CYLINDER WITH BLOCKING

Abstract: The invention relates to a cylinder (1) for manipulating a load, comprising: a cylinder housing (2) with a cylinder chamber (3) therein; an assembly, movable in the cylinder chamber of a piston (4) in the cylinder chamber and a piston rod (5) connected to the piston and extending outside the cylinder chamber, wherein the cylinder has a substantially non-linear force characteristic and the load has a force characteristic substantially differing herefrom, and a variable force balancing which acts substantially on the cylinder housing and the assembly and which variably balances the difference between the forces associated with the load and with the cylinder.

Description: CYLINDER WITH BLOCKING The present invention relates to a cylinder for manipulating a load, comprising: - a cylinder housing with a cylinder chamber therein; - an assembly, movable in the cylinder chamber, of a piston in the cylinder chamber and a piston rod connected to the piston and extending outside the cylinder chamber, wherein the cylinder has a substantially non-linear force characteristic and the load has a force characteristic substantially differing herefrom. Such cylinders are known and common, wherein use is for instance made of friction elements. Gas springs are for instance known wherein the sealing of the cylinder chamber round the piston rod exerts extra friction force on the friction rod so as to prevent the force applied by the load being able to cause displacement of the assembly in the cylinder chamber at undesired moments. A situation can be envisaged where a blocking is de-activated and it is not desired that the gas spring compresses immediately herein under the action of the load, but remains in position. A cylinder with such a configuration has the drawback that a constant friction force is applied in the whole operating range of the force characteristics, so that a balancing occurs only at determined points in this operating range. At other points in the operating range of the force characteristics however, the difference is on the contrary magnified so much that operation is hampered. A gas spring can be envisaged which forms for instance the height adjustment for a chair. In order to then set the chair lower - to compress the gas spring - the resistance added with the friction element often has to be overcome again by a user, which then involves great forces which the user must exert . Convenience of operation is therefore low. The present invention has for its object to obviate the drawbacks of the above described known art, for which purpose a cylinder is provided which is distinguished from the known cylinders by a variable force balancing which acts substantially on the cylinder housing and the assembly and which variably balances the difference between the forces associated with the load and with the cylinder. Convenience of operation is optimized by an active, variable balancing according to the present invention. The resistance provided by the force balancing is adjustably variable, so that an effect with a high convenience of use is ensured through the whole operating range of the force characteristics of the cylinder and the load, without a user having to exert great forces for this purpose. By varying, i.e. progressively increasing or decreasing, the effect provided by the force balancing, a force balancing is achieved automatically, which is manifest in the displacement and/or at least displaceability of the load with a minimal effort by the user. In a preferred embodiment the cylinder comprises a blocking acting on the assembly and the cylinder housing, whereby the assembly can be fixed in a position occupied thereby relative to the cylinder chamber. Such a blocking can be separate from the force balancing but both provisions can alternatively form a unit . By way of example the force balancing can be or comprise a continuously adjustable clamping member which can be designed as a clamping sleeve. A clamping sleeve provides precisely the desired functionality as described above within the scope of the present invention. In energized state the clamping sleeve fixes the cylinder chamber and the assembly relative to each other and, by decreasing the friction force exerted by the clamping sleeve by progressively de-energizing the clamping sleeve, wherein the friction force produced hereby decreases, the point with a balance between all acting forces is reached automatically, wherein the load can be displaced practically without any difficulty. In a favourable embodiment a cylinder according to the invention is such that, along at least a portion of the length of the piston rod, the clamping sleeve is arranged therearound and is connected to the cylinder