Anatomically fully functional cranio-mandibular simulator

Abstract

The utility model relates to medical instrument field relates to a dissection full -functional cranio -maxillo -facial simulator, the utility model discloses the mandibular body, the maxillary body and the cutting guide needle disc assembly, the cutting guide needle disc assembly sets up between the mandibular body and the maxillary body, the mandibular body includes the base, the vertical adjustable measuring frame and the ball lever, and the vertical adjustable measuring frame is fixed to the both sides of base, and the ball lever is fixed to the inboard of vertical adjustable measuring frame, the maxillary body includes the upper plate, the axle assembly and the joint disc assembly, and the axle assembly is fixed to the lower end of upper plate, and the joint disc assembly rotationally sets up in the both sides of axle assembly, and the cooperation connection of the forward stretching condylar inclination of joint disc assembly and ball lever is controlled through the adjustment axle assembly, and the upper end of joint disc assembly is equipped with adjusting assembly no.

Description

Technical Field

[0001] This utility model relates to the field of medical devices, specifically to a fully functional anatomical craniomaxillary simulator. Background Technology

[0002] The anatomical full-function craniomaxillary simulator is a key tool in the field of oral medicine used to simulate the movement of the human craniomaxillary joint, assist in denture fabrication, and perform occlusal analysis. Its core function is to simulate the movement trajectory of the mandible relative to the maxilla through mechanical structures. The ball part of the rod can represent the human condyle, while the articular disc assembly and other structures correspond to the articular disc of the temporomandibular joint and related motion constraint components.

[0003] Existing craniofacial simulators have several limitations: First, their adjustment range is limited, with narrow adjustment ranges for key parameters such as lateral condylar inclination, condylar protrusion guide inclination, and condylar protrusion distance, making it difficult to cover complex individual anatomical differences. Second, the adjustment operation is cumbersome, requiring additional tools (such as screwdrivers) for most parameter adjustments, and the stability after adjustment is insufficient. Third, they have poor compatibility, making it difficult to adapt to different brands of denture fabrication systems (such as Artex, Ivoire, KAVO, etc.). Fourth, they lack negative adjustment functions (such as negative adjustment of condylar protrusion and condylar elevation), failing to simulate joint movements under special occlusal conditions. Therefore, there is an urgent need for an anatomical jaw frame with a wide adjustment range, convenient operation, and strong compatibility to meet clinical and research needs. Utility Model Content

[0004] This invention provides a fully functional craniofacial simulator to address the problems of existing technologies.

[0005] The objective of this utility model can be achieved through the following technical solution: A fully functional anatomical craniomaxillary simulator includes: a mandibular body, a maxillary body, and a cutting guide needle plate assembly; the cutting guide needle plate assembly is disposed between the mandibular body and the maxillary body; the mandibular body includes a base, a vertically adjustable measuring frame, and a ball rod, the vertically adjustable measuring frame being symmetrically fixed on both sides of the base, and the ball rod being fixed on the inner side of the vertically adjustable measuring frame; the maxillary body includes an upper plate, a central axis assembly, and an articular disc assembly, the central axis assembly being fixed to the lower end of the upper plate, and the articular disc assembly being rotatably disposed on both sides of the central axis assembly, the anterior condylar inclination of the articular disc assembly and its connection with the ball rod being controlled by adjusting the central axis assembly; an adjustment component one is provided at the upper end of the articular disc assembly, the lateral condylar inclination of the ball rod within the articular disc assembly being adjusted by adjusting component one; an adjustment component two is provided at the rear side of the articular disc assembly, the anterior condylar extension distance of the ball rod within the articular disc assembly being driven by adjusting component two.

