WO1994019564A1

WO1994019564A1 - Pumps for viscous liquids or slurries

Info

Publication number: WO1994019564A1
Application number: PCT/NZ1994/000011
Authority: WO
Inventors: Derek Martin Stewart
Original assignee: Stewart, Marie, Teresa
Priority date: 1993-02-18
Filing date: 1994-02-17
Publication date: 1994-09-01
Also published as: AU6117494A

Abstract

A pump (10) for viscous fluids or slurries, such as liquid concrete or liquefied ground bone meal, has a steel frame (15) in which is mounted a large diameter cylinder (11) leading to a tapered outlet (12). An inlet (25) having a hopper (18) is mounted close to the outlet (12), and has a non-return valve (25) therein. A piston (19) is driven by a hydraulic ram (26) mounted on the frame (15). The hydraulic ram (26) is driven by high pressure hydraulic fluid via a control valve (30) to control the reciprocation of the ram (26) and the piston (19) to pump fluid material from the cylinder (11). The pump (10) is designed to be mounted at the rear of a concrete truck so that it can be driven by the truck's hydraulics. The pump (10) is readily transportable and can be carried on to site by an excavator or other machine.

Description

PUMPS FOR VISCOUS LIQUIDS OR SLURRIES

TECHNICAL FIELD OF THE INVENTION

This invention relates to pumps, particularly though not solely, to pumps suitable for pumping viscous liquids or slurries.

BACKGROUND

Pumps of the above kind are frequently used for pumping fluid concrete on building sites. For example, when concrete footings are required, it is normal practice to order ready-mixed concrete to be delivered by a concrete delivery truck and also to hire a concrete pump on a separate truck or trailer. The concrete and the concrete pumps are usually provided from different contractors, which means that the pump may not be available at the correct time, causing delays in the work. Such pumps are typically continuous acting rotary pumps and need to be carefully cleaned at the end of each job, with high maintenance and running costs.

OBJECT

It is one object of the present invention to provide an improved pump for pumping viscous fluids or slurries, or one which will at least provide the public with a useful choice.

STATEMENT OF THE INVENTION

According to one aspect of the present invention there is provided a pump for viscous fluids or slurries comprising a hollow body having a first end and a second end, a chamber communicating with said first end, an inlet and an outlet from said chamber, a

SUBSTITUTE SHEET non-return valve associated with said inlet, a reciprocally movable piston within said body to displace fluid material from within the body, the piston having a piston rod extending from the second end of the body, characterised in that the hollow body is mounted on a longitudinal support frame and a hydraulic ram is mounted on said support frame in line with said hollow body with said hydraulic ram being connected to said piston rod, said hydraulic ram being connectable to a source of high pressure hydraulic fluid via control valves to control the reciprocation of said ram and said piston to pump fluid material from said body.

Preferably the hollow body is a cylinder of larger diameter than the diameter of said hydraulic ram, and said chamber tapers from said cylinder down to an outlet which is connectable to a hose. Typically the cylinder may have a bore of about 250 mm, a stroke of about 6S0 mm and the chamber and outlet taper down to fit a hose of about 50 mm bore. Such a hydraulically controlled pump with its long slow stroke (when compared to short stroke mechanical pumps) provides a relatively quiet and efficient pump for pumping concrete or grout to building sites.

Preferably for pumping concrete the inlet is positioned on top of said chamber and is surrounded by a hopper with a one way valve mounted in said inlet. Alternatively for suction pumping (eg draining ponds or the like) it is preferred that the inlet is in line with said cylinder and said outlet is mounted on top of or to one side of the chamber, and both said inlet and said outlet have one way valves associated therewith.

Preferably the control valves are mounted on said frame and include an overcompensating valve to stop the ram and the piston in case of blockage in the pump.

Preferably the control valves include ports capable of being connected to fluid lines communicating with a source of fluid pressure, a reservoir and with the ram, with said overcompensating valve being capable of diverting fluid from said ram to a reservoir if the fluid pressure exceeds a predetermined limit

Preferably the overcompensating valve is set to a limit of about 3000psi.

