GB2214598A

GB2214598A - Flexible vacuum hose

Info

Publication number: GB2214598A
Application number: GB8800438A
Authority: GB
Inventors: Frank Zamuner; Anthony Asquith
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-01-09
Filing date: 1988-01-09
Publication date: 1989-09-06
Also published as: GB8800438D0

Abstract

A vacuum hose comprises a plain rubber tube 12, which is stretched over helically coiled wire 14. The rubber tube 12 is not moulded to, nor bonded to, the coil 14. The resulting hose is light and flexible, yet resistant to buckling. The hose may be joined to a fume-extracting welding gun or torch 1 by screwing the wire 14 onto a helical groove 10 formed in the handle of the gun. Because the rubber cover 12 is not attached to the coil 14, it can be peeled back during screwing/unscrewing. The joint is very secure and robust, yet is free of protrusions such as clamps, etc, which might snag. <IMAGE>

Description

FLEXIBLE VACUUM HOSE This invention relates to vacuum hoses. It relates also to welding torches of the type which include a means for extracting fumes and smoke, and in particular to the vacuum hose through which the fumes from the welding arc or flame are extracted.

BACKGROUND TO THE INVENTION One of the problems encountered with the extraction-type of welding torch is that the vacuum hose, being typically some 5 or 6 cm in diameter, is very cumbersome. Compared with a non-extracting torch, which does not have a trailing vacuum hose, the smoke-extracting torch is unwieldy, and its use can be very tiring to the welder operator, especially if the nature of the work calls for the torch often to be twisted and orientated in order that the torch may be properly presented to the work.

The invention is aimed at providing a vacuum hose, preferably which is suitable for use with a welding torch, in which the flexibility of the hose is enhanced, but in which the other aspects of the performance of the hose, particularly its resistance to distortion, and its service life, are not compromised by its enhanced flexibility.

THE PRIOR ART The conventional vacuum hose is made of rubber, or elastomeric plastic material. The rubber is moulded into tubing, and the walls of the tubing are often convoluted.

Convoluted tubing is used because it can be bent, and yet, when bent, it retains its resistance to the distortion of its circular cross-section.

It is known for the tubing to be reinforced with textile fibres moulded into the rubber, the fibres being introduced during manufacture of the rubber itself, ie while the rubber is in the liquid, uncured form.

It is also known for the tubing to be reinforced with metal wire, which is wound helically into coils, and which again is embedded in the liquid rubber, prior to curing.

The reinforcement of rubber tubing in general is usually done for the purpose of making the tubing more resistant to an internal pressure, ie. to resist the tendency of the tubing to burst due to pressure contained within the tubing.

A vacuum tube is not of course subject to that tendency.

Vacuum tubing, as contrasted with pressure tubing, may still have to be reinforced, however, but because of the requirement of the tubing to retain its cross-sectional shape and to resist collapse.

Convoluted tubing does have the disadvantage that the tubing may easily snag, when dragged over, for example, the edge of a workbench. Also, although convoluted tubing is able to bend without buckling, ie without losing its cross-sectional shape, nevertheless its stiffness and resistance to such bending can be quite high.

An example of a hose of convoluted tubing is shown in US 4057705 (Nov 1977, COCKRUM).

An example of a vacuum hose in which these disadvantages were addressed is shown in US 4496823 (Jan 1985, MANN).

Here, a vacuum hose is made as a plain cylindrical (unconvoluted) tube of un-reinforced elastomeric material.

Such a hose can be expected to be more flexible in bending than the conventional convoluted tubing.

The cross-sectional shape of such a hose is maintained, as the vacuum tube bends, by means of spokes, which are extruded into the cross-sectional shape. The spokes divide the tubing into compartments, which serve to house the various services needed by the torch, including not only the vacuum, but the flexible conductor supplying electrical current to the arc, the consumable welding rod, the small rubber tube conveying the supply of anti-oxidation gas (eg C02), the control leads from the trigger switch, etc. These service lines are fed through the compartments.

In the spokes-type of hose, however, the spokes are only marginally effective at preventing the hose from buckling and collapsing when the hose is bent. Even though the vacuum passage may not be completely stopped, after buckling, the size of the smoke passage can be much reduced.

