GB2145219A - Hand-held device for directing a jet of compressed air - Google Patents

Abstract

A hand-held device for directing a jet of compressed air onto a workpiece or tool for clearing debris therefrom has a housing with an outlet nozzle (9) and a duct joining it with an air inlet port (7). In the duct there are two valves put in series and one of which is a manual control valve (5) and the other is a safety valve (30) which responds to a back pressure on its downstream side by shutting off the duct. The housing is made up of three synthetic resin parts that are interlocked with each other, namely a shell member (1), a valve assembly (10) and a nozzle head (45). The synthetic resin parts have all valve elements and a trigger (4) for operation of the valve mounted between them. They are joined together by drilling holes therein when assembled and placing pins in the holes. <IMAGE>

Description

SPECIFICATION A hand-held device for directing a jet of compressed air The present invention relates to hand-held devices for directing a jet of compressed air for cleaning and other purposes, and more particularly, but not exclusively, to such a device comprising a housing with a duct therein forming a connection between a compressed inlet port and outlet nozzle, and a manual control valve joined in series with a safety valve that shuts off the duct as soon as there is a back pressure on the downstream side of the safety valve in excess of a certain value.

Such devices are used i n i in industry for cleaning tools and workpieces when they are being used and machined respectively. More specially such a device may be used for clearing shavings and other debris out of holes and the like as part of an industrial production process. The passage of compressed air through the duct in the housing connecting the air inlet port with the outlet nozzle is controlled by the manual valve, that is operated by a trigger or the like on a pistol grip. The control valve is spring-loaded into its shut position and it is opened to a greater or lesser degree by the user when an air jet is to be discharged from the outlet nozzle. In this respect the control valve makes it possible for the flow of compressed air to be turned fully on and fully off and set at intermediate values as well.

Furthermore there may be a safety valve in the housing of the device, such valve being placed in series with the control valve through which the compressed air has to pass. The purpose of the safety valve is to stop an excessively powerful air jet being directed against a surface, such as a workpiece to be cleaned or the body of the person using the pistol, which might cause injury. The safety valve is to limit the pressure of the air coming from the device to a relatively low value, which in keeping with present German safety regulations is about 2.5 bar. A further point is that the safety valve is to make it impossible for the device to be used very close to a surface by having means to cut off the flow of compressed air when the device is near the surface.

For this purpose a safety valve may be placed upstream or downstream in relation to the control valve. It shuts off the duct carrying the compressed air when there is a build up of back pressure on the downstream side in excess of a given limit.

Known devices for directing a jet compressed air of the sort noted have been very complex to produce because of the design of the separate parts, and furthermore the outer form of such devices is not very well adapted to everyday working conditions.

One aim of the present invention is to put an end to these shortcomings and to create a device for directing a jet of compressed air that is well conceived from the ergonomic aspect and furthermore may be simply and cheaply produced and assembled.

In order to effect these and further aims the present invention consists in a hand-held device for directing a jet of compressed air onto a workpiece, comprising a housing with a compressed air inlet port, with an outlet nozzle and with a duct running from the port to the nozzle, a manual control valve in the duct and a safety valve connected in series with the control valve to shut off the flow of air through the duct when back pressure at a point downstream from the safety valve exceeds a given value, said housing being made up of three interlocking synthetic resin parts, namely of of an L-like outer shell member, whose first part adjoining an end thereof takes the form of a grip member adapted to the held in the hand and with an opening for the compressed air port, whereas a second part of the said shell member adjoining another end thereof is at about 90" to the said first part and is alined with the outlet nozzle, of a valve assembly fitting within said steel member and functioning as part of said duct, and of a nozzle head joined to an outlet end of the said valve assembly and having the nozzle head mounted in it, all such synthetic rein parts forming an enclosure for all valve elements of said device, and a trigger for operation of the control valve, and being joined together by pins fitted in holes produced in the said synthetic resin parts when fitted together in the process of assembly.

An account will now be given of one working example of the invention using the accompanying drawing whose single figure is a lengthways section through a device for directing a jet of compressed air.

The device has a housing that is completely made of synthetic resin. An important principle of the present invention is that, by using synthetic resin for their manufacture, all the housing parts are to have a configuration and outline such that they may be quite readily produced and rapidly assembled in a few manual steps. To this end the housing is made of three synthetic resin parts that may be plugged together. A first part of the housing has the form of an L-like shell member 1, that forms a large part of the outer surface of the device and gives it its characteristic shape. The lower part of the shell member 1 is in the form of a cylindrical hollow body 3 that is rounded off at its end 2 and is shaped as a grip to be clasped in the hand like the grip of a pistol.

