GB2426036A

GB2426036A - Vertical Northey compressor

Info

Publication number: GB2426036A
Application number: GB0509495A
Authority: GB
Inventors: Jorge Carao
Original assignee: BERNARD WHICHER
Current assignee: BERNARD WHICHER
Priority date: 2005-05-10
Filing date: 2005-05-10
Publication date: 2006-11-15
Also published as: GB0509495D0

Abstract

A positive displacement rotary compressor of the hook and claw or Northey type is intended for use in a vertical orientation (i.e. vertical rotor shafts 1, 2). Shafts 1, 2 are supported in bearings 3 through a main plate 4 with rotors 17 above the plate to provide access and timing gears 5 below. Drive is via a magnetic coupling of coaxial or radial (Fig. 3) type to enable the compressor to be hermetic whilst involving ceramic materials to avoid needing a cooling system. The rotors and wear plates 15, 16 may be of carbon graphite to eliminate rotor seizing and allow high speed operation. Outer wear plate 15 has inlet and delivery ports and is replaceable to modify pressure ratios and flow rates.

Description

1 2426036 VERTiCAL ROTARY COMPRESSOR The purpose of the invention is to

modify the construction of the hook and claw "Northey" type compressor to provide a totally hermetic compressor. The invention also expands the machine output flow range, whilst improving the ease of maintenance.

Examples of the type of machine herein described are: GB 429171, GB 661749, GB 752437, and GB 900881.

The objectives of the invention are met by arranging the machine in such a way that the compression cavity with the rotating pistons or rotors is located at one end of the machine where the inlet and outlet connections shall be incorporated. This significantly simplifies access to the key components within the compressor chamber for easier maintenance or change of parts such as rotors, wear plates, or seals.

The carbon graphite rotors are contained between two carbon graphite plates at each end of the compression chamber. Fine clearances are maintained between all the moving parts in the compression chamber with the use of spacer shims. The sliding properties of the carbon graphite materials allow the use of smaller clearances than those employed with metal rotors, and also eliminate the possibility of the machine seizing due to the improved wear properties of the material.

The added advantage provided by these materials is the insulating characteristic that protects the rest of the machine from reaching the temperatures of the working chamber.

A magnetic coupling is used to drive the compressor and also to contain the compressor hermetically. The coupling is attached to the driver or prime mover at one end of the compressor assembly.

Two types of magnetic coupling could be employed with the described invention; a co-axial magnetic coupling where the permanent magnets are aligned in the direction of the shafts axis, or a radial magnetic drive where the magnets are laid out radially in a transverse plane to the shaft axis.

Since during the normal functioning of the coupling high temperatures are attained due to eddy currents, both magnetic couplings contain ceramic (non-metallic) materials in its construction to avoid the need for a cooling system.

Description of the preferred embodiment:

FIGURE 1 is a section view of the compressor.

FIGURE 2 is a front view of the port plate of the compressor.

FIGURE 3 is a section view of the compressor with an alternative magnetic coupling device used to drive the compressor.

Shown in figure 1 are two main shafts 1 and 2 that carry the rotors 17 which counter rotate.

These are supported in parallel by locating bearings 3 in the main plate 4 from where these two extend to both sides of the plate. The gearing 5 is located in the gear case 6 immediately next to the main plate; this transmits the power from the driving shaft to the driven shaft. Both shafts are fixed radially in an end plate 7 adjacent to the gear case with non-locating bearings 8. Beyond this plate the driving shaft extends and is connected to the outer rotor 9 of a co-axial magnetic coupling. This section of the compressor above described is isolated from the exterior by a static housing 10 surrounding the outer rotor of the coupling and a fixed ceramic non-metallic cylindrical shroud ii that is enclosed around the periphery of the inner face of the outer rotor of the magnetic coupling.

A small radial clearance is observed between the above mentioned rotor and the static shroud as to ensure no contact takes place during the normal functioning. The inner rotor 12 of the magnetic coupling transmits the rotating movement through the static shroud via magnetic forces from the aligned magnets of both rotors of the couplings. The inner rotor of the magnetic coupling that revolves in the in-side of the shroud is directly coupled to the prime mover 13 at the end of the assembly.

Also, in the other side of the main plate sits the compressor chamber 14. Between two wear plates 15 and 16 attached to the end faces of the compressor housing the rotors 17 are fixed in both shafts. The materials employed for the rotors and wear plates provide them with improved wear properties hence completely avoiding the dangers of the machine seizing. Rotors 17 of the special material also act as insulators to the shafts; whereas the wear plate 16 of a similar material acts as insulator to the adjacent components. As a result the compressor chamber is allowed to work at higher speeds. Northey machines historically have been able to work at rotational speeds as great as 1450 rpm due to thermal constraints. This new design permits the apparatus to double that speed, which translates into higher volume flows, smaller clearances in between the moving parts and higher output volume efficiencies. In this sense, a machine such as is described herein with the use of these special rotors could deliver at 3000 rpm 12% more flow than a bigger machine 1.5 times its size running at 1450 rpm made of traditional cast iron or steel.