Preferably the ram has reversing means which includes a change-over valve having an inlet connected to a feed line to carry said pressurised fluid from the source, an outlet connected to a return line to carry said fluid back to the source, and first and second lines connecting the valve to opposite ends of the motor, the valve being adapted, in a first position to connect the feed line to said first line and the return line to the said second line, and in a second position to connect the feed line and the return line to the second line and the first line respectively.

Preferably the reversing means includes electrical switch means operable at each end of the pump travel to operate electrical actuator means connected to move the change-over valve alternatively between said first and second positions thereof.

In another aspect the invention provides a concrete delivery truck having a rotatable drum mounted thereon and having an outlet therefrom wherein a pump as previously described is mounted on the truck beneath the outlet from the drum, and said pump is connected to the hydraulic system of the truck so that concrete can be transferred from the drum to the pump and pumped onto site as required.

Preferably the pump is adapted to be operated by pressurised fluid from a source thereof on a machine such as an excavator, earth mover, tractor, bull dozer, back hoe, concrete delivery truck or the like.

In one version of the invention the ram may be a ram which forms part of existing equipment, eg the dipper ram of an excavator or like machine. However for most applications the cylinder and ram are preferably mounted on the same frame so that the pump can be transported as a single unit and then connected to a suitable pressurised fluid source.

According to another aspect of the invention there is provided a machine, such as an excavator, earth mover, tractor, bull dozer, back hoe, concrete delivery truck or the like fitted with a pump as mentioned above.

According to a further aspect of the invention there is provided a reciprocable pump connected to be driven by a motor operable by pressurised fluid from a source thereof including reversing means actuated at each end of the reciprocating travel of the pump, to reverse the flow of said pressurised fluid to and from the motor. The reversing means may include a change-over valve having an inlet connected to a feed line to carry said pressurised fluid from the source, an outlet connected to a return line to carry said fluid back to the source, and first and second lines connecting the valve to opposite ends of the motor, the valve being adapted, in a first position to connect the feed line to said first line and the return line to the said second line, and in a second position to connect the feed line and the return line to the second line and the first line respectively.

The reversing means may conveniently include electrical switch means operable at each end of the pump travel to operate electrical actuator means connected to move the change-over valve alternatively between said first and second positions thereof.

The electrical actuator means may be a solenoid or a reversible electric motor.

Alternatively, the reversing means preferably includes a mechanical connection between the change-over valve and a body connected to the pump or motor, adapted to move the change-over valve between said first and second positions at each end of the reciprocating travel.

Furthermore, the reversing means may include a further valve means operable at each end of the reciprocating travel and adapted to apply pressurised fluid to alternating ends of the change-over valve, to move it between said first and second positions.

If required, the valve means controlling the flow of pressurised fluid to the motor may be controlled by means of a remote control, such as a radio link.

According to yet another aspect of the present invention, there is provided two of said reciprocable pumps operable by one or two of said motors, the or each motor being connected to the source of pressurised fluid such that as one pump is on a delivery stroke the other pump is on a suction stroke and vice versa.

Preferably the pumps are positioned together and have common feed means and common discharge means. DRAWINGS

Various embodiments of the invention are described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a side elevation of one embodiment of a pump according to the invention.

Figure 2 is an end view of the pump shown in Figure 1.

Figure 3 is a side elevation of another embodiment of the invention.

Figure 4 is a plan view of a further embodiment of the invention.

Figure 5 includes plan and sectional views of yet another embodiment of the invention.

Figure 6 illustrates details of the piston assembly of the embodiment of Figure 5.

Figure 7 illustrates part of a ready-mixed concrete delivery truck, with a concrete pump affixed to its rear.

Figure 8 illustrates further improvements to the invention about the pump assembly.

Figure 9 illustrates one "anti-pulse" device at the delivery point at the end of the hose.

Figure 10 illustrates another embodiment of the delivery point for use at either end of the hose.

FIRST EMBODIMENT

In the drawings, a concrete pump 10 for pumping fluid concrete is conveniently made of sheet steel and is formed as a hollow body portion 11 of constant cross-section (in this version it is of square-cross section although in the other embodiments it is cylindrical) leading into a convergent nozzle portion 12 having an outlet fitting 13 adapted for connection to a hose pipe 14. The hose pipe 14 is used to conduct the concrete to various locations where it is required, in the usual way. The cylinder 11 is conveniently of rectangular or square cross-section, but can be circular if required.

