Force measurement device and method for can bodies

Abstract

A device 100 for measuring forces applied to a can body 102, during necking or seaming, includes a longitudinal axis (118, Figure 3) and a mandrel member 114. A double open ended can body 102 having

Description

TECHNICAL FIELD The present invention relates to a device and method for measuring forces applied to can bodies, such as beverage can bodies, in particular, but not exclusively, during the necking or seaming processes. BACKGROUND Manufacturing cans, such as beverage cans, involves multiple manufacturing processes that must be performed accurately to ensure that the cans meet strict quality requirements. For example, care must be taken to ensure that the double seam used to secure the can end to the can body is manufactured with the correct dimensions to reduce the risk of failure and spoilage of food or beverage stored within the can. Conventionally, double seam quality is monitored by collecting samples of cans that have been manufactured and cutting through the cans so that the dimensions of the seams can be measured. However, this process is time consuming, requires skilled operators and may potentially lead to large numbers of faulty cans being manufactured before a problem is identified. Unscheduled interruptions to manufacturing may also occur because of the need to adjust, repair or replace machinery to correct any problems identified with the cans. Reducing downtime and wastage arising from quality issues is therefore an important goal for can producers, particularly given the high speeds and volumes of modern-day can production. Real-time monitoring of can manufacturing processes allows some of these issues to be mitigated or avoided. As one example, JP2000271687 describes a device for measuring the load on a can body as the can body is lifted against a seamer chuck during seaming. However, measuring the load requires that a custom-made “short” can body is placed on top of the device (and attached using adhesive tape) so that the loads measured by the device are indicative of those experienced by the other (taller) can bodies as they are being seamed. The device is also not suitable for incorporating into a production line as the short can body is not securely attached to the device. SUMMARY According to a first aspect of the present invention, there is provided a device for measuring forces applied to a can body, such as during manufacturing of cans, e.g. during one or more of necking, flanging, filling or seaming, or during transportation of the can bodies, e.g. along a production line. The device has a longitudinal axis and comprises a mandrel member about which to mount a double open ended can body having first and second openings and a sidewall extending therebetween. The device also includes a force sensor for measuring forces, such as axial load, applied through the can body when the can body is mounted about the mandrel member. The force sensor may be a load cell or an inertial sensor (e.g. an accelerometer), for example. In use, the can body is mounted about the mandrel member. That is, the can body at least partially receives the mandrel member through the first or second opening, e.g., such that the sidewall of the can body forms a sleeve around the mandrel member. The mandrel member can be adapted to engage with the inside of the sidewall of the can body to attach the can body to the device. The combination of the device and the can body is herein referred to as a “test can” or “dummy can”. The can body may derive from a three-piece can prior to the can ends having been seamed onto the can body. In this example, the can body may be flanged or unflanged at either or both ends. A portion of the can body may have been removed. Alternatively, the initial can body may derive from a two-piece can. In this example, a portion of the can body (including the integral base portion) is removed prior to use with the device in order for the can body to be mounted about the mandrel member. Removing the portion of the (two-piece or three-piece) can body results in a circumferentially extending cut edge. The device can be used to measure axial loads applied to the can body, i.e. forces applied through the can body that have a component acting along a longitudinal axis of the can body, such as those occurring during, necking, flanging and / or seaming of the can body. During measurement of an axial force, the force is transmitted through the can body to the force sensor of the device. Force measurements obtained using the device can be used to trigger preventive maintenance or adjustment of machinery in the can production line, e.g. parts of a can seamer (e.g. the seamer chuck and / or lifter), to reduce the risk of faults occurring or degradation in the quality of the cans. As the can body is mounted about the mandrel member of the device, the mandrel member supports the sidewall of the can body and thereby prevents the sidewall of the can body being deformed or damaged as manufacturing processes are applied to the can body. For example, in some implementations, the mandrel member may support the inside of the sidewall of the can body around the circumference of the can body. Thus, collapse or wrinkling of the sidewall of the can body, which may affect the validity of the force measurements obtained by the device, is avoided. The test can may have the same or similar properties as other cans that are being manufactured or transported, such that the forces measured using the test can are indicative of the forces experienced by other cans / can bodies. For example, the device may be cylindrical with a maximum outer diameter that matches (i.e. is substantially the same as) the outer diameter of a standard beverage can, e.g. a 202, 204, 206, or 211 can. As the test cans may be made using hitherto conventional can bodies, there is no need to manufacture “custom” can bodies having the appropriate dimensions (e.g. height) to fit the device. Typically, the initial can body is a beverage can body, e.g. a drawn and (wall) ironed can, referred to as a DWI or D&l can, although the invention may also be used with other types of can body, such as two- or three-piece cans, as commonly used for food packaging, with the dimensions of the device being adapted for these other types of can body. Other two-piece cans include those produced using draw and redraw (DRD) processes, and these may also be used with the device. In some implementations, the mandrel member comprises one or more abutment surfaces that extend laterally outwardly relative to the longitudinal axis to stop and prevent further axial movement of the can body following mounting of the can body about the mandrel member. For example, the one or more abutment surfaces may be provided as a stepped or tapered portion (e.g. a lip) that extends at least partially circumferentially around the mandrel member. As one example, the one or more abutment surfaces may be provided by a stepped or tapered portion that has a radius that is greater than a (maximum) radius of the remainder of the mandrel member. The one or more abutment surfaces ensure that the force measurements are reproducible by (i) preventing the can body from being excessively pushed down onto the device when loads are applied to the can body; and (ii) ensuring the height of the test can is correct when the can body is first attached to the device, e.g. avoiding variations in the force measurements depending on how an operator fits the can body to the device. Preferably, the one or more abutment surfaces extend laterally from the mandrel member by a distance that matches (or is greater than) a thickness of a sidewall of the can body, e.g. by from around 0.08 mm to