Electric motor spindle drive

Abstract

Electromotive spindle drive (2), in particular for use in a beverage machine, comprising - an electric motor (4) with a rotor (8) which drives a threaded spindle (10) in rotation, - a spindle nut (16) which is rigidly connected to a piston rod (24) arranged coaxially to the threaded spindle (10) and which is in engagement with the threaded spindle (10), - a housing part (28) in which the spindle nut (16) and the piston rod (24) are guided linearly in the axial direction (A) by means of a guide element (20), characterized by - a linear guide (22) for the guide element (20) arranged in the housing part (28) coaxially to the piston rod (24) and separate from the housing part (28), and - a passage (53) arranged in the linear guide (22) which is aligned in the radial direction (R) with a filling opening (40) provided in the housing part (28) for an operating medium or lubricant, wherein the filling opening (40) is provided and designed both to receive a closure (42) for tightly closing it and to receive a tubular refill element (44) for supplying the operating medium or lubricant, in particular to the piston rod (24), to the threaded spindle (10) and / or to the spindle nut (16).

Description

[0001] The invention relates to an electromotive spindle drive, in particular for use in a beverage machine, wherein the spindle drive comprises an electric motor with a rotor which drives a threaded spindle in rotation, and a spindle nut which is rigidly connected to a piston rod arranged coaxially to the threaded spindle, and wherein the spindle nut is in engagement with the threaded spindle.

[0002] In such a spindle drive, a rotary motion of a rotor is converted into a linear adjustment motion of a piston rod along an axial direction (relative to the motor or shaft axis). For this purpose, a threaded nut engages a threaded spindle driven by the rotor. The spindle nut is supported (secured) against rotation and guided linearly along the axial direction. In particular, the spindle nut is also coupled to the piston rod, so that upon rotation of the threaded spindle, the spindle nut and the piston rod coupled to it are adjusted linearly.

[0003] A lubricant is typically used in the spindle drive, particularly to reduce friction. To supply this lubricant, for example, during initial commissioning or during maintenance of the spindle drive, the spindle drive has a filling device, which can be designed, for example, as a grease nipple or an (openly) accessible lubrication hole.

[0004] For example, DE 10 2008 050 993 B4 discloses a spindle motor with an electric motor and a spindle drive driven by the electric motor, comprising a spindle and a linearly movable spindle nut. A piston rod is screwed to the spindle nut, which is why it moves with the spindle nut. The piston rod has a grease nipple for supplying lubricant, allowing lubrication to be accessed from the outside at all times. The area of the piston rod containing the grease nipple protrudes axially above a housing section surrounding the piston rod, even when fully retracted.

[0005] DE 10 2009 007 958 A1 discloses a spindle motor comprising an electric motor with a rotor connected to a threaded spindle. The threaded spindle engages a spindle nut, which in turn is connected to a piston rod. Linear guidance of the spindle nut is achieved by means of guide parts connected to linear devices, so that the spindle nut is moved axially when the threaded spindle rotates. The spindle motor further comprises an oil filler on a housing part, which opens into a space outside the piston rod.

[0006] DE 198 60 513 C1 discloses a linear actuator. Its slide unit comprises a circular-cylindrical tubular body with an axis, a spindle receiving channel extending in the axial direction, and a radially outer circular-cylindrical guide surface. Furthermore, the linear actuator comprises a guide unit having a guide channel with a radially inner circular-cylindrical guide surface. The radially outer circular-cylindrical guide surface of the tubular body is in sliding guide engagement with the radially inner guide surface of the guide channel, essentially over its entire overlapping length. The spindle nut and a receiving chamber for at least part of the coupling unit are accommodated within the tubular body.

[0007] A linear motion device is known from DE 10 2009 032 345 A1. This device comprises a housing extending in a longitudinal direction, in which a longitudinally movable slider is accommodated. The housing has a lubricant supply device via which the slider can be supplied with lubricant. The lubricant supply device comprises a plunger mounted on the housing, which is movable transversely to the longitudinal direction. A spring is provided with which the plunger can be urged against the slider, whereby a lubricant supply connection to the slider can be established via the plunger.

