WO2009072129A1

WO2009072129A1 - A vacuum pump for injection of fluid additive into a pressurized fluid line

Info

Publication number: WO2009072129A1
Application number: PCT/IL2008/001583
Authority: WO
Inventors: Dan Bron
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-12-05
Filing date: 2008-12-04
Publication date: 2009-06-11
Anticipated expiration: 2010-06-05
Also published as: IL187911A0

Abstract

Vacuum pump (2) for the injection of a fluid additive under low pressure into a pressurized fluid line. The body (4) is σonnectable inline to a main fluid line including: two back-to-back inlet and outlet funnels (6, 8) delimiting an internal space and defining a fluid inlet space (10), a fluid outlet space (12) and a neck portion (14), interposed between and connecting the funnels; a feeding port (18) for introducing additive in fluid communication with the internal space about the neck portion; and an elongated pin assembly (20) coaxially guided and movable inside the outlet funnel (8). The pin assembly includes a pin head (22) protruding into and along a part of the neck portion to partially reduce the free fluid flow path in the neck portion. The pin head coaxially engages and is freely slidable with respect to a stem (24), the other end of which stem is anchored to the pump body. Pin head and stem enclose a control-space (30) communicating with the fluid pressure in the internal space of the pump, via a fluid flow-restricting control port (32, 34, 46, 38).

Description

A VACUUM PUMP FOR INJECTION OF FLUID ADDITIVE INTO A PRESSURIZED FLUID LINE

Field of the Invention

The present invention relates to vacuum pumps, and more particularly to an automatic vacuum pump for the injection of fluid additive under low pressure, into a pressurized fluid line. Background of the invention

Vacuum pumps are common for the injection of fluid additive at ambient pressure into a pressurized fluid line, to be mixed with the fluid inside the line. The line fluid flow traverses the pump body, shaped like two coaxial back-to-back funnels connected via a short neck. The line fluid flow is accelerated under high pressure via the narrow neck and, upon reaching a critical speed, negative pressures develop about the internal periphery of the neck, to admit the additive from the outside, where the suction feeding means are located.

The main drawbacks of this device are the big pressure-drop that is required to propel the main line fluid flow via the neck to achieve and exceed the critical fluid flow speed and to sustain suction, and the fact that fluid passage in the neck fits only a narrow range of line fluid flowrates. Fluid flowrates on the low side of the range are insufficient to achieve suction, while fluid flowrates on the upper side of the range cause high pressure drop on the pump. Summary of the Invention

According to the present invention there is provided a vacuum pump for the injection of a fluid additive under low pressures, into a pressurized fluid line, comprising a body connectable inline to a main fluid line including two back-to-back inlet and outlet funnels delimiting an internal space having an axis, and defining a fluid inlet space, a fluid outlet space and a neck portion, interposed between and connecting, said funnels, a feeding port for introducing additive, being in fluid communication with the internal space about the neck portion, an elongated pin assembly, substantially coaxially guided and movable inside said outlet funnel, said pin assembly includes a pin head, protruding into and along at least part of the neck portion, to at least partially reduce the free fluid flow path in the neck portion, said pin head coaxially engages, and is freely slidable with respect to a stem, the other end of which stem being anchored to the pump body, said pin head and stem enclosing a control-space communicating with the fluid pressure in the internal space of the pump, via at least one fluid flow-restricting control port. Brief Description of the Drawings

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figure so that it may be more fully understood.

With specific reference now to the figure in detail, it is stressed that the particulars shown are by way of example and for purpose of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawing making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawing:

Fig. 1 illustrates a cross-sectional view of an embodiment of an automatic vacuum pump, according to the present invention. Detailed Description of the Preferred Embodiments

