GB1599330A

GB1599330A -

Info

Publication number: GB1599330A
Application number: GB23293/78A
Authority: GB
Original assignee: Festo Maschinenfabrik Gottlieb Stoll Firma
Current assignee: Festo Maschinenfabrik Gottlieb Stoll Firma
Priority date: 1977-08-01
Filing date: 1978-05-26
Publication date: 1981-09-30
Also published as: SE7808266L; CH632940A5; DE2734584A1; IT1097346B; IT7826162A0; SE429412B

Abstract

The compressed air blower gun has a pistol body (1) which has a compressed air inlet, an outlet nozzle, a channel (2) connecting the compressed air inlet with the outlet nozzle and a first valve device (10), which can be actuated from the outside, and which determines the passage through the channel. Furthermore, another second valve device (20) is additionally connected in the channel (2) arranged in series with the first valve device (10) and upstream of this in the direction of flow, the closure element (29) of which second valve device, independently of the closure element (12) of the first valve device (10), permits passage through the channel (2) or blocks it if the pressure in the channel section downstream of the closure element (29) of the second valve device (20) is beneath or above a safety threshold value. With the aid of the second valve device, a reduction in noise, a reduced air consumption and greater safety for the operator are achieved. <IMAGE>

Description

(54) COMPRESSED AIR CLEANING APPARATUS (71) We F E S T O - MASCHINENFABRIK GOTTLIEB STOLL, a Company organised under the laws of the Federal Republic of Germany of Ulmer Strasse 48, 7300 Esslingen a.N, Federal Republic of Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a compressed air cleaning apparatus.

Compressed air cleaners of the kind comprising in a gun body. a compressed air inlet, an ejection nozzle, a channel connecting the compressed air inlet with the ejection nozzle. and a first valve assembly which controls the passage of air through said channel and is operable from externally, for example by means of a release lever, are used in industry in order to clean tools and components during manufacture for example metal machining, to blow the chips off, or to blow out bore holes and the like in various devices.

According to the present invention there is provided a compressed air cleaning apparatus comprising an inlet for compressed air, communicating through a channel with an ejection nozzle, a first valve assembly which is operable from externally of the apparatus and which controls the passage of compressed air through the channel, a second valve assembly mounted in the channel in tandem with the first valve assembly said second valve assembly having a valve closing member controlling the passage of air through the channel independently of a closing member of the first valve assembly such that the channel is maintained open under normal operating conditions and closed when the air pressure in the channel section downstream of the valve closing member exceeds a predetermined limiting value.

Preferably the valve closing member of the second valve assembly which is adjustable relative to its valve seat, defines a piston surface on each of two opposite sides, one of which piston surfaces is exposed to air pressure in the channel in the direction of air flow, and the other of which is exposed to air pressure in a direction opposite to the direction of air flow.

The advantages of the new design are that the noise level at the discharge-end is reduced in proportion to the reduction of the operating pressure and that the sound pressure level in general has been lowered by up to 50%. In addition to this it is considered an advantage of the new design that as a result of using a lower pressure the consumption of compressed air has been lowered by approximately 40% so that operations are more economical.

Apart from the above the operator is working under much safer conditions. On the one hand, he cannot inadvertently cause injuries to his body (the second valve assembly closes the passage through the gun as soon as the pressure at the ejection nozzle becomes excessive, for example when the gun is directed against a baffle board or approaches a wall or other surface - even the operators free hand - too closely). On the other hand, a curtain of compressed air is formed when an object is blown out, and this prevents any chips or the like from causing injuries when thrown in the direction towards the operator. Similarly the danger of chips or the like damaging sensitive machine parts or measuring instruments when blown off at a dangerously high speed, is eliminated by the design characteristics of the new gun and as a result of working at a reduced pressure which may, for example, be adjusted to a maximum limiting value of 2.5 bar.

In the drawing a number of embodiments of the invention, are shown. In particular, Figure 1 is a side view of a compressed air cleaner shown in an axial section, Figure 2 depicts a detail "A" of the embodiment according to Figure 1 again in an axial section and side view, at an enlarged scale; Figure 3 is a variant of the embodiment shown in Figure 1, again in an axial section, in side view; Figure 4 shows a number of valve elements illustrating a valve which may be incorporated to the advantage of the compressed air cleaner, the elements being shown in perspective in an exploded presen tation; Figure 5 shows the valve according to Figure 4 in the assembled state in a side view, part of it being in section. The scale is again enlarged.

