US2208257A - Fastening device - Google Patents

Fastening device Download PDF

Info

Publication number
US2208257A
US2208257A US255690A US25569039A US2208257A US 2208257 A US2208257 A US 2208257A US 255690 A US255690 A US 255690A US 25569039 A US25569039 A US 25569039A US 2208257 A US2208257 A US 2208257A
Authority
US
United States
Prior art keywords
band
elements
grooves
slidable
legs
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US255690A
Inventor
Charles B Greenberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US255690A priority Critical patent/US2208257A/en
Application granted granted Critical
Publication of US2208257A publication Critical patent/US2208257A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • AHUMAN NECESSITIES
    • A44HABERDASHERY; JEWELLERY
    • A44CPERSONAL ADORNMENTS, e.g. JEWELLERY; COINS
    • A44C5/00Bracelets; Wrist-watch straps; Fastenings for bracelets or wrist-watch straps
    • A44C5/18Fasteners for straps, chains or the like
    • A44C5/22Fasteners for straps, chains or the like for closed straps
    • AHUMAN NECESSITIES
    • A41WEARING APPAREL
    • A41FGARMENT FASTENINGS; SUSPENDERS
    • A41F1/00Fastening devices specially adapted for garments
    • A41F1/008Adjustable fasteners comprising a track and a slide member
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S24/00Buckles, buttons, clasps
    • Y10S24/30Separable-fastener or required component thereof
    • Y10S24/43Separable-fastener or required component thereof including member having distinct formations and mating member selectively interlocking therewith
    • Y10S24/47Selectively interlocking member having movably attached or biased interlocking component
    • Y10S24/48And cavity for guiding movement of formations
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T24/00Buckles, buttons, clasps, etc.
    • Y10T24/45Separable-fastener or required component thereof [e.g., projection and cavity to complete interlock]
    • Y10T24/45005Separable-fastener or required component thereof [e.g., projection and cavity to complete interlock] with third detached member completing interlock [e.g., hook type]
    • Y10T24/45016Separable-fastener or required component thereof [e.g., projection and cavity to complete interlock] with third detached member completing interlock [e.g., hook type] for jewelry

