Attachment part for replacement head of electric toothbrush

Abstract

A replacement toothbrush head includes a tubular sleeve having a brush at one end and a drive shaft receptacle at an opposite end. The receptacle extends into the sleeve from a mouth at the end of the tube to a shoulder spaced from the mouth within the tube. A coupling member is inserted into the receptacle, and a spring clip is positioned between the receptacle and the coupling member, the spring clip having a base positioned between the shoulder and a distal end of the coupling member, and a pair of spring arms overlying a side wall of the coupling member. At least one of the spring arms engages a flexible region of the coupling member, causing the flexible region to flex to engage a drive shaft inserted into the coupling member and retain the replacement head on the drive shaft.

Description

Technical Field

[0001] The present invention generally relates to a replacement head for an electric toothbrush, and more particularly to an attachment portion for retaining a replacement head on an electric toothbrush drive unit. Background Art

[0002] An electric toothbrush generally has a drive unit including a handle portion and a drive shaft. The drive mechanism is housed in the handle portion, and the drive shaft extends from the handle portion and is driven in rotation by the drive mechanism or by a selected oscillation angle. A removable replacement brush head assembly fits onto the extended drive shaft. The brush head assembly generally includes a hollow sleeve that supports the brush head at one end and includes an attachment portion at the opposite end. The attachment portion includes a coupling member that fits into the attachment end of the sleeve. The drive shaft extends into and is retained by the coupling member.

[0003] The interface between the drive shaft and the coupling component must reliably transmit the torque that moves the drive shaft to the brush head and maintain the torque transfer under load. The load refers to the combination of the torque generated by the inertial mass of the oscillating brush head and the forces generated by the interaction with the user's mouth. The interface must also be sufficient to hold the brush head axially on the drive shaft during operation of the toothbrush, while also allowing the user to easily remove the brush head. Axial retention can be a challenging aspect of such an arrangement if the replacement brush head is to be removed regularly for cleaning or other purposes. The arrangement must be such that the functions of torque transfer and axial retention do not degrade even after the replacement head has been repeatedly cycled during the service life of the replacement brush head. Summary of the invention

[0004] The present invention provides a replacement toothbrush head that is attached to a toothbrush drive unit in a manner that retains the brush head on the drive unit and prevents angular rotation of the brush head relative to the drive unit. In addition, the present invention accommodates tolerances of various molded plastic parts to provide a tight fit between the brush head and the drive shaft and provides clear feedback to the user that the brush head is properly seated on the drive shaft.

[0005] In one embodiment, the replacement head includes a sleeve having a longitudinal length, a first end, and a second end opposite the first end, the first end having a head supporting a plurality of cleaning elements extending from the head, and the second end forming an opening extending along the longitudinal length for inserting a drive shaft. The replacement head further includes an attachment portion having a coupling element and a spring clamp component. The coupling element includes a base end; a distal end extending into an opening in the second end of the sleeve; a sidewall extending between the base end and the distal end, the distal end facing the first end of the sleeve; and a drive shaft opening for receiving at least a portion of the drive shaft. In one embodiment, the spring clamp component includes a base and a pair of spring clamp arms extending from a first side of the base, the first side of the base extending over at least a portion of the distal end of the coupling component, the spring clamp arms extending over the sidewalls and biased against the sidewalls so that portions of the sidewalls are bent inwardly for axially retaining the drive shaft.

[0006] In one embodiment, the side wall of the coupling element includes a flexible bridge portion at least partially spaced apart from the remainder of the side wall, wherein one of the spring clip arms is aligned on the bridge portion and causes the bridge portion to flex inwardly. In another embodiment, the exterior of the coupling element may have a key shape corresponding to a matching key shape of the sleeve to prevent angular rotation of the coupling element relative to the sleeve.

[0007] The spring clip may include at least one assembly tab extending from the second side of the base in a direction away from the coupling element. The attachment portion of the sleeve may include a shoulder within the opening, and the at least one assembly tab may abut the shoulder to provide a stop for the coupling component and the spring clip within the sleeve.

