Pumps – Expansible chamber type – Elongated flexible chamber wall progressively deformed
Reexamination Certificate
2002-02-20
2004-05-18
Tyler, Cheryl J. (Department: 3746)
Pumps
Expansible chamber type
Elongated flexible chamber wall progressively deformed
C417S477800, C417S477300
Reexamination Certificate
active
06736617
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a peristaltic pump for fluid transfer, such as blood circulation, dialytic fluid circulation or fluid medicine injection, and more particularly, to an adjustable occlusion peristaltic pump having an automatically adjusting bushing.
BACKGROUND OF THE INVENTION
Peristaltic pumps are commonly utilized in medical applications. For instance, such pumps are often employed during cardiovascular surgery to facilitate circulation of blood between a patient and a heart-lung machine. Other common medical uses are the transfer of blood between a patient and a kidney dialyzer, and intravenous feeding of IV solutions. Generally, peristaltic pumps are simply structured, generate a constant flow, and employ disposable tubes as a member for fluid transfer.
Peristaltic pumps are relatively simple in construction and typically include a housing having rollers which progressively compress a flexible tube at spaced intervals against an arcuate surface or raceway so as to flatten or locally reduce the cross-sectional area of the tube. In this manner, fluid leading to the flexible tube is continuously forced through the flexible tube by one or another of the rollers as it proceeds along the flexible tube over the arcuate surface or raceway.
A conventional roller pump
10
, as shown in
FIG. 1
, comprises a drive mechanism
14
furnished with a drive shaft
12
, a rotating shaft
16
which rotates according to the rotation of drive shaft
12
, and a hollow pump head
20
fixed to a housing
18
to which drive mechanism
14
is attached. This pump head
20
integrally incorporates a bearing block
24
through which rotating shaft
16
is inserted and rotatably supported by a pair of bearings
22
and a stator
26
arranged on the upper portion of bearing block
24
. On the upper surface of stator
26
is formed a recess
28
through which the upper end of rotating shaft
16
is protruded. While this recess
28
is radially and outwardly spaced at a certain distance from the outer circumferential surface of rotating shaft
16
, its inner circumferential surface
28
a
is coaxial with rotating shaft
16
.
A rotor assembly
30
is attached to the upper portion of rotating shaft
16
in such a way as to be placed inside recess
28
of stator
26
and to stay opposite the inner circumferential surface
28
a
thereof. This rotor
30
is fixed to rotating shaft
16
through a bolt
32
, and is so constructed as to integrally rotate along with rotating shaft
16
. On the outer circumferential surface of rotor
30
, at least one roller
34
is arranged so as to rotate about its own axes. A tube
36
which is filled with blood or other fluid material is placed between rotor
30
and stator
26
. Tube
36
is clamped between respective rollers
34
, which are attached to rotor
30
, and inner circumferential surface
28
a
of stator
26
, thereby maintaining tube
36
in a closed state at the point at which it is clamped.
Thus, in a conventional roller pump
10
, rotor
30
is rotated by the rotational motion of rotating shaft
16
driven by drive mechanism
14
, and the clamped portions of tube
36
move according to the revolution of rollers
34
around rotating shaft
16
. Therefore, fluid inside tube
36
is transferred according to the revolution of rollers
34
. The rate of rotation of the rotating shaft
16
and hence the rollers
34
is normally adjustable so that the pumping rate of the fluid within tube
36
can be adjusted. However, the pumping rate can also be adjusted by adjusting the degree to which the rollers compress the flexible tube. This can be done in peristaltic pump assemblies by providing an adjustment mechanism for adjusting the distance between the axes of the rollers and hence the distance between the roller surface and the inner circumferential surface
28
a
of stator
26
. Another important reason for peristaltic pumps to be adjustable in this fashion is that the compressibility, size, and other qualities of the flexible tube can vary considerably.
A rotor assembly
30
′ having an adjustable occlusion capability, as shown in
FIG. 2
, comprises a rotor hub
40
, and opposing roller slides
42
, each of which carries at least one roller
34
on the outer circumferential surface thereof. The roller slides
42
are extended or retracted from the hub
40
by turning the knob
44
on the top of the rotor hub. The extension or retraction of the roller slides thereby changes the occlusion of the flexible tube within the peristaltic pump. The roller slides
42
should be held securely to avoid knocking of the slides on the side, top, or bottom surfaces of the slot in the hub
40
, particularly as the rollers
34
roll onto or off of the flexible tube in the pump. Because the flexible tube in a peristaltic pump is typically located in an approximately 180° arc around the rotating rotor, each roller
34
rolls onto and then off of the flexible tube once during each revolution of the rotor. Any knocking of the roller slides against the walls of the rotor hub produces a noise which has been found unacceptable in a surgical environment.
The roller slides in a peristaltic roller pump must therefore be held securely in order to avoid the unacceptable noise of the roller slide knocking against the hub. In order to prevent this knocking noise, the gap between the roller slide and the hub surface must be within approximately 0.001 inch on both the sides and the top and bottom of the slide. It is difficult and expensive to fabricate the hub and roller slides to maintain the gaps within this specification. The roller slides and hub are typically fabricated of aluminum and are anodized after machining. Considering the variation in geometry introduced by the anodization process, the height and width of the roller slides and hub must be machined to tolerances of approximately +/−0.0001 inch in order to obtain a 0.001 inch or less gap between the roller slides and hub. It is not practical to machine the parts to these tolerances. For the various occlusion mechanisms on the market, the most common approach used to obtain the 0.001 inch or less gap between the roller slides and hub relies on part size classification and custom fitting of parts. As a result, the roller slides in one pump do not necessarily fit properly in the hub of another pump, and hence classification and custom fitting of parts does not allow for easy service or replacement of the roller slides.
Accordingly, there is a need in the art for an improved system for mounting the roller slides in the hub of a rotor assembly which substantially eliminates the potential for knocking noises and significantly relaxes the machining tolerances for the roller slides and hub.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of the prior art by providing an adjustable bushing for use in a roller pump. The adjustable bushing comprises a preferably wedge shaped bushing member and a spring. The spring biases the wedge shaped bushing member in a recess in a portion of the roller pump; thereby compensating for any gap or spacing between the roller slide and the hub.
More particularly, the present invention is directed to a roller pump comprising a stator, a rotor assembly including a rotor hub, a first roller slide and a second roller slide slidingly disposed within the rotor hub, and each of the roller slides supporting a roller. At least one adjustable bushing is mounted within at least one of the roller slides to compensate for any gap or spacing between the roller slide and the hub. In a preferred embodiment, at least one of the roller slides includes a recess and the at least one adjustable bushing is at least partially disposed within the recess. The at least one adjustable bushing preferably comprises a bushing member and a spring member, the spring member biasing the bushing member within the recess. More preferably, the bushing member has a wedge shaped configuration and the recess is correspondingly tapered within a surface of one of the roller slides.
In a
Burns Doane , Swecker, Mathis LLP
Terumo Cardiovascular Systems Corporation
Tyler Cheryl J.
LandOfFree
Peristaltic pump having automatically adjusting bushing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Peristaltic pump having automatically adjusting bushing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Peristaltic pump having automatically adjusting bushing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3202751