GB2041143A

GB2041143A - Stroke adjustment mechanism for reciprocating positive displacement pumps

Info

Publication number: GB2041143A
Application number: GB8000550A
Authority: GB
Original assignee: BRAN and LUEBBE
Current assignee: BRAN and LUEBBE
Priority date: 1979-01-30
Filing date: 1980-01-08
Publication date: 1980-09-03
Also published as: DE2903395A1; FR2448050A1; BR8000415A; IT1126904B; IT8047734A0

Abstract

An adjustment mechanism for changing the stroke of a reciprocating apparatus, for example a positive displacement pump is described. The stroke of a connecting rod 10 is changed by changing the relative axial position of an inclined crank 1, such as a wobble shaft bushing 1, which is rotated by a drive shaft 2. The axial adjustment of the crank 1 is performed by a suitable axial screw 4, 5. The connecting rod 10 is coupled to the inclined crank 1 via a swivel joint, in particular a swivel ball bearing 11, the outer race of which is held slidingly between bearing surfaces 12 of a housing 7. <IMAGE>

Description

SPECIFICATION Stroke adjustment mechanism for reciprocating positive displacement pumps The invention relates to a stroke adjustment mechanism for a reciprocating positive displacement pump with an inclined crankshaft mounted on a drive shaft.

Adjustment mechanisms of this general type are known and are manufactured commercially in various configurations. For example, the German laid-open Application No.

1,400,689 describes a crank drive in which the throw of the crank, i.e. the radius, may be changed by means of an axially movable tongue equipped with an oblique wedge cooperating with a radially movable eccentric guide block which holds the tongue and wedge. The two moving parts are rotatably coupled by a slot which is engaged by the wedge and rotate together. The rotary motion of the crankshaft is transmitted into a reciprocating motion by connecting rods which engage an annular groove in the eccentric guide block. The inclinations of the groove and the wedge must be precisely equal so as to prevent any lateral wobbling motion of the eccentric guide block.

The stresses exerted on the moving parts alternate in direction during the reciprocating motion and cause a to-and-fro tilting of the eccentric guide block on the adjustment tongue which has detrimental effects on the endurance of the coupling.

German Patent Specification No.

1,653,579 describes a mechanism in which the crankshaft is an inclined crank pin which may be axially adjusted in the direction of the crankshaft bearing. The power transmission takes place via an eccentric guide block. The inclined crank pin has a round cross section and the eccentric guide block has an inclined bore but the two parts must be fixedly coupled in rotation to as to prevent jamming of the guide block. Furthermore, this coupling requires that the inclined crankshaft and the bore have exactly the same phase relationship which requires substantial effort during manufacture of these parts.

It is thus an object of the invention to provide for reciprocating positive displacement pumps an adjustment mechanism which is improved with respect to the prior art by dispensing with an eccentric guide block and thereby overcoming the aforementioned disadvantages of the known mechanisms. It is an associated object of the invention to provide an adjustment mechanism which is of relatively simple construction and relatively low cost yet which provides long life and reliability.

According to the present invention there is provided a mechanism for adjusting the stroke of a reciprocating pump, comprising a housing, a drive shaft extending into said housing, an inclined crank adjustably mounted on said drive shaft, and a connecting rod attached to said inclined crank via a swivel joint having an inner part that is arranged to co-rotate with said inclined crank and an outer part that is held slidingly in said housing.

The inclined crankshaft is preferably in the form of a wobble shaft bearing and the connecting rod may be attached to the crankshaft bearing via a ball joint. The outer race or ring of the ball joint is held slidingly between guide surfaces. In one embodiment of the mechanism, the swivel joint is a swivel ball bearing, while in another embodiment of the mechanism, the swivel joint is a swivel sleeve bearing.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example and embodiment thereof, and in which: Figure 1 is a side view of a reciprocating pump incorporating an adjustment mechanism according to the invention, and Figure 2 is a section through the mechanism of Fig. 1 along the line Il-Il.

Referring now to the drawings, there is shown an adjustment mechanism for a reciprocating pump, the adjustment mechanism comprising an inclined crankshaft 1 formed as a wobble shaft bushing which is slidingly held on a drive shaft 2 of a motor or transmission of the pump and is coupled to the shaft 2 by a groove and spring means 3 which provides for the transmission of rotary forces.

The inclined crank 1 may be axially displaced by means of a hand wheel 4 which turns a threaded shaft 5. The hand wheel 4 and the shaft 5 are prevented from moving axially within a housing 7 of the mechanism by a disc 6. Mounted on the inclined crankshaft 1 is an axial flange 8 which holds the inner race of a ball bearing 9 the outer race of which is held within the housing 7.

A connecting rod 10 is coupled to the outer circumference of the inclined crank 1 via a ball joint 11 the outer ring of which slides between guide surfaces 1 2 of the housing 7, and which is a press-fit within the connecting rod 10.

Rotation of the hand wheel 4 causes axial displacement of the inclined crankshaft, thereby changing the eccentricity of the entire drive. A change of the eceentricity changes the stroke of the connecting rod 10 and therefore also changes the diplacement of a diaphragm 1 3 of the pump or a piston of the pump when the mechanism is used to power a piston-type dosing pump. The end of the connecting rod 10 is attached directly and without intermediary joint to the double diaphragm 1 3 shown in Fig. 2 or to a wrist pin or other internal structure of a piston, depending upon which is used in the pump.

The degree of stroke adjustment set by the hand wheel 4 may be indicated by a suitable clock-type indicating mechanism 14. The adjustment is made self-locking by an annular surface seal having a disc spring which also serves to prevent the leakage of transmission lubricant around the adjustment shaft.

The magnitude of the stroke adjustment is determined by the length of the wobble shaft bushing and the angle between the axis of rotation of the shaft and the wobble axis.

The ball joint 11 eliminates the possibility of wear and gear which takes place in previously proposed mechanisms due to the relative tilting or canting between the inclined crankshaft and the oblique bore within the eccentric guide block.

The ball joint 11 which compensates for the wobbling motion is preferably formed as a swivelling roller bearing. However, in another embodiment of the invention, the ball joint 11 may be formed as a swivelling sleeve bearing.

Due to the fact that no rotatably fixed connection exists between the inclined crank and the outer ring of the ball joint, the present mechanism does not require a very precise adjustment of the relative phase relationship of the coupling which is necessary in heretofore proposed adjustment mechanisms.

The present adjustment mechanism has a simple construction and is thus capable of being produced at relatively low cost. The absence of the normally required eccentric guide block results in particularly reliable operation, long life and low service requirements.

Claims

1. A mechanism for adjusting the stroke of a reciprocating pump, comprising a housing, a drive shaft extending into said housing, an inclined crank adjustably mounted on said drive shaft, and a connecting rod attached to said inclined crank via a swivel joint having an inner part that is arranged to co-rotate with said inclined crank and an outer part that is held slidingly in said housing.

2. A mechanism as claimed in claim 1, wherein said inclined crank is a wobble shaft bushing.

3. A mechanism as claimed in claim 1, wherein said swivel joint is a swivel ball bearing.

4. A mechanism as claimed in claim 1 or 2, wherein said swivel joint is a swivel sleeve bearing.

5. A mechanism as claimed in any preceding claim and further comprising rotatable shaft means for engaging said inclined crank and changing the axial position thereof relative to said connecting rod.

6. A mechanism for adjusting the stroke of a reciprocating pump substantially as here inbefore described with reference to the accompanying drawings.