Dynamic mixer

1 228077/2

Dynamic mixer

The invention relates to a dynamic mixer. A dynamic mixer of this type is advantageously used to mix a plurality of components which are supplied from a multicomponent cartridge. A dynamic mixer is known from WO 2007/041878 for mixing components having different volume proportions, in particular for manufacturing dental impression materials. An antechamber is arranged in the inner space of the mixer housing within which the mixing rotor has a distribution body for distributing the components about its axis of rotation in order thereby to achieve a correct mixing ratio between the components and to avoid air inclusions. Subsequently, the premixed components move into a main chamber through at least one passage opening for their complete mixing.

It is particularly difficult to keep the correct mixing ratio constant and to maintain a good mixing in particular for high mixing ratios of viscous or pasty components. The mixing generally takes place by shear forces, with the components being urged through the mixer. The mixer has a housing and a rotor element which is rotatably arranged in the housing, the housing having one respective inlet opening for at least two components and at least one outlet opening. A ring-shaped intermediate space is provided between the rotor element and the housing in which there is arranged a mixing element attached to the rotor element.

The rotor element comprises the body element and the mixing element. This mixing element is formed as a vane element which projects away 02222153\82-01 2 228077/2 from the body element into the intermediate space. Preferably, a plurality of such vane elements are present. In addition, static mixing elements can also project from the inner wall of the housing into the intermediate space, which are, however, difficult to manufacture. The components are rearranged repeatedly by the vane element or elements and by the optionally provided static mixing elements in a kneading manner.

It is furthermore known from WO2007/041878 to divide the intermediate space into an antechamber and a main chamber. The antechamber serves the purpose of delaying the conveying of a component A in comparison with a component B so that the component A reaches the main chamber later than the component B. It is hereby ensured that the first portion of the mixture corresponds to the desired mixing ratio. A distributor body connected to the rotor element is used to ensure a filling of the antechamber with the component A and its distribution which is free of bubbles. As the distributor body is moved along with the rotor element, the liquid resistance and consequently the pressure loss remains low. It is furthermore ensured that the smallest possible distance is observed between the inlet opening and the lead chamber so that the liquid resistance can remain small. On the contrary, it is disadvantageous that the two components arrive at the main chamber substantially unmixed.

In order to achieve a mixing effect it is aimed to produce a phase boundary area between the components which is as large as possible to generate a plurality of fine layers by dividing and rearranging the flowing components. For this purpose, the components were commonly directed from the antechamber into the main chamber in which the components were contacted for the first time. In the main chamber, the fluid mass flows are divided transversely to the main direction of flow by mixing elements attached to the rotor element as a consequence of the movement 02222153\82-01 3 228077/2 of the rotor element and the filler compound is mostly urged away against the main direction of flow. Consequently, the filler compound can flow in behind the mixing element and a rearrangement and layer formation of the components of the filler compound can be achieved in this manner.

More difficult mixing tasks result in longer mixers, a larger force expenditure and thus increased energy consumption for the mixer drive unit and in greater resistance to urge the components through the mixer.

The following disadvantageous consequences therefore had to be coped with up to the present moment: a longer mixer, an increased energy consumption and also an increased pressure loss. Accordingly, larger and heavier drive units and batteries for the discharge device have to be provided, which restricts the handling for the application of the mixture, increases the energy requirement and reduces the duration of operation of the discharge device in the case of battery operation.

Since the components react with one another and harden in the mixer on an interruption of the discharge, the mixer must be replaced and disposed of after use and together with the components contained therein.

It is therefore the object of the invention to find a mixer for difficult mixing tasks which is short and manages with as little energy effort for the rotor element as possible as well as with a smaller pressure loss as compared to the prior art mixer. The mixers are produced in high volumes. Small mixers provide savings with respect to the material for the mixer, the components and also costs for the disposal of the used mixers.

The object of the invention is satisfied by a dynamic mixer for a plurality of fluid components which contains a housing and a rotor element which is rotatably arranged in the housing. The housing has an inlet opening for 02222153\82-01 4 228077/2 at least one respective component and at least one outlet opening, with a ring-shaped intermediate space being provided between the rotor element and the housing in which a mixing element connected to the rotor element is arranged. The housing includes a first antechamber, a second antechamber and a main chamber, with the second antechamber being arranged downstream of the first antechamber so that the first antechamber can be traversed by the components before the components enter the second antechamber.

