Abstract:
A toy drive mechanism having extensions such as leg and neck members covered with a plush covering. The drive mechanism is operative to move the leg, back, and head members in coordinated movements imitating an animal tugging or pulling on a rope. The realistic movement is provided by a series of rotating devices, some on differing axes relative to the drive shaft, and an information processor activated by one or more switches located throughout the body. One switch in particular, located between the neck and head and motivated by a user pulling on the rope in the toy&#39;s mouth, will cause the toy to exert a pulling motion accompanied by sound effects.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and is a continuation-in-part of U.S. application Ser. No. 10/698,930 filed Nov. 3, 2003, titled “Electromechanical Toy,” which claims priority from and is a continuation-in-part of U.S. application Ser. No. 10/425,992 filed Apr. 30, 2003, now U.S. Pat. No. 6,843,703 titled “Electromechanical Toy,” which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electromechanical toys or dolls. More particularly, the invention relates to a doll featuring realistic movements in response to a user&#39;s interaction. 
     2. Description of the Related Art 
     Toys and dolls that have moving parts are well known. For example, dolls and plush toys such as stuffed animal are made with moveable appendages. However, the movement of a doll&#39;s appendages is limited by the technology available. The result is often a doll that, while able to interact with a user, does not do so in a way that is life-like or realistic. 
     As with technology, consumer demands are constantly evolving. The ability for toys to capture the evolving technology into toys that can interact with the user through life-like mannerisms characteristic of the animal the toy is attempting to imitate is a realistic concern of the toy industry. 
     To imitate a life-like animal, the toy must be capable a capturing two distinct aspect. One is the imitation of the mannerisms displayed by the animal, which must be accomplished through a system of inexpensive linkages and gears as cost is a constant restriction on the toy industry. With the cost constraint ever present, modern toys often lack the innate intricacies of the subtle movements of living animals. 
     The second aspect inherent in creating a lifelike toy is creating a triggering mechanism to activate the toy that does not disrupt the fantasy aspect of the user. Current toys often feature simple on/off switches, which reduce the ability for a child to make-believe the toy is alive. Reduction of this disruption increases the user&#39;s interaction with the toy, consequently, increasing the entertainment value of the toy. 
     A need exists, therefore, to create a toy capable of exhibiting realistic mannerisms characteristic of the animal the toy is attempting to imitate, while being actuated in a way that is inherent to a user&#39;s interaction with the animal such as tugging on a rope in a dog&#39;s mouth causing the dog to respond by tugging back on the rope and growling. 
     SUMMARY OF THE INVENTION 
     The present invention solves the aforementioned needs by creating a toy or doll comprising a drive mechanism with a plurality of extensions such as leg and neck members covered with a plush covering configured to closely resemble a live animal and to respond to stimuli in a realistic manner that is consistent with the way in which a real animal would respond. 
     In particular, an embodiment of the present invention resembles a dog holding a rope in the dog&#39;s mouth. Tugging on a rope by the user will cause the dog to respond by tugging back on the rope and growling. The realistic motion is accomplished through the use of a pair of legs exhibiting a kneading motion that raises and lowers the dog&#39;s body. The tugging motion by the dog is actuated through a sensor in the dog&#39;s neck responsive to a user pulling on the rope in the dog&#39;s mouth. To compliment the realism of the invention an information processor coordinates the movements with sound effects such as growling typical of a live dog at play. 
     In general, the toy includes a body, a motor within the body, an appendage coupled to the body of the toy, and a neck device coupled to the body of the toy. The appendage is actuated by the motor to move along a first path. The neck device is actuated by the motor to move along a second path. 
     To achieve the realistic movement needed, movement of the neck device and the appendage may occur simultaneously and in coordinated movement by an information processor housed within the body. 
     To create the movements in the appendage, the toy may incorporate a drive shaft that couples the motor to the appendage. The toy may further include a cam that receives the drive shaft such that rotation of the drive shaft rotates the cam. The toy may also include an eccentric rod to which the appendage connects. 
     The toy may also include a pivot gear coupled to the body of the toy and a post that couples to a slot within the appendage. The toy may include gear teeth that extend from the cam and that mesh with gear teeth of the pivot gear such that rotation of the cam causes rotation of the pivot gear, which causes the appendage to move along the first path. 
