Stretch Wrapping Machine Analog Tension Control
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Solution Overview
Problem
Existing stretch wrapping machines using stretchable film face challenges such as imprecise film tension control, film breakage due to sharp corners, and inability to wrap vertical and top surfaces effectively, leading to inefficiencies and increased costs.
Innovation Solution
A machine with a base frame, turntable, and vertically moving carriage, equipped with an analogous displacement transducer and frequency changer, allowing for precise control of film tension and wrapping of vertical and top surfaces using pre-stretching rollers and a pneumatic cylinder with a magnet-driven piston, enabling proportional tension adjustment and accurate film wrapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital sensors with discrete values are used to control film tension, then the control system is simple, but the film tension cannot be adjusted precisely and continuously
Solution Approach 1:
The patent replaces the mechanical digital sensor system with an electronic analog measurement system. The inductive transducer converts the mechanical position of the swing arm into a continuous electrical signal, enabling precise and continuous film tension control while maintaining relatively simple device architecture.
Solution Approach 2:
The patent introduces a dynamically adjustable film tension control system. The brake force on the pre-stretching roller is continuously adjustable based on the analog signal from the inductive transducer, allowing the system to adapt to varying film tensions during operation rather than being fixed at discrete levels.
2Device complexity
If the film is led vertically without tilting, then the wrapping mechanism is simple, but the film cannot wrap the top surface of the load effectively
Solution Approach 1:
The patent makes the film path dynamic by introducing a tilting mechanism. The film is tilted from vertical to horizontal position during load rotation, enabling it to wrap the top surface. The tilting angle is continuously adjustable based on the load geometry and wrapping requirements.
Solution Approach 2:
The patent adds a spatial dimension to the film wrapping path by tilting it from the vertical plane to the horizontal plane. This dimensional change allows the film to reach and wrap the top surface of the load, transforming a two-dimensional vertical wrapping into a three-dimensional wrapping operation.
3Reliability
If high film tension is applied to ensure tight wrapping, then the wrapping security is improved, but the film breaks at sharp corners of the load
Solution Approach 1:
The patent introduces a pre-stretching process that changes the physical parameters of the film before wrapping. By pre-stretching the film to a controlled extent, the film's mechanical properties are optimized to reduce stress concentrations at corners while maintaining adequate wrapping tension, thereby preventing breakage.
Solution Approach 2:
The patent applies preliminary action by pre-stretching the film before it contacts the load. This preparatory step ensures the film is properly conditioned and tensioned in advance, preventing sudden stress spikes that would cause breakage at sharp corners during the wrapping process.
4Reliability
If the swing arm deviates along a circular arc under spring force, then the film tension is regulated, but the spring force is not linear resulting in progressive rather than constant tension
Solution Approach 1:
The patent replaces the non-linear spring-based tension regulation system with an electronic control system. The inductive transducer provides continuous feedback about the swing arm position, and the control system adjusts the brake force on the pre-stretching roller to maintain constant, linear film tension throughout the wrapping process.
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 machine achieves precise and consistent film tension control, reducing film breakage and enabling efficient wrapping of vertical and top surfaces with stretchable film, improving wrapping accuracy and reducing operational costs.
Implementation Method 1
an inductive transducer for following the angular displacement directly proportional to the film tension
Implementation Method 2
which is connected to a frequency converter, which is regulating the rotary speed of a pre-stretching motor
Implementation Method 3
one of them is driven by a pre-stretching motor
Data Source
Figure 1
Figure 2
AI summary
The subject of the invention is a machine for wrapping vertical and top surface of loads (13) with stretchable film. The machine of the invention is provided with a swinging film tension setting unit (22) connected to the end of a shaft (6), which unit has pre-stretching rollers (7A) provided with a pre-stretching motor (20), a leading roller (7B) containing an arm provided with a roller (7C), a tension setting pneumatic cylinder (16) provided with an analogous displacement transducer (17) and equipped with a piston provided with a magnet (16A), furthermore a pressure regulator (18) and a frequency changer (15) all fastened to a frame of the film holding and pre-stretching unit (23), wherein the film winded off from the film reel (7) is led between the pre-stretching rollers (7A), one connected to another with a transmission (19) and one of them is driven by a pre-stretching motor (20) then the film is led around the leading roller (7B) having the arm rotating around a center of rotation and provided with the roller (7C), it is connected to the piston provided with the magnet (16A), which is mounted in the tension setting pneumatic cylinder (16), the latter is provided with the analogous displacement transducer (17) and the piston provided with the magnet (16A) is connected to the pressure regulator (18) and the. frequency changer (15), which frequency changer (15) is connected also to the pre-stretching motor (20).