Background of the invention

The invention relates to an impact device for cleaning of surfaces, such as heat delivery surfaces, the impact device comprising

- a body,

- a hammer piece which is adapted to move back and forth, supported by the body, between a first extreme position and a second extreme positions, and which comprises a first end surface and a second end surface which is opposite in relation to the first end surface,

- an anvil unit which is adapted to receive the impact energy of the hammer piece as the hammer piece hits a stopping surface of the anvil unit,

- drive means for moving the hammer piece back and forth, supported the body, between the first extreme position where the second end surface of the hammer piece is at the maximum distance from the stopping surface of the anvil unit, and the second extreme position where the hammer piece strikes the anvil unit, for providing impact energy to the hammer piece, and

- a spring which is adapted to transfer impact energy from the hammer piece to the anvil unit.

At the second extreme position, where the hammer piece strikes the anvil unit, the hammer piece, naturally, is in contact with the stopping surface of the anvil unit.

An impact device of the aforementioned type is specifically intended to be used for cleaning heat delivery surfaces, such as boiler faces, convection pack ets and heat exchangers from soot and other dirt that gathers on the heat delivery surfaces during use.

Such an impact device is known from EP publication 2643104. This known impact device comprises a spring whose spring force is used to strike a hammer piece towards an anvil part ln applications requiring the hammer piece to strike the anvil part with high impact energy for efficient cleaning of the heat delivery surface, the spring force of the spring needs to be high, which in turn means that the spring has to be large. A large spring naturally adds to the size and weight of the impact device. This known impact device does not in practice allow wide-range adjustment of the impact force, because in practice the impact force is determined by the spring force of the spring, which is spring-specific and limits adjusting the impact force to within the scope of the selected spring. Brief description of the invention

lt is therefore an object of the invention to develop a new impact de vice which removes the usage limitations of known impact devices and allows easy adjustment of the operation of the impact device with the impact force and impact frequency in mind. To achieve this goal, the impact device of the invention is characterised in that

- the body comprises a first gas space defining an impact pressure chamber, and a second gas space defining a return motion pressure chamber, whereby the first end surface of the hammer piece abuts towards the first gas space, and the second end surface of the hammer piece abuts towards the second gas space,

- the drive means for moving the hammer piece from the first extreme position to the second extreme position comprise a source of pressurised gas which is adapted to pressurise a gas pressure accumulator which is, through a first valve, adapted to be charged with gas pressure by means of gas from the pressurised gas source through a feed line, from which gas pressure accumulator gas is adapted to be discharged through a second valve to the first gas space so that the force exerted by the gas pressure of the first gas space onto the hammer piece is higher than the force in the opposite direction exerted by the gas pres- sure of the second gas space onto the hammer piece, the drive means additionally comprising gas removal means for removing gas pressure from the second gas space as the hammer piece is moving towards the anvil part, the gas removal means comprising a gas removal line, and

- the drive means for moving the hammer piece from the second ex- treme position back to the first extreme position comprise adjusting means of the gas pressure and force to arrange the force exerted by the gas pressure in the second gas space on the hammer piece stronger that the force in the opposite di rection exerted by the gas pressure in the first gas space onto the hammer piece, whereby the first gas space is associated with a gas removal channel to lead gas away from the first gas space as the hammer piece is moving from the second ex treme position to the first extreme position. The gas pressure and force adjusting means advantageously comprise gas feeding means to feed gas to the second gas space. The gas pressure and force adjusting means advantageously comprise gas feeding means to feed gas to the second gas space because such gas pressure and force adjusting means are simple to implement with the same pressurised gas source by means of which the hammer piece is moved from the first extreme posi tion to the second extreme position.

The hammer piece is advantageously a piston-like member, and the body of the impact device defines a cylindrical space for the hammer piece, which accommodates the first gas space and the second gas space. Such a impact device of the piston/cylinder type is simple as regards its manufacture.

The gas feeding means are advantageously adapted to feed gas to the second gas space through a third valve, whereby the gas feeding means are adapted to receive gas pressure from the same pressurised gas source as the gas pressure accumulator.

The gas pressure accumulator of the impact device advantageously surrounds the cylindrical space. This allows the impact device to be small in size, which is important at sites that have little space for the impact device ln such a case, the gas pressure accumulator is also a tubular space that surrounds the cy lindrical space. The aforementioned allows the simple manufacture of the impact device.

