Tool measuring devices for machine tools

Abstract

A tool measuring device for a machine tool, such as a lathe or machining center, is described. The device includes a light projecting section (100) including a light source (102) for generating a light beam (104) and a light receiving section (300) including a detector for detecting the light beam (104), the light beam passing from the light source to the detector along an optical path. At least one of the light receiving section (300) and the light projecting section (100) includes a protection device including a gas exhaust opening (108) configured to exhaust bleed gas provided from an external gas source. The optical path also passes through the gas exhaust opening (108). The protection device further includes a check valve (112; 200) arranged in the optical path. Bleed gas is provided to the gas exhaust opening (108) through the check valve (112; 200), and a flow of the bleed gas through the check valve (112; 200) causes the check valve to be in an open configuration defining a passage through which the light beam (104) can pass. In this way, increased protection against cutting debris is provided.

Description

[Technical field]

[0001] This invention relates to tool measuring apparatus for machine tools, and in particular to improvements in protecting such apparatus against the ingress of machine tool contaminants such as cutting debris and coolant fluids. [Background technology]

[0002] It is known to mount tool measurement devices, such as laser tool measurement devices, within machine tool enclosures to enable measurement of various tools used in machining a workpiece. It is impractical to remove the tool measurement device after measuring the tools, and therefore such devices must be able to withstand the harsh conditions within the machine tool enclosure encountered during machining (e.g., cutting, grinding, etc.) of the workpiece. In particular, the tool measurement device must be resistant to damage from ejected cutting debris (swarf, chips, etc.) and exposure to high-pressure jets of corrosive liquid coolant.

[0003] EP 1 050 368 A1 and EP 1 502 699 A1 describe examples of tool measurement devices in which a laser beam passes from a light transmitter, through a free space region, and to a light receiver. The tool is measured by moving it in and out of the laser beam while measuring the amount of light passing through the receiver. To protect the various optical components of the device, the laser beam enters and leaves the device through narrow channels or conduits in each of the light transmitter and receiver. Each channel is formed (e.g. by a drill) at an oblique angle to the optical axis of the laser beam passing between the light transmitter and receiver. Gas is evacuated from the channels and is directed or angled away from the free space optical path of the laser beam to reduce the effects of turbulence that may reduce measurement accuracy. Such angled gas channels are shown, for example, in FIG. 4c of EP 1 050 368 A1 and in FIG. 4 of EP 1 502 699 A1.

[0004] Chinese Utility Model No. 203792103 describes another laser tool setter with a protective window that uses a protective flow of gas, which is supplied to the protective window via a duckbill valve.

[0005] It is also known to provide a movable shutter in the tool measuring device to protect the internal optical components. For example, US Patent No. 10,330,464 describes a spring-loaded gas pressure closing piston to protect the laser measuring part of the device when gas is not being exhausted (see, for example, Figures 5 and 6 and the related description). Various shutter configurations for tool measuring devices are also described in WO 2020 / 183155 and Chinese Utility Model No. 213615607.

[0006] The NC4 non-contact tool setting system is sold by Renishaw Public Limited, Wotton-under-Edge, UK. The system includes angled gas exhaust openings of the type described in EP 1 050 368 A and EP 1 502 699 A, in combination with gas pressure actuated spring return shutters upstream of the gas exhaust openings. These shutters prevent the ingress of debris when the gas supply is switched off, thereby protecting the optics of the system when the gas supply is absent. Summary of the Invention [Problem to be solved by the invention]

[0007] The above arrangements provide various levels of protection against contaminants. However, the inventors have discovered that these arrangements have certain shortcomings, especially when the arrangements are exposed to the harsh conditions found within machine tool systems. For example, venting or bleeding gas through an opening provides a compact solution, but this only provides protection while a flow of gas is being supplied. Protection can be provided even when there is no gas supply by using a gas pressure actuated shutter seal, but such an arrangement is not particularly compact and has various moving parts and seals that can wear over time and allow contaminants to enter. Combining gas pressure actuated shutters and gas bleed openings, such as the NC4 product mentioned above, can maintain protection even when gas is not being supplied, but under harsh conditions contaminants can still enter the openings even when gas is not being supplied. Such contaminants can accumulate in the gas flow path and / or reach the gas pressure actuated shutter, degrading or damaging the seal components. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a tool measurement device for a machine tool, comprising: a light projection unit including a light source for generating a light beam; a light receiving section including a detector for detecting a light beam, the light beam passing along an optical path from the light source to the detector; Equipped with At least one of the light receiving section and the light emitting section is provided with a protection device including a gas exhaust opening configured to exhaust bleed gas supplied from an external gas source, and the light path also passes through the gas exhaust opening; The protection device further comprises a check valve disposed in the light path, wherein the bleed gas is supplied through the check valve to the gas exhaust opening, and wherein a flow of the bleed gas through the check valve causes the check valve to assume an open configuration defining a passageway through which the light beam can pass.

