Sealed linear axis

Abstract

The invention relates to a motorized linear axis (1) comprising a sliding joint (10) guiding a carriage (20) driven by a pulley engaging a toothed belt (30) fixed to a U-shaped profile (11), according to an engagement profile such as an Ω, defined by return rollers of the carriage; the sliding joint (10) is disposed at the bottom of the U-shaped profile (11) defining a cavity whose opening (12) has a receiving space (13) for the belt (30), such that the opening (12) is hidden by the belt (30) outside the engagement profile, and in particular on either side of the carriage (20); characterized in that the receiving space (13) has straight edges (14) spaced by the width of the belt (30). Figure for the abstract: Fig. 3

Description

Title of the invention: Sealed linear axis Technical field

[0001] The invention relates to the technical field of motorized linear axes, as used in the field of robotics. Prior art

[0002] In the field of robotics, it is known to use motorized linear axes to move mechatronic assemblies, for example a robotic arm. The assemblies moved weigh from a few kilograms to several hundred kilograms, and the precision and repeatability of its positioning must be of the order of a tenth of a millimeter, including on linear axes that can measure several meters long, or even around twenty meters.

[0003] When these systems are used in the food, pharmaceutical or nuclear industries, it is important to provide the possibility of cleaning these axes in order to eliminate dirt from the environment, for example from manufactured foods.

[0004] Two trends are generally observed: - Either the design of a system as open as possible, facilitating its cleaning; - Either the design of a closed and watertight system, protecting the introduction of elements into the system.

[0005] In the case of a linear axis, it is for example known to use a system with a sliding connection on which a carriage slides by means of an external pinion and rack. The pinion and rack system is exposed to the environment, and is therefore easily cleanable. On the other hand, it is not possible to lubricate it with grease which would be likely to contaminate the environment. To guarantee the expected precision and repeatability of the system positioning, the pinion and rack are made of metal, so that the system is sufficiently rigid. But the resulting system is particularly noisy, which constitutes a nuisance for surrounding operators. The accessibility of the pinion and rack system is also dangerous for operators.

[0006] Also known from documents EP0448484 and EP0448485 are motorized linear axes comprising a belt transmission, making it possible to overcome the above drawbacks. However, these systems have a significant linear footprint due to the lengths required for twisting the belt. In addition, this twisting leads to accelerated aging of the belt.

[0007] Document FR2684034 proposes another design, in which a belt runs along the entire length of the axis. However, the free length of the belt is very important. Due to the intrinsic elasticity of the belt, the precision obtained for positioning the carriage is not sufficient.

[0008] Finally, document WO0260641 describes another design comprising a deflector defining a baffle. However, this protection is not sufficient for the food, pharmaceutical and nuclear sectors.

[0009] Other systems describe trolleys powered by a pulley engaging a static belt. However, the sealing of these systems is not satisfactory. Some of these systems also have retention zones, i.e. upward-facing cavities in which waste or water used for cleaning the systems could accumulate. Indeed, these retention zones would constitute privileged sites for the development of micro-organisms or bacteria. The food industry requires that retention zones be avoided. Invention statement

[0010] The aim of the invention is to overcome the drawbacks of the prior art, by proposing a motorized linear axis which is precise, waterproof, silent, durable, and safe for the operator.

[0011] For this purpose, a motorized linear axis has been developed comprising a sliding connection guiding a motorized carriage by a pulley engaging a toothed belt fixed to a “U” shaped profile, according to a meshing profile such as a “Q”, defined by return rollers of the carriage; - the sliding connection is arranged at the bottom of the “U” profile defining a cavity whose opening has a space for receiving the belt, so that the opening is masked by the belt outside the meshing profile, and in particular on either side of the carriage.

[0012] According to the invention, the receiving space has rectilinear edges spaced apart by the width of the belt. In this way, the belt is inserted into the receiving space in the manner of a seal making it possible to close the opening of the U-shaped profile, without there being a retention zone at the receiving space.