around 0.13 mm for typical beverage cans. Thus, when the can body is mounted about the mandrel member, the outer wall of the device is aligned with the sidewall of the can body to provide a continuous or nearly continuous outer surface of the test can. In some implementations, a lateral extent of the mandrel member is adjustable to allow insertion of the mandrel member into the opening of the can body and subsequent engagement of the mandrel member with the inside of the sidewall of the can body. The lateral extent of the mandrel member may be its diameter (in the case of the mandrel member being round) or, or more generally, its maximum extent along a direction transverse to the longitudinal axis of the mandrel member. For example, the mandrel member, or a portion of the mandrel member, may be compressible so as to allow insertion of the mandrel member into an opening of the can body and subsequent formation of an interference or frictional fit with the sidewall of the can body adjacent the opening. The adjustable lateral extent of the mandrel member allows easy fitting of the mandrel member into one of the openings of the can body and ensures that the can body does not rotate relative to the mandrel member, e.g. during seaming. To engage the inside of the sidewall of the can body effectively, the mandrel member may additionally comprise at least one resilient element, e.g. provided in or on a side wall of the mandrel member. The resilient element may, for example, comprise an O-ring, which may be fitted around the sidewall of the mandrel member, e.g. such that, in use, the O-ring is compressed between the respective sidewalls of the mandrel member and the can body to make a secure seal. In some examples, the resilient element may also provide frictional resistance to prevent the can body being rotated about the mandrel member. In some implementations, the device may further comprise an adjustment mechanism (or “locking mechanism”) operable to compress the at least one resilient element along a direction parallel to the sidewall of the mandrel member to thereby cause expansion or protrusion of (i.e. increase the extent of) the resilient element transverse to the mandrel member (i.e. laterally outwards with respect to the longitudinal axis). As one example, the mandrel member may comprise first and second parts (which may be referred to as jaws) having respective opposing surfaces that are spaced apart along the mandrel member to accommodate the at least one resilient element. The adjustment mechanism operates by reducing the separation between the surfaces of the first and second parts to compress the at least one resilient element. In some implementations, the first part comprises an external screw thread (i.e. a thread on an outwardly directed surface of the first part) and the second part comprises a corresponding internal screw thread (i.e. a screw thread on an inwardly directed surface of the second part) mated with the external screw thread, whereby relative rotation of the first and second parts moves the internal screw thread along the external screw thread (i.e. along the mandrel member) to vary the separation between the respective surfaces of the first and second parts. Such a threaded arrangement allows the lateral extent of the mandrel member to be accurately and reproducibly adjusted to ensure that the device will remain attached to the can body and so that accurate force measurements can be made. To adjust a height of the test can (e.g. to match the heights of other cans on a production line), the device may comprise a height adjustment mechanism for adjusting a spacing between the mandrel member (e.g. the one or more abutment surfaces) and a base surface of the device (e.g. the bottom surface of the device when the test can is stood upright). For example, the height adjustment mechanism may comprise a central column that extends along an axis of the device, away from the base surface of the device, and which supports the mandrel member. The height adjustment mechanism may then allow the mandrel member to be moved along the central column, e.g. by means of mated screw threads on the central column and the mandrel member, towards or away from the base surface of the device. In some implementations, the force sensor is a load cell, or an inertial sensor (e.g. an accelerometer and / or a gyroscope). The force sensor may be located in or on a base surface of the device spaced apart from the mandrel member (e.g. spaced apart from the one or more abutment surfaces). The measurements made by the sensor may be stored electronically in the device, e.g. using a flash memory card or other form of non-volatile memory and / or transferred in real-time from the device to another computer device (e.g. a mobile computing device, such as a smartphone) using a transmitter, e.g. a wireless transmitter such a Bluetooth, Wi-Fi or radio transmitter. According to a second aspect of the present invention, there is provided a test can comprising a device according to the first aspect above and a double open ended can body having first and second openings and a sidewall extending therebetween. The can body is mounted about the mandrel member and the mandrel member is engaged with an inside of the sidewall of the can body. The mandrel member therefore allows the can body to be attached to the device to form a robust single unit that can endure the forces during the can manufacturing and / or filling processes. One of the openings may contact the one or more abutment surfaces of the device that extend transversely, e.g. to prevent excessive movement of the edge of the opening of the can body along or past the mandrel member. Ideally, a portion of the can body will have been removed to produce a circumferentially extending cut edge. Even for three-piece can bodies that had hitherto been tubular, removing a portion of the can body to generate a cut edge is beneficial to minimise inaccuracies during force measurement collection, though it is not always necessary depending on upstream production process windows. For two-piece can bodies, the new opening is defined by the cut edge and it is the new opening that contacts the one or more abutment surfaces when the can body is mounted about the mandrel member. In some implementations, the device has a (cylindrical) sidewall that has an outer radius which matches, e.g. is substantially the same as, an outer radius of the can body, which facilitates the test can passing through a production line without manual intervention or modification to existing can handling machinery. For example, the outer radius of the cylindrical sidewall of the device may differ from the outer radius of the can body by less than 10% (preferably less than 5% or less than 1 %) of the outer radius of the can body. According to a third aspect of the present invention, there is provided a method for measuring forces applied to can bodies. The method comprises providing a double open ended can body having first and second openings and a sidewall extending therebetween; attaching the can body to a device comprising a force sensor to form a test can, the device extending into the can body through one of the openings and engaging the inside of the can body; and measuring forces through the can body using the force sensor. In some examples, the method comprises a preparation step of removing (e.g. by cutting away) a portion of a can body to create a circumferentially extending cut edge. For three-piece can bodies, this step is optional, as the can body forming process is typically well-controlled. However, for two-piece can bodies, this step is needed as the integral base (which includes the domed portion on a two-piece beverage can) must be