[0009] In this way, a tool measurement device suitable for measuring tools in a machine tool is provided. The light beam passes from the light emitter to the light receiver along an optical path. The optical path may include reflections from the tool to be measured. In a preferred embodiment, a blocking beam configuration is provided, in which the tool to be measured is carried by the machine tool and moved to block the light beam arranged to pass from the light source to the detector (in the absence of the tool). By analyzing the received light intensity at the light receiver, a dimension or characteristic of the tool to be measured can be determined. The environment of a machine tool can be harsh (e.g. due to coolant, cuttings, etc.), and at least one or preferably both of the light emitter and the light receiver include protection devices that help to prevent the ingress of contaminants. In particular, light may exit (in the case of the light emitter) and / or enter (in the case of the light receiver) the device via a gas exhaust opening through which a flow of gas (e.g. gas) also passes. This gas exhaust or gas bleed helps to prevent the ingress of contaminants from the machining process into the device through the gas exhaust opening.

[0010] In addition to the gas bleed, the protection device also includes a check valve for preventing the ingress of contaminants when gas is not being discharged from the gas discharge opening. The check valve, which in a preferred embodiment is a duckbill valve or the like, is disposed in the light path of the light beam, respectively in the light emitter and / or the light receiver. The check valve, also referred to as a one-way valve, is configured to open (i.e. assume an open configuration) when a flow of gas passes toward the gas discharge opening. Such a check valve does not need to be forced open using an actuator or other related means, but is only forced to open by the flow of gas through the check valve. In this open configuration, a passage exists through the check valve through which the light beam can also pass. In the absence of such gas flow, the check valve closes and can provide a fluid-tight seal, as described below. This prevents external contaminants, such as a jet of pressurized coolant liquid or cuttings directed toward the gas discharge opening, from passing through the check valve.

[0011] The tool measurement apparatus of the present invention has various advantages over prior art tool measurement apparatus. For example, the check valve can be much smaller than the prior art piston-actuated shutter arrangement. This allows the check valve to be much closer to the gas exhaust opening than the shutter arrangement, reducing the penetration depth of contaminants into the apparatus. In a preferred embodiment, the check valve can be located downstream (in terms of bleed gas) of the various optical components of the light emitter and / or receiver (including any optical openings), thus helping to prevent contaminants from reaching any of these optical components. As explained below, the check valve is also, in one embodiment, a typically low-cost item that can be easily replaced if damaged or worn. In this manner, an improved tool measurement apparatus is provided.

[0012] Advantageously, the check valve of the protection device is in a closed configuration when no bleed gas is supplied to its gas discharge opening. The closed configuration of the check valve can provide a seal that substantially prevents the ingress of fluids or cutting debris from the machine tool environment. In other words, the closed check valve advantageously blocks the forward passage of most fluids (or other contaminants) that may enter the gas discharge opening when there is no bleed gas discharged through that opening. A negative gas pressure can also be applied to close the check valve more tightly. Similarly, an external gas pressure (i.e., a pressure that would result in a backflow of gas in the absence of the check valve) can help close the check valve more tightly. The check valve can also substantially block the passage of the light beam along the light path when in the closed configuration. Thus, the tool measurement device may not be usable for measurements when no bleed gas is supplied. In other words, the closed check valve can provide a passive protection mode in which the use of the device for measurements is not possible.

