WO2008020786A1

WO2008020786A1 - Bone removing method and device

Info

Publication number: WO2008020786A1
Application number: PCT/SE2006/000947
Authority: WO
Inventors: Kari Koljonen
Original assignee: Exos Ab
Priority date: 2006-08-15
Filing date: 2006-08-15
Publication date: 2008-02-21

Abstract

For removing bones (2) from fish (1) by means of a power driven rotary drum (5) having bone engagement means (11, 12) distributed around the circumference of the drum, bones are gripped by engagement means and are pulled out from the fish by the rotation of the drum, whereby rotation of at least selected engagement means (11, 12) is automatically temporarily slowed down when any of said selected engagement means encounter a bone pull-out force (PF) exceeding a predetermined maximum value.

Description

TITLE: BONE REMOVING METHOD AND DEVICE

TECHNICAL FIELD

The present invention generally concerns removing bones from fish and specifically relates to methods and equipment for removing bones, such as pin bones, from fish.

BACKGROUND

Within the fish processing industry it is a well known fact that economical profit will be largely dependant upon the ability of effectively removing bones from processed fish, hi fact, for high quality and accordingly high-priced fish products, mainly fillets, it is a requirement that bones and bone remnants are effectively removed from the fish. A particular problem is in this context the removal of the so called pin bones from different filleted fish, such as salmon, trout, redfish, cod and perch. The pin bones are relatively thin, fine intramuscular bones that terminate near the skin of the fish and that remain in the fish after normal filleting.

hi view of the economical values involved, many attempts have been made during several years to provide effective fish deboning equipment, both handheld devices and automated machines. One type of handheld equipment makes use of a rotating drum carrying bone engagement means. The engagement means are distributed around the outer circumference of the drum to cooperate with a stationary bone guide acting also as a counter stay, to pull out bones gripped there between as the drum is rotated. One example of such equipment is disclosed in EP 0567515Bl. Other types of equipment, mainly automated machines, use revolving pivotally guided flaps to grip and pull out bones from fish, such as the one disclosed in EP 0934002B1.

A major problem for most existing pin bone removing equipment is that the time when pin bones maybe effectively removed is restricted, hi most cases it will be necessary to wait up to 48 hours before pin bones can be securely removed. At this point, in the so called post-rigor condition, the flesh has loosened its grip of the bones sufficiently to allow rapid and thereby economically rational pin bone removal processing of the fish. Naturally, this is an undesirable restriction since it not only delays delivery of fish products but also causes an undisputable lowering of the quality of the fish products. Yet another problem experienced with the existing equipment is that the requested high pin bone removal processing speeds many times cause pin bones to snap off during the high speed removal, causing small pieces of pin bones to remain hidden in the flesh. Such bone remnants are hard to discover, require the use of special identifying devices, such as X-ray devices, and must normally be removed completely manually.

SUMMARY

A general object of the present invention to improve the process of removing bones from fish so that bones may be removed securely and effectively from fish closer in time after slaughter than has been possible up to now.

A specific object of the invention is to provide an improved method of removing bones from fish, allowing controlled, secure removal of bones from fish practically irrespective of the time elapsed after slaughter.

Another object of the invention is to provide an improved apparatus for removing bones from fish, being designed for performing pin bone removal from fish based on the inventive principles.

Yet another object of the invention is to provide an improved bone removal drum for use in an apparatus of the invention.

These and other objects are met by the invention as defined by the accompanying patent claims.

The invention generally relates to devices of the kind that are intended for use in the fish processing industry for removing bones, such as pin bones, from fish and that comprise a power driven rotary drum carrying bone engagement means distributed around the circumference of the drum. Briefly, the present invention is based on the idea of allowing bone engagement means of the drum to be automatically temporarily slowed down when encountering a bone pull-out force that exceeds a predetermined maximum value.

hi one practical embodiment of the invention, favourable effects are achieved by providing the bone engagement means in at least two distinct groups, whereby the individual engagement means of each group are alternated around the drum. In another embodiment of the invention the favourable effects of the invention are achieved by providing a restricted-slip drive connection between a drive shaft of a drum drive motor and the drum bone engagement means.

