Split bellows
We manufacture custom-made split bellows that can be opened and securely closed again when installed – without the need to dismantle attachments, shafts or guides.
- Customised production
- Batch sizes 1 to 1 million units.
- Express production from 2 weeks
- 100% Reliability & proactivity
Bellows to drawing with integrated closure system
A classically closed bellows must be pulled axially over the shaft, spindle or guide for replacement or cleaning. This is frequently an intervention that requires the dismantling of adjacent components and noticeably extends a system's downtime. A split bellows solves this problem: a longitudinal separation with an integrated fastening system enables it to be opened and closed directly at the installation site. Since every system places different demands on sealing, frequency of operation and stress, we manufacture every split bellows individually according to drawing – the parting line, type of closure, sealing concept and connection geometry are tailored to your application.
The zipped bellow provides a tight seal and is suitable for frequent opening cycles. Waterproof and corrosion-resistant designs ensure high resistance to hygiene requirements and cleaning.
Bellows with zip
The bellows with hook-and-loop fastener is suitable for frequent opening and closing. It protects against dust and swarf and allows particularly quick access for maintenance and servicing.
Bellows velcro fastening
For short separation lines or where space is limited, press studs or magnetic strips are used. They allow for easy operation and are particularly suitable for cramped installation situations.
Bellows with press-stud fastening
The combination of zip and hook-and-loop fastener increases sealing performance, protection and service life. This relieves strain on the zip and protects it against wear.
Combined closure systems
Benefits of a divisible bellows
A split bellows is used when a traditional closed bellows can no longer meet the requirements for maintenance, cleaning or retrofitting economically or functionally.
- Reduced downtime: cleaning, visual inspection and replacement are carried out directly on the installed component. This means that work which takes hours with traditional bellows can be completed in just a few minutes.
- Improved cleaning: The split bellows can be opened completely. This facilitates cleaning and visual inspection, and reliably ensures high standards of hygiene.
- Faster replacement during servicing: the bellows can be replaced without dismantling the protected component. This significantly shortens service times and reduces unplanned downtime.
- Retrofit capability of existing systems: The split bellows can be retrofitted without dismantling the machine. This allows existing systems to be upgraded easily and efficiently.
- Lower risk of contamination: Simple cleaning reduces build-up and lowers the risk of contamination. This increases process reliability, especially in food and pharmaceutical plants.
- Lower life-cycle costs: Even though a splittable bellows has a higher purchase price than a standard closed bellows, the investment typically pays for itself after just a few maintenance or cleaning cycles.
Custom-made split bellows -
individually made by GUME
- In-house toolmaking: moulds are created internally, with no external waiting times
- Express production possible: first samples already available in 2–3 weeks
- Flexible sizes and quantities
- Custom production from single items to large-scale series
The right material
to your split bellows
Not every split bellows has to meet the same requirements. Through our in-house development and manufacturing, we tailor the geometry, material and split precisely to your application.
Cost-effective processing especially for quantities of 1,000 units and above
Resistant to UV radiation, ozone and hot water, not suitable for oils and fuels
For bellows that come into contact with hydraulic fluids, mineral oils & fuels
Even higher resistance to chemicals, fuels and heat than NBR.
High-performance material with resistance to aggressive chemicals and at temperatures up to +200 °C.
Resistant at low temperatures down to −50 °C and at high temperatures up to +220 °C, FDA- compliant and predestined for food and medical technology applications
The all-rounder for weather resistance, ozone resistance and moderate contact with oils, greases and refrigerants
Use cases for shared and retrofitted bellows
Split and retrofittable bellows are used wherever conventional installation is not possible due to the system design or where regular opening for maintenance and cleaning is required. Thanks to zip, hook-and-loop or hybrid closure systems, the protective covers can be opened and closed quickly without dismantling the system.
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Robotics & Automation
In food, beverage and pharmaceutical processing equipment, the area beneath the bellows must be cleaned and visually inspected on a regular basis. A split bellows with a zip fastener allows it to be opened completely directly on the machine, thorough cleaning of the surface area, and subsequent closing without disassembly.
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Longer covers
For long strokes or long protective covers, sometimes only a defined inspection section with access is required. In this case, we manufacture the bellows as a hybrid solution: a closed main body with a separable inspection segment that can be opened, for example, by means of a zip.
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Hygiene-sensitive areas
In automated systems with frequent sensor or actuator changes, tool-free operability is a direct productivity factor. The bellows Velcro fastener allows quick opening and closing without tools, which simplifies intervention for operating personnel and reduces changeover times.
Design of the separation zone of split bellows
The separation zone is the most structurally demanding element of a divisible bellows. It must maintain the flexibility of the bellows without the fastener being overloaded by the movement of the folds and restoring forces.
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Course of the dividing line
Normally, the dividing line runs axially along one side of a fold. In the case of heavily curved or conical bellow geometries, we design the dividing line along a stress minimum line so that the movement of the folds does not periodically pull the closure apart.
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Reinforcement in the closure area
The parting line is reinforced in the vulcanisation process with an increased wall thickness or an embedded fabric tape. This ensures that the pleat geometry remains stable even along the parting line, and the force application into the closure is distributed evenly.
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Sealing concept
Behind the closure runs a moulded elastomer lip which, when closed, rests against the opposite lip under pre-tension. This sealing lip performs the actual sealing function, while the zip or hook-and-loop fastener primarily applies the mechanical closing force. For requirements involving protection classes of IP65 and above, we test the sealing concept using a water jet test.