[0013] Advantageously, the check valve comprises a duckbill valve. As explained below, the duckbill valve typically comprises two or more flexible lips. Such lips may be provided, for example, by suitable slit surfaces or by a plurality of resiliently flexible flaps. Such lips may be shaped like a duck's beak. The flexible lips provide an open passage for gas to pass through the valve in a first direction. The lips do not separate but remain sealed in the absence of gas flow or when the gas flow is directed in a direction opposite to the first direction. The duckbill valve thus functions as a one-way or check valve preventing the reverse flow of fluid. The duckbill valve is arranged to open when gas passes through in a direction towards the associated gas discharge opening. Gas therefore flows from a gas inlet or other conduit within the device through the duckbill valve and is discharged through the gas discharge opening. A gas supply device may also be provided to supply such a gas flow to the inlet. The duckbill valve may be formed from an elastomeric material (e.g., silicone, fluorocarbon, or hydrocarbon resistant fluorosilicone rubber). The duckbill valve may include a first end including a flange and a flexible (e.g., elastomeric) lip extending from the flange. The duckbill valve may be disposed within a housing within the transmitter / receiver that retains the flange and limits outward deflection of the flexible member. While duckbill valves are preferred, it should be noted that any check valve may be used that provides a passage for the light beam when the check valve is open. For example, cross slit valves, gate valves, reed valves, etc. are suitable.

[0014] Advantageously, the gas exhaust opening of the protective device comprises a conduit that is inclined at an angle to the optical path so that the exhausted bleed gas is directed away from the optical path, thereby reducing turbulence of gas along the free space portion of the optical path that might otherwise result in measurement uncertainties. The conduit may also be appropriately sized so as not to interact with the optical beam passing therethrough.

[0015] As explained above, the light transmitter and receiver can be arranged in a blocking beam configuration where the light path passes from the light source to the detector through a region of free space where a tool can be placed to obscure the light beam. For example, the light source can direct the light beam along a straight light path that is placed to coincide with the detector. The tool to be measured can then be placed to block the light beam (i.e., enter the light path) in the free space region located between the light transmitter and receiver. A tool that "blocks" the light beam changes the amount of light that reaches the detector. Alternatively, the light beam can be reflected from the tool to be measured. In such an example, the receiver can be arranged to collect light emitted from the light transmitter that is reflected from the tool. In such an example, the light path includes the reflection from the tool. The light transmitter and receiver can be co-located in such a reflecting arrangement or can be incorporated into the same unit.

[0016] The light-transmitting section may include a protection device. The light-receiving section may include a protection device. In a preferred embodiment, both the light-transmitting section and the light-receiving section include a protection device. Thus, the light-transmitting section may constitute a protection device and the light-receiving section may also constitute a (different) protection device. Thus, references in this specification to a "protection device" include references to one or each protection device of the device, as appropriate. In other words, in a preferred embodiment, the device is preferably composed of two protection devices. The light-transmitting section may constitute a first protection device and the light-receiving section may constitute a second protection device. The first and second protection devices of the light-transmitting section and the light-receiving section are preferably identical (e.g. interchangeable) for simplicity. However, the first and second protection devices of the light-transmitting section and the light-receiving section may be different. For example, the size and angle of the gas exhaust opening, the size and type of the check valve may be different for the protection devices of the light-transmitting section and the light-receiving section. Each of the first and second protection devices may have any or all of the features of the protection devices described herein.

[0017] In a preferred embodiment, at least one of the light transmitting and receiving sections comprises an optical aperture for defining the dimensions of the light beam. Both the light transmitting and receiving sections may include such an optical aperture. The optical aperture may be dimensioned to control the characteristics of the light passing therethrough. For example, a circular optical aperture may be provided to control the diameter of the light beam and / or to block stray light from entering the optical system of the light transmitting and / or receiving sections. In such an example, even slight contamination of the optical aperture may reduce the measurement accuracy (e.g., by blocking, diverting or reflecting the light beam). Therefore, such an optical aperture is preferably provided upstream of the protection device. In other words, the check valve (in the closed state) preferably protects the optical aperture from external contaminants.

[0018] The protective device(s) of the light emitter and / or receiver may provide a seal against contaminants alone in the absence of gas flow through the gas exhaust opening. Alternatively, at least one of the light emitter and receiver may further include a shutter assembly movable between an open position and a closed position. The shutter assembly may be provided upstream (from the perspective of the bleed gas) of the protective device. In other words, the shutter assembly may be provided behind the protective device or behind each protective device. The shutter assembly may thus provide a secondary seal to prevent the ingress of contaminants that have somehow passed the check valve of the protective device (e.g., if the check valve is damaged or worn). The light emitter and / or receiver may also include further check valves (e.g., further duckbill valves) in addition to those of the protective device. For example, such check valves may be provided in the light emitter or receiver along the light beam path.