[0006] In a further improvement, the joint disc assembly includes a joint disc, a protective plate, and an angle buckle. The angle buckle is rotatably disposed inside the joint disc. The protective plate is slidably inserted into the lower end of the joint disc. The central shaft assembly is fixed to the lower end of the upper plate. The central shaft assembly includes a center lock, a plug rod, a locking screw, an outer sleeve, a coilover inner shaft, and an inner rotating shaft. The inner rotating shaft is rotatably disposed inside the outer sleeve. The center lock is fixed to the outer side of the inner rotating shaft. The coilover inner shafts on both sides are threadedly engaged with the threads inside the inner rotating shaft, and the threads on both sides of the inner rotating shaft are reversed. The plug rod is connected to the outer side of the coilover inner shaft. By rotating the center lock, the two sets of plug rods are driven to penetrate into the ball shafts on both sides. The joint disc is rotatably disposed on the outer side of the outer sleeve. The outer sleeve has a disconnect groove. The locking screw is threadedly connected to both sides of the outer sleeve. By rotating the locking screw, the outer sleeve is driven to retract inward in the disconnect groove to clamp and fix the joint disc. The inner side of the joint disc has an annular groove that matches the locking screw.

[0007] In a further improvement, the adjustment component includes a scale plate, a knob, and a locking screw. The scale plate is fixed to the upper end of the joint disc in the joint disc assembly. The lower end of the knob passes through the scale plate and is fixedly connected to an angle buckle located inside the joint disc. The locking screw is located above the knob and the lower end of the locking screw is threadedly connected to the angle buckle.

[0008] In a further improvement, the second adjustment component includes a back block, a fourth locking screw, and a fifth locking screw. The back block is slidably disposed in the groove of the joint disc in the joint disc assembly and its position is fixed by the fifth locking screw. The fourth locking screw is threadedly connected to the interior of the back block in the middle, and the baffle at the front end of the fourth locking screw abuts against the cue stick.

[0009] In a further improvement, the vertically adjustable measuring frame includes a side bracket, an adjusting component, and two locking screws. The side bracket is symmetrically fixed on both sides of the base. The adjusting component is vertically slidably installed on the upper end of the side bracket. The height of the ball's condyle is adjusted by moving the adjusting component. The two locking screws are threaded to one side of the adjusting component, and the adjusting component is fixed to the side bracket by rotating the two locking screws. The ball is fixed to the inner side of the adjusting component.

[0010] In a further improvement, magnetic plates are magnetically connected to the middle of the upper end of the base and the middle of the lower end of the upper plate.

[0011] In a further improvement, the cutting guide needle assembly includes a cutting guide needle and a cutting guide plate. The cutting guide plate is fixedly installed on the upper front side of the base by screws, and the cutting guide needle is fixedly installed on the lower front side of the upper plate by screws. The lower end of the cutting guide needle abuts against the upper end face of the cutting guide plate. The cutting guide needle includes a front needle, an upper needle, and a lower needle. The upper needle is slidably disposed at the lower end of the front needle and its side end is fixed by a locking screw. The lower needle is installed at the lower end of the upper needle by a threaded assembly.

[0012] Compared with existing technologies, the beneficial effects of this novel anatomical full-function craniomaxillary simulator are as follows: It enables comprehensive adjustment of key motion parameters of the craniomaxillary joint, covering multi-dimensional motion simulation such as protrusion, lateral movement, and height, solving the problem of limited adjustment range of existing jaw frames; each adjustment component is integrated into the main body of the structure, and parameter adjustment can be completed without additional tools, significantly improving the ease of operation; the overall structural design is compatible with mainstream denture fabrication systems such as Artex, Ivoire, and KAVO, broadening the applicable scenarios. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 2 This is a structural schematic diagram from another perspective of the present invention. Figure 3 This is a schematic diagram of a partial structure of the present invention. Figure 4 This is a schematic diagram of the second partial structure of the present invention. In the diagram, 1-Mandibular body, 11-Base, 12-Side support, 13-Adjusting component, 14-Crank, 15-Vertically adjustable measuring frame, 16-Securing screw two, 2-Maxillary body, 21-Upper plate, 22-Central axis assembly, 221-Central lock, 222-Insertion rod, 223-Securing screw one, 224-Outer sleeve, 2241-Disconnect groove, 225-Coil inner shaft, 226-Inner rotating shaft, 23-Articular disc, 231-Annular groove, 232-Slide groove, 24-Protective plate. 25-Adjustment component one, 251-Scale plate one, 252-Knob one, 253-Locking screw three, 26-Adjustment component two, 261-Retracting block, 262-Locking screw four, 263-Locking screw five, 264-Baffle plate, 27-Joint disc assembly, 28-Angle buckle, 29-Support rod, 3-Guide needle cutting disc assembly, 31-Guide needle cutting, 311-Front needle, 312-Upper needle, 313-Lower needle, 314-Locking screw six, 32-Guide needle cutting disc, 4-Magnetic plate. Detailed Implementation

