TITLE: "ORBITING-SPIRAL SCROLL PUMP OR COMPRESSOR"

DESCRIPTION

The invention relates to fluid machines such as so-called scroll pumps or compressors, the operating principle of which is based on variation in the volumes intercepted by at least two cup-shaped modules or stages, with the lateral cylindrical surface having a straight line as a generatrix and a spiral for example in the form of an involute of a circle as a directrix, one of the stages being fixed, while the other one is driven with an orbiting movement about a common axis of the two stages. Each profile has an associated closing base and the free edge of each profile makes frictional and sealing contact with the inner surface of the base of the other profile, with an energized composite seal arranged in between. For the sake of convenience of the description, below reference will be made to pumps alone, without this thereby excluding other intended uses of the fluid machine according to the invention. Again for the sake of convenience, reference will be made to forms consisting of a spiral in the form of an involute of a circle, without this excluding other forms, for example as described in US patent No. 4,527,964. The said two spiral profiles interpenetrate and face each other so as to form between them a series of pairs of sickle-shaped volumes, with a height equal to the depth of the said profiles, which extend open and with a greater breadth from the periphery of the pump which communicates with an intake mouth and which then close and gradually approach the centre, decreasing gradually in volume, until they reach a central discharge or delivery orifice. During operation of the pump, the two profiles rotate without substantially touching each other. This means that the operation of a scroll pump, since it has no parts which make frictional contact and are subject to centrifugal thrusts, is extremely silent and does not require the use of internal lubricants which would limit the area of use of the said pump. All these considerations are an impulse for research into this particular type of machine, also because in the version with an orbiting stage comprising two mirror-image and facing spirals, co-operating with corresponding spirals of fixed modules, it is possible to counter-balance and eliminate the axial thrusts acting on

the said orbiting stage during operation of the pump.

For the orbital movement of the moving stage, the latter is mounted with its central part, via roller bearings arranged in between and allowing freedom of axial movement, on an eccentric middle section of a shaft which is rotatably supported via other bearings by the stator of the pump and which projects from the latter for connection to a rotational motor, while with the pehmetral part the said moving stage is connected to one or more cranks with an axis parallel to that of the said shaft, which may be operated in synchronism with this shaft by positive drive means and may be situated outside the stator, as for example described in the patent DE 3,010,052, or may be operated in synchronism by the eccentric movement which the moving stage receives from the said main shaft and may be situated inside the stator or outside the latter, as for example described in the patents US 5,391 ,065 and US 5,258,046.

All the pumps or compressors of the known type pose problems due to their considerable axial and/or radial dimensions resulting from the presence of the said peripheral actuating cranks of the orbital movement stage as well as problems associated with the risk of internal contamination by the lubricant of the bearings of the said cranks and the bearings supporting the orbiting stage, when the latter are situated inside the pump.

The invention intends to overcome these and other drawbacks of the known art, with the solution as claimed in the accompanying Claim 1 and subsequent dependent claims, which may be summarised as follows. The internal orbital movement stage of the pump is fixed to the end of a drive shaft which passes through at least one of the stages forming the stator of the said pump and which projects from the latter with a section of adequate length, this shaft section being rotatably supported, via bearings with freedom of axial movement, by the internal through-seat with suitable eccentricity of a bush which is rotatably supported via bearings by the axially hollow

hub integral with the base of the fixed stage passed through by the shaft in question. This bush projects by a suitable amount from the stator of the pump and is supported rotatably not only by the bearings inside the stator, but also by external bearings supported by support means integral with the said stator so as to leave free a sufficient lateral part of the outer middle section of the bush in question. The section of the said main shaft which projects from the outer end of the said bush is connected to connecting-rod means which with their head co-operate with crank means rotatably supported by the adjacent stator of the pump. The rotational movement is imparted onto the outer middle section of the said bush by means of a drive system for example of the belt and pulley type, with the arrangement of the rotational motor parallel to the axis of the pump. The rotation of this bush about its axis, the eccentric supporting of the main drive shaft of the pump by the latter and the connection of this shaft to the said connecting-rod and crank means produce the orbital rotation of this shaft together with the middle stage of the pump in accordance with the law necessary for correct operation of the said scroll pump. The shaft of the said motor may have, keyed thereon, a secondary fan which produces an air flow with a suitable flowrate and pressure and which, by means of a special casing, which among other things safely conceals all the outer moving parts of the pump, is forced to flow over and adequately cool at least the body of the said pump and preferably also the outer surface of the said motor.

