JP2014097832A - Beverage container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent insufficient thread fastening when closing a lid of a beverage container.SOLUTION: Two or more independent screw threads 9 and 10 are disposed on a thread part 5 of a container 1 and on a thread part 8 of a lid 2. The screw threads 9 of the screw part 5 have the same shape and are disposed at equal intervals and at the same height, and the screw threads 10 of the screw part 8 are disposed similarly. Consequently, the individual screw threads 10 of the lid 2 can be screwed to any one of the screw threads 9 of the container 1, thereby reducing an amount of rotation of the lid 2 in order to screw in the screw part 8 of the lid 2 to the end.

Description

  The present invention relates to a beverage container provided with a container for containing a beverage and a lid that covers the mouth of the container.

  Conventionally, as a beverage container of this type, the container has a male or female threaded portion, the lid has a female or male threaded portion, and the lid is screwed into the threaded portion on the container side. What closes is widely used (for example, Patent Document 1).

JP 2011-99779 A

  However, since the conventional thread portion on the container side and the lid side has one thread, it is necessary to take a rotation amount of the lid to close the lid. For this reason, when closing the lid, the user may mistakenly think that the screw portion on the lid side has been completely screwed in, and the lid may loosen while being carried and the beverage in the container may leak.

  Therefore, a problem to be solved by the present invention is to prevent insufficient screw tightening when closing the lid of the beverage container.

  In order to solve the above-described problems, the present invention is such that the container has a male or female threaded portion, the lid has a female or male threaded portion, and the lid-side threaded portion is screwed into the container-side threaded portion. The container-side screw part has two or more independent threads, and the lid-side screw part also has the same number of independent threads as the container-side screw part. And having a configuration in which each screw thread on the lid side can be screwed to any screw thread on the container side.

  According to the above configuration, when the male screw portion and the female screw portion have two or more threads, and when the lid is fixed to the container, each one screw thread is screwed to the other nearest screw thread. Compared to the case, when the lid is closed, there is less idle rotation where the screw thread on the lid side and the screw thread on the container side do not slide, and the screw thread on the lid side and the screw thread on the container side are shortened in the circumferential direction. In addition, since the fastening force can be obtained with the total of each strip, the amount of rotation of the lid for screwing the screw portion on the lid side to the end can be reduced.

  More specifically, the screw threads on the container side are all the same shape and arranged in the circumferential direction and at the same height, and the screw threads on the lid side are both the same shape and are arranged in the circumferential direction and the same height. If it arrange | positions, each screw thread of a lid | cover side can be similarly screwed with respect to any screw thread of a container side. Further, since two or more threads are equally arranged in the circumferential direction, the amount of rotation of the lid required for screwing the screw portion on the lid side into the screw portion on the container side to the end can be made less than half a circle. If it is less than half a circle, it is easy to screw it to the end with one twist of the wrist.

  Further, of the lid side and the container side, one of the advancing / retracting members and the engaging portion on the other side are hooked to resist loose rotation of the lid, and the advancing / retreating member is released from the engaging portion by a release operation. And a locking mechanism that can loosen the lid, and only one advance / retreat member is incorporated, and the same number of the engaging portions as the number of the strips are arranged according to the circumferential arrangement interval of the thread on the container side. It may be arranged in the direction. Thereby, even if the number of the advancing / retreating members is one, when the lid is closed, the advancing / retreating member can be prevented from loosening with any of the engaging portions. If it is possible to separately prevent the lid from rotating loosely with the locking mechanism, the lead angle of the screw pressure side flank can be set freely large to obtain the screw lead and the fastening force, so the amount of rotation of the lid can be easily reduced.

  Further, the pressure side flank of at least one of the thread portions on the container side and the lid side is low in contact with the other side thread at the lowest height when the screwing is performed to the end. It is preferable that the lead angle of the local contact surface portion is smaller than the remaining portion. At least the pressure side flank of the thread on one side has the shape in which the lead angle of the lower side contact surface part that makes contact with the thread on the other side at the lowest height is smaller than the rest when the screwing is performed to the end. Therefore, it is possible to make it difficult for the threaded portion to loosen and rotate without extending the circumferential length of the thread. If this is used, the lead angle and the fastening force can be obtained by setting the lead angle of the remaining portion of the pressure side flank to be large, so that the amount of rotation of the lid can be easily reduced. Here, “reduced lead angle” means that the lower side contact surface portion does not have a lead angle, that is, has a slope that does not contribute to the lead with respect to a plane perpendicular to the screw axis, or is along the plane. It means to include.