housing, and in energized state engages the outer surface of the piston rod over substantially the portion of the length and in at least partly de-energized state releases the assembly for movement relative to the cylinder chamber. In this embodiment the friction force produced by the clamping sleeve is exerted on a large surface area of the piston rod. The necessary resistance forces are thus distributed over the surface of the piston rod, so that no damage to the outer surface of the piston rod can occur. Such damage, when moving through the seal of the cylinder chamber, could cause leakage of fluid under pressure from the interior of the cylinder chamber, which is thus effectively prevented in this embodiment. In another preferred embodiment the clamping member and the associated control are arranged outside the cylinder chamber. Alternatively, the clamping member and the associated control can be arranged in the cylinder chamber if conditions therein allow. When the cylinder chamber contains a considerable quantity of lubricant, which can also include hydraulic fluid, a clamping sleeve or such a clamping member is possibly less effective. In such cases the whole will preferably be arranged outside the cylinder chamber. In the case of a gas spring, which is filled only with gas under pressure and a very limited quantity of fluid which can be considered lubricant, the clamping member can be arranged in the interior of the cylinder chamber. In an embodiment where the clamping member and the associated control are situated outside the cylinder chamber, the cylinder housing preferably extends beyond a longitudinal outer end of the cylinder chamber and the clamping sleeve (with the control) is arranged in the part of the cylinder housing extending beyond the longitudinal outer end of the cylinder chamber. Not only is an aesthetically attractive continuous exterior of the whole cylinder thus provided on the outside but, due to the continuous form of the cylinder housing in which both the cylinder chamber and the clamping member are arranged, mounting of the cylinder during assembly of a total system is also facilitated relative to the case wherein the cylinder housing only extends as far as said longitudinal outer end of the cylinder chamber and the force balancing is arranged outside thereof. In a further embodiment the clamping member is arranged immediately adjacently of a longitudinal outer end of the cylinder chamber through which the piston rod extends. The assembly of the cylinder chamber, clamping member and control herein takes up a minimal amount of space in longitudinal direction of the cylinder when the clamping member and the control are arranged outside the cylinder chamber. In the case where the clamping member and the control are arranged in the interior of the cylinder chamber, the piston still has a maximum freedom of movement in the cylinder chamber. The invention further relates to a force balancing for a cylinder, as is evidently intended and suitable for application in a cylinder according to the invention, for instance comprising an elongate clamping member for arranging along at least a part of a piston rod of the cylinder. Modification of existing cylinders which heretofore have had an inferior or no force balancing is thus possible with such a blocking. The cylinder according to the present invention can, as is immediately apparent and stated above, be a gas spring, but the cylinder can alternatively also be a hydraulic or a pneumatic cylinder. As will be apparent herefrom, the invention has many application possibilities in cylinders in general. Only two embodiments of cylinders according to the present invention will be described hereinbelow by way of example and with reference to the annexed drawing, in which: fig. 1 shows a partly cut-away perspective view of a cylinder according to the present invention in a blocked state of the assembly of piston and piston rod relative to the cylinder chamber; fig. 2 shows a view corresponding with fig. 1 in the released state; fig. 3 is a partly cut-away perspective view of an alternative embodiment of a cylinder according to the present invention; and fig. 4 shows a number of alternative embodiments of cylinders with a force balancing designed as clamping sleeve. The cylinder 1 shown in fig. 1 is a gas spring, which comprises a cylinder housing 2 having therein a cylinder chamber 3 and a piston 4 which is arranged in cylinder chamber 3 and on which a piston rod 5 is arranged to form an assembly with piston 4. Piston rod 5 protrudes through a ring 6 forming a longitudinal outer end of cylinder chamber 3, wherein a seal 7 is arranged between ring 6 and piston rod 5 in order to maintain the pressure in the interior of cylinder