Locking Device For Sewing Machine Cabinet Support Platforms

Abstract

A sewing machine cabinet having a sewing machine support platform pivotable about a fixed axis from a stored position within the cabinet to a substantially horizontal operative position where it is locked in place by means of a pair of bolts mounted on opposite sides of the platform, and received within sockets formed on corresponding keepers pivotably mounted on brackets secured on the cabinet side walls. Each keeper includes three cam surfaces, two of which are effective to rotate the keeper in a first direction when acted upon by respective bolts. A spring secured to each keeper to oppose the rotation of keeper in the first direction until the keeper rotates to a position where the spring swings over-center and thereafter aids turning the keeper in this direction. The third cam surface is effective to turn the keeper in the opposite direction to that of the first two cam surfaces. As the platform is pivoted into the operative position the bolts engage the first cam surface and rotate the keeper against the bias of the springs. When the bolts are above the sockets the springs return the keepers to the normal positions and the platform may be lowered to position the bolts into the socket. To store, the platform is pivoted upwardly until the bolts engage the second surface rotating the keepers until the springs have moved over-center. The platform is then moved downwardly free of the sockets and engage the third surface to rotate the keepers into their original position.

Description

BACKGROUND OF THE INVENTION

This invention relates to a locking device, and more particularly to a mechanism for supporting and locking a sewing machine cabinet support platform in the operative position, and for releasing the same for movement of the platform to the stored position.

In sewing machine cabinets of the drop-head type, a platform carrying the sewing machine is lifted into the sewing machine operating position and lowered to its stored position within the cabinet. Some means must, of course, be provided for securing the platform in the operative position and for releasing the same for movement into the stored position. In the prior art various arrangements have been provided for accomplishing this result. These vary from merely resting the sewing machine base on the cabinet top by using a hinged front rail to complicated devices used in conjunction with the platforms that translate vertically. These arrangements are either unsatisfactory for cabinets designed for sewing machines operable in both flat bed and cylinder bed mode, or are exceedingly expensive. Moreover, these arrangements require that both hands be utilized to release the platform, some even requiring the placing of a hand in a blind location and may thereby create a dangerous condition to an operator.

SUMMARY OF THE INVENTION

These objections and deficiencies of the prior art are overcome by the present invention which provides an efficient, inexpensive and safe device for cabinets having pivotably mounted sewing machine support platforms for locking and securing the platform in the operative position and for releasing the platform for pivoting into the stored position. The device comprises a pivotable keeper having a socket, three cam surfaces and a spring secured to the keeper at a location which effects an over-center shifting of the spring when the keeper is pivoted beyond a predetermined position. The platform has a bolt adapted to be received within the socket of the keeper after turning the keeper by its action with the first cam surface. To release the platform it is first lifted so that the bolt turns the keeper by means of the second cam surface until the spring moves over-center and holds the keeper against a stop. At this point, the platform may be pivoted downwardly, the bolt engaging the third cam surface to return the keeper and spring to their initial positions.

It is therefore a primary object of this invention to provide a simple, safe and inexpensive mechanism for locking and supporting a pivotable sewing machine platform in the operative position and for releasing the platform to allow it to pivot into a stored position within a cabinet.

It is another object of this invention to provide a pivotable keeper on a sewing machine cabinet to cooperate with a bolt mounted on a sewing machine support platform for locking and supporting the platform in an operative position and for releasing the platform for storage within the cabinet.

It is a further object of this invention to provide a pivotable keeper and a shiftable biasing member to cooperate with a bolt mounted on a sewing machine support platform for locking and supporting the platform in an operative position and for releasing the platform for storage within the cabinet.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will become apparent from the following description of the invention taken in connection with the following drawings, in which:

FIG. 1 is a perspective view, partly in section, of a portion of a sewing machine cabinet having a pivotably mounted sewing machine support platform in the stored position and illustrating a preferred embodiment of the locking device of the present invention;

FIG. 2 is an enlarged perspective view, partly in section, of a portion of the cabinet of FIG. 1 with the sewing machine support platform in the operative position, but with the bolt disassembled from the keeper for clarity;

FIG. 3 illustrates diagrammatically an initial position of the locking device as the platform is raised;

FIG. 4 is a view similar to that of FIG. 3 showing the positions just prior to locking of the platform in the operative position;

