Hinge mechanism for a trunk support apparatus

Note: This nonprovisional application claims the benefit of U.S. Provisional Patent Application Serial No. 60/129,978, which was filed on Apr. 19, 1999 and was entitled “Hinge Mechanism For a Trunk Support Apparatus.”

I. BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention relates to support mechanisms in seats and, in particular, to a convenient trunk support mechanism for a wheelchair.

b. Prior Art

By way of introduction,

FIG. 1

illustrates a wheelchair seat

10

according to the present invention, on which is mounted a trunk support mechanism

12

. The trunk support mechanism

12

serves to limit the lateral range of motion of the patient, so that his or her torso does not shift to the left or right within the wheelchair. The seat

10

of

FIG. 1

is a prototype that is presented here strictly for the purpose of illustration, and it has a trunk support mechanism on only one side of the seat. In practice, the respective trunk support mechanisms will be mounted on both the left and right sides of the seat.

Continuing our introduction, the seat

10

of

FIG. 1

has a bottom cushion

14

and a back seat cushion

16

. A pelvic stabilizer mechanism

18

serves to retain the patient's pelvis within the chair. A suitable pelvic stabilizer is described in a co-pending patent application filed concurrently herewith entitled “Pelvic Stabilizer Mechanism for a Wheelchair” and in U.S. Provisional Patent Application No. 60/130,046, both of which are incorporated by reference herein. In practice, the seat

10

will be mounted on a base having wheels and other components that are typical of a wheelchair.

FIG. 2

illustrates a prior art trunk support mechanism

20

that is awkward to use. The mechanism includes a padded trunk support arm

22

. The mechanism is mounted on the rear of the back seat cushion

24

with a mounting mechanism

26

. The trunk support mechanism

20

has a hinge

28

, with a rear hinge portion

30

and a front hinge portion

32

. The trunk support mechanism is in a locked position in

FIG. 2

, but it can be disengaged from the locked position so that the support arm

22

can swing outwardly and away from the patient. The arm is normally swung outwardly when the patient is being put into or removed from the seat, or when the patient's position must be changed.

The prior art mechanism of

FIG. 2

is cumbersome to use. The user must lift up on the front hinge portion

32

at a specific point

34

(

FIG. 3

) in order to disengage a spring-loaded pin (not shown) in the upper portion

36

of rear hinge portion

30

from engagement with a receptacle

38

(

FIG. 4

) that has an indentation to receive the spring loaded pin. The mechanism is awkward to use because the user must push up at exactly point

34

, or the rear and front portions of the hinge will not disengage from one another, and the hinge will not rotate. Even when the user does push up at the proper point

34

, the patient must be moved off to one side of the seat, so that he or she is not leaning against the trunk support mechanism

20

. Otherwise, the weight of the patient prevents the user from unlocking the support arm and, again, the arm will not unlock.

U.S. Pat. No. 5,678,798 to Little discloses a swing-away support bracket having a housing, an axle mounted for rotation in the housing, a toggle with a protrusion, and a tapered recess in the axle to receive the protrusion. To lock the swing-away support bracket, the user engages the protrusion into the axle. The arrangement is inconvenient, because the toggle is located within a narrow recess in the housing. The lock is also weak, because the protrusion on the toggle is small, with only a small portion of the toggle engaging with the tapered recess.

II. SUMMARY OF THE INVENTION

Broadly defined, the present invention is a support arm mechanism that is simpler and/or more reliable in use than support arm mechanisms of the prior art. The invention also relates to an improved hinge that can be used in a trunk support arm mechanism, and in other applications.

One embodiment of the present invention is a locking trunk support hinge that is convenient to lock and unlock. For example, the hinge can have a lock with a front hinge portion and a rear hinge portion. A locking member, having a locking head and a lever, is rotatably mounted to one of hinge portions, and a locking channel extends in the other one. The hinge has a locked mode in which the locking head is engaged in the locking channel and the hinge cannot be swung, and an unlocked mode in which the locking head is not engaged in the locking channel and the hinge can be swung open. The locking mechanism can have a compression spring that biases the locking head into the locked mode when the front and rear hinge portions are aligned.

In accordance with a particular embodiment of the present invention, a durable locking mechanism for a wheel chair trunk support apparatus has a back bracket, a front bracket, and a hinge piece that extends from the back bracket toward the front bracket. The hinge piece has a top and a bottom, with the bottom including an elongated open channel defined by first and second walls. A locking member is rotatably mounted on the front bracket. The locking member has an angled lever and an elongated locking head that is configured to fit within the open channel of the hinge piece. The lever extends downwardly from the front bracket, and the locking head extends forwardly. The locking mechanism has a first, locked mode in which the locking head is situated within the open channel and in between the first and second walls, and a second, unlocked mode in which the locking head is situated outside of the open channel. The locking mechanism may also include a compression spring mounted within the hinge piece and adjacent to the locking member, to maintain the locking head in the open channel when the locking mechanism is in the first, locked mode.

Particular embodiments may incorporate various features. For example, the locking head may be at least ½ inch long. The front and rear brackets and the hinge piece may be ½″ or less thick in order to limit the bulk of the support. In the locked position, the entire length of locking head may be engaged in the locking channel. The lever of the locking member may extend at an angle of between about 10 degrees and 60 degrees, and preferably from between about 20 degrees and 45 degrees, downwardly from the front bracket. This angled lever provides a convenient means of engaging the locking member to unlock the hinge mechanism. The lever and hinge member are typically metal, and portions of the mechanism may be made from steel for particular strength and durability. The hinge piece may be separate from but attached to the front bracket, or it may be unitary with the front bracket. The trunk support may be one component in a convenient system for releasably retaining a person in the wheelchair. Such a system can include a wheelchair seat, a trunk support mechanism as described above, and a pelvic support mechanism as described in a co-pending patent application filed concurrently herewith entitled “Pelvic Stabilizer Mechanism for a Wheelchair” and in U.S. Provisional Patent Application No. 60/130,046.