Further characteristic features of the invention and the advantages arising therefrom will emerge more clearly from the following description of a preferred embodiment thereof, illustrated purely by way of a non-limiting example in the figures of the accompanying pages of drawings, in which:

Fig. 1 is a top plan view of the motor/pump unit, with the pump cross-sectioned along an ideal plane which contains the axes of rotation and revolution of the main components of the said pump;

Fig. 2 shows an elevation view of the motor/pump unit from the front side indicated by the arrow K in Figure 1.

In Figure 1 , 1 and 1 ' denote the two cup-shaped bodies or shells which form the stator of the pump and which are fixed against each other by perimetral means (not shown here) and with seals 2 arranged in between. The inner surfaces of the bases of the bodies 1 , 1' usually support integrally the respective spirals for example in the form of an involute of a circle 201 , 201 ' which co-operate with the corresponding circle involute spirals 103, 103' of the orbital-movement middle stage 3 so as to form the variable-volume chambers of the pump which are closed frontally by the sealed co-operation, on one side, of the spirals 103, 103' of the moving stage 3 with the flat inner surfaces 301 , 301 ' of the bases of the shells 1 , 1 ' and, on the other side, by the sealed co-operation of the stator spirals 201 , 201 ' with the flat sides 203, 203' of the orbiting stage 3. The frontal seal between the relatively moving parts is ensured by composite energized seals 5 of the known type.

In the example in question, both the shells 1 , 1' support internally, integrally and in an axial position, respective hubs 401 , 401 ' provided on the free edges with seats for containing composite seals 5' and 5" of the same type as those 5 described above for the spirals of the pump, via which they co-operate so as to form a frontal seal with the opposite sides 203 and 203' of the flat body of the moving stage 3 of the said pump. The hubs 401 , 401 ' define with the middle disk 3, chambers of sufficient depth for containing means 7, 107 and 8 for axially fixing and keying to the central enlarged part 403 of the said disk 3 the flanged end 109 of the cylindrical shaft 9 for rotation of the pump which, via roller bearings 10 arranged in between and allowing it freedom of axial movement, passes through the suitably eccentric inner seat 11 of the bush 12 which with its outer surface is rotatably mounted, via the bearing 13 for example of the roller type, inside the hub 401 '.

The bush 12 projects by a suitable amount from the stator shell 1 ' and from the said

corresponding hub 401' and terminates with a tapered section 112 which internally seats one of the said roller bearings 10 for supporting the shaft 9 and which externally is in turn rotatably supported, via the bearing 14, for example of the ball type, by a ring 29 which has an opening in the form of a radial incision 30 and is provided with tangential tightening means 31 (Fig. 2), by means of which this ring may be fixed onto the outer race of the said bearing 14 and may if necessary be easily disassembled from the latter, for the purposes indicated further below. The ring 29 may be fixed with respective screws 32 on three projections 33 which are formed for example integrally with the shell 1 ', are angularly spaced at 120 from each other and on which the bearings 26 are mounted, said bearings supporting the bottom end of the cranks 25 which with their heads co-operate with the bearings 24 of a connecting-rod star or cross piece 22 which by means of the cotter 23 and the axial fixing dowel 123 is keyed onto the end of the shaft 9 which projects from the said bush 12.

The middle part of the bush 12 is designed externally so as to form a pulley 34 of suitable diameter, which is coaxial with the bearings 13, 14 and on which a belt 35 is driven, said belt obtaining its movement from a corresponding pulley 134, for example with a diameter smaller than that of the previous pulley 34 and keyed onto the shaft of a motor 36, for example of the electric or any other suitable type, with suitable characteristics, which is situated on the side of the pump in question, parallel to the latter, and which in the example in question is flanged onto an extension 601 ' of the bottom wall of the shell 1 '. 135 denotes a roller mounted adjustably on the said wall 601 ' so as to ensure the correct degree of tensioning for the return section of the said belt 35.