According to an embodiment, the components are guided radially from the housing in the direction of the rotor element in the second antechamber and are premixed by mixing elements attached at the housing side or at the rotor element before they are led into the main chamber after a deflection in the axial direction. A mixing element is preferably provided in the second antechamber. A mixing element can be provided in the first antechamber.

In accordance with an embodiment, the mixing element can be formed as a pin element. In accordance with a further embodiment, the mixing element can be formed as a carrier element or as an arm element. The carrier element or arm element can in particular have a curvature, with the curvature of the front side in particular being convex and/or the curvature of the rear side being concave.

In accordance with a further embodiment, the mixing element in the main chamber can have at least one vane element which can be formed as a directing element for conveying the components from the inlet opening to the outlet opening. The at least one vane element can in particular not cover more than 50% of a plane which is placed through the intermediate 02222153\82-01 5 228077/2 space, which contains the vane element and which is aligned normal to the rotor axis. A first vane element and a second vane element can be arranged downstream of the first vane element, with the shortest spacing between the first vane element and the second vane element amounting to at least one third of the spacing between the rotor element and the main chamber defined by the boundary of the second housing part.

In accordance with a further embodiment, an outlet opening for the passage of the components is provided between the second antechamber and the main chamber and the housing. In accordance with a further embodiment, a rotary surface is arranged between the second antechamber and the first antechamber.

The rotor element can in particular be supported in the first housing part in accordance with each of the preceding embodiments. An apparatus for piercing a container containing the components can be provided at at least one of the inlet openings of the first housing part.

The mixing ratio of the first and second components can be 1:1, but can also lie at 1:10 to 1:50 or even higher.

The use of the dynamic mixer preferably takes place for viscous or thick two-component systems such as seals, bond connections, impression materials disposed in autonomous hand discharge units or in stationary desktop units.

If the components are distributed evenly in space, albeit not mixed, in a first premixing step in accordance with the invention, it is possible to 02222153\82-01 6 228077/2 achieve a good mixing by a local mixing action involving much less energy expenditure compared to previously known solutions. It could also be shown that the dwell time of the components in the dynamic mixer can be reduced for a required mixing effect and the dynamic mixer can thus be constructed more compactly overall and with less volume content.

The invention will be explained in the following with reference to the drawings. There are shown:

Fig. 1a a section through a dynamic mixer in accordance with a first embodiment of the invention along the rotor axis; Fig. 1b a section through the dynamic mixer in accordance with Fig. 1 through the first antechamber; Fig. 1c a section through the dynamic mixer in accordance with Fig. 1 through the second antechamber; Fig. 2a a section through a dynamic mixer in accordance with a second embodiment of the invention; Fig. 2b a section through the dynamic mixer in accordance with Fig. 2a through the first antechamber; Fig. 2c a section through the dynamic mixer in accordance with Fig. 2a through the second antechamber; Fig. 2d a section through the dynamic mixer in accordance with Fig. 2a through the main chamber; 02222153\82-01 7 228077/2

Fig. 3 a view of a rotor element for a dynamic mixer.

Fig. 1a shows a dynamic mixer for a plurality of fluid components. The dynamic mixer 1 has a housing 2 and a rotor element 3 which is arranged rotatably about a rotor axis 8 in the housing 2. In the present embodiment, the housing 2 is made in two parts; it contains a first housing part 4 in which the inflow of the components is located and a second housing part 5 which serves for the production of a mixture from the plurality of fluid components. The first housing part 4 is connected to the second housing part 5 via a latch connection, a snap-in connection or a weld connection as soon as the rotor element 3 is received in the second housing part 5. The first housing part 4 has an inlet opening 12, 13 for at least one respective component. The inlet openings 12, 13 can have different diameters which are dependent on the desired mixing ratio of the components. The inlet openings open into corresponding inlet passages 10, 11 which are arranged in the first housing part 4. The inlet passages 10, 11 open into the first antechamber 21 which is provided with outlet openings which are not shown in Fig. 1 and which open into an inner space 15 of the second housing part 5.