[0008] In another embodiment, the drive shaft of the toothbrush drive unit may extend through the coupling component and abut the spring clip when the drive shaft is fully inserted into the replacement head to provide metal-to-metal user feedback that the replacement head is placed on the drive shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is an exploded view of a replacement brush head according to one embodiment;

[0010] Figure 2 is a perspective view of a spring clip according to one embodiment;

[0011] Figure 3 is its front view;

[0012] Figure 4 is its side view;

[0013] Figure 5 is a side view of a coupling component and a spring clip according to one embodiment;

[0014] Figure 6 is its perspective view;

[0015] Figure 7 is along Figure 6 A side cross-sectional view thereof taken along line VII-VII in FIG. 1 ; and

[0016] Figure 8 is its cross-sectional perspective view;

[0017] Fig. 9 is a side cross-sectional view of the coupling component and replacement head with the drive shaft inserted.

[0018] Before explaining the embodiments of the present invention in detail, it should be understood that the present invention is not limited to the details of operation or the details of construction and the arrangement of the components described in the following description or shown in the drawings. The present invention can be implemented in various other embodiments, and can be implemented or executed in alternative ways that are not clearly disclosed in this article. Moreover, it will be understood that the phrases and terms used in this article are used for the purpose of description and should not be considered as restrictive. The use of "comprising" and "including" and their variants is meant to cover the items listed hereafter and their equivalents, as well as additional items and their equivalents. In addition, enumeration can be used for the description of various embodiments. Unless otherwise clearly stated, the use of enumeration should not be interpreted as limiting the present invention to any specific order or number of components. The use of enumeration should not be interpreted as excluding any additional steps or components that can be combined or combined with the enumerated steps or components from the scope of the present invention. DETAILED DESCRIPTION

[0019] Embodiments of the invention described herein relate to a replacement head for an electric toothbrush, and more particularly to an attachment system for retaining a replacement head on a drive shaft of an electric toothbrush. A replacement head is generally shown in Figure 1 and are generally marked as 10.

[0020] I. Overview

[0021] According to one embodiment, the replacement head 10 comprises a sleeve or tube 12 having a head 14 at one end and a receptacle 16 at the opposite end. The head 14 comprises a plurality of cleaning elements 18. The replacement head 10 further comprises a coupling member 20 and a spring clip 22 for insertion into the receptacle 16 of the sleeve 12.

[0022] II. Structure

[0023] See also Figure 1 and Fig. 9, sleeve 12 is a pipe with a first end 24 and a second end 26. Sleeve 12 can be formed by molded plastic, wherein, at least partly, it is hollow at the second end 26. Sleeve 12 generally forms a longitudinal axis extending along the center of the sleeve length and passing through the hollow portion of sleeve 12. First end 24 supports head 14, which can be one of many conventional toothbrush head arrangements. In the illustrated embodiment, head 14 has a generally flat upper surface 28 and a lower surface 30 relative to the upper surface 28. Upper surface 28 supports a plurality of cleaning elements 18, which extend outwardly from upper surface 28 and can be bristles, elastomeric cleaning elements, or a combination of bristle elements and elastomeric cleaning elements arranged into bristle tufts. In one embodiment, head 28 may also include one or more elastomeric soft tissue cleaners, such as an elastomeric portion covering the lower surface 30 of head 14.

[0024] The second end 26 of the sleeve 12 includes a receptacle 16 that forms an opening 31 in the sleeve 12. The opening 31 may extend all or part of the longitudinal length of the sleeve 12, and the receptacle 16 may include all or part of the opening 31. In the illustrated embodiment, the receptacle 16 extends from a mouth 32 at the second end 26 of the sleeve 12 to a shoulder 34 spaced from the mouth 32 along the longitudinal length of the sleeve 12 and within the opening 31. The diameter of the receptacle 16 may increase as it approaches the mouth 32, and the inner wall 33 of the sleeve 12 within the receptacle 16 may include structure for receiving and retaining the coupling member 20. As shown, the shoulder 34 includes a radially inwardly extending wall portion facing the second end 26 of the sleeve 12. In one embodiment, an intermediate shoulder 36 is positioned between the shoulder 34 and the mouth 32, and a rounded annular rib 38 protrudes inwardly from the inner wall 34 adjacent the mouth 32. In another embodiment, one or more of the ribs 38 and shoulders 34 , 36 may be moved or removed as needed to retain the coupling member 20 within the receptacle 16 .

