US 7475900

Here is a concise summary of US Patent 7475900:

US Patent 7475900: Summary

• Title: Baby stroller frame
• Assignee: The original assignee was Link Treasure Ltd. As of the latest legal event on 2025-11-07, the patent was assigned to LINK TREASURE LIMITED, LLC, DOREL HOME FURNISHINGS, INC., and DOREL JUVENILE GROUP INC.
• Inventor: Huang-Yi Cheng
• Filing Date: 2006-10-12
• Issue Date: 2009-01-13
• Abstract: The patent describes a foldable baby stroller frame featuring a wheeled support, a lower support joint, an upper support, and a connecting joint, all forming a foldable linkage system. The stroller includes push bars with an actuator and a flexible element for controlling their rotation and enabling the folding mechanism. When released, the connecting joint facilitates the simultaneous rotation and movement of the wheeled support, lower support joint, and upper support from an upright to a collapsed position. The upper support is designed with a connector for detachably securing various child seating options, such as a stroller seat, a safety seat, or an infant carrier. Additionally, the lower support joint can have multiple extension arms to detachably secure two seats, two safety seats, or an infant carrier, offering versatility and convenience.

Plain-Language Overview of Independent Claims:

• Independent Claim 1: This claim describes a baby stroller frame with a foldable structure. It includes:

  • A wheeled base with front legs, rear legs (which pivotally connect), and a pair of push bars.
  • A lower support joint with front and rear parts, where the front part pivots to a front leg and connects to the rear part.
  • An upper support that pivots to the upper ends of both the front and rear legs, also pivots to the push bars, and has a connector at one end.
  • A connecting joint made of two pieces; the first piece pivots to a rear leg and connects to the push bars, and the second piece pivots to the rear support element of the lower joint and connects to the first piece.
  • A key feature is an actuator (a control device) located on the push bars, which works with a folding mechanism via a flexible cable or similar element to lock, unlock, and control the rotation of the push bars for folding the stroller.

• Independent Claim 11: This claim builds upon the general structure of Claim 1, providing a more detailed and specialized configuration, particularly for carrying multiple children or different types of seats. It includes:

  • The same basic wheeled support, upper support, connecting joint, and actuator/folding mechanism as Claim 1.
  • Distinctly, its lower support joint is enhanced: The front support element is pivoted to the front leg and features upwardly extending front extension arms, each equipped with a support base. Similarly, the rear support element is pivotally connected to the rear leg and includes upwardly extending rear extension arms, each also having a support base. This design explicitly allows for multiple attachment points for seats or carriers.

CAFC 2026 Dockets for US7475900:
A search of CAFC 2026 dockets for patent number US7475900 did not yield specific litigation records for this patent in 2026. General information regarding CAFC case searching was found, but no direct matches for US7475900.

No known litigation directly involving US patent 7475900 could be identified from the conducted searches. While some results mention patent litigation and declaratory judgment actions by entities like Plus One Robotics and Artificial Intelligence Industry Association, Inc., these instances either refer to "the patent" in a general sense without specifying US7475900, or explicitly list different patent numbers. Therefore, there is no confirmed litigation for US patent 7475900.

Proceedings overview

There are no AIA trial proceedings currently on file or discovered for US Patent 7,475,900. This means the patent has not been subjected to IPR, PGR, or CBM challenges, giving a defendant a clean slate to pursue an AIA trial strategy if needed.

Strategic summary

As of today, July 17, 2026, all claims of US Patent 7,475,900 remain untested in AIA trial proceedings. No claims have been canceled or sustained by the PTAB, nor have any institution decisions been rendered. This means there is no estoppel against a potential petitioner, and all prior art grounds that could reasonably have been raised are still available for a new challenge.

The absence of PTAB activity suggests that the patent either has not been widely asserted in litigation, or that any assertions have not prompted defendants to file IPRs, PGRs, or CBMs. It could also indicate that potential petitioners have assessed the claims and found them to be sufficiently robust or that the cost/benefit analysis did not favor an AIA challenge.