From Figure 1 it can be seen how with the solution in question, the shaft 9 is made to rotate orbitally with the rotational movement being imparted onto a broad middle section of the bush 12 situated between its two ends close to the main bearings 13 and 14, while the resistive forces are applied in a balanced manner at the opposite

ends of the said shaft 9, with the outer end which drives the cross piece 22 with the orbiting crank mechanisms 25, and with the inner end which drives the orbiting middle stage 3 of the pump, such that operation of the said shaft 9 is balanced and without vibrations.

With the solution described it is also possible to operate the pump using a - for example electric - motor 36, of limited speed and power, owing to the possibility of using a high -efficiency drive system such as that comprising belt 35 and reducer pulleys 34, 134. Owing to the high speed of rotation of the motor 36 it is also possible to provide the unit with means for forced cooling of the pump, as described further below.

From Figures 1 and 2 it can be seen that, to counter-balance eccentric positioning thereon of the shaft 9, the bush 12 may be provided with an eccentric mass 212 and, in opposition to this, may be provided with a segment of weight-reducing holes 37, in order to provide effective dynamic balancing of the entire moving part of the pump, without the need for providing special-purpose counterweights.

The periodic replacement of the belt 35 requires a few simple operations which consist in slackening the fixing dowel 123 in order to remove the connecting-rod rim

22 from the end of the shaft 9, after which it is sufficient to remove the screws 32 and slacken the tangential screw 31 according to Figure 2 so as to be able to widen and remove the ring 29 from the bearing 14. With these few operations the space between the pulley 34 and the supports 33 can be accessed from the outside so that it is possible to remove and insert the belt 35 from/into this space. With similar reverse operations, the aforementioned components 29 and 22 may be reassembled.

From Figure 1 it can be seen that one or more holes 27 may be provided for example on the bush 12 and/or in another position useful for keeping at least the internal chamber of the hub 401' situated ahead of the inner bearings 13 and 10 in free

communication with the exterior, both in order to discharge freely outside any products resulting from wear of these bearings and in order to ensure proper cooling of these same components and the central part of the pump.

5 Since a high-speed motor 36 is provided, as mentioned above, it is possible to key onto the shaft thereof the impeller 38 of a centrifugal fan enclosed inside a casing 39 which is fixed to special lugs on the wall 601' of the pump and which, opposite the axis of the said impeller 38, is provided with an opening 40 with filter where necessary, through which the said fan may draw in air from the outside and may

10 force it inside the casing 39 which is designed to distribute the cooling air onto the outer vanes 701 ' and 701 of the shells 1 ' and 1 of the pump, there being mounted on the said shell 1 a box 41 which with its base 141 collects the air from the said casing 39 and conveys it along a winding path, indicated by the arrows F, so that it flows over the outer vanes of the hub 401 , at a short distance therefrom, and then

15 discharges the air flow onto the outer vanes of the stator of the motor 36 which is in turn cooled by its own internal fan 136. It is also clear how the casing 39 also performs effectively a (not secondary) accident-prevention and protective function owing to the fact that it is able to conceal all the external moving parts of the motor/pump unit.

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The box 41 is also provided with filter means for connection within a circuit to the intake mouth A of the pump and means with the usual one-way valve are provided for connection to the discharge mouth B of the said pump which may be, for example, intercepted by a specially shaped aperture 42 provided on the central disk

.5 3 and which operates adjacent to and on the outer part of the axial hubs 401 , 401 ", as described in the known state of the art or according to solutions protected by separate patents in the name of the same applicant. Reference numeral 801 denotes feet for being able to fix the motor and pump unit, as described, to any support surface, these feet being integral with the said wall 601' and the outer surfaces of the

50 stator bodies 1 , 1 ' of the pump.