The pump 10 is mounted in a frame 15 comprising a base 16 and side walls 17. The frame 15 is conveniently of angle iron construction with metal mesh infilling. The base of the pump 10 preferably slopes downwards relative to the base 16 towards the outlet fitting 13.

The upper end of the top wall of the cylinder 11 is provided with a hopper 18 opening into the upper part of the cylinder 11.

A piston 19 in the form of a steel plate is a close sliding fit within the cylinder 11. The edges of the piston 19 may be provided with sealing strips 20, conveniently of a material incorporating PTFE. A cup seal made of leather may be provided on the periphery of the piston face exposed to the concrete.

A piston rod 21 extends substantially normal to the piston 19 and terminates in a first fork 22. Structure 23 connecting the higher end of the piston 11 to the base 16 is formed as a second outward facing fork 24.

A typical use of the pump described above is on the boom of an excavator, back hoe or the like. Firstly, the bucket digging tool, or other implement is removed from the boom, the standard end fitting of the dipper boom of the excavator or the like is connected to the second fork 24 by a pin therethrough. The first fork 22 is connected by another pin to the standard end fitting of the dipper ram of the excavator or the like.

To use the pump 10, it is lowered on the dipper boom until the base 16 rests reasonably horizontally on the ground. The dipper ram is retracted until the piston 19 reaches stops (unshown), to the position shown in figure 1. Concrete is poured from the concrete delivery truck through the hopper 18 into the cylinder 11 until it and the nozzle portion 12 are nearly full of fluid concrete, the supply of concrete is then halted. When pressurised hydraulic fluid is supplied to the dipper ram, it extends, thereby pushing the piston rod 21 and the piston 19 along the cylinder 11, concrete therein being displaced through the hose pipe 14. When the dipper ram is reversed, it pulls the piston rod 21 and draws the piston 19 back to the above mentioned stops. A one-way valve, such as a flap valve may be provided in the outlet fitting 13 to prevent fluid concrete being drawn back into the nozzle portion 12 as the piston 19 is retracted. If required, an air admission valve may be used to allow free flow of air into the cylinder 11.

For some purposes the pump 10 may be double-acting, the cylinder 11 extending in opposite directions from the hopper 18 and the piston 19 then being reciprocable between opposite ends of the cylinder 11.

As an alternative to using an existing source of pressurised fluid, which is normally used for purposes other than driving the pump 10, a self-contained source of pressurised fluid may be carried with or mounted on the pump 10, or associated with it. For example, a hydraulic pump driven by an internal combustion engine.

The pressurised fluid may be pressurised oil or other hydraulic fluid or may be compressed air. By the provision of a suitable outlet valve, the pump 10 may be used to pump water, mud, grout, standard concrete, sludge, granular solids or other fluid materials over a wide range of viscosities

When the hose pipe 14 is not in use it can be stored or transported by wrapping it around the pump 10 between the side walls 17.

This first version of the piston pump can quickly connect to the dipper ram of a digger. In practice it takes about five minutes to remove the bucket and attach the dipper ram onto the end of the piston pump. There are various rams on diggers, but the dipper ram is the easiest one to use.

This first embodiment of the ram (with square cross-section piston body) has a stroke of 750 mm, and expels between 0.15 cu metres to 0.2 cu metres per stroke. This square section design with square conical end is especially suitable for use as a pump that can be fitted to the end of a digger. It is also easy to drop onto the back of a truck. It is relatively large because it pushes/pumps 0.2 cu metres in about 10 seconds. Then there is about an 10 second wait time with the ram coming back quickly and then filling the body before the next stroke takes place. This creates an advantage for the operator because the person at the end of the hose (typically 40m in length) can then move the hose from one hole to another without spilling concrete everywhere which happens with existing continuous acting pumps.

With this design the operator can coil 40m of hose around the pump between the pump body and the frame. This can remain connected to the pump, and simply washed out by filling the pump body with water and squirting it through the hose. With existing pumps the operator has to break down the hoses and wash them carefully, all of which is time wasting.

