WO2005005781A1

WO2005005781A1 - Volume screw machine of rotary type

Info

Publication number: WO2005005781A1
Application number: PCT/IB2004/000194
Authority: WO
Inventors: Alexander Gorban
Original assignee: Elthom Enterprises Limited
Priority date: 2003-07-14
Filing date: 2004-01-15
Publication date: 2005-01-20

Abstract

A rotary screw machine which can be set in a hub of a back wheel of a bicycle comprises an outer stator (1), two intermediate screw elements, namely a two-sided rotor-satellite (2) and a two-sided central rotor (3) as well as an inner screw element, a rotor-satellite (4). The rotor-satellite (4) comprises a longitudinal cavity (17). In that cavity (17, a working medium can be transported from one side of the machine to the other side, thereby providing a very compact design of a rotary screw machine.

Description

SCREW MACHINE

FIELD OF THE INVENTION The invention relates to a volume screw machine of rotary type (rotary screw machine). In particular, it relates to a screw pneumatic motor of volumetric type, for example to be set in a hub of a back wheel of a bicycle.

PRIOR ART Volume screw machines of rotary type comprise conjugated screw elements, namely an enclosing (female) screw element and an enclosed (male) screw element. The enclosing (female) screw element has an inner profiled surface (female screw surface), and the enclosed (male) screw element has an outer profiled surface (male screw surface). The profiled surfaces (screw surfaces) are non-cylindrical and limit the elements radially. They are centred about respective axes which are parallel and which usually do not coincide, but are spaced apart by a length E (eccentricity). A rotary screw machine of three-dimensional type of that kind is known from US 5,439,359, wherein an enclosed element surrounded by a fixed enclosing element is in planetary motion relative to the enclosing element. A first component of this planetary motion drives the axis of the male surface to make this axis describe a cylinder of revolution having a radius E around the axis of the female surface, which corresponds to an orbital revolution motion. In other words, the axis of the enclosed (male) element rotates around the axis of the enclosing (female) element, wherein the latter axis is the principal axis of the machine. A second component of this planetary motion drives the male element to make it rotate about the axis of its screw surface. This second component (peripheral rotation) can also be called swivelling motion. Instead of providing a planetary motion, a differential motion can be provided. Usually, synchronizing coupling links are used therefor. However, the machines can also be self-synchronized by providing suitable screw surfaces. In most cases, the screw surfaces of the rotary screw machines have cycloidal (trochoidal) shapes as it is for example known from French patent FR-A-997957 and US 3,975,120. Rotary screw machines of volume type of the kinds described above are known to transform energy of a working substance (medium), gas or liquid, by expanding, displacing, and compressing the working medium into mechanical energy for engines or vice versa for compressors, pumps, etc. They are in particular used in downhole motors in petroleum, gas or geothermal drilling. The transformation of a motion as used in motors has been described by V. Tiraspolskyi, "Hydraulical Downhole Motors in Drilling", the course of drilling, p.258-259, published by Edition TECHNIP, Paris. The effectiveness of the method of transforming a motion in the screw machines of the prior art is determined by the intensity of the thermodynamic processes taking place in the machine, and is characterized by the generalized parameter "angular cycle". The cycle is equal to a turn angle of any rotating element (enclosing element, enclosed element or synchronizing link) chosen as an element with an independent degree of freedom. The angular cycle is equal to a turn angle of a member with independent degree of freedom at which an overall period of variation of the cross section area (or overall opening and closing) of the working chamber, formed by the enclosing and enclosed elements, takes place, as well as an axial movement of the working chamber by one period P_m in the machines with an inner screw surface or by one period P_f in the machines with an outer screw surface, wherein P_m, P_f are pitches (periods) of a screw turn of the end sections around central axes of the respective elements. The known methods of transforming a motion in volume screw machines of rotary type with conjugated elements of the curvilinear shape realized in the similar volume machines have the following drawbacks: - limited technical potential, because of an imperfect process of organizing a motion, which fails to increase a quantity of angular cycles per one turn of the drive member with an independent degree of freedom; - limited specific power of similar screw machines; - limited efficiency; - existence of reactive forces on the fixed body of the machine. SUMMARY OF THE INVENTION It is an object of the invention to provide an improved rotary screw machine which is in particular very compact such that it can be used for example in a hub of a back wheel of a bicycle, The rotary screw machine according to the invention comprises an outer enclosing screw element having a profiled inner surface, an inner enclosed screw element having a profiled outer surface, at least two intermediate screw elements which are both enclosing and enclosed and have both a profiled inner and a profiled outer surface, wherein all screw elements form a series of coaxial elements of which each enclosed element is housed in a respective next enclosing element. In the rotary screw machine according to the invention, the inner enclosed screw element comprises a longitudinal cavity which is open at both of its ends. That feature allows for a very compact rotary screw machine because the longitudinal cavity in the interior of the inner enclosed screw element can be used in a very efficient manner. In particular, it can be used to transport a working medium from one side (one end) of the machine to the other (opposite) side (other end) of the machine. The working medium can be transported either directly in that cavity. The cavity can also house at least one further element. In one alternative, the working medium is transported in the space surrounding that