Back sack

I claim the ornamental design for a back sack, as shown and described.

FIG. 1 is a front perspective view of a "back sack" showing my new design in a collapsed condition;

FIG. 2 is a front perspective view, shown expanded, and in an open position; and,

FIG. 3 is a rear perspective view, shown expanded, and in a closed position.

Patent	Priority	Assignee	Title
10582757,	Mar 13 2014		Storage container with adjustable, convertible strap
10973308,	Mar 13 2014		Storage container with adjustable, convertible strap
11464320,	Mar 13 2014		Storage container with adjustable, convertible strap
11672315,	Nov 01 2017		Convertible bag and a method for operating a convertible bag
D634926,	Jun 03 2009		Rucksack for seating
D644834,	Jun 03 2009		Rucksack seat with two water resistant containers
D687627,	Feb 16 2011		Backpack
D692653,	May 25 2009	MICHE, LLC	Interchangeable handbag and backpack assembly
D718529,	Dec 19 2013		Storage bag with strap
D728923,	Jun 12 2013		Game bag
D734941,	Aug 22 2013	SC Affiliated Networks, LLC; SC AFFILIATED NETWORKS, LLC DBA SURGE BUSINESS DEVELOPMENT	Transparent bag having a resealable zipper and a flap having an opaque privacy shield insertable through a slit
D759370,	Oct 02 2014	Make Great Days, Inc.	Tote bag
D780525,	Nov 24 2015	Thermos L.L.C.	Lunch bag with convertible handle
D821092,	Jun 12 2014	PHS GENERAL DESIGN SCA	Duffle bag
D889119,	Mar 02 2018		Convertible backpack

Patent	Priority	Assignee	Title
3225806,
3254816,
3802613,
4089447,	Jul 05 1977		Back pack device
4213549,	Jun 18 1979	Phoenix Products, Inc.	Waterproof storage bag and backpack
4273274,	Jun 07 1979		Convertible handbag and backpack
4674664,	Dec 31 1985		Backsack
4974709,	Jul 20 1989		Commuter case
4988216,	Apr 21 1989		Insulated container insertable into a backpack
5570828,	Jul 19 1995		Disposable promotional back pack and method of fabricating same
5577652,	Oct 08 1991	Cher (Int'l) Pty. Ltd.	Convertible backpack
5653337,	Feb 16 1993		Reversible tote bag
5704528,	Oct 07 1996		Multi-purpose valise
5957354,	Sep 30 1996		Backsack
5975392,	Apr 10 1996		Backpack with harness for toy figure
6112959,	Oct 22 1998		Waterproof carrying bag and backpack
6164509,	Jul 19 1999	Zero g Technologies, LLC	Ergonomic bookpack
688671,
D333565,	May 09 1989	LOUIS VUITTON MALLETIER	Rucksack
D390003,	Aug 02 1995	British Dependent Territories - Hong Kong	Bag
D391755,	Jun 18 1996	LION LICENSING, LTD	Umbrella case backpack
D415344,	Aug 11 1998		Backpack with lighted message display
D428249,	Mar 23 1995		Backpack dispenser for beverage containers
D439040,	Oct 01 1998	Maxworld, Inc.; MAXWORLD, INC D B A PROMOLINES	Convertible zipper wallet

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