The outermost wear plate 15 incorporates the profile of the inlet and delivery ports as shown in Figure 2. It is possible to change this wear plate for others with different port sizes to achieve different flows and pressures ratios. It should be noted that the machine is capable of being used as a compressor and vacuum pump.

It should also be appreciated that the invention described above could work employing a radial or disc type magnetic coupling instead for the same purposes of the design as shown in Figure 3.

The coupling consists of two opposing plates or rotors with magnets on the facing surfaces. This type of coupling offer advantages over the co- axial type initially described. Parallel misalignment and angular misalignment are tolerated without losing performance in the transmission of torque. Also, the overall length of the coupling section of the compressor is reduced to half. For this arrangement the compressor-side coupling rotor 20 is attached to the driving shaft 21 and contained inside the coupling housing 22. The prime mover coupling rotor 23 is direct coupled to the prime mover 24. Both rotors are separated by a ceramic flat plate 25 sitting in-between and attached to the housing 22, so the magnets on each coupling rotor, face each other in a perpendicular direction to the compressor shaft axis. The ceramic plate 25 attached permanently to the coupling housing avoids any leakage from the compressor to the exterior. The ceramic plate also enables running the coupling at high speeds; hence withstanding the high temperatures generated by eddy currents.

Claims

1. A Positive Displacement Rotary Compressor of the Hook and Claw type, designed for operating in a vertical position.

2. A compressor as in Claim 1, characterised by a co-axial magnetic coupling that both drives and hermetically seals the compressor.

3. A compressor according to any preceding claim that offers the flexibility to incorporate either a co-axial magnetic coupling aligned in the direction of the drive shaft axis, or, a radial magnetic drive positioned in a transverse plane to the shaft axis. Both couplings employing ceramic materials thereby eliminating the need for a separate cooling system to be attached to the compressor.

4. A compressor according to any preceding claim, being arranged in a vertical position and incorporating a ceramic shell that is permanently affixed to the coupling thereby preventing any leakage from the chamber or other components of the machinery.

5. A compressor according to any preceding claim in which carbon graphite materials are used for both the rotors and wear plates enclosing the compression chamber.

6. A compressor according to any preceding claim whereby the compression cavity with the rotating members or pistons is located at one end of the machine. This assembly allows easy access to the chamber thereby greatly simplifying maintenance and exchange of parts. This further eliminates the need to dismantle the machine for offsite maintenance. Together with the materials referred to in the preceding claims, this significantly reduces the down time' of machines and extends the lifecycle of components.

6. A compressor according to any preceding claim which makes novel use of materials thereby enabling the machine to work at higher speeds and process higher volume flows than previous models of said machine type. The properties of the said materials completely eliminate the risk of the machine seizure.

7. A compressor according to any preceding claim whereby the compression cavity with the rotating members or pistons is located at one end of the machine. This assembly allows easy access to the chamber thereby greatly simplifying maintenance and exchange of parts. This further eliminates the need to dismantle the machine for offsite maintenance. Together with the materials referred to in the preceding claims, this significantly reduces the down time' of machines and extends the lifecycle of components.

Amendments to the claims have been filed as follows

A Positive Displacement Rotary Compressor of the Hook and Claw type, characterised by a co-axial magnetic coupling that both drives and hermetically seah the compressor, being designed for operating in a vertical position.

2. A compressor according to any preceding claim that offers the flexibility to incorporate either a co-axial magnetic coupling aligned in the direction of the drive shaft axis, or, a radial magnetic drive positioned in a transverse plane to the shaft axis. Both couplings employing ceramic materials thereby eliminating the need for a separate cooling system to be attached to the compressor.

3. A compressor according to any preceding claim, being arranged in a vertical position and incorporating a ceramic shell that is permanently affixed to the coupling thereby preventing any leakage from the chamber or other components of the machinery.

4. A compressor according to any preceding claim in which both the rotors and wear plates, made in their entirety of carbon graphite, are enclosing the compression chamber.

5. A compressor according to any preceding claim which makes novel use of carbon graphite materials in the compression chamber thereby enabling the machine to work at higher speeds and process higher volume flows than previous models of said machine type. The properties of the said materials completely eliminate the risk of the machine seizure.