An essential feature of the invention is that the back and forth trans ferring of the hammer piece is based on the transferring being taken care of by gas pressure whereby springs may be parted with for the purpose of transferring the hammer piece.

Preferred embodiments of the invention are disclosed in the attached dependent claims.

The biggest advantage of the impact device of the invention is that the impact force and frequency are simple and extensive to adjust ln addition, the use of springs to transfer the hammer piece may be stopped, whereby the impact device may be made lightweight. A further advantage is that is has no breaking springs.

Brief description of the drawings

The invention is now described in closer detail by means of a pre ferred embodiment, with reference to the accompanying drawings in which

Figure 1 shows a first operational position of the impact device, in which the hammer piece of the impact device is at a first extreme position,

Figure 2 shows a first intermediate position of the impact device, in which the hammer piece of the impact device is moving towards a second ex treme position of the impact device, Figure 3 shows a second operational position of the impact device, in which the hammer piece of the impact device is very close to the anvil part of an anvil unit,

Figure 4 shows a second intermediate position of the impact device, in which the hammer piece of the impact device is moving back towards its first ex treme position, and

Figure 5 is a schematic view of the impact device of Figures 1 to 4.

Detailed description of the invention

The impact device of Figures 1 to 4 comprises a body 1 supported by which a hammer piece 8 is adapted transferable back and forth between a first ex treme position and a second extreme position. Figures 1 to 4 show different usage positions of the impact device ln the usage position of Figure 1, the hammer piece 8 is in the first extreme position, and in the usage position of Figure 3 the hammer piece is very close to its second extreme position. Figures 2 and 4 show different two intermediate positions of the hammer device.

The hammer piece 8 of the impact device is a piston-like member, which comprises a first end surface 102 and a second end surface 103, which is opposite to the first end surface. The body 1 of the impact device is formed cylin drical whereby the hammer piece 8 and body 1 form a cylinder/piston unit. The body 1 defines a cylindrical space which accommodates a first gas space 100 and a second gas space 101, disposed on opposite sides of the hammer piece 8. The first gas space 100 is defined by a first end surface 102 of the hammer piece 8 and the cylindrical space of the body 1; the second gas space 101 is defined by a sec ond end surface 103 of the hammer piece 8, which is opposite in relation to the first end surface 102, and the cylindrical space of the body 1.

An anvil unit 7 of the impact device comprises an anvil body 7a and an anvil part 7b adapted to be supported by the body 1 of the impact device. The an vil body 7a has a flange 7c to which a first end 4 of the impact device body 1 is fas tened by means of a plurality of longitudinal elements 3 which allow the body 1 to flex in relation fo the anvil body 7a, preferably in relation to the longitudinal di rection of the anvil body. Flexing is implemented by means of springs (not shown) attached to the elements 3. For reasons of simplicity, the flange 7c and longitudi nal elements 3 are shown in Figure 1, only. The anvil part 7b is adapted for trans fer supported by the body 1 and for receiving impact energy from the hammer piece 8 when the second end surface 103 of the hammer piece hits the stopping surface 107 of the anvil part 7b. The moving of the anvil part 7b in the body 1 is minor, a few millimetres, for example.

Between the anvil part 7b and anvil body 7a there is a spring 6 which is preferably formed, as in the figures, of two or more cup springs setting against each other (the figures have two cup springs against each other). The spring 6 transfers impact force from the anvil part 7b to the anvil body 7a. When the anvil part 7b, due to the strike by the hammer piece 8, moves supported by the body 1 towards the spring 6, the latter flexes. Because the compression of the spring 7 is minor, the moving of the anvil part 7b in the body is also minor. The entire impact energy received by the anvil part 7b is preferably transferred to the anvil body 7a by means of the spring 6, whereby the anvil part 7b does not directly contact the anvil body 7a. lt is feasible that the anvil part 7b hits the anvil body 7a in a direct contact, but the force of this hit is only a fraction of the force that the spring 6 transfers from the anvil part 7b to the anvil body 7a.

