Chuck with an interchangeable chuck head and interchangeable coupling

Abstract

A chuck (10) with an interchangeable chuck head (20) that can be inserted into and connected to an interchangeable coupling (30), wherein the interchangeable chuck head (20) has a tool shank receptacle (22) for a tool shank (42) of a rotary tool (40) driven about a longitudinal axial axis (A) of the chuck (10). The interchangeable chuck head (20) and the interchangeable coupling (30) each have at least one first locking element (50) which, in a connected state, prevents mutual rotation. The interchangeable chuck head (20) also has at least one second locking element (60) which, in a non-operational state of the interchangeable chuck head (20) in which no tool shank (42) is located in the tool shank receptacle (22), engages in a spring-loaded, releasable manner in at least one second locking element (60) of the interchangeable coupling (30).In an operational state, in which a tool shank (42) is located in the tool shank holder (22) and is inserted into the chuck (10) up to a stop, the second locking elements (60) are locked in the quick-change coupling (30) by the tool shank (42).

Description

Field of invention

[0001] The present invention relates to a chuck with an interchangeable chuck head and an interchangeable coupling according to the preamble of claim 1 and a medical, podiatric or cosmetic device with a corresponding chuck. State of the art

[0002] Chucks for drills, milling cutters, or other rotating tools in handheld medical, podiatric, or cosmetic devices should generally be operated under hygienically safe conditions. For this reason, dust is usually extracted directly from the device, which, however, leads to clogging or necessitates disassembly for cleaning.

[0003] German patent DE 20 2006 006 551 U1 describes a medical or cosmetic processing device comprising a housing and a rotary drive for a rotary tool, which can be held in a clamping device arranged in the housing. The clamping device has a rotating clamping sleeve with a first axial bore and a collet chuck arranged in this bore for fixing the rotary tool in a further axial bore provided rotationally symmetrically in the collet chuck. In the rear region of the first axial bore, an element is provided to support the collet chuck axially and to mechanically influence the surface of the rear region. The collet chuck has bearing recesses for clamping pins which, in conjunction with the clamping sleeve, fix the rotary tool in the further axial bore during rotation, with the clamping pins being arranged in the front region, preferably in the front two-thirds of the collet chuck.The dust accumulating in the collet must be extracted after each use of the rotary tool, or the entire collet must be removed from the housing for cleaning. Due to the design of the collet, thorough cleaning is difficult because the collet chuck, which is fixed inside, prevents unobstructed access to the collet, particularly the collet itself.

[0004] From DE 10 2012 005 178 B4, a medical or cosmetic processing device is known, comprising a handpiece with a housing and a rotary drive for a rotary tool. In an operating state of the processing device, the tool can be received in an axial bore of a clamping device arranged in the housing. The axial bore is accessible via an insertion opening provided on the end face of the housing. Furthermore, the processing device has a extraction channel arranged in the housing, at least partially surrounding the clamping device, for removing material removed by the rotary tool in front of an insertion opening of the extraction channel by means of a extraction device. The device also has at least one further bore arranged on the rear side in or behind the clamping device.In cleaning mode, a sealing element in the intake opening of the extraction channel seals the intake opening, whereby air enters the extraction channel through the axial bore and the further bore via the extraction device with the rotary tool removed. Here too, complete cleaning of the clamping device, consisting of a collet and collet, is only possible by means of extraction in cleaning mode under difficult conditions.

[0005] DE 11 77 280 B discloses a clamping device for rotating dental tools by means of a clamping sleeve made of resilient material, which can be inserted into the drive sleeve and has resilient tongues formed by several axially parallel longitudinal slots and secured against axial displacement in the drive sleeve. The resilient tongues of the clamping sleeve are bent outwards approximately halfway along the length of the longitudinal slots. They are loosely inserted into the bore of the drive sleeve, with their outer ends bearing against it under clamping pressure. Lateral projections formed by a collar of the clamping sleeve divided by the longitudinal slots engage behind the drive sleeve and form an outwardly resilient constriction at their bending points. The clamping sleeve has two collars at a short distance from each other at its slotted end. The collar set back from the free end of the sleeve engages in an annular groove of the drive sleeve.The collet can be removed from the drive sleeve directly from the front of the drive sleeve after the rotary tool has been removed from the collet and the collars have been disengaged from the ring groove. However, this design neither prevents dust from entering the collet and drive sleeve nor prevents the collet and drive sleeve from rotating relative to each other.

