GB2070909A - End closure for sausage casings - Google Patents

Abstract

A strand of sausage casing is closed at one end by an end closure constituted by a twisted end portion of the strand invaginated into the strand and axially compressed against the end wall of the strand produced by the invagination. The strand is preferably a shirred strand of a thin-walled sausage casing, e.g. collagen casing. A method of, and apparatus for, end-closing a strand of sausage casing are also described, the apparatus comprising a tubular mandrel with a slidably mounted piston which co-acts with a movable anvil to compress the closure. The casing strand is normally in shirred condition. <IMAGE>

Description

SPECIFICATION End closure for sausage casings This invention relates to an improved shirred strand of tubular food casing and more particular to a shirred strand having an end closure, to a method and apparatus for producing it.

Tubular food casings, particularly sausage casings are supplied to the sausage manufacturers as a hollow shirred strand open at both ends. In order to manufacture a sausage product, individual shirred strands of casing are placed on stuffing horns and filled with the sausage emulsion. Prior to commencement of the said filling, it is necessary for an operator to manually de-shirr a short length of casing from the end of the shirred strand to effect a closure, or alternatively to hold it closed until sufficient sausage emulsion has been extruded into the end of the casing so as to prevent the flow of the sausage emulsion out of the casing. This manually performed operation considerably slows the sausage manufacturing procedure.

Automated machines have now been developed for the stuffing and/or stuffing and linking of shirred sausage casings and the use of these machines, as for example that disclosed in the U.K. Patent Specification No.

1,563,571, can greatly increase the rate of sausage production. With the advent of high speed automatic sausage stuffing machines, there is a need for a shirred casing strand having a closed end so that the shirred casing strand can be placed, manually or automatically, on a stuffing horn and filled with sausage emulsion without further action on the part of the machine operator.

Recent attempts have been made to close the end of a shirred casing strand by various techniques, twisting as shown in U.K. Patent Specification No. 1 ,082,222 and U.S. Patent No. 4,070,729 and 4,075,938, compressed plugs as shown in U.S Patent No.

3,892,869 and U.K. Patent Specification No.

1 ,080.387. the use of adhesives as shown in U.K. Patent Specification No, 1,426,355 as well as knotting and heat sealing the casing materiai.

However, if has been found that when the shirred casing is of thin walled construction, e.g. edible collagen casing of wall thickness .0007 to .001 inches, a number of problems occurs.

In some cases the closure that is formed has insufficient strength to prevent blowout of the end under pressure of the sausage emulsion. In other cases the closure formed allows a double thickness of casing material to be trapped between the stuffing horn and the control chuck or breaking ring during loading of the shirred strand. This usually results in casing rupture as it is subjected to the pressure of the sausage emulsion. Thirdly, the end seal may be of such integrity that there is no possibility that the pressure of the incoming sausage meat on entrapped air be dissipated.

This equally results in casing rupture.

The present invention provides a strand of sausage casing, particularly a shirred strand or thin walled sausage casing, closed at one end by an end-closure constituted by a twisted end portion of said strand invaginated into said strand and axially compressed against the end wall of said strand.

By the use of an end-closed sausage casing in accordance with the present invention the necessity for a manual end-closing operation is avoided, the end closure penetrates 'cleanly' the stuffing horn control chuck during the loading operation, and has sufficient residual strength to withstand the pressure of the sausage emulsion as well as dissipate air pressure build-up.

The present invention further provides a method of end-closing a strand of sausage casing, particularly a shirred strand of thinwalled sausage casing, comprising twisting an end portion of said strand into an axially extended cord, invaginating said cord into said strand to form an end wall, and axially compressing said invaginated cord against said end wall.

The present invention further provides apparatus for end-closing a strand of sausage casing, particularly a shirred strand of thin-walled sausage casing, comprising a tubular mandrel for supporting said strand of sausage casing, a piston axially slidable within said mandrel, means for twisting an end portion of said strand into an axially extending cord, means for controlling the tension of said cord, and an anvil movable into, and out of, abutment with the end of said mandrel to provide a compression surface for co-action with said piston.

The means for twisting may be a tool adapted to invaginate said cord into said strand.

The means for controlling tension may comprise, for example, a plurality of tensioning fingers arranged radially in a common plane and spaced axially from the end of the mandrel, said fingers each being movable axially thereof into and out of a tension-controlling position.