FIG. 5 is a similar view, but illustrating the relative positions of the elements of the locking device of the present invention as the platform is initially lifted from the operating position to disengage the bolt from the keeper;

FIG. 6 is a position similar to FIG. 5 illustrating the location of the elements as the direction of movement of the platform changes from upward to downward and just subsequent to the spring shifting over-center of the keeper pivot axis; and

FIG. 7 is a view similar to that of FIG. 6 but illustrating the location of the elements as the platform is lowered to the stored position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the accompanying drawings in which like reference numerals denote similar parts throughout the various views, FIG. 1 illustrates a sewing machine cabinet generally designated as 10 and including a pair of side walls 12 and 14 supporting a substantially U-shaped top 16. Hingedly secured to the top may be a leaf 18 for aesthetically covering the top and for providing an extended work surface area during sewing. A front door 20 may be hingedly secured to one of the walls 14 to enclose the front portion of the cabinet during nonuse. A front rail 22 which may be pivoted as disclosed in copending U.S. Pat. application Ser. No. 351,667, filed Apr. 16, 1973, now U.S. Pat. No. 3,797,425, is located between the sides 12 and 14 at the front edge of the top. Pivotably mounted within the cabinet by means of hinges 24, (only one of which is illustrated), is a sewing machine support platform 26. The hinges 24 are secured to the platform 26 and to the bottom surface of the top 16 and defines an axis about which the support platform may be pivoted into and from the stored vertical position as illustrated in FIG. 1, to a substantially horizontal operative position as illustrated in FIG. 2. The bed 28 of a sewing machine, generally illustrated as numeral 30, is conventionally secured to the platform 26 so as to be positioned at the proper elevation relative to the cabinet top 16 when the platform is in the operative position. To lock and secure the platform 28 in the horizontal operative position there is provided by this invention, a mechanism comprising a stud or bolt 32 preferably located at each side of the platform adjacent the front edge thereof, and a pivotably mounted cam and socket means 34 preferably mounted on the interior of the walls 12 and 14 as hereinafter described.

The member 32, as will be clearly understood as this description proceeds, is a securing element movable into cooperative engagement with a keeper member and is herein designated a "bolt" to be consistent with the terminology used in the locking art. It should, however, be understood that the bolt 32 is secured to the platform 28 and therefore moves in a circular path about the axis provided by the hinges 24. The cam and socket means 34 preferably includes a substantially U-shaped (in plan) bracket 36 secured at the cross leg 38 by conventional screws 40 to the inside surfaces of the walls 12 and 14. The bracket is conveniently designed so that its outstanding walls 42 and 44 may serve purposes which will hereinafter become clear. The cross leg 38 preferably includes an apertured boss 45 within which is journaled a stud shaft 46. Secured to the stud shaft 46 is a unique movable keeper 48, the stud shaft being understood to define a pivot axis for the keeper. The term "keeper" being a lock art term designating the part which receives the bolt and this term will be utilized herein.

As illustrated, the keeper 48 is somewhat U-shaped in elevation, being secured on its cross leg 50 to the stud shaft 46 and preferably having a pair of normally substantially downwardly extending legs 52 and 54. Connected at one end in a hole 57 in the cross leg, preferably spaced from and above the stud shaft 46, is an extension spring 56 having its other end secured in a hole 58 formed in the bracket leg 42, The spring is spaced from the stud shaft 46 to normally bias the keeper counterclockwise, as illustrated in the drawings, about the stud shaft 46 and to bias it clockwise when the keeper has turned clockwise to a position in which the spring swings over-center. The spring is of a size such that the keeper is properly positioned in the initial position of FIG. 3 as hereinafter described. However, to allow for manufacturing tolerances the bracket leg 44 may act as a stop to prevent the keeper from turning counterclockwise from its normally disposed position.

