US 3552269 A
Description (OCR text may contain errors)
United States Patent Inventor Friedrich-Karl Arndt Essen, Germany Appl. No. 809,902 Filed Mar. 24, 1969 Patented Jan. 5, 1971 Assignee Fried.Krupp Gesellschafl mit beschrankter Haitung Essen, Germany Priority Mar. 27, 1968 Germany No. 1,703,061
HYDRAULICALLY OPERABLE LINEAR MOTOR 7 Claims, 2 Drawing Figs.
US. Cl 91/277, 9l/278, 91/291,91/300, 91/321 int. Cl F011 25/06, F011 31/00 Field ofSearch 91/291,
300, 278, 304(cursory), 321(cursory), 277
 References Cited UNITED STATES PATENTS 2,325,138 7/1943 Kyle et al 91/278 2,729,941 1/1956 Rose et al. 91/300 3,412,646 11/1968 Johnston 91/300 FOREIGN PATENTS 651,732 11/1962 Canada 91/300 820,599 11/1951 Germany 91/291 Primary Examiner-Paul E. Maslousky At!orneyAlbert H. Reuther ABSTRACT: A hydraulically operable linear motor comprising a cylinder and a piston reciprocable in said cylinder and having one side connected with a piston rod extending through said cylinder so as to define on said one piston side an annular effective surface which is continuously subjected to the working pressure while the other side is alternately subjected to the working pressure and to an exhaust pressure, hydraulically operable control valve means governing the communication of said other side with the working pressure and the exhaust pressure while groove means in said cylinder at both sides of said piston and communicating with said control valve are controlled by said piston.
P ATENTEUJAH 5197: 3552.269
sum 2 (IF 2 FIG. 2
- tinuously subjected to the working pressure of a fluid while the drawbacks with the heretofore known designs according to which the reciprocatory piston itself is provided with corresponding control edges and recesses. lnthis connection it may be mentioned that the working cylinder, in view of the required axial length of the piston,'has to have at least twice the length of the piston stroke. This is particularly undesirable when a larger working stroke is necessary. Moreover, a changein the working stroke and thereby in the working 9 frequency will not be possible with constant working pressure.
It is, therefore, an object of the present invention to overcome the above mentioned drawbacks.
It is another object of this invention to provide'a hydraulically operable linea'r'motor with reciprocatory piston which will make it possible to design the working cylinder only slightly longer than the piston stoke, and whichwill also make will appear more clearly from thefollowing specificationin connectionwith the accompanying drawings, in which:
it possible tovary the speed of the working frequency.
These and other objects and advantages of the invention control valve 7 for efiecting a control adjustment is efiected hydraulically, for instance, in the following manner.
Through the intervention of one hydraulic throttle each ll, 12 and 13 a conduit section 14 communicates with two annular grooves 15 and 16 in the working cylinder 1 and with a passage 17 leading to the exhaust line 9. The control pressure FIG. 1 shows a longitudinal section through a first embodiment of the present invention.
' F K). 2 represents a section through a modified embodiment of the invention which makes it possible to influence the working frequency by changing the piston stroke.
The hydraulically operable linear motor according to the present invention is'characterized primarily in that the variable control pressure for actuating the control valve is formed in a conduit section which communicates with two'annular grooves in the working cylinder which grooves are alternately covered up by the reciprocatory piston, the conduit section also communicating with the exhaust line through a hydraulic throttle. With this arrangement, the working piston has no control edges or the like and consequently canbe so short that the working cylinder is immaterially longer than the piston stroke. I
In order to be able to vary the speedof'the changes in the control pressure and thereby also the working frequency, the present invention provides that the cross sections of the throttles are variable. A change in the working stroke and thus in the working frequency is also'possible, due to the fact that, according to a further development of the invention, the working cylinder in the vicinity of that end thereof which is alternately subjected to the pressure in the pressure line is provided not only with one annular groove but with a plurality of axially serially arranged annular grooves each of which is adapted selectively to be connected with the conduit section.
Referring now more specifically to the drawings, the working cylinder 1 of the linear motor has two working chambers 2 and 3 which are separated from each other by the piston 5 connnected to the piston rod 4. The end face F, of the piston 5 delimits the working chamber 2 which through the feeding passage 6 and the control valve 7 is alternately connected to the pressure line 8 or theexhaust line 9, whereas the smaller annular surface F which surface F issmaller than the surface F 1 by the cross section of the piston rod 4, delimits the work ing chamber 3.
lf, as shown in FIGS. 1 and 2, the left-hand working chamber 2 communicates with the pressure line 8, piston 5 the left. The necessary movement of the valve spool 10 in the p,, which' builds win this conduit section 14 acts upon the left-hand end face F of the valve spool 10. The right-hand end face F of the valve spool 10 which is somewhat less in cross section than the end face F is continuously subjected to the working pressure p prevailing in the pressure line 8. The cylindrical inner chamber of the control valve 7 is in communication with three annular grooves 18, 19 and 20 which successively are connected with the exhaust line 9, the feeding passage 6 and the pressure line 8. The valve spool 10 also has an intermediate recess 21.
At a certain control pressure p,,;, which is less than the working pressure p,,, the'forces acting upon the surfaces F and F cancel each other out. When p, increases, the valve spool 10 moves to the illustrated right-hand end position in which the left-hand working chamber 2 of the working cylinder is through thefeeding passage 6, the annular groove 19, the recess 21, and the annular groove 20 in communication with the pressure line 8. With lower p however, the valve spool 10 moves to its left-hand end position in which the working chamber 2 communicates through feeding passage 6, annular groove 19, recess 21, and annular groove 18 with the line 9.