further element. In a preferred embodiment, however, the cavity houses a rotatable shaft which comprises a longitudinal channel in its interior (or a plurality of such channels). By using such a channel for the transport of the medium, the working medium can be more efficiently guided in the interior of the inner enclosed screw element. That feature is in particular in connection with a feature provided in a further preferred embodiment in which the shaft is a crank shaft performing a planetary motion. Due to the planetary motion, the channel(s) also rotate(s). Therefore, working medium from different inlet portions can be transported in the interior of the inner enclosed screw element. In a further preferred embodiment, the crank shaft is adapted to rotate about a fixed longitudinal body which is suited to stabilize the whole construction. Of course, it does only make sense to transport the working medium from one end of the machine to the other end if either the working medium can only be provided at one end thereof and must exit the machine at the same end or if the working medium is intended to be transported in working chambers in different portions of the machine into the same direction. Hence, in a preferred embodiment, the machine comprises two kinematic mechanisms. The machine is arranged in such a manner that in each kinematic mechanism, working chambers are formed in which upon motion of screw elements, a working medium is transported in a predetermined direction. This direction is equal for both kinematic mechanisms. In order to provide a compact rotary screw machine, the working medium in one of these kinematic mechanisms does not directly exit the machine. Rather, it is transported in the channel in the opposite direction such as to be fed into the second kinematic mechanism. In order to facilitate the entering of the working medium into the interior of the inner enclosed screw element, the kinematic mechanism in which the working medium is at first transported should be the innermost kinematic mechanism. In other words, the rotary screw machine should comprise an input channel for providing a working medium to that innermost one of the kinematic mechanisms. The working medium can then be transported in the interior of the inner enclosed screw element and there should be provided a means to feed that working medium to the outer one of the kinematic mechanisms. That principle of how a compact rotary screw machine can be provided can also be expressed in the following manner: A rotary screw machine according to the invention comprises at least two kinematic mechanisms including conjugated screw elements one housed in the interior of the other one, wherein it is constructed in such a manner that in each mechanism, upon motion of screw elements, a working medium is transported in a predetermined direction from a first side of the machine to a second side thereof, and wherein that direction is equal for both kinematic mechanisms. In the invention, a means for guiding said working medium from the second side back to the first side is provided. As mentioned above, that means is preferably nothing else than a cavity or a channel in one of the screw elements, namely the innermost one. According to an aspect of the present invention, a rotary screw machine comprises an outer enclosing screw element having a profiled inner surface, an inner enclosed screw element having a profiled outer surface, at least two intermediate screw elements which are both enclosing and enclosed and have both a profiled inner and a profiled outer surface, wherein all screw elements form a series of elements of which each enclosed element is housed in a respective next enclosing element. In that aspect, the inner enclosed screw element is a planetarily moving screw element. That feature also contributes to providing a very compact rotary screw machine because it is the planetary motion which ensures the formation of working chambers in different portions of the machine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more apparent from the following description of preferred embodiments thereof, which are given with respect to the accompanying drawings, in which: Fig.l shows a longitudinal section of a three-dimensional screw pneumatic motor of volumetric type which is for example set in a hub of a back wheel of a bicycle, and Fig.2 shows a cross section of the machine of fig.l along the lines II-IL A rotary screw machine which is shown in fig.l comprises an outer enclosing screw element, namely a fixed stator 1 having a profiled inner surface 201. It comprises an inner enclosed screw element, namely a rotor-satellite 4 having a profiled outer surface 104. There are two intermediate screw elements provided, namely a two-sided satellite 2 which is set up to rotate on a crank 7 of a shaft 6, and a two-sided central rotor 3. These elements have both a profiled outer surface 102 and 103, respectively, and a profiled inner surface 202 and 203, respectively. The screw elements 1, 2, 3 and 4 form a series of coaxial elements which are each housed in the respective next outer one. The inner enclosed screw element, the rotor-satellite 4 comprises a longitudinal cavity. The single screw elements are rotationally symmetrical, with the outer stator 1 having a symmetry order of 6, the two-sided rotor- satellite having a symmetry order of 2, the two-sided central rotor 3 having a symmetry order of 4, and the rotor-satellite 4 having a symmetry order of 3. The rotary screw elements form two groups of elements which together form different mechanisms. The first group comprised of the elements 1 and 2 and the outer surface 103 of the rotor 3 together with the crank 7 forms a planetary mechanism. That group has three degrees of freedom of mechanical rotation. One of these degrees - the rotation of the rotor 3 - is independent. The second group comprised of the rotor-satellite 4, the crank 5 and the inner surface 203 of the rotor 3 forms a planetary differential mechanism having three degrees of freedom of mechanical rotation. Two of these degrees of freedom, namely the rotation of the rotor 3 and the rotation of the crank 5 are independent. The stator 1 and the movable shaft 6 are set in the fixed body 8. The movable rotor 3 is mechanically connected through a shaft 9 serving as an output shaft. The channel 17 in the crank 5 serves to transport the working medium from one side (in fig.l the left-hand side) of the rotary screw machine to the other, opposite side (left-hand side in fig.l). In the rotary screw machine of the invention as shown in fig.l, the working medium can therefore be twice transported from the right-hand side in fig.l to the left-hand side: It enters the machine via an inlet stub 18. The channels in the body 8 are arranged in such a manner that the working medium (gaseous medium) reaches a gas distributor guiding the gaseous working medium into working chambers 500 provided in the innermost of the planetary mechanisms, namely the planetary differential mechanism formed by the inner surface of the rotor 203, the rotor-satellite 4 and the crank 5. The working medium which has reached the other side of the machine then enters the channel 17 (and the other channels in the crank 5) and is transported to an opening in the body 8 which is practically opposite to the gas distributor 16 when seen with respect to the central axis Z of the machine. Via channels in the body 8, the working medium is then transported to outer working chambers 300 and 400 formed in the outer group of screw elements, namely in the group formed by the outer surface 103 of the rotor 3, the two-sided rotor-satellite 2 and the central external stator 1 together with the crank 7. The working medium then exits the machine via a stub tube 15. Of course, the inner profiled surface 103 and the outer profiled surface 203 of the rotor 3 are mechanically connected to one another. In other words, the innermost element of the outer kinematic mechanism and the outermost element of the inner kinematic mechanism are mechanically coupled to one another. The rotor is coupled via a free wheel 11 to an input rotor 9 and to a wheel hub of the motor. If compressed air is supplied through the stub tube 18 and the channel of the body 8 to the gas distributor 16, the planetary element 2 is set into planetary motion, thereby setting the rotor 3 into rotation, and therewith the planetary rotor 4 and the shaft 6. That cavity houses a crank 5 of the shaft 6. That crank 5 is adapted to rotate around a fixed body which is indicated at 8, namely a rotor-shaped portion thereof attached to an outer structure of the whole machine. The crank 5 further comprises three channels, namely a main channel 17 in which a working medium can be transported. The compressed air rotates the rotor 3 with an angular velocity α)3, and via the clutch 11 it rotates the rotor 9 and the hub 10 with the angular velocity ω_n=ω₃. The directions and the values of the angular velocities of the independent rotations for each kinematic mechanism are defined by the synchronizing shaft 6 which is common to these groups. Thereby, the rotors-satellites 2 and 4 execute a planetary motion in equal directions of revolutions about respective centres O₂ and O₄ which are spaced apart from the central axis Z with an eccentricity of E₂ and E₄. The conjugated elements 1 to 4 jointly advance the working medium by motion of their conjugation contacts in the chambers 300, 400 and 500 and further through the ports of the body 8 and the stub tube 15 to the outside of the machine. A complete cycle of an axial movement of the six working chambers 300 with the working medium occurs with the symmetry orders of the screw elements as mentioned above in 180° of rotation of the rotor 3, i.e. twice during one rotation of the shaft 6. A complete cycle of an axial movement of the five working chambers 400 occurs under the same circumstances in 150° of rotation of the output rotor 3, i.e. 2.4 times during one rotation of the rotor. A complete cycle of an axial movement of the four working chambers 500 occurs under the same circumstances in 120° of rotation of the output shaft 6, i.e. thrice during one rotation of the rotor 3. If the relative angular velocity of the rotation of the rotor ω₃ is taken to be unity, ω₃=l and in view of the fact that the stator 1 is fixed, o)ι=0, one obtains a relative angular velocity of the revolution ω_re.₂ of a line O₂-O of the rotor-satellite 2 about the axis Z by ω_re by using the formula (ω₃-ωre.2)/(ωι-ω_re.2)=nm.ι/nm.₃ or ω_re.₂=-2 (n_m.ι=6 is the symmetry order of the stator 1, n_m.3=4 is the symmetry order of the rotor 3. The swivelling velocity ω_s.₂ of the rotor-satellite 2 around its centre O₂ is determined by using the formula (ω_s.₂=-ω_re.₂)/(ωι- ω_re.₂)=nm.ι/nm.₂, wherein n_m.₂=5 is the symmetry order of the element 2, thereby obtaining ω_s.₂=2/5. Turning now to the inner kinematic mechanism, one obtains for the relative angular velocity of the revolution of a line ω₄-ωo of the rotor- satellite 4 about the Z-axis ω_re.₄=ω_re.₂=-2. The rotor-satellite 4 swivels around the axis O₄ with a relative angular velocity ω_s.₄ which can be determined by using the formula (ω_s.4-ωre.4)/(ω3-ω_re.4)=nm.3/nm.4 or ω_s.4=2, wherein n_m.₄=3 is the symmetry order of the element 4. One obtains ω_s.₄=2. In other words, the planetary motion takes place in such a manner that the centres O₂ and O₄ are placed uniformly along the circumferences. If the eccentricities E₂ and E₄ are chosen such as to obtain a statically balanced system, it is also dynamically balanced. The rotor 9 and the hub 10 may rotate with the help of the motor drive (rotor 3, clutch 11, rotor 9, hub 10). However, they can also be driven by a muscular drive, via a gear wheel 13, a clutch 12 and the rotor 9 and the hub 10. When the motor drive is in operation and the gear wheel is fixed, the clutch 12 slides. When the gear wheel is in operation and the motor drive is fixed, the clutch 11 slides. Furthermore, a simultaneous operation of both the motor drive and the muscular operated drive is possible, if the rotor 3 via the clutch 11 and the gear wheel 13 via the clutch 12 rotate the rotor 9 and the hub 10. When the wheel 13 is reversed such as to use it as a breaking wheel, rollers of the clutch 12 slide and rollers of a reverse clutch 14 are engaged with a friction break 15 which breaks the hub 10. An advantage of the invention lies in the decreasing of the angular extent of the thermodynamic cycles, in the decreasing of resultant momentum and by providing a decrease of reactive forces on the motor supports. The screw volume motor according to the invention has very good specific characteristics. The motor is of very compact design and can therefore be used in bicycles without having too much weight and consuming too much space.

