GB2204333A - A feed roller lifting means for sewing machine - Google Patents

Abstract

A feed roller lifting means for a sewing machine, lifts the feed roller by a driving arm 12 supported on a frame. A first and second guiding element 20a and 20b respectively provided at the upper and lower end of the frame 11 and a first and second sliding element 19a and 19b respectively provided at the upper and lower end of the driving arm 12 cooperate for the driving arm 12 to ascend and descend. The curvature defined by the second guiding element 20b is similar or identical to that defined by the heel A, of the pressor foot A whereby the driving arm 12 may be lifted along a curved course. <IMAGE>

Description

A FEED ROLLER LIFTING MS4NS FOR SEEING }MACHINE This invention relates to a feed roller lifting means for sewing machine, more particularly to one wherein the feed roller is lifted along a curved course.

The feed roller lifting means for sewing machine of this invention comprises a frame secured to the machine body at the same end where the press or foot is provided, a driving arm supported at the upper and lower end of the frame, an extending element secured onto the lower end of the driving arm, a feed roller connected to the lower end of the extending element, a transmission means provided in the extending element, a connecting rod connected to the driving arm, a handle connected to the connecting rod, a first and second sliding element respectively provided at the upper and lower end of the driving arm and a first and second guiding element respectively provided at the upper and lower end of the frame wherein the curvature of the second guiding element is similar or identical to that of the heel of the pressor foot.

The feed roller is used to solve the sewing difficulties such as puckering , slipping , uneven ending, and so on. The following three prior arts respectively as shom in Figs. 1, 2, 3 , 3A & 3B are typical ones. As shown in Fig. 1, the feed roller B1 behind the pressor foot A is driven by a driving shaft C. With a driven roller D provided thereunder, the desired function can be performed. Owing to the fact that the diameter of the feed roller B1 of this prior art is great, the following defects are innevitable: 1. The distance G between the force exerting point E of the feed roller B1 and the needle F is too long to obtain a balanced clothing pulling effect; 2.The distance G is too long to allow the cloth to turn as a result of which only a straight seam can be obtained; 3 The distance G is too long to obtain a sound effect of pulling cloth when small pieces of cloth are to be sewed.

The prior art as shown in Fig. 2 shortens the diameter of the feed roller B1 of the prior art as shown in Fig. 1 to obviate the above defects. However, it bears the following defects: 1. When the feed roller is not needed in some specific cases, the feed roller B2 once lifted will contact the heel A of the pressor foot A as a result of which the height the feed roller B2 is allowed to ascend is quite limited; 2. The above disclosed defect will cause the machine left at leisure to bring about the lagging of manufacturing progress and the increasing of the production cost.

To obviate the defects of the prior art as shown in Fig,2, the prior art as shown in Fig. 3 arranges the fee & roller B3 in a tilted type. However, this prior art still bears the following defects: 1. When the feed roller 23 is not needed, the feed roller B3 and the pressor foot A have to be lifted synchronously.

Thus, a link plate I having a slot thereon for a pressor foot driving shaft J to extend therethrough is connected to the driving arm H. In this way, the pressor foot A and the feed roller B3 are capable of being lifted synchronously. Nevertheless, for the driving arm H and the working table of the sewing machine K form a tilted O angle and the press or foot A is vertically lifted , the link plate I, when the pressor foot A is vertically lifted, is pulled upward and forced leftwise in relation to the pressor foot A. As shown in Fig. 3A, assuming that S is a force exerted by a spring ( not shown in the figure ) on the driving arm H, P1 a lifting force, R1 & R2 respectively a reaction force exerted from the frame on two different points of the driving arm H, F1 & F2 friction forces brought about by the reaction forces R1 & R2 , and F3 a friction force formed by the pressor foot A on the link plate I, to lift the driving arm H, the component P1y of the force P1 has to be greater than the resultant of S, F1, F2, and F3y, that its, P1 > P1y = P1 sin# > S + F1 + F2 + F3 cose .If e = 900, P2y = P2 sin 900 = P2 + F1 + F2 . P1 > P2 ( P1 is a vertical upward force when e 900 and P2 a vertical upward force when e = 900 ) means that the needed force to lift the pressor foot A when the driving arm H is in a tilted e angle is greater than that when the driving arm H is vertical. In one word, it is more difficult to lift the driving arm H.

2. As shown in Fig. 3B, F as disclosed above may be divided into a horizontal force Qsino and a vertical force Q cose wherein Qcose is equal to the reaction force N. The resultant Q'= Q on B3 makes H to bring about a bent moment of force. Therefore, it is more difficult to lift the driving arm H.

3, In the case that the cloth is laid in layers uneven, the uneven portions is difficult to pass under the feed roller B3.

It is also not able to solve the above problems to lengthen the foot pressor. To meet a variety a variety of specific needs in sewing, a lot of foot pressors in different length are required and this is not ecnomic.

To obviate the above defects, one object of this invention is to provide a feed roller lifting means for sewing machine the diameter of the feed roller of which can be as short as possible.

Another object of this invention is to provide a feed roller lifting means for sewing machine the feed roller of which may be as close as possible to the pressor foot.