removed to enable mounting about the mandrel member. Preferably, the test can has substantially the same height (e.g. within 5%) as the can body before the portion of the can body is removed. Preferably, the device comprises a sidewall that has an outer radius which matches an outer radius of a sidewall of the can body (e.g. within 5%). In some implementations, the forces are measured as one or more manufacturing operations are performed on the test can, such as during necking, flanging or seaming of the can body, or during filling of the can with food or beverage. The method may comprise adjusting one or more parameters of a machine (e.g. a necker or a seamer) that performs the manufacturing operation may be adjusted in response to the force measurements obtained using the test can. Alternatively or additionally, one or more can bodies (or cans) on which the machine has performed the manufacturing operation may be selected for rejection or quality inspection in response to the force measurements. The forces on the test can may be measured whilst the test can is in a production line with other can bodies that do not comprise the device, e g. can bodies that have not been modified to accommodate the device. Thus, the measurements of the forces on the test can may provide information about the forces that are likely to be applied to the other can bodies as they move through the production line. In some implementations, the forces are measured during transportation of the test can, e.g. along a production line, or during distribution along with other can bodies (or cans) following manufacturing, e.g. during distribution to a customer site. To ensure that the test can behaves like the other can bodies in the production line, the mass of the test can may additionally match a mass of each of the other can bodies in the production line, e.g. after filling and prior to seaming. For example, the mass of the test can may be within 10% of the mass of the other can bodies in the production line. In other implementations, the mass of the device may be reduced, e.g. by making the device from aluminium, titanium, carbon fibre, a plastics material, or another lightweight material, so that the mass of the device is closer to the mass of the other can bodies before they are necked. For example, the mass of the device may be less than 100 g, or less than 50 g. This is especially important when the test can is to be used within the necking process as the can bodies are held and transported horizontally, unlike during the seaming process where they are oriented vertically. According to a fourth aspect of the present invention, there is provided a cutting tool for cutting a sidewall of a can body to divide the can body into two parts (e.g. to create a partial can for use with the device according to the first aspect above). The cutting tool comprises a cutting element (which may be referred to a “first” such cutting element), such as a blade or cutting wheel, for cutting the sidewall of the can body to create a circumferentially extending cut edge; and a supporting surface for positioning against the sidewall of the can body on a side of the sidewall opposite the cutting element to support the sidewall as the edge is being created. The cutting tool further comprises an actuator for moving the cutting element between (i) a retracted configuration in which the cutting element is spaced apart from the supporting surface to allow the can body to be inserted between the supporting surface and the cutting element, and (ii) an engaged configuration in which the cutting element cuts the sidewall of the can body. In use, the cutting element may be rotated around the inner or outer circumference of the can body to create the circumferentially extending cut edge, e.g. by moving the cutting element or the can body or both. The supporting surface ensures that a well-defined cut edge can be formed without damaging or distorting the sidewall of the can body, such that the partial can body may be used as part of a test can to make accurate force measurements. The cutting tool may be operated manually, e.g. without requiring the assistance of any other tools, and is preferably a hand-held (or hand-holdable) tool. In some implementations, the edge created by the cutting element divides the can body into two parts and the supporting surface is configured to support the sidewall of both parts of the can body as the cut edge is being created, e.g. the supporting surface supports the sidewall of the can body above and below the cutting element. The supporting surface may comprise a channel for receiving the blade to prevent the blade from contacting the supporting surface during cutting, e.g. to prevent damage to either the cutting element or the supporting surface. In some implementations, the cutting tool further comprises a housing having an opening for receiving an open end of the can body into an inner volume of the housing. The housing is configured to limit passage of the can body through the inner volume to position the cutting element at a predetermined distance along the can body. Thus, the cutting tool can be used to produce partial can bodies that each have the same height such that force measurements obtained using the partial can bodies are comparable and reproducible. In some implementations, the housing may comprise a movable barrier for limiting passage of the can body through the inner volume, such that the position of the barrier can be varied (e.g. between a number of predetermined positions) so that partial can bodies of different heights can be created, such that the force-measuring device can be used in production lines set up for different heights of can. In some implementations, the supporting surface is provided on an inner surface of the housing for supporting the outside of the sidewall of the can body. For example, the supporting surface may extend around a circumference of the inner surface of the housing, e.g. such that the sidewall of the can body is supported in all (radial) directions during the cutting to minimise distortion of the sidewall. In some implementations, the actuator is configured to bias (e.g. using one or more springs) the cutting element towards the supporting surface. Thus, the actuator may be used to retract the cutting element when the can body is being introduced into the cutting device, and subsequently released so that the cutting element automatically engages the sidewall of the can body for cutting. In some implementations, no additional force is needed for the cutting element to cut the sidewall, which may ensure that the cutting is uniform and that there is less variability between different operators of the cutting tool, or indeed when the same operator uses the cutting tool on different occasions. In other implementations, the supporting surface is configured to support the inside of the sidewall of the can body during cutting of the sidewall of the can body, i.e. the supporting surface is within the can body after the can body is inserted into the cutting tool. In some examples, the cutting tool further comprises a roller on which the supporting surface is provided. The roller is adapted for rolling the supporting surface around an inner surface of the sidewall of the can body during cutting, e.g. to allow the can body or cutting tool to be rotated more easily, resulting in a smoother cutting motion. In some implementations, the cutting tool is suitable for receiving a necked can body, i.e. a can body comprising a necked portion adjacent the open end of the can body that has a smaller diameter than the majority of the can body. For example, the cutting tool may additionally comprise a mechanism for moving the supporting