[0019] In a preferred embodiment, both a shutter assembly and an optical aperture are provided. The shutter assembly is preferably located upstream of the optical aperture. Thus, the optical aperture can be located between the protection device and the shutter assembly. In this way, the protection device protects the optical aperture from contaminants entering the gas exhaust opening, but the optical aperture is located in front of the shutter assembly (and therefore the shutter assembly cannot protect the optical aperture from external contaminants). In this way, the shutter assembly provides additional protection for certain optical components (e.g., detectors and light sources) that are deep within the device, but protection of the optical aperture is provided by the protection device alone.

[0020] Advantageously, at least one of the light projecting and receiving parts is configured with a baffle provided outside the gas discharge opening of the protection device. As will be understood by those skilled in the art, a baffle in this context means a device (plate, wall, screen, etc.) that deflects the passage of a fluid (such as a flow of cooling liquid). Preferably, both the light projecting and receiving parts are configured with such a baffle. The baffle is advantageously arranged to protect the gas discharge opening from the ingress of fluids and debris without blocking the optical path. In other words, each baffle is designed and arranged to deflect the incident fluid from the gas discharge opening without blocking the beam path. The baffle may partially surround the gas discharge opening. The baffle may include a partial conical shape. For example, a baffle consisting of a segment or part of a cone can be arranged to protect the gas discharge opening. The bleed gas discharged from the gas discharge opening is preferably directed away from the baffle. This prevents the baffle from directing the bleed gas into the optical path, which may cause turbulence.

[0021] The device may be formed as a one-piece (one-piece) item that is not intended to be disassembled after manufacture or that can be disassembled. Advantageously, at least one of the light emitter and receiver comprises a removable cap incorporating a protection device. In other words, the removable cap may incorporate a protection device and is attachable to the body of at least one of the light emitter and receiver. Two such removable caps may be provided for attachment to the light emitter and receiver, respectively. The removable caps may also incorporate optional baffles and / or optional optical apertures as described above. In such an example, the caps may be removed from the device and replaced as required. For example, various different caps may be provided for different measurement configurations (e.g. different sizes of light beams, different amounts of gas bleed, different shapes or orientations of baffles, etc.). It is also possible to remove the caps for replacement or repair. For example, check valves may become worn or damaged over time, but can be easily replaced as needed by either replacing the cap portion (i.e., replacing the entire cap portion with a replacement cap portion) or by removing the cap portion and replacing / repairing the check valve. This is particularly advantageous when using duckbill valves or similar check valves made from elastomeric materials.

[0022] In addition, a machine tool including the above-mentioned tool measuring device can be provided. That is, a machine tool combined with the above-mentioned tool measuring device can be provided. For example, the tool measuring device can be attached to the bed of the machine tool.

[0023] Also described herein is a protection device for a tool measurement device. The protection device comprises a gas exhaust opening and a check valve, the check valve adopting an open configuration in which flow gas through the check valve in a first direction causes the check valve to define a passage through which a light beam can pass. The protection device may include any of the features described above in relation to the tool measurement device. The protection device may also comprise an attachment mechanism configured to allow the protection device to be releasably attached to a housing of the light emitter or light receiver of the tool measurement device.

[0024] Also described herein is a tool measurement apparatus for a machine tool, the tool measurement apparatus comprising a light projector for generating a light beam and a light receiver for detecting the light beam, the light beam passing from the light projector to the light receiver along an optical path (e.g., in which a tool may be inserted), and at least one check valve disposed in the optical path. The check valve is preferably configured to adopt an open configuration when a gas flow passes therethrough, the open configuration of the check valve defining a passage through which the light beam may pass. The apparatus may include any of the other features described above.

[0025] Also described herein is a tool measurement device for a machine tool. The tool measurement device may comprise a non-contact tool setter. The device may comprise a light projector. The light projector may comprise a light source for generating a light beam. The device may comprise a light receiver. The light receiver may comprise a detector for detecting the light beam. The light beam may be passed from the light source along a light path to the detector. The tool may be insertable into the light path. The light projector and / or the light receiver may comprise a protection device. The protection device may comprise a gas exhaust opening. The gas exhaust opening may be configured to exhaust bleed gas supplied to the device from an external gas source. The light path may pass through the gas exhaust opening. The protection device may comprise a check valve. The check valve may be disposed in the light path. The bleed gas may be supplied to the gas exhaust opening through the check valve. A flow of the bleed gas through the check valve may cause the check valve to adopt an open configuration (i.e., the check valve may be a flow-activated check valve). The open configuration can define a passageway through which a light beam can pass. The apparatus can include any of the other features described above. [Brief description of the drawings]