[0006] German patent DE 196 50 204 A1 describes a surgical punch comprising a tubular shaft with a distal annular cutting edge and a movable cutting body. The cutting body is held on a feed component, which can be moved within the shaft by means of an actuating element at the proximal end of the shaft. The cutting body and the feed component, or a housing that carries the cutting edge, are detachably connected to the shaft. The detachable connection is achieved by radially elastically displaceable locking lugs attached to one part, which engage in a locking position behind recesses on the other part. The two parts are secured against axial movement. The locking lugs are prevented from moving radially out of the recesses by the tight fit of the sliding elements in the shaft or housing against the locking lugs.When the connection is released, the feed component and the cutting body can move freely axially along the shaft, so that radial movement is no longer prevented. Summary of the invention

[0007] The invention is therefore based on the objective of providing a chuck with an easily replaceable quick-change chuck head that can be easily cleaned of contaminants such as dust and skin residue and reprocessed for the next treatment, offers a high level of sealing of the quick-change coupling against dust and at the same time reliably prevents mutual rotation of the quick-change chuck head and the quick-change coupling. Description of the invention

[0008] This is achieved with a chuck according to the features of claim 1. In this chuck, the interchangeable chuck head and the interchangeable coupling overlap at least partially, preferably completely, in a connected state in a radial direction to the longitudinal axis and each has at least one first locking element that engages with each other and prevents mutual rotation. Furthermore, the interchangeable chuck head has at least one second locking element which, in a connected and non-operational state in which no tool shank is in the tool shank holder, releasably engages in at least one second locking element of the interchangeable coupling at a preferably closed end of the interchangeable coupling, which is opposite an open end.Furthermore, in a connected and operational state, in which the tool shank is located in the tool shank holder and is inserted into the chuck up to a stop, the second locking elements at the preferably closed end of the quick-change coupling permanently lock the tool shank together.

[0009] This is also achieved with a medical, podiatric, or cosmetic device comprising a handpiece in which a corresponding chuck is arranged, with the features according to claim 12. The partial, preferably complete, radial overlap of the interchangeable chuck head and the interchangeable coupling, as well as at least partial positive locking of the interchangeable chuck head in the interchangeable coupling, ensures maximum sealing of the interchangeable coupling against dust. Simultaneously, the first locking elements reliably prevent mutual rotation of the interchangeable chuck head and the interchangeable coupling. The first locking elements can be configured in both the axial and radial directions with respect to the longitudinal axis of the chuck. For example, the first locking elements can be polygonal, i.e.,The interchangeable clamping head must have a triangular, square or generally polygonal outer shape and the interchangeable coupling must have an at least partially corresponding inner shape.

[0010] This allows for the use of a new / cleaned interchangeable chuck for each customer. Disassembly and cleaning of the entire handpiece is no longer necessary. After removing the chuck, the chuck's mounting bore can be easily cleaned from the outside with a cotton swab or similar and disinfectant. This improves hygiene during treatment.

[0011] An advantageous anti-rotation feature is achieved by interlocking, for example, the teeth of the quick-change chuck with the teeth of the quick-change coupling during insertion. This is advantageously confirmed by an audible click, which occurs when the rear part of the quick-change chuck is pressed over a narrow passage.

[0012] Advantageous further developments are the subject of the dependent patent claims. The features listed individually in the patent claims can be combined with one another in a technologically meaningful way and can be supplemented by explanatory facts from the description and by details from the figures, thereby showing further embodiments of the invention.

[0013] In a preferred embodiment improving the maintenance and cleaning of the chuck, particularly the quick-change coupling, the quick-change chuck head has, at an end opposite an insertion opening of the rotary tool into the tool shank receptacle, a clamping element with multiple slots along the longitudinal axis, in particular a cylindrical clamping sleeve, with at least one spring-like clamping segment designed as a second locking element and a radially external clamping segment projection formed at its end. Furthermore, the quick-change coupling has an interior with a portion, spaced apart from the open end of the quick-change coupling, that decreases in circumference, in particular tapers conically, and has at least one adjoining groove-like undercut designed as a second locking element, which preferably closes the interior.In the non-operational state, with no tool shank in the tool shank holder, the interchangeable clamping head can be inserted into the interchangeable coupling along its longitudinal axis. During this insertion, the at least one spring-like clamping segment, with its radially outward clamping segment projection formed at its end, moves radially inward through the decreasing portion of the interchangeable coupling, initially against the spring force of the clamping segment. Upon reaching the at least one undercut, it moves radially outward with the spring force of the clamping segment and engages with the at least one undercut of the interchangeable coupling via the clamping segment projection, snapping into place.

