US3675172A

US3675172A - Damping apparatus for a linear actuator device

Info

Publication number: US3675172A
Application number: US144084A
Authority: US
Inventors: Neil J Petusky
Original assignee: Decision Data Corp
Current assignee: IIS Inc
Priority date: 1971-05-17
Filing date: 1971-05-17
Publication date: 1972-07-04
Anticipated expiration: 1989-07-04
Also published as: FR2137958A1; DE2223732A1; CA961518A; FR2137958B1; IT955580B; GB1383520A

Abstract

A damping system used for controlling the rebound of actuator members used in high speed printers or the like is disclosed. The system involves the use of the principle that when masses collide in an elastic collision, the kinetic energy of the system remains constant. In the system, a secondary mass is free for limited movement between restraining walls at least one of which is of energy absorptive material and is positioned in the path of a rebounding actuator element. The collision between the actuator element and the mass results in a transference of kinetic energy to the secondary mass which energy is rapidly dissipated as the secondary mass collides with the energy absorptive material. Also disclosed is a holding coil for holding the actuator element following the collision with the primary mass and an intermittently operable firing coil which when energized overrides the holding force and fires the actuator element.

Description

United States Patent Petusky 1 July 4, 1972 DAMPING APPARATUS FOR A LINEAR ACTUATOR DEVICE [72] Inventor: Neil J. Petusky, Norristown, Pa.

[.73] Assignee: Decision Data Corporation, Warminster,

[22] Filed: May 17, 1971 [21] Appl. No.: 144,084

[52] U.S. Cl. ..335/257, 335/277, 101/93 C [51] Int. Cl ..H01f 7/08 [58] Field of Search ..335/247, 248, 258, 277; 101/93 C [56] References Cited UNITED STATES PATENTS 2,625,100 l/l953 Williams et al. ..101/93 2,735,047 2/1956 Garner et a1. ...335/257 X 3,134,932 5/1964 Ray ..335/257 Primary Examiner-George Harris Attorney--Synnestvedt & Lechner [5 7] ABSTRACT A damping system used for controlling the rebound of actuator members used in high speed printers or the like is disclosed. The system involves the use of the principle that when masses collide in an elastic collision, the kinetic energy of the system remains constant-1n the system, a secondary mass is free for limited movement between restraining walls at least one of which is of energy absorptive material and is positioned in the path of a rebounding actuator element. The collision between the actuator element and the mass results in a trans-- ference of kinetic energy to the secondary mass which energy is rapidly dissipated as the secondary mass collides with the energy absorptive material. Also disclosed is a holding coil for holding the actuator element following the collision with the primary mass and an intermittently operable firing coil which when energized overrides the holding force and tires the actuator element.

15 Claims, 3 Drawing Figures Patented July 4, 1972 o BWMR 2 INVENTOR.

NEIL J. PETUSKY A TTORNE YS DAMPING APPARATUS FOR A LINEAR ACTUATO DEVICE FIELD or THE INVENTION This invention relates to high speed reciprocating-actuators and while not limited, thereto is especially directed to an actuator used in a printer or other data recording device.

BACKGROUND OF THE INVENTION which is propelled against a record medium to effect a recording of data on the record medium. The data may be recorded in the form of a perforation caused by the movable actuator member or in case of a printer, the actuator member typically operates in conjunction with a rotatable print wheel carrying type representative of data to be imprinted on the record medium. In this type of device, the record medium is locatedbetween the print wheel and actuator member and the latter is selectively propelled so that it causes the record medium to impact against the print wheel thereby causing the print wheel to imprint a type character on the record medium. Immediately after the actuator member strikes the record medium it is returned to its initial position, largely by the rebound force resulting from the impact but also in some cases with the assistance of a spring or other return means, as the actuator must be removed from the record medium rapidly enough to prevent blurring or smearing of the characterjust printed.

Moreover the time requirements imposed are such that a cycle must be completed in extremely short intervals, such as mil liseconds and therefor the return portion of the cycle must be of an extremely short duration, so that the acutator is ready to begin the next cycle as soon as possible.

As the actuator member returns to its rest position,'a large quantity of kinetic energy is associated with it and if this energy is not rapidly and effectively dissipated it may cause the member to bounce back and strike the record medium a second time thereby making a second imprint on the medium. Even if the member does not strike the record medium the rebound oscillations are undesirable as the member should be essentially at rest before the beginning of the next print cycle if the system is to have reliability of perfonnance.