[0013] The axle according to the invention is therefore silent thanks to the use of a belt rather than a rack and pinion system. In addition, the belt is mainly static within the axle because it is only mobile at the level of the meshing profile, so that the source of noise emission is localized at a single point on the axle.

[0014] Then, the transmission of forces is centered under the load of the carriage, while the rack and pinion systems are offset, which implies an overhang on the sliding connection. The sliding connection of the invention is therefore preserved.

[0015] Advantageously, the belt rests on a shoulder at the bottom of the space of reception. This shoulder ensures that the belt cannot sink into the cavity inside the profile if it is subjected to pressure. This could happen under the pressure of a high-pressure water jet directed at the belt during cleaning.

[0016] So that there is no retention zone on an upper face of the belt, the height of the edges is at most equal to the thickness of the belt, so that the belt is flush with an upper face of the profile, or projects relative to the upper face of the profile.

[0017] In a preferred embodiment, the receiving space has teeth adapted to the toothed belt. The teeth hold the belt, and the free length of the belt is reduced to the meshing profile only, i.e. only around ten centimeters while the module measures several meters. Only the free length is subjected to the forces of the motorization, which improves the positioning precision of the system.

[0018] In this case, the height of the edges is greater than the thickness of the teeth of the toothed belt. In this way, the gaps between the notches of the belt are indeed masked by the edges. Otherwise, the gaps between the notches would constitute entry points towards the opening.

[0019] Advantageously, a spacing between the two edges is adjusted tightly relative to the width of the belt, preferably according to a tolerance interval of the order of 0.4% relative to the width of the belt. Due to the slightly tight embedding of the belt in the receiving space, the seal between the belt and the profile is guaranteed.

[0020] To ensure proper insertion of the belt into the receiving space, the height of the edges is less than the thickness of the belt. The belt therefore projects from the receiving space, and the passage of the return rollers over the belt packs it into the receiving space. This characteristic is particularly advantageous in the case where the adjustment between the width of the belt and the spacing of the edges is adjusted tightly, and where insertion of the belt requires effort.

[0021] The carriage comprises an extension connecting an external part of the carriage to pads of the sliding connection inside the profile. In order to improve the protection of the opening at the level of the meshing profile, the extension has: - a solid section sized to hide the opening of the profile; and / or - an envelope covering the opening of the profile.

[0022] Still for this purpose, the trolley may comprise: - longitudinal deflectors masking a gap between the carriage and the profile, on either side of the carriage, and constituting a baffle; - scraper seals arranged against an upper face of the profile, and closing a gap between the carriage and the profile in the manner of a seal. In addition, scrapers transverse elements arranged at the front and rear of the carriage allow the removal of elements which would be deposited on the upper face, when the carriage moves. In this way the belt and / or the profile are cleaned before passing under the carriage, at the level of the meshing profile where the opening is no longer hidden by the belt.

[0023] In the case where the receiving space has teeth, one of the rollers is preferably mounted in sliding connection with the carriage, which makes it possible to adjust the tension of the belt between the rollers, in order to preload the belt.

[0024] In order to ensure that the belt is properly held, and in particular that it is flat, pressers are mounted at the ends of the profile and are configured to press the ends of the belt into the receiving space. The pressers preferably have a length greater than or equal to 50 mm. Brief description of the figures.

[0025] [Fig-1] is a perspective diagram of an axis on the invention.

[0026] [Fig.2] is a section of the axis, seen from the front.

[0027] [Fig.3] is a section of the axis, seen from the side.

[0028] [Fig.4] is a partial view of the axis, in perspective, illustrating the profile meshing within which the belt is not engaged with a toothing of the receiving space of the profile.

[0029] [Fig.5] is a perspective section of the axis illustrating the cowling of the opening at mesh profile level.

[0030] [Fig.6] is a perspective diagram illustrating the reception space in a mode of favorite achievement.

[0031] [Fig.7] is a diagram illustrating the relationships between the heights of the fields, the thickness of the belt, and the height of the teeth.