Definitions

  • This invention relates *to adjustable fasteners, particularly of the type adapted for use on wrist watch straps, belts and the like.
  • Another object of this invention is to facilitate the fabrication of a device of "this class by enabling, in'one form of my invention, certain fastening elements to be'readily alignedand assem bled into operative position.
  • Figure 1 is a perspective of-a wrist watchsand strap, showing a few of the fastening elements embodied in my invention on an exposed portion of the band.
  • Figure 2 is a fragmentary longitudinal cross 45 section of the fastening device constituting this invention when the band is in extended and uncurved condition, the locking element being shown by dot-dash lines its disengaged position.
  • Figure 3 is a transverse cross section of Figure 2 taken along line 3-3.
  • Figure 4 is a fragmentary longitudinal end view of the device of Figure 1, showing the band in curved position in accordance with .its configuration when positioned about a wrist.
  • - Figure '5 is a perspective view of one of the fastening elements.
  • Figure 6 is a plan view of a series of fastening elements of modified form, showing their longitudinal disposition upon aband, and
  • Figure 7 is a plan view of another longitudinal series of fastening elements adapted for use on a flexible band in accordance with this invention, the arrangement shown illustrating aninterlocking structure.
  • the flexible band 8 comprises preferably two layers of material 9 and II] suitably secured together by'mucilaginous or other suitable means.
  • the outer layer I0 thereof has attached thereto a plurality of longitudinally disposed fastening elements these being of *H-shaped configuration in the form of my invention shown in Figures 1 to 4. These elements are arranged in close juxtaposition to each other and are preferably contiguous to each other when 20 the band is in uncurved condition as shown in FigureZ.
  • the said elements I I each containlateral slots I2 and I3 therein, substantially parallel to the upper and lower faces of the elements,'a'nd also contain intermediate recesses I4 and I5 in the forward and rear portions thereof.
  • Each of the said fastening elements II is secured to the outer layer I0 of the band by means of the post I6 positioned preferably at the center of the member, the said post extending through suitably spaced holes in the said layer I0 and being secured in operative position by means of the rivets and rings I1 and washers I8. It will be noted, upon an examination of Figure 2, that the layer I0 is compressed between the said washers I8 and the 1 portion of member I I in facing'relation thereto.
  • the elements I I When the elements I I are positioned as aforesaid, they will form two parallel substantially continuous channels or grooves I9 and 20.
  • My invention provides for a'slidable element affixed to the overlapping portion 2
  • the overlapping or movable portion of the 'band to which the said slidable member is affixed preferably contains two layers of material 23 and 24, the inner layer being hollowed out to form a central longitudinal recessedportion 25 within which certain ,parts of the slidable locking member are positioned.
  • the housing 26 having an aperture 21 therein to accommodate the release lever 28 pivotally mounted at 29 on the ears 30 and 3
  • the said release lever is coextensive with the locking finger 33 adapted to enter the said apertures 22.
  • the said channellike member 32 contains two inwardly extending legs 34 and 35 positioned within the grooves l9 and 20 "and adapted to slidably move therein. It will be noted that the said member embraces the lower section 36 of the members II.
  • the preferred shape of the legs 34 and 35 is slightly arcuate in a longitudinal direction, as can be observed from Figure 2.
  • the locking finger 33 is adapted to enter any of the apertures 22 as aforesaid, thereby preventing the sliding element and the portion of the band to which it is attached from moving in relationlto theband-B under conditions of normal use.
  • the said element 33 is yieldably held in,-.
  • The'band is so designed as to keep all metallic elements out of engagement with the object being embraced, and the structure prevents a disengagement of the cooperative elements even upon ,abending or curving of ,the 1 band.
  • a fastening device for flexible band a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed portions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof. to form two parallel substantially continuous longitudinal grooves therein, and a slidable memberattached to another portion of the band and containing two inwardly extending legs in slidableengagement with the walls of-said grooves and aretractible locking finger I adapted to enter any of said spaces and hold said slidable member against movement with respect to said fastening elements.
  • a flexible band consisting of two-layers of materialsuitably secured togethen a plurality of longitudinally disposed fastening elements-each containing a post extending through one: of said layers and suitably secured thereto, portions of adjacent elements being in contiguous engagement when the band is in its inoperative.
  • the elements containing recessed portions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached'to'another portion of the band and containing twoinwardly extending legs in slidable engagement with -th'walls of said grooves and a retractible locking finger adapted toent'er any of said spaces and hold said slidable member against movement with ments.
  • a fasteningidevice for a flexible band a plurality of longitudinally disposed fastening elements suitably-secured to the band, portions of adjacent elements being in contiguous engagement when the band'is in its inoperative unflexed condition, the elementscontaining recessed portions to form laterally enclosed spaces therebetween, and having slotted portions .
  • the lateral sides thereof to form two parallel respect to said fastening elesubstantially continuous longitudinal grooves therein and a slidable member attached to another portion of the band and containing two inwardly extendinglegs in slidable engagement with the walls of said grooves, said legs being of slight arcuate contour substantially throughout the length thereof and curved in the general direction of the band" when operatively flexed, the terminal of said legs being constantly confined within said grooves, and a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movementwith respect to said fastening elements.
  • a fastening device for a flexible band a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed portions to form laterally enclosed spaces therebetween, and having'slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached'to another portion of the band and containing two inwardly extending legs in slidable engagement with the walls of said grooves, and a pivotally mounted lever having at one end a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movement and at the other end a releasing member adapted upon manual manipulation to retract said finger from its locking position and thereby release said slidable member for operative movement,
  • a fastening device for fiexible band a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed por tions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached to another portion of the band and containing two inwardly extending legs in slidable engagement with the walls of said grooves, a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movement, and spring means i normally urging said finger into its locking position towards and into saidspaces.