chamber 3 without leakage between ring 6 and piston rod 5. Cylinder 1 further comprises a force balancing 8 with which a control co-acts so as to fix the piston rod, and thereby piston 4, in a predetermined position relative to cylinder chamber 3. The force balancing 8 comprises a clamping sleeve 10 which extends between two rings 11 while forming an elongate clamping member, which rings 11 are pushed apart by the action of a spring 12 which is arranged therebetween and which extends round clamping sleeve 10. The lower ring 11 in fig. 1 is fixed to cylinder housing 2, while the upper ring 11 in fig. 1 can be moved up and down in the direction of double arrow A. Under the influence of spring 12 the upper ring 11 in fig. 1 is thus pushed upward. Clamping sleeve 10, which forms the clamping member, is herein stretched in longitudinal direction and tensioned round the outer surface of piston rod 5. Owing to the friction force occurring herein between clamping sleeve 10 and piston rod 5, which friction force is distributed over the outer surface of piston rod 5 in radial direction and over a distance in longitudinal direction corresponding to the length of the clamping sleeve, damage to the outer surface of piston rod 5 is effectively prevented. Such damage to the outer surface of piston rod 5 could occur with a mechanical blocking, which engages the piston rod very locally, and such damage could result in leakage of fluid from the cylinder chamber if the damage moves through the seal 7 on the piston rod. The control 9 comprises a tilting arm 13 on a hinge 14. Arranged on tilting arm 13 is a stop 15 which lies against the upper ring 11 in fig. 1, and further a handle 16 which can be grasped by a user from outside cylinder housing 2 for selective control of the force balancing 8. For the purpose of a favourable play of forces, and particularly a good distribution of forces, more stops 15 are preferably arranged than the single stop shown in fig. 1, 2. Such stops, for instance two, can then be arranged on either side of the ring. The connecting line between the stops preferably then lies transversely of the tilting direction of tilting arm 13 and transversely of the length direction of piston rod 5. Clamping sleeve 10 is made shorter by engaging and moving downward the handle 16 in fig. 1, as shown in fig. 2 with arrow B, wherein the upper ring 11 in fig. 2 is pressed downward counter to the spring force of spring 12. The resistance produced by force balancing 8 is progressively decreased herein until the point is reached where a balance occurs . At this point of balance the assembly of piston 4 and piston rod 5 can be displaced in cylinder housing 2 practically without a user having to produce any force. Piston rod 5 is released for movement in cylinder chamber 3, wherein piston 4 can move up and downward. A highly sensitive control of the blocking is herein possible, wherein movements of the piston can be made very gradually. The engagement of the piston rod with the clamping sleeve can be effected in any gradation for optimal control of the movement of piston 4. In the case shown in fig. 1 and 2 of a cylinder 1 designed as a gas spring, piston 4 will move downward in the direction indicated with arrow C, unless a force greater than that corresponding to the gas pressure in cylinder chamber 3 is exerted in the opposite direction on piston rod 5. In this latter case the piston 4 is therefore displaced in cylinder chamber 3 in the direction opposite to that of arrow C. Fig. 3 shows an alternative embodiment of a cylinder 17 according to the present invention. In fig. 3 the same or similar components of figures 1, 2 and 3 are designated with the same reference numerals as those used in fig. 1 and 2. Cylinder 17 differs from the embodiments shown in fig. 1 and 2 in that clamping sleeve 10, and hereby control 9, are arranged in the interior of cylinder chamber 3. This is also apparent from the view of fig. 3, wherein ring 6 and seal 7 are positioned on the side of clamping sleeve 10 opposite to that in the configuration of fig. 1 and 2. The operation of cylinder 17 of fig. 3 is otherwise the same as that described above for figures 1 and 2. By grasping handle 16 and moving tilting arm 13 downward the upper of the rings 11 in fig. 3 is moved downward, whereby clamping sleeve 10 progressively loses contact with the outside of piston rod 5 and piston rod 5 is released for movement relative to cylinder chamber 3. When handle 16 is released by the user, the upper of the rings 11 in fig. 3 is pressed upward again under the influence of the spring force of spring 12, and clamping sleeve 10 is hereby stretched once again and tensioned in close-fitting manner round the outer surface of piston rod 5, whereby