Preferred developments of the basic inventive idea as well as embodiments thereof are specified in the dependent subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, will be best understood by reference to the following description taken together with the accompanying drawings, in which:

Fig. IA is a schematical top view of a prior art drum for a bone removing device;

Fig. IB is a schematical end view of the prior art drum of Fig. IA;

Fig. 2 is an exploded view of an embodiment of a bone removing device of the invention;

Fig. 3 A is a top view of parts of the drum of Fig 2, in an assembly position;

Fig. 3B is an end view as seen from the lower end of the drum of Fig. 3 A;

Fig. 3C is an end view of the rotor member of the slip drive connection of Fig. 2;

Fig. 3D illustrates a spring of the slip drive connection of Fig. 2;

Fig.4A is a cross section along a line A-A of Fig. 3A, through an assembled device of the embodiment of the invention, in a normal drive phase;

Fig.4B is a cross section along a line B-B of Fig. 3 A, through an assembled device of the embodiment of the invention, in the normal drive phase;

Fig. 5A is a schematical illustration of an overload phase of the operation of the bone removing device of the invention;

Fig. 5B is a schematical illustration of another overload phase of the operation of the bone removing device of the invention; Fig. 6A is a very schematical illustration of an exemplary handheld bone removing apparatus being equipped with a device of the invention; and

Fig. 6B is a very schematical illustration of an exemplary automated bone removing machine being equipped with at least one device of the invention.

DETAILED DESCRIPTION

Figs. IA-B very schematically illustrate a typical drum 105 of the general kind that was described in the introduction and that has been and is currently being frequently used in bone removing equipment of the handheld type as well as in automated machines, for removing pin bones from fish fillets. The drum 105 consists of a solid drum base 114 that has a central bore 115. In the bore 115 is received a drive shaft 137 of a drive motor (not illustrated) of the apparatus. The drum 105 is fixed to the drive shaft 137 by a suitable fixed drive connection (not specifically shown), using for example splines or keys. This means that the drum rotates as a unit with the drive shaft. On the outer circumference of the drum base 114 are formed a number of equally spaced bone engagement means 111 that cooperate with a bone guide 140 being supported in the apparatus. The bone guide may be fixed in position but attempts have been made with bone guides being adjustable against a spring force, as is schematically illustrated by means of the spring 141 in Fig. IB.

The described design has been reasonably effective for removing pin bones from fish fillets in the post-rigor condition, but will even then sometimes cause bones to snap immediately as they are gripped. This problem is to a certain degree related to the fact that the rotational speed of drums is increased to improve the processing capacity and is only partially solved by making the bone guide adjustable. Bone removal prior to the post-rigor condition of the fish is in essence impossible with said described design. Bones requiring larger pull-out forces will inevitably break either initially as they are gripped or during the later part of the removal. In the latter case smaller bone remnants will be left in the flesh, which are very hard to identify. Accordingly, the presently used equipment is far from satisfactory.

The invention aims at solving problems experienced with prior art equipment of this general kind having a power driven rotary drum with bone engagement means distributed around the outer drum circumference, whereby bones are gripped between engagement means and a bone guide acting as a counter stay, and are pulled out from the fish by the rotation of the drum. Specifically, the invention is concerned both with the general problem of bones snapping or breaking during pull-out and with the inability of prior art equipment to remove bones from fish prior to the post- rigor condition. To achieve this aim the invention principally suggests a method of removing bones from fish, wherein rotation of at least selected engagement means is automatically temporarily slowed down when any of said selected engagement means encounter a bone pull-out force exceeding a predetermined maximum value. This measure has the surprising effect of allowing bones to be effectively and securely pulled out from fish without breaking neither outside, normally occurring during the initial bone gripping phase, nor inside, frequently occurring during the last half or third of the pull-out phase, the flesh of the fish. Performed tests have furthermore shown that this basic feature of the invention has the unexpected result that such effective and secure bone removal may be performed not only in the post-rigor condition but also in the pre-rigor condition and, even more astonishing, in the actual or full rigor condition of the fish. It appears that this temporary slowing down of the respective active engagement means significantly reduces the sudden initial impact of the engagement means against a gripped bone, thereby eliminating the primary cause of the early cutting-off of bones outside the flesh, namely between engagement means and bone guide. In the same manner this slowing down of the active engagement means takes effect again when the pull-out force increases during the last half or third of the pulling-out phase of a bone, which is normally the case. This tendency for the pull-out forces to increase during the latter half of the pull-out phase is the main cause of small bone fragments remaining in the fish. Thus, the invention also eliminates said risk of smaller bone remnants being left inside the flesh of the fish.