surface towards or away from the cutting element to allow a necked or flanged portion of the can body to be inserted between the supporting surface and the cutting element. In some implementations, the cutting tool may further comprise: a second cutting element for cutting the sidewall to create the circumferentially extending cut edge together with the first said cutting element; a second supporting surface for positioning against the sidewall of the can body on the side of the sidewall opposite the second cutting element to support the sidewall as the cut edge is being created; and a second actuator for moving the second cutting element between (i) a retracted configuration in which the second cutting element is spaced apart from the second supporting surface to allow the can body to be inserted between the second supporting surface and the second cutting element, and (ii) an engaged configuration in which the second cutting element cuts the sidewall of the can body The second cutting element may be arranged to cut the sidewall of the can body at a location that is diametrically opposite the first said cutting element. Such an arrangement may reduce or avoid deformation of the can body as the sidewall is being cut. According to a fifth aspect of the present invention, there is provided a method of cutting a sidewall of a can body to divide the can body into two parts. The method comprises clamping a sidewall of a can body between a cutting element and supporting surface; and rotating the cutting element around an inner or outer circumference of the can body to create a circumferentially extending cut edge, thereby enabling removal of a portion of the can body, wherein the supporting surface is positioned against the sidewall of the can body on a side of the sidewall opposite the cutting element to support the sidewall as the cut edge is being created by the cutting element. According to a sixth aspect of the present invention, there is provided a method of assembling a test can for measuring forces on can bodies. The method comprises using the method of the firth aspect to create a can body from which a portion has been removed; mounting the can body about the mandrel member of a device according to the first aspect; and engaging the mandrel member with the can body. According to a seventh aspect of the present invention, there is provided a kit of parts for manufacturing a test can for measuring forces on can bodies. The kit of parts comprises a device according to any to the first aspect; and a cutting tool according to the fourth aspect. In some cases, the kit of parts may further comprise one or more adapter sleeves configured to fit around the device to enable it to be used with larger diameter can bodies. Although the above aspects of the present invention have focussed on measuring forces, it will be appreciated that the device may comprise one or more sensors that is not a force sensor, either in addition to or instead of the force sensor. For example, the device may comprise one or more of: a temperature sensor; a geographic location sensor, e.g. a GNSS or GPS sensor; a chemical sensor for sensing a concentration of one or more chemicals; and an induction sensor, such as an eddy current sensor. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG. 1 is a schematic perspective view of a test can comprising a can body and a forcemeasuring device; FIG. 2 is a schematic perspective view of the can body of FIG. 1; FIG. 3 is a schematic perspective view of the force-measuring device; FIG. 4 is a schematic perspective view of a vertical cross-section of the test can of FIG. 3; FIG. 5 is a schematic perspective view of a cutting tool; FIG. 6 is a schematic perspective view the cutting tool of FIG. 5 in another configuration; FIG. 7 is a schematic perspective view of the cutting tool of FIGS. 5 and 6 in use with a can body; FIG. 8 is a schematic vertical cross-section of the cutting tool of FIGS. 5 and 6 in use with the can body; FIG. 9 is a schematic perspective view of the vertical cross-section of the cutting tool of FIG. 8 in use with the can body; FIG. 10 is a schematic perspective view of a vertical cross-section of another cutting tool receiving a can body; FIG. 11 is a schematic perspective view of the vertical cross-section of the cutting tool of FIG. 10 cutting the sidewall of the can body and FIG. 12 is a schematic perspective view of a vertical cross-section of the cutting tool of FIGS. 10 and 11 after cutting the sidewall of the can body. DETAILED DESCRIPTION The present invention relates to a device and method to measure forces applied to cans (e.g. beverage cans) during manufacturing, subsequent transportation and / or filling. In particular, the present invention enables rapid and early detection of variation or drift in operational parameters during manufacturing, e g. such that faults, wear or misalignments in the machinery used to manufacture the cans can be identified and corrected. This is achieved by creating a “test can” that incorporates a force sensor and which can, for example, be processed along with regular (i.e. unmodified) cans in a manufacturing production line without needing to interrupt the manufacturing process. As another example, the test can may be used to calibrate multiple pieces of equipment that perform the same process on a can body so that variation between the multiple pieces of equipment is minimised or avoided. As one example, the present invention may be used to monitor the loads placed on can bodies during the seaming process, in which a can end or lid (e g. beverage end) is attached to the open end of an unseamed can body by curling and interlocking the flanged edges of the can end with the flanged opening of the can body to create a double seam. At the start of the seaming process, a lifter is used to clamp the end and the can body against a seaming chuck and first and second operation rollers are used to form the double seam. Various critical parameters of the double seam are affected by the forces applied to the can body during these processes, such as the tightness rating, actual overlap and seam gap. It is therefore crucial that the lifter applies forces to the can body that are of the correct magnitude and duration to ensure that the double seam forms robust, hermetic, and in many cases pressure-resistant, seams consistently. As another example, the present invention can be used to monitor the loads placed on can bodies during the necking process, in which the diameter of an upper portion of a can body is reduced to create a tapered neck and the rim of the can body flanged outwards ready for seaming to a can end. The necking process needs to be performed consistently and accurately in order for the seaming process to be successful. FIG. 1 shows a test can 100 comprising a “partial” can body 102 mounted on a forcemeasuring device 104. Referring to FIG. 2, the can body 102 is generally cylindrical. In this example, the can body 102 has a necked and flanged first opening 106 at one end which has been produced in a conventional manner. It is not essential that first opening 106 is necked and / or flanged. At an opposing end, a portion of the can body 104 has been removed to create a second opening 108, and such that can body 102 has a circumferentially extending edge 110. The portion of the can body 102 may be removed using, for example, the cutting tools described below in relation to FIGS. 5-11. Attaching the can body 102 to the force-measuring device 104 allows the test can 100 to have substantially the same dimensions and other attributes as those of other cans in a production line, such that the force-measuring device 104 can provide representative measurements of forces acting