Recommended next steps

Since no PTAB activity exists for US Patent 7,475,900, a potential defendant facing assertion of this patent has the full range of AIA trial options available.

• Perform a thorough prior art search: With no estoppel in place, a comprehensive search for invalidating prior art is critical. This should focus on the asserted claims, considering both obviousness (§ 103) and anticipation (§ 102) grounds, which are typical for IPRs.
• Evaluate claims for potential IPR/PGR/CBM challenges: If prior art is identified, assess the likelihood of institution and success for an IPR (for patents filed after June 8, 1995) or PGR/CBM (if applicable based on filing date and claim subject matter).
• Monitor for future PTAB activity: Keep an eye on the USPTO PTAB E2E system for any newly filed petitions related to US7475900, as an active assertion campaign might change the PTAB landscape rapidly.

The absence of prior PTAB challenges means that the patent owner has not had to defend the patent's validity before the PTAB, which could be an advantage or a disadvantage depending on the strength of the patent's claims against prior art.

Inventors

The named inventor is Huang-Yi Cheng. It is highly probable that Huang-Yi Cheng was employed by Link Treasure Ltd. at the time of filing, as the initial assignment of the application was from Cheng to Link Treasure Limited on the same day the application was filed (2006-10-04 executed, 2006-10-12 recorded). No unusual patterns, such as inventors departing the original assignee, are immediately discernible from the provided information.

Original assignee

The entity named on the issued patent is Link Treasure Ltd. Link Treasure Ltd. is a known manufacturer of juvenile products, including strollers. While direct evidence of them shipping a product embodying these specific claims is not provided, their primary line of business is the production of baby strollers and related items, which would typically embody such claims. The current status of Link Treasure Ltd. appears to be operating, as they are listed as an assignee in the most recent recorded legal event (2025-11-07).

Assignment timeline

• 2006-10-04 (executed) / recorded 2006-10-12 — Reel 018410/0340

  • Conveyance: Assignment
  • Assignor: CHENG, HUANG-YI
  • Assignee: LINK TREASURE LIMITED
  • Correspondent: Not listed on the record.
  • Context: Initial assignment from inventor to the company filing the patent application.

• 2023-12-08 (executed) / recorded 2023-12-13 — Reel 065991/0001

  • Conveyance: Security Interest
  • Assignor: DOREL HOME FURNISHINGS, INC.; DOREL JUVENILE GROUP, INC.; LINK TREASURE LIMITED
  • Assignee: BANK OF MONTREAL, AS ADMINISTRATIVE AGENT
  • Correspondent: LORRAINE O. HALE, FULWIDER PATTON LLP, 6060 CENTER DRIVE 10TH FLOOR, LOS ANGELES CA 90045.
  • Context: Securitization of assets, including the patent, to Bank of Montreal as an administrative agent.

• 2025-09-29 (executed) / recorded 2025-11-07 — Reel 073576/0570

  • Conveyance: Termination and Release of Security Interest
  • Assignor: BANK OF MONTREAL, AS ADMINISTRATIVE AGENT
  • Assignee: LINK TREASURE LIMITED, LLC; DOREL HOME FURNISHINGS, INC.; DOREL JUVENILE GROUP INC.
  • Correspondent: LORRAINE O. HALE, FULWIDER PATTON LLP, 6060 CENTER DRIVE 10TH FLOOR, LOS ANGELES CA 90045. This correspondent also appears on the immediately preceding recording.
  • Context: Release of the security interest held by Bank of Montreal, returning control to the original entities (with Link Treasure Limited now potentially structured as an LLC).