Another disadvantage with the spokes-type of hose is that such a hose tends to have the wrong characteristics of resistance to torsion or twisting of the hose. The portion of the hose which receives heavy abuse is the portion immediately adjacent to the handle of the torch. The abuse often is a combination of bending the tubing and twisting the tubing. In the spokes-type of hose, the service lines cannot move around within the tubing, being confined by the spokes, and the combined twisting and bending is thus able to place an undue stress on the lines. Particularly vulnerable is the C02 line, which can be squashed or even torn by such abusive action.

This problem is not significant when the tubing has no spokes, ie when the service lines are free to float radially and circumferentially within the hose, and it is an aim of the invention to provide a vacuum hose in which the flexibility is enhanced, but in which the service lines running internally within the hose are free to move, and not liable to premature failure.

Another aspect of the design of welding torch hose that should be addressed is that of servicing a worn or damaged hose. Welding torch hoses are susceptible to damage particularly at the point where the hose is attached to the torch. It is an advantage if the design is such that the damaged end of the hose can be simply cut away, so that the still-serviceable remainder of the hose can be re-used. The spokes-type of hose is extruded directly onto the electrical conductor, which means that it is virtually impossible for the torch operator himself to shorten the hose, as a routine service task. It is an aim of the invention to provide a vacuum hose in which it is a simple task to remove a damaged end of the hose.

GENERAL DESCRIPTION OF THE INVENTION In the invention, the vacuum hose comprises an outer cover of rubber or other elastomeric material, and a former of helically-coiled metal wire. The rubber is tubular and is stretched circumferentially over the coils. The rubber is not bonded or moulded-on, nor attached to the coils in any way.

Such a construction would not be suitable for a pressure-containing hose, because the (internal) former of the hose of the invention could play no part in withstanding an internal pressure. But the construction is suitable for a vacuum hose: the former is perfectly able to assist in holding the walls of the tubing apart against a tendency of the walls to be drawn inwards.

If, in the hose of the invention, the coils of the former were able to slip relative to the rubber cover, and if the coils were able consequently to bunch together, it might be feared that gaps would be left between adjacent coils, which would permit the hose to buckle. However, this problem does not occur in the invention, because the outer cover is stretched tightly over the coils,-and the resulting friction serves to prevent slippage of the coils relative to the rubber, and serves to maintain the built-in spacing between the coils. The presence of vacuum in the tubing tends to draw the rubber more tightly onto the coils, but, since the hose will sometimes be bent and twisted when the vacuum is not present, it is important that the rubber cover be naturally tight on the coils of the former.

Compared with previous hoses of comparable strength of resistance to collapsing and buckling, the vacuum hose of the invention is of extremely light construction. The hose of the invention is flexible and highly manoeuvrable; qualities which are appreciated by the welder who wishes to maintain a good level of productivity while using the torch throughout a work shift.

In fact, the core through which the sevices are conveyed to the torch has its own rigidity, which defines the lower limit of the manoeuvrability of a welding torch, even without the vacuum hose. The hose of the invention imparts hardly any further restriction on manoeuvrability than is inherent in any event in the service-transmitting core. Thus a fume-extracting torch that is equipped with the vacuum hose of the invention can be almost as easy to handle as a non-extracting torch that has no hose at all.

The vacuum hose of the invention therefore is light in weight, and is highly flexible, yet the hose is amply strong enough to resist collapse due to suction. The hose of the invention may be smooth on its outer surface and so will not snag.

Also, the vacuum hose of the invention has other advantages which will now be described.

The problem of attaching a vacuum hose to the welding torch, and to adapters, etc, must be addressed, and the requirements of the manner of attachment must be considered, during the design of the hose. In the invention, the rubber outer cover is quite separate from the coil springs of the former, and this fact can be used to provide a very efficient method of attaching the hose. In the method, the outer cover is peeled back to expose a few coils at the end of the former. A helical groove is formed into the material of the torch or adapter to which the hose is to be attached.

The former is screw-threaded onto the adapter. When the former is in place, the outer cover may be unfolded back over the coils, to render the joint airtight.

It is known that it is an easy matter to screw-thread a helical coil spring into a pre-formed helical groove. This is because the torque applied to the spring, to overcome friction between the wire and the groove, tends to make the coils open out, and thus become easier to screw on.