  In particular, if the low-side contact surface is along a plane perpendicular to the screw axis, the fastening force is loosened at the low-side contact surface and no rotational torque is generated, and the fastening force obtained by screwing is not wasted. You can make use of it.

  Furthermore, if the screw part on the container side and the lid side respectively have the low side contact surface part, it will prevent loosening between the planar parts along a right-angled plane, so that the contact is linear or dotted. An anti-loosening effect superior to the case can be obtained.

  In the present invention, the thread portion on the container side and the lid side may have a flank having a sufficiently large lead angle and circumferential length so that at least one screw thread can obtain a fastening force. The thread may not have a flank along the coiled winding, but may be a straight projecting piece.

  Further, when the remaining part of the screw part on the container side and the lid side is subjected to a fastening force in a range that is longer in the circumferential direction with a larger lead angle than the low side contact surface part in the state where the screwing is performed to the end. The loosening prevention effect can be obtained even by friction between the remaining portions.

  In the present invention, when the lid of the beverage container is closed, the amount of rotation of the lid for screwing the screw portion on the lid side to the end is reduced by the adoption of the above configuration, so that insufficient screw tightening can be prevented.

(A) is an operation view showing the state immediately before the lid of the beverage container and the screw part of the container according to the first embodiment of the present invention are screwed together, and (b) is a drawing of (a) from the front. Operational diagram, (c) is an operational diagram showing the state in which the lid is rotated 1/6 clockwise from (a), (d) is an operational diagram depicting (c) from the front, (e) ) Is an action diagram showing the state in which the lid is rotated 1/6 clockwise from (c), and (f) is an action diagram depicting (e) from the front. Longitudinal front view showing the overall configuration of the beverage container according to the first embodiment of the present invention 2 is an exploded perspective view of the container of FIG. 2 is an exploded perspective view of the lid of FIG. Enlarged view of FIG. 2A is an overall perspective view of the advance / retreat member of FIG. 2, FIG. 2B is a rear view of the advance / retreat member, FIG. 2C is a front view of a part of the advance / retreat member, and FIG. Figure The longitudinal front view which shows the principal part of the drink container which concerns on 2nd Embodiment of this invention The longitudinal front view which shows the principal part of the drink container which concerns on 3rd Embodiment of this invention The longitudinal front view which shows the principal part of the drink container which concerns on 4th Embodiment of this invention The longitudinal front view which shows the principal part of the drink container which concerns on 5th Embodiment of this invention (A) is the action figure which showed the outline | summary of the drink container which concerns on 6th Embodiment of this invention in the state in the middle of screwing, (b) is the action figure which showed the state screwed from the said (a) to the last. (A) is the action figure which showed the outline | summary of the drink container which concerns on 7th Embodiment of this invention in the state in the middle of screwing, (b) is the action figure which showed the state screwed from the said (a) to the last. (A) is the action figure which showed the outline | summary of the drink container which concerns on 8th Embodiment of this invention in the state in the middle of screwing, (b) is the action figure which showed the state screwed from the said (a) to the last.

  Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 2, 1st Embodiment is provided with the container 1 which puts a drink, the lid | cover 2 which covers the opening | mouth of the container 1, and the lock mechanism which prevents the loose rotation of the closed lid | cover 2. As shown in FIG. As shown in FIGS. 2 and 3, the container 1 has a heat insulating container 3 with a shoulder cover 4 attached thereto. As the heat insulating container 3, for example, a thermos bottle or a stainless steel vacuum double container can be adopted. The shoulder cover 4 has a male screw part 5. As shown in FIGS. 2 and 4, the lid 2 has a plug portion 7 with a packing 6 and a female screw portion 8. 1 (a) to 1 (f), the screw portion 8 on the lid 2 side is changed to the screw portion 5 on the container 1 side so as to show the progress of rotation for closing the lid 2 (drawn with a two-dot chain line in the figure). The lid 2 is closed by screwing, and the lid 2 is fixed to the container 1 by the fastening force obtained by the screw action.

