EP0955814A1

EP0955814A1 - Hydraulic press

Info

Publication number: EP0955814A1
Application number: EP98935391A
Authority: EP
Inventors: Johannes Gerardus Cornelis Hoedjes; Jacobus Fransiscus Maria Kramer; Christiaan Arnoldus Wulffers
Original assignee: Machinefabriek PM Duyvis BV
Current assignee: Machinefabriek PM Duyvis BV
Priority date: 1997-08-05
Filing date: 1998-07-13
Publication date: 1999-11-17
Also published as: NL1006721C2; AU8465598A; WO1999007234A1

Abstract

A hydraulic press, for example for pressing cocoa mass and similar products, comprises a frame (1) which forms a hydraulic cylinder (3), which accommodates a plunger (4) capable of reciprocating movement therein, at one end and a retainer (6) at the other end. A cylinder shell (2) of said cylinder (3) and said retainer (6) are interconnected by means of connecting parts (7). One or more pressing elements (5) can be disposed between said plunger (4) and said retainer (6). At least the force-transmitting part of the cylinder shell (2) and the connecting parts (7) of the frame are substantially made in one piece, for example as a cylindrical tube or a tubular casting.

Description

Hydraulic press

The invention relates to a hydraulic press, for example for pressing cocoa mass and similar products, comprising a frame which forms a hydraulic cylinder, which accommodates a plunger capable of reciprocating movement therein, at one end and a retainer at the other end, wherein the cylinder shell and said retainer are interconnected by means of connecting parts, whilst one or more pressing elements can be disposed between said plunger and said retainer. A hydraulic press of this kind is known from practice, and it is used for pressing cocoa mass for forming cakes, which can be processed into cocoa powder, and for separating cocoa butter. With this known press, the hydraulic cylinder is formed in a cylinder block, which is connected to the retainer by means of two separate tie beams. The tie beams are passed through the cylinder block, and they are provided with enlarged heads or nuts, whose bearing surfaces butt against the cylinder block. The pressure forces must be transmitted from the hydraulic cylinder to said tie beams via the bearing surfaces of said heads, and subsequently to the retainer, and the curved lines of force and difficult transitions from part to part result in a great deal of stress peaks and thus to fatigue of the parts in question. In order to prevent fatigue fractures, it is necessary to use expensive and heavy parts. The object of the present invention is to provide a hydraulic press wherein the above drawback is overcome.

In order to accomplish that objective, the hydraulic press according to the invention is characterized in that at least the force-transmitting part of the cylinder shell and the connecting parts of the frame are substantially made in one piece.

Since there is no longer a separate block for the cylinder and separate tie beams for the connecting parts, the lines of force can continue directly from the cylinder shell to the connecting parts, rather than pass all kinds of bends via bearing surfaces . The circumferential portion of the cylinder and the connecting parts are preferably substantially in line, so that the lines of force can be substantially straight, seen in radial direction, as a result of which bending moments are reduced to a minimum.

According to a very advantageous embodiment of the press according to the invention, the frame consists of a tubular portion, such as a tube or a tubular casting, whose wall forms the cylinder as well as the connecting parts and a casing for attaching the retainer. This leads to a very simple but strong frame, which exhibits a very advantageous stress distribution. A major advantage of the absence of connecting parts or tie beams in the wall of the cylinder, is the fact that the diameter of the hydraulic plunger may be large locally in comparison with the external dimension of the frame, without this leading to bending moments being introduced in the end pieces of the frame. This makes it possible to use lower hydraulic pressures in the cylinder, whilst achieving the same pressures, so that standard hydraulic components can be used, which leads to a reduction of the costs. On the other hand, the improvement of the frame may be utilized for increasing the capacity of the press, for example by maintaining the high hydraulic pressure in the larger cylinder and enlarging the pressure elements. As a result of the advantageous stress distribution in the frame, said frame is very well capable of withstanding the higher forces that develop in the frame, which is not the case with presses according to prior art, which have reached the upper limits of their capacity.