[0008] DE 10 2011 100 707 A1 proposes an electrically actuated linear drive comprising an output unit arranged in a housing and driven by a drive spindle to perform a linear output movement. The output unit contains a spindle nut that engages the drive spindle. A lubrication opening formed in the housing provides access to an internal lubrication channel system. The lubrication opening also functions as a breather opening by being connected to a breather channel system independent of the lubrication channel system, which allows air to be exchanged between the interior of the linear drive housing and its surroundings.

[0009] DE 10 2007 043 391 A1 discloses an actuator. It comprises a threaded spindle with a rotational axis, a cantilever that is rigidly connected to a nut that engages the threaded spindle, and a housing in which the threaded spindle is rotatably mounted. An anti-rotation device is provided between the nut or the cantilever and the housing. The anti-rotation device comprises at least one separate, elongated sliding profile whose sliding surface is convex with respect to the rotational axis. The sliding profile is in guiding engagement with a guide groove in the housing that is adapted to its sliding surface. The sliding profile is secured to the nut or the cantilever.

[0010] If such spindle drives are to be used in the food industry, for example, when sealing glass bottles with crown caps, the spindle drives must comply with the relevant hygiene regulations and standards (hygienic design). In particular, a lubricant filler opening must be sufficiently tightly sealed.

[0011] The invention is based on the object of providing an electric motor spindle drive suitable for use in the food industry. This drive should enable the targeted supply of lubricant to desired components.

[0012] This object is achieved according to the invention by the features of claim 1. Advantageous further developments and embodiments are the subject of the subclaims.

[0013] For this purpose, the electromotive spindle drive, which is designed in particular for use in the food industry in a beverage machine, has an electric motor with a rotor which drives a threaded spindle in rotation. Furthermore, the spindle drive comprises a spindle nut which is rigidly connected, i.e. rotationally and displacement-proof, to a piston rod, expediently hollow-cylindrical, which is arranged coaxially to the threaded spindle. In other words, the spindle nut and the piston rod are connected or joined to one another in a rotationally and displacement-proof manner, for example in a form-fitting manner. The spindle nut is in engagement with the threaded spindle. Furthermore, the spindle nut and the piston rod connected to it are guided linearly in the axial direction in a housing part by means of a guide element. For this purpose, a linear guide for the guide element is arranged in the housing part on the circumference of the piston rod.

[0014] Furthermore, a passage is arranged in the linear guide, which is radially aligned with a filler opening for an operating fluid or lubricant provided in the housing part. The housing-side filler opening is provided and configured to accommodate both a closure for tightly closing the filler opening and a tubular refill element for supplying the operating fluid or lubricant, preferably to the spindle nut and alternatively or additionally to the piston rod and / or the threaded spindle.

[0015] In summary, it is particularly advantageous to insert or have inserted a refill element into the filler opening to simplify the supply of the lubricant or operating fluid. The filler opening can be sealed or closed tightly by means of the closure so that the lubricant or operating fluid cannot escape even at comparatively high temperatures and / or pressures, for example, during cleaning. Consequently, the spindle drive is suitable for use in the food industry.

[0016] According to a practical embodiment, the linear guide is tubular and has an opening on the casing side in which the guide element is seated. In other words, the linear guide is hollow-cylindrical. It is arranged circumferentially around the piston rod and the threaded spindle connected to it. The opening on the casing side is preferably elongated and expediently extends in the axial direction.

[0017] The guide element is suitably rigidly attached to the piston rod. For example, the guide element is screwed to the piston rod. In an alternative embodiment, the guide element is additionally or solely connected to the spindle nut.

[0018] According to an advantageous development, the piston rod is tubular, i.e., hollow-cylindrical. In the area of the spindle nut, the piston rod has an enlarged inner diameter. In other words, the inner diameter of the tubular piston rod is larger in the area of the spindle nut than in the rest of the piston rod.

[0019] The spindle nut is located on the end of the piston rod facing the electric motor. In summary, the inner diameter of the piston rod is enlarged in the area of the end facing the electric motor. The spindle nut expediently has an outer diameter that is smaller than in the area of the enlarged diameter, but larger than in the remaining area of the piston rod, so that the piston rod forms a stop for the spindle nut and thus holds it in the axial direction extending from the electric motor.