     The toy may include a linkage rod coupled to the body of the toy and to a slot within the appendage. Rotation of the cam causes the appendage to move along the first path. 
     These mechanisms can present a realistic kneading action by the appendages in the toy. 
     The drive shaft may couple the motor to the neck device. The toy may include a head connected to the neck device. The neck device may include a hinge attached to the body such that the neck device is configured to rotate about the hinge as the neck device moves along the second path. The toy may include a follower attached to the neck device and coupled to the drive shaft such that rotation of the drive shaft moves the follower in a periodic pattern and causes the neck device to move along the second path. There may also be a hinge present at the connection of the head to the neck device such that the head is configured to rotate about the hinge as the neck device moves along the second path. The connection of the head and neck device may also be coupled to allow the radial movement of the head. 
     The toy may include an information processor within the body and coupled to the motor, and a sensor connected to send a signal to the information processor. The information processor causes the motor to operate in response to a signal from the sensor. 
     The toy may include another appendage shaped like the appendage and coupled to the body of the toy. Each of the appendages may be positioned such that ends of the appendages move in non-circular paths that are aligned with each other. 
     Movement along the first path may include movement of an end of the appendage along a non-circular path. 
     The toy may also include a flexible skin surrounding the body of the toy. The flexible skin may include pile that resembles an animal&#39;s coat. The flexible skin may surround the appendage of the toy and may move as the appendage moves. 
     The drive mechanism is operative to move the leg, back, and head members in coordinated movements imitating an animal tugging or pulling on a rope. To achieve this realistic movement, a series of rotating devices, some on differing axes relative to the drive shaft, are employed. 
     The information processor activated by a plurality of switches located throughout the body coordinates the toy. One switch in particular, located between the neck and head and motivated by a user pulling on the rope in the toy&#39;s mouth, will cause the toy to exert a pulling motion accompanied by sound effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a toy; 
         FIG. 2A  is a perspective view of an internal structure of an alternative embodiment of the toy of  FIG. 1 ; 
         FIG. 2B  is an exploded perspective view of the internal structure of  FIG. 2A ; 
         FIGS. 2C and 2D  are views illustrating is a present embodiment of the toy; 
         FIGS. 3A and 3B  are perspective views of an alternative embodiment of the toy of  FIG. 1 ; 
         FIG. 3C  is a perspective view of a present embodiment of the toy; 
         FIG. 4  is a block diagram of the toy of  FIG. 1 ; 
         FIG. 5  is a perspective view of an interior of a bottom portion of the internal structure of the toy of  FIG. 1 ; 
         FIG. 6A  is a perspective view of the internal structure including a tail device of the toy of  FIG. 1 ; 
         FIG. 6B  is a side view of a part of the tail device of the toy of  FIG. 1 ; 
         FIGS. 7A and 7B  are side views of the internal structure of an alternative embodiment of the toy of  FIG. 1 ; 
         FIG. 8  is a flow chart of a method of operating the toy; 
         FIGS. 9A-9G  are side views of an appendage of the internal structure of  FIG. 2A ; 
         FIG. 10  is a perspective view of an underside of the toy of  FIG. 1 ; 
         FIGS. 11A and 11B  are side and partial cutaway views of the appendage and an external flexible skin of the toy of  FIG. 1 ; and 
         FIG. 12  is a side view of an appendage of the internal structure of the toy of  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a toy  100  is designed to provide realistic movement in response to a sensed condition. To this end, the toy  100  includes an external flexible skin  110 . The external flexible skin  110  may be made of a resilient material that is covered with one or more external soft layers, such as pile that resembles an animal&#39;s coat. As shown, the toy  100  is in the shape of a puppy and the external flexible skin  110  resembles the coat of a puppy. The external flexible skin  110  has an opening  112 , an opening  114 , and an opening  116  formed into the skin to facilitate the fitting of the external flexible skin  110  over an internal structure,  200 , as shown in the alternative embodiments of  FIGS. 2A and 2B . 