A trigger 4 is mounted in this grip part for the operation of a control valve 5. At the lower end 2 of the hollow body 3 there is an opening for the compressed air port. A connector 7 is placed in this opening 6, such connector being for example part of a standardized hose coupling or high-speed connection unit for joining up with the source of compressed air. The upper end part 8 of the shell member 1 is at an angle of about 90" to the grip part of the housing member. The upper end part 8 has a discharge nozzle 9 mounted therein so that the air coming out of the nozzle follows generally the direction in which the upper end part 8 is pointed, that isto say generally at a right angle to the direction to the grip part with the trigger 4.For this reason compressed air flowing through the housing is deflected through about 90" and the issuing jet will be generally at a right angle to the grip part.

This design is of particular value for many everyday tasks, as for example blowing debris out of drilled holes, and makes the device easy to use, inasfar as it is readily held in the hand.

The interior of the shell member 1 has a valve assembly 10 therein through which the air has to pass. The valve assembly 10 is in the form of an L-like duct part that is open at both ends. There is a connection with a female inlet bush 11 at the inlet port that is generally cylindrical and opens to the opening 6 in the shell member 1. The inner diameter of the inlet bush 11, which is generally the same as the size of the opening, fits the connector 7, by way of which the compressed air is led into the valve assembly 10. The connector7 has its end resting against a shoulder 12 in the inlet bush 11, such shoulder in fact representing a narrowing part of the inlet bush. The connector 7 is sealed off inside the inlet bush 11 with an O-ring 13 and it is locked in its fitted position by two pins 14 so that it may not drop out of place.

Running upwards from the inlet brush 11 there is a first pipe section 15 as part of the valve assembly 10.

The pipe section runs in the middle of the structure and generally parallel to the length direction of the hollow body 3, that forms the grip part of the device.

The pipe section 15 opens into valve chamber 16 of the control valve at a point upstream from a moving valve member 17 which is spring loaded into its shut position. The valve chamber 16 is formed within a bush-like member 18 of the valve assembly 10 therein and being at a right angle to the first pipe section 15. This bush-like member 18 has a head 19 fitting into it, that is formed on the inside of the shell member 1. The head has a cylindrical outer face and it has an O-ring 20 on it that rests against a step in the member 18. The valve assembly 10 is in this way located in place by being clamped in the shell member 1 and sealingly jointed with the same. The cylindrical bush-like member 18 becomes narrower to the left so that a valve seat 21 is formed therein for the valve member 17, that as well is conical.The valve member 17 fits in the valve seat 21 and is pushed into such sealing position by the force of a compression spring 22, that in the present working example of the invention will be seen to be in the form of a helical wire spring. The compression spring 22 is mounted on an axial guide pin forming part of the valve member 17 with its left-hand end abutting against a collar on the valve member 17.

The other right-hand end of the said compression spring is guided in the head 19. For this purpose the head 19 is made with a generally cylindrical socket 23 of ring-like cross section that widens slightly towards the valve seat 21 conically. This socket is placed coaxially in the head 19 and the compression spring 22 has its right end resting on the floor of the socket. To economize in the use of material and to simplify production, the middle part of the head is made hollow at 24 so that the end effect is that the head 19 has two coaxial walls with the end of the compression spring 22 therebetween.

The valve member 17 is able to be pushed clear of the valve seat 21 by a plunger 25. This plunger 25 may be shifted axially and is slidingly supported in a guide bush 26 that is also molded as part of the valve assembly 10. The said guide bush 26 is coaxial with the bush-like member 18 and runs out from the assembly 10 on the opposite side thereof; that is to say it is also at a right angle to the lengthways axis of the grip part. The plunger 25, that slides, and is sealed in the guide bush 26, has its one end resting against the valve member 17. The other end 27 of the said plunger 25 sticks out of the guide bush 26. It is rounded and is acted on by the trigger 4, that is pivotally mounted on the housing of the device.

Using the trigger or operating lever 4 the valve member 17 may be lifted clear of the valve seat 21 to the amount desired so that a larger or smaller passage is made free for the compressed air and a jet of graded strength will issue from the outlet nozzle 9.

The compressed air comes out of the valve chamber 16 and moves into a second pipe section 28 of the valve assembly 10. This pipe section 28 runs parallel to the first pipe section, 15 but is offset therefrom towards the nozzle 9, i.e. the section 28 also runs in the lengthways direction of the grip part.

