Radial pump

Radial pump with a rotary shaft (4) on which an eccentric (6) is fitted. A sleeve (8) to which a plurality of pistons (12) is connected is fitted rotatably on the eccentric (6). The connection between the sleeve (8) and the pistons (12) is achieved by a part made of elastically deformable material (9) which is fitted around the sleeve (8). A controlled opening and closing movement of the pistons is thus obtained through rotation of the pump shaft (4). More than one series of pistons can be fitted around the shaft.

The invention relates to a radial pump to the preamble of claim 1. 
BACKGROUND OF THE INVENTION 
A radial pump is known from the book "Die Pumpen Arbeitsweise Berechnung 
Konstruktion", 13., neubearbeitete Auflage", published by Springer-Verlag 
Berlin Heidelberg New York 1977, FIG. 74.5 of Hellmuth Schulz. In this 
case the connecting part is designed as in the case of a crosshead 
internal combustion engine, i.e. it is composed of a piston-cylinder guide 
which is connected at one side to the eccentric by means of a drive rod 
and at the other side to the pump piston by means of a fixed pin which 
carries out only a to and fro movement. This produces a complex 
construction with a large number of bearing points. All these bearing 
points have to be lubricated. If adequate lubrication cannot be ensured, 
rolling bearings must be used. This involves a large amount of space and 
more noise during rotation. Although rolling bearings have lower 
requirements as regards lubrication than plain bearings, it nevertheless 
remains necessary to provide lubrication. 
European Patent Specification 0,165,876 discloses a radial pump in which no 
sleeve is fitted on the eccentric and the pistons run as cam followers on 
the eccentric. Although the large number of bearings mentioned above is 
not necessary in such a design, it does mean that the lubrication 
requirements are greater, due to the surfaces of the piston and the 
eccentric moving along each other. It is also necessary to provide special 
means for moving back the piston. In the European patent this is achieved 
by means of coil springs. The disadvantage of this is that control of the 
return movement is difficult to manage at higher speeds of rotation, 
certainly if a low spring pressure is being aimed at, in order to limit 
the power consumption by the pump as much as possible. 
A radial pump according to the preamble of claim 1 is known from 
FR-A-2123032. From this specification frictional engagement of the plunger 
to the sleeve is known. The plunger is urged against the sleeve by means 
of a resilient leaf spring. Several of such leaf springs are provided and 
each leaf spring connects to opposite positioned plungers and is for that 
reason circular shaped. No further support for each circular leaf spring 
is provided. This means that return movement of the plunger is controlled 
by spring characteristics of the leaf springs. The eccentric to which the 
end of the plunger engages will not only urge the plunger to-and-fro but 
will also displace laterally relative to the contact face between the 
plunger and the sleeve surface. This means that there will be some 
friction between the sleeve and the plunger end. 
SUMMARY OF THE INVENTION 
The invention aims to avoid such friction forces between the sleeve and the 
plunger end whilst on the other accurate control of the plunger relative 
to the sleeve is guaranteed, i.e. both during the work hub and during the 
return hub the plunger path has to be accurately controlled by the sleeve. 
According to the invention this is realized with the measures of the 
characterizing part of claim 1. Instead of using plain or rolling bearings 
for fixing of the "drive rods" to the sleeve, according to the invention a 
part made of elastically deformable material in which the drive rods are 
accommodated is used. This eliminates the problems with lubrication, but 
controlled to and fro movement of the pistons is still ensured. The nature 
of the elastically deformable material ensures that load peaks can be 
avoided. Through the avoidance of load peaks, premature wear and excessive 
noise caused by the pump can be limited considerably. Due to the fact that 
the lubrication requirements are lower now, it is possible to use the pump 
described above for pumping fluids in the case of which the seal to the 
control mechanism produces very many problems, and the fluids themselves, 
for example liquefied petroleum gas (LPG), have very poor lubrication 
properties. 
The piece of material can be placed as a ring around the sleeve and fixed 
to it. It is, of course, possible for the sleeve and the elastically 
deformable material to be made of one piece of the same material. 
According to an advantageous embodiment of the invention, the elastically 
deformable material is a rubber material. In rubber technology many 
materials which can be elastically deformed a very great number of times 
without showing fatigue symptoms are known. In addition, the damping 
properties of rubber material are advantageous, in order to avoid load 
peaks as much as possible. 
According to a further advantageous embodiment of the invention, each 
piston contains a diaphragm wedged in the pump chamber which achieves 
guidance of the piston. This means that the piston can tilt slightly, and 
a particularly good seal can be achieved between the pump chamber and the 
space in which the eccentric with the elastically deformable part is 
placed. There are consequently still possibilities for providing 
lubrication between the sleeve and the eccentric. 
According to a further advantageous embodiment of the invention, the piston 
is provided with a rod firmly fixed to it, which rod in turn engages in 
the elastically deformable material. Where rubber is used as the 
elastically deformable material, fixing by vulcanisation has proved to be 
particularly advantageous.