  As shown in FIGS. 1 and 3, the screw portion 5 has two or more independent threads 9, 9, 9. In the example shown, there are 3 items. As shown in FIGS. 1 and 4, the screw portion 8 has three independent thread threads 10, 10, and 10, similar to the screw portion 5. As shown in FIG. 1, the threads 9, 10 are formed of protrusions that are relatively in sliding contact with each other while being displaced in the circumferential direction by the rotation of the lid 2. A fastening force is generated by a screw action therebetween, and the fastening force is directly received in a direction along the screw axis with the lid 2 closed. The circumferential direction means a circumferential direction around the screw axis. The threaded portions 5 and 8 are generally right-handed screws, and the illustrated example is also the same.

  A stopper portion 11 for determining the position where the screw portion 8 on the lid 2 side is screwed to the screw portion 5 on the container 1 side is connected to the pressure side flank 12 of the screw thread 9. The pressure side flank is a surface that connects the top and bottom of the thread, and is a portion that receives a direct load when it is screwed and loaded.

  As shown in FIGS. 1 and 3, the screw threads 9, 9, 9 of the screw portion 5 are all the same shape. The screw threads 9, 9, 9 are arranged at the same height in the circumferential direction. The same height means that the positions considered in the direction along the screw axis are the same. As shown in FIGS. 1 and 4, the screw threads 10, 10, and 10 of the screw portion 8 are all the same shape. The screw threads 10, 10, and 10 are also equally arranged in the circumferential direction and at the same height. Therefore, when the lid 2 is closed as shown in FIG. 1, each screw thread 10 on the lid 2 side can be screwed in the same manner with any screw thread 9, 9, 9 on the container 1 side.

  As shown in FIG. 1 and FIG. 3, the screw thread 9 is located in any one of the three regions obtained by dividing the container 1 into three in the circumferential direction (for the number of strips). As shown in FIGS. 1 and 4, the threads 10, 10, and 10 are also located in any one of the three regions obtained by dividing the lid 2 into three in the circumferential direction. Accordingly, when the lid 2 is closed as shown in FIG. 1, the idling of the lid 2 becomes 1/3 rotation or less, so that the user needs more idling than the thread portion of one thread. It is difficult to misunderstand that I turned. Further, since the circumferential length of each screw thread 9 and 10 is 1/3 or less, the rotation amount of the lid 2 required for screwing until the thread thread 10 hits the stopper 11 is 1/3 rotation. That's it. For this reason, it is easy to screw in to the end by twisting the wrist.

  As shown in FIGS. 1 and 5, the pressure side flank 12 and 13 of the threads 9 and 10 have the lowest height with the other thread (10 and 9) in the state where the screwing is performed to the end. The lead angle of the low-side contact surfaces 14 and 15 that are in contact with each other is smaller than that of the remaining portions 16a, 16b, and 17. The remaining portions 16a, 16b, and 17 occupy the largest circumferential portion of the pressure side flank 12 and 13, and are slidingly contacted in the direction along the screw axis to generate a fastening force by screw action. The remaining portions 16a and 16b on the screw thread 9 side are a main portion 16a having a lead angle β1 that occupies most of the circumferential direction of the pressure side flank 12, and a lead angle β2 that is larger than the lead angle β1 and a circumferential tip on the upper side from the main portion 16a. It is composed of a high-end side end portion 16b that continues to the end. The remaining portion 17 on the screw thread 10 side has a lead angle β1. Since the screw threads 9 and 10 in the illustrated example are parallel screws, the lead angles β1 and β2 are the spiral winding along the main portion 16a and the remaining portion 17, the spiral winding along the high-end side end portion 16b, and one point thereon. This corresponds to an angle formed by a plane perpendicular to the screw axis passing through. The lead angles β1, β2 are defined as 1 when the main portion 16a, the high-end side end portion 16b, and the portion 17 are assumed to be independent screws, and the main portion 16a, the high-end side end portion 16b, and the remaining portion 17 are aligned. When the radius from the screw axis at one point on the spiral winding is r, it can be calculated by tan β1, β2 = 1 / 2πr.

  The lead angles β1 and β2 may be determined as appropriate so that a required fastening force can be secured by the remaining portions 16a, 16b, and 17 with the rotation amount of the lid 2 as a premise. In the example shown in the drawing, it is sufficient to ensure it by 1/3 rotation.