[0014] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model; unless otherwise expressly specified and limited, the terms "installed," "connected," and "joined" should be interpreted broadly, for example, they can refer to fixed connections or detachable connections, etc. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0015] The following is a description of the embodiments and appendices. Figures 1-4 The technical solution of this utility model will be further described below.

[0016] Example 1 A fully functional anatomical craniomaxillary simulator includes: a mandibular body 1, a maxillary body 2, and a cutting guide needle assembly 3; the cutting guide needle assembly 3 is disposed between the mandibular body 1 and the maxillary body 2; the mandibular body 1 includes a base 11, a vertically adjustable measuring frame 15, and a ball bar 14, the vertically adjustable measuring frame 15 being symmetrically fixed on both sides of the base 11, and the ball bar 14 being fixed to the inner side of the vertically adjustable measuring frame 15; the maxillary body 2 includes an upper plate 21, a central axis assembly 22, and an articular disc assembly 27, the central axis assembly 22 being fixed to the upper plate. At the lower end of plate 21, the articular disc assembly 27 is rotatably mounted on both sides of the central axis assembly 22. Adjusting the central axis assembly 22 controls the anterior condylar inclination of the articular disc assembly 27 and its connection with the ball club 14. The upper end of the articular disc assembly 27 is provided with an adjustment component 25, which adjusts the lateral condylar inclination of the ball club 14 within the articular disc assembly 27. The rear side of the articular disc assembly 27 is provided with an adjustment component 26, which drives the ball club 14 to extend anteriorly within the articular disc assembly 27. A support rod 29 is threadedly connected to the upper end of the upper plate 21 for support after the maxillary body 2 is opened.

[0017] like Figures 1-4 As shown, the working principle of this utility model is as follows: The ball-and-ball joint of the mandibular body represents the condyle of the human body, the articular disc assembly of the maxillary body corresponds to the articular disc and motion constraint structure of the temporomandibular joint, and the incisor guide disc assembly simulates the incisor guide relationship of the anterior teeth area. The whole structure reproduces the protrusion, lateral movement of the mandible relative to the maxilla through mechanical structure.

[0018] Specific adjustment process: Forward condyle inclination adjustment: The clamping state of the outer sleeve on the joint disc is controlled by the locking screw of the central axis assembly. After unlocking, the joint disc can rotate around the central axis assembly, thereby adjusting the inclination of the movement trajectory of the condyle (ball part of the club) during forward movement.

[0019] Lateral condyle inclination adjustment: By adjusting the angle buckle inside the joint disc, the lateral movement constraint angle of the club within the joint disc is changed, simulating the tilt trajectory of the condyle during lateral movement.

[0020] Condyle extension distance adjustment: The condyle extension distance can be adjusted by adjusting the back block of component two and locking screw four to push or limit the front and back position of the club.

[0021] Condylar height adjustment: The height of the ball stick can be changed by sliding the adjustment part of the vertically adjustable measuring frame up and down to simulate the raised or lowered state of the condyle.

[0022] It enables comprehensive adjustment of key motion parameters of the craniomaxillary joint, covering multi-dimensional motion simulation such as protrusion, lateral movement, and height, solving the problem of limited adjustment range of existing jaw frames; each adjustment component is integrated into the main body of the structure, and parameter adjustment can be completed without additional tools, significantly improving the ease of operation; the overall structural design is compatible with mainstream denture fabrication systems such as Artex, Ivoire, and KAVO, broadening the applicable scenarios.

