand shrinking device.

aufweist, wobei

T =

Höhe des Austrittsendes

l =

axiale Länge der Brennkammer vor dem Flammenhalter

L =

axiale Länge der Brennkammer vor dem Flammenhalter plus axiale Länge der Flachdüse

D =

Durchmesser der Flachdüse am Eintrittsende

ist.This object is achieved in that a plurality of mixing nozzles are arranged one behind the other in the direction of flow, the respectively upstream mixing nozzle with its outlet opening protruding into the suction end of the respectively downstream mixing nozzle, and in that the outlet end of the flat nozzle has dimensions in accordance with the ratio $$\frac{\text{T}}{\text{l}}\text{=}\frac{\text{L}}{\text{D}}$$

has, wherein

T =

Exit end height

l =

axial length of the combustion chamber in front of the flame holder

L =

axial length of the combustion chamber in front of the flame holder plus axial length of the flat nozzle

D =

Diameter of the flat nozzle at the inlet end

is.

By connecting several mixing nozzles in series, the mixture of fuel gas and combustion air is accelerated and the hand shrinking device can be built shorter for the same output or designed for higher output. A version is recommended in which the cross sections of the outlet orifices of the mixing nozzles increase in the direction of flow, so that the flow velocities within the hand shrinking device remain within reasonable limits. This will result in complete combustion reached in the area of the combustion chamber and outlet nozzle and ensured that no flames emerge from the outlet nozzle.

In a preferred embodiment of the invention, the mixing nozzle arranged in front of the combustion chamber is a Venturi nozzle, in which in particular the outlet mouth widens up to the cross section of the combustion chamber. Then a largely calmed flow enters the combustion chamber, which is usually designed and e.g. is also equipped with a flame holder.

The mixing nozzles are expediently housed in a housing which has air inlet openings on the circumference, which lead to the suction ends of the mixing nozzles. Since considerable suction noises and / or mixing noises can occur with such a hand-shrinking device, it is advantageous if the housing is surrounded by a soundproofing jacket at least in the area of the air inlet openings.

A preferred embodiment of the invention is characterized in that the flat nozzle has a wall made of a material with low thermal conductivity and high heat resistance. In particular, the wall of the flat nozzle should consist of ceramic. The wall can also have an inner jacket and / or outer jacket made of sheet metal. The effects of the high temperatures in the area of the outlet nozzle on the hand shrinking device itself can thus be largely reduced, so that it is also possible to accommodate the flat nozzle in a housing section of the hand shrinking device. This in turn improves the overall stability of the device.

In order to ensure that the combustion of the mixture of fuel gases and combustion air only begins shortly before entering the outlet nozzle, it is expedient if a turbulence grille, a flame holder and an ignition device are arranged in the region of a combustion chamber arranged in the flow direction in front of the flat nozzle Ignitor consists of an electrically conductive ignition cable embedded with housing parts and a free end of the ignition cable protrudes into the pipe section. It is understood that the pipe section is open on the combustion chamber side and ends at the flame holder or in the flow direction behind the flame holder and that the free end of the ignition cable is arranged in the open end of the pipe section, so that an ignition spark can always ignite only the mixture located in the combustion chamber.

The stability of the flame in the combustion chamber is not only guaranteed by the flame holder arranged there, but can also be supported by appropriate design of the components preceding in the direction of flow, the arrangement of the fuel gas nozzle being particularly important. Here, the invention recommends arranging the fuel gas nozzle at a distance L1 from the outlet opening of the next mixing nozzle, which corresponds to 1.5 to 2.5 times the diameter D1 of this outlet opening. If the fuel gas nozzle beyond has a teardrop shape, with the slender end pointing in the direction of flow, very high fuel gas velocities essential for the injector effect are achieved.

Fig. 1

schematisch und teilweise einen Längsschnitt durch ein Handschrumpfgerät,

Fig. 2

eine andere Ausführung des Gegenstandes nach Fig. 1,

Fig. 3

im vergrößerten Maßstab einen Ausschnitt aus dem Gegenstand nach Fig. 2 im Bereich der Austrittsdüse,

Fig. 4

den Gegenstand nach Fig. 3 mit weiteren Einzelheiten,

Fig. 5

im vergrößerten Maßstab einen Ausschnitt aus Fig. 2 im Bereich der Brenngasdüse.