In a practical, presently preferred embodiment of said principal method, wherein the bone engage- ment means are arranged extending in a generally axial direction of the drum, as is known in the art, the engagement means are arranged in at least two distinct groups. The individual engagement means within each group are supported in mutually fixed positions and the engagement means of said at least two groups are alternated around the outer circumference of the drum, with a gap provided between each of said alternating engagement means of said at least two groups.

Thereby the engagement means of the respective group may be slowed down independently of the engagement means of any other group. This concept will be of importance especially in cases where the length of the pulled out bones is such that two successive engagement means of two separate groups engage one and the same bone during removal. In such a case the second engagement means of the two will engage the bone during the later half of the removal phase, so that the increase of the pull-out force during said phase will be compensated for by the independent slowing down of said second engagement means belonging to a second group.

Ih a further practical, presently preferred embodiment of the method according to the invention slowing down of the engagement means of the group or groups is performed purely mechanically. A motor is used for driving the drum through a drive shaft and the temporary slowing down of the selected bone engagement means is performed by providing a restricted-slip drive connection for allowing restricted relative slip between the drum or selected engagement means thereof and the drive shaft and, in the applicable case, also between groups of engagement means. Thus, a driving force is temporarily yieldingly transmitted from the drive shaft to the or each group of engagement means, said yielding of the force transmission being related to the pull-out force encountered by active engagement means of the or the respective group. Specifically, the drive connection allows slip when an engagement means of a respective group encounters an excessive pull-out force. Preferably the yielding of the force transmission to the engagement means is accomplished by means of one spring member for the or each group, in which an excessive pull- out force is stored when said force exceeds the chosen maximum value. When the pull-out force returns to an acceptable value the stored excessive force acts to return the transmission to a normal drive condition, ready for a new bone gripping phase. The yielding force transmission realized by establishing a slip drive connection may be said to act functionally as a friction clutch between said drive shaft and the drum or the engagement means or the respective group of engagement means, and could also be called a force-related driver means acting there between.

The invention will now be explained in detail with reference especially to an exemplifying embodiment of a bone removing device 3, which is illustrated in the accompanying drawing figures 2, 3A-B, 4A-B and 5A-B. Said exemplifying embodiment of the invention relates to an application of the basic inventive principles to a partially and schematically outlined drum assembly for a general kind of bone removing equipment. It shall be emphasized, though, that the illustrations are for describing a preferred embodiment of the invention and are not intended to limit the invention to the use thereof on or for any specific design of such equipment. In Fig. 2 is illustrated a bone removing device 3 for use in equipment for removing bones 2 from fish 1, such as the handheld apparatus 50 that is very schematically exemplified in Fig. 6A or the automated bone removing machine 50' that is very schematically exemplified in Fig. 6B. The bone removing device 3 comprises a drive shaft 37 that will be drivingly connected to a motor 41, 41' (Figs. 6A and B) of the bone removing equipment 50, 50'. The device 3 further comprises a drum 5 with generally rib-shaped, axially, with regard to the drive shaft 37, extending bone engagement means 11, 12. The engagement means 11, 12 are distributed around the outer circumference of the drum 5 for engaging and removing fish bones 2 in cooperation with a bone guide 40 (see especially Figs. 5 A and 5B) during rotation of the drum 5. In the illustrated embodiment the drum 5 consists of two individual parts 6, 7 each comprising a body portion 15, 16 carrying a group Gl, G2 of bone engagement means 11 and 12, respectively, around their outer periphery. Said body portions 15, 16 each have an inner, generally circular through bore 10 (Fig. 3B) forming an inner circumference thereof and being intended for rotatably receiving a later described drive connection rotor 17.