OBJECTS OF THE INVENTION With the foregoing in view, an object of the invention is the provision of means for rapidly reducing the kinetic energy of a rebounding actuator member.

Another object of the invention is the provision of means for preventing secondary print impressions in a high speed printing mechanism.

A more specific object of the invention is the provision of apparatus using momentum effects for transferring energy between masses and dissipative collisions for dissipating the kinetic energy transferred.

In summary, the foregoing and various other objects of the invention are achieved by the provision of a secondary mass positioned in the rebound path of the actuator member so that the actuator member collides with the secondary mass in an elastic collision. The invention takes advantage of the principle that in an elastic collision between two masses the kinetic energy of the system remains constant. According to the invention the secondary mass collides with a restraining wall following its initial collision with the rebounding actuator member. Restraining walls are positioned on both sides of the secondary mass and one or both of the restraining walls are formed of a material which is highly energy absorptive. Thus, it can be appreciated that when the actuator member strikes the secondary mass a quantum of its energy can be transferred to the secondary mass and that as the ratio of the masses approaches unity virtually all of the energy can be transferred. If the secondary mass is slightly heavier than the actuator point of impact of and the secondary mass will move at a relatively large velocity in the same direction as the actuator member was moving just prior to the time of collision. Since the secondary mass is confined by the two walls, it almost immediately collides with the first of these walls and if that wall is made of energy absorptive material it'loses a large portion of the kinetic energy to that wall. According to the preferred embodiment of the invention when the secondary mass rebounds from the energy absorptive wall it almost immediately impacts on the other wall and if that wall is also of an energy absorptive material it loses a large percentage of the remaining kinetic energy. Collisions of the secondary mass with the two walls'will continue until all of the kinetic energy in the secondary mass is dissipated. Because of the proximity of the walls relative to the secondary mass, the kinetic energy in the secon dary mass is dissipated in a relatively short period of time, i.e., before the actuator member strikes it a second time. should there be suflicient kinetic energy remaining in the actuator biasing it towards the secondary mass. The holding coil may 4 be constantly energized and a firing coil which is not normally energized may provide an impelling force on the actuator member which is greater than the holding force in order to propel the actuator member. The motion of the actuator element is typically rectilinear but actuators incorporating the principles of the invention need not follow straight line paths and may move in arcuate or other paths.

Turning to the illustrative embodiment of the invention reference will be made to the drawings in which:

FIG. 1 is a plan sectional view of a preferred embodiment of the invention;

FIG. 2 is an enlarged view of a portion of the invention of FIG. 1; and,

FIG. 3 is a graphical representation showing mass and energy relationships involved underlying the invention.

Referring now to FIGS. 1 and 2, in the illustrative embodiment of the invention, the actuator device comprises a block 10 in which is mounted a coil assembly 11. Coil assembly 11 comprises a tube or core 12 formed of a non-magnetic material such as glass. Pole pieces l3, l4 and 15 are mounted on the tube 12. A firing coil 16 is provided intermediate poles l4 and 13 and a holding coil 17 having a relatively small number of ampere turns with respect to the ampere turns of the firing coil 16 is provided between

pole pieces

14 and 15. Leads 18 are provided for energizing the coil 16 and leads 19 are provided for energizing the coil 17.

Mounted within the tube 12 is the actuator member or slug element 20 which in the preferred embodiment of the invention is formed of a substantially non-compressible magnetic material. Preferably the slug element 20 is held in position by the holding coil 17 and to this end means are provided for energizing the holding coil. Holding coil 17 applies a holding force on the element which in the absence of a greater force applied by the firing coil is sufficient to ordinarily hold it against movement.

Upon energization of the selectively operable firing coil 16, a force is applied axially of the tubel2 which is sufliciently great to overcome the holding force and propel the element 20 from the tube. In the case of a printer, the-element 20 is propelled against the record medium which may be a punch card, paper tape or the like with sufiicient force so that is impacts on the record medium thereby forcing it against a printing wheel and effecting a printing operation.