[0026] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a laser tool setter apparatus mounted within a machine tool housing. [Diagram 2] Figure 2 shows a prior art protective device of the type used in Renishaw's NC4 product. [Diagram 3] FIG. 3 shows a cross-sectional view of a tool setter apparatus including a protection device of the present invention. [Figure 4] FIG. 4 shows an enlarged view of the protection device of the device of FIG. [Figure 5A] FIG. 5A illustrates a schematic of a duckbill valve in a closed configuration. [Figure 5B] FIG. 5B illustrates a schematic of the duckbill valve in an open configuration. [Figure 6]FIG. 6 shows a duckbill valve design suitable for use in the apparatus of FIGS. [Figure 7A] FIG. 7A shows an image of a duckbill valve in a closed configuration. [Figure 7B] FIG. 7B shows an image of the duckbill valve in an open configuration. [Figure 8] FIG. 8 is an external perspective view of the tool measuring device of FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] 1 there is shown a schematic diagram of a (non-contact) laser tool setter 2 installed within a machine tool housing 4. In particular, the laser tool setter 2 is mounted to the bed 6 of the machine tool adjacent a workpiece 8 to be machined (cut).

[0028] The laser tool setter 2, an example of a tool measuring device, comprises a light emitter 10 including a laser diode and suitable optics (not shown) for generating a light beam 12. A light receiver 14 is spaced apart from the light emitter 10 and includes a photodiode and suitable optics (not shown) arranged to receive the light beam 12. In the arrangement shown, the light emitter 10 and the light receiver 14 are both fixed to a common base 16, so that they maintain a fixed spacing and orientation relative to each other. The base 16 is rigidly attached (e.g. bolted) to the bed 6 of the machine tool. Other configurations of the device would be possible. For example, a single (common) housing for the light emitter and receiver could be provided, or separate light emitter and receiver units could be mounted to the machine tool. The laser tool setter 2 could also be mounted to other parts of the machine tool, such as the machine tool casing or a moveable tool setting arm.

[0029] The laser tool setter 2 is arranged such that the light beam 12 passes from the light transmitter 10 to the light receiver 14 through a region of free space. A tool 20, mounted on a tool shank 22 carried by a movable spindle 24 of the machine tool, can be moved to interrupt the light beam 12. In particular, the spindle 24 can be moved relative to the bed 6 under the control of the machine tool controller 26. A detector in the light receiver 14 measures the intensity of the light passing from the light transmitter, and the beam intensity signal is passed to the tool setter interface 28 for analysis. The interface 28 consists of a processor that analyzes the beam intensity signal and generates a so-called "trigger signal" when the received light intensity exceeds a certain threshold value (e.g. 50%). This trigger signal is passed to a skip input of the machine controller 26. The position of the tool measured by the machine tool is captured upon receipt of the trigger signal from the interface 28, thereby enabling the measurement of the tool size (e.g. tool length and diameter). It should be noted that the trigger signal can be output in a number of different ways, depending on the configuration of the controller 26. For example, the trigger signal may be communicated by latching a voltage on a line connected to a skip input of controller 26, or by generating a pulse or series of pulses that are passed to that skip input. The trigger signal may alternatively be passed to controller 26 via a digital data bus (e.g., as described in WO 2018 / 134585).

[0030] The laser tool setter 2 allows various tools, such as the tool 20, to be measured before they are used in the cutting procedure. In the subsequent cutting procedure, the tool, for example a rotary drill or a milling tool, is brought into contact with the workpiece 8 and performs the required cutting operation. A coolant pipe 30 is carried by the spindle and can direct a spray or jet of coolant in the illustrated cone 32 towards the tip of the tool 20. Although the coolant spray is normally only activated during cutting to submerge the workpiece 8, the tool setter 2 will then be exposed to splashes, reflected coolant jets and cutting debris. This is especially true when the tool setter 2 needs to be mounted in close proximity to the workpiece 8, such as in a machine tool set-up.

[0031] Referring to FIG. 2, a cutaway view of the light projection 50 of the prior art NC4 tool setter discussed above is provided.