DETAILED DESCRIPTION OF THE INVENTION 
The radial pump according to the invention is indicated in its entirety by 
1. It comprises a motor part 2 and a pump part 3. This radial pump can be 
fitted in, for example, a pressure vessel for liquefied petroleum gas. Of 
course, the pump is not limited to this application. 
A drive shaft 4, which is supported in pump part 3 by bearing ring 5, comes 
out of motor part 2. An eccentric 6 is fixed on motor shaft 4. Needle 
bearings 7, which are accommodated in a sleeve 8, are provided around 
eccentric 6. A part 9 made of elastically deformable material, such as 
rubber, is firmly fixed on sleeve 8. It is provided with holes 10 in which 
rods 11 (one shown) of pistons 12 engage. Pistons 12 are provided with 
diaphragms 13, which are clamped on the head of the piston by means of a 
clamping plate 14, and at the other side are wedged in the pump housing 15 
for the purpose of bounding a pump chamber 16. Pump chamber 16 is provided 
with an inlet valve 18 and an outlet valve 17. Since these valves are not 
important for the functioning of the present invention, they are shown 
only schematically. Inlet valve 18 is connected to an inlet 20, while 
outlet valve 17 is connected to an outlet 19. Pump housing 15 is coupled 
by means of bolts 21 to motor 2. 
The device described above works as follows: 
During the operation of the pump, shaft 4 will turn. Eccentric 6 will turn 
with it, while sleeve 8 will remain in place through the presence of 
bearing ring 7, but will carry out a to and fro movement. Since only one 
rod 11 can be fixed to the sleeve 8 in that position, it is necessary to 
provide for the possibility of movement of a series of pistons for the 
other rods 11. According to the invention, this is achieved by the 
presence of the part made of rubber material in which the rods 11 are 
accommodated, more particularly the holes 10 in the part made of rubber 
material. This accommodation can be achieved by, for example, 
vulcanisation. The piston 12 is guided at the other side into the pump 
chamber by means of diaphragm 13. During the rotation of shaft 4, piston 
12 will carry out a slightly tilting to and fro movement, in the course of 
which rod 11 carries out a pivoting movement in the deformable part 9. The 
occurrence of vacuum or excess pressure in chamber 16 will cause valve 18 
or 17 respectively to open and material to be pumped out of inlet 20 under 
raised pressure to outlet 19. The use of elastically deformable material, 
which is preferably rubber material, means that it is no longer necessary 
to provide a large number of components for bearing. In addition, load 
peaks of the piston, which occur particularly in the bottom and top dead 
center, will be damped as much as possible, with the result that the noise 
of the pump decreases and its service life increases. The degree of 
damping and the elasticity before the rod 11 can be regulated by a 
suitable choice of the quantity of material surrounding rod 11 and the 
distance from sleeve 8. In the case of the construction described above it 
is possible to achieve a great displacement volume in a very limited 
space. The pump described above can be used in particular for pumping LPG, 
but it must be understood that it is not limited to that use, and that it 
is possible to pump other fluids with such a pump. 
In FIG. 2 a further embodiment of the pump according to the invention is 
shown. This pump can be driven with the same motor as the pump shown in 
FIG. 1 and because of that details relating thereto have been omitted. 
In contrast to the embodiment of FIG. 1 rod 11 is not received in an 
elastically deformable bush but it is received in opening 24 of sleeve 23. 
Rod 11 is provided near its end to be received in sleeve 23 with a 
circumferential projection 25. At both sides of this circumferential 
projection elastically deformable links 26, such as O-rings, are provided. 
In this way a rubber elastic pivot point is arranged. 
From comparison of both the embodiments of FIG. 1 and FIG. 2 it is clear 
that the elastically deformable part can be realized in several ways. For 
the invention it is only essential that the pivot between the rod and the 
sleeve comprises an elastically deformable material.