[0020] According to an advantageous development, the piston rod has a guide slot extending axially from the end faces facing the electric motor to form a rotationally fixed (torsion-resistant) seat for the spindle nut. A joining element, for example, molded onto the outer circumference of the spindle nut, is seated in this guide slot. This joining element preferably does not protrude above the piston rod during assembly. During initial assembly, the rotationally fixed seat of the spindle nut in the piston rod is thus achieved by simply pushing the two elements together.

[0021] Furthermore, for example, a locking ring is arranged on the end face of the spindle nut facing the electric motor, which prevents any adjustment of the spindle nut relative to the piston rod in the axial direction towards the electric motor. For this purpose, the piston rod has a receiving groove on its inside, i.e. the side facing the threaded spindle, in which the locking ring is received. The receiving groove is expediently arranged in a plane perpendicular to the axial direction. For example, in addition to the stop for the spindle nut, which is formed by the diameter expansion of the inner diameter of the piston rod, a second locking ring is arranged on the end face of the spindle nut there to prevent adjustment in the axial direction, whereby the locking ring there also serves as a fitting ring.

[0022] According to a particularly advantageous development, the piston rod and the spindle nut, which is particularly located therein, have aligned passages. When the piston rod is extended, these passages are radially aligned with the passage of the linear guide and thus with the filling opening.

[0023] The tubular refill element, which is housed in the filler opening and guided through the passage of the linear guide, enables the lubricant or operating fluid to be supplied to the threaded spindle and, particularly preferably, to the spindle nut. If the piston rod is extended to the position in which the passage of the linear guide is also aligned with the passages of the piston rod and the spindle nut, it is advantageously possible to guide the refill element to the passages. In this way, the lubricant or operating fluid can be supplied directly into the passages and thus directly to the threaded spindle using the tubular refill element. Furthermore, the lubricant or operating fluid can be supplied to the piston rod using the refill element in any extended state.For this purpose, the refill element is in particular at least partially introduced into the passage of the linear guide, whereby the refill element preferably does not protrude upwards towards the linear guide on the side facing the piston rod.

[0024] In summary, the refill element and the passages form a lubrication channel that is only temporarily formed during the supply of the lubricant or operating fluid, i.e., as long as the refill element is accommodated in the spindle drive. This advantageously creates a lubrication channel for supplying the lubricant or operating fluid to the corresponding components without requiring additional installation space for a permanent lubrication channel.

[0025] In a suitable refinement, the passage of the piston rod tapers toward the passage of the spindle nut. Preferably, the passage at the end opposite the spindle nut has a diameter that is larger than the diameter of the tubular refill element. This provides, in particular, a guide for the refill element when it is inserted into the spindle drive.

[0026] According to an advantageous development, the housing part forms a flat contact surface for the closure in the area of the filling opening. In this way, the closure, which in a particularly simple embodiment also has a flat contact surface (flange) on its side facing the housing part, can be arranged or is arranged on the housing part in such a way that the contact surfaces of the closure and the housing part run parallel to one another. This makes it easier to arrange the closure in a sealing manner on the housing part without the formation of unwanted gaps. Consequently, the accumulation of dirt particles or cleaning residues between the closure and the housing part is avoided, and the tightness of the closure is increased.

[0027] According to an expedient further development, the passage of the linear guide has a thread by means of which the closure or the refill element can be fastened, in particular screwed in.

[0028] For this purpose, the closure consists of a hygienic screw and a (hygienic) seal arranged between it and the housing part. A hygienic screw is defined as a screw suitable for use in the food industry. In particular, the hygienic screw has a comparatively low surface roughness, preventing dirt particles from adhering to it. Furthermore, the hygienic screw has no indentation, recess, or serration, which also prevents the accumulation of dirt particles.

[0029] According to an advantageous development, a motor housing part comprising the electric motor has, in particular for improved heat dissipation, the largest possible surface on its outer side facing away from the electric motor. This aspect represents an independent invention. Such an electromotive spindle drive, which is intended and configured in particular for use in a beverage machine, then has an electric motor with a rotor which drives a threaded spindle in rotation, and a spindle nut which are rigidly connected to a piston rod arranged coaxially to the threaded spindle, and wherein the spindle nut and the piston rod are guided linearly in the axial direction in a housing part which comprises the piston rod and the spindle nut. In this case, a motor housing part, in particular on its outer side (the electric motor orThe outer side (i.e., the outer side facing away from the rotor and stator) has a housing structure that enlarges the housing surface of this motor housing part. Preferably, the design guidelines and standards for use in the food industry (hygienic design) with regard to the motor housing part are adhered to. The motor housing encompasses (encloses) in particular the stator and rotor of the electric motor.

