阅读说明：本技术 一种注塑模具 (Injection mold ) 是由 张丽 阳溶冰 何朝武 于 2020-11-14 设计创作，主要内容包括：本申请公开了一种注塑模具,包括前模、前模板、后模和后模板,其特征在于：还包括上模和下模,所述上模和下模均设于所述后模和前模板之间,所述前模上连接有上斜导柱和下斜导柱,所述上斜导柱和下斜导柱分别与所述上模和下模滑动连接；开模过程中,所述前模横向平移时,所述上斜导柱和下斜导柱分别驱动所述上模和下模向上和向下移动。本发明的好处是生够生产中部小两端大的注塑产品。(The application discloses injection mold, including front mould, front mould board, back mould and back template, its characterized in that: the upper die and the lower die are arranged between the rear die and the front die plate, the front die is connected with an upper inclined guide pillar and a lower inclined guide pillar, and the upper inclined guide pillar and the lower inclined guide pillar are respectively connected with the upper die and the lower die in a sliding manner; in the die opening process, when the front die transversely translates, the upper inclined guide post and the lower inclined guide post respectively drive the upper die and the lower die to move upwards and downwards. The invention has the advantage of being capable of producing injection products with small middle parts and large ends.)

1. The utility model provides an injection mold, includes front mould, front mould board, back mould and back template, its characterized in that: the upper die and the lower die are arranged between the rear die and the front die plate, the front die is connected with an upper inclined guide pillar and a lower inclined guide pillar, and the upper inclined guide pillar and the lower inclined guide pillar are respectively connected with the upper die and the lower die in a sliding manner; in the die opening process, when the front die transversely translates, the upper inclined guide post and the lower inclined guide post respectively drive the upper die and the lower die to move upwards and downwards.

2. An injection mold according to claim 1, characterized in that: the die comprises a front die, a rear die and an upper die, and is characterized by further comprising an upper die plate and an upper guide pillar, wherein the upper guide pillar is fixedly connected with the rear die plate, the front die, the rear die and the upper die plate are all in sliding connection with the upper guide pillar, the upper die plate is arranged between the front die and the rear die, and the upper die plate is arranged above the upper die;

the top of the upper die is provided with a first connecting nail, the first connecting nail comprises a connector and a connecting column, the connector is arranged at the top of the connecting column, the upper die plate is provided with a first connecting hole, the longitudinal section of the first connecting hole is in a T shape, and the first connecting hole comprises a vertically arranged transition part and a horizontally arranged clamping part;

the upper guide pillar is provided with an upper locking groove with an upward opening, the upper template is provided with an upper mounting hole, the upper mounting hole is connected with an upper locking block through a spring, the rear side wall of the front side wall of the upper locking block is an inclined plane, the front side surface and the rear side surface of the upper locking groove are inclined planes, and the upper locking block is connected with the upper locking groove;

the mold opening process comprises the following steps:

s2, the front die moves forwards, the upper inclined guide post drives the upper die to move upwards, and the connector slides upwards in the transition part;

s3, the connector slides into the clamping portion, the clamping portion blocks the connector from moving upwards, and the upper die stops moving upwards;

s4, the upper die moves forward along with the front die, and under the action of the upper locking block and the upper locking groove, the upper die plate, the upper guide pillar and the rear die are relatively static, so that the connector and the clamping part move a certain distance transversely;

s5, under the blocking action of the connecting column, the upper template and the upper die are relatively static, the upper locking block is pressed into the upper mounting hole, the upper locking block is disconnected with the upper locking groove, and the upper template, the upper die and the front die move forwards together.

3. An injection mold according to claim 2, characterized in that: the lower die comprises a front die plate, a rear die plate and a lower die plate, wherein the front die plate is fixedly connected with the front die plate, the rear die plate and the lower die plate are all in sliding connection with the lower guide pillar, the lower die plate is arranged below the front die plate and the lower die plate, and the lower die plate is arranged between the rear die plate and the front die plate;

the front template is connected with a limiting block, the rear end of the limiting block extends to the front die, a limiting groove is formed in the limiting block, a limiting bulge is arranged on the front die, and the limiting bulge is connected with the limiting groove in a transverse sliding mode;

