The present invention relates to a machine for stretching a pelt prior to fastening it to a pelt board for drying.

BACKGROUND

In preparing pelts from e.g. mink or fox, the pelts are after skinning of the animal and a cleaning of the leather side of the pelt stretched out on a pelt board with the leather side facing the board for drying of the pelt. Formerly, the pelts were fixated by means of staplers penetrating the pelt and anchoring into the pelt board, more recently the pelts are secured by means of a sleeve or by means of winding material applied to the fur side of the pelt. The price of a pelt is established from a number of features, including the final length of the dried pelt from the nose to the beginning of the tail. The pelts are classified in sizes according to the length in classes, which at least for mink have 6 centimetres interval. Thus, by stretching a pelt sufficiently to reach a higher size before it is fastened to the pelt board, the value of the pelt may be increased, however with the risk of reducing the value due to overstretching or damages to the pelt.

Danish patent No. DK 169 525 discloses a machine for stretching of pelts on pelt boards, where a first stretch force is applied to stretch the pelt and, in case it is detected that the pelt length is close to the next higher classification size, a second, higher stretch force is applied to the pelt.

International patent application No. WO 02/44428 discloses a further development of this machine by adding a vibrating movement to the pelt during the stretching thereof, whereby an increased stretching of the pelt is achieved without causing damages to the pelt. In the international patent application No. WO 2005/028682 a device for stretching of pelts is disclosed, where holding elements are provided to grip, engage and fasten the pelt along the whole periphery of the lower end of the pelt, thereby applying the stretch force more uniformly to the pelt and allowing for an increased stretching thereof. The pelt is secured in the stretched position by means of a sleeve drawn over the fur side of the pelt from a tip of the pelt board, i.e. from the nose end of the pelt.

In the international patent application No. WO 2005/080607 the pelt is secured to the pelt board after stretching of the pelt by means of a winding material, such as a band, which is wound around the lower end part of the pelt, i.e. near the tail part.

It is an object of the present invention to provide an improved method for stretching pelts on pelt boards before drying where an improved quality of the pelt is achieved resulting in a higher price being paid for the pelt and preventing damages to the pelt caused by the stretching.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is reached with the method according to claim 1 for stretching a pelt comprising the steps of arranging the pelt on a pelt board, determining a measure of the length of the pelt, stretching the pelt with a stretch force determined from said determined length of the pelt, and securing the pelt to the pelt board. The pelt board may be any type of pelt board were the pelt having a tube-like shape can be slipped over so that the nose end of the pelt, i.e. the end that formerly covered the cranium of the animal, will rest at a tip end of the pelt board. The known pelt boards are normally of a tapered shape with the tip end having the smallest circumference. Wooden pelt boards with a flat cross section have been widely in use and are suitable for fastening staples into, whereas more modern pelt boards are made of plastics material and are of an elliptic or oval cross-section with internal openings for improving the drying of the pelt arranged thereon.

The measure of the length of the pelt may be an actual length of the pelt as measured from the nose of the pelt to the beginning of the tail, or it may be an indirect measure, such as the position of the lower end of the pelt board or of the tip end of the pelt board relatively to another part of the apparatus carrying out the method, in particular relatively to pelt holders for gripping at least parts of the tail end of the pelt. The measure of the length of the pelt is preferably established when the pelt is arranged on the pelt board but could also in accordance with the present invention be determined prior to the pelt being arranged on the pelt board, e.g. by a vision system.

It has by the present inventor been determined that the optimal force that can be applied to a pelt, i.e. the stretch force that will cause the maximum stretching of the pelt without causing damages to the pelt, can be determined at least partially from the length of the pelt prior to the stretching thereof. Other factors are e.g. the sex of the animal, for which the apparatus for stretching the pelt normally will be adjusted.

The stretch force is preferably determined from a predefined monotonic relation between the determined length of the pelt prior to stretching thereof and the stretch force, i.e. so that a longer pelt will be exposed to a higher stretch force. In particular, the stretch force may be determined from a continuous relation, such as a linear relation between the determined length of the pelt prior to stretching thereof and the stretch force. Alternative relations in accordance with the present invention include stepwise relations and polynomial relations.

In order to ensure a uniform and consistent determination of a measure of the length of the pelts, the method preferably comprises the step of gripping at least a part of the lower periphery of the pelt by pelt holders prior to determining the length of the pelt prior to stretching thereof. Furthermore, the method may comprise the steps of determining a measure of a stretched length of the pelt when said determined stretch force is applied to the pelt, and selectively reducing the stretch force based on said determined stretched length before securing the pelt to the pelt board. This is done in order to limit the stretching of the pelt to the degree necessary to reach the highest classification size possible.