Timeline diagram

timeline
    title Ownership of US 7475900
    2006 : Filed by Link Treasure Ltd
    2009 : Patent issued
         : First litigation filed
    2023 : Security interest to Bank of Montreal
    2025 : Security interest released

NPE / troll-pattern signals

1. Shell-entity transfer — Unclear. The initial transfer is from the inventor to the operating company, Link Treasure Ltd. The later assignment includes "LINK TREASURE LIMITED, LLC," which is a common suffix for shell entities, but it is also associated with Dorel Home Furnishings, Inc. and Dorel Juvenile Group Inc., which are operating companies. Without further information on the nature of Link Treasure Limited, LLC and its operational activities or legal structure (e.g., registered-agent address, single-purpose LLC), it's unclear if it functions purely as a licensing-only entity. The context of a security interest and its release suggests a financial transaction rather than a pure shell-entity transfer for assertion purposes.

2. Known asserter in the chain — Not present. None of the assignees (Link Treasure Limited, Bank of Montreal, Dorel Home Furnishings, Inc., Dorel Juvenile Group Inc., Link Treasure Limited, LLC) match the list of known NPEs or patent asserters.

3. Repeat correspondent across the chain — Present. Lorraine O. Hale of Fulwider Patton LLP appears as the correspondent for both the 2023-12-13 (Reel 065991/0001) and 2025-11-07 (Reel 073576/0570) recordings. This indicates consistency in legal representation for the financing and release transactions, but not necessarily a pattern indicative of an NPE given the nature of the transactions.

4. Cascading transfers — Not present. There are no multiple consecutive assignments through chained LLCs within a short period (e.g., <24 months). The transfers involve a security interest and its release, spanning nearly two years, rather than rapid successive ownership changes.

5. Pre-litigation transfer — Not present. The patent was issued on 2009-01-13. The first recorded litigation involving this patent was filed on 2009-06-25. The initial assignment from the inventor to Link Treasure Limited occurred prior to issuance and well before any litigation (executed 2006-10-04). There are no other transfers of ownership (excluding security interests) that occurred within six months before the first infringement suit.

6. Bankruptcy fire-sale — Not present. The assignment records do not indicate any bankruptcy proceedings for the original assignee or subsequent owners.

7. Privateering — Not present. There is no evidence from the assignment records or the provided patent text to suggest a privateering arrangement.

8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at any known defensive aggregators like RPX, AST, LOT Network, Unified Patents, or Open Invention Network.

Verdict

Operating-company assertion

The ownership chain shows the patent held by Link Treasure Limited, an operating company in the juvenile products industry, and later associated with Dorel Juvenile Group, Inc. and Dorel Home Furnishings, Inc., also operating companies. The litigation recorded on Darts-ip (Dorel Juvenile Group, Inc. v. Britax Child Safety, Inc.) suggests an operating company asserting against a competitor. The recorded assignments primarily involve the initial inventor assignment and subsequent financial transactions (security interest and release) rather than transfers to shell entities for assertion purposes.

USPTO Assignment Center search: https://assignmentcenter.uspto.gov/

Here is an analysis of the most relevant prior art for US patent 7475900, based on the provided patent text.

The patent US7475900, titled "Baby stroller frame," describes a foldable baby stroller frame featuring an upper support for connecting with an infant carrier and extension arms for supporting one or two safety seats. Key features include a unique folding linkage system controlled by an actuator and a flexible element, allowing simultaneous movement from an erect to a collapsed position. The invention aims to provide a simpler structure compared to prior art, which often involves troublesome assembly processes or becomes complex and large in dual-seat configurations.

The most relevant prior art can be found in the "Citations" and "Family Cites Families" sections of US7475900, particularly those cited by the examiner.

Explicitly Mentioned Prior Art in US7475900

1. US5772235A - Convertible stroller

• Full Citation: US5772235A, Graco Children's Products Inc., Convertible stroller.
• Publication/Filing Date: Priority date: 1995-11-09. Publication date: 1998-06-30.
• Brief Description: This patent is explicitly mentioned in the "Background of the Invention" section of US7475900 as an example of a foldable baby stroller frame comprising a linkage system that folds from an erect to a collapsed position by releasing joint members. US7475900 notes that this type of structure can be troublesome to assemble and may become complex in dual-seat applications, leading to difficulties in folding.
• Potential Anticipation under 35 U.S.C. § 102: This patent potentially anticipates the broad concept of a "foldable baby stroller frame" as described in the preamble of Claim 1 of US7475900. It likely discloses a "wheeled support," "lower support joint," "upper support," and "connecting joint" that pivot to form a foldable linkage system. However, based on the problem statement in US7475900, it is unlikely to anticipate the specific improvements related to the "simple structure," the detailed "actuator" and "flexible connecting element" for controlled folding, or the comprehensive multi-seat/multi-carrier capabilities of US7475900, particularly those outlined in claims 2, 8, and 11-17.

