LYSHOLM COMPRESSOR PDF

A twin-screw supercharger with improved sealing between the two rotors when compared with a Roots blower. One rotor has thin blades with a thick ridge, while the other has thick teardrop-shaped lobes and a sharp edge Access to the complete content on Oxford Reference requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription. Please subscribe or login to access full text content. If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

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The present invention relates to compressors of the rotary screw type in which two or more cooperating rotors mounted within a suitable casing operate to provide compression spaces, the volume of which varies upon rotation of the rotors to effect compression of the working fluid within the compressor. In compressors of this type, compression spaces on each of two cooperating rotors are brought into communication with each other and thereafter the two spaces work together as a common compression space until further rotation of the rotors brings one or the other or both of these spaces into communication with an outlet port in the casing.

We have discovered that the action of the rotors in previously proposed forms of screw type compressors is such that reduction in volume of any given compression space in one rotor commences prior to reduction in volume of the compressor space in the cooperating rotor with which the first space is brought into communication.

The result of this is that two compression spaces are brought into communication with a certain amount of compression having already taken place in one, whereas it has not taken place in the other. Consequently, when communication between the two spaces occurs, equalization of pressure between the two spaces takes place and the pressure of the working fluid which has already been partially compressed is reduced.

This reduction in the pressure of the working medium which has already been partially compressed results in an increase in entropy with a corresponding loss of work. Accordingly, the present invention has for a major object the provision of improved compressor apparatus of the kind described in which this partial compression in one compression space prior to its communication with another compression space in which compression has not commenced is avoided and in which the compression occurring in any two compression spaces which come into communication with each other is substantially the same.

The more detailed nature of the invention and the manner in which the above stated and other and more detailed objects of the invention may be advantageously accomplished will appear more fully in the ensuing portion of this specification in which suitable embodiments of apparatus for carrying the invention into effect are described.

In the accompanying drawings forming a part of this specification:Fig. The compressor illustrated in Figs. It will be understood that insofar as the present invention is concerned, the number of rotors employed is not limited to two. The casing part 14 is advantageously provided with a jacket space 15 for water or other cooling fluid.

Rotors 10 and 12 are preferably made integral with the shaft parts and are advantageously mounted in roller bearings 16 and 18, and 20 and 22, respectively, which bearings carry the radial load.

Also, ball bearings 24 and 26 are advantageously provided to take up end thrust. The bearings are carried by casing parts 28 and which are suitably secured to the ends of the casing part 14 and which provide the end walls for the casing.

In the form of apparatus shown, the end walls limit the axial extent of the compression spaces. Packings 32, 34, 36, and 38 are provided around the shaft parts between the end walls and the bearings. The compressor is driven from the shaft 40 connected to the rotor 10 and drive is transmitted to the rotor 12 by means of gears 42 and 44 mounted respectively on the shafts of the rotors 10 and Preferably the rotors are mounted so that a slight clearance is maintained between the rotors and the casing and also between the intermeshing surfaces of the rotors, the clearance between the latter surfaces being maintained by the gear drive through gears 42 and The rotors as well as the casing may advantageously be cooled and for this purpose may be constructed as shown with hollow shafts provided with concentrically spaced inner pipes 46 and 48 respectively.

Cooling fluid for cooling rotor 10 is introduced through the nozzle 50 to the interior of the pipe 46, flowing longitudinally of the rotor in the direction of the arrow 52 inside the pipe and returning through the space between the pipe and the bore of the shaft in the direction indicated by arrows 54 and Cooling o the rotor 12 is -, inih'ei o the compre' sfor for the fluid to be conirp '. The inlet port, t:; i:s :i i. As will be seen from Figs. These grooves may be con. In the position of the rotors shown in Fig.

The working fluid which has previously entered the compressor to the suction space 74 has been confined in the space or pocket P in the rotor I0,. This equalization of pressure results in a lowering of the pressure in the pocket P as compared with the pressure just prior to communication between the pockets, with consequent loss.

In the present embodiment of the apparatus, this loss is avoided by providing a pressure relief passage 80 in the casing part Passage 80 terminates in two ports 82 and 84 located as shown in Fig. If full advantage is to be secured from the provision of the passage 80, the ports should be arranged so that they are uncovered not later than the instant when the thread S commences to enter the pocket P, so that no compression can be effected in the pocket P prior to the establishment of communication by means of passage 80 between this pocket and pocket R.

By interconnecting the pockets in this way, compression cannot occur in one of the pockets prior to the commencement of compression in the other of the pockets and there is consequently no time during the compression period when a pressure equalization takes place between two spaces which entails any appreciable drQp in pressure of fluid previously compressed to a higher pressure. In the arrangement shown, commencement of compression occurs substantially simultaneously in both pockets, some of the working fluid from pocket P flowing through the passage 80 to the pocket R during that portion of the compression period when the volume of pocket P is being reduced and prior to direct communication between the two pockets.

It will be evident that in order to effect the desired purpose, the passage for connecting the two pockets need not be situated in the end member of the casing, although this provides an advantageous location, but may be situated in the cylindrical portion of the casing with its terminal ports located so as to be opened by the radially outer edges or surfaces of the rotor threads or teeth, as illustrated by the modification shown in Fig.

In this embodiment, the pockets P and R may be connected by a passage 80a provided in the cylindrical portion 14 of the casing and terminating in two ports 82a and 84a.