In the following an embodiment of the invention shown in the drawing is explained; show it:

Fig. 1

schematically and partially a longitudinal section through a hand shrinking device,

Fig. 2

another embodiment of the object of FIG. 1,

Fig. 3

on an enlarged scale, a section of the object according to FIG. 2 in the area of the outlet nozzle,

Fig. 4

3 with further details,

Fig. 5

on a larger scale, a detail from FIG. 2 in the area of the fuel gas nozzle.

The hand shrinking device shown in the drawing is intended for shrinking shrink film which, for example, surrounds a stack of goods. The basic structure of the hand shrinking device consists of an elongated housing 1 and a handle 2 connected to it. A fuel gas hose (not shown) can be connected to the handle 2 and can thus be connected to a fuel gas line 3 guided inside the handle 2. A not shown belongs to the fuel gas line 3 Valve, which is housed in the handle 2, which can also contain other control devices and an ignition device. The fuel gas line 3 opens at a fuel gas nozzle 4 through which the fuel gas emerges in the longitudinal direction of the housing or in the flow direction 5.

In the flow direction 5, 4 mixing nozzles 6, 7 and a Venturi nozzle 8 are arranged behind the fuel gas nozzle. The respective upstream mixing nozzles 6 project with their outlet opening 9 into the suction end 10 of the mixing nozzle 7 arranged downstream. The fuel gas nozzle 4 is arranged in the region of the suction end 10 of the upstream mixing nozzle 6. The downstream mixing nozzle 7 projects with its outlet opening into the suction end 10 of the Venturi nozzle 8 or is arranged in the region of this suction end.

The cross sections of the outlet openings 9 of the successive nozzles increase in the flow direction 5. The housing 1 has peripheral air inlet openings that lead to the suction ends 10 of the mixing nozzles 6, 7 and the Venturi nozzle 10. In the area of the air inlet openings 11, the housing 1 is surrounded by a soundproof jacket 12.

A mixing chamber 13 adjoins the outlet opening of the Venturi nozzle 8, the cross section of which corresponds to the cross section of the outlet opening 9 of the Venturi nozzle 8. The mixing chamber 13 is followed in the flow direction 5 by a combustion chamber 14 with an outlet nozzle 15. The mixing chamber 13 and the combustion chamber 14 can have customary internals, eg. B. a turbulence grid 16 in the mixing chamber and / or one Flame holder 17 in the combustion chamber 14.

wobei

T=

Höhe des Austrittsendes

l=

axiale Länge der Brennkammer vor dem Flammenhalter

L=

axiale Länge der Brennkammer vor dem Flammenhalter plus axiale Länge der Flachdüse

D=

Durchmesser der Flachdüse am Eintrittsende

ist (Fig. 1).In the embodiment shown in FIGS. 2 to 5, the housing 1 extends beyond the outlet nozzle 15 designed as a flat nozzle, so that this outlet nozzle 15 is embedded in a housing section. The outlet nozzle 15 has a wall 18 made of ceramic, which is covered on the outside by an outer jacket 19 made of sheet metal and on the inside by an inner jacket 20 made of sheet metal. The dimensions of the outlet nozzle 15 designed as a flat nozzle depend on the ratio $$\frac{\text{T}}{\text{l}}\text{=}\frac{\text{L}}{\text{D}}$$

in which

T =

Exit end height

l =

axial length of the combustion chamber in front of the flame holder

L =

axial length of the combustion chamber in front of the flame holder plus axial length of the flat nozzle

D =

Diameter of the flat nozzle at the inlet end

is (Fig. 1).

In the area of the combustion chamber 14 arranged in the flow direction in front of the flat nozzle, an ignition device 21 is arranged in the center in the area of the flame holder 17, which in the embodiment shown includes a pipe section 22 which is connected to housing parts in an electrically conductive manner. In the pipe section 22, an insulating bush 23 is used, the z. B. can consist of PTFE. In the insulating bush 23, an ignition cable 24 is embedded, the free End 25 protrudes into a chamber of the tube section 22 open towards the combustion chamber 14.

In the embodiment shown, the fuel gas nozzle 4 has a teardrop shape, the slimmer end pointing in the direction of flow 5. The end of the fuel gas nozzle 4 is arranged at a distance L1 from the outlet opening 9 of the next mixing nozzle 6, which corresponds to 1.5 to 2.5 times the diameter D1 of this outlet nozzle 9.