The second housing part 5 has at least one outlet opening 20. The mixture of the components exits the dynamic mixer through the outlet opening 20. The outlet opening 20 can be especially designed in accordance with the intended use. In the present case, a V-shaped incision is provided. The form of a triangular bead results on the discharge of the filler compound with the help of this V-shaped incision. The inner space 15 of the second housing part 5 serves for the reception of the rotor element 3. The inner space 15 is bounded by the inner wall 6 of the second housing part 5. The inner space 15 is formed, at least at the points at which the rotor element 3 is located, as a ring-shaped intermediate space. 02222153\82-01 8 228077/2

The inner space 15 has a second antechamber 17 and a main chamber 22. The components are directed from the second antechamber 17 to the main chamber 22. A premixing can already take place in the second antechamber 17. A plurality of mixing elements 18 are arranged in the second antechamber for this purpose. These mixing elements are designed, for example, as shown here, as pin elements which project into the second antechamber 17. The pin elements can be arranged on a rotary surface 19 of the rotor element 3 and/or can project from the inner wall of the housing bounding the antechamber into the antechamber 17. Shear forces are exerted onto the components by the rotary surface 19 and the pin elements 18.

Alternatively, a fixed disk element which can have pin elements as needs be can be arranged above the rotary surface 19. At least one outlet opening for the passage of the components into the second antechamber can be arranged in the disk element. The disk element can be clamped between the first and second housing parts. A ring-shaped intermediate space in which a mixing element 7 connected to the rotor element 3 is arranged is provided between the rotor element 3 and the inner wall 6 of the housing.

The mixing element 7 includes a plurality of vane elements 23 in the main chamber 22. The vane elements 23 protrude as projections into the inner space 15 which forms the main chamber 22. The complete mixing of the components takes place in this main chamber 22 in that the components are taken up by the vane elements and are rearranged. At least some of the vane elements can be formed as a directing element for conveying the 02222153\82-01 9 228077/2 components through the inner space 15 in the direction of the outlet opening 20.

The rotor element is formed at least partly as a hollow body. The central hollow space of the rotor element serves for receiving a drive shaft. The hollow space advantageously has an at least triangular shape so that a drive shaft can be rotationally fixedly connected to the rotor element so that the rotor element can be driven via the drive shaft.

The dynamic mixer accordingly contains at least two antechambers. The first antechamber 21 is used for introducing the components, with a coarse premixing being able to be achieved in the first antechamber. The second antechamber 17 serves for achieving a local mixing. The first antechamber 21 is designed such that two or more components are introduced into the first antechamber 21 such that the component having the smaller volume flow is introduced into the volume flow of the component having the larger volume flow. The first antechamber 21 is separated from the second antechamber 11 by a rotary surface 19, in particular a cover plate, which can be arranged at the rotor element 3. In the first antechamber 21, the one component is guided away from the inlet passage 11 to the outlet opening of the inlet passage 10 of the other component by means of a vane element attached to the rotor element and/or to the housing or a separate stator, whereby at least one first distribution of the components and/or a first premixing of the components to a filler compound takes place. The premixed components move from the first antechamber 21 into the second antechamber 17 via an outer ring gap, which is formed by the mixer housing and the cover plate. In the second antechamber 17, the premixed components move radially to the rotor axis 8 and are mixed further locally with little force expenditure over small obstacles such as pin elements. The filler compound is directed from 02222153\82-01 10 228077/2 the second antechamber 17 into the main chamber 22. After an axial deflection in the transition region between the first antechamber 17 and the main chamber 22, the filling compound moves to the centrally disposed outlet opening 20. A complete mixing takes place in the main chamber 22 using further vane elements or static mixing elements.

The first antechamber 21 is visible in Fig. 1b in a section through the dynamic mixer in the region of the first housing part 4. The position of the section is given by A-A in Fig. 1a. The section plane is laid normal to the rotor axis and extends through the first antechamber. The two inlet passages 10, 11 open into the first antechamber 21. An arm element 60 which is connected to the rotor element 3 is located in the first antechamber. A plurality of such arm elements 60 can naturally be provided; in Fig. 1b, four arm elements of the same type are shown.

The arm element 60 extends through the first antechamber 21 from the rotor element 3 up to the inner wall 65 of the first housing part 4 which bounds the first antechamber. The arm element 60 has a front side 61 by means of which the filler compound is displaced through the first antechamber 21 and has an oppositely disposed rear side 62. The rear side 62 has a concave curvature; the front side 61 has a convex curvature. The curvature radii of the curvatures of the rear side and of the front side are advantageously substantially the same. The arm element 60 extends from the base 68 up to the top 67 of the prechamber 21. The top 67 is only visible at the rotary surface 19 in Fig. 1a. A cut-out 63 can be provided in the arm element 60 when a part of the filler compound should escape from the front side 61 to the rear side 62.