[0025] See also Figure 5-9 , the size and shape of the coupling component 20 is set to be inserted into the receiving portion 16 and retained in the receiving portion 16. The coupling component 20 can be formed of molded plastic and includes a first end or distal end 40, a second end 42, and a sidewall 45 extending between the first end 40 and the second end 42. The sidewall 45 includes an inner surface 48 and an outer surface 50. In the embodiment shown, the coupling component 20 is tubular, wherein the inner surface 48 defines an interior space 44 extending from the distal end 40 to the second end 42. In another embodiment, the coupling component 20 is only partially hollow, for example, wherein the distal end 40 is closed.

[0026] In the illustrated embodiment, the coupling member 20 includes two portions. The first portion 46 extends from the distal end 40 to an inner shoulder 51 located within the conduit and extending radially inward from the inner surface 48. The second portion 52 extends from the shoulder 51 to the second end 42. The sidewall 45 of the first portion 46 includes a substantially flat left and right outer side surfaces 54, 56, and a substantially flat outer upper surface 58 and lower surface 59 to form a key shape that can cooperate with the spring clip 22 and the receiving portion 16. The inner surface 48 can define an opening 49 having a key shape to receive and angularly retain the drive shaft 80, for example, using a flat upper inner surface 60 and a lower inner surface 62. As shown, the portion of the sidewall 45 in the first portion 46 is flexible. In the illustrated embodiment, the flexible portion 47 is a bridge 47 that is partially separated from the sidewall 45 by a slot 66 that enables the bridge 47 to bend relative to the rest of the sidewall 45. In alternative embodiments, the flexible portion may be formed of a flexible material having different properties than the material of the coupling member 20, or may include multiple bridge portions. In the illustrated embodiment, as noted below, the inner surface 48 of the bridge 47 includes a raised portion 70 designed to interfit with the drive shaft 80. In yet another alternative embodiment, the side wall 45 may include one or more cutouts in addition to or in lieu of the flexible portion 47.

[0027] The second portion 52 of the coupling member 20 includes an outer surface 72 having a structure that cooperates with the receiving portion 16 in the sleeve 12. As shown, the diameter of the outer surface 72 increases as it approaches the second end 42 to generally match the shape of the receiving portion 16. The outer surface 72 may include an outer shoulder 74 that is spaced adjacent to or in abutting relationship with the intermediate shoulder 36 of the receiving portion 16. The outer portion 72 of the second portion 52 may also include a rounded annular groove 78 for snap-fitting with the annular protrusion 36 on the receiving portion 16 when the coupling member 20 is inserted into the receiving portion 16. The second portion 52 includes an inner surface 73 that defines an opening 75 extending from the shoulder 51 to the second end 42. As shown, the diameter of the opening 75 is greater than the diameter of the opening 49 in the first portion 46 of the coupling member 20 to accommodate a portion of the toothbrush drive unit, as described in more detail below.

[0028] The spring clip 22 is generally a stamped metal product, but other resilient materials and forming methods may also be used. In one embodiment, the spring clip 22 includes a base 90 and a pair of spring clip arms 92 extending from the base 90, but in alternative embodiments, the spring clip may include only a single spring clip arm 92. More specifically, the base 90 includes an outer surface 94, an inner surface 96 opposite the outer surface 94, and four lateral side edges 98. In one embodiment, the base 90 defines a through hole 93 that extends through the base 90 from the outer surface 94 and the inner surface 96. As shown, the base 90 is generally flat, and the spring arms 92 extend from two opposing side edges 98. The spring arms 92 are bent to extend at an angle from the base 90, and as shown, the spring arms 92 are all bent to extend outwardly in the same direction from the inner surface 96. The spring arms 92 each include a first portion 100 that is angled inwardly toward the other spring arm 92 such that the first portions converge together and a second portion 102 that is angled outwardly such that the second portions 102 diverge from each other as they approach the distal ends 104 of the spring arms 92. In one embodiment, the spring clip 22 also includes a pair of assembly tabs 106. The assembly tabs 106 extend from the other two opposing side edges 98 and are bent at an angle from the side edges 98 to extend away from the outer surface 94 of the base 90 and generally in a direction opposite to the spring clip arms 92. In the illustrated embodiment, the tabs 106 are bent from the base 90 at an angle of approximately 30 degrees, but other angles may also be used.