[0014] The interchangeable chuck head can also be extended from the interchangeable coupling along the longitudinal axis. In doing so, the at least one clamping segment, with its radially external clamping segment projection at its end, moves in reverse sequence, first radially inward against the spring force of the clamping segment, disengaging from the at least one undercut with the clamping segment projection. It then moves radially outward within the decreasing section of the interchangeable coupling, again with the spring force of the clamping segment. Furthermore, in the connected and operational state, where a tool shank is in the tool shank holder and inserted into the chuck up to a stop, the at least one clamping segment, with its radially external clamping segment projection at its end, locks into the at least one undercut of the interchangeable coupling.This design ensures easy maintenance and cleaning of the interchangeable coupling. Furthermore, it allows for quick replacement of the interchangeable clamping head while maintaining a consistently good seal.

[0015] In a further preferred embodiment, which ensures the rotational stability of the interchangeable chuck head and the interchangeable coupling of the chuck and enables the greatest possible sealing of the interchangeable coupling of the chuck, the interchangeable chuck head has a radially external clamping head projection. On its underside, opposite the open end of the interchangeable coupling, this projection has at least one first locking element. Furthermore, the interchangeable coupling also has at least one first locking element on a front face of its open end. When connected, the first locking elements of the interchangeable chuck head and the interchangeable coupling engage and lock together. This effectively prevents mutual rotation and reduces contamination of the interchangeable coupling by dust ingress.

[0016] In a preferred embodiment that facilitates the manufacture of the interchangeable chuck head and the interchangeable coupling of the chuck and their connection to each other, the first locking elements of the interchangeable chuck head and the interchangeable coupling are teeth. A tooth shape of the locking elements, in particular a triangular or rectangular shape, allows the connection of the interchangeable chuck head to the interchangeable coupling to be easily established and ensures a secure connection.

[0017] In a further preferred embodiment that facilitates the maintenance of the chuck, the quick-release coupling can be detachably connected to a drive shaft in the area of ​​its preferably closed end. This allows the entire chuck to be separated from the drive shaft and serviced separately.

[0018] Preferably, a blind hole is provided at the closed end of the quick-release coupling, in which any remaining contaminants such as dust and skin residue can collect as needed. The design of the chuck makes this blind hole easily accessible, allowing it to be advantageously cleaned after each treatment.

[0019] In a further preferred embodiment that facilitates the handling and sealing of the chuck, the interchangeable coupling is surrounded by a bearing housing in which it is mounted interchangeably and rotatably about the longitudinal axis. The bearing housing seals around the chuck and can directly form a handpiece by which a user guides the rotary tool.

[0020] In another preferred embodiment that facilitates handling and cleaning of the chuck, the bearing housing is fixedly or interchangeably arranged in a handpiece that connects the chuck to a drive shaft. Additionally, a channel may be provided between the handpiece and the bearing housing to allow dust extraction.

[0021] In a preferred embodiment that improves the sealing of the chuck, particularly the quick-release coupling, the quick-release coupling has a cover cap at its open end. This cap does not cover the open end or the at least one first locking element on the front of the open end and closes the bearing housing surrounding the quick-release coupling. The already high level of protection against contamination by dust and the ease of cleaning provided by the partially enclosed interior of the quick-release coupling are further enhanced by the cover cap.

[0022] In a further preferred embodiment, which enables the automatic locking of the rotary tool in the interchangeable chuck and facilitates the maintenance of the chuck, the interchangeable chuck has a two-part housing divided perpendicular to the longitudinal axis. A collet is arranged in a first partial housing with the insertion opening for the rotary tool for automatically locking the rotary tool in an operating state of the chuck in which the chuck drives the rotary tool. A second partial housing has the clamping element with multiple slots along the longitudinal axis. The two-part design, and in particular the separability of the partial housings, facilitates easy maintenance of the collet.

