GB2029905A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a reversible gerotor pump an outer rotor 16 is mounted eccentrically in a partially rotatable bearing sleeve 20; and to ensure turning of the sleeve through 180 DEG when the rotation direction reverses adequate friction between the sleeve and the said rotor is provided by e.g. leaf springs 34 in grooves 36 formed in the sleeve's inner surface. <IMAGE>

Description

SPECIFICATION Improvements relating to pumps This invention relates to pumps of the kind comprising a pair of generally complimentary and meshed rotors having respectively n and n + 1 lobes, which rotate together about eccentric axes at different speeds so that a series of chambers of constantly differing volume is formed between the lobes. Two spaced points swept by the lobes are connected to an inlet and an outlet respectively.

It is known to mount the outer rotor in an eccentric sleeve with limit means controlling alternative positions of the sleeve, so that if and when the direction of rotation of the rotor is reversed, the sleeve turns angularly in the new sense up to the limit stop, and this enables the direction of flow through the inlet and outlet to be maintained, constant, irrespective of rotor direction.

However, if the eccentric sleeve does not move when the rotor direction is reversed, the effect is that the direction of flow is reversed and the original outlet becomes an inlet and the original inlet becomes outlet. It is found in practice that the eccentric sleeve will stick, that is fail to shift, is some circumstances, and the object of the present invention is to provide an improved construction in which the possibility of such failure is substantially reduced.

In accordance with the present invention, a pump of the kind referred to is characterised by the provision of friction means effective between the outer rotor and the eccentric sleeve. Hence, the sleeve tends to be dragged with the outer rotor in whichever direction of rotation is employed.

Preferably, the friction means comprise a blade spring trapped between the outer rotor and the sleeve.

One presently preferred embodiment of the invention is now more particularly described by way of example and with reference to the accompanying drawings wherein: Figure 1 is an elevation of a pump with parts removed for clarity; Figure 2 is a section taken on the line 2-2 of Fig. 1; Figure 3 is an exploded perspective view showing components of the pump; and Figure 4 is an enlarged scale fragmentary sectional view on the line 4-4 of Fig. 2.

Referring now to the drawings, the pump comprises a body 10 provided with inlet and outlet connections 12 14, the body having a generally cylindrical chamber housing a pair of meshed rotors 1 6 1 8 and an eccentric sleeve 20. The chamber is closed by a cover plate 22. As illustrated, the rotor 1 8 has five lobes and driven by shaft 22, and the outer rotor 1 6 has six lobes, although other configurations can be employed.

The eccentric sleeve 20 is relieved at 24 between end abutments 26 28, either of which can register with abutments stop 30 fixed to the base of the chamber. As will be appreciated, the sleeve tends to turn in the same direction as the outer rotor 1 6 unless prevented by the abutment stop, and in the event of reversal of the direction of rotation, tends to turn so as to take the opposite abutment stop against the pin or like 30.

As explained, the object of the invention is to ensure that this reverse movement of the sleeve 20 takes place, and to this end blade springs 34 are provided and the sleeve 20 1 6 has peripherally extending shaliow grooves 36 to accomodate the blade springs, one to each groove. Each spring generally conforms to the curvature of the parts when assembled as shown in Fig. 2, but provides sufficient frictional engagement for the purpose mentioned.

It will be noted that the spring is of less width than the rotor, so that the rotor 1 6 has its full diameter a close fit in the sleeve 20.

1. A pump of the kind comprising a pair of generally complementary and meshed rotors having respectively n and n + 1 lobes, which rotate together about eccentric axes at different speeds so that a series of chambers of constantly differing volume is formed between the lobes, and having the outer rotor mounted in an eccentric sleeve with limit means controlling alternative positions of the sleeve for use in the reverse direction of rotation without reversing flow through the inlet and outlet opening to said chambers, characterised in that friction means are provided (34) effective between the outer rotor (16) and the eccentric sleeve (20).

2. A pump as claimed in Claim 1 characterised in that the friction means comprise one or more blade springs (34).

3. A pump as claimed in Claim 2 wherein the or each blade spring is of a width less than that of the outer rotor and lies in a groove provided in one or other of the said outer rotor and eccentric sleeve.