[0030] The motor housing part is preferably designed as a separate component; alternatively, it is designed as a single piece and connected to the housing part. It is expediently designed to be cylindrical, with the motor housing part preferably having a wave shape on its outer side. In other words, a thickness of the wall of the motor housing part, i.e. the difference between its outer and inner diameter or radius, is not constant. In particular, the thickness changes periodically along the axial direction to form the wave shape. The wave shape can also extend in the radial direction or obliquely over the housing circumference, for example in a spiral or screw or thread-like manner. The wave shape is preferably designed such that an average thickness of the wall of the motor housing part is as small as possible.

[0031] In addition, the motor housing part is formed, for example, from a corrosion-resistant material, such as stainless steel. Due to the enlarged surface area and the comparatively small average thickness—especially given the comparatively low heat dissipation due to the material—heat dissipation by convection and heat radiation from the motor housing part are advantageously improved, particularly compared to a smooth, featureless cylinder surface. Furthermore, the surface area of the motor housing part is preferably enlarged in such a way that, in particular, an accumulation of dirt particles is avoided. For example, there is no undercut on the outside of the motor housing part. Furthermore, the visual appearance of the spindle drive is improved.

[0032] According to an advantageous development, the threaded spindle is supported on the piston rod by means of a plain bearing. This aspect also represents an independent invention. Here, the electromotive spindle drive, which is intended and configured in particular for use in a beverage machine, comprises an electric motor with a rotor that rotatably drives a threaded spindle, and a spindle nut that is rigidly connected to a piston rod arranged coaxially to the threaded spindle and engages with the threaded spindle. A plain bearing bush is arranged on the inner circumference of the piston rod to guide a sliding body, forming a plain bearing. The sliding body is suitably fastened to a pin arranged on the end face of the threaded spindle facing away from the electric motor. In other words, the plain bearing bush is tubular and oriented coaxially to the threaded spindle.

[0033] To secure the sliding body, which is particularly hollow-cylindrical in shape, the threaded spindle has, for example, a pin in the corresponding end region, which extends in the axial direction and is / is encompassed by the sliding body. The sliding body is preferably made of a comparatively hard and wear-resistant material, for example, a thermoplastic with properties suitable for operation.

[0034] In this way, the threaded spindle, especially in its comparatively long version, is supported in the radial direction. In other words, operational radial forces acting on the threaded spindle are supported by the plain bearing bushing and the sliding body. Advantageously, a plain bearing formed in this way is cost-effective, low-maintenance, and low-wear, particularly compared to a rolling bearing or a combination of plain and rolling bearings, thus extending the service life of the bearing. Furthermore, such a plain bearing is advantageously comparatively quiet.

[0035] The advantages achieved by the invention are, in particular, that, due to the design of the closure in the form described above, the filling opening is sealed so tightly that the spindle drive can be used in the food industry in compliance with the required standards and regulations. Another advantage is that the refill element allows the lubricant or operating fluid to be supplied directly and precisely to the threaded spindle and / or the piston rod.

[0036] An embodiment of the invention is explained in more detail below with reference to a drawing. In the drawings: Fig. 1 in a perspective sectional view along the longitudinal axis of a spindle drive, which has a threaded spindle driven in rotation by a rotor of an electric motor and a spindle nut engaged therewith and supported against rotation, wherein a piston rod is connected to the spindle nut, Fig. 2 in perspective view a linear guide with an opening for a guide element attached to the piston rod for linear guidance of the spindle nut and the piston rod along an axial direction, Fig. 3 in an exploded view the piston rod and the spindle nut seated in it as well as two retaining rings which hold the spindle nut against axial displacement, Fig. 4 shows a partial longitudinal section of the spindle drive in the extended state, with a filling opening in a housing part in which a refilling element is accommodated, wherein the refilling element is guided through a passage of the linear guide to a passage of the piston rod, and Fig. 5 shows a partial longitudinal section of a spindle nut pin with a circumferential sliding body, which forms a plain bearing with plain bearing bushes arranged on the inner circumference of the piston rod.