The hand-held shrinking device shown works as follows: Under the injector action of the fuel gas emerging from the fuel gas nozzle 4, air is sucked into the mixing nozzle 6, which mixes with the fuel gas. The mixture passes through the outlet opening 9 of the mixing nozzle 6 into the mixing nozzle 7, in which air is in turn sucked in by the injector action. The same applies when the resulting mixture enters the Venturi nozzle 8. By arranging several mixing nozzles in a row, the length of the hand shrinking device can be kept shorter with a comparable hand shrinking device with the same performance. On the other hand, there is also the possibility to improve the performance of his hand shrinking device, i.e. H. to supply more fuel gas, which is then mixed up to the combustion chamber 14 with the intake of combustion air.

Claims (13)

1. Hand-held shrinking apparatus, including an injector burner which has an outlet nozzle adapted as flat nozzle (15) and a combustion gas nozzle (4) disposed in a mixing nozzle (6), which tapers inwardly with respect to the direction of flow and draws-in combustion air through its end having the larger cross-section, and a combustion chamber (14), characterised in that a plurality of mixing nozzles (6, 7, 8) are disposed behind one another when viewed with respect to the direction of flow (5), the mixing nozzle (6) which is respectively disposed upstream protruding with its outlet aperture (9) into the inlet end (10) of the mixing nozzle (7) which is respectively disposed downstream, and in that the outlet end of the flat nozzle (15) has dimensions in accordance with the equation $$\frac{\text{T}}{\text{l}}\text{=}\frac{\text{L}}{\text{D}}$$

   

   wherein

   T =   height of the outlet end;

   l =   axial length of the combustion chamber in front of the flame holder;

   L =   axial length of the combustion chamber in front of the flame holder plus axial length of the flat nozzle; and

   D =   diameter of the flat nozzle at the inlet end.
2. Hand-held shrinking apparatus according to claim 1, characterised in that the cross-sections of the outlet apertures (9) of the mixing nozzles (6, 7, 8) increase when viewed with respect to the direction of flow (5).
3. Hand-held shrinking apparatus according to claim 1 or 2, characterised in that the mixing nozzle disposed in front of the combustion chamber (14) is a Venturi nozzle (8).
4. Hand-held shrinking apparatus according to one of claims 1 to 3, characterised in that the outlet aperture (9) of the Venturi nozzle (8) widens up to the cross-section of the combustion chamber (14).
5. Hand-held shrinking apparatus according to one of claims 1 to 4, characterised in that the mixing nozzles (6, 7, 8) are accommodated in a housing (1), which has circumferential air inlet apertures (11) extending to the inlet ends (10) of the mixing nozzles (6, 7, 8).
6. Hand-held shrinking apparatus according to claim 5, characterised in that the housing (1) is surrounded by a sound-proofing covering (12) at least in the region of the air inlet apertures (11).
7. Hand-held shrinking apparatus according to one of claims 1 to 6, characterised in that the flat nozzle (15) has a wall (18) formed from a material having low thermal conductivity and high heat resistance.
8. Hand-held shrinking apparatus according to claim 7, characterised in that the wall (18) of the flat nozzle (15) is formed from ceramic material.
9. Hand-held shrinking apparatus according to claim 7 or 8, characterised in that the wall (18) has an internal covering (20) and/or an external covering (19) formed from sheet metal.
10. Hand-held shrinking apparatus according to one of claims 7 to 9, characterised in that the flat nozzle (15) is accommodated in a housing portion of the hand-held shrinking apparatus.
11. Hand-held shrinking apparatus according to one of claims 7 to 10, characterised in that a turbulence screen (16), a flame holder (17) and an ignition device (21) are disposed in the region of a combustion chamber (14), which is disposed in front of the flat nozzle (15) when viewed with respect to the direction of flow (5), and in that the ignition device (21) comprises a tubular portion (22), which is connected to housing members in an electrically conductive manner, and an ignition cable (24), which is embedded in said tubular portion in an insulated manner, a free end (25) of the ignition cable (24) protruding into the tubular portion (22).
12. Hand-held shrinking apparatus according to one of claims 7 to 11, characterised in that the combustion gas nozzle (4) is disposed at a spacing L1 from the outlet aperture (9) of the nearest mixing nozzle (6), which spacing corresponds to 1.5- to 2.5-times the diameter D1 of this outlet aperture (9).
13. Hand-held shrinking apparatus according to one of claims 7 to 12, characterised in that the combustion gas nozzle (4) has a teardrop-shaped configuration, the slimmer end pointing in the direction of flow (5).

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