However, if the outer cover were to be attached to the coils, for example by bonding, the coils could not easily expand in this manner, and consequently screwing the hose on would be more difficult if the coils were bonded to the rubber. In the invention, by exposing the coils of the former, this property a coil of wire has of being easily screwed onto a groove can be used with advantage.

After the former has been secured mechanically, the rubber cover may be folded back, to seal the joint.

The resulting screwed-on joint between the hose and the handle of the torch is mechanically strong, to the extent that the hose cannot slip off the torch simply by pulling on the hose. Also, the joint is robust and shockproof in that the stress of the mechanical connection is not concentrated into a small zone but is spread over a considerable area. The joint is located closely adjacent to where the operator's hands are gripping the handle of the torch, and hence it is important that the joint should not include protruberances which could snag the operator's glove or sleeve. It will be noted that the manner of connecting the hose, as just described, requires no clips or clamps in this critical area, but provides a smooth and regular transition from the protrusion-free outer surface of the hose to the protrusion-free outer surface of the handle.

To unscrew a screwed-on joint of the kind described is much more difficult than screwing the joint, because, during unscrewing, the torque tends to make the coils smaller.

Sometimes, it can be practically impossible to dismantle such a joint without damaging the components. In the invention, the fact that the outer cover can be easily peeled back to expose the screwed-on coils, means that access to the coils is much simplified, and removal of the hose from the torch is a relatively simple service task.

This is important because, even though the hose of the invention is able to bend and twist, nevertheless the environment in which the hose operates is a demanding one, and inevitably the hose does tend to deteriorate, especially in the area immediately adjacent to the point of attachment of the hose to the torch. With the attachment method of the invention, it is an easy matter to remove the damaged hose, and replace it with a new hose.

The manner of manufacturing the hose of the invention may be described as follows.

The elastomeric outer cover preferably comprises tubing of a regular cylindrical form, although other shapes, eg a tapering shape, could be envisaged. The diameter of the tubing is a little less than the diameter of the coils of the former.

The former is inserted into the outer cover, either by simply pushing the former into the cover, or by a combination of pushing and turning. This insertion process however leaves the coils bunched and irregular within the cover. In the invention, for the purpose of evening out the coils, the cover is inflated. This breaks the contact between the cover and the coils, and allows the coils to space themselves out evenly.

In order to simplify the insertion of the former into the outer cover, the following procedure may be followed. A rod is provided, of a length corresponding to the required length of hose. The rod is passed axially through the coils which will make up the former of the length of hose, and one end of the rod is secured to the end coils of the former.

The rod is then rotated through several turns, thus winding up the former. The former is wound up until the diameter of its coils has been sufficiently reduced to enable the former to fit freely inside the outer cover. Once the coiled-up former has been inserted inside the outer cover, the rod may be reversed, released from the coils, and then withdrawn lengthwise from the hose. Again, it is preferred to inflate the hose after the former has been inserted, in order to smooth out any bunching-up of the coils, or other irregularities which may have been induced between the former and the outer cover.

It is important that the hose be straight when the inflation is carried out. If the former were crooked at that time, the hose would take on the crooked shape permanently when the inflation pressure was withdrawn. It is important also that the hose not only be straight but that the hose should also be horizontal during inflation; if the hose were to hang vertically, for example, the coils at the bottom would be closer together than the coils at the top, due to the weight of the coils, and this unevenness would be retained in the finished hose. Of course, if such unevenness were seen to be advantageous for some reason, it could be provided.

Preferably, in the invention, the inflation of the cover takes place inside a horizontal pipe. In fact, the inflation of the cover may be achieved by sealing the ends of the cover to the pipe, and by applying a vacuum between the pipe and the cover, to cause the cover to expand. With the cover expanded, the coiled former can be inserted without difficulty into the outer cover. The vacuum is then released, and the cover shrinks onto the former.

In the invention, the hose construction can be light, yet strong enough to maintain the shape of the hose against a tendency to buckle when the hose is bent. Friction, due to contact of the coils with the rubber, prevents adjacent coils approaching each other and bunching up. It is an easy matter to make the hose of the invention strong enough to maintain its shape during bending without buckling or collapsing, because a vacuum produces only a limited force, and no allowance need be made for over-pressure.