[0037] Corresponding parts are provided with the same reference numerals in all figures.

[0038] Fig. 1 shows a spindle drive 2. This comprises an electric motor 4 with a stator 6 and a rotor 8. The rotor 8 drives a threaded spindle 10 by means of a rotor shaft 12 connected to the spindle. The threaded spindle 10 is rotatably mounted on the motor side by means of a bearing 14, which, according to this embodiment, is designed as an axial angular contact ball bearing.

[0039] A spindle nut 16 is engaged with the threaded spindle 10. In particular, an internal thread of the spindle nut 16 (not shown here) engages with an external thread 18 of the threaded spindle 10. The spindle nut 16 is supported against rotation by means of a guide element 20 and a tubular linear guide 22 surrounding the piston rod ( Fig. 2 and Fig. 3), so that when the threaded spindle 10 rotates, the spindle nut 16 is adjusted (moved) linearly along a (longitudinal) axial direction A of the threaded spindle 10. A tubular piston rod 24, which is arranged coaxially to the threaded spindle 10, is rigidly connected to the spindle nut 16, i.e., rotationally and displacement-proof with respect to the spindle nut, so that the piston rod 24 is moved when the spindle nut 16 is adjusted. A piston head 26 is attached to the end face of the piston rod 24 facing away from the electric motor 4, in particular screwed in according to this exemplary embodiment, in which piston head 26, for example, a further tool for pressing a crown cap onto a bottle when the spindle drive 2 is used in a beverage machine.

[0040] In particular to avoid friction losses and to distribute the heat generated due to friction, a lubricant such as oil is provided and introduced into the interior of the spindle drive 2 which accommodates the threaded spindle 10 and is closed off circumferentially by means of a housing part 28.

[0041] The piston rod 24 has a lubricant bore 30 extending in the axial direction A and a radial bore 32 connected to the latter and arranged on the motor side of the spindle nut 16, through which air and / or a lubricant or operating medium can flow, in particular to prevent overpressure during an adjustment movement. Furthermore, the housing part 28 is arranged coaxially and spaced from the linear guide 22, wherein the space 34 formed between the linear guide 22 and the housing part 28 is also connected to the space 38 surrounding the threaded spindle 10 via an opening 36 in the linear guide 22 for pressure equalization.

[0042] The housing part 28 has a filling opening 40 for the lubricant or operating fluid. According to the Fig. 1, a closure 42 formed from a hygienic screw 42a and a corresponding seal 42b is accommodated in the filling opening 40 for tightly closing the filling opening 40, but this is, as in Fig. 4, is also provided and arranged to receive a tubular refill element 44 for operating fluids or lubricants.

[0043] The housing part 28 has a flat contact surface 28a in an area associated with the filling opening 40, so that the hygiene screw 42 together with the associated seal 42b tightly closes the filling opening 40 without forming cavities (dead spaces).

[0044] Furthermore, in the end region of the linear guide 22 facing away from the electric motor 4, a guide ring 46 designed as a plain bearing bush is arranged between the linear guide 22 and the piston rod 24. Furthermore, a removable wiper ring 48 for a wiper 50 is seated on the end face of the linear guide 22 facing away from the electric motor 4, so that the interior of the threaded spindle is sealed from the outside. In an alternative embodiment not shown in detail, instead of the wiper ring 48, another plain bearing bush is arranged between the linear guide 22 and the piston rod 24, which then acts as a wiper 50.

[0045] Furthermore, the electric motor 4 of the spindle drive 2 is enclosed by a motor housing part 51. This has a comparatively large surface on its outer side facing away from the electric motor 4, i.e. a surface that is larger than a smooth surface (cylindrical surface). For this purpose, the motor housing part 51 has a wave shape with wave crests 51a and wave troughs 51b as a surface-enlarging structure (structural elements). In this case, a thickness of the wall of the motor housing part 51 - and thus also the diameter of the motor housing part 51 - changes, forming the wave shape along the axial direction A. Such a wave shape or wave structure 51a, 51b with wave crests 51a and wave troughs 51b can also extend in the radial direction on the surface of the motor housing part 51.A wave structure with wave crests and wave troughs running obliquely over the outer circumference of the housing part 51, for example a thread-like or helical surface structure, is also conceivable.