The measure of the stretched length of the pelt may be detected as discussed previously with respect to the un-stretched length of the pelt, i.e. by detecting the longitudinal position of the pelt board with respect to e.g. the pelt holders or by means of a vision system. Alternatively, the detection system as disclosed in Danish patent No. DK 169 525 as discussed previously may be employed.

The advantage of reducing the stretch force in those cases where a substantial reduction in the stretched length of the pelt may be obtained without the pelt when dried will be classified in a lower classification size is that the reduced stretching will automatically cause the density of the fur as measured in number of hair per skin area unit will increase, which again may lead to a higher classification of the fur quality of the pelt with higher value of the pelt. The stretch force may preferably be reduced until the length of the pelt is a predetermined distance longer than one of a plurality of predetermined classification size lengths so as to allow for some shrinkage of the pelt during drying thereof and after removal from the pelt board without changing the classification size of the pelt. At least some of said predetermined classification size lengths have mutual intervals of 6 centimetres as is currently the case for at least mink pelts.

Said predetermined distance may be in the range of 3 to 15 millimetres, preferably in the range of 8 to 12 millimetres. The present invention furthermore relates to an apparatus for stretching a pelt on a pelt board in accordance with the method described above, the apparatus comprising a pelt board holder for holding one end of the pelt board, pelt holders arranged to grip at least a part of the lower periphery of the pelt when arranged on the pelt board, driver for mutually displacing the pelt board placed in the pelt board holder and the pelt holders in a longitudinal direction of the pelt board, controller for controlling the operation of the driver, and length measuring device for determining a measure of the length of a pelt on the pelt board placed in the pelt board holder and providing an output accordingly to the controller, wherein the controller is arranged to determine a stretch force based on said output from the length measuring device and control the driver to apply the determined stretch force to the pelt.

The apparatus may be arranged and equipped for being able to carry out the method according to the various preferred embodiments discussed above.

The step of reducing the stretch force may be applied to any stretch force and is thus not limited to the method of determining a stretch force as discussed previously but may be regarded as an independent invention. Thus, the present invention also relates to a method for stretching a pelt comprising the steps of arranging the pelt on a pelt board, stretching the pelt with a stretch force, determining a measure of a stretched length of the pelt when said stretch force is applied to the pelt, and selectively reducing the stretch force based on said determined stretched length before securing the pelt to the pelt board. This method may furthermore comprise any of the preferred relevant embodiments related to the reduction of the stretch force as discussed above. Also, the present invention relates to an apparatus suitable for carrying out this method, an apparatus for stretching a pelt on a pelt board comprising a pelt board holder for holding one end of the pelt board, pelt holders arranged to grip at least a part of the lower periphery of the pelt when arranged on the pelt board, driver for mutually displacing the pelt board placed in the pelt board holder and the pelt holders in a longitudinal direction of the pelt board, controller for controlling the operation of the driver to apply a stretch force to the pelt, length measuring device for determining a measure of the stretched length of the pelt when said stretch force is applied to the pelt and provide an output accordingly to the controller, wherein the controller is arranged to selectively reduce the stretch force based on said second output from the length measuring device by controlling the driver.

This apparatus may be arranged and equipped for being able to carry out the method according to the various preferred embodiments discussed above.

BRIEF DESCRIPTION OF THE DRAWING

A preferred embodiment of the present invention is illustrated with the enclosed drawing, of which

Fig. 1 is a diagram showing the relation between the length of the pelt prior to stretching of the pelt and the stretch force,

Fig. 2 shows the pelt arranged on the pelt board and gripped by the pelt holders at the lower periphery of the pelt prior to stretching of the pelt,

Fig. 3 shows the pelt on the pelt board when the determined stretching force is applied to the pelt, and Fig. 4 shows the pelt on the pelt board when the stretch force has been reduced until the length of the pelt is a predetermined distance longer than one of a plurality of predetermined classification size lengths. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The method according to the present invention involves the measurement of a length of the pelt 1 that is to be fastened to the pelt board 2 prior to drying of the pelt. The length Li of the pelt 1 is defined to be from the nose at the nose end 3 of the pelt to the beginning of the tail at the tail end 4 of the pelt 1. In Fig. 1 is shown a diagram of the function according to which the controller of the apparatus for stretching the pelt 1 and securing it to the pelt board 2 determines the stretch force Fs to be applied to the pelt 1. The operator of the apparatus has prior to the operation defined a minimum stretch force Fs, _m in to be applied to a pelt 1 having a defined minimum length Lmin and a maximum stretch force Fs _,max to be applied to a pelt 1 having a maximum length L _max . According to the function shown in Fig. 1 , a simple linear interpolation between these two extreme sets of values is performed for determining the stretch force Fs _, i to be applied to a given pelt 1 of a length Li that has been determined when the pelt 1 is arranged on the pelt board 2 in the apparatus.