[0029] The replacement head 10 is designed to be attached to an electric toothbrush drive unit 110. The structure and operation of the drive unit may vary, but generally will include a housing that forms a handle and houses a motor, and a drive shaft that is driven by the motor and extends from one end of the housing. The drive shaft may be driven in one or more of a variety of motions, including but not limited to rotational oscillation, angular displacement, and axial oscillation. See FIG. Fig. 9 , the replacement head 10 is shown as one embodiment attached to a drive unit 110. A small portion of the housing handle 112 is shown, as well as an attachment portion 114 of the housing extending from the housing handle 112. A drive shaft 80 extends outwardly from the attachment portion 114. The drive shaft 80 is provided with a key shape that will be inserted into the coupling portion 20 and will resist angular rotation relative to the coupling portion 20. In the embodiment of the drive shaft shown, the drive shaft 80 has a flat upper surface 116 and a lower surface 118 for interfitting with the coupling portion 20. In one embodiment, the lower surface 118 includes a recessed portion 120 that is shaped to receive the raised portion 70 of the coupling member 20.

[0030] III. Assembly

[0031] exist Figure 5-8FIG. 4 shows an assembly scheme of the coupling component 20 and the spring clip 22, wherein the drive shaft 80 is inserted into the coupling component 20 and Fig. 9 A fully assembled version of the replacement head 10 attached to the toothbrush drive unit 110 is shown in FIG. Figure 5-8 The clip 22 is shown attached to the coupling component to enable the drive shaft 80 to be retained within the coupling component 20. The spring clip 22 is attached to the distal end 40 of the coupling component 20, for example, by sliding the spring clip arms 92 over the distal end 40 so that the arms 92 engage the flat upper surface 58 and lower surface 59 of the first portion 50 of the coupling component 20. One of the clip arms 92 engages the flexible portion 47 of the side wall 45 to bend the flexible portion inwardly. In the embodiment shown, the clip arms 92 engage the bridge 47 and bend the bridge 47 inwardly. When the clip 22 is mated to the coupling component 20, the base 90 abuts the distal end 40 of the coupling component 20, and the assembly tabs 106 extend in a direction away from the distal end 40. In one embodiment, the through hole 93 is aligned with the opening in the distal end 40 to enable drainage through the sleeve 12 and the coupling component 20.

[0032] like Figure 5-8 As further shown in FIG. 1 , with the spring clip 22 in place on the coupling component 20, the coupling component 20 functions to simultaneously prevent angular rotation of the coupling component 20 relative to the drive shaft 80 and axial removal of the coupling component 20 from the drive shaft 80. Angular rotation is prevented primarily by the corresponding key-shaped shapes of the drive shaft 80 and the inner surfaces 48 of the coupling component 20. More specifically, in the illustrated embodiment, angular rotation is prevented by engagement of the flat upper and lower surfaces 116, 118 of the drive shaft 80 with the flat inner surfaces 60 and 62 within the coupling component 20. The force of the spring clip 22 acting on the flexible bridge 47 to prevent axial removal (i.e., pulling the coupling component 20 away from the drive shaft 80) is transmitted to the drive shaft 80 extending into the coupling component 20, wherein the inner surface 48 of the bridge component 47 presses against the surface 118 of the drive shaft 80. In embodiments where the inner surface 48 of the bridge 47 includes raised portions 70, the raised portions may interfit into the recessed portions 120 of the drive shaft 80 to help prevent axial removal. In alternative embodiments where the sidewall 45 of the coupling member 20 includes a cutout instead of the flexible member 47, the spring clip 22 may fit over the coupling member 20 such that the clip arms 92 extend through the cutout and directly engage the drive shaft 80 to axially retain the drive shaft.

[0033] Fig. 9 The assembled brush head 10 is shown with the drive shaft 80 inserted. More specifically, Fig. 91 shows a cross section of a portion of the sleeve 12, wherein the coupling component 20, the spring clip 22, the drive shaft 80 and the attachment portion 114 of the drive unit 110 are inserted. The spring clip 22 is mounted on the coupling component 20, and the drive shaft 80 is inserted and retained in the coupling component 20, as described above in conjunction with Figure 5-8 16. The coupling component 20 and spring clip 22 are inserted into the receptacle 16 in the sleeve 12. As shown, the coupling component 20 snap fits within the receptacle 16. In the illustrated embodiment, the snap fit occurs between the rounded annular groove 78 on the coupling component 20 and the annular protrusion 36 on the receptacle 16, but other alternative snap fit or friction fit retention mechanisms may be used. The keyed outer shape of the coupling component 20 and the inner shape of the receptacle 16 cooperate with each other to prevent angular rotation of the coupling component 20 relative to the sleeve 12.