the bottom of the lower die is provided with a second connecting nail, the lower die plate is provided with a second connecting hole, the bottom of the second connecting nail is in sliding connection with the top of the lower die plate, and the second connecting nail is arranged right to the second connecting hole;

the lower guide pillar is provided with a lower lock groove with a downward opening, the lower template is provided with a lower mounting hole, the lower mounting hole is connected with a lower lock block through a spring, the front side wall and the rear side wall of the lower lock block are both inclined planes, the front side surface and the rear side surface of the upper lock groove are both inclined planes, and the lower lock block is connected with the lower lock groove;

step S1 is further included before step S2;

s1, under the action of the lower locking block and the lower locking groove, the front template drives the lower guide pillar and the lower template to move forwards together until the rear end of the limiting groove is abutted against the limiting protrusion, and meanwhile, the second connecting hole moves to the position below the second connecting nail;

step S2, the lower die is driven to move downwards by a lower inclined guide post, the second connecting nail moves downwards in the second connecting hole, the lower guide post moves forwards continuously along with the front template, the lower guide post and the lower template slide transversely and relatively, and the lower locking block is disconnected from the lower locking groove;

step S3 further includes the lower die abutting against the lower die plate and stopping downward movement of the lower die.

4. An injection mold according to claim 3, characterized in that: the core pulling device is characterized by further comprising an upper mold core, a lower mold core and a core pulling block, wherein the core pulling block is fixedly connected with the front template, an avoiding through hole is formed in the front mold, the core pulling block is connected with the avoiding through hole in a sliding mode, a core pulling part is arranged at the rear part of the core pulling block, an upper core pulling groove with the front end inclined upwards is formed in the top of the core pulling part, a lower core pulling groove with the front end inclined downwards is formed in the bottom of the core pulling part, and the upper mold core and the lower mold core are respectively connected with the upper core pulling groove and the lower core pulling; the upper mold core and the lower mold core are both in vertical sliding connection with the front mold plate, and the upper mold core and the lower mold core are arranged between the upper mold and the lower mold.

5. An injection mold according to claim 3, characterized in that: and in the step S2, after the upper die and the lower die vertically move for a certain distance, the sliding groove and the sliding key are disconnected.

6. An injection mold according to claim 3, characterized in that: the number of the upper guide pillars and the number of the lower guide pillars are more than two.

Technical Field

The application relates to the field of molds, in particular to an injection mold.

Background

For plastic products with small cross sections and large two ends, the plastic products can not be molded by injection. In the prior art, the product is generally divided into at least two parts, and the product with a large middle part and small two ends is obtained by welding or clamping and the like after each part is injected.

The problems existing in the prior art are that the production period or the complexity of a product can be increased by welding or clamping, the design difficulty and the processing difficulty of the product are increased, and the production efficiency is reduced.

Disclosure of Invention

The technical problem that this application will solve is: the utility model provides an injection mold, enough production middle part is little both ends big injection product.

The solution for solving the technical problem is as follows:

the utility model provides an injection mold, includes front mould, front mould board, back mould and back template, its characterized in that: the upper die and the lower die are arranged between the rear die and the front die plate, the front die is connected with an upper inclined guide pillar and a lower inclined guide pillar, and the upper inclined guide pillar and the lower inclined guide pillar are respectively connected with the upper die and the lower die in a sliding manner; in the die opening process, when the front die transversely translates, the upper inclined guide post and the lower inclined guide post respectively drive the upper die and the lower die to move upwards and downwards.