The volumes of the first gas space 100 and second gas space 101 are defined by the position of the hammer piece 8 in the body 1, cf. Figures 1 to 4. When the hammer piece 8 is in the position of Figure 1 the second end surface 103 of the hammer piece 8 is at the maximum distance SI from the stopping sur face 107 of the anvil part 7b, the volume of the second gas space 101 is at its larg est, and the volume of the first gas space 100 is very small or zero; and when the hammer piece 8 is in the position of Figure 3, its second end surface 103 contacts or nearly contacts the stopping surface 107 of the anvil part 7b, whereby the vol ume of the first gas space 100 is at its largest, ad the volume of the second gas space 101 is very small or zero ln the intermediate positions of the hammer piece 8, shown in Figures 2 and 4, the volumes of the first gas space 100 and second gas space 101 are roughly of the same size ln Figure 2, the hammer piece 8 is moving towards the anvil 7, and in Figure 4 the hammer piece is moving away from the anvil.

The back and forth movement of the hammer piece 8 of the impact de vice is established by drive means which comprise a pressurised gas source 104 and gas feed lines with their valves, which is described next.

The impact energy to move the hammer piece 8 from the position of Figure 1 to the position of Figure 3 is established by abruptly pressurising the first gas space 100 by the pressure P2, as a result of which the hammer piece 8 moves and strikes towards the anvil part 7b. The gas space 100 is preferably pressurised by air, but another gas or gas mixture suitable for the usage may be used instead of air. One may say that the first gas space 100 defines the impact pressure chamber. Said pressure P2 is obtained into the first gas space 100 from the gas pressure accumulator 105 which is pressurised by the pressure PI, such as 4 to 6 bar. The gas pressure accumulator 105 surrounds the body 1 of the im pact device in a tubular or cylindrical manner. The reference number 110 denotes connecting channels related to the valve 109, between the gas pressure accumula tor 105 and the first gas space 100. Gas may be led from the gas pressure accumu lator 105 through the connecting channels 110 to the first gas space 100. The gas pressure accumulator 105 is charged before it is emptied to said pressure PI by gas coming from the pressurised gas source 104 which is conducted to the gas pressure accumulator through a feed line 115 and connecting channels 110 asso ciated with the first valve 109. When the gas pressure accumulator 105 is being charged, the closing part of the first valve 109 is moved to the left by the gas pres sure in the feed line 115 towards the hammer piece 8, whereby the connecting channels 110 between the gas pressure accumulator 105 and the first gas space 100 close (the figures do not show the position of the first valve 109 when its closing part is on the left), and gas can flow to the gas pressure accumulator. The closing part of the first valve 109 is preferably a closing member made of rubber, which by the effect of the pressure (the pressure is approximately 4 bar or more) from the pressurised gas source 104 moves from the position of Figure 1 towards the hammer piece 8. lf the pressure in the first gas space 100 is higher than the gas pressure in the feed line 115, the closing part of the first valve 109 is on the right.

Reference number 108 denotes a pressure removal channel, which connects the first gas space 100 to outside air. The pressure removal channel 108 is small in size so that gas would not leave to any greater extent through it from the first gas space 100 when the hammer piece 8 is moving towards the anvil unit 7. lf gas could exit the first gas space 100 to a great extent and fast to the pressure removal channel 108 and the atmosphere, the impact force of the hammer piece 8 would be weak as it strikes the anvil 7. The purpose of the pressure removal channel 108 is to remove gas from the gas space to the atmosphere at the time the hammer piece 8 is moved to the right towards the second end 5 of the body, whereby the pressure in the first gas space 100 is lower than the pressure in the second gas space 101. The pressure removal channel 108 is preferably made in a second end flange 2 of the body. When it is desired that the hammer piece 8 is struck towards the anvil unit 7, the pressure PI in the gas pressure accumulator 105 is released through the connecting channels 110 associated with the first valve 109 to the gas space 100 whereby this acquires the pressure P2. The pressure PI on the gas pressure accumulator 105 may be referred to as charge pressure until the pressure in the gas pressure accumulator is released. The pressure PI in the gas pressure accu mulator 105 is released by decreasing the pressure in the feed line 115, which re sults in that the closing part of the first valve 109 shifts, due to the gas pressure stored in the gas pressure accumulator 105, away from the hammer piece 8, that is, to the right to the closing position of Figure 1, whereby at the same time or with a desired delay gas can flow from the gas pressure accumulator 105 through the connecting channels 110 to the first gas space 100. Before the hammer piece 8 moves towards the anvil 7, the pressure P3 of the gas in the second gas space 101 is typically approximately 1 bar. The pressure difference P1-P3 between the first gas space 100 and second gas space 101 in practise achieves the moving of the hammer piece 8 and its striking towards the anvil part 7b.