Description

July 16, 1940. c. B. GREENBERG FASTENING DEVICE Original Filed May 8, 1936 INVENTOR kaz'las BY B. fireerzbely Q ATTORNEY Patented July 16, 1940 UNITED STATES PATENT wore-ICE 785613, May 8, 1936.
This application February 10,1939, Serial No. 2553590 5 Claims.
This invention relates *to adjustable fasteners, particularly of the type adapted for use on wrist watch straps, belts and the like.
In many devices where-adjustable fasteners are '5 employed, it is frequently essential to effectuate variable adjustments either over very small or large ranges, and it is one of the objects of my invention to accomplish this purpose in asimple manner and by employing a readily fabricated l and relatively inexpensive structure.
In wrist watch straps particularly, there is need for an adjustable device to accommodate-wrists of various sizes, and to produce "this result many intricate structures have been devised, some of which contain metallic elements in engagement with the wrist. It is another'one of my objects to permit a positive variable adjustment without having any metallic parts touch the skin, and this I accomplish by employing a non-'metalli'c strap .20 containing fastening elements remotely positioned from'the wrist.
In certain devices of this class where interlocking elements are employedg-tlrereis frequently the danger of a disengagement of the parts during the adjusting operation, particularly where the curvature of the strap 'or belt is very sharp or pronounced, and it is hence-another object of this invention to overcome this shortcoming by enabling the "interlocking elements to constantly remain in engageme t regardless of the curvature of the embracing band.
Another object of this invention "is to facilitate the fabrication of a device of "this class by enabling, in'one form of my invention, certain fastening elements to be'readily alignedand assem bled into operative position. Y
Other objects, features and advantages will appear from the drawing and the description hereinafter given. 1
Figure 1 is a perspective of-a wrist watchsand strap, showing a few of the fastening elements embodied in my invention on an exposed portion of the band. I
Figure 2 is a fragmentary longitudinal cross 45 section of the fastening device constituting this invention when the band is in extended and uncurved condition, the locking element being shown by dot-dash lines its disengaged position.
Figure 3 is a transverse cross section of Figure 2 taken along line 3-3. a
Figure 4 is a fragmentary longitudinal end view of the device of Figure 1, showing the band in curved position in accordance with .its configuration when positioned about a wrist.
-Figure '5 is a perspective view of one of the fastening elements.
Figure 6 is a plan view of a series of fastening elements of modified form, showing their longitudinal disposition upon aband, and
Figure 7 is a plan view of another longitudinal series of fastening elements adapted for use on a flexible band in accordance with this invention, the arrangement shown illustrating aninterlocking structure.
In the drawing, the flexible band 8 comprises preferably two layers of material 9 and II] suitably secured together by'mucilaginous or other suitable means. The outer layer I0 thereof has attached thereto a plurality of longitudinally disposed fastening elements these being of *H-shaped configuration in the form of my invention shown in Figures 1 to 4. These elements are arranged in close juxtaposition to each other and are preferably contiguous to each other when 20 the band is in uncurved condition as shown in FigureZ. The said elements I I each containlateral slots I2 and I3 therein, substantially parallel to the upper and lower faces of the elements,'a'nd also contain intermediate recesses I4 and I5 in the forward and rear portions thereof. Each of the said fastening elements II is secured to the outer layer I0 of the band by means of the post I6 positioned preferably at the center of the member, the said post extending through suitably spaced holes in the said layer I0 and being secured in operative position by means of the rivets and rings I1 and washers I8. It will be noted, upon an examination of Figure 2, that the layer I0 is compressed between the said washers I8 and the 1 portion of member I I in facing'relation thereto.
When the elements I I are positioned as aforesaid, they will form two parallel substantially continuous channels or grooves I9 and 20. My invention provides for a'slidable element affixed to the overlapping portion 2| of the band adapted to slide within said grooves, said slidable member containing a movable locking element adapted to enter the apertures 22 between the elements I I formed by the .said recessed portions I4 and I5 thereof, for detachable locking engagement, all as will be more fully hereinafter described.
. The overlapping or movable portion of the 'band to which the said slidable member is affixed preferably contains two layers of material 23 and 24, the inner layer being hollowed out to form a central longitudinal recessedportion 25 within which certain ,parts of the slidable locking member are positioned. Suitably secured to the movable portion of the strap, preferably to the layer 23 grooves .Hl'and 2! n In the form of my invention disclosed in Figure thereof, is the housing 26 having an aperture 21 therein to accommodate the release lever 28 pivotally mounted at 29 on the ears 30 and 3| forming preferably an integral part of the slidable channel-like member 32. The said release lever is coextensive with the locking finger 33 adapted to enter the said apertures 22. The said channellike member 32 contains two inwardly extending legs 34 and 35 positioned within the grooves l9 and 20 "and adapted to slidably move therein. It will be noted that the said member embraces the lower section 36 of the members II. The preferred shape of the legs 34 and 35 is slightly arcuate in a longitudinal direction, as can be observed from Figure 2.
In the operation of this device, it will be seen that the locking finger 33 is adapted to enter any of the apertures 22 as aforesaid, thereby preventing the sliding element and the portion of the band to which it is attached from moving in relationlto theband-B under conditions of normal use. The said element 33 is yieldably held in,-. and .urgedrinto, its locking position within the said apertures by the spring 31 which is suitably retained-in place bythe housing .26; Upon manipulating the movable portion of the band and the said slidable member to theleft, in the direction of the arrow (Figure 2), the finger 33 will be forced outof engagement with the aperture when it comes into contact withthe recessed wall-thereof,causing it to assume the position shown in dot-dash lines in Figure 2, and resulting-in a pivotal ,movement of the releasing lever 28 outwardly. By holding this lever in its projected position, the sliding portion of this device can be manipulated in either direction, the legs 34,- and until a predetermined position'is-reached. Upon a release of the member 28, the spring-37 will urge the finger 33 into one of the apertures 22, and consequently cause the lever 28, to. assume its original position flush with the exposed outer surface of the housing 26. Should the finger 33 come to a stop, at a point intermediate one of the apertures 22, a slight continued movement will bringit adjacent one of said apertures to permit the spring 3,! to operatively actuate it and urgeit into, locking position. In this manner adjustments can be readily made, it being obvious that v the smaller the pitchbetween elements ll, themore minute the adjustment.