In the embodiment illustrated in Figs. In this embodiment, the suction ends of the rotors are not entirely covered by the end wall of the casing part 30a at the suction end of the compressor, the latter being advantageously recessed to provide what is in effect an end plate 88 having the contour shown in Fig. Obviously, the end plate 88 may project from an inner plane surface of the end part of the casing.

Regardless of the specific form of construction of the part 30a, the ends of the rotors at the suction end of the compressor are in contact, or substantially in contact, only with an end wall surface limited by the lines e, f, g, h, k, m, n. With this arrangement, the pocket P remains in communication with the suction space 74 until the front edge a of the thread Ti reaches the position ai, in which position it has just passed the edge e of the end wall Until edge a passes edge e, no compression takes place in the pocket P and the position of the edge e is arranged so that it substantially coincides with the position of the edge a at the instant ivhen the point G on the thread S passes the point M.

When the edge e is located in this manner, no compression is effected prior to the time of direct communication between pockets P and R and thereafter compression commences, with the two pockets in communication so that simultaneous and like compression takes place in both pockets. While we prefer to connect the pocket P with the suction chamber of the compressor until the two pockets are brought into direct communication with each other, it will be evident that the passage which prevents compression in pocket P prior to compression in pocket R may lead directly to atmosphere if the compressor is being employed to compress atmospheric air or to any zone of pressure substantially equal to the inlet pressure of the fluid being compressed.

It will also be evident that the pressure relief passage providing communication between pocket P and the desired zone of low pressure need not necessarily be formed by special configuration of-the end member of the casing but may be formed by special configuration of a part of the casing radially enclosing the rotor.

It will further be evident that the special configuration of the end member 30a with respect to the portions f, g, h, and k need not be exactly as shown in the illustrated embodiment. In Fig. Certain novel features of compressor construction relating to thread structure and porting disclosed but not claimed herein are not our joint invention but constitute the sole inventions of Alf Lysholm forming the claimed subject matter of U.

From the foregoing description, it will be evident that the invention may be embodied in many different specific forms of apparatus differing from the embodiments hereinbefore described by way of example and it is further to be noted that the invention is independent of the number of rotors employed, the number of pockets provided per rotor and of the specific form or configuration of the pockets or threads defining the pockets.

We claim: 1. A compressor of the rotary screw type including a casing having an inlet and an outlet for fluid, a first rotor and a second rotor mounted in said casing, said rotors having interengaging screw threads forming pockets therein formed and arranged together with the inner walls of said casing to provide compression spaces registering at different times with said inlet and said outlet and decreasing in volume between the time of registry with said inlet and the time of registry with said outlet, said compression spaces including a first pocket in the first rotor and a second pocket in the second rotor, said first pocket and said second pocket being disposed.

A compressor of the rotary screw type including a casing having end walls having an inlet and an outlet for fluid, a first rotor and a second rotor mounted in said casing between said end walls, said rotors having interengaging screw threads forming pockets therein formed and arranged together with the inner walls of said casing to provide compression spaces registering at different times with said inlet and said outlet and Ito decreasing in volume between the time of registry with said inlet and the time of registry with said outlet, said compression spaces including a first pocket in the first rotor and a second pocket in the second rotor, said first pocket and said.

All rights reserved. A SumoBrain Solutions Company. Login Sign up. Search Expert Search Quick Search. Rotary compressor. United States Patent The present invention relates to compressors of the rotary screw type in which two or more cooperating rotors mounted within a suitable casing operate to provide compression spaces, the volume of which varies upon rotation of the rotors to effect compression of the working fluid within the Click for automatic bibliography generation.

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Rotary-screw compressor

The present invention relates to compressors of the rotary screw type in which two or more cooperating rotors mounted within a suitable casing operate to provide compression spaces, the volume of which varies upon rotation of the rotors to effect compression of the working fluid within the compressor. In compressors of this type, compression spaces on each of two cooperating rotors are brought into communication with each other and thereafter the two spaces work together as a common compression space until further rotation of the rotors brings one or the other or both of these spaces into communication with an outlet port in the casing. We have discovered that the action of the rotors in previously proposed forms of screw type compressors is such that reduction in volume of any given compression space in one rotor commences prior to reduction in volume of the compressor space in the cooperating rotor with which the first space is brought into communication. The result of this is that two compression spaces are brought into communication with a certain amount of compression having already taken place in one, whereas it has not taken place in the other. Consequently, when communication between the two spaces occurs, equalization of pressure between the two spaces takes place and the pressure of the working fluid which has already been partially compressed is reduced.

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About Lysholm

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EP0828079A3 - Lysholm compressors - Google Patents

A rotary-screw compressor is a type of gas compressor , such as an air compressor , that uses a rotary-type positive-displacement mechanism. They are commonly used to replace piston compressors where large volumes of high-pressure air are needed, either for large industrial applications or to operate high-power air tools such as jackhammers and impact wrenches. For smaller rotor sizes the inherent leakage in the rotors becomes much more significant, leading to this type of mechanism being unsuitable for small air compressors. The gas compression process of a rotary screw is a continuous sweeping motion, so there is very little pulsation or surging of flow, as occurs with piston compressors. This also allows screw compressors to be significantly quieter and produce much less vibration than piston compressors, even at large sizes, and produces some benefits in efficiency. Rotary-screw compressors use two very closely meshing helical screws , known as rotors, to compress the gas. In a dry-running rotary-screw compressor, timing gears ensure that the male and female rotors maintain precise alignment without contact which would produce rapid wear.

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