Another shaft coupling connection challenge was successfully solved by the Helical flexible beam product available through Abssac Limited. Abssac's customer had an application where a precision encoder was being connected to a carpet manufacturing machine output shaft. The machines are used to manufacture man-made fibre twisted loop pile carpets for domestic use. If the vibration and movement present at the output shaft was transmitted to the encoder, it would cause signal errors and ultimately prematurely destroy the encoder. Ultimately this would lead to below standard carpet being produced due to loom operational irregularities. Whilst very little torque was required in the application, torsional stiffness and zero backlash were important design parameters.
The customer also wanted a low maintenance solution. From a shaft coupling design aspect, the application required large axial motion and parallel misalignment because of the assembly tolerances. The customer was originally using a multi-part bellows shaft coupling, but the required angular and axial movements had lead to premature failure. Additionally, under certain operating conditions, the bellows coupling allowed too much vibration to reach the encoder.
When looking at Flexible Solutions - Flexible Couplings - Flexured U-Joints, one of the greatest advantages of the Helical Shaft coupling product is the ease in which it can be adapted from a standard and into a cost effective, multi-functional bespoke design. It is the perfect solution where flexibility is required for critical applications.
By altering the characteristics of coiled beam area, torque capacity, angular and parallel misalignment capabilities, (torsional and lateral bending rates of flexured u-joints) can be modified to suit specific specifications and or requirements.Once the performance dynamics of the coupling are decided, we then look at the way the shaft coupling attaches in the application or perhaps how we can add other parts of the total mechanism into the single piece shaft coupling. We like to refer to the adaptable flexible element in the product as the "FLEXURE".
The flexure is determined by six major characteristics:
1. Flexure outside diameter
2. Flexure inside diameter
3. Coil thickness
5. Number of coils
6. Number of coil starts
By varying the thickness of the coils a flexure can accommodate increasing amounts of torque and radial loads.
By varying the Number of Coils the torque capability remains unchanged but the angular, parallel and skewed offset capability increases.
By varying the Inside Diameter so does the torque capacity, torsional stiffness and axial spring rate
By varying the Number of Coil starts with One, two or three helical beams provide higher torsional stiffness.
In a rotating system, constant velocity refers to the relative rotational speed of the input and output shafts. In a constant velocity system the driven end of the coupling turns exactly the same rate as the driver end. When operating under a uniform load the helical flexure design provides constant velocity and can alleviate problems such as Backlash. The helical flexure has zero backlash. Angular misalignment can induce large fluctuations in rotational velocity in certain coupling designs.The Helical flexure has a constant spring rate at all points of rotation. Torsional variations can induce differences in hub to hub velocity when subjected to dynamic loading are minimal in steady state applications on the helical flexure. Concentricity can be an issue when there is a lack of it, particularly in the case of couplings with backlash or where production variation is difficult to prevent. The Helical flexure one piece integrity minimises sinusoidal variations and has zero backlash.
The flexing capacity of the flexure can compensate for a variety of misalignments including parallel, angular, axial and skewed shaft misalignment. Optimised Torque Capacity – The basic requirement of a flexible coupling is to transmit torque loads without permanent distortion or damage and without imposing undue bending or radial loads upon the driver or driven components. Once the working torque rating of the flexure coupling is established, based on design criteria, its operational life is virtually unlimited.
Every Flexible coupling has some torsional flexibility. Torsional flexibility reflects the amount of twist in a system; torsional stiffness the degree of resistance against twist. The flexure uniquely can be configured to provide the exact amount of torsional flexibility required in an application. The Helical flexure maintains a very constant radial and bending load at all points of rotation, providing exceptionally uniform and smooth bearing loads.
The Heli-Cal flexure product is available Aluminium, high strength alloys, Titanium, MP35N, Delrin to name a few and have been successfully used in medical, energy, military, aerospace and industrial automation.
By simply allowing the development of innovative connection solutions from the standard helical beam shaft coupling design, has opened up a plethora of opportunities to the design engineer. The hidden potential of expanding how a shaft coupling physically connects within an application, which is often left to standard grub screw or locking clamp, can enhance the overall efficiency of an application. With Abssac’s Heli-Cal beam coupling product, customers have been able to take their standard coupling designs to the next level, by incorporating features into the original shaft coupling design. In many cases, the final shaft coupling design is normally an amalgamation of separate parts that include such items as external gears, splines, threads and tangs. However, most importantly, it enables the design engineer to achieve far greater usage from one item in the total machine which inevitably leads to greater efficiency. How the standard shaft coupling connectability is enhanced, is really up to the designer. Abssac is so confident with the products success rate that in many cases it offers a free sample for the customer to test and evaluate. Stacey Taylor at Abssac says, “When you consider the Heli-Cal beam couplings capability as a shaft coupling and then add this ability to integrate the design engineers own end attachment ideas, you have a formidable product combination that other coupling manufacturers can not supply”.
Utilising years of experience and flawless production techniques, the single piece construction totally eliminates any form of friction wear within its design, whilst also ensuring a zero-backlash and no torque loss operation. If you require further technical information on this product, please do not hesitate to contact our sales engineers who will be more than happy to help you.
Telephone ABSSAC : 01386 421005