[0032] The laser module 52 includes a laser diode and optics to generate a collimated light beam 51. Although a collimated light beam 51 is shown, focusing elements may be provided to generate a focused light beam. The light beam passes through an optical aperture 56 (defining the diameter of the light beam 51) and exits the light projection section 50 through an angled gas exhaust opening 58. The interior of the light projection section 50 is arranged to include a flow path that directs a flow of gas from an external compressed gas source through the optical aperture 56, around it, and out of the device via the gas exhaust opening 58. The supply of compressed gas also acts on a gas pressure actuator (piston) mechanism that moves a shutter 60 out of the light path against the restoring force of a compression spring 62. In the absence of a supply of compressed gas, the spring 62 moves the shutter 60 upward, thereby sealing the hollow flow path through the light projection section. This shutter seal and actuator arrangement is provided to prevent contaminants from reaching the laser module 52.

[0033] Although the above NC4 tool setting system has been found to provide very robust and market leading protection against contaminants, with or without the supply of compressed gas, it still has disadvantages when used under the most extreme conditions. In particular, when gas is not supplied, cooling water and debris can enter the gas exhaust opening 58 and this can accumulate in the part of the flow path located in front of the shutter 60. Most of this contamination is discharged from the device the next time the gas supply is turned on and the shutter 60 opens, but over time debris can also accumulate. This includes contaminants reaching and damaging the shutter 60 and associated actuator parts, or reaching the laser module 52. This can result in a loss of optical performance and deterioration of the seal made by the shutter 60 over time, requiring the device to be disassembled and cleaned. It should be noted that while the light emitter is illustrated in Figure 2, the corresponding light receiver can also suffer from similar problems.

[0034] 3 and 4, a light projector 100 in accordance with the present invention is illustrated. As shown in FIG. 3, similar to the prior art light projector 50 described above, a laser module 102 is provided which generates a light beam 104 which passes through an optical aperture 106 and exits the light projector via a gas exhaust aperture 108. A gas pressure actuated shutter 110 is also provided between the optical aperture 106 and the laser module 102.

[0035] The light projector 100 further includes a duckbill valve 112 disposed in the optical path between the gas exhaust opening 108 and the optical opening 106. An external baffle 114 is also provided to help divert incoming contaminants (e.g., cooling water flow) away from the gas exhaust opening 108. The complete layout of the light projector is shown in FIG. 3, and FIG. 4 shows a protective cap portion 120 that is removable from the remainder of the light projector. In this example, the protective cap portion 120 is comprised of the baffle 114, the gas exhaust opening 108, the duckbill valve 112, and the optical opening 106. Once the protective cap portion 120 is removed, the interior of the remainder of the light projector 100 can be cleaned. The entire protective cap portion 120 (or just the duckbill valve 112 in the protective cap portion 120) can also be replaced if worn or damaged.

[0036] During a measurement, compressed gas is introduced into the device. This gas passes through the duckbill valve 112 and is exhausted from the light projection 100 via the gas exhaust opening 108. As described below, the duckbill valve 112 consists of a resilient flexible plastic tube with a lip or flap (having the general shape of a duckbill) that expands (valve open) when there is a flow of gas passing through in one direction (i.e., out of the device). This arrangement is such that the light beam 104 can also pass through the duckbill valve 112 when the compressed gas flow opens the internal passage of the duckbill valve 112. The supply of compressed gas also activates the piston actuator to move the shutter 110, thereby exposing the laser module 102. Thus, the light beam 104 is unobstructed when there is a flow of compressed gas through the light projection and out of the gas exhaust opening 108. The activation of this gas flow or gas bleed also inhibits contaminants from entering the gas exhaust opening 108. It should be noted that appropriate placement of the angled conduits forming the gas exhaust opening 108 will direct the bleed gas away from the external baffle 114, minimizing gas turbulence along the free space portion of the optical path. The apparatus may also include a suitable gas inlet for receiving gas (or any suitable gas) from an external source (e.g., a compressed gas source).

[0037] When no compressed gas is supplied to the light transmitter 100, the shutter 110 seals off the laser module 102 and also closes the passage through the duckbill valve 112 (i.e. the lips on the end of the resilient flexible plastic tube close and the valve seals itself). Thus, it can be seen that there are two different protective seals in the optical path. The duckbill valve 112 is located just behind the gas exhaust opening 108 and when sealed due to the absence of gas flow, acts to protect the optical opening 106 from contaminants. Further protection of the laser module 102 is provided by the shutter 110. This double seal arrangement reduces the ability of contaminants to enter the gas supply flow path within the light transmitter 100, improving protection against the ingress of contaminants. Also, the compactness of the duckbill valve 112 means that it can be placed closer to the gas exhaust opening than the relatively large shutter 110 placement, thereby reducing the depth of ingress of contaminants into the device. Again, only the light transmitter has been described here, but a similar arrangement is used for the light receiver as well.