on the other can bodies in the production line. In this example, the forcemeasuring device 104 comprises a load cell 112 that provides a base of the force-measuring device 104, and which, in use, measures the axial loads through the can body 102. As the test can 100 has the same key dimensions as an unmodified can (e.g. diameter and height), the test can 100 is able to be introduced into a production line together with other, unmodified can bodies to obtain in-line force measurements while the production line is operational. Thus, the test can 100 can be a “drop in” replacement for a conventional can body. That is, the test can 100 is able to be conveyed along the production line and to have various manufacturing operations (such as necking, flanging, filling and / or seaming) applied to the can body 104 whilst other can bodies are being similarly conveyed and having those operations applied to them. FIG. 3 shows the test can 100 with the can body 102 removed to expose a mandrel member 114 of the force-measuring device 104 that is used to attach the can body 102 to the forcemeasuring device 104. The mandrel member 114 is proportioned to allow it to be inserted through the second opening 108. Following insertion, the mandrel member 114 engages with an inner surface of the can body 102 to thereby secure the can body 104 to the forcemeasuring device 104. One way in which this attachment can be achieved is described below with reference to FIG. 3, but other approaches are also possible, such as selecting dimensions for the mandrel member 118 that allow an interference fit with the can body 102, or by using adhesive, or some other fastening mechanism, to ensure that the can body 102 remains attached to the device 104 during manufacturing and / or transportation of the test can 100. In the present example, the force-measuring device 104 further comprises an abutment surface in the form of a circumferentially extending flange or lip 116. An abutment surface 116 is located below the mandrel member 114, i.e. it is axially spaced apart from an end of the mandrel member 114 that is to be inserted into the second opening 108 of the can body 102. The abutment surface 116 extends transversely from the mandrel member 114, i.e. radially away from a longitudinal axis 118 of the mandrel member 114. The abutment surface 116 serves to prevent the edge 110 of the can body 102 from moving past the mandrel member 114 after the can body 102 has been mounted about the mandrel member 114. That is, the abutment surface 116 is configured to prevent the force-measuring device 104 from being further pushed into can body 102 when an axial load is applied to the can body 102, e.g. during seaming, thereby allowing the axial load to be transferred to the load cell 112. The force-measuring device 104 comprises an adjustment mechanism 202 for adjusting the diameter of the mandrel member 114, i.e. the lateral extent of the mandrel member 114 transverse to the axis 118 of the mandrel member 114. In the present example, the adjustment mechanism 202 comprises a horizontal notched wheel 204 located beneath the mandrel member 114. The notched wheel 204 enables an operator to set the diameter of the mandrel member 114 by rotating the wheel clockwise or anticlockwise about axis 118. The adjustment mechanism 202 can be used to ensure that there is clearance between the outside of the mandrel member 114 and the inside surface of the can body 102, or that there is otherwise minimal resistance, when the can body 102 is mounted about the mandrel member 114. Thus, wrinkling or other damage to the can body 102, which might for example affect the validity of the force measurements made by the device 104, can be avoided or mitigated. After insertion of the mandrel member 114 into the can body 104, the adjustment mechanism 202 can be used to increase the diameter of the mandrel member 114 and thereby cause the outer surface of the mandrel member 114 to engage with the inner surface of the can body 104. The can body 102 may therefore be held in place on the mandrel member 114 by a frictional force between the outer surface of the mandrel member 114 and the inner surface of the can body 102. The mandrel member 114 supports a sidewall 120 of the can body 104 such that deformation or buckling of the sidewall 120 is prevented when a load is applied to the can body 102, which may not be possible if, instead of being inserted into the can body 102, the device 104 were fitted around the outside of the sidewall 120 of the can body 102. In some examples, an adjustment mechanism 202 may not be present and the device may, for example, be attached to the can body 102 by a push-fit or interference connection, e.g. by including a resiliently deformable element such as an O-ring (e.g. a rubber O-ring) around the mandrel member 114. FIG. 4 shows a vertical cross-section of the device 104, which comprises a central column 302 that joins mandrel member 114 to load cell 112. The central column 302 is externally threaded for connecting with mandrel member 114. The central column 302 is aligned with axis 118. The mandrel member 114 comprises a cylindrical upper part 304 and a cylindrical lower part 306 fitted as a collar to the upper part 304 and on which the lip 116 (abutment surface) is provided. The upper part 304 comprises a flange 304A that extends radially over the lower part 306 to prevent the lower part 306 from being axially movable past the upper part 304. The lower part 306 is separated from the flange 304A by a resiliently deformable O-ring 308 that engages with the inside of sidewall 120 when the device 104 is in use. The lower part 306 is supported from beneath by the notched wheel 204, i.e. the lower part 306 and the O-ring 308 are located between the flange 304A of the upper part 304 and the notched wheel 204. The upper part 304 also extends axially alongside the lower part 3O6.The upper part 304 also comprises an axially-recessed surface having an internally threaded neck portion 304B that engages with a corresponding exterior thread on the central column 302 to secure the upper part 304 to the central column 302. A retaining nut 310 is fitted to the central column 302 to prevent the upper part 304 from being unscrewed and detached from the central column 302. The height of the mandrel member 114 above the load cell 112 is adjustable by rotating the upper part 304 about the central column 302. The upper part 304 also has an externally threaded portion 304C that descends from the internally threaded portion 304B (i.e. extends towards the load cell 112) and surrounding, but spaced radially apart from, the central column 302. The externally threaded portion 304C engages with a corresponding internal thread on notched wheel 204 such that rotation of the wheel 204 about the axis 118 causes the notched wheel 204 to move along the central column 302, either towards or away from the upper part 304 depending on the direction of the rotation. Movement of the notched wheel 204 towards the upper part 304 causes corresponding movement of the lower part 306 along the axis 118 to vary the separation between the lower part 306 and the flange 304A. Such movement may compress the O-ring 308 axially, or otherwise allow the O-ring 308 to expand axially. To install a can body 102 onto the device 104, the notched wheel 204 is rotated so that the O-ring 308 is not compressed, which allows the mandrel member 114 of the device 104 to be inserted into the opening 108 of the can body 102 without damaging the sidewall 120 of can body 102. The notched wheel 204 is then rotated to compress the O-ring 308 along the axial direction, which causes O-ring 308 to expand radially (i.e. transverse to the axis 118) to engage with the