There is illustrated in Fig. 1 a schematic representation of the preferred embodiment of the automatic vacuum pump 2, according to the present invention. Shown is a tubular body 4, coaxially housing all of the elements of the pump 2. The body 4 is configured as two back-to-back funnels 6 and 8, comprising a fluid inlet 10 and a fluid outlet 12, respectively connectable inline to a main fluid line and defining a fluid inlet space and a fluid outlet space. The funnels 6 and 8 are connected by a short cylindrical neck 14 at the downstream side of which, there is an annular suction groove 16, connected to a suction additive inlet port 18, constituting the additive feeder. Coaxially with the neck 14, there is located a pin assembly 20, commonly of a circular cross-section, having a tapered pin head 22, e.g., a conical edge, slidably coupled with a stem 24. The downstream end of the stem 24 is anchored to the body 4 by a perforated flange 26 and a screw 28. The pin head 22 and the stem 24 enclose an expandable control space 30 between them, which space is connectable to the fluid pressure inside the pump via a fluid flow-restricting, annular clearance, control port 32 and another small fluid flow control port 34. The pin head 22 is coaxially guided in the outlet funnel 8 by a set of ribs 36. A control port 38 communicates with the control space 30 via the bore 40 in the pin head 22. The upstream end of the stem 24 has a plunger 42 fitted with a plunger head 44, coaxially protruding from the stem 24, configured to reciprocate along the bore 40 to interrupt communication between the control port 38 and the control space 30 along a selected sliding length of the pin head 22. There is also shown an optional fluid control port 46 made in the head tail portion 48 surrounding the annular clearance control port 32, to render a similar effect to that of the control port 34.

Fig. 1 further illustrates the pump 2 in a rest state. The entire diameter of the pin head 22 blocks the fluid flow-path from the fluid inlet 10 through the neck 14. When fluid flow under pressure from the fluid inlet 10 starts, the pin head 22 is pushed back under the dragging force of the mains fluid flow, until this force is equally opposed by the control force created in the control space 30. Hence, the sliding of the tapered head stops and is held in position by two opposite equal forces: a) the flow drag of the main fluid line upon the pin head 22, loading downstream, and b) the pressure in the control space 30, loading upstream.

In operation, the incoming fluid flow drags the pin head 22 downstream at a force proportional to the fluid-flow speed. This force has to be matched by an opposite pressure existing inside the pump that communicates with the control space 30 via control ports 32, and 34 or 46, to bias the rear surface of the pin head 22, upstream. The control port 38 is blocked at the first sliding motion of the plunger head 44 and, is therefore neutralized. This is required for maintaining high bias pressure inside the control space 30 for low range flowrates. As the flowrates increase, lower bias is required, and therefore, upon the pin head 22 sliding downstream, the plunger head 44 will correspondingly move upstream along the bore 40 and clear the path for low pressure fluid introduced via port 38 to reach the control space 30. Simultaneously, control port 34, exposed to high pressure, will be blocked by the sliding of the head tail portion 48, overlapping the port 34. The pin assembly 20 will retreat and stop in the position where the two forces acting on it will be equal, while keeping the free cross-section of the neck 14 at its optimal size for fluid suction under minimal pump pressure drop.

When the flowrate decreases, the procedure will repeat itself in the reverse. The control space 30 with its flow-restricting control ports serves to effectively prevent possible axial vibrations of the pin head 22.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

WHAT IS CLAIMED IS:

1. A vacuum pump for the injection of a fluid additive under low pressure, into a pressurized fluid line, comprising: a body connectable inline to a main fluid line including two back-to-back inlet and outlet funnels delimiting an internal space having an axis, and defining a fluid inlet space, a fluid outlet space and a neck portion, interposed between and connecting, said funnels; a feeding port for introducing additive, being in fluid communication with the internal space about the neck portion; an elongated pin assembly, substantially coaxially guided and movable inside said outlet funnel; said pin assembly includes a pin head, protruding into and along at least part of the neck portion, to at least partially reduce the free fluid flow path about the neck portion, said pin head coaxially engages, and is freely slidable with respect to a stem, the other end of which stem being anchored to the pump body, said pin head and stem enclosing a control-space communicating with the fluid pressure in the internal space of the pump, via at least one fluid flow-restricting control port.

2. The vacuum pump according to claim 1, wherein said control port is constituted by an annular clearance formed between a tail portion of the pin head and the stem.

3. The vacuum pump according to claim 1, wherein said pin head has an axial bore leading into the control space and said stem has a plunger axially traversing said control space, and a plunger head located in said bore and slidable therein, for at least partially interrupting fluid communication between the fluid inlet and fluid outlet of the pump.

4. The vacuum pump according to claim 2, wherein at least one fluid control port is made in the stem at a point along the stem where said tail portion can interrupt fluid flow during its sliding movement.

5. The vacuum pump according to claim 1, wherein at least one control port is made at the tail portion of the pin head, for cutting off fluid flow upon a sliding movement of the pin head along the stem.