[0034] In one embodiment, when the coupling component 20 and spring 22 are longitudinally inserted into the mouth 32 through the opening 31 of the receiving portion 16, the spring clip arm 92 is clamped between the inner wall 34 of the receiving portion 16 and the coupling component 20, and the base 90 of the spring clip 22 is clamped between the distal end 40 of the coupling component 20 and the shoulder 34 at the end of the receiving portion 16. Fig. 9 As shown in , the spring assembly tabs 106 are angled outward to abut and engage the shoulder 34 on the sleeve 12, which can be used to account for tolerances in various molded plastic parts and can provide a force within the assembly that creates a tight fit between the parts to reduce unwanted noise. Fig. 9 As shown in , the drive shaft 80 extends through the distal end 40 of the coupling component 20 to abut the base 90 of the spring clip 22. In this embodiment, the spring clip 22 provides an end of travel for the drive shaft 80, which acts to provide the user with a clear metal-to-metal feel and give the user feedback that the brush head 10 is fully installed. Finally, when fully inserted, the attachment portion 110 of the drive unit 110 is positioned within the opening 75 of the coupling component 20.

[0035] The above description is a description of the current embodiment of the present invention. Various modifications and changes may be made without departing from the spirit and broader aspects of the present invention as defined by the appended claims, which are interpreted according to the principles of patent law including the doctrine of equivalents. The present disclosure is presented for illustrative purposes, and the present disclosure should not be interpreted as an exhaustive description of all embodiments of the present invention, or the scope of the claims should be limited to the specific elements shown or described in conjunction with these embodiments. For example, without limitation, any individual element of the invention described may be replaced by an alternative element, which provides substantially similar functions or otherwise provides appropriate operations. For example, this includes currently known alternative elements, such as alternative elements currently known to those skilled in the art, and alternative elements that may be developed in the future, such as alternative elements that those skilled in the art may recognize as alternatives when developing. Further, the disclosed embodiments may include multiple features, which are described consistently and may provide a series of benefits in a collaborative manner. Except for the scope otherwise explicitly set forth in the disclosed claims, the present invention is not limited to those embodiments that include all of these features or provide all of the benefits indicated. Any reference to claim elements in the singular (eg, using the articles "a," "an," "the," or "said") should not be construed as limiting the element to the singular.

Claims

1. A replacement toothbrush head, comprising: a sleeve including a longitudinal length, a first end having a head supporting a plurality of cleaning elements extending therefrom, and a second end opposite the first end, the first end defining an opening extending along the longitudinal length for inserting a drive shaft; as well as an attachment portion including a coupling member and a spring clip member, the coupling member including a base end, a distal end extending into the opening in the second end of the sleeve, and a sidewall extending between the base end and the distal end, the distal end facing the first end of the sleeve, the coupling member including a drive shaft opening for receiving at least a portion of the drive shaft, the spring clip member including a base and at least one spring clip arm extending from a first side of the base, the first side of the base extending over at least a portion of the distal end of the coupling member, the at least one spring clip arm extending over and biased against the sidewall so that portions of the sidewall flex inwardly to retain the drive shaft; Wherein the spring clip base has a second side opposite the first side, wherein the spring clip base includes at least one assembly tab extending from the second side of the base.

2. The replacement toothbrush head according to claim 1, characterized in that: The side wall of the coupling component includes a flexible bridge portion at least partially spaced apart from the side wall, wherein the at least one spring clip arm is aligned on the bridge portion and causes the bridge portion to flex inwardly.

3. A replacement toothbrush head according to claim 1 or 2, characterized in that: The spring clip base defines a through hole.

4. A replacement toothbrush head according to claim 1 or 2, characterized in that: The coupling member includes a structure for cooperating with the second end portion of the sleeve.

5. A replacement toothbrush head according to claim 1 or 2, characterized in that: One of the sidewall of the coupling component and the second end of the sleeve includes an annular protrusion, and the other of the sidewall of the coupling component and the second end of the sleeve includes an annular channel such that the protrusion snap fits into the channel.

