Reciprocating Pump Cam Mechanism for Motion Law Adaptability
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Solution Overview
Problem
Existing reciprocating pumps face issues with harmonic motion limitations, cam follower breakage, and increased radial size due to the need for a connecting rod-crank mechanism and cam lobes, which restrict the ability to impart different motion laws and adapt speeds and accelerations to pumping steps.
Innovation Solution
A reciprocating pump design featuring a drive shaft with a thrust cam and a return cam, along with rocker arms, allows for different motion laws by using a cam follower with multiple bearings and a tappet element to distribute forces, reducing the radial size and enhancing mechanical strength, while enabling adjustable speeds and accelerations through separate cams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a connecting rod-crank mechanism with a single circular cam is used to actuate the piston, then the mechanism is simple in structure, but the piston can only move with harmonic motion and cannot achieve different motion laws
Solution Approach 1:
The single cam is segmented into two separate cams: a first cam for actuating the piston during the delivery stroke and a second cam for actuating the piston during the suction stroke. This segmentation allows each cam to be independently designed with different profiles to achieve different motion laws for each stroke, thereby improving motion law adaptability while keeping the overall mechanism relatively simple.
2Reliability
If a cam follower with a rotary bearing mounted on a support pin is used, then the cam follower can rotate to reduce friction, but the support pin is subjected to bending forces and can easily break
Solution Approach 1:
The rotary bearing is extracted from the support pin structure and mounted directly on the cam follower body. This removes the support pin from the load-bearing path, eliminating the bending forces that caused it to break. The cam follower now has a more robust structure where the bearing is directly integrated into the follower body, significantly improving reliability without compromising strength.
3Adaptability or versatility
If the cam follower is positioned away from the rotation axis to allow insertion into the guide channel, then different motion laws can be imparted, but the radial extension of the pump increases
Solution Approach 1:
The cam follower is designed to be movable along the piston rod, allowing dynamic adjustment of its position relative to the rotation axis. This enables the cam follower to be positioned at different radial distances depending on the required motion law, providing adaptability in motion control. The follower can be adjusted during operation or maintenance to optimize the radial footprint while achieving the desired piston motion characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enables flexible motion laws, reduces radial size, and enhances reliability and assembly efficiency, allowing for precise control of piston motion and fluid pumping parameters.
Implementation Method 1
a thrust cam (10), which is fixed on the drive shaft (9) and is actuatable to rotate around a rotation axis (Y) of the drive shaft (9), in order to move each piston (8) from the release position to the compression position
Implementation Method 2
a return cam (15), which is fixed on the drive shaft (9) and is actuatable to rotate around the rotation axis (Y) of the drive shaft (9), in order to move each piston (8) from the compression position to the release position
Implementation Method 3
each piston (8) being provided with a rocker arm (11), which is movable around a pin (12) extended parallel to the rotation axis (Y) of the drive shaft (9) and having a first lever arm (13) acting on the piston (8) and a second lever arm (14) opposite to the first lever arm (13) with respect to the pin (12)
Implementation Method 4
a pumping chamber (5), which is closed by a membrane (6), which is actuatable in a reciprocating manner in order to expand the volume of the pumping chamber (5), so as to convey a fluid to be pumped into the same pumping chamber (5) through a corresponding suction channel (34), and in order to reduce the volume thereof, so as to expel the aforesaid fluid through a corresponding delivery channel (35)
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Reciprocating pump (1), comprising a casing (2) having guide seats (3) extended along a corresponding radial direction (X), heads (4) mounted on the casing (2) at respective guide seats (3) and each defining a pumping chamber (5), and membranes (6) each delimiting a pumping chamber (5). In addition, the reciprocating pump (1) comprises actuation means (7) housed inside the casing (2) and comprising pistons (8), each of which carrying a membrane (6) fixed thereto and susceptible of sliding in a guide seat (3) between a release position and a compression position, in which the membrane (6) respectively expands and reduces the volume of the pumping chamber (5), and a thrust cam (10) in abutment against the pistons (8) and rotating in order to move them from the release position to the compression position. In addition, the actuation means (7) comprise one or more rocker arms (11), each of which provided with a first lever arm (13) acting on a corresponding piston (8) and an opposite second lever arm (14), and a return cam (15), which is fixed on the drive shaft (9) and is actuatable to rotate around the rotation axis (Y) in order to move each rocker arm (11) around a corresponding pin (12). Each rocker arm (11) is also movable between an operative position, in which the return cam (15) acts against the second lever arm (14) in order to return, by means of the first lever arm (13), the piston (8) to slide from the compression position towards the release position, and a non-operative position, in which the return cam (15) releases the second lever arm (14) in order to free the piston (8) to slide from the release position towards the compression position.