QQAn examination of Figure 4 will show that when the bandis .curved, the legs 34 and 35 of .the-channel-like member 32 are still contained, throughout the entire length thereof, within. the grooves J9 and 2E]. Thisenables a continued sliding movement to be elfectuated even with the .hand curved, therebeing no possibility of said legs emerging through the spaces 38 between the elements I l. Such spaces 38 are relatively small and are only formed upon a bending of the band, and. can readily be dimensionally designed so as tofprevent a. disengagement of the said legs 34 and 35Vfrom their path of travel within the said 6, insteadof H-shapedelements ll Z-shaped elements 39 are employed, causing a staggered arrangementof the abutting edges All and of contiguous elements. Upon a curving of the b and to which such elements are attached, the spaces formed at such section 40 and 41. will similarly be staggered, thereby preventing the inwardly extending legs of the channel-like mem- ',ber 32 from becoming disengaged from thegroove inasmuch as a terminal portionofthe one of 32 actually 35 sliding withinthe grooves I S and 2i) said legs will at all times be relatively remote from the spaces at 40 or 4!.
In Figure 7 is shown another arrangement where instead of the H-shaped elements H of Figure 5 or the Z-shaped elements of Figure 6 interlocking elements 42 are employed, each element containing at one end thereof a recessed portion 43 to receive the extended portion of the contiguous element. In this manner it is apparent'that the element can be readily positioned in perfect alignment for best operative functionmg.
It will be seen that the invention as described and set forth in the various forms thereof permits of a variable adjustment of a band and -which.can readilybe manipulated at all times.
The'band is so designed as to keep all metallic elements out of engagement with the object being embraced, and the structure prevents a disengagement of the cooperative elements even upon ,abending or curving of ,the 1 band.
'It is of course understood that the various embodiments above described and shown in the drawing are merely illustrative of my invention, and that numerous changes and modifications may be made within the scope of the appended claims without departing from the spirit of thin invention.
What I claim is:
1. In a fastening device for flexible band, a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed portions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof. to form two parallel substantially continuous longitudinal grooves therein, and a slidable memberattached to another portion of the band and containing two inwardly extending legs in slidableengagement with the walls of-said grooves and aretractible locking finger I adapted to enter any of said spaces and hold said slidable member against movement with respect to said fastening elements. Y
2. Inafastening device, a flexible band consisting of two-layers of materialsuitably secured togethen a plurality of longitudinally disposed fastening elements-each containing a post extending through one: of said layers and suitably secured thereto, portions of adjacent elements being in contiguous engagement when the band is in its inoperative. unflexed condition, the elements containing recessed portions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached'to'another portion of the band and containing twoinwardly extending legs in slidable engagement with -th'walls of said grooves and a retractible locking finger adapted toent'er any of said spaces and hold said slidable member against movement with ments.
3. In a fasteningidevice for a flexible band, a plurality of longitudinally disposed fastening elements suitably-secured to the band, portions of adjacent elements being in contiguous engagement when the band'is in its inoperative unflexed condition, the elementscontaining recessed portions to form laterally enclosed spaces therebetween, and having slotted portions .in the lateral sides thereof to form two parallel respect to said fastening elesubstantially continuous longitudinal grooves therein, and a slidable member attached to another portion of the band and containing two inwardly extendinglegs in slidable engagement with the walls of said grooves, said legs being of slight arcuate contour substantially throughout the length thereof and curved in the general direction of the band" when operatively flexed, the terminal of said legs being constantly confined within said grooves, and a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movementwith respect to said fastening elements.
4. In a fastening device for a flexible band, a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed portions to form laterally enclosed spaces therebetween, and having'slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached'to another portion of the band and containing two inwardly extending legs in slidable engagement with the walls of said grooves, and a pivotally mounted lever having at one end a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movement and at the other end a releasing member adapted upon manual manipulation to retract said finger from its locking position and thereby release said slidable member for operative movement,
5. In a fastening device for fiexible band, a plurality of longitudinally disposed fastening elements suitably secured to the band, portions of adjacent elements being in contiguous engagement when the band is in its inoperative unflexed condition, the elements containing recessed por tions to form laterally enclosed spaces therebetween, and having slotted portions in the lateral sides thereof to form two parallel substantially continuous longitudinal grooves therein, and a slidable member attached to another portion of the band and containing two inwardly extending legs in slidable engagement with the walls of said grooves, a retractible locking finger adapted to enter any of said spaces and hold said slidable member against movement, and spring means i normally urging said finger into its locking position towards and into saidspaces.
CHARLES B. GREENBERG.
US255690A 1939-02-10 1939-02-10 Fastening device Expired - Lifetime US2208257A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US255690A US2208257A (en) 1939-02-10 1939-02-10 Fastening device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US255690A US2208257A (en) 1939-02-10 1939-02-10 Fastening device