This system has an advantage not only cost saving but also the fact that it can pump liquids of different viscosities, including water. Traditional concrete pumps on the back of trailers are designed to pump either grout or standard concrete, and thus you need to hire two different pumps for the two different operations. This first embodiment of the pump can operate both grout or standard concrete or water or mud or other liquids including viscous liquids and slurries.

SECOND EMBODIMENT

In Figure 3 the hopper 18 is positioned at the discharge end of the pump 10 and an automatic inlet valve 25 is fitted between the hopper 18 and the cylinder 11 so that fluid material can pass from the hopper 18 into the cylinder 11 but is prevented from flowing back into the hopper 18.

A motor in the form of a double-acting hydraulic or pneumatic ram 26 is fitted in the frame 15 coaxial with the piston 19 and connected to or integral with the piston rod 21. The ram 26 is pivoted on a fork 27 to the frame 15.

Pressurised oil or air is fed from the source through a line 28 and is returned thereto through a line 29. The lines 28, 29 are connected to a change-over valve 30 of known kind, having a spool or shuttle valve member moved between opposite ends of the valve 30 by a solenoid 31 or similar reversible electric motor. First and second lines 33, 34 connect the valve 30 to opposite ends of the ram 26. Thus, when the spool is at one end of the valve 30 lines 28 and 33 are connected together and lines 29 and 34 are connected together, thereby the piston 19 is moved to the right in Figure 3 to expel the contents of the cylinder 11. When the solenoid 31 is actuated to move the spool to the opposite end of the valve 30 the lines 28 and 34 are connected together and the lines 29 and 33 are connected together so that the ram 26 draws the piston 19 towards the left, during a suction stroke.

Electrical power to operate the solenoid 31 may be provided through a manual switch, so that the piston 19 can be moved at will, between the ends of its stroke. Alternatively, as shown in Figure 3, provision may be made for movement of the piston 19 to be reversed each time it reaches one or other end of its stroke. For this purpose a rod 35 is fastened at one end to the piston 19 and carries at the other end a body 36. Adjacent each end of the ram 26 a pair a switches 37, 38 are fastened to the frame 15 and connected by wires 39 to the solenoid 31. As the piston 19 approaches the end of the suction stroke, the body 36 reaches the switch 37 to actuate the solenoid 31 to reverse the connection between the lines 28, 29, 33, 34. This causes the piston 19 to execute a delivery stroke at the end of which the body 36 reaches the switch 38 to de-activate or reverse the solenoid 31, again reversing the connections between the lines 28, 29, 33, 34.

If preferred, instead of electrical operation of the change-over valve 30 the spool may be moved between its end positions by fluid pressure, in known manner. In this case, further valves are used in place of the switches 37, 38. Alternatively, the rod 35 or similar body can be connected to move the spool of the valve 30 through a mechanical connection. Other types of valve 30 may be used instead of a spool valve.

If required, the valve means controlling the flow of pressurised fluid to the motor may be controlled by means of a remote control, such as a radio link. In this way, the delivery may be controlled from the discharge end of the hose pipe 14, or elsewhere.

This embodiment of the pump has been produced as pump which is 2.1 m long, 350mm wide, 400mm high, and weighs about 200kg. The outlet hose is preferably a high pressure reinforced rubber hose (capable of operating up to 3000 psi) and it is preferred that a lighter gauge more flexible hose is used at the outlet (eg a flexible helical hose such as a Heliflex 50mm hose) which has some ability to expand or contract to minimise surges or pulsing at the outlet end of the hose line. It is also easier for the operator to handle a lighter gauge hose.

THIRD EMBODIMENT

Figure 4 shows two of the above mentioned pumps mounted with their cylinders 11 and rams 26 side by side in the same frame 15. The cylinders 11 are fed from a common hopper 18 and the nozzles 12 feed a common discharge line 40. The feed lines to and from the rams 26 are cross-connected, so that as one pump is on the suction stroke the other is on the delivery stroke and vice versa.