Still another object of this invention is to prove a feed roller lifting means for sewing machine the feed roller of which may be lifted along a curved course when it is not needed.

Further objects will appear apparent from the following descriptions, taken in conjunction with the accompanying drawings, in which: Fig. 1 is a side sectional view of a prior art; Fig. 2 is a side sectional view of another prior art; Fig. 3 is a side sectional view of still another prior art; Fig. 3L is a diagram of force analysis as shown in Fig. 3; Fig. 3B is a diagram of force analysis as shown in Fig. 3; Fig. 4 is a perspective view of a preferred embodiment of this invention; Fig, 5 is a side sectional view of a preferred embodiment of this invention; Fig, 6 is a sectional view talcen along line 6-6 of Fig. 5; Fig. 7 is a sectional view taken along line 7-7 of Fig, 6; Fig. 8 is a sectional view taken along line 8-8 of Fig. 7.

This invention relates to a feed roller lifting means for sewing machine , more particularly to a means in which the feed roller is guided in a curvature to ascend, As shorn in Figs. 4 & 5, a frame 11 of this invention is secured onto one end of a machine body L. A driving arm 12 is supported on the upper and lower ends Ila & llb, the driving arm 12 being able to move longitudinally. A handle 3 is connected to a connecting rod 15 by means of an eccentric pin 14. The connecting rod 15 is connected to the driving arm 12 by means of a pin 16. To longitudinally move the driving arm 12, it is required to pull the handle 13. At the lower end of the driving arm 12 an extending element 17 is provided.A feed roller B at the lower end of the extending element 17 is connected to a transmission means 21 which comprises a first gear 21a fixed to the driving shaft 18 of the machine body L, a second gear 2lb meshed to the first gear 21a and a third gear 21c meshed to the second gear 21b, The feed roller B is actuated by the driving shaft 18 to perform the function of pulling the cloth. A link plate I is connected with one end to the driving arm 12 and the other end to the upper edge of the pressor foot A. The link plate I is provided with a slot thereon for the upper edge of the pressor foot A to insert through. Therefore, when the pressor foot A is lifted , the link plate I will ascend to lift the feed roller B.

As shown in Figs. 4, 5, 6, 7 & 8, a first sliding element 19a and a second sliding element 19b are respectively provided at the upper and lower end of the driving arm 12. It is preferred that the first and second sliding elements are made in the type of pin. Correspondingly, a first guiding element 20a and a second guiding element 20b are respectively provided at the upper and lower end of the frame 11. The preferred embodiment of the first and second guiding elements 20a & 20b are sliding slots. The curvature defined by the second guiding element 20b is similar or identical to that of the heel A1 of the pressor foot A. The first guiding element 20a may appear in a straight line or in a curvature similar or identical to those of the second guiding element 20b and the heel A1 of the pressor foot A.However, the first guiding element 20a in a straight line can perform the desired function well. Then the handle 13 is pulled to lift the driving arm 12, the first and second sliding elements 19a & 19b will ascend respectively along the course defined by the first and second guiding elements 20a & 20b of the frame 11. For the second guiding element 20b appears in a curvature similar or identical to that of the heel A1 of the pressor foot A, the feed roller B will ascend along the above said curvature without contacting the heel A1 of the pressor foot A. In other words, the center of the feed roller B will move along the curved course Bo and ascend from Ba to Bb. Therefore , the feed roller B may be lifted when it is not needed and as close as possible to the pressor foot A. The curvature mentioned above includes bent lines.

It is another preferred embodiment of this invention that ths first and second guiding elements 20a & 20b are flanged bars and the first and second sliding elements l9a & 19b are clips so that the clips may slide along both sides of the flanged bars. Still it is another preferred embodiment of this invention that the first and second guiding elements 20a & 20b are rails and the first and second sliding elements 19a & 19b are sliding rollers whereby the sliding rollers may slide along the rails. The slots, flanged bars and rails of the above said preferred embodiments according to this invention may be provided in the driving arm 12 and the pins, clips, and sliding rollers in the frame 11.

It is to be noted that the above description aims to explain however not to limit the concept of this invention.

Claims (2)

CLADIS

1. A feed roller lifting means -'or sewing machine comprising: a machine body; a pressor foot provided at one end of said machine.body, the heel of said pressor foot appearing in a curvature; a frame secured onto said machine body at the same end where said pressor foot is provided', a driving arm supported at the upper and lower end of said frame; an extending element secured onto the lower end of said driving arm, a feed roller connected to the lower end of said extending element; a link plate connected with one end to said driving arm and the other end to the upper edge of said pressor foot by means of a slot provided on said link plate for the upper edge of said pressor foot to insert through; ; a transmission means provided in said extending element, said transmission means being connected with one to the driving shaft of said machine body and the other end to said feed roller; a connecting rod connected to said driving arm, a handle connected to said connecting rod; a first and second sliding element respectively provided at the upper and lower end of said driving arm, and a first and second guiding element respectively provided at the upper and lower end of said frame; wherein the curvature defined by said second guiding element is at similar to that defined by the heel of said pressor foot.

2. A feed roller lifting means for sewing machine substantially as herein described with reference to the accompanying drawings.