In the case that the tube or the casting has a circular section, at least internally, it is possible to carry out turning operations on the tube or other rotational operations, which makes machining of the frame much easier. Of course this applies even more if the tube has a circular section externally as well.

In order to facilitate the mounting and dismounting of the plunger, it is preferred to use a detachable cover as the cylinder head. The transmission of forces from the cylinder head to the cylinder shell need not present any problems, it may for example be realised via bolt connections comprising a large number of bolts. In that case, the cover will extend into the frame with a collar, to a point beyond the holes in. the cylinder shell.

Alternatively, the cover may be screwed into the cylinder shell. In either case a sealant may be used.

The invention will be explained in more detail hereafter with reference to the drawings, which shows embodiments of the hydraulic press according to the invention.

Fig. 1 is a longitudinal sectional view of the embodiment of the hydraulic press for pressing cocoa mass. Fig. 2 is a perspective, exploded view of the main components of the hydraulic press of Fig. 1 with the exception of the pressing elements.

Fig. 3 is a sectional view corresponding with Fig. 1, wherein the parts of Fig. 2 are shown with the plunger in a different position. Fig. 4 is a sectional view along line IV- IV in Fig.

3.

Fig. 5 is a sectional view corresponding with Fig.

1, in mirror symmetry, of an alternative embodiment of the hydraulic press according to the invention. Figs. 6, 7 and 8 are views corresponding with Figs.

2, 3 and 4 of the frame of the hydraulic press of Fig. 5.

The drawings, and in the first instance Figs. 1 - 4 thereof, show a first embodiment of a hydraulic press according to the invention, which is in this case designed for pressing cocoa mass, whereby cocoa cakes to be processed into cocoa powder and cocoa butter pressed therefrom are obtained. Said pressing process and the corresponding pressing elements are known per se, and they will be discussed only briefly herein.

The hydraulic press shown in Figs. 1 - 4 comprises a frame 1, in the form of a tube having a round or circular internal and external section in this embodiment. Said tube 1 forms a cylinder shell 2 of a pressure cylinder 3 at one end, the left-hand side in the drawing. A plunger 4 is accommodated in said cylinder so that it is capable of reciprocating movement therein. Said plunger 4 is capable of exerting a pressure on a larger number of pressing elements 5. Said pressing elements are supported at the end remote from plunger 4 by a retainer 6, which in this embodiment consists of an element which is screwed into the end of tube 1 remote from cylinder shell 2, or which is otherwise secured therein, for example by means of bolts. The casing for retainer 6 and cylinder shell 2 are interconnected by means of tie beams or connecting parts 7, which are likewise made up of the wall of cylindrical tube 1. The pressure cylinder 3 is closed by a cylinder head 8, which consists of a separate cover, which is attached to the cylinder shell 2 by means of a detachable connection, in this case a bolt connection comprising a large number of bolts, which are screwed into bolt holes 9, which are formed in the end face of tube 1 and which are uniformly distributed over the circumference. Cylinder head 8 projects into the cylinder shell with a collar 10 so as to obtain a proper sealing and protect the part of the cylinder shell 2 in which the bolt holes 9 are present against pressure from inside.

In the present embodiment, the connecting parts 7 are made up of the three wall portions of tube 1 that remain after elongated recesses 11 have been formed in the wall of tube 1. Said recesses 11 are uniformly distributed over the circumference of tube 1, and the opposite walls 12 of each recess 11 extend parallel to each other and to the radial centre plane 13 of the respective recess 11, thus providing a maximum width of the recess whilst retaining connecting parts 7 having a maximum cross-sectional area (see Fig. 4) . The width of recesses 11 is selected so that the cocoa cakes formed in pressing elements 5 can be discharged through the lowermost recess 11 without any problem. Recesses 11 are furthermore used for introducing and exchanging internal parts, in particular of pressing elements 5, and for supplying and discharging media, such as said cocoa mass, steam, cocoa butter and the like. In the illustrated embodiment, three recesses 11 and three connecting parts 7 are provided, because they provide adequate stability against torsion during pressing. Other distributions are also possible, however. The ends of recesses 11 are rounded, approximately in the shape of the segment of a circle, in order to obtain maximally advantageous lines of force from cylinder shell 2 to connecting parts 7 and avoid stress concentrations. The ends may also be rounded or curved differently, of course, for example elliptical with a tangential leading portion.