While the first pipe section 15 opens into the valve chamber 16 at a point upstream from the valve member 17, the second pipe section 28 runs from the valve chamber 16 at a point downstream from the valve member 17. The second pipe section 28 joins with the foot of a further valve chamber 29 forming part of a safety valve 30. The valve chamber 29 is in this respect formed in a head 31 of the valve assembly 10, that is set at about 90O to the second pipe section 28 and runs out to the left in the form of a muzzle member 32. The valve chambers 16 and 29 of the control valve 5 and of the safety valve 30 are so alined that their axes are parallel to each other, but they are on opposite sides of the valve assembly.

The top head 31 of the valve assembly 10 is made with a coaxial spring socket 33 that is open in a downstream direction and is of ring-like crosssection. The socket is limited on the outside by the wall of the muzzle member 32. The radially inner wall of the socket 33 is formed by a central pipe 35 with a passage 34 therein for the compressed air.

This pipe 35 further functions as a guide member and as a valve seat for a valve member 36 of the safety valve 30.

The safety valve 36 has a washer-like main body 37 with a central hole therethrough and on one side thereof there is a guide rim 38 of lesser diameter.

The valve member 36 is slidingly mounted on the pipe 35 with the guide rim 38 running on the pipe 35 and pointing in the upstream direction. The arrangement is in this respect such that the inner face of the main body 37 runs on the pipe 35 and its outer face or edge is rested on the inner face of the wall of the muzzle member 32. The main body 37 is slidingly glanded on the latter by a lip running round it. The socket 33 is for this reason sealed off from the path taken by the compressed air and it is vented by way of a hole (not shown) running into the outside atmosphere.

Inside the socket 33 there is a driving spring 39 whose one end rests against the floor of the socket 33 whereas its other end is on the valve member 36.

The driving spring is placed round the outer face of the guide rim 38 and abuts against the end of the main body 37. The sizes of the socket 33 and of the valve member 36 are matched to each other, and more specially the outer diameter of the guide rim 38 and the inner diameter of the socket 33 are generally equal at the one end thereof. The inner diameter of the socket then becomes less at a step 40 so as to be the same in size as the hole through the valve member 36, and between this step 40 and the front edge of the guide rim 38 there is a gap, that makes is possible for the valve member to be moved suffi ciently for operation of the valve.

A closing member 41 is formed on the main body 37 to cover over the opening of the pipe 35.

Preferably the closing member41 has a conical guide point 42 running into the pipe 35. The pipe 35 forms a sealing seat for the closing part 41 so that when there is sealing engagement with the pipe 35 the passage 34 will be obturated and air the flow of compressed air therethrough will be cut off. For shutting off the air the valve member 36 is moved axially onto the pipe 35 and the valve member 36 is deformed, this taking place when the pressure upstream of the outlet nozzle 9 gets to a certain level.

This may be best made clear on considering the forces acting on the valve member 36. The valve member 36 is in the first place loaded by the driving spring 39 so that it is in the open position in which the closing member 41 is lifted clear of the pipe 35 and the air is able to go through to the outlet nozzle 9. There is a further force acting in the same direction, that is due to the atmospheric pressure acting in the socket 33 and taking effect on the sealed main body 37 of the valve member 36. Finally the closing member 41 of the valve member 36 forms a piston surface, that is acted upon by the pressure of the compressed air coming in via the control valve 5.

The effective area on which this pressure acts is the perpendicular projection of the valve member 36 at the opening of the pipe 35. The resultant forces so far considered all have the tendency of shifting the valve member 36 on the pipe 35 into an open position, in which the compressed air is let off towards the outlet nozzle 9. The safety valve is for this reason normally open. When however the device is moved very close to a piece of work to be cleaned or or something else with the effect of a baffle, there will be a build-up of back pressure on the outlet side of the valve member 36, that takes effect on the outlet side of the main body 37 and of the closing member 41 and when the resultant force overcomes the forces acting in the opening direc tion, the valve member 36 will be moved on the pipe 35 axially and the passage 34 shut down.By a judicious choice of the size of the valve member 36 and of the driving spring 39 the equilibrium of the forces may be set at a safety value for the back pressure that may just be tolerated for operation of the outlet nozzle 9. When this value for the back pressure is exceeded, the flow of compressed air is cut off. Between the second pipe section 28 of the valve assembly 10 and the pipe 35 in the safety valve 30, the compressed air is deflected through about 90". In a form of the valve assembly 10 that is particularly easy to produce the design may be such that the bore of the second tube section 28 runs through the wall of the valve assembly 10, the opening then produced being plugged by a stopper 43. The stopper 43 is preferably bonded to the valve assembly 10.To ensure specially efficient deflection of the flow it is best for the stopper 43 to have a slanting end face 44 for the purpose of guiding the compressed air towards the safety valve 30.