With the embodiment according to Figure 1 and Figure 2, the gun body 1 of the new compressed air cleaner comprises a channel 2 for the passage of the compressed air, and it may for example be a casting manufactured in a known manner. The channel 2 accommodates two valve assemblies 10, 20 for the control of the compressed air; they are arranged in tandem in such a manner that the compressed air has to pass through both assemblies consecutively, whereby the closure of one of the two valves suffices to prevent the air from passing through the blow gun.

The valve assembly 10 is designed for manual operation through the operator.

The valve components are shown in Figure 2 at an enlarged scale. This assembly comprises a valve seat 11 which is preferably conical in shape, and a valve closing element 12 which is adjustable relative to the valve seat 11, as indicated by the arrow 12a. This valve closing element 12 has the shape of a truncated cone forming a plug at the end of an operating rod 14 which extends through the gun body 1 (see Figure 1) and is longitudinally adjustable relative to the latter. To control the valve seat, the operator uses a release lever 15 which is pivoted at point 15a on the gun body 1, and interacts with the lower end of the operating rod 14 (Figure 1) both parts together constituting the control unit: the rod is displaced when the operator picking up the gun, depresses the lever. The valve closing element 12 is resiliently pressed against its seat by the action of a compression spring 16 which is accommodated in the gun body 1 and acts at the upper end of the valve closing element 12 while its other end is supported against a ring 18 which is fixed to the cylindrical wall 19 which surrounds it. This wall 19 is formed by a wider section of the channel extending through the gun body (See Figures 1 and 2): the recess defined by this wider section or rather the cylindrical wall 19, may for example be formed by providing the gun body with a corresponding, transverse, bore, but there are alternative methods of manufacture, which are explained further below. Needless to say, the ring 18 may be replaced by any other fixed stop capable of supporting the spring 16.

The cylindrical wall moreover encloses the elements of an additional valve assembly 20.

This valve assembly 20 incorporates a casting 21 with a tubular extension 21a projecting towards the other valve assembly and comprising a continuous, axial bore which connects with the channel 2 through the gun body 1 (Figure 2). This tubular extension of the casting 21 has a cylindrical outer wall 22 which interacts with other elements of the valve assembly 20 and is concentric with the internal wall 19, forming an annular space between them. A valve closing ring 25, located inside the annular space between the cylindrical walls 19 and 22 seals the gap between the walls 19 and 22 (Figure 2). This closing ring 25 comprises a disc like annular main body 26 with a central bore, and a flexible sealing lip 28 around its outer circumference. A sealing plug 29 for the valve closing ring 25 is located centrally relative to the open space, its conical surface being capable of resting against the end section of the rim surrounding the channel of said extension of the casting 21, so that it constitutes a valve seat. The internal diameter of the passage through the closing ring 25 is such that the ring fits around the cylindrical outer surface of the tubular extension of the casting 21, while the sealing lip 28 is in surface contact with the cylindrical wall 19, so that the closing ring 25 may move along the cylindrical walls 19 and 22 in the longitudinal direction of the tubular extension of the casting 21. In the course of this linear movement the sealing plug 29 of the closing ring 25 is pressed against the end of the tubular extension 21a, preventing air from passing through this extension.

In order to protect the user of the compressed air cleaner 10 against hazards due to excessive air pressure, the displacement of the closing ring 25 has the functions of an equalising movement, creating equilibrium conditions between a spring load which acts on the closing element 25, and air pressures acting against the piston areas of this closing element. In particular. a compression spring 30 is provided for the loading of the closing member 25, which causes the latter to move relative to the end of the tubular extension of the casting 21.

The forces interacting with the spring force comprise upstream air pressure which is effective at the end of the bore through the casting 21 and acts against the valve closing element 25, air pressure downstream of the latter acting against an annular piston surface of the valve closing element 25 in a direction opposite to the direction of air flow, and environmental atmospheric pressure acting against another annular piston surface of the valve closing element 25 in the direction of air flow.