Since cylinder shell 2, the casing for retainer 6 and the connecting parts are aligned, seen in longitudinal direction, and since they are made in one piece, a very advantageous transmission of forces is obtained. The diameter of pressure cylinder 3 may furthermore be relatively large, without this leading to the introduction of bending moments in the end pieces of frame 1, in particular at the location of retainer 6. Said larger diameter of the pressure cylinder makes it possible to use a lower hydraulic pressure in pressure cylinder 3 whilst still achieving the required pressure in pressing elements 5. When cocoa mass is being pressed, the maximally required pressure is about 1000 - 1100 bar, and in the illustrated embodiment this can be achieved with a hydraulic pressure in pressure cylinder 3 of about 350 bar, rather than the 550 bar which are used for pressing according to the prior art . This lower pressure in pressure cylinder 3 results in a reduction of the stress concentrations in frame 1, and thus it is possible to use cheaper materials, in particular steel, with no special methods for refining the material being required. Frame 1 can thus be made considerably cheaper. The circular internal and external diameters of tube 1 make it possible to carry out rotational operations thereon, which would otherwise not be possible. The plunger 4 extends into pressure cylinder 4 separately from pressing elements 5, its bottom edge may come into engagement with a pressure plate 14 for transmitting the hydraulic pressure in cylinder 3 to pressing elements 5. A retracting cylinder 15 is furthermore attached to said pressure plate 14, which retracting cylinder ensures, via pressure plate 14 among other things, that the beds of pressing elements 5 can be closed quickly without having to move plunger 4, so that there is no need for large amounts of oil to be pumped quickly. Retraction cylinder 15 is driven by a plunger rod 16, which is passed through the head of plunger 4 and which is attached to cylinder head 8. A small plunger 17 is present at the end of plunger rod 16, whilst plunger rod 16 is hollow for the purpose of supplying and discharging a hydraulic medium to retraction cylinder 15 via openings 18 in plunger rod 16. The operation of the retraction cylinder is known per se, but in this embodiment the retraction cylinder 15 is disposed within plunger 4 in an advantageous manner, so that a compact construction is obtained and the hydraulic components are concentrated near one end of the frame as much as possible.

Figs . 5 - 8 show a second embodiment of the hydraulic press according to the invention, wherein frame 1 is indeed at least substantially tubular, but wherein said frame is a casting. This enables a slightly greater freedom as regards the shape of frame 1. Also in this embodiment frame 1 comprises a cylinder shell 2 surrounding a pressure cylinder 1, in which a plunger 4 is accommodated so that it is capable of reciprocating movement therein. Retainer 6 is attached to frame 1 in the same manner as cylinder head 8 in this embodiment, namely by means of a large number of bolts. Frame 1 again comprises three connecting parts 7, which each have a diameter different from that of the connecting parts of the first embodiment as shown in Fig. 4, however.

As is shown in Fig. 8, the cross-sectional area of connecting parts 7 is larger than in the first embodiment, because of the fact that the radial outer side is positioned further away from the central axis of frame 1 than the radius of cylinder shell 2, and because said radial outer side is furthermore straight rather than circular. The sides of the connecting parts 7 are rounded as much as possible, and they are adapted to achieve a satisfactory transmission of the tensile forces and avoid the occurrence of stress peaks at the transition to and from connecting parts 7.