Furthermore, the arm element 60 has a guide cut-out 64. The arm element slides by means of the guide cut-out 64 on a projection 69 of the 02222153\82-01 11 228077/2 first housing part. The rotor element is also held by the projection in the dynamic mixer.

Fig. 1c shows a section through the second antechamber 17. This section through the dynamic mixer is laid between the first housing part 4 and the second housing part 5 in the region of the connection. The position of the section is given by B-B in Fig. 1a. The section plane is laid normal to the rotor axis 8. The rotary surface 19 forms the base of the second antechamber 17. The filler compound enters into the second antechamber through a ring gap 70 and exits the second antechamber via a ringshaped outlet opening 71 which is only visible in Fig. 1a. A plurality of pin elements 18 are located in the second antechamber. The pin elements 18 project from the top 72 into the second antechamber 17. The filler compound is urged at least partly into a rotary movement by shear forces which are introduced by the rotary surface 19. When the filler compound reaches one of the pin elements, it divides into two part flows, whereby a rearrangement and a premixing of the components of the filler compound take place with a minimal force expenditure. Wall element sections 73 can additionally be provided. The wall element sections 73 are arranged substantially around the outlet opening 71 (see Fig. 1a) and enforce a uniform throughflow of the second antechamber before the entry into the main chamber. The wall element sections 73 project from the top 72 into the second antechamber 17. The wall element sections 73 are designed as cylinder segments. The inner diameter of the cylinder segments substantially corresponds to the inner diameter of the outlet opening 71 or respectively corresponds to the inner diameter of the main chamber 22 formed by the second housing part 65 at its inlet.

Fig. 2a shows a section through a dynamic mixer in accordance with a second embodiment of the invention for the mixing of a plurality of fluid 02222153\82-01 12 228077/2 components. The dynamic mixer 100 has a housing 102 and a rotor element 103 which is arranged rotatably about a rotor axis 108 in the housing 102. In the present embodiment, the housing 102 is made in two parts; it contains a first housing part 104 in which the inflow of the components is located and a second housing part 105 which serves for the production of a mixture from the plurality of fluid components. The first housing part is connected to the second housing part via a latch connection, a snap-in connection or a weld connection as soon as the rotor element 103 is received in the second housing 105. The first housing part 104 has a respective inlet opening 112, 113 for at least one respective component. The inlet openings 112, 113 can have different diameters which are dependent on the desired mixing ratio of the components. The inlet openings open into corresponding inlet passages 110, 111 which are arranged in the first housing part 104. The inlet passages 110, 111 open into the first antechamber 121 which is provided with outlet openings 130, 131 which open into the second antechamber 117 of the second housing part 105.

The second housing part 105 has at least one outlet opening 120. The mixture of the components exits the dynamic mixer through the outlet opening 120. The main chamber of the second housing part 105 serves for the reception of the rotor element 103.

The components are directed from the second antechamber 117 to the main chamber 122. A further mixing can take place in the second antechamber 117. A mixing element 118 is arranged in the second antechamber for this purpose. The mixing element 118 is formed as a vane element which is connected to the rotor element 103. A ring-shaped intermediate space in which a mixing element 107 connected to the rotor 02222153\82-01 13 228077/2 element 103 is arranged is provided in the main chamber 122 between the rotor element 103 and the inner wall of the housing.

The mixing element 107 includes a plurality of vane elements 123 in the main chamber 122. The vane elements 123 protrude as projections into the inner space 115 which forms the main chamber 122. The complete mixing of the components takes place in this main chamber 122 in that the components are taken up by the vane elements and are rearranged. At least some of the vane elements are formed as a directing element for conveying the components through the inner space 115 in the direction of the outlet opening 120.

It is also not necessary that adjacent vane elements arranged behind one another with respect to the rotor axis 108 have the same spacing from one another. The spacing of the vane element 123 arranged closest to the outlet opening 120 from the vane element 126 is, for example, smaller than the spacing of the vane element 126 from the vane element 128.