[0023] As a further preferred embodiment, the articulated disc assembly 27 includes an articulated disc 23, a protective plate 24, and an angle buckle 28. The angle buckle 28 is rotatably disposed inside the articulated disc 23. The protective plate 24 is slidably inserted into the lower end of the articulated disc 23. The central shaft assembly 22 is fixed to the lower end of the upper plate 21. The central shaft assembly 22 includes a center lock 221, a plug rod 222, a locking screw 223, an outer sleeve 224, a coilover inner shaft 225, and an inner rotating shaft 226. The inner rotating shaft 226 is rotatably disposed inside the outer sleeve 224. The center lock 221 is fixed to the outer side of the inner rotating shaft 226. The coilover inner shafts 225 on both sides are threadedly engaged. The insert rod 222 is connected to the outside of the inner shaft 225 of the coiled rod. By rotating the center lock 221, the two sets of insert rods 222 are driven to penetrate into the ball rods 14 on both sides. The joint disc 23 is rotatably disposed on the outside of the outer sleeve 224. The outer sleeve 224 is provided with a disconnect groove 2241. The locking screw 223 is threaded to both sides of the outer sleeve 224. By rotating the locking screw 223, the outer sleeve 224 is driven to retract inward in the disconnect groove 2241 to clamp and fix the joint disc 23. The inner side of the joint disc 23 is provided with an annular groove 231 that matches the locking screw 223.

[0024] The articular disc mimics the temporomandibular joint in the human body, providing a movement track for the cue (condyle); the angle buckle is used to constrain the lateral movement angle of the cue; and the protective plate protects the internal structure of the articular disc, preventing foreign objects from entering during adjustment.

[0025] Connection and locking of the central shaft assembly: Rotating the central lock drives the inner shaft to rotate. Because the threads on both sides of the inner shaft are reverse threads, the two sets of threaded inner shafts move synchronously in opposite directions, driving the insert rod to insert or withdraw from the club, realizing the quick connection or separation of the club and the joint disc assembly.

[0026] Adjustment of the protractor guide angle of the central axis assembly: The disengagement groove design of the outer sleeve gives it elastic contraction capability. After loosening the locking screw one, the outer sleeve no longer clamps the joint disc, and the joint disc can rotate around the outer sleeve to adjust the angle; after the angle is determined, tighten the locking screw one, and the outer sleeve contracts through the disengagement groove to clamp the joint disc and cooperate with the inner annular groove of the joint disc to achieve stable fixation.

[0027] The quick connection and separation structure of the insert and the ball joint simplifies the assembly and disassembly process of the jaw frame and improves operational efficiency; the elastic clamping design of the outer sleeve, combined with the annular groove, ensures that the articular disc can be stably fixed at any angle, solving the problem of easy loosening after adjustment of existing jaw frames; the rotatable structure and locking mechanism of the articular disc realizes flexible adjustment of the anterior condyle guide angle, covering a wider range of individual anatomical differences.

[0028] As a further preferred embodiment, the adjustment component 25 includes a scale plate 251, a knob 252, and a locking screw 253. The scale plate 251 is fixed to the upper end of the joint disc 23 in the joint disc assembly 27. The lower end of the knob 252 passes through the scale plate 251 and is fixedly connected to an angle buckle 28 located inside the joint disc 23. The locking screw 253 is located above the knob 252 and the lower end of the locking screw 253 is threadedly connected to the angle buckle 28.

[0029] The scale plate 1 visually displays the adjustment angle of the lateral condyle inclination, with an adjustment range of -5 degrees to 35 degrees for precise control. The knob 1 directly connects to the angle latch inside the articular disc; rotating the knob 1 rotates the angle latch, thus changing the lateral constraint angle of the angle latch on the cue (condyle), achieving lateral condyle inclination adjustment. The locking screw 3, tightened after adjustment, secures the angle latch to the scale plate 1 via a threaded connection, preventing angle shift. The quick-locking function of the locking screw 3 allows for angle fixation without additional tools, simplifying operation and solving the cumbersome problem of traditional jaw brace adjustments requiring screwdrivers and other tools.

