Beater with linear drive

Abstract

The invention relates to a hammer (10) and a method for operating a hammer (10). The hammer comprises a housing (12), a striking piston (26) linearly movable along an axis (a) in the housing (12), and a spring element (30) that can be pre-tensioned along the axis in a pre-tension direction and that is supported on one side against the housing (12) and on the other side against the striking piston (26). The hammer also comprises a coupling element (28) that can be connected to the striking piston (26) by frictional or positive locking and is linearly movable in the housing (12), and a linear drive that drives the coupling element (28) along the axis (a), wherein the coupling element (28) is configured to release the striking piston (26) when a pre-tension threshold is exceeded.

Description

[0001] The invention relates to a knocker comprising a housing, a percussion piston that is linearly movable along an axis in the housing, and a spring element that can be preloaded along the axis in a preload direction and that is supported on one side against the housing and on the other side against the percussion piston. The invention further relates to a method for operating such a knocker.

[0002] Such knockers have long been known as pneumatic knockers, which are used, for example, to knock off materials or substances adhering to the wall of a container. The housing of such a pneumatic knocker forms a pneumatic cylinder in which the impact piston moves up and down in a pressure-tight manner. The compressed air is controlled in such a way that the pressure chamber located on the underside of the impact piston opposite the spring element is initially pressurized, moving the impact piston upwards and compressing the spring element in the preload direction. When a defined position is reached, a valve switches so that pressure is equalized between the pressure chamber on the underside of the piston and the spring chamber on the top of the piston. The energy stored in the spring element is then released and the spring element accelerates the impact piston downwards until it hits a base plate of the housing.

[0003] Such impactors have the disadvantage of requiring compressed air or another gaseous or vaporous medium. However, this isn't available everywhere. A separate compressor is often required to operate the impactor. The same applies to the medium supply line to the compressor.

[0004] The object of the invention is therefore to provide a knocker which can be operated more flexibly and with the same efficiency as the known compressed air-operated knockers.

[0005] The object is achieved in a knocker of the type mentioned at the outset in that it further comprises a coupling element which can be connected to the percussion piston in a force-locking or form-locking manner and which is linearly movable in the housing, and a linear drive which drives the coupling element along the axis, wherein the coupling element is designed to release the percussion piston when a preload threshold is exceeded.

[0006] The "preload threshold" refers herein to a state of maximum preload, beyond which the energy stored in the spring element is released, i.e., converted into kinetic energy of the piston. The implementation of the teachings of the invention does not necessarily require that this preload threshold be recorded or known as a physical threshold value. "Exceeding the preload threshold" can be achieved both by actually exceeding a certain force and by passing a predetermined axial position, with which a defined preload force correlates due to the defined compression of the spring element.

[0007] A novel feature of the impactor according to the invention is the coupling element, which is designed to form a force-locking or form-locking connection with the impact piston, which can be automatically released when the preload threshold is exceeded. Due to the force-locking or form-locking connection, the coupling element entrains the impact piston in the housing during its linear movement in the preload direction, thereby preloading the spring element. If the defined preload threshold is exceeded, the force-locking or form-locking connection is overcome or canceled, and the coupling element releases the impact piston, whereupon it is accelerated by the spring element in the usual way and executes a striking movement.

[0008] According to a first advantageous operating principle of the invention, the spring element, on the one hand, and the frictional connection existing between the percussion piston and the coupling element, on the other hand, are dimensioned such that the preload of the spring element exceeds the frictional connection when the preload threshold is exceeded. From the moment the force equilibrium is reached between the spring force applied by the compressed spring element, on the one hand, and the maximum holding force between the percussion piston and the coupling element, and the coupling element is moved further in the preload direction, the percussion piston is released from the coupling element and accelerated by the spring element until the percussion piston impacts, for example, a striking plate of the housing, in a manner known per se.

[0009] Preferably, the coupling element and the percussion piston are connectable to one another by means of a magnetic holding force. This can be achieved either by the coupling element comprising a permanent magnet and the percussion piston being magnetizable, or conversely, by the percussion piston comprising a permanent magnet and the coupling element being magnetizable. The former configuration is preferred in order to prevent the permanent magnet from being subjected to strong vibration during impact, i.e., when the percussion piston strikes the impact plate.