     As shown in  FIGS. 2A and 2B , posts shaped as, for example, eyes  202 , a nose  204 , and a tongue  206  inter-fit with cavities  208 , a cavity  210 , and a cavity  212 , respectively, of the internal structure  200  to secure the external flexible skin  110  to the internal structure  200 . The posts consist of a wider portion and a narrower portion. The flexible skin  110  is placed over the internal structure  200  such that the openings  112 ,  114 , and  116  fit over the cavities  208 ,  210 , and  212 , respectively. The narrower portions of the eyes  202 , nose  204 , and tongue  206  are inserted into the cavities  208 ,  210 , and  212 , respectively. The wider portions of the posts hold the flexible skin  110  in place. 
     The internal structure  200  includes a body  214  which can be separated into a top portion  216  and a bottom portion  218 . The bottom portion  218  houses many of the components that control operation of the toy  100 . Connected to these components are one or more appendages  220 , as well as a neck device  222  for connecting the body  214  to a head  224 , and a tail device  226 . The internal structure  200  may be made of any suitable combination of materials. For example, the body  214  and the appendages  220  may be made of plastic and/or metal. 
     Any combination of the appendages  220 , a first extension  220  and a second extension  220  in the present embodiment, the neck device  222 , a third extension  222  in the present embodiment, and the tail device  226  may be actuated during operation of the toy  100  in response to input received from one or more input devices in the form of sensors  228  and  230 . The first extension  220  is motivated to rotate around a first axis, or appendage axis. Likewise, the second extension  220  is motivated about a second axis, which in the present embodiment is parallel and also known as an appendage axis. The third extension  222  reciprocates about a third axis, or neck axis, which in the present embodiment is also parallel to the first axis. In the present embodiment, the head  224  is coupled to the neck device  222  to allow radial movement about the third extension  222 . This allows the head  224  to rotate in along a fourth axis, or head axis, that, in the present embodiment, is perpendicular to the third axis. 
     Referring also to  FIG. 3A , the sensor  228  is a pressure sensitive switch that is depressed and pushes an underlying button switch when a user touches the toy  100  at a location  330  near the sensor  228 . Referring also to  FIG. 3B , the sensor  230  is a magnetic switch, such as, for example, a reed switch or a Hall effect sensor, that is actuated by a magnet within an accessory  340  when the accessory  340  is placed at a location  345  near the sensor  230 . 
     As shown in  FIG. 3C , in the present embodiment, a rope  341  can be placed at the head  224  of the toy. The head  224  includes a lower jaw  205  for receiving the rope  341  and compressing the rope  341  against the head  341  to prevent removal when a user is pulling on the rope  341 . 
     As shown in  FIG. 4 , internal circuitry  402  and an output device in the form of an audio device  404  are housed within the body  214 . The sensors  228  and  230  and the audio device  404 , a speaker in the present embodiment are connected to the circuitry  402 , an information processor in the present embodiment. The circuitry  402  receives power from an energy source  406  and controls operation of a motor  408  housed within the body  214 . The energy source  406  may be provided by batteries  409 , shown in  FIG. 2B , that are placed within a compartment on an underside of the body  214 . The circuitry  402  is turned off and on by a switch  410  that is accessible on the body  214 . A driving device  412  that is housed within the body  214  couples the motor  408  to the neck device  222 , the appendages  220 , and the tail device  226 , which is attached to one appendage  220  by a long connector piece  414 . 
     Referring to  FIG. 5 , the motor  408  includes a pulley  502 , a flexible belt  504 , a pulley  506 , a worm gear  508 , and a shaft system  510  (discussed below). The pulley  502  is mounted on and frictionally engages a shaft  512  of the motor  408 . The flexible belt  504  is connected to the pulley  502  and the pulley  506 , such that rotation of the pulley  502  causes rotation of the pulley  506 . The pulley  506  and the worm gear  508  are mounted on and fixed to a shaft  514  that is connected the body  214 . 
     Referring also to  FIGS. 2B ,  5 , and  6 , the drive shaft system  510  includes a disk shaft  516  that spans the width of the bottom portion  218  and is connected to centers of a pair of cams  518 . The shaft system  510  also includes a gear  520  that is fixed on the disk shaft  516  and coupled to the worm gear  508 . The shaft system  510  includes a gear  522  having teeth that mate with teeth of the gear  520  and a rounded piece  524  having an eccentric protrusion  526 . The gear  522  and the rounded piece  524  are mounted to a shaft  528  (shown in  FIG. 2B ). 
