A centralizer apparatus (1) for centralizing a rod (100). The centralizer apparatus (1) has a guide roller (2) which contacts the rod (100) and a pressure adjustment member (5) to enable the contact pressure of the guide roller (1) against the rod (100) to be adjusted. Mounting plates (3a, 3b, 4a, 4b) mount the centralizer apparatus (1) so that it is fixable relative to the rod (100). The centralizer apparatus (1) enables the orientation of the guide roller (2) to be adjusted relative to the rod (100) about two orthogonal axes (25,26). The guide roller (2) is also locatable relative to the circumference and length of the rod (100) at selected locations.

BACKGROUND OF THE INVENTION 
The present invention relates to a centralizer apparatus for centralizing a 
rod. 
1. Field of the Invention 
Reciprocating rods are used in machinery for a range of purposes. 
2. Description of the Prior Art 
For example, a reciprocating rod (also referred to as a polished rod or 
lifting rod) is used with below ground well pumps. The reciprocating rod 
is connected to a pump at the bottom of the well, eg by sucker rods, and 
is reciprocated by a drive means at ground level such that the pump pumps 
well fluids to the surface. 
In a further example, a reciprocating rod is used in a hydraulic ram in 
which it extends from and retracts into the hydraulic ram cylinder. 
It is desirable to maintain such rods centralized in the machinery in which 
they are reciprocating. 
In the case of a polished rod in a pump, the well bore in which the pump is 
located is often not perfectly perpendicular. This leads to the problem of 
the polished rod and the well head rubbing against one another and wearing 
at locations where the polished rod and well head engage, eg at the 
stuffing box of the well head. 
In the case of a hydraulic ram, the ram may be disposed at various angles 
depending upon the application of use of the ram. The extension and 
retraction of the rod from and into the ram cylinder can cause wear of the 
rod and the cylinder at locations where the rod bears against the 
cylinder. Such wear increases in instances where the rod is heavy and 
long, as significant rubbing causing wear can occur between the rod and 
cylinder particularly when the rod continuously extends from and retracts 
into the cylinder. 
Such wear reduces the operational life of parts prone to wear leading to 
replacement of parts with attendant operational downtime of equipment to 
enable the replacement of worn parts to be carried out, all of which are 
undesirable. 
SUMMARY OF THE INVENTION 
In accordance with a first aspect of the present invention there is 
provided a centralizer apparatus for centralizing a rod comprising at 
least one guide roller means to contact the rod, mounting means to mount 
the centralizer apparatus such that it is fixable relative to the rod, and 
pressure adjustment means to enable the contact pressure of the guide 
roller means against the rod to be adjusted. 
Preferably, the orientation of the guide roller means relative to the rod 
is adjustable. 
Preferably, the guide roller means is movable relative to the rod about an 
axis substantially transverse to the axis of the rod to enable the 
orientation of the guide roller means relative to the rod in a first 
orientational direction to be adjusted. 
Preferably, the guide roller means is movable relative to the rod about an 
axis substantially parallel to the axis of the rod to enable the 
orientation of the guides roller means relative to the rod in a second 
orientational direction to be adjusted. 
Preferably, the guide roller means is locatable at a selected location 
relative to the rod. 
Preferably, the guide roller means is movable relative to the rod about the 
axis of the rod such that the guide roller means is locatable at a 
selected location relative to the circumference of the rod. 
Preferably, the guide roller means is movable relative to the rod in a 
direction substantially parallel to the axis of the rod such that the 
guide roller means is, locatable at a selected location along the length 
of the rod. 
Preferably, the guide roller means is rotatably supported by support means 
and the support means is movable to move the guide roller means toward and 
away from the rod, and the pressure adjustment means is operable to exert 
a force on the support means and adjust the pressure of the guide roller 
means against the rod. 
Preferably, the pressure adjustment means comprises a first rotatable 
member rotatable in a first direction to increase the force exerted on 
said support means and rotatable in a second direction to decrease the 
force exerted on said support means. 
Preferably, two guide roller means are provided and are disposed on 
diametrically opposed sides of said rod. 
The present invention will now be described, by way of example, with 
reference to the accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
In FIG. 1, there is shown a centralizer apparatus 1 for centralizing a rod 
100 comprising a guide roller 2 to contact the rod 100, mounting plates 
3a, 3b, 4a and 4b to mount the centralizer apparatus 1 such that it is 
fixable relative to the rod 100, and a pressure adjustment screw 5 to 
enable the contact pressure of the guide roller 2 against the rod 100 to 
be adjusted. 