The engagement means 11, 12 of each drum part 6, 7 are arranged with their major portion canti- levered from one end of the respective body portion 15, 16 and with a smaller portion thereof extending past the opposite end of the body portion 15, 16, for reasons that will be described below. The engagement means 11, 12 of each group Gl, G2 are provided in fixed mutual positions on their respective body portion 15, 16 and they are spaced evenly or regularly from each other around the circumference of the drum 5 by a gap 13, 14. The drum parts 6, 7 are assembled with their respective major, cantilevered engagement means 11, 12 pointing in opposite directions, each being received in the gaps 13, 14 between the engagement means 11, 12 of the respective other group Gl, G2. Thereby, the engagement means 11, 12 of the two groups Gl, G2 will be provided alternating around the outer circumference of the drum 5. The gaps 13, 14 are wider than the actual engagement means 11, 12 so that relative rotation around the drive shaft 37 is possible between the drum parts 6, 7. Specifically, relative rotation of the two parts and their engagement means is thereby allowed when an engagement means of either group encounters an excessive bone pull-out force PF (Figs. 5A-B).

A rotor 17 forming part of a restricted-slip drive connection between the drive shaft 37 and the drum 5 is functionally positioned there between. Specifically, the rotor 17 has a central bore 17B (Fig. 3C) having a slightly larger diameter than a corresponding section of the drive shaft 37, so that it may be slid into position on the latter. The rotor 17 has an outer cylindrical surface 17A being of slightly smaller diameter than the inner through bore 10 of the drum parts 6, 7, so that it may be guidingly received in said through bore 10, allowing for relative rotation between the drum parts 6, 7 and the rotor 17. To promote such relative rotation, the rotor 17 is coated with or preferably formed of a low fiiction material, such as a suitable plastic material.

When the rotor 17 has been slid onto the drive shaft 37 and the drum 5 has in turn been slid onto the rotor 17, the rotor 17 is fixed onto the drive shaft 37, being drivingly connected thereto. This is accomplished by sliding the rotor 17 onto the drive shaft 37 until a polygonal drive step 39 of the drive shaft tightly engages a complementary-shaped recess 20 in one end face of the rotor. Finally, a rotor lock 30 is securely attached to a forward, free end of the drive shaft 37, clamping the rotor 17 in axial direction between a rotor engagement surface 30B at one end of the lock 30 and the drive shaft drive step 39. Specifically, the rotor lock 30 has a blind bore 31 for receiving the free end of the drive shaft 37 and being provided with a circumferential groove 32. A corresponding groove 38 is formed near the free end of the drive shaft 37. In the assembled condition a locking means 36, such as an 0-ring, is provided in said grooves 32, 38, locking the drive shaft to the rotor lock 30.

With the described configuration, the rotor lock 30 also axially fixes the rotor relative to the drum 5 and thereby indirectly fixes the drum axially to the drive shaft 37. In the assembled condition an enlarged head 30A of the rotor lock 30 engages and axially blocks a first forward part 6 of the drum 5, whereas a rear, enlarged flange 21 of the rotor 17 engages and axially blocks a second rearward part 7 of the drum 5. To further secure free relative rotation between the individual drum parts 6, 7 as well as between said drum parts 6, 7 and the rotor 17 and its lock 30, slide bearings 33, 34 and 35 are supported on the outer surface of the rotor 17. The slide bearings 33, 34 and 35 are preferably ring-shaped and likewise preferably formed of a low friction material, such as a suitable plastic material, hi the assembled condition they are clamped between the enlarged head 30A of the rotor lock 30 and the body portion 15 of the forward drum part 6, between the body portions 15, 16 of the drum parts 6, 7 and between the body portion 16 of the rearward drum part 7 and the enlarged flange 21 of the rotor 17, respectively. The two drum parts 6, 7 are thus assembled with their body portions 15, 16 in indirect engagement with each other through the central slide bearing 34. The radial dimensions of the bearing rings are also such that in said assembled condition the bearing rings 33, 34, 35 are received inside the engagement means 11, 12, so that in particular the two outer bearing rings 33, 35 simultaneously provide sliding support for the respective free ends of the major cantilevered portions of said engagement means 11, 12.

