FR2695965A1 - Reciprocating pump for industrial liquids with security seals on piston rods - has bellows seals separating pump working chamber from driving piston space - Google Patents

Abstract

The piston in the chamber (1) drives the piston rods (3, 3') in reciprocation, causing the rods (3, 3') to move the pump pistons (2,2') with seals (9,9') to and fro in their cylinders. Each pump cylinder is connected to an inlet port (5,5') and a discharge port (7,7'). On the suction stroke, the piston rod pulls a piston inwards, and liquid passes through the crown of the pump piston, ready for discharge. On the discharge stroke, the piston rod closes the ball valve (6, 6') and drives the liquid through the non return valve (8,8'). The piston rods work in conventional seals (10,10'), and have flexible seals (11, 11') made of a suitable material fixed securely to the piston rods at one end and at the other to be end of the pump working chamber. USE/ADVANTAGE - Used in air or steam driven pumps handling abrasive or corrosive liquids, with the advantage of protecting the piston rods and seals from damage.

Description

 The present invention relates to the field of pumps with reciprocating longitudinal movement.

 Many modes of pumps intended for transferring chemically, mechanically aggressive products, viscous products, are known. This type of pump, with reciprocating longitudinal movement conventionally comprises one or more cavities, each provided with an inlet port, an outlet port, a suction valve, a discharge valve and a piston in tight connection with the internal walls of these cavities, this piston being driven by a motor by means of a piston rod in tight connection with this motor. They may be single or double acting pumps, the piston rod of which may or may not be in contact with the product to be pumped.

 It can thus quickly result from the wear of the so-called high-pressure sealing means isolating the piston from the internal walls of the cavities, a leak of product in the chamber of the cavity where the piston rod is located, in the pump configurations. in which the piston rod is not in contact with the product to be pumped. In this case, and in pump configurations where there is contact, in working order, of the piston rod and of the product, the crucial problem of leakage of product to be pumped from the piston rod to the element engine arises. It also turns out that conventional sealing means such as seals insulating the piston rod from the driving element do not usually provide a sufficient solution to this problem.

 The present invention precisely results in avoiding such leakage of products from the piston rod to the motor element.

 According to the present invention, this result is achieved by a reciprocating longitudinal movement pump comprising one or more cavities, each provided with an inlet orifice associated with a suction valve, with an outlet orifice associated with a check valve. delivery of a piston driven by a motor by means of a piston rod, first sealing means between the piston and the internal walls of the cavity and second sealing means between the piston rod and the wall end of the cavity located on the motor side, characterized in that the said second sealing means consist of a bellows disposed around one or each of several piston rods, fixed to a first end in a manner integral with the piston rod, and fixed to the other end integrally with said end wall of the cavity constituting a sealed isolation of the cavity from the motor.

 In the implementation of such a pump according to the invention, the product only circulates between the supply tank connected to the suction circuit, the cavity of the pump and the delivery circuit, without any possibility of leakage towards the outside, and in particular towards the motor element. Thus, the presence of the bellows according to the invention makes it unnecessary to use a conventional seal between the piston rod and the end wall of the cavity located on the side of the engine, in said end wall. .

However, nothing prevents associating such a seal with the present bellows.

 On the other hand, it is essential that the bellows or bellows be made, like the other sealing means of the pump, of a material resistant mechanically and chemically to the product to be pumped, under conditions of high pressure, and on important durations. In fact, these products to be pumped consist essentially, but not exclusively, of solvent-based paints and varnishes, water-based paints, ceramics and liquid enamels, loaded and abrasive products, viscous products.

 Another characteristic of the invention is therefore that the bellows or bellows are made, like the other sealing means of the pump, of high molecular weight polyethylene and / or of polytetrafluoroethylene whether or not charged and / or of polyurethane when the product to be pumped does not contain solvents and / or metal provided, as far as the bellows are concerned, that the piston stroke is reduced.

 Although the pump according to the invention can have various configurations, a pump with a horizontal axis, central air motor, double effect and four valves, the two pistons of which each have a single high pressure seal, is particularly suitable.

 Such a pump constitutes precisely the example of implementation of the invention now described with reference to the appended figure, which is a block diagram seen in section. The terms right and left used below should be understood in relation to this figure.