[0030] As a further preferred embodiment, the adjustment component 26 includes a retracting block 261, a locking screw 4 262, and a locking screw 5 263. The retracting block 261 is slidably disposed in the groove 232 of the joint disc 23 in the joint disc assembly 27 and the position of the retracting block 261 is fixed by the locking screw 5 263. The locking screw 4 262 is threadedly connected to the interior of the retracting block 261 in the middle, and the baffle 264 at the front end of the locking screw 4 262 abuts against the cue stick 14.

[0031] Forward adjustment: The retractor slides in the groove of the joint disc. After being fixed in position by locking screw five, rotating locking screw four causes the front end plate to push the ball stick (condyle) forward, thereby achieving forward adjustment of the condyle extension distance.

[0032] Negative adjustment: After loosening the locking screw five, adjust the back block backward. At this time, the protective plate must be removed first. The position of the cue stick is restricted in the opposite direction by the baffle of the locking screw four, so as to achieve negative adjustment of the condyle extension distance.

[0033] It integrates positive (0~6mm) and negative (-3~0mm) adjustment functions. The negative adjustment is unique in the market and can simulate special occlusal states such as condylar posterior displacement, breaking through the limitation of existing jaw frames that can only be adjusted in the positive direction. The cooperation between the retracting block and the locking screw ensures the stability of the position after adjustment and avoids parameter deviation during movement.

[0034] As a further preferred embodiment, the vertically adjustable measuring frame 15 includes a side bracket 12, an adjusting member 13, and a second locking screw 16. The side bracket 12 is symmetrically fixed on both sides of the base 11. The adjusting member 13 is vertically slidably installed on the upper end of the side bracket 12. The height of the condyle of the ball rod 13 is adjusted by moving the adjusting member 13. The second locking screw 16 is threaded to one side of the adjusting member 13, and the adjusting member 13 is fixed to the side bracket 12 by rotating the second locking screw 16. The ball rod 14 is fixed to the inner side of the adjusting member 13.

[0035] The side bracket provides a vertical sliding track for the adjustment component. The adjustment component drives the ball rod (condyle) to move up and down to change the height of the condyle, achieving a height range adjustment of 0~3.5mm. After adjustment, tighten the second locking screw to fix the adjustment component on the side bracket through thread pressure to prevent height deviation.

[0036] It enables flexible adjustment of condylar height, simulating the anatomical state of condylar elevation or depression, thus solving the problem of insufficient adjustment range of existing jaw frame height; the sliding fit between the adjustment component and the side support and the quick fixation of the second locking screw make it easy to operate and highly stable.

[0037] As a further preferred embodiment, magnetic plates 4 are magnetically connected to the middle of the upper end of the base 11 and the middle of the lower end of the upper plate 21. Through magnetic attraction, oral models (such as plaster models or digital model bases) can be quickly adsorbed and fixed without the need for rigid connections such as bolts.

[0038] As a further preferred embodiment, the cutting guide needle assembly 3 includes a cutting guide needle 31 and a cutting guide disc 32. The cutting guide disc 32 is fixedly installed on the upper front side of the base 11 by screws. The cutting guide needle 31 is fixedly installed on the lower front side of the upper plate 21 by screws. The lower end of the cutting guide needle 31 abuts against the upper end face of the cutting guide disc 32. The cutting guide needle 31 includes a front needle 311, an upper needle 312 and a lower needle 313. The upper needle 312 is slidably disposed on the lower end of the front needle 311 and its side end is fixed by a locking screw 314. The lower needle 313 is installed on the lower end of the upper needle 312 by a threaded assembly.

[0039] The incisor guide plate simulates the incisor plane of the anterior teeth. The lower incisor needle contacts the incisor guide plate, replicating the guiding relationship of the anterior teeth during protrusion or lateral movements. The upper needle slides within the anterior needle, and its length is fixed by a locking screw. Combined with the thread adjustment of the lower needle, it can adapt to different anterior overbite and overjet relationships, adjusting the contact depth and angle between the incisor needle and the incisor guide plate. The multi-segment adjustment structure (anterior needle, upper needle, lower needle) makes the simulation of the incisor guidance relationship more accurate and can match the anterior tooth anatomy characteristics of different individuals.