The present invention also provides a method of making sausages using a strand of sausage casing in accordance with the present invention.

A preferred embodiment in accordance with the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a side elevation, partly in section, of an open-ended shirred strand of sausage casing; Figure 2 is a side elevation, partly in sec tion, of the strand of sausage casing of Fig. 1 supported on a mandrel at the commencement of the end-closing method of the present invention; Figures 3 to 6 illustrate further steps in the end-closing method; Figure 7 is a sectional side elevation of an end-closed shirred strand of sausage casing in accordance with the present invention; Figure 8 is a perspective view of a multipoint twisting tool which may be used in the method of the present invention;; Figure 9 is a perspective view of a clamp for preventing rotation of the supported strand during the end-closing procedure; and Figure 10 is a perspective view of said clamp in the operative position.

Referring to Fig. 1 of the drawings an open-ended tubular strand 1 of sausage casing extruded from coiiagen has been shirred with a multitude of pleats 2 in a manner well known to those versed in the art. The casing is thin-walled e.g. the thickness of the casing wall is about 0.0007 to 0.001 inches. Openended strands of other thin-walled sausage casings may be end-closed by the method of the present invention.

Referring to Fig. 2, the shirred strand 1 of Fig. 1 is shown supported on a tubular mandrel 3 after insertion of the mandrel 3 into the bore 1 a of strand 1. Fitted into the bore 4 of mandrel 3 is an axially slidable compression piston 5.

Also illustrated in Fig. 2 is a multipoint twisting tool 6 having a hollow ground tip 7.

This tool is shown in more detail in Fig. 8.

The shaft 7a of tool has a diameter of about 0 125" In use, the tip 7 of twisting tool 6 is pressed against the end shirred pleat 8 of the strand 1 and the tool is rotated. As this rotation takes place, the twisting tool 6 is slowly drawn away linearly from the strand 1.

With this drawing away of the tool 6, deshirring of the end portion of the strand 1 takes place and this de-shirred end portion is twisted. During the twisting step, the supported strand 1 is prevented from turning about its axis by means of a clamp such as described hereinafter with reference to Figs. 9 and 10.

Fig. 3 illustrates the result of the rotating and withdrawal of the twisting tool 6 and shows that a small number of pleats 2 has been de-shirred and twisted into an axially extending cord or rove 9. In order to ensure that the cord 9 is-twisted with the correct degree of tension, tensioning fingers 10 arranged radially in a common plane and spaced axially from the end of mandrel 3 are held against the casing material as it is being de-shirred and twisted. Once a sufficient number of twists has been obtained, the linear direction of movement of the twisting tool 6 is reversed so that the twisted cord 9 is pushed back through itself (invaginated) into the mandrel bore 4 while the rotation of the twisting tool 6 is maintained in the same direction.

During this step the tensioning fingers 10 act as guides for the twisted cord 9 so that it is inserted axially into the mandrel bore 4.

Fig. 4 illustrates the twisted cord 9 invaginated into the bore 4 of the mandrel 3, thus forming an end wall 11 for the strand 1. The twisting tool's rotational direction is reversed and is withdrawn linearly away from the twisted invaginated casing material. This reverse twisting of the tool 6 is sufficient to disengage the tool 6 from the twisted cord 9, and the tensioning fingers are maintained in position to ensure that no invaginated cord 9 is withdrawn from the mandrel bore 4 as the twisting tool 6 is disengaged and withdrawn.

Fig. 5 illustrates the shirred strand 1 with the twisted cord 9 of the casing material invaginated into the mandrel bore 4. The tensioning fingers 10 have been withdrawn from the tension controlling position, and an anvil 1 2 has been moved into a position so that its compression surface 1 3 abuts the end of the shirred strand and mandrel 3. It is against this compression surface 1 3 that the compression piston 5 compresses the twisted cord 9. The force applied to piston 5 is preferably in the range 45 to 65 Ibf (200N to 289 N).

Fig. 6 illustrates the shirred strand 1 with the twisted cord 9 invaginated in the mandrel bore 4 and compressed between the piston 5 and the anvil 12, so that the twisted cord 9 is compressed against the end wall 11 into a hard compacted knot 1 4 contained within the mandrel bore 4. The mandrel 3 is then removed from the shirred strand, but to avoid withdrawal of the knot 14 with the mandrel 3, it is necessary to maintain the pressure on the piston 5 while the mandrel 3 is partially withdrawn and this will cause the complete knot 14 to be ejected from the mandrel 3.