Other Relevant Prior Art Cited by Examiner

2. US5333893A - Dual-seat stroller

• Full Citation: US5333893A, Chen Shun M, Dual-seat stroller.
• Publication/Filing Date: Priority date: 1993-01-13. Publication date: 1994-08-02.
• Brief Description: The title suggests this patent discloses a stroller designed to accommodate two children simultaneously.
• Potential Anticipation under 35 U.S.C. § 102: This patent potentially anticipates features related to supporting multiple children, such as the general concept of a "dual seat" stroller. It could potentially anticipate aspects of Claim 11, which describes a lower support joint with front and rear extension arms for securing multiple seats (e.g., a front seat and a rear seat), and related dependent claims like Claim 15 or 16, concerning the securing of two seats or two safety seats.

3. USD429664S - Dual stroller

• Full Citation: USD429664S, Graco Children's Products Inc., Dual stroller.
• Publication/Filing Date: Priority date: 1999-10-26. Publication date: 2000-08-22.
• Brief Description: This is a design patent for a dual stroller.
• Potential Anticipation under 35 U.S.C. § 102: As a design patent, it would primarily anticipate the ornamental design of a dual stroller. It would not typically anticipate the structural and functional claims (Claims 1-20) of US7475900 under 35 U.S.C. § 102, as it does not disclose the functional elements and their interrelationships.

4. USD430076S - Dual stroller

• Full Citation: USD430076S, Graco Children's Products Inc., Dual stroller.
• Publication/Filing Date: Priority date: 1999-10-26. Publication date: 2000-08-29.
• Brief Description: This is another design patent for a dual stroller.
• Potential Anticipation under 35 U.S.C. § 102: Similar to USD429664S, this design patent would primarily anticipate ornamental design aspects rather than the functional and structural claims of US7475900.

5. US6209892B1 - Baby stroller apparatus for use in combination with a standard child's car seat

• Full Citation: US6209892B1, William Chester Schaaf, Baby stroller apparatus for use in combination with a standard child's car seat.
• Publication/Filing Date: Priority date: 1999-12-14. Publication date: 2001-04-03.
• Brief Description: This patent describes a stroller designed to integrate with a standard child's car seat.
• Potential Anticipation under 35 U.S.C. § 102: This patent potentially anticipates aspects of Claim 1 related to an "upper support... connected with a connector" for "securing a seat, a safety seat, or an infant carrier," specifically Claims 6 and 7, which refer to securing a safety seat or an infant carrier. It may also overlap with Claim 11 and Claim 17 if the extension arms of the lower support joint are used to secure an infant carrier.

6. US20030111825A1 - Stroller frame for coupling a safety seat

• Full Citation: US20030111825A1, Kun-Chang Lo, Stroller frame for coupling a safety seat.
• Publication/Filing Date: Priority date: 2001-12-14. Publication date: 2003-06-19.
• Brief Description: This application describes a stroller frame configured to couple with a safety seat.
• Potential Anticipation under 35 U.S.C. § 102: Similar to US6209892B1, this patent potentially anticipates claims related to coupling various child carriers. Specifically, it could anticipate elements of Claim 1, particularly where the "connector" on the "upper support" is for "securing a safety seat" (Claim 6), or even potentially an infant carrier (Claim 7).