As was mentioned above, an essential part of the invention is the provision of a drive connection that allows the drum 5, in the present case each individual drum part 6, 7, to slip and thereby to slow down temporarily relative to the drive shaft rotation and in dependence upon the encountered pull-out force. In the illustrated embodiment such a restricted-slip drive connection comprises a pair of resilient driver members in the form of springs 24, 25 (see also Fig. 3C), one each for and provided in association with the respective drum part 6, 7. Said springs 24, 25 are each received in a groove 18 and 19, respectively. Said grooves 18, 19 are each extended circum- ferentially around a major portion of the rotor 17, are axially displaced from one another and are displaced in relation to each other around the circumference of the rotor 17. The extent of this circumferential displacement is dependent upon the pitch between adjacent engagement means 11, 12 of the respective group Gl, G2. The springs are pivotally supported, at a first end 24A, 25A thereof, on pins 28 and 29, respectively, that are pushed into axially directed blind bores 22 and 23, respectively, opening in the respective end faces of the rotor 17, and through holes 27 provided in said first spring ends. The springs generally have the shape of an open ring. A second end 24B, 25B thereof is formed as an enlarged head having a width larger than the distance from a bottom 18 A, 19A (see Figs. 5 A and 3C, respectively) of the associated groove 18, 19 to the outer cylindrical surface 17A of the rotor and thereby to the inner circumference 10 of the respective drum body portion 15, 16 in the assembled condition, the purpose of which will be described later, hi mounted condition the springs 24, 25 extend approximately from one end to the other of the respective groove 18, 19. Finally, between said first and second ends 24A, 25A and 24B, 25B an inner surface of the springs is provided with a support boss 26 for supporting the springs on the bottom 18A, 19A of the respective groove 18, 19.

To complete the slip drive connection, the drum parts 6, 7 are on the inner circumference 10 of their body portions 15, 16 each provided with a relative-slip recess 8, 9 cooperating wifii a corresponding second free end 24B, 25B of the associated resilient driver member or spring 24,

25. The relative-slip recesses 8, 9 in the inner circumference 10 of the drum parts 6, 7 each comprise a steep end 8A, 9A and a cam surface 8B, 9B rising inwardly towards the centre C of the drum 5 in the direction of rotation R (Figs. 4A-B and 5 A-B). The steep ends 8 A, 9A and cam surfaces 8B₅ 9B form respective end stops Sl, S2 cooperating with the enlarged heads 24B, 25B at the free second ends of the spring driver members 24, 25 to restrict relative slip in two directions, as will be explained further in connection with Figs. 4A-B and 5A-B. It should be noted also that the two drum parts 6, 7 are identical except for the positioning of the relative-slip recesses 8, 9 and their end stops 8A, 8B, 9A, 9B, which will be adapted to the drive shaft rotation and to the fact that the two drum parts 6, 7 are assembled as mirror images. In other words said restricted-slip recesses 8, 9 are both positioned with a trailing steep end 8A, 9A and a leading cam surface 8B, 9B, with respect to the direction of rotation R of the drum 5 in use.

The mutual association of the parts of the slip drive connection and the basic function thereof will now be explained with reference to Figs. 4A-B and 5A-B, respectively. Figs. 4A-and 4B show cross-sections through the device 3 along lines A-A and B-B, respectively, passing through the spring driver member 25, 24 associated with the respective drum part 7 and 6, respectively. Said drawing figures illustrate the drum 5 during a normal or idling driving condition prior to the gripping of a bone, in turn meaning that none of the bone engagement means 11, 12 has encountered an excessive pull-out force PF. In such a situation the enlarged heads 24B, 25B of both springs 24, 25 are in their normal driving position engaging the trailing steep end 8A, 9A of the recess 8, 9 in their respective drum part 6, 7. The springs 24, 25 are maintained in said position since any tendency of the springs to leave the steep end 8A, 9A will be counteracted by the increased resisting spring force that would result from a relative movement of the enlarged head 24B, 25B along the inwardly rising cam surface 8B, 9B, in turn causing loading of the spring.