  Since the low side contact surfaces 14 and 15 are along a plane perpendicular to the screw axis, the lead angle β3 is considered to be substantially 0 °. In the drawing, in order to conceptually explain the lead angle β3, it is exaggerated and indicated by an arrow. Since the low-side contact surfaces 14 and 15 receive the fastening force in the normal direction, no loose rotation torque is generated. Accordingly, it is possible to make it difficult for the screw portions 5 and 8 to rotate loosely as compared with the case where the lead angle of the low side contact surfaces 14 and 15 is β1. The low-side contact surfaces 14 and 15 increase the resistance to loosening rotation per unit circumferential length without changing the circumferential length of the threads 9 and 10, thereby preventing loosening. What is necessary is just to determine suitably in the range of 0 degrees <= β3 <β1, (beta) 2, as long as an effect is acquired. Even if it has a locking mechanism, if the beverage container is carried in a bag together with other items, there is a possibility that the other items will hit and disengagement will occur. It is preferable to use together the prevention of loosening by the surface portions 14 and 15.

  Since the main portion 16a and the remaining portion 17 of β3 <β1 are subjected to a fastening force with a lead angle larger than that of the low side contact surface portions 14 and 15 and long in the circumferential direction in a state where screwing is performed to the end, The friction between 16a and the remaining portion 17 also contributes to the prevention of loose rotation.

  In particular, it is preferable that the low-side contact surfaces 14 and 15 prevent loose rotation of the screw portions 5 and 8 due to an increase in internal pressure when hot water is poured into the container 1. Hot water refers to drinking water at 65 ° C to 100 ° C. When hot water is added and the lid 2 is closed, the internal pressure of the container 1 rises and the lid 2 receives pressure. The pressure received by the lid 2 generates a loose rotational torque of the screw portions 5 and 8, and this continues during carrying. Because of the loosening prevention effect of the low-side contact surfaces 14 and 15, the fastening of the screw portions 5 and 8 that surely exceed the loose rotational torque derived from the increase in internal pressure is obtained. 9, 10 itself can prevent it. Thereby, even if the lock mechanism is neutralized, the lid 2 can be prevented from loosening.

  Since the planar low-position side contact surfaces 14 and 15 along the right-angled plane become a loosening stopper that receives the fastening force, the low-location side contact surface portion 14 or 15 is made into a linear or dotted low-position side contact surface portion. It is possible to obtain a loosening prevention effect that is superior to that of the case.

  The reason why the lead angle β2 of the high end 16b of the screw thread 9 is made larger than the lead angle β1 is that sliding contact starts from a lead angle β3 smaller than the lead angle β1 when the lid 2 starts to close. This is because the high-end side end portion 16b on the container 1 side prevents the low-side contact surface portion 15 on the lid 2 side from abutting in the circumferential direction, and the screw thread 10 is smoothly screwed.

  The pressure side flank 12 and 13 in the illustrated example exemplify general square screw types that are straight in the cross-sectional shape including the screw axis in order to place importance on the lead due to the screw action. The shape can be selected as appropriate, such as a type, a triangular screw type, a round screw type, or a cross-sectional curve shape close thereto. The play side flank of the screw threads 9 and 10 has a surface shape substantially along the remaining portions 16a, 16b and 17 in order to guide the screwing until the remaining portions 16a, 16b and 17 are screwed together.