[0023] Preferably, the exchange can be easily carried out using a puller. The interchangeable chuck has a chuck undercut located on the outer side of a wall surrounding the tool shank holder, near the insertion opening. The chuck undercut can be connected to a tool undercut located on the inner side of a wall surrounding a cavity of a puller. For this purpose, the puller has a recess in its wall that interrupts the tool undercut and allows the puller, with the cavity, to be pushed over the wall of the interchangeable chuck in a direction radial to the longitudinal axis. In the pushed-on position, the tool undercut engages behind the chuck undercut.

[0024] The features listed individually in the patent claims can be combined in a technologically meaningful way and can be supplemented by explanatory facts from the description and by details from the figures, showing further embodiment variants of the invention.

[0025] The invention will now be explained in more detail using an exemplary embodiment. The figures shown are: Fig. 1 a chuck with an interchangeable chuck head inserted into an interchangeable coupling, Fig. 2a a changeover chuck, Fig. 2b a quick-change coupling with bearing housing, Fig. 3 a two-part interchangeable chuck housing, Fig. 4a a sectional view of an interchangeable clamping head, Fig. 4b a sectional view of the quick-release coupling with bearing housing, Fig. 5a a rotary tool, Fig. 5b a sectional view of a quick-change chuck inserted into a quick-change coupling, Fig. 6. A close-up of two locking elements in the unlocked state. Fig. 7 a sectional view of an interchangeable chuck head inserted into an interchangeable coupling with a rotary tool inserted, Fig. 8 a close-up of two locking elements in the locked state, Fig. 9 perspective views of a changeover chuck head exchange with prior sliding on of a puller tool (a, b) and subsequent sliding off of the puller tool (c, d), Fig. 10 perspective views of an interchangeable chuck head and interchangeable coupling in the unconnected state (a), in the connected state (b) and with a rotary tool inserted (c). Description of preferred embodiments

[0026] Before the invention is described in detail, it should be noted that it is not limited to the respective components of the device or the respective process steps, as these components and processes can vary. The terms used here are intended solely to describe particular embodiments and are not used restrictively. Furthermore, where the singular or indefinite articles are used in the description or in the claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0027] The in Fig. The chuck 10 shown in Figures 1 to 9 has an interchangeable chuck head 20 and an interchangeable coupling 30 that can be connected to a drive shaft, wherein the interchangeable chuck head 20 can be inserted into and thus connected to an open end 32 of the interchangeable coupling 30 in a longitudinal axial direction of the chuck 10, as shown in the figures. Fig. 2, Fig. 4, Fig. 10a and Fig. 10b indicated. In this case, the interchangeable clamping head 20 and the interchangeable coupling 30 lie at least partially in the direction of the open end 32 ( Fig. 4b, Fig. 10a) the interchangeable coupling 30 at least partially, preferably completely, engage with each other in a form-fitting manner. The interchangeable clamping head 20 has a tool shank receptacle 22 with an insertion opening 24, corresponding to the Fig. 4a, Fig. 5b, for receiving a tool shank 42 of a rotary tool 40 driven about a longitudinal axial axis A, as in the Fig. 5b, Fig. 7 and Fig. Figure 10c shows that the interchangeable clamping head 20 and the interchangeable coupling 30 overlap at least partially, preferably completely, in a connected state in a direction radial to the longitudinal axis A and each have at least one first locking element 50 which lock together and prevent mutual rotation, as shown in particular in the Fig. 2, Fig. 4, Fig. 10a and Fig. 10b shown.

[0028] The interchangeable clamping head 20 has at least one second locking element 60 ( Fig. 2a, Fig. 3, Fig. 4a and in particular Fig. 6 and Fig. 8), which, in a connected and non-operational state in which no tool shank 42 is located in the tool shank receptacle 22, releasably engages in at least a second locking element 60 of the quick-change coupling 30 at a preferably closed end 33 of the quick-change coupling 30, which is opposite the open end 32 ( Fig. 4, Fig. 5b and in particular Fig. 6) In the connected and operational state, in which the tool shank 42 is located in the tool shank receptacle 22 and is inserted into the chuck 10 up to a stop, the second locking elements 60 at the preferably closed end 33 of the quick-change coupling 30 are permanently locked together by the tool shank 42 ( Fig. 4, Fig. 7 and especially 8).