[0032] [Fig.8] is a view of the axis in partial section and in perspective, illustrating the drawer of voltage adjustment.

[0033] [Fig.9] is a perspective diagram, illustrating an axis equipped with several carriages.

[0034] [Fig. 10] is a perspective diagram, illustrating another axis equipped with several carriages. Detailed description of the invention

[0035] With reference to Figures 1 to 4, the invention relates to a motorized linear axis (1). The axis (1) comprises a carriage (20) movable by means of a notched and motorized pulley (21). The motor is not shown so as not to overload the figures.

[0036] The toothed pulley (21) meshes with a toothed belt (30), fixed to each of the ends of the linear axis (1). The carriage (20) is connected by a sliding connection (10) to a profile (11). This profile (11) has a general “U” shape so as to define a cavity in which the sliding connection (10) is located, which is for example of the type with ball bearing slide (10b) cooperating with a rail (10a).

[0037] The carriage (20) comprises an extension (27) connecting an external part (20e) on which the pulley (21) is mounted, and an internal part (20i) on which the pads (10b) are fixed.

[0038] The belt (30) is arranged at the end of the two parallel branches of the U so as to mask the opening (12) of the profile (11).

[0039] According to the invention, a receiving space (13) receiving the belt (30) has rectilinear edges (14). In this way the belt (30) is inserted into the receiving space (13) and effectively closes the opening (12) of the profile (11), on either side of the carriage (20), without creating a retention zone.

[0040] The sliding connection (10) is effectively protected within the profile (11). It is possible to use lubricants without risk of pollution.

[0041] Within the carriage (20), the belt (30) follows a meshing profile (31) around the toothed pulley (21). Indeed, it is known that to have an efficient transmission, the belt (30) must be wound around the pulley (21) over a predetermined minimum angular sector. In order to obtain this winding, the belt (30) follows a meshing profile (31) such as an omega, by means of return rollers (22). Other meshing profiles are of course conceivable, the essential thing being that the belt (30) is wound around the toothed pulley (21) over the determined angular sector. The axes of the pulley (21) and the rollers (22) are parallel.

[0042] With particular reference to [Fig. 4], at the level of the meshing profile (31), that is to say between the return rollers (22), the opening (12) of the profile (11) is not masked by the belt (30).

[0043] Depending on the level of protection required, the carriage (20) may comprise: - A full section (27), and / or - An envelope (23).

[0044] The solid section (27) is preferably part of the extension connecting the internal part (20i) and the external part (20e) of the carriage (20). It is arranged at the level of the meshing profile (31), between the return rollers (22), so as to mask the opening (12).

[0045] The envelope (23) extends beyond the meshing profile (31) on either side, i.e. on either side of the return rollers (22), so as to completely cover the meshing profile (31) and therefore the opening (12). The width of the envelope (23) is preferably greater than the width of the profile (11).

[0046] With particular reference to [Fig. 3], a gap (i) between the carriage (20) and the upper face (1 It) of the profile (11) is likely to constitute a point of entry of water or waste in the direction of the opening (12). In order to perfect the protection of the axis (1), the carriage (20) advantageously comprises scraper seals (25) and / or deflectors (24), on either side of the median plane of the carriage (20): - The scraper seals (25) ensure contact between the carriage (20) and the profile (11), and close the gap (i). - The deflectors (24) define a baffle against the penetration of water or food via the gap (i).

[0047] The scraper seals may be longitudinal (251) and / or transverse (25t). When the scraper seals (25) are transverse, i.e. arranged on a front face or a rear face of the carriage (20), they make it possible to remove the elements deposited on the upper face (bed) of the profile and on the belt (30), when the carriage (20) moves.

[0048] A single single-piece scraper seal (25) can be arranged around the entire periphery of the carriage (20).

[0049] The carriage (20) further comprises a lubricating device (28) for distributing lubricant within pads (10b) of the sliding connection (10). This lubricating device preferably comprises a lubricating nipple (28a) intended to be connected to a lubricating can, distribution channels (28b) for the lubricant from the nipple (28a) towards the pads (10b), and connection means (28c) between the channels (28b) and the pads (10b).