Once the knot 14 has been ejected, the mandrel 3 and compression piston 5 can readily be removed from the bore 1a of strand 1.

Fig. 7 illustrates the result of the end closing procedure. The hard compressed knot 14 can be seen positioned centrally of the shirred strand 1.

It will be seen that the present invention provides a strand of sausage casing closed at one end by an end-closure constituted by a twisted end portion of said strand invaginated into said strand and axially compressed against the end wall of said strand. The basic advantage of this type of end closure is that during the loading on a stuffing machine horn the hard knot will be pushed through the stuffing horn chuck cleanly, avoiding the likelihood of a double thickness of casing material being trapped between the horn and chuck.

Further, during the initial pressure surge of the sausage emulsion. the knot 1 4 can par tially untwist to withstand any sudden shock load which could cause casing rupture.

By varying the twisting tension of the end closure, for example by changing the position or applied force of the tensioning fingers 10, and the force applied on the compression piston 5, the degree of untwisting during the initial surge of sausage emulsion can be controlled. This results in an end closure for thinwalled sausage casing being able to withstand a variety of shock load conditions.

This control is demonstrated by the following procedure. Following engagement of the twisting tool 6 with the end shirred pleat 8 of the strand 1, it is withdrawn axially away from the strand 1 for a distance of one inch (2.54 cm) while rotating six complete turns. The following Table sets forth the relationship between the gap between the spaced tensioning fingers 10 and the amount of casing used to produce a cord or rove 9 fitting within the gap.

Tensioning finger Casing length gap Inches (cms) Inches (cms) 1/16 (0.16) 2 (5.1) 1/8 (0.32) 21 (6.4) 3/16 (0.48) 2i (7.0) 1/4 (0.64) 1 (8.9) As mentioned above, the force applied to piston 5 is preferably in the range 45 to 65 Ibf (200N to 289N). Using the smallest tensidn finger gap and the largest force, a hard compact knot or plug 14 is formed. Using the largest gap and a lower force, a knot or plug which will freely expand on stuffing is obtained. This demonstrates the versatility of an end-closure produced in accordance with the present invention, as compared with known end-closures, in that it can be adjusted to suit the requirements of particular sausage-stuffing machines.

Figs. 9 and 10 show one suitable clamp 1 5 for preventing the supported strand 1 from turning about its longitudinal axis during the twisting step in the formation of the endclosure. The clamp 1 5 comprises a rectangular backing plate 1 6 mounting on its lower face a co-terminus inverted V-section strip 1 7 of polyurethane foam. The clamp 1 5 may be lowered from the raised position shown in Fig.

9 onto the supported strand 1 as shown in Fig. 10 by means of an operating cylinder 1 8 and piston 19, so that in the lowered, operative position of clamp 15, the strand 1 is gripped by strip 1 7 and prevented from rotating.

Claims (8)

1. A strand of sausage casing closed at one end by an end-closure constituted by a twisted end portion of said strand invaginated into said strand and axially compressed against the end wall of said strand.

2. A strand according to Claim 1 which is shirred.

3. A strand according to Claim 1 or Claim 2 extruded from collagen.

4. A strand according to any one of Claims 1 to 3 which has a wall thickness of 0.0007 to 0.001 inches.

5. A method of end-closing a strand of sausage casing comprising twisting an end portion of said strand into an axially extending cord, invaginating said cord into said strand to form an end wall, and axially compressing said invaginated cord against said end wall.

6. Apparatus for end-closing a strand of sausage casing comprising a tubular mandrel for supporting said strand of sausage casing, a piston axially slidable within said mandrel, means for twisting an end portion of said strand into an axially extending cord, for controlling the tension of said cord, and an anvil movable into, and out of, abutment with the end of said mandrel to provide a compression surface for co-action with said piston.

7. Apparatus according to Claim 7 wherein said means for controlling tension comprises a plurality of tensioning fingers arranged radially in a common plane and spaced axially from the end of said mandrel, said fingers each being movable axially thereof into and out of a tension-controlling position.

8. A method of making sausages using a strand of sausage casing in accordance with any one of Claims 1 to 4, or when made by the method of Claim 5, or when made by the apparatus of Claim 6 or Claim 7.