[0029] The at least partial, preferably complete, radial overlap of the interchangeable clamping head 20 and the interchangeable coupling 30, as well as the at least partial and complete positive locking of the interchangeable clamping head 20 in the interchangeable coupling 30, ensures maximum sealing of the interchangeable coupling 30 against dust. Simultaneously, the first locking elements 50 reliably prevent relative rotation of the interchangeable clamping head 20 and the interchangeable coupling 30.

[0030] The anti-rotation device is advantageously confirmed by an audible clicking sound, which occurs when the rear part of the interchangeable chuck 20 is pressed over a narrow passage.

[0031] The first locking elements 50 can be configured in both axial and radial directions with respect to the longitudinal axis of the chuck 10. For example, the first locking elements 50 can be configured by a polygonal, i.e., triangular, square, or generally polygonal, outer shape of the interchangeable chuck head 20 and an at least partially corresponding inner shape of the interchangeable coupling 30.

[0032] In an embodiment advantageous for the maintenance and cleaning of the chuck 10, the interchangeable clamping head 20 can have a clamping element 25, in particular a cylindrical clamping sleeve, with multiple slots along the longitudinal axis A at one end opposite the insertion opening 24 of the rotary tool 40 into the tool shank receptacle 22. The clamping element 25 has at least one spring-like clamping segment 27 designed as a second locking element 60 with a radially external clamping segment projection 62 formed at its end. Fig. 2a, Fig. 3, Fig. 4a).

[0033] The interchangeable coupling 30 has an interior 34 with a part 36, spaced apart from the open end 32 of the interchangeable coupling 30, which decreases in circumference, in particular tapers conically, and has at least one adjoining groove-like undercut 38 designed as a second locking element 60, which defines the interior 34 according to Fig. 4b closes.

[0034] In the non-operational state, in which no tool shank 42 is located in the tool shank holder 22, the interchangeable clamping head 20 can be inserted into the interchangeable coupling 30 along the longitudinal axis A, whereby the at least one spring-like clamping segment 27 with the radially outer clamping segment projection 62 formed at its end initially moves radially inwards against the spring force of the clamping segment 27 through the part 36 of the interchangeable coupling 30 that decreases in circumference. Upon reaching the at least one undercut 38, it moves radially outwards with the spring force of the clamping segment 27 and engages with the clamping segment projection 62 in a snap-fit ​​manner with the at least one undercut 38 of the interchangeable coupling 30, as shown in Fig. 6 shown.

[0035] Likewise, the interchangeable clamping head 20 can be extended from the interchangeable coupling 30 along the longitudinal axis A. In doing so, the at least one clamping segment 27, with the radially external clamping segment projection 62 formed at its end, moves in reverse sequence, first radially inwards against the spring force of the clamping segment 27, whereby it separates from the at least one undercut 38 with the clamping segment projection 62, and then moves radially outwards in the part 36 of the interchangeable coupling 30 which decreases in circumference, with the spring force of the clamping segment 27.Furthermore, in the connected and operational state, in which a tool shank 42 is located in the tool shank receptacle 22 and is inserted into the chuck 10 up to a stop, at least one clamping segment 27 is locked with the radially external clamping segment projection 62 formed at its end in the at least one undercut 38 of the quick-change coupling 30 ( . Fig. 8).

[0036] In a further advantageous embodiment which ensures the rotational stability of the interchangeable chuck head 20 and the interchangeable coupling 30 of the chuck 10 and enables the greatest possible sealing of the interchangeable coupling 30 of the chuck 10, the interchangeable chuck head 20 has a radially external chuck head projection 29, which has at least one first locking element 50 on its underside, which is opposite the open end 32 of the interchangeable coupling 30 ( Fig. 2a, Fig. 3, Fig. 4a, Fig. 10a). Furthermore, the interchangeable coupling 30 has at least one first locking element 50 on a front side of its open end 32 ( Fig. 2b, Fig. 4b, Fig. 10a), wherein the first locking elements 50 of the interchangeable clamping head 20 and the interchangeable coupling 30 interlock and lock together in the connected state ( Fig. 1, Fig. 5b, Fig. 7, Fig. 10b).