As a further improvement of the above technical solution, the mold further comprises an upper mold plate and an upper guide post, wherein the upper guide post is fixedly connected with the rear mold plate, the front mold, the rear mold and the upper mold plate are all slidably connected with the upper guide post, the upper mold plate is arranged between the front mold and the rear mold, and the upper mold plate is arranged above the upper mold; the top of the upper die is provided with a first connecting nail, the first connecting nail comprises a connector and a connecting column, the connector is arranged at the top of the connecting column, the upper die plate is provided with a first connecting hole, the longitudinal section of the first connecting hole is in a T shape, and the first connecting hole comprises a vertically arranged transition part and a horizontally arranged clamping part; the upper guide pillar is provided with an upper locking groove with an upward opening, the upper template is provided with an upper mounting hole, the upper mounting hole is connected with an upper locking block through a spring, the rear side wall of the front side wall of the upper locking block is an inclined plane, the front side surface and the rear side surface of the upper locking groove are inclined planes, and the upper locking block is connected with the upper locking groove; the mold opening process comprises the following steps: s2, the front die moves forwards, the upper inclined guide post drives the upper die to move upwards, and the connector slides upwards in the transition part; s3, the connector slides into the clamping portion, the clamping portion blocks the connector from moving upwards, and the upper die stops moving upwards; s4, the upper die moves forward along with the front die, and under the action of the upper locking block and the upper locking groove, the upper die plate, the upper guide pillar and the rear die are relatively static, so that the connector and the clamping part move a certain distance transversely; s5, under the blocking action of the connecting column, the upper template and the upper die are relatively static, the upper locking block is pressed into the upper mounting hole, the upper locking block is disconnected with the upper locking groove, and the upper template, the upper die and the front die move forwards together.

As a further improvement of the above technical solution, the die further comprises a lower template and a lower guide pillar, wherein the lower guide pillar is fixedly connected with the front template, the front die, the rear die and the lower template are all slidably connected with the lower guide pillar, the lower template is arranged below the front die and the lower die, and the lower template is arranged between the rear die and the front template; the front template is connected with a limiting block, the rear end of the limiting block extends to the front die, a limiting groove is formed in the limiting block, a limiting bulge is arranged on the front die, and the limiting bulge is connected with the limiting groove in a transverse sliding mode; the bottom of the lower die is provided with a second connecting nail, the lower die plate is provided with a second connecting hole, the bottom of the second connecting nail is in sliding connection with the top of the lower die plate, and the second connecting nail is arranged right to the second connecting hole; the lower guide pillar is provided with a lower lock groove with a downward opening, the lower template is provided with a lower mounting hole, the lower mounting hole is connected with a lower lock block through a spring, the front side wall and the rear side wall of the lower lock block are both inclined planes, the front side surface and the rear side surface of the upper lock groove are both inclined planes, and the lower lock block is connected with the lower lock groove; step S1 is further included before step S2; s1, under the action of the lower locking block and the lower locking groove, the front template drives the lower guide pillar and the lower template to move forwards together until the rear end of the limiting groove is abutted against the limiting protrusion, and meanwhile, the second connecting hole moves to the position below the second connecting nail; step S2, the lower die is driven to move downwards by a lower inclined guide post, the second connecting nail moves downwards in the second connecting hole, the lower guide post moves forwards continuously along with the front template, the lower guide post and the lower template slide transversely and relatively, and the lower locking block is disconnected from the lower locking groove; step S3 further includes the lower die abutting against the lower die plate and stopping downward movement of the lower die.

As a further improvement of the technical scheme, the core pulling device further comprises an upper mold core, a lower mold core and a core pulling block, wherein the core pulling block is fixedly connected with the front template, the front mold is provided with an avoidance through hole, the core pulling block is connected with the avoidance through hole in a sliding manner, the rear part of the core pulling block is provided with a core pulling part, the top of the core pulling part is provided with an upper core pulling groove with an inclined upward front end, the bottom of the core pulling part is provided with a lower core pulling groove with an inclined downward front end, and the upper mold core and the lower mold core are respectively connected with the upper core pulling groove and the lower core pulling groove in a; the upper mold core and the lower mold core are both in vertical sliding connection with the front mold plate, and the upper mold core and the lower mold core are arranged between the upper mold and the lower mold.

As a further improvement of the above technical solution, the upper die and the lower die are both provided with a sliding key, the rear die is provided with a sliding groove adapted to the sliding key and arranged along the vertical direction, and in step S2, after the upper die and the lower die vertically move for a certain distance, the sliding groove and the sliding key are disconnected.

As a further improvement of the technical scheme, the number of the upper guide posts and the number of the lower guide posts are more than two.

The beneficial effect of this application is: the rear mold and the front mold are used for molding the inner side wall of a product, and the upper mold and the lower mold are respectively used for molding the upper part and the lower part of the outer side wall of the product.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures are only some embodiments of the present application, not all embodiments, and that a person skilled in the art will be able to derive other designs and figures from these figures without inventive effort.