[0010] According to an alternative preferred embodiment of a magnetic force connection, the coupling element comprises at least one electromagnet, wherein the percussion piston is in turn magnetizable. This embodiment can also be designed to fulfill the first advantageous operating principle by dimensioning the maximum holding force of the electromagnet, on the one hand, and the spring element, on the other, such that the preload of the spring element, when the maximum holding force (preload threshold) is exceeded, detaches the percussion piston from the coupling element and accelerates it toward the impact plate.

[0011] The use of an electromagnet also offers the possibility of dimensioning the electromagnet more powerfully and switching it off when the preload threshold is exceeded, thus triggering the percussion piston. In this way, the preload threshold and thus also the percussion pulse can be easily set or selected in terms of control technology. In the case of this second advantageous operating principle of the invention, the knocker preferably has a sensor unit which is configured to detect when the preload threshold is exceeded and to trigger a switching signal to switch off the electromagnet. Exceeding the preload threshold can be detected, for example, by the sensor unit monitoring the passage of the coupling element or the piston at a predetermined axial position in the housing.Alternatively, the sensor unit can monitor the force stored in the spring element or required to move the coupling element and the piston, for example by measuring the power consumption of the linear actuator.

[0012] A third advantageous operating principle of the invention provides an embodiment in which the coupling between the coupling element and the percussion piston is not realized by force connection, but by form connection. To create the form connection, a release device is preferably provided, which detachably connects the coupling element and the percussion piston. Furthermore, an actuating element is preferably provided, which is designed to actuate the release device when the preload threshold is exceeded and thereby cancel the form connection. This can be achieved, for example, in that the release device arranged on the coupling element comprises a pawl, which engages with the percussion piston and entrains it during movement in the preload direction and which is position-controlled, iein a certain axial position, is disengaged by means of the actuating element, for example in the form of a cam, thereby releasing the impact piston, which in turn is accelerated towards the impact plate by the spring element.

[0013] The linear drive preferably comprises an electric motor. In contrast to the pneumatic knockers mentioned above, the knocker according to the invention requires an electric motor control and an electrical power supply and is not dependent on compressed air as an operating medium. The availability of electrical power is not a problem in most situations, which is why its use is more flexible and cost-effective compared to pneumatically driven knockers. The motor control is preferably a separate element of the knocker, protected from the vibrations caused by the striking movement. A further advantage of such an electric-driven knocker is its significantly higher efficiency compared to a pneumatic knocker, which always requires an upstream unit to generate pressure.

[0014] The linear drive particularly preferably comprises a stepper motor. This allows precise position determination of the drive, and thus also of the coupling element and the impact piston, even during movement without the use of additional sensors. As an alternative to a stepper motor, a spindle position sensor can also be used in conjunction with any motor.

[0015] The linear drive is preferably implemented by a threaded spindle arranged axially parallel and particularly preferably coaxially to the center axis of the percussion piston, which, together with the coupling element, forms a helical gear. In this case, the coupling element can also be referred to as a spindle nut, which is threaded onto the spindle and is itself prevented from rotating, thus allowing it to be driven into a linear movement along the axis when the spindle rotates.

[0016] Furthermore, the housing preferably has a peripheral wall extending in the direction of the axis, a base plate, and an upper part, wherein the peripheral wall, the base plate, and the upper part define an interior space in which the percussion piston is arranged facing the base plate, the coupling element in the center, and the spring element is arranged facing the upper part. The spring element extends from the upper part through recesses, openings, or bores in the coupling element to the percussion piston, and the preload direction is directed toward the upper part. This arrangement can be cylindrical in shape, similar to known pneumatic knockers. In contrast to pneumatically driven pistons, the percussion piston does not necessarily have to be sealed against the peripheral wall because the interior space and the percussion piston are not part of a pneumatic drive, but rather the movement is mediated by means of the linear drive via the coupling element.The base plate preferably forms the striking plate, in which cases the two terms are used synonymously.