The guide roller 2 is rotatably supported by a support member 7 via roller 
bearing assemblies 8. The support member 7 is in the form of a yolk having 
a pair of arms 9 extending from a back plate 10. Respective roller bearing 
assemblies 8 are provided in the arms 9. The arms 9 have openings therein 
which accommodate the roller bearing assemblies 8. 
The arms 9 have respective slits 11 therein at their distal parts. The 
slits 11 divide the distal parts (ie the parts between the ends of the 
arms 9 and the openings accommodating the roller bearing assemblies 8) of 
the arms 9 into portions 9a and 9b which are spaced apart by the slits 11. 
The slits 11 extend from the ends of the arms 9 to the openings which 
accommodate the roller bearing assemblies 8. Respective bolts 12 pass 
through the portions 9a and 9b of the arms 9, at their distal parts, 
transverse to the slits 11 and through the slit 11. 
The bolts 12 can be tightened which results in the portions 9a and 9b of 
each arm 9 moving toward one another thereby narrowing the slits 11. This 
movement of the portions 9a and 9b acts to securely clamp the roller 
bearing assemblies 8 in the arms 9. When the bolts 12 are loosened, the 
roller bearing assemblies 8 and guide roller 2 can be removed from the 
support member 7. 
The support member 7 has a shank 13 which projects from the back plate 10 
on the side opposed to that from which the arms 9 extend. 
The shank 13 is accommodated in an opening (obscured) in a support post 14. 
The support post 14 is provided with a slit 15 which extends from its end 
to the opening which accommodates the shank 13. The slit 15 divides the 
end region of the support post 14 (ie the region between the end of the 
support post 14 and the opening accommodating the shank 13) into two 
portions 14a and 14b. 
A bolt 16 passes through the portions 14a and 14b of the support post 14 
and the slit 15, in a direction transverse to the slit 15. 
The bolt 16 can be tightened which results in the portions 14a and 14b of 
the support member 14 moving toward one another thereby narrowing the slit 
15. This movement of the portions 14a and 14b acts to securely clamp the 
shank 13 in the support post 14. 
The pressure adjustment screw 5 engages with a screw threaded hole in a 
support plate 17 and can be turned in the direction of arrows A (as shown 
in FIG. 1) and bear against the shank 13. The support plate 17 is 
connected with the support post 14 by a connection plate 18 offset from 
the support post 14. 
The lower portion 20 of the support post 14 is accommodated between the 
mounting plates 3a, 3b, 4a and 4b. Each mounting plate 3a, 3b, 4a and 4b 
is provided with a pair of recesses 21. Each recess 21 of the mounting 
plates 3a and 3b is opposed to a recess 21 of an adjacent mounting plate 
4a and 4b, respectively. The lower portion 20 is accommodated by a pair of 
opposed recesses 21 of adjacent mounting plates 3a and 4a and adjacent 
mounting plates 3b and 4b. 
As can be seen in FIG. 1, two sets of recesses 21 are provided and enable 
the lower portion 20 to be supported at either of two locations, on 
diametrically opposite sides of the rod 100, between the mounting plates 
3a, 3b, 4a and 4b. 
Alternatively, the two sets of recesses 21 may support the lower portions 
20 of two support posts 14, with each support port 14 supporting a support 
member 7 with a guide roller 2 mounted therein. 
The mounting plates 3a and 3b and the mounting plates 4a and 4b are 
connected together by connection strips 3c and 4c, respectively. This 
allows easier handling of the mounting plates 3a, 3b, 4a and 4b during 
installation and removal of the centralizer apparatus 1. 
Each mounting plate 3a, 3b, 4a and 4b is provided with a further recess 22. 
The recesses 22 accommodate a part of a well head 101, which supports the 
rod 100, that is fixed relative to the rod 100. Each recess 22 of the 
mounting plates 3a and 3b is opposed to a recess 22 of an adjacent 
mounting plate 4a and 4b, respectively. 
The well head 101 is accommodated by a pair of opposed recesses 22 of 
adjacent mounting plates 3a and 4a and adjacent mounting plates 3b and 4b. 
Bolts 23 pass through adjacent mounting plates 3a and 4a and adjacent 
mounting plates 3b and 4b to fixedly clamp the mounting plates 3a, 3b, 4a 
and 4b around the well head 101. In this way, the mounting plates 3a, 3b, 
4a and 4b mount the centralizer apparatus 1 such that it is fixable 
relative to the rod 100. The centralizer apparatus 1 can be removed from 
the well head 101 by undoing the bolts 23 to detach the mounting plates 
3a, 3b, 4a and 4b from the well head 101. 