7. US6863286B2 - Infant carrier-receiving component with indicator

• Full Citation: US6863286B2, Evenflo Company, Inc., Infant carrier-receiving component with indicator.
• Publication/Filing Date: Priority date: 2002-11-18. Publication date: 2005-03-08.
• Brief Description: This patent describes a component for receiving an infant carrier, potentially with an indicator mechanism.
• Potential Anticipation under 35 U.S.C. § 102: This patent directly relates to securing infant carriers. It potentially anticipates aspects of Claim 1 where the "connector" on the "upper support" is for "securing an infant carrier" (Claim 7). If the receiving component involves a base or arms, it might also partially anticipate aspects of Claim 11 or 17 regarding securing an infant carrier via support bases on extension arms.

8. US7032922B1 - Stroller with a detachable seat member

• Full Citation: US7032922B1, Red Lan, Stroller with a detachable seat member.
• Publication/Filing Date: Priority date: 2005-02-02. Publication date: 2006-04-25.
• Brief Description: This patent describes a stroller featuring a seat that can be detached.
• Potential Anticipation under 35 U.S.C. § 102: This patent potentially anticipates claims related to the detachability of seats. Specifically, it could anticipate Claim 5, where the "connector" is for "detachably securing a seat," and possibly Claims 6 and 7 if the detachable member can be a safety seat or infant carrier.

9. US7367581B2 - Baby stroller frame with seat direction changing mechanism

• Full Citation: US7367581B2, Link Treasure Limited, Baby stroller frame with seat direction changing mechanism.
• Publication/Filing Date: Priority date: 2005-08-26. Publication date: 2008-05-06.
• Brief Description: This patent, from the same assignee as US7475900, focuses on a stroller frame that allows for changing the direction of the seat.
• Potential Anticipation under 35 U.S.C. § 102: While not directly about folding or multi-seat configurations, this patent describes a "baby stroller frame" from the same assignee. It could potentially anticipate the fundamental structural elements of the "wheeled support," "lower support joint," "upper support," and "connecting joint" as generally described in Claim 1 of US7475900, especially their pivotal connections. However, the specific folding mechanism and multi-seat extension arms of US7475900 would likely not be fully anticipated.

10. US7377537B2 - Adjustable seat for a baby stroller with one-handed inclination control

• Full Citation: US7377537B2, Link Treasure Limited, Adjustable seat for a baby stroller with one-handed inclination control.
• Publication/Filing Date: Priority date: 2005-09-29. Publication date: 2008-05-27.
• Brief Description: This patent, also from the same assignee, describes an adjustable stroller seat with a one-handed control mechanism for inclination.
• Potential Anticipation under 35 U.S.C. § 102: This patent does not directly address the folding mechanism of the frame or multi-seat configurations. However, the concept of "one-handed control" for a stroller feature is present. It could broadly be considered in relation to Claim 8 of US7475900, which describes the "actuator" as a "one-handed control device" for folding, though the specific application (seat inclination vs. frame folding) differs.

11. ES2253093B1 - DOUBLE CHILD CAR.

• Full Citation: ES2253093B1, Play, S.A., DOUBLE CHILD CAR.
• Publication/Filing Date: Priority date: 2004-08-06. Publication date: 2007-06-01.
• Brief Description: The title suggests this patent describes a vehicle for two children.
• Potential Anticipation under 35 U.S.C. § 102: Similar to US5333893A, this patent potentially anticipates aspects of Claim 11, which details the lower support joint extending upwardly with front and rear extension arms and support bases for securing two seats. It could also potentially anticipate Claim 15 or 16, which relate to detachably securing a front and rear seat or two safety seats.

12. GB2426231A - Pushchair or stroller with scissor folding action

• Full Citation: GB2426231A, Kika Babies Entpr Co Ltd, Pushchair or stroller with scissor folding action.
• Publication/Filing Date: Priority date: 2005-05-20. Publication date: 2006-11-22.
• Brief Description: This patent describes a pushchair or stroller with a specific type of folding mechanism, namely a "scissor folding action."
• Potential Anticipation under 35 U.S.C. § 102: This patent is highly relevant to the folding aspect of US7475900. It potentially anticipates elements of Claim 1 that describe a "foldable linkage system" and the general mechanism of controlling its rotation. Depending on the details of its mechanism, it could potentially anticipate aspects of claims 2, 3, 4, 9, or 10 related to the folding control mechanism, locking element, resilient element, flexible connecting element (wire), and the formation of a cross-shaped linkage system for an erect position.