4. A pump as claimed in Claim 3 wherein said eccentric sleeve (20) is provided with a pair of diametrically related grooves (36) each of which accommodates a corresponding blade spring (34) frictionally to contact the outer rotor.

5. A pump of the kind referred to and substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to pumps This invention relates to pumps of the kind comprising a pair of generally complimentary and meshed rotors having respectively n and n + 1 lobes, which rotate together about eccentric axes at different speeds so that a series of chambers of constantly differing volume is formed between the lobes. Two spaced points swept by the lobes are connected to an inlet and an outlet respectively. It is known to mount the outer rotor in an eccentric sleeve with limit means controlling alternative positions of the sleeve, so that if and when the direction of rotation of the rotor is reversed, the sleeve turns angularly in the new sense up to the limit stop, and this enables the direction of flow through the inlet and outlet to be maintained, constant, irrespective of rotor direction. However, if the eccentric sleeve does not move when the rotor direction is reversed, the effect is that the direction of flow is reversed and the original outlet becomes an inlet and the original inlet becomes outlet. It is found in practice that the eccentric sleeve will stick, that is fail to shift, is some circumstances, and the object of the present invention is to provide an improved construction in which the possibility of such failure is substantially reduced. In accordance with the present invention, a pump of the kind referred to is characterised by the provision of friction means effective between the outer rotor and the eccentric sleeve. Hence, the sleeve tends to be dragged with the outer rotor in whichever direction of rotation is employed. Preferably, the friction means comprise a blade spring trapped between the outer rotor and the sleeve. One presently preferred embodiment of the invention is now more particularly described by way of example and with reference to the accompanying drawings wherein: Figure 1 is an elevation of a pump with parts removed for clarity; Figure 2 is a section taken on the line 2-2 of Fig. 1; Figure 3 is an exploded perspective view showing components of the pump; and Figure 4 is an enlarged scale fragmentary sectional view on the line 4-4 of Fig. 2. Referring now to the drawings, the pump comprises a body 10 provided with inlet and outlet connections 12 14, the body having a generally cylindrical chamber housing a pair of meshed rotors 1 6 1 8 and an eccentric sleeve 20. The chamber is closed by a cover plate 22. As illustrated, the rotor 1 8 has five lobes and driven by shaft 22, and the outer rotor 1 6 has six lobes, although other configurations can be employed. The eccentric sleeve 20 is relieved at 24 between end abutments 26 28, either of which can register with abutments stop 30 fixed to the base of the chamber. As will be appreciated, the sleeve tends to turn in the same direction as the outer rotor 1 6 unless prevented by the abutment stop, and in the event of reversal of the direction of rotation, tends to turn so as to take the opposite abutment stop against the pin or like 30. As explained, the object of the invention is to ensure that this reverse movement of the sleeve 20 takes place, and to this end blade springs 34 are provided and the sleeve 20 1 6 has peripherally extending shaliow grooves 36 to accomodate the blade springs, one to each groove. Each spring generally conforms to the curvature of the parts when assembled as shown in Fig. 2, but provides sufficient frictional engagement for the purpose mentioned. It will be noted that the spring is of less width than the rotor, so that the rotor 1 6 has its full diameter a close fit in the sleeve 20. CLAIMS

1. A pump of the kind comprising a pair of generally complementary and meshed rotors having respectively n and n + 1 lobes, which rotate together about eccentric axes at different speeds so that a series of chambers of constantly differing volume is formed between the lobes, and having the outer rotor mounted in an eccentric sleeve with limit means controlling alternative positions of the sleeve for use in the reverse direction of rotation without reversing flow through the inlet and outlet opening to said chambers, characterised in that friction means are provided (34) effective between the outer rotor (16) and the eccentric sleeve (20).

2. A pump as claimed in Claim 1 characterised in that the friction means comprise one or more blade springs (34).

3. A pump as claimed in Claim 2 wherein the or each blade spring is of a width less than that of the outer rotor and lies in a groove provided in one or other of the said outer rotor and eccentric sleeve.

4. A pump as claimed in Claim 3 wherein said eccentric sleeve (20) is provided with a pair of diametrically related grooves (36) each of which accommodates a corresponding blade spring (34) frictionally to contact the outer rotor.

5. A pump of the kind referred to and substantially as described with reference to the accompanying drawings.