[0050] The axis (1) obtained is therefore easy to maintain, because it is possible to renew the grease of the slide (10) without there being any need to dismantle parts of the axis (1).

[0051] With reference to [Fig.5], it can be seen that the uncovered part of the opening (12) at the level of the meshing profile (31) is reduced to its minimum.

[0052] In a preferred embodiment, the profile (11) has teeth (16) corresponding to the notches of the belt (30). In this way, outside the meshing profile (31), the belt (30) is not under tension because it is firmly held by the teeth (16) of the profile (11).

[0053] This solution makes it possible to obtain a linear axis (1) in which the length of the belt (30) subjected to the tensions necessary for setting the carriage (20) in motion is reduced to its minimum: that is to say to the portion of the belt (30) included in the meshing profile (31).

[0054] This mode is particularly suitable for large axes (1) (around twenty meters). In the case of a large axis (1), the deformation of the belt (30) would be several millimeters, which does not meet the requirements of the field considered.

[0055] In addition, the belt (30) being at rest outside the meshing profile (31), this solution guarantees the good maintenance of the belt (30) within the receiving zone (13), therefore a better seal of the axis (1).

[0056] With reference to [Fig.6], so that the edges (14) are straight despite the presence of the teeth (16) machined within the receiving space (13), the receiving space (13) has a space between the teeth (16) and the edge (14), which allows the machining tool to be released from the teeth (16), without modifying the geometry of the edge (14).

[0057] With reference to [Fig.7], the height (h4) of the edges (14) of the receiving space (13) must be at most equal to the thickness (h3) of the belt (30). If the edges (14) were higher, then the belt (30) could be inserted into the receiving space (13) beyond an upper face (1 It) of the profile (11): then the upper face of the belt (30) would define a retention zone over the entire length of the axis (1), which is to be avoided.

[0058] The height (h4) of the edges (14) must therefore be less than or equal to the thickness (h3) of the belt (30). But the height (h4) of the edges (14) must be greater than the thickness (h5) of the notches of the belt (30) so that the gaps between the notches of the belt (30) do not define entry points within the opening (12) of the profile (11).

[0059] In the illustrated embodiment, the height (h4) of the edges (14) is strictly less than the thickness (h3) of the belt (30), so that the return rollers (22) of the carriage (20) can vertically compress the belt (30) within the receiving space (13), when the carriage (20) moves.

[0060] This embodiment is particularly suitable for the case where the spacing between the two edges (14) is adjusted tightly relative to the width of the belt (30).

[0061] Indeed, a tight fit between the belt (30) and the receiving space (13) makes it possible to obtain an even better seal, capable for example of resisting the pressure of a water jet used for cleaning the linear axis (1) during a cleaning operation.

[0062] The tightening is for example of the order of 0.4% (edge ​​spacing (14) of 49.8mm for a belt width (30) of 50mm, i.e. a tightening of 0.2mm for 50mm).

[0063] Nevertheless, a tight fit between the belt (30) and the receiving space (13) is synonymous with a force to be applied to the belt (30) to make it enter the receiving space (13).

[0064] If the height (h4) of the edges (14) is less than the thickness (h3) of the belt (30), that is to say that the belt (30) projects above the upper face (1 It) of the profile (11): then the movement of the carriage (20) involves a settling of the belt (30) within the receiving space (13). The belt protrudes for example by 0.2 to 1 mm from the upper face (bed).

[0065] For this purpose, the distance (h2) between the return rollers (22) and the shoulder (15) of the bottom of the receiving space is at most equal to the thickness (h3) of the belt (30).

[0066] A height (h4) of the edges (14) less than the thickness (h3) of the belt (30) also avoids contact between the return rollers (22) and the profile (11), which would be a source of noise.