 A central air motor 1 simultaneously drives two pistons 2 and 2 'located respectively to its right and to its left, alternately from left to right then from right to left, by means of two piston rods 3 and 3'. The two pistons 2 and 2 'are placed in two cavities 4 and 4' isolated from each other, provided with - inlet pipes 5 and 5 'connected to two separate product tanks or to a common tank not shown in the figure, these pipes 5 and 5 'being additionally respectively associated with suction valves 6 and 6', in this case mounted inside the pistons 2 and 2 ', and - outlet pipes 7 and 7 'on which are directly disposed discharge valves 8 and 8'.

High pressure seals 9 and 9 'ensure the seal between the pistons 2 and 2' and the internal cylindrical walls of the cavities 4 and 4 '. Other sealing means 10 and 10 ′ can be placed in a conventional manner between the rods 3, 3 ′ and the end walls of the cavities 4 and 4 ′ located on the side of the motor 1, in said end walls, sealing between the rods 3, 3 'and the motor 1
Finally, the bellows 11 and 11 'are mounted in leaktight connection with the rods 3 and 3' at one end, and fixed at the other end so that communication between the internal volume of the bellows 11 and 11 'and the ambient air is provided, in particular by means of openings made on part of the cylindrical walls of the cavities 4 and 4 ', in the vicinity of the said end walls of the cavities 4 and 4', watertight seals 12 and 12 'then being fixed on the unopened part of said cylindrical walls in the vicinity of said end walls. Such communication with the ambient air makes it possible both to avoid variations in pressures in the internal volume of the bellows i1 and 11 ′, and to see a product leak appear towards the outside when a bellows is damaged.

In the type of pump shown, the chambers of the cavities 4 and 4 'located towards the motor are always filled with product to be pumped. During a movement to the right of the pistons 2 and 2 ′, as shown in the appended figure, the valve 6 closes, the valve 8 opens, product is brought by suction through line 5 into the chamber left of the cavity 4 and the product in the right chamber is gradually expelled from it through the pipe 7, while the valve 8 'closes, that the valve 6' opens to let pass the product which is sucked in the left chamber of the cavity 4 'due to the depression which appears there
When the pistons 2 and 2 'move to the left, the opposite occurs.

 Thus, the outlet pipes 7 and 7 'alternately supply products which may be identical or different, so that, if they are identical, a continuous supply can be obtained by connecting the pipes 7 and 7'.

Claims (4)

 1. Reciprocating longitudinal movement pump comprising one or more cavities (4, 4 '...), each provided with an inlet orifice (5, 5' ...) associated with a suction valve (6, 6 '...), an outlet orifice t7, 7' ...) associated with a discharge valve (8, 8 '...), a piston (2, 2' ...) driven by a motor (1> by means of a piston rod (3, 3 '...), first sealing means (9, 9' ...) between the piston (2, 2 '.. .) and the internal walls of the cavity (4, 4 '...) and second sealing means 11, 11' ...) between the piston rod (3, 3 '...) and the wall end of the cavity (4, 4 '...) located on the motor side (1), characterized in that said second sealing means (11, 11' ...) consist of a bellows (it, it '...) arranged around one or each of several piston rods (3, 3' ...), fixed to a first end integrally with the piston rod (3, 3 '..) , and at the other end integral with said wall d 'end of the cavity (4, 4' ...), constituting a sealed isolation of the cavity (4, 4 '. ..> relative to the engine (1).  2. Pump according to claim 1, characterized in that it comprises sealing means (10,10 '...) auxiliary of the bellows (11, 11' ...), places between the piston rod (3 , 3 '...) and the end wall of the cavity (4, 4' ...) located on the side of the motor tl), in said end wall.  3. Pump according to claim 1 or 2, characterized in that the bellows (11, 11 '...) is constituted, like the other sealing means of the pump C9.9' ... and 10, 10 ' ...) when they are present, of high molecular weight polyethylene and / or of polytetrafluoroethylene loaded or not and / or of polyurethane when the product to be pumped does not contain solvents and / or metal provided, as far as relates to the bellows (11, it '...), that the stroke of the piston (2, 2' ...? be reduced.  4. Pump according to one of claims 1 to 3, characterized in that it has a horizontal axis, double effect, comprises a central air motor (1), four valves (6, 6 ', 8, 8') , two pistons (2, 2 ') fitted with simple high-pressure seals (9, 9').