Publications (1)

Publication Number Publication Date
US2208257A true US2208257A (en) 1940-07-16

Family

ID=22969474

Family Applications (1)

Application Number Title Priority Date Filing Date
US255690A Expired - Lifetime US2208257A (en) 1939-02-10 1939-02-10 Fastening device

Country Status (1)

Country Link
US (1) US2208257A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2618036A (en) * 1950-05-27 1952-11-18 Statham Noel Shoe having adjustable fastener
US4338706A (en) * 1979-03-19 1982-07-13 Yoshida Kogyo K.K. Adjustable fastener
WO1985004559A1 (en) * 1984-04-04 1985-10-24 Tesch A.G. Link band, particularly watchband

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2618036A (en) * 1950-05-27 1952-11-18 Statham Noel Shoe having adjustable fastener
US4338706A (en) * 1979-03-19 1982-07-13 Yoshida Kogyo K.K. Adjustable fastener
WO1985004559A1 (en) * 1984-04-04 1985-10-24 Tesch A.G. Link band, particularly watchband

Similar Documents

Publication Publication Date Title
US3712652A (en) Adjustable ski pole
US3113362A (en) Catch for wrist bands and the like
US2667739A (en) Resiliently expansible multisectional metallic bands
US2208257A (en) Fastening device
US1702640A (en) Coupling member for attaching devices
US2461605A (en) Headgear
US2502901A (en) Slider for adjustable fasteners
US2957303A (en) Expansible band
US1661877A (en) Island
US1689556A (en) Drive chain
US2141068A (en) Extension device
US2109244A (en) Instrument for curling the lashes of an eye
US2457200A (en) Foldable bracelet catch
US1740230A (en) Artificial limb
US2287968A (en) Means to remotely control devices
US2376633A (en) Expansible wrist watch band, bracelet, or the like
US3307347A (en) Expansible band
US2808751A (en) Latch for adjusting worm of a movable jaw wrench
US1861263A (en) Clasp
US2445023A (en) Extensible connector
US1840103A (en) Riveting tool
US2544147A (en) Clasp
US1776142A (en) Flexible closure
DE2313286A1 (en) RING-SHAPED JEWELRY
US1556223A (en) Ornamental chain