Keyed insert plate for curved rotary lobe pump chamber walls

A rotary lobe pump comprises a pump housing defining an obround pump chamber and a pair of lobe rotors in the pump chamber. The rotors are mounted on rotatable shafts which are connected by timing gears such that the rotors rotate to cause a fluid to displace through the chamber. The pump chamber is defined in the pump housing by opposed front and rear end walls which are perpendicular to the axes of the rotors and by arcuate side walls with which the rotors make sealing contact and which gradually wear out thereby reducing the tightness of the seal and thus the pumping efficiency of the rotary lobe pump. The rear end wall includes two removable end wear plates which each include a rearwardly projecting key engaged in a corresponding keyway defined in the pump housing with bolts extending from outside of the housing inwardly towards the end wear plates and engaging the keys thereof for securing the end wear plates to the housing. The arcuate side walls take the form of removable curved wear plates which are each semi-cylindrical in shape and which each include an outwardly directed radial curved key which is engaged in a corresponding curved keyway defined in the housing. Bolts which extend through the housing into the keys retain the curved wear plates in position in the pump chamber. The rear ends of the curved wear plates are supported by the peripheral edges of the end wear plates.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to rotary lobe pumps and, more particularly, 
to a keyed wear plate for the curved chamber walls of such rotary lobe 
pumps. 
2. Description of the Prior Art 
Rotary lobe pumps are well known industrial pumps which have been in common 
use for about forty years. A pair of counter rotating interlocking lobe 
rotors in a pump chamber draw fluid from an input port and expel the fluid 
through an output port. The pump is well suited to low velocity, high 
density fluid, especially sludge-like fluids. Examples of typical 
applications of rotary lobe pumps are chemical slurries, milk and sewage. 
Such rotary lobe pumps typically include a pump chamber which houses the 
two lobe rotors and which defines an obround side wall with a removable 
front cover plate being provided at a front end of the pump chamber for 
selectively allowing access thereto. One lobe rotor is mounted on a drive 
shaft and the other on a driven shaft with the latter being driven by the 
drive shaft via timing gears. The pumping action of the pump results from 
the lobes which are interlocked and which turn at a same angular speed 
while maintaining the same relative phase angle. The rotors during the 
rotation thereof make peripheral sliding sealing contact with the walls 
defining the pump chamber, namely the obround side wall and the end walls 
which include the front cover plate and a rear wear plate. 
With time, the lobe rotors wear out the obround side wall of the pump 
chamber thereby slowly reducing the efficiency of the seal which exists 
and which is necessary between the lobe rotors and the obround side wall. 
Furthermore, the end walls of the pump chamber, namely the front cover 
plate and the rear wear plate, also wear out in view of the sliding 
sealing contact thereof with the end surfaces of the lobe rotors, whereby 
these components have to be periodically replaced in order to ensure an 
appropriate seal. On the other hand, the peripheral obround side wall is 
not replaceable without replacing the pump housing of the rotary lobe 
pump. 
SUMMARY OF THE INVENTION 
It is therefore an aim of the present invention to provide a replaceable 
wear plate for the curved walls of the pump chamber of rotary lobe pumps. 
It is also an aim of the present invention to provide a rotary lobe pump 
defining a pump chamber which is lined with a replaceable curved wear 
plate for each lobe rotor thereof. 
It is a further aim of the present invention to provide a replaceable wear 
plate for the curved chamber walls of a rotary lobe pump, wherein the wear 
plate is keyed into position in the body of the pump radially outwardly of 
the pump chamber thereof and is retained to the pump body with bolts 
extending through the pump body and into the key provided on the outer 
surface of the wear plate. 
Therefore, in accordance with the present invention, there is provided a 
rotary lobe pump comprising a pump housing, a pump chamber defined in said 
housing and having input and output ports provided in a side wall of said 
pump chamber, first and second rotors rotatably mounted in said pump 
chamber, said rotors having parallel axes of rotation, said pump chamber 
also having end walls perpendicular to said axes and said side wall, said 
rotors making continuous rolling sealing contact with each other and 
sliding sealing contact at the periphery thereof with at least part of 
said side wall, said side wall comprising first and second curved wear 
plates removably mounted to said pump housing in said pump chamber at 
locations of said side wall where said first and second rotors 
respectively make said sliding sealing contact. 