Fig. 2 shows the pelt 1 arranged on the pelt board 2. Parts of the lower periphery of the pelt 1 are gripped by the pelt holders 5 and the length Li of the pelt prior to stretching of the pelt 1 is determined. The lower, thick end 6 of the pelt board 2 is placed in the pelt board holder 7 of the apparatus, and pelt board holder 7 is moved upwards without applying a stretching force to the pelt 1 until the pelt 1 is tight, where after a measure of the length L] of the pelt 1 is determined from the position of the pelt board holder 7 and the type of pelt board 2 detected by the pelt board holder 7. The type of pelt board 2 is selected from the size of the pelt 1 which is determined largely by the sex of the animal from which the pelt origins. Male pelts 1 are longer and wider for which reason the pelt boards 2 for the male pelts 1 are longer and has a larger cross-sectional circumference than pelt boards 2 for female pelts 1. Alternatively, the pelt board 2 type is entered by the operator into the controller of the apparatus as the apparatus in many cases has to be adjusted generally for the type of pelt boards 2, e.g. by selecting pelt holders 5 suitable for male pelts or for female pelts. The length limits L _m j _n , L _max as well as the stretch force limits Fs.min, Fs, _m ax may also be adjusted selectively for male pelts and for female pelts, respectively.

When the determined stretch force Fsj is being applied to the pelt by moving the pelt board holder 7 upwards relatively to the pelt holders 5 as shown in Fig. 3, where the result is that the pelt 1 is stretched to a new, stretched length of L ₂ .

The stretched length L ₂ of the pelt 1 is determined in the same manner from the position of the pelt board holder 7 and the controller of the apparatus compares the determined stretched length L ₂ with the classification size lengths for the particular type of pelt 1. In case the pelt 1 is a mink pelt, the classification size length of the pelts 1 have mutual intervals of 6 centimetres and in case the overshoot with respect to the nearest, lower classification size length is sufficient, e.g. more than 2 centimetres, the reduction step is initiated.

The reduction step comprises in one embodiment a gradually reduction of the stretch force Fs applied to the pelt and a consecutive repeated measurement of the stretched length Ls until the stretched length Ls is a predetermined distance L _d longer than the nearest, lower classification size length. The determined stretch force Fs,i is then as shown in Fig. 4 reduced by an amount dF so that the stretched length L ₂ when the determined stretch force Fs.i is applied to the pelt 1 will be reduced by a length dL whereby the final stretched length Ls is reached.

The length of the predetermined distance L _d is set to ensure that the pelt after drying and removal from the pelt board 2 will still be of the intended length classification size. The distance L _d is thus intended to compensate for further shrinkage of the pelt after it has been removed from the pelt board as well as possible shrinkage when it is arranged on the pelt board and secured thereto, where some of the securing methods, such as wrapping as well as the use of a sleeve on the fur side of the pelt inherently has a higher risk of some shrinkage of the pelt when secured to the pelt board. For the use of wrapping as securing method, a predetermined distance L _d of 10 millimetres has proven to be advantageous.

In an alternative embodiment, the reduction step comprises a stepwise reduction of the stretch force Fs and a subsequent determination of the stretched length Ls of the pelt until the required length is reached.

In a further alternative, the reduction step comprises a one-step reduction of the stretch force Fs by a predetermined amount dF which is known to cause an acceptable reduction dL in stretched length Ls from the initial stretched length of the pelt.

The reduction step may be performed on any type of apparatus for stretching a pelt on a pelt board and is not confined to be used with the determination of the stretch force based on the length of the pelt as disclosed herein.

REFERENCE NUMBERS AND SIGNS

1 : pelt

2: pelt board

3 : nose end of the pelt

4: tail end of the pelt

5: pelt holders

6: lower, thick end of the pelt board

7: pelt board holder

Li : length of a given pelt prior to stretching thereof

L ₂ : length of the given pelt when the determined stretch force is applied to the pelt

dL: reduction of stretched length of the given pelt

Ls: stretched length of the pelt when a stretch force is applied to the pelt

L : predetermined length the reduced stretched length of the pelt is longer than the nearest, lower classification size length

Fs: initial stretch force to be applied to a pelt

Fs _, i : determined stretch force to be applied to a given pelt

dF: reduction of determined stretch force

Fs.min: minimum stretch force

Fs.max: maximum stretch force

L _m j _n : defined minimum length

L _max : maximum length