The environmental atmospheric pressure is directed into a chamber inside the gun body 1, passing through a channel 35 which extends from externally of the gun body 1 to the cylindrical wall 19 (Figures 1 and 2) and contributes to maintaining conditions of atmospheric pressure inside a chamber which is defined by the casting 21, the upper annular surface of the closing element 25, and the cylindrical wall 19. In this manner the air pressure acting against the area of the closing element 25 between the walls 19 and 22, creates a load which acts in the same direction as the compression spring 30, preventing the closing ring 25 from moving towards the seat.

An additional force acting against a movement of the closing ring 25 towards the seat, is the upstream air pressure, which is present at the end of the bore through the casting 21, and is directed against an area on the closing ring 25 which is defined by the plug 29 or rather its surface relative to the bore through the casting 21. This area corresponds to the projection of the plug surface in the closing surface of the bore through the extension 21a of the casting 21.

Finally, the downstream air pressure which is present at the end of the bore through the extension 21a, acts against the annular piston surface defined by the internal diameter of the cylindrical wall 19. Thus it becomes evident that the forces created by the pressures in the pneumatic system, which act against the piston surfaces of the closing ring 25, and by the effects of the compression spring 30, cause the closing ring 25 to reciprocate between a position at the end of the tubular extension (when the pressure of the compressed air streaming through the channel 2 is higher in the downstream direction of the ring 25, exceeding a given limiting value) and a position where the ring is lifted off (when this pressure is below the predetermined limiting safety pressure). If then the operator actuates the lever 15 opening the valve assembly 10 so that compressed air may pass through the channel 2 of the compressed air cleaner, the equilibrium of forces which acts at the closing ring 25 will normally be such that the passage for the compressed air is opened so that compressed air may be delivered for whatever operating purpose.

Should the operator handle the gun ineffi ciently, so that the nozzle approaches an object too closely - this may, for example, be his free hand - the danger of injury is averted by a back pressure being built up in the channel 2, downstream of the two valve assemblies 10 and 20. As a result of this pressure build-up, the forces trying to press the valve closing ring 25 against its seat will increase, closing the channel 2. The back pressure in the channel 2 at which this reversal takes place is preferably such that it conforms to the regulations of industrial operating safety. It follows from the above that the operator handling the gun of the compressed air cleaner according to the invention is efficiently protected against hazards caused by excessive pneumatic pressures.

The casting 21 comprises means to ensure that the chambers and passages in the gun body are reliably sealed and that no compressed air can escape unintentionally. For this purpose an O-ring has been provided which separates the bore through the casting 21 from the chamber which receives atmospheric pressure through the channel 35. A second O-ring 38 (Figures 1 and 2) seals the outer end of the casting 21 preventing compressed air from escaping from the assembly. In order to ensure that the desired quantity of compressed air may pass through the channel 2 in the gun body 1, the casting is provided with a continuous groove around its periphery, enabling air to reach the bores through the casting. The advantage of this circumferential groove is that a threaded locking pin 39 may be used for holding the casting 21 in its correct position inside the gun body, the threaded pin projecting through the gun body wall.

Figure 3 shows a variant to the embodiment described above, presenting a compressed air cleaner 40 in which the two valve assemblies may be arranged in the reversed order. The gun body 41 corresponds to the gun body 1 according to Figure 1. The embodiment depicted in the Figures 1 and 2 differs from that shown in Figure 3 in so far as the valve assembly 42, which corresponds to the valve assembly 10 in Figure 1, comprises means by the aid of which the lift of the valve closing element 43 (corresponds to 12) is limited. This lift limiter enables the quantity of compressed air to be regulated and controlled which is delivered by the manually operated valve assembly 42. This offers certain advantages for the pneumatic cleaning gun 40, depending on its service conditions. To limit the lift as required, a pin 44 is used which extends upwards and is movable relative to an adjustable threaded element 45. Additional differences between the embodiment according to Figures 1 and 2 on the one hand, and Figure 3 on the other, are due to the different design and arrangement of the second valve assembly 51. With this valve assembly, the cylindrical wall 46 (this corresponds to the cylindrical wall 19) is constituted by a threaded, sleeve shaped, member 47. One end of this threaded sleeve- like member 47 engages with an external thread on the gun body, so that the substantially cylindrical internal wall 46 of the threaded sleeve element 47 surrounds an end section of the gun body which is designed in such a manner that it constitutes the element 48 (this corresponds to the casting 21). The opposite end of the sleeve element 47 is provided with an internal thread which corresponds to the thread of a nozzle section capable of directing the compressed air stream as required (see Figure 1). The spring 49 used with the design according to Figure 3 may be somewhat different from the spring 30 shown in Figure 2, whereas the closing ring 50 is identical with the closing ring 25 described with the first embodiment of the invention.