The leg 52 is substantially wider than the leg 54 and is formed with an inclined surface 60 which defines a first cam surface. The cam surface 60 steeply extends from a point 62 at its lower end to a point 64 at its upper end from whence the surface extends at an obtuse angle until its termination at point 66. Spaced inwardly from the cam surface 60 toward the body of leg 52 and recessed below the point 66 is a socket 68 of a size sufficient to receive the bolt 32 with a minimum of play therebetween. With particular reference to FIG. 3, it is seen that the bolt 32 moves along a path designated as BP, and that in the normal position of the keeper the bottom edge 62 of the cam surface 60 is at or below said path. Thus, as the platform 28 is lifted manually the bolt 32 will engage the cam surface 60 and turn the keeper clockwise about the shaft 46. The steepness of the cam surface 60 insures a gradual turning of the keeper until it has turned so that the point 64 passes the path BP. From this point the keeper no longer turns but as the bolt continues to move upwardly it is elevated above the socket 68. Thus, when the bolt passes the termination point 66, the cam surface leaves the path of the bolt and the spring 56 effectively returns the keeper counterclockwise about the shaft 46 to its initial position. The platform may then be lowered to the horizontal position whereby the bolt is received within the socket 68 which thereby locks and supports the bolt and the platform therewith. The steps during the locking operation are illustrated sequentially in FIGS. 3 and 4, and the platform locking position is illustrated in FIG. 2.

The inner facing edge 70 of the leg 52 is inclined upwardly from the socket along a straight line substantially approximating the path of the bolt and is spaced from the center of the socket, so that when the platform is lifted to remove the bolt from the socket, the keeper preferably does not turn. However, since it is more economical to manufacture the edge 70 as a straight surface rather than the true radius of path BP, the keeper practically turns slightly as illustrated in FIG. 5. The edge 70 extends to a first inner edge 72 of the leg 50 at a point 74 from whence the edge 72 extends to a point 76 substantially vertically below the stud shaft 46 when the keeper is in the normal or initial position. The edge 72 defines a second cam surface effective during the returning of the platform 28 to the stored position. Since the relation of the cam surface 72 to the path BP is initially almost perpendicular, the bolt 32 causes the keeper to turn rapidly clockwise about the pivot 46. Substantially, when the bolt is located at the point 76, the keeper has turned to a position where the spring 56 crosses from above the pivot shaft 46 to below the shaft. This over-center movement of the spring quickly snaps the keeper further clockwise about the axis 46. To prevent the keeper from spinning and to stop its motion, the keeper leg 52 has a surface 78 adapted to abut against the bracket leg 42. Thus, when the keeper is in the stopped position the platform direction may change from the upward direction to a lowering. The relative positions of the bolt and keeper in this stopped position of the keeper is illustrated in FIG. 6.

Extending from the point 76 of the cam surface 72 is a second inner edge 80 of the leg 50. This edge is inclined so that a downward movement of the platform when the bolt is located at the stop position of FIG. 6 is ineffective to turn the keeper. The leg 54 of the keeper includes on its inner surface a substantially straight abutment or third cam surface 82 having at least a portion lying in the path BP when the keeper is located as illustrated in FIG. 6. Thus, with the bolt in this position, the platform is lowered and the bolt strikes the surface 82 to rotate the keeper counterclockwise. This lowering is done with a single continuous motion and as the keeper turns to a position where the spring 56 is again above the pivot axis 46, the spring quickly snaps the keeper to the initial position (such as that of FIG. 3) as the bolt freely passes between the legs 52 and 54. The platform is thereby released to return to the stored position of FIG. 1.

Although the description has centered on the keeper and bolt on one side of the cabinet only, it is to be understood that a similar arrangement may be located on the other side of the cabinet so as to insure that the platform is stable when in the operating position of the sewing machine. Moreover, it should be understood that the spring 56, although in the preferred embodiment is normally located above the pivot axis 46, may be initially located somewhat differently than disclosed. However, the important thing about the spring 56 is that it swings over-center of the pivot axis when the keeper has reached a certain predeterined position to quickly turn the keeper in a direction opposite to that initially biased by the spring and to aid in stopping the keeper from moving and positioning it for the lowering of the platform.