Fig. 5A illustrates the drive situation when one engagement member 11 of the drum part 6 first grips a bone 2 in cooperation with its associated bone guide 40. Ih this situation, the engagement means 11 normally encounters a very large initial pull-out force PF that has often lead to an abrupt cutting-off of the bone 2. However, Fig 5A illustrates that with the inventive device 3 the excessive force PF causes the drum part 6 to slow down in relation to the rotation of the drive shaft 37 and the rotor 17. This relative movement between the drum part 6 and the rotor 17 causes the enlarged head 24B of the spring 24 to move along the cam surface 8B, in turn causing the forward part of the spring 24 to bend inwardly around the support boss 26 abutting the bottom of its associated groove 18, whereby the pull-out force PF may be said to be loaded in the spring 24. After the initial, temporary slowing down of the first drum part 6 the enlarged head 24B reaches a leading end stop position S2 on the cam surface 8B where the head 24B is clamped between the bottom 18A of the groove 18 and the cam surface 8B so that a fixed drive connection is once more established as long as the excessive pull-out force PF remains. At this stage, no pull-out force has been applied to the other drum part 7, so that it remains in its normal driving condition with the enlarged head 25B engaging the steep end of its associated recess 9. When the pull-out force PF encountered by the first drum part 6 then decreases during a following pull-out phase or after a completed pull-out of a bone 2, the force loaded in the spring 24 causes the drum part 6 to rotate quicker as the spring moves back along the cam surface 8B, returning to the trailing first end position Sl at the steep end 8 A of the recess 8 (Fig 5B). Accordingly, the return of the drum part to the basic position occurs when the force of the spring overcomes the bone pull-out resistance encountered by the drum part.

Fig. 5B illustrates the continued pull-out process of the bone 2, when an engagement means 12 of the second drum part 7, trailing behind the first active engagement means 11 of the first drum part 6, grips the bone 2 during the last half or third of the entire pull-out process. At this stage an increased pull-out force PF is normally encountered again. In the past this has often caused the bones 2 to break, leaving short bone remnants inside the flesh, which is a serious problem. With the device 3 of the invention this repeated increase of the force PF will be dealt with in the same manner as described above. Thus, the enlarged head 25B of the spring 25 moves from its first end stop Sl at the steep end 9 A of the recess 9 to tiie second end stop S2 at the recess cam surface 9B, causing the second drum part to slow down, temporarily relieving the bone 2 and stopping it from breaking. Then, as the excessive force disappears the second drum part 7 and its engagement means 12 will return to the first end stop Sl position, as described above in relation to the first drum part 6, and the bone 2 will be fully pulled out in one piece from the fish 1. The pull out process will then be repeated for further bones in the same and following fish fillets 1.

In the illustrated embodiment all of the parts of the device may be disassembled quickly and easily by simply removing the rotor stop 30 from the drive shaft 37 and then sliding off the remaining parts therefrom. This is an essential practical feature and allows for rapid exchange of parts of the device 3 as well as the necessary cleaning of the device after use. It also enables rapid exchange of the springs 24, 25 for stronger or weaker ones. This may be done to adapt the device for different circumstances, such as for the deboning of different types of fish having bones requiring different settings for the maximum allowed pull-out force. This maximum allowed pull- out force may be determined in optional ways that will not be specifically described here, but that may be based on experience or on actual, performed tests.

Based on the above description of the exemplary embodiment of a device according to the invention it will now be clear that the invention achieves all of the initially summarized objects thereof. With the proposed solution bones may be efficiently and securely pulled out from fish in one piece, without leaving any bone fragments, large or small, in the fish. As mentioned, tests performed with a device configured and operated in accordance with the invention have proven that the inventive principles permit safe and full removal of bones not only from fish in the post- rigor state but also from fish in the pre-rigor state and, quite astonishingly, even from fish in full rigor. The favourable effects achieved by means of the described invention are of great eco- nomical value to the fish industry For the first time safe and full deboning of fish is allowed during the most practical time period after slaughter, when the fish is still of the highest quality.

Fig. 6 A illustrates a practical appli cation of the invention in a very schematically shown hand held bone removing apparatus 50. The bone removing device 3 may comprise one drum 5 with an associated bone guide 40, or two drums, with corresponding bone guides, arranged side by side for enhanced efficiency. The apparatus 50 has a main housing 51 serving as a handle and accommodating a drive motor 41. The output shaft 52 of the motor drives the drive shaft 37 or drive shafts of the bone removing device 3 through a suitable transmission 42, as is well known.