Figure 2 illustrates the moving of the hammer piece 8 to the left to wards the anvil unit 7. When the hammer piece 8 moves towards the anvil unit 7, the volume of the first gas space 100 increases and pressure decreases. While the hammer piece 8 moves to the left, gas can escape from the second gas space 101 through a gas removal line 106 so that the pressure in the second gas space 101 would not rise so that it would prevent the fast and fierce moving of the hammer piece 8 towards the anvil part 7b and so that the impact energy of the hammer piece would not be lost, to any detrimental amount anyway, before the hammer piece hits the anvil part. The acceleration of the hammer piece 8 in the body 1 may typically be 6 to 10 m/s ² . Gas exits the gas removal line 106 through a third valve 111. The third valve 111 is a quick exhaust valve which allows quick release of the gas from the line 106. The type of the third valve 111 is a three-way valve. The third valve 111 is opened just before the release of the gas pressure accumu lator 105 is carried out, whereby the gas release from the gas space 101 will be fast.

ln Figure 3, the hammer piece 8 has struck the anvil part 7b and con veyed its impact energy through the spring 6 to the anvil body 7a, and is about to start its moving away from the anvil part 7b (to the right) towards the second end 5 of the body 1, this end 5 having the end flange 2. To move the hammer piece 8 towards the second end 5 of the body 1, a gas pressure is directed to the second gas space 101, which exceeds the gas pressure prevailing in the first gas chamber 100. Figure 4 illustrates the moving of the hammer piece 8 away from the anvil part 7b towards the second end 5 of the body 1. The gas pressure required for the moving is obtained from the pressurised gas source 104 through a pressure re duction component 112 and the third valve 111, from which gas is fed to the gas removal line 106 from which gas passes on to the second gas space 101. The pres sure reduction component 112 is advantageously a pressure reduction valve. Moving the hammer piece 8 towards the first extreme position, shown in Figure 1, does not require a high gas pressure because the pressure in the first gas space 100 is low due to the fact that gas has escaped from it through the pressure re moval channel 108; the pressure required for moving may be, for example, 1.5 to 2 bar. The pressure reduction component 112 takes care of lowering the pressure supplied by the pressurised gas source 104 to the second gas source 101 to a de sired value.

So, the gas pressure for returning the hammer piece 8 from the posi tion of Figure 3 to the position of Figure 1 is acquired through the same gas re moval line 106 as used to remove gas from the second gas space 101.

The operation of the first valve 109 and the associated connecting channels 110 is therefore the following: when the closing member of the first valve 109 is on the right, gas can flow from the gas pressure accumulator 105 to the first space 100 but not to the feed pipe 115 (whereby impact force for the hammer piece 8 is achieved); when the closing member of the first valve 109 is on the left, gas can flow from the feed line 115 to the gas pressure accumulator 105 but not to the first space 100 (whereby the gas pressure accumulator 105 is charged to the charging pressure).

The return motion time of the hammer piece 8 is set as required by adjusting the pressure provided by the pressure reduction component 112. The recommended return motion time may be approximately 1 s. While the hammer piece 8 is moving towards the second end 5 of the impact device, gas can escape from the impact device through the pressure removal channel 108 associated with the first gas space 100. Because the second gas space 101, or in fact the gas pressure within, acts to return the hammer piece 8 back to the first extreme posi tion, the second gas space 101 determines the return motion pressure chamber.

The reference number 113 denotes a fourth valve for feeding gas from the pressurised gas source 104 optionally to the gas pressure accumulator 105 through the feed line 115, or to the second gas space 101 through the gas removal line 106. The fourth valve 113, which is advantageously a three-way valve, is a control valve of the impact device (a pressure control valve). The fourth valve 113 makes sure that the first valve 109 stays in the position of Figure 1 during a strike.

A fifth valve 114 is adapted in the feed line 115 to adjust the delay. The fifth valve 114 is advantageously a throttle check valve which is adapted to adjust the pressure prevailing in the feed line 115 so that the third valve 111 opens be fore the first valve 109. The fifth valve 114 provides resistance for the gas flow from the first valve 109 to the fourth valve 113 but allows unrestricted or power ful gas flow from the fourth valve 113 to the first valve 109. The fifth valve 114 slows down the release of the gas pressure in the feed line 115 to the surround ings, that is, the atmosphere.