It is an aim of the invention to provide a hose which is highly flexible and manoeuvrable, without compromising the strength or service life of the hose.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The specification of the invention will now be taken further, by the description of an actual vacuum hose which incorporates the invention.

In the drawings: Fig 1 is a longitudinal cross-section of part of a welding torch, and of a portion of a flexible hose attached to the torch; Fig 2 is a general elevation of the welding torch, the hose, and of the services conveyed through the hose; Fig 3 is a pictorial view showing the hose about to be attached to the welding torch.

The welding torch 1 includes a hood 2 for collecting smoke and fumes from the arc or flame of the torch.

A vacuum pump and fume extraction means are provided, which are indicated diagrammatically by numeral 3. The vacuum is conveyed to the torch through a length 4 of flexible hose.

The torch includes two half-round plastic mouldings 5 which, when assembled together, form a hollow handle 6 for the torch. The hollow interior of the handle 6 comprises a chamber 7 through which the fumes are conveyed from the hood 2, and into the hose 4.

The outer surface of the handle 6 includes a plain cylindrical nose 9. Moulded into the nose 9 is a helical groove 10, which comprises several turns.

The hose 4 comprises an outer cover 12 and a former 14. The outer cover 12 comprises a length of tubing, made of neoprene rubber. The tubing 12 is plain cylindrical, and is not convoluted but has a regular diameter along its length.

The former 14 comprises a length of steel wire, which is wound into helical coils so as to resemble a spring. The coils are open axially, and lie roughly at the same pitch as the turns of the helical groove 10 on the nose 9 of the handle 6. The diameter of the coils is slightly smaller than the diameter of the groove 10.

To assemble the hose 3 onto the handle 6, the end portion 16 of the outer cover 12 is folded back, so as to expose a few coils of wire at the end of the former. The wire is then screwed into the groove 10 and onto the nose 9.

After the former is securely in place, the end 16 of the rubber cover 12 may be drawn or folded forwards over the end coils, to seal the joint. A length 18 of adhesive tape may be wrapped around the end of the cover 12, to complete the vacuum-tight seal, and to prevent the end of the cover from being damaged in service. It may be noted that the tape 18 is not needed to aid in the mechanical strength of the joint.

The handle 6 is provided with annular grooves 17, which improve grip, and serve to insulate the operator from the handle 6, which can become hot.

At its other end, the hose is coupled to the vacuum pump, etc 3. The connection to the pump is via a metal Tee-piece 19, which it is generally convenient to make solid with a workbench, or other structure. The hose 4 is not coupled directly to the Tee-piece 19, but is coupled, via an adapter 20, to a short length 21 of conventional plain (or convoluted) tubing, which is in turn coupled directly to the Tee-piece 19. The hose 4 is screwed onto the adapter 20 in the same manner as the hose was screwed onto the handle of the torch 1, whereas the tubing 21 is secured to the adapter 20 in the usual way, ie by means of a clamp 23.

The presence of the tubing 21 has two advantages. First, the tubing 21 can be stiffer than the hose 4. The joint between the hose and the frame is perhaps even more vulnerable to abuse and damage than the joint between the hose and the torch, and stiff tubing 21 serves as a buffer to prevent stress concentrations at the joint from being felt by the hose 4. The second advantage of the presence of the tubing 21 is that the two screw threaded joints between the hose and, respectively, the torch and the adapter, can be made before clamping the tubing 21, so that no twist is locked into the hose 4.

The services located at the end of the hose are, in addition to the vacuum pump and fume extraction means 3: a source 25 of carbon dioxide or other oxidation-inhibiting gas; a source 27 of consumable welding rod; an electrical supply 28 to provide welding current; and a control circuit 29, by means of which the welding current, the drive to the welding rod, and the supply of anti-oxidation gas are controlled, the circuit 29 being itself under the control of the trigger switch 30 located on the torch. The vacuum would usually be controlled separately from the trigger switch, so that the vacuum-induced airflow can be left on after welding has stopped, in order to clear smoke and to keep the torch cool.

These services 25,27,28,29 are connected to the torch 1 through a central core 36. The various seervices are transmitted through the various components of the core, which are arranged concentrically. Innermost is the welding rod 37, which is driven at a constant speed through the hose and torch. The rod 37 is guided within a conduit 38, which is stationary in the core 36.