Various other objects and features of the invention will become apparent in the Detailed Description below, in the drawings and in the claims.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of a prototype wheelchair seat fitted with a trunk support assembly and a pelvic stabilizer mechanism;

FIG. 2

is a detail view of a prior art trunk support assembly;

FIG. 3

is a detail view of a user adjusting the prior art trunk support assembly of

FIG. 2

;

FIG. 4

is top perspective view of the prior art trunk support assembly of

FIG. 2

, in the open position.

FIG. 5

is a detail view of one embodiment of a trunk support assembly according to the present invention;

FIG. 6

a bottom perspective view of the trunk support assembly of

FIG. 5

in a locked mode;

FIG. 7

is a another bottom perspective view of the trunk support assembly of

FIG. 5

in a locked position, showing a compression spring mounted within the trunk support assembly;

FIG. 8

is a side-detail view with a cut-away portion illustrating the locking member

72

and a biasing ring

74

that biases the locking member into a locked position;

FIG. 9

is a bottom perspective view of the trunk support assembly of

FIG. 5

in a swing mode, after the lever has been disengaged and the padded arm is free to rotate inwardly or outwardly,

FIG. 10

is a detail view of the trunk support assembly of

FIG. 5

with the padding removed and showing,the channel into which the lever engages;

FIG. 11

is a bottom perspective view of the trunk support assembly of

FIG. 5

with a portion of the padding pushed back to show the hinge attached to the plate about which the padding extends; and

FIG. 12

is an interior perspective view of the trunk support assembly of

FIG. 5

in which the support is in a locked mode.

IV. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 5

illustrates a presently preferred embodiment of the present invention. A trunk support mechanism

112

is mounted on a wheelchair seat

10

. The trunk support mechanism

112

serves to limit the lateral range of motion of the patient, so that his or her torso does not shift to the left or right within the wheelchair. There is another trunk support mechanism (not shown) on the opposite side of the seat, such that the pair of trunk support mechanisms serve together to laterally secure the patient within the seat.

Returning to

FIG. 5

, the trunk support mechanism

112

includes a padded portion

50

that is mounted on a plate or bracket

52

(FIGS.

9

and

10

), which is in turn fixedly mounted on a forward hinge portion

54

. The forward hinge portion

54

is rotatably mounted onto a rear hinge portion

56

. A pin

58

interconnects forward and rear hinge portions

54

and

56

, respectively, such that forward hinge portion

54

can rotate relative to the rear portion

56

when the hinge is not in a locked mode.

The rear hinge portion

56

is mounted onto a back plate

60

(see also

FIG. 6

) that is mounted onto the rear

62

of back seat cushion

16

with bolts and/or other conventional fastening means. In the presently preferred embodiment, the back plate

60

includes one or more mounting slots

64

(

FIG. 6

) or other known arrangements to permit adjusting the lateral position of the trunk support mechanisms. That is, for a particular user, the respective trunk support mechanisms can be mounted to extend farther out from the side of the chair than is shown in the figures.

A feature of the preferred embodiment of the present invention is that the profile of the trunk support hinge is quite narrow, due to the locking mechanism

70

that

FIGS. 6-9

illustrate. The locking mechanism

70

includes a pivoting locking member

72

, a compression spring

74

and a channel

76

. The pivoting locking member

72

has an angled lever portion

77

and a locking head

78

. The locking member

72

is rotatably mounted on the forward hinge member

54

, as

FIG. 8

illustrates. When the hinge is in the locked mode of

FIGS. 6 and 7

, the locking head

78

is engaged in the locking channel

76

. That is, the locking head

78

extends from the forward hinge portion across and into the locking channel

76

. The locking head

78

then prevents hinge from rotating.

When the user pushes the lever

72

back against the compression spring to lift the locking head

78

out of the locking channel, the hinge is then free to rotate to an open position. In a presently preferred embodiment, the compression spring has a free length of 0.75 inches, has an outer diameter of 0.240 inches and is made with wire having a thickness of 0.032 inches. Of course, these dimensions are merely examples, and various other springs can be used with similar effect.

FIG. 9

illustrates the locking head

78

having been removed from the locking channel

76

, and the padded portion

50

having been rotated inwardly toward the interior surface of the back seat cushion

16

. In practice, the user will normally rotate the padded portion

50

outwardly, in the opposite direction of

FIG. 9

, in order to either enable the patient to be removed from the seat or to allow the patient to enter the seat.

FIG. 9

illustrates the padded portion

50

having been rotated inwardly solely for the purpose of illustrating the locking mechanism.

FIG. 10

further illustrates the trunk support mechanism, as it has been removed from the wheelchair and with the padding removed.

FIG. 10

particularly illustrates the locking channel

76

, into which the locking head

78

extends.

FIG. 11

illustrates the junction between the front plate

52

, which can also be called the forward plate or bracket, and the forward hinge portion

54

. The two can be interconnected with screws, rivets, or other standard fastening means.

The presently preferred embodiment is generally made with aluminum components, which are lightweight, and a stainless steal lever

72

. The forward and rear aluminum plates are typically anodized. The hinge is therefore lightweight and, because of its compact design, has a maximum thickness of only ½″. The hinge stays out of the way of the patient, as compared to bulkier prior art designs.

The foregoing has described a presently preferred embodiment of the invention. However, it should be understood that this is just one example of the present invention. Various changes can be made within the scope of the invention. As one example, the locking mechanism can go on the top of the hinge rather than on the bottom. Consequently, the present invention is not limited by the preferred embodiment.