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End point of the dividing line
The end points are designed in such a way that no voltage peaks occur at the fastener outlet. An integrated end stop and a reinforced outlet zone, which prevent the parting line from tearing under dynamic load, are common.
You have questions about
split bellows
We have answers!
When is a bellows with a zip the right choice?
A zipped bellows is the right choice when a defined, tight closing process is required – for example in food processing, pharmaceutical or cleanroom systems, in the event of splash water exposure, or during frequent cleaning with alkaline or acidic media. Waterproof profiled zips with elastomer-coated tapes achieve protection classes up to IP65 or higher, depending on the design.
When is a bellows with a Velcro fastener more practical than one with a zip?
A bellows Velcro fastener is the right choice when quick, tool-free opening is the priority and complete airtightness is not required – for example, for swarf protection, dust protection or as a privacy screen in maintenance-intensive areas. High-strength Velcro systems retain their holding power over several thousand closing cycles and are less sensitive to contamination by coarse particles than a zip.
Can an existing standard bellows be split retrospectively?
From a functional safety perspective, we advise against this. The parting line of a separable bellows must be specifically designed, the reinforcement moulded into the tool, and the sealing concept coordinated with the movement of the convolutions. A standard bellows that has been subsequently cut open loses its protective effect and typically tears along the parting line under dynamic load. Therefore, we manufacture the separable bellows from the outset as a retrofittable bellows. Subsequent installation refers to the finished bellows on your system, not to cutting open an existing component.
What level of tightness does a split bellows achieve compared to a closed bellows?
With a waterproof zip and a correctly designed overlapping sealing lip, a split bellows achieves protection classes up to IP65, and even higher in special versions. The specific protection class that can be achieved depends on the closure system used, the sealing concept, the bellows geometry and the motion profile, and is verified on the initial sample.
How many opening cycles does a bellows with a zipper or hook-and-loop fastener achieve?
High-quality waterproof zips achieve several thousand to several tens of thousands of opening and closing cycles, depending on the application and load profile, whilst high-strength hook-and-loop systems typically achieve numbers in the thousands. For very high cycle requirements, we recommend combined fastening systems consisting of a zip and a covering hook-and-loop fastener, which distribute the load across two independent fastening levels.
Which materials are suitable for split bellows?
In principle, all rubber materials (NBR, HNBR, EPDM, silicone, FKM, SBR, NR, etc.) that we also process for closed bellows can be used. The specific selection depends on media contact, temperature range and hygiene requirements. Material compatibility between the bellows material and the closure system is important: at high cleaning temperatures, zip tapes and hook-and-loop systems must be selected accordingly to prevent material fatigue in the closure.
Can the dividing line also run transversely to the direction of the folds instead of axially?
As a rule, the parting line runs axially along one side of a fold, because this means the folding movement only exerts a lateral load on the closure. A separation running transversely to the direction of the folds is technically possible, but is subjected to significantly greater stress due to the fold kinematics: with every stroke, the closure is cyclically pulled apart and compressed again, which reduces the service life. We therefore only use transverse separations if the installation situation does not permit an axial parting line – usually in conjunction with a defined end stop in the tool, so that the closure is not reached in the heavily loaded stroke range. In such cases, a hybrid bellows is often the better solution, in which the separable segment lies outside the dynamically loaded fold zone.
How does the closure affect the axial flexibility and restoring force of the bellows?
A zip or hook-and-loop tape along the dividing line stiffens the bellows in its longitudinal direction, as the fastening tape itself is hardly stretchable. We compensate for this structurally by adding an extra number of folds in the fastening area or by using a soft fastening tape with an elastomer-coated base structure. The restoring force of a splittable bellows is typically 10–30 % higher than that of a comparable closed bellows of the same geometry, depending on the fastening system and the design of the separation zone. In applications with a defined spring characteristic or limited actuator force – such as pneumatic drives with low switching pressure – the fold geometry and wall thickness are adjusted accordingly.
Are metal-free fastening systems possible, for instance for X-ray or MRI applications?
Yes. For applications where metallic components must be excluded – such as in MRI imaging, X-ray fluoroscopy, or in metal-detectable production environments within the food industry – we manufacture split bellows with completely metal-free closure systems. Common options include zippers with plastic coils and plastic sliders, hook-and-loop systems with plastic mushroom-head tapes, and rows of plastic press studs. If required, we can supply a material declaration confirming the metal-free nature of the entire assembly, including the closure.
Are closure systems made from FDA-compliant materials available?
Yes. For applications involving contact with food, drinking water, or pharmaceuticals, we use closure systems made from certified materials – in particular zips and hook-and-loop tapes whose backing materials (PE, PA, POM) and coatings (TPU, TPE) meet the requirements. We can supply declarations of conformity directly with the initial sample upon request, allowing the component documentation to be seamlessly integrated into your equipment records.
What information is required for a reliable enquiry regarding a divisible bellows?
For a reliable initial estimate, we ideally require a 2D drawing and a 3D model (STEP) of the installation situation. In addition, the following information will help us: stroke and movement profile, required protection class or sealing requirement, frequency and type of opening (for example, daily cleaning, occasional inspection, or one-off service event), environmental conditions (temperature range, media contact, cleaning procedures), desired quantity per year, and any compliance requirements.