inside of the sidewall 120 of the can body 102 such that frictional forces between the O-ring 308 and the sidewall 120 prevent the mandrel member 114 from being withdrawn from the can body 104 when the device 104 is in use. The O-ring 308 also prevents rotation of the can body 102 relative to the device 104, e.g. during seaming when torques are exerted on the can body 102 by the first and second operation rollers used to form the double seam. The amount of compression applied to the O-ring 308 can be monitored based on how far the notched wheel 204 has been rotated, e.g. using markings provided on the outside of the device 104. In the present example, the extent of the rotation is communicated audibly through the use of pins 312 (or “indexing plungers”) extending between the notched wheel 204 and a corrugated underside of the upper part 304, i.e. an underside of the upper part 304 that has a number of equi-angularly spaced ridges or recesses. The pins 312 are biased towards the upper part 304 by springs such that a “clicking” sound is generated as the pins are dragged by rotation of the wheel 204 over the corrugations in the underside of the upper part 304. Thus, an operator can set the amount of compression applied to the O-ring 308 by counting the number of times the clicking sound is generated. Subsequent rotation of the notched wheel 204 to reverse the axial compression of the O-ring 308 allows the device 104 and the can body 102 to be separated, thereby allowing the device 104 to be re-used. The device 104 further comprises a cylindrical body portion 314 housing electronic circuitry 316, including a power source (not shown), for obtaining force measurements from the load cell 112. In the present example, the measurements are stored in memory and a USB port 318 (although other ports or connectors can be used) is provided for wired transmission of the measurements to a computer device after the device 104 has been used, e.g. passed through the production line. However, wireless data transmission capabilities may be provided instead, or as an addition, to allow the measurements to be transmitted from the device 104 to a suitable receiving device in real-time. In some examples, the upper part 304 is sealed (e g. using a sealing agent such as epoxy resin or a waterproof membrane) so that liquid (e.g. beverage) introduced into the can body 102 through the open first end 106 of the can body can be retained, e.g. without damaging the electronic circuitry 316. To create test cans, such as the test can 100 described above with reference to FIG. 1, a cutting tool can be used to cut through the sidewall 120 of a can body to create the circumferential edge 110 defining the opening 108 through which the mandrel member 114 of the device 102 is inserted. FIGS. 5-9 show one example of a cutting tool 400 to divide a can body into two parts. The cutting tool 400 comprises a housing 402 having a cylindrical inner volume with an opening 404 for receiving the open end 106 of a can body 604 that is to be cut, and a pair of blades 406A, 406B (best seen in FIG. 8) diametrically spaced apart from one another and mounted on respective actuator arms 408A, 408B that extend radially and project through corresponding holes in the housing 402. The actuator arms 408A, 408B are biased radially away from the opening 404 (e.g. using springs) so that the blades 406A, 406B are initially maintained in a retracted configuration, away from a sidewall 410 of the can body 604. To cut through the sidewall 410 of can body 604, the actuator arms 408A, 408B are moved radially inwards (by gripping the actuator arms 408A, 408B) to cause the blades 406A, 406B to engage and then cut the sidewall 410. The blades 406A, 406B are oriented parallel to the opening 404 so that subsequent rotation of the can body 604 relative to the opening 404 whilst the blades 406A, 406B are in this engaged configuration causes the blades 406A, 406B to cut through the sidewall 410 of the can body 604. The cutting tool 400 further comprises a pair of rollers 412A, 412B located within the housing 402 and oriented parallel to the opening 404. As shown in FIG. 5, the rollers 412A, 412B are initially located centrally within the opening 404 so as not to contact the flanged or necked end of the can body 604 when the can body 604 is inserted into the opening 404. As best seen from FIGS. 8 and 9, the rollers 412A, 412B are mounted on respective axles 414A, 414B that extend through an end 416 of the housing 402 opposite the opening 404 in respective slots 418A, 418B that allow each the rollers 412A, 412B to be moved radially outwards from the central location along a curved path to bring them into contact with the sidewall 410 of the can body 604. Each of the rollers 412A, 412B comprises a channel 420A, 420B that extends circumferentially around the roller for receiving the corresponding blade 406A, 406B during cutting of the sidewall of the can body 604. Each channel 420A, 420B is aligned with the corresponding blade 406A, 406B such that the sidewall 410 of the can body 604 is supported on either side of the blade 406A, 406B during cutting (i.e. above and below the blade in the orientation shown in the figures), which allows a consistent and well defined edge to be made, e.g. without causing the sidewall 410 of the can 604 to wrinkle. FIGS. 10-11 show another cutting tool 900 that cuts the sidewall of the can body 604 from the inside to the outside, rather than from the outside to the inside as for the cutting tool 400 shown in FIGS. 5-9. The cutting tool 900 comprises a tubular housing 902 having a central column 904 that is spaced radially apart from an interior wall 906 of the housing 902 to create a tubular cavity 908 for receiving the open end of a can body 604. The central column 904 comprises a pair of diametrically opposed cutting wheels 910A, 910B attached to respective actuator arms 912A, 912B that can be used by an operator to move the cutting wheels 910A, 910B radially inwards to allow the can body 604 to be inserted into the housing 902. FIG. 10 shows this retracted configuration. The actuator arms 912A, 912B are biased radially outwards from the central column, e.g. by springs (not shown), such that the cutting wheels 91OA, 91 OB are forced against the inside of the sidewall of the can body 604 when the actuator arms 912A, 912B are released. FIGS. 11 and 12 show this extended configuration. The housing 902 comprises a groove (channel) 914 that extends circumferentially around the interior wall 906 of the housing 902 and is aligned with the cutting wheels 910A, 910B such that the edges of the cutting wheels 910A, 910B can be received by the groove 914 after cutting through the wall of the can body 604. The interior wall 906 of the housing 902 supports the sidewall 410 of the can body 604 on either side of (i.e. above and below) the cutting wheels 910A, 910B to ensure that the sidewall 410 of the can body 604 is otherwise not deformed during cutting. FIG. 12 shows the partial can body 1100 created by cutting through the sidewall of the can body 604, before it has been removed from the cutting tool 900. The cutting tools 400, 900 are reusable and the only consumable items are the cutting elements. It is preferable, but not essential, that two cutting elements are used (e.g. blade(s) and / or cutting wheel(s)) to reduce distortion of the sidewall of the can body and to create a uniform edge, e.g. to reduce the possibility that the start and end of the cut formed by a single blade or cutting wheel are not aligned with one another. More than two cutting elements can also be used in some cases. In the present example, the cutting wheels 910A, 910B are 18 mm in diameter, but other diameters could be used.