     Each of the first extension  220  and second extension  220  includes a first end  530 , a second end  532 , and a slot  534  that extends between the first and second ends  530  and  532 . In the present embodiment, the first cam  518 A attached to the first extension  220 A acts as a first rotating device  518 A. Likewise, in the present embodiment, the second cam  518 B attached to the second extension  220 B acts as a second rotating device  220 B. The cams  518  couple the appendages  220  to the disk shaft  516 . Each cam  518  includes an eccentric rod  536  that is positioned along and is integral with an outer surface of the cam  518 . The first end  530  of the appendage  220  includes a first screw  538  for connecting the eccentric rod  536  to the appendage  220 . 
     The bottom portion  218  of the body  214  includes a linkage rod  540  that is positioned along and integral with an outer surface of the bottom portion  218 . The slot  534  of the appendage  220  is wide enough to accommodate the linkage rod  540 , which is engaged with the slot  534 . The linkage rod  540  is constrained to the slot  534  by a second screw  542 . 
     The first end  530  of the appendage  220  is rotatably fixed to the eccentric rod  536  and the second end  532  of the appendage  220  is free to move along paths constrained by the engagement of the linkage rod  540  with the slot  534  and the second screw  542 . In this way, overall motion of the appendage  220  is constrained by the engagement of the slot  534  with the fixed linkage rod  540  and by the fixed connection of the first end  530  to the eccentric rod  536 . 
     Referring to  FIG. 6A , the tail device  226  includes a tail-shaped piece  602 , a shaft  604  extending from the tail-shaped piece  602 , a middle piece  606  fixed to the shaft  604 , and a lower piece  608  fixed to the shaft  604 . The tail device  226  is coupled with the disk shaft  516  through a long connector piece  414 . 
     Referring also to  FIG. 6B , the long connector piece  414  includes a shaft  610  that protrudes from an end  612  of the piece  414  and fits within a groove  614  of one of the cams  518 . The groove  614  is created by an inner wall  616  and an outer wall  618  of the cam  518 . The groove  614  is circular except for a shallow u-shaped curve  620  caused by a protrusion  622  in the outer wall  618  and a dimple  624  in the inner wall  616 . 
     Referring to  FIGS. 2B ,  7 A and  7 B of an alternative embodiment, the neck device  222  includes a first piece  702  attached to the head  224 , a second piece  704  attached to the first piece  702 , and a third piece  706  attached to the second piece  704 . 
     In the preferred embodiment, as shown in  FIGS. 2C and 2D , the second piece  704  connected to the head  224  by connection  705 . Connection  705  could be an assortment of connection types that allow for movement such as a pivot, joint, or hinge as in the present embodiment that allows for the head  224  to move in along a fifth axis, or hinge axis, perpendicular to the fourth axis. Located at connection  705 , is switch  707 . Activation of switch  707  occurs when the head  224  is motivated in the dorsal direction. Switch  707  is connected to driving device  412 , which will coordinate the neck device  222  into a tugging motion and appendage  220  into a kneading motion when activated. The activation of switch  707  will likewise trigger audio system  404  to issue sound effects that are coordinated with the movements of the neck device  222  and the appendage  220  through the internal circuitry  402  acting as an information processor, microprocessor, or controller. 
     In an alternative embodiment, as shown in  FIG. 2B , one end  708  of the third piece  706  is attached to the top portion  216  at a hinge  710 . Another end  712  of the third piece  706  is attached to a follower  714  by a bolt  716 . The follower  714  is shaped with a first hole  718  for receiving the bolt  716  and a second hole  720  for connecting with the protrusion  526  of the rounded piece  524 . The follower  714  includes a middle pliable portion  722  having a zigzag shape between the holes  718  and  720 . 