The electric current is conveyed through flexible copper strands 39. The strands 39 are assembled over an inner rubber tube 40, and are surrounded by an outer rubber tube 41. A compression fitting 45 couples the strands 39 to a copper tube 46 within the handle 6.

The copper tube 46 is suspended within the hollow handle 6 on spiders 47, so that the core is held radially in the centre of the hose 4 at the location of the joint between the hose and the torch. This spacing of the core away from the hose walls tends to protect the hose at the vulnerable joint area. The core 36 will tend to rest against the inside wall of the hose 4 along the length of the hose, but the hose is less prone to damage along its length, away from the joints.

The anti-oxidation gas is contained by the inner rubber tube 40. The gas passes through the conduit 38, which is of coiled construction, for flexibility, and is not gastight.

The leads 48 to the trigger switch pass alongside the strands 39, between the inner and outer rubber tubes 40,41.

Such a central core 36, though a complex structure, is adapted to be flexible. The vacuum hose of the invention, however, can be even more flexible than such a core, in contrast with prior hoses, where the limit on flexibility came from the hose, not from the core.

Although light and flexible, the hose of the invention is not likely to collapse, nor to buckle or fold when bent and twisted. These properties have not been gained at the expense of extra bulk inside the hose: the vacuum passage is large and regular and unobstructed, along the length of the hose, and at the joint between the hose and the torch.

In addition to these qualities of the hose itself, the hose of the invention has the above described advantages relating to the joint area between the hose and the torch, ie: the hose is easy to assemble and dismantle; once assembled, the hose is totally secure against slipping off; the joint provides a smooth, gradual transition between hose and torch, to protect the hose from stress concentrations; and the joint area has no protuberances to snag in the operator's clothing.

Claims

CLAIM 1. A flexible hose, which is suitable for use to

convey vacuum, wherein: the hose includes an outer cover, and a former; the outer cover is in the form of a length of tubing; the length of tubing is made of elastomeric material; the former is in the form of a length of wire, wound helically into a coil; the former is placed inside the outer cover; and the outer cover is not attached to the former, in that the former remains separate, and separable, from the former.
CLAIM 2. Hose of claim 1, wherein: the dimensions of the former and of the outer cover are such that the outer cover is stretched diametrally over the former.
CLAIM 3. Hose of claim 1, wherein: the outer cover is of neoprene rubber.
CLAIM 4. Hose of claim 1, wherein: the tubing which forms the outer cover is right cylindrical, and uniform at all points along its length.
CLAIM 5. Method of manufacturing the hose of claim 1, including the steps: of providing the said outer cover of elastomeric material, and the said former of helically coiled wire; of inserting the former inside the outer cover from one end of the outer cover; of rendering airtight the outer cover; and of inflating the outer cover, sufficiently to cause the outer cover to expand diametrally far enough that the outer cover is clear of the former.
CLAIM 6. Method of claim 5, combined with a method of assembling the hose on to an adapter, which includes the steps: of forming a helical groove in the adapter; of screw threading the helical coils of the former into the said helical groove of the adapter.
CLAIM 7. Combined method of claim 6, including the steps: before screw-threading the former onto the adapter, of withdrawing the end of the outer cover so as to expose the end few coils of the former; and, after screw-threading the former onto the adapter, of replacing the outer cover back over the coils.
CLAIM 8. Assembly of a welding torch and the vacuum hose of claim 1, wherein: the hose is connectable to a vacuum pump and a fume extraction means; the torch includes a hollow handle of generally tubular form, the hollow interior of which includes a vacuum chamber; the arrangement is such that smoke and fumes from the flame of the torch are conveyed through the vacuum chamber, and then through the hose, by the vacuum pump, to the fume extraction means; the hollow handle is provided with a helical groove; a few coils at one end of the former of the hose are screw-threaded into the helical groove; and the outer cover lies over the said end few coils, in such a manner that that the hose is thereby rendered substantially vacuum-tight with respect to the handle.
CLAIM 9. Assembly of claim 8, wherein: the assembly includes also a central core, which includes an electrical conductor for transmitting electric current to the welding flame, and the central core lies inside the hose; and the cross-sectional dimensions of the hose are such that the cross-section includes an ample opening for the passage of smoke and fumes along the hose, around the said central core.