--- publication_id: "OT-2026-000004043" title: "Bellows cup vacuum gripper, two zone face, two stage ejector, pressure verified at each zone" published_at: "2026-09-16T07:10:04.630563Z" canonical_url: "https://opentechnical.org/p/OT-2026-000004043" categories: - "robotics-automation/end-effectors/vacuum-grippers" - "lifting-positioning-manipulation/vacuum-lifting/sealing-and-suction-pads" - "sensors-controls-machine-vision/position-and-presence-sensing/inductive-sensors" - "industrial-motion-power-transmission/fluid-power/vacuum-generation" keywords: - "bellows cup" - "contact detector" - "ejector" - "mounting flange" - "pressure sensor" - "vent valve" - "zone branch" - "grip verification" - "end of arm tooling" - "plastic" --- # Bellows cup vacuum gripper, two zone face, two stage ejector, pressure verified at each zone ## Abstract An end effector for vacuum end-of-arm tooling with compliant bellows cups is described. The tool comprises a mounting flange (10), a bellows cup (12), a ejector (14), a zone branch (16), a contact detector (18), and a pressure sensor (20), a vent valve (22). The arrangement addresses knowing that the workpiece is actually held before the arm moves, where a cup that has not sealed looks the same as a cup that has, and the difference only appears when the load is already in the air. The description covers where the pressure is measured, the condition that counts as a secure grip, and what the motion is not permitted to do until that condition holds. Every connection is stated with the medium it carries, and the operating sequence is given as conditions on named operations. ## 1. Technical Field [0001] This disclosure relates to vacuum end-of-arm tooling with compliant bellows cups. It concerns the arrangement of a gripping interface, the supply that feeds it, the distribution and control between them, and the sequence in which those parts act on a workpiece. FIG. 1 shows the arrangement as a block diagram with the reference numerals used throughout this description. ## 2. Technical Context [0002] The arrangement addresses knowing that the workpiece is actually held before the arm moves. The difficulty is that a cup that has not sealed looks the same as a cup that has, and the difference only appears when the load is already in the air. A tool that does not address it is still usable on a narrow range of workpieces, and the cost appears as cycle time, dropped parts or air consumption rather than as an outright failure. What follows covers where the pressure is measured, the condition that counts as a secure grip, and what the motion is not permitted to do until that condition holds. ## 3. System Overview [0003] The tool comprises the mounting flange (10), the bellows cup (12), the ejector (14), the zone branch (16), the contact detector (18), the pressure sensor (20), the vent valve (22). FIG. 1 shows how these blocks are connected and which medium each connection carries. The blocks are not interchangeable by name: a connection is made only where one block offers a medium that another needs, and each connection below is stated together with the medium it carries. [0004] FIG. 2 shows elevation of the gripping face on its mounting. [0005] FIG. 3 shows signal path between the controlled elements and the cell controller. - The mounting flange is bolted to the robot flange (10). - Each bellows cup is connected to the ejector by a vacuum line that runs into the bellows body (12). - Each bellows cup is mounted on the mounting flange (12). - Compressed air is fed to the ejector from the compressed air supply of the cell (14). - Each zone branch is taken from the ejector, so that the branch carries the vacuum of its own zone only (16). - The detector watches the bellows cups and reports when a workpiece is present at that face (18). - The pressure sensor is tapped into the line at the ejector and reads the pressure in that line (20). - The vent valve is connected to the circuit at the ejector and opens that circuit to atmosphere when it is actuated (22). - The vent valve is switched by the contact detector (22). ## 4. Components [0015] **Mounting Flange (10).** The mounting flange (10) is provided once in this arrangement. The flange carries the whole assembly and presents the bolt pattern that meets the robot. [0016] **Bellows Cup (12).** The bellows cup (12) is provided once in this arrangement. Each cup is folded so that it shortens under vacuum and takes up a height difference between the face and the workpiece. Each cup carries 1 folds. The cups are made of plastic. [0017] **Ejector (14).** The ejector (14) is provided once in this arrangement. The ejector draws the circuit down by passing compressed air through a nozzle, so it needs no moving part at the tool. The ejector is built with 2 stages. [0018] **Zone Branch (16).** The tool carries 1 zone branches. Each branch feeds one zone of the face, so the zones can be treated separately. The zone branch (16) is configured with material plastic. The face is divided into 2 zones. [0019] **Contact Detector (18).** The contact detector (18) is provided once in this arrangement. The detector watches the face and reports the moment a workpiece is present against it. The detector is placed on the frame. [0020] **Pressure Sensor (20).** The pressure sensor (20) is provided once in this arrangement. The sensor taps the line and reports the level it reads, which is what makes the state of the grip observable. The pressure is measured at each zone. [0021] **Vent Valve (22).