' The change in the control pressure p is brought about when the reciprocatory piston 5 in the working cylinder 1 covers the annular grooves 15 and 16 or relieves the same. The change in the control pressure p,, is, more specifically, brought about in the following manner.
As mentioned above, in the illustrated position, the lefthand working chamber 2 communicates with the pressure line 8. Thus, in both working chambers 2 and 3 the same pressure p prevails and since the surface F is larger than the surface F the piston 5 moves toward the right. Moreover, in the conduit section 14, the maximum possible control pressure p,, is built up because the full-working pressure p,, acts upon both throttles 11 and 12.
As soon as with the piston movement toward the right the annular groove 16 is covered up by piston 5, the pressure p acts only upon the throttle l1..Consequently p decreases. When p drops below p the valve spool 10 moves to its lefthand end position in which the working chamber 2 and thus also the throttle 11 communicates with the exhaust line 9 so that the control pressure p,, drops still further. The pi ton will then, in view of the pressure p,, acting upon the ann lar surface F move toward the left and while doing so frees first the annular groove 16 whereby p,, increases again but remains still below the value p However, as soon as the piston 5 covers up the annular groove 15, the control pressure p, increases again. When p, exceeds p the valve spool 10 again moves to its right-hand end position, and the next piston stroke toward the right will start.
The reversal of the-piston movement could be effected also only when the piston 5 during its leftward movement has completely moved beyond the annular groove 15 and the latter thereby is in communication with the right-hand working chamber 3 where the working pressure p, continuously prevails. This depends primarily on the selection of the crosssectional ratio F :F and on the design of the hydraulic throttles ll, 12 and 13. If the cross sections of these throttles are variable, it is also possible to influencethe difference AP,, between the maximum and minimum control pressure in the 'conduit section 14 and thereby the reversing period of the valve spool 10, in other words the working frequency of the linear motor.
FIG. 2 shows another possibility of influencing the working frequency, namely by changing the piston stroke. To this end,
j the annular groove 15 in the left-hand portion of the working cylinder 1 illustrated in FIG. 1 has been replaced by five axigrooves to another one, which may also be interpreted as an axial displacement of the annular groove in FIG. 1, brings about a corresponding change in the piston stroke and thereby in the working frequency.
The embodiment of P16. 2 furthermore differsfrom that of FIG. 1 in that the control valve 7 for increasing the control impulse is, in the manner known perse, designed as servo valve which in its turn actuates the main control valve 7 with the main control spool 10', valve 7 being similar to valve 7 but having larger dimensions. j It is, of course, to be understood that the present invention is, by no means, limited tothe particular embodiments shown in the drawings but also comprises any modifications within the scope of the appended claims,
1. A hydraulically operable linear motor, which includes: a cylinder having first and second end walls respectively arranged at opposite ends of 'said cylinder, a double-acting ,control valve means to said second position,- said control valve piston-reciprocally mounted in said cylinder, a piston rod extending through one of said cylinder end walls and being connected to one side of said piston so as to form on said one side an annular piston surface, first conduit means leading into said cylinder and continuously communicating with said annular said annular piston surface for continuouslyconveying fluid pressure to said annular piston surface when said first conduit piston surface for continuously conveying fluid pressure to means is connected to a source of fluid pressure, second co'nduit means continuously communicating with the other side of said piston, controlva lve means interposed between said first and second conduit means and movable to a first position to connect said second conduit means to said first conduit means and also movable to a second position to connect said second conduit means to an exhaust, said control valve means including first surface means in continuous communication with said first conduit means and fluid pressure operable to move said means also including second fluid operable surface means for moving said control valve means to said first position, and a fluid conveying control conduit system having first linemeans and second line meansrespec'tively leading into said cylinder on opposite sides of said piston when the latter is in atposi't'ion intermediate its end position sgsaid corit rol conduit system also having third line means communicatingwith said second fluid operable surface means and also f havir'ig' fourth line'means communicating with saidlfir'st andseco and third line means and leading to an eithati'st',,and thr'ott mean's' rspectively' arranged in said-first and second andfoii ifthlline'me'ans;
2. A motor "according to claim 1', in \fllll said'first surface means has-a smaller sui'face'area than s'afid second surface means. I x
3. A motor according to claim 1 in wh'ich at least one' of said throttle means is ia'djus't'able as to its" through-awashtrolling cross section.
4. A motor according to claim 1, in which said cylinder at the regions where said'first lin 'mea'ris'fand'said second line means lead into said'cylind'er is'provided with annular grooves respectively communicating with said'first and second line means. i I f' 5. A motor'aceofiiing to claim l, in which said cylinder in the 'area where said first'line-meahs lead into saidcylinder is provided with a plurality of circular grooves spaced from each other in the axial direction 'of said cylinder and'ada'pted to be successively covered bysaid pis'tonduring the movement of the latterin onea'nd-th'e same direction and also adapted selectively to be placed int'o and out of fluid communication with said first line means.
6. A motor according to claim-5, which includes a plurality of adjustable-throttle meansxassociated with said circular grooves and said firstline means adapted to communicate therewith. v i I 7. A motor according to claim 1;; whichtincludes'seivovalve -.means associatedwith said control valve means-for increasing the control impulses exerted upon the :latter, s'aid servovalve means being interposed between and in fluid communication with said first conduit means on one hand and said first jand secondline means on the other hand. i