6. A replacement toothbrush head according to claim 1 or 2, characterized in that: The attachment portion includes a shoulder within the opening, and wherein the at least one assembly tab of the spring clip abuts the shoulder.

7. A replacement toothbrush head, comprising: a hollow tube having a brush at one end and a drive shaft receptacle at an opposite end, the tube having a longitudinal axis, the receptacle extending into the tube along the longitudinal axis from a mouth at the end of the tube to a shoulder within the tube spaced from the mouth along the longitudinal axis; a coupling component inserted into the receiving portion, the coupling component having an open end, a distal end, and a side wall extending between the distal end and the open end, the distal end facing the shoulder, the side wall including a flexible area, the coupling component defining an interior space having a key shape for preventing rotation of a drive shaft inserted into the coupling component and the receiving portion; as well as a spring clip positioned between the receiving portion and the coupling member, the spring clip having a base and a pair of spring clip arms extending from the base, the spring clip arms overlying at least a portion of the side wall, at least one of the spring clip arms engaging the flexible region of the side wall and causing the flexible region to bend toward the interior space of the coupling member; Wherein the spring clamp arms extend from the base in a first direction, wherein the spring clamp includes a pair of spring assembly tabs extending from the base in a second direction, the spring assembly tabs engaging the shoulder.

8. The replacement toothbrush head according to claim 7, characterized in that: The flexible region is a bridge at least partially spaced apart from the sidewall.

9. The replacement toothbrush head according to claim 8, characterized in that: The base overlies the distal end of the coupling member.

10. The replacement toothbrush head according to claim 9, characterized in that: The distal end defines a coupling component drain hole, and wherein the base defines a spring clip drain hole aligned with the coupling component drain hole.

11. The replacement toothbrush head according to claim 10, characterized in that: The bridge includes an outer surface that engages the spring clip and an inner surface opposite the outer surface, the inner surface including a raised portion for engaging a toothbrush drive shaft.

12. A system for attaching a replacement toothbrush head to an electric toothbrush driver, comprising: a drive shaft drivable to oscillate at a desired frequency, the drive shaft extending along a longitudinal axis, the drive shaft having an outer surface defining a key shape; a replacement brush head comprising a hollow tube having a brush at one end and a drive shaft receptacle at an opposite end, the tube extending along the longitudinal axis, the receptacle extending into the tube along the longitudinal axis from a mouth at the end of the tube to a shoulder within the tube spaced from the mouth along the longitudinal axis; a coupling member inserted into the receiving portion, the coupling member having an open end, a distal end, and a side wall extending between the distal end and the open end, the distal end facing the shoulder, the coupling member defining an interior space having a key shape corresponding to the key shape of the drive shaft for preventing the drive shaft inserted into the coupling member and the receiving portion from rotating; as well as a spring clip positioned between the receiving portion and the coupling member, the spring clip having a base and a pair of spring clip arms extending from the base, the base being positioned between the shoulder and the distal end; wherein the drive shaft is inserted into the interior space of the coupling component and at least one of the spring clip arms engages at least one of the side wall and the drive shaft to axially retain the coupling component on the drive shaft; Wherein the spring clamp arms extend from the base in a first direction, wherein the spring clamp includes a pair of spring assembly tabs extending from the base in a second direction, the spring assembly tabs engaging the shoulder.

13. The system for attachment according to claim 12, characterized in that The side wall includes a flexible bridge at least partially spaced apart from the side wall, at least one of the spring clamp arms overlies the flexible bridge and bends the flexible bridge toward the interior space of the connecting component so that the flexible bridge engages the drive shaft to axially retain the connecting component on the drive shaft.

14. The system for attachment according to claim 12, characterized in that The key shape of the drive shaft includes at least one flat surface, and wherein the key shape of the interior space of the coupling component includes at least one flat surface that aligns with the drive shaft flat surface.

15. The system for attachment according to claim 12, characterized in that The drive shaft engages the spring clip base.

16. The system for attachment according to claim 15, characterized in that The flexible bridge includes an outer surface engaging the spring clip and an inner surface opposite the outer surface, the inner surface including a raised portion, wherein the drive shaft includes a recess aligned with the raised portion, the raised portion and the recess cooperate to prevent axial removal of the drive shaft.

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