Figs. 5 - 8 furthermore show that frame 1 comprises radially outwardly projecting supporting parts 19 disposed in line with connecting parts 7. The lateral surfaces 20 of said supporting parts 19 form triangles which project beyond the circumference of frame 1, which triangles each comprise lateral surfaces 20 extending parallel to those of the other triangles, so that frame 1 can be supported in three different angular positions on a base (not shown) or other supporting surface. This possibility of turning frame 1 makes it possible to ensure that the wear, which occurs on the inside of connecting parts 7 as a result of the pressing elements 5 sliding along said inside under the influence of gravity, will remain uniform by turning the frame 1 through 120° at regular intervals. The supporting parts 19 have a strongly rounded shape in this embodiment as well, so as to avoid stress peaks.

Fig. 5 furthermore shows that the shape of plunger 4 has been adapted so as to reduce its weight. Plunger 4 and retraction cylinder 15 are furthermore made in one piece with pressure plate 14. This leads to a considerably simpler and lighter construction in comparison with the embodiment according to Fig. 1. From the foregoing it will be apparent that the invention provides a hydraulic press comprising a frame which provides a highly advantageous transmission of forces from the cylinder head of the pressure cylinder to the retainer, which can be manufactured in a simple manner and which ensures a reliable operation without any risk of fatigue fractures.

The invention is not limited to the above-described embodiments as shown in the drawings, which can be varied in several ways within the scope of the invention.

Claims

1. A hydraulic press, for example for pressing cocoa mass and similar products, comprising a frame (1) which forms a hydraulic cylinder (3) , which accommodates a plunger (4) capable of reciprocating movement therein, at one end and a retainer (6) at the other end, wherein a cylinder shell (2) of said cylinder (3) and said retainer (6) are interconnected by means of connecting parts (7) , whilst one or more pressing elements (5) can be disposed between said plunger (4) and said retainer (6) , characterized in that at least the force-transmitting part of the cylinder shell (2) and the connecting parts (7) of the frame are substantially made in one piece.

2. A press according to claim 1, wherein said cylinder shell (2) and said connecting parts (7) are substantially in line.

3. A press according to claim 2, wherein said frame (1) consists of an at least approximately tubular portion, for example a casting or a tube, whose wall forms the cylinder shell (2) as well as the connecting parts (7) and a casing for attaching the retainer (6) .

4. A press according to claim 2 or 3 , wherein said frame (1) has a circular section, at least internally, which is preferably the same over the entire length.

5. A press according to claim 4 , wherein a number of recesses (11) , preferably three, are formed in the frame

(1) at the location of said pressing elements (5) , between which said connecting parts (7) are located, and which are uniformly distributed over the circumference of the tube

(1) .

6. A press according to claim 5, wherein the ends of said recesses (11) directed towards the cylinder shell

(2) and the retainer (6) are rounded.

7. A press according to claim 4 or 5 , wherein the walls (12) of said recesses (11) extend parallel to the radial centre plane (13) of the respective recesses.

8. A press according to any one of the preceding claims, wherein a cylinder head (8) of said cylinder (3) consists of a detachable cover, which is preferably secured to the cylinder shell (2) of the frame (1) by means of bolts, whilst the cover extends into the cylinder shell (2) with a collar (10) , to a point beyond the holes (9) for the bolt connection.

9. A press according to claims 2 - 6, wherein said retainer (6) is secured to the end of the tube, preferably by means of bolts.

10. A press according to any one of the preceding claims, wherein said frame is provided near its two ends with a number of supporting parts, which number corresponds with the number of connecting parts, for supporting the frame on a base in various angular positions.

11. A press according to any one of the preceding claims, wherein said plunger (4) is provided with a retraction cylinder (15) provided internally therein, which has a smaller diameter than the pressure cylinder (3) , and which functions to move the pressing elements (5) quickly, in particular for the purpose of closing said pressing elements at the beginning of the press stroke.