FOURTH EMBODIMENT

A further preferred embodiment of the pump is illustrated at 500 in Figure 5, and in detail in Figure 6.

504 is the connection to the feed hopper (see Figure 8), and 505 is the connection to the supply hose or optionally to the hose via the pulse-minimising coupling 1000; the outer walls of the hydraulic ram are shown as 500 and 602. This ram is substantially attached to the pump body 501, 610 by welds (e.g. 607) and bolts 609 at 506, using an incomplete ring so that the interior of the pump and the rear of the piston are accessible. A frame, preferably made of two lengths of box-section steel supports the assembly and is shown at 512, 510, and 503. As can be seen at 512, the box sections lie on each side of the cylindrical pump, which is preferably welded to it at 507 and 508. Section 509 through the pump at the level of 508, shows a cross member of the frame. Section 511 (at a different scale) shows the ring 507.

The piston itself, being expected to move suspensions of solid material within the space 601, includes a "Lurethane" lip seal 604 held in place by a washer 613 which is in turn held in place (during the return stroke) by a nut 606. Forward thrust to the piston body 605 from the ram 602 is carried by its spear 603. 612 is one of many oil nipples for lubrication purposes. 611 is an "O"-ring seal in a groove. The interior of the pump 610 is preferably chromium-plated.

Figure 7 illustrates a pump in one suitable application, as an accessory fro a ready-mixed concrete truck 700. In this illustration the pump 706 is powered by a hydraulic ram 705, controlled by the truck driver with controls 703 adjacent to the usual drum motor controls that these trucks are provided with for the extraction of concrete from the drum by reversing its direction of rotation. A portion of a delivery hose 707 is shown, but this may be much longer. In this application the pump and its control mechanism is preferably protected by a cover, such as one of a clear polycarbonate material. The hopper 7022 may be cleaned after use.

Figure 8 illustrates some improvements made to the pump 800. The hopper is provided with a stout mesh covering to exclude unwanted large stones. The non-return valve 806 is provided with a long stem 802, which may be grasped from time to time by an operator as when water is being pumped by the pump as it may not move correctly by itself. The valve 806, which is preferably made in the shape of a disk and at least partly of a rubberised urethane compound, is able to move up and down between apertures 805 and 807. A support bar 804 includes a preferably grease-lubricated collar with O-rings to grip the stainless steel shaft, to maintain the orientation of the shaft during use.

The control of the hydraulic fluid fed through pipes 810 to the actuator 809 of the pump is carried out at a valve 812 by (a) an operator with a hand-piece 815 bearing control buttons, which may be at the end of a long cable 814 so that the person holding the pipe end may also control the pump, and (b) inner and outer limits to strokes are sensed by means of proximity detectors 811a adjacent to an indicator rod or shaft 811 protruding from the rear of the piston 808 within the pump body. Suitable proximity detectors are magnetic devices. The position of the indicator rod can also be checked visually. A supply of hydraulic power - e.g. a pump with a bleed valve and a reserve tank of fluid - is indicated at 813 although in practice this may be part of adjacent machinery such as an excavator.

A further optional shaft affixed to the rear of the piston is a compression ram 818, which may be used to pump air or fluid into a storage tank 819 for use either in general around the site or for cleaning purposes after the concrete pump has completed its task. Preferred dimensions as used in embodiments of the pump are: pump diameter 250 mm, stroke length 650 mm, wall thickness 10 mm, chromium plating 1/100th inch (about 250 microns), ram diameter 100 mm with a 12.5 mm wall, spear diameter 50 mm, piston thickness 40 mm, and delivery line internal diameter 50 mm. A preferred stroke rate is 5 seconds delivery, three seconds return. It has surprisingly been found that this apparently slow rate, taken together with the funnelling down to the pipe diameter, allows the concrete mix to be delivered without the use of compressed air. The slow rate (as compared to other pumps) also tends to minimise settling of the mixture. A flow control valve is incorporated in the hydraulic system to decrease or increase cycle times to match pumped volumes to requirements for each job.