Finally, Fig. 6B illustrates a further practical application of the invention in an automated bone removing machine 50' having a main machine housing 51' accommodating one or several drive motors 41 that likewise drive a bone removing device 3 through a transmission that is not shown in the drawing. Below the machine housing 51' is provided a conveyor 43 on which fish fillets 1 are conveyed in a direction M through the machine, past the bone removing device 3. For improved efficiency of the bone removing, the bone removing device 3 may consist of an optional number of drums 5, three indicated here, and their respective bone guide 40 arranged side by side in the direction of movement M of the conveyor. Likewise, the capacity of the machine may be increased by providing drums 5 in multiple rows parallel to the conveying direction M.

In alternative, but not specifically illustrated embodiments of the invention variations of the different illustrated parts of the bone removing device and drum, respectively, may be employed without departing from the scope of the invention. As an example of such variations, the invention may be applied to the common type of unitary drum consisting of one single part, whereby the entire drum and all of its bone engagement means are slowed down by means of a single slip drive connection when one of them encounters an excessive force. Such an application would primarily be considered for removing very short bones that during their removal are only gripped by one engagement means. It is likewise possible to configure the drum so that it consists of more than two individually relatively moveable parts, each likewise having their own group of engagement means and individual slip drive connection function. Such applications would primarily be considered for removing very long bones that during their removal have to be gripped by more than two engagement means.

It should be specifically noted that the invention is not restricted to the illustrated and described embodiment of the parts forming what has been referred to as the restricted-slip drive connection. Instead, the invention covers all kinds of differently configured drive connections having the same basic function of allowing restricted slip between the drum engagement means and the drive shaft or, in the applicable case, individually between separate groups of drum engagement means and the drive shaft, said slip being dependent upon the bone pull-out force encountered by said engagement means and being restricted between two end positions. For instance, other means than the illustrated springs may be used to resiliently counteract rotation of the drum or drum parts and to store the pull-out force, as described above.

Although the invention has been described and illustrated with specific reference to the application thereof to common types of bone removing equipment that have been schematically illustrated and described herein, the invention is in no way restricted to such applications. The basic principles of the invention may therefore be applied to any other appropriate, present or future type of bone removing equipment. The invention has been described in connection with what is presently considered the most practical and preferred embodiment, but it is to be understood that the invention is not limited to the disclosed embodiments. The invention is therefore intended to cover various other modifications and equivalent arrangements not specifically mentioned above but included within the spirit and scope of the appended claims.

Claims

PATENT CLAIMS

1. A method of removing bones (2) from fish (1) by means of a power driven rotary drum (105;5) having bone engagement means (111; 11, 12) distributed around the outer circumference of the drum, whereby bones are gripped by engagement means and are pulled out from the fish by the rotation of the drum, characterized by automatically temporarily slowing down the rotation of at least selected engagement means (11, 12) when any of said selected engagement means encounter a bone pull-out force (PF) exceeding a predetermined maximum value.

2. A method according to claim 1, wherein said bone engagement means are arranged extending in a generally axial direction of the drum (5), characterized by arranging the engagement means (11, 12) in at least two distinct groups (Gl, G2), by providing the individual engagement means within each group in a mutually fixed position and by alternating said engagement means of said at least two groups around the circumference of the drum (5).

3. A method according to claims 1 or 2, characterized by providing a gap (13, 14) between each of said alternating engagement means (11, 12) of said at least two groups (Gl, G2) to allow relative rotation of the groups.

4. A method according to any of claims 1-3, using a motor (41; 41 ') for driving the drum (5) through a drive shaft (37), characterized by mechanically slowing down the selected bone engagement means (11, 12) or group (Gl, G2) of engagement means by providing a restricted- slip drive connection (17, 24, 8, 25, 9) between the drive shaft and the drum or the respective group of engagement means of the drum.