the piston rod is again fixed relative to piston chamber 3. Many alternative embodiments, which will occur to the skilled person after perusal of the foregoing, are possible within the scope of the invention. It is for instance possible that the cylinder housing does not extend beyond the ring with the seal for passage of the piston rod so as to provide space for the force balancing 8 outside the piston chamber, but that a separate housing is used for this purpose which is then for instance fixedly connected to a fixed object in the surrounding area to which cylinder housing 2 is also fixed, so that the piston rod can be fixed relative to the cylinder chamber. Such an addition has the advantage that existing cylinders can be modified in simple manner in order to realize the present invention. Components other than a clamping sleeve as shown in figures 1-3 can also be used. Because in the shown and described embodiments the blocking is situated in each case in the close vicinity of the longitudinal outer end, space is saved as described above. It is however equally possible for the blocking and the associated control to be situated at a greater distance from the longitudinal outer end of the cylinder chamber through which the piston rod is placed, and so on. For the force balancing according to the invention it is even quite possible for the clamping sleeve or a similar measure not to engage the piston rod, but an element connected thereto, such as a coupling rod 18 or a telescopic member 19 as shown schematically in fig. 4A and 4B. The same of course applies for the connection to the cylinder housing; the clamping sleeve can even be arranged round the cylinder housing, as shown schematically in fig. 4C. Fig. 4 shows three such alternative embodiments with a force balancing designed as clamping sleeve. The scope of the present invention is thus limited only by the appended claims and not to the embodiments explicitly described above and shown in the annexed drawing.

Claims: CLAIMS 1. Cylinder for manipulating a load, comprising: - a cylinder housing with a cylinder chamber therein; - an assembly, movable in the cylinder chamber, of a piston in the cylinder chamber and a piston rod connected to the piston and extending outside the cylinder chamber, wherein the cylinder has a substantially non-linear force characteristic and the load has a force characteristic substantially differing herefrom, and - a variable force balancing which acts substantially on the cylinder housing and the assembly and which variably balances the difference between the forces associated with the load and with the cylinder. 2. Cylinder as claimed in claim 1, which comprises a blocking acting on the assembly and the cylinder housing, whereby the assembly can be fixed in a position occupied thereby relative to the cylinder chamber. 3. Cylinder as claimed in claim 1 or 2, wherein the force balancing comprises a continuously adjustable clamping member. 4. Cylinder as claimed in claim 3, wherein the clamping member is a clamping sleeve. 5. Cylinder as claimed in claim 4, wherein along at least a portion of the length of the piston rod the clamping sleeve is arranged therearound and is connected to the cylinder housing, and in energized state engages the outer surface of the piston rod over substantially said portion of the length and in at least partly de-energized state releases the assembly for movement relative to the cylinder chamber. * 6. Cylinder as claimed in any of the claims 3- 5, wherein the clamping member and the associated control are arranged in the cylinder chamber. 7. Cylinder as claimed in at least one of the claims 3-5, wherein the clamping member and the associated control are arranged outside the cylinder chamber . 8. Cylinder as claimed in claim 7, wherein the cylinder housing extends beyond a longitudinal outer end of the cylinder chamber through which the piston rod extends, and the clamping sleeve is arranged in the part of the cylinder housing extending beyond the longitudinal outer end of the cylinder chamber. 9. Cylinder as claimed in any of the foregoing claims, wherein the clamping member is arranged immediately adjacently of a longitudinal outer end of the cylinder chamber through which the piston rod extends. 10. Cylinder as claimed in any of the foregoing claims, wherein the cylinder is a gas spring. 11. Cylinder as claimed in any of the foregoing claims, wherein the cylinder is from a group comprising one of a hydraulic and a pneumatic cylinder.

Inventors: OLDE HEUVEL BERNARDUS JOHANNES, OLDE HEUVEL, BERNARDUS, JOHANNES, MARIA
Applicants: OLDE HEUVEL BERNARDUS JOHANNES, OLDE HEUVEL, BERNARDUS, JOHANNES, MARIA
Application year: 2001
Main classification: F16F7
IPC codes: F16F7, F16F9