The channel 52 corresponds to the channel 35 of the variant according to Figures 1 and 2, and the plug 53 corresponds to the plug 29 used with the above described variant. 54 is a release lever corresponding to the part 15; 55 is an operating bar which corresponds to part 14, 56 is the channel which corresponds to the channel 2 through the assembly according to Figures 1 and 2. The functions of the valve assembly 51 in Figure 3, which reacts to pressures, are the same as the functions of the valve assembly 20 in the design shown in the Figures 1 and 2. This means that the closing ring 50 assumes its closing position when the back pressure in the section downstream of the valve increases, thus averting the danger of excessive air pressures being directed towards the user of the pneumatic cleaning device.

The present invention moreover provides for an alternative form of the valve assemblies 20 and 51 described with the compressed air cleaners according to Figures 1, 2 and 3, respectively, which may be assembled with existing guns used with other industrial applications where pressure control is considered important. The design of this alternative assembly is such that only a slight modification of the existing assembly is necessary of the valve unit serving for pressure control to satisfy the current industrial safety regulations. A valve assembly for pressure regulation 60 of this kind is shown in Figures 4 and 5. According to this presentation the valve assembly 60 (which corresponds to the valve assembly 20) comprises a sleeve like member 61 and a casting 62, which are substantially interacting as shown in Figure 5 in relation to the sleeve member 47 and casting 48 discussed above.

With this alternative assembly, the casting 62 has an external thread at either end, one group of thread turns interacting with the sleeve 61 while the other group of threads are formed in such a manner that they replace a discharge nozzle element which would normally be provided at the gun body of an existing compressed air cleaner. In order to modify an existing gun and thus to obtain the advantages of the present invention, all that is necessary is to exchange the existing nozzle element for a valve assembly 60 according to the Figures 4 and 5. 63 corresponds to the channel 35 of the variant shown in Figures 1 and 2, 64 corresponds to the cylindrical wall 19, the closing plug 65 corresponds to the plug 29 of the variant shown in Figures 1 and 2, the tubular extension 66 corresponds to part 22, the closing ring 67 corresponds to the ring 25, the lip 68 corresponds to the lip 28, of the variant shown in the Figures 1 and 2, and the spring 69 shown in the Figures 4 and 5 corresponds to the spring 30 of the variant according to Figures 1 and 2.

WHAT WE CLAIM IS: 1. A compressed air cleaning apparatus comprising an inlet for compressed air, communicating through a channel with an ejection nozzle, a first valve assembly which is operable from externally of the apparatus and which controls the passage of compressed air through the channel, a second valve assembly mounted in the channel in tandem with the first valve assembly said second valve assembly having a valve closing member controlling the passage of air through the channel independently of a closing member of the first valve assembly such that the channel is maintained open under normal operating conditions and closed when the air pressure in the channel section downstream of the valve closing member exceeds a predetermined limiting value.

2. Apparatus according to Claim 1, wherein the valve closing member of the second valve assembly is of conical configuration.

3. Apparatus according to Claim 1 or 2 wherein the valve closing member of the second valve assembly which is adjustable relative to its valve seat, defines a piston surface on each of two opposite sides, one of which piston surfaces is exposed to air pressure in the channel in the direction of air flow, and the other of which is exposed to air pressure in the channel in a direction opposite to the direction of air flow.

4. Apparatus according to Claim 3, wherein the channel has a section which accommodates the second valve assembly and a fixed member associated with the channel defines a bore which is of a smaller diameter than said channel section, the valve seat being defined at the mouth of said bore and the valve closing member being accommodated in said section downstream of the fixed member and the valve seat.