     Referring to  FIG. 8 , the user turns on the toy  100  and the circuitry  402  by actuating the switch  410  (step  802 ). Upon receipt of a sensed condition (step  804 ) (for example from an input device  228  or  230 ), the circuitry  402  actuates the motor  408  (step  806 ), which actuates some combination of movements of the appendages  220  (step  808 ), the neck device  222  (step  810 ), and the tail device  226  (step  812 ) (described below). To further enhance realism, the circuitry  402  sends a signal to the audio device  404  (step  814 ) to output a sound such as, for example, a bark, a pant, or a purr, as the motor actuates the combination of movements (steps  808  through  812 ), 
     Referring also to  FIG. 5 , actuation of the motor  408  (step  806 ) causes the motor shaft  512  and the pulley  502  mounted on the shaft  512  to rotate. The rotation of the pulley  502  moves the flexible belt  504 , which causes the pulley  506  to rotate. The actuation of pulley  506 , in turn, rotates the shaft  514  and thereby rotates the worm gear  508  mounted the shaft  514 . The rotating worm gear  508  engages and rotates the gear  520 , which actuates the disk shaft  516 . 
     With reference to  FIGS. 2B ,  5 ,  6 ,  7 A, and  7 B, as mentioned, actuation of the motor  408  (step  806 ) causes actuation of the neck device (step  810 ). Rotation of gear  520  on the disk shaft  516  causes the gear  522  to rotate. Rotation of the gear  522  causes the rounded  15  piece  524  and the protrusion  526  on the rounded piece  524  to rotate. The rotation of the protrusion  526  translates into a motion of the lower end of a follower  714 , which is attached to the protrusion  526  at the second hole  720 . In the present embodiment follower  714  acts as a third rotating device  714 . In particular, the motion of the rounded piece  524  drives the protrusion  526 , which drives the lower end of the follower  714  in a circular path. An upper end of the follower  714  that includes the first hole  718  describes a radial path that is constrained by the hinge  710  attached to the first hole  718 . The motion of the follower  714  moves the neck device  222 , which is attached at the third piece  706  to the follower  714  by the bolt  716 . The actuation of the neck device  222  moves the head  224 , which is attached to the neck device  222 . The motion of the follower  714  translates into a reciprocating up and down motion of the neck device  222  and the head  224 . 
     As the motion of the follower  714  reaches its apogee, the neck device  222  and the head  224  are raised, as shown by an arrow  720  in  FIG. 7A . As the motion of the follower  714  reaches its perigee, the neck is lowered, as shown by an arrow  722  in  FIG. 7B . 
     As mentioned above, actuation of the motor  408  (step  806 ) causes actuation of the appendages  220  (step  808 ). With particular reference to  FIGS. 9A-9G , actuation of the 30 driving device  412  results in the simultaneous rotation of the cams  518 . In particular, as discussed, the motor  408  rotates the disk shaft  516 . The rotation of the disk shaft  516  causes the cams  518  to rotate. Referring to  FIGS. 9A-9G , as a cam  518  rotates, the first end  530  of the appendage  220  that is attached to the cam  518  by the eccentric rod  536  and the first screw  538  rotates with the cam  518  in a circular path. As the first end  530  rotates, the motion of the appendage  220  is constrained by the second screw  542  and the fixed linkage rod  540 . This limitation arises as a result of the contact of the linkage rod  540  with edges  902  and  904  of the slot  534 . Rotation of the first end  530  of the appendages  220  causes the appendage  220  to pivot about and move transversely to the linkage rod  540 , which causes the second end  532  to move in a non-circular or irregular path as shown by the sequence of  FIGS. 9A-9G . 
     As mentioned, with reference to  FIGS. 6A and 6B , the actuation of the appendages  220  drives the tail device  226 . The inner wall  616  and the outer wall  618  contain the 10 movement of the shaft  610  as the cam  518  rotates relative to the shaft  610 . As the circular I portion of the groove  614  rotates and engages the shaft  610 , the arm  414  does not move significantly and remains in a default position. As the cam  518  continues to rotate, an upper portion  626  of the shallow u-shaped curve  620  engages the shaft  610 , and the long connector piece  414  moves down and inward toward the center of the cam  518  as a result of the dip of the shallow u-shaped curve  620 . As the cam  518  continues to rotate, a lower portion  628  of the shallow u-shaped curve  620  engages the shaft  610 . As the cam  518  continues to rotate, the lower portion  628  disengages the shaft  610  and the long connector piece  414  moves up and away from the center of the cam  518  and back to its default position. 