Following the printing stroke of the element, it is returned to its initial position of rest shown in FIGS. 1 and 2. In the case of a high speed printer wherein the slug element acts as a hammer forcing the record medium against an element bearing type characters, the element is possessed of sufficient member the actuator member will rebound slightly from the kinetic energy to rebound rapidly away from its position at impact and to move with high velocity towards its initial position. In some systems, however spring means or some other means providing an assisting force may be provided to assist in the return of the actuator element to its initial position.

In either event, the invention is intended to damp the high quantity of kinetic energy which the element 20 may possess during its return or rebound movement. In order to dampen the rebound movement so as to prevent the element from again striking the record medium, the invention involves the use of a secondary mass or energy transfer element 22 located so that it is in axial alignment with the element 20 in position so that the element 20 collides with it during its return movement. Element 22 is preferably formed of a non-compressible material and is mounted between a pair of

walls

23 and 24.

Each of

walls

23 and 24 is positioned in proximity to the mass 22. At least one of the walls is formed of an energy absorptive material. An example of an energy absorptive material producing excellent results is a high density polymer sold under the trademark GAR-DUR by Garland Mfg. C0,, Soco, Maine. According to the literature GAR-DUR is an ultra high molecular weight polyethylene.

As noted above the collision between the actuator element and the energy transfer element is theoretically an elastic collision although perfectly elastic collisions are unknown except perhaps between atoms, molecules and electrons. For the purposes of this invention however, it is contemplated that substantially any materials may be employed for the actuator element and the energy transfer element which do not substantially compress when they collide under the conditions of use contemplated. The suitability of the materials to be employed may be readily determined by a few field trials.

Attention is now directed to FIG. 3 which illustrates th mass and energy relationships involved in the invention. The curves in FIG. 3 represent the case where a collision has occurred. The curves E and V indicate the kinetic energy and velocity of the first mass that is, of the actuator or slug element 20. Curves E and V indicate the energy and velocity of the secondary mass or energy transfer element 22. It can be seen from FIG. 3 that as the ratio K of the two masses approaches unity, the energy and velocity of mass I that is, the actuator element 20, drop to 0. Where K is between about 0.5 and about 2, substantial energy transfer can be achieved.

In devices of the kind illustrated, best results are obtained when K is slightly greater than unity. In that case, as shown in FIG. 3, the velocity of element 20 is negative following the collision so that element 20 rebounds slightly following the collision. The significance of this is that the two elements separate more rapidly for a given transfer of energy during the time that the secondary mass is vibrating off the two

walls

23 and 24. Because of this, the energy of the secondary mass is not retransferred to the primary mass in an elastic collision before its energy is absorbed by the energy absorbing material. In actual practice, best results are achieved when the ratio of the masses is between L2 and 1.5 but these values may vary somewhat depending on the materials actually employed.

As explained above holding coil 17 biases the actuator element towards its original point of impact and it should be sufficient to constrain the actuator element within the tube from excessive movement when it rebounds from the energy transfer element or secondary mass. Desirably, the coil biasing force should be just sufficient to return the actuator element to its point of impact with the energy transfer element at about the time that the energy transfer element has transferred all of its energy to the energy absorptive material.

In most instances it has been found that there is so little kinetic energy remaining in the actuator 20 that it may be considered to be at rest for engineering purposes following the first or second collision with the energy transfer element and it has been found that in actual trials in printers and punches wherein the cycle time is about 5 milliseconds that this is the case. In some instances however, several collisions between the actual element and the transfer element can take place but these collisions occur at an ever increasing rate with ever decreasing residual energy so that the time for the actuator element to come to rest is quite short.

I claim:

1. Apparatus for damping the rebound oscillations of a first reciprocating element used in the recording of data on a record medium, said apparatus comprising a secondary .element located in the rebound path of the first element for collision with said first element during its rebound motion, wherein the ratio of the mass'of said secondary element to said first element approaches unity, said secondary element being mounted for limited movement in the direction of motion of the reciprocating element following a collision therewith and a body of energy absorptive material for limiting movement of the secondary mass.

2. Apparatus according to claim 1 wherein the ratio. of masses of the secondary element relative to the first element is greater than I.

3. Apparatus according to claim 2 wherein the ratio of the masses of the secondary element relative to the first element is between about 1.2'and 1.5.

4. Apparatus according to claim 1 wherein the length of the path of movement of. the reciprocating element is long relatively to the length of path of movement of the secondary element.