Fig. 1 is one of cross-sectional views of the present application when the mold is closed;

fig. 2 is a second cross-sectional view of the present application when the mold is closed;

FIG. 3 is one of the cross-sectional views of the mold of the present application at step S2;

FIG. 4 is a second cross-sectional view of the mold of the present application at step S2;

FIG. 5 is one of the cross-sectional views of the mold of the present application at step S3;

fig. 6 is a second cross-sectional view of the mold of the present application at step S3;

FIG. 7 is one of the cross-sectional views of the mold of the present application at step S4;

fig. 8 is a second cross-sectional view of the mold of the present application at step S4;

FIG. 9 is one of the cross-sectional views of the mold of the present application at step S5;

fig. 10 is a second cross-sectional view of the mold of the present application at step S5;

FIG. 11 is an enlarged view of portion A of FIG. 7;

FIG. 12 is an enlarged view of portion B of FIG. 6;

fig. 13 is an enlarged view of a portion C of fig. 8.

In the figure: 1-front die, 11-upper oblique guide post, 12-lower oblique guide post, 13-limiting protrusion, 2-front template, 21-limiting block, 211-limiting groove, 3-rear die, 4-upper die, 5-upper template, 51-first connecting hole, 511-transition part, 512-clamping part, 52-upper locking block, 6-upper guide post, 61-upper locking groove, 7-first connecting nail, 71-connecting head, 72-connecting column, 8-lower die, 81-second connecting nail, 9-lower template, 91-second connecting hole, 92-lower locking block, 10-lower guide post, 101-lower locking groove, 102-upper die core, 103-lower die core, 104-core-drawing block.

Detailed Description

The conception, specific structure, and technical effects of the present application will be described clearly and completely with reference to the accompanying drawings and embodiments, so that the purpose, features, and effects of the present application can be fully understood.

Referring to fig. 1 to 13, the injection mold of the present application specifically includes:

an injection mold comprises a front mold 1, a front mold plate 2, a rear mold 3, a rear mold plate, an upper mold 4 and a lower mold 8, wherein the upper mold 4 and the lower mold 8 are arranged between the rear mold 3 and the front mold plate 2, the front mold 1 is connected with an upper inclined guide pillar 11 and a lower inclined guide pillar 12, and the upper inclined guide pillar 11 and the lower inclined guide pillar 12 are respectively connected with the upper mold 4 and the lower mold 8 in a sliding manner; in the die opening process, when the front die 1 transversely translates, the upper inclined guide post 11 and the lower inclined guide post 12 respectively drive the upper die 4 and the lower die 8 to move upwards and downwards. In the invention, when the mold is opened, the front mold 1 is moved forwards, the upper mold 4 and the lower mold 8 are respectively opened upwards and downwards, the product is left on the rear mold 3, and the product is taken down from the rear mold 3 after the mold is opened. The rear mold 3 and the front mold 1 are used for molding the inner side wall of a product, and the upper mold 4 and the lower mold 8 are respectively used for molding the upper part and the lower part of the outer side wall of the product.

In a preferred embodiment, the die further comprises an upper die plate 5 and an upper guide post 6, the upper guide post 6 is fixedly connected with the rear die plate, the front die 1, the rear die 3 and the upper die plate 5 are all slidably connected with the upper guide post 6, the upper die plate 5 is arranged between the front die 1 and the rear die 3, and the upper die plate 5 is arranged above the upper die 4; the top of the upper die 4 is provided with a first connecting nail 7, the first connecting nail 7 comprises a connector 71 and a connecting column 72, the connector 71 is arranged at the top of the connecting column 72, the upper die plate 5 is provided with a first connecting hole 51, the longitudinal section of the first connecting hole 51 is in a T shape, and the first connecting hole 51 comprises a transition part 511 which is vertically arranged and a clamping part 512 which is horizontally arranged; the upper guide pillar 6 is provided with an upper locking groove 61 with an upward opening, the upper template 5 is provided with an upper mounting hole, the upper mounting hole is connected with an upper locking block 52 through a spring, the rear side wall of the front side wall of the upper locking block 52 is an inclined surface, the front side surface and the rear side surface of the upper locking groove 61 are inclined surfaces, and the upper locking block 52 is connected with the upper locking groove 61.