[0038] While the described double seal arrangement has been found to provide good protection, it is possible to omit the shutter 110 and rely only on the duckbill valve 112 to prevent contamination from entering the apparatus when there is no gas supply. In such an example, it would be possible to provide a more compact tool setter apparatus. It should also be remembered that these examples are non-limiting and various other options and variations are possible. For example, the external baffle could be omitted, the gas exhaust opening could be sized to also provide an optical opening, the collimated laser beam could be replaced with a focused laser beam, etc.

[0039] Next, the working principle of the duckbill valve will be described in more detail with reference to Figures 5A and 5B. The duckbill valve is an example of a check valve and is usually made from rubber or a synthetic elastomer. Duckbill valves usually have two or more lips or flaps, which are usually shaped like a duck's beak.

[0040] Figure 5A shows a duckbill valve 150 formed from two flaps 152a and 152b in a closed configuration. In this configuration, there is no fluid flow from left to right in the figure, and the resiliency of the two flaps 152a, 152b causes the flaps 152a, 152b to lie flat and engage with each other. This provides a fluid seal that prevents fluid flow from right to left in Figure 5A.

[0041] Figure 5B shows duckbill valve 150 in an open configuration, which is employed when fluid flow through the duckbill valve is unidirectional (from left to right in this example). In particular, as shown in Figure 5B, when fluid is pumped from left to right, the flattened ends of duckbill flaps 152a and 152b deform open, allowing pressurized fluid to pass.

[0042] Thus, the duckbill valve 150 functions as a check valve or one-way valve. Duckbill valves are often used in medical, fluid control applications to prevent contamination from backflow, and are similar in function to the mitral valve found in the heart. Recently, such duckbill valves have also been used in low-cost food packaging applications, for example to allow the controlled drainage of liquids (e.g., ketchup, mustard, etc.) from plastic bottles.

[0043] Referring to FIG. 6, a duckbill valve 200 suitable for use in the tool setter device described above is illustrated. The duckbill valve 200 includes a flange 202 and a lip 204. The flange 202 allows the valve to be fixed in a suitable recess in the light emitter or receiver of the tool setter device. Importantly, the dimensions of the duckbill valve 200 are selected to allow a laser beam to pass through the open valve channel when the valve is opened by supplying a flow of compressed gas. In particular, the lip 204 is designed to move apart and press against a cavity wall in the light emitter or receiver, thereby opening a channel having a diameter larger than that of the laser beam. In the absence of gas flow outside the device, a configuration such as that shown in FIG. 6 is employed that prevents backflow. The passage of light may be at least partially blocked by a closed valve. The duckbill valve 200 is formed of FKM or a similar elastomer.

[0044] Figure 7A is an image showing an end view of the duckbill valve when no gas is passing through it. From Figure 7A, it can be seen that the two lips that define the slit are close together (i.e., there is only a small gap between them). When there is a slight negative pressure inside the device or pressurized gas tries to backflow through the valve, these lips seal more tightly (i.e., prevent the backflow of gas through the duckbill valve).

[0045] Figure 7B is an image showing the end face of the duckbill valve as gas passes through in a direction towards the camera that took the image. Note that the magnification used to take image 7B is lower than that of Figure 7A in order to allow the structures surrounding the duckbill valve to be seen. From Figure 7B, it can be seen that the lips have moved away from each other and there is an opening through which the light beam can pass. The opening is sized to be larger than the light beam and the light beam and valve are positioned such that the light beam is centered in the opening. Thus, the light beam can pass through the (open) opening unobstructed.

[0046] It should be noted that the elasticity of the duckbill valve can be adjusted to achieve the desired operational performance (e.g., to control the pressure and / or flow rate of gas required to open the valve). This can be done by selecting appropriate materials and / or by varying the dimensions of the valve components. In the above examples, an elastomeric duckbill valve is illustrated, in which case the valve can be closed in the absence of gas flow by the elasticity of the material alone, but additional closure elements can also be provided. For example, a return spring or the like can be coupled to the flexible lip of the duckbill valve to provide an additional spring force to close the valve (thereby requiring additional force due to the passage of gas to open the valve). Variations of the illustrated duckbill valve can also be used. For example, so-called cross-slit duckbill valves can be employed. Similarly, there are alternative check valves that achieve a similar function to the duckbill valve. These include reed valves (e.g., formed of flexible metals or composite materials), gate valves, hinged check valves, etc.