In the preceding description, the centralizer apparatus 1 was described as 
being fixably mounted relative to the rod 100 via the mounting plates 3a, 
3b, 4a and 4b being clamped around the well head 101. However, the 
centralizer apparatus 1 may be mounted to any suitable support such that 
it is fixable relative to the rod 100. Accordingly, alternative means 
other than the recesses 22 may be used to mount the centralizer apparatus 
1 to a support fixed relative to the rod 100. 
The manner of use and operation of the centralizer apparatus 1 will now be 
described. 
The manner of use and operation of the centralizer apparatus 1 in the 
following description will be with reference to the centralizer apparatus 
1 being mounted on a well head 101 as shown schematically in FIG. 3. 
When the centralizer apparatus 1 is to be mounted to a well head 101 to 
centralize a rod 100, the direction of the pressure being exerted on the 
rod 100 by the well head 101 is first noted. This can be readily done 
since the pressure exerted on the rod 100 causes a score line to appear on 
the rod 100 due to the metal contact between the rod 100 and the well head 
101 in the case of the rod 100 not being centralized. 
The centralizer apparatus 1 is mounted to the well head 101 by clamping the 
mounting plates 3a, 3b, 4a and 4b around the well head 101 with the well 
head 101 being received between the recesses 22. The bolts 23 are then 
tightened such that the mounting plates 3a, 3b, 4a and 4b are loosely 
clamped around the well head 101 such that the centralizer apparatus 1 is 
loosely mounted in place. 
Once the direction of the pressure being exerted on a rod 100 by the well 
head 101 has been determined, the mounting plates 3a, 3b, 4a and 4b can be 
rotated in one of the directions shown by arrows B such that the direction 
of the pressure exerted by the well head 101 on the rod 100 is opposed to 
the middle of the guide roller 2. In FIG. 1, the direction of the pressure 
exerted by the well head 101 on the rod 100 is shown by the arrow P. The 
old rod 100 can be removed from the well head 101 and a new rod 100 
inserted and held central. The centralizer device 1 is then mounted on the 
well head 101 with the mid point 2a of the guide roller 2 being opposed to 
the direction of pressure P as shown in FIG. 2. 
The rod 100 is held central and the support member 7 is moved toward the 
rod 100 such that the guide roller 2 is in contact with the rod 100. This 
can be done since the shank 13 is able to slide in the support post 14, 
with the bolt 16 loosened, in the directions shown by arrows C in FIG. 1. 
The pressure adjustment screw 5 is then turned in the appropriate 
direction, of arrows A, such that it bears against the end of the shank 
13. In this way, the pressure adjustment screw 5 exerts a force on the 
support member 7 and the guide roller 2 presses against the rod 100. The 
pressure adjustment screw 5 is then turned an additional amount, eg one 
turn, to ensure that the guide roller 2 is in snug contact with the rod 
100. Thus, the contact pressure of the guide roller 2 against the rod 100 
can be adjusted. The bolt 16 is then tightened to retain the support 
member 7 in fixed position, and such that the guide roller 2 is able to 
contact the rod 100 with a selected pressure. Similarly, the bolts 23 are 
tightened to fixably mount the centralizer apparatus 1 to the well head 
101. 
Tightening of the bolts 23 will also fix the lower portion 20 of the 
support post 14 in position. This will prevent movement of the support 
post 14 in the directions of arrows D and E shown in FIG. 1. 
The centralizer apparatus 1 enables the orientation of the guide roller 2 
relative to the rod 100 to be adjusted. This enables the guide roller 2 to 
be placed in snug contact with the rod 100 to maintain the rod 100 in a 
centralized condition, prior to the bolts 16 and 23 being tightened. 
Accordingly, the guide roller 2 is movable, relative to the rod 100, about 
an axis 25 which is substantially parallel to the axis 102 of the rod 100. 
This is done by rotating the lower portion 20 of the post 14 in one of the 
directions shown by arrows E in FIG. 1. Thus, the axis 25 is the axis of 
the support port 14. This movement enables the orientation of the guide 
roller 2 relative to the rod 100 in one direction to be adjusted. It can 
be described as a lateral movement of the guide roller 2 relative to the 
rod 100. When the bolts 23 near the ends of the mounting plates 3a, 3b, 4a 
and 4b at which the support post 14 is located are tightened, the support 
post 14 and the guide roller 2 are locked, in a selected position, from 
movement about the axis 25. 