The first antechamber 121 is visible in Fig 2b in a section through the dynamic mixer in the region of the first housing part 104. The position of the section is given by A-A in Fig. 2a. The section plane is laid normal to the rotor axis and extends through the first antechamber 121. The two inlet passages 110, 111 open into the first antechamber 121. In the first antechamber 121, disturbance elements 175 are arranged which project from the base 166 of the antechamber 121 into the antechamber. These disturbance elements are stationary and divide the filler compound flow.

In the direction of rotation 169, they advantageously have an initially continuously increasing cross-section which passes through a maximum and then continuously decreases. The cross-section can in particular be formed in diamond shape. The carrier elements 176 are designed in a 02222153\82-01 14 228077/2 similar manner to the disturbance elements 175. They project from the axis of rotation 129 into the first antechamber 121. These carrier elements 176 are moved along with the rotary surface 129 when the rotor element 103 carries out a rotary movement. The outer carrier elements 176 scrape off the components from the outlet openings of the passages 110, 111 and lead them into the first prechamber 121. An unchanging mixing ratio of the components is achieved by these measures. The carrier elements 176 and the disturbance elements 175 together effect a distribution of the components and a first premixing thereof in the filler compound before they move via outlet openings 130 and 131 into the second antechamber 117. The outlet openings 130, 131 are arranged in the rotary surface 129 and are shown in Fig. 2a.

The top 167 of the first antechamber is only visible at the rotary surface 129 in Fig. 2a. The inner wall 165 which is a part of the first housing part 104 extends between the base 166 and the top 167.

The inner carrier elements 176 can form a guide cut-out 164 together with the hub of the rotor element 103 and the rotary surface 129. The rotor element 103 slides by means of the guide cut-out 164 on a projection 169 of the first housing part. The rotor element 103 is also held by the projection 169 in the dynamic mixer.

Fig. 2c shows a section through the second antechamber 117. This section through the dynamic mixer is laid in the region of the connection between the first housing part 104 and the second housing part 105. The position of the section is given by B-B in Fig. 2a. The section plane is laid normal to the rotor axis 108. The rotary surface 119 forms the top of the second antechamber 117. The rotary surface 129 forms the base of the second antechamber 117. 02222153\82-01 15 228077/2

The filler compound enters in accordance with Fig. 2c through the outlet openings 130, 131 of the first antechamber 121 into the second antechamber 117 and exits the second antechamber 117 via at least one outlet opening 171 which is visible in Fig. 2d. A plurality of mixing elements 118 are located in the second antechamber 117. The mixing elements 118 project from the rotor element 103 or from the rotary surface 129 or from the rotary surface 119 into the second antechamber 117. The filling compound is urged at least partly into a rotary movement by shear forces which are introduced by the rotary surface 119 and by the rotary surface 129.

The mixing elements 118 can be designed as vane elements 177, 178, with the geometrical dimensions applying to the carrier element 176 being able to apply to the vane element 178. The components, are mixed both in a plane parallel to and in a plane perpendicular to the axis of rotation by the vane elements 178 at the rotary surface 119 together with the vane elements 177.

Additional cylinder segment blocks 179 are formed as part of the first housing part 104. Boundaries 172 are provided which are formed as part of the second housing part 105 to design the passage region from the second antechamber 117 into the main chamber 122 as a restriction. The filler compound has to be guided via this restriction so that it can only enter into the main chamber 122 after passing through the restriction, that is it is channeled in a restricting manner from the second antechamber 117 to the main chamber 122.

The entry region of the main chamber 122 is visible in Fig. 2d in a section through the dynamic mixer in the region of the second housing part 105. 02222153\82-01 16 228077/2

The position of the section is given by C-C in Fig. 2a. The side of the rotary surface 119 facing the main chamber 119 is partly covered by a top element 172 of the second housing part 105. The filler compound enters into the main chamber 122 through the outlet opening 171.

Additional guide elements 180 can be provided in or directly adjoining the outlet opening 171 to better distribute the inflow of the components into the main chamber 122.