Figures 9 and 10 illustrate two versions of "non pulse couplings" fitted to the ends of the delivery lines to eliminate surging between push strokes, coupled through the heavy pipe 816, 817, 901, 1001 to the end generally held by an operator. This surge is not only a problem in our pump, but also in existing pumps, sometimes even throwing personnel off structures. In Figure 9, 901 represents the end of the stout delivery pipe, which is securely joined to a final pipe 902 of lighter construction and preferably with a helical wire reinforcing (e.g. "Spiraflex") inside. The concrete emerges from the orifice 903. Pipe 902 decouples a substantial proportion of the pulses carried up the main pipe so that the operator, holding pipe 902, is protected from the pulses. Figure 10 illustrates in section another type of decoupler, in the shape of a nozzle 1000. The delivery pipe 1001 is tightly coupled to fixed part 1003-1004 (here shown separated for clarity). Concrete mixture (or the like) emerges from the orifice 1002, and owing to the two-part construction of this nozzle, part 1005 is able to slide or telescope over part 1004, generally being forced to elongate by both the flow of mixture when present and also the spring 1006. If the end of pipe 1001 jerks forward, the spring 1006 is compressed, tending to minimise the surging to the operator holding the nozzle 1000.

Preferably 1000 may be used as a coupling within the pipe rather than as a nozzle and in this case it may be made of heavier materials. When 1000 is placed at the exit from the pump body - eg where hose 816 meets the pump 800, it has the beneficial effects of reducing pulsation and wear in the hose, and of reducing pulsatile loads within the pump itself. Optionally, the pump can be used for other on-site tasks such as:

a. Steel bender. Couple or clamp a bending tool to the front of the pump and attach a ram rod to the front of the piston, thereby using the forward stroke of the pump to bend or shape steel, such as reinforcing steel on the site.

b. Use the forward thrust of the piston of the pump to force a spear through the ground, thereby creating a hole to pass pipes for underground ducting etc.

ADVANTAGES

The embodiment of figure 5 in particular offers a number of advantages over conventional (mechanically operated and typically very noisy continuously acting) concrete pumps. With the pump of figure 3 the operator can coil 40m of hose around the pump between the pump body and the frame. This can remain connected to the pump, and simply washed out by filling the pump body with water and squirting it through the hose. With existing pumps the operator has to break down the hoses and wash them carefully, all of which is time wasting.

This system has an advantage not only cost saving but also the fact that it can pump liquids of different viscosities, including water. Traditional concrete pumps on the back of trailers are designed to pump either grout or standard concrete, and thus you need to hire two different pumps for the two different operations.

The pump of figure 5 is a slow acting long stroke pump which pumps or pushes a relatively large volume of material on each forward stroke. For example the preferred pump has been produced as pump which is 2.1 m long (the combined length of the ram and cylinder and outlet chamber) 350mm wide, 400mm high, and weighs about 200kg. It can pump : (a) up to 14mm concrete or grout to a head of 75m, or (b) water to a head of 200m. Such a pump typically operates at 450 psi (ram pressure) supplied by hydraulic fluid from a hydraulic power pack or from a machine such as a digger, which can also be used to move the pump by connecting the digger boom to the flanges at the end of the frame 15.

The indicator rod allows the operator to check on the position of the piston and the pumping rate, and in particular to see if the pump is about to stall. The hand held controls enables the operated to check on the filling rate of the hopper and or the outlet of the hose and to remotely control the operation of the pump.

The pump shown in figure 3 typically has a cylinder bore of about 250 mm, a stroke of about 650 mm and the chamber and outlet taper down to fit a hose of about 50 mm bore. Such a hydraulically controlled pump with its long slow stroke (when compared to short stroke mechanical pumps) provides a relatively quiet and efficient pump for pumping concrete or grout to building sites.

Concrete containing metal aggregate (ie, stones) of up to 10-14 mm diameter can readily be pumped with this pump when connected to reinforced 50 mm high pressure rubber hose. For larger aggregate sizes it is preferred that a larger diameter hose be used (typically having a hose diameter five times the diameter of the aggregate) and that the inlet valve and inlet passage have a greater clearance than that shown in order to minimise blockages in the hopper or inlet passage.