5. A method according to claim 4, characterized in that when the engagement means (11, 12) or the respective group (Gl, G2) of engagement means (11, 12) encounter an excessive pull-out force (PF) a driving force is temporarily yieldingly transmitted from the drive shaft (37) to the engagement means or the respective group of engagement means through the slip drive connection (17, 24, 8, 25, 9) using a resilient driver member (24, 25) and acting functionally as a friction clutch between said drive shaft and the engagement means or the respective group of engagement means.

6. An apparatus (50; 50') for removing bones (2) from fish (1), comprising a motor (41; 41') for driving at least one bone removing device (3) through a drive shaft (137; 37), said device (3) having a drum (105; 5) with bone engagement means (111; 11, 12) distributed around its outer circumference for engaging and removing fish bones (2) during rotation of the drum, characterized by a restricted-slip drive connection (17, 24, 8, 25, 9) being functionally positioned between the drive shaft (37) and the drum (5) for allowing force-related restricted relative slip between at least selected engagement means (11, 12) and the drive shaft and having end stop means (24B, 8A, 8B, 25B, 9A, 9B) for restricting relative slip in two directions.

7. An apparatus according to claim 6, characterized by a mechanical restricted-slip drive connection (17, 24, 8, 25, 9) comprising a rotor member (17) being fixed to the drive shaft (37) and being axially fixed relative to the drum (5) but being received for rotation inside the drum and carrying at least one resilient driver member (24, 25) cooperating with end stops (8A, 8B, 9 A, 9B) at an inner circumference (10) of the drum.

8. An apparatus according to claim 7, characterized in that the driver member or members (24, 25) are part-circular springs (24, 25) received in respective circumferential grooves (18, 19) in the rotor member (17) and having a free end (24B, 25B) cooperating with a corresponding relative-slip recess (8, 9) in the inner circumference (10) of the drum (5).

9. An apparatus according to claim 8, characterized in that the or each relative-slip recess (8, 9) in the inner circumference (10) of the drum (5) comprises a steep end (8 A, 9A) and a cam surface (8B, 9B) forming respective end stops (Sl, S2) in cooperation with an enlarged head (24B, 25B) in the free end of the spring driver member or members (24, 25).

10. An apparatus according to any of claims 6-9, characterized in that the drum (5) consists of at least two individual drum parts (6, 7) each carrying a group (Gl, G2) of engagement means (11, 12), in that the engagement means of the groups are provided alternating around the outer circumference of the drum (5) and in that the engagement means of each group are provided in fixed mutual positions and are evenly spaced from each other around the circumference of the respective drum part (6, 7), allowing relative rotation of the two parts and their engagement means when an engagement means of either group encounters an excessive bone pull-out force (PF).

11. An apparatus according to claim 10, characterized in that each drum part (6, 7) is provided with a relative-slip recess (8, 9) in the inner circumference (10) thereof, independently cooperating with a respective driver member (24, 25) of the restricted-slip drive connection.

12. A drum (5) for a fish bone removing apparatus (50; 50') according to any of claims 6-11, characterized in that it consists of two individual parts (6, 7) each comprising a body portion (15, 16) carrying a group (Gl, G2) of bone engagement means (11 and 12, respectively), in that the engagement means of each part are cantilevered from one side of the body portion and in that the drum parts (6, 7) are assembled with their respective group of cantilevered engagement means pointing in opposite directions and being received in gaps (13, 14) between the engagement means of the other group.

13. A drum (5) according to claim 12, characterized in that the two drum parts (6, 7) are assembled with their body portions (15, 16) in indirect engagement with each other through a slide bearing (34).

14. A drum (5) according to claims 12 or 13, characterized in that the free ends of the cantilevered engagement means (11, 12) are supported by a slide bearing (33, 35) in turn intended to be supported on a drive shaft rotor member (17) of the apparatus (50, 50').

15. A drum (5) according to any of claims 12-14, characterized in that one restricted-slip recess (8, 9) is provided in the inner circumferential surface (10) of each drum part (6, 7) and in that said restricted-slip recesses (8, 9) are both positioned with a trailing steep end (8A, 9A) and a leading cam surface (8B, 9B), with respect to a direction of rotation (R) of the drum in use.

16. The use of one or several drums (5) according to any of claims 12-15 in a handheld bone removing apparatus (50).

17. The use of one or several drums (5) according to any of claims 12-15 in an automated bone removing machine (50').