[0047] Referring to FIG. 8, a perspective view of the tool setter of the present invention is shown. The tool setter includes the light projector 100 and the light receiver 300 as detailed above. The light receiver 300 is similar in configuration to the light projector 100, but includes a light detector module (e.g., including a photodiode) rather than a laser module. The external baffle 114 of the light projector 100 is visible in the figure, and a similar baffle is also provided on the light receiver 300 (not shown). These baffles are appropriately angled to protect the gas exhaust opening. Both the light projector 100 and the light receiver 300 are mounted on a base 302, which can be mounted on a required portion of a machine tool. The light beam passes from the light projector 100 to the light receiver 300 through a region of free space where a tool can be placed. The tool placed in the light beam is measured by appropriately analyzing the received light signal.

[0048] It should again be remembered that the above is merely exemplary of the invention and that numerous variations and alternatives are possible. For example, any light source (not limited to laser diodes) could be used. Similarly, the detector need not be a single element photodiode. Also, an array of light detecting elements or pixels could be used. For example, one or two dimensional imaging arrays could be used. Although a blocked beam configuration has been described, the protection device could also be incorporated into other tool measurement devices, such as reflective tool sensors.

Claims

1. A tool measuring device for a machine tool, comprising: a light projecting unit including a light source for generating a light beam; a light receiving unit including a detector for detecting the light beam, the light beam passing along an optical path from the light source to the detector; Equipped with At least one of the light receiving unit and the light emitting unit includes a protection device including a gas exhaust opening configured to exhaust bleed gas supplied from an external gas source, and the light path passes through the gas exhaust opening; the protection device further comprising a check valve disposed in the light path, the bleed gas being supplied to the gas exhaust opening through the check valve, and the flow of the bleed gas through the check valve causing the check valve to be in an open configuration defining a passageway through which the light beam can pass.

2. 2. The apparatus of claim 1, wherein the check valve of the protection device is in a closed configuration when no bleed gas is supplied to the gas exhaust opening, the closed configuration substantially preventing the ingress of fluid or debris from the environment of the machine tool.

3. 3. The apparatus of claim 2, wherein the check valve, when in the closed configuration, substantially blocks passage of the light beam along the optical path.

4. The apparatus of claim 1 , wherein the check valve comprises a duckbill valve having multiple flexible lips.

5. 10. The apparatus of claim 1, wherein the gas exhaust opening of the protective device comprises a conduit that is angled obliquely relative to the optical path so that the exhausted bleed gas is directed away from the optical path.

6. 2. The apparatus of claim 1, wherein the light transmitting unit and the light receiving unit are arranged in a blocked beam configuration in which the light path passes from the light source to the detector through a region of free space in which a tool can be placed to obscure the light beam.

7. The apparatus of claim 1 , wherein each of the light emitting unit and the light receiving unit includes the protection device.

8. 2. The apparatus of claim 1, wherein at least one of the light transmitting portion and the light receiving portion includes an optical aperture for defining a size of the light beam, the optical aperture being provided upstream of the protection device.

9. The device according to claim 1 , wherein at least one of the light emitting unit and the light receiving unit further comprises a shutter assembly movable between an open position and a closed position, the shutter assembly being provided upstream of the protection device.

10. At least one of the light-emitting unit and the light-receiving unit has an optical aperture for defining the dimensions of the light beam, the optical aperture being provided upstream of the protection device; The apparatus of claim 9 , wherein the optical aperture is disposed between the shutter assembly and the protection device.

11. 2. The device of claim 1, wherein at least one of the light emitting unit and the light receiving unit includes a baffle outside the gas discharge opening of the protection device, the baffle being positioned to protect the gas discharge opening from the intrusion of fluids or debris without obstructing the optical path.

12. The apparatus of claim 11 , wherein the bleed gas discharged from the gas discharge opening is directed away from the baffle.

13. 2. The device of claim 1, wherein a removable cap incorporates the protection device, the removable cap being attachable to a body of at least one of the light emitting unit and the light receiving unit.

14. A machine tool in combination with the tool measuring device according to any one of claims 1 to 13.

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