[0046] The average wall thickness of motor housing part 51 is less than the wall thickness of housing part 28. This improves heat dissipation from the electric motor 4 to the surroundings of spindle drive 4, particularly by means of convection and heat radiation, so that the temperature of electric motor 4 remains comparatively low during operation. The motor housing part 51 configured in this way particularly satisfies the structural regulations and standards of hygienic design for the use of spindle drive 2 in the food industry. Furthermore, an (O-ring) sealing ring 52 is arranged between housing part 28 and motor housing part 51.

[0047] Fig. Figure 2 shows a perspective view of the linear guide 22, which is arranged coaxially to the piston rod 24 and is tubular in shape. This guide has the opening 36, which extends along the axial direction A and is designed as an elongated hole. In the assembled state ( Fig. 1 and Fig. 4), the guide element 20 is seated in the opening 36 in a linearly displaceable manner. The guide element 20 is screwed to the piston rod 24, so that the piston rod and the spindle nut 16 attached thereto are guided along the direction of extension of the opening 36, i.e., linearly along the axial direction A.

[0048] Furthermore, a passage 53 is arranged in the linear guide 22 with respect to the axial direction A between the opening 36 and a stop 54 for the housing part 28 arranged in the end region of the linear guide 22 facing away from the electric motor 4. In the assembled state, this is aligned with the filling opening 40 of the housing part 28 with respect to a radial direction R running perpendicular to the axial direction A. The passage 53 has a thread, not shown for the purpose of improved clarity, in order to secure the closure 42 ( Fig. 1) or the refill element 44 ( Fig. 4) Securely fasten by screwing or twisting.

[0049] In Fig. 3 shows an exploded view of the piston rod 24 and the spindle nut 16 which is rigidly connected to it, i.e. rotationally fixed and non-displaceable in the axial direction A. For the rotationally fixed connection, the piston rod 24 has a guide slot 56 extending from the end face facing the electric motor 4 along the axial direction A. According to the design of the Fig. 3, this is arranged on the side of the piston rod 24, which is circumferentially opposite a receptacle 58 for a screw element for fastening the guide element 20. During initial assembly, when the spindle nut 16 is inserted into the guide slot 56 of the piston rod 24, a joining element 60 arranged on the outer circumference of the spindle nut 16 is received and guided, so that in the assembled state it sits in the guide slot 56 and thus supports the spindle nut 16 against rotation against the piston rod 24. In the assembled state, the spindle nut 16 sits on the end face of the piston rod 24 facing the electric motor 4, wherein the spindle nut 16 additionally has an enlarged inner diameter in the area of the spindle nut 16 ( Fig. 1). As a result of the diameter expansion, the spindle nut 16 is already secured in the assembled state against displacement in the axial direction A away from the electric motor 4. Furthermore, a retaining ring 62 is arranged on each of the two axial end faces of the spindle nut 16. The retaining ring 62 arranged on the end face of the spindle nut 16 facing the electric motor 4 sits in a receiving groove 66 arranged on the inner side 64 of the piston rod 24. The spindle nut is thus secured against displacement in the axial direction A.

[0050] Fig. 4 shows the spindle drive 2 in the extended state. The piston rod 24 and the spindle nut 16 each have a passage 68 and 70, respectively, which are aligned with one another in the radial direction R. In the extended state of the piston rod 24, the aligned passages 68 and 70 are positioned such that they, in turn, are aligned with the passage 53 of the linear guide 22 and with the filler opening 40 in the radial direction R. In this way, the refill element 44 can be guided through the filler opening 40 and through the passage 53 to the passage 68. The lubricant or operating fluid to be supplied can thus be fed by means of the refill element 44 through the two passages 68 and 70 directly to the threaded spindle 10 and to the spindle nut 16. In addition, the passage 68 of the piston rod 24 tapers towards the passage 70 of the spindle nut 16.In this way, a simple guide for the refill element 44 is provided during its insertion into the spindle drive 2.