In a further preferred embodiment, the die further comprises a lower die plate 9 and a lower guide post 10, the lower guide post 10 is fixedly connected with the front die plate 2, the front die 1, the rear die 3 and the lower die plate 9 are all connected with the lower guide post 10 in a sliding manner, the lower die plate 9 is arranged below the front die 1 and the lower die 8, and the lower die plate 9 is arranged between the rear die 3 and the front die plate 2; the front template 2 is connected with a limiting block 21, the rear end of the limiting block 21 extends to the front mold 1, a limiting groove 211 is formed in the limiting block 21, a limiting bulge 13 is arranged on the front mold 1, and the limiting bulge 13 is connected with the limiting groove 211 in a transverse sliding mode; the bottom of the lower die 8 is provided with a second connecting nail 81, the lower die plate 9 is provided with a second connecting hole 91, the bottom of the second connecting nail 81 is slidably connected with the top of the lower die plate 9, and the second connecting nail 81 is arranged right to the second connecting hole 91; the lower guide pillar 10 is provided with a lower lock groove 101 with a downward opening, the lower template 9 is provided with a lower mounting hole, the lower mounting hole is connected with a lower lock block 92 through a spring, the rear side walls of the front side wall and the rear side wall of the lower lock block 92 are both inclined planes, the front side surface and the rear side surface of the upper lock groove 61 are both inclined planes, and the lower lock block 92 is connected with the lower lock groove 101.

Further, the number of the upper guide posts 6 and the lower guide posts 10 is two or more to prevent the upper and lower templates 5 and 9 from being rotationally displaced.

In a preferred embodiment of the present invention, the mold opening process comprises the following steps: s1, under the action of the lower locking block 92 and the lower locking groove 101, the front template 2 drives the lower guide pillar 10 and the lower template 9 to move forwards together until the rear end of the limiting groove 211 abuts against the limiting protrusion 13, and meanwhile, the second connecting hole 91 moves to the position below the second connecting nail 81; s2, the front mold 1 moves forward, the upper inclined guide post 11 drives the upper mold 4 to move upward, and the connecting head 71 slides upward in the transition portion 511; the lower inclined guide post 12 drives the lower die 8 to move downwards, the second connecting nail 81 moves downwards in the second connecting hole 91, the lower guide post 10 continues to move forwards along with the front template 2, the lower guide post 10 and the lower template 9 generate transverse relative sliding, and the lower lock block 92 is disconnected from the lower lock groove 101; s3, the connecting head 71 slides into the clamping portion 512, the clamping portion 512 blocks the connecting head 71 from moving upwards, and the upper die 4 stops moving upwards; the lower die 8 is abutted against the lower die plate 9, and the lower die 8 stops moving downwards; s4, the upper mold 4 moves forward along with the front mold 1, and under the action of the upper locking block 52 and the upper locking groove 61, the upper mold plate 5, the upper guide post 6 and the rear mold 3 are relatively stationary, so that the connector 71 and the clamping portion 512 move laterally a certain distance; s5, under the blocking action of the connecting column 72, the upper mold plate 5 and the upper mold 4 are relatively stationary, the upper block 52 is pressed into the upper mounting hole, the upper block 52 is disconnected from the upper locking groove 61, and the upper mold plate 5, the upper mold 4, and the front mold 1 move forward together. In the mold closing state, the second connecting hole 91 is on the left side of the second connecting nail 81, so that the lower mold 8 applies its gravity to the lower mold plate 9 through the second connecting nail 81, the gravity of the lower mold plate 9 and part of the gravity of the lower mold 8 are supported by the lower guide pillar 10, and the other part of the gravity of the lower mold 8 is supported by the lower inclined guide pillar 12; the advantage of setting up like this can avoid the gravity of lower mould 8 to be all applyed on lower oblique guide pillar 12, avoids because of the too big card pause of frictional force between lower oblique guide pillar 12 and lower mould 8. In step S1, the front mold plate 2 is separated from the front mold 1, so that the injection molding gate is separated from the injection molding product, the rear end of the limiting groove 211 abuts against the limiting protrusion 13, and in the following process, the front mold plate 2 can drive the front mold 1 to move forward together; meanwhile, the second connecting hole 91 is moved to the lower part of the second connecting nail 81, and the lower die 8 can be pushed downwards by the lower inclined guide post 12 in the process of moving the front die 1 forwards, so that the second connecting nail 81 is prevented from blocking the lower die 8 to move downwards. In step S2, the upper mold 4 and the lower mold 8 are pushed to open the mold upwards and downwards by the forward force of the front mold 1, and the lower mold plate 9 cannot move forward along with the lower guide pillar 10 due to the interaction between the second connecting pin 81 and the second connecting hole 91, so that the lower lock block 92 is disconnected from the lower lock groove 101, and the lower lock block 92 is pressed into the lower mounting hole by the lower guide pillar 10. In step S3, the upper mold 4 and the lower mold 8 stop being opened upward and downward due to the blocking effect of the engaging portion 512 on the connecting head 71 and the blocking effect of the lower mold plate 9 on the lower mold 8. In step S4, since the connector 71 enters the engaging portion 512 and the longitudinal cross-section of the first connecting hole 51 is T-shaped, the upper mold plate 5 and the first connecting pin 7 can move relatively, at this time, the front mold plate 2, the front mold 1, the upper mold 4, the lower mold 8, and the lower mold plate 9 all move forward, and the upper mold plate 5 does not move forward with the upper mold 4 under the action of the upper locking block 52 and the upper locking groove 61 until the front side of the first connecting pin 7 is attached to the first connecting hole 51, and the first connecting pin 7 prevents the upper mold plate 5 and the upper mold 4 from moving relatively laterally. Through step S5, the mold of the present invention can complete the mold opening operation, and the product is removed from the rear mold 3 after the mold opening operation.