5. Apparatus according to Claim 4, wherein the valve closing member of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. wall 19) is constituted by a threaded, sleeve shaped, member 47. One end of this threaded sleeve- like member 47 engages with an external thread on the gun body, so that the substantially cylindrical internal wall 46 of the threaded sleeve element 47 surrounds an end section of the gun body which is designed in such a manner that it constitutes the element 48 (this corresponds to the casting 21). The opposite end of the sleeve element 47 is provided with an internal thread which corresponds to the thread of a nozzle section capable of directing the compressed air stream as required (see Figure 1). The spring 49 used with the design according to Figure 3 may be somewhat different from the spring 30 shown in Figure 2, whereas the closing ring 50 is identical with the closing ring 25 described with the first embodiment of the invention. The channel 52 corresponds to the channel 35 of the variant according to Figures 1 and 2, and the plug 53 corresponds to the plug 29 used with the above described variant. 54 is a release lever corresponding to the part 15; 55 is an operating bar which corresponds to part 14, 56 is the channel which corresponds to the channel 2 through the assembly according to Figures 1 and 2. The functions of the valve assembly 51 in Figure 3, which reacts to pressures, are the same as the functions of the valve assembly 20 in the design shown in the Figures 1 and 2. This means that the closing ring 50 assumes its closing position when the back pressure in the section downstream of the valve increases, thus averting the danger of excessive air pressures being directed towards the user of the pneumatic cleaning device. The present invention moreover provides for an alternative form of the valve assemblies 20 and 51 described with the compressed air cleaners according to Figures 1, 2 and 3, respectively, which may be assembled with existing guns used with other industrial applications where pressure control is considered important. The design of this alternative assembly is such that only a slight modification of the existing assembly is necessary of the valve unit serving for pressure control to satisfy the current industrial safety regulations. A valve assembly for pressure regulation 60 of this kind is shown in Figures 4 and 5. According to this presentation the valve assembly 60 (which corresponds to the valve assembly 20) comprises a sleeve like member 61 and a casting 62, which are substantially interacting as shown in Figure 5 in relation to the sleeve member 47 and casting 48 discussed above. With this alternative assembly, the casting 62 has an external thread at either end, one group of thread turns interacting with the sleeve 61 while the other group of threads are formed in such a manner that they replace a discharge nozzle element which would normally be provided at the gun body of an existing compressed air cleaner. In order to modify an existing gun and thus to obtain the advantages of the present invention, all that is necessary is to exchange the existing nozzle element for a valve assembly 60 according to the Figures 4 and 5. 63 corresponds to the channel 35 of the variant shown in Figures 1 and 2, 64 corresponds to the cylindrical wall 19, the closing plug 65 corresponds to the plug 29 of the variant shown in Figures 1 and 2, the tubular extension 66 corresponds to part 22, the closing ring 67 corresponds to the ring 25, the lip 68 corresponds to the lip 28, of the variant shown in the Figures 1 and 2, and the spring 69 shown in the Figures 4 and 5 corresponds to the spring 30 of the variant according to Figures 1 and 2. WHAT WE CLAIM IS:

1. A compressed air cleaning apparatus comprising an inlet for compressed air, communicating through a channel with an ejection nozzle, a first valve assembly which is operable from externally of the apparatus and which controls the passage of compressed air through the channel, a second valve assembly mounted in the channel in tandem with the first valve assembly said second valve assembly having a valve closing member controlling the passage of air through the channel independently of a closing member of the first valve assembly such that the channel is maintained open under normal operating conditions and closed when the air pressure in the channel section downstream of the valve closing member exceeds a predetermined limiting value.

5. Apparatus according to Claim 4, wherein the valve closing member of the

second valve assembly comprises a valve closing ring which is reciprocable in said channel section and extends between an extension of the fixed member and an internal wall of the channel, sealing at its edges; and a valve plug is connected with the valve closing ring, a tip of the plug projecting into said bore of the fixed member when the valve closing member assumes its closing position.

6. Apparatus according to any of Claims 3 to 5, wherein means connects said one piston surface with the atmosphere and means is provided for biasing the valve closing member of the second valve assembly off its seat.

7. Apparatus according to any of the preceding claims wherein the second valve assembly in the direction of air flow is located upstream of the first valve assembly.

8. Apparatus according to any of the preceding claims wherein the valve closing member of the first valve assembly is arranged to be lifted off its seat by the action of a pin which is actuated by the operation of a release lever and which is engaged by one end of, to be biased in the opposite direction. by a spring, the other end of the spring being supported against a fixed ring located downstream of the second valve assembly.

9. Apparatus according to any of the preceding claims, wherein said predetermined limiting value is adjustable.

10. A compressed air cleaning apparatus substantially as hereinbefore described with reference to the accompanying drawings.