[0017] In this embodiment, the electric motor is preferably arranged outside the interior on the upper part, which has a rotary feedthrough. The rotary motion is transmitted through the rotary feedthrough to the linear drive, which preferably comprises the aforementioned threaded spindle.

[0018] Particularly preferably, the threaded spindle is guided through the rotary union into the interior and supported against the upper part by an axial bearing. The torque transmission from the electric motor's rotating shaft to the threaded spindle thus takes place outside the housing. The electric motor can therefore be installed or replaced without opening the impactor housing.

[0019] In particular, it has proven preferable to arrange a damping element between the electric motor and the upper part. This ensures that the bearing elements and the electrical components of the electric motor, such as windings, are protected from excessive vibration, thus increasing the service life of the motor.

[0020] In a preferred embodiment, a stop element is arranged on the housing, which contacts the percussion piston when the preload threshold is reached. In particular, the stop element can be formed as an element extending from the upper part toward the percussion piston, counter to the preload direction, or as a projection directed radially inward from the peripheral wall.

[0021] In the case of this fourth advantageous operating principle, the preload threshold is not determined by a force balance between the spring force on the one hand and the frictional connection between the coupling element and the impact piston on the other, but by the position in which the impact piston, raised against the upper housing section, hits the stop element. The maximum holding force can particularly exceed the spring force when the preload threshold is reached. In other words, the stop element defines the preload threshold. This means that the maximum stroke movement of the piston is always clearly defined. The spring travel and the stored spring energy upon contact between the impact piston and the stop element are not dependent on any material- or manufacturing-related fluctuations in the magnetic holding force, but are always determined by the end position of the piston in which it contacts the stop element.If the coupling element is then moved further in the preload direction, the impact piston is released from the coupling element, as in the case of the first operating principle, overcoming the frictional connection and accelerated towards the base plate by means of the spring element.

[0022] The spring element preferably comprises at least one compression spring. Particularly preferably, several compression springs are arranged rotationally symmetrically around the linear drive to ensure uniform force application and prevent jamming of the piston and / or the coupling element in the housing. In this case, the stop element is particularly preferably designed as a guide element for the compression spring(s). It is most preferably designed as a spring mandrel that projects into the compression spring. This enables a very compact design while simultaneously effectively guiding the spring. When the preload threshold is exceeded, the spring mandrel, together with the compressed spring(s), projects from the upper part through the recesses, openings, or bores in the coupling element to the impact piston.

[0023] An anti-rotation device is advantageously provided between the peripheral wall of the housing and the coupling element. This can be designed such that a projection is formed on the coupling element, which engages in a complementary, axially extending groove in the peripheral wall. Conversely, an axially extending, radially inward-facing rib can also be provided along the peripheral wall, which engages in a complementary groove in the coupling element. The groove can then also be partially or continuously continued in the percussion piston. Depending on the geometric conditions, the rib can also simultaneously serve as a stop element.

[0024] Furthermore, the base plate and the upper part are preferably sealed against the peripheral wall. This prevents dust and moisture from penetrating the interior of the housing and increases the service life of the impactor.

[0025] The object is also achieved by a method for operating a knocker of the type described above, in which the percussion piston is moved in the preload direction by means of the coupling element which is connected to it in a force-fitting or form-fitting manner and is driven linearly along the axis, under preload of the spring element, until the coupling element releases the percussion piston when a preload threshold is exceeded and the percussion piston is accelerated against the preload direction, at least partially releasing the energy stored in the spring element.

[0026] Further embodiments and advantages of the invention are explained below with reference to the figures. They show: Figure 1 shows a side view of the knocker according to the invention with electric drive; Figure 2 shows a longitudinal section through the knocker according to Figure 1 along the section plane BB; Figure 3 a cross section through the knocker according to Figure 1along the plane AA; Figure 4 a second longitudinal section through the knocker according to Figure 1 along the plane CC and Figure 5the knocker in the view of the Figure 2 when the preload threshold is reached.