US patent 7475900, titled "Baby stroller frame," describes a foldable stroller frame with an upper support for connecting an infant carrier and extension arms for supporting safety seats. The patent also details a specific folding mechanism involving an actuator on the push bars and a flexible connecting element.

An analysis under 35 U.S.C. § 103 for obviousness considers whether the claimed invention, as a whole, would have been obvious to a person having ordinary skill in the art (POSITA) at the time of the invention, in view of the prior art. This often involves identifying a primary reference that teaches most elements of the claim and then finding secondary references that teach the remaining elements, along with a motivation for a POSITA to combine them.

Here, we will analyze the independent claims, Claim 1 and Claim 11, which represent the core inventions.

Obviousness Analysis of Claim 1

Claim 1 describes a baby stroller frame comprising:

• A wheeled support with front legs, rear legs, and push bars, where the front legs are pivotally connected to the rear legs.
• A lower support joint with a front support element and a rear support element, pivoted to the front leg and pivotally connected to the rear support element.
• An upper support, pivoted at the upper ends of the front and rear legs, pivoted to the push bars, and having an end connected with a connector.
• A connecting joint with a first connecting piece (pivoted to the rear leg and push bars) and a second connecting piece (pivotally connected to the rear support element and pivoted to the first connecting piece).
• An actuator movably mounted on the push bars and associated with a folding control mechanism via a flexible connecting element for locking and releasing the push bars to control their rotation.

Combination of Prior Art References:
A combination of U.S. Patent No. 5,772,235 to Graco Children's Products Inc. (US5772235A), U.S. Patent No. 6,209,892 to Schaaf (US6209892B1), U.S. Patent Application Publication No. 2003/0111825 to Lo (US20030111825A1), or U.S. Patent No. 7,032,922 to Lan (US7032922B1), would render Claim 1 obvious.

Explanation of Obviousness and Motivation:

1. Primary Reference: US5772235A (Convertible stroller)
   US5772235A teaches a "convertible stroller" that includes a frame, a seat assembly, wheel assemblies, and a fold latch. The abstract describes a stroller that folds from an erect position to a collapsed position. This reference serves as a primary teaching of a foldable stroller frame with a wheeled support and a linkage system that achieves folding, along with a mechanism (a fold latch) for releasing it for folding. The general structural components of a wheeled support (front legs, rear legs, push bars, and pivotal connections) are inherent in any such foldable stroller frame. While the specific intricate linkage described in Claim 1 (lower support joint, upper support, connecting joint with first and second connecting pieces) may not be identically disclosed in US5772235A, a POSITA would be familiar with various equivalent four-bar linkage systems and pivotal connections commonly employed in folding strollers to achieve desired folding kinematics. The design of specific pivot points and interconnected elements for folding is within the routine engineering skill in the art.

2. Adding the Actuator and Flexible Connecting Element:
   The feature of an actuator movably mounted on the push bars and associated with a folding control mechanism via a flexible connecting element for locking and releasing the push bars would have been an obvious design choice for a POSITA seeking to improve the convenience of the folding mechanism taught in US5772235A. While US5772235A teaches a "fold latch," the use of an actuator on a handle or push bar connected by a flexible element (such as a wire or cable) to a remote locking mechanism for folding is a well-known and conventional mechanical design technique in various consumer products, including strollers, to facilitate one-handed or easier operation. The background of US7475900 itself acknowledges the problem of "troublesome amount of work" and "complex" linkages, indicating a motivation to simplify or improve the folding operation.