The impact device includes a control unit 120 which control the opera tion of the valve 113, at least. The control unit may additionally be adapted to control one or more of the valves 109, 111, 112, and 114 so that the desired oper ation of the impact device is achieved. At least part of the aforementioned valves may also be manually operated. Desired operation means that the impact energy to the anvil 7 and the impact frequency of the impact device is as required so that it fits the usage environment where it is used.

ln the above the invention is one described by means of one preferred embodiment, and it is therefore pointed out that the details of the invention may be implemented in various ways within the scope of the attached claims. So, for example, the gas accumulator 105 need not be formed of a tubular space which surrounds a cylindrical space defined by the body 1, but the gas pressure accumu lator may be a space attached to the body and not surrounding the cylindrical space: the gas pressure accumulator may even be separate from the body lt is, however, most recommended that the gas pressure accumulator surrounds the body 1 and cylindrical space of the impact device, forming a tubular pressure ac cumulator, because such a gas pressure accumulator only takes up little space and does not much add to the space the impact device requires. A small impact device is easy to install for different uses lt is set forth in the above that the same pres surised gas source 104 is included in the drive means for moving the hammer piece from both the first extreme position to the second extreme position and vice versa from the second extreme position to the first extreme position. This is most appropriate, but it is feasible that the same pressurised gas source is not used for said moving of the hammer piece, whereby the first pressurised gas source is used to move the hammer piece from the first extreme position to the second ex treme position and the second pressurised gas source is used to move the ham mer piece from the second extreme position to the first extreme position. The lat ter arrangement is, however, more complex than the arrangement set forth ln ac cordance with this, it is also feasible that the same gas removal line 106 is not used to feed gas to the second gas space 101 as the one used from removing gas from the second gas space. Using the same gas removal line 106 is, however, rec ommended when the purpose is to avoid unnecessarily increasing the number of components in the impact device and to keep the structure of the impact device simple lt is additionally feasible that the moving of the hammer piece 8 towards the second end 5 of the impact device body is implemented by sucking out gas from the first gas space whereby the suction may in the recommended way be carried out by connecting underpressure means (not shown) to the pressure re moval channel 108. ln such a case, a lower pressure is achieved in the first gas space 100 than the second gas space 101, and there is no need to feed gas pres sure to the latter (through the gas removal line 106) to move the hammer piece 8 to the right ln the detailed description of the invention, the anvil unit 7 compris es an anvil body 7a and anvil part 7b, between which there is a spring 6. lnstead, the spring 6 may be arranged between the hammer piece 8 and anvil unit 7 so that the spring 6 is located in the body 1 of the impact device, whereby the anvil unit is one-piece (no separate anvil part 7b and anvil body 7a) and its end is adapted inside the body 1 of the impact device so that it is able to shift slightly in relation to the longitudinal direction of the impact device body 1, that is, the strik ing direction of the hammer piece 8.

The following lists the markings used in the drawings.

l body

2 end flange

3 longitudinal elements

4 first end of body 1 of impact device

5 second end of body 1 of impact device

6 spring

7 anvil unit

7a anvil body

7b anvil part

7 c flange

8 hammer piece (advantageously a piston-like member) 100 first gas space (impact pressure channel)

101 second gas space (return motion pressure chamber)

102 first end surface of hammer piece 8

103 second end surface of hammer piece 8

104 source of pressurised gas

105 gas pressure accumulator

106 gas removal line (recommended to also work as gas feed line)

107 stopping surface of anvil unit 7 (stopping surface of anvil part 7b)

108 pressure removal channel

109 first valve

110 connecting channels associated with the first valve 109, between the gas pressure accumulator 105 and first gas space 100 and between the first gas pressure accumulator 105 and feed line 115

111 third valve (quick exhaust valve, advantageously a three-way valve)

112 pressure reduction component (advantageously a pressure reduc tion valve)

113 fourth valve (control valve of the impact device; advantageously a three-way valve)

114 fifth valve (advantageously a throttle check valve) in feed line 115

115 feed line

120 control unit

PI gas pressure in gas pressure accumulator 105

P2 gas pressure in the first gas space 100

P3 gas pressure in the second gas space 101