[0027] The Figures 1 - 5 always show the same embodiment of the knocker according to the invention in different representations. The knocker 10 has a housing 12 extending along an axis a and, flanged to the upper side thereof, an electric motor 14 as part of the linear drive. The housing 12 is formed by a peripheral wall 16, a base plate 18, and an upper part 20. The electric motor 14 is connected to the upper part 20 via a damping element 22 located therebetween.

[0028] The housing 12 defines an interior space 24. Arranged in this interior space 24 from bottom to top, i.e., from the base plate 18 to the upper part 20, in the following order are a percussion piston 26, a coupling element 28, and a spring element 30. Specifically, the spring element 30 consists of three compression springs 31, which are arranged rotationally symmetrically about the axis a. The compression springs 31 are each centered on the underside in a pocket or counterbore 32 formed in the percussion piston 26. Three through-bores 33, through which the compression springs 30 extend, are provided in the coupling element 28 with appropriate spacing.

[0029] On their upper side, the compression springs 30 are centered internally by means of a spring pin 34. Each centering pin 34 is connected to the upper part 20, so that the compression springs 30 each extend between the impact piston 26 and the upper part 20. In the Figures 2 and 4In the operating position shown, the percussion piston 20 is in its lower position, in which it rests on the base or percussion plate 18. In this position, the compression springs 31 are already under a preload, which holds the piston 20 down on the base plate 18.

[0030] In the coupling element 28, three permanent magnets 36 are pressed into a tight fit, either screwed in or glued in, also rotationally symmetrical about the axis a and angularly offset from the through-holes 33. Accordingly, the through-holes 33 and the permanent magnets 36 alternate in the circumferential direction of the coupling element 28, as shown in Figure 3can be seen. The rotational symmetry ensures that both the magnetic force connecting the coupling element and the magnetizable percussion piston 26, as well as the spring force with which the three compression springs 31 press onto the percussion piston 26 from above, act symmetrically around the axis a on the percussion piston 26. If, as shown here, the axis a coincides with the center axis of the percussion piston, which runs through its center of gravity, tilting moments are avoided as best as possible, and wear on the arrangement is minimized.

[0031] The percussion piston has two guide or sliding rings 37 circumferentially embedded in grooves, which slide up and down along the inside of the peripheral wall 16. These reduce friction and wear between the percussion piston 26 and the peripheral wall 16.

[0032] As part of the linear drive, the knocker 10 has a threaded spindle 38 parallel to and central to the axis a, which engages the coupling element 28 via a complementary internal thread. The threaded spindle 38 and the coupling element 28 form a screw thread. On the upper side, the threaded spindle 38 is guided through a rotary union 40 in the upper part 20 into the interior space 24 and is supported against the upper part 20 by means of an axial bearing 42 against the tensile forces exerted on the threaded spindle 38 by the compression springs 31.

[0033] The electric motor 14 has on its underside a drive shaft 44 which is received in a complementary receptacle 45 in the upper section of the threaded spindle 38 for transmitting torque.

[0034] Both the upper part 20 and the base plate 18 are sealed against the peripheral wall 16 of the housing 12 by means of sealing rings 46 and 47, for example, to make them dust-tight and / or to prevent moisture from penetrating the interior 24. It should be noted at this point that the peripheral wall 16 continues at its lower end with a flange 48, which in this sense is considered part of the peripheral wall. The flange 48 also has another function. Mounting screws 50 extend through it, by means of which the knocker 10 can be attached, for example, to a container to be emptied. To protect the screw connection and the entire housing, the mounting screws 50 are each supported against the flange 48 by means of spring assemblies 52. The flange can, for example, be formed integrally or by means of a material fit onto the cylindrical part of the peripheral wall.Alternatively, the flange 48 can also be a separate component of the peripheral wall and be tightly connected to the cylindrical part of the peripheral wall by means of a further seal (not shown).

[0035] The peripheral wall 16 is formed by a profile tube having a substantially circular inner circumference and four radially projecting ribs 53 extending axially on its outer surface. These ribs, in turn, have axially extending through-bores 54 into which threads are cut from the top and bottom surfaces. These threads serve to screw the upper part 20 and the flange 48 to the peripheral wall 16 by means of screws 55. The profile tube of the peripheral wall can be purchased inexpensively as a commercially available extruded profile.