  As shown in FIGS. 1 and 2, the locking mechanism resists loose rotation of the lid 2 by being caught by an advancing / retracting member 20 incorporated only on the lid 2 side and an engaging portion 21 provided on the container 1 side. (See the advancing / retracting member 20 drawn with a solid line in FIG. 2), and when the advancing / retreating member 20 is released from the engaging portion 21 by the release operation (see the advancing / retreating member 20 drawn with a two-dot chain line in FIG. 2) It is a mechanism that can loosen the lid 2. As shown in FIGS. 1 to 3, the engaging portion 21 is a protruding portion located on the inner peripheral surface of the shoulder cover 4. As shown in FIGS. 2, 4, and 6, the advancing / retracting member 20 has a push surface 23 exposed to the outside of the lid 2, an engagement wall 24, and a spring receiving portion 25 that holds the spring 22. The advance / retreat member 20 is supported by the spring 22 in the advance / retreat direction with respect to the lid 2. The forward / backward direction in the illustrated example is set in a direction perpendicular to the screw axis. When the lid 2 is closed, the engagement wall 24 comes into contact with the engagement portion 21 at the time before screwing to the end. At this time, the spring 22 is compressed and the engagement wall 24 smoothly gets over the engagement portion 21 ( 1 (c) and FIG. 1 (e)), the spring 22 rebounds to return to the standby position before contact. Immediately after this, the screw thread 10 abuts against the stopper 11 and the screw parts 5 and 8 are screwed to the end. For this reason, if the lid 2 unexpectedly loosens and rotates for some reason, such as an increase in the internal pressure of the container 1 or another object is caught on the lid 2, the engaging wall 24 moves in the direction of loosening rotation of the engaging portion 21 and the lid 2. The hook 2 is prevented from loosening and rotating. When the release operation of pushing the push surface 23 is performed, the spring 22 is compressed and the advance / retreat member 20 is retracted, whereby the engagement wall 24 is retracted in a direction perpendicular to the screw axis, and the advance / retreat member 20 is engaged with the engagement portion 21. The lid 2 can be loosened while maintaining the state of escape.

  When the screw thread 10 on the lid 2 side can be screwed to any screw thread 9 on the container 1 side and only one advance / retreat member 20 is provided, the circumferential position of the advance / retreat member 20 is changed each time the cover 2 is closed. It will not be the same. For this reason, the same number of engagement portions 21, 21, 21 as the number of threads 9 of the thread 9 are arranged in the circumferential direction at intervals corresponding to the circumferential arrangement interval of the threads 9. Since the engaging portion 21 and the screw thread 9 are in a one-to-one relationship, and the positional relationship between the engaging portion 21 and the screw thread 9 is the same in any pair, at the beginning of the closing of the lid 2, Regardless of the position of the direction, when the lid 2 is closed, the engagement wall 24 of the advance / retreat member 20 can prevent any of the engagement portions 21 from loosening.

  Since the locking mechanism can separately prevent the lid 2 from rotating loosely, the lead angles β1 and β2 (see also FIG. 5) of the pressure side flank 12 and 13 can be freely set large to lead the screw parts 5 and 8 Since the fastening force can be obtained, the amount of rotation of the lid 2 can be easily reduced.

  There is no particular limitation as to which of the male screw portion and the female screw portion is assigned to the container 1 and the lid 2, and the engaging portion 21 of the lock mechanism may be disposed at a place other than the inner periphery of the container 1. Further, the advance / retreat member 20 may be arranged on the container 1 side, and the engaging portion 21 may be arranged on the lid 2 side. Further, the screw threads 9 and 10 on both sides are composed of the low-side contact surface portions 14 and 15 and the remaining portions 16a, 16b and 17, but the remaining screw portions are omitted, and the remaining screw threads are substantially low. You may comprise only a place side contact surface part. These examples will be described in other embodiments. Hereinafter, only differences from the first embodiment will be described.

  For example, as in the second embodiment shown in FIG. 7, the female screw portion 5 is disposed on the inner periphery of the shoulder cover 4 of the container 1, and the male screw portion 8 is disposed on the outer periphery of the plug portion 7 of the lid 2. be able to.

  Further, as in the third embodiment shown in FIG. 8, the engaging portion 21 of the lock mechanism can be arranged on the outer periphery of the shoulder cover 4 of the container 1.

  Further, as in the fourth embodiment shown in FIG. 9, a female screw portion 5 is formed on the inner periphery of the shoulder cover 4 of the container 1, and a male screw portion 8 is formed on the outer periphery of the plug portion 7 of the lid 2. be able to. Also in this example, the engaging portion 21 of the lock mechanism can be formed on the outer periphery of the container 1.

  Further, as in the fifth embodiment shown in FIG. 10, the container 1 has a detachable mouthpiece member 31, and the mouthpiece member 31 is formed by the close contact between the packing 32 attached to the mouthpiece member 31 and the inner periphery of the container 1. Can be fixed to the container 1, and the engaging portion 21 of the lock mechanism can be disposed on the inner periphery of the drinking hole member 31. Moreover, the screw part 5 can be directly formed in the outer container 33 of the container 1 of the double structure in the drinking / feeding member 31 and the stopper part 7 in the advance / retreat member 20. In this example, the screw portions 5 and 8 have screw threads 9 and 10 that are more than half a circle and less than one circle.