In a preferred embodiment of the invention, the mould closing process comprises the following steps: s6, the rear mold 3 and the upper guide post 6 are moved forward relative to the upper mold plate 5 until the upper lock piece 52 is connected to the upper lock groove 61; s7, the upper die plate 5 moves forward along with the upper guide pillar 6 until the connector 71 is disconnected from the clamping part 512, and the upper die 4 is abutted to the rear die 3; s8, the rear die 3, the upper die plate 5, the upper die 4, the lower die 8 and the lower die plate 9 move forwards relative to the front die 1 and the front die plate 2, and simultaneously the upper die 4 moves downwards and the lower die 8 moves upwards until the upper die 4 and the lower die 8 are matched in place; s9, the front template 2 drives the lower template 9 to move backwards relative to the front template 1 and the lower template 9, and the second connecting nails 81 are staggered with the second connecting holes 91 until the die assembly is completed.

In a preferred embodiment, the mold further comprises an upper mold core 102, a lower mold core 103 and a core pulling block 104, wherein the core pulling block 104 is fixedly connected with the front mold plate 2, an avoidance through hole is formed in the front mold 1, the core pulling block 104 is connected with the avoidance through hole in a sliding manner, a core pulling part is arranged at the rear part of the core pulling block 104, an upper core pulling groove with an inclined upper front end is arranged at the top of the core pulling part, a lower core pulling groove with an inclined lower front end is arranged at the bottom of the core pulling part, and the upper mold core 102 and the lower mold core 103 are respectively connected with the upper core pulling groove and the lower core pulling groove in a; the upper mold core 102 and the lower mold core 103 are both connected with the front mold plate 2 in a vertically sliding manner, and the upper mold core 102 and the lower mold core 103 are arranged between the upper mold 4 and the lower mold 8. In step S2, the core block 104 is advanced with the front mold plate 2, and the upper mold core 102 and the lower mold core 103 slide downward and upward, respectively, with respect to the front mold 1. In this embodiment, a mold cavity is formed between the upper mold core 102 and the upper mold 4, and another mold cavity is formed between the lower mold core 103 and the lower mold 8, so that two injection molded products with large middle parts and small ends can be molded simultaneously.

Further, all be equipped with the sliding key on last mould 4 and the lower mould 8, be equipped with on the back mould 3 with the sliding key adaptation and the spout that sets up along upper and lower direction, in step S2, after going up a section distance of mould 4 and 8 vertical movements of lower mould, spout and sliding key break away from the connection. In the mold clamping condition, the slide groove and the slide key are connected with each other. The present embodiment has an advantage of restricting the positions of the upper mold 4 and the lower mold 8 in the mold clamping state, and improving the accuracy of mold clamping.

While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited to the details of the embodiments, but is capable of various modifications and substitutions without departing from the spirit of the invention.