It should thus be clear that a simple and effective locking, securing and releasing device is provided by the present invention which meets all the objectives of this application and overcomes the deficiencies of the prior art. Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Claims

Having thus set forth the nature of the invention, what is claimed herein is:

1. In a sewing machine cabinet having a sewing machine support platform adapted to pivot about a first axis from a substantially vertically inclined stored position within the cabinet to a substantially horizontally inclined operative position, mechanism for supporting and locking the platform in the operative position and for releasing the same for pivoting into the stored position, said mechanism comprising: a bolt mounted on said platform spaced from said axis for movement in a path about said first axis; a keeper comprising first, second and third cam surfaces and a socket normally lying in said path and adapted to receive said bolt; journal means for mounting said keeper on said cabinet for pivotable movement about a second axis spaced from said path; said first and second cam surfaces having portions normally lying in said path, whereby movement of said platform to engage said bolt selectively with said first and second cam surfaces turns said keeper in one direction; each of said first and second surfaces being inclined so that continued upward movement of said platform from the stored position continues to move said keeper in said one direction; biasing means acting on the keeper for exerting a turning force about said second axis in opposition to said one direction and upon said keeper reaching a predetermined position in said one direction for exerting a turning force about said second axis in said one direction; said first cam surface terminating above said socket at a point which leaves said path prior to said keeper reaching said predetermined position, whereby said socket is returned to said path and said bolt may be lowered therein; said second cam surface being disposed above said socket and substantially terminating at a point crossing said path when the keeper is in said predetermined position; stop means for preventing further movement of said keeper in said one direction substantially beyond said predetermined position; said third cam surface being spaced from said first cam surface and having a portion lying in said path when said keeper is in the predetermined position, whereby said keeper may be turned in a direction opposite to said one direction when said platform is lowered to said stored position, said biasing means thereafter returning said keeper in said one direction.

2. In a sewing machine cabinet as recited in claim 1 wherein said biasing means comprises a spring, means securing one end of said spring to said cabinet, means for connecting the other end of said spring to the keeper at a location normally positioned on one side of said second axis and which is on the other side of said second axis when the keeper is turned to said predetermined position.

3. In a sewing machine cabinet as recited in claim 2 wherein said journal means comprises a bracket secured to said cabinet, a pin journaled on said bracket, and means for mounting said keeper on said pin.

4. In a sewing machine cabinet as recited in claim 3 wherein said stop means comprises a ledge formed on said bracket.

5. In a sewing machine cabinet as recited in claim 4 wherein said means for securing said one end of the spring to the cabinet includes said ledge.

6. In a sewing machine cabinet as recited in claim 4 wherein said bracket includes a second ledge, said second ledge providing a stop for preventing movement of said keeper in a direction opposite to said one direction when said platform is in the operative position.

7. In a sewing machine cabinet as recited in claim 1 wherein a bolt is mounted on opposite sides of said platform and a corresponding keeper is mounted on opposite sides of said cabinet.

8. A keeper mechanism for receiving a bolt secured to a pivotable sewing machine cabinet support platform for locking and supporting said platform in a substantially horizontally inclined operative position, and for releasing the same for storage in a substantially vertically inclined storage position within the cabinet, said keeper mechanism comprising: a pivotable keeper adapted to be mounted on the cabinet for pivotable movement about an axis spaced from a path defined by movement of said bolt; said keeper including a socket, first, and second cam surfaces having portions normally lying in said path, whereby movement of said platform to engage said bolt selectively with said first and second cam surfaces turns said keeper in one direction; each of said first and second surfaces being inclined so that continued upward movement of said platform from the stored position continues to move said keeper in said one direction; biasing means acting on the keeper for exerting a turning force about said axis in opposition to said one direction and upon said keeper reaching a predetermined position in said one direction for exerting a turning force about said axis in said one direction; said first cam surface terminating above said socket at a point which leaves said path prior to said keeper reaching said predetermined position, whereby said socket is returned to said path and said bolt may be lowered therein; said second cam surface being disposed above said socket and substantially terminating at a point crossing said path when the keeper is in said predetermined position; stop means for preventing further movement of said keeper in said one direction substantially beyond said predetermined position; said keeper further including a third cam surface spaced from said first cam surface and having a portion lying in said path when said keeper is in the predetermined position, whereby said keeper may be turned in a direction opposite to said one direction when said platform is lowered to said stored position, said biasing means thereafter returning said keeper in said one direction.

9. A keeper mechanism as recited in claim 8 wherein said biasing means comprises a spring, means adapted for securing one end of said spring to said cabinet, means for connecting the other end of said spring to the keeper at a location normally positioned on one side of said axis and which is on the other side of said axis when the keeper is turned to said predetermined position.