[0036] On the inner side of the peripheral wall 16, two axially extending grooves 56 with a circular segment-shaped profile are provided, which are designed to receive corresponding guide projections 58 on the coupling element 28. The connection between the guide projections 58 and the grooves 56 creates a positive fit between the coupling element 28 and the housing 12, which secures the coupling element 28 against rotation, so that the coupling element 28 has only one degree of freedom of movement and moves up and down in a defined manner along the axis a upon rotation of the threaded spindle 38.

[0037] The percussion piston 26 shown here has a central through-bore for the threaded spindle 38 and, on its underside, a larger counterbore 62 offset from this. The counterbore naturally serves the same function as the through-bore: to create space for the spindle. At the same time, it also serves to save mass. In this way, percussion pistons of the same axial height with different masses can be produced from the same material, allowing different percussion pulses to be generated in the same housing using the same linear drive and the same spring elements.

[0038] The working process of the knocker 10 according to the invention is described below: In the Figures 2 and 4In the initial position shown, the percussion piston 28 is at the lower end of its stroke in contact with the base plate or percussion plate 18. At the same time, the coupling element 28 is also in the lower position, in which it rests directly on the percussion piston 26. The percussion piston is magnetizable, which is why in this position a frictional connection is established between the coupling element 28 and the percussion piston 26 by means of the permanent magnets 36 located in the coupling element 28. The spring element 30 or the compression springs 31 have their maximum axial extension in this so-called rest position, wherein they are slightly preloaded between the spring mandrel 34 and the bottom of the pockets 32 in the percussion piston 26.

[0039] In response to a control signal, the electric motor 14 rotates the threaded spindle 38. This rotation is translated into a lifting movement of the coupling element 28 together with the impact piston 26 in the preload direction 60. As the preload of the spring element 30 increases, the piston is thus raised further.

[0040] In Figure 5the percussion piston 26 has reached its upper end position. In this position, the spring mandrels 34 rest with their lower end surface 35 on the bottom of the counterbores 32 in the percussion piston 26 and form a stop element that prevents it from moving further upwards. If, due to a continued rotation of the threaded spindle 38, the linear drive raises the coupling element 28 further, the preload threshold begins to be exceeded from this point on. This causes the coupling element 28 to move away from the percussion piston 26 in the axial direction, whereby the magnetic holding force decreases until it falls below the preload of the spring element 30 or the compression springs 31. The compression springs 31 then accelerate the percussion piston 26 downwards, which then strikes the base plate 18.

[0041] After reaching a preset upper end position of the coupling element 28, the direction of rotation of the electric motor 14 is reversed and the coupling element is transported downwards again on the threaded spindle 38, and the return movement begins. This downward movement ends when the coupling element 28 again reaches the Figure 4 has reached the starting position shown. Then the return movement is completed and a new cycle can begin.

[0042] A controller (not shown) of the electric motor 14 can be programmed in a variety of ways. For example, the knocker 10 can be configured to perform a continuous knocking motion, meaning that the described cycle is repeated without interruption until the next control signal, or to perform a specific number of repetitions or individual knocking motions.

[0043] In the present case, only one embodiment is shown with one of the previously described operating principles. As mentioned above, the invention also encompasses impactors that provide a positive coupling between the coupling element and the impact piston instead of a frictional connection.

[0044] Alternatively, one or more electromagnets can be provided instead of the permanent magnets 36.

[0045] In yet another alternative embodiment, the spring pins 34 do not form the upper stop for the percussion piston 26, for example if the holding force of the magnets and the spring constant of the spring element are dimensioned such that on the way to the upper end position of the coupling element, a force equilibrium is achieved in which the spring force exceeds the holding force and thus the preload threshold is exceeded. List of reference symbols