5. Apparatus for damping the rebound oscillations of a linear actuator element used in the recording of data on a record medium comprising intermittently operable firing force applying means for propelling said element towards the record medium, an energy transfer member in the rebound path of said actuator element for collision with the actuation element during its rebound motion, said energy transfer member being mounted for limited movement along the path of movement of the actuator element upon a collision with the actuator member, said member and said element being formed of a relatively non-compressible material and an energy absorptive material positioned in the path of movement of said energy transfer member for absorbing the kinetic energy of said energy transfer member upon a collision therewith.

6. Apparatus according to claim 5 comprising holding force applying means for holding said actuator member following rebound from said energy transfer member.

7. Apparatus according to claim 6 wherein said holding force means applies said holding force at a value which is small relative to said firing force.

8. Apparatus according to claim 5 wherein said actuator member is formed of a magnetic material, said firing force means comprising a coil surrounding said actuator member and energizable to propel said actuator member in a first direction, and wherein the number of ampere turns of the holding coil is relatively small with respect to the ampere turns of said firing coil.

9. Apparatus according to claim 5 wherein the ratio of the mass of the actuator element to the energy transfer element is between about 1.2 and about 1.5.

10. Apparatus for damping the rebound oscillations of a slug element used for high speed printing or the like comprising firing force applying means for driving the element against a record medium, an energy transfer element located in the rebound path of said slug element, said energy transfer element having a surface against which said slug element impacts when it rebounds from the surface of said record medium and being mounted for movement in response to the impact with the slug element, and an energy absorptive element on at least one side of said energy transfer element in the path of movement of the energy transfer element and positioned for collision therewith, said energy absorptive element being adapted to absorb the energy of said transfer element during rebound oscillationsof said element.

11. Apparatus according to claim 10 wherein an energy absorbing element is mounted on both sides of the energy transfer element.

12. Apparatus for damping the rebound oscillations of a slug element following the firing of the element towards a 13. Apparatus according to claim 12 wherein both of said secondary impact members are formed of an energy absorptive material.

14. Apparatus according to claim 13 wherein the said energy transfer element is heavier than the slug element.

15. Apparatus according to claim. 14 wherein the ratio of the weight of the energy transfer element to the weight of the slug element is about 1.2 to about l.5.

Claims

1. Apparatus for damping the rebound oscillations of a first reciprocating element used in the recording of data on a record medium, said apparatus comprising a secondary element located in the rebound path of the first element for collision with said first element during its rebound motion, wherein the ratio of the mass of said secondary element to said first element approaches unity, said secondary element being mounted for limited movement in the direction of motion of the reciprocating element following a collision therewith and a body of energy absorptive material for limiting movement of the secondary mass.

2. Apparatus according to claim 1 wherein the ratio of masses of the secondary element relative to the first element is greater than 1.

3. Apparatus according to claim 2 wherein the ratio of the masses of the secondary element relative to the first element is between about 1.2 and 1.5.

4. Apparatus according to claim 1 wherein the length of the path of movement of the reciprocating element is long relatively to the length of path of movement of the secondary element.

10. Apparatus for damping the rebound oscillations of a slug element used for high speed printing or the like comprising firing force applying means for driving the element against a record medium, an energy transfer element located in the rebound path of said slug element, said energy transfer element having a surface against which said slug element impacts when it rebounds from the surface of said record medium and being mounted for movement in response to the impact with the slug element, and an energy absorptive element on at least one side of said energy transfer element in the path of movement of the energy transfer element and positioned for collision therewith, said energy absorptive element being adapted to absorb the energy of said transfer element during rebound oscillations of said element.

12. Apparatus for damping the rebound oscillations of a slug element following the firing of the element towards a reaction surface comprising an energy transfer element located in the rebound path of said slug element, said energy transfer element being movable upon collision occurring during the rebounding of said slug element to thereby transfer kinetic energy from said slug element, secondary impact members located on either side of said transfer element in proximity thereto, at least one of said members being formed of an energy absorbing material for absorbing the kinetic energy imparted by said slug element to said transfer element.

13. Apparatus according to claim 12 wherein both of said secondary impact members are formed of an energy absorptive material.

15. Apparatus according to claim 14 wherein the ratio of the weight of the energy transfer element to the weight of the slug element is about 1.2 to about 1.5.