[0051] Alternatively, the lubricant or operating fluid can also be fed in the non-extended state through the filling opening 40 directly into the space 34 outside the linear guide 22 or by means of the refill element 44 of the piston rod 24 into the space between the latter and the linear guide 22.

[0052] In addition, the refill element 44 has a grease nipple 72 at the end to facilitate the supply of the lubricant or operating fluid.

[0053] Fig.5 shows, on an enlarged scale, a section of the spindle drive 2. The threaded spindle 10 has, on its end face facing away from the electric motor 4, an annular pin 74 which, according to this exemplary embodiment, is integrally formed with the threaded spindle 10 and through which the lubricant bore 30 extends in the axial direction A. A sliding body 76 is arranged on the outer circumference of the pin 74. The sliding body 76 supports the threaded spindle 10 in the radial direction R against the plain bearing bushes 78 arranged on the inner circumference of the piston rod 24. These extend with respect to the axial direction A from the piston head 26 to the spindle nut 16, so that the sliding body 76, together with the plain bearing bushes 78, forms a plain bearing which supports the threaded spindle 10.According to this embodiment, several plain bearing bushes are arranged adjacent to one another in the axial direction 78, but according to an embodiment not shown in detail, a single plain bearing bush 78 is arranged on the inner circumference of the piston rod 24.

[0054] The pin 74 of the threaded spindle 10 has a diameter which is smaller than the diameter of the area of the threaded spindle 10 provided with the external thread 18. In this way, a stop 80 is formed to prevent its adjustment in the axial direction A. The sliding body 76 has an outer circumference which is larger than the outer circumference of the threaded spindle 10, so that the threaded spindle 10 is supported on the output side of the electric motor 4 only by means of the plain bearing, the spindle nut 16 and the bearings 14. Furthermore, the pin 74 of the threaded spindle 10 has a groove 82 on its circumference at the end facing away from the electric motor 4, in which groove a retaining ring 84 for the sliding body 76 is received. In addition, a fitting ring 86 is seated between the retaining ring 84 and the sliding body 76.

[0055] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention.

[0056] In particular, the spindle drive 2 with a motor housing part 51 with an enlarged surface represents an independent invention. The electromotive spindle drive 2, which is intended and configured in particular for use in a beverage machine, has an electric motor 4 with a rotor 8, which drives a threaded spindle 10 in rotation, and a spindle nut 16, which are rigidly connected to a piston rod 24 arranged coaxially to the threaded spindle 10, wherein the spindle nut 16 and the piston rod 24 are guided linearly in the axial direction A in a housing part 28, which comprises the piston rod 24 and the spindle nut 26, and wherein a motor housing part 51 comprising the electric motor 4 has a surface structure on its outer side (facing away from the electric motor 4) which enlarges the housing surface.Design guidelines and standards for use in the food industry (hygienic design) are complied with with regard to the motor housing part 51.

[0057] Furthermore, the spindle drive 2 with a plain bearing between the piston rod 24 and the pin 74 of the threaded spindle 10 represents a further independent invention. The electromotive spindle drive 2, which is intended and configured in particular for use in a beverage machine, has an electric motor 4 with a rotor 8, which drives a threaded spindle 10 in rotation, and a spindle nut 16, which is rigidly connected to a piston rod 24 arranged coaxially to the threaded spindle 10 and is in engagement with the threaded spindle 10, wherein a plain bearing bush 78 is arranged on the inner circumference of the piston rod 24 for guiding a sliding body 76 to form a plain bearing, which sliding body 76 is fastened to a pin 74 arranged on the end face of the threaded spindle 10 facing away from the electric motor 4. List of reference symbols 2 spindle drive 4 electric motor 6 Stator 8 Rotor 10 threaded spindle 12 Rotor shaft 14 camps 16 spindle nut 18 external threads 20 guide element 22 Linear guide 24 Piston rod 26 Piston head 28 Housing part 28a contact surface 30 Lubrication hole 32 radial bore 34 Space outside the linear guide 36 Opening of the linear guide 38 spatial area encompassing the threaded spindle 40 Filling opening 42 closure 42a Hygiene screw 42b Seal 44 Refill element 46 Guide ring 48 scraper ring 50 scrapers 51 Engine housing part 51a Wave structure / wave crest 51b Wave structure / wave trough 52 Sealing ring 53 Implementation 54 Appendix 56 guide slot 58 recording 60 joining element 62 retaining ring 64 Inside of the piston rod 66 mounting groove 68 Passage of the piston rod 70 Passage of the spindle nut 72 grease nipples 74 cones 76 sliding bodies 78 plain bearing bush 80 stops 82 groove 84 Retaining ring for the sliding body 86 fitting ring A axial direction R Radial direction