[0037] Advantageous for the manufacture of the interchangeable chuck head 20 and the interchangeable coupling 30 of the chuck 10 and their connection to each other is according to Fig. 1, Fig. 2, Fig. 4 and Fig. 10a, if the first locking elements 50 of the interchangeable chuck 20 and the interchangeable coupling 30 teeth are.

[0038] The interchangeable coupling 30 can be advantageously connected to a drive shaft via its preferably closed end 33 for the maintenance of the chuck 10.

[0039] Similarly, a blind hole 39 can advantageously be provided at the closed end 33 of the interchangeable coupling 30, in which residual contaminants such as dust and skin residue can collect. Due to the design of the chuck, this blind hole 39 is easily accessible and can thus be advantageously cleaned after each treatment as needed.

[0040] In an advantageous embodiment facilitating handling and sealing of the chuck 10, the interchangeable coupling 30 is surrounded by a bearing housing 35 in which it is mounted interchangeably and rotatably about the longitudinal axial axis A ( Fig. 4b, Fig. 5b, Fig. 7) This bearing housing 35 can also be designed as a handpiece.

[0041] The handling and cleaning of the chuck 10 can also be advantageously facilitated if the bearing housing 35 is arranged fixedly or interchangeably in a handpiece which connects the chuck 10 to a drive shaft.

[0042] The sealing of the chuck 10, in particular the quick-change coupling 30, is advantageously improved if the quick-change coupling 30 has a cover cap 37 at its open end 32, which does not cover the open end 32 and the at least one first locking element 50 on the front of the open end 32, and the bearing housing 35 surrounding the quick-change coupling 30 according to Fig. 4b, Fig. 5b, Fig. 7 closes.

[0043] In an additional advantageous embodiment which enables the automatic locking of the rotary tool 40 in the interchangeable clamping head 20 and facilitates the maintenance of the interchangeable clamping head 20, the interchangeable clamping head 20, in particular according to Fig. 2a, Fig. 3, Fig. Figure 4a shows a two-part housing 28 divided perpendicular to the longitudinal axis A. In a first partial housing 21 with the insertion opening 24 for the rotary tool 40, a collet 26 is arranged for automatically locking the rotary tool 40 in an operating state of the chuck 10, in which the chuck 10 drives the rotary tool 40. The collet 26 can have a mechanism known from the prior art, such as centrifugally actuated clamping pins. A second partial housing 23 has the clamping element 25, which is slotted multiple times along the longitudinal axis A.

[0044] Advantageous for replacing the interchangeable clamping head 20 according to the Fig. 9a to 9d, if the interchangeable clamping head 20 has a clamping head undercut 71 arranged on an outer side of a wall surrounding the tool shank receptacle 22, near the insertion opening 24. The clamping head undercut 71 can be connected to a tool undercut 73 arranged on an inner side of a wall surrounding a cavity 72 of a puller 70. The puller 70 has a recess 74 in its wall, which interrupts the tool undercut 73 and by means of which the puller 70 with the cavity 72 can be pushed over the wall of the interchangeable clamping head 20 in a direction radial to the longitudinal axis A ( Fig. 9a, Fig. 9b). In the pushed-on state, the tool undercut 73 engages behind the chuck undercut 71. By pulling the puller 70 along the longitudinal axis A while simultaneously holding the bearing housing 35, the interchangeable chuck 20 can be pulled out of the interchangeable coupling 30 and subsequently the puller 70 can be pushed off the interchangeable chuck 20 ( Fig. 9c, Fig. 9d).

[0045] The chuck 10 can be used in a medical, podiatric, or cosmetic device. The device has a handpiece in which a chuck 10 is arranged. Reference symbol list A longitudinal axis, 10 chucks, 20 interchangeable chuck heads, 21 first sub-housing, 22 Tool shank holder, 23 second sub-housing, 24 insertion opening, 25 multi-slotted clamping elements, 26 collet chuck, 27 spring-like clamping segment, 28 two-part housing, 29 Clamping head projection, 30 interchangeable couplings, 32 open ending, 33 closed end, 34 Interior 35 bearing housings, 36 part decreasing in size, 37 Cover cap, 38 groove-like undercut, 39 dead end, 40 rotary tools 42 Tool shaft, 50 first locking elements, 60 second locking elements, 62 Tension segment cantilever, 70 Puller tool, 71 Chuck undercut, 72 cavity, 73 Tool undercut, 74 recesses.

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