Claims

1. A device for measuring forces applied to a can body during necking or seaming, the device having a longitudinal axis and comprising:a mandrel member about which to mount a double open ended can body having first and second openings and a sidewall extending therebetween, anda force sensor for measuring forces applied through the can body after the can body is mounted about the mandrel member2 The device of claim 1, the mandrel member comprising one or more abutment surfacesextending laterally outwardly relative to the longitudinal axis to stop axial movement of the can body following mounting of the can body about the mandrel member.

3. The device according to claim 1 or 2, wherein a lateral extent of the mandrel member is adjustable to engage and disengage the mandrel member with the inside of the can body sidewall.

4. The device according to any one of claims 1 to 3, wherein the mandrel member comprises at least one resilient element.

5. The device according to claim 4, wherein the at least one resilient element is an O-ring.

6. The device according to claim 4 or 5, further comprising an adjustment mechanism operable to axially compress the at least one resilient element to thereby cause lateral expansion of said resilient element.

7. The device according to claim 6, wherein the mandrel member comprises first and second parts having respective opposing surfaces that are axially spaced apart to accommodate the at least one resilient element.

8. The device according to claim 7, wherein the adjustment mechanism is operable to reduce the separation between said opposing surfaces of the first and second parts to compress the at least one resilient element.

9. The device according to claim 8, wherein the first part comprises an external screw thread and the second part comprises a corresponding internal screw thread mated with theexternal screw thread, whereby relative rotation of the first and second parts varies the separation between the respective opposing surfaces of the first and second parts.

10. The device according to any one of the preceding claims, further comprising a height adjustment mechanism for adjusting a spacing between the mandrel member and a base surface of the device.

11. The device according to any one of the preceding claims, wherein the force sensor is a load cell or an inertial sensor.

12. The device according to any one of the preceding claims, wherein the force sensor is located in or on a base surface of the device, spaced apart from the mandrel member.