The guide roller 2 is movable, relative to the rod 100, about an axis 26 
that is substantially transverse to the axis 102 of the rod 100. This is 
achieved since the shank 13, which is connected to the support member 7, 
can rotate about axis 26 in either of the directions shown by arrows F. 
This effectively rotates the guide roller 2 about axis 26. When the bolt 
16 is tightened, the shank 13 is firmly held and the support member 7 and 
the guide roller 2 are locked, in a selected position, from rotation about 
axis 26. This movement enables the orientation of the guide roller 2 
relative to the rod 100 in another direction to be adjusted. 
The axes 25 and 26 are substantially orthogonal. 
In addition, the ability of the shank 13 to slide in the directions of 
arrows C enables the guide roller 2 to be brought into initial contact 
with rod 100 prior to the pressure adjustment screw 5 being operated to 
adjust the contact pressure of the guide roller 2 against the rod 100. 
Again, tightening of the bolt 16 will firmly hold the shank 13 such that 
the support member 7 is locked from movement in the directions of arrows 
C. 
The guide roller 2 is also movable, relative to the rod 100 in a direction 
substantially parallel to the axis 102 of the rod 100. This is achieved 
since the support post 14 is movable in the directions shown by arrows D. 
This can be done by loosening the bolts 23 near the support post 14 to 
slide the support post 14 (in the directions of arrows D) in the mounting 
plates 3a, 3b, 4a and 4b. This enables the guide roller 2 to be located at 
a selected location along the length of the rod 100. This adjustment is 
conveniently carried out at the time that the centralizer apparatus is 
mounted in place. 
The guide roller 2 is also movable relative to the rod 100, about the axis 
102 of the rod 100. This can be done by loosening the bolts 23 and moving 
the mounting plates 3a, 3b, 4a and 4b in either of the directions shown by 
arrows B. In this way, the guide roller 2 will also move relative to the 
rod 100 about the axis 102 of the rod 100. This enables the guide roller 2 
to be located at a selected location relative to the circumference of the 
rod 100. 
This adjustment is generally carried out at the time that the centralizer 
apparatus 1 is mounted in place. However, it also enables the centralizer 
apparatus 1 to be relocated at any time by slightly loosening the bolts 23 
and turning the mounting plates 3a, 3b, 4a and 4b in either of the 
directions of arrows B. When the guide roller 2 has been relocated to the 
desired location relative to the circumference of the rod 100, the bolts 
23 are again retightened. 
The guide roller 2 has a surface 2c which is of concave shape. The surface 
2c is in contact with the rod 100 around substantially half the 
circumference of the rod 100 as can be best seen in FIG. 2. 
In use, the rod 100 reciprocates in the directions shown by arrows R in 
FIG. 1. This reciprocatory action of the rod 100 causes the guide roller 2 
to rotate back and forth in the directions of arrows G shown in FIG. 1. 
Thus, the ability of the guide roller 2 to rotate in the directions of the 
arrows G in means that the reciprocatory action of the rod 100 is not 
impeded by the centralizer apparatus 1. 
If the bearing assemblies 8 become worn, they may be removed, along with 
the guide roller 2 as previously described, and replaced. 
The guide roller 2 would not normally need to be replaced, though if 
necessary, it can also be removed and replaced as previously described. 
Preferably, the guide roller 2 is made of mild steel. 
It is also possible that pressure is exerted on the rod 100 by the well 
head 101 in two diametrically opposed directions. Where a rod 100 has been 
reciprocating in such a situation, it will have two diametrically opposed 
score lines. 
In such a situation, it is preferable that two diametrically opposed guide 
rollers 2 are provided. The second guide roller 2 (not shown) is also 
rotatably mounted in its own support member 7 which is in turn supported 
by its support post 14. This second support post 14 is accommodated in the 
(vacant) recesses 21 (as shown in FIG. 1) on the opposite side of the rod 
100. 
The second guide roller 2 is adjusted in a similar manner as previously 
hereinbefore described. 
Whilst the preceding embodiment has been described with reference to the 
centralizer apparatus 1 being used with a rod 100 in the form of a 
polished rod of a well pump, it is to be understood that the centralizer 
apparatus 1 of the present invention may be used in other applications 
where a reciprocating rod must be held in a centralized condition. In such 
other applications, the mounting means for the centralizer apparatus 1 may 
need to be modified to enable the centralizer apparatus 1 to be mounted 
such that it is fixable relative to the reciprocating rod to be 
centralized. 
Modifications and variations such as would be apparent to a skilled 
addressee are deemed to be within the scope of the present invention.