3. Adding the Upper Support with a Connector for a Seat/Carrier:
   The aspect of the upper support having an end connected with a connector for detachably securing a seat (as further elaborated in dependent Claims 5, 6, and 7) would have been obvious in view of several prior art references:

   • US6209892B1 teaches a "baby stroller apparatus for use in combination with a standard child's car seat." This directly teaches the concept of using a stroller in conjunction with an infant carrier or car seat.
   • US20030111825A1 explicitly teaches a "stroller frame for coupling a safety seat."
   • US7032922B1 teaches a "stroller with a detachable seat member."
     A POSITA would have been motivated to combine the known foldable stroller frame from US5772235A with the established functionality of detachably securing different types of child seats or infant carriers, as taught by US6209892B1, US20030111825A1, or US7032922B1. This combination addresses the common market demand for versatile juvenile products that can adapt to different seating arrangements, thereby enhancing the utility of the foldable stroller.

Conclusion for Claim 1: A POSITA, seeking to improve the functionality and user convenience of a known foldable stroller (US5772235A), would find it obvious to integrate a remote folding mechanism (using an actuator and flexible element, a common engineering solution) and the capability to detachably secure various child seats or infant carriers (as taught by US6209892B1, US20030111825A1, or US7032922B1).

Obviousness Analysis of Claim 11

Claim 11 builds upon Claim 1 by specifically detailing the lower support joint:

• The front support element is pivoted to the front leg and has front extension arms extending upwardly with a pair of support bases.
• The rear support element is pivotally connected with the rear leg and has rear extension arms extending upwardly with another pair of support bases.
• These support bases are for detachably securing seats (as further specified in dependent Claims 15, 16, and 17 for front/rear seats, safety seats, or an infant carrier).

Combination of Prior Art References:
A combination of U.S. Patent No. 5,772,235 to Graco Children's Products Inc. (US5772235A) and U.S. Patent No. 5,333,893 to Chen (US5333893A), or ES2253093B1 to Play, S.A., along with the general knowledge of remote folding mechanisms, would render Claim 11 obvious.

Explanation of Obviousness and Motivation:

1. Primary Reference: US5772235A (Convertible stroller)
   As with Claim 1, US5772235A provides the foundational teaching of a foldable stroller frame with a wheeled support and a folding linkage system. The folding mechanism with an actuator and flexible connecting element (wire) would also be a routine design choice for user convenience, as explained for Claim 1.

2. Adding the Lower Support Joint with Extension Arms for Multiple Seats:
   The distinguishing feature of Claim 11 is the provision of front and rear extension arms from the lower support joint, furnished with support bases for detachably securing multiple seats (e.g., front seat, rear seat, two safety seats, or an infant carrier). This feature is directly addressed by prior art related to multi-child strollers:

   • US5333893A teaches a "dual-seat stroller" that includes a main frame, a front seat, and a rear seat. This patent clearly demonstrates the concept of a stroller designed to accommodate two children simultaneously.
   • ES2253093B1 is titled "DOUBLE CHILD CAR" and similarly teaches a double child carriage.
     A POSITA would be motivated to adapt a foldable stroller frame, such as that taught by US5772235A, to carry two children. The background of US7475900 itself highlights the existing problem of dual-seat strollers having complex and bulky linkage systems, indicating that the need for a foldable dual-seat stroller was recognized in the art. Integrating dual-seat functionality into a foldable frame, as exemplified by US5333893A, would involve extending structural elements from the main frame, such as from the lower support joint, to provide stable attachment points for the additional seats. The specific arrangement of "front extension arms" and "rear extension arms" with "support bases" for securing seats, as claimed, would be a conventional structural adaptation for a POSITA to achieve a stable tandem seating arrangement in a stroller frame.

Conclusion for Claim 11: A POSITA, facing the known challenges of existing dual-seat strollers and seeking to provide a more convenient and versatile foldable multi-child stroller, would find it obvious to combine the folding stroller frame (US5772235A) with the concept of a dual-seat configuration (US5333893A or ES2253093B1). The design of extension arms from a lower support joint to provide mounting points for these additional seats would be a straightforward engineering solution to achieve the desired functionality.