  Further, as in the sixth embodiment shown in FIG. 11A, the lower side contact surface portion 14 of the screw thread 9 has an R chamfered shape, and the pressure side flank of the screw thread 9 is substantially composed of only the remaining portion 16a. can do. The term “substantially” means that the pressure side flank corner or the chamfered portion of the corner is the low side contact surface portion 14. In this case, as shown in FIG. 11 (b), the low side contact surface portion 15 and the R chamfered low side contact surface portion 14 are in line contact to prevent loosening. There is an effect.

  Further, as in the seventh embodiment shown in FIG. 12A, the pressure-side flank of the screw thread 10 may be substantially constituted by only the low-side contact surface portion 15 as a further modification from the sixth embodiment. it can. The term “substantially” means that the pressure side flank corner or chamfered portion of the screw thread 10 is the remainder. In this case, as shown in FIG. 12 (b), the screwing is performed to the end, and the loosening prevention effect is achieved only by the line contact between the low side contact surface portion 15 and the R side chamfered low side contact surface portion 14. Play.

  Further, as in the eighth embodiment shown in FIG. 13 (a), the thread 9 can be substantially constituted by only the low side contact surface portion 14. “Substantially” means that the pressure side flank corner or chamfered portion of the thread 9 is the remaining portion. Further, an R-chamfered lower portion side contact surface portion 15 is arranged at the upper circumferential end portion of the pressure side flank of the screw thread 10, and the pressure side flank is substantially composed of only the remaining portion 17 as in the sixth embodiment. You can also In this case, as shown in FIG. 13 (b), the loosening prevention effect is achieved only by the line contact between the low side contact surface portion 14 and the R chamfered low side contact surface portion 15. Play. The technical scope of the present invention is not limited to the above-described embodiment, but includes all modifications within the scope of the technical idea based on the description of the scope of claims.

DESCRIPTION OF SYMBOLS 1 Container 2 Lid 5, 8 Thread part 9, 10 Thread 12, 13 Pressure side flank 14, 15 Low part side contact part 16a Main part 16b High part end part 17 Remaining part 20 Advancement / retraction member 21 Engaging part 22 Spring 23 Push Surface 24 engaging wall

Claims (5)

The container (1) has a male or female threaded part (5), the lid (2) has a female or male threaded part (8), and the threaded part (8) on the lid (2) side is connected to the container ( 1) In a beverage container in which the lid (2) is closed by screwing into the screw part (5) on the side,
The thread part (5) on the container (1) side has two or more independent threads (9), and the thread part (8) on the lid (2) side is also a thread part on the container (1) side. (5) has the same number of independent threads (10) as each thread (10) on the lid (2) side with respect to any thread (9) on the container (1) side. A beverage container which can be screwed together.   The threads (9) on the container (1) side are all in the same shape and arranged in the circumferential direction and at the same height, and the threads (10) on the lid (2) side are both in the same shape and in the circumferential direction. The beverage container according to claim 1, wherein the beverage containers are arranged equally and at the same height, and the circumferential length of each screw thread (9, 10) is equal to or less than a half circumference.   Of the lid (2) side and the container (1) side, the forward / backward member (20) on one side and the engaging part (21) on the other side are hooked to resist the loose rotation of the lid (2), and the release operation And a locking mechanism capable of loosening the lid (2) when the advancement / retraction member (20) is released from the engagement portion (21), and only one advancement / retraction member (20) is incorporated, The beverage container according to claim 1 or 2, wherein the same number of the engaging portions (21) are arranged in the circumferential direction according to a circumferential arrangement interval of the threads (9) on the container (1) side.   Of the threaded portions (5, 8) on the container (1) side and the lid (2) side, the pressure side flank (12, 13) of the thread (9, 10) on at least one side ends the screwing. The lead angle of the lower side contact surface portion (14, 15) that makes contact with the other thread (10, 9) at the lowest height in a state where the operation is performed is smaller than the remaining portion (16a, 16b, 17). The beverage container according to any one of claims 1 to 3.   5. The beverage container according to claim 4, wherein the low side contact surface portion (14, 15) is along a plane perpendicular to the screw axis.

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