Also in accordance with the present invention, there is provided a curved 
wear plate for use in rotary lobe pumps which each comprise a pump 
housing, a pump chamber defined in the housing and having input and output 
ports provided in a side wall of the pump chamber, a pair of rotors 
rotatably mounted in the pump chamber and making a continuous rolling 
sealing contact with each other, the rotors having parallel axes of 
rotation, the pump chamber also having end walls perpendicular to the axes 
and the side wall, a pair of said curved wear plates being adapted to be 
removably mounted to the side wall at locations in the pump chamber where 
peripheral surfaces of the rotors are required to make a sliding sealing 
contact, said curved wear plate defining an inner arcuate surface where 
said sealing contact with a respective rotor occurs and comprising 
mounting means outwardly of said inner surface for removably securing said 
curved wear plate to the pump housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the present invention, FIG. 1 illustrates a rotary lobe 
pump P which comprises a gearbox 10 and a pump housing 12 removably 
mounted at a front end of the gearbox 10. The pump housing 12 defines 
therein a pump chamber 14 (see FIG. 2), upper and lower lobe rotors 16 and 
16' adapted for rotation in the pump chamber 14, a removable front cover 
plate 18 which closes the pump chamber 14 and which is secured to the pump 
housing 12 by way of bolts 20 for allowing access to the pump chamber 14, 
a main drive shaft 22 and a second auxiliary driven shaft 24, the upper 
and lower lobe rotors 16 and 16' being fixedly mounted to the drive shafts 
22 and 24, respectively. 
The main drive shaft 22 extends outwardly rearwardly of the gearbox 10 so 
as to be rotatably driven by a motor (not shown). With reference to U.S. 
Pat. No. 5,318,415 issued on Jun. 7, 1994, the second auxiliary shaft 24 
within the gearbox 10 is driven by the main drive shaft 22 by way of 
timing gears so that both shafts 22 and 24 and thus the upper and lower 
lobe rotors 16 and 16' rotate at a same angular speed in order that the 
lobe rotors 16 and 16' can efficiently pump a desired fluid by way of the 
interlocking interaction between the lobe rotors 16 and 16' which again 
turn at the same speed while maintaining a same relative phase angle. 
Appropriate durable seals are provided in the gearbox 10 in order to seal 
the shafts 22 and 24 to the pump chamber 14. The shafts 22 and 24 are each 
journaled in the gearbox 10 to front and rear bearings for rotatably 
mounting the shafts 22 and 24 in the gearbox 10. The front bearings are 
provided close to the pump housing 12 so that the lobe rotors 16 and 16' 
which are mounted at the front ends of the shafts 22 and 24 respectively 
resist displacement even when subjected to the various forces encountered 
during pumping. 
Now mainly referring to FIG. 2, the pump housing 12 comprises an input port 
26 and an output port 28 which are in fluid communication with the pump 
chamber 14 so that a rotation of the lobe rotors 16 and 16' causes the 
fluid to be pumped to enter the rotary lobe pump P by way of the input 
port 26 in the direction of arrow 30, to be pumped through the pump P by 
way of the interaction of the rotating lobe rotors 16 and 16', and to exit 
the pump P through the output port 28 along arrow 32. 
More particularly, the pumping action of the rotary lobe pump P is created 
by the rotating lobe rotors 16 and 16' which interlock and turn at a same 
angular speed while maintaining the same relative phase angle. The lobe 
rotors 16 and 16' which can be rubber coated make sliding sealing contact 
with the side walls which define the pump chamber 14 having a generally 
obround shape, wherein these side walls include upper and lower arcuate 
side walls 34 and 34', respectively, a front end wall 36 (see FIG. 1), and 
upper and lower rear end walls 38 and 38' respectively. 
Still referring to FIG. 2, the pumping action of the lobe rotors 16 and 16' 
results from the upper rotor 16 rotating clockwise along arrow 40 while 
the lower rotor 16' rotates counterclockwise along arrow 42. Due to the 
shape of the rotors 16 and 16', there is a continuous rolling sealing 
contact made between the rotors 16 and 16' as they turn, and the rotors 
each make peripheral sliding sealing contact with the arcuate side walls 
34 and 34' respectively. 