Claims

[1] Electromotive spindle drive (2), in particular for use in a beverage machine, comprising - an electric motor (4) with a rotor (8) which drives a threaded spindle (10) in rotation, - a spindle nut (16) which is rigidly connected to a piston rod (24) arranged coaxially to the threaded spindle (10) and which is in engagement with the threaded spindle (10), - a housing part (28) in which the spindle nut (16) and the piston rod (24) are guided linearly in the axial direction (A) by means of a guide element (20), characterized by - a linear guide (22) for the guide element (20) arranged in the housing part (28) coaxially to the piston rod (24) and separate from the housing part (28), and - a passage (53) arranged in the linear guide (22) which is aligned in the radial direction (R) with a filling opening (40) provided in the housing part (28) for an operating medium or lubricant, wherein the filling opening (40) is provided and designed both to receive a closure (42) for tightly closing it and to receive a tubular refill element (44) for supplying the operating medium or lubricant, in particular to the piston rod (24), to the threaded spindle (10) and / or to the spindle nut (16). [2] Spindle drive (2) according to claim 1, characterized by that the linear guide (22) is tubular and has an opening (36) in which the guide element (20) is seated in a linearly displaceable manner and which extends in the axial direction (A). [3] Spindle drive (2) according to claim 1 or 2, characterized by that the guide element (20) is rigidly attached, in particular screwed, to the piston rod (24). [4] Spindle drive (2) according to one of claims 1 to 3, characterized by that the piston rod (24) is tubular, wherein the piston rod (24) has an enlarged diameter of its inner diameter in the region of the spindle nut (16), wherein the spindle nut (16) is seated on the end face of the piston rod (24) facing the electric motor (4). [5] Spindle drive (2) according to claim 4, characterized by that the piston rod (24) has a guide slot (56) extending in the axial direction (A) from its end face facing the electric motor (4) for a joining element (60) arranged on the outer circumference of the spindle nut (16) for the rotationally fixed seating of the spindle nut (16) in the piston rod (24). [6] Spindle drive (2) according to one of claims 1 to 5, characterized by that the piston rod (24) and the spindle nut (16) have passages (68, 70) that are aligned with one another. [7] Spindle drive (2) according to claim 6, characterized bythat the mutually aligned passages (68, 70) of the piston rod (24) and the spindle nut (16) seated therein are aligned with the passage (53) of the linear guide (22) in an extended state of the piston rod (24) in the radial direction (R). [8] Spindle drive (2) according to claim 6 or 7, characterized by that the passage (68) of the piston rod (24) has a taper towards the passage (70) of the spindle nut (16). [9] Spindle drive (2) according to one of claims 1 to 8, characterized by that the housing part (28) forms a flat contact surface (28a) for the closure (42) in the area of the filling opening (40). [10] Spindle drive (2) according to one of claims 1 to 9, characterized by that the passage (53) of the linear guide (22) has a thread for fastening the closure (42) or the refill element (44). [11] Spindle drive (2) according to one of claims 1 to 10, characterized bythat the closure (42) is formed from a hygienic screw (42a) and a corresponding seal (42b). [12] Spindle drive (2) according to one of claims 1 to 11, characterized by , - that a motor housing part (51) comprising the electric motor (4) has, on its outer side facing away from the electric motor (4), a surface-enlarging structure (51a, 51b), in particular an axial, radial or circumferentially inclined wave structure, and / or - that design guidelines and standards for use in the food sector are observed. [13] Spindle drive (2) according to one of claims 1 to 12, characterized by , - that a plain bearing bush (78) for guiding a sliding body (76) is arranged on the inner circumference of the piston rod (24) to form a plain bearing,

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