[0040] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A fully functional anatomical craniomaxillary simulator, characterized in that, include: The mandibular body, maxillary body, and incisor guide plate assembly are disposed between the mandibular body and the maxillary body. The mandibular body includes a base, a vertically adjustable measuring frame, and a ball rod. The vertically adjustable measuring frame is symmetrically fixed on both sides of the base, and the ball rod is fixed on the inner side of the vertically adjustable measuring frame. The maxillary body includes a top plate, a central axis assembly, and an articular disc assembly. The central axis assembly is fixed to the lower end of the top plate, and the articular disc assembly is rotatably disposed on both sides of the central axis assembly. The anterior condylar inclination of the articular disc assembly and its connection with the ball rod are controlled by adjusting the central axis assembly. An adjustment component one is provided at the upper end of the articular disc assembly to adjust the lateral condylar inclination of the ball rod within the articular disc assembly. An adjustment component two is provided at the rear side of the articular disc assembly to drive the anterior condylar extension distance of the ball rod within the articular disc assembly.

2. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The joint disc assembly includes a joint disc, a protective plate, and an angle buckle. The angle buckle is rotatably disposed inside the joint disc. The protective plate is slidably inserted into the lower end of the joint disc. The central shaft assembly is fixed to the lower end of the upper plate. The central shaft assembly includes a center lock, a plug rod, a locking screw, an outer sleeve, a coilover inner shaft, and an inner rotating shaft. The inner rotating shaft is rotatably disposed inside the outer sleeve. The center lock is fixed to the outer side of the inner rotating shaft. The coilover inner shafts on both sides are threaded into the threads inside the inner rotating shaft, and the threads on both sides of the inner rotating shaft are reversed. The plug rod is connected to the outer side of the coilover inner shaft. By rotating the center lock, the two sets of plug rods are driven to penetrate into the ball shafts on both sides. The joint disc is rotatably disposed on the outer sleeve. The outer sleeve has a disconnect groove. The locking screw is threaded to both sides of the outer sleeve. By rotating the locking screw, the outer sleeve is driven to retract inward in the disconnect groove to clamp and fix the joint disc. The inner side of the joint disc has an annular groove that matches the locking screw.

3. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The adjustment component includes a scale plate, a knob, and a locking screw. The scale plate is fixed to the upper end of the joint disc in the joint disc assembly. The lower end of the knob passes through the scale plate and is fixedly connected to an angle buckle located inside the joint disc. The locking screw is located above the knob and the lower end of the locking screw is threadedly connected to the angle buckle.

4. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The second adjustment component includes a retracting block, a fourth locking screw, and a fifth locking screw. The retracting block is slidably disposed in the groove of the joint disc in the joint disc assembly and its position is fixed by the fifth locking screw. The fourth locking screw is threaded in the middle and connected to the inside of the retracting block. The baffle at the front end of the fourth locking screw abuts against the cue stick.

5. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The vertically adjustable measuring frame includes a side bracket, an adjusting component, and two locking screws. The side bracket is symmetrically fixed on both sides of the base. The adjusting component is vertically slidably installed on the upper end of the side bracket. The height of the ball's condyle is adjusted by moving the adjusting component. The two locking screws are threaded to one side of the adjusting component, and the adjusting component is fixed to the side bracket by rotating the two locking screws. The ball is fixed to the inner side of the adjusting component.

6. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The upper middle part of the base and the lower middle part of the upper plate are both magnetically connected to magnetic plates.

7. The fully functional craniomaxillary simulator according to claim 1, characterized in that, The cutting guide needle assembly includes a cutting guide needle and a cutting guide plate. The cutting guide plate is fixedly installed on the upper front side of the base by screws. The cutting guide needle is fixedly installed on the lower front side of the upper plate by screws. The lower end of the cutting guide needle abuts against the upper end face of the cutting guide plate. The cutting guide needle includes a front needle, an upper needle, and a lower needle. The upper needle is slidably disposed at the lower end of the front needle and its side end is fixed by a locking screw. The lower needle is installed at the lower end of the upper needle by a threaded assembly.

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