13. A test can comprising the device according to any one of the preceding claims and a double open ended can body having first and second openings and a sidewall extending therebetween, wherein the can body is mounted about the mandrel member and the mandrel member is engaged with an inside of the sidewall of the can body.

14. The test can according to claim 13, wherein the double open ended can body is provided by a three-piece can body prior to the ends having been seamed on.

15. The test can according to claim 13, wherein the double open ended can body is provided by a two-piece can body.

16. The test can according to any one of claims 13 to 15, wherein a portion of the can body has been removed to create a circumferentially extending cut edge.

17. The test can according to any one of claims 13 to 16, wherein the sidewall contacts one or more abutment surfaces extending transversely from the longitudinal axis of the device.

18. The test can according to any one of claims 13 to 17, wherein at least a body portion of the device has an outer radius which matches an outer radius of the can body.

19. A method of measuring forces applied to can bodies, the method comprising: providing a double open ended can body having first and second openings and a sidewall extending therebetween;attaching the can body to a device comprising a force sensor to form a test can, the device extending into the can body through one of the openings and engaging the inside of the can body; andmeasuring forces through the can body using the force sensor.

20. The method of claim 19, wherein the forces on the test can are measured during necking, flanging or seaming of the can body.

21. The method of claim 19 or 20, wherein the forces on the test can are measured whilst the test can is in a production line comprising other can bodies that do not comprise the device.

22. The method of claim 21, wherein a mass of the test can prior to seaming matches a mass of each of the other can bodies in the production line after the other can bodies have been filled and prior to seaming.

23. The method of any one of claims 19 to 22, wherein a portion of the can body is removed to reduce the height of the can body before the can body is attached to the device and, optionally, the test can has the same height as the can body before the portion of the can body is removed.

24. A cutting tool for cutting a sidewall of a can body to divide the can body into two parts, the cutting tool comprising:a cutting element for cutting the sidewall to create a circumferentially extending cut edge;a supporting surface for positioning against the sidewall of the can body on a side of the sidewall opposite the cutting element to support the sidewall as the cut edge is being created; andan actuator for moving the cutting element between (i) a retracted configuration in which the cutting element is spaced apart from the supporting surface to allow the can body to be inserted between the supporting surface and the cutting element, and (ii) an engaged configuration in which the cutting element cuts the sidewall of the can body.

25. The cutting tool of claim 24, wherein the cut edge created by the cutting element divides the can body into two parts and the supporting surface is configured to support the sidewall of both parts of the can body as the cut edge is being created.

26. The cutting tool of claim 24 or 25, wherein the supporting surface comprises a channel for receiving the cutting element to prevent the cutting element from contacting the supporting surface during cutting.

27. The cutting tool of any one of claims 24 to 26, further comprising a housing having an opening for receiving an open end of the can body into an inner volume of the housing, wherein the housing is configured to limit passage of the can body through the inner volume to position the cutting element at a predetermined distance along the can body.

28. The cutting tool of claim 27, wherein the supporting surface is provided on an inner surface of the housing for supporting the outside of the sidewall of the can body29. The cutting tool of claim 28, wherein the supporting surface extends around the entire inner surface of the housing.

30. The cutting tool of any one of claims 24 to 29, wherein, the actuator is configured to bias the cutting element towards the supporting surface.

31. The cutting tool of any one of claims 24 to 30, wherein the supporting surface is configured to support the inside of the sidewall of the can body during cutting of the sidewall of the can body.

32. The cutting tool of claim 31, comprising a roller on which the supporting surface is provided, the roller being adapted for rolling the supporting surface around an inner surface of the sidewall of the can body during cutting.

33. The cutting tool of claim 30 or 31, further comprising a mechanism for moving the supporting surface towards or away from the cutting element to allow a necked or flanged portion of the can body to be inserted between the supporting surface and the cutting element.

34. The cutting tool of any one of claims 24 to 33, further comprising:a second cutting element for cutting the sidewall to create the circumferentially extending cut edge together with the first said cutting element;a second supporting surface for positioning against the sidewall of the can body on the side of the sidewall opposite the second cutting element to support the sidewall as the cut edge is being created; anda second actuator for moving the second cutting element between (i) a retracted configuration in which the second cutting element is spaced apart from the second supporting surface to allow the can body to be inserted between the second supporting surface and the second cutting element, and (ii) an engaged configuration in which the second cutting element cuts the sidewall of the can body.

35. The cutting tool of claim 34, wherein the second cutting element is arranged to cut the sidewall of the can body at a location that is diametrically opposite the first said cutting element.

36. A method of cutting a sidewall of a can body to divide the can body into two parts, the method comprising:clamping a sidewall of a can body between a cutting element and supporting surface; androtating the cutting element around an inner or outer circumference of the can body to create a circumferentially extending cut edge and thereby enabling removal of a portion of the can body, wherein the supporting surface is positioned against the sidewall of the can body on a side of the sidewall opposite the cutting element to support the sidewall as the cut edge is being created by the cutting element.

37. A method of assembling a test can for measuring forces on can bodies, the method comprising:using the method of claim 36 to create a can body from which a portion has been removed; andmounting the can body about the mandrel member of a device according to any one of claims 1 to 12, andengaging the mandrel member with the can body.

38. A kit of parts for manufacturing a test can for measuring forces on can bodies, the kit comprising:a device according to any one of claims 1 to 12; anda cutting tool according to any one of claims 24 to 35.

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