Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
  • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
  • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
  • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
  • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
  • F01C1/00—Rotary-piston machines or engines
  • F01C1/08—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing
  • F01C1/082—Details specially related to intermeshing engagement type machines or engines
  • F01C1/084—Toothed wheels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
  • F01C1/00—Rotary-piston machines or engines
  • F01C1/08—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing
  • F01C1/12—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing of other than internal-axis type
  • F01C1/14—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
  • F01C1/16—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C2/00—Rotary-piston machines or pumps
  • F04C2/08—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing

Definitions

• the present invention relates to a screw-type rotary machine intended for the compression or expansion of an elastic fluid and comprising at least two rotors, a male rotor and a female rotor, provided with helically extending lands and grooves, of which rotors at least one is compris ⁇ ed substantially of a plastics material located preferably on a metal shaft or core.
• Screw rotors are normally manufactured by machine cutt ⁇ ing solid metal blanks.
• the screw rotors have a complicated geometric form, which demands a high degree of accuracy in manufacture.
• the amount of material cut-away during manufacture is very considerable.
• these drawbacks result in long manufacturing times and high costs. Consequently, it has long been desired to produce the rotors of such machines in a simpler fashion and with less stringent requirements on precision and accuracy, in order to enable the rotors to be manufactured in very large quan ⁇ tities at reasonable costs.
• Endeavours have been made as early as in 1953 to produce the rotors from plastics, as evident from the U.S. Patent Specification Serial No. 2,868,442.
• the object of the present invention is therefore to provide a screw-type rotor machine of the aforesaid kind, with which the rotors thereof can be manufactured quickly and cheaply, in a manner which enables the rotors to be produced in large number at a low labour input.
• the rotor which is made at least predominantly of a plastics material is the female rotor, which is injec ⁇ tion moulded from a plastics material having a modulus of elasticity of at most 25000 N/mm ⁇ , and in that the thick ⁇ ness of the lands of the female rotor is so adapted in respect of said modulus of elasticity that the lands are able to spring away, be deflected resiliently, when clash ⁇ ing contact occurs with the other rotor, as a result of dimensional deviations caused by hardening or solidifica ⁇ tion of the plastics material and the temperature varia ⁇ tions to which it is subjected, but not solely as a result of the pressure exerted thereon by the working fluid.
• the invention is thus based on the concept that not all clashing contact or unintended contact which can occur as a result of minor deviations from the profile intended, and which hitherto has normally led to damaged rotors, shall be avoided whatever the cost, but that such contact shall be permitted while preventing damage to the rotor/lands, by providing lands which yield or deflect resiliently to such contact, to a given extent, i.e. lands which are not shape- stable, this being in complete contradistinction to pre ⁇ vailing views on the construction of the female rotor. Because the rotor is injection moulded, the surfaces ob- tained are sufficiently smooth to obviate the need for sub ⁇ sequent machining, which is one prerequisite of a success ⁇ ful solution to the aforementioned problem.
• Figure 1 is an end view of a female rotor 1 and a male rotor 2.
• the female rotor 1 has helically extending lands 3 and intermediate grooves 4, and the male rotor 2 has heli ⁇ cally extending lands 5 and grooves 6.
• the female rotor 1 comprises a plastics part 7 which is moulded on a steel shaft 8, by an injection moulding process utilizing the mould illustrated in Figure 2.
• the male rotor 2 may be made of aluminium or steel in a conventional manner, or of extruded aluminium or plastics.
• the shaft 8 of the female rotor may have a circular cross-section, but since manufacture is effected by mould ⁇ ing the plastics directly onto the shaft, the plastics is preferably distributed as uniformly as.possible around the periphery of the shaft, i.e. constant thickness, in order to ensure a uniform hardening or solidifying process in the absence of irregular dimensional changes. Because of this, the shaft 8 has been milled-out slightly, so as to form helical edges or lands 10 at the base of each land 3 and concave surfaces 11 which extend parallel with the grooves 4 at a distance a, therefrom, this distance being substan ⁇ tially equal to the mean thickness a of the lands 3.
• the lands 3 are thinner than is normal for steel rotors, and the thickness of said lands is care ⁇ fully calculated so as to afford, in combination with the modulus of elasticity of the plastics material, the afore ⁇ said resilient deflection of the lands by an amount corre ⁇ sponding to such profile-deviations from a perfectly true profile as those which are liable to occur as a result of changes in the moulded shape of the plastics material while hardening or solidifying, or as a result of prevailing changes in temperature.
• the modulus of elasticity can be placed at a level sufficiently low to provide a certain degree of surface elasticity, in a known manner, but not so low as to result in deformation due to the pressure exerted by the working fluid.
• Figure 2 illustrates schematically a mould 20 which is closed at one end and incorporates an inner wall which is profiled to correspond to the profile of the desired female rotor 1.
• the mould 20 includes a removable end-wall 21.
• the closed end 22 of the mould 20 has located centrally therein an aperture 23, and the removable end-wall 21 has a similar central aperture 24.
• the apertures 23 and 24 are each adap ⁇ ted to accommodate a shaft 8 having formed thereon the helical edges or lands 10 illustrated in Figure 1, said shaft being placed in the mould prior to fitting the remov ⁇ able end-wall 21.
• the requisite amount of plastizied plas- tics material is injected into the mould through one or more injection holes 25, the plastics material preferably comprising a ther osetting resin incorporating millimetre long reinforcing fibres, e.g. glass fibres, and having a modulus of elasticity not higher than 8000 N/mm 2 .
• the plas- tics material fills the cavity between the shaft 8 and the internal surfaces of the mould, during which process air present in the mould is forced therefrom through air vents not shown.
• Measuring of the female rotor 1 manufactured in this way shows that the shape of the rotor deviates from the intend ⁇ ed shape mainly in that the lands 3 under the influence of the solidification of the plastics have lengthened somewhat giving rise to a changed pitch of the lands 3 at the end portions of same.
• the deviation measured perpendicular to the surfaces of the lands just beneath the top radius may amount to round 0.1 mm for a rotor having a diameter of 50 mm.
• a solution of the defined problem has been obtained by realizing the possibility of designing the female rotor in accordance with the invention such that a sufficient yielding of the lands is achieved, and tests for more than one year under normal operating conditions have verified that it is possible now to manu- facture screw rotor machines with as well as without synch ⁇ ronizing gears in an uncomplicated and inexpensive way without subsequent machining of the profile produced by moulding the rotors from a plastics material.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Rotary Pumps (AREA)
• Applications Or Details Of Rotary Compressors (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20359509

Family Applications (1)

Country Status (8)

Cited By (6)

Families Citing this family (15)

Citations (5)

Family Cites Families (5)

• 1985
  • 1985-03-15 SE SE8501280A patent/SE463829B/sv not_active IP Right Cessation
• 1986
  • 1986-03-13 DE DE8686902071T patent/DE3666607D1/de not_active Expired
  • 1986-03-13 US US06/934,445 patent/US4761124A/en not_active Expired - Lifetime
  • 1986-03-13 JP JP61501796A patent/JPH0660561B2/ja not_active Expired - Fee Related
  • 1986-03-13 EP EP86902071A patent/EP0257029B1/en not_active Expired
  • 1986-03-13 KR KR1019860700809A patent/KR950001995B1/ko not_active IP Right Cessation
  • 1986-03-13 WO PCT/SE1986/000109 patent/WO1986005555A1/en active IP Right Grant
• 1987
  • 1987-09-14 FI FI873978A patent/FI96537C/sv not_active IP Right Cessation

Patent Citations (5)

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