In accordance with the present invention, the upper and lower arcuate side 
walls 34 and 34' are respectively defined by upper and lower arcuate wear 
plates 44 and 44' which are removably mounted to the pump housing 12. The 
arcuate wear plates 44 and 44' each have substantially the shape of a half 
cylinder so as to coincide with the substantially semi-spherical upper and 
lower ends of the obround pump chamber 14. Each of the wear plates 44 and 
44' defines on the outer surface thereof a substantially semi-annular key 
46 and 46' which is engaged in a corresponding, that is of substantially 
semi-annular shape, groove or keyway 48 and 48' defined in the pump 
housing 12 at the upper and lower arcuate ends of the pump chamber 14, the 
engagement of the keys and keyways resist movement of the arcuate wear 
plates in the axial direction of the pump. The keyways 48 and 48' are 
defined forwardly of radially oriented threaded holes 50 which are defined 
in the outer surface of the pump housing 12 and which are adapted for 
receiving an eyebolt 52 for use in handling the rotary lobe pump P (a 
similar eyebolt 52' is engaged in a threaded hole which is identical to 
hole 50' and which is defined in the outer surface of the gearbox 10 as 
seen in FIG. 1). 
The arcuate wear plates 44 and 44' are secured to the pump housing 12 by 
way of bolts 54 (see FIG. 2) which extend from outside of the pump housing 
12 radially inwardly towards respective lobe rotors 16 and 16' and which 
threadably engage the keys 46 and 46' of the wear plates 44 and 44'. In 
the illustrated embodiment there are two such bolts 54 for each one of the 
wear plates 44 and 44'. As best seen in FIG. 1, the wear plates 44 and 44' 
are supported at the rear end thereof by the peripheral edges of the rear 
end walls 38 and 38'. 
The rear end walls 38 and 38' are herein embodied in a pair of rear wear 
plates 56 and 56', respectively. The rear wear plates 56 and 56' each have 
the shape of disc which is missing a segment at the point of abutment of 
the two rear wear plates 56 and 56' centrally in the pump chamber 14 and 
reference is made to FIG. 2. Also, the rear wear plates 56 and 56' each 
define centrally thereof an opening for allowing the drive shafts 24 and 
26 to extend forwardly to the lobe rotors 16 and 16'. The rear wear plates 
56 and 56' each comprise on a rear surface thereof a rearwardly projecting 
curved key 58 and 58', respectively, which engages an arcuate keyway 60 
and 60' defined in the rear wall of the pump housing 12 adjacent the 
gearbox 10, as best seen in FIGS. 1 and 3. Bolts 62 which extend inwardly 
through the rear wall of the pump housing 12 engage the rear wear plates 
56 and 56' to secure the same to the pump housing 12. The outer peripheral 
ends of the rear wear plates 56 and 56' support the rear ends of the 
arcuate wear plates 44 and 44' so as to retain the latter in position in 
outward abutment against the pump housing 12. 
For replacing the rear wear plates 56 and 56', the bolts 20 are removed to 
separate the front cover plate 18 from the pump housing 12 (and from a 
peripheral torus-shaped gasket or seal 64 mounted in the pump housing 12 
opposite the front cover plate 18); the lobe rotors 16 and 16' are 
disengaged from the drive shafts 22 and 24 and removed from the pump 
housing 12, and finally the bolts 62 are removed to disengage the rear 
wear plates 56 and 56' from the pump housing 12 thereby allowing for the 
removal and replacement of the rear wear plates 56 and 56'. 
If the arcuate wear plates 44 and 44' need to replaced, the bolts 54 are 
removed, whereby, with the rear wear plates 56 and 56' and the lobe rotors 
16 and 16' being removed, the arcuate wear plates 44 and 44' can be 
disengaged and removed from the pump housing 12 by displacement thereof 
towards the center of the pump chamber 14, that is in a direction so as to 
withdraw the keys 46 and 46' thereof from the keyways 58 and 58'. New 
arcuate wear plates 44 and 44' can then be installed followed by the 
installation of the same or of new rear wear plates 56 and 56'. The lobe 
rotors 16 and 16' are mounted to the drive shafts 22 and 24 and the front 
cover plate 18 is secured to the pump housing 12.