     The movement of the long connector piece  414  towards and away from the center of the cam  518  causes the long connector piece  414  to pull on and release the lower piece  608  of the tail device  226 . Movement of the lower piece  608  causes the shaft  604  to rotate, which causes the tail device  226  to rotate. The overall movement of the tail device  226  imparts a realistic appearance of a dog wagging its tail. 
     Referring also to  FIGS. 10 ,  11 A, and  11 B, a portion  1000  of the external flexible skin  110  is fastened to the second end  532  of the appendage  220 . For example, the portion  1000  may be sewn with thread  1010  to an eye  110  formed in the second end  532 . As the second end  532  traverses the range of motion shown in  FIGS. 8A-8G , the portion  1000  of the skin is periodically pulled toward (tensioning) and away from (slackening) the second end  532 . This periodic tensioning and slackening causes the skin  110  in the portion  1000  to deform during the cycle. The overall motion of the appendages  220  and the skin  110  of the toy  100  imparts a realistic appearance of a dog moving its paws. 
     Other implementations are within the scope of the following claims. For example, the toy  100  may be of any design, such as, for example, a toy, a plush toy such as a stuffed animal, a dog or other animal, or a robot. 
     One or more of the sensors  228  or  230  may be touch-sensitive devices. For example, one or more of the sensors  228  or  230  may be a pressure sensing device such as, for example, a pressure-activated switch in the form of a membrane switch. As another example, a sensor  228  or  230  may be made of a conductive material and may be an inductively-coupled device. In this case, when a user touches the toy  100  at the location of the inductive sensor, a measured inductance associated with the inductive sensor changes and the change is sensed. As a further example, a sensor  228  or  230  may be made of a conductive material and may be a capacitively-coupled device such that when a user touches the toy  100  at the location of the capacitive sensor, a measured capacitance associated with the sensor changes and the change is sensed. One or more of the sensors  228  or  230  may be a light-sensing device, such as, for example, an IR-sensing device or a photocell. Additionally or alternatively, one or more of the sensors  228  or  230  may be a sound-sensing device such as, for example, a microphone. 
     The output device may be an optical device, such as, for example, a lamp or a light emitting diode, or an electro-mechanical device. The flexible skin  110  may include a resilient material to further enhance realism of the toy  100 . 
     In another implementation, actuation of the driving device  412  results in an in-phase motion of the appendages  220 . Thus, for example, as one appendage  220  reaches an apex of the cycle, the other appendage  220  reaches an apex of the cycle. In another implementation, actuation of the driving device  412  results in an out-of-phase motion of the appendages  220 . Thus, for example, as one appendage  220  reaches an apex of the cycle, the other appendage  220  reaches another point of the cycle. 
     Referring to  FIG. 12 , in another implementation, the appendages  220  are coupled to the disk shaft  516  with a crank gear  1202  and a pivot gear  1204 . The crank gear  1202  includes a center shaft  1212  that is connected to and driven by the disk shaft  516 . The appendage  220  is rotatably fixed to the crank gear  1202  at a point  1203 . The pivot gear  1204  includes a center post  1214  rotatably mounted to the body  214  and teeth that mesh with teeth of the crank gear  1202 . The pivot gear  1204  includes a post  1206  that is rotatably and slidably received within the slot  534  of the appendage  220 . 
     In operation, the disk shaft  516  drives the crank gear  1202 , which in turn drives the pivot gear  1204 . The motion of the pivot gear  1204  allows the post  1206  in the slot  534  to move back and forth through the slot  534  about an arc defined by the shape of the slot  534 . The resulting motion moves the appendage  220  through a path that is repeatable for every one revolution of the crank gear  1202 . 
     The pivot gear  1204  may have half the number of gear teeth as the crank gear  1202 , such that the pivot gear  1204  operates at twice the speed of the crank gear  1202 . Thus, as the pivot gear  1204  completes one revolution, the crank gear  1204  completes one half of a revolution. 
     It should be appreciated that a wide range of changes and modifications may be made to the embodiments of the inventions as described herein. It is intended that the foregoing detailed description be regarded as illustrative rather than limiting. While there have been illustrated and described particular embodiments of the inventions, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover those changes and modifications which fall within the true spirit and scope of the present invention.