By using a single cylinder, slow acting pump (with a push stroke of about five seconds) and a 40 m hose it is possible to readily fill concrete blockwork with concrete and to re-position the hose during the suction stroke (about four seconds) with minimum wastage of concrete.

The slow stroke and large volume of the cylinder enables the pump to work quietly and efficiently with minimum maintenance. If concrete is pumped the pump is washed out with water at the end of the concrete pumping operation, and a wad of foam rubber is inserted into the start of the hose (connected to the tapered position) and then water is poured into the hopper and the water and foam wad are pumped through this rubber hose (in the manner of a fire piston) to clear the interior of the hose and remove any sediment.

VARIATIONS

Although the pump has been described as a reciprocable piston-in-cylinder pump, other types of reciprocable pump may be used, such as swinging-vane arcuate pumps.

Similarly, a continuously rotating pump may be used, in which case a rotary fluid pressure-operable motor is also used. Generally, it is most convenient to use pumps and motors of the same configuration eg. both linear reciprocable, both arcuate reciprocable or both continuously rotatable. The motor may be connected to the source of pressurised fluid by a flexible hose, especially where the source of pressurised fluid forms part of another machine, or is a self-contained source of pressurised fluid.

Finally, it will be appreciated that various alterations or modifications may be made to the foregoing without departing from the scope of this invention as set forth in the following claims.

Claims

CLAIMS:

1. A pump for viscous fluids or slurries comprising a hollow body having a first end and a second end, a chamber communicating with said first end, an inlet to said hollow body or said chamber, an outlet from said chamber, a non-return valve associated with said inlet, a reciprocally movable piston within said body to displace fluid material from within the body, the piston having a piston rod extending from the second end of the body, CHARACTERISED IN THAT the hollow body is mounted on a longitudinal support frame and a hydraulic ram is mounted on said support frame in line with said hollow body with said hydraulic ram being connected to said piston rod, said hydraulic ram being connectable to a source of high pressure hydraulic fluid via control valves to control the reciprocation of said ram and said piston to pump fluid material from said body.

2. A pump as claimed in claim 1, CHARACTERISED IN THAT the hollow body is a cylinder of larger diameter than the diameter of said hydraulic ram, said chamber tapers from said cylinder down to an outlet which is connectable to a hose, and said inlet communicates with the interior of said chamber.

3. A pump as claimed in claim 2, CHARACTERISED IN THAT the inlet is positioned on top of said chamber and is surrounded by a hopper with a one way valve mounted in said inlet

4. A pump as claimed in claim 1, CHARACTERISED IN THAT said inlet is in line with said cylinder and said outlet is mounted on top of or to one side of the chamber, and both said inlet and said outlet have one way valves associated therewith.

5. A pump as claimed in claim 1, CHARACTERISED IN THAT said control valves are mounted on said frame and include an overcompensating valve to stop the ram and the piston in case of blockage in the pump.

6. A pump as claimed in claim 5, wherein the control; valves include ports capable of being connected to fluid lines communicating with a source of fluid pressure, a reservoir and with the ram, with said overcompensating valve being capable of diverting fluid from said ram to a reservoir if the fluid pressure exceeds a predetermined limit.

7. A pump as claimed in claim 6, wherein the overcompensating valve is set to a limit of about 3000psi.

8. A pump as claimed in claim 1, wherein the ram has reversing means which includes a change-over valve having an inlet connected to a feed line to carry said pressurised fluid from the source, an outlet connected to a return line to carry said fluid back to the source, and first and second lines connecting the valve to opposite ends of the motor, the valve being adapted, in a first position to connect the feed line to said first line and the return line to the said second line, and in a second position to connect the feed line and the return line to the second line and the first line respectively.

9. A pump as claimed in claim 1, wherein the reversing means includes electrical switch means operable at each end of the pump travel to operate electrical actuator means connected to move the change-over valve alternatively between said first and second positions thereof.

10. A concrete delivery truck having a rotatable drum mounted thereon and having an outlet therefrom CHARACTERISED IN THAT a pump as claimed in claim 3 is mounted on the truck beneath the outlet from the drum, and said pump is connected to the hydraulic system of the truck so that concrete can be transferred from the drum to the pump and pumped onto site as required.