The outlet nozzle 9 of the device in keeping with the present invention is mounted in an nozzle head 45, that like the shell member 1 discussed earlier herein and the valve assembly 10 is made of synthetic resin. The nozzle head 45 forms the outer limit of the valve assembly 10. It has a hollow neck 46 plugged into the muzzle member 32 of the valve assembly and there is an O-ring 47 between the two to form a seal. The said O-ring is placed between steps on the nozzle head 45 and of the muzzle member 32. In such position it limits the degree to which the nozzle head 45 may be pushed into the muzzle member 32. To form a connection with the rest of the parts of the housing the nozzle head 45 has an extension 48, that joins with the end edge of the shell member 1. Furthermore the outer casing of the nozzle head 45 has a bar 49 fitting onto the outer side of the muzzle member 32.

It will be seen from this that the muzzle member 32 takes up a position between the hollow neck 46 and the bar 49 of the nozzle head 45 so that it is very securely held in place.

In the assembled condition of the nozzle head 45 the hollow neck 46 running into the muzzle member 32 takes the form of a stop for the valve member 36 to limit axial shifting thereof. In this respect a pipe-like rim 50 on the nozzle head 45 plays the part of an abutment, that at the same time keeps the O-ring 47 in place on its outer face. The pipe-like rim 50 has its end resting against the main body 37 of the valve member 36. It forms a housing, that fits round the closing part 41 of the valve member 36 and makes it possible for air to pass round the valve member 36 when the safety valve 30 is open.

Downstream from the pipe-like rim 50 in the nozzle head 45 there is an adjoining axial connection duct 51 running into an opening 52 in the housing with a large diameter. This opening 52 of the housing has the same shape as an outlet nozzle 9 that is fitted into the opening 52 in the housing. The outlet nozzle 9 is joined up by way of a central supply hole 53 with the connecting duct 51. The supply hole 53 becomes narrower towards the end of the outlet nozzle 9 to take the form of a nozzle duct 55 through which the main flow of the compressed air may issue as an alined jet into the outside atmosphere. Furthermore there is at least one leak duct 56 branching out to an outer groove 57 running round the outer face of the outlet nozzle 9 so that air may leak out through this groove 57 around the tip 54 of the outlet nozzle 9 as a side air flow that gives useful effects aerodynamically and keeps dirt out of the outlet nozzle.

At the free end of the nozzle head 45 there is a second handle or grip 58 that is normal to the outlet nozzle 9 and is molded on the nozzle head 45. This handle 58 is generally parallel to the grip part of the shell member 1. It makes it possible for the device to the easily held in both hands. In the interests of economizing in material and keeping down the weight the handle 58 may be fashioned in the form of a hollow body, the cavity therein being marked at 59.

The three housing parts, i.e. the shell member 1, the valve assembly and the nozzle head 45, made of synthetic resin interlock with each other on assem bly, preferably with a force fit. The necessary seal between the housing parts is produced by the O-rings 13, 20 and 47. The housing parts form an enclosure for all the valve elements and the trigger 4 between them so that no complex structures are necessary for fixing the parts in place, and in fact all the parts are simply put loosely in place and moved into their functional positions when the housing is assembled. When this has been done the synthetic resin elements 1, 10 and 45 have holes bored therethrough so that they may be pinned together, suitable locations for the such pins being marked at 60.This design of the housing as part of the invention is characterised by very simple manufacture and a great economy in the use of materials.

The trigger 4 is pivotally mounted on the bar 49 sticking out from the nozzle head 45. In this respect the bar 49 comes to an end in the form of a rounded lip 61. The trigger 4 is L-like with one end of one limb 62 resting against the lip 61, such end tapering in a round form to a point Turning down from this point of engagement the long limb 62 runs at a slant out from the grip part of the shell member 1 to a point 63 at which it is furthest from the grip part and then runs back in the form of shorter limb 64 at an obtuse angle to the shell member 1. The plunger 25 of the control valve 5 is placed about half the way along the long limb 62 and has its rounded end 27 resting on the longer limb 62, that may be pulled inwards for operation of the valve.In the assembled condition the trigger 4 is placed in position between the lip 61 and the edge 65 of the opening in the housing therfor and is retained so that there is no chance of its dropping out. When the trigger 4 is pivoted the short limb 64 is taken up in the inside of the shell member 1, the necessary amount of motion being allowedforthe design of the valve assembly 10. Its first pipe section 15 is spaced sufficiently from the wall of the grip part for there to be room for the short limb 64 of the trigger 4 in the hollow body 3. The trigger 4 and for this reason the control valve 5 may be moved steplessly by hand. As part of a further development of the invention however means may be used to arrest the trigger 4 in one or more positions with varying degrees of opening of the control valve 5 so that air will continuously issue from the device. The arresting means may for example be in the form of a push button.

