WORK FEED CONTROL

• US 3,736,894 A
• Filed: 11/03/1971
• Issued: 06/05/1973
• Est. Priority Date: 11/03/1971
• Status: Expired due to Term

• Current Assignee: Leighton R. Mckeen
• Original Assignee: Leighton R. Mckeen
• Inventors: McKeen, Leighton R.
• Primary Examiner(s): Schroeder, Werner H.
• Application Number:
  US05/195,240
• Time in Patent Office: 580 Days
• Field of Search: 112/47,90,102,118,121.11,121.12,203,204,205 188/317,318,314
• US Class Current: 112/315
• CPC Class Codes: D05B 27/22 with means for setting length of stitch
• CPC Class Codes: D05D 2207/02 Pneumatic or hydraulic devices

Abstract

In a sewing machine having a work feed plate for supporting and reciprocally moving an article to be sewn between first and second positions beneath the sewing head of the machine at varying speeds and in a predetermined sequence in order to vary the spacing between stitches sewn into the article, means is provided for reciprocating the plate in accordance with the predetermined sequence, which means includes a double acting hydraulic ram or air cylinder applying a uniform pressure to the plate to move it between its first and second positions and means for variably resisting movement of the plate in accordance with the predetermined sequence to vary the speed of movement of the plate from its first to its second position. The resisting means includes a hydraulic control cylinder having at least two ports therein, a fluid reservoir in communication with the cylinder through the ports and a plunger in the cylinder operatively connected to the plate and cooperating with fluid in the cylinder to resist movement of the plate. The plunger initially returns fluid in the cylinder to the reservoir through only one of the ports, then through both ports and finally through only one port so that movement of the plate is variably resisted and the plate is moved faster between the first and second position when fluid is returned to the reservoir through both of the ports than when fluid is returned to the reservoir through only one of the ports.

Claims

1. A device for reciprocating a work element between first and second positions at varying speeds in a predetermined sequence comprising, means operably connected to said work element for applying a uniform force to said element to move the element between said first and said second positions, and means for variably resisting movement of said work element in accordance with said predetermined sequence to vary the speed of movement of said element from said first to said second position, said resisting means including a hydraulic control cylinder having at least two ports therein, a fluid reservoir in communication with said cylinder through said ports, and plunger means in said cylinder operatively connected to said work element and cooperating with fluid in said cylinder for resisting movement of said work element by said force applying means and for sequentially returning said fluid to said reservoir from said cylinder as said work element is moved from its first to its second position by said force applying means, initially through only one of said ports, then through both ports, whereby movement of said work element is variably resisted and said work element is moved faster between said first and second positions when fluid is returned to said reservoir through both of said ports, than when fluid is returned to said reservoir through only said one port.

2. A device as defined in claim 1 wherein said reservoir is connected to said cylinder ports by independent conduit means, and said conduit means include restrictions therein resisting fluid flow therethrough.

3. A device as defined in claim 2 wherein said force applying means comprises a double acting hydraulic ram.

4. A device as defined in claim 2 including check valve means interconnecting said reservoir to said cylinder for permitting free flow of fluid therethrough from said reservoir to said cylinder as said work element is returned by said force applying means from its second to its first position.

5. A device for reciprocating a work element between first and second positions at varying speeds in a predetermined sequence comprising, means operably connected to said work element for applying a uniform force and said element to move the element between said first to said second positions and means for variably resisting movement of said work element in accordance with said predetermined sequence to vary the speed of movement of said element from said first to said second position, said resisting means including a hydraulic control cylinder having at least two ports therein, a fluid reservoir in communication with said cylinder through said ports, and plunger means in said cylinder operatively connected to said work element and cooperating with fluid in said cylinder for resisting movement of said work element by said force applying means and for sequentially returning fluid to said reservoir from said cylinder as said work element moves from its first to its second position, initially through only one of said ports, then through both ports, and finally through only said one port whereby movement of said work element is variably resisted and said work element is moved faster between said first and second positions when fluid is returned to said reservoir through both of said ports than when fluid is returned to said reservoir through only said one port during the initial and final portions of movement thereof.

6. A device as defined in claim 5 wherein said reservoir is connected to said cylinder ports by independent conduit means, and said conduit means include restrictions therein resisting fluid flow therethrough.

7. A device as defined in claim 5 wherein said force applying means comprises a double acting hydraulic ram.

8. A device as defined in claim 5 including check valve means interconnecting said reservoir to said cylinder for permitting free flow of fluid therethrough from said reservoir to said cylinder as said work element is returned by said force applying means from its second to its first position.

9. A device as described in claim 6 wherein said plunger means comprises a pair of spaced operatively interconnected pistons defining a first fluid chamber therebetween in said cylinder, said plunger means being moved with said element by the force applying means from a first to a second position corresponding to the first and second positions of said element to selectively close said one port at the initial and final portions of movement of said element.

10. A device as defined in claim 9 wherein the other of said ports is located adjacent one end of said cylinder and said one end defines a second fluid chamber with said one piston, the latter having at least one bleed bore therein to provide communication between said first and second chambers for equalizing fluid pressure therein.

11. In a sewing machine having a work feed plate for supporting and moving an article to be sewn beneath the sewing head of the machine and wherein the feed plate is mounted for reciprocal movement between first and second positions at varying speeds and in a predetermined sequence for varying the spacing between stitches sewn into the fabric, means for reciprocating the plate at varying speeds comprising a ram operatively connected to said plate for applying a uniform force thereto to move the plate between said first to said second positions and means for variably resisting movement of said plate in accordance with said predetermined sequence to vary the speed of movement of said plate from said first to said second position and thereby vary said stitch spacing including, a hydraulic control cylinder having at least first and second ports therein, a plunger in said cylinder operatively connected to said work feed plate for movement therewith under the influence of said ram between first and second positions corresponding respectively to the first and second positions of said plate, said plunger having first and second spaced operatively interconnected pistons defining a first fluid chamber in said cylinder, a reservoir, independent conduit means respectively connecting said reservoir to said ports, said first ports being located for communication with said first chamber and said second port being located for communication with a second fluid chamber defined by said first piston and one end of said cylinder, said first piston having at least one bleed bore therein to provide communication between said first and second chambers for equalizing fluid pressure therein and said pistons cooperating with fluid in said cylinder for resisting movement of said plate by said ram in accordance with said predetermined sequence, said first piston closing said first port in the first position thereof and forcing fluid in said second chamber through said second port during initial movement of said plunger from its first to its second position and opening said first port to said first chamber after said initial movement, movement of said second piston thereafter forcing fluid in said second chamber through said first port to said reservoir, while movement of said first piston continues to force fluid to said reservoir through said port, thereby decreasing the resistance to movement of said plate, said second piston thereafter being moved into position to close said first port as said plunger approaches its second position while said first piston continues to force fluid to said reservoir through said second port, whereby the speed of movement of said plate is sequentially varied to provide relatively small spacing between stitches at the beginning and ends of movement of said plate from its first to its second position and wider spacing between stitches at the intermediate portion of said movement.

12. A device as defined in claim 11 wherein said conduits have fluid flow restrictors therein.

13. A device as defined in claim 12 wherein said ram is a double acting ram adapted to return said plate from its second to its first position.

14. A device as defined in claim 13 wherein one of said conduits includes a conduit portion bypassing the flow restrictor therein and a check valve in said bypass permitting free return of fluid in said reservoir to said cylinder as said plate and plunger are returned from their second to their first positions.