[0067] [Fig. 8] illustrates an embodiment in which one of the return rollers (22) of the carriage (20) is slidably mounted, so as to be able to adjust the tension of the belt (30) within the meshing profile (31), inside the carriage (22). In the illustrated embodiment, this is achieved by means of a drawer (26) carrying a roller (22), and the drawer (26) is slidably mounted relative to the carriage (20). Its position is adjustable by means known to those skilled in the art, for example by means of a screw.

[0068] The use of such a tensioner within the meshing profile (31) facilitates the design of the carriage (20). Without a tensioner, it would be necessary to arrange the axes of the rollers (22) and the pulley (21) in such a way that the length of the meshing profile (31) is exactly a multiple of the pitch of the belt (30): otherwise, the notches of the belt would not coincide with the teeth (16) of the receiving space (16). With a tensioner, it is possible to adjust the length of the meshing profile (31) by moving a roller (22), and thus to ensure the correct meshing of the belt (30) on the teeth (16) when the carriage (20) moves.

[0069] Furthermore, the axis (1) can be shaped differently from the examples given without departing from the scope of the invention, which is defined by the claims.

[0070] With reference to figures 9 and 10, depending on the load to be handled and in particular its overhang with respect to the axis (1), or even the location of the axis (1), this may comprise: - Several trolleys (20), as illustrated [Fig.9]; and / or - Several slides (10), as illustrated [Fig.10].

[0071] When there are several trolleys (20), it is possible to combine motorized trolleys (20a) and non-motorized trolleys (20b).

[0072] These constructions make it possible to obtain a more robust axis (1), in the case where more than one carriage (20) is connected to each other.

[0073] Several carriages (20) arranged on the same slide (10) also make it possible to implement “pilgrim step” type kinematics.

[0074] Furthermore, the technical characteristics of the different embodiments and variants mentioned above can be, in whole or in part, combined with each other. Thus, the axis (1) can be adapted in terms of cost, functionality and performance.

Claims

Claims

1. Motorized linear axis (1) comprising a sliding connection (10) guiding a carriage (20) motorized by a pulley (21) engaging a toothed belt (30) fixed to a “U” shaped profile (11), according to an engagement profile (31) such as a “Q”, defined by return rollers (22) of the carriage; - the sliding connection (10) is arranged at the bottom of the “U” shaped profile (11) defining a cavity whose opening (12) has a receiving space (13) for the belt (30), so that the opening (12) is masked by the belt (30) outside the engagement profile (31), and in particular on either side of the carriage (20); characterized in that the receiving space (13) has rectilinear edges (14) spaced apart by the width of the belt (30), and the height of the edges (14) is at most equal to the thickness of the belt (30).

2. Linear axis (1) according to claim 1, characterized in that the receiving space (13) has teeth (16) adapted to the toothed belt (30), and the height of the edges (14) is greater than the thickness of the teeth of the toothed belt.

3. Linear axis (1) according to claim 2, characterized in that one of the rollers (22) is mounted in sliding connection with the carriage (20) to adjust the tension of the belt (30) between the rollers (22).

4. Linear axis (1) according to one of the preceding claims, characterized in that a spacing of the edges (14) is tightly adjusted relative to the width of the belt (30), preferably according to a tolerance interval of the order of 0.4% relative to the width of the belt (30).

5. Linear axis (1) according to one of the preceding claims, characterized in that the height of the edges (14) is less than the thickness of the belt (30).

6. Linear axis (1) according to one of the preceding claims, characterized in that the carriage (20) comprises a cover (23) masking the opening (12) of the profile (11) at the level of the meshing profile (31).

7. Linear axis (1) according to one of the preceding claims, characterized in that the carriage (20) comprises deflectors (24) closing a gap (i) between the carriage (20) and the profile (11).

8. Linear axis (1) according to one of the preceding claims, characterized in that the carriage (20) comprises scraping devices (25) of the profile (11) and / or the belt (30) AR / AV / D / G.

9. Linear axis (1) according to one of the preceding claims, characterized in that it comprises pressers (17) mounted at the ends of the profile (11), configured to press the ends of the belt (30) within the receiving space (13), the pressers (17) preferably have a length greater than or equal to 50mm.

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