The components inflowing in the axial direction and forming a pasty filler compound are redirected in the middle, that is transversely to the rotor axis 108, into a mixing chamber which was called a first antechamber in the above. The component flowing into the first antechamber 121 having the smaller volume flow is integrated as much as possible into the volume flow of the component having the larger volume flow, by vane elements or carrier elements 176 arranged at the rotor element 103 from the outlet openings of the inlet passages 110, 111 and is directed into the first antechamber 121 where the filler compound is subjected to a first coarse mixing by the vane elements 60, 160 and/or the carrier elements 176 and/or the disturbance elements 175. The first antechamber 121 is bounded in the direction of the outlet opening 120 by a disk element which is located at the rotor element 103 and which forms a rotary surface 129. This disk element has at least one opening and/or forms a ring gap with the housing at the periphery. The opening and/or the ring gap allow a throughflow of the filler compound into a second antechamber 117. The components can be further admixed here by radial and/or axial vane elements 177, 178. The openings foreseen in the second antechamber 117 subsequently direct the filler compound into the mixing region of the main chamber 22, 122 into which they can flow radially. The axial, arcuate vane elements 138 especially applied as needs be in the 02222153\82-01 17 228077/2 inflow region of the main chamber 122 shear off the filler compound directly on the entry into the main chamber 122 and convey the filler compound in the direction of the rotor axis 108. At least some of the vane elements 123, 126, 128, 137 have radial directing elements conveying in the direction of the outlet opening 120. Beside the dynamic mixer components of the rotor element and any present fixed directing and/or disturbance elements, the dynamic mixer can also additionally have static mixer components in the main chamber 122.

It has been shown that the mixing task in the main chamber 22, 122 is substantially reduced by the introduction of the second antechamber 17, 117 in which an additional premixing takes place by a local distribution of the components with a relatively small flow resistance and a small torque of the rotor element 3, 103. Therefore the construction length of the dynamic mixer in accordance with each of the embodiments can be shortened overall substantially, the content can be reduced and the mixing energy to be applied can be decreased.

Fig. 3 shows a view of a rotor element for use in one of the dynamic mixers in accordance with one of the preceding embodiments. The rotor element corresponds to the rotor element 103 shown in Fig. 2a so that the same reference numerals as in Fig. 2a are used for the same parts. However, this reference is not to be understood as a restriction such that the rotor element can only be used in connection with the embodiment in accordance with Fig. 2a. It is rather the case that the rotor element can likewise be used in a housing in accordance with any one of the other embodiments with a slight adaptation of the geometry of the housing. The rotor element 103 has a rotor axis 108 along which a rotor element hub 135 is arranged. The rotor element hub 135 carries a rotary surface 129 which contains the outlet openings 130, 131. The components which are 02222153\82-01 18 228077/2 supplied from the inlet passages 110, 111 (see Fig. 2a) to the first antechamber exit into the second antechamber 117 through these outlet openings 130, 131. A second bounding of the second antechamber 117 is formed by the rotary surface 119 which is attached downstream of the rotary surface 129 on the rotor element hub 135. At the peripheral side, the second antechamber 117 is bounded by the second housing part 105 (see Fig. 2a).

The components are premixed in a plane parallel to the rotor element hub 135 by a mixing element 118, which is arranged in the second antechamber 117 on the rotor element hub 135, in a plane perpendicular to the rotor element hub and by any further mixing elements, which project from the rotary surface into the second antechamber 117. To move into the main chamber 122 (see Fig. 2a), the components flow around the rotary surface 119. A narrow ring- shaped gap through which the components pass remains between the rotary surface 119 and the inner wall of the second housing part. Furthermore, vane elements 123, 126, 128 which can be designed as directing elements and in this case exert a conveying effect on the filler compound in the direction of the outlet opening 20, 120, are arranged downstream of the rotary surface 119 in the main chamber 22, 122. In addition, vane elements 137 can be provided which are formed in diamond shape as described, for example, in WO98/43727. Furthermore, an arcuate vane element 138 is shown which is directly adjacent the rotary surface 119 and shears off the filler compound from the inlet openings and directs it into the main chamber 22, 122. Similar vane elements can also be arranged further downstream and effect a scraping of the filler compound from the wall of the main chamber 22, 122. 02222153\82-01 19 228077/2

Vane elements of the same type are preferably arranged opposite one another at the same height, with the height being measured along the rotor axis 108. 5 Alternatively, the rotor element can extend only up to the input region into the main chamber 22, 122, in accordance with any of the preceding embodiments. A static mixing element can be arranged in the main chamber itself, which is not shown in the drawing. 10 02222153\82-01