** The vent valve (22) is provided once in this arrangement. The vent valve opens the circuit to atmosphere, which is what ends the grip. The circuit is vented after set-down. ## 5. Operation [0022] The operating sequence is given as conditions on named operations. Each condition names the event it depends on and the operation it governs, so the order of events is explicit rather than implied by the order of the sentences. FIG. 2 shows the gripping face referred to in these steps. The tool is presented to the workpiece square to the face, and the numbered operations below are what the arrangement does from that point. - When the bellows cups seal the workpiece, the bellows cups are evacuated by the ejector. - After the contact detector has detected the workpiece, the vacuum supply is actuated. - When the vacuum level exceeds the gripping threshold, a secure grip is signalled by the pressure sensor. - The workpiece may not be lifted unless the pressure sensor signals a secure grip. - After the workpiece has reached the set-down position, the vacuum circuit is vented by the vent valve. - The workpiece is held until the vent valve has opened the circuit. [0029] An operation whose condition is not met does not run. A condition that is stated with UNLESS holds except while its event is true, and one stated with UNTIL ends the operation at the moment its event becomes true. With the workpiece released, the tool returns to the pick position and the cycle repeats. ## 6. Example Embodiments [0030] In one embodiment the gripping face carries 1 bellows cups on a common mounting, fed as shown in FIG. 1, and the tool is presented to the workpiece square to the face. In a second embodiment the same face is arranged in two rows so that a long workpiece is supported at both ends, with the connections of FIG. 1 unchanged. In a third embodiment the face is built at half the pitch and the number of bellows cups is doubled for the same envelope, which suits a workpiece that is lighter but less rigid. ## 7. Alternative Configurations [0031] The gripping face may instead use a folded bellows cup, which takes up height differences at the cost of lateral stiffness. The gripping face may instead use an array of discrete cups, which concentrates the holding force at the lips and needs a sealing surface. A gripping face of this kind may also be replaced by fingers closing on the workpiece, which removes the air circuit entirely and requires access to two opposed surfaces of the workpiece. The ejector may be replaced by a pump at the tool, which stops the continuous air draw and adds mass to the moving assembly, or by a connection to a plant vacuum line, which removes the generator from the tool and couples the tool to the rest of the site. An isolation valve may be added in the line to each zone, which allows one part of the face to be cut from the circuit while the rest holds its vacuum. The vent may be supplemented by a blow-off pulse, which clears the face rather than waiting for it to refill. ## 8. Parameter Variations [0032] Each parameter below is stated with what it changes in the arrangement. The folds of the bellows cup is 1 in the arrangement described; varying it changes the travel taken up at the face and the lateral stiffness under load. The material of the bellows cup is plastic in the arrangement described; varying it changes the friction at the lip and the resistance of the fold to fatigue. The stages of the ejector is 2 in the arrangement described; varying it changes the flow drawn at low vacuum and the air consumed to hold a sealed face. The zones of the zone branch is 2 in the arrangement described; varying it changes how much of the face can be isolated at once and how small a workpiece the tool can still hold. The placement of the contact detector is on the frame in the arrangement described; varying it changes whether contact is reported for the face as a whole or for one part of it. The placement of the pressure sensor is at each zone in the arrangement described; varying it changes whether the reading describes the whole circuit or one zone of it. The timing of the vent valve is after set-down in the arrangement described; varying it changes whether the workpiece is released before or after it is supported. ## 9. Additional Implementations [0033] The whole assembly may be carried on a tool-change interface so that it can be exchanged between jobs without dismantling the tool. A separating element may be added so that a workpiece which follows the face upwards after release is pushed off positively. The arrangement may be duplicated on one mounting so that two workpieces are handled in one cycle, with the distribution fed from a common inlet and each face controlled on its own. ## 10. Provenance and method [0034] This document is an original combination composed from a typed library of mechanism blocks. Each block was derived from the published patent literature and carries typed connection points, the parameters its source states, and its own construction and operating description. The combination described here is proposed rather than taken from any one source, and it is not asserted to have been constructed. The published documents behind the blocks used in this arrangement are EP-4489564-B1, US-10549431-B2, US-11427405-B1, US-2022339798-A1, WO-2008134339-A4, WO-2026020244-A1. Their text is not reproduced here; the description above is generated from the structure of the combination. ## 11. Figures ![FIG. 1](figures/fig-001.svg) Block diagram of the tool, with the medium carried by each connection. ![FIG. 2](figures/fig-002.svg) Elevation of the gripping face on its mounting. ![FIG. 3](figures/fig-003.svg) Signal path between the controlled elements and the cell controller.