Claims

1. A rotary screw machine, comprising: An outer enclosing screw element (1) having a profiled inner surface (201), an inner enclosed screw element (4) having a profiled outer surface (104), - at least two intermediate screw elements (2, 3) which are both enclosing and enclosed and have both a profiled inner and a profiled outer surface (102, 103; 202, 203), - all screw elements (1, 2, 3, 4) forming a series of coaxial elements of which each enclosed element is housed in the respective next enclosing element, wherein the inner enclosed screw element (4) comprises a longitudinal cavity which is open at both of its ends.

2. The rotary screw machine of claim 1, wherein said longitudinal cavity is adapted to house at least one further element.

3. The rotary screw machine of claim 2, wherein said cavity houses a rotatable shaft (5), said shaft (5) comprising a longitudinal channel (17) in its interior.

4. The rotary screw machine of claim 3, wherein said shaft is a crank shaft (5) which is preferably adapted to rotate around a fixed longitudinal body (8).

5. The rotary screw machine of claim 3 or 4, wherein the machine comprises two kinematic mechanisms, said machine being arranged in such a manner that in each kinematic mechanism, working chambers are formed in which upon motion of screw elements, a working medium is transported in a predetermined direction, said direction being equal for both kinematic mechanisms, and wherein said working medium is transported in said channel (17) in the opposite direction.

6. The rotary screw machine of claim 5, comprising an inlet stub (18) for providing a working medium to the innermost one of the kinematic mechanisms.

7. A rotary screw machine, comprising: At least two kinematic mechanisms, including conjugated screw elements one housed in the interior of the other one, wherein in each mechanism, upon motion of the screw element, a working medium is transported in a predetermined direction from a first side of the machine to a second side thereof, said direction being equal for both kinematic mechanisms, and a means (17) for guiding said working medium from the second side back to the first side.