[0046] 10 Knocker 12 Housing 14 Electric motor 16 Peripheral wall 18 Base plate, impact plate 20 Upper part 22 Damping element 24 Interior 26 Impact piston 28 Coupling element 30 Spring element 31 Compression spring 32 Counterbore, pocket 33 Through-bore 34 Spring mandrel 35 End face 36 Permanent magnet 37 Guide ring, sliding ring 38 Threaded spindle 40 Rotary union 42 Axial bearing 44 Drive shaft 45 Mounting 46 Sealing ring 47 Sealing ring 48 Flange 50 Mounting screws 52 Spring assembly 53 Rib 54 Through-bore 55 Screw 56 Groove 58 Guide projection 60 Preload direction 62 Counterbore a Axis

Claims

1. Knocker (10) with a housing (12), a percussion piston (26) which is linearly movable along an axis (a) in the housing (12) and a spring element (30) which can be prestressed along the axis in a prestressing direction (60) and which is supported on the one hand against the housing (12) and on the other hand against the percussion piston (26), characterized by a coupling element (28) which can be connected to the percussion piston (26) in a force-fitting or form-fitting manner and which is linearly movable in the housing (12), and a linear drive which drives the coupling element (28) along the axis (a), wherein the coupling element (28) is designed to release the percussion piston (26) when a pre-tensioning threshold is exceeded.

2. Knocker (10) according to claim 1, characterized by that the spring element (30) and the force connection between the coupling element (28) and the percussion piston (26) are dimensioned such that the preload of the spring element (30) exceeds the force connection when the preload threshold is exceeded.

3. Knocker (10) according to one of the preceding claims, characterized by that the coupling element (28) and the percussion piston (26) can be connected to one another by means of magnetic holding force.

4. Knocker (10) according to claim 3, characterized by that the coupling element (28) comprises at least one permanent magnet (36) and that the percussion piston (26) is magnetizable, or that the coupling element (28) comprises at least one electromagnet and that the percussion piston (26) is magnetizable.

5. Knocker (10) according to claim 4, characterized by a sensor unit which is configured to detect an exceeding of the pre-tension threshold and to trigger a switching signal to switch off the electromagnet.

6. Knocker (10) according to claim 1, characterized by that the form closure is achieved by means of a notching device.

7. Knocker (10) according to claim 6, characterized byan actuating element which is designed to actuate the release device when the pre-tensioning threshold is exceeded and through this to cancel the formal closure.

8. Knocker (10) according to one of the preceding claims, characterized in that the linear drive comprises an electric motor (14) and in particular a stepper motor.

9. Knocker (10) according to one of the preceding claims, characterized by that the linear drive comprises a threaded spindle (38) arranged parallel to the axis, which together with the coupling element (28) forms a helical gear.

10. Knocker (10) according to one of the preceding claims, characterized by thatthe housing (12) has a peripheral wall (16) extending in the direction of the axis (a), a base plate (18) and an upper part (20), wherein the peripheral wall (16), the base plate (18) and the upper part (20) define an interior space (24) in which the percussion piston (26) is arranged facing the base plate (18), the coupling element (28) is arranged in the middle and the spring element (30) is arranged facing the upper part, wherein the spring element (30) extends from the upper part (20) through recesses, openings or bores (33) in the coupling element (28) to the percussion piston (26), and wherein the prestressing direction (60) points towards the upper part (20).

11. Knocker (10) according to one of the preceding claims, characterized by that a stop element is arranged on the housing (12) which contacts the impact piston (26) when the preload threshold is reached.

12. Knocker (10) according to one of the preceding claims, characterized by thatthe spring element (30) comprises at least one compression spring (31).

13. Knocker (10) according to one of claims 12 to 18, characterized by that an anti-twist device is provided between the peripheral wall (16) and the coupling element (28).

14. Knocker (10) according to one of claims 12 to 19, characterized by that the base plate (18) and the upper part (20) are sealed against the peripheral wall (16).

15. Method for operating a knocker (10) according to one of the preceding claims, in which the percussion piston (26) is moved in the pretensioning direction (60) by means of the coupling element (28) which is connected to it in a force-fitting or form-fitting manner and is driven linearly along the axis (a) until the coupling element (28) releases the percussion piston (26) when a pretensioning threshold is exceeded and the percussion piston (26) is accelerated counter to the pretensioning direction (60) with at least partial release of the energy stored in the spring element (30).

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