Claims (15)

1. A hand-held device for directing a jet of compressed air onto a workpiece, comprising a housing with a compressed air inlet port, with an outlet nozzle and with a duct running from the port to the nozzle, a manual control valve in the duct and a safety valve connected in series with the control valve to shut off the flow of air through the duct when back pressure at a point downstream from the safety valve exceeds a given value, said housing being made up of three interlocking synthetic resin parts, namely of an L-like outer shell member, whose first part adjoining an end thereof takes the form of a grip member adapted to be held in the hand and with an opening for the compressed air port, whereas a second part of the said shell member adjoining another end thereof is at about 900 to the said first part and is aligned with the outlet nozzle, of a valve assembly fitting within said shell member and functioning as part of said duct, and of a nozzle head joined to an outlet end of the said valve assembly and having the nozzle head mounted in it, all such synthetic resin parts forming an enclosure for all valve elements of said device, and a trigger for operation of the control valve, and being joined together by pins fitted in holes produced in the said synthetic resin parts when fitted together in the process of assembly.

2. A device as claimed in claim 1 wherein the valve assembly is L-like and comprises an inlet bush, a first pipe section formed on the inlet bush as an axial extension thereof and which opens upstream from a valve member in the valve chamber, a second pipe section running out from said valve chamber downstream from the valve member, said first and second pipe sections being parallel to each other, said second pipe section joining with a valve chamber of the safety valve, which safety valve chamber is set at an angle of roughly 900 to the second pipe section, and a muzzle member axially alined with and on the downstream side of the said safety valve chamber.

3. A device as claimed in claim 2 wherein the valve chamber of the control valve is formed within a bush-like member that is perpendicular to the two pipe sections and forms part of the valve assembly, said bush-like member fitted around a head formed on the inside of the said shell member.

4. A device as claimed in claim 3 wherein said head has a cylindrical socket therein to take up a spring for loading the control valve into a closed position thereof.

5. A device as claimed in any one of claims 2 to 4 wherein the valve chambers project from opposite sides of the valve assembly.

6. A device as claimed in any one of claims 2 to 5 wherein the bore of the second pipe section is elbowed and an opening therefrom through the wall of the second pipe section is closed by a stopper.

7. A device as claimed in claim 6 wherein said stopper is bonded in place in said valve assembly.

8. A device as claimed in any one of claims 1 to 7 wherein said nozzle head has a neck fitting in a muzzle member forming part of the valve assembly, said nozzle head further having a bar on its outside which bar is placed on the outside of the muzzle member.

9. A device as claimed in claim 8 wherein said trigger is pivoted on a rounded lip on the end of the said bar.

10. A device as claimed in any one of the claims 1 to 9 having means for locking said trigger in at least one position in which the control valve is open.

11. A device as claimed in claim 10 wherein said locking means comprises a push button.

12. A device as claimed in any one of claims 1 to 10 wherein said control valve comprises an axially moving valve member whose stroke is limited by its abutting against the nozzle head.

13. A device as claimed in any one of the claims 1 to 11 comprising a handle fixed on a free end of the nozzle head and running normal to the outlet nozzle, said handle furthermore being parallel to the said grip part of the shell member.

14. A device as claimed in claim 1 substantially as described above with reference to the accompanying drawing.

15. A hand-held device for directing a jet of compressed air onto a workpiece, the device comprising a housing having a compressed air inlet port, an outlet nozzle and a duct communicating between the port and the nozzle, a control valve in the duct and a safety valve connected in series with the control valve to shut off the flow of air through the duct when back pressure at a point downstream from the safety valve exceeds a given value, the housing comprising three interlocking components of a plastics material, a first of the components being a shell member, a first part of which at one end has the form of a grip member adapted to be held in the hand and with an opening for the compressed air port, and a second part of which at another end extends at substantially 90" to the said first part and is aligned with the outlet nozzle, a second of the components being a valve assembly fitting within the shell member and functioning as part of said duct, and the third of the components being a nozzle head joined to an outlet end of the valve assembly and having the outlet nozzle mounted therein, the three components forming an enclosure for all valve elements of the device, and a trigger for operation of the control valve, the components being interconnected by connecting members fitted in holes produced in the components and aligned in the process of assembly.